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In this paper, a radar signal processing system, which combines pulse doppler mode and stepped frequency mode, is proposed. The pulse doppler mode is used to detect targets and measure their velocity accurately, and then the stepped frequency mode is used to image the targets. The signal processing system has been implemented on the domestic Huarui No. 2 digital signal processor.

Radar receivers must be extremely sensitive to detect faint target signatures. To this end pulse-Doppler processing of pulse compression waveforms integrates faint target echoes across multiple pulses by matching to the Doppler shift of target returns. Therefore, the combination of receiver sensitivity and exploitation of the target return frequency structure implies that radar signal processing will be sensitive to structured interference, such as that from communications systems. To explore this sensitivity, we examine the impact of a popular communications waveform, orthogonal frequency division multiplexing (OFDM), on the output of pulse-Doppler signal processing. Understanding the impact of cross-function interference will improve requirements generation for both dual-function and shared spectrum systems.

Automotive radar is an all-weather sensing technology that makes direct measurements of target motion thereby aiding in unmanned driving. Continuous-wave (CW) radars which use linear frequency modulation (FM) have been the most popular automotive sensing systems because of lower cost, higher range resolution, and lower transmit power than a pulse Doppler radar. The available spectrum for vehicular systems is limited and, therefore, avoiding mutual interference from multiple automotive radars operating in the same spectrum in a crowded traffic scenario is a major challenge. To address this, we present a Reduced bandwidth FMCW (ReMCW) radar that consumes less spectral resources without decreasing the range resolution and enables interference-free operation. Our CW radar waveform transmits few randomly chosen slopes within the original FMCW sweep. This waveform avoids range- Doppler coupling encountered in conventional FMCW radars. The parameters used for the design of this waveform conform to current automotive radar requirements. Numerical experiments with ReMCW show great savings in spectrum over the conventional FMCW radar.

This thesis analyzes and develops waveforms and signal processing techniques that are used to improve the performances of range, velocity, and direction-of-arrival (DOA) estimation for multiple-input-multiple-output (MIMO) radar systems with colocated transmit and receive antennas. The main contributions of this work consist of four parts, which are summarized as follows. The starting point of this work is MIMO radar waveform design. The freedom to transmit non-coherent waveforms, i.e., the waveform diversity, enables many new features for MIMO radar to improve target detection and parameter estimation. However, it also introduces new challenges for the waveform design, e.g., minimiz-ing the cross-ambiguity functions (CAF’s). To tackle this problem, we consider the extension of two frequency-hopping waveforms from single-input-single-output (SISO) radar to MIMO radar, the Costas array coded (CAC) waveforms and the quadratic congruence coded (QCC) waveforms. Exhaustive search is carried out for suboptimal solutions to .nding a set of codes that mutually exhibit least cross-ambiguity properties. The general problem of the code selection for global optimum is formulated as an open question. The suboptimal Costas and quadratic congru-ence codes are used throughout this thesis when other designs are considered. The second contribution of this thesis is on receiver instrumental variable .lter (IVF) design for joint range and Doppler sidelobe suppression. The commonly used matched .lter (MF) maximizes the signal-to-noise ratio (SNR) of its output. However, it is ine.cient in improving the signal-to-clutter ratio (SCR). Alterna-tively, an IVF enables a trade-o. between the SNR and SCR at the receiver. We .rst analyze the performances of existing range domain only IVF designs using integrated sidelobe level (ISL) constraint and zero sidelobe (ZS) constraint, respec-tively. The results indicate the possibility of using phased-array radar for improved performance. Then a rectangular area centered at the origin on the range-Doppler plane is considered for joint clutter sidelobe suppression, where both MIMO and phased-array radar are considered. Closed-form solutions and simulation results are provided. The conclusion is then drawn in a trade-o. manner. Compromis-ing the waveform diversity, the phased-array radar design turned out to be more e.cient in terms of sidelobe suppression, SNR loss, and computational complexity. Another advantage introduced by MIMO radar waveform diversity is the .exible design of transmit beampatterns, which is the topic of the third part of this thesis. Existing works have provided many solutions. However, little attention has been paid to several aspects of the performance such as the ripple within the energy focusing section, the sidelobe attenuation, and the transition bandwidth. Hence, we propose a feasibility problem (FP) formulation based on the nonlinear mapping from MIMO radar transmit beampattern design to multiple-input-single-output (MISO) .nite impulse response (FIR) .lter design. One of the advantages of the proposed method is that it takes quantitative controls of the above parameters in the design. Moreover, the minimum number of transmit antenna to achieve a given transmit beampattern is obtained. Via simulations, the transmit beampattern formula, which has a similar form as Kaiser’s formula, is obtained for antenna selection given a set of design speci.cations. In addition, a robust design method is proposed. The robust design establishes a trade-o. between the radio-frequency ampli.er (RFA) requirements and the number of transmit antennas. It also leads to signi.cant relaxation of waveform correlation requirements. As a result, the robust design uses a set of easily generated and wildly used linear frequency modulated (LFM) waveforms to achieve the transmit beampattern identical to that designed under ideal orthogonality assumption. The last contribution of this thesis is presenting a fairer comparison between MIMO and phased-array radar. Throughout this thesis, the performance of phased-array radar is considered in comparison with MIMO radar in various aspects. The most signi.cant di.erence between the two systems is that phased-array radar transmits coherent waveforms whereas MIMO radar transmits non-coherent wave-forms. Implicitly, it is the coherent gain versus the diversity gain. The two systems establish a trade-o. for researchers and engineers to choose under di.erent objec-tives, design environments, and given conditions. Via the comparisons on the basic system models, receiver identi.ability, receiver IVF design, and transmit beampat-tern design, we conclude that MIMO radar outperforms phased-array radar when multiple targets exist whereas the latter outperforms the former when one is dealing with only a single target. ELECTRICAL and ELECTRONIC ENGINEERING

