Non-coherent Integration Research Articles

Novel noncoherent radar pulse integration to combat noise jamming

In conventional noncoherent radar pulse integration (NCPI), the radar receiver sums the envelope detector outputs obtained in multiple pulses from the target within one scan. A novel modification to NCPI is proposed in which the receiver first normalizes the envelope detector output in each range bin by the sum of envelope detector outputs corresponding to all range bins of a pulse. It is shown that the proposed scheme yields significant performance gain against noise jamming.

LOW COST X BAND RADAR SYSTEM FOR MULTIPLE TARGET DETECTION

Radar based object detection systems have been in place for about a century serving various purposes like detection of ships aircrafts, spacecraft, navigation, reading weather formations and terrain mapping. With the advent of better packing technologies and signal conditioning circuits radars have become compact and affordable thus offering comparatively low cost solutions than other systems based on imaging. This paper describes an X band Radar System for multiple target detection that can work as an effective solution for obstacle detection and collision avoidance system to be used in automated braking systems. This radar system is capable of detecting multiple targets from the clutter encountered by the radar signals within a range of 20 metres. The paper discusses various moving target indicator techniques employed for multiple target detection and speed of the object in real time. This is particularly useful in automotive industries where the low cost motion sensors are needed in variety of applications which are necessary to ensure the safety of the passengers. To ensure a good signal to noise ratio we have used non coherent integration so that the radar signal is recognizable among the clutter. Moving Target Indicator techniques are used primarily to detect the number of objects in the range of the radar. This is carried out along with adaptive constant false alarm thresholding technique so that the object can be detected among the clutter and noise accurately. An Arduino Uno is used for detecting the objects and speed after processing on the non-coherently integrated pulse.

Polarimetric passive coherent location

In this paper the exploitation of different linear polarimetric channels is considered as a way to mitigate the effect of interfering sources and to improve the target detection capability in an FM radio-based passive radar. The signals emitted on same/adjacent frequency channels by potential transmitters (other than the illuminator of opportunity) located in the surveillance area are shown to significantly affect the performance of the considered system in terms of both disturbance cancellation and target detection. Moreover, it is verified that the achievable performance is dependent on the adopted polarization at both the reference and the surveillance channel since employing vertically or horizontally polarized antennas might yield very different results. Therefore effective approaches are introduced to jointly exploit the diversity of information conveyed by different polarizations at both the reference and surveillance channels. The results are shown against a real data set collected by an experimental multichannel passive radar prototype developed and fielded at the DIET Dept. of the University of Rome “La Sapienza,” Italy. A significant performance improvement is achieved with the proposed processing schemes that always provide better results than the standard processing of the signals collected at the best polarimetric reference and surveillance channels. Besides the expected improvement due to noncoherent integration of target echoes received on multiple channels, the proposed multipolarimetric operation is shown to yield a remarkable improvement when operating in a severe interference scenario so that it can be regarded as practical solution for robust and effective passive coherent location (PCL).

A novel [z log(z)]-based closed form approach to parameter estimation of k-distributed clutter plus noise for radar detection

In this paper, we present a novel [z log(z)]-based approach to the evaluation of estimators of the K-distributed clutter plus thermal noise parameters. In doing this, we start by deriving expressions of log-based moments of the received data, i.e., means of [log(z)] and [z log(z)], which are related to the parameters of the K plus noise distribution, the digamma, and the hypergeometric functions. Then, by accommodating a single pulse and noncoherent integration of N pulses, respectively, we first determine the new estimators in terms of log-based moments and first- and second-order moments. As the computation of these nonlinear estimates requires the use of numerical routines, we resort to the inverse of the harmonic mean of the received data to get equivalent but more interesting estimates in which expressions are independent of the confluent hypergeometric functions. Monte Carlo simulations show that the proposed estimators are more efficient than existing methods for various clutter plus noise situations.

A Simple and Efficient Scan Correlation Algorithm for Sea Surveillance Radar

In most sea surveillance radars based on non-coherent integration, the scan integration which improves signal to noise ratio and mitigates unwanted echo with a small correlation time such as sea clutter is widely used. The problems of the conventional scan integration are: (a) the target trail is generated through integrating prior scan and current scan; (b) it is difficult to detect a small and fast moving target because of the attenuated small target echo caused by scan integration. In this paper, the conventional scan integration algorithm is analyzed in order to overcome the above problems, and then a simple and efficient scan correlation algorithm is proposed to remove the target trail. The proposed scan correlation algorithm uses the difference the current and the prior CFAR processed scan video. Compared to the conventional scan correlation algorithm, the proposed method is very simple and efficiently removes the target trail. The computer simulation results show that the proposed algorithm can extract a fast moving target without a target trail.

