User Manual
22
UM-20 Low-cost Oven-controlled Crystal Oscillator (OCXO) Assembly
Figure 9: OCXO131-40 waveform (blue) compared to
Z3805A GPS-disciplined waveform (yellow)
Summary
The low-cost OCXO PCB assembly achieves the stated
performance of the IsoTemp OCXO131-40, and includes some
user-friendly features that improve on the original, MTI-based
unit
12
that became Option 115 in later XL Microwave 3xxx units.
The tuning range is a function of the fixed resistors
R6
and
R8
in
the design. The design can conceivably be used for other
applications.
The frequency stability of the IsoTemp OCXO131-40 remains less
than that of its larger sibling, the IsoTemp OCXO36-44, which was
apparently used as Option 115 on earlier Model 3xxx frequency
counters.
Future Work / Enhancements
A small microcontroller (MCU) that sensed temperature and could
drive a digital / programmable divider or voltage source would be
an even better way to set
V_TRIM
; with a terminal interface to the
MCU and with non-volatile memory (NVM), the MCU could
implement a control algorithm to maximize oscillator performance
during warmup and over a wide temperature range, with the ability
to store critical parameters in NVM. A command and telemetry
interface would permit this to be automated.
12
Interestingly, MTI now offers the 220-series OCXO in standard, hi-rel and space
versions.
Содержание UM-20
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