Amplitude Shift Keying
In Amplitude Shift Keying (ASK), each symbol in the message signal gives a unique amplitude to the carrier wave. There are two types of ASK, Binary and M-ary. In Binary ASK, logic 1 is associated with certain amplitude of carrier wave e.g. 12V and logic 0 is associated with different amplitude other than 12V e.g. 0V. In M-ary ASK, a group of log2M bits are considered together rather than 1 bit at a time and the amplitude level is associated with this group of bits.
For example, in 16-ary ASK, a group of 4 bits are considered and are given a respective amplitude. Since there are 16 possible 4 bit binary numbers (24), 16 different amplitude levels are required for modulation. If all such amplitudes are created using a single carrier wave, then it is called as coherent ASK. If multiple carrier wave each with different amplitudes are used for modulation then it is called as non-coherent ASK.
Block Diagram of Amplitude Shift Keying
Given Below is the Block Diagram of Amplitude Shift Keying
The analog message signal is converted to digital signal using Analog to Digital Converter. This digital signal is then passed to a multiplier which takes two inputs. A sine wave with high frequency is considered as carrier signal and is multiplied with the digital signal. When symbol present in the digital signal m(t) gets multiplied with the carrier Asin(2πft+p) it results in m(t)Asin(2πft+p).
When m(t) is high, the carrier wave is passed as it is. But when m(t) is logic 0, then the result of multiplication is 0. Hence ASK wave is generated. However this ASK wave contains abrupt changes in amplitude which causes unnecessary high bandwidth usage. Hence this signal is passed through Band Pass Filter which limits the bandwidth usage.
For demodulating, the ASK wave is passed through a multiplier again where the carrier wave is multiplied again which results in m(t)Asin2(2πft+p). This signal is passed through Low Pass Filter where the original digital message is received. This digital signal is converted to analog wave using Digital to Analog Converter.
Digital Modulation Techniques
Modulation is the Fundamental Process in Communication Systems, In Modulation Low-Frequency Message Signal Blends with High-Frequency Carrier Frequency to Enable Efficient Transfer of the Signal. In this article, we will be going through Digital Modulation Techniques, First we will start our Article by Defining Modulation, Then we will go through the Three types of Digital Modulation techniques with Their Wave, At Last we will conclude our Article With their Application, Advantages, Disadvantages and Some FAQs.
Table of Content
- Modulation
- Digital Modulation Techniques
- Amplitude Shift Keying
- Frequency Shift Keying
- Phase Shift Keying
- M-ary Encoding
- Applications
- Advantages
- Disadvantages