Geraschenko A. "Research and development of high linear power amplifiers of the microwave transmitters for mobile communication systems".Abstract

Introduction

To the modern mobile communication networks makes high demands, both in relation to high data rates and providing of QoS. A progress of these systems demonstrates the permanent increase of data rates, caused foremost displacement of users priority on multimedia, business aplications, Internet. The evolution of wireless communication networks was reflected on complication of transmittion technologies, and accordingly and on the equipment of these systems.

For achieving high data rates and simultaneously high spectral efficiency are used difficult, complex methods of radio signal modulations, whith considerable changes of signal envelope. First of all there are 3G, 4G systems with QAM modulation , however the signals with phase modulation also don't have permanent envelope because are passing through filtration process. In addition these systems are characterized by high spectral efficiency, i.e. by a maximal compression and rapprochement of nearby channels, for example OFDM are realized in the fourth generation systems. This is conduces to growth of base stations equipment linearity requirements with the purpose of intermodulation distortion minimization and reduction of parasitic spectral components in nearby channels. A power amplifier is a part of the base station transmitter, provides amplifying of radio signal and acts not unimportant part in the providing of linearity requirements.

Design of special linearization systems and output passband filters, choise of active element type and his class of work can improve linearity of power amplifier. Except linearity requirements to power amplifiers makes demands of high efficiency for power consumption minimization and cooling system simplification.

Scientific novelty

The high-linear power amplifier is developed on the basis of microstrip technology with the use of pre-distorting circle and defected ground structure ( DGS ) technology. Linearization of PA is providing by predistortion network with AM-AM and AM-PM tuning capabilities. Defected ground structure technology is innovative and used for matching network dimensions optimization and creation of passband output filter with minimal geometry dimensions for high order intermodulation components filtration.

Actuality of work

Actuality of work consists a necessity of high-linear power amplifier development, meeting demands of modern wireless communication standards.

Subject of research: research of modern ways for power amplifier linearity increasing, creation of broadband matching circuits, an opportunity of application of defected ground structure technology with the purpose of power amplifier characteristic optimization.

Object of research: power amplifier as a structure element of wireless network

The purpose of work: the purpose of work is research and development of high linearity power amplifiers for transmitters of mobile communication systems, research of modern ways for power amplifier characteristics optimization.

Power amplifier structure

The developed power amplifier is realized on the basis of microstrip technology and generally consists of three basic parts: a predistortion network, the non-linear power amplifier and the defected ground structure passband filter.

General power amplifier structure

Figure 1 General power amplifier structure

Necessity of the predistortion circle is caused by high requirements of maintenance of power amplifier transfer characteristic linearity with the purpose of the intermodulation distortion and parasitic harmonics in the adjacent frequency channels minimization. Analog predistortion circle can be realized on the diode basis, tuning of the transfer characteristic is performed by biasing of the diode.

Non-linear power amplifier is presented by the balanced class C amplifier with common base transistors and Lange directed coupler .

Realization of the balancing amplifier is justified by such advantages as:

Opportunity of high-power amplifiers construction by association of several amplifying modules;

Increase in reliability of the amplifier as in case of failure of one amplifying module, the second will continue to work and it will not lead to failure of all wireless channel;

Absorption on balancing loading of the bridge of the reflected wave owing to a mismatch of the amplifier with the next cascades.

The amplifier works in a class C because it can provide high power efficiency and problems of stability of the transistors included under the common base scheme are minimized. The choice of the common base scheme is caused first of all by advantage to realize any power gain, as function from input and outpur resistance, and also increase in linearity of the transfer characteristic.

The output filter is intended for a parasitic intermodulation harmonics filtration and realized on the basis of defected ground structure technology. The given technology provides the minimal geometrical sizes and high filtering properties.

	Geraschenko Alexander Myhailovich Faculty of Computer Information Technologies and Automatics Department of Automation and Telecommunication TSN 07m Тheme : "Research and development of high linear power amplifiers of the microwave transmitters for mobile communication systems" Scientific adviser: Doctor of technical science, Professor Vorontsov Alexander Grigorevich

Abstract
	Introduction To the modern mobile communication networks makes high demands, both in relation to high data rates and providing of QoS. A progress of these systems demonstrates the permanent increase of data rates, caused foremost displacement of users priority on multimedia, business aplications, Internet. The evolution of wireless communication networks was reflected on complication of transmittion technologies, and accordingly and on the equipment of these systems. For achieving high data rates and simultaneously high spectral efficiency are used difficult, complex methods of radio signal modulations, whith considerable changes of signal envelope. First of all there are 3G, 4G systems with QAM modulation , however the signals with phase modulation also don't have permanent envelope because are passing through filtration process. In addition these systems are characterized by high spectral efficiency, i.e. by a maximal compression and rapprochement of nearby channels, for example OFDM are realized in the fourth generation systems. This is conduces to growth of base stations equipment linearity requirements with the purpose of intermodulation distortion minimization and reduction of parasitic spectral components in nearby channels. A power amplifier is a part of the base station transmitter, provides amplifying of radio signal and acts not unimportant part in the providing of linearity requirements. Design of special linearization systems and output passband filters, choise of active element type and his class of work can improve linearity of power amplifier. Except linearity requirements to power amplifiers makes demands of high efficiency for power consumption minimization and cooling system simplification. Scientific novelty The high-linear power amplifier is developed on the basis of microstrip technology with the use of pre-distorting circle and defected ground structure ( DGS ) technology. Linearization of PA is providing by predistortion network with AM-AM and AM-PM tuning capabilities. Defected ground structure technology is innovative and used for matching network dimensions optimization and creation of passband output filter with minimal geometry dimensions for high order intermodulation components filtration. Actuality of work Actuality of work consists a necessity of high-linear power amplifier development, meeting demands of modern wireless communication standards. Subject of research: research of modern ways for power amplifier linearity increasing, creation of broadband matching circuits, an opportunity of application of defected ground structure technology with the purpose of power amplifier characteristic optimization. Object of research: power amplifier as a structure element of wireless network The purpose of work: the purpose of work is research and development of high linearity power amplifiers for transmitters of mobile communication systems, research of modern ways for power amplifier characteristics optimization. Power amplifier structure The developed power amplifier is realized on the basis of microstrip technology and generally consists of three basic parts: a predistortion network, the non-linear power amplifier and the defected ground structure passband filter. Figure 1 General power amplifier structure Necessity of the predistortion circle is caused by high requirements of maintenance of power amplifier transfer characteristic linearity with the purpose of the intermodulation distortion and parasitic harmonics in the adjacent frequency channels minimization. Analog predistortion circle can be realized on the diode basis, tuning of the transfer characteristic is performed by biasing of the diode. Non-linear power amplifier is presented by the balanced class C amplifier with common base transistors and Lange directed coupler . Realization of the balancing amplifier is justified by such advantages as: Opportunity of high-power amplifiers construction by association of several amplifying modules; Increase in reliability of the amplifier as in case of failure of one amplifying module, the second will continue to work and it will not lead to failure of all wireless channel; Absorption on balancing loading of the bridge of the reflected wave owing to a mismatch of the amplifier with the next cascades. The amplifier works in a class C because it can provide high power efficiency and problems of stability of the transistors included under the common base scheme are minimized. The choice of the common base scheme is caused first of all by advantage to realize any power gain, as function from input and outpur resistance, and also increase in linearity of the transfer characteristic. The output filter is intended for a parasitic intermodulation harmonics filtration and realized on the basis of defected ground structure technology. The given technology provides the minimal geometrical sizes and high filtering properties.