CA1206538A - Microwave oscillator - Google Patents
Microwave oscillatorInfo
- Publication number
- CA1206538A CA1206538A CA000444066A CA444066A CA1206538A CA 1206538 A CA1206538 A CA 1206538A CA 000444066 A CA000444066 A CA 000444066A CA 444066 A CA444066 A CA 444066A CA 1206538 A CA1206538 A CA 1206538A
- Authority
- CA
- Canada
- Prior art keywords
- waveguide
- frequency
- oscillator
- coupling means
- locking signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B9/00—Generation of oscillations using transit-time effects
- H03B9/12—Generation of oscillations using transit-time effects using solid state devices, e.g. Gunn-effect devices
- H03B9/14—Generation of oscillations using transit-time effects using solid state devices, e.g. Gunn-effect devices and elements comprising distributed inductance and capacitance
- H03B9/145—Generation of oscillations using transit-time effects using solid state devices, e.g. Gunn-effect devices and elements comprising distributed inductance and capacitance the frequency being determined by a cavity resonator, e.g. a hollow waveguide cavity or a coaxial cavity
- H03B9/146—Generation of oscillations using transit-time effects using solid state devices, e.g. Gunn-effect devices and elements comprising distributed inductance and capacitance the frequency being determined by a cavity resonator, e.g. a hollow waveguide cavity or a coaxial cavity formed by a disc, e.g. a waveguide cap resonator
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B2200/00—Indexing scheme relating to details of oscillators covered by H03B
- H03B2200/006—Functional aspects of oscillators
- H03B2200/0074—Locking of an oscillator by injecting an input signal directly into the oscillator
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B2201/00—Aspects of oscillators relating to varying the frequency of the oscillations
- H03B2201/01—Varying the frequency of the oscillations by manual means
- H03B2201/014—Varying the frequency of the oscillations by manual means the means being associated with an element comprising distributed inductances and capacitances
Landscapes
- Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)
- Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
Abstract
ABSTRACT
"Microwave oscillator"
A microwave oscillator suitable for millimeter wavelengths comprises a Gunn diode (3) coupled to a waveguide (1) by a resonant-cap structure (5,6). The diode (3) generates microwave energy both at a fundamental frequency fo which is below the cut-off frequency of the waveguide (1) and at a second harmonic frequency 2fo above cut-off.
To control the generation of microwave energy at 2fo, energy at fo may be coupled into the waveguide (1), e.g. from an adjacent further waveguide (9) above its cut-off, by means of an electric probe (8) extending close to the cap (5). The probe (8) may couple in a locking signal at or close to the free-running value of fo from another oscillator having better noise performance and electronic tuning, thereby locking 2fo to twice the frequency of the locking signal, or alternatively may couple to a varactor-tuned cavity resonant at fo.
"Microwave oscillator"
A microwave oscillator suitable for millimeter wavelengths comprises a Gunn diode (3) coupled to a waveguide (1) by a resonant-cap structure (5,6). The diode (3) generates microwave energy both at a fundamental frequency fo which is below the cut-off frequency of the waveguide (1) and at a second harmonic frequency 2fo above cut-off.
To control the generation of microwave energy at 2fo, energy at fo may be coupled into the waveguide (1), e.g. from an adjacent further waveguide (9) above its cut-off, by means of an electric probe (8) extending close to the cap (5). The probe (8) may couple in a locking signal at or close to the free-running value of fo from another oscillator having better noise performance and electronic tuning, thereby locking 2fo to twice the frequency of the locking signal, or alternatively may couple to a varactor-tuned cavity resonant at fo.
Description
~)65i315 PHB 32.947 l 23~ 1983 "Microwave oscillator"
This invention relates to a microwave oscillator which is particularly suitable for generating microwave energy at milli-metre wavelengths, for example at frequencies a~ove 60 GHz.
More specifically, the invention relates to a micrcwave oscillator comprising a waveguide having a cut-off frequency, the oscillator further comprising means, including a negative-resistance oscillator device, for generating microwave energy in the waveguide, wherein the generating means are operable to generate microwave energy simultaneously at a fundamental frequency which is belcw the cut-off frequenc~7 of the waveguide and at a harmonic frequency which is an integral multiple of the fundamental frequency and which is above said cut-off frequency, the generating ~eans further comprising first means which in operation couple the oscillator device to the waveguide at said harmonic frequency and on which the values of said fundamental frequency and said harmonic frequency depend.
A typical such oscillator using a Gunn diode is described in the article "Oscillators Lock and Tune at W. Band" by M. Crandell and F.J. Bernues, Microwave Systems News, Decel~ber 1980, pages 54-60.
As indicated in the article, the resonant disc (also called "resonant cap") arrangement used in the described oscillator is the preferred approach for determining the resonant properties of the milli~etre wave circuit. It has ncw been established (see, for example, "Operating Modes of Millimetre Wave Transferred Electron Oscillators" by I.G.
Eddison and D.M. Brookbanks, Electronics Letters, Vol. 17, No. 3 25 (5th February, 1981), pages 112-113, and "Wideband Waveguide System Identifies GaAs Oscillator Harmonics at 94 GHz" by W.H. Haydl, Microwave Systems News, February 1982, pages 99-103) that the negative-resistance oscillator device in such an oscillator generates microwave energy both at a fundamental frequency and at at least a second harmonic thereof: however, since the cut-off frequency of the waveguide in which the oscillator device is disposed is a~ove the funda~ental fre-quency, only the harmonic frequency energy can propagate along the ~ waveguide. The disc or cap is thought to function as a radial line ;S3~
PHB 32.947 2 23~ 19~33 transformer.
For electronically tuning such an oscillator, a varactor diode cannot suitably be used in the manner that is conventional with ordinary oscillators, i.e. spaced along the waveguide frcm the oscillator device. On the one hand, because the basic oscillation phenomenon occurs at the fundamental frequency, coupling the varactor diode to-the oscillator device only at the harmonic frequency wsuld enable it to have very little effect on the oscillating frequencies.
On the other hand, placing the varactor diode very close to the oscillator device so that they might be coupled by the evanescent mcde present at the fundamental frequency would result in the varactor diode presenting a low impedance across the oscillator device and hence cosiderably reducing the output power, It is generally not possible to reach an acceptable compromise between a useful width of electronic tuning range and an insignificant reduction in output power.
As mentioned in the article by Crandell and Bernues, the perferred method for electronically tuning such an oscillator is to vary the bias voltage applied to the Gunn diode. However, this has the disadvantages that because of the high tuning sensitivity (e.g. 2 GHz/volt), the bias voltage must be very well-regulated to to minimise additional FM-noise and accurately controlled to achieve the desired frequency variation, and that the power output varies significantly with the bias voltage; furthermore, this method can be used to vary the frequency only at a fairly low rate.
To improve the FM-noise performance of the oscillator, the article proposes -the use of a phase-lock~d loop; this requires the use of a considerable amount of additional equipment.
