Design of low cost linearly-polarized microstrip grid array antenna for 24 GHz doppler sensors

A microstrip grid array antenna for 24 GHz Doppler sensor is proposed for the first time. It is designed on 0.787 mm thick Rogers Duroid 5880 (ε_r = 2.2 and tan δ = 0.0009) with 0.017 mm copper cladding. Wet etch PCB process is used to fabricate the grid array antenna for cost consideration. Dimensions of the antenna are 40 mm × 40 mm × 0.787 mm. Simulated results show that impedance bandwidth of the antenna is from 22.7 GHz to 25.4 GHz, the highest gain is 17.5 dBi at 24 GHz, and the radiation bandwidth from 22.15 GHz to 25.5 GHz. The simulated beamwidth is 26° and 22° on E- and H-plane respectively. Measured results show that the antenna has achieved impedance bandwidth 20.5 GHz - 25.7 GHz, the highest gain is 18.4 dBi at 24.15 GHz, and radiation bandwidth 22.7 GHz - 24.7 GHz. The measured beamwidth is 20° and 22° on E- and H-plane respectively. The simulated and measured results agree well with each other. It is a capable candidate for 24 GHz Doppler sensor application.