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# What are Digital Modulation Techniques?

The analog signals were used for long distance communication. This analog form of communication has many problems in transmission such as interference, security problems etc. The basic digital modulation techniques are ASK, PSK, FSK and MSK as explained below. In order to make communication more safer and reliable digital signals are used.

## Basic Digital Modulation Techniques

In this method signal level is represented by variations in the amplitude of the signal. In ASK only the amplitude is varied keeping phase and frequency constant.

### Frequency Shift Keying (FSK)

In this method also signal level is represented by variations in the frequency of the signal. In FSK only the frequency is varied keeping amplitude and phase constant. We then use different frequency levels to show the signal levels 0 and 1.

### Phase Shift Keying (PSK)

The variation in phase of the signal in this method represents the signal level. In PSK only the frequency is varied keeping amplitude and frequency constant. Also we use different phases to show the signal levels 0 and 1.

The basic and simple form of PSK is Binary Phase Shift Keying (BPSK). In this modulation two different phases represent the two signals. Another method in PSK is Quadrature PSK (QPSK). In this method four different phases then transmit two bits of information.

### MSK

For converting digital signals to analog signals we use this technique. There is delay in Q component in this method. Then the delay is equal to half of the symbol period. In MSK encoding is in alternating bits which are between the quadrature components. Also it is the most efficient and easy technique amongst all the above techniques. Its implementation is easy compared to PSK, FSK and ASK.

• Basically, the position of even and odd bits for a given bit stream are important along with their bit positions frequency table.
• Also, this method can manage the variation of bits from 1 to 0 very easily and efficiently. Hence, they are used widely compared to other techniques.

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