Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
  • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
  • G01S19/13—Receivers
  • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system

Definitions

• the present invention relates to methods for processing navigation signals when they also include one or more additional modulations making it possible to transmit data which complement the information intrinsically contained in the elementary signal. It applies more particularly to the processing of navigation signals transmitted by satellites.
• Radio navigation by satellite currently mainly uses the signals emitted by the GPS system, and incidentally those of the GLONASS system. In the future, it will use the signals from the GALILEO system.
• This radio navigation makes it possible to obtain the position of the receiver by processing the signals transmitted by at least three satellites and by performing phase measurements and code measurements on these signals. Code measurements are not very precise but unambiguous, while phase measurements are much more precise but ambiguous.
• the signals transmitted by the satellites contain data bits which make it possible to transmit navigation messages. These messages are used in the calculation algorithms to determine the position, speed and time of the receiver.
• the received phase rotates and it is then necessary to use an integration system, which makes it possible to obtain a reactive control over this phase.
• the invention proposes a method of processing a navigation signal containing data, in which a first DBPSK type carrier band for demodulating navigation signals, and in which a second BPSK type loop is also used to identify the data tests.
• the code 101 and carrier 102 oscillators are controlled by the error signals which are described below. They make it possible respectively to obtain a point code and a ⁇ code in a generator 103 and sin signals. and cos. in phase shifters 104 and 105.
• the punctual signals, ⁇ , cos. and sin. are applied to a correlator 106 which makes it possible, from the received signal, to obtain the signals l p , l ⁇ , Q p and Q ⁇ in a conventional manner using a set of multipliers 107 and blocking samplers 108.
• these signals are sampled at a given frequency.
• two demodulators are used, a first demodulator of the DBPSK type for the carrier and a second demodulator of the DBPSK type for the data.
• the signals sampled at the output of the correlator 106 are multiplied together in a module 109 to obtain crossed products l p . I ⁇ , l Q ⁇ > Qp • I ⁇ and Q p . Q ⁇ .
• These cross products are integrated into a set of blocking integrator circuits 110, to then obtain the variables A, B, C and D defined by the formulas:
• the signals l p and Q p are subjected to a so-called "squaring" treatment, which consists in performing a complex product l p x / Q p .
• These signals are themselves integrated into a second set of blocking integrators 112.
• the signal ⁇ is then applied to a code corrector 114 which performs a conventional filtering operation. After sampling at the loop frequency, this filtered signal ⁇ forms the error signal applied to the input of the code oscillator 101.
• the signals l p 'and Q p ' coming from "squaring" are applied to the discriminator carrier type DBPSK 115 which will be described later.
• the signal ⁇ coming from this discriminator 115 is applied on the one hand to the code discriminator 113, and on the other hand to a carrier corrector 116, which also performs a simple known filtering operation.
• the signal ⁇ is thus filtered and then sampled at the loop frequency to form the error signal of the carrier oscillator 102.
• the signals l p 'and Q p ' are first applied to a differentiator 201.
• the signals at the output of this differentiator are then applied to a BPSK 202 type discriminator which performs the tangent arc operation (x, y) in an interval - ⁇ + ⁇ .
• This discriminator 202 is then applied to an integrator 203, which operates conventionally with an adder 213 and a generator 223 with a function in Z "1 .
• a ⁇ n + 1 argument (l n + 1 + iQ n + 1 ). - argument ⁇ + iQ n )
• the identification of the data bits is done in an identifier 117 from the signals l p and Q p supplied by the correlator 106.
• This identifier operates on the basis of a BPSK type discriminator. The phase discrimination is therefore then limited between - ⁇ and + ⁇ and the time constant Te / K is chosen small enough to decorrelate the successive bit errors.
• the signals l p and Q p are applied to a complex multiplier 301, which also receives the signals at the output of a module 302 which will be described later.
• the signals I and Q coming from this complex conduit are then applied to a discriminator 303 of the BPSK type, which performs the tangent arc operation (x, y) on a signal bounded between - ⁇ / 2 and + ⁇ 12.
• the signal at the output of this discriminator is multiplied by a constant K in an amplifier 304, then it is applied to an integrator 305 in the structure is identical to that of the integrator 203 of FIG. 2.
• the signal ⁇ at the output of this integrator is applied to the module 302 which performs the operation e "1 ⁇ to give the signals provided above.
• the data bits are then obtained by determining, using a comparator circuit 306, the sign of the signal I leaving the complex product generator 301.

Landscapes

• Engineering & Computer Science (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Computer Networks & Wireless Communication (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2001
  • 2001-12-18 FR FR0116397A patent/FR2833714B1/fr not_active Expired - Fee Related
• 2002
  • 2002-12-13 WO PCT/FR2002/004349 patent/WO2003054575A1/fr not_active Application Discontinuation
  • 2002-12-13 CA CA002470375A patent/CA2470375A1/fr not_active Abandoned
  • 2002-12-13 EP EP02805387A patent/EP1456686A1/de not_active Withdrawn
  • 2002-12-13 US US10/494,259 patent/US20040260456A1/en not_active Abandoned

Non-Patent Citations (1)

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