The MICRF505 is a true single chip, frequency shift keying (FSK) transceiver intended for use in half-duplex, bidirectional RF links. The multi-channeled FSK transceiver is intended for UHF radio equipment in compliance with the North American Federal Communications Commission (FCC) part 15.247 and 249, as well as the European Telecommunication Standard Institute (ETSI) specification, EN300 220. The transmitter consists of a PLL frequency synthesizer and a power amplifier. The frequency synthesizer consists of a voltage-controlled oscillator (VCO), a crystal oscillator, dual modulus prescaler, programmable frequency dividers, and a phase-detector. The loop-filter is external for flexibility and can be a simple passive circuit. The output power of the power amplifier can be programmed to seven levels. A lockdetect circuit detects when the PLL is in lock. In receive mode, the PLL synthesizer generates the local oscillator (LO) signal. The N, M , and A values that give th