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The paper presents new results on the development of a method to generate ultrahigh-power short-microwave pulses by using a known principle of compression (reduction in pulse duration accompanying with increase in pulse amplitude) of a frequency-swept wave packet propagating through a dispersive medium. An oversized circular waveguide with helical-corrugations of its inner surface ensures an eigenwave with strongly frequency dependent group velocity far from cutoff. These dispersive properties in conjunction with high rf breakdown strength and low Ohmic losses make a helically corrugated waveguide attractive for increasing microwave peak power. The experiments performed at kilowatt power levels, demonstrate that an X-band microwave pulse of 80 ns duration with a 5% frequency sweep can be compressed into a 1.5 ns pulse having 25 times higher peak power by optimizing the frequency modulation of the input wave packet. [ABSTRACT FROM AUTHOR]

An effective five-channel quasi-optical multiplexer, which distributes microwave signals of the frequency range of 12-90 GHz on five frequency channels, Ku, K, Ka, U, and E (frequency ranges of standard single-mode waveguides), or combines these channels into a single wave stream, has been developed for the first time. A relatively homogeneous characteristic with a total loss level of about 1.5 dB is achieved in 90% of each range band. A detailed analysis of diffraction and ohmic losses in the frequency channels of the multiplexer has been carried out. [ABSTRACT FROM AUTHOR]

We consider in detail the method allowing one to input and output the microwave radiation produced by an elecrovacuum amplifier through the same barrier window, which was proposed earlier, in the context of its application in a traveling-wave tube based on a waveguide with a helically corrugated surface. Special attention is given to the splitter of differently polarized radiation, and the results of studying this splitter at wavelengths of about 6 and 1 mm theoretically and experimentally are presented. [ABSTRACT FROM AUTHOR]

We have developed, manufactured, and studied experimentally prototypes of microwave switches operated in the 70- and 260-GHz frequency ranges and controlled by pulses of optical laser radiation. The results of their numerical simulation by the finite-difference time-domain (FDTD) method are presented, along with the design parameters of the prototypes. The switch speed is equal to 1 ns, and the microwave tuning frequency range amounts to about 10%. The process of switching with the use of a low-cost semiconductor optical laser (with a wavelength of 532 nm and a continuous-wave power of 200 MW) is demonstrated experimentally at a switched-radiation frequency of 266.68 GHz. [ABSTRACT FROM AUTHOR]

The effect of passive compression of frequency-modulated pulses in dispersive media is used to raise the microwave radiation peak power to a multigigawatt level. A waveguide with a helically corrugated surface is applied as a dispersive medium, and a relativistic 3-cm backward-wave oscillator with an accelerating voltage decaying within the pulse duration serves as a source of frequency-modulated pulses. The compression of pulses to an FWHM of 2.2 ns attended by a rise in the peak power by a factor of 4.5 (to 3.2 GW) is demonstrated with a SINUS-6 accelerator. [ABSTRACT FROM AUTHOR]

We propose a modification of the iterative method for synthesis of waveguide mode converters, which allows obtaining various elements of microwave transmission lines with a wide operating frequency band. The efficiency of the synthesis is illustrated by the calculated waveguide components. This method makes it possible to synthesize converters with significantly improved characteristics, e.g., a converter of the TM0,1 mode to the rotating TE3,1 mode, a converter of the TM0,1 to the TE1,1 mode, a converter of the TE1,1 mode of a smooth waveguide to the HE1,1 mode of a corrugated waveguide, and a waveguide 90° bend for the TE1,1 mode. [ABSTRACT FROM AUTHOR]

We show theoretically that the use of a circular oversized waveguide with a helically corrugated internal surface as a dispersive medium ensures efficient compression of frequency-modulated microwave pulses up to peak powers of about 10 GW. According to the calculations, a pulse with the required frequency modulation can be obtained in a relativistic backward-wave oscillator operated in the 3-cm wavelength range and producing an output power of hundreds of megawatts. In a demonstration experiment, a 80-ns pulse of kilowatt power with frequency modulation in a 5% band was compressed to a 1.5-ns pulse with a 25-fold power amplification. [ABSTRACT FROM AUTHOR]

We propose a realization of the iterative method for synthesis of waveguide-mode converters in the case of a two-dimensional deformation of the waveguide. Examples of the converters calculated using this method are presented. The method allows finding essentially new solutions for the problems of development of mode converters. [ABSTRACT FROM AUTHOR]

We develop a method based on Huygens’ principle for calculation of the traveling-wave field in a cylindrical oversized waveguide with smooth and shallow wall corrugations with allowance for diffraction by the nonsymmetric end of the waveguide. Algorithms for synthesizing the specified field distribution on the surface of such a waveguide are proposed. The performed experiments confirm the adequacy of this approach for calculation of oversized electrodynamic systems. [ABSTRACT FROM AUTHOR]

We consider the problem of propagation of a microwave pulse with given transverse structure through a waveguide converter of the circular-waveguide modes from TM01 to TE11 The FDTD method is used for numerical study of the mode composition of the pulse at the converter output as a function of its duration.The frequency characteristic of the converter is obtained from the Fourier response to a wide-spectrum pulse. [ABSTRACT FROM AUTHOR]

We propose an iterative method for synthesis of waveguide mode converters. An application of this method for bent circular waveguides is considered. Examples of synthesized converters calculated using this method are presented. The method offers fundamentally new solutions to the problems of mode converter development. [ABSTRACT FROM AUTHOR]

The phenomenon of passive compression of frequency-modulated (FM) pulses in a dispersive media (DM) was used to increase the peak microwave power up to the multigigawatt level. A helically corrugated waveguide was used as the DM, while a relativistic X-band backward-wave oscillator (RBWO) with a descending-during-the-pulse accelerating voltage served as a source of FM pulses. Compression of pulses down to a halfwidth of 2.2 ns accompanied by a 4.5-fold power increase up to a value of about 3.2 GW has been demonstrated. [ABSTRACT FROM AUTHOR]

A gyrotron backward wave oscillator (gyro-BWO) with a helically corrugated interaction waveguide demonstrated its potential as a powerful microwave source with high efficiency and a wide frequency tuning range. This letter presents the theory describing the dispersion properties of such a waveguide and the linear beam-wave interaction. Numerical simulation results using the PIC code MAGIC were found to be in excellent agreement with the output measured from a gyro-BWO experiment. [ABSTRACT FROM AUTHOR]

For the first time, we demonstrate experimentally the possibility of Cherenkov superradiant generation with a phase imposed by an ultrashort seed microwave pulse. The phases of seed and initiated Ka-band microwave pulses were correlated with the accuracy of 0.5-0.7 rad for the power ratio down to --35 dB. Characteristics of such a process were determined in the frame of a basic theoretical model that describes both spontaneous and stimulated emission of an electron beam moving in corrugated waveguides. The obtained results open up opportunities of reaching extremely high radiation power density in phased arrays of short-pulse coherently operating microwave generators. [ABSTRACT FROM AUTHOR]