Varactor-loaded transmission-line phase shifter at C-band using lumped elements

The design of varactor-loaded transmission-line phase shifters using lumped elements is discussed in this paper. A monolithic-microwave integrated-circuit phase shifter is fabricated to verify the proposed topology. Only one control voltage is required for phase control. Within a continuously adjustable phase-control range of 360degrees and a frequency range from 5 to 6 GHz, a low transmission loss of 4 dB +/- 1.7 dB is measured. The phase shifter is realized with a commercial 0.6-mum gallium-arsenide MESFET process and requires a chip area of only 0.8 mm(2). To the knowledge of the authors, the best results reported to date are reached for a continuously adjustable passive phase shifter with comparable circuit size. The presented circuit is well suited for wireless adaptive antenna transceivers, operating in accordance to the 802.11a, high-performance radio local-area-network and high-speed wireless-access-network type-a standards.