Home' RTCA Documents for Review : DO-213A Change 1 Contents Appendix C
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DO-213A Change 1
The accuracy of the phase measurement and the accuracy and alignment of the positioning
system should be such that the corresponding error in the far field is negligible compared
to the specified transmission efficiency to be measured.
Usually the near-field measurements are made on a planar, spherical, or cylindrical surface.
Usually, near-field measurements are performed at a distance r < 2D2/λ corresponding to
the distance equal to the limit between the Fraunhofer and Fresnel zones with D
representing the maximum diameter of the radar antenna.
A distance r > 3λ is required for ensuring minimum separation between the object under
test and the measurement probe(s).
In order to construct the far field at any angle, the near field must be sampled at least at the
Nyquist rate. Conventional near-field acquisition and processing cause those sampling
criteria to be:
Planar geometry: spacing between measurement points < λ/2 in both scan
Cylindrical geometry: angular spacing < λ/2R (radians) in azimuth and spacing
< λ/2 in height with R representing the radius of the minimum sphere enclosing
the radar antenna (measurement with radar antenna only), or the radius of the
minimum sphere enclosing the radome (measurement with radar antenna and
Spherical geometry: angular spacing < λ/2R (radians) both in azimuth and
elevation with R representing the radius of the minimum sphere enclosing the radar
antenna (measurement with radar antenna only), or the radius of the minimum
sphere enclosing the radome (measurement with radar antenna and radome)
When first installed, a new type of near-field range should be crosschecked in terms of the
far-field radiation pattern. This cross check can be done by measuring a representative
radar antenna (size, directivity, sidelobes) without the radome, inside a compact antenna
test range having a sufficiently large quiet zone and having the following performances at
the operating frequency:
Amplitude taper: < 1 dB
Amplitude ripple relative to amplitude taper < ±0.6 dB (or 1.2 dB peak-to-peak)
Phase taper: < 5 deg.
Phase ripple relative to phase taper < ±5 deg. (or 10 deg peak-to-peak).
The differences observed in the far-field must be sufficiently small to be able to
The specified variations of sidelobe indicated in Table 2-2 of Paragraph 2.2.2
The specified variations of beam width indicated in Paragraph 2.2.3
The specified deflections of the beam indicated in Paragraph 2.2.5.
When first installed, a new type of near-field range should be crosschecked in terms of
mutual coupling between the measurement probe and a representative radar antenna (size,
directivity, sidelobes) without the radome. This cross check can be done by performing a
pair of full acquisitions with the probe separation varied by λ/4. If the corresponding
variation observed in the far field is negligible compared to the specified transmission
efficiency to be measured (i.e. variations < ± 0.1 dB or < ±2%), there is no need to average
over pairs of measurements separated by λ/4 both with and without the radome
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