Satilmis Topcu

Piecewise linear asymptotic waveform evaluation for transient simulation of electronic circuits

A general purpose circuit simulation program, PL-AWE (piecewise linear asymptotic waveform evaluator) is developed especially for the analysis of VLSI circuits. PL-AWE uses the asymptotic waveform evaluation (AWE) technique, which is a new method to analyze linear(ized) circuits, and piecewise-linear (PL) models to represent nonlinear elements. AWE employs a form of Pade approximation rather than numerical integration to approximate the behavior of linear(ized) circuits in either the time or the frequency domain. The authors discuss the internal workings of the program, and indicate its effectiveness in terms of several illustrative examples.<<ETX>>

A new approach to diffraction modelling for line-of-sight (LOS) paths

In this paper, we present a new knife-edge diffraction method based on Bullington method for the terrestrial line-of-sight (LOS) paths. The diffraction loss of our new knife-edge diffraction method is compared with the results obtained from the Delta-Bullington method and the measurement data existing in the literature for sample fixed terrestrial microwave line-of-sight (LOS)/ non line-of-sight (NLOS) radio links. The revised Bullington method is shown to perform significantly better than the Delta-Bullington method for both overland and coastal/overwater radio links.

A novel algorithm for DC analysis of piecewise-linear circuits: popcorn

A fast and convergent iteration method for piecewise-linear analysis of nonlinear resistive circuits is presented. Most of the existing algorithms are applicable only to a limited class of circuits. In general, they are either not convergent or too slow for large circuits. The new algorithm presented in the paper is much more efficient than the existing ones and can be applied to any piecewise-linear circuit. It is based on the piecewise-linear version of the Newton-Raphson algorithm. As opposed to the Newton-Raphson method, the new algorithm is globally convergent from an arbitrary starting point. It is simple to understand and it can be easily programmed. Some numerical examples are given in order to demonstrate the effectiveness of the proposed algorithm in terms of the amount of computation. >

Multipath fading effect on terrestrial microwave LOS radio links

In this paper, the calculation of both the total received power with the effect of the ground reflection and the fade margin to find out the link availability for terrestrial microwave LOS (line-of-sight) radio links is proposed. The expressions are derived from clear-air, rainfall propagation mechanisms and multipath fading due to multipath arising from surface reflection along the defined microwave LOS radio link. We verify the mathematical model by using the ATDI ICS telecom software over sample microwave LOS radio links located in Turkey.

The effect of terrain roughness in the microwave line-of-sight multipath fading estimation based on Rec. ITU-R P.530-15

Multipath fading is an important constraint on the prediction of path loss for terrestrial line-of-sight microwave links. The International Telecommunication Union - Radiocommunication (ITU-R) Rec. P.530 [1] is one of the most widely used methods providing guidelines for the design of terrestrial line-of-sight links. The purpose of the study presented in this paper is to make an investigation of the effect of both terrain roughness and geoclimatic factor parameters in the path loss characteristics of microwave line-of-sight (LOS) propagation in NATO Band 3+ (1350-2690 MHz) and NATO Band 4 (4440-5000 MHz) frequency ranges. The two parameters led to significantly different results for the link availability due to multipath fading as a function of the fade margin.

A GIS-Aided Frequency Planning Tool for Terrestrial Broadcasting and Land Mobile Services

Radio provides an important technology for emergency preparedness and emergency response. It not only offers rapid communication for emergency workers within the disaster area, but also affords the means of disseminating early warning of disasters and advice on how to respond to the public, and a means of monitoring of events and follow-up work in the wake of a disaster. Effective telecommunications are thus a vital part of emergency planning and response (Cate 1994, DHA 1995, Mulilis 1995, Zimmerman 1997). How well radio-based systems work, however, depends on a range of factors, including their geographic coverage, their population coverage, their field strength and their received power level. All these factors are highly dependent upon terrain. Moreover, due to the growing demands on the radio-frequency spectrum, there is a need to improve spectrum management techniques. The increase in the shared use of spectrum among administrations requires the use of more complex analysis methods. The efficient solution of spectrum managementproblems depends upon data storage and analysis capabilities, andconsequently requires the application of computer-aided techniques for data management and frequency assignment.

Computer aided frequency planning for the radio and TV broadcasts

The frequency planning of the VHF and UHF broadcasts in Turkey is described. This planning is done with the aid of computer databases and digital terrain map. The frequency offset is applied whenever applicable to increase the channel capacity. The offset assignment is done through simulated annealing algorithm. The international rules and regulations concerning Turkey are also considered.

Evaluating spatial diversity technique for mitigating multipath fading of fixed terrestrial point-to-point systems

Multipath fading is the dominant propagation factor for fixed terrestrial microwave line-of-sight (LOS) radio links operating at frequencies below 10 GHz. Fading due to multipath propagation attenuates received signals on line-of-sight links and thereby impair the performance of point-to-point systems. Several methods are used to reduce the effects of multipath fading without or with the need for diversity. Antenna spacing in spacing diversity is one of the most effective methods of mitigating multipath fading. This paper provides an evaluation of the concept of two antenna space-diversity configuration for fixed terrestrial microwave line-of-sight radio links. Multipath fading events due to multipath arising from ground reflection points have been analysed along the terrain path profile. A spatial diversity with two antenna configuration in different antenna heights above ground level is simulated over sample fixed terrestrial microwave line-of-sight radio links. The results have been evaluated in terms of the available signal power at the receiver.

Interference analysis of fixed terrestrial microwave LOS/NLOS radio links

In this study, interference modelling is investigated for fixed terrestrial microwave LOS (line-of-sight)/ NLOS (transhorizon) radio links operating in NATO Band 3+ (1350-2690 MHz) and NATO Band 4 (4400-5000 MHz) frequency bands. The calculation of the interference due to both clear-air and hydrometeor scattering interference mechanisms are made for the interfered-with receiver stations of fixed terrestrial point-to-point systems. Moreover, interference propagation mechnasims of the calculation of the clear-air interference basic transmission loss mentioned in the Rec. ITU-R P. 452 are examined. Interference analysis for several microwave radio links are analyzed using the interference propagation parameters such as interfering transmitter and interfered-with receiver station coordinates, antenna heights above ground level, antenna discrimination, polarization, radio refractivity index lapse, sea-level surface refractivity, time percentage for which the calculated basic transmission loss is not exceeded, clutter information, digital terrain elevation and climate data.

Outdoor propagation models: applications and considerations for real life problems

Implementation of propagation prediction models is discussed. It is shown that for real terrain and building data, the additional parameters and assumptions must be made. The determination of coverage percentages for digital communication is discussed. The results indicate that the field strength predictions depend on the implementation of the model.