User`s guide
Using the One Button Measurements to Measure N
dB
Bandwidth, Percent Amplitude Modulation, and Third Order
Intercept
(TOI)
The spectrum analyzer includes one-button measurement functions. With one key press they
make accurate measurements of:
w
N
dB
Bandwidth
n Percent Amplitude Modulation
n Third Order Intermodulation
The signal or signals being measured must be displayed before activating the measurement.
Measurements are made continuously, updating at the end of each sweep. This allows you to
make adjustments and see changes as they happen. The single sweep mode can also be used,
providing time to study or record the data. The individual measurements are described below.
N
dB
Bandwidth Measurement
It is often necessary to measure a signal response’s bandwidth, such as when testing a
band-pass filter. The signal to be measured must be centered on the display with a span that
includes the full response. Activate the measurement by turning the N
dB
PTS ON OFF key
(ON). The spectrum analyzer places arrow markers at the -3
dB
points on either side of the
response and reads the bandwidth. For other bandwidth responses enter the number of
dB
down desired, from 1
dB
to 80
dB.
No other signal can appear on the display within N
dB
of the highest signal. The measured
signal cannot have more than one peak that is greater than or equal to N
dB.
A signal must
have a peak greater than the peak excursion to be identified. The default value for the peak
excursion is 6
dB.
The N
dB
bandwidth measurement error is typically:
n about
*2%
of the span, for spans
~10
MHz
n about
f3%
of the span, for spans
>lO
MHz
16:38:08
12 MAR 1992
&
REF
.0
dGm
ATTEN
i0
dG
rLRK
LOG
-6.0dG
POINTS:
9.00 kHz
10
.;
dG/
:
N
dG
""
-6.00
dB
-I
CENTER 300.0000 MHz
SPAN 100.0 kHz
#RES GW 9.6 kHz
UGW 30 kHz
SWP 33.3
lnsec
R
Figure 4-34. N
dB
Bandwidth Measurement
Making Measurements 4-39