A Wideband Multibeam Pillbox Antenna Based on Differentially Fed Leaky-Wave Array

In this letter, a compact wideband multibeam pillbox antenna is proposed based on differential feeding technology. The proposed design focus on extending the operating frequency bandwidth of the leaky-wave antenna (LWA) array with a fixed broadside beam, since the bandwidths of the existing pillbox antennas are always limited by the radiators, especially considering the standard printed circuit board technology with limited layers. To overcome this limitation, a differentially fed LWA is used as the radiator. The two subarrays of the LWAs are excited with oppositely propagating waves through a coupled slot, generating two oppositely directed beams whose combination can produce a fixed broadside beam over a wide operating bandwidth. A 14-element LWA array is fabricated with a pillbox beamforming network (BFN) to verify its design theory. The simple feeding structure of the LWA makes the LWA array can be stacked on the top of the pillbox BFN, achieving antenna miniaturization. The measured results show that the proposed antenna can achieve the -10 dB impedance matched bandwidth from 14.0 to 16.0 GHz and seven beams with ±34° beam scanning range. The broadside beam has a gain variation range of 16.8-20.2 dB over the operating band.