Specifications

http://www.anritsu.com 377
NETWORK ANALYZERS
7
Measurement accuracy
•Transmission loss or gain measurement accuracy
Uncertainties from the frequency response of components are auto-
matically subtracted from test data during the path calibration proce-
dure. Overall accuracy is then:
Channel accuracy
+ Mismatch uncertainty
+ Distortion from source harmonics
Transmission measurement accuracy
Effects of source, test device, SWR autotester, and detector mismatch
can be significant. This mismatch uncertainty is minimized by the ex-
ceptionally low reflection characteristics of Wiltron’s detectors,
sources, and SWR autotesters. Anritsu’s ultra low source harmonics
maximize the accuracy.
Return loss measurement accuracy
Uncertainties resulting from SWR autotester and source frequency
response and from system open and short characteristics are sub-
tracted automatically from test data. Overall accuracy is then:
Channel accuracy
+ Autotester accuracy
+ Distortion from source harmonics
Return loss measurement accuracy
Autotester accuracy is composed of error due to directivity and error
due to test port match. Unless the DUT has very poor return loss (high
SWR), test port match will be negligible. When an adapter is used at
the test port, use effective directivity to determine possible errors.
•Return loss accuracy due to directivity
Improved directivity decreases SWR (or return loss) measurement
errors. The chart below identifies maximum error due to directivity.
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
+16 [phone]
Input power (dBm)
Accuracy (+/– dB)
Channel accuracy (25˚C)
•Distortion from source harmonics
Poor source harmonics cause large measurement errors. If the
sweep range is set wide enough, at some point during the sweep, the
harmonic will pass through the filter’s pass band. Since the trans-
mission detector is a broadband diode, the harmonic’s signal power
is measured. Thus, the analyzer displays the response of the har-
monic in addition to the fundamental sweep frequency.
•Bandpass filter, distortion from source harmonics
If the source has a –30 dBc second harmonic and a –35 dBc third
harmonic, at the beginning of the sweep, the harmonics pass
through the filter’s passband.
–30
–40
–20
–10
0
(dB)
f
c
1/2 f
c
1/3 f
c
Bandpass
filter
Frequency
Transmission loss
•Highpass filter, distortion from source harmonics
A highpass (or wide bandpass) filter responds similarly to the band-
pass filter, except the presence of the harmonic in the filter’s pass
band limits the useful dynamic range of the analyzer.
–30
–40
–20
–10
0
(dB)
f
c
1/2 f
c
1/3 f
c
Highpass
filter
Frequency
Transmission loss
−4.00
−3.00
−2.00
−1.00
0.00
1.00
2.00
3.00
4.00
10 dB 20 dB 30 dB 40 dB0 dB
20 dB
2
5
d
B
30 dB
35 dB
45 dB
50 dB
50 dB
20 dB
25 dB
30 dB
35 dB
40 dB
45 dB
40 dB
SWR autotester
directivity
Possible error (dB)
•Return loss accuracy due to effective directivity
Effective directivity is the reduction to directivity due to a test port
adapter’s SWR performance. Adapters severely degrade measure-
ment directivity. The chart below shows the maximum degradation to
a 40 dB directivity SWR autotester caused by test port adapters of
varying quality.
−4.00
−3.00
−2.00
−1.00
0.00
1.00
2.00
3.00
4.00
10 dB 20 dB 30 dB 40 dB0 dB
1.30
1.30
1.20
1.20
1.15
1.15
1.10
1.10
1.05
1.05
Adapter
SWR
Possible error (dB)
1
.
0
0
(
N
o
a
d
a
p
t
e
r
)
1
.
0
0
(
N
o
a
d
a
p
t
e
r
)
•Return loss accuracy due to source harmonics
Source harmonics are a significant source of return loss measure-
ment uncertainty when testing banded devices such as filters, re-
ceivers, transmitters, power amplifiers, and antennas. In many cas-
es, the harmonic errors are larger than uncertainty due to directivity,
which is typically assumed to be the largest uncertainty factor.
−4.00
−3.00
−2.00
−1.00
0.00
1.00
2.00
3.00
4.00
10 dB
20 dB
30 dB
40 dB
0 dB
Possible error (dB)
Source harmonic
level
−25 dB
−30 dB
−35 dB
−40 dB
−45 dB
−50 dB
−60 dB
−60 dB
−50 dB
−45 dB
−40 dB
−35 dB
−30 dB
−25 dB
This chart assumes full reflections of a single source harmonic at the
DUT input. Multiple harmonics can cause additional measurement
uncertainty.