alessio
Newbie level 5
Hi, i've a question for which need your help!!
I've simulated a microstrip antenna on ground plane for an UHF RFID tag with HFSS 10 and i've obtained a good matching for Zin and a good G(7dB).
After using Friis formula for reader range (r=(λ/4π)√(PtGtGrτ )Pth) where PtGt is EIRP power of the transmitter, Gr is the gain of tag, τ is the transmission coefficient of the tag (about 0,9) and Pth the power delivered to the load i've calculate theoretical reader range(about 3,3m).
After i've done an experimental measure with the tag and i've obtained a reader range that was half than that theoretical.(with theoretical formula i will be read to 3,3m but with experimental measure i'm reading at maximum distance of about 1,7m).
The measure was done not in an anechoic room but in a laboratory,i've used a low power transmitted for limit reflection with the wall (about 20mw to transmitter antenna), i've repeat the measure at different height from the floor but i've also a great difference in reader range.
I've seen that if height from the floor is bigger than reader range increased but more than 2 meters i can't go because after i'm too near the ceiling and the measure will be influenced from reflection. At the distance which i can read the tag i'm in far zone and for that Friis formulas is valid.
What can will be the reason for which i've that great difference in reader range??
The problem can will be reflection? or simulating parameter can suffer of error?
Please help me!! from few days i must write result in my work of thesis.
I've simulated a microstrip antenna on ground plane for an UHF RFID tag with HFSS 10 and i've obtained a good matching for Zin and a good G(7dB).
After using Friis formula for reader range (r=(λ/4π)√(PtGtGrτ )Pth) where PtGt is EIRP power of the transmitter, Gr is the gain of tag, τ is the transmission coefficient of the tag (about 0,9) and Pth the power delivered to the load i've calculate theoretical reader range(about 3,3m).
After i've done an experimental measure with the tag and i've obtained a reader range that was half than that theoretical.(with theoretical formula i will be read to 3,3m but with experimental measure i'm reading at maximum distance of about 1,7m).
The measure was done not in an anechoic room but in a laboratory,i've used a low power transmitted for limit reflection with the wall (about 20mw to transmitter antenna), i've repeat the measure at different height from the floor but i've also a great difference in reader range.
I've seen that if height from the floor is bigger than reader range increased but more than 2 meters i can't go because after i'm too near the ceiling and the measure will be influenced from reflection. At the distance which i can read the tag i'm in far zone and for that Friis formulas is valid.
What can will be the reason for which i've that great difference in reader range??
The problem can will be reflection? or simulating parameter can suffer of error?
Please help me!! from few days i must write result in my work of thesis.