BASK (Binary ASK) Modulation:
Transmits one of two signals: 0 or -√Eb, where Eb is the energy per bit. These signals represent binary 0 and 1.
BFSK (Binary FSK) Modulation:
Transmits one of two signals: +√Eb (On the y-axis, the phase shift of 90 degrees with respect to the x-axis, which is also termed phase offset) or √Eb (on x-axis), where Eb is the energy per bit. These signals represent binary 0 and 1.
BPSK (Binary PSK) Modulation:
Transmits one of two signals: +√Eb or -√Eb (they differ by 180 degree phase shift), where Eb is the energy per bit. These signals represent binary 0 and 1.
Simulator for BASK, BPSK, and BFSK Constellation Diagrams
Key Points
- For Binary Amplitude Shift Keying (BASK), binary bit '0' can be represented as lower level voltage or no signal and bit '1' as higher level voltage.
- For Binary Frequency Shift Keying (BFSK), you can map binary bit '0' to 'j' and bit '1' to '1'. So, signals are in phase.
- A phase shift of 0 degrees could represent a binary '1', while a shift of 180 degrees could represent a binary '0'. For example, we can map binary bit '0' with '-1' and bit '1' with '+1'. (read more ...)
This article will primarily discuss constellation diagrams, as well as what constellation diagrams tell us and the significance of constellation diagrams. Constellation diagrams can often demonstrate how the amplitude and phase of signals or symbols differ. These two characteristics lessen the interference between two signals or symbols.
Figure 1: Constellation diagrams of ASK, PSK, and FSK (Get MATLAB Code) The x-axis shows the real part, and the y-axis shows the imaginary part of the signal.
The constellation points for ASK, PSK, and FSK [↗] are located in a different pattern, and the distances between the constellation points vary. According to the above diagram, the distance between ASK constellation points is (√Eb -0) = √Eb (where Eb stands for energy per bit). From the above figure, you can also see the distances between constellation points for PSK and FSK are 2√Eb and √(2Eb), respectively. In a constellation diagram, if the distance between signaling points is less, then the probability of error (Pe) will be higher and vice versa.
Get MATLAB Code for ASK, FSK, and PSK
This illustration in Figure 1 above, known as a constellation diagram, graphically shows the complicated envelope of each potential symbol state. In a constellation diagram, the in-phase and quadrature components of the complex envelope are represented by the x- and y-axes, respectively. The spacing between the signals shows how diverse the modulation waveforms are on a constellation diagram, which also shows how well a receiver can distinguish between all potential symbols in the presence of noise. This concept will become more evident when you look at higher-order modulations like M-QAM, QPSK, M-PSK, etc. [Read More about M-QAM and M-PSK constellation diagrams] Unlike binary ASK, FSK, and PSK, where signal sets only consist of {0 and 1}, a signal set will contain many symbols.