An alternative approach is described in the paper "A wide-band, backshort-tunable second harominic W-band Gunn-oscillator" by H. Barth, 1981 IEEE MTT-S, International Microwave Symposium Digest, pages 334-337. Th~s descri~es oscillators in which one or more Gunn diodes are disposed in a central portion of rectangular wave-guide the cut-off frequency of which ls below the fundamental frequency of oscillation. One end of this central portion of waveguide is connected to an output rectangular waveguide the cut-off frequency of which is betw~en the fundamental and second harmonic frequencies of oscillation, so that only harmonic frequency energy is coupled out;
PHB 32.947 3 23-11-1983 the other end of the central wavegulde portion containing the diode(s) is connected to a circular waveguide which has the sa~e cut-off fre-quency (below the fundamental frequency) and which contains two coaxial movable short-circuits, one within the other. The inner short-circuit is operative at the second harmonic frequency but not the fundamental frequency,and is used in:the usual manner to optimise the power output at the second harmonic frequency; the outer short-circuit can be used for rr~echanically varyinq the fundamental (and hence the second harmonic) frequency. With a single Gunn diode an electronic tuning range of 300 MHz (at a second harmonic frequency of about 9O GHz) could be obtained by varying the Gunn diode bias voltage; this range is rather small. A configuration which gave a wider electronic tuning range comprised two Gunn diodes and a varactor diode spaced along the central rectangular-waveguide portion:
A tuning range of 1.5 GHz was achieved for a maximum output power variation of 3 dB. This is a rather large variation, and moreover this configuration is rrechanically quite complex. Furthermore, it may still be desirable to improve the noise performance of the oscillator.
It is an object of the invention to provide an improved microwave oscillator.
According to the invention, a microwave oscillator as set forth in the second paragraph of this specification is characterised in that the oscillator further comprises second rneans, extending into the waveguide and being spaced from the first coupling means, for coupling microwave energy at said fundamental frequency frorn outside said waveguide to the first coupling means and thence to the oscillator device, whereby to control the generation of microwave energy at said harmonic frequency.
Suitably, in an ernbodirrent wherein the first coupling means comprise a resonant cap structure, the second coupling means comprise an electric probe extending adjacent the cap. This provides a particularly simple arrangement for empirically optimising the extent of coupling of microwave energy at the fundamental frequency to the oscillator device !depending on the desired operating characteristics).
In such an ernbodiment wherein the waveguide is rectangular and the cap has a radial surface extending parallel to the broad walls of the waveguide, the probe may extend into the waveguide from and S3l~
P~IB 32.947 4 23~11-1983 normal to, a narrow wall of the waveguide. The probe may be spaced normal to the radial surface.
In such an em~odiment wherein the cap is substantially a disc, wherein the oscillator device is disposed between one surface of the disc and one broad wall of the waveguide, and wherein a post extends from the other surface of the disc to the other broad wall of the waveguide, the post having a substantially smaller cross-section parallel to the broad walls than the disc, the probe suitably is disposed on the side of the disc remote from the oscillator device.
In an em~odiment of the invention wherein the waveguide is terminated at one end by a short-circuit, and wherein the generating means are spaced along the waveguide from the short-circuit, the second coupling means may be longitudinally intermediate the generating means and the short-circuit.
Suitably, the second coupling means are adapted to inhibit the leakage of microwave energy at the harmonic frequency from the waveguide.
The oscillator may further comprise means for propagating a locking signal Erom a microwave source outside said waveguide to said second coupling means and thence via said first coupling means to the negative-resistance oscillator device, the frequency of the locking signal being approximately e~lal -to the value of the fundamental frequency in the absense of the locking signal, whereb~ to maintain the harmonic frequency at said integral multiple of the frequency of the locking signal.
Subharmonic injection locking of microwave oscillators is known from the two papers "Subharmonically Injection Phase-locked Gunn Oscillator Experiments" by H.G. Oltman and C.H. Nonnemaker, IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-17, September 1969, pages 728-729, and "Subharmonically Injection Phase-Locked IMPATT-Oscillator Experiments" by C.H. Chien and G.C. Dalman, Electronics Letters, Vol. 6, No. 8; 16th April 1970, pages 240-241.
HowPver, in at least the second of these two papers, the locking signal was supplied directly to the oscillator diode via a low pass coaxial bias circuit; moreover, there is no suggestion in the paper that the diode generates microwave energy at a frequency below that of the desired output signal. By contrast, an oscillator of the kind to which the present invention relates generates a signal at the same frequency )653~il P~ 32.947 5 23-11-1983 as the injected locking signal: this generated signal will be ccupled out of the oscillator waveguide by the same path and to the same extent ~j' as the locking signal is coup]ed in, tending to result in a loss of power and decrease in efficiency. It is therefore desirab]e to be able readily to vary the extent to which the locking signal is coupled to the oscillator diode, in order to optimise the operating conditions.
This would considerably complicate the design of a coaxial bias supply filter circuit (which, moreover, must substantially inhibit the propa-gation of energy at the desired har~onic output frequency),ecspecially iE the frequency of the locking signal is, for example, akout 35 GHz or more. In at least the first of the a~ove-mentioned two papers, the oscillator (Gunn) diode was mounted in a TEM cavity; the paper does not indicate exactly how the locking signal was coupled into this cavity, but since such a cavity does not have a cut-off frequency, there would be not great difficulty in co~pling a locking signal of any appropriate frequency to the diode. However, in an oscillator em~odying the invention, the waveguide is cut-off at the frequency of the locking signal.
~ecognising that the injection of a locking signal at the fundamental frequency by a path other than the bias supply line would considerably ease the problem of optimising the extent of coupling of the locking signal to the diode, the applicants have found that, contrary to general opinion, a locking signal at the fundamental frequency can be coupled into the cut-off waveguide and thence to the diode by coupling means which couple the locking signal to the means by which tne diode is itself 25 coupled to the waveguide.
Such an em~odiment of the invention provides the considerable advantage for oscillators which are to operate with a second harmonic frequency corresponding to millimetre wavelengths, for example 60-100 GHz, that varactor-tuned oscillators with an operating frequency of 30 half that value and with good noise performance are readily available.
By using such an oscillator as the source of the locking signal, the superior noise and tuning characteristics of this lower-frequency oscillator are substantially acquired, in a simple manner, by the higher frequency oscillator. Such lower-frequency oscillators also generally 35 have more than enough power for the purpose, permitting the use of a simple attenuator (rather than requiring a more complex non-reciprocal device) to provide isolation between the oscillators.
The source of the locking signal may be a varactor-tuned PHB 32.9~7 6 oscillator which provides a tuning characteristic with an unusually good degree of linearity and little pawer variation using an ordin ary abrupt tuning varactor.
As an alternative to the injection-locking arrangement, the oscillator may further comprise a resonant cavity having means for varying the resonant frequency thereof, microwave energy at said fundamental frequency being operably coupled between said resonant cavity and said first ooupling means by said second ooupling means, and said resonant frequency being approximately equal to the value of said fundamental frequency in -the absence of said resonant cav-ity, whereby to maintain said harm~nic frequency at said integral multiple of said resonant frequency. The means for varying the resonant frequency of said resonant cavity suitably ccmprise a var-actor diode~
In the injection-locking arrangement, the propagating means may aomprise, or in the cavi~.y-tuning arrangement, the reson-ant cavity may comprise a second wavegu~de into which said second coupling means extend, said second waveguide having a cut~off fre-quency below said fundamental frequency. In such an embodiment wherein the waveguide is rectangular, wherein the cap has a radial surface extending parallel to the broad walls of the waveguide, and wherein the probe extends into the waveguide from a narrow wall thereof, parallel to the broad walls, said narrcw wall of the first said waveguide from which said electric probe extends may be aam~on to a broad wall of said second waveguide, and said seaond coupling n~ns may comprise a further electric probe extending into said second wave-guide from said broad wall thereof, parallel to the narrow walls thereof.
