A Novel Compact Printed Antenna Used in TPMS or Other Complex and Variable Environments

A novel compact printed antenna used in tire pressure monitoring system (TPMS) is proposed and analyzed in this paper. The proposed antenna is printed on both sides of the dielectric substrate and the upper side consists of four parts: (1) the meandered radiating sections; (2) the additional strip line, which is used as a shorting connector and an additional radiating portion; (3) the feed microstrip line; and (4) the loading meandered sections, which are mainly used to improve the impedance bandwidth. The lower side consists of a meandered ground plane, which can also act as a balun choke and the extended parallel strap, which acts not only as a shorting connector but also as an impedance-tuning strap. A prototype of the proposed antenna with 0.17 lambda₀ in length, 0.017 lambda₀ in width and 0.0021 lambda₀ in height has been fabricated and tested. The relative impedance bandwidth of the proposed antenna reaches 22% (VSWR < 3.0) and 12% (VSWR < 2.0), and the antenna has an acceptable relative gain and its performance is relatively stable. Therefore, it also can be used in other complex and variable environments besides TPMS. When the length of the antenna is reduced to 0.098 lambda₀, the relative impedance bandwidth exceeds 28% (VSWR < 2.0). But the antenna's performance will become less stable, which may be the same as that of the conventional compact monopole antenna. Design details of the proposed antenna and the results of both simulations and experiments are presented and discussed.