Pulse modulation

Pulse modulation

1. PULSE MODULATION UNIT – 2 Presented By Mrs. M.P.Sasirekha

2. PULSE MODULATION Pulse modulation is a type of modulation in which the signal is transmitted in the form of pulses. It can be used to transmit analogue information. In pulse modulation, continuous signals are sampled at regular intervals. Pulse modulation can be classified into two major types. Analogue: Indication of sample amplitude is infinitely variable Digital: Indicates sample amplitude at the nearest predetermined level.

3. PULSE MODULATION A block diagram showing the basic classification of modulation techniques is given below.

4. SAMPLING

5. PAM

6. Pulse Amplitude Modulation (PAM) It is the simplest form of Pulse Modulation. In this type of modulation, each sample is made proportional to the amplitude of the signal at the instant of sampling. The PAM signal follows the amplitude of the original signal, as the signal traces out the path of the whole wave. Here a signal which is sampled at Nyquist rate can be reconstructed by passing it through an efficient Low Pass Filter (LPF) with exact cutoff frequency. It is very easy to generate and demodulate PAM. This technique transmits the data by encoding in the amplitude of a series of signal pulses.

7. T ypes of PAM There are two types of PAM. Single Polarity PAM: A fixed DC level is added to the signal so that the signal is always positive. Double Polarity PAM: Here the pulses are both positive and negative.

8. PAM it is clear that the pulse amplitude modulated signal is following the amplitude of the message signal. Advantages of PAM Both Modulation and demodulation are simple. Easy construction of transmitter and receiver circuits. Disadvantages of PAM Large bandwidth is required for transmission. More noise. Here the amplitude is varying. Therefore, the power required will be more.

9. PAM Applications of PAM Mainly used in Ethernet communication. Many microcontrollers use this technique in order to generate control signals. It is used in Photo-biology. It acts as an electronic driver for LED circuits.