Patent ID: 6064871
Filing Date: 2000-05-16
Classification: H03M

Abstract:
A low power sigma-delta converter comprising:a) a sampling mixer for frequency translating and sampling a modulated input signal utilizing a local oscillator signal to produce a sampled input signal;b) a subtracter for receiving and subtracting an analog feedback signal from said sampled signal and in response generating a difference signal;c) a passive path loop filter for receiving and filtering said difference signal;d) a comparator for receiving and quantizing said difference signal filtered by said passive path loop filter and in response generating an output digital code; ande) a digital-to-analog converter for receiving and converting said output digital code to said analog feedback signal and transmitting said analog feedback signal to said subtracter, wherein said sampling mixer further comprises a first switched capacitor having one terminal connected via a first switch to receive said modulated input signal and a second terminal connected via a second switch to ground, said first switch being clocked via said local oscillator signal, wherein said first and second switches are each of a size characterized by a width-to-length ratio (W/L) greater than 18/1.2 and the rise and fall times of said local oscillator signal are within a range characterized as substantially eliminating intermodulation distortion product, wherein said sampling mixer further comprises a third switch connected intermediate said one terminal and a source of positive reference voltage and a fourth switch connected intermediate said one terminal and a source of negative reference voltage, said third and fourth switches being clocked via inverted and non-inverted versions of said output digital code.