Modern Radar Systems Research Articles

Multiresonant metasurfaces for arbitrarily broad bandwidth pulse chirping and dispersion compensation

We show that ultrathin metasurfaces with a specific multiresonant response can enable simultaneously arbitrarily strong and arbitrarily broadband dispersion compensation, pulse (de)chirping, and compression or broadening. This breakthrough overcomes the fundamental limitations of both conventional nonresonant approaches (bulky) and modern singly resonant metasurfaces (narrowband) for quadratic phase manipulations of electromagnetic signals. The required nonuniform trains of resonances in the electric and magnetic sheet conductivities that completely control phase delay, group delay, and chirp are rigorously derived and the limitations imposed by fundamental physical constraints are thoroughly discussed. Subsequently, a practical, truncated approximation by finite sequences of physically realizable linear resonances is constructed and the associated error is quantified. By appropriate spectral ordering of the resonances, operation can be achieved either in transmission or reflection mode, enabling full space coverage. The proposed concept is not limited to dispersion compensation, but introduces a generic and powerful ultrathin platform for the spatiotemporal control of broadband real-world signals with a myriad of applications in modern optics, microwave photonics, radar, and communication systems.

A compact antipodal vivaldi antenna for modern surveillance systems

ABSTRACT Recent breakthroughs in modern surveillance systems combined with stealth and jamming technologies have led to the development of high-directional and high-gain antennas. This paper presents a compact-sized antipodal Vivaldi antenna (AVA) consisting of an elliptical shaped radiating flare with rectangular slots at the flare edges for modern surveillance systems. The proposed antenna provides improvements in the antenna characteristics, including a higher front-to-back ratio, increased main lobe gain, reduction in the side lobe level (SLL), and lower frequency limit. The results reveal that at 20 GHz, an improved gain of 3.8 dB and a front-to-back ratio of more than 40 dB have been realised. Additionally, in contrast to the antenna without edge slots, the impedance bandwidth, |S11| < −10 dB of 15 GHz, and a reduction in the lower operating frequency by 36.7% have also been achieved. The prototype antenna is developed and tested to verify with simulation results. The proposed antenna with the miniaturised structure may be suitable for surveillance applications in modern radar systems because of its ultrawide fractional bandwidth, high directive gain, and reduced SLL.

Optical Filter-Less Photonic FMCW Radar for Multi-Target Detection

Frequency modulated continuous wave (FMCW) radar monitors the instantaneous frequency difference between the transmitted and the received signal to determine the time of flight which is proportional to the range. Modern radar system necessitates multispectral sensing to enhance detection capability and anti-jamming efficacy that encourages the evolution from conventional electrical solutions to photonics-enhanced solutions. Photonics offers wide-bandwidth signal generation, parallel processing, and low propagation distortion. Most photonic-assisted radar models are based on optical filters to select the reference and reflected waveform to mix at the photodiode, which limits the system functionality due to the inability to operate in different frequency bands. We propose an optical filter-less photonics-based de-chirp processing of frequency-modulated continuous-wave radar waveforms that overcomes the issue of carrier frequency tunability and agility. A theoretical analysis is performed, followed by simulation, and validated by experiment. The proposed model is experimentally tested for detecting targets at different distances ranging from 150 cm to 210 cm. The system is emulated to detect multiple targets (up to four), showing a range resolution of <15 cm, and signal processing enables the estimation of the widths of different sizes of the targets.

Direction of Arrival Deception With Time-Modulated Scatterers

Modern radar systems can detect targets with high accuracy and are even able to classify them remotely. Their continuous advance is inevitably met with developing radar countermeasures, where passive radio-silent countermeasures begin to prevail over active jamming approaches. The direction of targets in respect to a radar system can be deduced from the correlation between the sampled phases in different antennas forming a receiving array. By breaking this coherent relationship, it is possible to cause the radar to estimate the wrong direction of arrival, deceiving it into concluding the object is elsewhere. A method for achieving this by controlling the reflected phase from a time-modulated scatterer is presented both theoretically and experimentally, showing suitability for implementation via time-dependent metasurfaces, supporting a semi-passive (battery-assisted) mode of operation. The method is also well suited for long range angular deception, complementing ’cross-eye’ jamming techniques that are most effective at short ranges. We demonstrate control over the radar-perceived angular location of the static concealed target, with proven ability to steer the direction of arrival on demand by over 5 degrees away from its true angular position regardless of range. Remarkably, this new type of electronic countermeasure works better with increasing radar bandwidth, turning its strength into an exploitable weakness.

