A novel phase shifter based on reconfigurable defected microstrip structure (RDMS) for beam-steering antennas

A low cost phase shifter based on a cascaded reconfigurable defected microstrip structure (RDMS) is proposed. This RDMS unit is produced by etching a slot to introduce a defect on a microstrip line and then PIN diodes are inserted in the defected area. By switching the PIN diodes, the RDMS unit is able to operate in two different states with a phase shift of 17° at 5.2 GHz. The RDMS units can be cascaded for higher phase shift values that may be determined by array design requirements. Phase shifters cascading three and six RDMS units were designed, fabricated, and measured. The measured results show that the two phase shifters introduce 45° and 90° phase shifts, respectively, with low insertion loss. Finally, a four element patch array is proposed with a beamforming network employing the phase shifters and Wilkinson power dividers. The array is able to switch its main beam direction to 0° and ±20° in the H plane and the impedance bandwidth covers the overlapping wireless local area network (WLAN) bands in the vicinity of 5.2 GHz.