US 3621481 A
Description (OCR text may contain errors)
United States Patent 72] Inventors Henry W. Perreault' Chelmsford; Howard Scharhnan, Lexington, both of Mass.  Appl. No. 33,742  Filed May 1, 1970  Patented Nov. 16, 1971  Assignee Raytheon Company Lexington, Mam.
 MICROWAVE ENERGY PHASE SHIFI'ER 7 Clnlml, 3 Drawing Figs.
 US. Cl 333/31, 3433/81. 3213/! l. 333/22 F [51 Int. Cl .t 03h 7/22  FleldoISearch 333/30,3l, 95, 6, 10, 98
 References Cited UNITED STATES PATENTS 2,579,327 12/1951 Lund 333/81 B 2,768,356 10/1956 Van de Lindt 333/81 13 2,634,331 4/1953 333/81 B 2,944,234 5/1960 333/98 2,812,500 11/1957 333/81 B 3,323,080 5/1967 Schwelb et a1 333/1 1 Primary Examiner-Herman Karl Saalbach Assistant Examiner-C. Baraff Attorneys-Harold A. Murphy, Joseph D. Pannone and Edgar 0. Rest ABSTRACT: Means for control of amplitude, as well as phase, of electromagnetic energy in microwave frequency transmission systems are disclosed incorporating variable energy reflection, as well as absorption load means, in a compact branch transmission line structure coupled by short-slot hybrid junction means to a main transmission line. Adjustment of the load-to-line coupling results in variation of the amplitude of the energy and variation of a terminal reflecting member results in adjustment of the phase of such energy. The adjustments in amplitude, as well as phase, are made independently and have exceedingly high power capabilities in the order of megawatts.
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" ATTORNEY BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to microwave energy phase shifter and amplitude control devices for electromagnetic wave transmission systems.
2. Description of the Prior Art Present-day transmission systems for the propagation of electromagnetic wave energy, particularly at microwave frequencies, have evolved with substantially higher power levels to present a continuing problem in the attenuation, and phase shift of the propagated energy-utilizing conventional microwave components having relatively low power-handling capabilities. Rather cumbersome phase shifting, as well as amplitude control systems, for handling the higher power levels have been utilized in the art to meet these needs. Such systems commonly include mode transducers, as well as numerous other components, including rotating midsections, together with extremely long external energy-absorbing loads which are relatively limited by the peak power-handling capability. Variable attenuators for such systems are quite elaborate with numerous sidewall or top wall couplers and phase shifters consuming many square feet in area. One such exemplary system for providing a desired phase shift of the propagated energy would incorporate many short-slot hybrid junction couplers together with plural variable short circuit members terminating a line to simply adjust the phase of the energy without any adjustment in the amplitude. The cost and weight problems of such prior art high-power handling systems, therefore, have been limiting factor in extensive utilization.
In addition, in numerous applications such as linear accelerators or long-range radar systems employing plural power sources, a need has arisen for compact and efficient phase shifter means to couple the high-frequency energy at spaced intervals into a rather lengthy main input transmission line. An anomalous situation, therefore, arises in that the conventional attenuators which could be developed to control amplitude at the high power levels can only provide a constant phase shift and conventional phase shifters are incapable of controlling the power levels Electrical performance characteristics have also been discouraging since the addition of the large number of prior art components has only resulted in intolerably high insertion loss values over the frequency bands of interest. Additionally, all prior art devices for varying the amplitude of energy in high-power systems are extremely frequency sensitive. Improved devices, therefore, of compact mechanical configuration and greatly reduced insertion loss characteristics are essential for more effective utilization of high-power microwave energy systems, particularly such systems having plural energy sources.
