WEEK-I
ELECTROMAGNETIC WAVES COMMUNICATION SYSTEMS
ELECTROMAGNETIC WAVES
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GENERATION OF ELECTROMAGNETIC WAVES
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APPLICATIONS OF ELECTROMAGNETIC WAVES
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USES OF ELECTROMAGNETIC WAVES
Different parts of the EM spectrum have different uses:
ELECTROMAGNETIC SPECTRUM
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The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus.
ELECTROMAGNETIC SPECTRUM
Computer Science & Engineering – 20CS33P
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| Wavelength (m) | Frequency (Hz) | Energy (J) |
Radio | > 1 x 10-1 | < 3 x 109 | < 2 x 10-24 |
Microwave | 1 x 10-3 - 1 x 10-1 | 3 x 109 - 3 x 1011 | 2 x 10-24- 2 x 10-22 |
Infrared | 7 x 10-7 - 1 x 10-3 | 3 x 1011 - 4 x 1014 | 2 x 10-22 - 3 x 10-19 |
Optical | 4 x 10-7 - 7 x 10-7 | 4 x 1014 - 7.5 x 1014 | 3 x 10-19 - 5 x 10-19 |
UV | 1 x 10-8 - 4 x 10-7 | 7.5 x 1014 - 3 x 1016 | 5 x 10-19 - 2 x 10-17 |
X-ray | 1 x 10-11 - 1 x 10-8 | 3 x 1016 - 3 x 1019 | 2 x 10-17 - 2 x 10-14 |
Gamma-ray | < 1 x 10-11 | > 3 x 1019 | > 2 x 10-14 |
COMMUNICATION SYSTEMS
Basic Elements of communication system
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The block diagram of a communication system will have five blocks, including the information source, transmitter, channel, receiver and destination blocks.
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2.Transmitter
3.Channel
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4.Receiver
5.Destination
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Commonly used terms in Electronic Communication Systems
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Different Types Of Modulation.
i. Amplitude Modulation (AM)
ii. Frequency Modulation (FM)
iii. Phase Modulation (PM)
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Communication Systems
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Elements of Communication Systems
Fig: Data Communication System
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Data Communication System characteristics
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Data Representation
text symbols are represented with a sequence of bits 0 or 1. Each sequence is called a code, and the process is called coding.
numbers are also represented with a sequence of 0 and 1. ASCII is not used for number representation.
DATA FLOW
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ANALOG AND DIGITAL SIGNALS
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Data can be Analog or Digital.
1. Analog Signal: They have infinite values in a range.
2. Digital Signal: They have limited number of defined values
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Fig: Comparison of analog and digital signals
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PERIODIC ANALOG SIGNALS
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Sine Wave
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A sine wave is characterized by three parameters:
Peak Amplitude
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Frequency
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Phase
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DIGITAL SIGNALS
Bit Rate
The bit rate is the number of bits sent in 1s, expressed in bits per second (bps)..
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Bit Length
The bit length is the distance one bit occupies on the transmission medium.
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Modulation
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Frequency Modulation: Frequency modulation occurs when a signal's amplitude and frequency have a constant state, but the carrier wave frequency changes or varies.
Phase Modulation: Phase modulation refers to a situation where the phase of a high-frequency carrier wave varies or changes due to a phase shift in the modulated signal, while the amplitude and frequency remain unchanged.
Amplitude Modulation: Amplitude modulation refers to a change in the amplitude of a carrier wave caused by a change in the modulation of the signal. The signal phase and frequency remain constant.
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Working of Modulation
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Demodulation
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which represents the binary data in the form of variations in the
amplitude of a signal.
Low input while it gives the carrier output for High input.
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binary High input and is low in frequency for a binary Low input.
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Difference between Demodulation and Modulation
Parameters | Demodulation | Modulation |
Description | Demodulation is the recovery of original information at the carrier’s far end. | The process of influencing data information on the carrier is known as modulation. |
Implementation | Demodulation occurs on the receiving end of a communication system. | Modulation occurs on the transmission side of a communication system. |
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Message Transmission | In demodulation, the carrier and message signals are separated to produce the original information signal. | The original message signal is mixed with a carrier wave whose parameters must be changed during modulation. |
Requirement | To recover the original signal, demodulation is required. | Modulation necessitates the use of a modulator section to mix the two signals. |
Conversion of Signals | The low-frequency signal is obtained from the high-frequency signal during demodulation. | Modulation transforms a low-frequency signal into a high-frequency signal. |
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Purpose | Demodulation is used to re-establish the original message signal. | Modulation is primarily used to send data over longer distances. |
Complexity | Demodulation is typically difficult. | Modulation is a relatively simple process. |