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Based on the long-known and well-described radar design techniques, this paper introduces a four-channel FMCW (Frequency Modulated Continuous Wave) radar system built from COTS (Commercial-Off-The-Shelf) elements for imaging purposes. Starting with a short historical view of the matter in question, general advantages, and motivations for the developed solution, the article presents the theory of operation of FMCW radar, as well as the construction of the analog part, the digital part, and the developed software. The most fundamental signal processing algorithms are also covered as a starting point for more advanced techniques, which may be further implemented. The developed radar system allows for the use of wide bandwidth - up to 1 GHz - which gives resolutions up to tenths of centimeters, and a high rate of pulse repetition frequency (8 kHz), which gives the opportunity to detect high-speed objects. The paper does not aim to provide any scientific novelties but rather to present the possibility of creating a simple and effective solution.

In this paper, we propose a deep learning-based indoor two-dimensional (2D) localization scheme using a 24 GHz frequency-modulated continuous wave (FMCW) radar. In the proposed scheme, deep neural network and convolutional neural network (CNN) models that use different numbers of FMCW radars were employed to overcome the limitations of the conventional 2D localization scheme that is based on multilateration methods. The performance of the proposed scheme was evaluated experimentally and compared with the conventional scheme under the same conditions. According to the results, the 2D location of the target could be estimated with a proposed single radar scheme, whereas two FMCW radars were required by the conventional scheme. Furthermore, the proposed CNN scheme with two FMCW radars produced an average localization error of 0.23 m, while the error of the conventional scheme with two FMCW radars was 0.53 m.

In this work, the modeling and realization of a 24-GHz Radar based on the BGT24MTR11 chipset is presented. The model has been implemented with the Visual System Simulator (VSS) tool available inside the AWR software. Two modular implementations of the designed Radar have been proposed. One in which the Radar is driven by a DAQ card from National Instruments and one in which the Radar is controlled by a PLL circuit. The circuit model has been validated through a comparison with analytical and experimental measurements considering as target a metallic sphere. The better performance of the architecture with the PLL has been also evidenced by considering a scenario with a panel target.

We study medium access in FMCW radar networks. In particular, we propose a slotted ALOHA protocol and analyze probability of interference between radars as a function of system parameters such as total number of radars, chirp duration, number of chirps in a repetition interval, as well as medium access probability. We see that the characteristics of interference probability in FMCW radar networks are very different from those in wireless communication networks. We observe that interference probability also depends on the number of chirps in a radar packet. We further propose a notion of throughput and study its variation with various parameters. We perform extensive simulations to verify our analytical results.

In this paper, we derive intermediate frequency (IF) level analytical formulation of radio frequency (RF) group delay for automotive frequency-modulated continuous-wave (FMCW) radar waveform under quasi-static approximation. To the best of our knowledge, this paper is the first to develop and simulate an IF-level analytical formulation of RF group delay, including random and deterministic variation for the FMCW radar waveform. Theoretical limitation for the tolerable RF group delay can be derived based on the proposed model. We demonstrated the impact of RF group delay on the FMCW radar sensor’s range spectrum in dynamic virtual traffic scenarios. The proposed model is integrated into a virtual FMCW radar sensor model implemented as a functional mock-up unit (FMU) using the standardized interfaces functional mock-up interface (FMI) 2.0 and the open simulation interface (OSI) 3.0.0. A virtual test scenario is implemented in an industry-standard simulation tool, CarMaker, to demonstrate the effect.

Due to an increasing demand in channel capacity and bandwidth, there has been a growing interest in the millimeter wave (mmWave) spectrum [1]-[3]. Many researchers overcame the challenges of implementing extremely high frequency systems and secured large bandwidths comparable to that of fiber optics [4]. The mmWave spectrum offers numerous advantages not only in the wireless communication field but also in the field of sensors and radar technology [5]. Indeed, transmitting shorter wavelengths helps radars achieve higher range accuracy with smaller antenna footprints.

The session is focused on key advances in mm-wave wireless communication and radar systems. It features papers describing a state-of-theart multi-user beamforming receiver, an early fusion radar-LiDAR system, self-interference cancellation techniques, FMCW radar MIMO transceivers, along with temperature-healing techniques and crystal-less transceivers.

