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.
The present paper reports on the recent development of several oversized millimeter wave transmission line components for different applications. The studies include a circular TE 11 -to-Gaussian beam mode converting horn, a TM 01 -to-rotating TE 31 mode converter, a TE 11 -mode 90°bend, a series of different HE 11 -mode transmission line components, a notch filter and a fast laser controlled semiconductor microwave switch.
It is known that the gyrotron radiation frequency may be unstable because of supply voltage fluctuations [1]. At the same time, some applications, such as plasma diagnostics, high resolution spectroscopy, and (possibly in the future) formation of a complex of coherently emitting gyrotrons in large setups for con trolled fusion, call for frequency stabilized radiation sources. In this study, we propose a method of gyrotron frequency stabilization by a wave reflected from a dis tant load. The influence of delayed reflections on the operation of active oscillators, including gyrotrons, has been investigated by many researchers (see, for example, [2][3][4][5][6][7][8]). However, specific schemes of gyrotron frequency stabilization by a reflected wave have not been discussed, because the reflected wave in a gyrotron with a conventional output quasi optical transducer returns to the operating space as a counter rotation mode, which weakly interacts with an elec tron beam [9]. Recently, a new type of output quasi optical transducers converting a wave arrived from the output channel (reflection or external signal) into the operating mode has been developed at the Institute of Applied Physics, Russian Academy of Sciences [10]. One might expect these transducers to make it possible to stabilize the gyrotron radiation frequency.In this Letter, we show that the wave reflected from a load, both resonant and nonresonant, can capture and stabilize the gyrotron radiation frequency if the difference in frequencies of the reflected and freely emitted (in the absence of reflections) waves does not exceed a value on the order of |R|ω 0 /Q (Q is the dif fraction Q factor and |R| is the magnitude of the reflec tance) [5]. This value is an analog of the capture band (or locking band) width when a specified external monochromatic force is exerted on the active oscilla tor [4].The self consistent equations of gyrotron, into which the wave arrives from the output waveguide after being reflected from the load, within the approxima tion of fixed longitudinal field structure and small reflectance, can be written as [2,3,9] (1)The electric field of the operating TE mode in the interaction space can be written as E = Re(E s (r ⊥ )G(z, t)), where ω 0 is the reference frequency; the gyrotron cavity is a cylindrical segment with a mean radius r 0 close to the critical one; E s (r ⊥ ) = -i[∇ ⊥ ψ, z 0 ]/k describes the transverse structure coinciding with the transverse structure of one of the cavity modes; k = ω 0 /c; ψ = J m (kr)e -imϕ ; r and ϕ are the radial and azi muthal coordinates, respectively; a(t) = |a(t)|e iφ(t) is the slowly varying in time dimen sionless complex field amplitude; f(z) = exp(-3(zz 0 ) 2 / ) is the longitudinal field structure (it is assumed that |f(0)| = |f(2z 0 )| = |f max |/e 3 ); a τ is the field amplitude at instant t -τ; τ is the delay time; ω r is the real part of the cold cavity frequency; R = |R|e iα is the complex coefficient of reflection from the load; p = (p x + ip y ) / ( β ⊥0 m e cγ 0 ) is the dimension le...
UDC 537.52We 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.
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