The design and results of an ultra-compact single-load reflective-type monolithic-microwave integrated-circuit phase shifter at 6.2 GHz for a satellite radar system is presented in this paper, which has been fabricated using a commercial 0.6-mum GaAs MESFET process. A 3-dB 90 degrees coupler with lumped elements enables significant circuit size reduction in comparison to former approaches applying microstrip branch line or Lange couplers. Phase control is enabled using MESFET varactors with capacitance control ratios (C-max/C-min) of only four. Equations are derived to precisely describe the phase control ranges versus capacitance control ratios for different load configurations to allow efficient optimizations. Furthermore, the design tradeoff between low loss and high phase control range is discussed. Within a phase control range of 210 degrees, a loss of 4.9 dB +/- 0.9 dB and a 1-dB input compression point of higher than 5 dBm was measured for the designed phase shifter. The circuit I size is less than 0.5 mm(2), which, to our knowledge, is the smallest reflective-type phase-shifter size reported to date.
