I. Introduction
The next generation radar systems require increasing demands such as large instantaneous bandwidth for increased resolution, wide operation frequency for multi-function and high radio frequency (RF) isolation for large-scale antenna phased array systems. These demands put electronic technologies under pressure. Thanks to the advantages of large bandwidth, high isolation and immunity to electromagnetic interference, photonic assisted microwave processing techniques provides new solutions for radar receivers [1]-[3]. In a traditional radar receiver, the ADCs which provide less than 10GSPS sampling rate and several GHz analog bandwidth become the bottleneck. To solve this problem, photonic ADC technology has been widely researched for several decades [4]-[5]. In recent years, the photonic ADC based on time-wavelength interleaving architecture attracts much attention. In the time-wavelength interleaved photonic ADC (TWI-PADC), high sampling rate is achieved by wavelength multiplexing of several optical pulse trains. After modulated with the analog electronic RF signal by an electro-optic modulator, the high repetition optical pulse train is wavelength-demultiplexed into several channels. Each channel can be converted to electronic signal by an array of photo detectors (PDs) and then quantized by an array of low speed electronic ADCs. Some results achieved with this approach include a 2.1GSPS photonic ADC with 7bits ENOB and a 40GSPS photonic ADC with 7.5bits ENOB [6]-[7].