When listening to broadcasts from AM and FM radio stations, the information is transmitted on a single, fixed frequency. While this is ideal for radio stations where you want everyone to be able to tune into the information, many applications require the data to be private and it is not desirable to allow eavesdroppers or other systems to receive the broadcast information.
Spread Spectrum technology is designed to spread the broadcasted signal over a larger bandwidth, making the signal more difficult to detect, interfere, or jam. Because of these advantages, spread spectrum has been used by the military for years and has found wide acceptance in consumer markets where reliability and security are necessary. The most common types of Spread Spectrum technology use Frequency Hopping Spread Spectrum (FHSS) or Direct Sequence Spread Spectrum (DSSS).
In FHSS systems, the carrier hops in a pseudo random order on a group of frequencies. In DSSS systems, a pseudo noise code is used to encode digital data before it is transmitted. The spreading code runs at much higher rate than the data rate and has the effect of spreading out the signal.
All of Digi’s radios have some form of Spread Spectrum capability. The XCite, XStream and XTend families all uses FHSS and the XBee and XPress Ethernet bridge use DSSS.