LW120 User Manual
gating signal goes low, is the last point on the waveform.
Burst Mode
The burst mode is an extension of the triggered mode where the
generator can be programmed to output a pre-determined number of
waveforms. The source to trigger the burst can be selected from a
front panel connector, GPIB trigger or from the built-in trigger
generator.
Frequency Agility
Using the latest DDS (direct digital synthesis) technology, the LW120
is extremely agile. Operations like sweep, FSK and FM are directly
derived from the DDS circuit by controlling its input bits. Frequency
agility is described below.
Sweep
The LW120 can sweep from minimum to maximum sample clock
frequency setting. You may select to sweep up or down using linear
or logarithmic steps. Sweep time is programmable from 1 ms to 1000
seconds with 7 digits. The sweep start and stop frequency program
the rear-panel sine output connector. You may also use the sweep
from the front panel as long as you do your own calculation of start
and stop frequencies, depending on the present sample clock
frequency and waveform length. You may use the sweep in
continuous mode, triggered, or gated. The LW120 will also sweep up,
or down, using linear or logarithmic increments.
FSK
FSK (frequency shift keying) function controls the sine output
connector. The trigger input is used to flag the LW120 when to output
carrier frequency (trigger false) or when it should switch to the shift
frequency (trigger true). You may also use the FSK function from the
front panel as long as you do your own calculation of carrier and
shifted frequencies, depending on the present sample clock frequency
and waveform length.
Ramped FSK
Ramped FSK is the same as the FSK function except the output is
ramped instead of switched to the shift frequency. Ramp time is
programmable with 3 digits from 100
µ
s to 1 seconds.
FM
The FM function modulates the LW120 sample clock frequency. You
can frequency modulate the output either with built-in waveforms, or
download complex waveforms to the modulation memory. Using the
latest DDS technology, the modulation is wide band and extremely
linear. FM can be used in continuous, triggered and gated modes.
The LW120 can generate two types of frequency modulation: 1)
Standard and 2) Arbitrary. In standard mode, the modulating
waveform is selected from a built-in library of 4 standard waveforms:
sine, triangle, square and ramped wave shapes. In arbitrary mode,
the modulating signal is downloaded to the modulation waveform
memory. There are 20,000 points allocated specifically for the
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