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研究生:劉惠平
研究生(外文):Hui-Ping Liu
論文名稱:低成本微衛星地面站之建立與廣播數據修正編碼傳輸實驗
論文名稱(外文):Establishment of Low-Cost Microsatellite Ground Station and Data Broadcasting Transmission with Error Code Correction
指導教授:蕭飛賓
指導教授(外文):Fei-Bin Hsiao
學位類別:碩士
校院名稱:國立成功大學
系所名稱:航空太空工程學系
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:1999
畢業學年度:87
語文別:英文
論文頁數:91
中文關鍵詞:微衛星微衛星地面站數位通訊業餘無線電向前修正編碼上傳下傳封包通訊
外文關鍵詞:MICROSATELLITEMICROSATELLITE GROUND STATIONCONVOLUTIONAL CODINGFORWARD ERROR CORRECTIONAMATEUR RADIOUPLINKDOWNLINKPACKET COMMUNICATION
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科技的日新月異,使得微衛星由最初的實驗性質進而實用性大增。目前已有多顆微衛星在軌道上運轉、提供遙測、科學籌載實驗、業餘數位封包通訊等多樣化的服務,其快速的研發周期、低廉的成本,已成為各國大力發展的目標。有鑑於此,本文將藉由探討成功大學微衛星地面站的系統特性、規劃、建造、系統整合、運作、資料的上下傳與處理等等,來建立一套低成本微衛星地面系統模式。並亦將討論都卜勒頻率飄移及時間精確度對於上下鏈通訊所造成的影響。此外,有鑑於微衛星數據廣播的應用越來越廣泛,因此通訊品質成為一項很重要的探討議題。來自業餘頻道的干擾及微衛星本身低功率的廣播訊號,使得數據常常要重覆下傳數次才能使用。藉由改變調變或頻寬方式改善通訊品質的方式已經廣泛被討論過,所以本篇論文將以通道編碼為主軸,探討應用錯誤修正編碼的迴旋碼( Convolutional Coding )技術於AX.25 UI微衛星廣播通訊協定的可行性。實驗分別將以1200 bps、9600 bps 兩種傳輸速率、業餘VHF 144 MHz與 UHF MHz 兩種通訊頻道、及AFSK與BPSK 兩種數位調變模式為條件下,利用兩個地面站來模擬微衛星數據廣播傳輸實驗。經過編碼的數據在傳送至接收端則採用Viterbi Maximum Likelihood Method 來進行解碼。 在以傳輸速率、頻率及調變方式為條件下,相互比較有編碼及未編碼的性能差異,以探討該方法對於AX.25 UI廣播通訊協定封包資料正確率的提升。此外,採用迴旋碼會使資料量增加一倍,因此資料正確率與資料量的增加間的取捨,優點與缺點亦會詳加討論。

As the technology develops, the microsatellites which work simply for the experimental purposes now are getting more and more practical. Nowadays there are already many Earth-orbiting satellites providing telemetry, remote sensing, scientific payload experiments and amateur digital packet communication services. Due to its short term design period and low manufacture cost, the development of microsatellite technology has been encouraged by many countries. This paper hence studies how to establish a low cost ground station through the analysis of data uplink and downlink, phase designing, building, system integration and operation. In addition, the downlink broadcasting quality affected by Doppler shift effect and timing accuracy will also be investigated. Due to fast growing usage of microsatellite data broadcasting, the quality of data transmission has become a very important issue. Due to interference from the amateur radio band and microsatellite's low transmitting power, the broadcast data can frequently be distorted. As the improvement from the frequency and modulation technique for amateur radio has widely been studied, this paper explores the forward error correction technique, called convolutional coding, to be incorporated with the transmission data packet of AX.25 UI Microsatellite Broadcasting Protocol in VHF 144MHz and UHF 430 MHz bands by using AFSK and BPSK digital modulation techniques. Then the present microsatellite broadcasting experiments will be simulated by two ground stations. The transmitted data are then decoded by the maximum likelihood decoding method, or called Viterbi algorithm, to enhance the broadcasting quality. From the experimental results, the performance of data coding and uncoding will be evaluated under the conditions of transmission rate, frequency and modulation techniques. As the usage of the Convolutional Coding will increase the data volume to the double, the compromise between the increased data volume and coding performance will also be discussed. After the employment of the convolutional coding, the results clearly show the increase of the transmission data volume due to its less redundancy and significant improvement of the bit error rate under a number of amateur radio frequency bands tested. This ascertains the merit of the present system applicable for use in the real harsh environmental data transmission.