Embodiments of the invention will now be descr.ibed, by way of example, with reference to the diagrammatic drawings, in which:
Figures 1 and 2 are respectively a transverse cross-sectional view and a longitudinal cross sec~ional view of an oscilla-tor e~kodying the invention~ the cross-section of Figure 1 being taken on the line I-I in Figure 2 and the cross-section of Figure 2 being taken on the line II-II in Figure l;
Figure 3 is a graph of locking or tuning range and of second harmonic frequency output power against injected locking signal power;
Figure 4 shows further curves of locking range against.
~6S38 P~ 32.9~7 7 23-11-1983 injected locking signal power, and Figure 5 is a longitudinal cross-section view, analogous to Figure 2, of another oscillator err~odying the invention.
Referring to Figures 1 and 2, an in~ection-lockable micro-wave oscillator embcdying the invention cornprises a rectangularwaveguide 1 of standard cross-section terrninated at one end by a rnovable non-contacting short-circuit 2. The waveguide is of a cross-section suitable for propagating rnillimetre wavelengths. A Gunn diode 3 designed for oscillation at a fundamental frequency below the cut-off frequency of the waveguide 1 is rnounted in a central longitudinal plane of the waveguide on a heat-sink 4 received in a bore in the lower wall of the waveguide. The diode 3 is coupled to the waveguide 1 and to a D.C. bias supply by rreans of a resonant cap structure cornprising a thin circular disc or cap 5 and a post 6 which extends to an R.F.
choke 7 mounted in a kore in the upper broad wall of the waveguide.
The disc 5 is in contact with the upper terrninal of the diode and - extends parallel to the broad walls of the waveguide. The R.F. choke 7 cornprises successive sections of alternately larger and srnaller diameter, the larger-diameter sections being isolated from the wave-guide housing at D.C. by a thin dielectric layer (now shGwn) there-between, and the lower face of the lowerrr~stlarger-diameter section being flush with the upper broad wall of the waveguide; the choke is dimensioned to have a cut-off frequency below the fundamental frequency of oscillation.
As so far described, the oscillator closely resembles known millimetre-wave oscillators. When a suitable bias voltage is applied to the Gunn diode 3 via the choke 7, the diode generates microwave energy both at a fundamental frequency fO and at a second har~onic frequency 2fo (and possibly also at higher harmonic frequencies), the values of the frequencies being mainly dependent on the resonant cap structure and particularly on the diameter of the disc 5; the position oftheshort-circuit 2 has little effect on the values of the frequencies but is adjustable to optimise the power output at 2fo.
The oscilla-tor further comprises an electric probe 8 extending linearly in the waveguide 1 so as to be adjacent the disc 5.
In this embodirrent, the probe extends from and normal to one of the narrow walls of the waveguide, above the disc 5 (i.e. on the side thereof remote from the Gunn diode 3), and longitudinally intermediate ;38 P~ 32947 8 23~ 1983 the short-circuit 2 and the transverse plane of ~he ~unn diode so as to be close to -the periphery of,and parallel to, the disc. The probe can be used to couple to the diode 3, via the resonant cap structure, a locking signal supplied along a further waveguide 9. The waveguide 9 extends parallel to the waveguide 1 and is of larger rectangular cross-section, with the broad walls of waveguide 9 being parallel to the narrow walls of waveguide 1; the waveguide 9 has a cut-off frequency below the fundamental frequency fO of the Gunn diode 3 mounted in the waveguide 1. The relative positions of the two waveguides are such that the probe 8 projects into the waveguide 9 in a central E-plane thereof, extending to the centre of the waveguide 9. Where the probe passes through the common wall of the t~ waveguides, it forms the central conductor of a coaxial line having longitudinally-successive portions 10 and 11 in which the outer conductor has larger and smaller diameters respectiv~ly. The portion 10 of the coaxial line has an impedance of 50 ohms, while the adjacent the adjacent portion 11 extending to the narrow wall of the waveguide1 has a much lower impedance. This latter portion 11 of the coaxial line is approximately a quarter wavelength long at the second harmonic frequency 2fo so that at that 20 frequency, the 50 ohms impedance of portion 10 is transformed to a very low impedance at the wall of the waveguide 1 and thereby inhibits the leakage of energy at that frequency, 2fol from the waveguide 1. The wave-guide 9 is terminated in a fixed short-circuit 12 at a distance beyond the proke 8 which is about a quarter-wavelength at the fundamental 25 frequency fO.
In operation, a locking signal is supplied along the waveguide 9 in the direction of the arrow 13 (Figure 2) at a frequency which is at or fairly close to the fundamental frequency fO of the oscillator in the absence of the locking signal. (This free-running 30 fundamental frequency is dependent on, inter alia, the extent to which the probe 8 projects into the waveguid 1.) Energy at a frequency which is twice that of the locking signal will then propagate along the waveguide 1 inthe direction of the arrow 14. If the frequency of the locking signal is varied, the harmonic frequency 2fo will remain locked 35 to twice the locking signal frequency over a tuning or locking range ~ (2fo) which increases as the power of the locking signal in waveguide 9 increase and as the extent to which the probe 8 projects into the waveguide 1, and hence the magnitude of the coupling to the resonant S3~
PHB 32.947 9 23~ 1983 cap structure, increases.
An emkodiment of the invention of the form shcwn in Figures 1 and 2 has been constructed with an oscillator waveguide size ~G 26 (WR 12), which has a cut-off frequency of a~out 48 GHz, and a locking signal supply waveguidesizeWG 22 (W~ 28). The Gunn diode was a Pleasey TEO141 device, which is intended for operation at a fundamental frequency of about 35 GHz. Various values of the diameter of the disc 5 and of the extent to which the probe 8 projected into the waveguide 1 were used; the value of the free-running second harmonic frequency depended on both these parameters. The probe 8, which had a diameter of 0.5 mm, was disposed 0.9 mm above the lower broad wall of the waveguide and 1.25 mm from the transverse plane of the Gunn diode; the upper surface of the disc 5, which had a thickness of about 100 /um, was disposed 0.45 mm above the lower broad wall of the waveguide. The diameter of the post 6 was 0.5 mm. Figure 3 shows by way of example the variation with the power Pi of the locking signal in the waveguide 9 of the tuning range ~ (2fo) (plotted on a logarithmic scale: solid line) over which the oscillator remained locked to the injected signal, and of the average power output PO at 2fo (dashed line). There was little variation in the output power PO over each tuning range. The free-running value of the second harmonic frequency was 85.9 GHz; the diameter of the disc 5 was 2.15 mm, and the probe 8 projected 2.2 mm into the waveguide 1. Figure 4 shows, with a somewhat different range of value of the injected locking signal power Pi and with a disc 5 of diameter 2.5 mm, the variation of the tuning range Q (2fo) with four different values of probe projection into the waveguide: - A:0 mm (giving a free-running second harmonic frequency of 79.7 GHz); B:0.6 mm (78.7 GHz); C:1.0 m~ (77.7 GHz); D:1.5mm (74.8 GHz). If desired, the diameter of the disc 5 could be reduced to compensate for the tendency for the frequency to decrease with increasing probe projection into the waveguide.
To further improve the noise performance, the source of the locking signal may be phase-locked: this can be done much more readily at the lower frequency of this source that at the frequency of the oscillator em~odying the invention if the latter has an output in the millimetre range.
