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Digital Modulation Part 4. How Does Phase Shift Keying Work? Explained with Constellation Diagrams!

Digital Modulation playlist.    • Digital Modulation Part 1. How Data S...   Constellation Diagram: Visualize Phase Shift Keying (PSK) in Digital Comm A constellation diagram is a graphical representation of the symbol used in a digital modulation scheme. It displays the amplitude and phase of each possible symbol in a 2D (I-Q) plane, where: The x-axis represents the In-phase (I) component (real part). The y-axis represents the Quadrature (Q) component (imaginary part). Purpose of Constellation Diagram Visualizes how symbols are encoded in amplitude and phase. Helps analyze noise, distortion, and interference in a communication system. Used for debugging and optimizing digital modulation schemes. Common Digital Modulation Schemes & Their Constellations ASK (Amplitude-Shift Keying) Only amplitude changes (2-ASK: two points on the I-axis). PSK (Phase-Shift Keying) Symbols differ in phase (BPSK: 2 points at 0° and 180°; QPSK: 4 points at 45°, 135°, 225°, 315°). QAM (Quadrature Amplitude Modulation) Both amplitude and phase vary (16-QAM: 16 symbols in a grid). For a given symbol, we can represent its amplitude and phase on an IQ plot. In the BPSK example, we discussed phases of 0 and 180 degrees. Let’s plot these two points on the IQ plot, assuming a magnitude of 1. In practice, the exact magnitude doesn’t matter much—a higher value simply means a higher-power signal, but you could also achieve the same effect by increasing the amplifier gain. The IQ plot illustrates what we will be transmitting—or more precisely, the set of symbols we’ll use for transmission. It does not include the carrier, so you can think of it as representing the baseband symbols. When we display all possible symbols for a given modulation scheme in this way, we refer to it as the constellation. Many modulation schemes are defined by their constellation.