基于平方律检波的二相编码信号 分段相关-视频积累方法研究

分析了载波多普勒下基于平方律检波的二相编码信号的分段相关-视频积累检测方法,推导了处理损耗公式.采用最大处理损耗最小化准则,分析了总积累时间给定和检测性能指标给定两种情况下最优中频积累时间的计算方法和变化规律.研究结果可用于指导扩频通信和导航系统接收机的设计.     

On the near-equivalence of envelope and square-law detection of correlated Gaussian noise

Postdetection integration of radar signals in correlated noise background results in degraded detection performance which is analytically tractable for a square-law detector, but not for the linear envelope detector usually employed in practical radar receivers. It is shown that for stationary Gaussian input noise with arbitrary correlation, the "effective number of integrated independent noise samples" (Ne) satisfies: 1 ≤ Ne(envelope)/Ne(square-law) ≤ 4(4 - π)π ≈ 1.093, thus suggesting near-equivalence of the detection performance and justifying results previously obtained by simulation techniques.     

Signal processing in an optical polarization diversity receiver for560-Mbit/s ASK heterodyne detection

Polarization diversity is an alternative technique for coherent receivers to prevent loss to signal due to variations in the states of polarization (SOP) of the received signal field. It is shown experimentally and theoretically that there is no significant power penalty difference between a receiver with optimally adjusted gains and receivers with linear envelope detection and square-law detection. Experimentally, two amplitude-shift keying (ASK) heterodyne polarization diversity receivers with envelope detectors were demonstrated at 560 Mb/s, one using linear rectifiers, the other using square-law rectifiers. In both cases, the receiver sensitivity of -35 dBm at BER=10 ^-9 was degraded by less than 1 dB as the received signal SOP was varied, in agreement with theory     

Envelope detection of a unit-index amplitude-modulated cartier accompanied by noise

The facts concerning the relative merits of linear and square-law envelope detection of a sinusoidally modulated carrier accompanied by Gaussian noise are clarified in this paper. The comparison when the carrier is weakly modulated and has mean power substantially greater than that of the noise in the input circuit has been fully covered in prior technical literature. In this special case the signal-to-noise ratio (SNR) in the detected output is the same for the two methods, and the distortion of the signal is worse with square-law operation because of inherent second-harmonic production. Since noise in the detected output is typically measured in the absence of signal modulation, the fact that the relative performance changes when the index of modulation approaches 100 percent tends to be overlooked. It is shown in the present paper that the noise performance of the square-law detector suffers a penalty approaching 1.8 dB when the carrier is strongly modulated. Also, the distortion in the square-law case is characterized by a second harmonic only 12 dB down from the fundamental, while the second harmonic in the output of the linear detector is practically negligible. These results are important in the evaluation of techniques in diversity reception.     

Multiuser square-law detection with applications to fiber optic communications

Optimal and suboptimal multiuser noncoherent detection for square-law receivers is studied in this paper. Great potential is found for the multiuser square-law detector when compared with the conventional single-user square-law detector. We study the optimal detector and two detectors with simpler structures: the asymptotically optimal detector and the pairwise linear detector. The saddle-point approximation method is used to study the error performance and its asymptotic behavior as noise reduces. Due to difficulty in optimizing the detectors at an arbitrary noise level, we propose to use the asymptotic efficiency for detector optimization. For a low-error-rate system like a fiber optic communication system, the asymptotic efficiency is found to be an efficient way to design detectors. Numerical results show that the asymptotically optimized detectors perform as well as the optimal detector, even for nonzero noise levels of practical interest. Despite their exponential complexity, these detectors are applicable to wavelength-division multiplexed systems in which only a few neighboring channels produce strong interference.     

On detection of sparsely sampled data

The problem of detecting pulses of unknown amplitude and arrival time from sparse, noisy samples is considered. Several approaches are found to result in the square-law video amplifier, the performance of which is compared graphically with both single-sample detection and clairvoyant matched filtering.     

