About the difference of frequency and phse modulation

2. What is frequency?
• Frequency is the number of complete waves that pass a point each second.
wave. Frequency is how often an event repeats itself over a set amount of time.
• The longer the wavelength the lower the frequency.
• Its symbol is Hertz (symbol Hz) is the unit of frequency.

3. What is Modulation?
• Modulation is the process of converting data into radio waves by adding
carrier signal.
• Modulation is what takes a signal from low frequencies (the message) and pulls it
carrier)
• While Frequency modulation transmits information over a carrier wave by varying
wave. Frequency modulation changes only one parameter (frequency) while
multiple parameters (amplitude and frequency) since FM signals could not travel

4. Application:
• The technology that uses frequency modulation are telecommunications, radio
and computing.

5. History:
• The history of FM dates back to 1936 when Edwin Howard Armstrong described
of reducing radio transmission disturbances at a Radio Engineers New York
Eventually, FM frequency is widely used in telecommunication devices to transmit

6. • There are two important components to form an FM signal, the first is the carrier frequency, and the second is
the audio frequency to modulate the carrier frequency. We will get an FM signal by varying the carrier
frequency by allowing the AF. The transistor of FM consists of an oscillator to form the RF signal.

7. What is Phase Modulation?
• Phase modulation (PM) is a technique that enables waveform to
be transmitted with minimum distortion. It is a variation of
frequency modulation (FM).
• While Phase Modulation uses variations in phase for carrying the
modulation. A phase modulation signal can be generated by
multiplying an FM signal with a carrier wave whose frequency has
been adjusted to match that of the FM signal. It is a special case
where the amplitude of the carrier wave remains constant, and
only its phase changes as a function of the information signal.

8. • The process of phase modulation is by adding the
baseband signal itself, rather than the integral of the
baseband signal, which causes the phase to vary
according to the baseband value. Thus, phase
modulation is actually a bit simpler than frequency
modulation.
• Phase modulation is sometimes used for analog
transmission, but it has become the basis for
modulation schemes used for carrying data and it is far
more widely used as a digital form of modulation where
it switches between different phases also known as
phase shift keying. Analog phase modulation is not
common; however, digital phase modulation is widely
used today.

9. • Phase modulation is used to transmit radio waves and is an integral part of many digital transmission coding
schemes. It's used to create signals in synthesizers or pianos such as the Yamaha DX7, which enables FM
synthesis. A related type of sound synthesis called phase distortion is used in Casio CZ synthesizers. But it is
mostly used in data communication systems
The modulating wave (blue) is modulating the carrier wave
(red), resulting in the Phase Modulation signal (green).

10. Phase and Frequency Modulation
Frequency Modulation Phase Modulation
1. In Frequency Modulation amplitude and phase 1. In Phase Modulation, the frequency and
same.
2. Frequency Modulation is inversely proportional
frequency.
2. Phase Modulation is proportional to modulating
3. Associated with the change in frequency, there
change.
3. Associated with the change in phase, there is
change.
4. Noise immunity is poorer than AM and PM. 4. Noise immunity is better than AM but worst than
5. Signal-to-noise ratio is better than in phase 5. Signal-to-noise ratio is poorer than in frequency
6. Frequency Modulation is widely used. 6. Phase Modulation is used in mobile systems.
7. In FM, the frequency derivation is proportional
voltage only.
7. In PM, the frequency derivation is proportional
voltage as well as modulating frequency.
8. In FM, the received signal is of high quality. 8. In PM, the received signal is of low quality.
9. It can be possible to receive FM on a PM receiver and vice versa.
10. Both Amplitude in FM and PM wave is constant.

11. Phase and Frequency Modulation

12. Phase Modulation (PM) and Frequency Modulation (FM)
Advantages of (FM) Frequency Modulation.
• Less interference and noise/ Increased immunity to noise.
• Power Consumption is less as compared to AM.
• Adjacent FM channels are separated by guard bands.
Disadvantage of (FM) Frequency Modulation.
• Equipment cost is higher. Has a large bandwidth.
• More complicated receiver and transmitter
• The antennas for FM systems should be kept close for better communication.

13. Phase Modulation (PM) and Frequency Modulation (FM)
Advantages of (PM) Phase Modulation.
• This kind of modulation is nearly immune to noise.
• When data is being transmitted without any interruption, speed can be observed.
• It allows for high-speed communication using telephone system.
Disadvantage of (PM) Phase Modulation.
• In this modulation, two signals are needed to consider the phase difference
• By using a frequency multiplier, the phase modulation index can be increased.
• The PM process requires more equipment than other conversion approaches
approach for each step.

14. FREQUENCY DEVIATION
The frequency deviation in a phase-modulated carrier is proportional to the
modulating signal both.

15. Frequency deviation is given by
.
For single tone modulation .
The frequency deviation becomes
DERIVATION:
A general expression for a phase- modulated wave is:
.
The instantaneous angle is given as:
.
The instantaneous frequency (in Hz) will obtained as

16. • In phase modulation, the maximum difference between the instantaneous phase angle of the
modulated wave and the phase angle of the carrier.
• Note: For a sinusoidal modulating wave, the phase deviation, expressed in radians, is equal to the
in radians, is equal to the modulation index.
• In phase modulation the instantaneous phase deviation of the carrier is proportional to the
message signal that is d(t)= kpm(t).
• Where kP is the phase deviation constant expressed in radians per unit of m(t). In frequency
modulation (FM), the instantaneous frequency deviation of the carrier is proportional to the
message signal that is :

17. • We can express the angle-modulated signal as
• Thus, in PM, the instantaneous frequency 𝜔𝜔𝑖𝑖 varies linearly with the derivative of the modulating signal, and
in FM, 𝜔𝜔𝑖𝑖 varies linearly with the modulating signal. Figure (1.1) illustrates AM, FM, and PM waveforms
produced by a sinusoidal message waveform.

