RF Transmitter in 90-nm CMOS for Multi-Band OFDM UWB Application

A compact, low voltage, variable gain, single side band RF transmitter is implemented in standard 90-nm CMOS technology for Orthogonal frequency division multiplexed (OFDM) ultra-wide-band (UWB) system operating in the "Band group A" channels at 3.432 GHz, 3.960 GHz and 4.488 GHz. The currents of I and Q up-converters are directly combined in a single load to eliminate the need of separate combiner for generation of a single-sideband. The variable attenuator at the RF port is used to compensate for gain variation over process, power supply and temperature variations. The measured results of the up-converter provide an output power between -7 to -13dBm with a variation of less than plusmn1.5 dB within each band, an OIP3 of +10 dBm, an image rejection of 49 dB and a LO rejection of 41 dB. All the circuit blocks are based on low voltage design and the combined power consumption of all the circuit blocks including power amplifier is 90 mW with a 1.2 V supply.