Design of a phased array antenna with scan loss reduction and gain enhancement by using reconfigurable subarrays

In order to reduce the scan loss and also obtain higher scanning gain for a phased array, a subarray design is proposed in this study. Different from the prior works, the number of active phase shifters utilised in this topology is identical to its counterpart without subarrays, which makes it more cost-effective. To achieve this valuable characteristic, a reconfigurable beam-former is proposed to enable the radiation pattern of a subarray to be switchable to different modes for different scanning regions. The proposed beam-former is based on substrate-integrated waveguide (SIW) and featured by extremely low-loss, due to its unique working mechanism. For validation, a fully integrated subarray module consisting of a beam-former and two Yagi-Uda antennas is designed and analysed. Furthermore, in order to show the effectiveness, five subarray modules with uniform spacing are utilised to construct a complete prototype operating at 15 GHz. Measurement results of the entire array indicate that the achieved gain is 2 similar to 3 dB higher than its counterpart without the subarray, from -45 degrees to +45 degrees in the beam-scanning plane. Meanwhile, the scan loss is decreased from +/- 1.45 dB to smaller than +/- 0.9 dB. Meanwhile, sidelobe levels are also improved for scanning angles between +/- 45 degrees. It should be pointed out that the proposed approach is also applicable to broaden the scanning angle of phased arrays with properly selected antenna elements. Since there is no need to increase the number of active phase shifters, this subarray-based approach can be considered more economic, and is very attractive for a variety of phased array systems.