Antenna design and matching

The radio chip is only half of the RF system. Antenna type (chip, PCB trace, flex or external), placement on the board, ground plane size and the materials around it determine range. Enclosure plastics, metal parts, batteries, displays and the user's hand all detune an antenna. A small matching network of inductors and capacitors between radio and antenna is tuned, using a network analyzer, in the final enclosure.

Poor antenna performance is a common cause of "it keeps disconnecting" complaints, and it can push radiated power or spurious emissions out of compliance.

Where it bites: late enclosure changes (a metallic finish, a moved battery) can wreck range. Pre-certified radio modules come with reference antenna designs and layout rules that must be followed to keep their certification valid.