US2433011A

US2433011A - Ultra high frequency energy coupling

Info

Publication number: US2433011A
Application number: US482341A
Authority: US
Inventors: John F Zaleski
Original assignee: Sperry Gyroscope Co Inc
Current assignee: Sperry Gyroscope Co Inc
Priority date: 1943-04-08
Filing date: 1943-04-08
Publication date: 1947-12-23
Anticipated expiration: 1964-12-23
Also published as: GB612410A

Description

Dec. 23, 1947. J. F. ZALESKI ULTRA-HIGH-FREQUENCY ENERGY COUPLING Filed April a, 1943 INVENTOR JOHN F. ZALESKI m-ro muzv Patented Dec. 23, 1947 ULTRA HIGH FREQUENCY ENERGY COUPLING John F. Zaleski, Queens Village, N. Y., assignor to Sperry Gyroscope Company, Inc., a corporation of New York Application April 8, 1943, Serial No. 482,341

14 Claims. 1 The present invention is related to the art including ultra high frequency energy-conducting apparatus, and, more specifically, relates to such conducting apparatus of the wave guide or dielectric guide type.

When transferring energy between a source and a load at ultra high frequencies or microwaves having wavelengths of the order of centimeters or less, it has become customary to utilize so-called wave guides or dielectric guides, which essentially comprise a hollow energy-conducting member having a boundary whose dielectric constant is different from that of the surrounding medium. Most usually, such boundaries are formed by thin metallic shells or pipes of various cross-sections, but may also be formed by pipes of dielectric material which may be hollow or solid, as is well known. Such apparatus will be termed wave guides in the following specification.

When coupling a source to a load by means of a high frequency wave guide, it is well known that certain precautions are necessary to assure full utilization of the capacity of the conducting system at highest efficiency. For this purpose it is necessary to match the source to the load to avoid the production of standing waves in the wave guide, which produce local high current intensities and increase losses in addition to decreasing the power flow through the conducting apparatus.

Considered from one viewpoint, a standing wave may be considered to be caused by the reflection of a wave traveling in the wave guide by a discontinuity in the conducting medium, such as may be caused by a sudden change of impedance of the medium, as where a change in dimension occurs or an impedance different from the characteristic impedance of the wave guide is connected to the wave guide. The reflected Wave thus produced inter-acts with the forwardtraveling wave to produce a standing wave. Such a standing wave may be eliminated by having an additional reflected wave introduced in the wave guide such that its phase is opposite and its magnitude equal to that of the reflected wave produced by the change in guide dimension or impedance. The phase and magnitude measurements of the two reflected waves must, of course, be made at the same oint along the wave guide. sual y, all undesired reflection occurs where a load is connected to the wave guide. Therefore, to eliminate the resulting standing waves, a second reflection must be provided having the proper characteristics to cancel the effect of the first undesired reflection. Apparatus for producing such a canceling reflection is usually termed an impedance transformer or an impedancematching device. As already discussed, such an impedance transformer must correlate both the amplitude and phase of the reflection it produces with that of the undesired reflection. Therefore,

two independent adjustments for such an impedance transformer are necessary to permit adjustment of its reflection to cancel that produced by the undesired impedance discontinuity. Roughly speaking, these adjustments may correspond respectively to amplitude adjustment and phase adjustment of the reflected wave produced thereby. Usually, however, one adjustment of the impedance transformer will produce a combination of amplitude and phase change in the reflected wave, and the other adjustment will likewise produce a combination of amplitude and phase change. So long as these combinations of amplitude and phase change are independent of one another, the two adjustments of the impedance transformer will be sufficient to match substantially any load to any source.

In the prior art it has been known to provide two separate adjustments for a wave guide impedance transformer in the form of adjustable stub wave guides connected in shunt with the main energy-conducting wave guide at separated points thereof. Such impedance-matching devices, while, useful, are inconvenient because of the extra, space required for locating them separately along the wave guide, and also because at certain spacings, correlated to multiples of a quarter-wavelength of the operating frequency, these separate adjustable devices are no longer independent of one another, so that the utility of the device is somewhat restricted.

