CMU Instrument Design and Function Description
1100.4903.82 3.9 E-4
tuning range of 84 MHz to 168 MHz in locked phase relation.
A fractional divider used in the feedback of the PLL provides the actual
value for the phase detector.
The output signal of the VCO is divided by two or four, buffered and
provided at the MMCX connector NETCLK 1 or NETCLK 2 and serves as
network-specific TTL clock for the DIGITAL BOARD.
Option OCXO REFERENCE OSC. CMU-B11 or B12
This option consists of a printed circuit board with the reference element OCXO (oven-controlled crystal
oscillator), the control circuit and a potentiometer for adjusting the OCXO.
Installation
The option OCXO REFERENCE OSC. is installed on the right side
below the instrument fan such that the potentiometer is easily
accessible from outside without the need for opening the CMU tube.
Connection
The option OCXO is directly inserted via a 10-pin connector on the
MOTHERBOARD and screwed to the module support by means of
three screws.
The options CMU-B11 and B12 are basically of the same design. The two options only differ from each
other in the technical data of the OCXO such as aging and frequency drift.
RF FRONTEND
Design
The printed circuit board of the RF FRONTEND is installed in a silver-
coated aluminum casing which is screwed to the instrument frame. The
RF FRONTEND is fitted at the right front of the CMU such that the four
RF N-type connectors which are directly connected to the FRONTEND
board are accessible on the front of the instrument frame of the CMU.
This is absolutely necessary to ensure a good VSWR (Voltage
Standing Wave Ratio).
Cooling system
The aluminum casing in which the RF FRONTEND is installed is
equipped with cooling fins in a special cooling duct and an extra
temperature-controlled fan for heat dissipation if high RX power is fed
in.
Control and supply
Control and supply of the RF FRONTEND are effected from
MOTHERBOARD1 via a 34-pin ribbon cable.
RF connectors
For the internal RF connection to the RXTX BOARD1 (RFRX1,
RFTX1) two SMA screw connections and coaxial solid-jacket cables
are used. Thus a high-quality RF connection is ensured.
Besides, two further internal RF connections (RFRX2, RFTX2) to the
optional RXTX BOARD2 are available.
Two bidirectional monitor inputs/outputs (RFRXTXAUX1/2) at the RF
FRONTEND permit to connect further RF devices via optional cables
leading to the integrated rear panel of the CMU.
As external RF interface, the RF FRONTEND is equipped with the four
N-type connectors RF1, RF2, RF3OUT, RF4IN, which permit to
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