Radio-frequency front-end for 5 GHz wireless local area network transceivers

A transceiver front-end for 5 GHz wireless local area network applications has been designed and implemented in a low-cost 46 GHz f_T pure-silicon bipolar technology. The transceiver front-end adopts a superheterodyne sliding-IF architecture and consists of a down-converter, an up-converter and an LO frequency synthesiser. By exploiting a 1 bit variable-gain low-noise amplifier, the down-converter is able to provide an excellent noise figure of 4 dB while ensuring an input 1 dB compression point of -10 dBm with a current consumption of 25 mA from a 3 V supply voltage. The transmitter front-end is implemented by means of a current-reuse variable-gain up-converter. The circuit provides an output 1 dB compression point of 5.3 dBm although consuming only 45 mA from a 3 V supply voltage. Moreover, a linear-in-dB gain control characteristic is achieved over a 35 dB dynamic range. The LO frequency synthesiser is implemented by means of an integer-N phase-locked loop. It features a phase noise of -117 dBc/Hz at 1 MHz offset from the centre frequency of 4.1 GHz and exhibits a tuning range of 1.2 GHz, from 3.47 to 4.65 GHz. The LO frequency synthesiser draws 20 mA from a 3 V supply voltage.