Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Uid: 317040564 (3635)Uid: 848325037Uid: 848325037Uid: 317040564 (3635)Uid: 848325037Uid: 317040564 (3635)Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭𝘦Jeffrie Caliva ⓘ 𝘠𝘰𝘶 𝘤𝘢𝘯'𝘵 𝘴𝘦𝘦 𝘵𝘩𝘪𝘴 𝘤𝘰𝘮𝘮𝘦𝘯𝘵 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘺𝘰𝘶 𝘢𝘳𝘦 𝘶𝘴𝘪𝘯𝘨 𝘢 𝘊𝘩𝘪𝘯𝘦𝘴𝘦 𝘮𝘰𝘣𝘪𝘭

1. Noise
Suppression
Effects of FM

2. Noise Suppression
Effects of FM
● Noise from lightning, motors, and any
power line switching that produces transient
signals.
● Noise is typically narrow spikes of voltage
with very high frequencies.
● FM radio has a special limiter circuit that
cuts off these spikes.
● The important information in FM radio is
carried by changes in frequency, not by the
signal strength.
● So, cutting off the spikes (amplitude
variations) doesn't affect the information.
● This is why FM radio is better than AM
radio at handling noise - it cuts out the
noise without losing the signal.

3. Noise Suppression
Effects of FM
● Noise from lightning, motors, and any
power line switching that produces transient
signals.
● Noise is typically narrow spikes of voltage
with very high frequencies.
● FM radio has a special limiter circuit that
cuts off these spikes.
● The important information in FM radio is
carried by changes in frequency, not by the
signal strength.
● So, cutting off the spikes (amplitude
variations) doesn't affect the information.
● This is why FM radio is better than AM
radio at handling noise - it cuts out the
noise without losing the signal.

4. Noise Suppression
Effects of FM
● Noise from lightning, motors, and any
power line switching that produces transient
signals.
● Noise is typically narrow spikes of voltage
with very high frequencies.
● FM radio has a special limiter circuit that
cuts off these spikes.
● The important information in FM radio is
carried by changes in frequency, not by the
signal strength.
● So, cutting off the spikes (amplitude
variations) doesn't affect the information.
● This is why FM radio is better than AM
radio at handling noise - it cuts out the
noise without losing the signal.

5. Noise Suppression
Effects of FM
● Noise from lightning, motors, and any
power line switching that produces transient
signals.
● Noise is typically narrow spikes of voltage
with very high frequencies.
● FM radio has a special limiter circuit that
cuts off these spikes.
● The important information in FM radio is
carried by changes in frequency, not by the
signal strength.
● So, cutting off the spikes (amplitude
variations) doesn't affect the information.
● This is why FM radio is better than AM
radio at handling noise - it cuts out the
noise without losing the signal.

6. Noise Phase Shift
● Noise can cause small wobbles in the FM
signal, even though FM is good at rejecting
noise.
● Imagine the signal and noise as arrows. The
size of the arrow represents strength, and the
direction represents its effect.
● Normally, noise is like a bunch of small arrows
spinning in different directions.
● But to simplify things, we can imagine noise as
just one strong, spinning arrow.
● The combined effect of signal and noise
creates a new, bigger arrow that wobbles
slightly.
● The maximum wobble happens when the noise
arrow is perpendicular to the signal arrow.

7. Noise Phase Shift
● Noise can cause small wobbles in the FM
signal, even though FM is good at rejecting
noise.
● Imagine the signal and noise as arrows. The
size of the arrow represents strength, and the
direction represents its effect.
● Normally, noise is like a bunch of small arrows
spinning in different directions.
● But to simplify things, we can imagine noise as
just one strong, spinning arrow.
● The combined effect of signal and noise
creates a new, bigger arrow that wobbles
slightly.
● The maximum wobble happens when the noise
arrow is perpendicular to the signal arrow.

8. Noise Phase Shift
● Noise can cause small wobbles in the FM
signal, even though FM is good at rejecting
noise.
● Imagine the signal and noise as arrows. The
size of the arrow represents strength, and the
direction represents its effect.
● Normally, noise is like a bunch of small arrows
spinning in different directions.
● But to simplify things, we can imagine noise as
just one strong, spinning arrow.
● The combined effect of signal and noise
creates a new, bigger arrow that wobbles
slightly.
● The maximum wobble happens when the noise
arrow is perpendicular to the signal arrow.

9. The amount of signal distortion caused by noise depends on a few
things.
• Higher frequencies are more affected: The higher the frequency of the
information being carried by the FM signal, the worse the wobble caused by
noise will be.
• Severity depends on allowed frequency range: FM signals can change
frequency within a certain limit. If this allowed range is large (high modulation
index), even a wobble caused by noise might be too small to matter. But if the
allowed range is small (low modulation index), noise can cause a bigger
wobble and potentially distort the signal more.
• Noise is usually brief: The good news is that noise spikes are usually very
short-lived. So, even if they cause a wobble, it's usually just for a moment.
• Impact on intelligibility: In most cases, even with heavy noise, the wobble
won't be bad enough to completely garble your speech. It might sound a little

11. Preemphasis
• Noise messes with
FM, especially high
frequencies: Noise
spikes have a lot of
high-frequency
content which can
overpower the actual
high-frequency parts
of the signal you want
to transmit (like high-
pitched sounds or
musical instruments).
This distortion can
make the signal
unintelligible.
doesn't need much
high frequency:
Most of what we say
in speech is at lower
frequencies. So, for
voice calls, FM can
handle noise pretty
well even without
needing all the high
frequencies.
frequencies for
quality: Instruments
use high frequencies
to create their unique
sounds. To transmit
high-fidelity music,
you need a wider
range of frequencies,
including those high
frequencies. But
these high
frequencies are also
weak, and noise can
easily wipe them out.

