Orthogonal chirp-division multiplexing (OCDM) has been recently proposed as an alternative scheme to orthogonal frequency-division multiplexing (OFDM) for data communication. Among the reasons for that are its superior robustness, e.g., to frequency selectivity of channels and intersymbol interference. Furthermore, channel estimation in the discrete-Fresnel domain has been investigated for both communication and sensing, without, however, considering the effects of frequency shifts. This article investigates the discrete-Fresnel domain channel estimation in OCDM-based radar systems as an alternative to the correlation-based processing from the conventional OCDM (C-OCDM) radar-communication (RadCom) system, which yields high, transmit-data-dependent sidelobe level. In this context, a mathematical formulation for the investigated channel estimation approach is presented. In addition, extensions to multiuser/multiple-input–multiple-output (MIMO) and to a sector-modulated OCDM (SM-OCDM) RadCom operation are introduced. Finally, the performance of the proposed schemes is analyzed based on simulation and measurement results for an emulated automotive scenario. In summary, both OCDM-based radar and SM-OCDM RadCom systems yield improved peak-to-average power ratio and comparable or improved radar performance in terms of sidelobe level and Doppler shift robustness to their C-OCDM and OFDM counterparts for practical range and velocity values. In addition, equal communication performance robustness to C-OCDM, which outperforms OFDM, is experienced in the SM-OCDM case.

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.

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.

Radar sensors are widely used to support further system automation as they reliably provide range, velocity, and angle information for multiple objects. Nevertheless, unique identification of an object is not within the typical function range of radar; often, supportive systems are required. To overcome this limitation, a multipurpose tag concept for fast chirp frequency-modulated continuous wave (FC-FMCW) radar is introduced. The Doppler tag applies an artificial frequency shift following the Doppler phenomenon for unique identification of tagged objects with conventional radar hardware. It enables simultaneous detection and feature estimation of tagged and untagged objects. The idea of the Doppler tag is presented together with a realization and the required signal processing to allow for identification and high-accuracy range estimation. Simulations and measurements are provided to support the overall understanding and prove the functionality of the radar-tag system.

This paper presents the development and application of an electrical impedance sensor allied with an optical fiber Bragg grating (FBG) sensor whereby both are integrated in fiberglass composite material. The use of composite material allows the integration of the sensors according to the desired geometry. In the field of oil and gas production it is of great importance to monitor the formation of clathrate hydrates (crystalline structures) because such solids may disrupt the flow causing risks and increasing extraction costs. As there is no fully established method for this sensing application, impedance spectroscopy allied to temperature technique is explored for the purpose. Hence, impedance spectra from 1 kHz to 5 MHz along with temperature readings are obtained during an exemplary hydrates experiment, showing that the developed system is able to monitor the hydrates formation in pipes.

In the context of all-digital radar systems, phase-modulated continuous wave (PMCW) based on pseudorandom binary sequences (PRBSs) appears a prominent candidate modulation scheme for applications such as autonomous driving. Among the reasons for that 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 that 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.