1.1 Background

The transmission of electrical energy via wires or cables has been of importance almost since the discovery of electricity itself. The transition from direct current (d.c.) to alternating current (a.c.) usage, and thence to the utilization of higher and higher frequencies, soon necessitated the development of some form of screened transmission line in order to prevent both excessive loss of energy via radiation and resultant interference with other circuits.

These requirements led, ultimately, to the introduction and widespread adoption of the now almost universal coaxial cable, which is as familiar to the "average householder" (in connection with his television) as to the expert microwave engineer.

However, the rapidly increasing demands of modern technology, particularly in such areas as telecommunications, satellites, electronic warfare, and computers, have led to the introduction of many other forms of transmission lines. Some are almost as adaptable as the ubiquitous "coax," whereas others are suitable only for certain rather specialized applications. The one common factor is that before any of these lines can usefully be incorporated into circuit designs, it is necessary to be able to calculate their impedance parameters. These are defined in Section 1.5, and the bulk of this book consists of formulae, tabulations, and graphs of these various impedances for most of the transmission-line configurations currently used in microwave and related technologies.

As mentioned in the Preface, much of the information to be presented has hitherto been available only in articles and papers widely scattered among the technical literature, and it...