US2514779A - Wave guide system - Google Patents

Description

J y 11, 1950. I c. A. MARTIN 2 51 WAVE GUIDE SYSTEM Filed May 14, 1947 11/045 POI/W5 r "f I7 5 ,7 5 l8 5 INVENTOR.

CHARLES A. MARTIN" Patented July 11, 1950 WAVE SYSTEM Charles A. Martin, Rocky Point, N. Y., asslgnor to Radio Corporation of America, a corporation of Delaware Application May14,1947, Serial No. 748,058

The present invention relates to a system for combining a number of microwave radio waves into a single wave guide or electromagnetic horn structure.

' An object of'the presentinventionis to provide a combining structure-for introducing a number of microwave radio waves into a single wave guide.

Another object of the present invention is the provision of a combining system as aforesaid in which each wave propagated in the wave guide is of thedominant type and, therefore, is more suitable for'immediate radiation by electromagnetic hornor other wave directive structure.

Another object of the present invention is to provide a combining system for high frequency radio waves in whichthefeed point of each wave does not disrupt the continuity of the wave guide system for any other wave in the guide. Another object of the present inventionis ,the provision of a combining system as aforesaid 14 Claims. (Cl. 178-44) point as far as all other waves, existing at the feed point in the wave guide, are concerned. Moreover, the adjustments necessary to regulate the rejection bands are substantially independent of those of the pass band and of each other, and,

therefore, the tuning of the system is simple and straightforward.

- While, for convenience, the foregoing brief description and the following detailed description are based on the assumption that the present invention is to be used for coupling a plurality of sources of high frequency energy to a high im-.- pedance horn antenna or load, it should be clearly understood that my invention is not limited thereto, but may also be used to couple a plurality of separateloads or receivers to a wave guide carrying a number of separate high frequencywaves wherein the energy from each source is prevented from entering the source, of anyother wave.

Still another. object of the. present invention is the provision of a microwave combining system in which each feed system is capableof feeding the .wave guide with arelatively wide 'ba nd of frequencies. I

Another object of the present invention is the provision of a microwave combining system in which the necessary adjustments may be simply made and are straightforward in character.

The basic principle uponrwhich the present invention is based is that no real power of an electromagnetic wave will propagate along awave guide having lateral dimensions less than a certain. critical magnitude: in other words, a wave guide inherently acts as a high passfilte'r. Thus, the present. invention contemplates utilizing a tapered wave guide section with the individual frequencies beingfed into the tapered wave guide at points such that the, waves may propagate only in one direction along the guide; that is, in the direction of increased dimensions- Trap circuits are provided so that the entrance points of the lower frequency waves are effectively short In the system of this disclosure a wide pass band is provided ineach feed system so that ,a number of signals of small wavelength dif-.

ferences may be'introduced at each feedpoint .of the wave guide by the usual practice of using filters. In addition, the remaining impedance =-function of each feed system is controlled to provide 1 an effective short circuit acrossv the. feed 2 4, circuited for high frequency waves originating in thesmaller portions of the guide system.

or to a horn antenna receiving, any one of a number of separate waves without adjustment or a number of waves simultaneously.

The present invention will be more fully understood by reference to the following detailedvdescription which is accompanied by a drawing in which:

Figure 1 illustrates in perspective and partly in section an embodiment ofv the present invention;

Figure 2 illustrates in perspective a modification of a portion of the structure of Figure 1, while Figure 3 illustrates a further modification thereof.

Referring now to Figure 1 there is shown a tapered wave guide '5. Three sources of high frequency energy A, B, and C of progressively lower frequency are shown. For the purpose of explaining the present invention but with no intent of limiting the invention to the particular dimensions suggested, let us assume that the wavelengths bearthe following relationship where AA,

is, and w are the wavelengths of three sources:

ie=1nsie=sic Now, at the point where the source A feeds its energy intowave guide 5, the dimension a of the waveguide is such that waves having a wavelength equal to that of source A may be propagated along this portion of the guide. The guide 5 expands in its dimensions until at the point Where wave guide section 3 joinsit, the width 1) permits the propagation ofnot only waves having a length equal to that of source A but also waves having a wavelength equal to thatof source B. Also, at a still largerpart of wave guide 5 where the dimension 0 is large enough to permit the propagation of all three waves, waves from source .Q-are introduced into the waveguideby the intermediate section 4 through throat 10. The following table gives the numerical relationship between these dimensions and certain other dimensions which will later be described:

It will be noted that the dimensions a, b, c, d, e, f, q and r are such that any real power of any of the waves is prevented from propagating back to the feed point of any other wave of shorter wavelength and such that electromagnetic waves of the dominant type and dominant type only are allowed to propagate from left to right in the figure.

