Pulse Compression Performance Research Articles

Simulation and Performance Analysis of Chaotic Sequences using Enhanced Cuckoo Search Optimization Method

The mostdesirable property required for pulse compression is that the output should have low peak sidelobes that prevent weaker targets from being masked off in the nearby strong targets. Pulse compression can be obtained with matched filter. Matched filter is an optimal linear filter used in radar signal processing and various communication fields to increase the signal to noise ratio. The output of matched filter consists of unavoidable sidelobes which causes false alarm for multiple target detection in many radar system design.For this purpose, mismatched filter is used after matched filter. Inthis paper a new method of design of mismatched filter is discussed which reduces these sidelobes in the compressed waveform. Here new version of cuckoo search algorithm is used along with differential evolution techniquefor complete design of proposed filter to compare the performance of chaotic sequence. The performance of pulse compression is measured in terms of peak sidelobe ratio. The simulation results showthatdevelopmentin the performance of chaotic sequence is obtained at the output of cascaded filter. And further improved performance is achieved with adaptive filters.

Photonic approach to linearly chirped microwave waveform generation with large time–bandwidth product capability

Photonic approach to generating linearly chirped waveforms with large time–bandwidth product (TBWP) is proposed and demonstrated. In the approach, a dual-output dual-parallel Mach–Zehnder modulator (DPMZM) is employed to generate dual-tone wavelengths in the two output ports. The polarization modulator (PolM) is employed to conduct complementary phase modulation of the dual-tone wavelengths. After driving PolM with parabolic signal, frequency-doubled chirped microwave waveform will be obtained from photodetector (PD). To enlarge the TBWP, parabolic waveform is split into time domain and convolved with binary sequences to increase the bandwidth and temporal duration of the generated signal simultaneously. Simulation results show that linearly chirped microwave waveforms with carrier frequency of 40 GHz, bandwidth of 12.5 GHz, time duration of 819.2 ns are generated. After splitting and code-convolving with binary sequence, TBWP of the generated signal is enlarged to 10,240. Pulse compression performances of the generated signal are analyzed, and structure stability is also investigated.

Novel radar signal to efficiently utilise spectrum based on continuous‐phase frequency‐shift keying

Aiming at the problem of high side-band spectrum for a general frequency-shift keying (FSK) radar signal, this study introduces a novel radar FSK signal based on continuous-phase frequency-shift keying (CPFSK) used in communication systems. Theoretical analysis, simulation and physical application results show that the CPFSK radar signal efficiently controls the spectral containment, whose roll-off performance of the CPFSK is ∼20 dB better than that of normal FSK; meanwhile, the modified signal possesses good ambiguity and pulse compression performances for radar application.

A Chirp-Rate-Tunable Microwave Photonic Pulse Compression System for Multi-Octave Linearly Chirped Microwave Waveform

A chirp-rate-tunable microwave photonic pulse compression system for multi-octave linearly chirped microwave waveform (LCMW) is proposed in this paper. The key components are a dual-parallel Mach-Zehnder modulator (DPMZM) and a dispersive loop (DL) structure based on a linear chirped fiber Bragg grating. By controlling the output of the DL to change the accumulated group velocity dispersion, the chirp rate of the system can be tuned. By adjusting the wavelength of the optical carrier to select the single sideband modulated optical signal (positive or negative sideband), the chirp direction (down or up chirped) can also be tuned. The performance of the multi-octave LCMW pulse compression can be improved by eliminating the second-order harmonic distortion through configuring the bias voltages of the DPMZM. Detailed theoretical analysis is conducted. A verification simulation demonstrates the pulse compression of the multi-octave LCMWs with the chirp rates of 23.877, 11.939, 3.979, and -3.979 GHz/ns. In the proof-of-concept experiment, the matched chirp rates 23.229, 12.051, -22.568, and -11.355 GHz/ns are obtained. The multi-octave LCMW pulse compressions with the compression ratios of 14.3, 29.3, 15.0, and 28.6 are verified. The simulation and experiment results are in good agreement with the theoretical analysis.

Application of Coded Excitation Signals for Measurement of Rock Ultrasonic Wave Velocity

The accurate measurement of ultrasonic velocity requires the detected waveforms to have a high signal-to-noise ratio (SNR). Coded excitation technique (CET) can improve the SNR without resolution loss. This study introduces the basic principles of phase-coded technology and gives a synthetic and experimental evaluation of Barker and Golay codes. All the results show that CET can increase the SNR, but the gain in SNR (GSNR) is lower than the theoretical value. The velocity measurements on red sandstone and granite verify that the Barker code has better pulse compression performance than the Golay code. Besides, the application of Barker-coded signals on the velocity monitoring of uniaxially compressed rock proves that the Barker CET is reliable.

