A Multifeed Antenna for High-Efficiency On-Antenna Power Combining

This paper presents a multifeed antenna structure that synthesizes the desired far-field radiation characteristics with on-antenna power combining and increases the total radiated power of a wireless transmitter. The driving signals at the multiple antenna feeds are scaled properly in amplitude and phase, so that they collectively synthesize the desired on-antenna current/voltage distribution and achieve the resulting desired far-field radiation pattern. The proposed multifeed antenna offers flexibility to optimize the antenna driving impedances based on the locations of the feeds. It also simplifies the passive impedance matching and power-combining networks between the antenna feeds and the transmitter outputs, substantially increasing the total transmitter power efficiency. Most importantly, the proposed multifeed antenna achieves on-antenna low-loss power combining, which, compared with antenna array-based spatial power combining, does not suffer from narrowed beamwidth or enlarged antenna panel size. As proof of concept, multifeed slot antennas and a multifeed square loop antenna are designed and characterized at 10.3 GHz. Conventional single-feed slot antennas and a single-feed square loop antenna are also implemented as reference designs. Well matched antenna gains and radiation patterns between the proposed multifeed antennas and the conventional single-feed antennas are achieved in the measurements, demonstrating the on-antenna power combining of the proposed multifeed antennas without distorting the far-field radiation patterns.