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3.2
Two-Tone OIP3 Test
The output third-order intercept point (OIP3) is a measure of the linearity performance of a nonlinear
device. It is measured by a two-tone test. The following exercise measures OIP3 following all listed steps
in
Section
3.1.
1. Press Mode → More (1 of 2) → Multitone.
2. Highlight row 11 for frequency offset = 4.5 MHz, press Toggle State, and then press Apply Multitone
to turn on a 4.5-MHz tone. Now, two tones with equal amplitude and frequencies, f
f
= 5.5 MHz, are configured for E4438C.
2
3. Measure the RF power of both RF tones, P
4. Measure the power, P
approximately –66.5 dBm after the cable loss compensation.
5. OIP
can be calculated by the equation OIP
3
either the low- or the high-frequency tone is selected as the OIP3 of the modulator. The OIP3 at 1 GHz
is approximately –29.8 dBm ± 1 dBm. Caution must be taken for accurately measuring the small P
when the large P
analyzer so that the IM3 component is at least 20 dB above the noise floor, as well as by increasing
the RF attenuator setting until P
f
-f
LO 2
SLWU084 – June 2013
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, of the third-order intermodulation product associated with each RF tone. It is
IM3
is present. It is helpful to reduce the span and RBW settings of the spectrum
0
is no longer varying with increased RF attenuation setting.
IM3
f
-f
f
LO 1
Figure 3. Two-Tone OIP3 Output Spectrum
Copyright © 2013, Texas Instruments Incorporated
, which must be between –1.8 dBm to –2.8 dBm.
0
= P
+ (P
– P
)/2. The worst OIP3 associated with
3
0
0
IM3
P
0_low
P
IM3_low
P
IM2
f
+(f -f )
f
LO
LO
2 1
LO 1
EVM Test Procedure
= 4.5 and
1
P
0_high
P
IM3_low
+f
f
+f
LO 2
TRF37T05EVM Evaluation Module
IM3
5
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