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42 Agilent E1441A Application Information
Chapter 2
FSK "Hop" Source FSK source: Internal or External. The default is Internal.
Internal Hop Source
When FSK:SOUR is INTernal, the rate at which the output frequency
“shifts” between the carrier frequency and hop frequency is determined by
the FSK rate specified. Figure 2-6 shows FSK operation with INTernal hop
control
External Hop Source
When FSK:SOUR is EXTernal, the output frequency is determined by the
signal level of the source selected by the TRIG:SOUR command. When a
“low”
TTL level is present on the Ext Trig BNC, the carrier frequency is
output. When a “high”
TTL level is present on the Ext Trig BNC, the hop
frequency is output. This logic sense is inverted for the TTLTRG lines.
Figure 2-7 shows FSK operation with external hop control
Use the following command to select the external FSK source:
Figure 2-6. Frequency Shift Keying with INTernal Hop Signal
Carrier period
FSK Output (sine)
INTernal Hop Signal
1/(FSK Rate)
Hop period
Figure 2-7. Frequency Shift Keying with EXTernal Hop Signal
Carrier period
FSK Output (sine)
Hop period
External Hop Signal
(selected by TRIG:SOUR
either EXT or TTLTRG<0-7>)
NOTE: TTLT polarity is always
the opposite of the of EXT TRIG