This work provides computer-aided design solution to single-band and dual-band design of Rat-Race Coupler (RRC) (i.e., 0 and 180 deg coupler) and Gysel Power Divider (GPD). The 180 deg phase shifters are designed using C-section, Pi-structure and T-structure. How to use Rat-race Coupler and Gysel Power Divider Designer: Download GPD_and_RRRC_Application_1.2.zip Extract the zip file. Open the main.exe file in Windows 11 Maximize the window. Display resolution 1200X600 or more is preferred. Users can switch between Power Divider and Coupler. At first, select the band: Single-Band/Dual-Band. Select PS: C-Section/Pi-Section/T-Section/TL-Section Enter f0, n, phi and TLip: Ch imp/ El len for single band design. Then, enter Z_beta or theta_beta and other parameters. Enter f1,f2, n1,n2 for dual-band design. Press the Design button to get the design schematic—Double-click on the schematic window to get the popup schematic window. Press the analysis button to get the S-parameters results. Users can switch the excitation port and Response type. Open YouTube video tutorial for more help: https://www.youtube.com/watch?v=3-lx_Ohci0c For additional queries, write to r.sinha30@gmail.com Video tutorial: Single/ Dual band Rat-race Coupler and Gysel Power Divider with unequal power division ratio (youtube.com)