Example 6: Offset Causes Valid Negative Source Settings - Agilent Technologies PSA Series User Manual

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FAQs and Helpful Hints and Tips
12E 9 ( )
Source Stop Freq = ----------------------------------------------------------------------------------------------------- -
But 7.02 GHz is not in the range of the signal source.
So the offset or stop frequency should be changed until the calculation
is less than the source maximum frequency. (Find the source maximum
frequency using the PSA command
SOURce:EXTernal:FREQuency:STOP? MAX)

Example 6: Offset Causes VALID Negative Source Settings

Using any PSA and any source:
PSA settings:
• Start Freq = 2.5 GHz
• Stop Freq = 3.0 GHz
• Sweep Points = 101
• Offset = − 3.1 GHz, On
• Harmonic = OFF
This will not cause the "Freq range of ext src exceeded" error.
Reason:
The signal source Start Frequency and the Stop Frequency are both
negative. In this case:
2.5E 9 ( )
Source Start Freq = -------------------------------------------------------------------------------------------------------------- -
3.0E 9 ( )
Source Stop Freq = -------------------------------------------------------------------------------------------------------------- -
In this case both the stop and start frequencies are negative, so this
example looks invalid. But in this special case, the PSA can change its
internal mixing to use a negative mixing harmonic. Then the PSA sets
the source start frequency to the positive value of the calculated stop
frequency. It also sets the source stop frequency to the positive value of
the calculated start frequency. This causes the mixing products to
sweep in reverse, and allows the measurement to be made.
72
12E 9 ( ) 10E 9 ( )
⎛
– ( 5E 9 ( ) )
----------------------------------------- -
+ +
⎝
101 1
1
3.0E 9 ( ) 2.5E 9 ( )
⎛
– ( 3.1E 9 ( ) )
-------------------------------------------- -
+ –
⎝
101 1
1
3.0E 9 ( ) 2.5E 9 ( )
⎛
– ( 3.1E 9 ( ) )
-------------------------------------------- -
+ +
⎝
101 1
1
⎞
–
⎠
–
7.02E 9 ( ) = 7.02 GHz
=
– ⎞
⎠
–
0.605E 9 ( ) = –605 MHz
= –
⎞
–
⎠
–
0.095E 9 ( ) = –95 MHz
= –
Chapter 5