New Spectrally Constrained Sequence Sets With Optimal Periodic Cross-Correlation

Spectrally constrained sequences (SCSs) play an important role in modern communication and radar systems operating over non-contiguous spectrum. Despite numerous research attempts over the past years, very few works are known on the constructions of optimal SCSs with low cross-correlations. In this paper, we address such a major problem by introducing a unifying framework to construct unimodular SCS families using circular Florentine rectangles (CFRs) and interleaving techniques. By leveraging the uniform power allocation in the frequency domain for all the admissible carriers (a necessary condition for beating the existing periodic correlation lower bound of SCSs), we present a tighter correlation lower bound and show that it is achievable by our proposed SCS families including multiple SCS sets with zero correlation zone properties.

ПРИСТРІЙ ФОРМУВАННЯ ПЕРЕВІРЯЮЧОГО ТЕСТУ ЦИФРОВОГО ТЕЗ РЛС 19Ж6

The general need to develop additional diagnostic equipment is that a fairly large number of complex technical objects are currently in use, which are morally but not physically obsolete, and therefore it is not possible to abandon their use today. Radar 19Ж6 belongs to such objects. The level of diagnostic support for this radar does not meet the requirements for modern models of radio electronic weapons (REW). The 19Ж6 was replaced by another radar with significantly improved diagnostic support. An automated diagnostic complex of the Diana series is used to diagnose and repair modern radar systems of domestic production. This complex is designed to diagnose and restore complex digital and digital-to-analog standard replacement elements. It is possible to adapt a modern diagnostic complex to diagnose outdated equipment, but within the limited funding, it is economically impractical. Accordingly, there is a task to develop modern means of diagnosing typical replacement elements of the 19Ж6 radar, which can be used to equip stations. Within the framework of the overall task, a number of partial tasks can be identified. One of these tasks is the development of a general methodology and a structural diagram of the device for determining the verification test for digital standard replacement elements (SRE) from the 19Ж6 radar. Thus, the article is devoted to the development of a block diagram of the device for forming a diagnostic test as a component of the device for monitoring the technical condition of digital SRE. The structure of the device is completely determined by the methodology of the test structure. The result of the diagnostic test is a decision on the operability or inoperability of the SRE. The need for such diagnostics stems from the fact that the built-in technical diagnostic system does not detect a single inoperable TES, but detects a group of suspected inoperable SRE. To separate the inoperable digital device, it is necessary to use additional equipment. The paper proposes to use an energy-static diagnostic method, the essence of which is that the value of the voltage on an additional resistance, which is measured in a steady-state operation mode, is used as a diagnostic parameter. The method of designing the verification test is the method of experimental evaluation of the length of the test sequence, and the sequence itself is a pseudo-random sequence of input influences.

IMPLEMENTATION OF THE COINCIDENCE FREQUENCY METER ON FPGA

Means of measuring various parameters and technical characteristics of radio equipment have always occupied leading positions in science and technology. Without an accurate definition of the relevant values, it is impossible to build modern high-quality radio communication systems, radar, navigation ground and satellite systems. In ultrasound diagnostics, which are used in medicine, the speed of blood flow in vessels is studied by determining the frequency of the reflected signal. At the same time, it is necessary to use high-speed frequency measurement tools in systems with active sensors used in telecommunication networks based on Internet of Things technology. For example, in active radar, using the frequency of the reflected signal, it is possible to calculate not only the coordinates, but also the circular speed of the moving target. Modern research is aimed at improving the metrological and technical indicators of existing measuring devices, in particular at developing new methods for correcting the characteristics of the transformation of the measuring channel, which is their main component. At the same time, most digital frequency meters are built on the method of counting the number of pulses N with an unknown period Tx that arrive at the input of the device during a calibrated time interval. All this leads to an increase in measurement time and requires additional hardware costs for fast processing of measurement results. The coincidence method belongs to vernier methods and is promising for use when measuring the frequency of periodic signals. This paper points out the shortcomings of known methods of measuring the frequency of a periodic signal. On the basis of the well-known method of coincidence, a functional scheme of a 16-bit device for measuring frequency, which is implemented on the basis of a FPGA from Intel (Altera), has been developed. The developed coincidence frequency meter has a dynamic range of 96dB. Representation of time diagrams obtained in the Quartus Prime 18.0 automated design environment and confirming the operability of the developed functional scheme of the 16-bit device for frequency measurement by the coincidence method. An analytical dependence for determining the frequency of a periodic signal during frequency measurement by the coincidence method is presented.

