Enhancement mode GaAs PHEMT LNA with linearity control (IP3) and phased matched mitigated bypass switch and differential active mixer

Abstract

A new front end IC has been designed using a single supply enhancement mode GaAs PHEMT 0.5 /spl mu/m process for WCDMA and other wireless applications. This front end has a single ended LNA, single ended in and differential out active balanced mixer with integrated LO, active balun, and buffer amplifier. The LNA also has CMOS logic controllable linearity (IP3) control and a phased matched mitigated bypass switch. The LNA draws 8.5 mA current when switched to high linearity mode and has 15 dB gain, 1 dB NF, -6 dBm IP/sub 1dB/ and 7.3 dBm IIP3. In low linearity mode, it draws 3.5 mA current and has 14 dB gain, 1.1 dB NF, -6 dBm IP/sub 1dB/ and 2 dBm IIP3. In LNA bypass mode, the total bypass loss is <3.5 dB and has 7 dB NF, 5 dBm IIP3 and it draws /spl sim/1 mA current. Also, the bypass switch circuit has an integrated active phase shift network which maintains a phase difference of <25/spl deg/ with LNA ON modes. In all conditions, the LNA/switch combo has >10 dB I/O return loss. The mixer, with active balun and buffer amplifier, consumes 8 mA current and has 12 dB gain, 7 dB noise figure, 0 dBm IIP3 and provides a differential IF out with a differential impedance of about 1000 ohms. The above performance is measured at 2.14 GHz for WCDMA applications.