Is it possible to use a Dual polarized antenna instead of CP antenna? For example in RFID: Which antenna can detect most of the tag? Circulsr or dusl polarized antenna?
circular polarisation is ofcourse nothing else than superposition of twp linear polarisations with the correct mutual phase shift. Now for such antenna design I would say it depends very much on the particular boundary conditions of the specific practical applications including criticality issues and crosspolarisation effects from the scatterer..from my point of view..do some tests and conclude then
Yes, in UHF RFID applications, it is possible to use dual-pol (DP) reader antenna instead of circular-pol (CP) antenna. Such scenario can even be recommended if you know the orientation (and polarization) of the LP tags used in your RFID system. If your tags are fixed along x-axis and y-axis of a coordinate system, you simply utilize the DP antenna with polarization along x-axis and y-axis and achieve the longest read range and 100% read rate. Remember that there is a 3dB loss if you use LP and CP antennas in a communication system. The reason the CP reader antennas are utilized in UHF RFID systems is that in the majority of practical applications we don't know actual orientation of the tags in the plane normal to the direction of propagation from the reader antenna so that to make sure ALL of them are interrogated by the reader (with the 100% read rate) the CP reader antenna must be used.
The above answers are representative of your conditions. CP should generally perform better than DP in your situation because the orientation (polarization) of the tag is arbitrary in most user scenarios, and most tags are linearly polarized.
Since the objective of deployment of antenna is for RFID application and in practical scenario orientation of RFID stick to specific object is not remain one fixed position/orientation thus it is always preferable to use circular polarized antenna. This is mainly because at any orientation at any specific time once E-Vector of both Tx and Rx will be matched and transformation of power will take place and thus make sure ALL of them are interrogated by the reader (with the 100% read rate)
Dear Debraj Kar ,
I think you already constructed your antenna.
But the circular polarized antenna will receive from either vertically or horizontally polarized antennas. The circular polarization is composed of two linear polarizations which are perpendicular to each other.
So, if you use double polarization it is preferred to be like the circular polarization.
Best wishes
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