Sedki M. Riad

Path-loss and time dispersion parameters for indoor UWB propagation

The propagation of ultra wideband (UWB) signals in indoor environments is an important issue with significant impacts on the future direction and scope of the UWB technology and its applications. The objective of this work is to obtain a better assessment of the potentials of UWB indoor communications by characterizing the UWB indoor communication channels. Channel characterization refers to extracting the channel parameters from measured data. An indoor UWB measurement campaign is undertaken. Time-domain indoor propagation measurements using pulses with less than 100 ps width are carried out. Typical indoor scenarios, including line-of-sight (LOS), non-line-of-sight (NLOS), room-to-room, within-the-room, and hallways, are considered. Results for indoor propagation measurements are presented for local power delay profiles (local PDP) and small-scale averaged power delay profiles (SSA-PDP). Site-specific trends and general observations are discussed. The results for path-loss exponent and time dispersion parameters are presented.

An optimization technique for iterative frequency-domain deconvolution

A technique for the optimization of the iteration (design) parameter of filters used in frequency-domain iterative deconvolution methods is presented. The technique allows the filter optimization to be performed in the frequency-domain instead of the time domain, which translates into tremendous saving of computation time. The technique provides a quantitative measure of the performance of the filter regarding noise reduction and filtration error. Illustrative examples using computer simulation as well as experimental data are given. The demonstrations show that the technique yields reliable results for the deconvolution of signals in the presence of noise. >

An Optimization Criterion for Iterative Deconvolution

An optimization criterion for the selection of the iteration parameter for the frequency-domain optimal compensation deconvolution is presented. The criterion is designed to minimize the deconvolution results noise content while maintaining its accuracy. Examples are presented to verify the criterion as well as to demonstrate its application.

UWB applications for through-wall detection

Preliminary experimental investigations on the application of UWB electromagnetic signals for through-wall detection are presented. Measurements are conducted using pulses with a full-width half-maximum (FWHM) nearly equal to 85 ps. This corresponds to a spatial resolution of about 26 mm. A simple signal processing approach is also introduced to extract the target image from the reflected fields.

UWB channel impulse response characterization using deconvolution techniques

UWB Channels can be measured by sounding the channel with pulses, and thereby obtain the impulse response. Multipath components have different waveforms depending on the type of transmitter and receiver antennas used and the angles of transmission and reception. A modified deconvolution technique is introduced to extract the UWB channel response. The application of deconvolution techniques results in resolving multipath components with waveforms different from that of the sounding pulse. Resolving more components should improve the design of the rake receiver. Accurate characterization for the impulse response of a UWB communication system facilitates performance evaluation studies such as simulating the effect of pulse shaping.

Filtering capabilities and convergence of the Van-Cittert deconvolution technique

The authors demonstrate the application of the Van-Cittert technique in iterative frequency-domain deconvolution. The technique is shown to have built-in filtering capabilities which can be used successfully to produce optimum deconvolution estimates. The Bennia-Riad optimization criterion for iterative deconvolution is jointly used with the Van-Cittert technique to optimize the number of iterations required to achieve acceptable (optimum) deconvolution results. An experimental example is provided to illustrate the application of the deconvolution technique and the optimization criterion. >

Ultra wideband material characterization for indoor propagation

The information on electromagnetic properties of building materials in the ultra wideband (UWB) frequency range provides valuable insights in assessing the capabilities and limitations of UWB technology. This research examines propagation through typical construction materials and their ultra wideband characterization. Ten commonly used construction materials are chosen for this investigation. Results for the insertion loss and the dielectric constant of each material over a frequency range of 0.5 to 15 GHz are presented.

Study and Performance Evaluation of Two Iterative Frequency-Domain Deconvolution Techniques

The performance of two iterative frequency-domain deconvolution techniques, the optimum compensation and the Guillaume-Nahman, is evaluated. The study involved the characterization of the adaptive filters utilized to reduce the deconvolution noise. Comparisons between the two techniques are performed for various classes of signals having different levels of acquisition noise. It is found that the Guillaume-Nahman technique is potentially more accurate but more sensitive to acquisition noise. It is also found that the optimum compensation deconvolution technique uses an adaptive filtet with the passbands coinciding with the frequency bands of the signal, thus optimizing noise filtration, while the Guillaume-Nahman technique utilizes a low-pass filter for all signals.

Modeling of the HP-1430A feedthrough wide-band (28-ps) sampling head

The theory and construction of the HP-1430A feed-through sampling head are reviewed, and a model for the sampling head is developed from dimensional and electrical measurements in conjunction with electromagnetic, electronic, and network theory. The model was used to predict the sampling-head step response needed for the deconvolution of true input waveforms. The dependence of the sampling-head step response on the sampling diode bias is investigated. Calculations based on the model predict step response transition durations of 27.5 to 30.5 ps for diode reverse bias values of -1.76 to -1.63 V.

Computing the complete fft of a step-like waveform

Methods for duration limiting a step-like waveform for fast Fourier transform (FFT) computation are surveyed and discussed, and a complete FFT method is introduced. The complete FFT has an enhanced resolution, and is complete in the sense that it has uniformly spaced DC and harmonic components.