无线电通信平台的实现算法的外文文献0130101142Word文档格式.docx

1、A radio direction finding （DF） system is an antenna array and a receiver arranged in a combination to determine the azimuth angle of a distant emitter. Basically, all DF systems derive the emitter location from an initial determination of the angle-of-arrival （AOA）.Radio direction finding techniques

2、 have classically been based on multiple-antenna systems employing multiple receivers. Classic techniques such as MUSIC 12 and ESPRIT use simultaneous phase information from each antenna to estimate the angle-of-arrival of the signal of interest. In many scenarios （e.g., hand-held systems）, however,

3、 multiple receivers are impractical. Thus, single channel techniques are of interest, particularly in mobile scenarios. Although the amount of existing research for single channel DF is considerably less than for multi-channel direction finding, single channel direction finding techniques have been

4、previously investigated.When considering single channel direction finding systems, we find that there are two distinct types of DF systems. The first type of DF system is the amplitude-based DF system. Amplitude-based systems determine the bearing of the signal （or the AOA） by analyzing the amplitud

5、es of the output voltages from each antenna element. Amplitude DF systems include the Watson-Watt technique using an Adcock antenna array .The second type of DF system is the phase-basedDF system. Phase-based systems use three or more antenna elements that are configured in a way so that the relativ

6、e phases of their output voltages are unique for every wavefront angle-of-arrival. Phase-based DF systems include the Pseudo-Doppler technique with a commutative switch based antenna array .Since both of the above techniques are primarily analog techniques and have been analyzed in previous work, we

7、 will investigate a new single channel direction finding technique that takes specific advantage of digital capabilities. Specifically, we propose a phase-basedmethod that uses a bank of Phase-Locked Loops （PLLs） in combination with an eight-element circular array. Our method is similar to the Pseud

8、o-Doppler method in that it samples antennas in a circular array using a commutative switch. In the proposed approach the sampled data is fed to a bank of PLLs which tracks the phase on each element. The parallel PLLs are implemented in software and their outputs are fed to a signal processing block

9、 that estimates the AOA.This thesis presents the details of the new algorithm and compares its performance to existing single channel DF techniques such as the Watson-Watt and the Pseudo-Doppler techniques. We also describe the implementation of the algorithm on a DRS Signal Solutions Incorporated （

10、DRS-SS）, WJ-8629A Software Definable Receiver with Sunrise . Technology and present measured performance results. Simulations on a signal with 10dB SNR have shown that the Watson-Watt algorithm and the Pseudo-Doppler algorithm have an accuracy that is worse than the proposed technique by approximate

11、ly an order of magnitude.The algorithm was implemented on a single-channel DSP-based software radio with a homemade eight-element circular antenna array. The WJ-8629A software defined radio receiver was provided by DRS-SS in order to implement our algorithm. The implementation was tested using a CW

12、signal at 1.57068 GHz in a low multipath laboratory environment and outdoors. The performance of the prototype is compared to the data provided by the simulations in Matlab.Implementation results focus on CW measurements in a relatively benign laboratory environment for proof-of-concept testing. Thi

13、s document will show that the basic version of the algorithm can result in a significant computational burden, thus we investigate a low-complexity approach and demonstrate its performance. It will be shown that a significant computational reduction can be achieved with minimal performance penalty.1

14、.1Software IntroductionDuring our research, all of the single-channel direction finding simulations were performed using the MATLAB 6.1 software. After the simulations were completed, the MATLAB code was then ported to hardware for implementation using the C programming language. The initial C progr

15、ams were written and tested to prove that the algorithms could be implemented on the TI based software radio. After the C programs were tested and compared to their Matlab counterparts, they were then optimized for the Texas Instruments TMS320C67x Digital Signal Processor.1.2Hardware Introduction1.2

16、.1DRS Signal Solutions, Incorporated WJ-8629A SoftwareTMDefinable Receiver with Sunrise . TechnologyThe implementation was performed on a Texas Instruments DSP-based WJ-8629A software defined radio provided by DRS-SS. It has a frequency range from 20 to 2700 MHz with 10-Hz resolution, receiver filte

17、ring with 22 filter slots （200 Hz to 1.23 MHz）, and 5 reserved slots for user-downloadable custom filters The main processing unit is the Texas Instruments TMS320C6701 DSP processor with a maximum computational rate of nearly 1GFlops. The radio allows one to develop algorithms for certain signal pro

