Measuring transmitters attack time through time frequency representations

Power and carrier frequency transients are very common in modern wireless transmitters. Transients can be responsible for harmful interference on transmitting and receiving devices operating on adjacent channels. This is the reason why the standard issued by the European Telecommunication Standard Institute (ETSI) on electromagnetic compatibility and radio spectrum matters includes a section dedicated to wireless transmitter transient behavior and related measurements. In particular, it imposes constraints on the duration of the transmitter attack time and proposes a measurement setup that involves several instruments to measure it. The paper presents the results of experiments carried out on a wireless transmitter, in which the transmitter attack time is measured by means of a method proposed by the authors. The method is based on digital signal processing and exploits time-frequency representations to extract the instantaneous power and frequency trajectories of the signal emitted by the transmitter under test, thus needing only a digital storage oscilloscope and a processing unit to operate.