(J3)
LMH9226
(J2)
LMH9226 RRL EVM
(J4)
Vector Network Analyzer
Zo(diff) = 100
Ÿ
Zo(se) = 50
Ÿ
EVM Overview
8
SBOU237 – December 2019
Copyright © 2019, Texas Instruments Incorporated
LMH9226 Evaluation Module
2.4
Stack up and Material
The LMH9226 EVM is a 56-mil, 4-layer board whose material type is Isola
®
370HR. The top layer routes
the power, ground, and signals to and from the device. The signal impedance is targeted at 49.9
Ω
. The
bottom 3 layers are ground layers.
Figure 7. LMH9226 EVM Stack-up (Units in Mils)
3
Test Setup Diagrams
This section includes general recommendations for S-parameter, noise figure, and two-tone OIP3 setup
while measuring the LMH9226 EVM.
3.1
S-Parameter Test Setup
Figure 8. S-Parameter Test Setup
Use the following guidelines for S-parameter measurement:
1. S-parameter measurement is typically done using a Vector Network Analyzer (VNA), as
shows. For measuring the LMH9226 EVM, a 4-port VNA is recommended which can generate and
receive truly differential signals at the input and output ports.
2. Before connecting the RF coax cables to the LMH9226 EVM, you must calibrate the VNA along with
the cables using a calibration kit. This accounts for any cable losses in the S-parameter calculation at
the VNA and helps set reference impedance at the cable ends.
3. Make sure the frequency sweep and output power level from the VNA is set within the linear operating
range of the LMH9226 devices. The resolution bandwidth (RBW) and dynamic range of the VNA can
be adjusted to give optimum sweep time for the measurement.
4. It is important to account for onboard trace losses at the input and output pins of the device. De-
embedding of the input and output traces is recommended to improve the S-parameter measurement