적응 배열 안테나를 이용한 DOA 추정 알고리즘의 측정 평가에 관한 연구

Abstract

Wireless communication technologies have greatly progressed in recent years and the markets, especially in the mobile communication, have been growing enormously. Moreover the next generation communication services will use higher frequency band, and require more channel capacity and wider bandwidth for a high-speed data communication. As a large increase in channel capacity and high transmission rates for wireless communications, the technologies for the power saving and efficient frequency usability are required. To meet the requirements of the next generation wireless communications, a system capable to automatically change the directionality of its radiation patterns in response to its signal environment must be indispensable.

An adaptive array antenna system uses spatially separated antennas called array antenna and processes received signals with a digital signal processor after analog to digital conversion. The main concept of an adaptive antenna is the automatic or adaptive control of antenna's beam pattern by digital signal processing with a software algorithm. A digital device capable of high speed real-time processing, consuming low power and programmable is required for practical use of an adaptive antenna in wireless communications. In recent year using a FPGA(Field Programmable Gate Array) for the implementation of an adaptive antenna meets the requirements of high performance processing, programmability and low power consumption.

This thesis describes a DOA(Direction Of Arrival) estimation algorithm using MUSIC(MUltiple SIgnal Classification) method with high resolution and evaluation of the DOA estimation measurement system using adaptive array antenna. The DOA estimation measurement system consists of linear array antenna, a DBF receiver, A/D control box and monitoring/control computer in the anechoic chamber. Transmitting part is composed broadband standard horn antenna and signal generator. The linear array antenna is fabricated and measured return loss is -16 dB and below at 2.09 GHz. The DBF(Digital Beam Forming) receiver is composed of 4-ch resistive FET mixer of low IF method. RF(Radio Frequency), LO(Local Oscillator) and an IF(Intermediate Frequency) signal considered in this thesis are 2.09 GHz, 2.08 GHz and 10 MHz, respectively. A/D control box has 12-bit resolution and sampling rates is up to 40 MHz. From results of the DOA estimation simulation using MATLAB, a zero IF is realized by DDC(Digital Down Conversion) and MUSIC algorithm with high resolution depends on the snapshot and antenna element number. In addition, A/D control box is implemented by MUSIC algorithm and IF signal generator. GUI(Graph User Interface) program for data control/monitoring in the computer is designed. From the results of the DOA estimation experiment, it confirms that a proposed DOA system is able to estimate the direction of incident wave.