Question

Explain some demodulation techniques.

Answer 1

Demodulation:

Demodulation is the process of separating the original information from the modulated carrier.

Demodulation techniques:

Given below are various techniques used for demodulation.

1 . Diode rectifier envelope detector:

1. In this process, the Amplitude modulated wave is detected and demodulated
2. The diode rectifies the incoming wave and allows only a half-wave.
3. Then the capacitor removes any unnecessary radio frequency signals leaving the original form of the wave

2 . Product Detector:

1. The term "product detector" comes from the fact that SSB (single sideband suppressed carrier) demodulation requires an output that is a product of the inputs. A mixer/product detector's job is to create a product or multiply the value of the inputs, while the phrase "product detector" was first used in the early days of SSB usage and is still in use today.
2. Demodulation is done using a product detector and with a local beat frequency oscillator or a carrier injection oscillator.
3. The incoming signal cannot be synchronized by the local oscillator carrier and should be of the basic form.
4. A detector for suppressed carrier AM signals works by multiplying the signal with a regenerated carrier. A diode detector used alone does not work for SSB (single sideband suppressed carrier) or DSBSC (double sideband suppressed carrier) because the envelope is different from that of AM.
5. A locally generated carrier can be injected along with the SSB signal into a diode detector, but it is better to use an arrangement similar to the one used to generate.
6. When used in receivers, such a device is called a product detector. detectors are multiplier circuits. They have a single output whose instantaneous amplitude is proportional to the product of the amplitudes of two input signals.

3 . Synchronous Detector:

1. It is the most optimum method. It has a product detector or a mixer with a local oscillator.
2. The local oscillator is synchronized to the incoming signal.
3. A simple diode rectifier is the most basic type of amplitude modulated signal detection. Synchronous demodulation is a type of demodulation that may be utilized to produce better performance.
4. It is helpful first to examine the spectrum of an amplitude modulated signal while examining the synchronous demodulation of an AM transmission. It is clear that the device consists of a carrier with two sidebands that convey audio or other information extending out on either side. Each of these two sidebands reflects the other. The demodulation technique aims to retrieve the sideband information with the least amount of distortion feasible.
5. Synchronous demodulation is accomplished using a mixer. The mixer's signal input receives the incoming signal, while the other input receives a local oscillator signal with the same frequency as the incoming signal's carrier. The carrier is converted to a 0Hz signal and the sidebands to their baseband frequency range during this mixing process, which reconstitutes the audio.
6. The output of the carrier, which has a frequency of 0 Hz, is seen as a DC voltage; the magnitude of the DC voltage depends on the phase between the carrier and the local oscillator. The original audio or other modulating signals will appear as the AM signal's sidebands relative to zero frequency.