The branch wave guide 4 coupling source C to the main wave guide 5 will now be described in detail. Trap circuit elements l5 and I6 branching from the branch guide 4 prevent coupling of sources A and B into source C and also maintain the continuity of the main wave guide 5 at junction In as far as the waves of sources A and B propagated in 5 are concerned.

The branch l6 has three parallel portions 6, 1 and 8 closed by plungers ll, l2 and [3 respectively. These three portions each have lateral dimensions a large enough to allow energy of source A to enter them but small enough to exclude energy from sources B and C. The position of the plungers H, l2 and i3 within the parallel guide sections may be varied to tune the circuit elements 6, 1 and 8 so that their effective impedance at the junction with the guide 4 may be made substantially infinite at the wavelength M. This effect may be obtained if, for example, the dimensions is and e are made approximately equal to a quarter of the guide wavelength of the source A. Now, by suitably choosing the dimension 7', the distance between element [6 and the junction of guide 4 and guide 5, the effective high impedance at the throat of guide I6 is converted at the throat ID to a short circuit effectively for waves of the wavelength of source A. Since the i.

dimension a is less than Ma and also less than /2 M3, the presence of the element l5 has but a small effect on waves of the sources B and C which may exist in the wave guide 4.

The branch [5 has the same function in reard to waves of source B that It has for waves of source A. The branch wave guide section of width b is large enough to admit energy of source B but small enough to exclude energy of source C. The plunger l4 may be varied to tune the circuit element [5 so that the effective impedance at the junction 9 is substantially infinite at the wavelength M3. Then by suitably choosing the dimension n, the distance between the branch I5 and the guide 5, the effective high impedance at the throat of I5 is converted at the throat I!) to a short circuit effectively for waves of the wavelength of source B. In'addition to the abovedescribed action on waves of source B, l5 may be used to have a favorable effect on waves from source 0. This is accomplished by constructing 15 so that it is composed of a section of width (the width of the guide 4) extending from wave guide 4 a distance p. This distance p may be selected so that this section of l at least partially compensates for the effects on waves of source C of the wave guide discontinuities at l0, 6, 1 and 8.

Trap 26 on wave guide 3 functions similarly to on 4. The dimensioning of 26 is such that the smaller wave guide section of width a prevents energy of source A entering guide 3 and the larger section of width b at least partially compensates for the discontinuity at the junction of 3 and 5.

While the elements described above may be classified as the essential elements of the system various modifications in dimensioning and construction of the elements may be necessary depending mainly on the wavelengths and the bandwidth of wavelengths which are to be transmitted. For example, it may be desirable to obtain a more favorable impedance match to the source C over a wide bandwidth by using such well known devices in the wave guide 4 as diaphragms 0r tuning screws. As a further example, supposing source A is to transmit a wide bandwidth of signals, it may be desirable to use an additional element such as l6 suitably positioned along 4. Then by varying the length of the various parallel portions of 16 and the added element a greater bandwidth of wavelengths near M may be prevented from entering wave guide 4.

A modified system is shown in Figure 2 in which the main wave guide 5 of Figure 1 is replaced by discontinuous sections in the form of hollow rectangular prisms 5, 5" and 5" joined by tapered or truncated pyramidal sections I1 and I8. Under some circumstances this form of construction may be desirable in that it provides more freedom in the longitudinal positioning in the feed point of branch guide 4. Losses in the main wave guide may also, under some circumstances, be reduced by the increase in the taper angle in the sections l1 and i8. Except as noted the structure of the modification of Figure 2 is the same as that described above with reference to Figure 1.

