Radar Receiver Research Articles

Design, Fabrication, and Characterization of a Hybrid Integrated Photonic Module for a Synthetic Aperture Radar Receiver

Design, Fabrication, and Characterization of a Hybrid Integrated Photonic Module for a Synthetic Aperture Radar Receiver

A High-Performance, Low-Cost, and Integrated Hairpin Topology RF Switched Filter Bank for Radar Applications.

Switched filter banks find widespread application in frequency-hopping radar systems and communication networks with multiple operating frequencies, especially in situations demanding elevated filter element isolation. In this paper, the design and implementation of a highly isolated switchable narrow-bandpass filter bank architecture using hairpin microstrip topology is presented. The filter bank has four discrete bandpass filters with passbands of 2.0-2.2 GHz, 2.3-2.5 GHz, 3.1-3.3 GHz, and 3.9-4.1 GHz. These filters span the radar S-frequency band (2.0-4.0 GHz). In order to switch between channels with a switching speed of nanoseconds, low-loss and highly isolated SP4T switches are implemented. Advanced design system (ADS) software is used to design the various filter functionalities, and the entire system is tested on a vector network analyzer (VNA). The proposed architecture makes it much easier to put the filter bank into practice and switch it to the desired frequency, which is useful for radar receiver applications.

Sub-Nyquist radar receiver based on photonics-assisted compressed sensing and cascaded dictionaries

Sub-Nyquist radar receiver based on photonics-assisted compressed sensing and cascaded dictionaries

Multibeam Beamforming Demonstration of a Hybrid Integrated Photonic Module for a Synthetic Aperture Radar Receiver

Multibeam Beamforming Demonstration of a Hybrid Integrated Photonic Module for a Synthetic Aperture Radar Receiver

Microwave photonic I/Q mixer for wideband frequency downconversion with serial electro-optical modulations.

In this paper, we propose a serial electro-optical (EO)-modulation-based microwave photonic in-phase and quadrature (I/Q) mixer and investigate its performance for wideband frequency downconversion. The proposed I/Q mixer uses two EO modulators and a programmable optical processor in a serially cascaded structure, which ensures good phase stability and flexibility to achieve high-performance broadband frequency downconversion. A proof-of-concept experiment is carried out in which the frequency downconversion of the RF signals in the range from 10 to 40 GHz is demonstrated with an average image rejection ratio of 38.66 dB. The spurious-free dynamic range (SFDR) measured at around 15 GHz is 86 dBc·Hz2/3. Based on this microwave photonic I/Q mixer, a broadband radar receiver is established and de-chirping of linearly frequency modulated (LFM) radar echoes with an instantaneous bandwidth of 8 GHz (10-18 GHz) is achieved. The results verify its feasibility for high-performance I/Q mixing in practical applications.

Sidelobes Reduction Technique for Binary Codes

Pulse compression techniques enable the radar designers to transmit long duration pulse to cater the need of high power at the transmitter and achieve the range resolution of short duration pulse at the radar receiver simultaneously. Due to easy generation and processing, binary codes are widely used as pulse compression codes in radars, sonars and spread-spectrum communication systems. But binary codes have high unwanted pulse compression sidelobes at the output of pulse compression receivers. In this paper, optimum binary codes reported in the literatures are overlaid on Discrete frequency sequences to reduce unwanted peaks sidelobes of optimum binary codes. The proposed approach not only reduced peak sidelobes of optimum binary codes but also increased the pulse compression ratio. In this paper, optimum discrete frequency sequences for overlaying with binary codes are optimized using the Modified Simulated Annealing Algorithm (MSAA). A Discrete Frequency Coded binary signal has a complex signal structure which will be difficult to detect and analyze by enemy Electronics Support Measures (ESM). In this paper, a unified adaptive radar model is also proposed to cater the needs of today's radar signal design requirements. The proposed model will help to improve range resolution, the detection capability of radar, reduce the peak sidelobes significantly, and also improve the ESM capability of radar systems.