Wireless sensing based on radar devices is used today in various environments to ensure sustainability and protection of natural resources, to save time and energy in industry and agriculture, and in many other applications. Development of radar technology, in particular in millimeter-wave frequency bands, has opened many new applications which are being currently developed. Important aspect of these systems is increased level of system autonomy based on the principles of machine learning or artificial intelligence. In order to exploit these advantages, we need to acquire as much as possible measured information which can be used later in various detection scenarios. Our aim is to perform a polarization sensitivity analysis for a simple S-band FMCW radar system. The acquired measured results demonstrate the differences when scanning the polarization and give us a indication on how this can be exploited in future systems with polarization diversity.

En las últimas décadas los sistemas avanzados de asistencia al conductor (ADAS) han evolucionado hasta estar disponibles en gran parte de los vehículos fabricados hoy en día; mantener actualizada la enseñanza en esta área es de vital importancia. Este artículo presenta un radar de onda continua modulado en frecuencia que trabaja en la banda de 24 GHz ISM. El propósito es evaluar su desempeño e idoneidad para usarse como herramienta didáctica en la enseñanza en las carreras de Ingeniería Automotriz y de Telecomunicaciones con énfasis en las asignaturas de Matemáticas y Telecomunicaciones con escenarios factibles de encontrar en los laboratorios universitarios. Para ello se describe el escenario de medición, así como el hardware, el firmware y un algoritmo genérico implementado en MATLAB basado en transformadas rápidas de Fourier para obtener mapas RangeDoppler que permiten junto con el algoritmo CFAR mejorar la detección de objetos al comparar con la detección a partir de un nivel fijo. Se presentan resultados que demuestran que la exactitud y precisión del radar se encuentran dentro de los parámetros para un radar de corto alcance para vehículos, encontrándose, además, una herramienta con gran potencial didáctico, con la cual los estudiantes pueden comprender las aplicaciones que hoy tienen las matemáticas en el ámbito de las telecomunicaciones, especialmente en radares que sirven a sistemas ADAS.//In recent decades, advanced driver-assistance systems (ADAS) have evolved to be available in much of the vehicles manufactured today; it is very im-portant to keep teaching in this area up-to-date. This paper presents a frequency modulated continuous wave radar that works in the 24 GHz ISM band. The purpose of this work is to evaluate its performance and suitability to be used as a didactic tool in teach-ing in the automotive and telecommunications engi-neering careers with an emphasis on the mathematics and telecommunications subjects, under scenarios feasible to be found in university labs. For this pur-pose, the measurement scenario is described, as well as the hardware, firmware and a generic algorithm implemented in MATLAB based on fast Fourier transforms to obtain Range-Doppler maps that allow, in conjunction with the CFAR algorithm, to improve detection of objects when compared to the detection from a fixed level. The results presented demonstrate that the accuracy and precision of the radar are within the parameters for a short-range radar for vehicles, also finding a tool with great didactic potential with which students can understand today´s applications of mathematics in the field of telecommunications, especially in radars that serve ADAS systems.

Millimeter-wave FMCW (Frequency Modulated Continuous Wave) radar is expected to be widely used for ADAS (Advanced Driver Assistance System) and automated driving car in near future. As FMCW radar uses 3–4 GHz bandwidth to achieve 10cm class range measurement resolution, its dense deployment can cause serious inter-radar interference resulting in miss-detection and/or false detection of the targets. This invited paper overviews inter-radar interference in automotive FMCW radars and describes its mitigation challenges including the proposals and results of our group.

Mutual interference between automotive radar sensors is becoming a major concern due to the rapid increase of vehicles equipped with such systems. While there has been a plenty of studies on the interference of frequency modulated continuous wave (FMCW) radars, no work on chirp sequence (CS) radars has been reported in the literature in spite of their growing popularity in the automotive field. In this regard, this work presents an investigation of mutual interference for automotive CS radars. We analytically derive formulas describing the probability of ghost target appearance, and the signal-to-interference mitigation gain for interference of different waveforms, including continuous wave, FMCW, and CS waveforms, with comparison to an equivalent FMCW radar model. The derived formulas on the signal-to-interference mitigation gain are also verified by simulation results.

