Specifications

Frequency converters
Figure 38. 85309 LO/IF distribution unit and 85320A/B mixer modules.
The85309BLO/IFdistributionunitandthe85320A/Bmixersdownconvertamicrowave
signal to an IF signal that can be measured by the PNA. The distributed frequency
converter uses external mixers for microwave downconversion. These mixers can be
located directly at the antenna under test. The frequency of operation depends upon the
frequency range of the external mixers selected.
Features
• Allowsmixerstobelocatedattheantennaundertest,minimizingRFcableloss
• Allowsfundamentalmixingto18GHzforbestsensitivity
• Providesbestrejectionofunwantedspurioussignals
Description
The85309BLO/IFdistributionunitcontainsLOsignalamplifiers,whichamplifyLOdrive
power through RF cables to the mixers. The high output power allows the mixers to be
locatedmorethansevenmetersfromthe85309B.Sincethe85309BusesaseparateLO
amplifier for each channel, channel-to-channel isolation of 100 dB is achieved, minimiz-
ing signal leakage from the reference to the test channel and improving the accuracy of
the measurement. There are also IF amplifiers located in the 85309B, which serve as a
preamplifier for the receiver, reducing the overall system noise figure significantly.
AlevelingdetectorinthereferencemixerisusedtoprovidetheproperLOdrivetothe
mixers. It is important to use equal length cables to both the reference and test mixers
toensurethesamecableloss,andprovidethesameLOdrivepowertobothmixers.
An internal filter in the reference IF channel is designed to pass frequencies below
20 MHz. This allows the proper IF signal to be passed for both PNA Option 014 and
PNA Option H11.
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