Wideband Anti-Leakage Interference CW Radar by Using Silicon Photonics Integrated Chip With Spectrum Predistortion

Continuous wave (CW) radar is widely used in both civil and military scenarios due to its advantages of blind-zone free detection and low probability of interception. To achieve higher resolution and longer detection range for new generation CW radar, the high-power, wide band leakage interference (LI) must be resolved. In this paper, a leakage interference cancellation scheme is proposed by using silicon photonics integrated (SPI) chip with spectrum predistortion, by virtue of the wide band photonic RF interference cancellation and the high fine spectrum processing. The amplitude and delay of the reference signal are regulated in optical domain on the SPI chip with operation band of 25.2 GHz, which is composed of the Mach–Zehnder modulator for electro-optic modulation, the optical amplitude adjuster for precise amplitude control, and the “switched waveguide + long spiral waveguide” delay line for continuous time tuning. The spectrum predistortion is applied for compensate the mismatch of frequency response between the reference and interference links. Experimental results show that the cancellation depth of 40.3 dB and 37.0 dB are realized over bandwidth of 300 MHz and 1 GHz, respectively. In the operation scenario with antennas, the LI cancellation depth of 23.3 dB and 19.1 dB are measured with the corresponding bandwidth. For distance measurement and inverse synthetic aperture radar imaging with the SPI chip-based CW radar system, the measured results demonstrate that the receiver saturation problem is successfully overcome and receiving sensitivity and image performance are improved greatly.