Design of a Single-Core Digital-to-Analog Converter with Ultra-Wideband and Low Power Consumption for CUWB-IR Applications

Data converters are intermediate circuits used to connect between two analog and digital ranges. Data converters are not only used for converting audio into a microphone or speaker, but also for converting audio into a camera or display, transferring information to a computer or digital signal processor. At these times, the need for data converters is not invested in every aspect of life. Digital to analog converters is a leading part of these converters, which are widely used in most audio and video circuits. In this thesis, we have proposed a 4-bit 1GS/s DAC for CUWB-IR usage. To enhance the above performance with superior speed and the need for linearity, every significant block containing the convenient sources, current switches, and deglitcher were designed optimally and a new DAC converter circuit was developed which improves the linearity. The designed DAC was performed using a commercial 130 nm CMOS process. DAC INL/DNL≤0.22LSB features more than high Nyquist bandwidth at extremely low power losses of 0.45 mW. The proposed DAC achieves the best FoMs at the right time for advanced DACs

Analysis of two coupled NLTL-based oscillators

A system of two coupled oscillators based on nonlinear transmission lines (NLTL) is proposed for pulsed-shaping applications. The maximum propagation frequency through the NLTL is calculated and optimized with a realistic numerical method. With additional design considerations, this is used to increase the waveform steepening capabilities of the NLTL and obtain an oscillator based on the shockwave concept. Coupling two of these oscillators with slightly different characteristics various pulse shapes can be achieved through composition of the individual waveforms. The coupled-system behavior is understood with the aid of a new reduced-order formulation, which takes into account the differences between the oscillator elements. The formulation is extended for stability and phase-noise analysis. It provides valuable insight into the impact of the individual oscillator characteristics on the coupled-system dominant poles and unsymmetrical stable phase-shift range. It also explains the variation of the spectral density with the phase shift, as well as the mechanisms for the phase noise corners observed when increasing the offset frequency. A more realistic analysis of the coupled system is also carried out with the conversion-matrix approach, using cyclostationary noise sources. The analysis and design techniques have been applied to several prototypes at 0.8 GHz.This work was supported by the Spanish Ministry of Science and Innovation under project TEC2011-29264-C03-01

Investigating Key Techniques to Leverage the Functionality of Ground/Wall Penetrating Radar

Ground penetrating radar (GPR) has been extensively utilized as a highly efficient and non-destructive testing method for infrastructure evaluation, such as highway rebar detection, bridge decks inspection, asphalt pavement monitoring, underground pipe leakage detection, railroad ballast assessment, etc. The focus of this dissertation is to investigate the key techniques to tackle with GPR signal processing from three perspectives: (1) Removing or suppressing the radar clutter signal; (2) Detecting the underground target or the region of interest (RoI) in the GPR image; (3) Imaging the underground target to eliminate or alleviate the feature distortion and reconstructing the shape of the target with good fidelity. In the first part of this dissertation, a low-rank and sparse representation based approach is designed to remove the clutter produced by rough ground surface reflection for impulse radar. In the second part, Hilbert Transform and 2-D Renyi entropy based statistical analysis is explored to improve RoI detection efficiency and to reduce the computational cost for more sophisticated data post-processing. In the third part, a back-projection imaging algorithm is designed for both ground-coupled and air-coupled multistatic GPR configurations. Since the refraction phenomenon at the air-ground interface is considered and the spatial offsets between the transceiver antennas are compensated in this algorithm, the data points collected by receiver antennas in time domain can be accurately mapped back to the spatial domain and the targets can be imaged in the scene space under testing. Experimental results validate that the proposed three-stage cascade signal processing methodologies can improve the performance of GPR system