Investigation of Non-coherent Discrete Target Range Estimation Techniques for High-precision Location

Ranging is an essential and crucial task for radar systems. How to solve the range-detection problem effectively and precisely is massively important. Meanwhile, unambiguity and high resolution are the points of interest as well. Coherent and non-coherent techniques can be applied to achieve range estimation, and both of them have advantages and disadvantages. Coherent estimates offer higher precision but are more vulnerable to noise and clutter and phase wrap errors, particularly in a complex or harsh environment, while the non-coherent approaches are simpler but provide lower precision. With the purpose of mitigating inaccuracy and perturbation in range estimation, miscellaneous techniques are employed to achieve optimally precise detection. Numerous elegant processing solutions stemming from non-coherent estimate are now introduced into the coherent realm, and vice versa. This thesis describes two non-coherent ranging estimate techniques with novel algorithms to mitigate the instinct deficit of non-coherent ranging approaches. One technique is based on peak detection and realised by Kth-order Polynomial Interpolation, while another is based on Z-transform and realised by Most-likelihood Chirp Z-transform. A two-stage approach for the fine ranging estimate is applied to the Discrete Fourier transform domain of both algorithms. An N-point Discrete Fourier transform is implemented to attain a coarse estimation; an accurate process around the point of interest determined in the first stage is conducted. For KPI technique, it interpolates around the peak of Discrete Fourier transform profiles of the chirp signal to achieve accurate interpolation and optimum precision. For Most-likelihood Chirp Z-transform technique, the Chirp Z-transform accurately implements the periodogram where only a narrow band spectrum is processed. Furthermore, the concept of most-likelihood estimator is introduced to combine with Chirp Z-transform to acquire better ranging performance. Cramer-Rao lower bound is presented to evaluate the performance of these two techniques from the perspective of statistical signal processing. Mathematical derivation, simulation modelling, theoretical analysis and experimental validation are conducted to assess technique performance. Further research will be pushed forward to algorithm optimisation and system development of a location system using non-coherent techniques and make a comparison to a coherent approach

An Experimental Study of Radar-Centric Transmission for Integrated Sensing and Communications

This study proposes a dual-function radar and communication (DFRC) system that utilizes radar transmission parameters as modulation indexes to transmit data to the users while performing radar sensing as its primary function. The proposed technique exploits index modulation (IM) using the center frequency of radar chirps, their bandwidths, and polarization states as indexes to modulate the communication data within each radar chirp. By utilizing the combination of these indexes, the proposed DFRC system can reach up to 17 Mb/s throughput, while observing a robust radar performance. Through our experimental study, we also reveal the trade-off between the radar sensing performance and communication data rate, depending on the radar waveform parameters selected in the DFRC system. This study also demonstrates the implementation of the proposed DFRC system and presents its real-time over-the-air experimental measurements. Consequently, the simulation results are verified by real-time over-the-air experiments, where ARESTOR, a high-speed signal processing and experimental radar platform, has been employed

An ultra high resolution FMCW radar

Bibliography: leaves 127-128.There is a great need for real-time non-intrusive measurements in industry. A short-range radar system can be used to make these measurements. A standard requirement for these type of applications is high resolution. This is a standard problem in radar. Using classical signal processing techniques, the range resolution is proportional to the bandwidth of the transmitted signal. This poses a serious problem in radar as very large bandwidths are required - typically lSOGHz for 1 mm range resolution. Alternative techniques have been sought which do not rely on large transmitted bandwidths, but which rely on large signal-to-noise ratio (SNR). Such techniques exist in modem spectral analysis eg. auto-regressive techniques. These techniques model the data. In other words, they assume a priori information. Linear frequency-modulated continuous-wave (FMCW) radar was utilized, since a pulsed radar would require very precise time measurements due to the short range (a few ns). The FMCW radar would have to be very linear for the modelling process to work properly. The frequency domain measurement of the received system data would then be proportional to range. An FMCW radar system was built and tested. The modem signal processing techniques were found to work well when injected with sinusoidal signals from signal generators. The hardware was also found to perform satisfactorily. However, amplitude modulation was observed in the mixing process and subsequently, the modelling process did not perform satisfactorily when interfaced to the hardware. Due to the amplitude modulation problem, two closely-spaced targets disrupted the high resolution properties of the modelling process. Nevertheless, a single target could be resolved within a resolution bin of better than 1 cm. A solution is proposed in chapter eight, however, it is out of the scope of this thesis

