A novel method for reducing the impact of non-ideal pseudo-random binary
sequence (PRBS) on microwave photonic random demodulators (RDs) in a
photonics-assisted compressed sensing (CS) system is proposed. Different from
the commonly used method that switches the bias point of the optical modulator
in the RD between two quadrature transmission points to mix the signal to be
sampled and the PRBS, this method employs a PRBS with lower amplitude to low
bias the optical modulator so that the impact of non-ideal PRBS on microwave
photonic RDs can be greatly reduced by compressing the amplitude of non-ideal
parts of the PRBS. An experiment is performed to verify the concept. The
optical modulator is properly low-biased via PRBS amplitude compression. The
data rate and occupied bandwidth of the PRBS are 500 Mb/s and 1 GHz, while the
multi-tone signals with a maximum frequency of 100 MHz are sampled at an
equivalent sampling rate of only 50 MSa/s. The results show that the
reconstruction error can be reduced by up to 85%. The proposed method can
significantly reduce the requirements for PRBS in RD-based photonics-assisted
CS systems, providing a feasible solution for reducing the complexity and cost
of system implementation.Comment: 9 pages, 5 figure