FCC and ETSI Requirements for Sub-1GHz ASK-Modulated Transmitters

Abstract: There are governmental restrictions on intentional and unintentional radiated power from unlicensed transmitters used for remote keyless entry (RKE), home automation, home security, Tire pressure monitoring systems (TPMS) and other applications requiring short-range devices (SRDs). These restrictions are established by regulatory agencies in each country or region. The two most influential agencies, based on the size of the markets that they impact, are the FCC in the United States and ETSI in Europe.This application note describes the FCC and ETSI radiation limits that apply to amplitude-shift-keyed (ASK) transmitters in the ISM band that includes 315MHz, 433.92MHz, 868.35MHz and 915MHz. The specific tests needed to demonstrate compliance with those limits, and the test parameters that can affect test results are all discussed. The calculated and measured spectrum of ASK modulation, as well as spectrum-analyzer traces of transmissions from the MAX41462 ASK transmitter illustrate what is necessary to pass these tests.