Matteo Conta

A 20 mW 3.24

The challenges in the co-existence of a GPS receiver with cellular phones for location based services are addressed in this paper. A fully integrated GPS radio, realized in a 0.18 mum SiGe technology, demonstrates a 1 dB gain desensitization at 1.9 GHz of -8 dBm, a noise figure of 5 dB, with 20 mW power consumption. Chip area is 3.24 mm2. The receiver includes a highly selective LNA, key to minimize desensitization and reciprocal mixing due to the large cellphone leakage, a novel quadrature VCO topology capable of directly driving quadrature passive mixer with high swing and low power consumption, complex bandpass filter, variable gain amplifier, automatic gain control, 2-bit quantizer, and a fractional-N sigma-delta-based PLL that can lock to any crystal frequency.

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This paper presents a 0.5 /spl mu/m CMOS mixer for RF applications. The core consists of a quad differential pair, with resistive degeneration, implemented with MOS transistors in the linear region. This topology proves to be suitable for low voltage, highly linear down-converters. Compared with a CMOS Gilbert cell, it features a better linearity with a lower supply voltage. The mixer is powered at 2 V supply and drains 3.8 mA; the IIP3 and the single side band NF are given respectively by 21 dBm and 24 dB. In terms of spurious free dynamic range, the present circuit compares favorably with other reported mixers, operated at low voltage, both in bipolar and CMOS technologies. This is true even though a significant contribution to the noise figure comes from the IF stage, due to the very low supply.

Fully Integrated GPS Radio for Location Based Services

Using a composite source-follower with positive feedback to synthesize complex poles, a single-branch CMOS biquad achieves large linearity at low overdrive voltage, saving power. In 0.18mum CMOS with a 1.8V supply, a 41h-order 10MHz filter for WLAN applications achieves 17.5dBm IIP3 and mu40dB HD3 for a 600mVpp_diff input signal amplitude. A 24muVrms noise gives a 79dB DR while drawing 2.25mA from 1.8V