Multiband dual- and cross-LFM waveform generation using a dual-drive Mach–Zehnder​ modulator

Linear frequency modulation (LFM) signals are widely used in modern radar systems owing to their intrinsic pulse compression capability but are restricted due to a limited range-Doppler resolution. On the other hand, dual- or cross-LFM signals have complementary LFM waveforms at the same time instant that reduces the range-Doppler coupling and thus improving range-Doppler resolution. We propose a simple microwave-photonic-based approach to generate multiband dual- and cross-LFM waveforms using only a single dual-drive Mach–Zehnder modulator (DDMZM). A theoretical analysis is carried out, which is modeled and verified through experiments. Dual- and cross-LFM waveforms at a carrier frequency of 6 GHz and 18 GHz with a bandwidth of 2 GHz is generated by controlling the DC and RF bias of the DDMZM. The tunability of the carrier frequency from 3 GHz to 9 GHz is also verified. A range resolution of 6.3 cm for dual- and cross-LFM waveforms, is obtained with a time-bandwidth-product (TBWP) of 20,000. The proposed technique is a promising solution for dual- and cross-LFM waveform generation in two-band multipurpose radar systems.

Silicon integrated frequency‐tunable microwave photonic bandpass filter

AbstractMicrowave photonic filters have been regarded as an alternative to traditional radio‐frequency filters because of their wide bandwidth and large tunability. Integrated microwave photonic filters can integrate all necessary components into a single chip and are highly demanded for future radio‐frequency applications. Here, a highly integrated frequency‐tunable microwave photonic bandpass filter based on a silicon platform is proposed and demonstrated. The integrated filter consists of a phase modulator, four cascaded microring resonators and a photodetector. The frequency‐tunable range of the integrated filter is from 6.1 to 35.9 GHz, and the reconfigurable bandwidth is from 0.22 to 0.54 GHz. A large spurious free dynamic range of 102.1 dB Hz2/3 is obtained. This highly integrated approach holds great promise for miniaturised, flexible, and high‐performance microwave signal processing in modern radar and communication systems.

Estimation and Classification of NLFM Signals Based on the Time-Chirp Representation.

A new approach to the estimation and classification of nonlinear frequency modulated (NLFM) signals is presented in the paper. These problems are crucial in electronic reconnaissance systems whose role is to indicate what signals are being received and recognized by the intercepting receiver. NLFM signals offer a variety of useful properties not available for signals with linear frequency modulation (LFM). In particular, NLFM signals can ensure the desired reduction of sidelobes of an autocorrelation (AC) function and desired power spectral density (PSD); therefore, such signals are more frequently used in modern radar and echolocation systems. Due to their nonlinear properties, the discussed signals are difficult to recognize and therefore require sophisticated methods of analysis, estimation and classification. NLFM signals with frequency content varying with time are mainly analyzed by time-frequency algorithms. However, the methods presented in the paper belong to time-chirp domain, which is relatively rarely cited in the literature. It is proposed to use polynomial approximations of nonlinear frequency and phase functions describing signals. This allows for applying the cubic phase function (CPF) as an estimator of phase polynomial coefficients. Originally, the CPF involved only third-order nonlinearities of the phase function. The extension of the CPF using nonuniform sampling is used to analyse the higher order polynomial phase. In this paper, a sixth order polynomial is considered. It is proposed to estimate the instantaneous frequency using a polynomial with coefficients calculated from the coefficients of the phase polynomial obtained by CPF. The determined coefficients also constitute the set of distinctive features for a classification task. The proposed CPF-based classification method was examined for three common NLFM signals and one LFM signal. Two types of neural network classifiers: learning vector quantization (LVQ) and multilayer perceptron (MLP) are considered for such defined classification problem. The performance of both the estimation and classification processes was analyzed using Monte Carlo simulation studies for different SNRs. The results of the simulation research revealed good estimation performance and error-free classification for the SNR range encountered in practical applications.