Photonic Generation and Transmission of Linearly Chirped Microwave Waveform With Increased Time-Bandwidth Product

Photonic generation and transmission of linearly chirped microwave waveform with the increased time-bandwidth product (TBWP) is proposed and demonstrated by phase-encoding and splitting parabolic waveform. In the approach, dual-polarization Mach-Zehnder modulator (DPol-MZM) along with polarization controller (PC) is employed to generate two orthogonally polarized wavelengths, and polarization modulator is driven by a parabolic signal. After splitting parabolic waveform and convolving with a binary pseudo random sequence, chirped microwave waveform with high bandwidth and large temporal duration is generated, corresponding to an improved TBWP. Dispersion-induced power fading can be effectively avoided in the approach, and chirped signal with constant initial phase can be achieved by adjusting the PC. The proposed approach is verified by simulations. Linearly chirped microwave waveform with the central frequency of 40 GHz, bandwidth of 12.5 GHz, and TBWP of 20160 is generated. RF spurious suppression ratios of the generated signal are investigated, and pulse compression performances are also analyzed. The system features filter-free, high tunability, compact structure, and large TBWP, which has potential application in the modern radar system.

Wideband Radar Signal Distribution With an Idler-Free Photonic Microwave Frequency Shifter

We demonstrate a novel scheme that combines photonic microwave frequency conversion and fiber transmission to achieve millimeter-wave (mm-wave) wideband radar signal generation and distribution for distributed radar systems. The principle is based on optical carrier-suppressed single-sideband modulation with an integrated polarization-division multiplexing dual-parallel Mach–Zehnder modulator. The idler frequencies in photonic microwave mixing are eliminated by controlling the modulator biases. And the fiber dispersion induced microwave power fading problem related with traditional double-sideband modulation is effectively avoided. The microwave phase distortions induced in the optical and electrical domains are investigated and compensated with electrical pre-distortion. Generation of an mm-wave wideband radar signal at a center frequency of 34.5 GHz with the bandwidth of 9 GHz and its transmission over a 40.8-km single-mode fiber with negligible degradation in pulse compression performance is achieved.

A Microwave Photonics Equalizer for Overcoming Dispersion-Induced Distortions on Wideband Signals in Radio-Over-Fiber Links

Chromatic dispersion (CD) has been considered as a significant issue that needs to be addressed over the past decades. Nowadays, as the bandwidth of radio frequency signals has expanded to multi-gigahertz, CD becomes increasingly troublesome for some wideband signals such as linear frequency modulated waveform (LFMW), which requires a flat amplitude response and a linear phase response. In this paper, we first investigate the CD-induced amplitude distortion and phase distortion that a wideband signal will suffer in traditional double-sideband (DSB) modulated and single-sideband (SSB) modulated radio-over-fiber (RoF) links with an emphasis on the LFMW. The detrimental impacts of the CD-induced distortions are subsequently discussed based on the pulse compression performance. Then, a two-tap microwave photonics equalizer (MPE) model is proposed and its operating principle for overcoming the CD-induced distortions is demonstrated. Based on the model, we design the MPE, which is mainly composed of an integrated dual-polarization dual-parallel Mach-Zehnder modulator and a differential group delay module. In the proof-of-concept experiment, the RoF link utilizing the proposed MPE is built, and a 1-10 GHz LFMW is transmitted over the 66.3-km single-mode fiber. Thanks to the MPE, both CD-induced amplitude distortion and phase distortion are successfully compensated. Pulse compression results show that the pulse, compared with the signal transmitted in the SSB-based link.

Photonic generation of binary and quaternary phase-coded microwave signals by utilizing a dual-polarization dual-parallel Mach-Zehnder modulator.

A photonic method to generate binary and quaternary phase-coded microwave signals using a dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM) is proposed and experimentally demonstrated. The upper DPMZM driven by a radio frequency (RF) signal acts as an optical wavelength shifter, while the lower DPMZM is used to generate a binary phase shift key (BPSK) or quadrature phase shift key (QPSK) signal. By combining the wavelength-shifted optical sideband and phase-modulated optical carrier, both binary and quaternary phase-coded microwave signals can be generated. Such signals with the carrier frequency of 10 GHz and 15 GHz are demonstrated. The pulse compression performance is also investigated.

