Advertisement
067-1011-00 DSG
Markers
The Digital Sweep Generator provides 1V marker outputs for
identification of nominal 1-MHz intervals during the sweep.
0.5V markers are provided in the same output at nominal 3.58 and
4.43 MHz points.
Fig. 2-11 shows markers being used in a frequency response
measurement application.
(See Figs. 2-1 or 2-2 for equipment
setups.) The markers are displayed through one vertical channel
of a dual channel oscilloscope, while the sweep amplitude is
displayed in the other channel through an amplifier having good
overdrive recovery capabilities.
NOTE
The MARKER output should not be terminated.
OPERATING CONSIDERATIONS
Harmonics of Digital Sweep
Digital data generated by the Digital Sweep Generator has 10-bit
accuracy and resolution.
This provides 1024 possible levels of
output from a digital to analog converter.
Every analog sample
point is rounded to the nearest discrete level.
Therefore, every
analog sample may have an error of up to 1/2048 of full scale.
DAC nonlinearities will also contribute to errors in the analog
output.
Different digital words are used to generate different
frequencies.
Taking all these factors into account harmonics of
the reconstructed analog signal will typically be 60 dB down but
are strongly dependent on the quality of the digital to analog
converter.
ECL Data Transmission
Transmission of digital data from the Digital Sweep Generator
uses differential ECL (emitter-coupled logic).
This offers good
speed and noise margin when received by a differential ECL
receiver.
Due to the speed of .ECL signals, the cables must be
viewed as a transmmission line and should be terminated with its
characteristic impedance at the receiving end.
ECL gate outputs
2-9
Advertisement
