US-20260129741-A1 - PLASMA RADIO-FREQUENCY WAVEGUIDE SWITCH

US20260129741A1US 20260129741 A1US20260129741 A1US 20260129741A1US-20260129741-A1

Abstract

The plasma radio-frequency (RF) waveguide switch utilizes the RF transmission cutoff frequency property of ionized gas (plasma) to implement an RF switch in waveguide. The plasma RF waveguide switch includes a waveguide defining an inner space and having an input port for receiving an RF signal and an output port, a plasma chamber placed in the inner space, ionizable gas contained in the plasma chamber, and at least one activator configured to activate the ionizable gas into a plasma state. The plasma chamber is self-contained and hermetically sealed, and therefore, the plasma RF waveguide switch does not require an external gas tank or gas supply device. The plasma chamber includes a first dielectric hermetic waveguide window at a side of the plasma chamber and a second dielectric hermetic waveguide window at an opposite side of the plasma chamber.

Inventors

Peter A. Stenger
Adeyemi Adegbite
Grant C. Miars

Assignees

NORTHROP GRUMMAN SYSTEMS CORPORATION

Dates

Publication Date: 20260507
Application Date: 20241101

Claims (16)

1 : A plasma radio-frequency (RF) waveguide switch, comprising: a waveguide defining an inner space and having an input port for receiving an RF signal and an output port; a plasma chamber placed in the inner space, wherein the plasma chamber is self-contained and hermetically sealed, and wherein the plasma chamber comprises a first dielectric hermetic waveguide window at a side of the plasma chamber and a second dielectric hermetic waveguide window at an opposite side of the plasma chamber; ionizable gas contained in the plasma chamber; and at least one activator configured to activate the ionizable gas into a plasma state.
2 : The plasma RF waveguide switch of claim 1 wherein the ionizable gas includes argon, xenon, neon, krypton, hydrogen and/or helium.
3 : The plasma RF waveguide switch of claim 1 wherein the first and second dielectric hermetic waveguide windows are λ/2 thick or electrically thin, where λ is a wavelength of the RF signal received in the waveguide.
4 : The plasma RF waveguide switch of claim 1 wherein the activator comprises one or more filaments placed inside the plasma chamber and filament electrodes through hermetic feedthroughs connecting the one or more filaments to a ballast.
5 : The plasma RF waveguide switch of claim 4 wherein the one or more filaments are placed along broad walls of the waveguide near the middle of a width of the plasma chamber, minimizing the parasitic effects on the RF signal since the electric field gradients are minimal at the center of waveguide broad wall.
6 : The plasma RF waveguide switch of claim 1 wherein the activator comprises a capacitor comprising a first electrode layer disposed outside the plasma chamber and a second electrode layer disposed outside the plasma chamber facing the first electrode layer.
7 : The plasma RF waveguide switch of claim 1 wherein the activator comprises an induction coil disposed outside the plasma chamber.
8 : A single pole double throw (SPDT) switch, comprising: a waveguide defining an inner space and comprising an input section for receiving an RF signal and a first and second output sections that separate from the input section at a waveguide junction of the waveguide; a first plasma chamber placed in the first output section, wherein the first plasma chamber is self-contained and hermetically sealed, and wherein the first plasma chamber comprises a first dielectric hermetic waveguide window at a side of the first plasma chamber and a second dielectric hermetic waveguide window at an opposite side of the first plasma chamber; a second plasma chamber placed in the second output section, wherein the second plasma chamber is self-contained and hermetically sealed, and wherein the second plasma chamber comprises a first dielectric hermetic waveguide window at a side of the second plasma chamber and a second dielectric hermetic waveguide window at an opposite side of the second plasma chamber; ionizable gas contained in the first and second plasma chambers; a first activator configured to activate the ionizable gas in the first plasma chamber into a plasma state; and a second activator configured to activate the ionizable gas in the second plasma chamber into a plasma state.
9 : The SPDT switch of claim 8 wherein a distance between the waveguide junction and the first plasma chamber is λ/4, where the λ is a wavelength of the RF signal received in the input section.
10 : The SPDT switch of claim 8 wherein a distance between the waveguide junction and the second plasma chamber is λ/4, where the λ is a wavelength of the RF signal received in the input section.
11 : The SPDT switch of claim 8 wherein the ionizable gas includes argon, xenon, neon, krypton, hydrogen and/or helium.
12 : The SPDT switch of claim 8 wherein the first and second dielectric hermetic waveguide windows of the first plasma chamber are λ/2 thick or electrically thin, and the first and second dielectric hermetic waveguide windows of the second plasma chamber are λ/2 thick or electrically thin, where λ is a wavelength of the RF signal received in the input section.
13 : The SPDT switch of claim 8 wherein the first activator comprises one or more filaments placed inside the first plasma chamber and filament electrodes connecting the one or more filaments to a ballast, and the second activator comprises one or more filaments placed inside the second plasma chamber and filament electrodes connecting the one or more filaments to the ballast.
14 : The SPDT switch of claim 13 wherein the one or more filaments of the first activator are placed along broad walls of the waveguide near the middle of a width of the first plasma chamber, and the one or more filaments of the second activator are placed along broad walls of the waveguide near the middle of a width of the second plasma chamber.
15 : The SPDT switch of claim 8 wherein the first activator comprises a capacitor comprising a first electrode layer disposed outside the first plasma chamber and a second electrode layer disposed outside the first plasma chamber facing the first electrode layer, and the second activator comprises a capacitor comprising a first electrode layer disposed outside the second plasma chamber and a second electrode layer disposed outside the second plasma chamber facing the first electrode layer.
16 : The SPDT switch of claim 8 wherein the first activator comprises an induction coil disposed outside the first plasma chamber, and the second activator comprises an induction coil disposed outside the second plasma chamber.

