Stanford Research Systems DS345, Manual

Page: 88 / 139

Performance Tests
5-10
SQUARE WAVE RISE TIME
This test measures the rise time and aberrations of the square wave output.
specification: rise time < 15 ns
overshoot < 5% of peak-to-peak output
1) Connect the output of the DS345 to the 350 MHz oscilloscope with a 50
Ω
terminator. Set the DS345 to square wave , 1 MHz, 10 Vpp.
2) Set the oscilloscope to 2 V/div vertical and 5 ns/div horizontal. Measure
the time between the 10% and 90% points and verify that it is less than 15ns.
Record the results.
3) Set the oscilloscope to 1 V/div vertical and 100 ns/div horizontal. Verify
that the overshoots and undershoots are less than ± 500 mV. Record the re-
sults.
SQUARE WAVE SYMMETRY
This test measures the symmetry of the square wave output.
specification: < 1% of 4ns
1) Connect the output of the DS345 to the A input of the time interval counter
and terminate into 50
Ω.
Set the DS345 to square wave, 1 MHz, 5 Vpp.
2) Set the time interval counter to measure the positive width of the A input.
Record the reading.
3) Set the time interval counter to measure the negative width of the A input.
This reading should be equal to the reading in step 2 < ±14 ns. Record the
result.
AM ENVELOPE DISTORTION
This test measures the distortion of the envelope when the DS345 is ampli-
tude modulating its output.
specification: < -35 dB at 1 kHz
1) Connect the DS345's output to the RF spectrum analyzer. Set the DS345
to sinewave, 1 MHz, 10 Vpp. Set the modulation to AM, sine wave, 1 kHz
rate, 80% depth. Turn the modulation on.
2) Set the spectrum analyzer to 1 MHz center frequency, 20 kHz span.
3) The 1 MHz fundamental output and the two modulation sidebands1 kHz
away should be visible. Verify than any harmonics of the sidebands (at
2kHz, 3 kHz, ... offset) are less than -35 dB down. Record the results.
THIS COMPLETES THE PERFORMANCE TESTS