This paper presents a technological demonstrator with traffic applications, which carries out three typical intelligent transportation system (ITS) tasks: traffic flow measurement, speed estimation, and vehicles classification. The proposed system is a frequency-modulated continuous wave radar working at 24 GHz, with side-looking installation. Two signal-processing modes, 1-D and 2-D, are introduced as detection scheme. Unlike other existing commercial systems, this demonstrator makes use of phase information from target echoes in order to perform clutter cancellation and target speed measurement. To this end, two different speed-estimating methods are proposed and compared by means of experimental results obtained from a complex scenario.

A fundamental drawback of the orthogonal frequency division multiplexing (OFDM), both in communication and radar, is its sensitivity to the Doppler effect. In this paper, we present a novel signal processing approach for OFDM radar and communication systems that overcomes the Doppler sensitivity of OFDM. We propose a scenario independent Doppler correction method that enables an intercarrier-interference free processing for OFDM. The Doppler robustness of the proposed approach opens new perspectives for system parameterization, enabling radar concepts not feasible before. We show in simulations that the proposed Doppler correction method is superior to the classical signal processing in many important aspects. Measurements with an OFDM-MIMO radar prototype are used to validate the proposed approach and to show its effectiveness in real-life applications.

This paper considers the problem of power minimization based robust orthogonal frequency division multiplexing (OFDM) radar waveform design, in which the radar coexists with a communication system in the same frequency band. Recognizing that the precise characteristics of target spectra are impossible to capture in practice, it is assumed that the target spectra lie in uncertainty sets bounded by known upper and lower bounds. Based on this uncertainty model, three different power minimization based robust radar waveform design criteria are proposed to minimize the worst-case radar transmitted power by optimizing the OFDM radar waveform, which are constrained by a specified mutual information (MI) requirement for target characterization and a minimum capacity threshold for communication system. These criteria differ in the way the communication signals scattered off the target are considered: (i) as useful energy, (ii) as interference or (iii) ignored altogether at the radar receiver. Numerical simulations demonstrate that the radar transmitted power can be efficiently reduced by exploiting the communication signals scattered off the target at the radar receiver. It is also shown that the robust waveforms bound the worst-case power-saving performance of radar system for any target spectra in the uncertainty sets.

The standard deviation in a frequency modulated continuous wave radar distance measurement using a charge pump phase-locked loop (PLL) is calculated analytically. The phase noise of the PLL is modeled as an Ornstein–Uhlenbeck process resulting in a Lorentzian spectrum. We calculate the distance error as a function of the receiver noise bandwidth and the target distance. Depending on the frequency estimation algorithm and the target distance, the rms distance error due to PLL phase noise increases by about 6–9 dB with doubling the target distance. By contrast, the white noise in the radar receiver raises the distance error by about 12 dB in the far field with distance doubling, making this error contribution dominant for large target distances. These findings are verified by measurements on a scalable 61/122-GHz radar sensor platform.

Coherent jamming technology is one of the most important development trends in the modern radar countermeasures. This study presents a method capable of generating a series of deceptive coherent false targets for countering linear frequency modulation (LFM) radar based on periodic 0-π phase modulation. Utilizing the structure of digital radio frequency memory (DRFM), we impose phase modulation onto the intercepted radar signal and retransmit it to the victim radar. The jamming signal model is developed and its characteristics are analyzed in detail. An investigation has been carried out to determine the matched filter properties of the jamming signal. The expressions of some main parameters are deduced step by step. Theoretical analysis and simulation results prove that by flexibly adjusting the phase modulation parameters, different deception jamming effects will be obtained. The proposed method provides an idea for the coherent jamming signal design.

[EN] Multiple-input multiple-output (MIMO) radars have been shown to improve target detection for surveillance applications thanks to their proven high-performance properties. In this paper, the design, implementation, and results of a complete 3-D imaging frequency-modulated continuous-wave MIMO radar demonstrator are presented. The radar sensor working frequency range spans between 16 and 17 GHz, and the proposed solution is based on a 24-transmitter and 24-receiver MIMO radar architecture, implemented by timedivision multiplexing of the transmit signals. A modular approach based on conventional low-cost printed circuit boards is used for the transmit and receive systems. Using digital beamforming algorithms and radar processing techniques on the received signals, a high-resolution 3-D sensing of the range, azimuth, and elevation can be calculated. With the current antenna configuration, an angular resolution of 2.9° can be reached. Furthermore, by taking advantage of the 1-GHz bandwidth of the system, a range resolution of 0.5 m is achieved. The radio-frequency front-end, digital system and radar signal processing units are here presented. The medium-range surveillance potential and the high-resolution capabilities of the MIMO radar are proved with results in the form of radar images captured from the field measurements.