Quantitative Comparison of Solid-State Microwave Detectors

A method for quantitative comparison of solid-state microwave square-law detectors is presented. The threshold response of the square-law detectors are compared for unit video bandwidth using the concept of noise equivalent power (NEP). NEP is the microwave input power required for unity signal-to-noise ratio in a 1 Hz bandwidth at the output of the detector. Contours of constant NEP in the microwave (RF) and video frequency plane clearly describe the dependence of threshold sensitivity on both video and radio frequencies, and thereby provide comparison of the threshold sensitivities of devices over the entire video and RF frequency spectrum. A criterion for the upper RF power lid of square-law operation for detectors is also presented. Dynamic range for a device can be found using this criterion and the threshold sensitivity of the device. Six solid-state detection devices are described briefly, then compared on the basis of the foregoing concepts. Four of these devices are familiar: the point-contact and planar Schottky-barrier ("hot carrier") diodes, and the tunnel and back diodes. Two relatively new devices are also discussed: the so-called "hot carrier" thermoelectric detector, and the space-charge-limited (SCL) dielectric diode.     

A distribution-free sequential probability-ratio test for multiple-resolution-element radars (Corresp.)

A distribution-free procedure applicable to the detection of a signal in some element of a multiple-resolution-element radar is described. The procedure is based on rank-order statistics and is applicable to either a sequential or fixed-sample-size test; however, emphasis is placed on the sequential procedure. Results are given showing the expected sample size and probability of detection for the case of envelope detection (square-law or linear) of a fluctuating signal (Swerling model 2). A comparison is made with the optimum parametric sequential procedure.     

On the detection and classification of quadrature digitalmodulations in broad-band noise

Optimal and suboptimal decision rules for the detection of constant-envelope quadrature digital modulations in broadband noise are derived and analyzed. The effect of various stochastic models for the carrier phase is examined in detail, while no epoch or frequency uncertainty is assumed. The delay-and-multiply type of detector is considered. A new binary/quadrature phase shift keying (BPSK/QPSK) classifier is compared to the more traditional ad hoc techniques of a square-law classifier and a phase-based classifier (weighting on the phase histogram). The new classifier is derived by approximating the likelihood-ratio functionals of phase-modulated digital signals in white Gaussian noise, hence is named the quasi-log-likelihood ratio (qLLR) rule. It is shown analytically that its performance is significantly better than that of intuitively designed phase-based rules or the conventional square-law classifier     

High-Spectral-Efficiency 114-Gb/s Transmission Using PolMux-RZ-8PSK Modulation Format and Single-Ended Digital Coherent Detection Technique

Employing spectrally efficient PolMux-RZ-8PSK modulation format and single-ended digital coherent detection technique, we demonstrate 8$,times,$114-Gb/s DWDM transmission over 640 km of SSMF on a 25-GHz grid with record spectral efficiency of 4.2 bit/s/Hz, utilizing no optical dispersion compensation or Raman amplification. We show that the distortion caused by the direct square-law detection of the signal component with single-ended photo detection can be effectively mitigated by a novel DSP algorithm.      

Performance of multiple-dwell pseudo-noise code acquisition with I-Q detector on frequency-nonselective multipath fading channels

Multiple-dwell pseudo-noise code acquisition with a noncoherent I-Q detector is analyzed for Rayleigh and Rician fading channels that takes into account the detection correlations resulting from multipath fading. Minimum mean acquisition times with optimized dwell times and thresholds are obtained, and the effects of multipath fading and frequency offsets are evaluated. In addition, a detailed comparison between I-Q and square-law detectors is conducted under various channel conditions.     

Limits of optical dispersion compensation using linear electrical equalizers

This letter considers optical dispersion compensation in the electrical domain. It is shown that after electrical detection the spectrum of the optical signal suffers a frequency cutoff. The maximum frequency, which can be detected by the square-law detector, is inversely proportional to dispersion in the optical line. This puts a limit on the maximum value of optical dispersion, which can be compensated by electrical equalizers.     

