#### Example 5.3 | #### Question 5.5

## Constellation diagrams

The constellation diagram is very similar to the vector diagram introduced earlier in the section, and is a method of representing the symbol states in a carrier modulated bandpass modem in terms of their amplitude and phase. Typically, the horizontal axis is taken as a reference for symbols that are in-phase with the carrier cos wct, and the vertical axis represents the quadrature carrier component, sin wct. With binary ASK, there are just two symbol states to map onto the constellation space: a(t) = 0 (no carrier amplitude, giving a point at the origin), and a(t) = A cos wct (giving a point on the positive horizontal axis at a distance A from the origin). |
| Multi-level ASK systems are represented by adding appropriate points on the constellation diagram. An 8-ary ASK system is depicted here.