Book

Broadband
Direct-Coupled and Matching
RF Networks

This practical guide is for engineers and technicians who design RF networks that filter and match impedances over wide bands or match at a just one frequency. The networks may consist of L's, C's, open- and short-circuited stubs and cascade transmission lines, and transformers. New techniques are described clearly and at a level between seminars and graduate-level instruction.

Direct-coupled filters consist of parallel (or all series) resonators coupled by reactive subnetworks and are found in many forms in all frequency bands. Simple couplings are combinations of L's and/or C's to provide all-pole or elliptic response shapes over any band width. Until now, direct-coupled filters were limited to narrow passband widths. Now broadband design is easy in terms of the loaded Q's of resonators. A wide range of positive element values is always available, with automatic adjustment of design parameters to useful criteria simplified by spreadsheet optimizers.

The grid approach to broadband impedance matching (GRABIM) maximizes or shapes power transfer between source and load described only by discrete-frequency impedance data. It reliably locates the neighborhood of the likely global solution by an efficient grid search based on knowing each benign reflection function versus element parameters. Then, a minimax-constrained gradient optimization precisely locates the solution while pruning any unnecessary elements from candidate networks. GRABIM replaces sophisticated polynomial mathematics by optimization with assured outcome.