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then observe the energy of the reflected signal. By analyzing the amplitude, duration and waveform of
the reflected signal, the impedance change of the kit under test can be determined. If time domain
measurement is performed in the cable and antenna mode but the incident impulse or step signal does
not create, and the frequency sweep measurement is performed, then it will calculate the time domain
information from the frequency domain measurement result by the Fourier algorithm, so it is also called
the frequency domain reflexometer.
The S5105D/E/F cable and cable and antenna analyzer mode measures S11 and then performs
time domain conversion measurement. The S11 reflection measurement is not a simple display of the
size of the reflected signal received by the A or B receiver, but shows the ratio measurement
between the measurement receiver and reference receiver. The S11 ratio measurement can be
used to remove system errors in the calibration. This is especially important for
DTF
measurements because the measurement reference plane is established by calibration, and the
calibration point becomes the zero point of the X time axis, and all time and distance data will use this
point as the reference point. In that case, time and amplitude data are very accurate due to calibration.
The time domain measurement of the microwave analyzer usually involves the following steps:
a)
Collect raw data of receiver (A and R) and perform a ratio operation;
b)
Perform error correction;
c)
Transform the frequency domain data into the time domain;
d)
Display measurement result
II. DTF Measurement Resolution and Range
This Section discusses how to observe the effective DTF data of the kit under test and how to set it up
for the higher resolution and maximum measurement range.
1.
Response Resolution
The microwave analyzer's DTF response resolution refers to the microwave analyzer's ability to
distinguish between two adjacent responses. For equal amplitude response, it is equal to the pulse width
of the impulse response defined by the 50% (6dB) amplitude point, or the rise time of step response
defined by 10%
～
90
％
amplitude point as shown in the following figure:
-6dB
-6dB
90%
10%
impulse
width
the step
rise-time
Figure 6-3 Time Domain Response Resolution
The time domain response resolution is subject to the several factors:
a) Frequency span
The figure below shows the effect of the frequency span on the response resolution:
