Constellation Diagrams: ASK, FSK, and PSK
Comprehensive guide to signal space representation, including interactive simulators and MATLAB implementations.
BASK Modulation
Transmits one of two signals: 0 or $\sqrt{E_b}$, representing binary 0 and 1. Simple but sensitive to noise.
BFSK Modulation
Transmits one of two signals: $\sqrt{E_b}$ on the Y-axis or $\sqrt{E_b}$ on the X-axis. These are orthogonal signals.
BPSK Modulation
Transmits $+\sqrt{E_b}$ or $-\sqrt{E_b}$ (antipodal signaling). Most efficient binary scheme.
Signal Space Simulator (Constellation)
Real-time Constellation Visualization with Noise Control
Theory & Key Points
- ✔BASK: Bit '0' is low voltage; bit '1' is high. Distance between points is $\sqrt{E_b}$.
- ✔BFSK: Bit '0' and '1' are orthogonal. Distance between points is $\sqrt{2E_b}$.
- ✔BPSK: Antipodal signaling. Distance between points is $2\sqrt{E_b}$. Detailed Theory [↗]
Figure 1: Typical Constellation diagrams (Real vs Imaginary).
Comparison Table (Distance Between Constellation Points)
| Scheme | Distance | Immunity |
|---|---|---|
| BPSK | $2\sqrt{E_b}$ | Highest |
| BFSK | $\sqrt{2E_b}$ | Medium |
| BASK | $\sqrt{E_b}$ | Low |
Comparison Table (Q-funtion)
| Parameter | BASK | BFSK | BPSK |
|---|---|---|---|
| Noise Immunity | Very Low | Medium | Highest |
| BER Formula | $Q(\sqrt{E_b/2N_0})$ | $Q(\sqrt{E_b/N_0})$ | $Q(\sqrt{2E_b/N_0})$ |