User's Manual
User Guide
___________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________
21
User Guide, WherePort IV D1300 REV A
© Copyright WhereNet, Corp. 2008 WhereNet Confidential
Random orientation means that the tag may take any of the possible positions relative to the WherePort
IV. Fixed tag orientation means that the motion of the object to which the tag is attached will always
present the tag in the same position relative to the WherePort IV. A major difference between the random
and the fixed orientation is the size of the uncertainty area. It is significantly reduced when the tag has
both a fixed and an optimum orientation in the field.
Figure 13 Overlapping Uncertainty Areas
7.4. Coverage Overlaps
When positioning WherePort IVs it is not always possible to prevent their fields from overlapping.
Overlapping the uncertainty areas of two WherePort IVs does not produce a guaranteed capture area. It
produces an area where a tag may be pinged by either one or the other WherePort IVs or none.
When the fields of two WherePort IVs must be overlapped to cover a large area (Figure 13) it is
necessary to set the phases of the two WherePort IVs. Both WherePort IVs (or more if more fields are
overlapping) must also have the same ID number. If the phases are not set, it may be impossible or
difficult for a tag in the field to accurately report the ID of the WherePort IV for the field it is in.
7.5. Phases
When two are more WherePort IVs are used to cover a large area they must be phased to reduce the
interference between the two fields. WherePort IVs mounted on the ceiling might be set to 0º and on a
wall 90º. Figure 14 shows the correct phase settings for four orientations of the WherePort IV. The
phases are set with reference to the orientation of the master WherePort IV.
Field Overlap