A 0.75–6.75 GHz receiver with a digitally controlled LO generator for software-defined radio

This paper describes a receiver composed of a wideband LNA, mixers, and a frequency generator toward multifunction and multistandard mobile terminals. The proposed frequency generator can cover the frequency range from 750 MHz to 6.75 GHz by following the frequency planning which consists of a VCO, two mixers, and four divide-by-2 dividers. Firstly, to achieve better phase noise, a low-phase noise wideband LC VCO is proposed. The power consumption of the VCO is 7.8 mW and its phase noise is -126 dBc/Hz at 1 MHz offset frequency. The LO generator is controlled for the targeted frequency range by turning on and off the mixer and divider input and output buffers. The total power consumption of the LO generator is 27.3~60.6 mW under 1.8 V supply. The phase noise at 1 MHz offset for each frequency band varies from -122 dBc/Hz to -136 dBc/Hz. A 2-stage wideband low noise amplifier has bandwidth of 6.6 GHz (0.2-6.8 GHz), power gain of 13.3 dB including 6 dB loss from buffers, and minimum noise figure of 3.7 dB.