Automotive radars play a crucial role in the reduction of traffic casualties and the realization of autonomous driving due to its robustness and adverse weather tolerance. However, as the penetration rate of automotive radars increases, concerns arise regarding the mutual interference. In contrast to the predominant Frequency-Modulated Continuous Wave (FMCW) radars, Phase-Modulated Continuous Wave (PMCW) radars might provide solutions for the interference problem by coding the waveforms, which brings an additional degree of freedom. In this thesis, a system level overview of the phase-coded radar is presented. Regarding the popular code families, particular attention was given to the Gold, Almost Perfect Autocorrelation Sequences (APAS), and Zero-Correlation Zone (ZCZ) sequences. This thesis has proposed three distinct designs for 16-TX-element MIMO Phase-Coded radar that drives the requirements of a Medium Range Radar (MRR). The conclusion can be drawn that APAS and ZCZ sequences have shown to provide a (sub)optimal design that is emphasized by their perfect correlation characteristics within the designated distance of interest. Furthermore, in full-transmit capacity MIMO, the proposed designs use semi-orthogonal waveforms to provide excellent performance in synchronous PMCW radars. However, performance degrades in case Doppler-shifted reflections are received, whereas sidelobes arise in range due to non-orthogonality. This thesis concludes that the APAS-coded waveforms are most tolerant to Doppler shift; besides, its Time Division Multiplexing (TDM) MIMO Transmission scheme is computationally more efficient than the Code Division Multiplexing (CDM) scheme used in Gold and ZCZ coded waveforms. Finally, the radar-to-radar interference investigation has proven that for uncorrelated PMCW- to-PMCW interference, the noise floor undergoes a consistent increase, which is according to the interference-plus-noise power level calculated from the link budget analysis. This thesis emphasizes these results, as the interference effect in FMCW-to-FMCW (provided by NXP Semiconductors) have seen similar phenomena. Therefore, results in this thesis support the conclusion that coded waveforms do not remove or suppress the energy levels of the interference. For correlated interference, ghost targets might be formed, but this depends on the starting time as well as the starting coded bit of the interferer, as the correlation peak can be formed outside the distance of interest.

Automotive radar is a key element in Advanced Driver Assistance Systems (ADAS). With the growth of Automotive industry, there is a high demand for the sensors used in assisting systems. As the number of sensors increases, probability that these systems being in close proximity will also increase. This will lead to situations where in multiple radar sensors will be operating in close proximity, this might lead to a sub-optimal performance of our radar system. Currently FMCW radar systems are most prevalent in the automotive radar market. For FMCW systems, interference mitigation techniques exist in time domain, frequency domain, polarization domain and etc. Most of these techniques insiston detecting and identifying the interference before mitigating it. In this thesis, we consider a FMCW radar system and first develop a MATLAB model for the three most important interference scenarios namely Continuous Wave(CW), FrequencyModulatedContinuousWave (FMCW) and PhaseModulatedContinuousWave (PMCW). We propose a signal model where interference can be localized over the beat signal, then we systematically study how interference can be detected. As a result, we will detect the interference even if the power level of the interferer is lower than the power level of the received reflected signal. Post detection of interference,we suggest a technique to identify the interference by estimating the slope from the detected interference samples. Starting with a simple existing mitigation technique, we look at how to mitigate the interference and suggest enhancements that can be done for these techniques post detection and identification. Considering a worst case scenario of interference being completely in band to the transmitted signal, we propose a novel avoidance technique which will also predict the bandwidth of the interferer. As a result we will be able to shift the center frequency of the transmitter to avoid the interferer. Finally we propose another novel time domain mitigation technique where in without detecting or identifying the interferer, we will mitigate the interference and compare the gain of Signal to Interference plus Noise Ratio (SINR) achieved by using this technique.