The target detection problem in multi-static passive radar systems (MS-PRS) is investigated, where multiple transmitters operate at a single frequency and a single multi-antenna radar receiver processes the received signals. In contrast to multi-frequency MS-PRS, the detector design is challenging due to the fact that the detector sees a mixture of transmitted signals which may not be separately treated. We propose the design of generalized likelihood ratio test (GLRT) receivers to optimize the detection performance. The beamformers at the radar receiver are optimized so that the received signals can be seen as statistically independent signals from multiple reference channels and a surveillance channel. The detector optimization problem is accurately approximated with a convex optimization algorithm. It is analytically shown that the performance of the proposed GLRT receiver approaches that of the active radar. Computer simulations verify the analytical results.

A multiple-input multiple-output (MIMO) method that shares the same frequency band can efficiently increase radar performance. An essential element of a MIMO radar is the orthogonality of the waveform. Typically, orthogonality is obtained by spreading different signals into divided domains such as in time-domain multiplexing, frequency-domain multiplexing, and code domain multiplexing. This paper proposes a method of spreading the interference signals outside the range bins of interest for pulse doppler radars. This is achieved by changing the pulse repetition frequency under certain constraints, and an additional gain can be obtained by doppler processing. This method is very effective for improving the angular accuracy of the MIMO radar for a small number of air targets, although it may have limitations in use for many targets or in high clutter environments.

Distance measurement tasks in micromachine tools need to be performed with micrometer accuracy. For such tasks, frequency-modulated continuous-wave (FMCW) radars with a combination of frequency and phase evaluations are a good choice. However, the accuracy cannot be indefinitely increased as there are constraints on the target size and placement imposed by the limited space inside micromachines. This paper investigates the influence of target geometry and position on the accuracy of its range estimation using a W-band FMCW radar with a bandwidth of 25 GHz. A relation between target geometry and accuracy is established through the Cramér-Rao lower bound (CRLB). Based on the measurements of different targets, an optimal shape and size is proposed, which provides an average accuracy in the single digit micrometer range. Furthermore, the influence of different bandwidths on the accuracy is investigated. It is also demonstrated how the CRLB can be used to optimize the size of a target, when a certain accuracy is needed. In addition, antenna field regions are analyzed for suitable target placements. Finally, the radar system is implemented in a machine tool and measurements with accuracies in the micrometer range are carried out.

Although radar and communication systems so far have been considered separately, recent advances in passive radar systems have motivated us to propose a unified system, capable of fulfilling the requirements of both radar and communications. In this paper, we provide performance tradeoff analysis for a system consisting of a transmitter, a passive radar receiver, and a communication receiver (CR). The total power is allocated for transmitting the radar waveforms and information signals in such a way that the probability of detection (PD) is maximized, while satisfying the information rate requirement of the CR. An exact closed-form expression for the probability of false alarm (PFA) is derived, whereas PD is approximated by assuming that the signal-to-noise ratio corresponding to the reference channel is often much larger than that corresponding to the surveillance channel. The performance tradeoff between the radar and communication subsystems is then characterized by the boundaries of the PFA-rate and PD-rate regions.

In this article, an analytical method for radar electromagnetic compatibility (EMC) in complex environment is proposed to deal with the radar system-level EMC problem. The complete procedure of thi...

To deal with the problems of range cell migration (RCM) and spectrum spread during the integration time induced by the motion of a target, this paper proposes a new coherent integration method based on Radon nonuniform fractional Fourier transform (NUFrFT) for random pulse repetition interval radar. In this method, RCM is eliminated via searching in the motion parameter space and the spectrum spread is resolved by NUFrFT along the searching trajectory. Simulation results demonstrate the effectiveness of the proposed algorithm.

A stepped-frequency radar that allows for adaptability in the radiated spectrum while maintaining high-resolution radar imagery has been developed. The spectrally agile frequency-incrementing reconfigurable (SAFIRE) radar system is a vehicle-mounted, ground-penetrating radar that is capable of producing high-resolution radar imagery for the detection of obscured targets (either buried or concealed surface targets). It can be easily transitioned between forward- and side-looking orientations. The SAFIRE system is capable of precisely excising subbands within its operating bandwidth, thus making the system “spectrally agile.” It is also highly reconfigurable thereby allowing for on-the-fly adjustment of many of the system parameters. The spectrally agile and reconfigurable aspects of the SAFIRE radar together with its enhanced IF processing scheme represent a novel contribution to the state of the art. This paper discusses the system design, implementation, and performance characteristics, and also presents preliminary high-resolution imagery.

Frequency-modulated continuous wave radar systems suffer from permanent leakage of the transmit signal into the receive path. Besides leakage within the radar device itself, an unwanted object placed in front of the antennas causes so-called short-range (SR) leakage. In an automotive application, for instance, it originates from signal reflections of the car’s own bumper. Particularly the residual phase noise of the downconverted SR leakage signal causes a severe degradation of the achievable sensitivity. In an earlier work, we proposed an SR leakage cancellation concept that is feasible for integration in a monolithic microwave integrated circuit. In this brief, we present a hardware prototype that holistically proves our concept with discrete components. The fundamental theory and properties of the concept are proven with measurements. Further, we propose a digital design for real-time operation of the cancellation algorithm on a field programmable gate array. Ultimately, by employing measurements with a bumper mounted in front of the antennas, we show that the leakage canceller significantly improves the sensitivity of the radar.

A new radio frequency interference (RFI) filter algorithm for weather radars is proposed in the two-dimensional (2D) range-time/sample-time domain. Its operation in 2D space allows RFI detection at lower interference-to-noise or interference-to-signal ratios compared to filters working only in the sample-time domain while maintaining very low false alarm rates. Simulations and real weather radar data with RFI are used to perform algorithm comparisons. Results are consistent with theoretical considerations and show the 2D RFI filter to be a promising addition to the signal processing arsenal against interference with weather radars. Increased computational burden is the only drawback relative to filters currently used by operational systems.

