This example describes the simulation of a waveguide filter that includes both E- and H-plane cavity-backed inverters in addition to several irises . The basic geometry is shown in CAD format in Figure 1 where the E-plane cavity-backed inverter is above the waveguide and the H-plane cavity-backed inverter is on the back side. The waveguide is WR-90 and the dimensions of the design including the spacing and dimensions of the cavities and irises are easily entered as parameters into the XFdtd model. The structure is meshed with a 0.4 mm base cell size and fixed points are used on all parts to ensure the FDTD grid lines overlap the CAD dimensions.
The input port has a fundamental mode applied as shown in the cut-away mesh view of Figure 2. The frequency for the input excitation is 12 GHz which ensures frequency content in the simulation over the 8 to 12 GHz range of the device. The output for the simulation will be the S-parameters at the input and output ports, some images of the transient electric field propagation though the device, and point sensors of the electric field versus time.
The simulation requires approximately 122 MB of computer memory and runs to -45dB convergence in just over 14 minutes on an NVIDIA C1060 Tesla GPU card.
Following the simulation, the resulting S-parameters at each port, shown in Figure 3, are found to be a good match to the measured values reported in the paper. The transient electric field at an instance in time through the cross-section of the filter is shown in Figure 4. The transient electric field at point locations centered just beside each of the ports is shown in Figure 5.
- Q. F. Zhang and Y. L. Lu, “Design of Wide-Band Pseudo-Elliptic Waveguide Filters With Cavity-Backed Inverters,” IEEE Microw. and Wirel. Comps. Letters, Vol. 20, Nov. 2010, pp. 604-606.