Reduced-complexity FFT-based method for Doppler estimation in GNSS receivers

In this article, we develop a novel algorithm for Doppler acquisition in fast Fourier transform (FFT)-based Global Navigation Satellite System (GNSS) receivers. The Doppler estimation is carried out in FFT domain by finding the frequency shift which maximizes the energy of the correlation vector. Subsequently, energy detection is used for preliminary decision about the presence of the target code. Then, the final decision and code phase estimation are done in the time domain after taking the inverse fast Fourier transform (IFFT). It is shown that the proposed algorithm has the potential for reducing the average number of required IFFTs in the acquisition process. For improving the sensitivity of the proposed approach, time-domain block averaging and FFT-domain non-coherent integration are investigated as alternative methods. They exhibit rather similar performance improvement, but the non-coherent integration approach is found to be computationally more effective.

Product-based pulse integration to combat noise jamming

A novel radar pulse integration technique is proposed in which the received signals in various returns from the target during one scan are multiplied with each other instead of the conventional summing up. Using the Mellin transform, mathematical expressions are derived that pave the way for computation of probability of detection and probability of false alarm in the context of this technique. Analytical and simulation results show that the proposed product-based pulse combining is more resistant to noise jamming, as compared to conventional noncoherent pulse integration, under certain conditions.

A novel acquisition strategy for weak GNSS signals based on map criterion

Detecting and processing Global Navigation Satellite System (GNSS) signals indoors and in urban canyons, have gained a great deal of attention due to the problems of very weak signals and hostile environments. The detection of GNSS signals is generally based on the application of a statistical test, derived from the maximum likelihood theory. The work presented here considers a new approach to the detection of weak GNSS signals using a Bayesian technique within a scenario where the search space size is already reduced to a few tens of cells using some kind of assisted information. The search space cells are considered as candidate cells, where each candidate cell is associated with a code delay and a Doppler frequency. For each candidate cell, a posteriori probability is propagated for a fixed number of operation cycles. At the end of the process, the maximum a posterior (MAP) criterion is used to select the correct cell. Simulation results are presented indicating that the proposed method provides a significant performance advantage over other reference schemes. They include a noncoherent integration scheme and another scheme which also utilizes the posterior probabilities as decision statistics but differs in the mechanism of probability propagation.

레이더 시스템에서 목표물 탐지 거리 추정을 위한 코히런트 집적과 비 코히런트 집적의 SNR 성능 비교

논문에서는 레이더 시스템에서 코히런트 집적과 비 코히런트 집적의 SNR 성능에 대해서 비교한다. 본 논문에서는 레이더 시스템에서 반사파와 전송파의 왜곡을 방지하기 위해 펄스파를 송신 파형으로 사용하였다. 본 논문에서는 포락선 검파기 앞에서 처리하는 코히런트 집적과 포락선 검파기 뒤에서 처리하는 비 코히런트 집적을 사용하여 목표물 탐지 거리를 추정하고 집적 방식에 따른 SNR 성능을 비교한다. 모의실험을 통해서 코히런트 집적과 비 코히런트 집적의 SNR 성능을 비교 분석하였다. 코히런트 집적이 비 코히런트 집적보다 SNR 성능이 우수함을 입증하였다. This paper compare with SNR performance of coherent integration and non-coherent integration in radar system. This paper to prevent distortion of transmit signal and radar return in radar system is used to pulsed waveform. This paper to estimate target detection range and to compare with SNR performance used to coherent integration performed before the envelope detector and non-coherent integration processed after the envelope detector. Through simulation, SNR performance of coherent integration and non-coherent integration were comparatively analyzed. SNR performance of coherent integration is good proof higher than non-coherent integration.