Analysis of Non Linear Frequency Modulation (NLFM) Waveforms for Pulse Compression Radar

Non Linear Frequency Modulation (NLFM) method can suppress the peak sidelobe level without additional windowing function. NLFM doesn’t require any weighting function because it has inbuilt one. NLFM has a variable frequency deviation function due to the relation between frequency and time of the signal which is not linear so that it is possible to suppress of peak sidelobe level. This paper studies the characteristic of various NLFM waveform, such as NLFM Tri Stage Piece Wise (TSPW), NLFM S, and NLFM Taylor. The study of Pulse Compression of NLFM waveform consists of three aspects. First, analysis of pulse compression performance. Second, analysis of background noise. Last, analysis of Doppler effects. The simulation is done using Matlab software. The lowest value Peak Sidelobe Level (PSL)of NLFM TSPW is about -20 dB while NLFM S and NLFM Taylor are about -32 dB and -39 dB. Additive White Gaussian Noise (AWGN) and Doppler Effect influenced the value of PSL for each NLFM waveform. NLFM Taylor has the best NLFM waveform when the Doppler Effect and AWGN cause the value of PSL become high. Comparison between NLFM Taylor and Linear Frequency Modulation(LFM) is done in radar surveillance applications to analyze the detectability performance where the condition of Radar Cross Section (RCS) for each target has different significant value. The three targets are commercial airplanes, helicopter and fighter. For detectability performance, NLFM Taylor can detect more clearly than LFM conventional.

Photonic Generation of Tunable Frequency-Multiplied Phase-Coded Microwave Waveforms

A novel photonic approach to generate frequency-multiplied phase-coded microwave waveforms with large frequency tunability is proposed and experimentally demonstrated. By using a dual-drive Mach-Zehnder modulator, biased at specially designed bias point, and a single-port photodetector, phase-coded microwave waveforms at the doubled or tripled frequency of the applied microwave reference signal are generated, with a large frequency tunable range limited by the bandwidth of the dual-drive Mach-Zehnder modulator. The proposed technique is experimentally verified. Phase-coded microwave waveforms at the doubled frequency from 16 to 30 GHz and the tripled frequency from 21 to 30 GHz are generated. The pulse compression performance of the generated phase-coded microwave waveforms is also studied.

Phase-coded microwave signals generation using a dual parallel construction including two phase modulators

A photonic approach to realizing binary phase-coded microwave signal generation using a dual parallel construction including two phase modulators (PMs) was proposed and demonstrated. A beam CW is split into two beams light wave with equal power in the dual parallel construction, one beam is modulated in a PM driven by a radio frequency (RF) microwave signal in the upper arm, and the other beam is modulated by another PM driven by a binary coding electrical pulse sequence in the under arm, then the two phase-modulated beams combine and interfere. When the interference light field is send to a high-speed photodetector (PD) for beating, 2 Gbit/s binary phase-coded 10 GHz and 2.5 Gbit/s phase-coded 20 GHz microwave waveform with a π phase shift was respectively achieved, and corresponding pulse compression ratio is 20 and 16.5, respectively. The obtained phase-coded microwave signals exhibit a good pulse compression performance, which can find potential applications in modern radar systems and wireless communications.

A Frequency-Tunable Binary Phase-Coded Microwave Signal Generator With a Tunable Frequency Multiplication Factor

A novel frequency-tunable binary phase-coded microwave signal generator with a tunable frequency multiplication factor is proposed. The key component of the proposed system is a dual-polarization quadrature phase-shift-keying (DP-QPSK) modulator, which is driven by the microwave reference signal and the coding signal. By properly controlling the bias points of the DP-QPSK modulator and the amplitudes of the microwave reference signal and the coding signal, a fundamental, frequency-doubled, frequency-tripled or frequency-quadrupled binary phase-coded microwave signal can be generated when two orthogonally polarized optical signals at the output of the DP-QPSK modulator are combined and then detected in a photodetector. The proposed system is experimentally evaluated. A binary phase-coded microwave signal is generated at the fundamental, doubled, tripled, or quadrupled frequency. The frequency tunability and the pulse compression performance of the generated phase-coded microwave signals are also experimentally studied.

RF design of an S-band spherical cavity pulse compressor

The pulse compressor plays an important role in accelerators by enhancing the RF peak power. An S-band (2856 MHz) spherical cavity pulse compressor consisting of a special 3 dB coupler and a single spherical energy storage cavity has been developed in Institute of High Energy Physics. The special 3 dB coupler converts the $$\hbox {TE}_{10}$$ mode in rectangular waveguide to two polarization degenerated $$\hbox {TE}_{11}$$ modes in cylindrical waveguide. It is also a circular polarizer and its general scattering matrix is given for the first time. The magnitude and the phase difference of the two $$\hbox {TE}_{11}$$ modes are −3.016, −3.005 dB and 90.02 $$^\circ $$ in HFSS, while it is −3.01, −3.01 dB and 89.79 $$^\circ $$ in CST. The simulated S parameters show agreement with the general scattering matrix. The $$\hbox {TE}_{114}$$ mode with an unloaded Q factor of 190,000 has been chosen to resonate in the spherical cavity. An energy multiplication factor of 1.75 and a peak power gain of 5.75 were obtained for the whole pulse compressor, which agrees with the design requirements. A good pulse compression performance is also proved by the CST time-domain simulation. In addition, the scheme for tuning and detuning is designed and given in detail. Compared to the traditional SLED type, the spherical cavity pulse compressor uses only one spherical cavity to realize the pulse compression, which makes it compact as a whole.

