Excitation Flexibility of On-Antenna Power Combining

In this letter, a design methodology is proposed for on-antenna power combining with flexible input power ratios. Designing multifeed antennas with direct power combining requires weighted driving signals to match the field distribution at the resonant mode of the antenna, imposing serious restrictions on their implementation. To overcome this drawback, we proposed a method to relax the excitation criterion by altering the impedance matching conditions of the multifeed antenna, giving the RF designers a degree of freedom. First, an eigenanalysis method is employed to extract the active impedance values for each port of the antenna. Then, according to a preferred input power distribution, proper impedance matching is built based on the active impedance values. The resulting multifeed antenna resembles the single-feed antenna in terms of the radiation performance with desired driving signals. A series of four-feed slot antennas were fabricated to validate the proposed method. Simulation and measurement results show that under different excitation scenarios the radiation performance of the antenna remains intact, demonstrating the flexibility for on-antenna power combining.