Transmitter identification: Experimental techniques and results

Abstract

The transient response patterns of several different radio transmitters were delineated in order to determine the patterns most useful in the development of a transmitter identification system. Using a high-speed data acquisition system, rise and fall data were first obtained for various transient response patterns that were produced by six different FM radio transmitters when the press-to-talk buttons were switched on and off. Next the effect of these transient patterns on the time domain and time-frequency spectrograms were evaluated by measuring the changes in the receiver input level at Pin = -120 dBm and SNR = 7.2 dB obtained from three different bandwidths: 250, 50, and 12 kHz. Similarly; spectrogram analysis was used to obtain information about the relationship between bandwidth and noise. Comparison of the spectrogram patterns obtained in both laboratory and field experiments independently corroborated the results. However, the transient patterns in the time domain could not be used because of extensive distortion related to noise and interference from neighboring radio stations. These results suggest that spectrogram analysis of transient response patterns may be the most effective way to secure reliable identification of the FM radio transmitters.