外文翻譯--一種新型的分析與單通道尋找在軟件無線電通信平臺的實現(xiàn)算法的方向

1、<p>　　Analysis and Implementation of a Novel Single Channel Direction Finding Algorithm on a Software Defined Radio Platform</p><p>　　John Joseph Keaveny</p><p><b>　　Capter1</b>

2、</p><p>　　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

3、location from an initial determination of the angle-of-arrival (AOA).</p><p>　　Radio direction finding techniques have classically been based on multiple-antenna systems employing multiple receivers. Classic

4、 techniques such as MUSIC [1][2] 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, multiple

5、receivers are impractical. Thus, single channel techniques are of interest, particularly in mobile scenarios. Although the amount of existing research f</p><p>　　When considering single channel direction fin

6、ding 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 t

7、he amplitudes of the output voltages from each antenna element. Amplitude DF systems include the Watson-Watt technique using an Adcock antenna array .</p><p>　　The second type of DF system is the phase-based

8、 DF system. Phase-based systems use three or more antenna elements that are configured in a way so that the relative phases of their output voltages are unique for every wavefront angle-of-arrival. Phase-based DF systems

9、 include the Pseudo-Doppler technique with a commutative switch based antenna array .</p><p>　　Since both of the above techniques are primarily analog techniques and have been analyzed in previous work, we w

10、ill investigate a new single channel direction finding technique that takes specific advantage of digital capabilities. Specifically, we propose a phase-based method that uses a bank of Phase-Locked Loops (PLLs) in combi

11、nation with an eight-element circular array. Our method is similar to the Pseudo-Doppler method in that it samples antennas in a circular array using a commutative swit</p><p>　　in software and their outputs

12、 are fed to a signal processing block that estimates the AOA.</p><p>　　This thesis presents the details of the new algorithm and compares its performance to existing single channel DF techniques such as the

13、Watson-Watt and the Pseudo-Doppler techniques. We also describe the implementation of the algorithm on a DRS Signal Solutions Incorporated (DRS-SS), WJ-8629A Software Definable Receiver with Sunrise . Technology and pres

14、ent measured performance results. Simulations on a signal with 10dB SNR have shown that the Watson-Watt algorithm and the Pseudo-Doppler algorit</p><p>　　The algorithm was implemented on a single-channel DSP

15、-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 C

16、W 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.</p><p>　　Implementation result

17、s focus on CW measurements in a relatively benign laboratory environment for proof-of-concept testing. This document will show that the basic version of the algorithm can result in a significant computational burden, thu

18、s 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.</p><p>　　1.1 Software

19、 Introduction</p><p>　　During 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 the

20、n ported to hardware for implementation using the C programming language. The initial C programs were written and tested to prove that the algorithms could be implemented on the TI based software radio. After the C progr

21、ams were tested and compared to their Matlab counterparts, they were then optimized for the Texa</p><p>　　1.2 Hardware Introduction</p><p>　　1.2.1 DRS Signal Solutions, Incorporated WJ-8629A Sof

22、tware Definable Receiver with Sunrise. Technology</p><p>　　The implementation was performed on a Texas Instruments DSP-based WJ-8629A software defined radio provided by DRS-SS. It has a frequency range from

23、20 to 2700 MHz with 10-Hz resolution, receiver filtering 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

24、DSP processor with a maximum computational rate of nearly 1GFlops. The radio allows one to develop algorithms for certain signal pro</p><p>　　1.2.2 MPRG Antenna Array</p><p>　　The antenna baseli

25、ne 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

26、 usually determines the aperture of an array, and since we are using circular arrays, the diameter of the entire circular array determines the array aperture .</p><p>　　In order to model the antenna array, a

27、ssuming a single plane wave impinging on thearray, the array manifold vector for a uniform circular array can be written as:</p><p>　　where R is the radius of the circular antenna array, is the elevation an

28、gle, θ is the angle of arrival (AOA) of the incoming plane wave, ηm is the angle of the mth antenna element in the azimuthal plane, and is the wavelength of the center frequency of interest. For simplicity, the elevatio

29、n angle is set to 90o in order to consider azimuth angles only. We do not consider the effects of different elevations in this study.</p><p>　　The MPRG antenna array as seen in Figure 1.1 is an eight-element

30、 antenna array with a diameter of ~19.1 cm. We desire to have a waveform that completes one wavelength over the diameter of the array which will be discussed in detail in later chapters. Therefore, the frequency of the C

