doc.: IEEE f Submission February, 2010 Andy Ward, UbisenseSlide 1 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Behaviour of spectrum analyzer RMS average detector Date Submitted: 25 th February 2010 Source: Andy Ward, Ubisense Address: St Andrew’s House, St Andrew’s Road, Chesterton, Cambridge, CB4 1DL, ENGLAND Voice: , FAX: , Abstract: Analysis of behaviour of spectrum analyzer RMS average detector, to assist TG4f with selection of PHY parameters Purpose:To be considered by TG4f Notice:This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release:The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P

doc.: IEEE f Submission February, 2010 Andy Ward, UbisenseSlide 2 Behaviour of spectrum analyzer RMS detector Andy Ward Ubisense

doc.: IEEE f Submission February, 2010 Andy Ward, UbisenseSlide 3 Overview We wish to have optional ‘Location Enabler Information’ (LEI) after the PHY payload to assist with signal measurements for UWB RFID location systems It is proposed that the LEI signal can either be sent immediately after the PHY payload, or after a short period of time –A gap between the end of the PHY payload and the start of the LEI signal allows manufacturers to take advantage of common UWB regulatory definitions which allow average power measurements to be taken over a 1ms period (even if the signal doesn’t extend over that whole period). –The gap allows the LEI signal and the rest of the message to be placed in different 1ms periods, so the two segments don’t contribute to the average power measurement of the other. We need to define the length of the gap between the end of the PHY payload and the start of LEI signal This may depend on the behaviour of the RMS detector used in by the spectrum analyzer –It’s worth checking, anyway!

doc.: IEEE f Submission February, 2010 Andy Ward, UbisenseSlide 4 The experiment We generated a prototypical UWB tag signal without LEI –Burst of 186 pulses at 1MHz PRF –20Hz burst repetition rate Then, we generated a prototypical UWB tag signal with LEI –Burst of 186 pulses at 1MHz PRF (represents the PHY preamble/header/payload) –A gap, which could be varied between 0.615ms and 1.215ms in 0.1ms increments –Another burst of 186 pulses at 1MHz PRF (represents the LEI signal) –20Hz burst-pair repetition rate We measured the conducted RMS average power of these signals An Agilent E7405A analyzer was used We used an averaging time of 1ms per point on the spectrum analyzer 185us burst, 1MHz PRF Variable between 0.615ms – 1.215ms

doc.: IEEE f Submission February, 2010 Andy Ward, UbisenseSlide 5 Results The results below are referenced to a 0dB level corresponding to the average RMS power of the non-LEI case –We want to find out what the minimum gap between PHY payload and LEI signal is, such that there is no measurable difference between the non-LEI and LEI case The table also shows the ‘theoretical’ difference in power above the non-LEI case assuming that the RMS detector works ‘as expected’ Gap between end of PHY payload and start of LEI signal (ms) Measured power relative to non-LEI case (dB) Theoretical power relative to non-LEI case (dB)

doc.: IEEE f Submission February, 2010 Andy Ward, UbisenseSlide 6 Conclusions The RMS detector (on this spectrum analyzer, at least) works as expected There is a good match between the theoretical and experimental results (within 0.5dB) With a 1MHz PRF, a 0.815ms gap between the end of the PHY payload and the start of the LEI signal is probably optimal