In this chapter, a novel method of designing a microwave diplexer circuit is presented. This technique involves merging a section of a dual-band bandpass filter (DBF) with a section of two separately designed bandpass filters (BPFs). The chapter covers the step-by-step procedures that informed the successful realization of the diplexer circuit model. The circuit model coupling arrangement, simulation, and results are also covered. The diplexer circuit developed here has been simulated using the Keysight ADS circuit simulator. The results presented show a very good isolation between the transmit and the receive bands of the diplexer circuit.
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Some of the different techniques employed in the design of diplexer circuit have been covered in chapter 1. In this chapter, a novel method of designing a microwave diplexer circuit is presented. This technique involves merging a section of a dual-band bandpass filter (DBF) with a section of two separately designed bandpass filters (BPFs). The chapter covers the step-by-step procedures that informed the successful realization of the diplexer circuit model. The circuit model coupling arrangement, simulation and results are also covered. The diplexer circuit developed here has been simulated using the Keysight ADS circuit simulator. The results presented show a very good isolation between the transmit and the receive bands of the diplexer circuit.
Conventional diplexer circuit design techniques usually involve the use of a non-resonant external junction to distribute energy to and from the transmit and the receive bands. The non-resonant external junction is sometimes a T-junction (Liu et al., 2013), or a Y-junction (Bastioli et al., 2009), or a circulator (Kodera & Caloz, 2010), or a manifold (Guglielmi, 1993), or even a common resonator (Yang & Rebeiz, 2013). The diplexer circuit reported in this chapter does not involve any non-resonant external junction, as each resonator contributes a pole to the diplexer circuit response. Figure 1 shows three diplexer circuit arrangements. Looking and Figure 1 (a) and (b), it is obvious that the non-resonant T-junction and the common out of band resonator would certainly add to the size of the diplexer. However, looking at Figure 1 (c), it is clear that the absence of neither the non-resonant external junction nor the common out of band resonator means reduced size and even simpler circuit. The diplexer circuit arrangement of Figure 1 (c) is less complex, as the continues adjustment requirements of the external junction is absent.
Figure 1. Diplexer circuit arrangements, (a) with a non-resonant external T-junction, (b) with a non-resonant external common resonator, (c) without any non-resonant external junction