8.1 DR Mounted on Microstrip

The use of dielectric resonators in microwave circuits necessitates accurate knowledge of the coupling between the resonator and the microwave circuits (lines, waveguides, loops, etc.) and also of the mutual coupling between two adjacent dielectric resonators. In this chapter we study these two kinds of coupling successively.

We start with a discussion of coupling of the TE _{01 ?} mode in the dielectric cylindrical resonator with a microstrip line. It is well known that the TE _{01 ?} mode in the dielectric resonator can be approximated by a magnetic dipole of moment M [1]. The coupling between the line and the resonator is accomplished by orienting the magnetic moment of the resonator perpendicular to the microstrip plane so that the magnetic lines of the resonator link with those of the microstrip line [2,3,4], as shown in Fig. 8.1.

Figure 8.1: Coupling between a microstrip line and a dielectric resonator

The dielectric resonator placed adjacent to the microstrip line operates like a reaction cavity which reflects the RF energy at the resonant frequency. The equivalent circuit of the resonator coupled to the microstrip line is shown in Fig. 8.2, [5], [6]. In this figure, L _r, C _r, R _r are the equivalent parameters of the dielectric resonator, L ₁, C ₁, R ₁ those of the line. The magnetic coupling is characterized by the mutual inductance L _m.

Figure 8.2: Equivalent circuit of the...