A COMPACT DUAL-POLARIZED BROADBAND ANTENNA WITH HYBRID BEAM-FORMING CAPABILITIES

A broadband dual-polarized four-port (DPFP) antenna is presented in this paper, which consists of a radiation element and a feed network. It is very compact in size, with the diameter of 150.0 mm and the height of 47.0 mm, with the following unique properties: (1) it has hybrid beam-forming capability and operates at two modes, which depends on its excitation; (2) its operating frequency range is from 0.96 to1.78 GHz, and the return loss is about 10 dB; (3) its insertion loss is (3 +/- 0.5) dB, with its balanced power splitting over the relative bandwidths of 37% at Mode 1 (180 degrees +/- 5 degrees phase shifting) and 55% at Mode 2 (+/- 5 degrees phase shifting), respectively; (4) an isolation of 30 dB at Mode 1 is obtained between the dual polarized ports, with the gain of 7.6 dBi and 42 degrees of the 3 dB-bandwidth at 1.25 GHz; and (5) the gain difference between Modes 1 and 2 is about 7 dB, within the angle of -15 degrees <= theta <= 15 degrees for the same polarization at 1.25 GHz. For the application of DPFP, a hybrid beam forming algorithm is proposed with an angular precision of 7 degrees and is validated by measurement.