A Novel Planar Reconfigurable Monopulse Antenna for Indoor Smart Wireless Access Points’ Application

In this paper, a novel planar reconfigurable monopulse antenna with compact size is proposed and studied for indoor smart wireless access points (WAPs) application. Circular polarization is achieved by using a dual-mode substrate integrated waveguide (SIW) slot antenna. Two diagonal ports are individually used to excite the SIW element antenna to achieve a 180° phase-shifting excitation. A reconfigurable $2 \times 2$ prototype is developed with the proposed element antenna, and it uses eight PIN diodes as four switches to implement the reconfiguration. Sum beams, difference beams in azimuth and elevation planes, and bidifference beams are generated. Measurement results verify the designed prototype, showing that the antenna has a null depth of over 30 dB and a peak sum beam gain of 12.29 dBi. The measured 10-dB return loss bandwidths are 5.72–5.96, 5.75–5.95, 5.73–5.97, and 5.76–5.94 GHz for the sum, elevation difference, azimuth difference and bidifference beams, respectively. And their measured 3-dB axial ratio (AR) bandwidths are 5.84–5.88, 5.86–5.90, 5.85–5.9, 5.85–5.9, and 5.84–5.91 GHz. The capability of reconfigurable monopulse beams ensures that the proposed antenna is a good candidate for smart WAP applications.