A Biphase Modulator Circuit for Impulse Radio-UWB Applications

This letter presents a circuit to provide binary phase shift keying to ultra-wideband (UWB) impulse transmitters. The circuit is based on a Gilbert-cell multiplier and uses active on-chip balun and unbalanced-to-balanced converters for single-ended to single-ended operation. Detailed measurements of the circuit show a gain ripple of +/-1 dB at an overall gain of -2 dB, an input reflection below -12 dB, an output reflection below -18 dB, a group delay variation below 6 ps and a -1 dB input compression point of more than 1 dBm in both switching states over the full 3.1-10.6 GHz UWB frequency range. A time domain measurement verifies the switching operation using an FCC-compliant impulse generator. The circuit is fabricated in a mu m Si/SiGe HBT technology, consumes 31.4 mA at a 3.2 V supply and has a size of 510 x 490 mu m(2), including pads. It can be used in UWB systems using pulse correlation reception or spectral spreading.