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AMPLITUDE SHIFT KEYING (ASK) PHASE SHIFT KEYING (PSK):
Amplitude Shift Keying (ASK) : Amplitude Shift Keying is the as changing amplitude of the carrier signal with respect to the binary information or digital signal.
Define Phase Shift Keying (PSK): Phase Shift Keying is the changing amplitude of the carrier signal with respect to the binary information or digital signal
Concept Of Amplitude Shift Keying In Detail:
The amplitude shit keying is also called on-off keying(OOK). This is the simplest digital modulation technique. The binary input data is converted to unipolar NRZ signal. A product modulator takes this NRZ signal and carrier signal. The output of the product modulator is the ASK signal, which can be expressed mathematically as,
Here fc is the carrier frequency
and d is the data bit, which is either 1 or 0.
Fig. 2.3.1 (a) shows the block diagram of the ASK modulator. The binary data sequence ‘d’ is given to the NRZ level encoder. This NRZ level encoder converts the input binary sequence to the signal suitable for product modulator. The product modulator also accepts a sinusoidal carrier of frequency fc. The output o the product modulator is passed through a bandpass filter for bandwidth limiting. The output of the bandpass filter is the ASK signal. This signal and other waveforms are shown in Fig. 2.3.1(b). Observe that the ASK signal. And when d=1, d=sin(2πfct). The ASK is very sensitive to noise. It is used for very low bit rates less than around 100 bps. The only advantage of ASK is that it is very simple to implement.
Or ASK, the ASK waveform is changed at the bit rate. Hence Baud rate is given as,
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