Quadrature compressive sampling for radar echo signals

Quadrature sampling is an effective technique for extracting digital in-phase and quadrature (I/Q) components in the modulated radio signals. Existing quadrature sampling techniques require the sampling rate to be at least twice of the band- width of the bandpass signal. The newly introduced compressive sampling theory makes sampling the analog signal at a low sampling rate possible if the signal has a sparse representation. This paper merges the two sampling techniques and develops a quadrature compressive sampling (QuadCS) system to obtain the digital I/Q components with low-rate samplers. The operation principle of the QuadCS system is described and the formulation to recover the I/Q components from the low-rate samples is developed. The simulation results demonstrate that the QuadCS is effective for acquiring and reconstructing the I/Q components sparse in waveform-matched dictionary. With the QuadCS system, the simulated signals can be sampled at about 10% Nyquist sampling rates. In addition, the output signal-to-noise ratio is improved about 15~20dB.