Wald Test for Adaptive Array Detection With General Configuration

Assume that a modern radar system has a general antenna array configuration consisting of primary channels with high-gain beams and reference channels with low-gain beams. We consider the target detection problem for such array radar systems in Gaussian disturbance with unknown covariance matrix. An adaptive detector is proposed according to the criterion of Wald test. The statistical properties of the proposed detector are provided in the mismatched case, where the nominal target steering vector may not be aligned with the true target steering vector. An analytical expression for the probability of false alarm is derived, which reveals that the proposed detector has a constant false alarm rate property with respect to the disturbance covariance matrix. Moreover, a closed-form expression for the detection probability is obtained in the mismatched case. Simulation results demonstrate that the proposed detector exhibits strong robustness against the target steering vector mismatch.

Photonic generation of dual-band complementary linearly chirped microwave waveforms based on phase modulator

A simple scheme to generate a dual-band complementary linearly chirped microwave waveform using a Mach–Zehnder modulator (MZM) paralleled with a phase modulator (PM) is proposed. In the scheme, a five-line optical frequency comb, generated by MZM, is combined with a phase modulated optical chirp waveform by a baseband parabolic signal or a single-chirp signal as two beams with inverse relative phases via a 2 × 2 optical coupler. After balanced detection with heterodyne beating, the dual-band complementary linearly chirped microwave waveform is generated for the two driving cases, and they demonstrate different enhanced performances. The dual-band complementary linearly chirped microwave waveforms with center frequency of 20 and 40 GHz are generated simultaneously for both cases by simulation. The generated two complementary linearly chirped waveforms with a baseband parabolic driving signal have a larger bandwidth of 7.6 GHz, corresponding to larger pulse compression ratios (PCRs) of 1462.86 and 1365.33, which could effectively improve the range Doppler resolution in modern radar systems, although their peak-to-sidelobe ratios (PSRs) are only 12.98 and 12.97 dB. Although for the case with a single-chirp driving signal, the PSRs of the two waveforms with a bandwidth of 4 GHz are higher, 13.66 and 13.67 dB, respectively, but with the PCRs of only 787.69 and 758.52, which is of practical significance for radar detection in weak targets and multitargets.

Microwave photonic multiform microwave frequency shift keying signal generator.

A photonic approach to realizing multiform microwave frequency shift keying (FSK) signal generation is proposed and demonstrated. In the scheme, a commercial dual-polarization quadrature phase shift keying modulator (DP-QPSKM) is employed to generate two orthogonally-polarized signals containing specific optical sidebands, and a subsequent Sagnac loop structure govern the interference results of these two signals. From a theoretical analysis, when the modulators are properly biased, microwave FSK signal with fixed double relationship or flexibly tunable subcarrier frequencies can be obtained, and high frequency multiplication can be realized in the meantime. Furthermore, a photonic-optimized coherent demodulation structure is designed to recover the binary coding data, which can effectively avoid the electronic bottleneck. Simulation has been performed to investigate the mechanism and the discussions about the robustness to non-ideal parameters including DC bias, phase shift and polarization angle are also given. In the proof-of-concept experiment, microwave FSK signal with subcarrier frequencies of 2/4, 2.2/3.8, 2.4/3.6, 2.6/3.4, 2.8/3.2 GHz are generated, and the correct binary coding data is successfully recovered with the aid of simulation platform. The simulation and experimental results can verify the feasibility of the proposed multiform microwave FSK signal generator, which may find applications in modern radar and communication systems.

Photonic Generation of a Tunable Dual-Chirp Microwave Waveform

A photonic-assisted tunable dual-chirp microwave waveform generator based on optical heterodyne detection is proposed and experimentally demonstrated. In the proposed scheme, a three-electrode distributed Bragg reflector laser diode (DBR-LD) is used to generate a broadband frequency-chirped optical pulse. A stable optical fiber laser and a Mach-Zehnder modulator (MZM) are used to perform a double-sideband suppressed carrier (DSB-SC) signal. The frequency difference between the two sidebands of the DSB-SC signal is larger than the frequency chirp range of the optical pulse. By tuning the center frequency of the optical pulse equals that of the DSB-SC signal and beating the optical pulse and the DSB-SC signal at a photodetector (PD), a dual-chirp microwave waveform is generated. The center frequency of the generated waveform is tuned by adjusting the modulated frequency of the DSB-SC signal. The tunability of the bandwidth and the temporal duration are achieved by tuning the optical pulse. Experimental results show that the center frequency, the bandwidth, and the temporal duration have tuning ranges from 7 to 13 GHz, 13 to 17 GHz, and 500 ns to 50 μs, respectively. Chirp rates up to ±26 GHz/μs for the up- and down-chirp waveforms are measured in the experimental demonstration, respectively. The demonstration shows new avenues to implement high-performance dual-chirp microwave waveform generators for applications in modern radar systems with improved range-Doppler resolution.

