Modelling software boosts RFID read rates

Flomerics reckons its MicroStripes 3D electromagnetic modelling software can improve RFID read rates by accurately simulating the performance of tag antennas under various conditions.

Flomerics has released details of a number of applications that demonstrate how its MicroStripes 3D electromagnetic modelling software can improve radio frequency identification (RFID) read rates by accurately simulating the performance of tag antennas under various conditions.

Many early RFID implementers have had problems meeting read rate requirements because of the difficulty in sorting out the many factors that can affect performance, such as the material to which the tags are attached, the orientation of the tags, power constraints, operating frequency variations and other factors.

MicroStripes helps engineers quickly determine the cause of the problem and evaluate potential solutions by predicting the return loss and radiation pattern of RFID tags under real-world operating conditions.

For example, Flomerics engineers recently used MicroStripes to model an UHF RFID tag with the goal of determining the influence of the material on which the tag is mounted on the return.

First they computed the response of the tag with no backing in free space.

The model was excited by means of a wire feed, placed between the two arms of the dipole.

The return of the antenna was calculated to be -17dB at 898MHz.

At this frequency, the dipole type radiation pattern was accurately predicted, presenting a directivity of 1.9dBi.

A higher-order resonance was also captured in the response at around 2.6GHz.

Next, engineers mounted the tag on a sheet of corrugated cardboard.

When the antenna was mounted on the cardboard, MicroStripes showed a frequency shift in the return of about 55MHz to 843MHz.

The return loss also improved by about 2dB to -19dB.

The radiation pattern remained consistent with the previous result, as did the directivity at around 1.9dBi.

The corrugated cardboard was then removed and, the antenna mounted on a 4mm thick plastic board of 200 x 100mm.

Once again, the results showed a significant shift in frequency.

The antenna showed a return of about -24dB at 683MHz.

The radiation pattern and directivity at this frequency were shown to be consistent with the previous two cases.

This example shows how the ability of MicroStripes to simulate the effects of mounting an RFID tag on different materials allows the designer to tune the antenna to resonate at the desired frequency in its installed environment.

In this example, engineers corrected the problem revealed in the simulation by making the dipole shorter.

Through careful design, the resonant frequency was brought back to around 900MHz.

However, further design would be needed to improve the return loss.

The application example clearly demonstrates MicroStripes' ability to simulate complex antenna structures with high accuracy.

MicroStripes can be used to simulate the full range of issues involved in achieving high RFID read rates, diagnose potential problems, and determine the impact of proposed solutions while minimising the need for expensive and time-consuming bench testing.

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