In-Band RCS Reduction and Isolation Enhancement of a 24 GHz Radar Antenna Using Metamaterial Absorber for Sensing and Automotive Radar Applications

A triple-band low radar cross-section (RCS) high isolation antenna is proposed for 24 GHz ISM band sensing and automotive radar applications. The proposed design consists of 2 x 2 patch array that acts as transmit and receive antennas. Low RCS and high isolation are achieved at 24 GHz by designing a metamaterial absorber (MA), which consists of a square ring with a resistor connected in its diagonal arm for the absorption of electromagnetic waves. The proposed MA shows near unity normalized impedance at 24.1 GHz with 90% absorptivity bandwidth of 1 GHz. An array of MA is placed in between and around the transmit/receive antennas to suppress surface current and reduce in-band RCS of the radar sensor. The −10 dB impedance bandwidths of the triple-band sensor antenna are 20.8 to 21.24 GHz, 23.94 to 24.55 GHz, and 27.18 to 27.5 GHz. The proposed sensor antenna achieves isolation of 34 dB between the transmit and receive ports, and peak RCS reduction of 11 dB, as compared to the reference antenna. The half-power beamwidth of the proposed sensor antenna is 38° for E-plane and 52° for H-plane at 24 GHz.