Constellation Diagram of ASK in Detail

A binary bit '1' is assigned a power level of $\sqrt{E_b}$ (or energy $E_b$), while a binary bit '0' is assigned zero power (or no energy).

Energy per bit (Eb):

For transmission of binary ‘1'

We know that all periodic signals are power signals. Now we’ll find the energy of ASK for the transmission of binary ‘1’.




**where Ac is the amplitude of the carrier signal

fc is the carrier frequency in Hz



To save transmitter energy, Eb should be small.

For transmission of binary ‘0’

Constellation Diagram

In constellation diagram the function whose energy is equal to 1 is said to be a normalized function.




In the above figure the reference axes corresponds to normalized functions.








High-order Amplitude Shift Keying (ASK) refers to using a large number of amplitude levels to represent digital data. For instance, in binary ASK (BASK), there are two amplitude levels, usually represented as 0 and 1. High-order ASK can have more than two amplitude levels, such as 4, 8, 16, 64, etc.

 

MATLAB Code For Constellation Diagram of ASK  

% The code is written by SalimWireless.Com % Clear previous data and plots clc; clear all; close all; % Parameters Tb = 1; % Bit duration fc = 10; % Carrier frequency N = 10; % Number of bits % Generate carrier signal t = 0:Tb/100:1; carrier_signal = sqrt(2/Tb) * sin(2*pi*fc*t); % Generate message signal rng(10); % Set random seed for reproducibility binary_data = rand(1, N); % Generate random binary data t_start = 0; t_end = Tb; for i = 1:N t = [t_start:0.01:t_end]; % Generate message signal if binary_data(i) > 0.5 binary_data(i) = 1; message_signal = ones(1, length(t)); else binary_data(i) = 0; message_signal = zeros(1, length(t)); end % Store message signal message(i,:) = message_signal; % Modulate message with carrier ask_signal(i,:) = carrier_signal .* message_signal; % Update time intervals t_start = t_start + (Tb + 0.01); t_end = t_end + (Tb + 0.01); end % Constellation Diagram figure(1); scatterplot(binary_data); title('Constellation Diagram of Binary ASK'); xlabel('n --->'); ylabel('b(n)'); grid on; %%%%%%%%%%%%%% ASK Demodulation %%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% ASK Demodulation %%%%%%%%%%%%%%%%%% t_start = 0; t_end = Tb; for i = 1:N t = [t_start:Tb/100:t_end]; % Correlator correlation = sum(carrier_signal .* ask_signal(i,:)); % Decision device if correlation > 0 demodulated_data(i) = 1; else demodulated_data(i) = 0; end % Update time intervals t_start = t_start + (Tb + 0.01); t_end = t_end + (Tb + 0.01); end % Constellation Diagram after demodulation figure(2); scatterplot(demodulated_data); title('Constellation Diagram of Binary ASK after Demodulation'); xlabel('n --->'); ylabel('b(n)'); grid on;

 

 

Output 

 

 

 

 

 

Effect of Noise on Constellation Diagram of ASK

At SNR = 5 dB

 

 

 

 At SNR = 10 dB

 

 

 

At SNR = 15 dB

 

 

 

At SNR = 30 dB

 

Read more about 

[1] Effect of Noise on the Constellation Diagram of ASK

 

[2] Constellation Diagram of FSK

[3] Constellation Diagram of PSK

[4] Constellation Diagrams of ASK, FSK, and PSK

 

[5] Constellation Diagrams of m-ary PSK

 

[6] Constellation Diagrams of m-ary QAM

 

[7] Simulation of ASK, FSK, and PSK using MATLAB Simulink