FSK Error Time (Digital Demod)

Menu Path: Trace > Data > FSK Error Time

(Available only when the digital-demodulation format is FSK or CPM)

When FSK Frequency Shift Keying: A form of modulation using multiple carrier frequencies to carry the digital information. The most common is the two frequency FSK system using the two frequencies to carry the binary ones and zeros. Error Time is selected, the VSA displays the FSK error, time-domain trace. This trace is the result of computing the error from corresponding points in the FSK measured and FSK reference signals, as follows:

If normalization is OFF,

 

Because the FSK Measured and FSK Reference traces contain REAL data, not complex data, the FSK error trace is REAL, not complex.

If normalization is ON, the FSK Error Time trace is normalized to the deviation. In other words, the FSK error is shown as a percentage of the peak deviation of the signal, as follows:

 

where Deviation is the peak deviation of the signal. The peak deviation is calculated and displayed on the Syms/Errs trace. See the Deviation topic for more information.

The VSA uses the first point in the FSK Measured and FSK Reference signals to compute the first point in the FSK error trace. Then the VSA uses the second point in each signal to compute the second point in the FSK error trace, and so forth.

It is important to remember that the FSK Error Time trace is a time record made up of REAL time-domain data. To make sense of the data, you must select an appropriate data format. For example, to see the FSK- error trace, select the Real(I) trace format.