SSB Single Side Band
Single Sideband (SSB) is a modulation technique used in communication systems to transmit information in a more efficient manner than traditional amplitude modulation (AM). SSB retains the same information as AM, but eliminates redundant parts of the signal, resulting in a more bandwidth-efficient transmission.
To understand SSB, let's first discuss AM modulation. In AM, the carrier signal is modulated by the message signal (voice, music, or data) by varying the amplitude of the carrier signal in proportion to the instantaneous amplitude of the message signal. The modulated signal contains two sidebands, the upper sideband (USB) and the lower sideband (LSB), along with the carrier frequency.
The spectrum of an AM signal consists of a double-sideband (DSB) with a carrier frequency (fc) and two identical sidebands, one above and one below the carrier frequency. The bandwidth required to transmit an AM signal is twice the maximum frequency contained in the message signal.
SSB modulation, on the other hand, eliminates one of the sidebands and the carrier, transmitting only the essential information contained in the message signal. This reduction in bandwidth improves spectral efficiency and allows for more efficient use of the available frequency spectrum.
There are two types of SSB modulation: Upper Sideband (USB) and Lower Sideband (LSB). In USB-SSB modulation, the carrier and the lower sideband are suppressed, transmitting only the upper sideband. In LSB-SSB modulation, the carrier and the upper sideband are suppressed, transmitting only the lower sideband.
To generate an SSB signal, a mixer (also called a modulator) is used to combine the message signal with a local oscillator signal at a higher frequency. This process is known as frequency translation. The mixer produces both sum and difference frequencies. By carefully selecting the frequencies, filtering out the unwanted sideband, and suppressing the carrier, an SSB signal is obtained.
At the receiver end, the reverse process takes place. The SSB signal is mixed with a local oscillator signal at the same frequency as the one used at the transmitter. The mixer produces the original message signal, which can then be amplified and demodulated to retrieve the original information.
SSB modulation has several advantages over AM modulation. First, it requires less power and bandwidth since one sideband and the carrier are suppressed. This makes it more suitable for long-distance communication and efficient utilization of the radio frequency spectrum. Additionally, SSB signals are less susceptible to interference and noise compared to AM signals.
In summary, Single Sideband (SSB) modulation is a technique that eliminates one sideband and the carrier from an AM signal, resulting in a more bandwidth-efficient transmission. It offers improved spectral efficiency, reduced power requirements, and better resistance to noise and interference, making it a popular choice for long-distance communication systems.