Instantaneous cross-correlation function type of WD based LFM signals analysis via output SNR inequality modeling

Linear canonical transform (LCT) is a powerful tool for improving the detection accuracy of the conventional Wigner distribution (WD). However, the LCT free parameters embedded increase computational complexity. Recently, the instantaneous cross-correlation function type of WD (ICFWD), a specific WD relevant to the LCT, has shown to be an outcome of the tradeoff between detection accuracy and computational complexity. In this paper, the ICFWD is applied to detect noisy single component and bi-component linear frequency-modulated (LFM) signals through the output signal-to-noise ratio (SNR) inequality modeling and solving with respect to the ICFWD and WD. The expectation-based output SNR inequality model between the ICFWD and WD on a pure deterministic signal added with a zero-mean random noise is proposed. The solutions of the inequality model in regard to single component and bi-component LFM signals corrupted with additive zero-mean stationary noise are obtained respectively. The detection accuracy of ICFWD with that of the closed-form ICFWD (CICFWD), the affine characteristic Wigner distribution (ACWD), the kernel function Wigner distribution (KFWD), the convolution representation Wigner distribution (CRWD) and the classical WD is compared. It also compares the computing speed of ICFWD with that of CICFWD, ACWD, KFWD and CRWD.

The Curious Case of Effective Isotropic Sensitivity

This paper establishes a solid mathematical model for Over the Air (OTA) test and characterization of 5G millimeter wave User Equipment (UE) in Compact Antenna Test Ranges (CATR). Special attention is paid to receiver characteristics and polarization mismatch problem which is encountered in spherical coverage tests. The received power of a UE with dual-polarized antenna system is derived and output SNR is calculated using Maximal Ratio Combining (MRC) principle. And finally, some of the misconceptions in 3rd Generation Partnership Project (3GPP) standards publications is addressed<br>

The Curious Case of Effective Isotropic Sensitivity

This paper establishes a solid mathematical model for Over the Air (OTA) test and characterization of 5G millimeter wave User Equipment (UE) in Compact Antenna Test Ranges (CATR). Special attention is paid to receiver characteristics and polarization mismatch problem which is encountered in spherical coverage tests. The received power of a UE with dual-polarized antenna system is derived and output SNR is calculated using Maximal Ratio Combining (MRC) principle. And finally, some of the misconceptions in 3rd Generation Partnership Project (3GPP) standards publications is addressed<br>

Study on Time Reversal Maximum Ratio Combining in Underwater Acoustic Communications

Time reversal (TR) can achieve temporal and spatial focusing by exploiting spatial diversity in complex underwater environments with significant multipath. This property makes TR useful for underwater acoustic (UWA) communications. Conventional TR is realized by performing equal gain combining (EGC) on the single element TR output signals of each element of the vertical receive array (VRA). However, in the actual environment, the signal-to-noise ratio (SNR) and the received noise power of each element are different, which leads to the reduction of the focusing gain. This paper proposes a time reversal maximum ratio combining (TR-MRC) method to process the received signals of the VRA, so that a higher output SNR can be obtained. The theoretical derivation of the TR-MRC weight coefficients indicates that the weight coefficients are only related to the input noise power of each element, and are not affected by the multipath structure. The correctness of the derivation is demonstrated with the experimental data of the long-range UWA communications conducted in the South China Sea. In addition, the experimental results illustrate that compared to the conventional TR, TR-MRC can provide better performance in terms of output SNR and bit error rate (BER) in UWA communications.

Sensitivity Analysis of the Simply Noise-matched Receiving Coil for NMR Experiments

The article analyzes the sensitivity of unmatched receiving coil for the NMR scanner. Receiver of the scanner was investigated from the point of view of noise features. Theory of the noise figure has been modified to utilize the receiver for digitization of its own noise and the noise figure calculation. The resulting noise figure has been measured with different source impedances and the optimal value has been acquired. Influence of the noise figure on the resulting signal-to-noise ratio has been calculated for the sensitivity judgement. The output SNR has been investigated for constant input SNR as well as for constant input voltage. Many results are depicted in figures. Also examples of theoretical results are depicted graphically.

A Novel Adaptive Stochastic Resonance Method Based on Tristable System and its Applications

Stochastic resonance systems have the advantages of converting noise energy into signal energy, and have great potential in the field of signal detection and extraction. Aiming at the problems of the performance of classical stochastic resonance system whose model is not perfect enough and the correlation coefficients between parameters is too large to be optimized by algorithm, then a novel model of the tristable potential stochastic resonance system is proposed. The output SNR formula of the model is derived and analyzed, and the influence of its parameters on the model is clarified. Compared with the piecewise linear model by numerical simulation, the correctness of the formula and the superiority of the model are verified. Finally, the model and the classical tristable model are applied to bearing fault detection in which the genetic algorithm is used to optimize the parameters of the two systems. The results show that the model has better detection effects, which prove that the model has a strong potential in the field of signal detection.

Robust Signals Detection Algorithm Based on Cyclostationarity in Impulsive Noise

A robust method for detecting the communication signals impinging on an antenna with interference and non-Gaussian impulsive noise is introduced in this paper. Degradation of the conventional cyclic detector which based on max-output-SNR criterion in impulsive noise is shown both theoretically and experimentally. By fusing second-order cyclostationarity and fractional lower-order statistics, a type of cyclic fractional lower-order statistics is developed which is defined for exploiting cyclostationarity property. Then, a new robust type of detection algorithm is developed using the theory of optimal filtering based on max-output-SNR criterion and alpha-stable distribution, including the fractional lower-order cyclic matched filter, which is formulated for detecting the communication signals in the presence of interference and non-Gaussian alpha-stable distribution impulsive noise. It is shown that the new method is robust to Gaussian and non-Gaussian impulsive noises, and is immune to the interfering signals which occupy the same spectral band as that of the received signal. Simulation results show the robustness and effectiveness of the proposed algorithm.