Broadcast technology is at the beginning of a new era. It is characterized by the intensive use of the most advanced digital modulations formats (8VSB, QAM, OFDM) in combination with high power RF amplifiers. To date the linearity required for these digital formats has only been accomplished in cumbersome low efficiency class A amplifier or even more cumbersome feed-forward systems. A potentially more efficient and cost effective approach is the combination of non linear power amplifiers and a predistortion technique capable of compensating for the non linear amplifiers. Digital predistortion will provide a highly linear output and improved efficiency. Itelco has developed a digital adaptive base band predistorter to provide for improved performance and cost. The technique is independent of the modulation type, the output frequency, or the signal bandwidth. Furthermore the capability of automatic adaptive predistortion to compensate for the environment (temperature, power supply variations, aging ,and even operation during replacement of a faulty module) is highly desirable.
The new digital standards adopted in Europe for broadcast communication systems use the Orthogonal Frequency Division Multiplexing (OFDM) technique [1][2] which is characterised by non constant envelope signals. This fact is in contrast with the employment of RF High Power Amplipers (HPAs) which are typically non linear and utilised with low Output Back Off (OBO) in order to maximise the power efficiency. The consequent generation of InterModulation Products (IMPs) is responsible for Bit Error Rate (BER) degradation and Adjacent Channel Interference (ACI). Aim of this work is to present the Itelco experience in this topics, outlining the DVB-T performance dependence from the OBO. Moreover the improvements achievable by AMIAM-AM/PM predistortion and by RF non-linear memory compensation will be analysed both by simulation and measurements.
Coded Orthogonal Frequency Division Multiplexed (COFDM) techniques, used by terrestrial European broadcasting systems (DAB, DVB-T), could be adopted in the last mile of the downlink channel for Wireless Broadband Communication System to provide Multimedia Services to mobile or nomadic users by cellular coverage techniques, as evinced from the actual research activity. COFDM signals are characterised by non-constant envelope (peak-to-mean power ratio > 10 dB) which forces to project amplifiers with low or well-counteracted nonlinear distortion effects. Our aim is to present Itelco experience to characterise non-linear distortions introduced by final amplifiers on COFDM signals (AM/AM, AM/PM and NonLinearities with Memory
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.