The ADF7011 is a low power OOK/ASK/FSK/GFSK UHF transmitter designed for use in ISM band systems. It contains and integrated VCO and sigma-delta fractional-N PLL. The output power, channel spacing, and output frequency are programmable with four 24-bit registers. The fractional-N PLL enables the user to select any channel frequency within the European 433 MHz and 868 MHz bands, allowing the use of the ADF7011 in frequency hopping systems. The fractional-N also allows the transmitter to operate in the less congested sub-bands of the 868 MHz to 870 MHz SRD band. It is possible to choose from the four different modulation schemes: Binary or Gaussian Frequency Shift Keying (FSK/GFSK), Amplitude Shift Keying (ASK), or On/Off Keying (OOK). The device also features a crystal compensation register that can provide ±1 ppm resolution in the output frequency. Indirect temperature compensation of the crystal can be accomplished inexpensively using this register. Control of the four on-chip registers is via a simple 3-wire interface. The devices operate with a power supply ranging from 2.3 V to 3.6 V and can be powered down when not in use.