Another emkodimPnt of the invention isshown in longitudinal cross-section in Figure 5 (atransverse cross-section would be similar to i538 P~IB 32.9~7 10 23-11-1983 Figure 1). In this case, the further waveguide 9A is terminated in a fixed short~circuit 12A at its end opposite -to the short-circuit 12 to form a resonan-t cavity. A varactor diode 21 is disposed adjacent to that broad wall of the further waveguide 9A a portion of which is common to a narrow wall of the waveguide 1; the diode is cGupled to said kroad wall both a tD.C. and at R.F. The varactor diode is coupled to the resonant cavity at R.F. and is biased with a direct voltage by means of a conductive post 22 which extends through the opposite broad wall of the waveguide 9A and is insulated therefrom at D.C. The resonant cavity also has a dielectric tuning screw 23 for mechanically adjusting the resonant frequency of the cavity.
In a constructed embodiment of the form shown in Figure 5, the second harmonic oscillator frequency of approximately 79 GHz could be varied by about 180 MHz by varying the bias on the varactor diode;
over this tuning range, the second harmonic power output varied by + 0~5 dB. Contrary -to a conventional cavity oscillator where the addition of a varactor diode to provide electronic tuning red-uces the Q-factor of the oscillator, it was found that the addition of the varactor-tuned cavity resonator to the harmonic oscillator did not significantly affect the effective Q-factor of the oscillator at the second har~onic frequency, as determined from load-pulling measurements.
No attempt was made in this constructed embodiment to optimise the longitudinal position of the varactor diode in the resonant cavity. In another constructed emkodiment, the varactor diode and post were omitted, and -the fixed short-circuit 12A ~as replaced by a movable short-circuit. Adjustment of the position of this short-circuit to present at the probe 8 a range of reactances corresponding to the range of capa~.itances of a varactor diode gave a tuning range of some 500 MHz, and it is therefore expected that a similar tuning range should be obtainable if the position of the varactor diode in the previously-mentioned constructed embodiment is optimised.
The non-linearity of the varactor tuning over a central 100 M~Iz portion of the tuning range was measured to be about 6%. The linearity might be improved by using two spaced varactor diodes in the resonant cavity in known manner.
In either of the embodiments descriked with reference to the drawings, the short-circuit 12 and/or 12A may be movable rather than fixed.
This invention relates to a microwave oscillator which is particularly suitable for generating microwave energy at milli-metre wavelengths, for example at frequencies a~ove 60 GHz.
More specifically, the invention relates to a micrcwave oscillator comprising a waveguide having a cut-off frequency, the oscillator further comprising means, including a negative-resistance oscillator device, for generating microwave energy in the waveguide, wherein the generating means are operable to generate microwave energy simultaneously at a fundamental frequency which is belcw the cut-off frequenc~7 of the waveguide and at a harmonic frequency which is an integral multiple of the fundamental frequency and which is above said cut-off frequency, the generating ~eans further comprising first means which in operation couple the oscillator device to the waveguide at said harmonic frequency and on which the values of said fundamental frequency and said harmonic frequency depend.
A typical such oscillator using a Gunn diode is described in the article "Oscillators Lock and Tune at W. Band" by M. Crandell and F.J. Bernues, Microwave Systems News, Decel~ber 1980, pages 54-60.
As indicated in the article, the resonant disc (also called "resonant cap") arrangement used in the described oscillator is the preferred approach for determining the resonant properties of the milli~etre wave circuit. It has ncw been established (see, for example, "Operating Modes of Millimetre Wave Transferred Electron Oscillators" by I.G.
Eddison and D.M. Brookbanks, Electronics Letters, Vol. 17, No. 3 25 (5th February, 1981), pages 112-113, and "Wideband Waveguide System Identifies GaAs Oscillator Harmonics at 94 GHz" by W.H. Haydl, Microwave Systems News, February 1982, pages 99-103) that the negative-resistance oscillator device in such an oscillator generates microwave energy both at a fundamental frequency and at at least a second harmonic thereof: however, since the cut-off frequency of the waveguide in which the oscillator device is disposed is a~ove the funda~ental fre-quency, only the harmonic frequency energy can propagate along the ~ waveguide. The disc or cap is thought to function as a radial line ;S3~
PHB 32.947 2 23~ 19~33 transformer.
For electronically tuning such an oscillator, a varactor diode cannot suitably be used in the manner that is conventional with ordinary oscillators, i.e. spaced along the waveguide frcm the oscillator device. On the one hand, because the basic oscillation phenomenon occurs at the fundamental frequency, coupling the varactor diode to-the oscillator device only at the harmonic frequency wsuld enable it to have very little effect on the oscillating frequencies.
On the other hand, placing the varactor diode very close to the oscillator device so that they might be coupled by the evanescent mcde present at the fundamental frequency would result in the varactor diode presenting a low impedance across the oscillator device and hence cosiderably reducing the output power, It is generally not possible to reach an acceptable compromise between a useful width of electronic tuning range and an insignificant reduction in output power.
As mentioned in the article by Crandell and Bernues, the perferred method for electronically tuning such an oscillator is to vary the bias voltage applied to the Gunn diode. However, this has the disadvantages that because of the high tuning sensitivity (e.g. 2 GHz/volt), the bias voltage must be very well-regulated to to minimise additional FM-noise and accurately controlled to achieve the desired frequency variation, and that the power output varies significantly with the bias voltage; furthermore, this method can be used to vary the frequency only at a fairly low rate.
To improve the FM-noise performance of the oscillator, the article proposes -the use of a phase-lock~d loop; this requires the use of a considerable amount of additional equipment.
An alternative approach is described in the paper "A wide-band, backshort-tunable second harominic W-band Gunn-oscillator" by H. Barth, 1981 IEEE MTT-S, International Microwave Symposium Digest, pages 334-337. Th~s descri~es oscillators in which one or more Gunn diodes are disposed in a central portion of rectangular wave-guide the cut-off frequency of which ls below the fundamental frequency of oscillation. One end of this central portion of waveguide is connected to an output rectangular waveguide the cut-off frequency of which is betw~en the fundamental and second harmonic frequencies of oscillation, so that only harmonic frequency energy is coupled out;
PHB 32.947 3 23-11-1983 the other end of the central wavegulde portion containing the diode(s) is connected to a circular waveguide which has the sa~e cut-off fre-quency (below the fundamental frequency) and which contains two coaxial movable short-circuits, one within the other. The inner short-circuit is operative at the second harmonic frequency but not the fundamental frequency,and is used in:the usual manner to optimise the power output at the second harmonic frequency; the outer short-circuit can be used for rr~echanically varyinq the fundamental (and hence the second harmonic) frequency. With a single Gunn diode an electronic tuning range of 300 MHz (at a second harmonic frequency of about 9O GHz) could be obtained by varying the Gunn diode bias voltage; this range is rather small. A configuration which gave a wider electronic tuning range comprised two Gunn diodes and a varactor diode spaced along the central rectangular-waveguide portion:
A tuning range of 1.5 GHz was achieved for a maximum output power variation of 3 dB. This is a rather large variation, and moreover this configuration is rrechanically quite complex. Furthermore, it may still be desirable to improve the noise performance of the oscillator.
It is an object of the invention to provide an improved microwave oscillator.
According to the invention, a microwave oscillator as set forth in the second paragraph of this specification is characterised in that the oscillator further comprises second rneans, extending into the waveguide and being spaced from the first coupling means, for coupling microwave energy at said fundamental frequency frorn outside said waveguide to the first coupling means and thence to the oscillator device, whereby to control the generation of microwave energy at said harmonic frequency.
