Modulation techniques are methods that are used to encode digital information in an analog world. The 3 basic modulation techniques are as follows:

a. AM (amplitude modulation)

b. FM (frequency modulation)

c. PM (phase modulation)

All 3 modulation techniques employ a carrier signal. A carrier signal is a single frequency that is used to carry the intelligence (data). For digital, the intelligence is either a 1 or 0. When we modulate the carrier, we are changing its characteristics to correspond to either a 1 or 0.

AM - Amplitude Modulation

Amplitude Modulation modifies the amplitude of the carrier to represent 1s or 0s.In the above example, a 1 is represented by the presence of the carrier for a predefined period of 3 cycles of carrier. Absence--or no carrier--indicates a 0.

Advantages:

· Simple to design.

Disadvantages:

· Noise spikes on transmission medium interfere with the carrier signal.

· Loss of connection is read as 0s.


FM - Frequency Modulation

Frequency Modulation modifies the frequency of the carrier to represent the 1s or 0s. In the above example, a 0 is represented by the original carrier frequency, and a 1 by a much higher frequency (the cycles are spaced closer together).


Advantages:

· Immunity to noise on transmission medium.

· Always a signal present. Loss of signal easily detected

Disadvantages:

· Requires 2 frequencies

· Detection circuit needs to recognize both frequencies when signal is lost.

PM - Phase Modulation

Phase Modulation modifies the phase of the carrier to represent a 1 or 0.

The carrier phase is switched at every occurrence of a 1 bit, but remains unaffected for a 0 bit. The phase of the signal is measured relative to the phase of the preceding bit. The bits are timed to coincide with a specific number of carrier cycles (3 in this example = 1 bit).

Advantage:

· Only 1 frequency used

· Easy to detect loss of carrier

Disadvantages:

· Complex circuitry that is required to generate and detect phase changes.

Established in 2000, the Soukacatv.com main products are modulators both in analog and digital ones, amplifier and combiner. We are the very first one in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world.

For more, please access to https://www.soukacatv.com.


CONTACT US

Dingshengwei Electronics Co., Ltd

Company Address: Buliding A,the first industry park of Guanlong,Xili Town,Nanshan,Shenzhen,Guangdong,China

Tel : +86 0755 26909863

Fax : +86 0755 26984949

Phone: +86 13410066011

Email:[email protected]

Skype: soukaken



Source: epq