18. • It is described as the ratio of the line-to-neutral inverter output voltage's fundamental component
amplitude to half of the available DC bus voltage.
Modulation Index in Frequency Modulation
• Changing the frequency of carrier wave to encode data
• On bit is encoded for each carrier wave change
• Changing carrier wave to a higher frequency
encodes a bit value of 1
• No change in carrier wave frequency means a
bit value of 0
Time

19. • Let us understand the modulation index in FM (Frequency Modulation). FM defines modulation
index as the frequency deviation (Fd) to modulating frequency ratio (Fm).
t is expressed as follows.
m = Fd/Fm
Example:
Max. frequency deviation of carrier = +/- 25KHz
Max. modulating frequency = 10 KHz
modulation index = 25/10 = 2.5
• When the maximum values of Fd and Fm are utilized in the computation, the result is referred to
as the deviation ratio.

20. • The baseband signal is multiplied by a sine or cosine function that represents the carrier to
determine the phase modulation.
• The modulation index determines how sensitive or not the phase fluctuations are to how the
baseband signal behaves.

21. The percent modulation is defined as the ratio of the actual frequency deviation produced
by the modulating signal to the maximum allowable frequency deviation.

22. • In amplitude modulation, it is common practice to express the
degree to which a carrier is modulated as a percentage of
modulation.
• When the peak-to-peak amplitude of the modulation signal is
equal to the peak-to-peak amplitude of the unmodulated
carrier, the carrier said to be 100 percent modulated.

23. • The peak-to-peak modulating voltage, EA, is equal to that of
the carrier voltage, ER, and the peak-to-peak amplitude of the
carrier varies from 2ER, or 2EA, to 0. In other words, the
modulating signal swings far enough positive to double the
peak-to-peak amplitude of the carrier, and far enough negative
to reduce the peak-to-peak amplitude of the carrier to 0.

25. • If modulating voltage is less than carrier voltage,
percentages of modulation below 100 percent
occur. If EA is one-half ER, the carrier is modulated
only 50 percent.
• When the modulating signal swings to its maximum
value in the positive direction, the carrier amplitude
is increased by 50 percent. When the modulating
signal reaches its maximum negative peak value,
the carrier amplitude is decreased by 50 percent.

26. • It is possible to increase the percentage of modulation to a
value greater than 100 percent by making EA greater than
ER. In figure 6, the modulated carrier is varied from 0 to
some peak-to-peak amplitude greater than 2ER.
• Since the peak-to-peak amplitude of the carrier cannot be
less than 0, the carrier is cut off completely for all negative
values of EA greater than ER. This results in a distorted
signal, and the intelligence is received in a distorted form.
Therefore, the percentage of modulation in a-m systems of
communication is limited to values from 0 to 100 percent.

30. • In frequency modulation, 100-percent modulation has a meaning different from that of AM. The modulating
signal varies only the frequency of the carrier.
• Therefore, tubes do not have varying power requirements and can be operated at maximum efficiency
and the FM signal has a constant power output. In FM a modulation of 100 percent simply means that the
carrier is deviated in frequency by the full permissible amount.

31. NOTE:

32. Calculate the modulation index and percentage of modulation for a waveform with a maximum voltage of
160v and minimum voltage of 50v.
Given:
Vmax= 160v
Vmin= 50v
m=
𝑉𝑚𝑎𝑥−𝑉𝑚𝑖𝑛
𝑉𝑚𝑎𝑥+𝑉𝑚𝑖𝑛
m=
160 𝑉−50 𝑉
160 𝑉+50 𝑉
m=
110
210
m= 0.5238
M= m x 100%
M= 0.5238 x 100%
M= 52.38% modulation

33. If the carrier signal of an AM amplifier is 2.13 volts and the modulation signal is 1volt, the modulation index is
_________ while the percentage of modulation is _______.
Given:
Vm= 1 V
Vc= 2.13 V
m=
𝑉𝑚
𝑉𝑐
m=
1 𝑉
2.13 𝑉
m=0.47
M= m x 100%
M= 0.47 x 100%
M= 47% modulation

34. Using Oscilloscope
Maximum Voltage= 7.2v Minimum Voltage = 4.8v

35. Using Oscilloscope

36. Using Oscilloscope
Values:
Maximum Voltage= 7.2v
Minimum Voltage = 4.8v
M=
𝑉𝑚𝑎𝑥−𝑉𝑚𝑖𝑛
𝑉𝑚𝑎𝑥+𝑉𝑚𝑖𝑛
x 100
M=
7.2−4.8
7.2+4.8
x 100
M=
2.4
12
x 100
M= 20% of modulation
Exact Reading :

37. The application of percent modulation is to compute the ratio of the actual frequency deviation produced by the modulating signal to
the maximum allowable frequency deviation if we change the voltage the amplitude of the carrier wave changes. Getting its modulation
percentage gives us an idea to prevent errors and to provide the exact power of the signal because it is mostly to provide high-range
transmissions, prevent overlapping of two different signals and enhance the quality of transmission so that the applications majorly
falling in the domain of electronic communications such as broadcasting, military and aircraft communication, etc.