RF Ports Return Losses

Introduction

It is possible to know the return losses at each RF port of the readers / systems.

Requirements

The requirements for this feature to work are:

Operation

Checking the value of the RF port return losses is as simply as

Stop any RF operation

Stop any ongoing RF operation

Check device parameters

Access the following URL

http://${device-ip}/device/antennaLosses

for older versions of AdvanNet use:

http://${device-ip}:3161/devices/${device-id}/reader/antennaLosses

The following is a capture of a request

Interpret result

Every entry defines the return losses for a certain antenna. The higher the value the better the impedance mismatch of the antenna, and the better the antenna will work.

An easy explanation of return losses can be the Wikipedia page: https://en.wikipedia.org/wiki/Return_loss

For example AdvanReader-m4-160:1:2:0=9 means:

• • Antenna connected at the reader port #1

  • Antenna connected at the output #2 of the AdvanMux

  • Ignore the '0', it is just used when two level multiplexers are used.

  • Has a return loss of 9 dB

Regarding values:

• • values from 0 to 2 means that there is no antenna connected, the cable is broken, etc.

  • Values between 3 - 5 mean a poor adaptation. The antenna may read but certainly below its capacity.

  • Values between 6 - 9 mean low adaptation. Sometimes the environment also reduces the adaptation.

  • ​Above 10, it's fine.

It's important also to keep track of changes over time. You will see the values returned will change.

Also having certain products close to the antennas will have an effect on those values.

Additional notes

This is not a precise measure, in the same conditions two measure may differ quite a lot.

Take several measures and take the highest value.

This is basically a diagnostic tool to discard major problems in the cabling, multiplexers or reader ports. Values below 2 mean there is a HW problem. Usually cabling related, RF ports are very robust and very seldom fail.

It also can be used as a prevention tool, by analysing the return losses daily and detecting antennas that:

• • Having a very low mismatch <3 may mean a loose cable or similar.

  • Checking variations if the antenna losses in the same antenna over time may provide useful information.

Wear is not usually a problem with antennas or fixed cables.