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

Studies have demonstrated the usefulness of micro-Doppler signatures for classifying dynamic radar targets such as humans, helicopters, and wind turbines. However, these classification works are based on the assumption that the propagation channel consists of only a single moving target. When multiple targets move simultaneously in the channel, the micro-Dopplers, in their radar backscatter, superimpose thereby distorting the signatures. In this paper, we propose a method to detect multiple targets that move simultaneously in the propagation channel. We first model the micro-Doppler radar signatures of different movers using dictionary learning techniques. Then, we use a sparse coding algorithm to separate the aggregate radar backscatter signal from multiple targets into their individual components. We demonstrate that the disaggregated signals are useful for accurately detecting multiple targets.

Multiple-input multiple-output (MIMO) radar enjoys the advantage of increased degrees-of-freedom and spatial diversity gain, but it cannot effectively resolves the targets closely spaced in the same angle cell (but different range cells). Frequency diverse array (FDA)-MIMO radar can handle this problem by exploiting its range-dependent beampattern. FDA-MIMO radar was, thus, suggested for range–angle estimation of targets. Nevertheless, it is necessary to provide theoretical performance analysis for such a relatively new radar technique. Since multiple signal classification (MUSIC) algorithm is widely adopted in most of the FDA-MIMO literature, this paper derives the Cramer–Rao lower bound and mean square error expressions in MUSIC-based range–angle estimation algorithms for a general FDA-MIMO radar. Furthermore, the corresponding range and angle resolution thresholds in target detection and localization are also derived. Numerical results verify that the FDA-MIMO indeed outperforms conventional MIMO radar in both range–angle estimation and resolution threshold performance.

[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.

We report recent progress towards miniaturizing and packaging an ultra wideband (UWB) radar developed for measurements of ice and snow over the 2–18 GHz range. The initial objective of this work is the close integration of the radar's RF section (composed of a receiver and a low-power transmitter) while maintaining or enhancing its electrical performance. First, we describe a connectorized reference system developed to serve as a performance benchmark for transmit and receive signal chains. Next, we discuss the use of drop-in modules to achieve a significant size reduction of the RF front-end. These modules are based on packaged chips and arranged in a planar configuration. We present system-level performance metrics of the reference system justifying the need for further integration. We briefly discuss other potential applications of the miniaturized radar and the direction of future packaging efforts as we work toward our future goal of integrating the complete radar “from antenna to bits” by using a system-in-package approach.

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.

Snow avalanche is a natural phenomenon, which annually causes infrastructure damage and leads to human casualties in many countries all over the world. As a result, a detailed hazard mapping is required to be able to understand the avalanche risk levels. Also, the scarcity of the areas suitable for constructing infrastructures in the mountains places a high premium on providing high precision hazard mapping. This paper presents the design and development of an advanced phased array antenna for an FMCW radar to produce a high resolution image of snow avalanche in range and cross-range. The proposed antenna is a 16-element fully populated phased array with ±14° azimuth beamwidth and ±22.5° fixed elevation angle. The designed phased array antenna has 14.4 dBi gain and -20.3 dB sidelobe level. In this design, subarraying overlapping technique has been used to eliminate undesirable grating lobes by means of spatial antialias filtering. A phased array power divider is proposed to allow tapering of the amplitude of the elements to achieve low sidelobe level.

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.

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.

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.

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.

This study presents design methodologies for high accuracy baseband detectors for use in automatic gain control (AGC) loops. These loops are used in many applications to stabilise the signal level in a transceiver chain. In a wireless frequency modulated continuous wave (FMCW) radar receiver for example, it is desired to maintain a constant baseband signal level at the receiver output prior to the analogue-to-digital converter. Due to the AGC loop feedback action, the accuracy of this output level directly depends on the detector accuracy. In this study, a detector design employing inherent cancellation of process, voltage and temperature (PVT) variations without the need for any complex compensation schemes is proposed. Measurement results of a fabricated test chip are in good agreement with simulations achieving ±0.15 dB accuracy over temperature, supply and part-to-part variations. The fabricated detector prototype on an IBM 0.18 µm technology has an active area of 0.05 mm2 and draws 1 mA from a 3 V supply. An integrated AGC loop including the proposed detector achieves a 52 dB dynamic range consuming an overall 9 mW power. To the best of the authors’ knowledge, the proposed detector has the highest uncalibrated accuracy reported up to date.

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.