Suitably, in an ernbodirrent wherein the first coupling means comprise a resonant cap structure, the second coupling means comprise an electric probe extending adjacent the cap. This provides a particularly simple arrangement for empirically optimising the extent of coupling of microwave energy at the fundamental frequency to the oscillator device !depending on the desired operating characteristics).
In such an ernbodiment wherein the waveguide is rectangular and the cap has a radial surface extending parallel to the broad walls of the waveguide, the probe may extend into the waveguide from and S3l~
P~IB 32.947 4 23~11-1983 normal to, a narrow wall of the waveguide. The probe may be spaced normal to the radial surface.
In such an em~odiment wherein the cap is substantially a disc, wherein the oscillator device is disposed between one surface of the disc and one broad wall of the waveguide, and wherein a post extends from the other surface of the disc to the other broad wall of the waveguide, the post having a substantially smaller cross-section parallel to the broad walls than the disc, the probe suitably is disposed on the side of the disc remote from the oscillator device.
In an em~odiment of the invention wherein the waveguide is terminated at one end by a short-circuit, and wherein the generating means are spaced along the waveguide from the short-circuit, the second coupling means may be longitudinally intermediate the generating means and the short-circuit.
Suitably, the second coupling means are adapted to inhibit the leakage of microwave energy at the harmonic frequency from the waveguide.
The oscillator may further comprise means for propagating a locking signal Erom a microwave source outside said waveguide to said second coupling means and thence via said first coupling means to the negative-resistance oscillator device, the frequency of the locking signal being approximately e~lal -to the value of the fundamental frequency in the absense of the locking signal, whereb~ to maintain the harmonic frequency at said integral multiple of the frequency of the locking signal.
Subharmonic injection locking of microwave oscillators is known from the two papers "Subharmonically Injection Phase-locked Gunn Oscillator Experiments" by H.G. Oltman and C.H. Nonnemaker, IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-17, September 1969, pages 728-729, and "Subharmonically Injection Phase-Locked IMPATT-Oscillator Experiments" by C.H. Chien and G.C. Dalman, Electronics Letters, Vol. 6, No. 8; 16th April 1970, pages 240-241.
HowPver, in at least the second of these two papers, the locking signal was supplied directly to the oscillator diode via a low pass coaxial bias circuit; moreover, there is no suggestion in the paper that the diode generates microwave energy at a frequency below that of the desired output signal. By contrast, an oscillator of the kind to which the present invention relates generates a signal at the same frequency )653~il P~ 32.947 5 23-11-1983 as the injected locking signal: this generated signal will be ccupled out of the oscillator waveguide by the same path and to the same extent ~j' as the locking signal is coup]ed in, tending to result in a loss of power and decrease in efficiency. It is therefore desirab]e to be able readily to vary the extent to which the locking signal is coupled to the oscillator diode, in order to optimise the operating conditions.
This would considerably complicate the design of a coaxial bias supply filter circuit (which, moreover, must substantially inhibit the propa-gation of energy at the desired har~onic output frequency),ecspecially iE the frequency of the locking signal is, for example, akout 35 GHz or more. In at least the first of the a~ove-mentioned two papers, the oscillator (Gunn) diode was mounted in a TEM cavity; the paper does not indicate exactly how the locking signal was coupled into this cavity, but since such a cavity does not have a cut-off frequency, there would be not great difficulty in co~pling a locking signal of any appropriate frequency to the diode. However, in an oscillator em~odying the invention, the waveguide is cut-off at the frequency of the locking signal.
~ecognising that the injection of a locking signal at the fundamental frequency by a path other than the bias supply line would considerably ease the problem of optimising the extent of coupling of the locking signal to the diode, the applicants have found that, contrary to general opinion, a locking signal at the fundamental frequency can be coupled into the cut-off waveguide and thence to the diode by coupling means which couple the locking signal to the means by which tne diode is itself 25 coupled to the waveguide.
Such an em~odiment of the invention provides the considerable advantage for oscillators which are to operate with a second harmonic frequency corresponding to millimetre wavelengths, for example 60-100 GHz, that varactor-tuned oscillators with an operating frequency of 30 half that value and with good noise performance are readily available.
By using such an oscillator as the source of the locking signal, the superior noise and tuning characteristics of this lower-frequency oscillator are substantially acquired, in a simple manner, by the higher frequency oscillator. Such lower-frequency oscillators also generally 35 have more than enough power for the purpose, permitting the use of a simple attenuator (rather than requiring a more complex non-reciprocal device) to provide isolation between the oscillators.
The source of the locking signal may be a varactor-tuned PHB 32.9~7 6 oscillator which provides a tuning characteristic with an unusually good degree of linearity and little pawer variation using an ordin ary abrupt tuning varactor.
As an alternative to the injection-locking arrangement, the oscillator may further comprise a resonant cavity having means for varying the resonant frequency thereof, microwave energy at said fundamental frequency being operably coupled between said resonant cavity and said first ooupling means by said second ooupling means, and said resonant frequency being approximately equal to the value of said fundamental frequency in -the absence of said resonant cav-ity, whereby to maintain said harm~nic frequency at said integral multiple of said resonant frequency. The means for varying the resonant frequency of said resonant cavity suitably ccmprise a var-actor diode~
In the injection-locking arrangement, the propagating means may aomprise, or in the cavi~.y-tuning arrangement, the reson-ant cavity may comprise a second wavegu~de into which said second coupling means extend, said second waveguide having a cut~off fre-quency below said fundamental frequency. In such an embodiment wherein the waveguide is rectangular, wherein the cap has a radial surface extending parallel to the broad walls of the waveguide, and wherein the probe extends into the waveguide from a narrow wall thereof, parallel to the broad walls, said narrcw wall of the first said waveguide from which said electric probe extends may be aam~on to a broad wall of said second waveguide, and said seaond coupling n~ns may comprise a further electric probe extending into said second wave-guide from said broad wall thereof, parallel to the narrow walls thereof.
Embodiments of the invention will now be descr.ibed, by way of example, with reference to the diagrammatic drawings, in which:
Figures 1 and 2 are respectively a transverse cross-sectional view and a longitudinal cross sec~ional view of an oscilla-tor e~kodying the invention~ the cross-section of Figure 1 being taken on the line I-I in Figure 2 and the cross-section of Figure 2 being taken on the line II-II in Figure l;
Figure 3 is a graph of locking or tuning range and of second harmonic frequency output power against injected locking signal power;
Figure 4 shows further curves of locking range against.
~6S38 P~ 32.9~7 7 23-11-1983 injected locking signal power, and Figure 5 is a longitudinal cross-section view, analogous to Figure 2, of another oscillator err~odying the invention.
Referring to Figures 1 and 2, an in~ection-lockable micro-wave oscillator embcdying the invention cornprises a rectangularwaveguide 1 of standard cross-section terrninated at one end by a rnovable non-contacting short-circuit 2. The waveguide is of a cross-section suitable for propagating rnillimetre wavelengths. A Gunn diode 3 designed for oscillation at a fundamental frequency below the cut-off frequency of the waveguide 1 is rnounted in a central longitudinal plane of the waveguide on a heat-sink 4 received in a bore in the lower wall of the waveguide. The diode 3 is coupled to the waveguide 1 and to a D.C. bias supply by rreans of a resonant cap structure cornprising a thin circular disc or cap 5 and a post 6 which extends to an R.F.
choke 7 mounted in a kore in the upper broad wall of the waveguide.
