Agilent Technologies HP 8642A/B Specifiche Pagina 268

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Description
Pulse Modulated Carriers
When a pulse modulated carrier is input to the phase detector, the PULSED
Carrier Type usually should be selected. Selecting the PULSED Carrier
Type configures the system to display the LNA Toggle softkey each time
the decision to switch the Low Noise Amplifier in or out must be made.
The user is responsible for choosing the correct state for the Low Noise
Amplifier (LNA). To determine if the LNA should be in or out, connect
an oscilloscope to the AUX. MONITOR port on the HP 11848A when the
Connect Diagram appears. If the AUX. MONITOR port output level is less
than 0.5 Vpk with the LNA In, leave the LNA switched in and proceed
with the measurement. If the AUX. MONITOR port output is greater than
0.5 Vpk and there is significant clipping of the noise waveform with the
LNA In, toggle LNA Out then proceed with the measurement. (In the
case of pulsed measurements, clipping of narrow spikes at each edge of
the pulse is acceptable (Refer to Figure
5-1).)
Note that the HP 3048A's
sensitivity (noise floor) is degraded by 20 dB when the LNA is out.
LNA In < 0.5 mV > LNA Out
Consideration for the Pulsed Carrier Function
When the PULSED Carrier function is selected and a phase noise
measurement is being made, other than the phase lock loop type, the user
is responsible for zero beating the sources and maintaining quadrature
during the measurement. Zero beat is accomplished by manually adjusting
the frequency of one of the sources so the beatnote frequency falls within
the capture range for the system ( < 10% of PTR). For quadrature,
monitor the dc level out of the HP 11848A AUX. MONITOR port with an
oscilloscope. If the LNA is switched out, the dc level seen on the scope
must be less than or equal to 20% of the Detector Constant value. If the
LNA is switched in, quadrature must be maintained so that the LNA does
not cause severe clipping.
5-10 Carrier Type
rev.05SEP89
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