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CHAPTER 2:
System Overview
Model CRX-6.5K Probe Station
2.5.4 Calibration with
the CS-5 Calibration
Standard
The following concepts are used with permission from the CS-5 instructions.
For the most accurate microwave measurements using a vector network analyzer
(VNA), calibration is required to eliminate the frequency dependent losses of the
associated connectors, cables, and probe tips. The CS-5 or CS-15 calibration substrate
can be used for this purpose. The CS-5 can be used for pitch ranges of 75 to 250 µm
and the CS-15 can be used for pitch ranges of 50 to 150 µm.
Standard elements for calibrating a microwave measurement system consist of
opens, shorts, matched loads, and throughs. These four elements have electrical
characteristics that are very different from one another, so that each one by itself
contributes an important part to the calibration.
FIGURE 2-33 shows the response of a pair of 67 GHz probes placed on a 50
)
through
test structure on the CS-5 calibration substrate. The measurements were made using
a commercial VNA calibration (using mechanical standards) that places the
measurement reference plane at the end of the VNA measurement cables that are
connected to the input connectors of the 67 GHz probe arms. FIGURE 2-33 shows the
frequency dependent characteristics of the probe station with the 67 GHz probes and
probe arms. The performance looks very good, with the transmission coefficients
S21/S12 remaining above -10 dB and the reflection coefficients S11/S22 remaining
below -10 dB over the entire frequency band. The gradual sloping increase in loss (the
decrease in S21/S12) as the frequency increases is expected.
FIGURE 2-34 shows the response of a pair of 67 GHz probes placed on a 50
)
through
test structure following a SOLT calibration using the CS-5 calibration substrate. This
calibration places the VNA measurement reference plane at the end of the probe tips,
and thus, removes the losses of the associated cabling and probes from the
measurement response of an unknown substrate.
FIGURE 2-33
S-parameter response of
67 GHz GSG microwave probes
FIGURE 2-34
Calibrated S-parameter response of 67 GHz GSG
microwave probes