Passive radar (PR) systems must be able to detect the presence of a target signal many orders of magnitude weaker than the direct signal interference (DSI). Due to the continuous nature of most PR signals, this interference, rather than thermal noise, determines the sensitivity of the system. Suppression of DSI and clutter prior to range-Doppler processing is crucial for maximizing the effective dynamic range, to increase detection range and improve overall system performance. A number of time-domain adaptive filtering techniques have been proposed to mitigate the effects of DSI, with varying levels of success. As such, an investigation of the primary factors affecting suppression performance is presented, using Advanced Television Systems Committee digital television (DTV) waveforms as an example, through simulation and extensive experimental trials. A number of spectral and spatially diverse DTV signals are considered to analyze suppression performance under a wide range of realistic scenarios. In particular, the fast block least mean squares filter is shown to provide good suppression performance with low computational requirements. Results of this analysis can be used to predict PR performance and stability. Practical metrics, such as suppression runtime and ease of implementation, also serve to counsel selection of DSI mitigation algorithms for experimental systems.

The instantaneous vital sign rates, which are related to physiological dynamics, are important indicators of human health condition. This paper presents a noncontact way to measure the human instantaneous vital signs using digital-intermediate frequency (IF) Doppler radar. The synchrosqueezing transform-based algorithm has been proposed to get a concentrated time-frequency (TF) distribution, so that the high-resolution instantaneous heartbeat and respiratory rates and the time-domain signals can be acquired. Moreover, the developed radar with customized radio frequency module employs the direct IF sampling technique to achieve high sensitivity to capture the tiny vital sign variations. Experiments with different human subjects and physiological conditions have been carried out. Compared with the landmark-based method and traditional TF algorithms, the results show that instantaneous vital signs can be acquired more accurately within 3 m at a −13 dBm transmit power by the proposed method. Therefore, the radar can be used for evaluating the physiological dynamics and assessing health condition.

the well-known range-Doppler coupling property of the LFM (Linear Frequency Modulation) pulse compression radar makes it more vulnerable to repeater jammer that shifts radar signal in the frequency domain before retransmitting it back to the radar. The repeater jammer, in this case, benefits from the pulse compression processing gain of the radar receiver, and generates many false targets that appear before and after the true target. Therefore, the radar cannot distinguish between the true target and the false ones. In this paper, we present a new technique to counter frequency shifting repeater jammers. The proposed technique is based on introducing a small change in the sweep bandwidth of LFM waveform. The effectiveness of the proposed technique is justified by mathematical analysis and demonstrated by simulation.

We consider a new hybrid radar paradigm consisting of an active array and a passive array. In this hybrid system, the radar transmits a probing signal from its active array and receives two types of echoes: One is the return from the cooperative active transmission and the other is the target return due to transmission from noncooperative illuminators of opportunity. The motivation for this approach is to exploit not only the active signal but also any passive signals that are present in the surveillance area, thereby maximizing the signal-to-interference-plus-noise ratio (SINR). Numerical results demonstrate that the proposed concept can achieve a significant improvement of the output SINR, compared with conventional methods for active-only or passive-only radar systems.

With more weather radars relying on low-power solid-state transmitters, pulse compression has become a necessary tool for achieving the sensitivity and range resolution that are typically required for weather observations. While pulse compression is well understood in the context of point-target radar applications, the design of pulse compression waveforms for weather radars is challenging because requirements for these types of systems traditionally assume the use of high-power transmitters and short conventional pulses. In this work, Weather Surveillance Radar-1988 Doppler (WSR-88D) antenna pattern requirements are used to illustrate how suitable requirements can be formulated for the radar range weighting function (RWF), which is determined by the transmitted waveform and any range-time signal processing. These new requirements set bounds on the RWF range sidelobes, which are unavoidable with pulse compression waveforms. Whereas nonlinear frequency modulation schemes are effective at reducing RWF sidelobes, they usually require a larger transmission bandwidth, which is a precious commodity. An optimization framework is proposed to obtain minimum-bandwidth pulse compression waveforms that meet the new RWF requirements while taking into account the effects of any range-time signal processing. Whereas pulse compression is used to meet sensitivity and range-resolution requirements, range-time signal processing may be needed to meet data-quality and/or update-time requirements. The optimization framework is tailored for three processing scenarios and corresponding pulse compression waveforms are produced for each. Simulations of weather data are used to illustrate the performance of these waveforms.

Developments in microwave and millimeter-wave systems have enabled remote sensing techniques traditionally used in long-range applications to be employed in the relatively closer range applications of detection and classification of human presence and measurement of human properties. This paper reviews the techniques used in microwave remote sensing of humans and discusses prominent examples of experimental systems from the literature. Radar techniques have been developed for measuring the time-varying scattering returns from the various parts of the human body during motion, which are used for human presence detection and the classification of human activities. The effects of breathing and heartbeat are also detectable using Doppler radar techniques, which is applicable to medical applications as well as search-and-rescue and security. Recent developments in distributed radars have enabled the direct measurement of the angular velocity of moving people, and passive systems have also been developed which provide a complementary detection mode that can aid in detection and classification of humans.

