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Topics Covered
Background
Introduction
Measurement Procedure and Instrumentation
PC Board Strip Line Semirigid Cable BeCu Probes
Background
Lake
Shore Cryotronics, Inc. is a privately held corporation which has been an
international leader in the development of innovative measurement and control
technologies since 1968. Lake Shore's philosophy has been to continue to reinvest in
itself with a research and development budget that is 100 percent above the
national average for instrumentation companies.
Introduction
Microwave measurements on a TTP4
probe station with semirigid coaxial arms with SMA connectors (K-085-K)
were
performed from 30 kHz to 6 GHz. The probe tips were BeCu (ZN50R-25-BeCu). All
measurements reported here were at
room temperature.
Measurement Procedure and Instrumentation
The transmission (S12) and reflection (S11) coefficients of a TTP4 probe
station with semirigid arms were measured. The measurements were
performed using a Hewlett-Packard HP8753ES S-parameter Network
Analyzer. The frequency range of the measurements was 30 kHz to 6 GHz.
This network analyzer has APC 7 mm connectors. A custom cable was manufactured
for the measurements. The cable was 3 ft of Trompeter SEMFLEX 50 Ω coax
with an APC 7 mm connector on one end and SMA connectors on the other end. Passive
50 Ω strip line was used for the measurements. Figure 1 is a picture of
the circuit. To measure the frequency response of the test circuit, two measurements
were performed. The first was with a 25 cm length of semirigid cable soldered
to the strip line. These soldered connections also had a signal ground directly
at the sample. In the data plots, these are referred to as "soldered connection".
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Figure 1. 50 Ω strip line circuit
PC Board Strip Line Semirigid Cable BeCu Probes
The measurements of the sample consisted of an 8 cm length of 50 Ω strip
line on a sample of printed circuit board. The
line was printed in an s-pattern to fit the available space, and simply served
as a sample to test the measurement
characteristics of the ZN50 probes and the probe station arms. The plots of
S21 and S22 are shown in figures 2 and 3. The
large spike in S21 at 400 MHz is related to the break in the ground from the
probe to the sample.
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Figure2. S21 (forward scattering parameter)
vs. Frequency, PC board strip line
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Figure 3. S11 vs. Frequency, PC board strip
line
Figure 4 shows similar measurements in a TTP6
probe station. We see that the attenuation peak has moved up to about 800
MHz.
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Figure 4 TTP6 Attenuation and Reflection
Source Lake Shore Cryotronics
For more information on this source please visit Lake
Shore Cryotronics