ACOUSTO-OPTICAL RECEIVER OF AN OBSTRUCTION PASSIVE RADAR SYSTEM

The subject of research in the article is the passive radar system of a warship. The purpose of the work was to review the characteristics use of the acousto-optical receiver in the new passive radar system of the warship, to investigate the peculiarities of acoustooptic effect and the relevant synthesis of methods and tools for measuring the photodetector photoelectric characteristics and, in addition, to investigate the energy-and-geometric parameters of laser radiation Justification. It is shown that the transition, impulse and frequency characteristics are taken as the main means to determine the operating and technical parameters of the acousto-optical delay line. It is not possible to unambiguously extrapolate these characteristics to the known models of the characteristics of the acousto-optic radar receiver created on AODL. Research results. In the context of this postulate, mathematical models of the main characteristics of AODL were developed. On the basis of the synchronous compensation pulse obstacles applied to the passive radar acousto-optic receiver on military ships, the full compensation of the obstacles is determined for the effective reception of signals from the acousto-optic receiver. In radar stations (radar), the main attention is focused on the statistical properties of the useful signal and passive obstacles, the speed (frequency) of the signal passing through the passive obstacle and the space-time differences. The recommendations. These features are recommended to be used only in special cases where the target is outside the reflectors for informational duration, amplitude and differences between passive obstacles, obstacle silencing and signal separation. Conclusion. Applying the full attenuation of the band filter and synphase barrier organizers, whose frequency characteristics do not depend on the tuning frequency, it is possible to provide full compensation of obstacles during the effective reception of signals by the acousto-optic receiver in the passive radar system of warships based on the proposed method for high resistance to obstacles, pulse obstacle compensation.

Time alignment quantum illumination based on single real-time coincidence counting

We propose and demonstrate an improved quantum illumination protocol based on the time correlation of twin photons, for the high signal-to-noise ratio (SNR) of target detection and signal reconstruction in the strong noise environment. The Hong-Ou-Mandel (HOM) interferometer is applied after the spontaneous parametric down-conversion (SPDC) process to construct a probing twin-beam in which the photon times are precisely aligned between the beams. At the radar receiver, we put forward a single real-time coincidence counting (SRCC) method on a series of time slices to reconstruct the probe signals of pulse radar and calculate the SNR advantages against the conventional pulse radar, as well as the quantum illumination (QI) protocol. Our main achievements in this research are the realization of real-time detection of quantum information while acquiring a higher SNR than QI and classical illumination (CI) protocols, as well as its demonstration of strong robustness to noise and losses, which also proposes what we believe to be a novel way for quantum target detection.

Joint radar and communication system based on a chaotic optoelectronic oscillator

We present a novel joint radar and communication (JRC) system that utilizes a chaotic optoelectronic oscillator (OEO) to generate a wideband radio frequency carrier. By mixing the carrier with an on-off keying (OOK) signal through intensity modulation and direct detection, a wideband JRC waveform is generated. One part of the waveform is used for transmitting, while the other serves as a reference for radar reception. The unique properties of the chaotic OEO signal, such as its randomness and large bandwidth, are leveraged to achieve superior system performance and eliminate the need for an electronic arbitrary waveform generator. In the proof-of-concept experiment, the JRC system achieves a radar range resolution of 7 cm and a wireless communication rate of 125 Mbit/s.

Multi-Label Radar Compound Jamming Signal Recognition Using Complex-Valued CNN with Jamming Class Representation Fusion

In the complex battlefield electromagnetic environment, multiple jamming signals can enter the radar receiver simultaneously due to the development of jammers and modulation technology. The received compound jamming signals aggravate the difficulty of recognition and subsequent counter-countermeasure. In the face of strong overlapping signals and unseen jamming signal combinations, the performance of existing recognition methods usually seriously degrades. In this paper, an end-to-end multi-label classification framework combining a complex-valued convolutional neural network (CV-CNN) and jamming class representations is proposed to automatically recognize the jamming signal components of compound jamming signals. A basic multi-label CV-CNN (ML-CV-CNN) is first designed to directly process time–domain complex signals and fully retain jamming signal information. Then, the jamming class representations are generated using prototype clustering implemented by learning vector quantization, and they are fused with the ML-CV-CNN using class decoupling implemented by the attention mechanism to construct a multi-label class representation CV-CNN (ML-CR-CV-CNN), which can better learn the class-related features required for recognition. Finally, an adaptive threshold calibration is adopted to obtain optimal recognition results by multi-threshold discrimination. Simulation results verify that the proposed method has superior recognition performance, which is reflected in the strong robustness to the varying jamming-to-noise ratio (JNR) and power ratio, faster convergence speed with high JNRs, and better generalization for unseen jamming signal combinations.

