An Angular-Displacement Microwave Sensor Using an Unequal-Length-Bi-Path Transversal Filtering Section

A class of angular-displacement microwave sensor based on a microwave signal-interference transversal filtering section (TFS) with unequal-electrical-length paths is reported for the first time. It consists of a bi-path TFS composed of two in-parallel transmission-line segments with distinct lengths, which is modified by adding a rotational open-circuit-ended stub as the rotor to a curved section as the stator of one of its line segments. In this manner, the spectral positions of the transmission zeros, which are produced in its filtering transfer function through destructive signal-energy interactions, are modified with the rotation of this additional stub. This allows single/multi-band angular-displacement microwave-sensing capabilities in terms of transmission-zero inter-spacing variation for passbands/stopbands and stopband-peak-level modification to be attained by means of the mechanical rotation of the rotor. The theoretical operational principles of this type of bi-path-TFS-based angular-displacement-microwave sensor and design curves for specific values of its electrical parameters are provided. Moreover, for experimental validation purposes, a proof-of-concept prototype of the devised TFS-based microwave-sensor approach operating at 961 MHz with 180 degrees dynamic range is prototyped in microstrip technology and measured. A comparative analysis of the developed angular-displacement microwave sensor with the state-of-the-art is also presented.