A Novel Plasma Jamming Technology Based on the Resonance Absorption Effect

Based on the resonance absorption effect of plasma, the mechanism of plasma jamming technology is studied and verified in this letter. Different from the power perspective, the effects of plasma on the radar echo waveform and the radar signal detection are studied. It is found that the radar echo waveform is distorted and the performance of pulse compression is degraded. Moreover, the phenomenon of radar false targets appears with several meters apart. Thus, plasma could not only act as electromagnetic wave absorbers, but also a kind of passive jammer. Finally, many optimal plasma parameters are presented to achieve desired jamming effects for different radar frequencies. These data provide some useful references to plasma jamming technology.

Performance of an Inline RZ-DPSK Pulse Compression Using Raman Amplifier and Its Application in OTDM Tributary

Performance of an Inline RZ-DPSK Pulse Compression Using Raman Amplifier and Its Application in OTDM Tributary

An efficient pulse compression method of chirp-coded excitation in medical ultrasound imaging

Coded excitation can improve the SNR in medical ultrasound imaging. In coded excitation, pulse compression is applied to compress the elongated coded signals into a short pulse, which typically requires high computational complexity, i.e., a compression filter with a few hundred coefficients. In this paper, we propose an efficient pulse compression method of chirp-coded excitation, in which the pulse compression is conducted with complex baseband data after downsampling, to lower the computational complexity. In the proposed method, although compression is conducted with the complex data, the L-fold downsampling is applied for reducing both data rates and the number of compression filter coefficients; thus, total computational complexity is reduced to the order of 1/L(2). The proposed method was evaluated with simulation and phantom experiments. From the simulation and experiment results, the proposed pulse compression method produced similar axial resolution compared with the conventional pulse compression method with negligible errors, i.e., ≫36 dB in signal-to-error ratio (SER). These results indicate that the proposed method can maintain the performance of pulse compression of chirp-coded excitation while substantially reducing computational complexity.

Development and performance evaluation of an improved complex valued radar pulse compressor

Pulse compression is an important and burning issue in radar signal processing. In the recent past, many adaptive and neural network based methods have been proposed to achieve effective pulse compression performance for real coded transmitted waveforms. Even though the radar signal is complex, it is mostly processed as real-valued in-phase and quadrature components. Hence it is desirable that for processing complex radar signal for pulse compression both the structure as well as the learning algorithm associated with it need to be complex in nature. Accordingly in this paper a novel adaptive method is proposed by employing a complex valued fully connected cascaded (CFCC) neural network. For training this network, a new complex Levenberg–Marquardt (CLM) algorithm is derived and used for imparting effective training of its weights. The new CLM based CFCC (CFCC-CLM) model offers superior convergence performance with the least residual mean squared error during training phase compared to those provided by the multilayer perceptron (MLP) trained with complex domain backpropagation (CDBP) and CLM based methods. Further the comparison of peak signal-to-sidelobe ratio (PSR) under noisy and Doppler shift conditions of the proposed method exhibits best performance compared to those offered by the MLP-CDBP, MLP-CLM and the matched filter (MF) based methods.

Signal compression in radar using FPGA

We present the hardware implementation of radar real time processing procedures using a simple, fast technique based on FPGA (Field Programmable Gate Array) architecture. This processing includes different window procedures during pulse compression in synthetic aperture radar (SAR). The radar signal compression processing is realized using matched filter, and classical and novel window functions, where we focus on better solution for minimum values of side-lobes. The proposed architecture exploits the parallel computing resources of FPGA devices to achieve better computation speed. Experimental investigations have shown that the best results for pulse compression performance have been obtained using atomic functions, improving the performance of the radar system in the presence of noise, obtaining small degradation in range resolution. Implementation of the signal processing in the radar system for real time mode is discussed here and the effectiveness of the proposed hardware architecture has been justified.

Wideband Waveform Design Principles for Solid-State Weather Radars

Abstract The use of solid-state transmitters is becoming increasingly viable for atmospheric radars and is a key part of the strategy to realize any dense network of low-powered radars. However, solid-state transmitters have low peak powers and this necessitates the use of pulse compression waveforms. In this paper frequency diversity in a wideband waveform design is proposed to mitigate the low sensitivity of solid-state transmitters. In addition, the waveforms mitigate the range-eclipsing problem associated with long pulse compression. An analysis of the performance of pulse compression using mismatched compression filters designed to minimize sidelobe levels is presented. The impact of the range sidelobe level on the retrieval of Doppler moments is discussed. Realistic simulations are performed based on both the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) and the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) Integrated Project I (IP1) radar data.