含有铁氧体圆杆的矩形波导的散射矩阵及其等效线路

本文尝试用四端网络法研究非互易微波铁氧体器件。首先,把一节含着一根铁氧体杆的三厘米波段的矩形波导看作四端网络,进行阻抗和散射系数的测量。由测得的散射矩阵求出了T形等效线路,结果表明,小直径铁氧体杆具有并联容性电纳的性质,电纳的数值随外磁场的变化范围很大,与可调螺钉的作用十分相似。其次,把两根铁氧体杆沿波导纵向排列,在实验中考察了这种相继阻碍物的等效线路,结果表示,只要相邻阻碍物的距离足够大,总的等效线路可用“单元”等效线路的串联表示。最后,以分析相移网络为例,说明了等效线路的应用。用这一方法研究波导中的多体散射,具有独特的优点。

SCATTERING MATRIX AND EQUIVALENT CIRCUIT OF AN X-BAND RECTANGULAR WAVEGUIDE CONTAINING FERRITE POSTS

This paper is intended to describe the properties of nonreciprocal microwave ferrite devices from the four-terminal network analysis. First, the impedance and the scattering matrix of an X-band rectangular waveguide containing a transversely magnetized ferrite post are measured as a function of the (1) diameter of the post, (2) position of the post in the waveguide, and (3) applied d. c. magnetic field. Then, the T-equivalent circuits are obtained from the scattering matrix measurements. Results prove that when a thin ferrite post is placed near a side wall of the guide, it acts essentially as a shunting capacitance. The susceptance decreases with d. c. mangetic field. As far as the impedance is concerned, the post itself behaves like a tuning screw. Finally, the equivalent circuit of a waveguide containing two or more ferrite posts is studied. It is found that when the distance between the two nearest posts is greater then λ/2, the equivalent circuit is simply the "single post" circuits connected in cascade. A phase shift network is used to illustrate the application of the principle of the circuit analysis.