Desain, Simulasi dan Analisis Peningkatan Range Resolution Sistem Radar FMCW

Range resolution as one of the parameters of the radar system becomes very important and need to be upgraded to provide accurate target distance information. Increased bandwidth can be done however is limited to devices for Direct Digital Synthesizer (DDS) that are used and will enlarge the noise and power consumption of system Frequency Modulated Continuous Wave (FMCW) radar. To improve range resolution, output signal and bandwidth linieritas chirp both plays is very important and the sampling rate of the engineering efforts for improved range resolution still experience barriers when based on peak detection. So to improve range resolution alternatives that can do that is maintain linieritas or increase bandwidth and not just based on peak detection. In this paper are discussed improved range resolution without increasing bandwidth using curve fitting method by way of comparing the output signal of the mixer and beat frequency shift signal mixer output to both match (match). Error of measurement range resolution is affected by the phase errors due to the lack of frequency of linieran beat, so that needs to be done shifted frequency curve fitting method using beat against the sweep of raw data (output ADC) to earn optimum beat frequency (optimum resolution range). Range resolution for Radar Demonstration Kit (RDK) using curve fittng methods obtained results an increase of 30% and the shifting of the beat frequency of 3KHz

X-Band Front-end Module of FMCW RADAR for Collision Avoidance Application

A frequency modulated continuous wave (FMCW) radar front-end module is developed as a laboratory prototype of NECTEC, NSTDA. The performance of proposed prototype is verified by the reflection test of aluminum plates in outdoor environment. The frequency domain data from a spectrum analyzer was measured at every 20 meters of the distance between the front-end prototype and the aluminum plate until the maximum distance of 200 meters is reached. The calculation of the beat frequencies at different range of reflecting aluminum plates is presented. The maximum error between measured and calculated distances does not exceed 5.02 percent. The effect of different radar cross section (RCS) of reflecting objects of 0.3, 0.8 and 1.5 m2 plate area are analyzed. The low value of different received power ratio per one squared meter unit area of 0.66 percent is obtained to prove the consistency of reflected power level over the different size of object under test.

A Spatio-Temporal Approach to Mitigate Automotive Radar Spoofing Attacks

Cyber-physical system (CPS) has become an integral part of human life, ranging from aircraft to health care systems. The security of these critical components ensures its wider acceptability. Traditionally, many works to secure cyber-physical system (CPS) has been done in the cyber domain, like securing inter/intra CPS communication, securing the exposed software, rebuilding control input derived from sensor data post-digitization, using sensor fusion. All of this security software suffers from a basic attack wherein an attacker compromises the physical/analog sensing system. Researchers have made some progress in mitigating such attacks on physical/analog signals of CPS, the current state of the art methodology proposed in PyCRA uses temporal random signals for physical challenge-response authentication. Though this approach immensely enhances the capability of identifying the sensor attacks, it fails to provide any recovery mechanism to the system. Recent work like Dutta et al., 2017 tries to address this by introducing recursive least squares (RLS) based recovery mechanisms over PyCRA. Although these systems provide some recovery in trivial scenarios, they fail during longer attacks and also result in loss of control because of longer/frequent random no-signal periods. Which could be catastrophic in real-time systems. This work presents Spatio-Temporal Challenge-Response (STCR), an authentication scheme designed to protect active sensing systems against physical attacks occurring in the analog domain. This system utilizes multiple beam-forming and provides physical challenge-response authentication (CRA) in both spatial and temporal domain. Thus providing a much more resilient authentication mechanism that not only detects malicious attacks, but also provides recovery from them. We demonstrate the resilience and effectiveness of STCR over the state of the art in detecting and mitigating attacks through several experiments using a car following (CF) model. This model deploys CPS in the follower car to sense the lead car’s relative position and maintain a safe distance by manipulating acceleration

Localization of multi-class on-road and aerial targets using mmwave FMCW radar

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