To Study FM- Demodulation and to Observe the Demodulated Wave Characteristics.
Demodulation is the act of extracting the original information- bearing signal from a modulated carrier wave or the process of separating the original information or signal from the modulated carrier wave. This process is used in the receivers to recover the original signal coming from the sender end n modulating form. We can say that its function is opposite to that of modulation process.
There are several ways to demodulation depending upon how parameters of the base-band signal are transmitted in the carrier signal, such as amplitude, frequency or phase. For a signal modulated with a linear modulation, like Amplitude modulation we can use a synchronous detector, for a signal modulated with an angular modulation use a Frequency demodulator.
The slope detector is a method of Frequency demodulation which converts the received FM signal to AM and demodulates with an envelope detector. Any circuit that outputs the time derivative of the input can perform the FM to AM conversion. In a FM signal the frequency is low, when the amplitude of the message signal is low and vice versa.Slope detection converts the FM signal to Amplitude modulated AM-FM signal using the slope of a filter circuit. Since the peak-to–peak amplitude of the FM signal is constant; on the up-slope of a band pass filter circuit is a lower frequency yield a lower voltage, a higher frequency will yield a higher voltage. When the output of the filter is envelope detected, the original message signal is recovered.