High-performance SiGe HBTs and advancements in packaging processes have enabled system-in-package (SiP) designs for millimeter-wave applications. This paper presents a 122-GHz bistatic frequency modulated continuous wave (FMCW) radar SiP. The intended applications for the SiP are short-range distance and angular position measurements as well as communication links between cooperative radar stations. The chip is realized in a 130-nm SiGe BiCMOS technology and is based on a fully differential frequency-multiplier chain with in phase quadrature phase receiver and a binary phase shift keying modulator in the transmit chain. On-wafer measurement results show a maximum transmit output power of 2.7 dBm and a receiver gain of 11 dB. The chip consumes a DC power of 570 mW at a supply voltage of 3.3 V. The fabricated chip is integrated in an embedded wafer level ball grid array (eWLB) package. Transmit/receive rhombic antenna arrays with eight elements are designed in two eWLB packages with and without backside metal, with a measured peak gain of 11 dBi. The transceiver chip size is 1.8 mm × 2 mm, while the package size is 12 mm × 6 mm, respectively. FMCW measurements have been conducted with a sweep bandwidth of up to 17 GHz and a measured range resolution of 1.5 cm has been demonstrated. 2D positions of multiple targets have been computed using two coherently linked radar stations.

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.

For an automotive surveillance radar system, fast-chirp train based FMCW (Frequency Modulated Continuous Wave) radar is a very effective method, because clutter and moving targets are easily separated in a 2D range-velocity map. However, pedestrians with low echo signals may be masked by strong clutter in actual field. To address this problem, we proposed in the previous work a clutter cancellation and moving target indication algorithm using the coherent phase method. In the present paper, we initially composed the test set-up using a 24 GHz FMCW transceiver and a real-time data logging board in order to verify this algorithm. Next, we created two indoor test environments consisting of moving human and stationary targets. It was found that pedestrians and strong clutter could be effectively separated when the proposed method is used. We also designed and implemented these algorithms in FPGA (Field Programmable Gate Array) in order to analyze the hardware and time complexities. The results demonstrated that the complexity overhead was nearly zero compared to when the typical method was used.

Ultra wideband (UWB) Doppler radar has many biomedical applications, including remote diagnosis of cardiovascular disease, triage and real-time personnel tracking in rescue missions. It uses narrow pulses to probe the human body and detect tiny cardiopulmonary movements by spectral analysis of the backscattered electromagnetic (EM) field. With the help of super-resolution spectral algorithms, UWB radar is capable of increased accuracy for estimating vital signs such as heart and respiration rates in adverse signal-to-noise conditions. A major challenge for biomedical radar systems is detecting the heartbeat of a subject with high accuracy, because of minute thorax motion (less than 0.5 mm) caused by the heartbeat. The problem becomes compounded by EM clutter and noise in the environment. In this paper, we introduce a new algorithm based on the state space method (SSM) for the extraction of cardiac and respiration rates from UWB radar measurements. SSM produces range-dependent system poles that can be classified parametrically with spectral peaks at the cardiac and respiratory frequencies. It is shown that SSM produces accurate estimates of the vital signs without producing harmonics and inter-modulation products that plague signal resolution in widely used FFT spectrograms.

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.

The presence of phase noise (PN) severely deteriorates the sensitivity and range of frequency-modulated continuous wave radar systems. Thus, characterization and continuous monitoring of the PN is indispensable, and its estimation is often employed directly on chip. Although many contributions investigate methods for PN estimation, almost all of them consider a continuous-wave (CW) input signal. Differently, in this paper, we aim to estimate the PN from a linear frequency modulated continuous wave (FMCW) signal. For that, we propose two methods utilizing a so-called artificial on-chip target and further digital signal processing. These methods are evaluated in real-time and are the first-known solutions to determine PN estimates during the operation of an FMCW radar transceiver. We prove our methods with both simulation and measurement results from a hardware prototype. Further, we present techniques to efficiently realize the concepts in digital hardware. Finally, we compare and trade off the proposed methods against computational complexity and performance. The novel techniques may be applied to arbitrary input frequencies and bandwidths, and do not require a reference-clock input.

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.

