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The Principle of BeiDou Navigation System and Its Receiver Modification

Course Code: GMAT9205By LeShu Wu

- Chinese Independent research and development of regional positioning system

2011.5.24 LeShu Wu

Contents

Introduction1

Positioning Principle2

Compare with GPS3

Receiver Modification4

Conclusion5

Reference6

2011.5.24 LeShu Wu

1.Introduction

1960s First Generation of Global navigation system based on Doppler principle

1970-1990 ， based on RNSS principle

U.S. and U.S.S.R. started to establish new generation global navigation system

GPS – U.S.GLONASS – U.S.S.R.

2011.5.24 LeShu Wu

Low cost & Short Circle - only 6 satellites can achieve Chinese region positioning

Why China Choose Beidou?

Communication – integrate positioning and communication on one platform which is important in disaster relief, search and rescue.

2011.5.24 LeShu Wu

2.Positioning Principle

BeiDou Navigation System BeiDou Navigation System (BDSS)(BDSS)

“Double satellites

positioning principle”

GEOSTAR system

“active satellite navigation and Communication

system”

1970s

American scientist

G. K. Oneill

2011.5.24 LeShu Wu

Positioning Process and Principle

Fig.1. Working Schematic Diagram of BDSS

2011.5.24 LeShu Wu

1st Time Delay

Table.1. Signal Transport Part-1

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2nd Time Delay

Table.2. Signal Transport Part-2

2011.5.24 LeShu Wu

Fig.2. Calculation Components

2(Ds1 + D1)

( D s1 + D1 + D s1 + D2 )

2011.5.24 LeShu Wu

3. Compare with GPS

2011.5.24 LeShu Wu

2011.5.24 LeShu Wu

Receiver Modification

Fig.3. Overall Receiver System Schematic

2011.5.24 LeShu Wu

Modulation

OQPSK Modulation： can avoid 180° phase shift

I slip ： Sinusoidal modulation Q slip ： Cosine modulation

Binary signal modulation ： NRZ“1 ， -1” Initial phase of “1” ： 0° Initial phase of “-1” ： 180°

2011.5.24 LeShu Wu

Fig.4. BDSS Signal modulation diagram

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1

Encode signals I slip & Q slip

Generator – 16kb/s NRZ bipolar signals

2

Multiply with 4.08Mb/s Short PN1 code (Kasami Sequence)

4.08Mb/s Long PN2 code (Gold Sequence)

3

Spread spectrum signal I slip delay half PN code period – Sin modulation

Q slip – Cos modulation directly

4

I slip + Q slip

send into the channel

2011.5.24 LeShu Wu

Final transmit signals

2011.5.24 LeShu Wu

Demodulation

Input Signal

Q slip

Only demodulate I slip which includes satellite position and time.

Q slip has nothing useful signals.

I Slip

Costas Central

2011.5.24 LeShu Wu

2011.5.24 LeShu Wu

Control VOC output frequency

Multiple I & Q

Multiple with local PN code

After Low-pass filter （ LPF）

I slip： Q slip：

2011.5.24 LeShu Wu

5. Conclusion

The Next Generation Of BDSS

Same Principle as GPS

More accurate on timing and positioning

Combination with old system

2011.5.24 LeShu Wu

6. Reference [1]

"The construction of BeiDou navigation system steps into important stage, "Three Steps" development guideline clear and certain" (China National Space Administration. 2010-05-19. http://www.BeiDou.gov.cn/2010/05/19/20100519101180c595f14a6d9938a42a2d796b56.html. Retrieved 2010-05-19.

[2]"Comparable with American and Russian in terms of performance, BeiDou-1 navigates for China" (in Chinese). China National Space Administration. 2003-05-30. http://www.cnsa.gov.cn/n615708/n620172/n677078/n751578/62676.html. Retrieved 2010-05-19.

[3]Pike, John. "BeiDou (Big Dipper)". Space. GlobalSecurity.org. http://www.globalsecurity.org/space/world/china/BeiDou.htm. Retrieved 2006-11-09.[dead link]

[4]Marks, Paul (2006-11-08). "China's satellite navigation plans threaten Galileo". NewScientist.com. http://www.newscientist.com/article/dn10472-chinas-satellite-navigation-plans-threaten-galileo.html. Retrieved 2006-11-09.

[5]"China puts new navigation satellite into orbit". . 2007-02-03. http://english.gov.cn/2007-02/03/content_516638.htm. Retrieved 2010-05-20.

[6]"BeiDou 1 Experimental Satellite Navigation System". . 2008-09-24. http://www.sinodefence.com/space/spacecraft/beidou1.asp. Retrieved 2010-05-20.

[7]"60-day works in space -- Story of reparation of the BeiDou satellite" (in Chinese). Sohu. 2007-04-18. http://news.sohu.com/20070418/n249522961.shtml. Retrieved 2010-05-23.

[8]"Compass due Next Year". Magazine article. Asian Surveying and Mapping. May 4, 2009. http://www.asmmag.com/news/compass-due-next-year. Retrieved 2009-05-05.

[9]"China successfully launched the third BeiDou satellite" (in Chinese). Sohu. 2010-01-17. http://news.sohu.com/20100117/n269631862.shtml. Retrieved 2010-05-19.

[10]"China sends Beidou navigation satellite to orbit". . 2010-06-02. http://www.spaceflightnow.com/news/n1006/02longmarch/. Retrieved 2010-06-04.

[11]"China successfully launches fifth satellite for its own global navigation network". Xinhuanet. 2010-08-01. http://news.xinhuanet.com/english2010/china/2010-08/01/c_13424634.htm. Retrieved 2010-08-01.

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