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8-9 RECEIVER MODE The Receiver Mode provides three distinct modes of operation:
q
Sweep/Source Lock mode, phase locks the internal source
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Synthesizer/Tracking mode, lets the receiver track a 67XXB,
68XXXB, or 69XXXA synthesizer
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Set-On mode, lets the VNA operate as a tuned receiver
Source Lock Mode The Source Lock mode enables the 37xxxE to phase lock to its internal
source.
Tracking Mode In the Tracking Mode, the 37xxxE steers its second local oscillator fre
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quency and phase signal so as to phase-lock itself to the reference sig
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nal. Typically the source is a synthesizer, since it must be accurate to
better than ±10 MHz for the 37xxxE to achieve lock. Due to the inher
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ent resolution of the 37xxxE, frequency resolution is limited to 1 kHz
intervals. If Option 3 is installed frequency resolution is limited to 1
Hz.
For receive frequencies outside the indicated test set range, the use of
external mixers and a synthesizer is required. Dual Source Control is
required in this case.
Set-on Mode In the Set-On mode, the source lock circuitry of the 37xxxE is com-
pletely by-passed. Reference signals are no longer necessary for system
operation. This allows all of the 37xxxE samplers to operate over their
full dynamic range. As a result, the source and the 37xxxE must be
locked to the same 10 MHz time base, otherwise coherent detection is
not possible. Only synthesized sources may be used in this mode. Dual
source control is required.
Due to the inherent resolution of the 37xxxE local oscillators, fre
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quency resolution is limited to 1 kHz intervals over the frequency
range of the VNA. If Option 3 is installed, frequency resolution is lim
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ited to 1 Hz.
RECEIVER MODE MEASUREMENTS
8-58 37xxxE OM