Description - HP 3585A Service Manual

General Information
On the title page of this manual is a Microfiche part number. This number can be used to
order 4 x 6 inch microfilm transparencies of these publications . The Microfiche package in­
cludes the latest Manual Changes supplement and all pertinent Service Notes.
1 ·4. DESCRIPTION
The 3585A is a 20 Hz to 40. 1 MHz, microcomputer controlled spectrum analyzer. It may be
utilized for spectrum analysis or network analysis (amplitude only) applications. As a spec­
trum analyzer, the 3585A provides a graphic display of the spectral components of the input
signal. For network analysis measurements, the 3585A Tracking Generator can be used as a
drive signal for the network under test. The network's output can then be applied to the
3585A input to obtain a graphic display of the network's amplitude versus frequency
response.
The 3585A is structured as a conventional triple-conversion, swept super-heterodyne spec­
trum analyzer. The addition of microcomputer hardware control and data manipulation
greatly enhances the analytical power of the 3585A. Flexible control of the displayed trace is
obtained through dedicated key subroutines that produce optimum displayed results in a
minimum amount of time.
Microcomputer control gives the 3585A several unique features. The most obvious feature is
the keyboard entry of parameters which replaces more conventional knobs. The input at­
tenuation and mixer levels are automatically set by the 3585A's Auto Range feature to main­
tain the specified dynamic range. Other microcomputer controlled features include: coupl­
ing of Frequency Span, Bandwidth and Sweep Time; centering of signals; moving signals to
the Reference Level and storage and measurement of frequency and amplitude Offsets.
Microcomputer control further allows the operator to override the automatic features of the
3585A.
The 3585A's Local Oscillator is fully synthesized using -hp-'s patented Fractional N techni­
que. This provides frequency settability of 0. 1 Hz over the 20 Hz to 40. 1 MHz range.
Beyond the advantage of high system resolution, the 3585A's Synthesized Local Oscillator
allows stable, repeatable frequency measurements. The advanced design of the 3585A's
Fractional N synthesized Local Oscillator also results in phase-continuous , linear sweeps
with low spurious sidebands.
The amplitude accuracy of the 3585A is enhanced by an Automatic Calibration system,
through which internal analog offsets and errors are removed using the internal 10 MHz
reference as a level and frequency standard and the Tracking Generator with an internal
calibrator as a flatness standard. The calibration system measures and corrects errors caused
by IF frequency and gain shifts, and input gain and flatness deviations. It also corrects the
Tracking Generator frequency.
The trace information displayed on the 3585A CRT is digitally stored in memory. As a
result, flicker-free, non-blooming displays are maintained independent of sweep time.
Marker information and Entry parameters are displayed above and below the CRT graticule
to give the operator the present instrument status. Prefaced parameters are intensified for
easy data entry.
1 -2
Model 3585A