On synthesizing high speed sigma-delta DACs by combining the outputs of multiple low speed sigma-delta DACs

The analog to digital converter (ADC) has received the lion´s share of attention in the DSP based radio community because most radios are in fact radio receivers. We see, for example, how receive-only satellite, cable, and television receivers dominate the consumer market. Consequently, the spurious free dynamic range (SFDR) performance of a digital to analog converter (DAC) lags behind that of an ADC with comparable conversion rate and bit width. There is high interest in wide dynamic range, high-speed DACs for use in various two-way communication systems. We present a technique to combine the analog outputs from two or more DACs operating at reduced conversion rate to synthesize a composite DAC operating at a higher conversion rate.