The disc 5 is in contact with the upper terrninal of the diode and - extends parallel to the broad walls of the waveguide. The R.F. choke 7 cornprises successive sections of alternately larger and srnaller diameter, the larger-diameter sections being isolated from the wave-guide housing at D.C. by a thin dielectric layer (now shGwn) there-between, and the lower face of the lowerrr~stlarger-diameter section being flush with the upper broad wall of the waveguide; the choke is dimensioned to have a cut-off frequency below the fundamental frequency of oscillation.
As so far described, the oscillator closely resembles known millimetre-wave oscillators. When a suitable bias voltage is applied to the Gunn diode 3 via the choke 7, the diode generates microwave energy both at a fundamental frequency fO and at a second har~onic frequency 2fo (and possibly also at higher harmonic frequencies), the values of the frequencies being mainly dependent on the resonant cap structure and particularly on the diameter of the disc 5; the position oftheshort-circuit 2 has little effect on the values of the frequencies but is adjustable to optimise the power output at 2fo.
The oscilla-tor further comprises an electric probe 8 extending linearly in the waveguide 1 so as to be adjacent the disc 5.
In this embodirrent, the probe extends from and normal to one of the narrow walls of the waveguide, above the disc 5 (i.e. on the side thereof remote from the Gunn diode 3), and longitudinally intermediate ;38 P~ 32947 8 23~ 1983 the short-circuit 2 and the transverse plane of ~he ~unn diode so as to be close to -the periphery of,and parallel to, the disc. The probe can be used to couple to the diode 3, via the resonant cap structure, a locking signal supplied along a further waveguide 9. The waveguide 9 extends parallel to the waveguide 1 and is of larger rectangular cross-section, with the broad walls of waveguide 9 being parallel to the narrow walls of waveguide 1; the waveguide 9 has a cut-off frequency below the fundamental frequency fO of the Gunn diode 3 mounted in the waveguide 1. The relative positions of the two waveguides are such that the probe 8 projects into the waveguide 9 in a central E-plane thereof, extending to the centre of the waveguide 9. Where the probe passes through the common wall of the t~ waveguides, it forms the central conductor of a coaxial line having longitudinally-successive portions 10 and 11 in which the outer conductor has larger and smaller diameters respectiv~ly. The portion 10 of the coaxial line has an impedance of 50 ohms, while the adjacent the adjacent portion 11 extending to the narrow wall of the waveguide1 has a much lower impedance. This latter portion 11 of the coaxial line is approximately a quarter wavelength long at the second harmonic frequency 2fo so that at that 20 frequency, the 50 ohms impedance of portion 10 is transformed to a very low impedance at the wall of the waveguide 1 and thereby inhibits the leakage of energy at that frequency, 2fol from the waveguide 1. The wave-guide 9 is terminated in a fixed short-circuit 12 at a distance beyond the proke 8 which is about a quarter-wavelength at the fundamental 25 frequency fO.
In operation, a locking signal is supplied along the waveguide 9 in the direction of the arrow 13 (Figure 2) at a frequency which is at or fairly close to the fundamental frequency fO of the oscillator in the absence of the locking signal. (This free-running 30 fundamental frequency is dependent on, inter alia, the extent to which the probe 8 projects into the waveguid 1.) Energy at a frequency which is twice that of the locking signal will then propagate along the waveguide 1 inthe direction of the arrow 14. If the frequency of the locking signal is varied, the harmonic frequency 2fo will remain locked 35 to twice the locking signal frequency over a tuning or locking range ~ (2fo) which increases as the power of the locking signal in waveguide 9 increase and as the extent to which the probe 8 projects into the waveguide 1, and hence the magnitude of the coupling to the resonant S3~
PHB 32.947 9 23~ 1983 cap structure, increases.
An emkodiment of the invention of the form shcwn in Figures 1 and 2 has been constructed with an oscillator waveguide size ~G 26 (WR 12), which has a cut-off frequency of a~out 48 GHz, and a locking signal supply waveguidesizeWG 22 (W~ 28). The Gunn diode was a Pleasey TEO141 device, which is intended for operation at a fundamental frequency of about 35 GHz. Various values of the diameter of the disc 5 and of the extent to which the probe 8 projected into the waveguide 1 were used; the value of the free-running second harmonic frequency depended on both these parameters. The probe 8, which had a diameter of 0.5 mm, was disposed 0.9 mm above the lower broad wall of the waveguide and 1.25 mm from the transverse plane of the Gunn diode; the upper surface of the disc 5, which had a thickness of about 100 /um, was disposed 0.45 mm above the lower broad wall of the waveguide. The diameter of the post 6 was 0.5 mm. Figure 3 shows by way of example the variation with the power Pi of the locking signal in the waveguide 9 of the tuning range ~ (2fo) (plotted on a logarithmic scale: solid line) over which the oscillator remained locked to the injected signal, and of the average power output PO at 2fo (dashed line). There was little variation in the output power PO over each tuning range. The free-running value of the second harmonic frequency was 85.9 GHz; the diameter of the disc 5 was 2.15 mm, and the probe 8 projected 2.2 mm into the waveguide 1. Figure 4 shows, with a somewhat different range of value of the injected locking signal power Pi and with a disc 5 of diameter 2.5 mm, the variation of the tuning range Q (2fo) with four different values of probe projection into the waveguide: - A:0 mm (giving a free-running second harmonic frequency of 79.7 GHz); B:0.6 mm (78.7 GHz); C:1.0 m~ (77.7 GHz); D:1.5mm (74.8 GHz). If desired, the diameter of the disc 5 could be reduced to compensate for the tendency for the frequency to decrease with increasing probe projection into the waveguide.
To further improve the noise performance, the source of the locking signal may be phase-locked: this can be done much more readily at the lower frequency of this source that at the frequency of the oscillator em~odying the invention if the latter has an output in the millimetre range.
Another emkodimPnt of the invention isshown in longitudinal cross-section in Figure 5 (atransverse cross-section would be similar to i538 P~IB 32.9~7 10 23-11-1983 Figure 1). In this case, the further waveguide 9A is terminated in a fixed short~circuit 12A at its end opposite -to the short-circuit 12 to form a resonan-t cavity. A varactor diode 21 is disposed adjacent to that broad wall of the further waveguide 9A a portion of which is common to a narrow wall of the waveguide 1; the diode is cGupled to said kroad wall both a tD.C. and at R.F. The varactor diode is coupled to the resonant cavity at R.F. and is biased with a direct voltage by means of a conductive post 22 which extends through the opposite broad wall of the waveguide 9A and is insulated therefrom at D.C. The resonant cavity also has a dielectric tuning screw 23 for mechanically adjusting the resonant frequency of the cavity.
In a constructed embodiment of the form shown in Figure 5, the second harmonic oscillator frequency of approximately 79 GHz could be varied by about 180 MHz by varying the bias on the varactor diode;
over this tuning range, the second harmonic power output varied by + 0~5 dB. Contrary -to a conventional cavity oscillator where the addition of a varactor diode to provide electronic tuning red-uces the Q-factor of the oscillator, it was found that the addition of the varactor-tuned cavity resonator to the harmonic oscillator did not significantly affect the effective Q-factor of the oscillator at the second har~onic frequency, as determined from load-pulling measurements.
No attempt was made in this constructed embodiment to optimise the longitudinal position of the varactor diode in the resonant cavity. In another constructed emkodiment, the varactor diode and post were omitted, and -the fixed short-circuit 12A ~as replaced by a movable short-circuit. Adjustment of the position of this short-circuit to present at the probe 8 a range of reactances corresponding to the range of capa~.itances of a varactor diode gave a tuning range of some 500 MHz, and it is therefore expected that a similar tuning range should be obtainable if the position of the varactor diode in the previously-mentioned constructed embodiment is optimised.
