Ultrawide Band (UWB) Multi-Band OFDM (MB-OFDM) systems have been proposed as an emerging solution to wireless communication applications requiring high data rates (up to 400Mb/s) over short distances [1]. In one proposed version, the modulated carrier with a bandwidth of 528MHz can hop to one of fourteen channels (2904 + 528·nMHz, n = 1, 2…14), divided into four groups of three channels and one group of two channels. To assure the widest possible adoption, RF portions of these systems should consume little dc power and die area, and be implemented in a standard CMOS process. These last requirements argue against the use of on-chip inductors wherever possible.A dynamically tuned UWB OFDM receiver front-end is presented in a 0.18µm CMOS technology. The receiver uses no on-chip inductors and consists of a dynamically tunable low-noise amplifier (LNA), a downconverter and a tunable intermediate frequency (IF) bandpass filter. The receiver is designed to work for the lower three groups; however, the concept can easily be extended to include the higher groups.A direct-conversion UWB receiver, while attractive for power consumption and simplicity of local oscillator (LO) scheme [2], has the well-known problems of time varying dc offset and sensitivity to narrowband jammers. Since the LO can vary from 3.5 to 10.3GHz, the dc offset present at the mixer output can vary significantly with every frequency hop, and the offset calibration loop has to settle to its final value well within the guard interval of 9ns. A differential heterodyne architecture largely eliminates the dc offset issues and provides the additional advantage of reduced second-order distortion, reducing the dc power requirements. One of the drawbacks of a heterodyne receiver; the need for an interstage filter, has been overcome in this design by creating a passive band-pass filter entirely with bond wires and onchip capacitors.To avoid the classical heterodyne receiver image rejection problem, the frequency plan was carefully designed for an IF of 2.64GHz, so that all the images fall below 2.4GHz. An external bandpass filter with a lower cut-off frequency of 3GHz, which is standard in UWB receiver designs, therefore suppresses all the images, as shown in Fig. 6.8.1. In addition, the LNA provides some image rejection, eliminating the need for an image reject mixer.The LNA (Fig. 6.8.2) is a differential cascode amplifier (to enable operation at 2.3V without breakdown) with an LC load. To eliminate the use of on-chip inductors, the load is realized with bond wires and on-chip capacitors. Input matching is achieved via resistive feedback and optimized device sizing. The output device capacitance and mixer input capacitance resonate with the bond wires at 7GHz. The tank's Q is then reduced by a shunt resistor, broadening the bandwidth of the circuit. This provides for good LNA gain in Group 3 (6.3 to 7.9GHz). When the received signal is in the lower-band Group 2 or Group 1, extra shunt capacitance is switched in, by setting bits b 0 and b 1 "high" successively, ...