Spread Spectrum Spread spectrum uses wide band, noise like ( pseudo-noise ) signals Spread spectrum transmitters use similar transmit power levels to narrow band transmitters, but because spread spectrum signals are so wide ,they can be transmitted at much lower spectral power density (measured in Watts per Hertz) , then narrow band transmitters. Since spread spectrum (SS) is transmitted with low power, but wide bandwidth, a SS and narrow band signal can occupy the same band with little to no interference.

Advantages resistant to noise, interference, jamming, and unauthorized detection. hard to intercept or demodulate. multiple user can use the same band used for ranging or radar.

Claude Shannon's equation C=W log (1+S/N) where; C=channel capacity, W=Bandwidth, S=signal power, and N=noise power. From this equation the result of increasing the bandwidth becomes apparent. By increasing W in the equation, the S/N may be decreased without decreased performance.

Syarat untuk Spread Spectrum Signal : Sinyal yang ditransmisikan jauh lebih besar daripada information bandwith. Beberapa fungsi selain mentransmisikan information ialah mendeterminasikan the resultant dari transmitted bandwidth.

Jenis – Jenis Spread spectrum Direct Sequence Spread Spectrum (DSSS) This process is achieved by by multiplying a radio frequency carrier with a psuedo noise. The pseudo noise (PN-code) is a binary signal which is produced at a much higher frequency then the data that is to be transmitted. Since this has a higher frequency, it has a large bandwidth, which spreads the signal in the frequency plain Frequency Hopping Spread Spectrum (FHSS) Time Hopping

Frequency Hopping Versi awal dari frequency hopping menggunakan piano-roll untuk mengganti diantara 88 frekuensi, dan ditujukan untuk untuk membuat radio-guided torpedo sulit dilacak maupun dijam oleh musuh Bandwith dalam Frequency Hopping dibagi menjadi beberapa broadcast frequencies yang kemudian dikirimkan. signal ditransmisikan dengan secara cepat memindah carrier di banyak frekuensi channel.

Advantages Frequency Hopping Spread Spectrum (FHSS) mempunyai data speed limitations dan lebih pendek dalam jangkauan Design FHSS lebih mudah untuk dibuat dan menghabiskan biaya yang lebih rendah. sangat bagus dalam menghindari narrow band interference dan user access yang tidak diinginkan dalam lingkungan frequency hopping. Mereka juga dapat dilokasikan dalam network yang berbeda di tempat yang sama tanpa saling memberi gangguan satu sama lain