How to Reduce the Challenge of GPS Integration

Have you been tasked with the integration of GPS (or GLONASS) chips into a product or system? If so you will be facing a number of challenges.

  • Selecting which chipset or module to use
  • Ensuring that the tiny RF signals are getting through
  • Evaluating the performance
  • Designing for test and manufacturability whilst providing rapid time to market.

Your first step should be to consider what characteristics you need in your receiver… they are NOT all the same! For example a receiver designed for high accuracy may not be optimised for a rapid start-up. Look at the manufacturers’ datasheets and you will find that they are often difficult to compare using slightly different parameter definitions. Testing the units yourself may be the only way to get a truly accurate and directly comparative set of results and repeated testing under identical test conditions is a job for a GNSS constellation simulator.

Having identified the receiver you wish to use, the next challenge is obtaining the same performance you observed on the evaluation board, but in your circuit. Once again, GNSS simulation provides a controllable, repeatable test. Any issues that arise during this stage can often be resolved by sharing the test scenario with your chosen vendor. Scenarios are portable between Spirent machines so provided your vendor has a Spirent simulator (and most do) problem resolution can be significantly fast.

Finally, you need to define a baseline performance that can be used for manufacturing and regression testing. Once again the control and repeatability aspects of the GNSS simulator are powerful allies in this task.

In summary, if you follow these 3 steps you'll sleep more peacefully:

  1. Choose your vendor after consideration of the cost and performance trade-offs offered. Perform an evaluation yourself. Confirm they use a GNSS simulator so that you can share troublesome scenarios.
  2. Develop your circuit and layout with consideration for RF losses and interference sources. Confirm operation using your GNSS simulator.
  3. Define a baseline performance that should be obtainable in production testing. A controlled, repeatable test using a GNSS simulator allows rapid evaluation of changes in the GPS (e.g., firmware) or surrounding circuitry (e.g., WiFi, Bluetooth, board layout, etc.).

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