Measuring Transmitter Attack Time through Time-Frequency Representations LEOPOLDO ANGRISANI 1 , MASSIMO D’APUZZO 2 , MAURO D’ARCO 2 , ROSARIO SCHIANO LO MORIELLO 1 , MICHELE VADURSI 3 1 Dipartimento di Informatica e Sistemistica 2 Dipartimento di Ingegneria Elettrica Università degli Studi di Napoli Federico II Via Claudio, 21 - 80125 Napoli, Italy ITALY 3 Dipartimento per le Tecnologie Università degli Studi di Napoli “Parthenope” Centro Direzionale di Napoli Isola C4 - 80143 Napoli, Italy ITALY Email: angrisan@unina.it; darco@unina.it; michele.vadursi@uniparthenope.it Abstract: - 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. Key-Words: transmitter testing, transmitter transient measurement, time-frequency representations, short-time Fourier transform, chirplet transform, electromagnetic compatibility (EMC), wireless communication systems. 1 Introduction Power and frequency transients occur any time a wireless transmitter is switched on. Very often, they can also be experienced during the typical functioning of a transmitter. This is the case, for example, of transmitters employed in communication systems which involve bursty transmission. As a further example, there are communication systems based on TDMA (Time Division Multiple Access), as well as spread spectrum communication systems, which involve quick and frequent changes in transmitted power, with the aim of minimizing battery consumption; not to mention systems based on FDMA (Frequency Division Multiple Access), whose transmitters regularly switch from one frequency channel to another. Power and frequency transients in wireless transmitters have to be carefully dealt with. They can, in fact, possibly determine interference on other transmitting and receiving devices which are operating in adjacent frequency bands. 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 on wireless transmitter transient behavior and related measurements [1]. ETSI standard [1] imposes constraints on the duration of the transmitter attack time, i.e. the time it takes to switch its output power on. Specifically, Recent Researches in Telecommunications, Informatics, Electronics and Signal Processing ISBN: 978-1-61804-005-3 201