HP 87114B, Руководство по обслуживанию

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This is very similar to the HP 8711B/12B formula:
RF
out
= (Fractional-N 2 256/4) 0 2340
The HP 8713B/14B fractional-N input frequency will vary from about 32 to 58 MHz as opposed
to the HP 8711B/12B variation of about 36.6 to 57 MHz. In both cases the pulse swallow
circuitry maintains the RF2 signal to be 27.778 kHz below the RF1 signal so that the nal LO
will be 27.778 kHz above the RF , thus generating the proper IF .
In bands 2 through 4, above 1.91 GHz, the RF1 and RF2 signals are divided by 2 to provide an
RF1 frequency of 1169.777778 MHz (the ratio is not exactly 1/2 due to dierences in the way
the pulse swallow circuitry works). The formula for RF output frequency now becomes:
RF
out
= (Fractional-N 2 512/7) 0 1169.777778
The Fractional-N signal now varies from about 42 to 57 MHz to
provide the 1910 to 3000 MHz
RF output in bands 2 through 4. This means that during a full band sweep of
.3 to 3 GHz, the
fractional-N output will rst sweep from about 32 to 58 MHz, then reset to 42 MHz, and sweep
again up to 57 MHz.
A5 Receiver Assembly
Besides the above mentioned coupler change , there is little functional dierence between
the HP 8711B/12B receiver and the HP 8713B/14B receiver assemblies . The most signicant
dierences are listed below:
The coupler is now an external microcircuit with a 16 dB coupling factor .
Some of the lters have dierent cuto/bandpass frequencies .
Some attenuators have dierent values .
A leveling loop is used to maintain proper LO power to the 3 mixers . This eliminates the
need for the LO power adjustment (adjustment #101).
Of course , all input components have been modied to perform at 3 GHz, but from a functional
point of view , little else is changed from the HP 8711B/12B receiver board.
6-8 Theory of Operation