A prototype implementation of a two-channel frequency-translating hybrid ADC

In this paper, a proof-of-concept prototype of a two-channel frequency-translating hybrid (FTH) analog-to-digital converter (ADC) is implemented using off-the shelf components. The FTH structure is suitable for high-bandwidth ADCs. In this architecture, the wideband input signal is decomposed into smaller frequency subbands (channels). Each channel consists of a two-path system that frequency translates its input signal to baseband, lowpass filters each path signal using identical analog baseband filters, and samples and digitizes each path signal using identical baseband lower-speed ADC circuits. Unlike conventional parallel architectures, sampling is accomplished after splitting the signal into narrow baseband components alleviating the need for high-speed S/H circuitry. After digitizing the signal in each channel, the low-rate subband samples are upconverted back to their respective center frequencies, filtered, and recombined to reconstruct the digital representation of the original wideband input signal. The digital filters are optimized to minimize the reconstruction error. It is shown that the effects of many major analog non-idealities can be compensated in the digital domain.