Agilent Technologies E1441A user service Internal Hop Source, External Hop Source, Chapter

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 2-6shows FSK operation with INTernal hop control

FSK Output (sine)

Carrier period Hop period

INTernal Hop Signal

1/(FSK Rate)

Figure 2-6. Frequency Shift Keying with INTernal Hop Signal

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 2-7shows FSK operation with external hop control

FSK Output (sine)

Carrier period

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

Figure 2-7. Frequency Shift Keying with EXTernal Hop Signal

Use the following command to select the external FSK source:

42 Agilent E1441A Application Information Chapter 2