The non-linearity of the varactor tuning over a central 100 M~Iz portion of the tuning range was measured to be about 6%. The linearity might be improved by using two spaced varactor diodes in the resonant cavity in known manner.
In either of the embodiments descriked with reference to the drawings, the short-circuit 12 and/or 12A may be movable rather than fixed.
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS
1. A microwave oscillator comprising a waveguide having a cut-off frequency, the oscillator further comprising means, including a negative-resistance oscillator device, for generating microwave energy in the waveguide, wherein the generating means are operable to generate microwave energy simultaneously at a fundamental frequency which is below the cut-off frequency of the waveguide and at a harmonic frequency which is an integral multiple of the fundamental frequency and which is above said cut-off frequency, the generating means further comprising first means which in operation couple the oscillator device to the waveguide at said harmonic frequency and on which the values of said fundamental frequency and said harmonic frequency depend, charac-terized in that the oscillator further comprises second means, extending into the waveguide and being spaced from the first coupling means, for coupling microwave energy at said fundamental frequency from outside the waveguide to the first coupling means and thence to the oscillator device, whereby to control the generation of microwave energy at said harmonic frequency.
2. An oscillator as claimed in Claim 1 wherein the first coupling means comprise a resonant cap structure and wherein the second coupling means comprise an electric probe extending adjacent the cap.
3. An oscillator as claimed in Claim 2 wherein the waveguide is rectangular, wherein the cap has a radial surface extending parallel to the broad walls of the waveguide, and wherein the probe extends into the waveguide from a narrow wall thereof, parallel to the broad walls.
4. An oscillator as claimed in Claim 3, wherein the probe is spaced normal to the radial surface.
5. An oscillator as claimed in Claim 4 wherein the cap is substantailly a disc, wherein the oscillator device is disposed between one surface of the disc and one broad wall of the waveguide, wherein a post extends from the other surface of the disc to the other broad wall of the waveguide, the post having a substantially smaller cross-section parallel to the broad walls than the disc, and wherein the probe is disposed on the side of the disc remote from the oscillator device.
6. An oscillator as claimed in Claim 1, 3 or 5 wherein the waveguide is terminated at one end by a short-circuit, wherein the generating means are spaced along the waveguide from the short-circuit, and wherein the second coupling means are longitudinally intermediate the generating means and the short-circuit.
7. An oscillator as claimed in Claim 1, 3 or 5 wherein the second coupling means are adapted to inhibit the leakage of microwave energy at the harmonic frequency from the waveguide.
8. An oscillator as claimed in Claim 1 further comprising means for propagating a locking signal from a microwave source outside said waveguide to said second coupling means and thence via said first coupling means to the negative-resistance oscillator device, the fre-quency of the locking signal being approximately equal to the value of the fundamental frequency in the absence of the locking signal, whereby to maintain the harmonic frequency at said integral multiple of the frequency of the locking signal.
9. An oscillator as claimed in Claim 8 in combination with said microwave source for generating the locking signal.
10. A combination as claimed in Claim 9 wherein said micro-wave source is a varactor-tuned oscillator.
11. An oscillator as claimed in Claim 2, 3 or 5 further cam-prising means for propagating a locking signal from a microwave source outside said waveguide to said second coupling means and thence via said first coupling means to the negative-resistance oscillator device, the frequency of the locking signal being approximately equal to the value of the fundamental frequency in the absence of the locking signal, whereby to maintain the harmonic frequency at said integral multiple of the frequency of the locking signal.
12. An oscillator as claimed in Claim 1 further comprising a resonant cavity having means for varying the resonant frequency thereof, microwave energy at said fundamental frequency being operably coupled between said resonant cavity and said first coupling means by said second coupling means, and said resonant frequency being approximately equal to the value of said fundamental frequency in the absence of said resonant cavity, whereby to maintain said harmonic frequency at said integral multiple of said resonant frequency.
13. An oscillator as claimed in Claim 12 wherein the means for varying the resonant frequency of said resonant cavity comprise a var-actor diode.
14. An oscillator as claimed in Claim 2, 5 or 8 further com-prising a resonant cavity having means for varying the resonant fre-quency thereof, microwave energy at said fundamental frequency being operably coupled between said resonant cavity and said first coupling means by said second coupling means, and said resonant frequency being approximately equal to the value of said fundamental frequency in the absence of said resonant cavity, whereby to maintain said harmonic fre-quency at said integral multiple of said resonant frequency.
15. An oscillator as claimed in Claim 8, 9 or 10 wherein the propagating means comprise a second waveguide into which said second coupling means extend, said second waveguide having a cut-off frequency below said fundamental frequency.
16. An oscillator as claimed in Claim 12 or 13 wherein the resonant cavity comprises a second waveguide into which said second coupling means extend, said second waveguide having a cut-off frequency below said fundamental frequency.
17. An oscillator as claimed in Claim 3 further comprising means for propagating a locking signal from a microwave source outside said waveguide to said second coupling means and thence via said first coupling means to the negative-resistance oscillator device, the fre-quency of the locking signal being approximately equal to the value of the fundamental frequency in the absence of the locking signal, whereby to maintain the harmonic frequency at said integral multiple of the frequency of the locking signal, wherein the propagating means comprise a second waveguide into which said second coupling means extend, said second waveguide having a cut-off frequency below said fundamental fre-quency and wherein said second waveguide is rectangular, wherein said narrow wall of the first said waveguide from which said electric probe extends is common to a broad wall of said second waveguide, and wherein said second coupling means comprise a further electric probe extending into said second waveguide from said broad wall thereof, parallel to the narrow walls thereof.
