A variable gain RF front-end, based on a Voltage-Voltage feedback LNA, for multistandard applications

Abstract

Employing feedback circuits in RF front-ends can be a key aspect for easy reconfiguration of multistandard receivers. A narrow-band filter can shape the frequency transfer function and, by reflection due to the feedback network, the input impedance. Switching one single filter component thus allows selecting a different standard. We introduce a voltage-voltage feedback low noise amplifier that, besides being easily reconfigurable, shows roughly the same noise and better linearity, for same power consumption, as the conventional inductively degenerated topology. A direct conversion front-end, including the LNA and I and Q mixers, tailored to WLAN applications in the 5-6 GHz range, has been realized in a 0.25-/spl mu/m SiGe BiCMOS process. Prototypes show the following performances: 2.5 dB NF, 31.5 dB gain, -9.5dBm IIP3, and +23dBm minimum IIP2 while consuming 16 mA from a 2.5 V supply.