(J3)
LMH9226
(J2)
LMH9226 RRL EVM
(J4)
RF Signal Gen 1
Spectrum Analyzer
Marki BAL-0010
or Similar
0°
180
°
2:1, Zo = 50
Ÿ
Zo(diff) = 100
Ÿ
3-dB pad
3-dB pad
3-dB pad
3-dB pad
Zo(se) = 50
Ÿ
RF Signal Gen 2
Power Splitter/
Combiner
6-dB pad
6-dB pad
Test Setup Diagrams
10
SBOU237 – December 2019
Copyright © 2019, Texas Instruments Incorporated
LMH9226 Evaluation Module
4. If the device output loss is significant, it is important to factor the output loss into the NF measurement.
5. Using the
Friis
equation is helpful when calculating combined NF of the measurement setup, and then
back calculating the individual device noise figure.
3.3
Two-Tone OIP3 Test Setup
Figure 12. OIP3 Test Setup
Use the following guidelines for two-tone OIP3 measurement:
1. As
shows, combine two signal generator outputs using an in-phase power splitter and
combiner. A 6-dB attenuator is recommended at the signal generator outputs to prevent the generators
from talking to each other and resulting in signal generator IMD3 spurs.
2. Set both the signal generator outputs to a power level and frequency spacing such that it would yield
the desired output power (P
OUT
) at the device.
3. TI recommends that the output power level is within the linear operation range of the LMH9226 device.
For example, if the total desired output power at the device is 8 dBm, then set the signal generators
such that each of the fundamental output power results in 2 dBm per tone. However, if each output
tone is at 8 dBm instead, the amplifier linearity will degrade as a result of higher total composite output
power of 14 dBm at the device outputs. As a general rule, it is recommended to keep the total output
power level approximately 6 to 8 dB lower than the 1-dB compression point. Also, see the device data
sheet for the recommended output power levels supported by the device.
4. For the OIP3 test, the two tones can be spaced ±10 MHz with respect to the desired center frequency
5. TI recommends setting the spectrum analyzer attenuation setting from 20 to 26 dB based on sweet
spot of the incoming input power level
6. Keep spectrum analyzer RBW and VBW settings identical for main tone and IM3 products
7. For output IP3 calculation, take into account combined losses at the desired frequency band between
the LMH9226 device output to the spectrum analyzer input. The combined power losses include loss
due to PCB output trace, RF coax cable, 0/180
◦
passive balun and any attenuator pad used for external
matching purposes. The calculated OIP3 is given in .
Output IP3 = (P
IN_SA
– IMD3) / 2 + P
IN_SA
+ P
LOSS
where,
•
P
IN_SA
= Input power per tone into the spectrum analyzer
•
P
LOSS
= Power loss from the device output to the spectrum analyzer input
•
IMD3 = Higher power of the two inter-modulation distortion products recorded at either 2f1 – f2 or 2f2 – f1
8. The thing to note in is the P
IN_SA
+ P
LOSS
= P
OUT
which is the amplifier output power per tone.