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It is considered and offered the waveguide band elimination filter with the working mode H10 that can be used in millimeter waves devices such as up, down-converters, mixer, etc. For example, if the millimeter wave up-converter operates with two input signals which have frequencies f1, f2 and the output signal has frequency f3 equals f1 + f2(f2 very much less than f1), we need in small level of the signal with the frequency f1 at the up- converter output. The filter consist of the rectangular metallic waveguide supporting mode H10 in which it is inserted the periodic dielectric structure (the Bragg structure). The structure cross-section is the same as the cross-section of the waveguide. The characteristics of the filter was calculated by using analogy in electromagnetic the waveguide propagation and optical the wave propagation in the medium with the specific refractive index vector N. This conception can be applied for party-filled waveguide in the case when the Brillouin decomposition of the waveguide waves into plane waves is correct and the transformation of the incident (propagating) mode into other the mode types is absent. In this work were calculated the spectrum energy transmittance T(f) in the filter stop band using formulae and the wavelength (lambda) $0) (or frequency f0 equals c/(lambda) 0, c is speed of light) in the center of this band using the characteristic equation obtained in the result of theoretical consideration. Dielectric structure of the filter is made in the form of the polystyrene plates's assemblage with the air gaps. Plates (the quantity n equals 10) have thickness t approximately equals 0.223 (lambda) 0 and the air gaps (the quantity m equals 9) have thickness l approximately equals 0.878 (lambda) 0. In the result of calculation we have following parameters of the filter: f0 approximately equals 32.93 GHz, (Delta) f equals fb2 - fb1 approximately equals 3.13 GHz, where fb2, fb are frequencies at T(t) approximately equals 0.6%, fb2 approximately equals 34.50 GHz, fb1 approximately equals 31.37 GHz. At the frequency fb3 approximately equals 35.2 GHz we have height transmittance T(fb3) approximately equals 0.99. It is also shown that an increase of the distance l between dielectric plate leads to a shift of frequency f0 to the side of low frequencies. There is an optimum distance l in which at the frequencies f less than fb3 the filter has low transmittance and at the frequencies f greater than fb3 the one has high transmittance. The described approach can be used for calculation and more complex multilayer the waveguide structures and can be applied at treatments different of the EHF devices.
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