Bandwidth Limited Noise - Stanford Research Systems DS360 Operating Manual And Programming Reference

3-16 Operation
the current value. If an out of range value is entered, the unit will beep, display " D epth
Err " and flash the ERR LED.
Gated Output
When the DS360 is set to gated output mode (see Burst Trigger Source) the output is
gated on and off from the TRIGGER/GATE IN BNC. A TTL high level outputs the
"ON" level and TTL low the "OFF" level. For sine and square waves, level changing
occurs at zero crossings. Because of this there is an uncertainty of between 0 and one
cycle from the rising edge of the TRIGGER/GATE IN BNC and the actual level change
of the output. Similarly there is an uncertainty at the falling edge. The BURST OUT
BNC signal, which is high while the "ON" level is active should be used if it is necessary
to synchronize the DS360 with an external device instead of the external gating signal.
This is not a problem for gated noise signals, since it isn't synchronized to anything.
1/2 Cycle Burst
The DS360 has a special mode where it can output a 1/2 cycle burst of a sine or square
waves. The polarity is fixed (positive for the positive output; negative for the negative
output). To use the 1/2 cycle burst count, type .5, followed by an entry key. The spin
knob cannot be used to enter this value. The burst rate can be set to any legal value and
all triggering modes are valid.

Bandwidth Limited Noise

Bandwidth limited noise is active for white noise only. The purpose of bandwidth limited
noise is to maximize the noise power in the frequency of interest. The bandwidth limited
white noise in the DS360 maintains a constant RMS voltage over nearly all bandwidths
and center frequencies (see information in the CENTER FREQUENCY section below
for more information). The bandwidth limiting is accomplished using a 3-Pole
Butterworth Filter, for both the high and low pass filters. Use the MODIFY FUNC
[ON/OFF] key to begin or end bandwidth limited noise.
Bandwidth
The Bandwidth of the bandwidth limited noise can be set to any of the following values:
100 Hz, 200 Hz, 400 Hz, 800 Hz, 1.60 kHz, 3.20 kHz, 6.40 kHz, 12.8 kHz, 25.6 kHz,
51.2 kHz or 102.4 kHz. These correspond to 1/2 bandwidth frequency spans, starting
from the full bandwidth of the white noise.
To display the current bandwidth, press the [BW] key. To enter a new value, type the
value followed by the appropriate units key (Hz or kHz). Or use spin knob to modify the
current value. If the bandwidth is not entered exactly, the DS360 will round down to the
next legal value for all values above 100 Hz; below 100 Hz will round to 100 Hz. If an
out of range value is entered, the DS360 will beep, display " F req Err " and flash the ERR
LED.
DS360 Ultra Low Distortion Function Generator