Active RFID tag spectrum shape and burst time casual measurement

The ADVANTEST R3463 spectrum analyzer is just arrived, it frequency range reached 3GHz and it's a synthesizer type of spectrum analyzer so it get rid of many problem for example frequency drift off the view, ofcause a 3GHz analyzer enabled measuring of abundant 2.4GHz radio systems, including WIFI, bluetooth, zigbee and also this one: 2.4GHz Active RFID Tag.

This little 2.4GHz radio tag is powered by CR2302 battery, firing a short burst of signal in 1 sec time interval. May be it could be used to locate a pet cat.

Because there are many WIFI routers nearby as interference and the tag is very low power (~0dBm), the tag have to put closely to the antenna.

The spectrum view of tag signal, using long time peak hold, because it firing a burst every second, which is quite infrequent. The center frequency is measured 2.457GHz and power -13.5dBm.

As we can see the SPAN setting of this screenshot is 10MHz, and every grid equal 1MHz, the -6dB bandwidth of the spectrum is roughly 1MHz (for compliance to FCC rule for non-frequency hoping system in 2.4GHz ISM band, the -6dB bandwidth should be wider than 500KHz).

One feature of this R3463 spectrum analyzer is Transient analysis, which is a power vs time measurement mode, by using this mode, we can obtain the power envelop of the signal burst, the burst time is 180uS, that's translate to 1/5555 duty cycle.