Bruker BLAH1000 E, Operating & Service Manual

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Operating & Service Manual Version 002 BRUKER BIOSPIN 27 (53)
Theory of Operation
RF Coupler
The bi-directional high dynamic coupler provides an approximate coupling of 1V
peak DC signal for full 1000W or 100W depending of the SEL H1000/H100
signal, and also a peak DC signal for the reflected power.
Both signals, forward and reflected, are analyzed by the BLA control board for
monitoring and protection setting on the MAIN and AUX outputs.
Isolators
The RF isolator is a three-port passive device where one port is permanently
connected to a load. It is made of magnets and ferrite material used to control the
direction of signal flow in a circuit and protects the output power transistor from
excessive signal reflection.
There is an isolator connected at the end of each RF board.
BLA Control Board 5.2.2
The BLA Control Board has 3 main functions:
1. Conditions the input blanking (BLNK) signal and delivers it to the above
mentioned RF Paths.
2. Allows Ethernet communication with the workstation.
3. Monitor the output characteristics of the amplifier thanks to the DC peak
detection of the bi-directional coupler.
Electronic circuitry processes the detection information and protect the
amplifier from overstress like :
•
Forward and reflected peak power
Figure 5.4. Peak Power Limitation
The peak power limitation is the maximum RF forward shape amplitude allowed
at the amplifier output.
Limitation range : from 1% to 200% of nominal power.
The peak power limitation is checked for each sample (10 million samples
per second), and the maximum peak value is latched then cleared by a
read operation (for monitoring purpose).
MAX. RF SHAPE AMPLITUDE
FORW. OR REFL.
RF SHAPE