A Potential Transmitter Architecture for Future Generation Green Wireless Base Station

Vandana Bassoo,Henrik Sjoland,Ellie Cijvat,Mike Faulkner,A K Mustafa,Kevin Tom

doi:10.1155/2009/821846

Abstract

Current radio frequency power amplifiers in 3G base stations have very high power consumption leading to a hefty cost and negative environmental impact. In this paper, we propose a potential architecture design for future wireless base station. Issues associated with components of the architecture are investigated. The all-digital transmitter architecture uses a combination of envelope elimination and restoration (EER) and pulse width modulation (PWM)/pulse position modulation (PPM) modulation. The performance of this architecture is predicted from the measured output power and efficiency curves of a GaN amplifier. 57% efficiency is obtained for an OFDM signal limited to 8 dB peak to average power ratio. The PWM/PPM drive signal is generated using the improved Cartesian sigma delta techniques. It is shown that an RF oversampling by a factor of four meets the WLAN spectral mask, and WCDMA specification is met by an RF oversampling of sixteen.

Highlights

The existing third generation network deployed around the world is not sufficient to meet the needs of new upcoming bandwidth intensive applications
This has lead to a renewed interest in architectures such as linear amplification with nonlinear components (LINCs), envelope elimination and restoration (EER), and pulse width modulation (PWM) [3,4,5]
A high efficiency all-digital transmitter architecture that uses a combination of EER and PWM/pulse position modulation (PPM) modulation is described

Summary

Introduction

The existing third generation network deployed around the world is not sufficient to meet the needs of new upcoming bandwidth intensive applications. The challenge is on the modulation stage to generate the appropriate drive signal which is optimised for efficiency and linearity This has lead to a renewed interest in architectures such as linear amplification with nonlinear components (LINCs), envelope elimination and restoration (EER), and pulse width modulation (PWM) [3,4,5]. The amplitude variation can be impregnated onto the phase modulated pulse position modulation (PPM) signal, sΣΔ, by applying pulse width modulation (PWM) on the PPM pulses of the input RF drive signal (Figure 2)

Switch Mode Power Amplifier

Digital

Bandwidth Limitation

Pulse Train Generation Using Sigma Delta Modulation Technique

Conclusion

ΣΔ filter