Investigation On Wave Propgation And Time Delay Characteristics Of Partially Filled Plasema Waveguide

The development of modern communication and radar technology raises higher and higher demands for high performance microwave devices. Combined with plasma technology, the performance of traditional wave devices can be greatly improved. The study in this paper mainly focuses on the wave propagation characteristics of partially filled cold plasma waveguide, aiming at learning the wave propagation characteristics of such waveguide and its potential value in microwave filter and microwave delay lines.This paper firstly discusses the general characteristics of plasma and wave propagation in plasma, and then studies the wave propagation characteristics in partially filled plasma waveguide by dividing the whole frequency domain into two parts:ω<ω_p,ω>ω_p. In each part, a characteristic equation is given. Additionally, further research is taken into the main modes (TEM, TM surface wave, TE surface wave). The work indicates that, whenω<ω_p, under the influence of frequency-based metal-like characteristics of plasma, the wave existing in partially filled cold plasma waveguide is surface wave, which has upper cut-off frequency, with velocity much lower than the speed of light, and have a lower cut-off frequency at 0. Whenω>ω_p, the performance of partially filled cold plasma waveguide is high pass, similar to the traditional double-layer dielectric-filled circular waveguide. From the perspective of whole frequency domain, the partially filled cold plasma waveguide has a stop band around plasma frequency. Based on these characteristics, further investigations are taken to study the low-pass characteristics,band-stop characteristics in middle band,adjustable time delay characteristics of partially filled cold plasma delay line. Design and simulate a plasma low pass filter with square ratio of 1.004, upper cut-off frequency at 1.72GHz, stop band from 1.72GHz to 100 GHz, out-band attenuation more than -50db. This filter is obviously different from traditional wave filter. In the specification of 5×5cm~2, design an L-band plasma double helix delay line with 29.8 ns instant time delay, -0.047 db / ns insertion loss. The comparison between plasma delay line and traditional microwave devices confirms that the delay line and low-pass filer based on partially filled cold plasma waveguide has the potential advantages which traditional microwave technology can't achieve.In a word, the work in this paper supports a theoretical basis for the possible solutions of new microwave components.