레이더 시스템에서 레이더 단면적에 따른 탐지 거리 추정을 위한 코히런트 집적과 비 코히런트 집적에 대한 비교

본 논문에서는 레이더 시스템에서 탐지 거리 추정에 영향을 미치는 레이더 단면적의 크기에 대한 집적 방식을 비교 분석한다. 본 논문에서는 레이더 단면적의 크기에 따라 크기가 작을 경우 스웰링 케이스 1, 클 경우에는 스웰링 케이스 3의 탐지 확률을 레이더 방정식에 적용하여 탐지 거리를 추정하였다. 모의실험을 통해서 스웰링 케이스의 차이에 따른 코히런트 집적과 비 코히런트 방식을 비교 분석하였다. 모의실험을 통해서, 비 코히런트 집적 방식이 추정 거리가 가장 우수하였고 코히런트 집적 방식은 스웰링 케이스를 적용한 탐지 거리 추정에 적합하지 않음을 알 수 있었다. This paper comparatively analyze to integration case to have a influence detection range estimation about radar cross section in radar system. This paper estimate detection range used to probability of detection in radar equation that used to swerling case 1 in case of radar cross section is small and used to swerling case 3 in case of radar cross section is large. Through simulation, coherent integration and non-coherent integration about swerling case difference were comparatively analyzed. Through simulation, non-coherent integration case is outstanding detection range and we known that coherent integration don't suitable for detection range estimation.

Centralized Passive MIMO Radar Detection Without Direct-Path Reference Signals

This work addresses the problem of target detection in passive multiple-input multiple-output (MIMO) radar networks without utilization of direct-path reference signals. A generalized likelihood ratio test for this problem is derived, and the distribution of the test statistic is identified under both hypotheses. Equivalence is established between passive MIMO radar networks without references and passive source localization networks. Numerical examples demonstrate important characteristics of the detector, namely, the asymmetric contributions to detection performance from transmitters and receivers, and non-coherent integration gain as a function of signal length. The ambiguity properties of this detector are also investigated, and it is shown that the salient ambiguities can be explained in terms of the time-difference of arrival, frequency-difference of arrival, and angle-of-arrival of the target signals.

Parameter Optimization of UWB SRR System Performance in Weibull Clutter Environment

The objective of this paper is to optimize the parameters of non-coherent detectors such as coherent and non-coherent integration number for various non-coherent detectors such as square law detector, linear detector and logarithmic detector in weibull clutter environment for Ultra Wide Band Short Range Radar in Automotive applications. The detection performance of the detectors is analyzed for fixed false alarm probability of 0.001 and simulation has been done in order to verify it.

Analysis of Steering Vector Mismatch on Adaptive Noncoherent Integration

Amplitude and phase errors can cause mismatches between the hypothesized signal vector and the steering vector of an antenna array. A generalized likelihood ratio test (GLRT) for signal detection with multiple coherent processing intervals (CPIs) in unknown interference is derived. The detection performance of the resulting adaptive noncoherent integration (NCI) algorithm is analyzed along with the effect of steering vector mismatch on detection performance. Detection performance and the effect of steering vector mismatch are illustrated with results for both a nonfluctuating signal model and a CPI-to-CPI fluctuating signal model. It is shown that a signal-to-interference-plus-noise ratio (SINR) loss factor inherent to the algorithm in effect limits the performance gain due to NCI of mismatched signals.

Optimizing Wideband Cyclostationary Spectrum Sensing Under Receiver Impairments

In the context of Cognitive Radios (CRs), cyclostationary detection of primary users (PUs) is regarded as a common method for spectrum sensing. Cyclostationary detectors rely on the knowledge of the signal's symbol rate, carrier frequency, and modulation class in order to detect the present cyclic features. Cyclic frequency and sampling clock offsets are the two receiver impairments considered in this work. Cyclic frequency offsets, which occur due to oscillator frequency offsets, Doppler shifts, or imperfect knowledge of the cyclic frequencies, result in computing the test statistic at an offset from the true cyclic frequency. In this paper, we analyze the effect of cyclic frequency offsets on conventional cyclostationary detection, and propose a new multi-frame test statistic that reduces the degradation due to cyclic frequency offsets. Due to the multi-frame processing of the proposed statistic, non-coherent integration might occur across frames. Through an optimization framework developed in this work that can be performed offline, we determine the best frame length that maximizes the average detection performance of the proposed cyclostationary detection method given the statistical distributions of the receiver impairments. As a result of the optimization, the proposed detectors is shown to achieve the performance gains over conventional detectors given the constrained sensing time. We derive the proposed detector's theoretical average detection performance, and compare it to the performance of the conventional cyclostationary detector. Our analysis shows that gains in average detection performance using the proposed method can be achieved when the effect of sampling clock offset is less severe than that of the cyclic frequency offset. The analysis given in this paper can be used as a design guideline for practical implementation of cyclostationary spectrum sensors.