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 the conventional 2D-FFT based target detection method, all range-Doppler cells are computed by FFT (Fast Fourier Transform) and scanned by CA-CFAR (Cell-Averaging Constant False Alarm Rate) detection. This results in high computational complexity and long processing time. In this paper, we developed an automotive 24 GHz BSD (Blind Spot Detection) FMCW (Frequency Modulated Continuous Wave) radar with a low complexity target detection architecture based on a ROI (Region Of Interest) pre-processing scheme. In the real BSD zone, because the number of cars to be detected is limited, the designed method only extracts their velocities corresponding to the range ROIs in which real targets exist. Moreover, the presence probability of vehicles with the same range-bin but different velocities is very low. Thus, in the designed method, some Doppler ROIs cells with a high magnitude are only applied for CA-CFAR detection. This architecture can dramatically reduce the amount of data to be processed compared to that of the conventional 2D FFT based method, resulting in enhanced processing time. We developed a 24 GHz FMCW radar system composed a transceiver, antennas, and signal processing module. The designed algorithm was implemented in a tiny micro-processor of the signal processing module. By implementing our proposed algorithm in the developed 24 GHz FMCW radar system in an anechoic chamber and a real road, we verified that the range and velocity of a car occupying the BSD zone were detected. Compared to that of the conventional method, the reduction ratio of the total processing time was measured to be 52.4 %.

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.

It is known that long-time integration is an effective method for improving the detection performance ofweak and maneuvering radar targets.However, with the increase of integration time, the problems of across range unit (ARU) and across Doppler unit (ADU) may severely limit the integration performance for high-speed and maneuvering targets. The generalized Radon-Fourier transform (GRFT) can optimally deal with the above problems, but its implementation needs an ergodic multidimensional search. To reduce the complexity, a novel hybrid integration approach is proposed in this paper to speed up the realization of GRFT. It divides a long integration time into several subapertures and implements coherent integration for each subaperture via Doppler filter banks. Subsequently, it accomplishes noncoherent integration among all subapertures with compensation of high-order ARU and ADU motions via generalized Radon transform. Due to the hybrid integration over a long time, the proposed method strikes a balance between integration performance and computational efficiency for the detection of high-speed and highly maneuvering targets. Finally, some results of numerical experiments are provided to demonstrate the effectiveness of the proposed method.

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.

A mixer-first single-RF-port duplexing RF frontend is proposed and implemented for frequency-modulated continuous-wave (FMCW) radar applications in this paper. The RF frontend is a bidirectional simultaneous frequency up-and-down converter. Equations of basic parameters of the frontend are derived to provide design criteria. The proposed radar architecture has been evaluated with an S-band (3.3-3.6 GHz) FMCW radar. The radar chip is fabricated in a 65nm CMOS process, and it consumes 190 mW of DC power under 1.2V supply. A wireless distance measurement has verified the function of the radar chip.

In the cost sensitive automotive market, frequency-modulated continuous-wave (FMCW) radars are expected to persist for a long period of time because of their cheap and simple circuitry. Further, more autonomous driving systems use radars than before and are, therefore, increasingly susceptible to mutual interference. We propose a system that cognitively adapts its chirp bandwidth and transmission time slot in interference scenarios. The resolution and detection performance of this cognitive radar is similar to a standard FMCW radar. Our measurements using an actual automotive radar with a corner reflector in a complex parking house show that a reasonable signal separability is obtained after reducing the chirp bandwidth by 25% and simultaneously extending the range by a factor of 16.

Mutual interference in automotive radar scenarios is going to become a major concern as the density of vehicles with radar sensors in the roads increases. The present work tackles the problem of frequency modulated continuous wave (FMCW) to FMCW and continuous wave interference. In this context, we propose a signal processing technique to blindly identify and remove interference by using the fast Orthogonal Matching Pursuit (OMP) algorithm to project the interference signals in a reduced chirplet basis, and separate it from the target signal with minimal loss of information. Significant reduction of the noise-plus-interference levels are observed in both simulated and measured data, the later acquired with state of the art automotive sensors.

The growing interest in connected and autonomous vehicles is expected to create significant traffic demands and impose serious challenge for currently allocated vehicular communication frequency bands such as 5.9 GHz band. Meanwhile, the wide bandwidth in 79 GHz band dedicated for automotive radar may greatly support such traffic demand if a joint automotive radar and communication system is deployed. In this demo, we present a preliminary proof of concept for a joint automotive radar and communication system based on commercial off-the-shelf automotive radars. In particular, the system modulates data using frequency shift keying (FSK) upon widely adopted frequency modulated continuous wave (FMCW) automotive radar.