Results 2
Conclusion 5
Title:
Frequency Modulation
Introduction:
The aim of this experiment is to examine Frequency Modulation. The experiment is divided into two parts, Experiment 1 and Experiment 2. Experiment 1 investigates frequency modulation as performed by amacom 2’s reactance modulator and varactor modulator circuits. The audio signal applied to the circuits modulating input modulates the frequency of a carrier sinewave. Experiment 2 investigates the Phase-Locked loop Detector.
Theory:
Fig 1
In a reactance modulator (Fig1) the base bias voltage increases as the oscillator frequency decreases. A varactor modulator behaves differently (Fig 2) with the base oscillator frequency increasing as the base bias voltage.
Fig 2
Frequency deviation =
Attenuation
Noise attenuation
where Ni is the noise input from the signal generator and No is the resulting noise output
Equipment:
Oscillator, Signal Generator, Reactance Modulator, Varactor Modulator, Phase-Locked Loop Detector, Amplitude Limiter, Multimeter and Voltmeter.
Experimental Method:
See handout for description of method
Results:
Experiment 1:
Reactance Modulator:
Frequency Deviation (Reactance Modulator):
B = 552ns
A= 193µs
Carrier Frequency = 455kHz
Frequency Deviation = 6.51 kHz
Frequency Deviation (Veractor Modulator):
B = 304ns
A= 94.5µs
Carrier Frequency = 455kHz
Frequency Deviation = 7.32 kHz
Experiment 2:
Vi = 1.87
Vo = 1.31
Experiment was unable to continue beyond this stage due to malfunctioning equipment
Conclusion:
Frequency Modulation was examined in this experiment especially with regards to the reactance and varactor modulators. Experiment 2 investigated the Phase-Locked loop Detector but was completed unsuccessfully as the result of the equipment malfunctioning.