SUMMARY OF THE INVENTION In accordance with the teachings of the present invention a high-power phase shifter and amplitude control device is provided in a novel integral compact structure. In a copending patent application, Ser. No. 846,397, filed July 31, 1969 by Henry W. Perreault, now US. Pat. No. 3,560,888 issued Feb. 9, 197 l, a novel energy termination device is disclosed having exceedingly high power absorption capabilities. The energyabsorbing means include both fluid or dry loads and are positioned within a transmission path oriented perpendicularly to the main transmission line. The entrance to the perpendicular energy-absorbing means is spaced a predetermined distance from a fixed energy-reflecting end wall terminating the main transmission line. Materials of a ceramic or plastic composition, as well as dielectric coolants, are disclosed for the absorbing means. By various impedance matching techniques the termination device provides low voltage standing wave ratio characteristics over a relatively broad frequency band.
In order to provide for an adjustable amplitude control device having a substantially flat attenuation response over a relatively broad frequency range, the present invention now discloses plural adjustable energy-absorbing load means mounted in juxtapositioned waveguide branch line means terminated by variable energy-reflecting, means. The branch line is coupled to the main transmission line by any suitable conjugate energy dividing means such as a 3 db. short-slot hybrid junction of the sidewall type. Movement of the energy-absorbing means to vary the depth of insertion within the waveguide branch line results in control of the amplitude of the energy reflected back to the main transmission line. The shunting absorbing means in the terminated branch line appear as shunt conductances over a wide frequency band. As a result, the device can be operated to control of the amplitude of the incident energy at any level, for example, I, 3 and 6 db. and then to variation of the energy-reflecting means terminating the branch line will provide an independent adjustment of the phase of the energy returned to the main transmission line. Adjustment of the shorting or reflecting plane will provide for any value of phase shift from a few degrees to Both variable adjustment means within the wave-guiding means of the branch line, as well as complete movement of a section of such wave-guiding means in a line stretcher arrangement will provide the desired phase shift characteristics.
Exemplary embodiments of the amplitude control phase shifter to be described at S-band frequencies have provided a peak power-handling capability of 4.7 megawatts in a system operating with pressurized air and a phase shift of :45 at the l, 3 and 6 db. power levels. The average power handled in this embodiment was 3.8 kilowatts and the pulse width was 2.0 microseconds at a duty cycle of 0.0008. The overall length of the branch line in this embodiment was 21 inches and the total height of the energy absorbing and adjusting means was approximately 12 inches to thereby provide a compact arrangement for use in high-power transmission systems. The device disclosed herein not only provides a means for filling the gap in the attenuator art for high-power devices but couples a unique phase-shifting capability heretofore unattainable in such devices. The disclosed invention is ideally suited for multitube chain sources in linear accelerator systems, as well as food and industrial processing systems, to bring the combined outputs of the individual energy source into an in-phase energy input to the utilization load. Each energy source may be fitted with the disclosed energy amplitude control and phase shifter device for combined integration of many different phase inputs and many power levels of operation may be utilized.
BRIEF DESCRIPTION OF THE DRAWINGS The invention, as well as the details for the provision of preferred embodiments, will be readily understood after consideration of the following detailed description and reference to the accompanying drawings. wherein:
FIG. I is a top view of the illustrative embodiment with a portion of a wall broken away to reveal internal structure;
FIG. 2 is an enlarged partial cross-sectional view of a portion of the embodiment shown in FIG. 1 taken along the line 2-2;
and FIG. 3 is an enlarged partial cross-sectional view of a portion of an alternative embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings the main transmission line 10 comprises input waveguide section ll and an output waveguide section 12 separated by a partition member 13. Conventional waveguide-mounting flanges 14 are attached adjacent the ends of waveguide sections 11 and I2. Coupled by conventional means to a sidewall of the combined main transmission line 10 is a 3 db. short-slot hybrid junction coupler 15. This component is a well known energy-dividing means in the microwave art and has. a plane of symmetry running the full length of the hybrid to define juxtapositioned waveguide passageways l6 and 17. A portion of a common wall 18 is removed to define a coupling iris l9 and permit coupling of energy between the two passageways. The operation of the hybrid junction is symmetrical and an efficient four-branch network is provided to conjugate electrically energy received at any one of the ports. In the present application the input port 20 at the end of passageway 17 is coupled to input waveguide section 11. The output port for the return of the reflected energy traversing the branch line circuit is designated by the numeral 21. The opposing ends of passageways l6 and 17 are connected by ports 22 and 23 to juxtapositioned waveguide sections 24 and 25 having a common wall member 26 therebetween.
