3-46 ES User’s Guide
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
.
2. To interpret the measurement, refer to Figure 3-17, “Example of an
S21 Measurement Display,” or your analyzer's display if you are
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:
where P
trans
= the power transmitted through the device and
where P
inc
= the incident power.
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
.
4. Note the marker readout in Figure 3-17 provides the frequency and
amplitude of the minimum insertion-loss point.
SCALE
Transmission dB() 10 log
P
trans
P
inc
--------------
=
MARKER
−
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