Keysight Technologies 33210A User Manual page 345

Tutorial 7
For example, consider a custom arbitrary waveform consisting of 10 cycles of a
sine waveform. When you set the function generator's frequency to 1 MHz, the
actual output frequency will be 10 MHz and the amplitude will be attenuated. As
you increase the frequency above 1 MHz, more attenuation will occur.
When creating arbitrary waveforms, the function generator will always attempt to
replicate the finite-length time record to produce a periodic version of the data in
waveform memory. However, as shown below, it is possible that the shape and
phase of a signal may be such that a discontinuity is introduced at the end point.
When the waveshape is repeated for all time, this end-point discontinuity will
introduce leakage errors in the frequency domain because many spectral terms
are required to describe the discontinuity.
Leakage error is caused when the waveform record does not include an integral
number of cycles of the fundamental frequency. Power from the fundamental
frequency, and its harmonics, is transferred to the spectral components of the
rectangular sampling function. You can reduce leakage errors by adjusting the
window length to include an integer number of cycles or by including more cycles
within the window to reduce the residual end-point discontinuity size. Some
signals are composed of discrete, non-harmonically related frequencies. Since
these signals are non-repetitive, all frequency components cannot be
harmonically related to the window length. You should be careful in these
situations to minimize end-point discontinuities and spectral leakage.
0°
90° 180° 270° 360°/0° 90° 180° 270° 360°
1 Cycle
Arbitrary Waveform with Discontinuity
Keysight 33210A User's Guide 345