ADU2 datasheet(30/162 Pages) ETC

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Page 18

ADU2 Operation and Reference Manual

Accuracy

Accuracy is directly proportional to the antenna

separation. Typical attitude accuracies versus antenna

separation are described in Appendix C. Also refer to the

references [2,3] in Appendix D. Pitch and roll accuracies

are typically a factor of two worse than the heading

accuracy when a square antenna array is used.

Multipath Migration

The reliability of the phase ambiguity resolution and the

attitude accuracy is degraded by multipath signals. The

antennas should be located on top of the vehicle (or

platform) to minimize the possibility of satellite signals

reflecting off metal objects near the antenna.

Stability

The ADU2 behavior depends upon the stability of the

four-antenna system. This means that the selected

antenna mounting locations should not move in any

direction (up/down, left/right) relative to the other

antennas. If the vehicle (or platform) moves, the entire

antenna system should move in the same manner. Use

care in mounting antennas on flexible structures such as

the mast of a ship or the wing tips of an airplane.

Maximum Length

The supplied cables have a maximum length for the

particular type of cable. Do not extend the cables beyond

30 meters without an in-line amplifier, provided as an

option, since the radio frequency (RF) signal presented to

the ADU2 will be degraded.

Geometrical Configuration

• Almost any geometric shape is acceptable provided

that none of the resultant vectors are co-linear (i.e. if

three antennas are arranged in a line, Antenna 1 may

not be one of those antennas (Figure 3.1).

• Antennas do not need to be co-planar, however, for

best results, at least two antennas should be at the

same height.

Table 3.1: Antenna Placement Suggestions (continued)

Antenna Consideration

Suggestion

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