A GaAs MONOLITHIC LINEAR-IN-DB WIDE-DYNAMIC-RANGE VARIABLE-GAIN AMPLIFIER WITH MATCHING COMPENSATION FOR 1.95-GHz APPLICATIONS

摘要

This paper describes a method to design a compact lin-ear-in-dB variable-gain amplifier (VGA.) with good input/output matching in a wide gain-control range. The method is theoretically supported and has been validated with the design of a 1.95-GHz GaAs fully monolithic VGA. Measured maximum gain is 18.8 dB with associated noise figure of 6.3 dB and 40-dB dynamic range with lower than ±1.5-dB deviation from linearity, under a low control voltage from -0,4 V to - 1.5 V. Good linearity with an output 1-dB compression of 12 dBm at maximum gain and associated 3n'-order intercept point better than 22 dBm are also shown. The adjacent channel power ratio (ACPR) was measured at the 1.95-GHz WCDMA band, showing values better than -48 dBc at 885-KHz offset and -70 dBc at 1.98-Mhz offset over the whole control range. The chip size is 2×1.0 mm{sup}2 and consumes only 34 mA from a supply voltage of 3.5 V.