Case Study Comparing ROC and PRC Curves for Imbalanced Data

Receiver operating characteristic curves are a mainstay in binary classification and have seen widespread use from their inception characterizing radar receivers in 1941. Widely used and accepted, the ROC curve is the default option for many application spaces. Building on prior work the Prognostics and Health Management community naturally adopted ROC curves to visualize classifier performance. While the ROC curve is perhaps the best known visualization of binary classifier performance it is not the only game in town. Authors from across various STEM fields have published works extolling various other metrics and visualizations in binary classifier performance evaluation. These include, but are not limited to, the precision recall characteristic curve, area under the curve metrics, bookmaker informedness and markedness. This paper will review these visualizations and metrics, provide references for more exhaustive treatments on them, and provide a case study of their use on an imbalanced prognostic health management data-set. Prognostic health management binary classification problems are often highly imbalanced with a low prevalence of positive (faulty) cases compared to negative (nominal/healthy) cases. In the presented data-set, time domain accelerometer data for a series of run-to-failure ball-on-disk scuffing tests provide a case where the vast majority of data, > 94%, is from nominally healthy data instances. A condition indicator algorithm targeting the hypothesized physical system response is validated compared to less informed classifiers. Several characteristic curves are then used to showcase the performance improvement of the physics informed condition indicator.

Beam-Space MIMO Radar for Joint Communication and Sensing With OTFS Modulation

Motivated by automotive applications, we consider joint radar sensing and data communication for a system operating at millimeter wave (mmWave) frequency bands, where a Base Station (BS) is equipped with a co-located radar receiver and sends data using the Orthogonal Time Frequency Space (OTFS) modulation format. We consider two distinct modes of operation. In <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Discovery</i> mode, a single common data stream is broadcast over a wide angular sector. The radar receiver must detect the presence of not yet acquired targets and perform coarse estimation of their parameters (angle of arrival, range, and velocity). In <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tracking</i> mode, the BS transmits multiple individual data streams to already acquired users via beamforming, while the radar receiver performs accurate estimation of the aforementioned parameters. Due to hardware complexity and power consumption constraints, we consider a hybrid digital-analog architecture where the number of RF chains and A/D converters is significantly smaller than the number of antenna array elements. In this case, a direct application of the conventional MIMO radar approach is not possible. Consequently, we advocate a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">beam-space approach</i> where the vector observation at the radar receiver is obtained through a RF-domain beamforming matrix operating the dimensionality reduction from antennas to RF chains. Under this setup, we propose a likelihood function-based scheme to perform joint target detection and parameter estimation in Discovery, and high-resolution parameter estimation in Tracking mode, respectively. Our numerical results demonstrate that the proposed approach is able to reliably detect multiple targets while closely approaching the Cramér-Rao Lower Bound (CRLB) of the corresponding parameter estimation problem.

Experimental Study of High Power Microwave Injection in Radar Receiving Front-end

In order to study the tolerance threshold and damage process of radar receiving front end against high power microwave pulse attack, the relationship between the damage of receiving front end and injected signal power, pulse width, and duration was obtained by injection test. The experimental results show that the damage of PIN limiter by high power microwave is a slow worsening process near the damage threshold. Based on the test results, the radar withstanding range of high-power microwave weapon attack is calculated theoretically, which can provide theoretical support for the radar receiving front-end design.

