2PrincipleofmeasuringtheoccupiedbandwidthusingFFT.docVIP

ECC RECOMMENDATION (06)01 Bandwidth measurements using FFT techniques Recommendation approved by the “Working Group Frequency Management (WGFM) Introduction The occupied bandwidth is one of the most important parameters to characterize an emission. The implementation of powerful FFT algorithms even in low cost analysers allows to perform more accurate and quicker measurements of the occupied bandwidth compared to conventional methods. This recommendation specifies those parameters which are essential to achieve correct and mutually acceptable results. “The European Conference of Postal and Telecommunications Administrations, considering that the bandwidth is an important parameter to characterize known and unknown signals; that there is an increasing number of different signal types that have to be measured by radio monitoring services; that FFT techniques allow to perform accurate measurements of the occupied bandwidth for nearly all types of signals; that the number of low cost digital signal analysers using FFT techniques being capable of performing accurate bandwidth measurements is increasing; that bandwidth measurement methods using FFT techniques offer advantages over conventional methods in terms of accuracy, storage of spectrum data, reproducibility and speed; that FFT techniques better measure time varying (gated, pulsed, or transient) signals and complex modulated dynamic signals by processing all frequencies of the measured spectrum simultaneously. recommends that the method and setup specifications described in the Annex are used for bandwidth measurements using FFT techniques. ANNEX General Among all the different definitions of bandwidth used in ITU-R Recommendation SM.328, there are only two which can directly be measured and hence are important for radio monitoring services. These are: The 99% (or β -%) occupied bandwidth: This is the frequency range in which a certain percentage of the total spectral power of a signal falls. The residual part of