Vladislav S. Igumnov

Formation of pulses with controlled parameters in a resonance microwave compressor employing oscillation-mode transformation

Results of an experimental study of the formation of rf pulses with controlled power, duration, repetition rate, and envelope parameters in a resonance compressor employing oscillation-mode transformation are presented. The pulse parameters are varied by using tuned intermodal coupling elements. A possibility of the formation of a series of subsecond and nanosecond rf pulses in the partial extraction of energy and nanosecond pulses of various durations in single complete extraction of energy from the compressor resonator is shown.

Analysis of microwave energy extraction process at the resonator with controlled transformation of oscillation modes

It is considered an operation of resonance microwave compressor with extraction of energy by means of controlled transformation of oscillations modes on a coupling window of the resonator with short-cut waveguide stub. Using dispersion matrix method with a device model we carried out the analysis of the extraction process in case of transformation of high-Q mode into down to the limit low-Q mode. There are obtained the expressions for description of the transient processes during accumulation and extraction processes. It is shown researched compressor is possible to shape the microwave pulses with controlled power, duration and envelope shape.

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.

Multichannel Systems of Resonant Microwave Pulse Compression

Different designs of multichannel resonant microwave pulse compression systems operating in X- and S-bands are described. The output pulsed microwave power of these systems is expected to be severalfold greater than that of compression systems with a single output channel. These compression systems can be used as compact sources of high-power nanosecond-duration microwave pulses, sources of synchronized sequences of microwave pulses, and sources for development of phased arrays of compressed microwave pulses. In particular, the authors describe the characteristics of a two-channel S-band resonant microwave pulse compression system with nanosecond-duration output pulse and an output pulsed microwave power of 1 GW. The operation of a four-channel X-band compression system with a possible eightfold output pulsed microwave power increase, relatively to the microwave power in the cavity, is also described. The design of an eight-channel system with a 16-fold output pulsed microwave power increase is reviewed. The parameters of an X-band compression system with multichannel output unit formed as a set of interference microwave switches extracting the energy in synchronism are presented.

Modeling of output power in a resonant microwave compressor with the transformation of the oscillations

The results of experimental studies of the interaction modes of communication on the window of a multimode waveguide resonator with a short train are presented. The experimentally determined dependence of the mode coupling parameters of the plume and windows due to the loop resonator. Based on these experiments, the model of the process of energy transfer from mode to mode in the microwave compressor with the output power fluctuations in the transformation of the resonator box with a train. Model describing a relation between the parameters of output pulses and the parameters of the compressor device mode coupling, which qualitatively agrees well with experimental data.

Modeling process of interaction electromagnetic waves in a resonant microwave compressor

The results of experimental studies of the interaction modes of communication on the window of a multimode waveguide resonator with a short train are presented. The experimentally determined dependence of the mode coupling parameters of the plume and windows due to the loop resonator. Based on these experiments, the model of the process of energy transfer from mode to mode in the microwave compressor with the output power fluctuations in the transformation of the resonator box with a train. Model describing a relation between the parameters of output pulses and the parameters of the compressor device mode coupling, which qualitatively agrees well with experimental data.

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.

Forming Nanosecond Microwave Pulses by Transformation of Resonant Cavity Mode

The microwave pulse compression procedure consists of excitation of a working mode in a resonant cavity and transforming the mode into an auxiliary one that is coupled to an output line. Both transforming and coupling involve switching. Transients were calculated by recursion relations giving higher accuracy at short time constants. Demonstration experiments were run in the X-band. The compressor prototype showed power amplification of 15 dB at an output pulse width of 2.7 ns and a peak power of 1.5 MW. Mode transformation efficiency approached 0.7. A sequence of nanosecond and sub-nanosecond microwave pulses within the length of an input feeding pulse can be, in principle, obtained.

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.

Formation of high power microwave pulses with adjustable parameters in active X-band RF compression systems

The work presents the results of theoretical and experimental studies of the formation of microwave pulses with the adjustable power, duration, repetition rate and the envelope form during energy output from the cavity by controlled transformation of the oscillation mode at the waveguide stub coupling aperture. Pulse parameters are changed by adjustable elements of the coupling of modes, which directly affect to the coefficient of the coupling of modes h. The possibility to form a series of subnanosecond MW pulses at a fractional energy output and nanosecond pulses of various pulse duration at a single complete output of high frequency energy from the compressor cavity is demonstrated. The envelope of the pulses is calculated through the recurrence relations between the amplitudes of waves in the system, the relations between which have been recorded according to the scattering matrix method. Using this approach on passive X-band RF pulse compression system, we obtained power gain of 8-9 dB, 8-10 ns pulse duration at 9.248 GHz.