Radar Receiver with Intrinsic Power Limiter Assisted by Microwave Photonics

This article presents an approach of a radar receiver that has an intrinsic power limitation based on photodetector power saturation. The radar signal power detection is implemented using optical self-homodyne detection. The proposed architecture uses a phase modulator (PM) to modulate the optical carrier and a fiber Bragg grating (FBG) to filter the spectrum and convert the phase to intensity modulation. The self-homodyne technique eliminates the optical carrier influence. It enables to reduce of shot noise influence and increases the photodetected optic power to improve the conversion gain. Moreover, the photodetection is performed at the radar pulse baseband, allowing to obtain transimpedance gain. An experimental demonstration is performed. A dynamic range of 56 dB is achieved for a pulsed radar operating at 20 GHz.

Spectral Characteristics of Phase Fluctuations at High Latitude

AbstractIt has long been established that ionospheric electron density irregularities cause random rapid amplitude and phase fluctuations in trans‐ionospheric radio signals. Various types of ground‐based measurements, including radar and Global Navigation Satellite System (GNSS) receivers, have been utilized to gain insights into the plasma mechanisms that could lead to the development of these ionospheric irregularities. The spectral characteristics of radio wave signals emitted by GNSSs and detected by the Canadian High Arctic Ionospheric Network Global Positioning System (GPS) receivers are analyzed to try and identify the spectral signatures of the ionospheric plasma irregularities. In the polar region, we have confirmed that phase fluctuations in the GPS signal are not always accompanied by amplitude fluctuations. For the first time, a systematic comparison is conducted on the spectral properties of phase‐fluctuation events in the absence and presence of amplitude scintillations, respectively. More specifically, a spectral characterization is performed on 41 events recorded by three receivers positioned within the auroral oval. When fluctuations above the background level are solely observed in the signal's phase, the spectrum of phase variations exhibits a consistent steepness. Conversely, the presence of amplitude scintillation is accompanied by an increase in power at higher frequencies, resulting in shallower spectra. This analysis provides yet another physical element suggesting that the rapid fluctuations observed in the signal's amplitude may be caused by Fresnel‐scale irregularities arising from a gradient‐drift‐like instability while the phase variations seem to be consistent with a refractive mechanism caused by large‐scale ionospheric structures.

Assessment of Techniques for Detection of Transient Radio-Frequency Interference (RFI) Signals: A Case Study of a Transient in Radar Test Data

The authors present a case study of the investigation of a transient signal that appeared in the testing of a radar receiver. The characteristics of the test conditions and data are first discussed. The authors then proceed to outline the methods for detecting and analyzing transients in the data. For this, they consider several methods based on modern signal processing and evaluate their utility. The initial method used for identifying transients is based on computer vision techniques, specifically, thresholding spectrograms into binary images, morphological processing, and object boundary extraction. The authors also consider deep learning methods and methods related to optimal statistical detection. For the latter approach, since the transient in this case was chirp-like, the method of maximum likelihood is used to estimate its parameters. Each approach is evaluated, followed by a discussion of how the results could be extended to analysis and detection of other types of transient radio-frequency interference (RFI). The authors find that computer vision, deep learning, and statistical detection methods are all useful. However, each is best used at different stages of the investigation when a transient appears in data. Computer vision is particularly useful when little is known about the transient, while traditional statistically optimal detection can be quite accurate once the structure of the transient is known and its parameters estimated.

Intelligent reflecting surface aided co-existing radar and communication system

This paper explores the potential of intelligent reflecting surfaces (IRS) as a solution for enhancing radar detection and communication data transmission in crowded areas, where co-existing radar and communication (CRC) systems face distinct channel impairments. The proposed approach involves jointly optimizing the phase shift matrix of the IRS and the beamforming of the radar and communication systems, with the objective of maximizing the signal-to-interference-plus-noise ratio (SINR), while adhering to user-specified SINR requirements, radar transmit power, and base station (BS) power. To tackle this complex optimization problem, we introduce a Constrained Concave-Convex Procedure (CCCP) based Bisection Search (CCCP-BI) iterative algorithm. This algorithm utilizes CCCP to obtain the beamformers of the radar and communication systems, followed by the iterative Bisection Search (BI) to derive a solution for the PSM. Considering the computational complexity of CCCP-BI, we also propose an alternative Semi-Definite Programming (SDP)-based Bisection Search (BI-SDP) algorithm. Extensive simulations demonstrate the effectiveness of the IRS in the (CRC) system. Furthermore, we conduct performance comparisons with other benchmarks, evaluating the impact of various parameters on the received SINR at the radar receiver.

