What are Digital Modulation Techniques ?

What is Modulation?

Modulation is the process of superimposing high-frequency carrier signals with low-frequency message signals resulting in a modulated wave. In modulation, one of the three parameters of the carrier wave is changed i.e. amplitude, frequency or phase according to the amplitude of the message signal at a given time instant. It is an important technique used to increase the range of communication, increase the signal-to-noise ratio, and decrease the size of the antenna....

What are Digital Modulation Techniques ?

There are mainly three types in Analog Modulation which are Amplitude Modulation, Frequency Modulation and Phase Modulation. Here the amplitude, frequency and phase of carrier wave changes with respect to amplitude of message signal. Whereas in Digital Modulation a process called as Shift Keying is used....

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....

Frequency Shift Keying

In Frequency Shift Keying (FSK), each symbol in the message signal gives a unique frequency to the carrier wave. There are two types of FSK, Binary and M-ary. In Binary FSK, logic 1 is associated with certain frequency of carrier wave e.g. 50MHz and logic 0 is associated with different frequency other than 50MHz e.g. 25MHz. In M-ary FSK, a group of log2M bits are considered together rather than 1 bit at a time and the frequency is associated with this group of bits....

Phase Shift Keying

In Phase Shift Keying (PSK), each symbol in the message signal gives a unique phase shift to the carrier wave. There are two types of PSK, Binary and M-ary. In Binary PSK, logic 1 is associated with certain phase shift of carrier wave e.g. 90° and logic 0 is associated with different phase shift other than 90° e.g. 0°. In M-ary PSK, a group of log2M bits are considered together rather than 1 bit at a time and the phase shift is associated with this group of bits....

M-ary Encoding

It Involves transmitting of more than two bits simultaneously on the same signal that can help to save bandwidth by efficiently utilizing the available frequency spectrum....

Applications of Digital Modulation Techniques

Military Communication Systems, where security and accuracy of the signal plays a crucial role. Digital Modulation can provide confidential and error free communication. Mobile Communication Systems, where the number of users are daily increasing and Digital Modulation can provide high capacity and less interference. Long distance communication can be easily done with the help of Digital Modulation. Digital Broadcasting, Digital modulation techniques are used in digital broadcasting standards such as Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), and Terrestrial Digital Multimedia Broadcasting (T-DMB) for transmitting audio, video, and data content efficiently. Radar Systems, In radar systems, digital modulation techniques like phase modulation (PM) and frequency modulation (FM) are used for transmitting radar pulses and modulating radar signals to detect and track objects accurately in various applications such as air traffic control, weather monitoring, and military surveillance....

Advantages of Digital Modulation Techniques

High Immunity to noise: Since the modulated wave consist of finite collection of amplitude/frequency or phase shifts, changes occurred in above parameters due to noise, distortion and dispersion is less as compared to difference in amplitude/frequency or phase shift between two distinct symbols. For e.g. An Amplitude Shift Keyed wave will have higher noise tolerance since the interference cannot bring 0V i.e. logic 0 to 12V which is representing logic 1. Hence the demodulated wave at the receiver highly represents the input message signal applied at the transmitter. High Security: Since the message signal is digital in Digital Modulation, encryption techniques can be employed to improve authenticity, confidentiality and integrity of data. After encrypting the digital message we can proceed with modulation process for transmitting the message. Such features are not available in Analog Modulation as message signal is of analog type. Efficient Usage of Bandwidth: By using compression techniques we can reduce the number of bits of the message signal without affecting the data content in it. Hence if we compress the message signal and modulate it then it will take less bandwidth as compared to modulating the original message signal. High Accuracy of Data: With the help of error detection and error correction techniques we can find the presence of errors in the demodulated wave at the receiver side and correct it accordingly to get the original message signal. High Capacity: We can use Time Division Multiple Access (TDMA) instead of Frequency Division Multiple Access (FDMA) in case of Digital Modulation as frequency or spectrum is limited and it is not possible to assign certain frequency per user as number of users is quite high compared to available channels. Hence capacity can be increased by letting the users access the channel for certain time period one after the other....

Disadvantages of Digital Modulation Techniques

Additional Circuitry: Analog to Digital Converter (ADC) must be connected before modulating the signal to convert analog message signal to digital signal at the transmitter side and Digital to Analog Converter (DAC) must be connected after demodulating the signal to convert digital signal back to analog wave. This can increase the cost of communication system. Synchronization: For proper detection and demodulation of received signal synchronization is required. This requires oscillator circuitry which must be present at both transmitter and receiver. High Power Consumption: While Shift Keying Modulation may consume less power than Analog Modulation, it still consumes more power as compared to Pulse Modulation techniques such as PAM, PWM and PPM where the message signal is analog but the carrier is rectangular wave....

Conclusion

Digital Modulation techniques offer numerous advantages such as high immunity to noise, enhanced security through encryption, efficient bandwidth utilization, and high data accuracy. Despite requiring additional circuitry and power consumption, the benefits outweigh the drawbacks, making Digital Modulation important in modern communication systems. Its applications is used in military communication, mobile networks, broadcasting, radar systems, and more, contributing to the advancement and reliability of global communication networks....

Digital Modulation Techniques – FAQs

Can we combine two or more modulation techniques?...