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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANS)

doc.: IEEE 802. 15-04-0322-01-003a. July 2004. 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: []

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANS)

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  1. doc.: IEEE 802. 15-04-0322-01-003a July 2004 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.

  2. The relationship between DAC and TX LPFto 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 ETRI

  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 ETRI

  4. -12 dB -20 dB C A B 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 ETRI

  5. Power spectral density at 128 IFFT output The TX LPF design is not easy to satisfy the Transmit PSD mask of MB-OFDM. ETRI

  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. ETRI

  7. Measurement for DAC Characteristic PSD after TX LPF PSD between DAC and TX LPF The characteristic of DAC as LPF is verified from PSD of OFDM system, the OFDM system used 2 over-sample rate at DAC. ETRI

  8. The PSD characteristics of several TX LPFs 5th order Chebyshev Type I LPF 5th order Butterworth LPF 5th orderChebyshev Type II LPF The PSD characteristics of Several 5th order LPFs used to satisfy the Transmit PSD mask. Three types all don’t satisfy the transmit PSD mask by itself ETRI

  9. 5th order Butterworth Ideal Before TX LPF • Simulation conditions 3dB Bandwidth = 260MHz data rate = 200Mbps(use time spreading) Channel = AWGN No FEC After TX LPF ETRI

  10. 5th order Chebyshev Type I Ideal Before TX LPF 3dB Bandwidth = 260MHz The passband ripple = 0.5dB After TX LPF ETRI

  11. 5th order Chebyshev Type II Ideal Before TX LPF 3dB Bandwidth = 260MHz The stopband ripple = 10 dB After TX LPF ETRI

  12. Summary of the 9th order TX LPFs 9th order Butterworth 9th order Chebyshev Type II Ideal Before TX LPF 9th order Chebyshev Type I Apply several 9th order TX LPF to satisfy the transmit PSD mask After TX LPF : 9th order Butterworth ETRI

  13. 2 times over-sampling at DAC Ideal Before TX LPF 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. After TX LPF ETRI

  14. Summary of simulations 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 5th TX LPF is almost analogous to that using 9th TX LPF ETRI

  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 5th 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. ETRI

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