Everything a radio chip does ends at the antenna, and a poorly chosen or badly placed one can erase the gains of an expensive transceiver. Options include chip antennas soldered to the board, traces printed on the PCB, flexible stick-on antennas inside the enclosure and external whip antennas on a connector. Each is a trade between size, cost, efficiency and how sensitive it is to its surroundings: a metal case, a hand, or a nearby battery can detune a small internal antenna badly.
Antenna performance feeds directly into the link budget, which decides whether a sensor in a basement reaches its gateway. Because the antenna and its matching network affect emissions, changes to them can require re-testing for FCC certification or CE marking, which is one reason many products use a pre-certified IoT module with an integrated antenna.
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