Understanding RF Absorption by Metals in RFID Testing

[kirr45]

Hi everyone.

I was wondering how badly aluminum affects RFID waves (860-960MHz)? Do they completely absorb, reflect, combination of the two? I'm having issues with my testing of RFID. I'm getting some dead zones and I think it could be because of the portal frame the antennas are mounted on. I have an aluminum frame connected to a 6 inch bracket antenna mount, then there antenna. Also, if you know about left hand and right hand circular polarization and in which setup they cancel each other out, that would be a big help. For example, if you have two of the same propagating, or two of the opposite propagating antennas, in which setup would be best, and which would be the worst(cancel each others performance)?

Thank you

 

[Enthalpy]

Aluminium blocks completely waves at 900MHz, with reflection, little loss and exactly zero propagation through it.

BUT things are complicated because the wavelength (0.3m) isn't very small as compared with your objects, so your radio waves are diffracted (say, like sound goes around obstacles) and do not behave at all like light does. So you cant' get a simple answer, alas.

 

[berkeman]

Hi everyone.

I was wondering how badly aluminum affects RFID waves (860-960MHz)? Do they completely absorb, reflect, combination of the two? I'm having issues with my testing of RFID. I'm getting some dead zones and I think it could be because of the portal frame the antennas are mounted on. I have an aluminum frame connected to a 6 inch bracket antenna mount, then there antenna. Also, if you know about left hand and right hand circular polarization and in which setup they cancel each other out, that would be a big help. For example, if you have two of the same propagating, or two of the opposite propagating antennas, in which setup would be best, and which would be the worst(cancel each others performance)?

Thank you

Welcome to the PF.

You should not have any metal near your antenna, unless it is explicitly part of the antenna structure (like the reflector and director elements of a directional Yagi antenna), or part of the antenna mast/support that is out of the antenna's pattern.