1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANS) Submission Title: [The relationship between DAC and TX LPF to satisfy the transmit PSD mask of MB-OFDM] Date Submitted: [July 2004] Revised: [] Source: [Sang-sung Choi, Cheol-Ho Shin] Company [Electronics and Telecommunications Research Institute] Address [161 Gajeong-dong, Yuseong-gu, Daejeon, 305-350 Korea] Voice : [+82-42-860-6722], FAX : [+82-42-860-5199], E-mail [sschoi@etri.re.kr] Re: [Technical contribution] Abstract: [This presentation presents the performance according to several TX LPF used to satisfy the Transmit PSD mask of MB-OFDM UWB system] Purpose: [Technical contribution to analyze the relationship between DAC and TX LPF to satisfy the transmit PSD mask proposed for MB-OFDM UWB system] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual or organization. The material in this document is subject to change in form and content after further study. The contributor reserves 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 P802.15. July 2004 doc.: IEEE 802. 15-04-0322-00-003a

2. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 2 The relationship between DAC and TX LPF to satisfy the transmit PSD mask of MB-OFDM Sang-Sung Choi (sschoi@etri.re.kr) Cheol-Ho Shin (chshin@etri.re.kr) www.etri.re.kr

3. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 3 Introduction The TX LPF is very important to determine the transmit PSD mask of MB-OFDM UWB system. Two methods are considered to design the TX LPF satisfying the transmit PSD mask. - fix 528MHz sampling rate of DAC, and design high order TX LPF - increase sampling rate of DAC, and reduce the order of TX LPF

4. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 4 Transmit PSD mask of MB-OFDM UWB system A: 260 MHz -> 0 dBr bandwidth not exceeding 260MHz B: 285 MHz -> -12 dBr C: > 330 MHz -> -20dBr -12 dB -20 dB AB C

5. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 5 Power spectral density at 128 IFFT output The TX LPF design is not easy to satisfy the Transmit PSD mask of MB-OFDM.

6. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 6 Power spectral density at DAC output The characteristic of DAC is similar to that of LPF, it can help to design the TX LPF.

7. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 7 Measurement for DAC Characteristic The characteristic of DAC as LPF is verified from PSD of OFDM system, the OFDM system used 2 over-sample rate at DAC. PSD between DAC and TX LPF PSD after TX LPF

8. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 8 The PSD characteristics of several TX LPFs The PSD characteristics of Several 5 th order LPFs used to satisfy the Transmit PSD mask. Three types all don’t satisfy the transmit PSD mask by itself Butterworth 5 차 Chebyshev Type I 5 차 Chebyshev Type II 5 차

9. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 9 5 th order Butterworth Ideal Before TX LPF After TX LPF 3dB Bandwidth = 260MHz

10. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 10 5 th order Chebyshev Type I Ideal 3dB Bandwidth = 260MHz The passband ripple = 0.5dB Before TX LPF After TX LPF

11. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 11 5 th order Chebyshev Type II Ideal 3dB Bandwidth = 260MHz The stopband ripple = 10 dB Before TX LPF After TX LPF

12. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 12 Summary of the 9 th order TX LPFs Chebyshev Type I 9 차 Butterworth 9 차 Chebyshev Type II 9 차 Ideal After TX LPF : 9 th order Butterworth Apply several 9 th order TX LPF to satisfy the transmit PSD mask Before TX LPF

13. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 13 2 times over-sampling at DAC Ideal 2 times over sample rate is used at DAC to design TX LPF easily. In this case, the degradation of performance is about 1 dB compared to Ideal condition for BER 10 -5. Before TX LPF After TX LPF

14. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 14 Summary of simulations 5 th 9 th 2 times over-sampling Butterworth 10.7 dB8.54 dB 7.6 dB ChebyShev Type I 8.0 dB8.05 dB ChebyShev Type II 8.3 dB9.8 dB BER 10 -5 기준 The higher order LPF is not always superior to the lower order LPF in the performance of system. In case of Chebyshev Type I, the system performance using 5 th TX LPF is almost analogous to that using 9 th TX LPF

15. Submission doc.: IEEE 802.15-04-0322-00-003a July 2004 ETRISlide 15 Summary There are two methods to satisfy the Transmit PSD mask of MB-OFDM 1) Fix the DAC sample rate as 528MHz, then give burden to TX LPF design. - the higher order TX LPF is necessary - but 5 th order TX LPF is enough to satisfy the transmit PSD mask considering the characteristic of DAC. 2) Use 2 times over-sample rate at DAC to design the TX LPF. - Reduce the order of TX LPF - It has advantage of the performance compared to method 1). There are trade-offs between two methods for considering power consumption and gate size etc.