Switchable Direct-Conversion Receiver for 2GHz and 5GHzwith Sub-harmonic Mixer

This paper reports on a fully-integrated CMOS switchable direct-conversion receiver for 2GHz, 5GHz. Switchable low noise amplifier is proposed for suiting for multiband (2GHz, 5GHz). Sub-harmonic mixing is used for down-conversion to minimize the DC-offset due to LO-leakage. The residual DC-offset is cancelled by a digital-to-analog converter at the output of mixer. For quadrature down-conversion with sub-harmonic mixing, octa-phase LO signals are generated by an integer-N type frequency synthesizer. Implemented in a 0.18m CMOS technology, the receiver dissipates 97mA from a 1.8V supply voltage and has 6.5dB noise figure (NF) and -4dBm input third-order intercept point (iIP3). The phase noise of the closed-loop VCO is -108dBc/Hz at 1MHz offset.