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1281A
User Manual
Start Frequency – programs the start frequency value for the
carrier waveform.
Stop Frequency – programs the stop frequency value for the
carrier waveform.
Sample Clk – This parameter specifies where the sweep will stop.
Note that sweep stop does not necessarily have to have lower
value than the sweep stop frequency. If you define sweep stop
frequency higher than the sweep start frequency, then the
generator will sweep up. You can also reverse the direction of the
sweep by using the sweep direction parameter.
Sweep Time – sets the time that will lapse for the 1281A output to
execute one complete sweep cycle.
Marker – defines a frequency of which, when transitioned through,
will output a marker pulse at the SYNC output connector. The
default position of the marker is the sweep start frequency.
Amplitude – programs the amplitude of the carrier waveform.
Offset – programs the offset of the carrier waveform.
Using the
Auxiliary
Functions
The 1281A has some auxiliary functions that are not directly related
to the operation of a traditional arbitrary waveform generator
however, since the hardware was there, the implementation was
done in firmware and software allowing transformation of the
waveform generator to entirely different entities.
The 1281A has two auxiliary functions: digital pulse generator and
counter/timer. Description of these functions is given below.
Digital Pulse
Generator
The Digital Pulse Generator feature adds capability to the 1281A in
a form that allows programming pulse parameters in units of time,
exactly as they are being programmed in a dedicated pulse
generator product except, the waveforms are bring generated from
a digital circuit and make use of the large bank of arbitrary
waveform memory that is available in the instrument.
Because the waveform is being generated digitally, the smallest
increment of the pulse definition is a function of the size of the
memory. The basic 1281A has 8 Million points of memory and
therefore the smallest increment can be designed as 1/8e6 of the
programmed period. For example, 2 ns of pulse width can be
designed within a maximum period of 16 ms. As another example;
Repetition rate of 1600 seconds can be designed with resolution of
200 µs.
The down side of the above feature is that the arbitrary waveform
and the digital pulse design share one memory and therefore, the
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