According to the present invention, an improved form of impedance-matching device is provided, in which two adjustments may be made at the same location along the wave guide, and which permits matching the impedances connected at either end of the wave guide section carrying the matching device over a wide range of values. In the present instance, this is done by providing a stub section in shunt with the main wave guide section and having an adjustable sliding short-circuiting piston plunger whose adjustment provides one of the two necessary matching adjustments. In addition to this, the resent device utilizes a conductor extending axially of the stub section and into the main wave guide, the amount of projection of this axial or inner conductor into the main wave guide being adjustable to provide the second required impedance-matching adjustment. In this manner both adjustments may be made at the same point, decreasing the space requirements of the impedance-matching device, and having a simpler construction by avoiding the necessity for dual sliding pistons as in prior devices, whereby the apparatus of the invention may be more simply manufactured and easily utilized.

The present invention is also adapted for use together with rotatable or otherwise adjustable wave guide joints, for producing a proper impedance match in the system when energy is conducted through such joints, as from a stationary source to a movable load, or vice versa.

Accordingly, it is an object of the present invention to provide an improved impedancematching device or impedance transformer for ultra high frequency energy.

It is another object of the present invention to provide an improved ultra high frequency impedance-matching device or transformer having a pair of adjustments at substantially the same location.

It is a further object of the present invention to provide an improved ultra high frequency impedance-matching device or transformer having a pair of conveniently adjustable portions for eliminating standing waves.

It is yet another object of the present invention to provide an improved form of impedance transformer or matching device which may be utilized to eliminate standing waves in ultra high frequency wave guides which may be fixed or relatively adjustable or rotatable.

It is another object of the present invention to provide an improved ultra high frequency impedance-matching or transforming device which is simple in construction and easy of adjustment.

It is a further object of the present invention to provide improved rotatable or adjustable joints for ultra high frequency wave guides which present a minimum of hindrance and a maximum of efficiency to the flow of ultra high frequency energy therethrough.

It is another object of the present invention to provide improved adjustable or rotatable joints for ultra high frequency wave guides utilizing an impedance transformer or matching device of the above-mentioned type for avoiding the production of standing waves, whereby increased efliciency and extended utility are derived.

Other objects and advantages of the present invention will become apparent from the specification, taken in connection with the accompanying drawing wherein the invention is embodied in concrete form.

In the drawing,

Fig. 1 shows a longitudinal cross-sectional view of the impedance transformer of the present invention operating in conjunction with a fixed wave guide section.

Fig. 2 shows a longitudinal cross-sectional view of an improved rotatable wave guide joint in cooperation with the impedance transformer of the present invention.

' Fig. 3 shows a cross-section of Fig. 2 along line 33 thereof.

Fig. 4 shows a cross-section of a modification of a portion of Fig.2.

Fig, 5 shows a longitudinal cross-sectional View of a modification of the invention of Fig. 2, also utilizing the impedance transformer 0f t P ent invention.

Referring to the drawing, and especially to Fig. 1, reference numeral II designates a main section of Wave guide adapted to conduct ultra high frequency energy from a source connected at one end to a load connected at the other end. Wave guide I! is illustrated as being rectangular in cross-section, although it is to be understood that any other shape of cross-section may be utilized, as desired or required by characteristics of the system. In order to match the impedance of the load to that of the source, Fig. 1 shows the impedance transformer E2 of the present invention, which comprises a tubular conductor l3 whose interior communicates with the interior of the wave guide Ii. Tube [3 is provided with a closure member or plug M at its upper end suitably conductively fixed within tube 23, as by pressing, soldering, welding or any other suitable manner. Plug M is centrally drilled and tapped to receive a correspondingly threaded rod which may be provided with a screw slot H at its upper end, whereby, upon rotation of rod it, it may be axially inserted for an adjustable distance Within wave guide H, as shown. The lower end of rod I6 is preferably slightly rounded to provide a smoother impedance adjustment and to eliminate sharp edges which may create corona effects at high electric field intensities and low barometric pressures such as may be encountered if the device is utilized on aircraft. However, any desired termination for the rod !6 may be utilized Where the above considerations do not apply.

