Cavity-backed patch antenna with low-profile, broad bandwidth, and wide beam-width for K-Band FMCW radar system

Abstract

As the proximity fuze has been developing to detonate at the height of burst (HOB) point accurately, and the frequency modulated continuous wave (FMCW) radar system of the proximity fuze has studied to detect the target within a blind zone of a short range in the air. For solving the problem, millimeter-wave (mmWave) antennas are required to have superior radio frequency (RF) performances regarding a low-profile design, a broad bandwidth, and wide beam-widths. In this paper, a cavity-backed patch antenna is proposed for detecting the target accurately and widely. For the low-profile and lightweight antenna design, the patch antenna and single layer substrate with 0.508 mm thickness are selected. In order to improve the bandwidth of the antenna, methodology of merging the TM01 mode with the generated 2nd zero mode from loading the shorting pin on the patch antenna is proposed. Furthermore, the cavity-backed structure based on substrate integrated waveguide (SIW) from arrayed conducting via holes connecting the parasitic loop and lower metal plates of the substrate is designed to have a half-power beam-width (HPBW). As the characteristic of the FMCW radar system, a multiple complementary split-ring resonator (MCSRR) between the transmitter (Tx) antenna and the receiver (Rx) antenna is positioned to enhance the isolation. As a leakage signal from the Tx antenna to the Rx antenna is cancelled thanks to the enhanced isolation, the FMCW radar system facilitate to improve the signal to noise ratio (SNR). However, two types of cavity-backed patch antenna for wide HPBW and high isolation are proposed because of trade-off between high isolation and wide HPBW. The proposed cavity-backed patch antenna for wide HPBW has a bandwidth covering 23.3 – 25.8 GHz and has radiation patterns over 100° at operating frequencies of the FMCW radar system in the azimuth plane and the elevation plane, respectively. The proposed cavity-backed patch antenna for high isolation has a bandwidth of 24.1 – 25.9 GHz, and isolation between the Tx antenna and the Rx antenna has a value of -47.1 dB at resonant frequency of the FMCW radar system. Due to excellent RF performances, the proposed cavity-backed patch antenna can be suitable candidate for the proximity fuze.