A High-Performance Low-Ringing Ultrawideband Monocycle Pulse Generator

Accurate detection of rebar location using Ground Penetrating Radar (GPR) proves to be very useful in assessing roadway/bridge deck concrete structure. Due to large signal processing resource needed to locate and image rebar on a whole road structure, more efficient signal processing method is needed. This paper proposes to combine two-dimensional (2D) entropy algorithm to narrow down the scope of interested data from large radar data set and Short Time Fourier Transform (STFT) algorithm to perform further feature characterization. To validate the analysis, experiments with different rebar setups are conducted. A. Windowing 2D Entropy MethodEntropy is a statistical measure of uncertainty in a collection of random data based on Shannon's theory [7]. A high entropy value indicates the high degree of similarities in a section of collected data whereas a low entropy value indicates distinctiveness. Assuming the received GPR reflection signal Y(t) can be modeled with the following equation:

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“…Its value is measured to be 4.1 approximately according to our measurements [9,10,11]. C is the speed of light in air.…”

Section: Experiments Results and Discussionmentioning

confidence: 83%

Two dimensional entropy and short time Fourier Transform application on ground penetrating radar data analysis

et al. 2013

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“…Splitting (4) into real and imaginary parts and solving for the synchronization frequency , one obtains the expression (7) where the product means the following operation and . Performing this operation, the synchronized oscillation frequency is given by (8) where (9) As gathered from (8), to first order, the oscillation frequency varies sinusoidally with the phase shift , with an offset depending on the original free-running point and the parameter of the 2 2 admittance matrix that describes the coupling network. The oscillation frequency excursion depends on the magnitudes that characterize the second oscillator (the oscillator that does not contain the tuning element), the ratio between the free-running voltages and the coupling-network parameter .…”

Section: Reduced-order Model Of the Coupled-oscillator Systemmentioning

confidence: 99%

“…They enable the implementation of comb generators [3], [4] providing harmonic signals spanning through a broad spectrum, often used for the calibration of test sites and instruments [4]. In addition, several impulse-radio ultrawideband transmitters at pulse repetition rates above 1 Gb/s have been reported in the literature [5], [6], with monocycle pulses having the advantage of containing less power in the dc and low-frequency bands that cannot be radiated through antenna [7], [8]. The pulse shaping can be achieved using nonlinear transmission lines (NLTL) [9]- [11], which are composed by inductor-varactor cells, where the capacitance decreases with increasing voltage .…”

Section: Introductionmentioning

confidence: 99%

Analysis of Two Coupled NLTL-Based Oscillators

Pontón

Suárez

2014

IEEE Trans. Microwave Theory Techn.

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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.Index Terms-Nonlinear transmission line (NLTL), oscillator, phase noise, stability. 0018-9480

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“…With a desired value of better than -10dB for good matching, the S 11 is between5dB and -10dB for most of the frequency band of interest. A second revision pulse generator has been designed to improve the performance of the first design [8]. The main operational components and features of the second generation pulse generator design are: -Very High bandwidth and slew-rate op-amp (THS3091) is used to convert the voltage swing from 0 to 5V to -5Vto+5V.…”

Section: Prototype Module Developmentmentioning

confidence: 99%

Compact programmable ground-penetrating radar system for roadway and bridge deck characterization

Busuioc¹,

Xia

Venkatachalam

et al. 2011

SPIE Proceedings

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A compact, high-performance, programmable Ground Penetrating Radar (GPR) system is described based on an impulse generator transmitter, a full waveform sampling single shot receiver, and high directivity antennas.The digital programmable pulse generator is developed for the transmitter circuit and both the pulse width and pulse shape are tunable to adjust for different modes of operation. It utilizes a step-recovery diode (SRD) and short-circuited microstrip lines to produce sub-nanosecond wide ultra-wideband (UWB) pulses. Sharp step signals are generated by periodic clock signals that are connected to the SRD's input node. Up to four variable width pulses (0.8, 1.0, 1.5, and 2.1 ns) are generated through a number of PIN switches controlling the selection of different microstrip lengths. A schottky diode is used as a rectifier at the output of the SRD in order to pass only the positive part of the Gaussian pulses while another group of short-circuit microstrips are used to generate amplitude-reversed Gaussian pulses. The addition of the two pulses results in a Gaussian monocycle pulse which is more energy efficient for emission.The pulse generator is connected to a number of UWB antennas. Primarily, a UWB Vivaldi antenna (500 MHz to 5 GHz) is used, but a number of other high-performance GPR-oriented antennas are investigated as well. All have linear phase characteristic, constant phase center, constant polarization and flat gain. A number of methods including resistive loading are used to decrease any resonances due to the antenna structure and unwanted reflections from the ground. The antennas exhibit good gain characteristics in the design bandwidth. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/15/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 7983 79831G-8 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/15/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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A High-Performance Low-Ringing Ultrawideband Monocycle Pulse Generator

Cited by 52 publications

References 14 publications

Two dimensional entropy and short time Fourier Transform application on ground penetrating radar data analysis

Two dimensional entropy and short time Fourier Transform application on ground penetrating radar data analysis

Analysis of Two Coupled NLTL-Based Oscillators

Compact programmable ground-penetrating radar system for roadway and bridge deck characterization

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