Description

BACKGROUND Waveguide based RF switching networks are used to route high power radio-frequency (RF) signals with very low loss in some paths and with very high isolation in other paths. Radar sensors require switching between a high power transmit signal path and receive path. This switching must often be performed rapidly (in less than 1 microsecond) for radar applications. This combination of requirements often limits radar system performance, warranting the active development of more waveguide switch options. High switching speeds, high power handling and high isolation are of utmost importance for radar and electronic warfare (EW) systems. State of the art waveguide switching devices include bias controlled positive-intrinsic-negative (PIN) diodes that connect across the waveguide height at the center where the voltage is maximum in the dominant transverse electric TE10 mode. Ferrite element switches are often implemented in the waveguide volume which use the Faraday rotator effect to achieve the ON/OFF switching states. Electromechanical waveguide switches are also used for high isolation applications, but they are quite large and slow. Plasma waveguide switches have been developed by using metallic or insulating cone configurations, or by using a gas reservoir. However, these designs are not considered practical to deploy as a commercial product or product line these days. There have been recent breakthroughs in using light to generate a free electron plasma in silicon and using the free electron plasma as a waveguide switch. This is another approach to the plasma waveguide switch, but is proprietary and considered to have lower performance such as in isolation and frequency range. SUMMARY The disclosed invention provides a plasma radio-frequency (RF) waveguide switch to solve the problems described above, and also provides RF-signal control apparatuses using the plasma RF waveguide switch of the disclosed invention. The plasma-based RF waveguide switch of the disclosed invention offers substantially enhanced performance in switching speed and isolation that make it highly desirable for radar applications. The plasma RF waveguide switch of the disclosed invention utilizes the RF transmission cutoff frequency property of ionized gas (plasma) to implement an RF switch in waveguide. The ionizable gas is in general highly transmissive when the gas is not ionized, but sufficient ionization of the gas results in a highly reflective RF media below the plasma cutoff frequency. The plasma RF waveguide switch of the disclosed invention includes a self-contained plasma volume that does not require an external gas tank or gas supply device. This configuration differs from previous laboratory plasma waveguide switches that use the reflective nature of plasma, because the plasma RF waveguide of the disclosed invention is much cheaper and simpler to build and operate, also providing enhanced performance practically applicable for radar and EW applications. These advantages and others are achieved, for example, by a plasma radio-frequency (RF) waveguide switch that includes a waveguide defining an inner space and having an input port for receiving an RF signal and an output port, a plasma chamber placed in the inner space, ionizable gas contained in the plasma chamber, and at least one activator configured to activate the ionizable gas into a plasma state. The plasma chamber is self-contained and hermetically sealed. The plasma chamber includes a first dielectric hermetic waveguide window at a side of the plasma chamber and a second dielectric hermetic waveguide window at an opposite side of the plasma chamber. The ionizable gas may include argon, xenon, non, krypton, hydrogen and/or helium. The first and second dielectric hermetic waveguide windows may be λ/2 thick or electrically thin, where λ is a wavelength of the RF signal received in the waveguide. The activator may include one or more filaments placed inside the plasma chamber and filament electrodes through hermetic feedthroughs connecting the one or more filaments to a ballast. The one or more filaments may be placed along broad walls of the waveguide near the middle of a width of the plasma chamber, minimizing the parasitic effects on the RF signal since the electric field gradients are minimal at the center of waveguide broad wall. In another embodiment, the activator may include a capacitor including a first electrode layer disposed outside the plasma chamber and a second electrode layer disposed outside the plasma chamber facing the first electrode layer. In still another embodiment, the activator may include an induction coil disposed outside the plasma chamber. These advantages and others are further achieved, for example, by a single pole double throw (SPDT) switch that includes a waveguide defining an inner space and including an input section for receiving an RF signal and a first and second output sections that separate from the input section at a w