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I'm trying to integrate a breakout board circuit from SparkFun into my own design. It uses an external coax antenna with a SMA connector. I've brought their circuit over in its entirety, and from a hookup standpoint, it's identical. I'm worried about routing the antenna input to the GPS chip in my circuit though, as I have servos on the same board. Are there any rules of thumb to follow here? It'll be hard to see, but here's a picture of the layout, with the current GPS line highlighted:

enter image description here

GPS datasheet: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/GPS/Venus/638/doc/Venus638FLPx_DS_v07.pdf

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GPS (or any radio) RF trace to the antenna should not go across the whole board because of the interference, as it appears in your design. Some common sense suggestions are:

  • Place the gps chip to the antenna connector as close as possible to shorten the route.
  • Avoid placing other components and even other traces near the antenna trace, this includes the other side of the board.
  • Make sure the impedance of the route matches the requirements for the chip and the design (for example, 50ohms). This depends on the material and thickness of the board and width of the trace. There are trace impedance calculators online, for example, the calculator at eeweb.com

In my opinion you should either use the SparkFun board that is properly tuned and tested, or transfer it completely, including the connector, and choose a PCB material that is similar if not exactly like the SparkFun board.

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