Transmission line design

For my class project I have to model a design a transmission line connected to a chip capacitor. Where do I start?

Comments

  • rtkrtk Pune, IndiaForum Coordinator

    Hi @prajput ,

    When modeling any design it is imperative to include a simulation of the design and all its discontinuities before prototyping the design. A discontinuity includes the junction between the transmission line and the chip capacitor as well as the landing pads of the chip capacitor where it meets the transmission line. Since you have a chip capacitor you will be designing a microstrip transmission line. If you are designing for 50 ohms make sure that the transmission line has the correct trace width for the PCB you are using. Include the suggested size of the landing pad as provided by the vendor and then include the s parameters for the chip component. 

  • The design frequency is 50 GHz. How do I obtain the correct trace width for the 50 ohm line using FR4?
  • cblaircblair Forum Coordinator
    If the loss tolerance is a critical component of your design, you may want to select a PCB material that may have a tighter loss tolerances at this microwave frequency. With that said it is important to know the effective permittivity that the trace will see as the permittivity above the trace will assumed to be air and the trace at some frequency about 50 GHz in the board dielectric may have a range of frequency dependent values. Knowing these values you can use a transmission line calculator and simulation tool to get the correct trace width.
  • Thank you for your reply. I now have a value for the width of the transmission line. How do I include the chip capacitor in the design?
  • cblaircblair Forum Coordinator
    You can include the chip capacitor response by including the s-parameter or touchstone file including the landing pads.
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