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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

  • 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 [[email protected]]

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.


The relationship between dac and tx lpf to satisfy the transmit psd mask of mb ofdm

The relationship between DAC and TX LPFto satisfy the transmit PSD mask of MB-OFDM

Sang-Sung Choi ([email protected])

Cheol-Ho Shin ([email protected])

www.etri.re.kr

ETRI


Project ieee p802 15 working group for wireless personal area networks wpans

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


Transmit psd mask of mb ofdm uwb system

-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


Power spectral density at 128 ifft output

Power spectral density at 128 IFFT output

The TX LPF design is not easy to satisfy the Transmit PSD mask of MB-OFDM.

ETRI


Power spectral density at dac output

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


Measurement for dac characteristic

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


The psd characteristics of several tx lpfs

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


5 th order butterworth

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


5 th order chebyshev type i

5th order Chebyshev Type I

Ideal

Before TX LPF

3dB Bandwidth = 260MHz

The passband ripple = 0.5dB

After TX LPF

ETRI


5 th order chebyshev type ii

5th order Chebyshev Type II

Ideal

Before TX LPF

3dB Bandwidth = 260MHz

The stopband ripple = 10 dB

After TX LPF

ETRI


Summary of the 9 th order tx lpfs

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


2 times over sampling at dac

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


Summary of simulations

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


Summary

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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