Transcript RTCA DO-160 Section 20 Working Group

RTCA DO-160 Section 20
Working Group
Billy M. Martin
Cessna Aircraft
Meetings
• Task Group conducted a telecom on Thursday Oct. 16th:
– the philosophical and technical discussions on susceptibility
mode stirring and mode tuning.
• Current procedure of Mode Tuning is too complex and as such is
not being used
• Stirring Technique does not have to be as “good” as mode tuning,
but only be as good as the current standard of “spot illumination” in
terms of
– Robustness and Repeatability
• Group understands that there are limitations to the
procedures and that improvements will need to be made,
however the desire to have a simple straight forward
procedure that can be “improved” upon, rather then one
that no one is using is helping to drive the effort.
Status
• The group decided to
– insert mode stirring procedures, and remove mode
tuning steps that weren't applicable to mode stirring.
– Jeff Phillips from Cessna provided a draft which will
be the starting point for this revision.
– Plan to distrubute the revised section to the task
group for discuss and will present an acceptable
revision to the full committee by the next meeting
• Need agreement from general committee in
regard to the approach
Additional Issue
• Spot Illumination Requirements for additional
aspect anlges:
– This proposal was agreed upon prior to Rev F
however was not incorporated
• REV F_537 is shown as “withdrawn” but that was a mistake,
it was not withdrawn; It was approved at the joint WG14/SC135 meeting at Marseille
• Agreed to “re-visit” spot illumination aspect angle proposal
• Proposal concerning “Antenna Distance”
Proposed Text
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RS Test Set-up
Set up the EUT, wiring, associated interface circuitry and test equipment per
Figure 20-2.
Signal generators, amplifiers, antennas and probes shall maintain required
RF field levels to properly illuminate the EUT and interconnecting wiring.
Position and aim antennas to establish the RF field strengths at the EUT
and interconnecting wiring. Define the 3 dB points of the radiated field
using antenna beamwidth specifications, or by mapping the area in which
the EUT is to be placed. The beamwidths of the antennas used in the test
should be stated in the test report. When the 3 dB beamwidth of the
antenna does not totally cover the EUT and wiring, perform multiple area
scans. Vertical and horizontal transmit antenna orientations are required.
Directly expose each face of the EUT that contains apertures (e.g.,
displays, CRTs, connectors) to the transmitting antenna. Any face that
was not exposed to the transmitting antenna has to be justified in the
test form.
Antenna Position
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Revise To:c. Radiating Antenna Position –
The separation distance between the antenna and the EUT and wiring
should be one meter or greater. If the transmitting antenna being used is a
pyramidal horn or similar radiator, as the dimensions of the antenna become
small and the frequency of interest becomes higher, it is permissible to
move the antenna closer to the EUT and wiring than one meter. This can
only be done when the far field distance of the transmitting antenna is
less than one meter.
The position of the transmitting antenna relative to the EUT must remain
equal to or greater than the far field distance of the transmitting antenna. If
the far field distance of the antenna is greater than one meter then the
standard one meter separation should be used.
The far field distance is calculated by the formula (2*D)2/λ, where D is the
largest dimension of the antenna, and λ is the wave length of the lowest
frequency of interest for that antenna.
If the test is to be conducted in shielded enclosures with anechoic material,
then the antenna should be at least 0.3 m away from the absorber surfaces.