ANALYSIS OF PECULIARITIES FOR USE OF MUZZLE VELOCITY MEASUREMENT SYSTEM SL – 520PЕ AND DOPPLER RADAR TRAJECTORY MEASUREMENT SYSTEM MFTR–2100/40 DURING TESTS OF ROCKET AND ARTILLERY ARMAMENT

The article presents a comparative analysis of test results in which the SL–520PЕ muzzle velocity measurement system and the MFTR – 2100/40 Doppler radar system were used. A set of recommendations is proposed, which are aimed at improving the efficiency of the organization and the quality of tests during which the parameters of the initial (muzzle) velocity of the measured objects are determined.&#x0D; Qualitative testing of a wide range of new and modernized models of rocket and artillery armament largely depends on modern radar measurement systems.&#x0D; Recently, the Armed Forces of Ukraine (Armed Forces of Ukraine) have been using the SL – 520PЕ muzzle velocity measurement system and the Doppler radar system MFTR – 2100/40 to determine the initial (muzzle) velocity and trajectory measurements of rocket and artillery armament.&#x0D; The issue of checking the compliance of the parameters of modern models of rocket and artillery armament with the stated specifications is well-timed and is constantly in the focus of attention of the leadership of the Armed Forces of Ukraine.&#x0D; The above mentioned determines the relevance of scientific research to solve the problem of testing rocket and artillery armament by developing a set of recommendations aimed at improving the efficiency of the organization and quality of tests during which the parameters of the initial (muzzle) velocity of measured objects are determined.&#x0D; Thus, anticipating the urgency of this issue there was an initiation of research on the feasibility for use of SL–520PЕ muzzle velocity measurement system and the MFTR – 2100/40 Doppler radar system, taking into account their practical employment. Therefore, the author's team considers it appropriate to contemplate certain test methods using the above measurement systems.&#x0D; The conducted research makes it possible to offer recommendations on setting the options Maximum Velocity, Tracking Time; to determine the magnitude of the minimum value of the start signal level, source of signal, and the optimal value of the angle (Elevation) of the SL–520PЕ antenna for reliable measurement of the initial (muzzle) velocity of artillery shells (mines) during a single shot or a series of shots of the artillery system; determination of the average initial (muzzle) velocity of artillery shells (min) in a series of shots; ensuring the transmission of measured data to the automated fire control system for calculation of ballistic range correction in the process of artillery firing and more efficient testing and certification of artillery weapons offered for procurement to the Armed Forces of Ukraine.

Experimental Study of Trajectory Features for the Recognition of Low-Flying Low-Speed Radar Targets Using Passive Coherent Radar Systems

Introduction. Small unmanned aerial vehicles (UAVs) are a growing threat due to their possible use for illegal activities. Currently, passive coherent radar systems are widely used to detect, track and recognize moving targets, including small UAVs, which makes them a promising tool for use in modern airspace radar monitoring systems. At the same time, recognition of small UAVs becomes a challenging task due the possibility of confusing them with birds, particularly in maritime areas with large bird populations. In a search for new solutions to the problem of recognizing small UAVs, trajectory features can be used.Aim. To analyze differences between the trajectory features of low-flying low-speed targets in order to verify the possibility of their use for recognition purposes.Materials and methods. Real radar measurements of UAVs and birds obtained by a passive coherent radar system were used. Specific characteristics of the trajectory parameters of target classes were built using computer statistical modeling in the MatLab environment. Differences in the movement trajectory of targets were established by comparative analysis.Results. Significant differences between the flight path of UAVs and birds were found. Specific features of the trajectory of small aerial targets of each type were investigated. On the basis of radar measurement, graphs of the characteristic trajectory parameters of UAVs and birds were plotted. The conducted comparative analysis allowed identification of the characteristics of the flight path of each target type in each movement segment. Trajectory features that can be used for recognition purposes were identified.Conclusion. The practical significance of the proposed trajectory features and the possibility of their implementation in the development of an algorithm for recognizing low-flying low-speed radar targets using passive coherent radar systems was established. The knowledge of differences between the flight path of UAVs and birds can improve the quality of the UAV recognition problem.