Surrounding rod l6 and within tube i3 is a sliding piston l8 which makes sliding contact with the inner wall of tube l3 and with the outer surface of rod It. Piston 18 may be suitably adjusted by a control member l9 connected thereto and passing through openings 2i in plug it. In this way it will be seen that rod it may be adjusted independently of piston l 8. By making suitable adjustments of these two adjustable members, the impedances of the load and source connected to opposite ends of Wave guide ii may be matched to eliminate standing waves in the Wave guide H. This could, of course, be indicated by any suitable type of standing wave indicator known to the art. In this manner the impedance transformer l2 of the present invention provides a simply constructable and easily adjustable impedance transformer operable over a wide range of impedance adjustments and frequencies of operation.

Fig. 2 illustrates the use of the impedance transformer of Fig. 1 with a rotatable wave guide joint. In the present instance, ultra high frequency energy is conducted between two

wave guides

22 and 23 which are movable in parallel planes and are rotatable about an axis mutually perpendicular to these planes and passing through the

wave guides

22 and 23. As is discussed more in detail in copending application Serial No. 447,524, granted September 10. 1946, as Patent 2,407,318, for High frequency apparatus, filed June 18, 1942, in the names of W. W. Mieher and J. D. Mallett, it is desirable to utilize the so-called TM mode of energization of a wave guide in which a rotatable joint is interposed in order to prevent modulation of the ultra high frequency energy due to the rotation of the two portions of the device, and also to produce maximum efficiency of energy transfer across the gap between the two relatively rotatable portions of the device.

Accordingly, in the present system of Fig, 2, the

wave guides

22 and 23, which are illustrated again as being rectangular, although they need not be necessarily so, are coupled by a I'M-excited section of circular wave guide 24 comprising adjacent cylindrical sections 24' and 24" in which the joint is placed, and the impedance transformer of the invention is utilized, in addition to its impedance-matching functions, to transform energ from the rectangular wave guide 22, which is usually excited in the TE mode, to the TM-excited circular wave guide 24. Thus, in Fig. 2 the rod 16 of the impedance transformer I2 is extended completely across the wave guide 22 and axially into the circular wave guide 24 through a gap 26 in the opposite wall 21 of wave guide 22. This wall 21 is made of appreciable thickness so that it forms a short section of concentric transmission line with rod [5. By a proper choice of the thickness of wall 21 and upon proper setting of rod I6 and piston 18, the entire coupling may be made relatively insensitive to changes in frequency. The rod l6 projects beyond the wall 21 axially of the circular wave guide 24 and thereby acts as an antenna to launch the TM mode of high frequency energy along the circular wave guide 24.

The wave guide 24 is formed in two

sections

24 and 24" which are separated by a gap 28 whereby they may be relatively adjusted. Surrounding the gap 28 and communicating therewith is the wave trap 29 which acts to prevent high frequency energy from leaking or radiating from gap 28. Wave trap 29 is formed by a pair of sleeves 3B, 30" mounted concentrically with respect to the two

part

24 and 24" of guide 24, and only slightly spaced therefrom. Sleeves 3t, 39" are connected to and supported from the respective sections 24', 24" by annular pieces 58', 56", which are spaced from the gap 28 by substantially a quarter wave length of the operating frequency.

In this manner, sleeves 3e, 39" form respective short circuited quarter wave transmission line sections and present a very high impedance looking outward from gap 28, so that little energy is lost through gap 28. Any impedance mismatch caused by gap 28 may be compensated for by a suitable setting of impedance transformer I2. It will be understood that any suitable type of wave trap may be utilized here, including any of the types shown in the above-mentioned Patent No. 2,407,313.

The portions of Fig. 2 thus far described serve to efficiently transfer ultra high frequency energy between wave guide 22 and Wave guide 24. It is also necessary to provide a similar apparatus for permitting efficient transmission of energy between wave guide 23 and wave guide 24. If desired, the apparatus thus far described may be repeated, that is, a second impedance transformer 12 identical to that already described may be utilized in the same manner to couple wave guide 23 and Wave guide 24. However, this would necessitate making four separate adjustments when adjusting the system to optimum operation.

