Coupled Resonator Circuits Coupled resonator circuits are of importance for design of RF/microwave filters, in particular the narrow-band bandpass filters that play a significant role in many applications. There is a general technique for designing coupled resonator filters in the sense that it can be applied to any type of resonator despite its physical structure. It has been applied to the design of waveguide filters [1–2], dielectric resonator filters [3], ceramic combline filters [4], microstrip filters [5–7], superconducting filters [8], and micromachined filters [9]. . | Microstrip Filters for RF Microwave Applications. Jia-Sheng Hong M. J. Lancaster Copyright 2001 John Wiley Sons Inc. ISBNs 0-471-38877-7 Hardback 0-471-22161-9 Electronic CHAPTER 8 Coupled Resonator Circuits Coupled resonator circuits are of importance for design of RF microwave filters in particular the narrow-band bandpass filters that play a significant role in many applications. There is a general technique for designing coupled resonator filters in the sense that it can be applied to any type of resonator despite its physical structure. It has been applied to the design of waveguide filters 1-2 dielectric resonator filters 3 ceramic combline filters 4 microstrip filters 5-7 superconducting filters 8 and micromachined filters 9 . This design method is based on coupling coefficients of intercoupled resonators and the external quality factors of the input and output resonators. We actually saw some examples in Chapter 5 when we discussed the design of hairpin-resonator filters and combline filters and we will discuss more applications for designing various filters through the remainder of this book. Since this design technique is so useful and flexible it would be desirable to have a deep understanding not only of its approach but also its theory. For this purpose this chapter will present a comprehensive treatment of the relevant subjects. The general coupling matrix is of importance for representing a wide range of coupled-resonator filter topologies. Section shows how it can be formulated either from a set of loop equations or from a set of node equations. This leads to a very useful formula for analysis and synthesis of coupled-resonator filter circuits in terms of coupling coefficients and external quality factors. Section considers the general theory of couplings in order to establish the relationship between the coupling coefficient and the physical structure of synchronously or asynchronously tuned coupled resonators. Following this a discussion .
