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

The Bi-directional Spatial Spectrum for MIMO Radar and Its Applications

<p>Radar systems have long applied electronically-steered phased arrays to discriminate returns in azimuth angle and elevation angle. On receiver arrays, beamforming is performed after reception of the data, allowing for many adaptive array processing algorithms to be employed. However, on transmitter arrays, up until recently pre-determined phase shifts had to applied to each transmitter element before transmission, precluding adaptive transmit array processing schemes. Recent advances in multiple-input multiple-output radar techniques have allowed for transmitter channels to separated after data reception, allowing for virtual non-causal "after-the-fact" transmit beamforming. The ability to discriminate in both direction-of-arrival and direction-of-departure allows for the novel ability to discriminate line-of-sight returns from multipath returns. This works extends the concept of virtual non-causal transmit beamforming to the broader concept of a bi-directional spatial spectrum, and describes application of such a spectrum to applications such as spread-Doppler multipath clutter mitigation in ground-vehicle radar, and calibration of a receiver array of a MIMO system with ground clutter only. Additionally, for this work, a low-power MIMO radar testbed was developed for lab testing of MIMO radar concepts.</p>Dissertatio

Multi-band Wideband Channel Measurements in Indoor and Outdoor Environments above 6 GHz for 5G Networks

This document presented the results of ultra-wideband of multi-bands measurements performed in three different indoor environments such as large office, factory like and small office and one outdoor street canyon scenario at the science site of Durham University, United Kingdom. The measurements conducted using a wideband chirp sounder developed at Durham University. An analytical review of the radio wave propagation mechanisms and formulas is presented in addition to the background of the channel characteristics parameters and statistics. The parameters reviewed are the received signal strength, path loss, the excess, average and RMS delay spread, in addition to the angular parameters such as the angle of arrival (AoA), angle of departure (AoD) and the RMS angular spread. A literature survey for about 80 paper of the previous work are studied and summarised for the measurements and simulation performed to estimate different parameters in both indoor and outdoor scenarios. Two different measurements set up were performed in three indoor environments and one outdoor scenario to measure mainly, the frequency dependency in various channel characteristics parameters. In the first set the measured parameters are the received signal strength, path loss, and the excess, average and the cumulative distribution function (CDF) and the RMS delay spread in three indoor environments. While in the second set the 3D angular parameters such as AoA, AoD and RMS angular spread in both Tx and Rx sides are studied in three indoor and one outdoor environment mentioned earlier. The measurements set up and procedures are presented for each set of measurement. The measurements were performed using a wideband channel sounder up to 6 GHz for both sets. Five different frequency bands (i.e.13.4 GHz, 26.8 GHz, 54.2 GHz, 62.6 GHz and 70 GHz) were used in the first set and three bands (i.e.13.4 GHz, 26.8 GHz, 62.6 GHz) for the second set. A steerable horn antenna at both side using 3D positioner in the second set of measurements, while an omnidirectional antenna was used at the receiver side in the first set. A summary and discussion the extracted results for each set of measurements are given. Conclusions about the achieved results and the recommended future work are provided