Fast Algorithm with Improved Circular Correlation Method for GPS Signal Acquisition

In order to improve acquisition speed and carrier frequency accuracy, a fast algorithm to acquire GPS signal is proposed. Signal-to-Noise Ratio is improved by coherent integration and non-coherent integration. The advantages of serial sliding algorithm and circular correlation algorithm are combined to achieve high carrier frequency accuracy. Removing the information of C/A code makes serial search from two-dimensional to one-dimensional to achieve less computation. Simulation shows weak signal of-30dB S/N is successfully acquired. The error of carrier frequency is controlled within 50Hz. So the data processing efficiency for the tracking loop is greatly increased.

Sidelobe Blanking with Generalized Swerling-Chi Fluctuation Models

The work presented here focuses on the performance analysis of the sidelobe blanking (SLB) system with noncoherent integration in the presence of white Gaussian noise and jammer entering through the sidelobes of the antenna. Closed-form performance probabilities, in terms of either the generalized Marcum or Nuttall Q-function, are derived for nonfluctuating target and jammer, both in the blanking and the detection regions. The analysis is then extended to account for arbitrary correlated, possibly nonidentically distributed, fluctuating target and/or jamming returns among a given number of integrated pulses. Finally, several numerical results are given, and the effects of typical SLB parameters are discussed.

Differential Coherent Algorithm for Interferometric Acquisition of GNSS-R Software Receiver

For the purpose of reducing the degradation of sensitivity performance due to the serious Squaring-Loss in interferometric processing, a differential coherent algorithm for interferometric acquisition of GNSS-R software receiver is explored in this paper. The sensitivity performance is investigated and compared with the conventional non-coherent algorithm. Analysis and simulation show that the proposed algorithm offers an obvious sensitivity gain over conventional noncoherent integration.

Detection Performance Analysis and Parameter Design Method of DSSS Signal Acquisition Algorithm Based on the MAX/TC Criterion

For the acquisition of week direct sequence spread spectrum (DSSS) signal in dynamic environment, an acquisition algorithm using MAX /TC criterion on bi-dimensional search region in noncoherent integrations is proposed. Detection performance of the proposed acquisition algorithm is deduced and the deduced formulas are simple and practicable. Based on these formulas, parameter design method is given for low signal-to-noise ratio (SNR). Computer simulation results demonstrate the correctness of the conclusion and effectiveness of parameter design method.

Hypothesis testing analysis and unknown parameter estimation of GPS signal detection

Hypothesis testing analysis and unknown parameter estimation of both the intermediate frequency (IF) and baseband GPS signal detection are given by using the generalized likelihood ratio test (GLRT) approach, applying the model of GPS signal in white Gaussian noise. It is proved that the test statistic follows central or noncentral F distribution. It is also pointed out that the test statistic is nearly identical to central or noncentral chi-squared distribution because the processing samples are large enough to be considered as infinite in GPS acquisition problem. It is also proved that the probability of false alarm, the probability of detection and the threshold are affected largely when the hypothesis testing refers to the full pseudorandom noise (PRN) code phase and Doppler frequency search space cells instead of each individual cell. The performance of the test statistic is also given with combining the noncoherent integration.

PERFORMANCE ANALYSIS OF MULTIPLE-SCAN DETECTION IN HEAVY HETEROGENEOUS SEA CLUTTER

Traditional detection approaches for the dim moving target are addressed under the background of homogeneous sea clutter. However, the realistic clutter commonly appears inhomogeneous, resulting in the low detectability. A heterogeneous multiple-scan detection framework is described in this paper, which combines the inhomogeneous coherent integration in the dwell of single scan and the non-coherent integration of the results from single-scan process across the multiple scans. In the inhomogeneous coherent integration, the Heterogeneous Single-scan Coherent Detector (HSCD) is derived, resorting to the two-step Generalized Likelihood Ratio Test (GLRT) criterion and a hybrid covariance matrix estimation scheme, where the nonhomogeneous Kelly detector and the inhomogeneous Adaptive Matched Filter (AMF) are also considered. Additionally, the Viterbi- Like (VL) algorithm is employed as the non-coherent integration strategy. Finally, the numerical simulations with Monte Carlo method analyze the performance of the nonhomogeneous multiple-scan detectors under amplitude and distribution clutter heterogeneity.