We also mentioned that Frequency Modulation (FM) and Phase Modulation equation. and then identify f as the wave's frequency. An alternative way to . This rule is a useful guide when we have to choose a system to carry an FM signal. The radio frequency waves have a constant amplitude and travel through space with The amplitude modulated wave is given by the equation. This is further divided into frequency and phase modulation. The difference between FM modulated frequency and normal frequency is termed as Frequency .
The amplitude and the phase of the carrier signal remains constant whereas the frequency of the carrier changes.
How to Use Scilab to Analyze Frequency-Modulated RF Signals
This can be better understood by observing the following figures. The frequency of the modulated wave remains constant as the carrier wave frequency when the message signal is at zero.Comm # 8 Angle Modulation Phase Modulation and Frequency Modulation
The frequency increases when the message signal reaches its maximum amplitude. Which means, with the increase in amplitude of the modulating or message signal, the carrier frequency increases. Likewise, with the decrease in the amplitude of the modulating signal, the frequency also decreases.
The deviation of the frequency of the carrier signal from high to low or low to high can be termed as the Carrier Swing. The modulation index is small.
This is used in mobile communications such as police wireless, ambulances, taxicabs, etc. The modulation index is large, i. Its spectrum consists of a carrier and infinite number of sidebands, which are located around it.
This is used in entertainment broadcasting applications such as FM radio, TV, etc. Phase Modulation In frequency modulation, the frequency of the carrier varies.
But in Phase Modulation PMthe phase of the carrier signal varies in accordance with the instantaneous amplitude of the modulating signal.
Principles of Communication Angle Modulation
The amplitude and the frequency of the carrier signal remains constant whereas the phase of the carrier changes. The detailed diagram showing the amplitude modulation process is given below.
Amplitude Modulation As shown above, the carrier wave has positive and negative half cycles. Both these cycles are varied according to the information to be sent. The carrier then consists of sine waves whose amplitudes follow the amplitude variations of the modulating wave.
The carrier is kept in an envelope formed by the modulating wave. From the figure, you can also see that the amplitude variation of the high-frequency carrier is at the signal frequency and the frequency of the carrier wave is the same as the frequency of the resulting wave.
Thus it can be ignored. Thus, the second and third cosine equations are more close to the carrier frequency.
The equation is represented graphically as shown below. The height of each vertical line is drawn in proportion to its amplitude. Since the angular velocity of the carrier is greater than the angular velocity of the modulating signal, the amplitude of sideband frequencies can never exceed half of the carrier amplitude. Two side banded frequencies will be produced when a carrier is amplitude modulated by a single frequency.
When a modulating signal has more than one frequency, two sideband frequencies are produced by every frequency.