Atek HP 8753D, User Manual, Page: 387 / 677

T able 6-9. Time Domain Reection F ormats
F ormat P arameter
LIN MA G Reection Coecient (unitless) (0 << 1)
REAL Reection Coecient (unitless) (01 << 1)
LOG MA G Return Loss (dB)
SWR Standing W ave Ratio (unitless)
Transmission Measurements Using Bandpass Mode
The bandpass mode can also transform transmission measurements to the time domain. F or
example , this mode can provide information about a surface acoustic wave (SA W) lter that
is not apparent in the frequency domain. Figure 6-63 illustrates a time domain bandpass
measurement of a 321 MHz SA W lter .
Figure 6-63. Transmission Measurement in Time Domain Bandpass Mode
Interpreting the bandpass transmission response horizontal axis . In time domain
transmission measurements , the horizontal axis is displayed in units of time . The time axis
indicates the propagation delay through the device . Note that in time domain transmission
measurements , the value displayed is the actual delay (not x2). The marker provides the
propagation delay in both time and distance .
Marker 2 in Figure 6-63 a indicates the main path response through the test device , which
has a propagation delay of 655.6 ns , or about 196.5 meters in electrical length. Marker 4 in
Figure 6-63b indicates the triple-travel path response at 1.91 s , or about 573.5 meters . The
response at marker 1 (at 0 seconds) is an RF feedthru leakage path. In addition to the triple
travel path response , there are several other multi-path responses through the test device ,
which are inherent in the design of a SA W lter .
Interpreting the bandpass transmission response vertical axis . In the log magnitude
format, the vertical axis displays the transmission loss or gain in dB; in the linear magnitude
format it displays the transmission coecient ( ). Think of this as an average of the
transmission response over the measurement frequency range .
Application and Operation Concepts 6-121