US2836814A - R-f phase shifter - Google Patents

Description

May 27, 1958 J. J. NAIL 2,335,814

R-F PHASE SHIFTER Filed June 25, 1952 ZSheets-Shee 1 IXMITTERI PHASE SHIFTER INVENTOR JAMES J.- NAIL ATTORNEY y 27, 1958 J. J. NAIL 2,836,814

R-F PHASE SHIFTER Filed June 25, 1952 2 Sheets-Shee 2 PHASE SHIFT ATTENUAT/n/V INVENTOR JAM5 J. NAIL ATTORNEY sector antenna system embodiment of this invention;

ram T This invention relates .to k-F phase shifters and more .particularly to high .sp'eedIRL-F. phase shifters of the capacitive type for use atultra-high frequencies.

It is often desirable to have azimuthal omnidirectional antenna pattern coverage, and yet in many situations this type of coverage cannotbe obtainedby the, installation of a single antenna dueto the physical characteristics of the antenna site. In such situations it .is possible to obtain omnidirectional coverage by arranging a number of udirectional antennas eachcoveringa sector of the azimuth.

Normal operation ofsuch an antenna system allows the coverage of aparticular port-ion of the azimuth at any instant of time,and if onlyone sectoris of interest, a higher antenna gain is obtainable through the use of the single directional antenna for that sector. However, if continuous omnidirectional coverage .is to be obtained from such a directional antenna system, it is possible to connect the individual antennas ingparallel, but then interference between the antenna patterns will cause regions to exist-"having deep minima radiationcharacteristics. If the phase of the signals fed to interfering antennas is shifted so that the input to one pair of anpair, it causes the minima and maxima regions of the antenna pattern to be interchanged, resulting in a sub- One of the objects of this invention therefore is to provide a high speed R.-F. phaseshifter for use with a toprovide substantial omnidirectional coverage.

Another object of this invention is to provide a high 2,836,814 Patented May 27, 1958 V antenna system azimuthal radiation pattern, shown therein by the solid lines, comprises the radiation patternsdue to four directional antenna arrays 1, 2, 3, and 4, each covering approximately a2 90 azimuth sector. It is seen from the pattern of Fig. 1 that the radiations due to adjacent directional antennas interfere with each other, distorting the normal directional pattern of each antenna and causing regions, such as 5, to exist wherein a plurality of radiation pattern lobes 6 will be present, between which areas of minimum signal intensity, such as 7, are present.

A receiver located in an area of minimum signal intensity 7 will not pick up any signals from the antenna sys tem. However, if opposite antennas 1 and 3 and 2 and 4 are tied together and the energy from transmitter .8 is fed directly to one pair of antennas and a, 180? phase shift is introduced by a phase shift-device .9 before the energy from transmitter 8 is coupled to the other pair of antennas, then the radiation pattern lobes 6 will shift, causing the position of the maxima and minimaradiation intensity to be interchanged, as shown by the dotted line 1 receiver now located at 10 will not receive any signals;

although the receiver at point 7 was able to receive the signals prior. to the introduction of the phase shift. If

Y a continuous phase shift is introduced into the radiated teams is 180 .out of phase with the input to the other 7 speed R-.-F. phase shifter whereby the phaseshift may be made a desired function of time.

'A further object of this invention is to provide ahigh speed'capacitive type R.-F. phase-shifter which may be utilized with a sector antenna system to provide omnidi rectional coverage without causing interference with the received signal. r I v The above-mentioned and other features and objects of V this invention will become more apparentby reference to the following description taken-in conjunction with the accompanying drawings, in which:

Fig. 1 is an illustration of the radiation pattern obtained from an omnidirectional antenna, system, utilizing four directional antennas;

Fig. 2 is a'schematicjdiagram in cross section off'one Fig. 2A is a schematicdrawing of the equivalent electrical circuit of the embodiment of this invention shown '1 inFig.2; w

. 7 Figs. 5 and 6 are "graphic illustrationshelpful in the explanation of this-invention; r

presented.

signals, the areas of maximum and minimum signal intensity will continuously vary, providing substantial omnidirectional coverage from the directional sectorarray. However, the frequency of the phase shift must be so selected that interference with the received signals is not In communication systems utilizing audio frequencies, the phase shift must be selected at a frequency outside the audible frequency pass band to 'prevent interference.