A further modification is shown in Figure 3 wherein the branch wave guides 3 and 4 of Figure 2 are bent at right angles at their junction point with the guides 5" and 5" in order to run parallel thereto. The junction between guide 3 and 5", now it will be seen, takes the form of a right angle corner. The planes 2! at the corners improve the match between the two merging wave guides and reduce reflections which would otherwise occur at a sharp right angle bend.

While I have illustrated a particular embodiment of the present invention, it should be clearly understood that it is not limited thereto since many'modifications may be made in the several elements employed and in their arrangement and it is therefore contemplated by the appended claims to cover any such modifications as fall within the spirit and scope of the invention.

What is claimed is: v

1. A wave guidesystem including a main guide adapted to be coupled to a load circuit at one end and having a source of high frequency energy coupled to the other end, said guide having increasing transverse dimensions in the direction toward said load, said dimensions at said other end being only large enough to transmit energy of the frequency of said source, and branch guides, each having a source of energy of lower frequency than said first mentioned source coupled to one end, said branch guides being coupled to said main guide at points therealong where its dimensions become large enough to transmit said lower frequency energies.

2. A wave guide system including a main guide adapted to be coupled to a load circuit at one end and having a source of high frequency energy coupled to the other end, said guide having increasing transverse dimensions in the direction toward said load, said dimensions at said other end being only large enough to transmit energy to said main guide at points therealong where its dimensions become large enough to transmit said lower frequency energies, each of said branch guides having waveguide elements coupled therewith to present a negligible impedance to the energy within said branch guide and being adjusted to present a substantially short circuit at the junction of said branch guides and said main guide to energy from sources of higher frequency.

, 3. A wave guide system according to claim2 in which said main guide has alternate rectangular hollow prismatic sections and hollow truncated pyramidal sections, said branch guides being coupled to said main guide in said prismatic sections.

4. A wave guide system including a main guide adapted to be coupled to a load circuit at one end and having a source of high frequency energy coupled to the other end, said guide having increasing transverse dimensions in the direction toward said load, said dimension at said other end being only large enough to transmit energy of the frequency of said source, a first branch guide having a source of energy of lower frequency than said first source coupled thereto and a second branch guide having a source of energy of lower frequency than either of the other of said sources coupled thereto, said branch guides being coupled to said main guide at points along said guide where its transverse dimensions are large enough to transmit energy from the source coupled thereto.

5. A wave guide system including a main guide adapted to be coupled to a load circuit at one end and having a source of high frequency energy coupled to the other end, said guide having'increasing transverse dimensions in the direction toward said load, said dimensions at said other of the frequency of said source, a first branch guide having a source of energy of lower frequency than said first source coupled thereto and a second branch guide having a source of energy of lower frequency than either of the other of said sources coupled thereto, said branch guides being coupled to said main guide at points along said guide where its transverse dimensions are large enough to transmit energy from the source coupled thereto, said first branch having a further branch guide coupled thereto, the transverse dimensions of said further guide being such as to be responsive only to energy from said first-mentioned source and having a length at which a low impedance i presented at the junction between said main guide and said first branch guide.

6. A wave guide system according to claim 5 in which said main guide'has alternate rectangularhollow prismatic sections and hollow truncated .6 of the frequency of said source, a first branch guide having a source of energy of lower frequency than said first source coupled thereto and a second branch guide having a source of energy of lower frequency than either of the other of said sources coupled thereto, said branch guides being coupled to said main guide at point a ong said guide where its transverse dimensions are large enough to transmit energy from the source coupled thereto, said first branch having a further branch guide coupled thereto, the transverse dimensions of said further guide being such as to be responsive only to energy from said firstmentioned source and having such length that at the junction between said main guide and said first branch guide a low impedance shunt is presented, said second branch guide having further branch guides coupled thereto, said further branch guides having transverse dimensions to render them responsive only to energy from said first and second sources of energy and having lengths at which a low impedance is presented to energy from said first and said second sources at the junction of said main guide and said second branch.

