Design and Fabrication of a Module for Coupling Signal Cancellation between Tx and Rx Antennas in FMCW Radar Systems

Because FMCW radar has separate Tx and Rx antennas, coupling signals continuously leak from the Tx antenna to the Rx antenna. If the transmission power is increased to extend the detection range, the coupling signal leakage to the Rx antenna increases, which causes the dynamic range of the ADC for signal processing to be exceeded. Therefore, to extend the detection range, it is important to reduce the magnitude of the coupling signal leaked to the Rx antenna. In this study, a coupling-signal cancellation module was designed to remove the coupling signal. The performance of the analog circuit domain cancellation method was theoretically analyzed. Based on the performance analysis results, the components were selected, and the module was manufactured. The performance test results showed that the theoretical analysis and test results are consistent. In addition, the module achieved a maximum signal attenuation performance of −52.22 dB at a single frequency, and it was experimentally proven that the 40 MHz LFM signal could be suppressed by −20.4 dB when installed in an actual radar equipment.