On-Chip RSSI vs. Reader RSSI

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This topic contains 1 reply, has 2 voices, and was last updated by  Brian Young 4 days, 13 hours ago.

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  • #1237

    Shircliff
    Community Member
    • ★★★★

    I am using RFM2100-ARF temperature sensors and the ThingMagic Astra-EX reader. For our sensors, we receive an “on-chip RSSI code” through the reserved bank. However, there is another RSSI value that we obtain. It appears that this other RSSI value comes directly from the reader. Is this RSSI value equivalent to the “on-chip RSSI code”? Why does RF Micron provide this “on-chip RSSI code” instead of using the reader’s RSSI?

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    #1238

    Brian Young
    RFMicron Team Member
    • ★★★★

    The on-chip RSSI code shows the strength of the reader’s signal as received by the sensor.  The RSSI number reported by the reader is the strength of the sensor’s backscattered signal as received by the reader.  The two together cover both paths: from the reader to the sensor, and from the sensor to the reader.

    Sensor codes can be pulled to lower values for high on-chip RSSI values.  Reading the on-chip RSSI value lets you know if the power levels are high enough to affect the sensor code.  For best accuracy in the sensor codes, on-chip RSSI values should be kept below about 20.  This limit can be implemented by the distance from the sensor to the reader, the reader output power, and by using a SELECT command to tell the sensors not to respond to the reader if the on-chip RSSI code is too high.  Under software control, the reader power can be adjusted such that the user does not have to be aware of the on-chip RSSI.

     

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