The Design of Frequency-Compensating Matching Sections

Frequency-compensating networks have been employed to improve the impedance bandwidth of antennas and other radio-frequency components. The general problem considered here is that of transforming an impedance which changes with frequency to a specified resistance which is, as nearly as possible, constant with frequency. A simple procedure for solving the general problem is established, and formulas for the design of the appropriate matching section are worked out. The formulas give the parameters of the matching section in terms of the impedance of the load at selected frequencies. The technique is mainly applicable where the half bandwidth is small compared with the center frequency. For the purpose of illustration, the method is described in terms of its application to coaxial lines, although it is equally applicable to any form of transmission line whose characteristic impedance is known.