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R 1 and R 2 establish base bias and R 3 establish collector bias. C 1 is the coupling capacitor  block DC from the input source. Figure 3.4: Diode Demodulator Figure 3.5: Transistor Demodulator Transistor Demodulator AM input is applied to Q 1 base (common emitter).

Voltage across C 1 follows the amplitude variation of carrier signal, not the carrier signal itself. RC time constant of R 1 and C 1 is made long enough so that C 1 does not have to discharge before the next pulse is received. The rectified signal will quickly charge C 1. Figure 3.3 Product Detector for AM and SSBĭemodulator Circuit Diode Demodulator D 1 rectifies the signal producing only positive result. This method will decode both AM and SSB, although if the phase cannot be determined a more complex setup is required. After filtering, the original audio signal will result. The product detector multiplies the incoming signal by the signal of a local oscillator with the same frequency and phase as the carrier of the incoming signal. Figure 3.2 Envelope detection of a conventional AM signalĪM Demodulation Demodulation of SSBSC AM For SSBSC, product detector is used to recover the signal. Major advantage of AM = ease of the demod process. The recovery of the baseband signal undergoes the process of rectifying the incoming signal, remove half of the envelop, then use low pass filter to remove the high frequency component of the signal. Figure 3.1 Receiver Block Diagram RF Section IF Section Demodulator AF StageĪM DEMODULATOR Demodulation of DSBFC AM Simplest demodulator for DSBFC is envelop detector. For AM, the most popular demodulator used are the Envelop Detector and Product Detector. Another common one is in a modem, which is a contraction of the terms modulator/demodulator.

The term is usually used in connection with radio receivers, but there are many kinds of demodulators used in many other systems. Topics AM Demodulators Tuned Radio Frequency Receivers Superheterodyne Receivers RF Section and Characteristics Path and Frequency Changing Intermediate Frequency (IF) & IF Amplifier Detector and Automatic Gain Control (AGC) ĭemodulator Definition: A demodulator is an electronic circuit used to recover the information content from the carrier wave of a signal.