Reduction of sampling rate in a time-interleaved photonic ADC for RF direct sampling

Abstract

Photonic RF direct sampling with multiple electronic analog-to-digital converters (ADCs) for time-interleaved quantization is an effective technique for digitally receiving RF signals. Since band-pass sampling is inevitable for RF direct sampling, the required total sampling rate of a photonic ADC system could be remarkably higher than the low-pass Nyquist sampling rate given by twice the bandwidth of input signal. In order to reduce the sampling rate and thus boost the efficiency of the photonic ADC hardware, we propose a method of introducing time errors between time-interleaved channels with post correcting algorithm in frequency domain. Simulation is performed based on a photonic ADC consisting of multiple 2-GSa/s sub-ADCs. A wideband signal covering the frequency band from ~4 GHz to ~9 GHz is employed as the input RF signal for direct sampling in the simulation. Reduction of the total sampling rate from the band-pass Nyquist rate of 18 GSa/s to the low-pass Nyquist rate of 10 GSa/s is achieved, through which the advantage of the proposed method is verified.