SIW Cavity
An overview on the SIW technology has been covered in Chapter 2. To proceed with the implementation of the SIW diplexer, three separate SIW cavities (i.e. resonators), were designed to resonate at the centre frequencies of the transmit (Tx), the receive (Rx), and the energy distributor (ED) component filters. As explained in Chapter 4; Tx, Rx, and ED correspond to the BPF1, the BPF2, and the DBF resonators, respectively. Using Eqn. (1) (Han et al., 2007; Nwajana, Yeo, Dainkeh, 2016); the Tx, the Rx and the ED cavities were designed to resonate at 1.788 GHz, 1.917 GHz, and 1.849 GHz, respectively.
(1a)(1b)The design was fabricated on a Rogers RT/Duroid 6010LM substrate with relative permittivity ɛr = 10.8, substrate thickness h = 1.27 mm and relative permeability µr = 1. The physical design parameters for the three SIW cavities are given in Table 1; where f is the fundamental resonant frequency of each cavity, d is the diameter of each metallic post (also known as via diameter), p is the distance between adjacent metallic posts (also popularly known as the pitch), w is the width of the SIW cavity, and l is the length of the SIW cavity. A full-wave simulation layout and the results, using Keysight EMPro FEM, for the Tx, Rx and ED cavities is shown in Figure 1, where fTx, fRx and fED are the fundamental resonant frequencies for the Tx, Rx and ED cavities, respectively.
Table 1.
Physical design parameters for the substrate integrated waveguide diplexer component filters cavities
Cavity | f (GHz) | d (mm) | p (mm) | w (mm) | l (mm) |
Tx | 1.788 | 2.0 | 3.725 | 37.25 | 37.25 |
Rx | 1.917 | 2.0 | 3.490 | 34.90 | 34.90 |
ED | 1.849 | 2.0 | 3.609 | 36.09 | 36.09 |
Figure 1. Full-wave simulation layout and the results for the Tx, the Rx, and the ED substrate integrated waveguide cavities at their respective fundamental resonant frequencies