KR100967196B1 - Apparatus for Tracking GPS and Galileo Signal in GPS/Galileo Receiver - Google Patents

Abstract

The present invention relates to an apparatus for tracking satellite signals of a GPS / Galileo receiver.

The present invention is a satellite signal tracking device of a GPS / Galileo receiver, receiving a clock of a specific phase, P code having a specific phase, L code behind a predetermined delay value based on a specific phase, further behind a specific delay value Generate an estimated PRN code including a VL code, an E code preceded by a specific delay value, and a VE code earlier than a specified delay value, and correlate it with the PRN code of the satellite signal to calculate a correlation value and calculate the calculated correlation value, BOC ( 1,1) The code phase error is calculated using the autocorrelation function and weight of the signal, so that the clock for generating the estimated PRN code for tracking the satellite signal while the output code phase error is within the satellite signal tracking range. It provides a satellite signal tracking device of the GPS / Galileo receiver, characterized in that the control to change the specific phase.

According to the present invention, there is an effect of providing a GPS / Galileo receiver having a satellite signal tracking device that solves the ambiguity problem caused by BOC (1,1) modulation to improve the tracking and acquisition performance of satellite signals.

GPS / Galileo Receiver, Very Early Minus Very Late (VEMVL), Weighted Double Early Minus Late Power (WDELP), Code Discriminator

Description

GPS signal tracking device for GPS / Galileo receivers {Apparatus for Tracking GPS and Galileo Signal in GPS / Galileo Receiver}

The present invention relates to an apparatus for tracking satellite signals of a GPS / Galileo receiver. More particularly, the present invention relates to a GPS / Galileo receiver having a satellite signal tracking device that solves the ambiguity problem caused by BOC (1,1) modulation to improve the tracking and acquisition performance of satellite signals.

The US Department of Defense has developed a Global Positioning System (GPS), a satellite navigation system for military purposes. Currently, GPS is not only limited to military use, but is immersed in real life. A typical example is a vehicle navigation device using GPS, which is a device that guides a road where a vehicle is not blocked by a satellite signal tracking. GPS is also used for friend finders and location tracking services.

Since GPS used in various fields is under the influence of the US Department of Defense, there may be restrictions on the accuracy and use of GPS depending on the needs of the United States. In addition, because it is easily interrupted by broadband radio waves, it is easy to malfunction in electronic warfare situations, and may cause serious errors in areas where reception of radio waves is difficult, such as in urban areas or in forests. Korea, China, and Israel are developing a satellite navigation system for the problems of GPS, and this is the "Galileo system". Since the Galileo system is intended for commercial service, it can guarantee the location accuracy of 1m level, can acquire the signal indoors, and when used with GPS, it can know the exact location even in the city center. Can improve. Therefore, researches on receiver technology capable of integrating the Galileo system and the existing GPS have been actively conducted.

In the aforementioned Galileo system, a new design for a signal is required, and a modulation technique that can be shared with a GPS BPSK modulated signal has been studied. Among these studies, a binary offset modulation (BOC) has emerged as an appropriate signal modulation technique.

However, the traditional BPSK demodulation technique used to demodulate GPS signals cannot be applied to the new Galileo signal demodulation for several reasons. This is caused by the fact that the BOC modulated signal is a signal obtained by multiplying a spreading code by a subcarrier signal having a frequency component that is a multiple of an extension code frequency.

Among the aforementioned BOC modulated signals, the BOC (1,1) signal to be used in the Galileo system has a new type of autocorrelation function including one main peak and two side peaks. This can be seen in 1.

Referring to FIG. 1, a subcarrier signal used for BOC (1,1) modulation has the same frequency component as a spreading code and generates one main peak and two side peaks having steep slopes in an autocorrelation function. Here, one main peak can improve code tracking (tracking) performance and alleviate multipath problems, while two side peaks can be used to track BOC (1,1) satellite signals. ) ". The aforementioned ambiguity problem occurs when the receiver is locked to the side peak in tracking the BOC (1,1) modulated signal, which may degrade the tracking and navigation performance of the satellite signal. However, a receiver equipped with a conventional Early Minus Late (EML) correlator cannot solve this ambiguity problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a GPS / Galileo receiver having a satellite signal tracking device that solves the ambiguity problem when demodulating a BOC (1,1) modulated signal, thereby improving the tracking and navigation performance of the satellite signal. have.

