Frequency Domain Split-band Scrambler
- Full Duplex Operation
- High Recovered Audio Quality
- Uses Split-Band Inversion
- Fixed or Rolling Code Capabilities
- Simple Serial Interface
- Low Power Requirement with Standby Mode
- Mobile Radio
- Fixed Code Voice Scramblers
- Rolling Code Voice Scramblers
- CMX264D5 - 24-pin SSOP
- 3.0V power supply
The CMX264 is a frequency domain scrambler for use in analogue cellular phone systems. It contains separate Tx and Rx paths for full duplex operation and operates under µProcessor control via a simple serial interface.
In the Tx path, scrambling is achieved by splitting the audio band into two parts, or sub-bands,
and frequency inverting each one.
The frequency at which the signal is split, the "split-point", can be either fixed or rolling
between four possible settings resulting in a transmitted audio signal which is unintelligible to eavesdroppers.
Descrambling is achieved by a receive device set to the same split point as the remote transmitter.
Thus if the Tx and Rx devices are synchronously cycled through the same sequence of split points,
a clear recovered signal will emerge at the output of the receiver
A 4.433619MHz crystal is used allowing up to four split points to be programmed. The device is designed to be compatible with existing cellphone circuitry.
Block Diagram
