sivutaajuus

Sivutaajuus, often translated as "side frequency" or "sideband frequency" in English, refers to frequencies that appear in a modulated signal above and below the carrier frequency. When a carrier wave is modulated by a signal, the original carrier frequency remains, but new frequencies are generated as a result of the interaction between the carrier and the modulating signal. These new frequencies are the side frequencies.

Specifically, in amplitude modulation (AM), two sidebands are produced: the upper sideband (USB) and the lower sideband (LSB). The upper sideband contains frequencies that are the sum of the carrier frequency and the modulating frequencies, while the lower sideband contains frequencies that are the difference between the carrier frequency and the modulating frequencies. For example, if a carrier frequency of 1 MHz is modulated by a 10 kHz audio signal, the upper sideband would contain frequencies around 1.01 MHz, and the lower sideband would contain frequencies around 990 kHz.

The bandwidth of a modulated signal is determined by the carrier frequency plus the bandwidth of the modulating signal (for USB) or the carrier frequency minus the bandwidth of the modulating signal (for LSB). In many communication systems, only one sideband is transmitted along with a reduced or suppressed carrier to save bandwidth and power. This technique is known as single-sideband (SSB) modulation. The specific choice of USB or LSB depends on the application and frequency allocation. Understanding sivutaajuus is crucial in radio communication, signal processing, and spectrum analysis.