To extract the original carrier signal from an amplitude modulated (AM) signal, you can use a process called demodulation. The demodulation process separates the carrier signal from the modulating signal, allowing you to recover the original waveform.
Here are the general steps to demodulate an AM signal and extract the carrier:
Bandpass filtering: Pass the AM signal through a bandpass filter centered around the carrier frequency. This filter should have a bandwidth wide enough to capture the entire AM signal spectrum but narrow enough to exclude other interfering frequencies.
Envelope detection: Use an envelope detector to extract the envelope of the filtered signal. An envelope detector typically consists of a diode and a capacitor. The diode rectifies the signal, and the capacitor smoothes out the rectified waveform, resulting in a signal that represents the varying amplitude.
Low-pass filtering: Apply a low-pass filter to the envelope-detected signal to remove any high-frequency components and noise. The cutoff frequency of the low-pass filter should be set to allow the carrier signal to pass while attenuating higher frequencies.
Optional: Carrier regeneration: If you require an accurate representation of the carrier signal, you can use a carrier regeneration technique. One common method is to multiply the filtered signal with a local oscillator operating at the carrier frequency. This process effectively shifts the filtered signal back to the carrier frequency.
After following these steps, you should have a signal that closely resembles the original carrier waveform without the influence of amplitude modulation.
It's important to note that the success of the demodulation process depends on various factors, including the quality of the original AM signal, the characteristics of the filtering and detection components, and the presence of noise or interference. Adjustments and optimizations might be necessary based on specific requirements and signal conditions.