Binary-Phase vs. Frequency Modulated Radar Measured Performances for Automotive Applications

Radars have been widely deployed in cars in recent years, for advanced driving assistance systems. The most popular and studied modulated waveform for automotive radar is the frequencymodulated continuous wave (FMCW), due to FMCW radar technology’s ease of implementation and low power consumption. However, FMCW radars have several limitations, such as low interference resilience, range-Doppler coupling, limited maximum velocity with time-division multiplexing (TDM), and high-range sidelobes that reduce high-contrast resolution (HCR). These issues can be tackled by adopting other modulated waveforms. The most interesting modulated waveform for automotive radar, which has been the focus of research in recent years, is the phase-modulated continuous wave (PMCW): this modulated waveform has a better HCR, allows large maximum velocity, permits interference mitigation, thanks to codes orthogonality, and eases integration of communication and sensing. Despite the growing interest in PMCW technology, and while simulations have been extensively performed to analyze and compare its performance to FMCW, there are still only limited real-world measured data available for automotive applications. In this paper, the realization of a 1 Tx/1 Rx binary PMCW radar, assembled with connectorized modules and an FPGA, is presented. Its captured data were compared to the captured data of an off-the-shelf system-on-chip (SoC) FMCW radar. The radar processing firmware of both radars were fully developed and optimized for the tests. The measured performances in real-world conditions showed that PMCW radars manifest better behavior than FMCW radars, regarding the above-mentioned issues. Our analysis demonstrates that PMCW radars can be successfully adopted by future automotive radars

Doppler Shift Tolerance of Accumulation and Outer Coding in MIMO-PMCW Radar

Phase-modulated continuous wave (PMCW) has been widely regarded as a promising modulation scheme for radar systems, e.g., in highly automated driving (HAD) applications. Although the so-called outer coding can efficiently enable the multiple-input-multiple-output (MIMO) operation of PMCW-based radar systems, the yielded processing gain in this multiplexing approach may be reduced at increasing Doppler shifts. In this context, this letter introduces a normalized Doppler shift parameter that enables predicting the Doppler-shift-induced degradation of the processing gain in a MIMO-PMCW radar system. Finally, simulation and measurement results confirm the usefulness of the introduced parameter in desigining MIMO-PMCW radars

Doppler Shift Tolerance of Typical Pseudorandom Binary Sequences in PMCW Radar

In the context of all-digital radar systems, phase-modulated continuous wave (PMCW) based on pseudorandom binary sequences (PRBSs) appears to be a prominent candidate modulation scheme for applications such as autonomous driving. Among the reasons for its candidacy are its simplified transmitter architecture and lower linearity requirements (e.g., compared to orthogonal-frequency division multiplexing radars), as well as its high velocity unambiguity and multiple-input multiple-output operation capability, all of which are characteristic of digital radars. For appropriate operation of a PMCW radar, choosing a PRBS whose periodic autocorrelation function (PACF) has low sidelobes and high robustness to Doppler shifts is paramount. In this sense, this article performs an analysis of Doppler shift tolerance of the PACFs of typically adopted PRBSs in PMCW radar systems supported by simulation and measurement results. To accurately measure the Doppler-shift-induced degradation of PACFs, peak power loss ratio (PPLR), peak sidelobe level ratio (PSLR), and integrated-sidelobe level ratio (ISLR) were used as metrics. Furthermore, to account for effects on targets whose ranges are not multiples of the range resolution, oversampled PACFs are analyzed

