Antenna impedance matching; two graphical methods of computation

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1967

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Abstract

In a communication system the impedance of the load is generally matched to that of the source in order to obtain the greatest power from the available equipment. The efficiency of power transfer is then only 50 per cent, but the total amount of power is comparatively small, and so the price paid for the higher output is not too great. It was the purpose of the study described in this thesis to develop two graphical methods for matching impedances. The method presented in Part I deals with networks used for matching purposes; where the graph involved yields the values of the elements of the Pi, T or L network used, the phase shift and the necessary data to compute the efficiency of the circuit. The method described in Part II deals with the practical task of matching an antenna to its feed line using a stub in parallel with the antenna. The graph involved shows when such an arrangement is possible, giving the data required for dimensioning the antenna and the matching stub. Both methods are developed by starting from elementary concepts, and both are based on impedance plots in the complex plane, such that they show intuitively the behavior of the circuit considered, making possible the design without the use of special charts. Part I as well as Part II are divided into three chapters. One chapter presents an introduction, a second chapter develops the theory of the proposed method, while a final chapter contains typical examples pointing out the design steps required.

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