Performance Analysis and System Implementation for Energy-Efficient Passive UAV Radar Imaging System

Due to the superior flexibility and cost-efficiency, unmanned aerial vehicle (UAV) is becoming an indispensable platform for advanced remote sensing applications. In this paper, the performance and implementation of the energy-efficient passive UAV radar imaging system is investigated. Equipped with a synthetic aperture radar (SAR) receiver, the UAV platform passively reuses the backscattered signal of an external illuminator, and achieves SAR imaging and data communication. Firstly, we present the system concept and block diagram. Then, the imaging performance and feasibility are analyzed for the typical illuminators. It is found that the system can achieve distinct mission performance with different kinds of illuminators, which offers more alternatives for various mission requirements. A set of mission performance evaluators is established to comprehensively assess the capability of the system, including UAV navigation, passive SAR imaging and communication. An energy-efficient path planning method is then presented to generate a UAV path with optimized mission performance. Numerical simulations are conducted to verify the effectiveness of the performance evaluators and path planning method. Finally, a real implementation of the system is given. The imaging results of an airborne passive SAR experiment using external illuminator further validates the imaging capability and performance analysis of the system.

Analysis On Drone Detection and Classification in LTE-Based Passive Forward Scattering Radar System

Long-Term Evolution (LTE) is most commonly used in connection with 4G networks with high spectral efficiency, high peak data rates, flexible in frequency and bandwidth.By utilizing LTE signal in passive forward scattering radar as transmitter, this system is able to create a microwave domain at the radar's receiver part which generated a moving object's Doppler signature.The emergence of guided missiles, humans, airplanes, and drones that travel through between the forward scatter radar systems can really be spotted with this passive radar system. This study's primary goal is to employ passive forward scattering radar and an LTE signal to detect drones, which are commonly used by individuals to violate or invade private and secure places. In detail, a drone was detected at two distinct heights of twometers(lower) and threemeters(higher) from the ground by utilizingpassive forward scattering radar to generate Doppler signature of the flying drone.This experimental work is conducted at two locations which are Taman Suria (UiTM, Shah Alam) and Teluk Kemang (Port Dickson), due to the telecommunication transmitter antenna transmits Long-Term Evolution (LTE) signal with frequency of 1.8 GHz and 2.6 GHz. The results of drone detection at various heights were evaluated using Principal Component Analysis (PCA)on all the experimental data obtained. According to the evaluation, the lower height of the drone performedbetter in classification and confusion matrices analysis than the upper height due to a larger cross-sectional area for the lower height of the drone that travelled through the forward scatter zone.In summary, the overall study clearly demonstrates the effective categorization of flying drone detection at upper and lower positions in Principle Component Analysis (PCA). For future contribution of this research, it can be used at the airport to detect any unwanted drones trespassing the flight departure area, and important areas such as the Federal Administrative Centre of Malaysia, Putrajaya for spying purposes.

Study of dynamic biasing InGaAs/InAlAs avalanche photodiodes with different active areas.

In this work, by comparing and analyzing dynamic biasing InGaAs/InAlAs avalanche photodiodes(APDs) with different active areas, it is found that they have different noise suppression frequency ranges. The upper limit frequency(defined as the frequency at which the noise suppression effect begins to fail) of InGaAs/InAlAs APDs with active area diameter of 50 µm, 100 µm and 200 µm are 2400 MHz, 1990MHz and 1400 MHz respectively. In addition, for InGaAs/InAlAs APDs with an active area diameter of 50 µm, 100 µm and 200 µm, their optimal frequencies of dynamic biasing (defined as the frequency corresponding to the optimal SNR) are 1877MHz, 1670 MHz and 1075 MHz respectively. At last, applying dynamic biasing technology, it achieves a useful gain of 6698.1, which is much greater than that of DC bias (47.2), and this technology has the potential to be applied in high sensitivity laser radar receivers.