Raw data measurements of Tree Mounted UHF RFID Tag

Measurements taken between 28-30 July 2014. UHF tag on thin mylar backing measured firstly on an adjustable height stand at heights of 1.4m and 1.9m. Objective to assess and compensate for read range variation caused by ground/tag distance. Tag read performance measured for read powers of 33dBm, 30dBm, 26dBm, 20dBm, and 10dBm using Favit UHF RFID 7dBic patch antenna provided with the system. Measurements taken in open area with dry ground. Tag then attached to mature Oak tree at 1m, then 2m above ground and successful read over 5m between reader antenna established at 1.5m and 0.5m heights.

Tag then mounted 4m high on tree and read antenna placed inside office window 5m from tag. Reader was allowed to repeatedly interrogate tag at maximum speed for 5 minute intervals and total successful read count recorded. Reader power as varied from 33dBm, 30dBm, 29dBm, 28dBm, 27.5dBm, 27dBm, to establish that reliable reading over 5m is lost for a reader power of less than 27.5dBm. It was noted that a certain aperture effect seemed to occur due to the presence of the window frame and this reduced the read range slightly. The read range was mounted as far forward in the window as possible to mitigate against this effect.

The read range data in the provided file has been compared with the open space Friis power relationship of received power being proportional to transmit power divided by transmission distance squared.