Directional‐coupler‐based microwave sensors for differential angular‐displacement measurement. Issue 10 (22nd June 2020)

• Record Type: Journal Article
• Authors: Chio, Chi‐Hou; Gómez‐García, Roberto; Yang, Li; Tam, Kam‐Weng; Choi, Wai‐Wa; Ho, Sut‐Kam
• Is Part Of: International journal of RF and microwave computer-aided engineering. Volume 30:Issue 10(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-06-22
• Subjects: angular‐displacement sensor -- microstrip coupler -- microwave sensor -- transmission zero -- transversal filtering section; Microwave devices -- Computer-aided design -- Periodicals; Computer-aided engineering -- Periodicals; 621.3813
• DOI: 10.1002/mmce.22338
• Languages: English
• ISSNs: 1096-4290

Abstract

Abstract: The novel application of microwave directional couplers to develop angular‐displacement microwave sensors is reported. The proposed sensor approach employs as stator a branch‐line‐type coupler arranged in transversal mode by loading its direct and coupled ports with two distinct‐length open‐ended stubs. Thus, by taking the isolated port of the coupler as the stator output node, a bandpass filtering transfer function with transmission zeros (TZs) is created. Then, a rotor made up of an angularly‐moveable open‐ended stub is attached to a curved section of the longest loading stub of the stator through physical contact, so that their interconnection point varies with the angular‐displacement of the rotor. In this manner, the sensor transfer function is altered with the stub rotation through TZ reallocation, angular‐displacement sensing capabilities are achieved. The theoretical operational foundations of the conceived branch‐line‐coupler‐based microwave angular‐displacement sensor, which features single/multi‐band sensing properties in terms of inter‐TZ spacing and stop band attenuation levels, along with design examples and curves are provided. The extrapolation of this sensor principle to other classes of power‐distribution circuits, such as the rat‐race‐type directional coupler, is also demonstrated. Finally, for experimental‐validation purposes, two 920 MHz microstrip prototypes of the conceived branch‐line‐coupler‐based angular‐displacement microwave‐sensor approach are built and measured.