Amplitude shift keying, Frequency Shift Keying, Binary Phase Shift Keying: Generation and Detection
Digital modulation schemes are techniques used to encode information into a carrier signal by varying its properties according to discrete signal levels or symbols. Here’s an overview of three common digital modulation schemes: Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), and Phase Shift Keying (PSK).
Amplitude Shift Keying (ASK) is the simplest digital modulation technique. In this method, there is only one carrier, which is switched ON or OFF depending on the input binary sequence to transmit symbols 0 and 1. The binary ASK system was one of the earliest forms of digital modulation used in wireless telegraphy.
For Frequency Shift Keying (FSK), two binary values are represented by two different frequencies. For example, we choose two carrier frequencies, f1 and f2, with f1 > f2. Then, binary bit "1" is modulated with f1, and binary "0" is modulated with f2, which is lower than f1.
In Phase Shift Keying (PSK), the carrier phase is modulated according to the current bit. Binary "1" is transmitted by changing the signal's phase by 180 degrees, while binary "0" is transmitted with the same phase as the preceding bit.
Each modulation scheme has its advantages and is chosen based on the specific requirements of the communication system, such as bandwidth, power efficiency, and noise resilience.