View And Interpret The S21 Measurement Results - HP 8712ES User Manual

Making Measurements
Measuring S21 Forward Transmission using an Enhanced Response Calibration
View and Interpret the S21 Measurement
Results
1. To view the entire measurement trace on the display, press
Autoscale .
2. To interpret the measurement, refer to
S21 Measurement Display,"
making this measurement on your instrument.
a. The values shown on the horizontal axis are the frequencies in
MHz. The values shown on the vertical axis are the power ratios
in decibels (dB) of the transmitted signal through the device
divided by the incident power. To display the result in logarithmic
magnitude format (designated by "Log Mag" at the top of the
measurement screen), the analyzer computes the measurement
trace using the following formula:
Transmission dB
where P = the power transmitted through the device and
trans
where P = the incident power.
inc
b. A level of 0 dB would indicate a perfect through cable or device (no
loss or gain). Values greater than 0 dB indicate that the DUT has
gain. Values less than 0 dB indicate loss.
3. To quickly determine the filter's minimum insertion loss, press
MARKER Marker Search
4. Note the marker readout in
amplitude of the minimum insertion-loss point.
3-46
Figure 3-17, "Example of an
or your analyzer's display if you are
P

trans
( )
= 10 log ------------- -

P
Max Search
Figure 3-17 provides the frequency and
SCALE


inc
−
Mkr > Max
ES User's Guide
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