31、W is defined as f = c/λor 1.57068 GHz.</p><p><b>　　Chapter2</b></p><p>　　Introduction to Single Channel Direction Finding</p><p>　　To date, the two primary methods that

32、have been examined for single channel direction finding are the Watson-Watt Method using an Adcock antenna array, and the Pseudo-Doppler Method using a commutative switch with a circular antenna array . While little is a

33、vailable in the open literature concerning these two techniques, what is available assumes an analog receiver and operates at relatively low frequencies. Specifically, the Adcock/Watson-Watt algorithm is typically used f

34、or frequencies up to a</p><p>　　2.1The Watson-Watt Method</p><p>　　Watson-Watt DF is an amplitude-based method that uses the relative amplitude of the output of two antenna arrays arranged accor

35、ding to the Adcock design. The Adcock design consists of four antenna elements in a perpendicular, crossed-baseline configuration as seen in Figure 2.1.</p><p>　　This method can be used for frequencies up to

36、 about 1000 MHz. One Adcock pair contains two antenna arrays (four antenna elements) in a perpendicular configuration, with element spacing of less than one half the wavelength at the highest operating frequency. The azi

37、muth gain pattern from each antenna array is obtained by a vector difference of signals from each of two antennas.</p><p>　　The signals seen on the four antennas in complex baseband notation are:</p>

38、<p>　　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 the AOA[6]. The Eas

39、t antenna represents our 0o reference.</p><p>　　The N and S antenna pair creates the Y-axis voltage, which has a maximum gain along the Y-axis. In other words when , the east and west signals are equal and t

40、hus x(t) =re(t)-rw(t) = 0, whereas y(t) = rn(t)-rs(t) = 2m(t). The E and W antenna pair creates the X-axis voltage, which has maximum gain along the X-axis. In other words when , the north and south signals are equal an

41、d thus x(t) = re(t)-rw(t) = 2m(t), whereas y(t) = rn(t)-rs(t) = 0.</p><p>　　Figure 2.1 Adcock Antenna Array used for Watson-Watt Algorithm</p><p>　　In order to pass the AOA data to the single re

42、ceiver, each of the X and Y axis voltages have to be combined into a composite signal. In our example in Chapter 4, the two signals are linearly combined to form an AM signal with dual tone modulation in order to pass th

43、e data to the single receiver.</p><p>　　After the linearly combined AM signal reaches the receiver and AM demodulation is performed, the estimated AOA (?) is calculated by taking the arctangent of the N-S di

44、fference divided by the E-W difference.</p><p>　　where the approximation holds for small values of , since for small values of x. If we use the antenna array described in Figure 2.1, we will encounter an 18

45、0o phase ambiguity since a negative ratio could correspond to either quadrant 2 or 4 whereas a positive ratio could correspond to either quadrant 1 or 3. If a centrally located omni-directional antenna is included in Fig

46、ure 2.1, then it can provide basic directional sensing to help eliminate the 180o phase ambiguity . In Chapter 4, we will </p><p>　　2.2 Pseudo-Doppler Algorithm</p><p>　　The Pseudo-Doppler techn

47、ique is a phase comparison method that exploits the Doppler shift on successive samples of circularly disposed antenna elements. Measurements of phase differences between the elements of a multi-element antenna array ena

48、ble the azimuth angle of the arriving signal to be determined. One system of this type is the Pseudo-Doppler method. In principle, an antenna element could be moved in a circular path so that the instantaneous frequency

49、of the received signal would be modi</p><p>　　Alternatively, a rotating commutative RF switch is used to couple a receiver in rapid sequence to the elements of the array, thereby introducing a frequency shif

50、t on the received signal which is extracted by a frequency discriminator. As the antenna moves, it imposes a Doppler shift on the arriving signal. The magnitude of the Doppler shift is at a maximum as the antenna moves d

51、irectly toward and away from the direction of the incoming wavefront. There is no apparent frequency shift when the ant</p><p>　　As in Figure 2.2, the value of φr changes with the sampling position which res

52、ults in a frequency shift of 0o when φ1 is exactly coincident with the incoming signal azimuth angle with an 180o phase ambiguity. Therefore, near zero frequency shift occurs at angles () and (). The ambiguity can be res

53、olved by finding the maximum negative frequency shift at () and the maximum positive frequency shift at ().</p><p>　　Figure 2.2 Pseudo Doppler Frequency Shift</p><p>　　Consider a linearly modula

54、ted signal impinging on an Na-element circular array</p><p>　　Assume that the receiver switches from the ith antenna to the (i + 1)th antenna every Ts seconds. Now each antenna imposes a phase shift of</p

55、><p>　　where R is the radius of the circular array, is the wavelength of interest, is the angle-ofarrival and i = 0.Na ? 1. Now if the switch changes to the neighboring antenna every Ts seconds, it imposes a

56、time varying phase shift</p><p>　　where u(t) is the unit step function. The received signal is then</p><p>　　Ignoring for the moment the message signal, the output of an FM discriminator is</

57、p><p>　　Now, since this is not a true differentiator, but a discrete approximation, there is a delay of Ts/2:</p><p>　　Now, after down-conversion, we can ignore the carrier term. Thus, we have</

58、p><p>　　The samples for every Na values can be entered into a vector:</p><p>　　Now, the FFT of this vector is</p><p>　　In the expression above, each sum will be zero for all values of

59、k except k = 1. Further, for k = 1,</p><p>　　Thus the estimated AOA is,</p><p>　　2.3 Advantages and Disadvantages of Direction Finding Systems</p><p>　　2.3.1 Watson-Watt</p>

60、<p>　　2.3.1.1 Advantages</p><p>　　With the appearance of low-cost, wide frequency receivers, many manufacturers realized that .stand alone. DF bearing processors could be interfaced with the new low-cos

61、t receivers at minimal cost. A well designed Watson-Watt direction finding array can be interfaced with almost any receiver with good results [8]. The Adcock antenna array.s diameter is small in size. Therefore, the arra

62、y is beneficial in mobile and transportable DF applications. </p><p>　　Since the DF antenna tone modulation technique is AM, FM listen-through capability is excellent due to the high AM rejection of most rec

63、eiver FM limiter/discriminators. Listen- through capability is also good for AM signals as a result of the fact that the DF antenna modulation tone frequencies are well below the low end of the voice spectrum and can thu

64、s be easily attenuated in the audio output channel [8].</p><p>　　The Adcock/Watson-Watt system is suited mainly for mobile applications especially if budgetary constraints dictate the use of low-cost receive

65、rs.</p><p>　　2.3.1.2 Disadvantages</p><p>　　The Adcock antenna array is inherently a narrow aperture. Since it is a narrow aperture, the DF resolution is affected. If a center antenna is not use

66、d, then the algorithm then suffers from an 180o phase ambiguity. A narrow aperture antenna is quite susceptible to multipath and reflection errors.</p><p>　　The Adcock array requires balanced sum and differe

67、nce hybrids, balanced modulators, phase-matched cables, and circuits for phase or gain imbalance. All of these components can escalate the cost of the array [7].</p><p>　　The Adcock/Watson-Watt algorithm has

68、 a limitation on the maximum frequency. Due to the more complex electronics circuitry required by the Adcock antenna, it is not feasible to manufacture a wideband DF antenna capable of good and consistent performance at

69、frequencies over 1000 MHz [8]. The Adcock/Watson-Watt algorithm also does not provide elevation measurements, which have greater influence over the azimuth at higher frequencies.</p><p>　　2.3.2 Pseudo-Dopple

70、r</p><p>　　2.3.1.1 Advantages</p><p>　　When compared to the Adcock/Watson-Watt DF system, the pseudo-Doppler systems have advantages in the areas of site error suppression, DF antenna economy, a

71、nd extended high frequency performance. </p><p>　　Due to the circular arrangement of the antenna elements, the array can be constructed as a wide aperture array. A wide aperture array can increase AOA resolu

72、tion and reduce site errors, but the size of the array then becomes an issue as the number of antenna elements increases. Because spacing between antenna elements should be λ/2 or more, as the number of elements increase

73、s, the size of the array increases. If the size of the array becomes too large, the feasibility of mobility diminishes [8].</p><p>　　The electronic circuitry required to implement a pseudo-Doppler system con

74、sists of GaAs FET high frequency RF switches, the necessary driver circuitry, and phase-matched cables [7]. The simpler pseudo-Doppler DF antenna array is more easily and economically designed and manufactured when compa

75、red to the Adcock/Watson-Watt system. Please note that the economic impact of the cheaper pseudo-Doppler system only applies to narrow-aperture designs. As the aperture becomes larger and more antenna eleme</p>&l

76、t;p>　　In contrast to the Adcock/Watson-Watt system, the Pseudo-Doppler algorithm should work at frequencies up to 2000 MHz and beyond due to the simplicity of the electronics associated with a pseudo-Doppler manufactu