A 94-GHz phased-array transceiver IC for frequency modulated continuous wave (FMCW) radar with four transmitters, four receivers, and integrated LO generation has been designed and fabricated in a 130-nm SiGe BiCMOS technology, and integrated into an antenna-in-package module. The transceiver, targeting gesture recognition applications for mobile devices, has been designed using phased-array techniques to reduce the total DC power while still maintaining the required link budget for FMCW operation. The complete array achieves state-of-the-art for W-band per-element power consumption of 106 mW per TX element and 91 mW per RX element, and measurements indicate a per-element output power of 6.4 dBm and single-sideband noise figure of 12.5 dB at 94 GHz. The array is able to achieve a beam steering range of ±20° while maintaining at least 3 dB main lobe to side lobe levels. The complete chip-antenna module has been tested to characterize basic FMCW radar functionality. Initial radar experiments suggest a sub-5-cm range resolution is possible with 3.68 GHz RF sweep bandwidth, which is in line with theoretical predictions.

The dynamic range of frequency modulated continuous wave (FMCW) radar sensors is often limited by the phase noise of the ramp signal. Especially at millimeter wave (mm-wave) frequencies, a low phase noise signal is very difficult to obtain. In this paper, a new system architecture, which is implemented in a low-cost, ultracompact FMCW radar monolithic microwave integrated circuit (MMIC) at 160 GHz, is proposed to address this topic. The approach is based on a frequency offset synthesizer, whose upconverting mixer is driven by a stabilized low phase noise local oscillator (LO) signal. This LO is generated by a fixed-frequency phase locked loop with a $2^{N}$ divider. The upconversion of the ramp signal with the stabilized LO signal leads to an excellent mm-wave phase noise of −89 dBc/Hz at a frequency offset of 1 MHz. By integrating the antennas on the MMIC, interconnects at mm-wave frequencies to package or printed circuit board are avoided and a simple assembly and interconnection technology is feasible. The ultracompact MMIC is realized on an area of only 2 mm2, including the integrated antennas. A precision below 5 $\mu \text{m}$ for range measurements is demonstrated with the radar sensor. Additionally, the radar performance is evaluated with two different voltage-controlled oscillators for the generation of the ramp signal.

A highly miniaturized and commercially available millimeter wave (mmw) radar sensor working in the frequency range between 121 and 127 GHz is presented in this paper. It can be used for distance measurements with an accuracy in the single-digit micrometer range. The sensor is based on the frequency modulated continuous wave (CW) radar principle; however, CW measurements are also possible due to its versatile design. An overview of the existing mmw radar sensors is given and the integrated radar sensor is shown in detail. The radio frequency part of the radar, which is implemented in SiGe technology, is described followed by the packaging concept. The radar circuitry on chip as well as the external antennas is completely integrated into an 8 mm $\times \,\, 8$ mm quad flat no leads package that is mounted on a low-cost baseband board. The packaging concept and the complete baseband hardware are explained in detail. A two-step approach is used for the radar signal evaluation: a coarse determination of the target position by the evaluation of the beat frequency combined with an additional determination of the phase of the signal. This leads to an accuracy within a single-digit micrometer range. The measurement results prove that an accuracy of better than $\pm 6~\mu \text{m}$ can be achieved with the sensor over a measurement distance of 35 mm.

Noise radars possess several advantageous properties, including low probability of detection and identification, especially when working in continuous-wave mode. One of the main drawbacks of such radars is the occurrence of the masking effect, when a weak target echo is masked by the sidelobes of a strong target echo. The sidelobes of the ambiguity function emerge on the level of the time–bandwidth product below the main peak and are spread in the entire range–Doppler plane. While most approaches to mitigate the masking effect focus on the processing of the received signal, it is possible to move the computation burden to the waveform design phase. This paper describes a filter-based method of creating noise-like waveforms that have very low sidelobes in the area of certain range and Doppler shifts. Both theoretical analysis and measurement results are presented and compared with the lattice filter method of masking effect cancellation.

The design and test of a radio detection and ranging (Radar) sensor signal acquisition and processing platform is presented in this paper. The Radar sensor operates in real time and is suited for surveillance applications in transport systems. It includes a front-end with a continuous-wave frequency-modulated transceiver operating in X-band, with a single transmitter and multiple receivers, and a multichannel high-speed A/D converter. Sensor signal processing and data communication tasks with external hosts are managed by a field-programmable gate array. The signal processing chain includes region of interest selection, multidimensional fast Fourier transform, peak detection, alarm decision logic, data calibration, and diagnostic. By configuring the Radar sensing platform in low-power mode (7-dBm transmitted power), it is possible to detect still and moving targets with a covered range up to 300-m and 30-cm resolution. The measuring range can be increased up to 2 km by adding an extra 34.5-dBm power amplifier. The Radar sensing platform can be configured for a maximum detected speed of 200 km/h, with a resolution of 1.56 km/h, or a speed up to 50 km/h with a resolution of 0.4 km/h. The cross-range resolution depends on the number of receiving channels; a tradeoff can be found between cross-range resolution of the Radar sensor and its complexity and power consumption. With respect to the state of the art of surveillance Radar sensors and light detection and ranging, the proposed solution stands for its high configurability and for the better tradeoff that can be found in terms of covered distance and power consumption.

