CMX990 GMSK Packet Data Modem and RF Transceiver

Brief Description
A single-chip GMSK packet-data modem and RF transceiver, the CMX990 provides the majority of circuits and functions to implement a full-feature "wireless modem" subsystem. The CMX990 can operate in RF ranges of 400MHz to 1GHz at data rates of 4 to 16 kbps and is fully Mobitex compatible.
With a minimum of external components and circuits, this half duplex device provides on-chip: a flexible, formattable GMSK packet and free-format modem, a dual synthesiser, IF and RF stages for both Rx and Tx modes, and auxiliary ADCs and DACs for system control and monitoring.
This versatile GMSK modem is programmable to both packet and free-format data operations via an efficient task-oriented Rx and Tx format and command structure, which is combined with data scrambling, interleaving and FEC and CRC capabilities. Rx data acquisition, extraction and tracking abilities, allied with Rx data quality feedback, allow the CMX990 to operate seamlessly in varying signal environments.
Tx includes an internal vector modulator to accurately generate the modulation. This is then translated to the final frequency using an offset-phased locked loop. In the Rx path an image-reject mixer is provided to minimise external RF filtering requirements. The output of the mixer goes off-chip to allow the circuit designer flexibility in the choice of IF filter. The CMX990 then provides AGC functions and I/Q mix down to generate baseband signals for the modem. Significant Rx selectivity is provided using internal I/Q baseband filters. Comprehensive internal and external system control and monitoring is provided by the 8-bit host interface registers and the on-chip ADCs and DACs. Requiring a power supply input in the range 3.0 to 3.6 volts, the CMX990 can be used in wireless products designed to comply with such standards as EN 300 113 and FCC CFR 47 Part 90. Operating over a temperature range of -40°C to +85°C, the CMX990 consolidates the core radio modem functions to enable a new generation of small, narrow-band wireless data modems. The CMX990 comes in a 64-pin low profile VQFN package.