A single-chip 2.4 GHz direct-conversion CMOS receiver for wireless local loop using one-third frequency local oscillator

A single-chip direct-conversion CMOS receiver for 2.4 GHz wide-band CDMA for wireless local loop (WLL) is described. The chip includes an LNA, a 12-phase down converter, a variable gain amplifier, a gm-C channel selection filter, a programmable PLL for 7 channel frequencies, and a 4-bit flash ADC. The proposed 12-phase down conversion scheme combined with a multi-phase sampling fractional-N prescaler, a cascaded DC-offset canceler and distributed AGC loops offers solutions to the problems of a direct conversion receiver. Experimental results show -115 dBm, sensitivity, 4.4 dB noise figure, and 95 dB dynamic range.