In this paper, improved signal processing techniques are developed for the analysis and classification of low probability of intercept (LPI) radar waveforms. The intercepted LPI radar signals are classified based on the type of pulse compression waveform. They are classified as linear frequency modulation, nonlinear linear frequency modulation, binary frequency shift keying, polyphase Barker, polyphase P1, P2, P3, P4, and Frank codes. The classification approach is based on the parameters measured from the preprocessed radar signal intercepted by electronic support (ES) or electronic intelligence (ELINT) system. First, signal embedded within the noise is estimated using Wigner Ville distribution to improve the signal-to-noise ratio (SNR). Next, features are extracted using the time-domain and frequency-domain techniques. Furthermore, parameters measured from the fractional Fourier transform are used for the classification. This type of techniques are required in various systems such as ES, electronic attack, radar emitter identification and multi input multi output (MIMO) radar applications. Extensive simulations are carried out with different LPI radar-modulated waveforms corrupted with additive white Gaussian noise of SNR up to –15 dB and impulse noise with 90% of noise density. The proposed algorithm outperforms the existing techniques of classification and can be used under strategic environment.

Radar technology is used for many applications of advanced driver assistance systems (ADASs) and is considered as one of the key technologies for highly automated driving (HAD). An overview of conventional automotive radar processing is presented and critical use cases are pointed out in which conventional processing is bound to fail due to limited frequency resolution. Consequently, a flexible framework for computationally efficient high-resolution frequency estimation is presented. This framework is based on decoupled frequency estimation in the Fourier domain, where high-resolution processing can be applied to either the range, relative velocity, or angular dimension. Real data obtained from series-production automotive radar sensor are presented to show the effectiveness of the presented approach.

This paper presents a CMOS transceiver IC for a single-antenna frequency-modulated continuous wave (FMCW) radar. Since transmitter (Tx) leakage is critical in a single antenna radar with CMOS technology, a comprehensive leakage canceling technique is proposed. It is able to cancel all the leakages caused by antenna reflection, asymmetry of a balanced structure, and lossy substrate without additional power or area. Even-order harmonic leakages from the power amplifier (PA) are also reduced by an even-harmonic filter, which is implemented simply by removing the real ground from the symmetrical point of the PA output transformer. Matching networks are simplified by using a modified coupler structure. A low-noise combining amplifier is used to make the combining circuit compact. As a result, the transceiver achieves the output power of −1.6 dBm, the phase noise of −105.44 dBc/Hz at 1MHz offset, the receiver (Rx) gain of 15.3 dB, and the noise figure of 11.6 dB. Tx leakages are canceled so that the isolation between Tx and Rx is 47.3 dB. The chip consumes 74.1 mA from a 1.5-V power supply. Despite the high integration level, the chip area including pads is 1.7 mm $\times $ 0.9 mm. A $ {K}$ -band FMCW radar module with a single antenna is implemented with this chip.

This paper discusses a distributed frequency modulation continuous wave radar system. This K-band radar system has high sensitivity, linearity, and flatness to detect low-radar cross section targets and measure their range and velocity. To reduce the leakage between a transmitter and a receiver, the system uses not RF cables but fiber-optic links that have low distortion characteristics and low propagation loss. The transmitter and the receiver are each mounted on a designed fixture to reduce the ground reflections. In addition, they are located on different platforms to reduce the leakage signal flowing directly from the transmitter to the receiver. Measurements in terms of the range and the velocity of a small drone have been carried out to evaluate the proposed distributed radar system. The results show that we can clearly detect the small drone within a 500 m range, which demonstrates the high sensitivity of the system and high isolation between the transmitter and the receiver.

The conventional phased array cannot effectively suppress the interferences that have the same direction angle but different ranges of the targets. To overcome this disadvantage, frequency diverse array (FDA) is proposed in recent years. However, FDA beampattern is time-variant, which makes targets illuminated only in a very short duration and causes poor detectability of targets. This letter presents a novel signal diverse array (SDA) radar, which provides greater degrees of freedom for space-time-frequency-phase control, permitting novel beampattern for special applications, through controlling more aspects of the transmit signals of each antenna element, including amplitude, frequency, and initial phase. Simulation results show the effectiveness and outperformance of the proposed SDA radar.

A novel application of time-modulated arrays to multiple-input-multiple-output (MIMO) radar is presented and studied. The proposed scheme is to partition the transmit antenna of MIMO radar to a number of time-modulated subarrays that are overlapped. A series of orthogonal waveforms are emitted by these time-modulated subarrays with the unidirectional phase center motion time scheme. The resulting system can be referred to as subarrayed time-modulated MIMO (STM-MIMO) radar. As the tradeoff of conventional phased-array and MIMO radars, the STM-MIMO radar can obtain the coherent processing gain and waveform diversity gain simultaneously. The performance in terms of output signal-to-interference-plus-noise ratio and transmit/receive beampattern for the STM-MIMO radar is highlighted and compared to that of phased-array and MIMO radars. Simulation results validate the effectiveness of the proposed STM-MIMO radar technique.

The frequency diverse array (FDA) has a range-angle-dependent transmit beampattern, which can provide the potential capability for novel radar application. However, the basic FDA's beampattern is periodic in range and coupled in range and angle dimensions, which limits the application of FDA in radar field. In this letter, we propose a novel FDA model with nonmonotone increasing frequency offset to form a narrow pencil beam, which eliminates the range periodicity and coupling of range and angle domains. Combining this new FDA with multiple-input–multiple-output radar, not only can multiple narrow pencil beams be formed to track multiple targets simultaneously, but also a flat-top transmit beampattern for targets searching can be synthesized. Simulation results show the effectiveness and outperformance of the proposed scheme compared to the existing Log-FDA, which uses the logarithmically increasing frequency offset.