77、rable wideband DF antenna. This allows for a greater range of applications such as cellular applications [8].</p><p>　　2.3.2.2 Disadvantages</p><p>　　Because the wide aperture pseudo-Doppler arr

78、ays can suppress site errors, the large circular arrays can limit mobility and covertness. In addition to the large arrays, the quality of the receiver needs to be more complex than the Adcock/Watson-Watt because the pse

79、udo-Doppler receiver requires more sensitivity than an Adcock/Watson-Watt receiver, and it also needs to control the switching circuit which chooses the correct antenna element. </p><p>　　Another disadvantag

80、e to pseudo-Doppler systems is that the listen-through capability is a problem. Because there is a desire to obtain an accurate AOA, a high commutative switching rate is needed. When there is a high commutative switching

81、 rate, the switching rate is placed in the audio range. FM voice audio is badly distorted due to the high switching rate because the commutative process creates FM modulation at the commutative rate. AM also suffers as a

82、 consequence of the soft-commutation swit</p><p>　　2.4 Motivation for a New Single Channel DF Method</p><p>　　After reviewing the above algorithms, we decided to try and develop an algorithm tha

83、t is loosely based on the pseudo-Doppler system. The goal of our algorithm and system was to provide the AOA resolution of a pseudo-Doppler system or better while maintaining a small aperture mobile circular antenna arra

84、y.</p><p>　　Our algorithm will be implemented on a software-defined radio which will take advantage of a digital implementation. It should provide equal or better performance than the algorithms or methods d

85、escribed above. The DF system should allow for listen-through capability which should be equal or better than the above algorithms. And last, the algorithm should be different from existing algorithms.</p><p&g

86、t;　　The Phase-locked loop (PLL) algorithm that is proposed in Chapter 3 is loosely based on the pseudo-Doppler system in that we will use a similar switched antenna array system. The advantage of the PLL algorithm is tha

87、t we are able to maintain a small aperture array while increasing the AOA resolution. Therefore, the PLL algorithm is an accurate direction finding system with mobile capabilities and listen through capabilities.</p&g

88、t;<p>　　一種新型的分析與單通道尋找在軟件無線電通信平臺的實現(xiàn)算法的方向</p><p><b>　　第1章</b></p><p>　　一個無線電測向（DF）的天線陣列系統(tǒng)是在一個組合安排，以確定一個遙遠的發(fā)射方位角一個接收器?；旧?，所有的測向系統(tǒng)，推導出從該角的落地（AOA）的初步測定發(fā)射器的位置。</p><p>　

89、　無線電測向技術已經是基于經典的多天線系統(tǒng)采用多個接收器。如音樂[1] [2]和ESPRIT經典技術使用每個天線同步相位信息估計角的，有用信號的到來。在（例如，手持系統(tǒng)）很多情況下，但是，多個接收器是不切實際的。因此，單聲道技術的興趣，特別是在移動的情況。雖然現(xiàn)有的研究單通道東風金額大大低于多通道測向少，單通道測向技術此前已進行調查。</p><p>　　當考慮單通道測向系統(tǒng)，我們發(fā)現(xiàn)有兩個不同類型的DF系統(tǒng)。對

90、DF系統(tǒng)的第一類是振幅的東風系統(tǒng)。振幅為基礎的系統(tǒng)，通過分析確定每個天線單元的輸出電壓的幅值的信號（或AOA）的影響。振幅東風系統(tǒng)包括屈臣氏瓦技術，使用一阿德科克天線陣列。</p><p>　　對DF系統(tǒng)第二類是逐步的東風系統(tǒng)。第一階段為基礎的系統(tǒng)使用三個或更多的天線，是要素配置的方式，使它們的輸出電壓的相對相位是每個波前角的，獨特的到來。相的東風系統(tǒng)包括天線陣列與基于交換開關偽多普勒技術。</p>

91、<p>　　由于上述兩種技術主要是模擬技術，并已在以往的工作分析，我們將探討新的單通道測向技術，它利用數(shù)字功能的特定優(yōu)勢。具體來說，我們提出了一個階段為基礎的方法，它使用一八元的鎖相環(huán)（PLL）的合并圓陣。我們的方法是類似的偽多普勒方法，在一個圓陣天線進行采樣用一個交換開關。在新方法中的采樣數(shù)據(jù)送入一個鎖相環(huán)儲備，跟蹤每個元素的階段。實施平行鎖相環(huán)在軟件和它們的輸出輸入到信號處理塊，估計到達角。</p><