CONTENTS
Page
ENGLISH ABSTRACT……………………………………………………………..…….i
CHINESE ABSTRACT…………..…………………………………………..…………..iii
ACKNOWLEDGEMENTS…………………….………………………………………..v
CONTENTS……………………...………….………………………………………..…..vi
LIST OF TABLES…………………..…………………………..……………………….x
LIST OF FIGURES………………….………………………………….………………..xi
NOMENCLATURE…………………………………………………………………..…xv
CHAPTER
IINTRODUCTION………………………………………….…….……………1
1.1 Background………………………………………..…………………………...…….1
1.1.1 Concept of Digital Packet Microsatellite…………….……………….…...1
1.1.2 Concept of Microsatellite Data Broadcasting….………………..………...1
1.1.3 Concept of Error Code Correction……………………………………..…2
1.2 Literature Review………..……………………………..………………….……..…2
1.3 Motivations and Objectives…………………………………………………………3
IIESTABLISHMENT OF LOW-COST MICROSATELLITE
GROUND STATION………………………....……………………….….………...5
2.1 Radio System……………………….…………………..……..…………….….….5
2.1.1 Antennas…………………………….…….…….…………………………5
2.1.2 Preamplifier……………………………………………………..………...5
2.1.3 Feedlines……………………………………………………….……….…6
2.1.4 Standing Wave Reading Meter…………………….……………………...6
2.1.5 Tranceivers………………………………………………….………….…6
2.2 Computer Control and Data Processing System…….……….…..…………………7
2.2.1 Personal Computer………………………….…………..………………….7
2.2.2 Ground Station Automation Software…………………..………………….7
2.2.3 Rotor Controller and KCT Interface Control Card……..………………….7
2.2.4 Terminal Node Controller (TNC)…….…………….………………………7
IIIDIGITAL MODULATION AND TRANSMISSION PROTOCOL …..….….…9
3.1 Digital Modulation Techniques…………..……………….…….….…………..….9
3.1.1 Audio Frequency Shift Keying (AFSK)………………..………….………9
3.1.2 Binary Phase Frequency Shift Keying (BPSK)………………….……....10
3.2 Transmission Protocol……………..………………………………...……………10
3.2.1 AX.25 Protocol…………….………………………………….……….…10
3.2.2 RS-232C Protocol for Serial Communication………..…………..………11
IVCONCEPT OF THE CONVOLUTIONAL CODING………………...…...…13
4.1 Convolutional Encoding Process………………………………………….………13
4.1.1 Trellis Diagram……………………………………………………….…16
4.1.2 State Transition Diagram……….…………………..……………………16
4.2 Viterbi Maximum Likelihood Decoding Process…………..……………………..17
VEXPERIMENTAL FACILITIES AND PROCEDURES…….……………..….19
5.1 Ground Station Uplink and Downlink Experiment………..……………………...19
5.1.1 Operational Procedures……………………………..……………………19
5.1.2 Keplerian Elements and Satellite News Update..……..…………………20
5.2 Ground Simulation for Microsatellite Broadcasting Experiment…….....………..20
5.2.1 Experimental Facilities………………………………..…………….….20
5.2.2 Experimental Procedures……..…………………………..…………21
VIRESULTS AND DISCUSSION………………………………....………………..24
6.1 Ground Station Operation……….…………………………..……………….…….24
6.1.1 Doppler Shift……..………………………….………………….………..24
6.1.2 TNC Wiring Connection………...………….…………….………….…24
6.1.3 Tranceiver Modification for 9600 bps AFSK Communication…………..25
6.1.4 Timing and Keplerian Element Precision…………….………….…...…26
6.1.5 Standing Wave Effect….…………….…………………….……………26
6.1.6 Data Uplink and Downlink …………………………………..…………26
6.1.7 Ground Station Operation…….……………….….………..……………27
6.2Automatic Repeated Requested (ARQ) versus Broadcasting………..………..…. 27
6.3Convolutional Coding Performance……………………………….………..……27
6.3.1 9600 bps and 1200 bps AFSK Transmission ……...……………...…...28
6.3.2 1200 bps BPSK Transmission…………….…………….…………….28
6.3.3 Convolutional Coding Performance for 9600 bps
AFSK Transmission…………………………..……………..…….………28
6.3.4 Convolutional Coding Performance for 1200 bps
AFSK Transmission………..……………..………………..….………….29
6.3.5Convolutional Coding Performance for 1200 bps
BPSK Transmission…………………..………………..………………..29
6.3.6Convolutional Coding Performance for UHF 430
MHz Transmission………………………………………………………30
6.3.7Convolutional Coding Performance for VHF 144
MHz Transmission………………………………………………………30
6.3.8Convolutional Coding Performance for Overall
Digital Modulation Technique Transmissions……………………………31
6.3.9General Discussion………………………………………………………31
VIICONCLUSIONS………………..………...…..………………..……….………..33
7.1 Ground Station Operation……………..…………….…..……….……...…...…….33
7.2 Convolutional Coding…………..…..….………………..…….………..……..……33
7.3 Future Work…………………………..………………..…………….………….…..35
REFERENCES…………………………………………………..………………………37
TABLES…………………….……………….……..………………………….……….…40
FIGURES………………………………………..….……………………………………43
VITAE…………….……………………………………………………………..…….90
PUBLICATION LIST………………………………………………………………….91

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[5] Karn, P., Convolutional Decoders for Amateur Packet Radio, 14th Digital
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[30] 官文霖, 微衛星數據接收與地面模擬影像籌載傳輸實驗, 國立成功大學航空太空工程研究所碩士論文, 1994.
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