This paper presents an innovative radar architecture to improve the isolation of the harmonic radar between the transmitter and the receiver. The proposed radar transmits two closely located frequencies to the transponder, and the transponder transmits a response signal at a mixed frequency. Because the frequency of the response signal is different from those of the clutter and leakage signals, the isolation is significantly improved. For a traditional harmonic radar, the leakage signals should be suppressed to a sensitivity lower than −106 dBm to avoid interference. The proposed radar requires only attenuation of leakage signals to a level lower than −8 dBm to avoid low-noise amplifier saturation. Harmonic radar transponders are compatible with the proposed radar system without additional design. This paper also proposes a new method for maintaining the correlation of transmitter and receiver phase noise. Field test results demonstrate that leakage signal interference in the proposed radar is far lower than that in the harmonic radar. The significant improvement in isolation reveals the advantages of applying the frequency mixing concept in the proposed radar.

This paper presents the design of a compact Radar for real-time detection of targets in smart mobility applications. The Radar integrates Fabry-Perot resonating antennas, X-band and configurable continuous wave transceiver, high-speed analog-digital-converter and low-power/low-cost FPGA for the baseband signal processing. The latter includes region-of-interest selection, 2D Fast Fourier Transform for range-Doppler map extraction, peak detection and alarm decision logic. The transmitted power can be configured from few mW to 1.8W. This allows for a trade-off between the maximum detection range, from few hundreds of meters up to 1.54km, and the Radar power consumption, from 2.56W to 11.66W. The measured speed is up to 40m/s. The speed and distance resolutions are 0.3m/s and 37.5cm, respectively. The configurable Radar features increased robustness vs. laser-scanners, video cameras, or induction loops detection techniques, and stands for its better trade-off in terms of covered range, size, and low-power consumption vs. state-of-the-art surveillance Radars. Design of a compact Radar module for real-time detection of targets in smart mobility applications.Real-time implementation of Radar signal processing tasks on low-cost and low-power FPGA, reducing power dissipation vs. state-of-the-art designs using GPU (Graphical Processing Units) and GPP (General Purpose Processors).Radar parametric analysis highlighting the inter-dependencies existing among Radar performance and analog and digital circuit parameters. This allows a co-design of the mixed-signal Radar transceiver with the FPGA-based digital signal processing, and a trade-off between the Radar performance and its implementation complexity.Coarse-grained and a fine-grained configurability of the Radar transmitted power, which allows for different trade-offs between the system power consumption and the maximum covered range.

A survey of radar systems used in the medical field is presented. First, medical applications of radars are described, and some emerging research fields are highlighted. Then, medical radars are analyzed in terms of block diagrams and behavioral equations and some implementations are shown as examples. A section is dedicated to the radiating structures used in these radars. Finally, human safety and environmental impact issues are addressed. The most investigated medical applications of radars are breast tumor diagnostics and remote monitoring of cardiorespiratory activity. New fields of interest are physiological liquid detection, and the monitoring of artery walls and vocal cord movements. Among the various topologies, continuous wave (CW) radars have been proven to yield the highest range resolution that is limited only by the system noise while the resolution of ultra wideband (UWB) and frequency modulated continuous wave (FMCW) radars is also related to the used frequency bandwidth. Concerning the maximum range, UWB radars have the best performance due to their ability to operate in the presence of environmental clutter. As for the radiating structures, planar antennas are preferred for diagnostic applications, due to their small dimensions and good matching when placed in contact with the human body. Radar systems for remote monitoring, instead, are designed by using high gain antennas and taking into account the complex radar cross section (RCS) of the body.

The incorporation of gallium nitride (GaN) power amplifiers (PAs) into future high-power aperture radar systems is certain; however, the introduction of this technology into multifunction radar systems will present new challenges to radar engineers. This paper describes a broad investigation into amplitude and phase transients produced by GaN PAs when they are excited with multifunction radar waveforms. These transients are the result of self-heating electrothermal memory effects and are manifested as interpulse instabilities that can negatively impact the coherent processing of multiple pulses. A behavioral model based on a Foster network topology has been developed to replicate the measured amplitude and phase transients accurately. This model has been used to develop a digital predistortion technique that successfully mitigates the impact of the transients. The moving target indicator improvement factor and the root mean square pulse-to-pulse stability are used as a metric to assess the impact of transients on radar system performance and to test the effectiveness of a novel digital predistortion concept.

Quadrature Compressive Sampling radar is a newly introduced radar for pulse Doppler processing with sub-Nyquist samples. This paper considers diverse transmitting pulses and proposes a scheme to perform the estimation of targets in the presence of a repeat jammer. The scheme first performs whitening processing on sub-Nyquist samples to suppress repeat jammers, and then with the principle of orthogonal matching pursuit, it estimates the targets by iteratively performing matched filter and discrete Fourier transform on sub-Nyquist samples in a coherent processing interval. The theoretical analyses conducted on the capability of rejecting the repeat jammers, reveal that the signal to interference plus noise ratio, after whitening processing, almost approaches to the input signal to noise ratio and is not affected by the strength of the repeat jammers. The simulation results further validate the effectiveness of the proposed scheme.