A study on an active square-law combining method for apolarization-diversity coherent optical receiver

A polarization-diversity coherent optical receiver which realizes ideal square-law combining with active gain control is described. This receiver can suppress the additional power penalty due to the demodulator dynamic range limitation by equivalently expanding the demodulator dynamic range. A low-power penalty less than 1 dB was attained with a 400-Mb/s FSK (frequency-shift keyed) single-filter detection system. Throughout a 25-h 183-km transmission experiment, the stable operation of this receiver was confirmed     

Analogue kurtosis detector for radio-frequency interference in microwave radiometers

An analogue system has been developed for radio frequency interference (RFI) detection in microwave radiometers. The detector measures the higher order moments of the signal and the kurtosis measurement is used to determine the presence of RFL The hardware comprises a square-law detector and a high-speed analogue multiplier. Because the circuit uses only analogue components at radio and/or intermediate frequencies, it can easily augment conventional radiometer architectures used in both airborne and spaceborne instruments.     

Performance analysis of the biased square-law sequential detectorwith signal present

A new method is proposed to analyze the performance of a biased square-law sequential detector when a signal is present. Starting from Albert's (1954) integral equations, the method evaluates the detection probability and the moments of the sample number very efficiently and accurately, using polynomial interpolations. Numerical examples show that the new method is much more efficient and/or accurate than the known methods. In addition, the analytical results are substantiated by computer simulations and Kendall's (1965) exact results for the cases of with and without signal present, respectively     

低信噪比下的比特同步设计

比特同步性能设计未有可直接引用的公式且其公式推导繁难,故而工程设计常停留在工程经验层面。针对此问题,以平方律检波比特同步设计为例,在高斯白噪声信道条件下,分析了其功率谱密度,推导了其输出信噪比表达式,总结了影响比特同步性能改善的因素,并在分析结果基础之上,给出了低信噪比下的比特同步设计方法,这对工程设计有着重要的指导意义。     

Detection of ship wakes using an airborne magnetic transducer

Wakes induced by the motion of vessels may extend for tens of kilometers and exist for hours under certain conditions in the open sea. This provides a useful feature for long-range ship detection. The authors present a method for passively detecting a ship wake using measurements obtained by an airborne SQUID magnetic transducer that measures the first order gradients of the magnetic signature induced by the wake. Analytical formulas for wake magnetic gradients are derived to provide guidelines for using the airborne detector. They also derive bounds on the probability of wake detection for cross correlation and square-law detectors, which can be used to predict the expected performance. Numerical examples are used to demonstrate the applicability of their results     

Generalized selection combining based on the log-likelihood ratio

We propose a generalized selection combining (GSC) scheme for binary signaling in which a subset of diversity branches providing the largest magnitude of log-likelihood ratio (LLR) are selected and combined. It is shown that the bit-error probability with maximum ratio combining (MRC) or square-law combining of L branches is identical to that with LLR-based GSC of L/2 branches. We also propose a simple, but suboptimal, GSC based on a noncoherent envelope detection and discuss its potential advantages over the conventional signal-to-noise-ratio-based GSC and MRC.     

基于Monte Carlo模型的FFH/BFSK合并技术研究

分析了FFH/BFSK接收机的两种合并方式:平方律线性合并和具有自适应增益控制(AGC)的平方律非线性合并;在部分频带噪声干扰下,使用Monte Carlo模型对这两种合并方式进行仿真得到误码率曲线,仿真结果与理论误码率吻合,并得出结论:在热噪声功率受限的情况下,使用AGC合并能有效的抑制部分频带噪声干扰.     

A versatile CMOS linear transconductor/square-law function

A simple CMOS circuit technique for realizing both linear transconductance and a precision square-law function is described. The circuit provides two separate outputs in the linear as well as square-law modes. The linear outputs both have a range of 100% or more of the total quiescent current value. The theory of operation is presented and effects of transistor nonidealities on the performance are investigated. Design optimization techniques are developed. Experimental results measured on nonoptimized prototypes are: distortion of 0.2% for input signals up to 2.4 V/SUB p-p/ in the case of linear transfer function and 1.3% in the case of the square-law transfer function, with a DC to -3-dB bandwidth of up to 20 MHz. Improved performance is expected when the optimization techniques developed are applied. The circuit is versatile in application: diverse applications are demonstrated in the fields of linear amplifiers, continuous-time filters, and nonlinear function implementation.