8. A wave guide system including a main guide adapted to be coupled to a load circuit at one endand having a source of highfrequency energy coupled to the other end, said guide having increasing transverse dimensions in the direction toward said load, said dimensions at said other end being only large'enough to transmit energy of .the frequency of said source, a first branch guide having a source of energy of lower frequency than said first source coupled thereto and a second branch guide having a source of energy of lower frequency than either of the other of saidsources coupledv thereto, said branch guides being coupled to said main guide at points along said guide where its transverse dimensions are large enough to transmit energy from the source coupled thereto, said first branch having a further branch guide coupled thereto, said further branch guide being so arranged that at the junction between said main guide and said first branch guide a low impedance is presented to energy from said first-mentioned source.

9. A wave guide system according to claim 8 in which said main uide has alternate rectangular hollow prismatic sections and hollow truncated pyramidal sections, said branch guides being coupled to said main guide in said prismatic sections.

10. A wave guide system including a main guide adapted to be coupled to a load circuit at one end and having a source of high frequency energy coupled to the other end, said guide having increasing transverse dimensions in the direction toward said load, said dimensions at said other end being only large enough to transmit energy of the frequency of said source, a first branch guide having a source of energy of lower frequency than said first source coupled thereto and a second branch guide having a source of energy of lower frequency than either of the other of said sources coupled thereto, said branch guides being coupled to said main guide at points along said guide where its transverse dimensions are large enough to transmit energy from the source coupled thereto, said first branch having a further branch guide coupled thereto, said further branch guide being so arranged that at the junction between said main guide and said first branch guide a low impedance is presented to energy from said: firstem'entioned source, said secondibranch guidehaving further branch guides coupled thereto; said further branch guides being so arranged thatrat-the junction of. said main guide and" said branch. guide a low impedance to energy from: said first and second sources is presented;

11. A wave guide-systemincluding a main guide adapted. to bev coupled to a load circuit at oneend and having asource ofhigh frequencyenergy coupled: to the other end, said guidehaving increasing transverse dimensions in the direction toward. said. load, said dimensions at said other end being only large enough to transmit energy or the frequency of said source, a first branch guide having a. source of energy of lower frequency than said first source coupled thereto and a second branch. guidehaving a source of energy of. lower frequency than either of the other of said sources coupled thereto, said branch guides being coupled to said main guide at points along said guide where its transverse dimensions, are large enough to transmit energy from the source coupled thereto, said first branch having coupled thereto a wave guide element having dimensions at which a high. impedance is presented to energy from said first source and to the energy from the source associated with said guide, the spacing between said wave guide element and the junction between said main guide and said first branch having a value at which. a low impedance across said branch is presented to energy from said first source.

12. A wave guide system including a main guide adaptedto be coupled to a load circuit at one end and having a source of high frequency energy coupled to the other end, said guide having increasing transverse dimensions in the direction toward said load, said dimensions at said other end being only large enough to transmit energy of" the frequency of said source, a first branch guide having a source of energy of lower frequency than said first source coupled thereto and a second branch guide having a source of energy of lower frequency than either of the other of said sources coupled thereto, said branch guides being coupled to said main guide at points along said guide where its transverse dimensions are large enough to transmit energy from the source coupled thereto, said first branch having coupled thereto a wave guide element having dimensions at which a, high impedance is presented to energy from said first source and the energy from the source associated with said guide, the spacing between said wave guide element and the junction between said. main guide and said first branch having a value at which a low impedance across said branch is presented to energy from said first source, said second branch having coupled thereto a number of high impedance wave guide elements spaced from the junction between said main guide and second guide to present a low impedance across said second branch to energy from said first sources and from the second of said sources.

13. A wave guide system according to claim 12 in which said main guide has alternate rectangular hollow prismatic sections and hollow truncated pyramidal sections, said branch guides being coupled to said main guide in said prismatic sections.

14. A wave guide system including a wave guide, a plurality of sources of high frequency energy of different frequencies coupled to said wave guide at spaced points along the longitudinal axis of said vave guide, said wave guide having dimensions transversely of said longitudinal axis between said spaced points at which energy from a source of lower frequency is prevented from flowing back over said wave guide toward a source of higher frequency.

CHARLES A. MARTIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,129,669 Bowen Sept. 13, 1938 2,407,318 Mieher Sept. 10, 1946 2,429,640 Mieher Oct. 28, 1947 2,432,093 Fox Dec. 9, 1947 2,441,574 Jaynes May 18, 1948

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