According to the present invention, it has been found possible to provide a non-adjustable coupling between wave guide 23 and wave guide 24, while still permitting the two adjustments of transformer [2 to conveniently and efiiciently match the entire system over a suitable range of frequencies. For this purpose, the wave guide 24 is caused to communicate directly with the wave uide 23 which is disposed at right angles thereto. By making the length of the wave guide 24 exactly equal to one-half wavelength or an integral multiple thereof of the operating frequency, as measured within wave guide 24 with the TM mode of energlzation, it has been found that a resonant condition is produced which very conveniently and efliciently serves to couple wave guide 23 to the circular wave guide 24 while still permittin proper matching by means of transformer l2.

If desired, the coupling between wave guide 23 and wave guide 24 may be modified slightly to provide an even more eflicient coupling of the TE-mode energy in the rectangular wave guide 23 with the TM mode energy in the circular wave guide 24, as shown in Fig. 4 which illustrates a modification of a portion of the apparatus of Fig. 2. In this instance, the bottom of the circular Wave guide 24" is supplied with a recessed cylindrical portion 3| whose diameter and depth are so selected that this recessed portion 3| acts substantially as a short-circuited, quarter-wave guide for the TM mode of energy in wave guide 24, while also acting as a short-circuited, half-wave wave guide for the TE mode in the circular wave guide 24. In this way any tendency for the TE mode to be set up in the wave guide 24 is substantially eliminated, and substantially only pure TM mode energy is permitted to exist in.the wave guide 24.

Fig. 5 shows another embodiment of the present invention in which a rotatable wave guide joint similar to that of Fig. 2 is provided. However, in this instance, the two wave guides 22 and 23 are coupled by a section of concentric transmission line 32 rather than by the circular wave guide 24, as in the prior figure. Effectively, the device of Fig. 5 may be considered to be formed by extending the thickness of wall 21 of Fig. 2 to join with the wall of wave guide 23. The rod 1 6 of the impedance transformer l2 of Fig. 2 is then extended to form the central conductor of this line 32 and extends further into the wave guide 22 in somewhat the manner shown in Fig, 1. The gap 33 is also formed in the outer conductor of line 32 and cooperates with the wave trap 34 in the same manner as in Fig. 2.

If desired, the position of the rod relative to the short-circuited ends of wave guides 22 and 23 may be adjusted in the device of Fig, 5 by providing the adjustable shorting plugs '36 and 31 therein respectively. A similar adjustment may be provided in the case of Fig. 2. Preferably these shorting plugs are set for a particular frequency or for a particular range of operating frequencies, and after being once set, are no longer adjusted. The onl adjustments then necessary to provide optimum operation are those of rod i6 and piston E8 of the transformer 52, in the manner already described with respect to Figs. 1 and 2. In this manner a simple, efiicient, and easily adjustable, rotatable wave guide joint is provided.

It is to be noted that the rotatable joint of Figs. 2 and 5 has the great advantage that all adjustments are made at a single point. Therefore, it is not necessary to have access to both ends of the coupling guide 24 or line so the construction of the apparatus and remaining apparatus associated therewith is substantially simplified because the necessary bearings and supports for the relatively rotatable apparatus, while not shown in the present case, since they form no part of the present invention, may materially complicate the space requirements for the various portions of the system. By rendering the adjustments accessible at asingl point and taking up space at but a single location, the

construction-pf the entire-apparatus; isrendered muchmore simples As-imany changes could-be-made in; the above construction and many" apparently widely different-embodiments of this-invention could be made-without departing from the scope thereof, it is, intended that all matter contained in the above description or shown'in" the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Whatis claimed is:

1.- Ultra hi hfrequency apparatus for transforming an impedanceconnectedto a wave guide section, comprising-a. tubular conductor connected to-and-communicating with said-wave guide section intermediate the ends thereof,'a solid conductive rod supportedcoaxially within said, tubular member and projecting transversel within said wave guide and havingv an end therein means for adjusting the position of the end of said rod withinsaidwave guide, and means for adjustabl" short-circuiting said tubular member and said rod, whereby animpedance connected. at one end of said wave guide section maybe transformed to a diiferent value at the other endthereof by adjusting the amount of said rod-projection and said short-circuited means.

