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AMB Trace A Minus Trace B
Description
The AMB command subtracts trace B from trace A (point by point), and sends the result to
trace A. The AMB function remains in effect until it is turned off by executing “AMB OFF;“.
The AMB command is a trace math command and subtracts trace B from trace A in
measurement units (see “CTA” for information about measurement units). Because subtracting
trace B from trace A can cause the result in trace A to be displayed off screen, the trace A
minus trace B plus display line (AMBPL) command can be used. As shown in example 2, if the
trace data value of trace A is 0
dBm
(8000 measurement units), and trace B is -10
dBm
(7000
measurement units), the result of executing AMB is 1000 measurement units. If the AMBPL
command is used instead of AMB, and the display line is set at -50
dBm
(mid-screen), the
result in trace A is kept at mid-screen.
A common use of trace subtraction is to normalize one trace with respect to another. For
example, traces are frequently subtracted to normalize the spectrum analyzer response when a
tracking generator is used. In such applications, amplitude units in
dBm
should be subtracted.
As shown in example 2, subtraction of measurement units is not equivalent to subtraction
of amplitude units. Correct results are obtained if the display line is set to 0
dBm
using DL,
and BML is used to subtract the display line from trace B. See example 3 for an example of
subtracting the display line from trace B.
Query Response
ON
OFF
002
Programming Commands 5-59