According to an aspect of the present invention for achieving the above object, in the satellite signal tracking device of the GPS / Galileo receiver for receiving and processing a signal modulated by a BOC (Binary Offset Carrier) (1,1) modulation technique from the satellite A P (Prompt) code having a specific phase, a L (Late) code that is delayed by a predetermined delay value based on the specific phase, and a VL (Very Late) that is further behind the specific delay value. A code generator for generating and outputting an estimated PRN code including an code, an E (Early) code preceding the specific delay value, and a VE (Very Early) code earlier than the specific delay value; The satellite signal is input to the estimated PRN code, the satellite signal is separated into an in-phase phase component and a quadrature phase component, and a correlation value is output by correlating the PRN code included in the separated satellite signal and the estimated PRN code, respectively. Correlator; A code comparison unit configured to calculate and output a code phase error using the output correlation value, the autocorrelation function of the BOC (1,1) signal, and two weights; And a code tracking loop controller configured to control the specific phase of the clock to be changed so as to track the satellite signal transmitted from the satellite while the output code phase error is within a preset satellite signal tracking range. It provides a satellite signal tracking device of the GPS / Galileo receiver comprising a.

As described above, according to the present invention, a GPS / Galileo receiver having a satellite signal tracking device which solves the ambiguity caused by the BOC (1,1) modulated signal and improves the tracking and navigation performance of the satellite signal is provided. It is effective to provide.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention unclear.

2 is a schematic block diagram of an apparatus 200 for tracking satellite signals of a GPS / Galileo receiver according to the present invention.

As shown in FIG. 2, a satellite signal tracking device 200 of a GPS / Galileo receiver for receiving and processing a signal modulated by a BOC (Binary Offset Carrier) (BOC) (1,1) modulation scheme from a satellite (200) ) Is a code generator 210 for generating an estimated PRN code having a phase similar to the PRN code included in the received satellite signal, and a PRN code included in the received satellite signal and an estimated PRN code generated by the code generator 210. The PRN code included in the satellite signal and the code phase of the estimated PRN code generated by the code generator 210 based on the correlation value output from the correlator 220 and the correlator 220 correlating the correlation value. A code comparator 230 for detecting an error and a code tracking loop controller 240 for controlling code tracking based on the code phase error detected by the code comparator 230 are included.

GPS / Galileo receivers are navigation data that includes satellite information, satellite time information, orbital information and history (Almanac), ephemeris, and coefficients for error correction, as well as unique information about the satellite. A satellite signal including a pseudo random noise (PRN) code, a subcarrier, a carrier, and the like, which is identification information, is received to acquire a satellite signal to demodulate navigation data. In order to acquire the satellite signal, an estimated carrier having a frequency similar to that of the satellite signal and an estimated PRN code having a phase similar to that of the satellite signal should be generated. The satellite signal mentioned above may include a GPS signal in a GPS system and a Galileo signal in a Galileo system.

The code generator 210 generates an estimated PRN code having a phase similar to the PRN code of the satellite signal. In the present invention, the code generator 210 has a specific phase controlled by the code tracking loop controller 240. P (Prompt, hereinafter referred to as "P") code having a specific phase from the clock input, L (Late, hereinafter referred to as "L") code that is later than a specific delay value set based on a specific phase, than a specific delay value A later VL (Very Late) code, an E (Early) code by a certain delay value, and a VE (Very Early, "VE") earlier than a certain delay value. Generates and outputs an estimated PRN code including the code.

In addition, the code generator 210 generates a code that is advanced or lag based on a specific phase in order to generate a large number of estimated PRN codes. In this case, the degree of leading or lag is set as the specific delay value mentioned above. The specific delay value is preset in units of chips and can be reset by changing the acquisition rate of the satellite signal and the performance of the receiver.

