Pulse Doppler Radar System Research Articles

Microwave local oscillator signal generation with low near-carrier phase noise based on cascaded optoelectronic oscillators

A new scheme to generate microwave local oscillator (LO) signals with low near-carrier phase noise is proposed based on cascaded optoelectronic oscillators (OEOs). In the proposed scheme, an active mode-locking OEO is utilized to generate a microwave comb with low near-carrier phase noise. Through injecting the generated microwave comb into another OEO with a well-designed loop delay, microwave LO signals with low near-carrier phase noise can be generated. The feasibility of the scheme is numerically and experimentally demonstrated. In the experiment, a microwave LO signal at 10.0005 GHz is generated with a spurious suppression ratio of 25 dB and a near-carrier phase noise of −91 dBc/Hz@100 Hz. Compared with the microwave LO signal directly generated by using the OEO without injection, the near-carrier phase noise is reduced by 23 dB. The proposed scheme can thus be used to enhance the sensitivity of the pulse Doppler radar system for detecting small targets with low altitude and slow speed.

Implementation of Digital Signal Processor for Pulse Doppler Radar

This paper presents the design and implementation of a digital signal processor (DSP) board, utilizing a TMS320C50 family DSP chip, for pulse-Doppler radar systems. Pulse-Doppler radar systems often encounter challenges such as strong clutter, noise, and jamming in dealing with echoes. To overcome these challenges, advanced digital signal processing techniques are employed. The main objective of this paper is to introduce a cost-effective signal processing solution that significantly enhances the performance of the radar system and brings it up to speed with modern radar technologies. The hardware described in this work can also be effectively utilized for implementing various types of signal processing algorithms. Additionally, as a secondary objective, the paper presents the digital realization of a radar detector. Traditionally, this detector was constructed using an analog Doppler filter bank. However, in this work, it is digitally implemented using N digital filters in place of the analog bank. By utilizing the designed DSP board and implementing the radar detector digitally, this paper demonstrates the potential for improved performance and efficiency in pulse-Doppler radar systems. The advancements made in this work contribute to the development of cost-effective and technologically advanced radar systems. The research results are presented for four different wind conditions, showcasing the effectiveness of the proposed approach. Furthermore, the paper suggests an algorithm that combines parametric and non-parametric techniques and provides a detailed explanation of its implementation. Finally, using the non-parametric technique, the probability of detection curves (PD) are simulated with respect to the signal-to-clutter ratio (SCR) for each wind condition, and the simulation results are depicted and compared. The achievements of this paper include the proposal of an efficient approach for clutter suppression in ground surveillance pulse Doppler radar, the comparison of different clutter suppression algorithms, and the development of an algorithm that combines parametric and non-parametric techniques. The simulation results provide valuable insights into the performance of the proposed algorithms under different wind conditions.

Range ambiguity suppression under high-resolution estimation using the MUSIC-AP algorithm for pulse-Doppler radar

Range ambiguity is a significant challenge in conventional pulse-Doppler radar systems with medium or high pulse repetition frequencies, greatly impacting radar detection and imaging capabilities. The classic approaches such as waveform diversity and compressed sensing are based on the isolation between pulses. However, these methods encounter issues like residual ambiguity and grid mismatch, resulting in poor range ambiguity suppression performance. In this paper, the multiple signal classification-alternating projection (MUSIC-AP) method is proposed to address these challenges and achieve high-resolution estimation. The proposed method converts the range-velocity estimate into a spectrum estimate, enabling the utilization of the MUSIC algorithm to solve the grid mismatch problem and improve echo reconstruction. Then, to mitigate the effect of ambiguous energy on reconstruction, the MUSIC reconstruction subprocess is embedded into the AP framework. Through iterative approximation, the method gradually suppresses ambiguous and noise energy, thereby further enhancing the echo reconstruction accuracy and range ambiguity suppression performance. Simulations demonstrate the effectiveness of the proposed method. Moreover, algorithm analysis is conducted, considering aspects such as resolution, robustness, and sparsity, which provides a basis for parameter selection and applicability conditions.

Improving Range Ambiguity Suppression in Pulse-Doppler Radar Systems With Nonlinear Processing and Joint Reversible Mismatch Filtering

Improving Range Ambiguity Suppression in Pulse-Doppler Radar Systems With Nonlinear Processing and Joint Reversible Mismatch Filtering

Folded Clutter Suppression for Pulse-Doppler Radar Based on Pulse-Agile Waveforms

Pulse-Doppler radar systems with medium/high pulse repetition frequencies (PRFs) usually produce severe range ambiguities, and strong nearby ground/sea clutter will then fold into a single range interval with weak remote target echoes, further limiting the dynamic range of radar. The existing methods for modeling or estimating clutter spectra are usually not applicable to the case of folded clutter. In recent years, pulse-agile waveforms have attracted an increasing amount of attention for resolving range ambiguities. However, cross-correlations among pulse-agile waveforms with the same frequency band, usually required for pulse-Doppler radar to coherently measure the Doppler shift, are not satisfactory for suppressing folded clutter since clutter echoes are much stronger than those of targets. In this paper, two algorithms based on the method of alternating projection (MAP) in the range-Doppler domain (RD-MAP) and the space-Doppler domain (SD-MAP) are proposed to suppress folded clutter and resolve range ambiguities for pulse-Doppler radar based on different types of pulse-agile waveforms. The effectiveness of these algorithms is verified based on several realistic simulations and a ground-based experiment. Iterative solutions and closed-form solutions are both provided for different computational complexity and accuracy requirements in certain application scenarios. Moreover, algorithm analysis, including algorithm boundary analysis, signal-to-noise ratio (SNR) loss, computational complexity and factor selection, is performed to provide an estimation of the applicable conditions and assess the performance of the proposed algorithms.

An Adaptive Filtering Algorithm in Pulse-Doppler Radar for Counteracting Range-Velocity Jamming

In this paper, an anti-jamming scheme based on transmitted multiple pulses through random initial phases and adaptive iterative filtering algorithm is considered for counteracting range-velocity deceptive jamming in Pulse-Doppler (PD) radar system. This anti-jamming scheme relies on the fact that the digital radio frequency memory (DRFM) repeated jammer needs more than one pulse repetition interval PRI (at least one PRI) to identify the radar transmitted pulses, and therefore uses the captured pulses of the lag PRIs to reproduce multiple false targets. As a consequence, an adaptive-iterative algorithm to estimate the range-Doppler plane of the real targets in range dimension processing and Doppler dimension processing can appropriately suppress the deceptive false targets, which employed the lagged PRIs for the radar deception. Firstly, the proposed method achieves the optimal estimation of the true targets and false targets in the range dimension. Then, with the estimation information in the range dimension, the presented method estimates the range-Doppler plane of the true targets and false targets. Based on these estimations the deceptive jamming can be easily suppressed with few numbers of iterations and outstanding suppression performance. Finally, we evaluate the performance of the proposed method as well as achieving a good trade-off between anti-jamming performance and computational complexity via numerical simulations.

Range‐ambiguity suppression for noise radar in cluttered environment via sparse recovery

Range ambiguity suppression is a significant problem in traditional pulse-Doppler radar systems, especially when the pulse repetition frequency is set high to avoid Doppler ambiguity. One possible way to deal with such problem is to apply the noise radar system, by transmitting pulse-agile waveforms and using a group of matched filters as the receiver to accumulate the power of unambiguous echoes while dispersing the range-ambiguous ones. However, when strong targets or heavy clutters exist, the dispersed ambiguous power is still high, which leads to high range-Doppler sidelobes and overwhelms the weak targets. This paper explores a new way to deal with the range-ambiguity suppression problem in noise radar. The range-ambiguity suppression as a sparse recovery problem is formulated, and then both the unambiguous and ambiguous targets (and/or clutters) can be simultaneously reconstructed. The proposed method can enhance the range-ambiguity suppression performance and synthetic an ambiguity-free range-Doppler map with a low sidelobe level, which ensures the weak target recovery performance even in a cluttered environment.

Method of controlling the parameters of the pulse-Doppler onboard radar station while ensuring the energy stealth of its operation on radiation

In the article, based on the mathematical apparatus of the statistical theory of optimal control in the state space, the synthesis of a method for controlling the parameters of the pulse-Doppler onboard radar system (BRLS) of a fighter aircraft is presented, in the interests of ensuring the energy stealth of its operation on radiation with a given probability, when detecting an air target-the carrier of a radio intelligence station, the optimal minimum local quality functional. The efficiency of the synthesized method is also evaluated on the basis of modeling. As part of the synthesis, the quality functional was determined and control signals were obtained for the parameters of the radar operation, which make it possible to ensure the energy stealth of the fighter's radar operation with a given probability in the process of approaching the radar carriers and the radio intelligence station (RTR). The indicators of the control signal efficiency determine the probability of correct detection of the radar of the air target carrier of the RTR station and the probability of non-detection by the RTR station of the sounding radar signal in the process of their approach. Based on the simulation, the effectiveness of the control signals is evaluated, which shows that in the process of approaching the fighter and the RTR carrier station, the energy stealth of the radar operation is provided with a given probability by controlling the parameters of the radar operation.

Sub-Nyquist sampling with independent measurements

This paper presents an efficient sub-Nyquist pulse-Doppler radar system via quadrature compressive sampling (QuadCS) in fast-time domain. QuadCS is a bandpass variant of random demodulation and inserts randomness into the measurement matrix by employing a random chipping signal. Different from conventional sub-Nyquist radars using fixed measurement matrices in all pulse repetition intervals (PRIs), namely the same chipping signals for our system, we utilizes independent chipping signals in each PRI. Hence we obtain a sequence of independent measurement matrices in a coherent processing interval, and the resulting sensing matrix has better restricted isometry property than that with fixed measurement. Theoretical analysis indicates that our system can further reduce the sampling rate or can identify more number of targets than that with fixed measurement. Moreover, the sampling rate and the number of transmitted pulses are exchangeable, thus providing more flexibility for the design of sub-Nyquist radars. The main challenge of independent measurement is that the computational efficient decoupled processing of fast-time and slow-time domains cannot be applied directly. We thus develop a first-order fast target recovery algorithm by exploiting the factorization of the proposed sensing matrix suitable for fast matrix-vector products. Numerical results validate the efficiency of the proposed system.

Implementation architecture of signal processing in pulse Doppler radar system based on FPGA

A kind of high speed and parallel hardware architecture is proposed and designed for digital signal processing of high frequency Pulse Doppler radar here. The platform is based on one XC7K410T FPGA, two XC7K325T FPGAs, one TMS320C6678 DSP, and four sets of MT41J256M8 DDR3. The details of implementation including pulse compression, moving target detection and constant-false-alarm rate are described. The simulation results and resource consumption are presented to demonstrate the advantages of the proposed FPGA implementation architecture.

Maximum Eigenvalue Matrix CFAR Detection Using Pre-Processing in Sea Clutter

For the pulse Doppler radar system with short pulse sequence, maximum eigenvalue-based matrix CFAR detector (MEMD) provides an effective solution to the problem of detecting moving targets in the background of K distribution sea clutter when the target Doppler frequency is within clutter spectrum. However, its performance is inferior to adaptive normalized matched filter method (ANMF) when the target Doppler frequency heavily deviates from the clutter spectrum. In essence, the reason for the better performance of ANMF method is the clutter is effectively suppressed by whitening and matched filter. Motivated by this, the fusion idea of eigenvalue detection and pre-processing via fast Fourier transform is considered taking advantage of the priori information of target steering vector. A pre-processing-based maximum eigenvalue matrix CFAR detection (P-MEMD) method is proposed to suppress the influence of clutter on detection performance. Finally, the numerical experimental results based on simulated data and real sea clutter data show that the proposed method achieves better detection performance and robustness than some conventional methods.

Sparse Detection Algorithms Based on Two-Dimensional Compressive Sensing for Sub-Nyquist Pulse Doppler Radar Systems

Sub-Nyquist pulse Doppler radar system has received wide attention recently because it can make the sampling rate lower than the Nyquist sampling rate. However, there are still two problems that must be addressed for sub-Nyquist pulse Doppler radar. One is that the large memory is required for sparse signal recovery. Another is that the performance of the sparse signal recovery will be distorted in the non-Gaussian impulse noise environment. For the first problem, this paper proposes four 2-D compressive sensing (CS) algorithms which are extended from the traditional 1-D CS algorithms (the ZAP, IHT, ISTA, and FISTA algorithms). The proposed 2-D-CS algorithms recover the signal in the delay-Doppler domain, which is a matrix domain. For the second problem, robust 2-D-CS algorithms are proposed for the non-Gaussian impulse noise environment. The proposed 2-D-CS algorithms can achieve comparable detection performance with lower memory requirement. The proposed robust 2-D-CS algorithms can eliminate the interference of impulsive noise in the non-Gaussian impulse noise environment. Simulation results are given to verify the effectiveness of the proposed algorithms.

Fast implementation for modified adaptive multi-pulse compression

This paper deals with the estimation of range-Doppler plane in pulse Doppler radar system, accounting both for clutter-free scenario and clutter scenario. A modified adaptive multi-pulse compression (MAMPC) algorithm including the estimation stages of range dimension and Doppler dimension is proposed for clutter-free scenario, where each stage is implemented based on the gain constraint adaptive pulse compression (GCAPC) algorithm. Additionally, the combination of whitening method removing the correlation of clutter component and MAMPC algorithm is presented for the considered clutter scenario. Numerical simulations are provided to validate the effectiveness of MAMPC in terms of estimation of range-Doppler plane and computation burden.

Research on the Airborne Pulse Doppler Radar Jamming System Tester

This paper introduces the design of an airborne pulse Doppler radar jamming system tester. Based on a detailed analysis of the functional structure of the radar-jamming system, we summarize the important failure mode. To achieve fault location and performance testing, we have developed an automatic detector for the radar-jamming system, the device uses a mode of hardware platform and software platform, and it can reach the purpose of fault location by a method of encouraging input and measuring the output of each of the radar-jamming system failure mode individually. The automatic test instrument has the features of simple operation, high degree of automation, real-time, scalable, and actual use of running proves it to reach the required design specifications, the test with good results.

Quantitative gait measurement with pulse-Doppler radar for passive in-home gait assessment.

In this paper, we propose a pulse-Doppler radar system for in-home gait assessment of older adults. A methodology has been developed to extract gait parameters including walking speed and step time using Doppler radar. The gait parameters have been validated with a Vicon motion capture system in the lab with 13 participants and 158 test runs. The study revealed that for an optimal step recognition and walking speed estimation, a dual radar set up with one radar placed at foot level and the other at torso level is necessary. An excellent absolute agreement with intraclass correlation coefficients of 0.97 was found for step time estimation with the foot level radar. For walking speed, although both radars show excellent consistency they all have a system offset compared to the ground truth due to walking direction with respect to the radar beam. The torso level radar has a better performance (9% offset on average) in the speed estimation compared to the foot level radar (13%-18% offset). Quantitative analysis has been performed to compute the angles causing the systematic error. These lab results demonstrate the capability of the system to be used as a daily gait assessment tool in home environments, useful for fall risk assessment and other health care applications. The system is currently being tested in an unstructured home environment.

도로 장애물 경보를 위한 Ka-대역 펄스 도플러 레이다 시스템 개발 및 성능시험

도로 장애물 경보를 위한 Ka-대역 펄스 도플러 레이다 시스템 개발 및 성능시험

Multiple model particle filter track-before-detect for range ambiguous radar

The middle pulse repetition frequency (MPRF) and high pulse repetition frequency (HPRF) modes are widely adopted in airborne pulse Doppler (PD) radar systems, which results in the problem that the range measurement of targets is ambiguous. The existing data processing based range ambiguity resolving methods work well on the condition that the signal-to-noise ratio (SNR) is high enough. In this paper, a multiple model particle filter (MMPF) based track-before-detect (TBD) method is proposed to address the problem of target detection and tracking with range ambiguous radar in low-SNR environment. By introducing a discrete variable that denotes whether a target is present or not and the discrete pulse interval number (PIN) as components of the target state vector, and modeling the incremental variable of the PIN as a three-state Markov chain, the proposed algorithm converts the problem of range ambiguity resolving into a hybrid state filtering problem. At last, the hybrid filtering problem is implemented by a MMPF-based TBD method in the Bayesian framework. Simulation results demonstrate that the proposed Bayesian approach can estimate target state as well as the PIN simultaneously, and succeeds in detecting and tracking weak targets with the range ambiguous radar. Simulation results also show that the performance of the proposed method is superior to that of the multiple hypothesis (MH) method in low-SNR environment.

Design and implementation of a hybrid digital and RF front-end module for 24-GHz intelligent transport system pulse-doppler radar

This article presents a hybrid digital and RF front-end module (FEM) of a 24-GHz pulse-Doppler radar system for intelligent transport system applications. The conventional pulse generators use analog components such as step recovery diode. It is difficult to control the parameters of the pulse. In addition, the heterodyne architecture based transceivers show good performance, but they are very expensive. To overcome these limitations, a digital pulse generator was developed based on field-programmable gate array platform to obtain high degree of freedom in a waveform design. Instead of the heterodyne architecture, a transceiver based on the homodyne architecture was developed. For the first time, hybrid digital FEM based 24-GHz pulse-Doppler radar was developed by combining a digital pulse generator and a homodyne-based transceiver. Experimental results showed the feasibility of using a hybrid digital FEM for a 24-GHz pulse-Doppler radar. The developed hybrid digital FEM contributes to the advancement of the digital radar field. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1631–1638, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27666

Hardware implementation of DIRLS mismatched compressor applied to a pulse-Doppler radar system

In this work, the hardware implementation of a digital mismatched pulse compressor and its application to a pulse-Doppler radar system are presented. The emphasis is to use one generalized compressor with reloading coefficient capability for several different types of signals. This implementation starts with a generic VHDL specification and then it is developed on FPGA architecture. The compression filter implementation on FPGA lets us eliminate special chips previously needed. The achieved design can be adapted to different computational requirements, easily modifying its data path and the length of the used signal sequence. From the experimental results it is known that this approach appears to work well for chirp and discrete phase matched/mismatched pulse compression and it outstands when TB is of order 1000. Also, it fits for arbitrary spread spectrum waveforms. The design performances have been analyzed modifying the used precision and the length of the used signal sequences.

PCA-Based Detection Algorithm of Moving Target Buried in Clutter in Doppler Frequency Domain

This letter proposes a novel technique for detecting a target signal buried in clutter using principal component analysis (PCA) for pulse-Doppler radar systems. The conventional detection algorithm is based on the fast Fourier transform-constant false alarm rate (FFT-CFAR) approaches. However, the detection task becomes extremely difficult when the Doppler spectrum of the target is completely buried in the spectrum of clutter. To enhance the detection probability in the above situations, the proposed method employs the PCA algorithm, which decomposes the target and clutter signals into uncorrelated components. The performances of the proposed method and the conventional FFT-CFAR based detection method are evaluated in terms of the receiver operating characteristics (ROC) for various signal-to-clutter ratio (SCR) cases. The results of numerical simulations show that the proposed method significantly enhances the detection probability compared with that obtained using the conventional FFT-CFAR method, especially for lower SCR situations.