The design of varactor-loaded transmission-line phase shifters usinglumped elements is discussed in this paper. A monolithic-microwaveintegrated-circuit (MMIC) phase shifter is fabricated to verify theproposed topology. Only one control voltage is required for phasecontrol. Within a continuously adjustable phase-control range of360/spl deg/ and a frequency range from 5 to 6 GHz, a low transmissionloss of 4 dB/spl plusmn/1.7 dB is measured. The phase shifter isrealized with a commercial 0.6-/spl mu/m GaAs MESFET process andrequires a chip area of only 0.8 mm/sup 2/. To the knowledge of the authors, the best results reported to date are reached for a continuouslyadjustable passive phase shifter with comparable circuit size. Thepresented circuit is well suited to wireless adaptive antenna transceivers,operating in accordance with the 802.11a, high-performance radiolocal-area-network and high-speed wireless-access-network type-astandard