US3801932A

US3801932A - Microwave high power phase shifter utilizing cascaded directional couplers and plasma thyratrons

Info

Publication number: US3801932A
Application number: US00358791A
Authority: US
Inventors: H Coldie
Original assignee: US Air Force
Current assignee: US Air Force
Priority date: 1973-05-09
Filing date: 1973-05-09
Publication date: 1974-04-02
Anticipated expiration: 1991-04-02

Abstract

A microwave high power phase shifter is formed by two pairs of cascaded short slot hybrids whose slots are filled by low pressure gaseous volumes. Activation of the gas to the plasma state provides single-bit phase shifting action in the milliwatt to megawatt power range.

Description

United States Patent M/DPA A/VE Coldie [451 Apr. 2, 1974 1 MICROWAVE HIGH POWER PHASE [56] References Cited SHIFTER UTILIZING CASCADED UNITED STATES PATENTS DIRECTIONAL COUPLERS AND PLASMA 3,008,097 11/1961 Tctenbaum et al 333/10 X THYRATRONS 3,229,205 1/1966 Pitts et a1. 333/10 ux 5 Inventor; Han-y Comic Randaustown? 3,324,420 6/1967 Blachier et a1 333/7 [73] Assignee: The United States of America as represented y the Secretary of the Primary ExammerPaul L. Gensler Air Force, Washington; DC.

22 Filed: May 9, 1973 [57] ABSTRACT A microwave high power phase shifter is formed by [21] Appl' 8 two pairs of cascaded short; slot hybrids whose slots are filled by low pressure gaseous volumes. Activation Cl. 333/31 333/7 PL ofthe gas to the plasma state provides single-bit phase [51] Int. Cl. H0lp 1/18 shifting action in the milliwatt to megawatt power [58] Field of Search 333/7 R, 10, 31 A, 98 S, range.

2 Claims, 2 Drawing Figures TERM/M4750 fl/VM 17 MICROWAVE HIGH POWER PHASE SHIFTER UTILIZING CASCADED DIRECTIONAL COUPLERS AND PLASMA THYRATRONS BACKGROUND OF THE INVENTION The operation of short slot waveguide hybrids is well known and their ability to operate as a unity coupler when two are cascaded has been an important function in balanced duplexers at high power levels. The present invention uses a unique combination of four short slot hybrids whose common wall containss a gas-filled quartz vial or a plasma thyratron switch to effect a high power single-bit phase shift action. The RF voltage in the slot of a hybrid is known to be less than that in the midplane of the input waveguide. Thus, a gas filled vial/tube located in the slot will be in a region of relatively low RF voltage, thus inhibiting an RF discharge. This inability to cause a discharge in a gas under the influence of RF electric fields is referred to as holdoff. The higher the RF holdoff potential, the greater will be the RF power that can be passed without a discharge. The plasma necessary for switching action would normally be created by applying video pulses at low potentials to suitable grids located in the plasma thyratron tubes.

SUMMARY OF THE INVENTION delay will occur depending uponthe firing ofthyratrons. In a modification, the extra line lengthis made adjustable.

DESCRIPTION OF THE DRAWINGS FIG. l shows an embodiment of the invention including four cascaded short slot hybrids, four associated thyratrons, and an inserted line length; and

FIG. 2 illustrates schematically a modification of FIG. 1 wherein an adjustable short slot hybrid is substituted for the aforesaid inserted line length.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to FIG. 1, there-is shown four cascaded short slot hybrids II, 12, 13 and 14 containing four gas-filled quartz vials l5, 16, 17 and 18 in their respective common-wall openings. At the input there is provided arm A, and at the output, arm B. Arms C and D are terminated with any conventional RF absorbent material. By inserting transmission line 19 with a preselected length l, a high power single-bit phase shifter is formed. Transmission line 19 is compatible with short slot hybrids. Vials 15, I6, 17 and 18 are connected to low potential video pulse 20, each pulse resulting in plasma for switching.

In the operation of the phase shifter, with power incident at arm A, the input power splits in nybrid 11 and recombines in hybrid 12 in C' with C and A decoupled. This action is well known and is covered in many papers, as for example, Design Aspects of Short Slot Hybrids, by R. J. Mohr in Microwave Journal, published June, 1962, and The Short Slot Junction, by H. V. Riblet in IRE Proceedings, published February, 1952. After traveling the line length l, the same action occurs from D to 'B in hybrids l3 and 14. When the plasma switches are active, the common-wall slots become conductors, the RF conductivity depending 0 strongly on the electron density in the plasma, and the power incident at arm A travels unperturbed to output arm B. The phase shift occurs because of the difference in signal travel length in each path. A further adaptation is shown in FIG. 2, where the extra path length is It is emphasized that the present invention provides a unique combination of short slot hybrids containing active elements in the common-wall slot region (such as gas vials, triggered plasma thyratrons, or other active elements). A single-bit two-part waveguide phase shifter is formed which will operate over a broad range of power levels. The phase shift magnitude can be made trimmable by using a short slot hybrid with ganged plungers as the added line length.

What is claimed is:

1. A microwave high power phase shifter comprised of first, second, third and fourth thyratrons normally in the passive state, first, second, third and fourth short slot hybrids cascaded in the recited numerical sequence, said short slot hybrids having a common-wall with an opening in said common-wall of each of said short slot hybrids, an input RF power and output arm at said first and fourth hybrid, respectively, a terminated arm at each of said firstand fourth hybrids, a transmission line of preselected length in accordance with a desired phase shift, said transmission line being .inserted at the junction of said second and third short shift action.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, ,93 Dated pril 2, 197

Inventor-(n) Harry Goldie It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On front; age, after Data Element Identifier [19] change "Coldie"'to Goldie On front page, after Data Element Identifier [75] chenge"'Coldie" to Goldie Signed and sealed this 5th day of November 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents

Claims

1. A microwave high power phase shifter comprised of first, second, third and fourth thyratrons normally in the passive state, first, second, third and fourth short slot hybrids cascaded in the recited numerical sequence, said short slot hybrids having a common-wall with an opening in said common-wall of each of said short slot hybrids, an input RF power and output arm at said first and fourth hybrid, respectively, a terminated arm at each of said first and fourth hybrids, a transmission line of preselected length in accordance with a desired phase shift, said transmission line being inserted at the junction of said second and third short slot hybrids, each of said openings in each of said short slot hybrids containing one of said thyratrons, each of said thyratrons being located in each of its respective openings to be in a region of relatively low RF voltage to inhibit an RF discharge, and means to video pulse said thyratrons to provide plasma therein for switching to effect a high power single-bit phase shift action.

2. A microwave high power phase shifter as described in claim 1 wherein said inserted transmission line is adjustable to provide a trimming of said phase shift action.