The paper proposes a high resolution tunable MicroElectroMechanical Systems (MEMS) phase shifters for radar phased array antenna to steer the beam. Two phase shifters are considered the first is a switched line phase shifter; the second is a reflection type phase shifter. The resolution of the designed phase shifters is two degree phase shift using 8 bit control circuitry. The proposed circuit is based on dividing the tuning range into coarse and fine tuning sections which change the phase by 30o and 2o steps respectively to achieve the desired phase. A microstrip phase shifters have been designed at 3 GHz suitable for surveillance radar applications. The development of RF MEMS switches over the past years has enabled system designers to consider replacing the GaAs phase shifters with RF MEMS phase shifters. MEMS phase shifter exhibit excellent characteristics, including low insertion loss and low DC power consumption. The designed phase shifters are simulated and tested using Advance Design System circuit simulation package (ADS) and the results demonstrated
using the graphics capability of Matlab Program. The results show that the worst case insertion loss is less than 0.17 dB and 0.05 dB for switched line and reflection type phase shifters respectively. The return loss for the two proposed phase shifters is less than -60 dB.