J.L. Garcia

New channel impulse response model for UWB indoor system simulations

This paper provides the description and results of a recently developed statistical UWB multipath channel model. A new set of statistical parameters has been defined and obtained from a large measurement campaign process. The parameter values, a detailed model description and final results, are covered in this contribution.

A Simple Approach to a Statistical Path Loss Model for Indoor Communications

Path-loss in indoor environments is investigated at 1.8 GHz, using a power-law model where the exponent of the distance is the descriptive random variable. The model is extremely simple and easily applicable in practice by working engieers who need only make a few measurements to get a knowledge of path loss sufficient for many applications. The model fits well experimental data in various environments under different propagation conditions, including cross polarization, and the observed behavior of the exponent suggests the possibility of using only one distribution function to statistically characterize path loss.

Channel modeling and characterization at 17 GHz for indoor broadband WLAN

This paper provides the results of a complete study about the indoor radio propagation channel at 17 GHz. Wideband parameters, as coherence bandwidth or rms delay spread, and coverage are analyzed for the design of an OFDM-based broadband WLAN. A discussion of some adequate system parameters is also included. The report presents the characterization results as well as a previously developed indoor channel model; both of them have been checked and compared to bibliography results in order to verify their reliability.

Ultra wideband channel model for indoor environments

This paper presents an in-depth study of a UWB indoor radio channel between 1 and 9 GHz, which was used for the subsequent development of a new statistical UWB multipath channel model, focusing on short range indoor scenarios. The channel sounding process was carried out covering different indoor environments, such as laboratories, halls or corridors. A combination of new and traditional parameters has been used to accurately model the channel impulse response in order to perform a precise temporal estimation of the received pulse shape. This model is designed specifically for UWB digital systems, where the received pulse is correlated with an estimated replica of itself. The precision of the model has been verified through the comparison with measured data from equivalent scenarios and cases, and highly satisfactory results were obtained.

Modal Analysis of Discontinuities in Planar Transmission Lines: using Orthogonality as the Criterion for Selecting Modes

The technique of modal analysis has been used together with the spectral domain approach (SDA) to analyze single and cascaded step discontinuities in planar transmission lines, particularly in boxed microstrip and finlines. These kinds of discontinuities appear frequently in MICs and MMICs. Convergence was studied as a function of the number of modes (propagating, evanescent and complex modes) in order to determine the scattering matrix parameters and represent each component of the fundamental mode on each side of the discontinuity. This study showed that these sets of modes may be non-orthogonal and, consequently, a selection of modes based on orthogonality is made. Finline and microstrip discontinuities have been studied with this criterion. It is possible to obtain good convergence and satisfactory behavior of the components of the fields if the number of modes used is sufficient and if they form a complete set.

Study of a Low-Pass Filter in Microstrip Line Applying Modal Analysis in the Spectral Domain

An abrupt change in microstrip linewidth, commonly called a microstrip impedance step, is a discontinuity that appears frequently in MMICs, such as, stepped impedance transformers and matching networks for example. Therefore, the accurate description of these step-discontinuties is important for the computer-aided design of conventional and monolithic MICs. In this work we have studied the set of modes that appears in a boxed microstrip in order to apply modal analysis in the spectral domain to the study of simple and cascaded step discontinuities. In order to check its precision, our method has been applied to a nine section low-pass filter, made up of a cascade of microstrip step discontinuities. Several filters have been designed, built and tested at different frequencies. We have compared these designs with Touchstone and shown that at low frequencies both methods give similar results, but when the frequency is higher, the Touchstone results are farther from the experimental results than the design obtained with the modal analysis method.

Optimizing VTO-MESFET at Microwave Frequencies

This paper present a method of multiharmonic optimization to varactor tuned oscillators (VTO). For this purpose we have developed a formulation in matrix form based on an analytical gradient algorithm. After this study, we have made a small signal analysis of a VTO and, with this starting point, we have optimized and compared with the experimental results.