The correlator 220 receives the satellite signal and the estimated PRN code generated by the code generator 210 and receives the satellite signals in-phase (I) components and quadrature-phase (Q). The signal is separated into components, and the correlation value is output by correlating the PRN code included in the separated satellite signal and the estimated PRN code. At this time, the satellite signals of the in-phase and quadrature components show a phase difference of 90 degrees.

The correlator 220 will be described in more detail. The correlator 220 estimates an in-phase component of a satellite signal by using an estimated PRN code (VE code, E code, P code, L) generated by the code generator 210. Code and VL code) to generate an IVE correlation value, an IE correlation value, an IP correlation value, an IL correlation value, and an IVL correlation value. In addition, the quadrature phase component of the satellite signal is correlated with the estimated PRN codes (VE code, E code, P code, L code, and VL code) generated by the code generator 210 to QVE correlation value, QE correlation value, and QP correlation. Generate a value, a QL correlation value and a QVL correlation value.

The code comparing unit 230 detects a phase difference between the PRN code of the received satellite signal and the estimated PRN code generated therein, like a phase detector, and is also referred to as a "code discriminator." .

The code comparison unit 230 calculates and outputs a code phase error using a correlation value and two weights output from the correlator 220 to detect a phase difference.

In calculating the code phase error, the code comparison unit 230 described above may include the IVE correlation value, the IE correlation value, the IL correlation value, the IVL correlation value, the QVE correlation value, the QE correlation value, and the QL correlation value output from the correlation part 220. And a QVL correlation value, using two preset weights, and calculating through Equation 1 below. However, when w _{1 is set} to 0 and w ₂ is set to 1 in Equation 1, the output of the code comparator used in the conventional GPS receiver is output.

The correlation values output from the correlation unit 220 and the autocorrelation function have a relationship as shown in Equation 2 below.

The above-described code comparator 230 sets the above two weights w ₁ and w _{2 such} that the slope sign of the output code phase error with respect to the chip delay ε is always equal to or greater than zero. By using the two weights w ₁ and w ₂ set as described above, if the output code phase error with respect to the chip delay ε shown in FIG. 5 is controlled to have no inflection point, the BOC (1) in the conventional GPS / Galileo receiver is controlled. 1) It is possible to solve the "Ambiguity Problem" caused by tracking the side peak of the signal, thereby improving the tracking and navigation performance of the satellite signal. This can be confirmed through FIGS. 5 and 6 showing the results of tracking satellite signals.

Assume that the chip spacing d ₁ of VEMVL (Very Early Minus Very Late) in Equation 1 above is assumed to be 1, and the following Equation 3 is obtained. However, assuming that the chip spacing d ₂ of the EML (Early Minus Late) in Equation 1 described above is a constant, the chip spacing d ₁ of the VEMVL may be arranged as a variable. However, since the performance of the satellite signal tracking device 200 of the GPS / Galileo receiver is more sensitive to the chip spacing d ₂ of the EML than the chip spacing d ₁ of the VEMVL, the chip spacing d ₁ of VEMVL. Is assumed to be a constant, and the following Equation 3 is derived for the chip spacing d ₂ of the EML.

The w ₁ in the above-described [Equation 3] to zero, setting the w ₂ to 1, there is an output value code comparison unit used in a conventional GPS, wherein three gradient (marks) in the second period of the formula 3] As it changes, an inflection point occurs, resulting in an ambiguity problem. Therefore, the inflection point can be eliminated by changing the two weights according to the correlator chip spacing so as to satisfy Equation 4 below.

If, in Equation 2 above, when the chip spacing d ₂ of EML is 0.2, two weights w ₁ and w ₂ satisfying Equation 4 described above are set to 2 and 1, respectively. , [Equation 3] can be rearranged as shown in [Equation 5].

5 is a graph illustrating the above-described Equation 5 showing a code phase error that is an output of the code comparing unit 230.

Referring to FIG. 5, it can be seen that the code phase error is controlled not to have an inflection point, thereby solving the conventional ambiguity problem. However, the chip spacing d ₁ of the Very Early Minus Very Late (VEMVL), the chip spacing d ₂ of the Early Minus Late (EML), and the two weights (w ₁ , w ₂ ) are described in Equation 4 above. And it can be changed in consideration of the performance of the satellite signal tracking device 200.

