Amplitude Shift Keying ASK is a type of Amplitude Modulation which represents the binary data in the form of variations in the amplitude of a signal. The binary signal when ASK modulated, gives a zero value for Low input while it gives the carrier output for High input. …

Amplitude shift keying (ASK) is a popular modulation technique used in digital data communication for a large number of low-frequency RF applications. The source transmits a large amplitude carrier when it wants to send a ‘1’, and it sends a small amplitude carrier when it wants to send a ‘0’ in its simplest form.

Binary ASK(BASK) or On-Off Keying (OOK) • Although we can have several levels (kinds) of signal elements, each with a different amplitude, ASK is normally implemented using only two levels. This is referred to as binary amplitude shift keying.

Amplitude shift keying – ASK – in the context of digital communications is a modulation process which imparts to a sinusoid two or more discrete amplitude levels 1. These are related to the number of levels adopted by the digital message. Thus the modulated waveform consists of bursts of a sinusoid.

In ASK, the input binary signal is multiplied with the carrier signal along with its time intervals. Between the first time interval of input binary signal multiplied with the first time interval of carrier signal voltage and the same process continues for all time intervals.

Advantages of ASK modulation ➨It has simple receiver design. ➨ASK modulation can be used to transmit digital data over optical fiber. ➨ASK modulation and ASK demodulation processes are comparatively inexpensive. ➨Its variant OOK is used at radio frequencies to transmit morse codes.

As with analog modulation, there are three parameters of the carrier wave to vary and therefore three basic types of shift keying:

• Amplitude Shift Keying (ASK)
• Frequency Shift Keying (FSK), and.
• Phase Shift Keying (PSK).

Audio frequency-shift keying (AFSK) is a modulation technique by which digital data is represented by changes in the frequency (pitch) of an audio tone, yielding an encoded signal suitable for transmission via radio or telephone.

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.

FSK signals can be generated at baseband, and transmitted over telephone lines (for example). In this case, both f1 and f2 (of Figure 2) would be audio frequencies. Alternatively, this signal could be translated to a higher frequency. Yet again, it may be generated directly at ‘carrier’ frequencies.

Frequency-shift-keying (FSK) signals with modulation index m = 0.5 have two significant properties. They have no discrete frequency components and nearly all the signal energy is contained within a narrow frequency region equal to /frac{3}{2} of the bit speed even without any band limiting.

The Fast FSK is a particular kind of FSK (Frequency Shift Keying) which is useful for the transmission of digital data over an r.f, channel which is limited in both bandwidth and power. A method that is particularly suited when the r.f. link is restricted in both peak power and bandwidth, is the “Fast FSK”.

Demodulator : The process of retrieval of information from the carrier wave at the receiver is called demodulation and Electronic Circuit used for it is called demodulator. It is an electric circuit that is used to recover information from modulated carrier wave.

The diode detector is the simplest form of detector or demodulator used for AM demodulation – it detects the AM signal envelope. The diode detector is the simplest and most basic form of amplitude modulation, AM signal detector and it detects the envelope of the AM signal.

Advantages and Disadvantages of Amplitude Modulation

Modulation is simply a widely used process in communication systems in which a very high-frequency carrier wave is used to transmit the low-frequency message signal so that the transmitted signal continues to have all the information contained in the original message signal.