Abstract
A quadrature bandpass /spl Delta//spl Sigma/ modulator IC facilitates monolithic digital-radio-receiver design by allowing straightforward "complex A/D conversion" of an image reject mixer's I and Q, outputs. Quadrature bandpass /spl Delta//spl Sigma/ modulators provide superior performance over pairs of real bandpass /spl Delta//spl Sigma/ modulators in the conversion of complex input signals, using complex filtering embedded in /spl Delta//spl Sigma/ loops to efficiently realize asymmetric noise-shaped spectra. The fourth-order prototype IC, clocked at 10 MHz, converts narrowband 3.75-MHz I and Q inputs and attains a dynamic range of 67 dB in 200-kHz (GSM) bandwidth, increasing to 71 and 77 dB in 100- and 30-kHz bandwidths, respectively. Maximum signal-to-noise plus distortion ratio (SNDR) in 200-kHz bandwidth is 62 dB. Power consumption is 130 mW at 5 V. Die size in a 0.8-/spl mu/m CMOS process is 2.4/spl times/1.8 mm/sup 2/.
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