E.A. Hosny

Nonlinear system and subsystem modeling in time domain

Nonlinear models of microwave subsystems are identified from time domain measurements. Scattering functions in the form of nonlinear time domain functions are used to derive a system identification model instead of an equivalent circuit. The advantage being the simplicity of the measurement and the developed models and the speed and accuracy of the simulation of the entire system.

Time domain measurement and identification of microwave systems

Models of non-linear subsystems are idenfied from time domain measurements. Each subsystem is identitied separately and then the overall system is analysed using the identified models. The models are not based on equivalent circuits and this offers flexibiliy and saving in the amount of data stored for each model. The method also offer considerable saving in simulation time.

Chaotic Behaviour of Gunn Oscillators

The purpose of this paper is to demonstrate that chaotic behaviour can occur in practical microwave non-linear circuits and to present methods of analysis that can predict such behaviour. Theoretical and practical results are presented for Gunn diode oscillators. The methods of analysis presented help the designer to understand the behaviour and to design chaos free oscillators.

Chaos in Microwave Systems

The presentation reviews microwave circuits that exhibit chaotic behaviour and will emphasise the need for microwave designers to examine the possibility of circuits becoming chaotic. The paper gives the basic analysis tools for examining the stability of microwave circuits and several examples reported in the literature will be presented.

Non-linear system and subsystem modelling in the time domain

This work describes how non-linear subsystems can be modelled from time domain measurements. The advantage being the simplicity of the measurement and the developed models and the speed of the simulation of the entire system.

Simulation of nonlinear and anisotropic structures in 3D TLM

The Transmission Line Matrix (TLM) method has been modified to include structures that are nonlinear, anisotropic or both. The new development offers the possibility of solving a wide range of problems which include nonlinear dielectric, ferrites, plasma and semiconductor regions.

The Time and Frequency Domain Analysis and Synthesis of Distributed and Lumped/Distributed Networks

Using state-space techniques, a method has been developed for the computer-aided analysis and synthesis of networks containing both lumped and distributed elements. The method is very powerful as it can deal with any network topology and the same basic equations can be used in either the frequency or time domains. The method does not require the application of the Fast Fourier Transform which is not suitable for lumped/distributed networks since the frequency response is neither periodic nor monotonically decreasing. Computer-aided procedures based on this method have been developed and several examples of time and frequency domain analysis and design are given.

Analysis of chaotic behaviour in lumped-distributed circuits applied to practical microwave oscillators

A general method for the analysis of pre-chaotic and chaotic behaviours in lumped-distributed circuits has been developed. Examples of practical microwave oscillators, namely Gunn and IMPATT oscillators were designed. The simulation and measurement results showed that these oscillators possess regions of periodic, quasi-periodic, and chaotic spectra. The method could be used by circuit designers to design chaos free oscillators.<<ETX>>

A family of modular fully differential witched capacitor filters for simulating ladder filters

The switched capacitor filters proposed in this paper are based on the simulation of LC ladder filters through the state variable equations. They include all-pole and finite transmission zero, lowpass filters, bandpass and highpass filters. The introduced family of filters has a fully differential structure; consequently it has the advantages of improved power supply and common mode rejection ratios and extended dynamic range. Since the proposed family of filters simulates LC ladder filters, it inherits their low passband sensitivities. One of the main advantages of this family of filters is that it has a modular structure composed of key and auxiliary circuits. This modular structure results in easier design and implementation procedures in VLSI fabrication. The double-sampling concept is applied to the introduced modular blocks, which is essentially needed in high-frequency applications. A comparison with similar published work available in the literature is presented and illustrative examples are given.

Calculating the impedance of patch antennas using TLM

The 3-D transmission line matrix (TLM) method is used to calculate the input impedance of patch antennas. The feed line to the antenna is simulated using a TEM line consisting of two electric and two magnetic walls. This simulation has the advantages of matching to the input microstrip and of having a known reference impedance. These two advantages makes accurate calculation of the input impedance possible. The results were compared to previously published measured data.