Fresnel plan (representation of a modulated signal as a vector)
This graph shows the path of a 4PSK / 140 Mbit/s modulated signal at the output of a transmission channel. As the channel is intersymbol-free, the signal crosses a ±0.707 ± j 0.707 point at every symbol. The roll-off has been chosen very small (R = 0.2, very sharp filter edges) to increase overshoots.
This graph can be used as a tutorial illustration of digital modulations, showing the large variations of the signal envelope.
This graph is displayed by the third module of the following canal :
A very simple canal (only three modules)
The three following figures display the parameters of each module :
Parameters of the first module ("NO" in the third line means standard PSK.)
Parameters of the second module (a unique filter with 100% percentage of the total roll-off gives the same result as two cascaded filters with 50% percentage)
Parameters of the third module
Other examples : Eye diagram Group delay of a feeder Group delay of a filter Interferences Bit Error Rate Multicarrier amplification Constellation Differential gain