Tuesday, March 5, 2013



Frequency modulation (FM) is a method of providing information on the carrier wave by varying the frequency, the system is different from amplitude modulation (AM) systems in which the amplitude of the carrier wave AM varied while the frequency remains constant .
FM transmission system with technology invented by Edwin Howard Armstrong that can transmit high quality sound via radio waves.
FM story began in 1936 when Edwin Howard Armstrong menperkenalkan FM frequency as a method to reduce interference with radio broadcasts on Radio Engineers conference in New York on November 6, 1936. FM frequencies are widely used in telecommunications equipment to transmit sound without noise (interference). In analog applications, the instantaneous frequency of the carrier (the carrier frequency) is proportional to the instantaneous value of the input signal. The digital data can be sent by changing the carrier frequency of a set of discrete values, a technique known as frequency modulation.

Characteristics of the FM signal

One. The most important characteristic of frequency modulated (FM) is immune to interference signal amplitude. The modulation is done by changing the variation frekuensi.Artinya, any waveform amplitude signal will not affect the audio output, while the radio signal from the transmitter is within range of a radio receiver.
2nd. FM has a resistance to noise and interference. The reason why FM is used for the transmission of high-quality broadcasts.
3rd. Another important feature associated with the FM broadcast. audio modulation can be applied during low power transmitters, and it is not necessary to use a linear form of reinforcement to increase the power level of the signal to the end.
4th. The FM broadcasts can use an RF amplifier for amplifying nonlinear signal FM transmitter. This is more efficient than linear RF amplifier, so for the same output transmit power, FM transmitter more efficient than the other transmitters.
To generate the FM signal, the radio carrier frequency must be changed according to the amplitude of the input audio signal. When the audio signal is modulated on a radio frequency carrier wave radio frequency waves will move up and down. The rate at which the wave moves up and down are known as "diversion" and represented one kilohertz deviation. For example, if the wave signal has a deviation of 4 kHz, the carrier wave is made to move from one transmission 4 kHz. FM band generally use between 88 to 108 MHz, with a deviation of about 75 kHz. This distortion is known as "bandwidth FM or WBFM. This signal has a large bandwidth and support for transmission with good quality. A bandwidth (broadband) is less used in communication systems FM. Two-way communication system (such as HT) using a narrow band FM, with a deviation of 3 kHz.
Broadcast FM
FM is commonly used at VHF radio frequencies to transmit voice and music with high quality. The sound of a normal TV also broadcast using FM. Band FM used in broadcast is generally called gamma-FM (FM broadband) or W-FM. In a two-way radio, FM narrowband (N-FM) is used to save bandwidth. Furthermore, FM is also used to send signals to the space. FM bandwidth (W-FM) requires a bandwidth wider than the system of amplitude modulation (AM) modulation signal with one equivalent, but the FM signal bandwidth is more resistant to noise and interference. Frequency modulation is also more robust than the sound effects are less clear.
FM radio receiver uses a special detector for FM signals and sometimes detector presents a phenomenon called the capture effect, which can be clearly tuner receives signals from two stations transmitting on the same frequency. An FM signal can also be used to carry a stereo signal using multiplexing and demultiplexing before and after the process of FM.
Share this Artickel :

No comments:

Post a Comment