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.