92、;p>　　本論文提出了新算法的細節(jié)，并比較其性能，以現(xiàn)有的東風，如沃森瓦和偽多普勒技術，技術單一渠道。我們還描述了在一個DRS的信號解決方案公司（DRS的不銹鋼），WJ-8629A軟件可定義接收機日出算法的實現(xiàn)。目前測得的性能技術和成果。在具有10dB的信噪比模擬表明，沃森瓦算法和偽多普勒算法有一個精確度比提出的技術差了大約一個數(shù)量級。</p><p>　　該算法上實現(xiàn)單通道基于DSP的軟件無線電與自制八元

93、圓形天線陣列。 WJ公司的-8629A軟件定義無線電接收機提供了DRS的衛(wèi)隊，以執(zhí)行我們的算法。測試使用的實施是在?1.57068 GHz的低多了實驗室環(huán)境和戶外的CW信號。該樣機的性能進行比較，通過Matlab的模擬提供的數(shù)據(jù)。</p><p>　　執(zhí)行結果集中在一個相對良性的實驗室環(huán)境下對連續(xù)測量證明了概念測試。這份文件將表明，該算法的基本版本可以計算的結果會有很大的負擔，因此我們研究了低復雜性的方法，并展示

94、其性能。這將是一個重要的計算表明，可減少性能損失達到最小。</p><p><b>　　1.1 軟體簡介</b></p><p>　　在我們的研究，單聲道模擬的方向尋找進行了利用MATLAB6.1軟件。模擬完成后，當時的MATLAB代碼移植到硬件使用C編程語言實現(xiàn)。最初的C程序進行編寫和測試證明，該算法可以在TI基于軟件無線電實現(xiàn)。 C程序后進行了測試和比較，其Mat

95、lab的同行，他們是那么優(yōu)化德州儀器TMS320C67x數(shù)字信號處理器。</p><p><b>　　1.2 硬體介紹</b></p><p>　　1.2.1 DRS的信號解決方案，成立WJ-8629A軟件可定義接收機技術</p><p>　　實施上進行德州儀器DSP為基礎WJ-8629A定義DRS的黨衛(wèi)軍提供無線軟件。它有一個頻率??范圍從2

96、0到2700 MHz的10 Hz的分辨率，接收器22過濾槽（200 Hz至1.23兆赫），以及用戶可下載自定義5預留插槽過濾過濾器的主要處理單元是德州儀器TMS320C6701的DSP的處理器，最高運算速度近1GFlops。無線電允許一個開發(fā)某種信號在C編程語言或TMS320C67x匯編語言處理模塊算法。收音機的其他細節(jié)，這里沒有列出，因為它們的專有性。在本論文中，我們將只包括那些細節(jié)的正確理解，實施必要的。</p>&l

97、t;p>　　1.2.2 MPRG天線陣列</p><p>　　該天線基線是天線單元之間的互連幾何線。天線孔徑的定義是靠近天線平面面積，通過它的輻射流量最大。天線單元之間的間距通常決定了一個陣列孔徑，因為我們使用的是圓形陣列，整個圓陣的陣列孔徑的直徑決定。</p><p>　　為了模擬天線陣列，假設一個單一的平面波thearray沖擊，陣列為均勻圓陣列流形向量可表示為：</p&g

98、t;<p>　　其中為半徑的圓形天線陣，是仰角，為到來傳入的平面波（AOA）的角度，是在方位平面?zhèn)€天線單元的角度，是波長感興趣的中心頻率。為了簡單起見，仰角設定為90度，以考慮方位角只。我們不認為在這項研究中的不同海拔高度的影響</p><p>　　該MPRG天線陣列，如圖1.1看到的是一個有著?19.1厘米，直徑八元天線陣列。我們渴望有一個波形，完成了對將在以后的章節(jié)中詳細討論陣列直徑一波長。因此

99、，連續(xù)波頻率被定義為的1.57068千兆赫。</p><p>　　第2章 介紹單通道測向</p><p>　　迄今為止，已為單通道測向檢驗了兩個主要方法是屈臣氏瓦法使用阿德科克天線陣列，和偽多普勒方法使用的圓形天線陣交換開關。雖然很少在公開文獻中關于這兩種技術可以，有什么可假定一個模擬接收機并以相對較低的頻率運行。具體來說，阿德科克/華信惠瓦算法通常用于頻率高達約1000兆赫，而偽多普勒算