Accurately Characterizing the Coupling Effects of Patch Antennas With Complex- and Frequency-Dependent J/K Inverters

This paper proposes an accurate and general method to calculate and characterize the couplings of patch antennas. It is found that the coupling effects of open-/short-circuited patches can be represented by J/K inverters. Unlike traditional ones, these J/K inverters should be with complex- and frequency-dependent values. Three different patch antennas are used to exemplify how to characterize couplings with J/K inverters. Once the values of J/K inverters are successfully extracted, the total equivalent circuits of these patch antennas can be easily given in a unified way. J/K inverters can also help us see how the couplings affect antenna bandwidth. To present advantages of the proposed method, comparison with traditional coupling calculation approach based on characteristic modes is conducted. Technical limitations and potential applications of the proposed method are also discussed.