Nordic ID NUR-05WL2, Implementation Manual, Page: 24 / 43

2013 ‐ 09 ‐ 27
NUR ‐ 05WL2 Implementation Guide v1.1
8 DIAGNOSTIC FUNCTIONS
8.1 REFLECTED POWER MEASUREMENTS
This measurement can be used to check what is the matching of the antenna(s) and feed line(s). When this
function is triggered will NUR ‐ 05WL2 module put carrier wave ON at full power and then measure the
absolute power level that is coming to receiver port. Attenuation in the RX ‐ line is 11 dB and full output
power is 27 dBm. Based on these two values you can determine antennas return loss (S11) value using
formula below:
Antennas return loss = Power to antenna – (RX ‐ line attenuation + reflected power meas.)
Antennas return loss = 27 – 11 – (reflected power meas.)
When leakage cancelation is used these calculations are no longer absolute return loss values because
cancellation circuitry eliminates some amount of the signal reflecting back from the antenna. In this case
this value is the absolute power value that is leaking into the receiver due to imperfect coupler isolation or
antenna mismatch.
8.2 CHANNEL SCANNER
This function can be used to monitor the interferences in the current frequency band. It is also useful if you
want to check if some fixed channel is in use. When you trigger this function NUR ‐ 05WL2 will scan all the
channels in current region and return the RSSI ‐ value of each channel. Returned values are absolute power
levels in receiver. Loss between RF_OUT pin and receiver is 11 dB so actual values are about 11dB higher.
8.3 RECEIVED SIGNAL STRENGTH (RSSI)
When reading a tag NUR ‐ 05WL2 module also returns received signal strength indication values if wanted.
Two values are returned per one tag. One is the absolute power level (dBm) and second is the scaled power
level value of the tags backscatter signal. NUR ‐ 05WL2 module automatically adjusts receiver according to
output power levels. Causing that maximum and minimum absolute RSSI power levels will vary depending
from the used output power levels. That is why scaled RSSI value is also available. Scale is 0 – 100.