Yiming Pi

A novel approach to improve Doppler tolerance of polyphase code

Polyphase codes have a large mainlobe-to-sidelobe ratio in matched filter processing. However, the conventional matched filter processing of polyphase codes suffer severe signal loss in performance under large Doppler environment. The basic approach for overcoming the Doppler effect is to use a bank of Doppler-matched filters. Each of the Doppler-matched filters is designed to match a different Doppler frequency. However, the brute force method causes heavily computed burden. This paper proposed a novel correlator based on partial match filter (PMF), followed by the FFT and maximum output selector. The method can simultaneously search all possible Doppler frequencies. The processing scheme can cancel the phase rotation resulted from Doppler frequency, therefore, improve Doppler tolerance when detecting polyphase codes. The performance for the Doppler tolerance improves with decreasing of size of partial correlator and FFT. The scalloping loss can be compensated by zero-padding FFT.

Polarization decomposition with S and T matrix of a PolSAR image

Polarization decomposition is an important approach for polarimetric SAR image classification. In this paper, decomposition methods with different data format are discussed. Especially, A new decomposition method which is Krogagger decomposion with T matrix is proposed. Simulation results show that decompositions with T matrix have less speckle.

The Nonlinear Adaptive Filters for Narrow-band Interference Suppression in DS Spread Spectrum Communications

In this paper, we discussed several kinds of nonlinear filters. In the end, inspired by these filters, a new kind of nonlinear filter called nonlinear LTJ filter was proposed. We discussed their SNR improvement and convergence speed in narrow band interference suppression in DS-SS communications and their complexity

An airborne radar system for three dimensional SAR tomography

In this paper, a new airborne radar system for three dimensional SAR tomography is proposed. The multiple antennas are amounted under the wing of airplane with one transmitter element and all receivers. The signal model of this system is presented and the unambiguous elevation is given. The feasibility is validated by simulation results both from single flight and multiple sparse flights.