Spread spectrum technology represents the latest advancement in RC radio control systems. This article will show you how spread spectrum technology works, and introduce you to some of the technical terms which you may encounter.
Unlike conventional PPM (pulse position modulation) and PCM (pulse code modulation) radio systems which operate on distinct frequencies, spread spectrum radios broadcast over a large range of frequencies simultaneously. These frequencies are all members of the 2.4 Ghz band, which removes them from the frequencies often used by other communication devices. Because of this, spread spectrum radio systems are already immune to interference caused by non RC radio systems.
Spread Spectrum technology has another advantage though: there is no need for frequency control.
Spread spectrum radio systems broadcast over a multitude of radio frequencies, and the user is never aware of what they are. This works because:
- The transmitter is assigned a unique identification code when it is manufactured.
- The receiver is programmed to seek and lock to this same code.
- After the transmitter is powered on, it encodes the signals it sends with its identification code.
- The receiver scans for this code, and locks to the frequencies that the transmitter is operating on.
Each identification code is globally unique, meaning that no other radio system is using it. Because of this, the individual frequencies that the radio is operating on are irrelevant, so as a result an unlimited number of spread spectrum radios can operate simultaneously.
The most noticeable consequence of this technology is that spread spectrum radios are immune to radio interference. Spread spectrum radios also allow an extremely fast servo response time, because the entire encoding, decoding, and execution of radio commands happens in milliseconds.
Spread spectrum technology is becoming more prevelant in RC radio systems, and will shortly replace conventional FM radio systems entirely.