GNGTS 2015 - Atti del 34° Convegno Nazionale

162 GNGTS 2015 S essione 3.3 estimate the variance of the I and Q components at each tone as follows: (1) where indicates the algebraic average value, and are the tone and the trace indexes, respectively. The generic comprehensive variance of the tone of the trace can be naturally defined as (2) Then, as an index of the intensity of the interference on the tone (independently of the trace along the calibration Bscan) we have chosen the quantity (3) The choice of the maximum is conservative, in the sense that it is based on the most disturbed k th tone along all the traces of the Bscan. Indeed, since the selected frequency step was 2.5 MHz, the sequence vs. can be reliably confused with the graph of the continuous function , so that the quantity in Eq. 3 can be regarded as the variance vs. the frequency, evaluated all over the calibration Bscan. So, from the calibration Bscan we can work out and visualize automatically the behaviour of the variance of the tones vs. the frequency, and from this one we can decide whether the reconfiguration is needed or not. This decision is left as a heuristic choice here, on the basis of the comparison (done ones at for all) between some Bscan gathered two times, once with the default integration times and once with reconfigured integration times. We do not have and so can not give a general quantification, because the default integration time is variable from instrument to instrument, and in general also the amplification and quantization chain depend from the equipment at hand. So, the calibration is to be meant as referred to the system at hand, and the order of magnitude of is meaningful or less meaningful only in relationship Fig. 2 – Experimentally measured I and Q components close to an FM broadcast radio repeater. The disturbed tones (that correspond to the FM band 88-110 MHz) are characterised by a strongly oscillating behaviour.