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RF Electronics Chapter4: Transmission Line Transformers and Hybrids Page 70 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. If internet speeds to the AWR DE website are too slow, local vendor libraries need to be installed and used. The Appendix shows how these can be installed. Then simply select the Library parts and footprints from the local libraries instead of the web site. The rest of the PCB schematic can now be made. The 70.71 Microstrip lines are made using MLIN elements. The two 70.71 lines need to be joined to the 50 line, using a MTEE. There are different versions of this. The most basic one is MTEE, where every connecting line width needs to be specified. MTEE$ is an intelligent version, which automatically uses the line widths of the connecting lines. MTEEX is an EM based model of the junction and is more accurate. MTEEX$ is the corresponding intelligent version of this and this element is used in the circuit. To get the most accurate results, EM based models should be used whenever possible. Figure 4.9. Schematics for Wilkinson hybrid PCB layout, using TLIN (Left) and MCLin (Right). To enable the SMD resistor to be incorporated as shown in figure 4.10, the two 70.71 lines are separated by more than 4 mm. That also keeps the coupling between the lines small. This is achieved by using the two 90 degree bends with 2 mm radius each. In Circuit Elements Microstrip Bends, there are 4 different versions of curved bends. Since an intelligent MTEEX$ is used, the width of the curved track should be specified. The MCURVE2 element uses EM mode matching and is the most accurate, but will take longer to be evaluated. The length of the 70.71 lines, TL1 and TL2, is made variable, to allow the hybrid to be tuned to the correct centre frequency. Two more MTEEX$ elements are used to allow the resistor to be connected correctly. Two small lines, TL13 and TL14, with a suitable width to allow the isolation resistor R1 to be soldered to it are connected to the MTEEX$ elements. Three 10mm long tracks, TL7, TL11 and TL12 are used, to allow connections to be made to the circuit. Figure 4.10. PCB layout of a Wilkinson hybrid. The PCB layout of the circuit can be seen by selecting View View Layout. To connect all the lines together, select Edit Select All (or Ctrl A) and then select Edit Snap Together. That will snap all the elements together. Check that there are no red crosses on the layout, which indicate that the elements are not properly connected together. If that is the case, change line lengths such as L2 for TL13 and TL14 to ensure that the layout fits RF Electronics: Design and Simulation 70 www.cadence.com/go/awr

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