1. Submission Title: [Spectral Properties of tg4a Signals]
Sept 2005
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Spectral Properties of tg4a Signals]
Date Submitted: [30-Sep-2005]
Source: [Laurent Ouvry, Samuel Dubouloz, Mathieu Sambuq]
Company [CEA-Leti]
Address [17 rue des Martyrs Grenoble]
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E−Mail:
Re: [ a.]
Abstract: [Spectral Properties of tg4a Signals]
Purpose: [To promote discussion in a.]
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
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

2. Objective Determine impact of :
Sept 2005
Objective
Determine impact of :
Peak PRF
Burst length
Scrambling (polarity and time)
Symbol duration (& mean PRF)
on signal average power (with FCC definitions)
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

3. Average Power Measurements
Sept 2005
Average Power Measurements
Measure in a 1MHz RBW Bandwidth
Averaging time lower or equal to 1ms
Use of functions given in doc #354r1-UWB-Power-Measurements
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

4. Signal Models Burst composed by N pulses repeated at peak PRF
Sept 2005
Signal Models
Burst composed by N pulses repeated at peak PRF
Symbol time Ts
Mean PRF is therefore N/Ts
Scrambling is used
Pulse polarity codes
Burst position scrambling codes
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

5. Worst Case : No polarity code, no time scrambling
Sept 2005
Worst Case : No polarity code, no time scrambling
Signal can be expressed as:
According to doc # 354r1:
Burst of N impulsions p(t)
Pulse Spectrum composed by spectral lines
spaced by PRF and convolved by a sinc function of
N/PRF width
Burst every Ts TF
Pulse PSD, lower than dBm/MHz
RBW < 1/Ts
Spectral lines amplitudes, not depending on PRF
RBW ≥ 1/Ts
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

6. Example (No polarity code, no time scrambling)
Sept 2005
Example (No polarity code, no time scrambling)
Measurement
Calculation
PRF = 247 MHz
Amplitude = *log10(RBW * N) – 60 =
Difference (negligible) is due to sinc
Function sidelobes
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

7. No Modulation – No Time Scrambling
Sept 2005
No Modulation – No Time Scrambling
Burst Size (N)
+ 3 dB
Y-scale is what is above –41.3dBm/MHz (in previous simple example, would be 8.6dB)
identical
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

8. Modulation Effects PPM Modulation Sept 2005
It is worst with PPM modulation only
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

9. Modulation Effects (2) PPM + Polarity Sept 2005
PPM + Polarity is better than PPM only
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

10. Time Scrambling Effects
Sept 2005
Time Scrambling Effects
 No Difference between simple modulation (2-PPM, 4-PPM) and fine time scrambling
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

11. Polarity Codes Effect Sept 2005
Each pulse has a random polarity
Standard deviation is about 0.25dB
Polarity Codes are required for spectrum smoothing
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti

12. Sept 2005
Conclusions
Peak PRF has no influence on the average transmitted power (w.r.t. FCC)
Time scrambling has a minor effect on spectrum smoothing and is not better than PPM Modulation in this respect
Random Polarity codes are required as soon as bursts of pulses are used
Burst size and symbol time do not influence the spectrum anymore with random polarity codes
A power backoff (margin) of about 1.5dB is required  compliant with doc # 605r1
L. Ouvry, S. Dubouloz, M. Sambuq CEA-Leti