18. An oscillator as claimed in Claim 3 further comprising means for propagating a locking signal from a microwave source outside said waveguide to said second coupling means and thence via said first coupling means to the negative-resistance oscillator device, the fre-quency of the locking signal being approximately equal to the value of the fundamental frequency in the absence of the locking signal, whereby to maintain the harmonic frequency at said integral multiple of the frequency of the locking signal, wherein the resonant cavity comprises a second waveguide into which said second coupling means extend, said second waveguide having a cut-off frequency below said fundamental fre-quency and wherein said second waveguide is rectangular, wherein said narrow wall of the first said waveguide from which said electric probe extends is common to a broad wall of said second waveguide, and wherein said second coupling means comprise a further electric probe extending into said second waveguide from said broad wall thereof, parallel to the narrow walls thereof.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08236654A GB2133649A (en) | 1982-12-23 | 1982-12-23 | Microwave oscillator |
| GB8236654 | 1982-12-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1206538A true CA1206538A (en) | 1986-06-24 |
Family
ID=10535208
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000444066A Expired CA1206538A (en) | 1982-12-23 | 1983-12-22 | Microwave oscillator |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4568890A (en) |
| EP (1) | EP0114437B1 (en) |
| JP (1) | JPS59133713A (en) |
| CA (1) | CA1206538A (en) |
| DE (1) | DE3370733D1 (en) |
| GB (1) | GB2133649A (en) |
Families Citing this family (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2172763A (en) * | 1985-03-22 | 1986-09-24 | Philips Electronic Associated | Microwave oscillator |
| GB2227386A (en) * | 1989-01-20 | 1990-07-25 | Philips Electronic Associated | Compact tunable waveguide oscillators |
| US6232789B1 (en) * | 1997-05-28 | 2001-05-15 | Cascade Microtech, Inc. | Probe holder for low current measurements |
| US6545553B1 (en) * | 1998-10-08 | 2003-04-08 | Mitel Semiconductor Limited | Oscillator for generating microwave radiation, and method of assembling an oscillator |
| GB2351401B (en) * | 1999-04-20 | 2001-03-14 | Dynex Semiconductor Ltd | An oscillator |
| JP3528702B2 (en) * | 1999-09-29 | 2004-05-24 | 株式会社村田製作所 | Oscillator and wireless device |
| JP3460644B2 (en) * | 1999-10-07 | 2003-10-27 | 株式会社村田製作所 | Oscillator and wireless device |
| DE20114544U1 (en) * | 2000-12-04 | 2002-02-21 | Cascade Microtech Inc | wafer probe |
| US6549106B2 (en) * | 2001-09-06 | 2003-04-15 | Cascade Microtech, Inc. | Waveguide with adjustable backshort |
| WO2003100445A2 (en) * | 2002-05-23 | 2003-12-04 | Cascade Microtech, Inc. | Probe for testing a device under test |
| US7057404B2 (en) * | 2003-05-23 | 2006-06-06 | Sharp Laboratories Of America, Inc. | Shielded probe for testing a device under test |
| KR100960496B1 (en) * | 2003-10-31 | 2010-06-01 | 엘지디스플레이 주식회사 | Rubbing method of liquid crystal display device |
| DE202004021093U1 (en) * | 2003-12-24 | 2006-09-28 | Cascade Microtech, Inc., Beaverton | Differential probe for e.g. integrated circuit, has elongate probing units interconnected to respective active circuits that are interconnected to substrate by respective pair of flexible interconnects |
| KR20070058522A (en) * | 2004-09-13 | 2007-06-08 | 캐스케이드 마이크로테크 인코포레이티드 | Double sided probing structures |
| US7449899B2 (en) * | 2005-06-08 | 2008-11-11 | Cascade Microtech, Inc. | Probe for high frequency signals |
| US7443186B2 (en) * | 2006-06-12 | 2008-10-28 | Cascade Microtech, Inc. | On-wafer test structures for differential signals |
| US7764072B2 (en) * | 2006-06-12 | 2010-07-27 | Cascade Microtech, Inc. | Differential signal probing system |
| US7723999B2 (en) * | 2006-06-12 | 2010-05-25 | Cascade Microtech, Inc. | Calibration structures for differential signal probing |
| US7403028B2 (en) * | 2006-06-12 | 2008-07-22 | Cascade Microtech, Inc. | Test structure and probe for differential signals |
| US7876114B2 (en) * | 2007-08-08 | 2011-01-25 | Cascade Microtech, Inc. | Differential waveguide probe |
| WO2010059247A2 (en) | 2008-11-21 | 2010-05-27 | Cascade Microtech, Inc. | Replaceable coupon for a probing apparatus |
| DE102015116811B4 (en) * | 2015-10-02 | 2017-04-13 | Dynamic E Flow Gmbh | joint |
| DE102017130728A1 (en) * | 2017-12-20 | 2019-06-27 | Endress+Hauser SE+Co. KG | Measuring device for determining the dielectric value |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS509663B1 (en) * | 1970-12-14 | 1975-04-15 | ||
| US3824485A (en) * | 1973-04-30 | 1974-07-16 | Sperry Rand Corp | Stabilized oscillator with output having high spectral purity |
| JPS5275958A (en) * | 1975-12-20 | 1977-06-25 | Matsushita Electric Ind Co Ltd | Microwave oscillation unit |
| DE2710164A1 (en) * | 1977-03-09 | 1978-09-14 | Licentia Gmbh | Broadband microwave oscillator with IMPATT diode - has rectangular waveguide with decoupling point in middle remote from ends |
| US4264875A (en) * | 1978-01-26 | 1981-04-28 | Hughes Aircraft Company | System for optical injection phase locking and switching of microwave oscillators |
| DE2805254C2 (en) * | 1978-02-08 | 1985-12-05 | ANT Nachrichtentechnik GmbH, 7150 Backnang | Arrangement for stabilizing a microwave oscillator |
| DE2812410C2 (en) * | 1978-03-22 | 1985-10-03 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Microwave oscillator |
| US4222014A (en) * | 1978-12-26 | 1980-09-09 | Alpha Industries, Inc. | Microwave/millimeterwave oscillator using transferred electron device |
| GB2046046B (en) * | 1979-03-19 | 1983-04-20 | Philips Electronic Associated | Microwave oscillator |
-
1982
- 1982-12-23 GB GB08236654A patent/GB2133649A/en not_active Withdrawn
-
1983
- 1983-12-06 US US06/558,657 patent/US4568890A/en not_active Expired - Fee Related
- 1983-12-15 EP EP83201795A patent/EP0114437B1/en not_active Expired
- 1983-12-15 DE DE8383201795T patent/DE3370733D1/en not_active Expired
- 1983-12-22 CA CA000444066A patent/CA1206538A/en not_active Expired
- 1983-12-23 JP JP58242318A patent/JPS59133713A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| EP0114437B1 (en) | 1987-04-01 |
| EP0114437A1 (en) | 1984-08-01 |
| DE3370733D1 (en) | 1987-05-07 |
| GB2133649A (en) | 1984-07-25 |
| JPH0439802B2 (en) | 1992-06-30 |
| US4568890A (en) | 1986-02-04 |
| JPS59133713A (en) | 1984-08-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1206538A (en) | Microwave oscillator | |
| US4580108A (en) | Tunable waveguide oscillator | |
| US5059927A (en) | Microwave oscillator with reduced phase noise | |
| US4521746A (en) | Microwave oscillator with TM01δ dielectric resonator | |
| US4514707A (en) | Dielectric resonator controlled planar IMPATT diode oscillator | |
| US4541120A (en) | Transmitter-receiver module | |
| US4565979A (en) | Double dielectric resonator stabilized oscillator | |
| Makino et al. | A highly stabilized MIC Gunn oscillator using a dielectric resonator | |
| US5294895A (en) | Microwave oscillators and transmitters with frequency stabilization | |
| KR960003621B1 (en) | Coaxially coupled tunable oscillator | |
| US3919666A (en) | Solid state microwave cavity oscillator operating below cavity cutoff frequency | |
| US6344779B1 (en) | Oscillator and radio equipment | |
| US4099144A (en) | Injection-locked ultra-high frequency solid-state oscillator | |
| US4560952A (en) | Cavity-stabilized microwave oscillator | |
| US4309672A (en) | Negative resistance oscillator/amplifier accumulator circuit | |
| US4583058A (en) | Broadband power combiner | |
| Knöchel | Design and performance of microwave oscillators in integrated fin-line technique | |
| KR100587901B1 (en) | NRD Guide Gunn Oscillator and Frequency Locking Method using Ceramic Resonator | |
| US4155051A (en) | Harmonically tuned high power voltage controlled oscillator | |
| Gross et al. | Design of series feedback millimeter wave oscillators employing whispering gallery mode dielectric resonators | |
| Che et al. | Phase-adjustment technique of the digital-latching ferrite phase shifter | |
| Vendelin | A Ku-band integrated receiver front end | |
| Ondria | Quartz microstrip radial disk fundamental and second harmonic mmW Gunn oscillators | |
| Bhatti | Local oscillator for millimeter-wave receivers | |
| GB2227141A (en) | Integratable transceiver |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |