Pulse Compression Radar Research Articles

Area Optimized FPGA Implementation for Generation of Radar Pulse Compression Sequences

Area Optimized FPGA Implementation for Generation of Radar Pulse Compression Sequences

Jamming de-chirping radar using interrupted-sampling repeater

Interrupted-sampling repeater jamming (ISRJ) is a novel jamming mode for pulse compression radar in principle. In this paper, a jamming approach of applying ISRJ to de-chirping radar is presented. The principles of ISRJ are expounded, and the ways to achieve a train false target for de-chirping radar are analyzed. The characteristics of false target, including time-domain characteristic, frequency-domain characteristic and amplitude characteristic, are described. Based on this, the power requirement for jammer is put forward and the key elements that determine the space distribution location between true and false targets are discussed in detail. At last, simulation results are presented and addressed. This work is beneficial to the jamming design and use of ISRJ.

Quasi-Orthogonal Wideband Radar Waveforms Based on Chaotic Systems

Many radar applications, such as those involving multiple-input, multiple-output (MIMO) radar, require sets of waveforms that are orthogonal, or nearly orthogonal. As shown in the work presented here, a set of nearly orthogonal waveforms with a high cardinality can be generated using chaotic systems, and this set performs comparably to other waveform sets used in pulse compression radar systems. Specifically, the nearly orthogonal waveforms from chaotic systems are shown to possess many desirable radar properties including a compact spectrum, low range sidelobes, and an average transmit power within a few dB of peak power. Moreover, these waveforms can be generated at essentially any practical time length and bandwidth. Since these waveforms are generated from a deterministic process, each waveform can be represented with a small number of system parameters. Additionally, assuming these waveforms possess a large time-bandwidth product, a high number of nearly orthogonal chaotic waveforms exist for a given time and bandwidth. Thus the proposed generation procedure can potentially be used to generate a new transmit waveform on each pulse.

Preceded False Target Groups Jamming Against LFM Pulse Compression Radars

Preceded False Target Groups Jamming Against LFM Pulse Compression Radars

Some considerations for different time-domain signal processing of pulse compression radar

Radar technology has for a long time used various systems that allow detection under high-resolution conditions, while emitting at the same time low peak power. Among these systems, transmitted pulse encoding by means of biphasic codes has been used for the advanced ionospheric sounder that was developed by the AIS-INGV ionosonde. In the receiving process, suitable decoding of the signal must be accomplished. This can be achieved in both the time and the frequency domains. Focusing on the time domain, different approaches are possible. In this study, two of these approaches have been compared, using data acquired by the AIS-INGV and processed by means of software tools (mainly Mathcad©). The analysis reveals the differences under both noiseless and noisy conditions, although this does not allow the conclusive establishment as to which method is better, as each of them has benefits and drawbacks. Normal 0 14 false false false IT X-NONE X-NONE

Analysing and compensating the effects of range and Doppler frequency migrations in linear frequency modulation pulse compression radar

The pulse compression and Doppler processing (PCDP) method has been extensively used to detect low-speed and uniform-speed targets in linear frequency modulation (LFM) pulse compression radar. However, the PCDP method is affected by range migration (RM) and Doppler frequency migration (DFM) when detecting high-speed and accelerating targets. In this paper, the authors analyse and quantify these effects, and obtain the relationships of the optimal number of pulses and the threshold number of pulses with RM and DFM. It shows that when the number of pulses equals its optimal value, the maximum output signal-to-noise ratio can be obtained; when the number of pulses is greater than its threshold value, the migrations should be compensated. Then the authors propose a method based on the scaling processing and the fractional Fourier transform to remove the two migrations. In the end, the authors give a target detection experiment to show that the proposed method can effectively compensate these migrations.

Non-linear effects of intensity-modulated and directly detected optical links on receiving a linear frequency-modulated waveform

Limitations imposed by the non-linearity of optical links, in the front end of a receiving array antenna, on the performance of a pulse compression radar are studied. Particularly linear frequency-modulated waveforms backscattered from a pair of targets are inspected. Inter-modulation and gain compression by noise are presented as two remarkable phenomena. For an interconnection of two dual-drive Mach-Zehnder modulators, the sensitivity of the compressed echo at the output of a matched filter receiver to certain tunable parameters is studied numerically. Finally, certain values of DC bias and phase shift between the modulators- electrodes are recommended.

Comparison of Radar Waveforms for a Low-Power Vertical-Incidence Ionosonde

Vertical-incidence (VI) ionosonde is a kind of high-frequency radar. The sounding waveform is an important characteristic for measurement by ionosondes. This letter compares, both theoretically and practically, four different biphase-coded pulse compression radar waveforms which can be employed in the Wuhan Ionosphere Comprehensive Sounding System at VI sounding, including interpulse-coded m sequence, interpulse-coded Wolfman-Goutelard sequence, intrapulse-coded Barker sequence, and intrapulse-coded complementary sequence pairs. The experimental results demonstrate that among the four waveforms, the intraphase-coded complementary-sequence pairs have the best performance.

24-Bit 5.0 GHz Direct Digital Synthesizer RFIC With Direct Digital Modulations in 0.13 $\mu$m SiGe BiCMOS Technology

This paper presents a 24-bit 5.0 GHz ultrahigh-speed direct digital synthesizer (DDS) with direct digital modulation capabilities used in a pulse compression radar. This design represents the first DDS RFIC in over-GHz output frequency range with direct digital modulation capabilities. It adopts a ROM-less architecture and has the capabilities for direct digital frequency and phase modulation with 24 bit and 12 bit resolution, respectively. The DDS includes a 24-bit ripple carry adder (RCA) accumulator for phase accumulation, a 12-bit RCA for phase modulation and a 10-bit segmented sine-weighted digital-to-analog converter (DAC) for phase-to-amplitude conversion (PAC) as well as digital-to-analog conversion. The DDS core occupies 3.0 × 2.5 mm2 and consumes 4.7 W of power with a single 3.3 V power supply. This 24-bit DDS has more than 20,000 transistors and achieves a maximum clock frequency of 5.0 GHz. The measured worst case SFDR is 45 dBc under a 5.0 GHz clock frequency and within a 50 MHz bandwidth. At 1.246258914 GHz output frequency, the 50 MHz narrowband SFDR is measured as 82 dBc. The best Nyquist band SFDR is 38 dBc with a 469.360351 MHz output using a 5.0 GHz clock frequency. This DDS was developed in a 0.13 μm SiGe BiCMOS technology with fT/fMAX = 200/250 GHz and tested in a CLCC-68 package.

An Efficient Approach for Adaptive Pulse Compression of MIMO Radar

摘要: 发射信号的分离是MIMO雷达的一个重要环节，该文基于最小均方误差准则，提出了一种有效的MIMO雷达自适应脉冲压缩方法，从每个接收阵元接收到的信号中分别自适应地估计每个距离单元的脉冲压缩滤波器的权系数，从而获得期望的脉冲压缩性能，更好地完成发射波形的分离。该方法不仅能够抑制信号本身的距离旁瓣，降低信号之间的互相关电平，还对目标本身的多普勒频率具有很强的适应性。计算机仿真验证了该方法的有效性。 关键词: MIMO雷达; 最小均方误差; 自适应脉冲压缩; 波形分离

Dimensionality Reduction Techniques for Efficient Adaptive Pulse Compression

Adaptive filtering for radar pulse compression has been shown to improve sidelobe suppression through the estimation of an appropriate pulse compression filter for each individual range cell of interest. However, the relatively high computational cost of full-dimension, adaptive range processing may limit practical implementation in many current real-time systems. Dimensionality reduction techniques are here employed to approximate the framework for pulse compression filter estimation. Within this approximate framework, two new minimum mean square error (MMSE) based adaptive algorithms are derived. The two algorithms are denoted as specific embodiments of the fast adaptive pulse compression (FAPC) method and are shown to maintain performance close to that of full-dimension adaptive processing, while reducing computation cost by nearly an order of magnitude (in terms of the discretized waveform length N).

Low autocorrelation binary sequences: Number theory-based analysis for minimum energy level, Barker codes

Low autocorrelation binary sequences (LABS) are very important for communication applications. And it is a notoriously difficult computational problem to find binary sequences with low aperiodic autocorrelations. The problem can also be stated in terms of finding binary sequences with minimum energy levels or maximum merit factor defined by M.J.E. Golay, F=N22E, N and E being the sequence length and energy respectively. Conjectured asymptotic value of F is 12.32 for very long sequences. In this paper, a theorem has been proved to show that there are finite number of possible energy levels, spaced at an equal interval of 4, for the binary sequence of a particular length. Two more theorems are proved to derive the theoretical minimum energy level of a binary sequence of even and odd length of N to be N2 and N−12 respectively, making the merit factor equal to N and N2N−1 respectively. The derived theoretical minimum energy level successfully explains the case of N=13, for which the merit factor (F=14.083) is higher than the conjectured value. Sequence of lengths 4, 5, 7, 11, 13 are also found to be following the theoretical minimum energy level. These sequences are exactly the Barker sequences which are widely used in direct-sequence spread spectrum and pulse compression radar systems because of their low autocorrelation properties. Further analysis shows physical reasoning in support of the conjecture that Barker sequences exists only when N⩽13 (this has been proven for all odd N).

Employing fractional autocorrelation for fast detection and sweep rate estimation of pulse compression radar waveforms

Fractional autocorrelation of a signal defined for a fractional domain at an arbitrary angle of the time–frequency plane exactly corresponds to the radial slice of the radar ambiguity function (AF) of that signal at that particular angle. In other words, any radial cross-section of the radar AF, that itself serves as a two-dimensional correlation function, can be readily obtained by computing fractional autocorrelation, which is one-dimensional. In this manuscript, we employ a novel fast detection statistic derived utilizing this property of fractional autocorrelation for computationally efficient detection of pulse compression radar waveforms such as the step linear frequency modulated (SLFM) signal, Frank code, and P1 and P4 codes. As a byproduct, the detection algorithm also serves as an unbiased estimator of the sweep rate (chirp rate) of the considered radar waveforms. Through receiver operating characteristic (ROC) curves, we investigate the performance of the detection statistic and compare it against the matched filter and generalized likelihood ratio test (GLRT) detectors of the linear frequency modulated (LFM) signal. Performance of the accompanying sweep rate estimator is also demonstrated using mean square error (MSE) curves and compared with the optimum maximum likelihood (ML) estimator of the sweep rate parameter of the LFM signal.

Doppler Compensation & Single Pulse Imaging using Adaptive Pulse Compression

The effects of target Doppler are addressed in relation to adaptive receive processing for radar pulse compression. To correct for Doppler-induced filter mismatch over a single pulse, the Doppler-compensated adaptive pulse compression (DC-APC) algorithm is presented whereby the respective Doppler shifts for large target returns are jointly estimated with the illuminated range profile and subsequently incorporated into the original APC adaptive receive filter formulation. As a result, the Doppler-mismatch-induced range sidelobes can be suppressed thereby regaining a significant portion of the sensitivity improvement that is possible when applying adaptive pulse compression (APC) without the existence of significant Doppler mismatch. In contrast, instead of compensating for Doppler mismatch, the single pulse imaging (SPI) algorithm generalizes the APC formulation for a bank of Doppler-shifted matched filters thereby producing a sidelobe-suppressed range-Doppler image from the return signal of a single radar pulse which is applicable for targets with substantial variation in Doppler. Both techniques are based on the recently proposed APC algorithm and its generalization, the multistatic adaptive pulse compression (MAPC) algorithm, which have been shown to be effective for the suppression of pulse compression range sidelobes thus dramatically increasing the sensitivity of pulse compression radar.

Noncoherent Radar Pulse Compression Based on Complementary Sequences

Noncoherent pulse compression (NCPC), suggested recently, uses on-off keying (OOK) signals, obtained from Manchester coding a binary sequence with favorable a-periodic autocorrelation. This paper investigates the use of binary complementary pairs as a basis for NCPC. It shows that a pair of Manchester coded, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -element binary complementary sequences will yield a peak sidelobe (PSL) ratio of 1/(2 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> ).

Comparison of the performance of different radar pulse compression techniques in an incoherent scatter radar measurement

Abstract. Improving an estimate of an incoherent scatter radar signal is vital to provide reliable and unbiased information about the Earth's ionosphere. Thus optimizing the measurement spatial and temporal resolutions has attracted considerable attention. The optimization usually relies on employing different kinds of pulse compression filters in the analysis and a matched filter is perhaps the most widely used one. A mismatched filter has also been used in order to suppress the undesirable sidelobes that appear in the case of matched filtering. Moreover, recently an adaptive pulse compression method, which can be derived based on the minimum mean-square error estimate, has been proposed. In this paper we have investigated the performance of matched, mismatched and adaptive pulse compression methods in terms of the output signal-to-noise ratio (SNR) and the variance and bias of the estimator. This is done by using different types of optimal radar waveforms. It is shown that for the case of low SNR the signal degradation associated to an adaptive filtering is less than that of the mismatched filtering. The SNR loss of both matched and adaptive pulse compression techniques was found to be nearly the same for most of the investigated codes for the case of high SNR. We have shown that the adaptive filtering technique is a compromise between matched and mismatched filtering method when one evaluates its performance in terms of the variance and the bias of the estimator. All the three analysis methods were found to have the same performance when a sidelobe-free matched filter code is employed.

Range sidelobes blanking by comparing outputs of contrasting mismatched filters

Range sidelobes, a major shortcoming of radar pulse compression, are often reduced through the use of mismatched filters. The authors propose to blank the remaining sidelobes by using two or more mismatched filters, whose sidelobes are designed to peak at different delays. The authors show how to design such filters and present promising simulation results with two or more mismatched filters.

Pulse compression radar reflectometry to measure electron density in plasma with parasitic reflections

Pulse compression radar reflectometry is used to obtain electron density profile in plasma with parasitic reflections in this article. The pulse compression radar relies on the relation between the temporal width of a pulse and the frequency bandwidth of this pulse: Deltat proportional, variant1Deltaf. So a set of sweep-frequency microwaves within a bandwidth Deltaf can be introduced sequentially into the plasma to obtain the same information as the one obtained by a real pulse. By applying a Fourier transform to the data of reflectivity array in the frequency domain, the temporal response in the time domain is obtained. The limitation of the parasitic reflections on measurement can be eliminated from the temporal response by the method of time gate. This is a prominent advantage when this method is compared to the traditional reflectometry. For this method, an appropriate compromise between the spatial resolution and the electron density resolution is important. Experimental results show that the profile obtained from pulse compression radar reflectometry is similar to that from a double Langmuir probe.

Chirped RF Pulse Generation Based on Optical Spectral Shaping and Wavelength-to-Time Mapping Using a Nonlinearly Chirped Fiber Bragg Grating

Chirped radio-frequency (RF) pulse generation based on optical spectral shaping and nonlinear wavelength-to-time mapping in a nonlinearly chirped fiber Bragg grating (NLCFBG) is investigated. In the proposed approach, the spectrum of a femtosecond pulse generated by a mode-locked fiber laser is shaped by an optical filter that has a sinusoidal frequency response. The spectrum-shaped optical pulse is sent to the NLCFBG, to implement nonlinear wavelength-to-time mapping. A chirped electrical pulse with the central frequency and chirp rate determined respectively by the first- and second-order dispersions of the NLCFBG is then obtained at the output of a high-speed photodetector. An approximate model that describes the chirped RF pulse generation is derived, which is verified by numerical simulations. Chirped pulse generation with a pulse compression ratio as high as 450 is demonstrated. The key device in the chirped RF pulse generation system is the NLCFBG, which is investigated in detail with an emphasis on the influence of its group delay ripples on the performance of the pulse generation system. Techniques to design and fabricate the NLCFBG are also discussed. The proposed approach provides a potential solution for the generation of chirped RF pulse with a high central frequency and large chirp rate for applications in pulse compression radar systems.

Photonic Generation of Phase-Coded Millimeter-Wave Signal Using a Polarization Modulator

A novel approach to generating phase-coded millimeter-wave (mm-wave) signal in the optical domain is proposed. In the proposed system, a radio frequency signal is applied to a Mach-Zehnder modulator that is biased at the minimum transmission point to generate two optical sidebands with suppressed carrier. A differential group delay device is utilized to rotate the polarization states of the optical sidebands to ensure they are orthogonally polarized. The two sidebands are then sent to a polarization modulator (PolM), with their polarization directions aligned with the two principal axes of the PolM, to achieve phase coding. A 33-GHz mm-wave signal that is phase coded by an 8.28 Gb/s digital sequence is experimentally demonstrated. The approach has potential applications in mm-wave pulse compression radar and wireless communications.