Document 343 -1
Transmission Line Model
These transmission line models accurately simulate the
frequency-dependent behavior of Coilcraft surface mount
“Spring” air core inductors within the frequency limits
shown in the accompanying table for each individual
inductor. They are based on de-embedded measure-
ments using a 2-port network analyzer.
The model schematic, shown below, combines an ideal
transmission line model with lumped elements. Each
model should be analyzed only as a whole at the input and
output ports. Conclusions based on individual lumped
element values may be erroneous. The individual element
values R1, R2, C, Z0, EL, and F0 are listed in the table for
each individual spring inductor.
C
R1
Calibration
plane
Mini
Springs™
Table 1. Test Gap
Size
Size A
Size B
Gap Width (inch / mm)
0.060 / 1,524
0.120 / 3,048
Pad
Air gap
Pad
Brass
ground
plane
P1
50 Ohm
TL1
Z0
EL
F0
Figure 1. Test Setup
R2
P2
50 Ohm
(50 Ohm) wide traces of tinned gold over 25 mil thick
alumina, and were not included in the gap. The TRL*
calibration plane is also illustrated in Figure 1.
The lumped element values were determined by matching
the simulation model to an average of the measurements.
This method results in a model that represents as closely
as possible the typical frequency-dependent behavior
of the component within the specified frequency limits of
the model. The lumped element models were used to
generate our 2-port S-parameters and therefore give
identical results with the same number of simulation
frequency points. The S-parameters are available on
our web site at
http://www.coilcraft.com/models.cfm.
Effects due to different circuit board traces, board
materials, ground planes or interactions with other com-
ponents are not included. They
will
have a significant
effect when comparing the simulation to measurements
of the individual inductors using other production verifi-
cation instruments and fixtures.
Typically, the Self-Resonant Frequency (SRF) of the
inductor model will be higher than a measurement of the
component mounted on a circuit board. The parasitic
reactive elements of a circuit board or fixture will effec-
tively lower the circuit resonant frequency, especially for
very small inductance values. Data sheet specifications
are based on typical production measurements. These
models are based on de-embedded 2-port measurements
as described below, so the model results may be different
from the data sheet specifications.
Disclaimer
Coilcraft makes every attempt to provide accurate mea-
surement data and software, representative of our com-
ponents, in a usable format. Coilcraft, however, disclaims
all warrants relating to the use of its data and software,
whether expressed or implied, including without limitation
any implied warranties of merchantability or fitness for a
particular purpose. Coilcraft cannot and will not be liable
for any special, incidental, consequential, indirect or
similar damages occurring with the use of the data and/
or software.
Lumped Element Modeling Method
The measurements were made over a brass ground plane
with each component centered over an air gap, as
illustrated in Figure 1. The gap width for each size
component is given in Table 1. The test pads were 30 mil
Specifications subject to change without notice.
Document 343-1 Revised 05/21/03
Electronics Design Contest
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