Substrate Integrated Waveguide Diplexer Design

Substrate Integrated Waveguide Diplexer Design

DOI: 10.4018/978-1-7998-2084-0.ch006

Abstract

This chapter implements the microwave diplexer circuit model established in Chapter 4, using the twenty-first substrate integrated waveguide transmission line technology. No separate junction (resonant or non-resonant) was utilised in achieving the diplexer, as the use of an external junction for energy distribution in a diplexer normally increases design complexity and lead to a bulky device. The design also featured a novel input/output coupling technique at the transmit and the receive sides of the diplexer. The proposed SIW diplexer has been simulated using the full-wave finite element method (FEM), Keysight electromagnetic professional (EMPro) 3D simulator. The design has also been validated experimentally and results presented. Simulated and measured results show good agreement. The measured minimum insertion loss achieved on the transmit and the receive channels of the diplexer are 2.86 dB and 2.91 dB, respectively. The measured band isolation between the two channels is better than 50 dB.
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Introduction

In this chapter, the 10-pole (10th order) microwave diplexer circuit model established in Chapter 4, is being implemented based on the twenty-first substrate integrated waveguide transmission line technology. A brief review of literatures that have reported diplexers based on the SIW technique have been covered in Chapter 1. No separate junction (resonant or non-resonant) was utilised in achieving the diplexer, as the use of an external junction for energy distribution in a diplexer normally increases design complexity and lead to a bulky device. The design also featured a novel input/output coupling technique at the transmit and the receive sides of the diplexer. The proposed SIW diplexer has been simulated using the full-wave finite element method (FEM), Keysight electromagnetic professional (EMPro) 3D simulator. The design has also been validated experimentally and results presented. Simulated and measured results show good agreement. The measured minimum insertion loss achieved on the transmit and the receive channels of the diplexer are 2.86 dB and 2.91 dB, respectively. The measured band isolation between the two channels is better than 50 dB.

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.

978-1-7998-2084-0.ch006.m01
(1a)
978-1-7998-2084-0.ch006.m02
(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
Cavityf (GHz)d (mm)p (mm)w (mm)l (mm)
Tx1.7882.03.72537.2537.25
Rx1.9172.03.49034.9034.90
ED1.8492.03.60936.0936.09
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

978-1-7998-2084-0.ch006.f01

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