2. In. combination with. a hollow-pipe wave guide having a first opening for entrance of ultra high frequency electromagnetic waves, a second opening for discharging electromagnetic waves, and-a third opening intermediate said first and second openings, the apparatus comprising a tubular conductor adjoining said wave guide at said third opening and extending therefrom externally of saidwave guide, a solid inner conductor supported substantially coaxially within said tubular conductor and projecting through said third opening into said wave guide and terminatingtherein, an axially movable conductive element connecting said tubular conductor to said inner con-ductorfor varying the impedance at said opening between said tubular conductor and said inner conductor, and means-for adjusting the length of said inner conductor projecting within said wave guide for varying the coupling thereof with said wave guide.

3. In combination with a hollow-pipe wave guide coupled to a source of ultra-high frequency energy and also coupled to a load for said energy to transmit energy from said source to said load, said wave guide having an opening through the wall thereof intermediate said source and said load; the apparatus comprising a tubular conductor adjoining said wave guide at said opening and extending therefrom externally of said wave guide, a solid inner conductor supported coaxially within said tubular conductor and projecting through said opening into said Wave guide and having an end therein, and an axially movable conductive element connecting said tubular conductor to said inner conductor for varying the impedance at said opening between said tubular conductor and said inner conductor.

4. Ultra high frequency apparatus for transforming an impedance connected to a section of hallow ultra high frequenc energy conductor, comprising an adjustable length of concentric transmission line connected to said conductor intermediate the ends thereof and having a solid inner conductor positioned within said hollow conductor, and means for adjusting the position of said inner conductor Within said hollow conductor, whereby an impedance connected at one end of said hollow conductor section may be transformed'to a different-impedance value at the opposite end of said conductor by adjusting the length of said concentric line section and the position of said inner conductor.

5. An ultra high frequency variable impedance network for attachment to a ho11owpipe wave guide, comprising a tubular conductor adapted to be joined to said wave guide at an opening therethrough to extend from said opening angularly to and exteriorly of said Wave guide, a solid rod positioned coaxially within and extending beyond said tubular conductor for projecting through said opening into said wave guide for coupling therewith, means for-varying the axial position of said rod, and means for adjustably short-circuiting said tubular conductor and-said rod, whereby the impedance presented to said wave guide may be varied.

6. Ultra high frequency variable impedance wave guide apparatus, comprising a section of hollow-pipe wave guide having an opening through the conductive wall intermediate the ends thereof, tubular ccnductorjoined to said wave guide wall at said opening and extending therefrom exteriorly and transversely to said wave guide, an axially adjustable solid rod positioned coaxially within said tubular conductor and extending therefrom through said opening into said wave guide, means for adjusting the position of said rod within said wave guide, andmeans for adjustably short-circuiting said tubular conduc tor and said rod, whereby theimpedance of said Wave guide may be adjusted as desired.

7. Apparatus for transferring ultra high frequency energy between a hollow-pipe wave guide conductor and another ultra high frequency energy conductor, comprising a section of circular wave guide, means including an adjuscable section of concentric transmission line, on said Wave guide conductor and cooperating with aligned openings in said wave guideconductor and said wave guide section for coupling said wave guide section to said wave guide conductor in a manner to excite TM waves in said wave guide section,

means for coupling said circular wave guide section. to the other of said conductors to transfer said TM energy to said other conductor, said circular wave guide section having a length substantially equal to an integral multiple of half wavelengths of said TM energy mode in said circular wave guide section.