Referring to Fig. 2, a high band R.-F. phase shifter shown therein "in accordance with the. principles of this invention comprises a coaxial transmission line 11 having a slot 12 cut in the circumference of its outer conductor 13. A section of the inner conductor 14 is cut away to form gap 15 in line withslot 12. A form of endless carrier, such as disc 16, consisting of a non-conducting low loss material, such as fiberglass, is caused to revolve with the peripheral edge passing through'slot 12 so that I a metallic rim 17 or other conductive parts attached to ;inductance22. Thus it is apparent that the high pass filter of Fig. 2A is the equivalent schematic diagram of the structure ofFig. 2.

Referring to Fig. 3, the rotating disc 16 of Fig. 2 is shown comprising a non-conducting low less material having an attached metallic rim 17. As the metallic 0 rim 17 moves in gap 15, it causes a capacitive coupling tooccur between the separated portions of inner conducsion of metallic teeth 23 pass through gap 15, the width A of metal bridging gap will vary as a sinusoidal function of time, causing a change in capacitance proportional to the change in width of the metallic rim 17 passing through gap 15. Since the input energy to the coaxial transmission line 11 is of constant frequency, a variation in the capacitance of the circuit will cause a proportional shift in the phase of the energy flowing through the transmission line. Since the capacitance changes as a sinusoidal function of time, the phase shift of the energy flowing through coaxial line 11 will vary as a sinusoidal function of time. The size of the disc 16, the speed of rotation, and the distance between minimum and maximum rim thickness are dependent upon the frequency of phase shift that is desired. Thus for a disc 16 having a 12-inch diameter rotated at 5000 R. P. M. with a distance between points of minimum and maximum rim thickness of one-quarter inch produces a phase shift of 6300 C. P. S.

Referring to Fig. 5 a graphic illustration of a series of curves each representing a different capacitance is shown wherein the ordinate shows the phase shift, due to a change in capacitance, for a given frequency which is measured along the abscissa. If at any instance of time the value of capacitance introduced into transmission line 11 by the metallic rims 17 of disc 16 is equal to C the energy transmitted through line 11 at frequency w will have a phase angle equal to 13 as shown in Fig. 5. If the value of capacitance 21 is changed to C then the phase 4. and 40 are coupled to line 37 between the discs 34, 35, and 36, which may be made very thin and spaced a distance just sufiicient to allow a stub to be placed between them.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by -way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims. I

I claim:

l. A phase shifter type device comprising a coaxial transmission line having the inner conductor thereof with a gap therein, a coaxial inductive stub disposed adjacent said gap with the outer and inner conductors thereof coulied to the inner and outer conductors, respectively, of

of the energy transmitted through line 11 at frequency w will be equal to 5 Thus if the capacitance introduced into gap 15 by rim 17 is varied between C and C the phase angle of the energy transmitted by line 11 will vary between 18 and fi or in other words, a phase shift equal to B2B1 will be introduced into transmission line 11 when the input energy is at frequency 01 As shown in Fig. 6, for a given input frequency m there is a critical capacitance C below which any change will cause attenuation of the energy flowing through line 11. If the capacitance introduced into gap 15 is made to vary between C and C the energy flowing through the transmission line 11 .at frequency w will be alternately transmitted and attenuated.

If rim 17 is composed of alternate teeth, metallic ones 26 and insulating ones 27, as shown in Fig. 7, the capacity introduced into line 11 may be made to vary between 'with an almost instantaneous return to zero is desired, the

teeth of the metallic rim 17 may be shaped in a triangular manner, as shown in Fig. 8, causing a sawtooth change in phase.

If a phase shift is desired which will vary between two predetermined angles, the teeth of metallic rim 17 may be made alternately wide and thin, as shown in Fig. 9.

When a large phase shift is desired over a relatively large bandwidth, it is necessary to introduce a large change in capacitance. As shown in Fig. 10, this is possible by driving several discs 30, 31, and 32 from the same shaft 33 through a plurality of gaps 34, 35, and 36 Y in coaxial transmission line 37. Inductance stubs 38, 39,

said line, the outer conductor of said line having a slot in alignment with said gap, a shaft disposed for rotation about an axis parallel to said coaxial line, means including'a body carried on said shaft for movement during a rotation movement of said shaft through said slot and said gap, said body varying in dielectric-affecting material in a direction circumferential along the path of movement of said body to thereby continuously change the total value of the dielectric across said gap, thus giving rise to a continuously varying capacitance.

