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The RFMAX Power Mapper for RFID installation: How It Works

Posted by Michael Crudele on

We wanted to provide some background info on our RFMAX Power Mapper: our antenna field meter.

The RFID antenna power mapper from RFMAX was originally designed for students at Cambridge University, so they could see the RF field and how nulls were created due to the coherent reflections. It has come a long way since then; it has become an industry-standard tool for RFID Gen 2 and Rain installations.

So how does it work? Using this product for antenna evaluation is very simple:

The antenna on the meter is linearly polarized and so when it is in line with a linear antenna the meter will read a high level. If the meter or the linear transmitter is rotated by 90 degrees the power reading on the meter will drop dramatically. Now, if the transmitting antenna is circularly polarized, when the antenna or meter is rotated by 90 degrees the reading will stay the same.

Note that the antenna on the meter can be removed and other antennas attached for experimentation, evaluation and simple comparison.

The DC output from the back of the meter is useful for data logging and getting an accurate reading over a wider power range. You can use a simple voltmeter on this output. The voltage output will follow the curve below if the voltmeter or oscilloscope has a high impedance. 1M Ohm for example.

There are many voltmeters on the market that come with a Bluetooth App. The lowest price for one of these is about $30. ANENG AN9002; however, there are better models. Pocket oscilloscopes and Pico scopes can be used to log data into laptops etc.

There is a fast slow switch on the meter. When in fast mode the modulation on the received signal can be viewed on an oscilloscope. When in slow mode the internal detector is slowed down to help with data logging the received power.

You will be quite shocked at the results from on-site measurements in comparison to open-field measurements. Also, if people are walking around the area the power will vary tremendously. Within the RFID installation; move the power mapper up and down vertically to see nulls at various highs. Also, use the meter horizontally as well as upright, especially when dealing with circularly polarized transmitting antennas.

The Power mapper can be used as a simple mapping tool for anybody when in Map Mode. In 0dBm mode, it becomes a very sophisticated and accurate tool for detailed analysis of RFID installations and equipment.

If you have any further questions about the RFMAX Mapper, please do not hesitate to reach out to our Tech Support

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