Rigorous Analysis and Design of Resistor-Loaded Patch Antennas with Flexible Gain for Indoor Radar Sensors

A high-precision cavity model of resistor-loaded patch antenna (RLPA) with adjustable gain is proposed and rigorously studied in this article. In our analysis, the loaded resistors are perceived as controlled current sources, thus the RLPA can be solved as a modified cavity model. Accurate expressions of field distribution, input impedance, and radiation patterns are derived in this way, and a gratifying agreement has been achieved between the calculated and simulated results. Based on this approach, RLPAs for indoor motion radar are designed and analyzed. Comprehensive analysis is conducted to reveal the loading effect on radiation gain, radiation efficiency, and quality factor of RLPAs under various circumstances. Through altering the value of the loaded resistance, its radiation gain and coverage range can be flexibly adjusted. Besides, enhanced operating bandwidth and improved performance stability are also achieved due to the loaded resistors. Last but not least, several indoor motion radars based on the proposed patches are carried out and measured, which demonstrates the validity of the proposed method and design.