Each waveguide section 24 and 25 supports an energy-absorbing load means which may be either of a dry or fluid composition shown generally as 27 and 28 adapted to be introduced therein and extending perpendicularly to the Ion gitudinal axis of each section. Simultaneous actuation by common control means 29 regulates the degree of insertion and coupling of energy between the absorbing means and branch line.
The terminal ends of waveguide sections 24 and 25 are provided with variable energy-reflecting means 30. A movable short circuiting conductive member 31 and 32 is axially disposed within each of the waveguide sections. Such conductive members may comprise a plunger-type arrangement defining a choke section 33 as shown more specifically in FIG. 2. This terminating arrangement provides for variable reflection plane for energy incident thereupon and the choke overall distance is conventionally one-quarter of a guided wavelength. It will be noted also that the conductive walls of the plunger are spaced in a noncontacting relationship with the walls of the waveguide sections as indicated by numeral 34 to minimize losses. The short circuiting plungers 31 and 32 are simultaneously actuated by means of a ganged drive mechanism incorporating rods 35 and 36 joined to yoke member 37. The rods 35 and 36 extend within suitable apertures in wall 38 enclosing the ends of the waveguide section 24 and 25. Yoke member 37 threadably engages actuator 39 which is externally driven by knob member 40 and supported by a substantially U-shaped frame member 41 joined to the exterior wall surfaces of waveguides 24 and 25. This frame member serves to anchor the rotatable component which in turn moves the ganged short circuiting plunger members 31 and 32. Simultaneous movement of the short circuiting plungers will result in a change in the reflecting plane of the energy incident thereupon and provide for the return of the reflected energy to the main transmission line through waveguide section 12 with the desired shift in phase. The short-slot hybrid junction coupler together with waveguide sections 24 and 25 housing the dual energy-absorbing load means 27 and 28 and variable energy reflection means 30 collectively comprise the branch line 42 coupled to the main transmission line 10.
Each of the energy-absorbing means comprises a cylindrical housing member 43 joined to the top broad wall of the waveguide sections and supports a fluid coolant containing shell member 44 having a substantially tapered section to provide impedance-matching means of the energy-absorbing means to the branch line. A material for example quartz glass or plastic materials such as No. 7900 glass containing approximately 96 percent silicon and cross-linked polystyrene thermosetting plastics are preferably employed for the shell member 44. The upper end of this member is connected to a threaded sleeve member 45 by a threaded end cap member 46. Plural O-ring members (not shown) maintain a fluidtight relationship within the energy-absorbing means. Inlet and outlet fluid conduit means 47 and 48 of a suitable lossy dielectric medium having high energy absorption qualities are provided within the shell member to absorb the coupled microwave energy.
Further particulars with regard to the internal structure within the energy-absorbing load means may be seen in FIG. 3. Additional features and details of the construction of such energy-absorbing means are enumerated in the aforereferenced patent application and need not be further described for the purposes of the present invention. The
simultaneous variation of the degree of insertion of the energy-absorbing means will, therefore, control the amplitude of the energy returned to the transmission line. Such variation of the degree of insertion and resultant load-to-line coupling is achieved by rotation of actuator means 29 driven by tuner knob 49 or any other suitable arrangement. It is also understood that other fluidtight energyabsorbing means such as the socalled "reentrant coaxial type" may be utilized in the practice of the invention. Such devices are disclosed in copending patent application, Ser. No. 889,383, filed Dec. 31, 1969 by Henry W. Perreault, as well as the type disclosed in US. Pat. No. 3,044,027, issued July 10, I962 to D. D. Chin et al. and entitled Radio Frequency Load. In applications where the energy levels are lower the solid energy-absorbing means may be utilized and the high-level energy levels will preferably be handled by the fluid coolant absorbing means. Dielectric, as well as probe coupling, may be utilized with the energy-absorbing means.
