A Self-Structuring Impedance Matcher for In-Vehicle Digital Audio Broadcasting Applications

Abstract

This paper proposes an adaptive impedance matching subsystem, called self-structuring impedance matcher (SSIM), for in-vehicle digital audio broadcasting (DAB) applications. The goal of the SSIM is to make antennas originally aiming at other vehicular applications, such as a digital television (DTV, 470–894 MHz) and an interphone car radio (136–174 MHz), operate in the targeted DAB frequency band (170–240 MHz), thereby lowering the startup cost of DAB devices. The SSIM consists of a template of a matching circuit, a microprocessor, and a receiving-type sensor. The template uses a nonuniform microstrip line interconnected with relay switches. To enhance the dynamic range and reduce the insertion loss for the template simultaneously, this work employs a new design technique based on solving the mathematical programming problem of matching requirements. The resultant matching domain covers a large area of the Smith chart, although only five switches are used. Experimental results show that the SSIM successfully adapts an interphone/DTV antenna into a DAB receiving mode. The operational bandwidth meets the DAB specification, and the transducer gain is larger than −1.83 dB.