Taajuushyppäys

Taajuushyppäys is a radio transmission technique used to spread a signal over a wide range of radio frequencies. In this method, the carrier frequency of a single data stream is made to change rapidly and pseudo-randomly among a set of discrete frequencies. This rapid switching is controlled by a pseudo-random code sequence, which is also known to the receiver. The pattern of frequency changes appears random to an observer but is deterministic and reproducible by both transmitter and receiver.

The primary advantage of taajuushyppäys is its robustness against interference. If a particular frequency is experiencing jamming or interference, the signal only stays on that frequency for a very short period before hopping to another. This makes it difficult to disrupt the entire transmission. It also offers a degree of security, as an unauthorized listener would need to know the exact hopping sequence to follow the transmission. This technique is a form of spread spectrum technology.

Taajuushyppäys can be implemented in two main ways: slow frequency hopping (SFH) and fast frequency hopping (FFH). In SFH, the hopping rate is slower than the data rate, meaning multiple bits are transmitted on each frequency. In FFH, the hopping rate is faster than the data rate, with multiple hops occurring for each bit transmitted. This technique is used in various wireless communication systems, including Bluetooth, and some military communication applications.