In the operation of the disclosed device the incidence of microwave energy in the main line section 11 results in the introduction of such energy at the original transmitted power level to the input port 20 of hybrid junction coupler 15. In the hybrid junction the energy is divided into two portions with one-half traversing passageway 17 to port 23 and the remaining half traversing the coupling iris 19 to enter the passageway 16. In accordance with the well-known functioning of this component the energy in passageway 16 arrives at port 22 with a delay relative to the energy entering port 23. The amplitude of the desired energy transmission is adjusted by means of energy-absorbing load means 27 and 28. Independently, the energy reflection means 31 and 32 are varied to provide a new reflecting plane to result in a shift of the energy returned through the hybrid junction 15 to the output waveguide section 12. The depth of insertion of the energy-absorbing means within the waveguide sections 24 and 25 provides for the independent control of the amplitude while the simultaneous adjustment of the short circuiting plunger members 31 and 32 provides a new reflection coefficient for the energy incident thereupon.
Each time the reflected energy traverses the coupling iris 19 it divides into symmetrical wave components with one-half propagating directly through to the port aligned at the opposite end of the hybrid junction and the other half crossing over to the adjacent passageway. In view of the 90 phase lag with each traversal of the coupling iris the half of the energy reflected through passageway 16 arrives at port 20 out of phase with the energy arriving there from passageway 17. As the result of this orientation there is phase cancellation and no reflected energy will be redirected through the input waveguide section 11 to the main transmission line. The remaining energy from passageways l6 and 17, however, arrives at output port 21 reenforced in phase and the resultant sum of the microwave energy is propagated through output waveguide section 12 at the new amplitude of power relative to the original incident energy and an additional phase shift provided by the variable energy-reflecting means. In the conventional operation of short-slot hybrid junctions it is well known that if two cotenninous ports are simultaneously short circuited by fixed energy reflection means the energy introduced through the input port will be reflected through the output port without a relative phase shift. In the applications heretofore enumerated where a shift is desired varying from a few degrees to possibly i 90 such a variable phase shift may now be furnished at any power level by means of variation of the short circuiting members disposed at the terminal ends of the branch line.
Referring next to FIG. 3 an alternative embodiment of the invention will be described which incorporates variation of a total waveguide section terminating the branch line. In this embodiment the energy-absorbing means will be similar to those heretofore described and are indicated generally by numeral 50.
.luxtapositioned slidably adjustable waveguide sections fill are terminated by a fixed reflecting end wall member M which is spaced at fixed distance from the coupling aperture to the shell member M conventionally, one-quarter of a guided wavelength. The inner end of the waveguide section 511 is provided with a choke arrangement 53 defined with the adjacent wall surfaces of a waveguide section 545. conventionally, the length of the choke section 53 is one-half of a guided wavelength. Microwave transmission line stretcher has a similar arrangement and it will be noted that waveguide sections 51 are disposed in a telescoping manner with waveguide section 54L A side drive is provided by a threaded screw member 55 anchored to collar member 56 and provided with a clearance hole in collar member 57 while threadably engaging collar member The latter collar member 5% is permanently secured to the movable waveguide sections fill. A guiding rod member 59 also engages the collar members 56, 57 and Etl on the opposing side to thereby support the movable structure. Actuation of the movement of the waveguide sections 51 relative to waveguide section 5% is achieved by control knob an engaging threaded actuator 55. The energyabsorbing means are adjusted to provide the amplitude of energy desired and the phase shift characteristic is then provided for the reflected unabsorbed energy by variation of the complete section. It will be noted that as in the previous described embodiment the dual combined energy absorbing and reflecting means are simultaneously actuated in the juxtapositioned waveguide arrangement.
