Difference between Circular, Rectangular and Free form Antenna??

[former_member202208]

Hi All,

What is the difference between a Circular, Rectangular and a Free form field Antenna other than the physical appearance?

Thanks,

Shridhar..

[former_member202208]

Resolved.

[Former Member]

Hi Shridhar,

RFID Antennas

RFID antennas are always connected to an interrogator. This allows for the transmission of signals to and from the tag.

Antenna Design

Depending on the design, antennas can be either mono-static or bi-static:

•Mono-static antennas are based on a principle by which a single antenna transmits a signal coming from the interrogator to the area as well as receives a signal coming from tags and these functions are switched in fractions of seconds. This requires use of a circulator in a reader that multiplexes the receive and transmit signals through a single port. There is some loss and phase distortion due to the use of a circulator.

•Bi-static antennas include two antennas, where one antenna is dedicated to transmitting, and the other antenna is dedicated to receiving. Both dedicated antennas can be but do not have to be in the same casing. In bi-static antenna, a circulator is not required, which improves the performance and sensitivity of the antenna.

Antenna Polarity

Antenna polarity is very important because it affects the quality of communication between the interrogator and tag.

The interrogator's antenna and the tag's antenna should have the same polarization. If polarization is not realized, a severe loss in signal, along with a drastic decrease in a read range, which results in unsuccessful communication with a tag, can be experienced.

<b>Polarization can be either circular or linear.</b>

Linear polarization is relative to the surface of the earth.

<b>Linear polarization can also be either horizontal or vertical:</b>

•Horizontally polarized signals propagate parallel to the earth.

•Vertically polarized signals propagate perpendicular to the earth.

Antennas with circular polarization can receive signals from both the vertical and horizontal planes by injecting the signal at two points on the antenna radiated slightly out of phase creating a rotating effect on the field. However, there is a slight loss of signal strength, due to the constructive and deconstructive effect of the field being slightly out of phase.

Refer this link to get the other details regarding the Antenna Design

http://www.ibmpressbooks.com/articles/article.asp?p=413662&seqNum=2&rl=1

Also the Refer this link to get the detailed Antenna Anatomy

http://americanrfidsolutions.com/members/download/3.pdf

I hope This answers your question.

Regards ,

Pawan