Historically, an introduction of bandpass electrical filters invented independently by Karl W. Wagner and George A. Campbell played a vital role in their successful development in high-frequency wireless telegraphy, wireless telephony, or multiplex wire telephony transmitting systems when a maximum number of channels could simultaneously operate on a given circuit with a minimum frequency interval between adjacent channels [1,2]. In addition to separating the various channels from each other in multiplex line, it was found convenient from an operating standpoint to separate, within the toll offices, the carrier frequencies as a group (using a high-pass filter) from the frequencies intended for ordinary telephony and telegraphy (using a low-pass filter), and transmit them by separate lines [3].

This chapter discusses the basic types of radio frequency (RF) and microwave filters based on the low-pass or high-pass sections, and bandpass or bandstop transformation. Classical filter design approaches, using image parameter and insertion loss methods, are given for low-pass and high-pass LC filter implementations. The quarterwave-line and coupled-line section, which are the basic elements of microwave transmission-line filters, are described and analyzed. Different examples of coupled-line filters including interdigital, combline, and hairpin bandpass filters are given. Special attention is paid to microstrip filters with unequal phase velocities that can provide unexpected ...

Get RF and Microwave Transmitter Design now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.