The disclosed invention provides for simultaneous movement of both the shunt conductance provided by the energyabsorbing means, as well as adjustment of the reflection plane to thereby alter the phase of reflected unabsorbed energy returned to the main transmission line. The aforesaid adjustments are independent and provide in an integral mechanical configuration a very efficient microwave energy phase shifter device for any level of power.
Various modifications and alterations will readily occur to those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims. It is intended, therefore, that the embodiments shown and described herein be considered as illustrative only and not in a limiting sense.
What is claimed is:
1. A microwave energy phase shifter device comprising:
means for guiding said energy along a main transmission line;
means for guiding said energy along a branch line coupled to said main line and terminating in variable energyreflecting means;
said branch line further comprising energy-dividing means and juxtapositioned energy-guiding means coupled to said dividing means;
means for absorbing said energy coupled to each of said branch line guiding means at a point spaced from said reflecting means and being adapted to be removably inserted therein;
means for simultaneously adjusting the depth of insertion of said energy-absorbing means in each associated guiding means to control the amplitude of reflected energy returned to the main transmission line;
and means for varying the spacing of said absorbing means relative to said reflecting means to thereby vary the phase characteristics of said reflected energy.
2, A microwave phase shifter device according to claim ll wherein said variable energy reflecting means comprise movable short circuit conductive members disposed within each associated guiding means and means for simultaneously actuating said movable members.
3. A microwave energy phase shifter device comprising: means for guiding said energy along a main transmissions line; means for guiding said energy along a branch line coupled to said main line and terminating in variable energy reflectin means; said branc lme further comprising energy-dividing means and juxtapositioned energy-guiding means coupled to said dividing means;
means for absorbing said energy coupled to each of said branch line guiding means and being adapted to be removably inserted therein;
said absorbing means being coupled to said branch line at a point spaced a tired distance from said energy-reilecting means;
means for simultaneously adjusting the depth of insertion of said energy-absorbing means to control the amplitude of reflected energy returned to the main transmission line;
and means for varying the distance of said energy-absorbing means and energy-reflecting means relative to the energydividing means to vary the phase characteristics of said reflected energy.
4. A microwave energy phase shifiter device according to claim 3 wherein said variable energy-reflecting means include separate energy-guiding section supporting said energy-absorbing means slidably disposed within said juxtapositioned guiding means and actuating means for simultaneously adjusting the spacing of the movable and juxtapositioned guiding sections relative to one another.
5. A microwave energy phase shifter device comprising:
waveguide means having broad and. narrow walls providing a main transmission line;
a branch waveguide line coupled to a narrow wall of said main line and terminating in variable energy-reflecting means;
said branch line further comprising a hybrid junction having a common wall defining juxtapositioned passageways with a coupling iris opening and waveguide means connected to each of said passageways;
means for absorbing said energy disposed parallel to the narrow walls of each branch waveguide means and being adapted to be inserted a variable distance within said waveguide means;
a conductive housing member secured to a broad wall of each branch waveguide means and encircling said energy absorbing means;
means for simultaneous movement of said energy-absorbing means relative to said housing members to control the amplitude of energy in said branch line;
and means for simultaneously adjusting the distance of said energy-reflecting means relative to said hybrid junction to thereby vary the phase characteristics of the energy reflected back to the main transmission line.
b. A microwave energy phase shifter according to claim 5 wherein said means for varying the energy-reflecting means comprise gang-tuned movable short circuit conductive members.
7. A microwave energy phase shifter device according to claim 5 wherein said means for varying said energy-reflecting means comprise a separable waveguide section including said energy-absorbing means and housing members slidably supported within said juxtapositioned waveguide means con nected to said hybrid junction and actuating means for controlling the movement of said separable waveguide section.