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Battery assisted tags aka semi-passive tags are typically very sensitive (around -20 to -30 dBm power on tag). When testing these tags at a short distance, some extra attenuation is required at the transmit port. Without additional attenuation, the transmit power required to wake up a tag is lower than the typical Tagformance range.
When testing battery assisted tags with the Voyantic Tagformance, it is often enough to move the 6 dB attenuator from the receiver port to the transmit port. The 6dB attenuator is delivered as a part of the Circulator belonging to the Voyantic Tagformance Hand Carry Kit and Field Engineer Kit. It is also available as a separate accessory (code TF-AC-CRC).
Then, the measurement setup needs to be updated in the software. Use Voyantic Reference Tag in measuring a new setup, or adjust the attenuation values in the calculated setup. With the new setup the system works down to tag sensitivity of about -25 dBm power on tag with a measurement distance of 30 cm.
In case lower power levels are needed (the tag is even more sensitive), the measurement distance can be increased, or more attenuation to the transmit port can be added. One possibility is to use an adjustable attenuator such as FW Industries Model 50DR-061 N.