Another reason to modulate a signal is to allow the use of a smaller antenna. AM receivers are very cheap as no specialized components are needed. AM waves can travel a longer distance. AM waves have low bandwidth. The technology is used for communication systems such as telemetry, weather balloon radiosondes, caller ID, garage door openers, and low frequency radio transmission in the VLF and ELF bands. BFSK uses a pair of discrete frequencies to transmit binary 0s and 1s information.
Disadvantages of Amplitude shift keying ASK technique is not suitable for high bit rate data transmission. Poor bandwidth efficiency. Highly susceptible to noise and other external factors.
As you say in your comment, PSK signals are more bandwidth efficient, but FSK signals have good noise rejection for their data rates. FSK Demodulation. In this, the frequency shift is generally proficient by motivating a VCO with the binary data signal. It includes a tap voltage controlled delay line and a bit binary-weighted DAC with a time interleaved structure. An analog to digital converter ADC , converts any analog signal into quantifiable data, which makes it easier to process and store, as well as more accurate and reliable by minimizing errors.
Additionally, with analog modulation, you can superimpose any arbitrary waveform on top of the laser signal. This can be extremely useful for applications which non-binary amplitude modulation is needed. Learn more. Difference between encoding and modulation in transmission Ask Question. Asked 8 years, 2 months ago.
Active 2 years, 4 months ago. Viewed 8k times. Improve this question. Add a comment. Active Oldest Votes. Improve this answer. Twaha Kabika Twaha Kabika 31 1 1 bronze badge. Evil 9, 11 11 gold badges 29 29 silver badges 51 51 bronze badges. Mgh Gh Mgh Gh 21 2 2 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. It has positive thin pulses Zero time or width corresponding to the starting edge of a PWM pulse and negative thin pulses corresponding to the ending edge of a pulse.
The signals in PCM are binary; that is, there are only two possible state, 1 and 0. Basic Block diagram of PCM 1. Sampling: The process of generating pulses of zero width and of amplitude equal to the instantaneous amplitude of the analog signal.
The number of pulses per second is called sampling rate. Quantization: The process of dividing the maximum value of the analog signal into a fixed number of levels in order to convert the PAM into a Binary code. The levels obtained are called Quantization levels. PCM Three different methods of sampling According to the Nyquist theorem, the sampling rate must be at least 2 times the highest frequency contained in the signal.
Figure Quantization and encoding of a sampled signal Need synchronization Not compatible to analog system. Digital signal- is a sequence of discrete discontinuous voltage pulses. Bit duration- the time it takes for the transmitter to emit the bit.
Issues: Bit timing Recovery from signal Noise Immunity The common types of line encoding are unipolar, polar, bipolar and Manchester encoding. Line codes are used commonly in computer communication networks over short distances. NRZ Bipolar-AMI and Pseudoternary Manchester Encoding Differential Manchester Encoding Keying is a family of modulation forms where the modulating signal takes one of a specific predetermined number of values at all times.
The goal of keying is to transmit a digital signal over an analog channel. The name derives from the Morse code key used for telegraph signaling. Modulation is the general technique of shaping a signal to convey information.
When a digital message has to be represented as an analog waveform, the technique and term keying. Several keying techniques exist, including phase-shift keying, frequency-shift keying and amplitude-shift keying. Bluetooth, for example, uses phase-shift keying to exchange information between devices. Keying In view of the fact that both amplitude and phase variations are present it may also be considered as a mixture of amplitude and phase modulation.
QAM is extensively used as modulation scheme for digital telecommunication system such as Advantage: increase the efficiency of transmission for radio communications systems by utilizing both amplitude and phase variations Disadvantage: it is more susceptible to noise because the states are closer together. Total views 5, On Slideshare 0.
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