VHF / UHF Filters and Multicouplers: Application of Air Resonators

Chapter 10

Helical Resonators

10.1. Introduction

The radio-communications industry, under an impressive pace of development, is at the same time the creator and the requestor of new technologies. Now, those discussed in this work, besides the fact that they are not new, are not taught in their technological details in traditional courses, and the acquisition of this knowledge in the profession demands such a considerable time that little is left for research. Consequently, this is not a field where we expect to see shattering discoveries, to the point that we often have the feeling that everything that was to be found has already been so. This is an additional reason to try to become familiar with it, if not completely, then at least in the fundamental aspects of the tools it makes available to us.

Straight quarter- or half-wave resonators constitute the basis of highperformance filtering products. Their geometrical simplicity leads to simplicity in the modeling that has allowed an exhaustive theoretical study and made it a reference in the study of resonant TEM-mode systems. We can say the same thing about the planar circuits or microstrips that are added to them, without creating competition, but that benefit with respect to them from particular perspectives essentially related to the discovery and development of new substrates. Besides these two essential families, there exist other less conventional objects that could nevertheless prove to be of great utility, such as for example ...