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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.

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To enlarge the range of wireless fronthaul and backhaul communication links operating close to the millimeterwave (mmW) region, this work presents a novel Line-of-Sight (LoS) Multiple-Input Multiple-Output (MIMO) relay system. The analog relay system consists of a simple 90°hybrid coupler to separate two uncorrelated transmit data streams realizing a lowcomplex and cheap system. The functional capability is proven within measurements of two independent 2 × 2 LoS MIMO links at 28 GHz connected by the relay system. A high decoupling of the two independent transmitted data streams of more than 27 dB after the 90°hybrid coupler and a high modulation error rate (MER) at the last receiver of around 22 dB could be reached for QPSK and 16-QAM modulated signals.