Seite - 26 - in Adaptive and Intelligent Temperature Control of Microwave Heating Systems with Multiple Sources

2. IntroductionofHEPHAISTOS Waveguide The role of waveguides is to transmit the electromagnetic wave from one point to another. In the microwave heating system, it is used to propagate microwaves from the generator to the microwave cavity. Thewaveguideis importantforthewholemicrowaveheatingsystem, because it directly determines how much power can be fed to the mi- crowave cavity. There are a variety of different types of waveguides, such as dielectric waveguides, coaxial cables, microstrips or hollow metal pipes [HB01]. Hollow metal pipes are the most common one used atmicrowavefrequencies, suchas infigure 2.11. Figure 2.11. Hollow metal waveguides [web]. 26 In HEPHAISTOS, there are two types of waveguides used. One is the WR-340 waveguide, which is a rectangular hollow metal waveg- uideusedtotransmitmicrowavesrangingfrom2.20GHzto3.30GHz [BBG+03] (as in figure 2.12a). The other one is the slotted waveg- uide, which acts as an antenna and omits the microwave to the exter- nal space [ST12] (such as shown in figure 2.12b). Each magnetron is directly mounted with a WR-340 waveguide, and every WR-340 waveguide is further connected to a slotted waveguide. The mi- crowaves are transmitted from the microwave generator to the slot- ted waveguide via the WR-340 waveguide, and then directly radi- atedintothemicrowavecavitythrough the slots of the slotted wave-