11- Analog Pulse Modulation
Analog Pulse Modulation

11- Analog Pulse Modulation

Analog Pulse Modulation

After the continual wave modulation, the following division is Pulse modulation. Pulse modulation is additional divided into analog and digital modulation. The analog modulation methods are primarily categorised into Pulse Amplitude Modulation, Pulse Length Modulation/Pulse Width Modulation, and Pulse Place Modulation.

Analog Pulse Modulation -Pulse Amplitude Modulation

Pulse Amplitude Modulation (PAM) is an analog modulating scheme through which the amplitude of the heartbeat provider varies proportional to the instantaneous amplitude of the message sign.

The heartbeat amplitude modulated sign, will comply with the amplitude of the unique sign, because the sign traces out the trail of the entire wave. In pure PAM, a sign sampled on the Nyquist fee is reconstructed, by passing it via an environment friendly Low Go Frequency (LPF) with actual cutoff frequency

The next figures clarify the Pulse Amplitude Modulation.

Analog Pulse Modulation

Although the PAM sign is handed via an LPF, it can’t recuperate the sign with out distortion. Therefore to keep away from this noise, flat-top sampling is finished as proven within the following determine.

Flat-top sampling is the method through which sampled sign may be represented in pulses for which the amplitude of the sign can’t be modified with respect to the analog sign, to be sampled. The tops of amplitude stay flat. This course of simplifies the circuit design.

Analog Pulse Modulation -Pulse Width Modulation

Pulse Width Modulation (PWM) or Pulse Length Modulation (PDM) or Pulse Time Modulation (PTM) is an analog modulating scheme through which the length or width or time of the heartbeat provider varies proportional to the instantaneous amplitude of the message sign.

The width of the heartbeat varies on this technique, however the amplitude of the sign stays fixed. Amplitude limiters are used to make the amplitude of the sign fixed. These circuits clip off the amplitude, to a desired degree and therefore the noise is proscribed.

The next figures clarify the forms of Pulse Width Modulations.

There are three variations of PWM. They’re −

  • The forefront of the heartbeat being fixed, the trailing edge varies in line with the message sign.
  • The trailing fringe of the heartbeat being fixed, the vanguard varies in line with the message sign.
  • The middle of the heartbeat being fixed, the vanguard and the trailing edge varies in line with the message sign.

These three sorts are proven within the above given determine, with timing slots.

Analog Pulse Modulation -Pulse Place Modulation

Pulse Place Modulation (PPM) is an analog modulating scheme through which the amplitude and width of the pulses are saved fixed, whereas the place of every pulse, with regards to the place of a reference pulse varies in line with the instantaneous sampled worth of the message sign.

The transmitter has to ship synchronizing pulses (or just sync pulses) to maintain the transmitter and receiver in synchronism. These sync pulses assist preserve the place of the pulses. The next figures clarify the Pulse Place Modulation.

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Pulse place modulation is finished in accordance with the heartbeat width modulated sign. Every trailing of the heartbeat width modulated sign turns into the place to begin for pulses in PPM sign. Therefore, the place of those pulses is proportional to the width of the PWM pulses.

Benefit

Because the amplitude and width are fixed, the ability dealt with can also be fixed.

Drawback

The synchronization between transmitter and receiver is a should.

Analog Pulse Modulation -Comparability between PAM, PWM, and PPM

The comparability between the above modulation processes is offered in a single desk.

PAM PWM PPM
Amplitude is diverse Width is diverse Place is diverse
Bandwidth is determined by the width of the heartbeat Bandwidth is determined by the rise time of the heartbeat Bandwidth is determined by the rise time of the heartbeat
Instantaneous transmitter energy varies with the amplitude of the pulses Instantaneous transmitter energy varies with the amplitude and width of the pulses Instantaneous transmitter energy stays fixed with the width of the pulses
System complexity is excessive System complexity is low System complexity is low
Noise interference is excessive Noise interference is low Noise interference is low
It’s just like amplitude modulation It’s just like frequency modulation It’s just like section modulation

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