For synchronous demodulation process we demodulate the received signal with the help of carrier signal generated by local oscillator. For example, for demodulation of DSB-SC and PAM signal, we use multiplier to retrieve the original message signal. We pass the modulated signal and carrier signal thru the multiplier in these case.
Synchronous demodulation is a technique used in communication systems to recover the original information signal from a modulated carrier wave. In modulation, information is typically impressed onto a carrier wave to allow for efficient transmission. The carrier wave undergoes changes in amplitude, frequency, or phase to represent the information being transmitted.
In synchronous demodulation, the demodulator is synchronized with the carrier wave, meaning it is phase-locked or frequency-locked to the carrier signal. This synchronization is crucial for accurate demodulation because it ensures that the demodulator is sampling the incoming signal at the correct points in time, aligning with the modulation changes.
The main advantage of synchronous demodulation is its ability to minimize the effects of noise and interference. By synchronizing with the carrier signal, the demodulator can precisely track and recover the original information signal. This helps improve the signal-to-noise ratio and enhances the overall performance of the communication system.
There are various methods of synchronous demodulation depending on the modulation scheme used, such as amplitude modulation (AM), frequency modulation (FM), or phase modulation (PM). Each method involves maintaining synchronization with the carrier wave to accurately extract the transmitted information.
On the other hand, asynchronous demodulation is a demodulation technique used in communication systems where the demodulator is not synchronized with the carrier wave. Unlike synchronous demodulation, which requires precise synchronization with the carrier signal, asynchronous demodulation does not rely on maintaining phase or frequency lock with the carrier.
In asynchronous demodulation, the demodulator recovers the original information signal without prior knowledge of the carrier signal's phase or frequency. This approach is often used when synchronization is challenging or impractical, especially in situations where the carrier signal's characteristics may vary unpredictably.