Detailed Characterization of Laboratory FQIS Installation

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power was applied to a matched RF termination

Detailed Characterization of Laboratory

were measured. More details may be found in [5].

FQIS Installation

Aircraft measurements established that an RF

source located in the passenger cabin coupled to the

RF Connector Box

Test Position 2

CWT mostly via the FQIS connection.

The FQIS provides 4 copper paths by which to

introduce RF power into the CWT (LO Z, LO Z

Comp, HI Z, HI Z Shield). This results in 4

common-mode paths (each line to chassis), in

addition to the differential combinations. The

largest loop areas, and therefore the dominant

modes for coupling externally induced signals were

from the common mode paths. By design, the LO Z

and LO Z Comp conductors are connected to the

outside cylinder, while the HI Z conductor is

connected to the inside cylinder of the fuel probes.

Test Position 6

Because of the large surface area between these

exposed conductors, laboratory measurements

Figure 6. Laboratory FQIS Current/ Voltage

included these 2 differential, plus the 4 common

Enhancement Locations

mode excitations (LO Z-to-Chassis, LO Z Comp-to-

Chassis, HI Z-to-Chassis, HI Z Shield-to-Chassis,

LO Z to-HI Z and LO Z Comp-to-HIZ).

Laboratory testing for discharge, excessive

heating (C(f))

With all CWT FQIS components installed in

the reverberation chamber, and data to establish

comparability between the laboratory and aircraft

installations, it was then possible to apply

increasing levels of RF power, and monitor for a

discharge or excessive heating event. Considerable

effort was applied to the problem of detecting such

events. The primary tool for detecting electrical

discharge was a AMT MO-32 night vision scope,

attached to a standard 8mm video camcorder with

Figure 5. FQIS Connector

low-lux light capability. The primary tool for

measuring heat emissions from the FQIS was an

Using a vector network analyzer and

Inframetrics model 600, nitrogen-cooled thermal

specialized high-frequency voltage and current

imaging system. A photograph of these tools is

probes, the entire laboratory FQIS installation was

shown in Figure 7, and details regarding their use

characterized in terms of voltage and current

may be found in [5].

induced when excited by each of the 6 excitation

To simulate the condition of estimated worst-

modes, at frequencies from 1 MHz to 1000 MHz, at

case PED coupling onto FQIS wiring (based upon

each of at least 10 locations. From the

aircraft measurements of maximum possible path

measurement data, RF power applied at two

factor (B(f))), 100 mW of RF power (from 1 MHz

particular excitation modes (LO Z-to-Chassis, LO Z

to 1 GHz) was applied to the three dominant

Comp-to-Chassis) were found to produce maximum

excitation modes (LO Z-to Chassis, LO Z Comp-to-

enhancements at two specific test locations (Pos.

Chassis, HI Z-to Chassis). Testing at this level did

#2, max current: HI Z-to-Chassis; Pos. #6, max

not yield any evidence of discharge or detectable

voltage: LO Z Comp-to-Chassis), respectively.

heating.

(See Figure 6.) At location 6, voltage

enhancements up to 22 times higher than if the RF