Modulation Tests on Bluetooth Transmitters Through

A new digital-signal-processing method for perform- ing modulation tests on Bluetooth transmitters is presented and validated. No preliminary demodulation of the radio frequency transmitted signal is needed to gain the instantaneous frequency trace, on which standard measurement procedures have to be applied. The aforementioned task is, in fact, fulfilled through the application of the short-time Fourier transform (STFT), a typical time-frequency representation, to the acquired samples of the aforementioned signal. Moreover, no specific information concerning the operating conditions of the transmitter under test, such as carrier frequency and hopping sequence, is needed, thus facilitating measurement automation. The optimal tuning of STFT parameters, which are capable of providing the best reconstruc- tion of the instantaneous frequency trajectory as well as the most accurate measurement outcomes, is established as the result of an exhaustive experimental activity. Index Terms—Bluetooth systems, modulation quality assess- ment, radio frequency (RF) measurements, short-time Fourier transform (STFT), time-frequency representations (TFRs), trans- mitter measurements.