Where is amplitude shift keying used

Here when you reached your destination you are not considering the bus which you helped to reach your destination. You are using the bus as just for a medium. So, here also to complete the modulation process, the input binary sequence signal using the carrier signals to reach its destination point. One more important point is to consider here, the carrier signal amplitude is should be greater than the input binary signal amplitude.

Within carrier amplitude range we are going to modulate the binary input signal amplitude. If the carrier signal amplitude is less than the input binary signal voltage, then such a combination modulation process leads to over modulation and under modulation effects. So to achieve perfect modulation carrier single should have more amplitude range than input binary signal. In amplitude shift keying theory, input binary signal amplitude varies according to the carrier signal voltage. 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.

If the input binary signal is logic HIGH for certain time interval, then the same should be delivered at the output ports with increment in voltage level. So the main aim of the amplitude shift keying modulation is to changing or improving the voltage characteristics of the input binary signal concerning the carrier signal.

The below diagram indicating the Amplitude shift keying block diagram. When the switch is closed — for all the logic HIGH time intervals i. When the switch is opened — when the input signal having logic 0, the switch is opened and there is no output signal will be generated. Because the input binary signal logic 0 having no voltage, so during these intervals when the carrier signal multiples with it, zero output will come. The output is zero for all logic 0 intervals of the input binary signal.

Mixer circuit having the pulse shaping filters and band-limited filters for shaping the ASK output signal. Amplitude shift keying modulation circuit can be designed with timer IC as an astable mode. The band-limiting filter, shapes the pulse depending upon the amplitude and phase characteristics of the band-limiting filter or the pulse-shaping filter. The clock frequency at the transmitter when matches with the clock frequency at the receiver, it is known as a Synchronous method , as the frequency gets synchronized.

Otherwise, it is known as Asynchronous. The Asynchronous ASK detector consists of a half-wave rectifier, a low pass filter, and a comparator. Following is the block diagram for the same. The modulated ASK signal is given to the half-wave rectifier, which delivers a positive half output.

The low pass filter suppresses the higher frequencies and gives an envelope detected output from which the comparator delivers a digital output. The entire setup consists of a signal generator that can produce a high-frequency sinusoidal waveform, a bandpass filter, and a digital input signal. When the bit is 1, the voltage is high and the switch is closed.

This allows the carrier wave to get transmitted. However, when the bit is 0 i. That is why the output signal appears only at higher voltage levels. The band limiting filter is used to reshape the pulse in accordance with the characteristics of the filter. We can vary the carrier signal by using R1, R2 and C. We can calculate the carrier frequency using the formula.

We will apply the input digital binary sequence at pin 3 and the modulated wave will be generated at pin 3. Demodulation is the process by which we can reconstruct the original signal at the receiver end. The input signal is reproduced at the output stage of the receiver.

ASK detection is of two types:. In this process, the carrier signal at the receiver end is in the same phase and frequency as the replica carrier signal.

The signal received at the receiver stage is passed through a low pass filter to eliminate any kind of distortion and noise. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available. In ASK, only the amplitude of the carrier signal is modified in modulation. The simplest version is on—off keying OOK. In OOK, either bursts of a carrier wave are transmitted or nothing is transmitted depending whether the input message signal is 1 or 0.

Other versions of ASK use differing non-zero amplitudes to represent 1 and 0. Figure 1. One level represents 1 and the other represents 0. The unmodulated carrier is illustrated in Figure 1. These different carrier states are what are known as symbols. If there are more than two possible carrier states — that is, more than two symbols available — then it is possible for each symbol to represent more than one bit. With four symbols available, each symbol can be uniquely represented with a two-bit binary number.

This is because there are just four possible two-bit binary numbers: 11, 10, 01 and If there were eight symbols, each could represent three data bits.