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This paper proposes an effective method for frequency spectrum estimation using multi-channel co-prime sampling. Previous work has adopted a multi-channel sampling system to sense sparse signals, but its model suffers from the grid mismatch problem and the average sampling rate is high due to the redundancy among different channels. In this paper, we design a multi-channel co-prime sampling scheme...
In this paper, we propose a polarization filtering-based transmission scheme to enhance the physical layer security in the dual-polarized satellite communication. To prevent eavesdropping, this paper first divides the information sequence into two parts and modulates them independently. Subsequently, a pair of dual polarization states (PSs) is selected to carry the two modulated signals based on the...
In this paper, a novel transmission scheme based on constellation rotation and weighted fractional Fourier transform (WFRFT) is proposed to enhance the physical-layer security in polarization modulation (PM)-based dual-polarized satellite communications. Typically, by appropriately selecting the WFRFT order, the distribution of the signals processed by WFRFT can be close to Gaussian, which makes them...
In this paper, a directional polarization modulation (DPM) scheme is proposed to enhance the secure transmission performance of the dual-polarized satellite multi-input multi-output (MEMO) system. Indeed, the signal's polarization state (PS) is determined by its two components and two orthogonally polarized arrays are designed to transmit these two components in the proposed scheme. In this way, the...
In this paper, we present a new family of sparse measurement matrices and low complexity reconstruction algorithm in compressed sensing (CS). Our CS system is designed from the generalized low-density parity check code (GLDPC), and to reconstruct the signal by using a simple verification-based (VB) algorithm. In particular, our scheme also can cope with the case of noisy measurements, comparing with...
Low frequency radio wave has efficient long-range propagation in the so-called earth-ionosphere waveguide and it is widely used in communication and navigation. However, low frequency radio wave is suffered from intensive atmospheric noise. In order to extract signal of interest from atmospheric noise, adaptive soft limiter is used to suppress the impulsiveness of the atmospheric noise. And then the...
In this paper, the ELF atmospheric noise measured by a low-temperature superconducting receiver is analyzed and modeled. The measured data are firstly reconstructed by wavelet transform to remove baseline wandering. And then the harmonics radiated by power line are estimated and subtracted by least square estimation. After preprocessing the measured data, Hall model and symmetric a stable (SaS) distribution...
The problem of joint frequency and direction of arrival (DOA) estimation for multiple narrowband signals is addressed here. Previous work has employed co-prime arrays and co-prime samplers to estimate the frequency and DOA individually. Though this can increase the degrees of freedom (DOFs) in the space or time domain, the drawback lies in that it requires an extra procedure to pair these two kinds...
The corrosion and corrosion resistance current of the submarine modulated by the propeller rotation will produce extremely low frequency (ELF) electromagnetic field in the seawater, which can be used as the attack feature for underwater weapons. However, ELF noise is highly process-sensitive, rendering it as a non-stationary signal, and, hence, traditional Fourier analysis method is not adequate....
In this paper, a new class of deterministic sparse matrices derived from Quasi-Cyclic (QC) low-density parity-check (LDPC) codes is presented for compressed sensing (CS). In contrast to random and other deterministic matrices, the proposed matrices are generated based on circulant permutation matrices, which require less memory for storage and low computational cost for sensing. Its size is also quite...
The measurement matrix plays an important role in the hardware implementation of wideband sub-Nyquist sampling. In modulated wideband converter (MWC), the measurement sequences are derived from binary measurement matrix, e.g., random Bernoulli matrix, which can be easily implemented by M ×N shift registers. Utilizing the special cyclic structure, partial circulant measurement matrix only needs N shift...
Chirp spread spectrum (CSS) technique has been extensively studied in the application of Ultra-wide band (UWB). Considering the long distance propagation capacity and low intercepted probability of chirp signal, we propose to apply the CSS technique to the very low frequency (VLF) communication system. First, we discuss the CSS system based on fractional Fourier transform (FRFT), including the definition...
In this paper, a new beamformer with improved robustness against the small sample size is proposed. This beamformer first employs the modified sparse Bayesian learning (SBL) algorithm to obtain an accurate estimate of the covariance matrix. To further improve the robustness, subspace projection is implemented subsequently. In addition, due to the inherent decorrelation capability of the SBL algorithm,...
Error vector magnitude (EVM) is extensively applied as a measure of wireless communication systems' performance. In this paper, the effects of amplitude and phase errors for satellite digital beam-forming (DBF) multi-beam phased array antenna systems on EVM are investigated. The analytic expression for EVM about array channels' amplitude and phase errors is derived and verified by computer simulation.
A transmitting beam shaping scheme with limited amplitude weighted values for satellite active phased array antenna is presented to meet lower sidelobe and higher power amplifiers efficiency. The scheme is implemented by a dual coding genetic algorithm (GA) .Phase and amplitude of array weight vectors for shaped beam are encoded by real coding and finite length binary coding, which, maintaining accuracy...
Network Simulator has become an essential tool of studying network performance and designing network programme. NS-2 is an universially used network simulate software of various protocols, which can realize the simulation of network topology, protocol and the amount of sending data; therefore, it can get every network performance parameter from the simulated network act and control the network's running...
The enduring changes of operate demands in network stimulate the production & development of new protocols and new algorithms. But designing and calculating these protocols and algorithms concern many problems. Although it is valuable of the practical experiment in the real circumstance like laboratory and test bed, they lack proper flexibility and expansibility. Under this circumstance, Network...
Network simulator (NS) is a kind of enwlation software with powerful functions. Its biggest function is that it can check and compare the performances of various kinds of protocols and provide experimental data for researchers to analyse whether their performances are good or bad. This paper proposes a method to design network topology and script program, then uses NS to compare performances of network...
A method for the analysis of simultaneous switching noise (SSN) on power distributions networks is developed. To alleviate the ill-conditioned matrix problem in constructing the macromodels of power distribution networks, the modified Gram-Schmidt orthogonal method is used to implement the matrix decomposition in QR form. Meanwhile a simple equivalent circuit model is presented for transient simulations,...
The anti-jamming performance of adaptive array used in satellite mobile terminal is limited in the wideband jamming plus multipath environment. A new subband adaptive array method based on LS-CMA is proposed, which can eliminate wideband jamming and theirs multipath when degree of freedom is limited. The formula of this method is deduced theoretically. The relationship of subband adaptive processing...
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