Design of electronically steerable passive array radiator (ESPAR) antennas

Electronically steerable passive array radiator (ESPAR) antennas are proposed for low-cost analog adaptive beamforming. The configuration and design of these antennas and some simulation results, especially on their beam/null steering capability, are presented. From the results of a numerical analysis, it was found that 5-element ESPAR antennas can offer a beam gain of 9 dBi/spl plusmn/1 dB and a null deeper than -50 dBi in an arbitrary direction. In this case, the beam gain and null were obtained separately. It was also found that 7-element ESPAR antennas can achieve continuous steering in almost all directions, with a simultaneous 8 dBi beam gain and 30 dBi null, excluding the region where the direction of the beam and the direction of the null are within about 45-degrees however 5-element ESPAR antennas are unable to achieve steering in a number of directions, even with a simultaneous 5 dBi beam gain and -15 dBi null.