A transformer-based receiver front-end for 5-GHz WLANs

In this paper a transformer-based receiver front-end for 5-GHz wireless local area networks is presented. The circuit is implemented in a low-cost 46-GHz-fT silicon bipolar process and includes a variable-gain low noise amplifier and a double-balanced mixer. The front-end does not require any external input balun for the single-ended-to-differential conversion of the RF signal, which is provided by the transformer load of the low noise amplifier. The receiver front-end exhibits a 4.3-dB noise figure and a power gain of 21 dB. By adopting a 1-bit gain control, the circuit achieves an input 1-dB compression point of -11 dBm, while drawing only 22 mA from a 3-V supply voltage. Finally, thanks to integrated notch LC filters, the front-end provides an on-chip image rejection ratio as high as 50 dB, thus reducing the required selectivity and hence the cost of the external RF filter