12. Preemphasis
De-emphasis at transmitter
● A de-emphasis circuit is used at the
receiver to return the frequency response
to normal.
● It's a simple low-pass filter with the same
time constant (75 μs) as the pre-emphasis
circuit.
● This results in a cutoff frequency of 2123
Hz for the de-emphasis circuit.
● Frequencies above this cutoff are
attenuated at 6 dB per octave.
● The de-emphasis effectively cancels out
the pre-emphasis, providing a flat
frequency response overall.

13. Preemphasis
● Pre-emphasis boosts high
frequencies before sending: To
combat this, FM radio uses a trick
called pre-emphasis. It boosts the
high frequencies of the signal a bit
before sending it out. This way, even
if noise messes with them, they're
still strong enough to be received
clearly.
● De-emphasis weakens high
frequencies at receiver: There's a
matching process at the receiver
called de-emphasis. It weakens the
high frequencies a bit to bring them
back to their normal level and
prevent them from overpowering the
lower frequencies

14. Preemphasis
Pre-emphasis at transmitter
● This circuit boosts high frequencies before
sending the signal.
● This is achieved using a simple RC high-
pass filter with a time constant (τ) of 75
μs.
● The chosen time constant results in a
cutoff frequency (fL) of approximately
2123 Hz.
● Frequencies above fL are boosted at a
rate of 6 dB per octave.
● Strengthens high frequencies in the signal

15. Preemphasis
Pre-emphasis at transmitter
● This circuit boosts high frequencies before
sending the signal.
● This is achieved using a simple RC high-
pass filter with a time constant (τ) of 75
μs.
● The chosen time constant results in a
cutoff frequency (fL) of approximately
2123 Hz.
● Frequencies above fL are boosted at a
rate of 6 dB per octave.
● Strengthens high frequencies in the signal

16. Preemphasis
Pre-emphasis at transmitter
● This circuit boosts high frequencies before
sending the signal.
● This is achieved using a simple RC high-
pass filter with a time constant (τ) of 75
μs.
● The chosen time constant results in a
cutoff frequency (fL) of approximately
2123 Hz.
● Frequencies above fL are boosted at a
rate of 6 dB per octave.
● Strengthens high frequencies in the signal

17. Preemphasis
Pre-emphasis at transmitter
● This circuit boosts high frequencies before
sending the signal.
● This is achieved using a simple RC high-
pass filter with a time constant (τ) of 75
μs.
● The chosen time constant results in a
cutoff frequency (fL) of approximately
2123 Hz.
● Frequencies above fL are boosted at a
rate of 6 dB per octave.
● Strengthens high frequencies in the signal

18. Preemphasis
De-emphasis at transmitter
● A de-emphasis circuit is used at the
receiver to return the frequency response
to normal.
● It's a simple low-pass filter with the same
time constant (75 μs) as the pre-emphasis
circuit.
● This results in a cutoff frequency of 2123
Hz for the de-emphasis circuit.
● Frequencies above this cutoff are
attenuated at 6 dB per octave.
● The de-emphasis effectively cancels out
the pre-emphasis, providing a flat
frequency response overall.

19. Preemphasis
De-emphasis at transmitter
● A de-emphasis circuit is used at the
receiver to return the frequency response
to normal.
● It's a simple low-pass filter with the same
time constant (75 μs) as the pre-emphasis
circuit.
● This results in a cutoff frequency of 2123
Hz for the de-emphasis circuit.
● Frequencies above this cutoff are
attenuated at 6 dB per octave.
● The de-emphasis effectively cancels out
the pre-emphasis, providing a flat
frequency response overall.

20. Preemphasis
Overall Effect of Preemphasis and
Deemphasis
● The pre-emphasis circuit amplifies high-
frequency components of the signal more
than low-frequency components, and the
de-emphasis circuit attenuates high-
frequency components. The ideal
outcome is that these opposing effects
cancel each other out, resulting in a flat
frequency response.

21. Frequency
Modulation Versus
Amplitude
Modulation

22. • Superior Noise Immunity: FM signals are much less susceptible to noise
compared to AM signals. This is because FM uses a clipper limiter circuit that
removes noise variations, resulting in a constant-amplitude signal.
• Capture Effect: In situations with two FM signals on the same frequency, the
stronger signal "captures" the channel, eliminating the weaker one entirely.
This prevents interference from weaker stations. AM signals, on the other
hand, can mix and create an unintelligible mess.
• Higher Efficiency: FM transmitters use class C amplifiers which are more
efficient than the linear amplifiers required for AM. This allows FM to achieve
higher power levels with less wasted energy.
Advantages of FM over AM radio

23. Excessive Spectrum Usage:
• FM signals require a much wider band of frequencies (bandwidth) compared to
AM for similar information. This is because FM encodes information by varying
the carrier wave's frequency.
• Reducing the bandwidth (modulation index) to save spectrum space also
reduces FM's key benefit - noise immunity.
• FM is typically used at higher frequencies (VHF, UHF, microwave) where wider
bandwidth is available.
Circuit Complexity (Historical Disadvantage):
• In the past, FM equipment required complex circuits for modulation and
demodulation compared to simpler AM circuits.
• This disadvantage is no longer significant due to the widespread use of
integrated circuits (ICs). While FM ICs are intricate, they are affordable and
easy to use.
Disadvantages of FM over AM radio

24. Preemphasis
Pre-emphasis and de-emphasis work together
to:
● Strengthen high frequencies during
transmission.
● Reduce the impact of noise on those
frequencies.
● Result in a clearer and more enjoyable listening
experience, especially for music.