System Modeling of Next Generation Digitally Modulated Automotive RADAR (DMR)

abstract: State-of-the-art automotive radars use multi-chip Frequency Modulated Continuous Wave (FMCW) radars to sense the environment around the car. FMCW radars are prone to interference as they operate over a narrow baseband bandwidth and use similar radio frequency (RF) chirps among them. Phase Modulated Continuous Wave radars (PMCW) are robust and insensitive to interference as they transmit signals over a wider bandwidth using spread spectrum technique. As more and more cars are equipped with FMCW radars illuminate the same environment, interference would soon become a serious issue. PMCW radars can be an effective solution to interference in the noisy FMCW radar environment. PMCW radars can be implemented in silicon as System-on-a-chip (SoC), suitable for Multiple-Input-Multiple-Output (MIMO) implementation and is highly programmable. PMCW radars do not require highly linear high frequency chirping oscillators thus reducing the size of the final solution. This thesis aims to present a behavior model for this promising Digitally modulated radar (DMR) transceiver in Simulink/Matlab. The goal of this work is to create a model for the electronic system level framework that simulates the entire system with non-idealities. This model includes a Top Down Design methodology to understand the requirements of the individual modules’ performance and thus derive the specifications for implementing the real chip. Back annotation of the actual electrical modules’ performance to the model closes the design process loop. Using Simulink’s toolboxes, a passband and equivalent baseband model of the system is built for the transceiver with non-idealities of the components built in along with signal processing routines in Matlab. This model provides a platform for system evaluation and simulation for various system scenarios and use-cases of sensing using the environment around a moving car.Dissertation/ThesisMasters Thesis Engineering 201

Low-complexity hardware and algorithm for joint communication and sensing

Joint Communication and Sensing (JCAS) is foreseen as one very distinctive feature of the emerging 6G systems providing, in addition to fast end reliable communication, the ability to obtain an accurate perception of the physical environment. In this paper, we propose a JCAS algorithm that exploits a novel beamforming architecture, which features a combination of wideband analog and narrowband digital beamforming. This allows accurate estimation of Time of Arrival (ToA), exploiting the large bandwidth and Angle of Arrival (AoA), exploiting the high-rank digital beamforming. In our proposal, we separately estimate the ToA and AoA. The association between ToA and AoA is solved by acquiring multiple non-coherent frames and adding up the signal from each frame such that a specific component is combined coherently before the AoA estimation. Consequently, this removes the need to use 2D and 3D joint estimation methods, thus significantly lowering complexity. The resolution performance of the method is compared with that of 2D MUltiple SIgnal Classification (2D-MUSIC) algorithm, using a fully-digital wideband beamforming architecture. The results show that the proposed method can achieve performance similar to a fully-digital high-bandwidth system, while requiring a fraction of the total aggregate sampling rate and having much lower complexity.Comment: 13 pages, 9 figures. Submitted to IEEE Transactions on Wireless Communication

ON FUNDAMENTAL OPERATING PRINCIPLES AND RANGE-DOPPLER ESTIMATION IN MONOLITHIC FREQUENCY-MODULATED CONTINUOUS-WAVE RADAR SENSORS

The diverse application areas of emerging monolithic noncontactradar sensors that are able to measure object’s distance and velocity is expected to grow in the near future to scales that are now nearly inconceivable. A classical concept of frequency-modulated continuous-wave (FMCW) radar, tailored to operate in the millimeter-wave (mm-wave) band, is well-suited to be implemented in the baseline CMOS or BiCMOS process technologies. High volume production could radically cut the cost and decrease the form factorof such sensing devices thus enabling their omnipresence in virtually every field. This introductory paper explains the key concepts of mm-wave sensing starting from a chirp as an essential signal in linear FMCW radars. It further sketches the fundamental operating principles and block structure of contemporary fully integrated homodyne FMCW radars. Crucial radar parameters like the maximum unambiguously measurable distance and speed, as well as rangeand velocity resolutions are specified and derived. The importance of both beat tones in the intermediate frequency (IF) signal and the phase in resolving small spatial perturbations and obtaining the 2-D range-Doppler plot is pointed out. Radar system-level trade-offs and chirp/frame design strategies are explained. Finally, the nonideal and second-order effects are commented and the examples of practical FMCW transmitter and receiver implementations are summarized