Stanislav Gorev

Analysis of microwave interference switches with distributed power of switched wave and plasma gas-discharge switching

This paper reports on development of effective cascade type microwave interference switches using waveguide H-tees providing total transition attenuation value of about -50dB at the non-transmitting state, the power losses of -2-3dB at the transmitting state, and the working power compared to the one of a regular waveguide. These switches have different types of connections of two or three H-tees. Different designs provide different distributions of switched wave power between tees and provide different power levels of the switched wave. Characteristics of the switches made of tees matched from their side arms and of unmatched ones were calculated using the scattering matrix method. It was shown the matched tees used in the design allow decreasing by several times the power level of the switched wave and that increases the operating power and stability of the switching process. While some definite combination of unmatched tees allow increasing the power level of the switched wave and may provide effective switching of the transmitted wave at decreased power level. It was shown experimentally the cascade switches could be used as effective energy extraction device in an active resonant microwave compressor also.

High-power microwave pulse compressors with a variable geometry of accumulative resonant cavity

We propose a new approach to designing the geometry of large accumulative systems of compact Microwave Pulse Compressors (MPCs) used to generate ∼10-ns rectangular pulses in the S- and X-bands. A resonant system having a variable geometry replaces the traditional cylindrical, spherical, or prism-shaped storage cavity. Our design uses standard structural elements made from single-mode or moderately multimode waveguide sections with ends terminated by waveguide tees or their analogs. One arm of each T-junction connects to a section of the resonant cavity, the second arm is close-circuited, and the third arm connects to an adjacent linear section. The plasma switch, used to Q-spoil the cavity, mounts in the side arm of another tee. Thus, the accumulative system is formed using compact planar and three-dimensional structures (or combinations thereof) by alignment of standard elements through the arms of tees or their analogs. The proposed approach leads to develop of very compact systems. Integration of an MPC into an existing RF generator is also straightforward without significantly expanding its footprint. We present schemes for several types of MPCs with variable geometry of the accumulative system. Our work shows that a specific architecture of the accumulative system, accounting for the relevant distribution of energy and method for pulse extraction, is useful in building MPCs with discretely controlled output pulse parameters. We also show that the variable geometry of the accumulative system makes it possible to design compact, cascade compression systems with power multiplication of the traveling wave in the resonant cavity. This paper also demonstrates the first results from an experimental study of MPCs with a planar accumulative system.

Switching of circular waveguide H11 mode by plasma of gas microwave discharge

The report presents the results of experimental study of switching the H11 mode by gaseous discharge plasma formed in microwave switches made of S-band circular waveguides. The objective of the study was switching executed by a microwave discharge inside a quartz tube located in the polarization plane of the switched wave in a regular waveguide or switching arm of the waveguide H-tee. The main conditions of the effective switching of H11 mode in the waveguide capable to transmit the higher E01 mode as well were determined by model experiments at low power level by imitating a plasma channel by a section of thin wire inserted into the discharge area. The portions of total power in transmitted, reflected and dissipated waves during the switching process in nitrogen, argon and argon and SF6 mixture was also estimated during the experiments run at high power level. The switching was realized inside the tube under insulating gas pressure of ~10-760 Tor and with transmission of microwave pulse with pulse power 2 MW and pulse width of 3mcs along the switch. It was found out that the switching process is more effective during first 10-20 ns. In particular it was determined that during this time the working mode power may be amplified by the plasma of microwave discharge. Therefore the assumption about the possible overestimation of the active microwave pulse compressor amplification with plasma gas discharge switches was formulated. The first data concerning switching of H11 mode in the regular waveguide with the diameter close to the critical diameter for H01 and E11 modes, switching in the H-ee made of such waveguides and switching in the transmitting type cavity which is cut off for the upper resonant modes were obtained. The influence of mode coupling and weak reflections forming resonant cavities inside the waveguide on the switching process were noticed. Operation of working prototypes of S-band active pulse microwave compressors demonstrated that the use of plasma microwave switches with the H11 mode of circular waveguide allowed producing steady nanosecond microwave pulses with the pulse power of up to 1 GW, pulse repetition frequency of up to 100 Hz and when the power losses were about 1...2 dB.