Foreign object debris (FOD) on airport runways must be removed immediately. To detect small debris, we proposed and developed an optically-connected distributed-type 96 GHz millimeter-wave radar system based on radio-over-fiber (RoF) technology and an optical fiber network. The proposed distributed-type radar system offers both improved FOD detection characteristics and cost performance. This paper details the design and field feasibility evaluation of the 96 GHz frequency-modulated continuous wave radar system that uses RoF and an optical frequency multiplier. Firstly, the problem of long distance RoF transmission, which limits the practical use of the RoF networked radar system in the airport environment, is discussed. Secondly, the concept and architecture of the millimeter-wave radar system are discussed and demonstrated focusing on its use in actual airports. Then, the results of a field experiment are shown to confirm the feasibility of the radar system. Finally, the effectiveness of the high-speed signal processing and generation circuits inside the central unit is evaluated at an actual airport based on the results of non-coherent and coherent signal integration.

In this paper, we introduce a novel concept for frequency-modulated continuous-wave radar. The approach is based on an interlaced chirp sequence waveform, which is controlled by phase-locked loops (PLLs). The use of PLLs improves frequency chirp linearity and reduces phase noise compared with open-loop voltage-controlled oscillators commonly used to generate the fast chirps. In contrast to basic range–Doppler processing, it enables higher target velocities to be detected unambiguously at the same resolution, which makes it suitable for automotive applications. Separate frequency synthesizers generate the interlaced ramps in the system. An RF switch combines these two signals to suppress transients caused by oscillator overshoot and to avoid incoherencies due to programming times of the PLL ICs. We built a prototype radar system in K-band. The test results are promising and bode well for other applications.

To fully appreciate the benefits of arbitrary waveform design capability for transmit adaptive systems, the trade space between constraints (employed to increase the measure of practicality for radar) and the usual performance driver (signal-to-interference-plus-noise ratio) needs to be better defined and understood.We address this issue by developing performance models for radar waveforms with cumulative-modulus and energy constraints. Radar waveforms typically require a constant-modulus (constant-amplitude) transmit signal to efficiently exploit the available transmit power. However, recent hardware advances and the capability for arbitrary (phase and amplitude) designed waveforms have forced a reexamination of this assumption in order to quantify the impact of the nonconstant modulus property.We develop performance models for the signal-to-interference-plus-noise ratio as a function of the cumulative modulus for a random colored interference environment and validate the models against measured data.

In this paper, a CMOS multichannel transceiver (TRX) is proposed for angular identification in automotive car radar applications. Two transmitters (TXs) and six receivers (RXs) are placed on the same die using 65-nm CMOS technology with chip size $3.5 \times 3$ mm2. To generate a millimeter-wave (MMW) frequency-modulated continuous-wave signal, an injection-lock frequency sextupler cascaded a 1-to-8 Wilkinson power dividing network with wideband isolation is designed as the LO-chain to convert external source from 12.5–13.7 to 75–82.2 GHz for both the TXs and RXs. Each TX achieves above 11-dBm output power and the RXs achieve 30-dB conversion gain from 75 to 82 GHz, and the total power dissipation of whole chip is 1.43 W. Compared with other published multichannel TRXs in silicon germanium (SiGe) process, this paper demonstrates compatible performances and the potential of multichannel TRX using CMOS for MMW automotive car radar application.

In this paper, we study spectral coexistence between rotating radar and power-controlled cellular networks in radar bands. For two systems to spectrally coexist, they must be able to operate effectively without causing harmful electromagnetic interference to each other. Very short radar-cellular system separation distances are required during 83.3% of time due to the narrow main beam width of the rotational radar antenna. We propose a spatio-temporal analytical approach with adaptive base station (BS) power control for adjacent spectrum sharing between the two systems. We develop a new model for the aggregate interference from power-controlled cellular BSs using log-normal approximation. The cellular system is allowed to transmit at high power when the radar antenna’s main beam is pointing elsewhere from it. On the other hand, the cellular system reduces its transmit power only for a short period when the radar directional antenna main beam is pointing toward it. We use the degradation of the radar signal-to-interference plus noise ratio and cellular outage probability as our performance metrics. Numerical results show that power control of cellular BS highly reduces separation distance between the BS and radar, while yielding marginal degradation of outage performance. In addition, the mathematical results given by the log-normal approximation closely follow our simulated results. Detail system level assessments and investigations are presented to comprehensively understand secondary access to this band opportunistically.

In the recent years, short-range radar such as automotive radar has been attracting attention. In the radar, transmission method and signal processing achieve a high range resolution, and long range detection performance is required. In this paper, we propose the stepped multiple-frequency CPC radar that is expected to achieve a high range resolution and long range detection performance. In the proposed method, the transmission sequence and the phase correction process are expected to suppress the intersymbol interference and reduce the effects of Doppler frequency. A simulation result on the side-lobe level of CPC pulse compression is shown to verify the effectiveness of the method on the effect of Doppler shift. The other simulation result is shown to verify the improvement of S/N ratio by the signal processing. The results of the experiments also indicated that the radar could achieve high range resolution with narrowband receiver.

The authors propose a two-stage approach to design radar dynamic environmental knowledge base (DEKB), which provides a priori information for knowledge-based (KB) signal processing and radar system design. Specifically, the first stage is to use historical knowledge such as maps to establish the static environmental knowledge base (SEKB), which is the initial state of the DEKB. The second stage is to employ radar returns and other sensors information to update the knowledge base dynamically. Moreover, an exemplar establishment of the SEKB based on real scene and a specific update method based on two Anderson–Darling tests are introduced. Finally, as an application of the DEKB, the authors present a new KB constant false alarm rate (CFAR) detector utilising multidimensional knowledge from the DEKB. The performance of the new detector is analysed by real radar data, collected by a linear frequency-modulated continues wave radar, and compared with the classical cell averaging CFAR detector and the KB CFAR detector which uses only one kind of knowledge.