8. Apparatus for transferring ultra high frequency energy between two ultra high frequency energy conductors comprising a, section of circular wave guide, means for coupling said wave guide to one of said conductors in a manner to excite TM waves in said wave guide section, means for coupling said circular wave guide section to the other of said conductors to transfer said TM energy to said other conductor, said circular wave guide section having a length sub stantially equal to an integral multiple of half wavelengths of said TM energy mode in said circular wave guide section, one of said conductors comprising a rectangular wave guide and one of said coupling means comprising an adjustable section of concentric transmission line havin the inner conductor thereof extending across said rectangular wave guide and coaxially within said circular wave guide section, and means for adjusting the amount of projection of said inner conductor within said circular wave guide.

9. Apparatus for-transferring ultra high frequency energy comprising two spaced wave guides adapted to propagate energy in substantially'parallel directions, a first conductor extending perpendicularly with respect to said wave guides, completely across one of said wave guides and into the other of said wave guides, a hollow tubular conductor concentrically surrounding said first conductor between said wave guides and forming a concentric transmission line section therewith, a second hollow conductor concentrically surrounding the portion of said first conductor projecting on the other side of said first wave guide and forming a concentric transmission line section therewith, means for adjustably short-circuiting said first conductor and said second hollow conductor, and means for adjusting the projection of said first conductor within said other wave guide, whereby ultra high frequency energy may be transferred between said wave guides substantially without reflection or the creation of standing waves by suitably adjusting said short-circuiting means and the amount of projection.

10. Apparatus for transferring ultra-high-frequency energy comprising two spaced ultra-highfrequency energy conductors adapted to transmit energy in substantially parallel directions, one of said conductors being a rectangular wave guide, a section of circular wave guide formed of two relatively rotatable coaxial portions fixed respectively to said conductors and having an axis of propagation substantially perpendicular to said conductors, whereby said two conductors may be rotated relative to one another without interfering with the flow of ultra-high-frequency energy therebetween, means for coupling said wave guide to one of said conductors in a manner to excite TM waves in said circular wave guide section, and means for coupling said circular wave guide section to the other of said conductors to transfer said TM energy to said other conductor, one of said coupling means comprising an adjustable section of concentric transmission line having the inner conductor thereof extending across said rectangular wave guide and coaxially within said circular wave guide section.

11. The apparatus defined in claim 10, further including means for adjusting the amount of projection of said inner conductor within said circular wave guide,

12. Apparatus for transferring ultra-high-frequency energy between two wave guides, comprising a first conductor extending completely across one of said wave guides and into the other of said wave guides, a first hollow tubular conductor concentrically surrounding said first conductor between said wave guides and formin a concentric transmission line section therewith, a second hollow conductor concentrically surrounding the portion of said first conductor projecting on the other side of said first wave guide and forming a concentric transmission line section therewith, means for adjustably short-circuiting said first conductor and said second hollow conductor, and means for adjusting the projection of said first conductor within said other wave guide, whereby ultra-high-frequency energy may be transferred between said wave guides substan tially without reflection or the creation of standing waves by suitably adjusting said short-circuiting means and the amount of projection, said hollow tubular conductor being formed in two relatively rotatable sections, and said first conductor being supported solely from said second hollow conductor whereby said wave guides may be rotated relative to one another substantially without influencing the flow of high frequency energy therebetween.

13. Apparatus for transferring ultra-high-frequency energy between two wave guides, comprising a section of concentric transmission line extending between openings through the sides of said wave guides and having the inner conductor thereof projecting within one of said wave guides transversely thereof, means for adjusting the amount said inner conductor projects within said one wave guide to vary the coupling thereto, a short-circuited stub concentric transmission line connecting said inner conductor and the other of said wave guides, and means for adjusting the effective electrical length of said stub line.

14. Apparatus for transferring ultra-high-frequency energy comprising a pair of wave guides having openings in the side walls thereof, a section of coaxial transmission line extending between said openings, said line having its outer conductor formed of two relatively rotatable coaxial sections connected respectively to said two guides and also having a unitary inner conductor fixed relative to one of said outer conductor sections and to its connected guide and projected transversely within the other of said guides short of the wall thereof, opposite said line.

JOHN F. ZALESKI.

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

UNITED STATES PATENTS FOREIGN PATENTS Country Date Australia Nov. 4, 1942 Number Number