Frequency Modulation Basic Theory

Frequency Modulation Basic Theory:

Generation of Frequency Modulation : The Generation of Frequency Modulation system is a variable output frequency, with the variation proportional to the instantaneous amplitude of the modulating voltage. The subsidiary requirements are that the unmodulated frequency should be constant, and the deviation independent of the modulating frequency. If the system does not produce these characteristics, corrections can be introduced during the modulation process. FM Methods: One method of Generation of Frequency Modulation suggests itself immediately. If either the capacitance or inductance of an LC oscillator tank is varied, frequency modulation of some form will result. If this variation can be made directly proportional to …


Noise and Frequency Modulation : Noise and Frequency Modulation is much more immune to noise than amplitude modulation and is significantly more immune than phase modulation. In order to establish the reason for this and to determine the extent of the improvement, it is necessary to examine the effect of noise on a carrier. Effects of Noise on Carrier—Noise Triangle: A single Noise and Frequency Modulation will affect the output of a receiver only if it falls within its bandpass. The carrier and noise voltages will mix, and if the difference is audible, it will naturally interfere with the reception of wanted signals. If such …


Theory of Frequency Modulation and Phase Modulation : Frequency Modulation and Phase Modulation is a system in which the amplitude of the modulated carrier is kept constant, while its frequency and rate of change are varied by the modulating signal. The first practical system was put forward in 1936 as an alternative to AM in an effort to make radio transmissions more resistant to noise. Phase modulation is a similar system in which the phase of the carrier is varied instead of its frequency; as in FM, the amplitude of the carrier remains constant. Let’s assume for the moment that the carrier of …