Digital modulation schemes transform digital signals like the one shown below into waveforms that are compatible with the nature of the communications channel.



There are two major categories of digital modulation. One category uses a constant amplitude carrier and the other carries the information in phase or frequency variations (FSK, PSK). The other category conveys the information in carrier amplitude variations and is known as amplitude shift keying (ASK).



The past few years has seen a major transition from the simple amplitude modulation (AM) and frequency modulation (FM) to digital techniques such as Quadrate Phase Shift Keying (QPSK), Frequency Shift Keying (FSK), Minimum Shift Keying (MSK) and Quadrate Amplitude Modulation (QAM).



For designers of digital terrestrial microwave radios, their highest priority is good bandwidth efficiency with low bit-error-rate. They have plenty of power available and are not concerned with power efficiency. They are not especially concerned with receiver cost or complexity because they do not have to build large numbers of them.



On the other hand, designers of hand-held cellular phones put a high priority on power efficiency because these phones need to run on a battery. Cost is also a high priority because cellular phones must be low-cost to encourage more users.



Accordingly, these systems sacrifice some bandwidth efficiency to get power and cost efficiency. Every time one of these efficiency parameters (bandwidth, power or cost) is increased, another one decreases, or becomes more complex or does not perform well in a poor environment. Cost is a dominant system priority. Low-cost radios will always be in demand.



In the past, it was possible to make a radio low-cost by sacrificing power and bandwidth efficiency. This is no longer possible. The radio spectrum is very valuable and operators who do not use the spectrum efficiently could lose their existing licenses or lose out in the competition for new ones. These are the tradeoffs that must be considered in digital RF (Radio Frequency) communications design. If you understand the building blocks, then you will be able to understand how any communications system, present or future, works.



HDMI Encoder Modulator,16in1 Digital Headend, HD RF Modulator at Soukacatv.com




SKD3013 3 Channel HD Encode Modulator



SKD121X Encoding & Multiplexing Modulator



SKD19 Series 1U Rack 12CH Encode Modulator






Household Universal Encoding & Modulation Modulator


Why use Digital Modulation?



The move to digital modulation provides more information capacity, compatibility with digital data services, higher data security, better quality communications, and quicker system availability. Developers of communications systems face these constraints:

available bandwidth

permissible power

inherent noise level of the system



The RF spectrum must be shared, yet every day there are more users for that spectrum as demand for communications services increases. Digital modulation schemes have greater capacity to convey large amounts of information than analogue modulation schemes. The Fundamental Trade-off:

Industry trends over the past few years a major transition has occurred from simple analogue Amplitude Modulation (AM) and Frequency/Phase Modulation (FM/PM) to new digital modulation techniques. Examples of digital modulation include:

FSK (Frequency Shift Keying)

QPSK (Quadrature Phase Shift Keying)

QAM (Quadrature Amplitude Modulation)

MSK (Minimum Shift Keying)

Now that we understand the basic principles of modulation you should be ready to take the first tutorial.



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

Company: DingShengwei Electronics Co., Ltd

Address: BldgA,the first industry park of Guanlong, Xili Town,Nanshan,Shenzhen,Guangdong,China

Tel: +86 0755 26909863

Fax: +86 0755 26984949

Mobile: 13410066011

Email: [email protected]

Website: https://www.soukacatv.com

Source: ukessays