Broadly tunable and ultra-highly selective detection of radio frequency signals enabled by a silicon photonic chip.

Precise and agile detection of radio frequency (RF) signals over an ultra-wide frequency range is a key functionality in modern communication, radar, and surveillance systems, as well as for radio astronomy and laboratory testing. However, current microwave solutions are inadequate for achieving the needed high performance in a chip-scale format, with the desired reduced cost, size, weight, and power. Photonics-based technologies have been identified as a potential solution but the need to compensate for the inherent noise of the involved laser sources have prevented on-chip realization of wideband RF signal detection systems. Here, we report an approach for ultra-wide range, highly-accurate detection of RF signals using a conceptually novel feed-forward laser's noise cancelling architecture integrated on chip. The technique is applied to realization of an RF scanning receiver as well as a complete radar transceiver integrated on a CMOS-compatible silicon-photonics chip, offering an unprecedented selectivity > 80 dB, spectral resolution < 1 kHz, and tunability in the full 0.5-35 GHz range. The reported work represents a significant step towards the development of integrated system-on-chip platforms for signal detection, analysis and processing in cognitive communication and radar network applications.

Broadband multi-frequency microwave photonic up-conversion with tunable phase shift

A broadband multi-frequency microwave photonic up-conversion scheme with a tunable phase shift is proposed and demonstrated based on a cavity-less ultrashort optical pulse source and a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM). In this scheme, the intermediate-frequency (IF) signal is loaded onto the optical frequency comb from a cavity-less ultrashort pulse source via carrier-suppressed double-sideband (CS-DSB) modulation by using a DP-DPMZM and a 90° electric hybrid coupler (HC). Through mutual beating between multi-groups of optical modulation sidebands and multi-tone optical carrier at the photodetector (PD), multi-frequency up-converted microwave signals are obtained after coherent superposition. Meanwhile, the phase of the generated signals can be continuously tuned through varying the bias voltages of the DP-DPMZM. Simulation results show that the multi-frequency up-conversion is with a 3-dB operation bandwidth of 36 GHz and a phase shift tuning range over 360°. Hence, this scheme is a potential candidate to simultaneously realize broadband multi-frequency operation and generate the large-scale tunable phase shift in modern radar systems.

Single-Ridge Waveguide Compact and Wideband Hybrid Couplers for X/Ku-Band Applications

Hybrid couplers are important devices that combine or divide signals in various microwave applications. Wideband performance, low losses and small size are key features in most modern radar and communication systems. This paper presents a new geometry for single-ridge, air-filled waveguide quadrature hybrid couplers at the X/Ku band on a single layer using multiple pairs of slots cut on a common ridge coupling section. Bandwidth can be progressively extended by increasing the number of slot pairs. Two designs characterized by compact size and state-of-the-art performance are proposed, leading to a fractional bandwidth up to 46.88% and a maximum dimension of 1.18 wavelengths. A tolerance analysis is presented to highlight the design robustness and reliability.

Broadband pulse generator based on a self-injection-locked Fourier domain mode-locked optoelectronic oscillator

A novel broadband pulse generator based on a Fourier domain mode-locked optoelectronic oscillator (FDML-OEO) is proposed and experimentally demonstrated. The system consists of a dual-loop self-injection-locked OEO with an on-off keying (OOK) bias-controlled Mach–Zehnder modulator (MZM) as an optical switch. By applying a square-wave voltage onto the bias port of the MZM the broadband pulses are directly generated by slicing the outputs of the FDML-OEO. The duty cycle can be easily changed by just tuning that of the square wave. Different microwave pulses with the duty cycles of 1:1, 1:10 and 1:100 are demonstrated. In particular, the tunability of the central frequency and the bandwidth of the generated signal is also displayed. Furthermore, the amplitude coherence superposition of 8 pulses is increased by ∼16 times and the frequency modulated pulse with different central frequencies are also demonstrated. The proposed broadband microwave signal pulse generator based on the injection-locked FDML-OEO can generate signals with large time bandwidth product (TBWP), and the linearly chirped microwave waveforms (LCMWs) are widely used in modern radar systems to achieve high-resolution detection and imaging.