HF Radio Systems & Circuits
Written for the engineer working in radio communications, regardless of frequency, this comprehensive reference book explains the design of high frequency communications systems and equipment.
TABLE OF CONTENTS HF Radio Systems & Circuits
Chapter 15: Antenna Matching Techniques
Glenn R. Snider
The role of the antenna coupler is to provide an impedance matching function in either of two ways: narrowband or broadband. With narrowband matching a near perfect impedance match is achieved at a single frequency. With broadband matching a less than perfect impedance match is accepted in order to get an optimal match over a broad range of frequencies.
Section 15.1 presents the current techniques used for narrowband antenna couplers. Included is the basic approach to be followed, some of the pitfalls, and general engineering advice. It is assumed that the reader has a computer at his/her disposal. Section 15.2 considers broadband matching of antennas in applications where it is advantageous.
15.1 Narrowband Antenna Couplers
The discussion of narrowband couplers will be subdivided into three topics: R/ X plane, two examples, and control techniques. The R/ X plane is a very useful graphical representation of how individual RF elements affect the input impedance of a coupler. By visualizing the loci of points on a graph with axes of resistive and reactive impedances, one can determine which RF network to choose, as well as how to automatically position the elements to the tune point. Two antenna coupler designs, shunt and whip, will demonstrate the practical application of the R/ X plane graph and provide general information for the construction and specification of the RF elements. The last subdivision will deal with impedance measuring devices and the methods used to automatically control the...
Copyright Noble Publishing Corporation 1998 under license agreement with Books24x7
