All internal antennas require some adjustment for the different PCB and enclosure characteristics unique to each product. Although manufacturers do have “reference” designs, these are only used as a starting point. The Matching Circuit enables the optimal transfer of RF energy flowing to or from the radio chip to the outside world.
Without carefully adjusting (tuning) the components in this network, the product’s operational range will be degraded. Receivers will suffer from reduced sensitivity. Transmitters will suffer from reduced radiated power. This can be easily 3dB to 20dB. (Every 6dB results in a doubling or halving of range.)
The RF instrument that I use for Tuning is a Vector Network Analyzer (VNA). It provides a view of how efficiently the matching circuit is working. A perfect match is 100% wherein all of the RF energy is transferred and none is lost or reflected. By changing the value of one of the matching circuit components at a time, the results can be accurately measured. As these components interact, the process of requires many different iterations before the optimum combination can be discovered.
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