18、cessing modules in the C programming language or the TMS320C67x assembly language. Other details of the radio are not listed here due to their proprietary nature. Throughout this thesis we will include only those details necessary for proper understanding of the implementation.1.2.2MPRG Antenna Arra

19、yThe antenna baseline is the geometric line of interconnection between antenna elements. Antenna aperture is defined as the plane surface area near the antenna through which most of the radiation flows. The spacing between antenna elements usually determines the aperture of an array, and since we ar

20、e using circular arrays, the diameter of the entire circular array determines the array aperture .In order to model the antenna array, assuming a single plane wave impinging on thearray, the array manifold vector for a uniform circular array can be written as:u eAR sin z-1e2 二 R , sincos 2where R is

21、 the radius of the circular antenna array, : is the elevation angle, 0 is the angle of arrival （AOA） of the incoming plane wave, n mis the angle of the mthantenna element in the azimuthal plane, and is the wavelength of the center frequency of interest. For simplicity, the elevation angle is set to

22、90。in order to con sider azimuth an gles only. We do not con sider the effects of differe nt elevati ons in this study.The MPRG antenna array as see n in Figure 1.1 is an eight-eleme nt antenna array with a diameter of 19.1 cm. We desire to have a waveform that completes one wavelength over the diam

23、eter of the array which will be discussed in detail in later chapters. Therefore, the frequency of the CW is defined a1s= c/ 入 or 1.57068 GHz. Chapter2Introduction to Single Channel Direction FindingTo date, the two primary methods that have bee n exam ined for sin gle cha nnel direct ion finding ar

24、e the Wats on-Watt Method using an Adcock antenna array, and the Pseudo-Doppler Method using a commutative switch with a circular antenna array . While little is available in the open literature concerning these two techniques, what is available assumes an analog receiver and operates at relatively

25、low frequencies. Specifically, the Adcock/Wats on-Watt algorithm is typically used for freque ncies up to about 1000 MHz, while the Pseudo-Doppler algorithm typically has an operati onal bandwidth from 2-2000 MHz. In this chapter, we will discuss the amplitude-based Wats on-Watt tech niq ue, the pha

26、se-based Pseudo-Doppler method, and an amplitude-based Pseudo-Doppler tech nique developed as part of the curre nt research. We will discuss their stre ngths and short-co min gs a nd motivate the in vestigati on of new tech niq ues.2仃 he Watson-Watt MethodWatso n-Watt DF is an amplitude-based method

27、 that uses the relative amplitude of the output of two antenna arrays arranged according to the Adcock design. The Adcock desig n con sists of four antenna eleme nts in a perpe ndicular, crossed-baseli neconfiguration as seen in Figure 2.1.This method can be used for freque ncies up to about 1000 MH

28、z. One Adcock pair contains two antenna arrays （four antenna elements） in a perpendicular con figurati on, with eleme nt spaci ng of less tha n one half the wavele ngth at the highest operati ng freque ncy. The azimuth gai n patter n from each antenna array is obta ined by a vector differe nee of si

29、g nals from each of two antenn as.The sig nals see n on the four antennas in complex baseba nd no tati on are:where r（t） is the received signal, R is the radius of the circular antenna array, is the wavelength of the center frequency of interest, m（t） is a linearly modulated message signal and is th

30、e AOA6. The East antenna represents our 0o referenee.The N and S antenna pair creates the Y-axis voltage, which has a maximum gain along the Y-axis. In other words when ：-90, the east and west signals are equal and thus x（t） =re（t）-rw（t） = 0, whereas y（t） = rn（ t） -rs（t） = 2m（t）. The E and W antenna

31、 pair creates the X-axis voltage, which has maximum gain along the X-axis. In other words when ：=0 , the north and south signals are equal and thus（t） = re（t）-rw（t） =2m（t）, whereasy（t） = rn（t） -rs（t） = 0.TargetQXT OOAFigure 2.1 Adcock Antenna Array used for Wats on-Watt AlgorithmIn order to pass the

32、 AOA data to the single receiver, each of the X and Y axis voltages have to be comb ined in to a composite sig nal. I n our example in Chapter 4,the two signals are linearly combined to form an AM signal with dual tone modulation in order to pass the data to the single receiver.After the linearly combined AM signal reaches the receiver and AM demodulation is performed, the estimated AOA （ * ） is calculate