AR 10013164, Руководство по эксплуатации и обслуживанию

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Rev J 9
2. THEORY OF OPERATION
2.1 DESIGN OF THE PROBE KIT
The Model FL7006/FL7030/FL7218/FL7040/FL7060 Probe Kit consists of two principal functional units: the
probe and the probe interface. The two units are connected by two pairs of fiber optic (F/O) cables. Power to
operate the probe and commands to the probe are provided from the interface on one of the F/O cables.
Responses from the probe to the interface are provided on a second F/O cable. The other F/O pair is a safety
loopback connection ensuring properly connected cables prior to laser turn on.
Each probe has been calibrated at the factory in a CW field at a single frequency, and the resultant calibration
tables have been loaded into probe non-volatile memory. The calibration tables provide the basis for the
conversion of the digitized signal, from the sensor/detector/pre-amplifier/A to D converter path, to electric
field measurement values for each axis. A composite field level is then derived by calculating the square root
of the sum of the squares of the individual axis field values. This calculation method is generally quite precise
relative to the extent to which all the individual axis antenna patterns are those of very short electrical dipoles
(sine function) at all frequencies.
In addition to the operating program and calibration tables (firmware), each probe’s memory also contains the
serial number of the probe, the revision of the probe’s firmware, and the probe’s most recent calibration date.
The probe interface sits between the probe and the host and provides all of the specified communication
protocols to the host. The two functional units are described in greater detail below.
2.2 PROBES
The probes incorporate three orthogonal sensors, one for each axis, labeled X, Y and Z. The sensors feed
detectors and the detected signals are routed through high-resistance leads to low noise preamplifiers in the
housing. Circuitry within the housing, including a programmed micro-controller, processes the amplified
detected levels to create a stream of digital information light encoded onto a fiber optic cable exiting the
housing. Power (to operate) and commands to the electronic circuitry are received on a second fiber optic
cable.
2.2.1 Sensors
2.2.1.1 FL7006 Sensor
Sensors in this probe include a simulated tapered resistance, and feed diode detectors. This configuration
offers a nominally flat response with frequency. Sensors and detectors for each axis are housed in protective
radomes. Additional details of the characteristics of sensors used in this series of probes are described
extensively in United States Patent 6,593,896 granted July 15, 2003.
2.2.1.2 FL7030 Sensor
Sensors in this probe use a FET (Field Effect Transistor) preamplifier/buffer and feed diode detectors. DC
power for the FET is supplied from a regulator in the housing. The FET preamplifier/buffer extends the low
frequency response. The FET preamplifier/buffer offer a nominally flat response over the specified operating
frequency range while additional RF filtering controls out of band response roll off. Sensors and detectors for
each axis are housed in protective radomes.