2. A phase shifter type device according to claim 1, wherein said capacitive body includes an endless element of conductive material of varying width.

3. A phase shifter type device according to claim 2, wherein said element includes a plurality of distinct conductive parts.

4. A phase shifter type device according to claim 3, wherein said parts are in a spaced series relation.

5. A phase shifter type device according to claim 3, wherein the width of each of said parts varies in a sinusoidal manner.

6. A phase shifter type device according to claim 3, wherein said parts are each of a triangular shape in cross section.

7. A phase shifter type device according to claim 3, wherein said parts are of varying width.

8. A' phase shifter type device comprising a coaxial transmission line having the inner conductor with a plurality of spaced gaps therein, a plurality of inductive coaxial stubs, one spaced adjacent each of said gaps and having its outer and inner conductors coupled to the outer and inner conductors of said transmission line, the outer conductor of said line having a plurality of slots each respectively in alignment with one of a plurality of said gaps, a shaft disposed for rotation about an axis parallel to the said coaxial line, means including a plurality of bodies respectively carried on said shaft for movement during the rotation movement of said shaft through corresponding ones of said slots and said gaps, each of said bodies varying in dielectric-affecting material in a direction circumferential along the respective paths of movement thereof to continuously change the total value of the dielectric across the said gaps, thereby giving rise to a continuously varying capacitance.

9. In an omnidirectional antenna system having a plurality of directional antennas coupled to a source of energy by a coaxial transmission line; means to continuously vary the phase of the energy fed to one or more of said directional antennas comprising a section of said coaxial transmission line having the inner conductor thereof with a gap therein, an inductive coaxial stub having the outer and inner conductors thereof coupled to the outer and inner conductors, respectively, of said line, the outer conductor of said line having a slot in alignment with said gap, a shaft disposed for rotation around an axis parallel to said coaxial line, means including a body carried on said shaft for movement during a rotation move- -ment of said shaft through said slot and said gap, said body varying in dielectric-affecting material in a direction circumferential along the path of movement thereof to continuously change the total value of the dielectric across said gap, thereby giving rise to a continuously varying capacitance which in turn gives rise to a continuously varying phase shift in the energy flowing along said transmission line.

10. In an omnidirectional antenna system having four antenna arrays each having a directional radiation pattern of substantially 90", wherein alternate antenna arrays are coupled together, the combination of patterns having narrow nulls between radiation lobes, means to i, continuously vary the phase of energy fed to one or more of said coupled antenna arrays comprising a coaxial transmission line having an outerconductor with a slot therein and an inner conductor with a gap therein in alignment with said slot, a coaxial stub having the inner and outer conductors thereof coupled to the inner and outer conductors, respectively, of said line, a shaft disposed for rotation about an axis parallel to said coaxial line, means including a body carried on said shaft for movement during a rotation movement of said shaft 1 through said slot and said gap, said body varyingin ditinuously varying pattern directivity so as to interchange said narrow nulls with said radiation lobes, whereby the resulting phase shift varies the pattern directivity to interchange said narrow nulls with said radiation lobes.

11. A phase shifter type device according to claim 1, wherein the said body comprises a disc of insulating material having conductive material carried by the peripheral portion thereof, said conductive material being of a radial dimension equal to a fraction of the diameter of the outer conductor of said coaxial line.

12. A device according to claim 8, wherein said plurality of bodies comprises a plurality of discs each composed of insulating material having conductive material carried respectively by the peripheral portion thereof, said conductive material being of a radial dimension equal to a fraction of the diameter of the outer conductor of said coaxial line.

References Cited in the file of this patent UNITED STATES PATENTS 2,253,958 Luck Aug. 26, 1941 2,284,529 Mason May 26, 1942 2,422,110 Luck n. June 10, 1947 2,426,992 Folland et a1. Sept. 9, 1947 2,485,617 Lundberg Oct. 25, 1949 2,577,511 Cohn Dec. 4, 1951 2,602,895 Hansen July 8, 1952

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