Chapter 9 363
Assembly Descriptions and Block Diagrams
RF and LO Section for 8590L, 8591E, and 8591C Spectrum Analyzers
A6 YIG Tuned Oscillator (YTO)
The A6 YTO contains a YIG (yttrium-iron-garnet) which is a
ferro-magnetic material polished into a small sphere and precisely
oriented in a magnetic field. The A7 analog interface assembly provides
the control current that alters the magnetic field to generate the
required YTO frequency.
The YTO provides the 2.1214 GHz to 3.9214 GHz first LO. The YTO
output is sent to a power splitter in the A4 first converter assembly. The
power splitter routes the first LO signal to the first mixer and the
A25A1 sampler.
A7 Analog Interface
The A7 analog interface assembly receives digital control input on the
I/O bus control lines from the A16 processor/video assembly, and
produces analog control signals for most of the analyzer functions. This
section describes several of the control functions illustrated on
Figure 9-1.
The A7 analog interface assembly provides control voltages for the
Sweep Generator and Span Dividers:
• The SWEEP RAMP output is 0 to +10 V.
• The RAMP output is −10 V to +10 V for any span.
• Two SPAN signals, MAIN SPAN and FM SPAN, are generated by
attenuating the RAMP signal. The MAIN SPAN and FM SPAN
signals are fed to the YTO drivers to sweep the YTO frequency. The
amplitude of the SPAN signals depends on the span setting selected.
If the LO span is greater than 10 MHz, then the MAIN SPAN
signal is used.
If the LO span is less than or equal to 10 MHz, then the FM
SPAN signal is used.
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