HP 70427A User Manual page 436

13
General Theory of
Operation: Microwave
Deck Assemblies
NOTE
Block Diagram
There are three versions of the Microwave Deck (Assembly A5) used in the
HP 7042XA family of products. The simplest version is used in the
HP 70428A Microwave Source. This assembly generates a low noise,
microwave reference signal from 2.4 GHz to 25.8 GHz in 600 MHz steps,
and will overrange to 26.4 GHz. The microwave signal is generated by
frequency multiplication of the 600 MHz Reference Module output
(Assembly A7).
The HP 70428A opt 002 Microwave Source uses the microwave step
reference function generated by the HP 70428A's deck to frequency
up-convert an external RF Source between 120 MHz and 700 MHz to
produce continuous frequency coverage from 2.4 GHz to 26.5 GHz.
The HP 70427A Microwave downconverter fundamentally mixes external
microwave signals between 2.4 GHz and 26.5 GHz with the microwave step
reference function generated by the HP 70428A's deck to produce an
Intermediate Frequency (IF) between 5 MHz and 1200 MHz.
The tuning sensitivity of the 600 MHz Reference is present on the
microwave stepped reference. Tuning sensitivity of the 600 MHz Reference
is adjustable in three steps, 0.05 ppm/V, 1 ppm/V and 20 ppm/V, plus the
default mode of 0 ppm/V. Tuning is done by injecting the voltage control
signal, from the front panel, into one of the three different oscillators in the
600 MHz Reference.
The tuning sensitivity must be adequate to acquire and maintain phase-lock
with the device under test (DUT) during a phase noise measurement, without
degrading the measurement of the DUT. The 600 MHz Reference phase
noise, close to the carrier, degrades as the tuning sensitivity is increased
above 0.05 ppm/V, but allows for a greater drift tracking range to be used
with noisy DUTs.)
HP 70427A/HP 70428A User's Guide 13-1