FIG. 6 is a graph comparing the results of tracking satellite signals in order to confirm whether the satellite signal tracking apparatus 200 solves the problem of performance and ambiguity. FIG. 6 (a) shows a conventional satellite signal tracking result. 6 (b) is a graph of satellite signal tracking results according to the present invention.

As shown in FIG. 6 (a), the conventional GPS correlator tracks only the side peak of the BOC (1,1) signal, while the correlator according to the invention as shown in FIG. 6 (b) shows the main peak. You can see it tracking. This can be inferred from the fact that the correlator output value shown in FIG. 6B is about four times larger than the correlator output shown in (A).

Meanwhile, the code tracking loop controller 240 described above determines that the satellite signal is acquired when the code phase error output from the code comparator 230 falls within the preset satellite signal tracking range, and determines the preset satellite signal tracking range. If off, it is determined that the satellite signal is missed. Therefore, the code tracking loop control unit 240 controls the satellite signal tracking to be repeatedly performed after the satellite signal is acquired until the satellite signal is missed.

For the control of the satellite signal tracking, the code tracking loop control unit 240 is a satellite signal transmitted from the satellite while the code phase error calculated and output from the code comparator 230 is within the preset satellite signal tracking range. In order to track the specific phase of the clock to be changed to be input to the code generator 210, the code generator 210 to generate a delay code for the changed specific phase. Because of this, the code tracking loop control structure has a delayed locked loop (DLL) structure.

The code generator 210 in the GPS signal tracking device 200 of the GPS / Galileo receiver according to the present invention has two estimated PRN codes (VL code and VE code) than L codes, P codes, and E codes that are conventionally generated. Is further generated, the correlation unit 220 correlates with the PRN code of the satellite signal using the generated estimated PRN code, and the code comparison unit 230 uses two weighting values w ₁ and w ₂ . In order to acquire and track satellite signals by calculating code phase errors, the correlator 220 in the satellite signal tracking device 200 of the GPS / Galileo receiver is also referred to as a "Very Early Minus Very Late Correlator". An algorithm for calculating a code phase error using Equation 1 including a weight in the code comparator 230, which is a code discriminator, is referred to as a "weighted double early minus late power (WDELP) algorithm". In Equation 1, the code phase error is D _WDELP ( ε).

Meanwhile, in the above description, the code generator 210 generates five estimated PRN codes including the VL code, the L code, the P code, the E code, and the VE code, and the correlator 220 uses the satellite signals. The code comparator 230 calculates a code phase error using two weights w ₁ and w ₂ to obtain and track a satellite signal, but the code generator 210 uses the VL code. One or more codes that are later than the phase of the code and one or more codes that are earlier than the phase of the VE code may be further generated as estimated PRN codes. In this case, the correlation unit 220 correlates the additionally generated estimated PRN code with the in-phase (I) component and the quadrature-phase (Q) component of the satellite signal, respectively, and the code comparison unit 230. ) Further uses the weight to calculate the code phase error. For example, if the code generator 210 additionally generates two estimated PRN codes including one or more codes that are later than the phase of the L code and one or more codes that are earlier than the phase of the VE code, the code correlator 220 is generated. ), Four correlation values are additionally output, and the code comparison unit 230 calculates a code phase error by changing the above-described Equation 1 using one additional weight W ₃ .

Meanwhile, in the above description of the satellite signal tracking device 200 of the GPS / Galileo receiver according to the present invention, a satellite signal including a navigation data, a PRN code, a subcarrier and a carrier wave is received to acquire a satellite signal to demodulate the navigation data. In order to obtain and track a satellite signal through a code tracking loop control that generates an estimated PRN code and correlates it with a PRN code of a satellite signal to generate an estimated PRN code of the same phase as that of the satellite signal. Although the description has been given, the satellite signal tracking device 200 of the GPS / Galileo receiver according to the present invention generates an estimated carrier as shown in FIG. 3 and correlates it with the carrier of the satellite signal so that the frequency of the carrier and the estimated carrier of the satellite signal are the same. Add carrier tracking loop control unit 340, carrier generation unit 310, carrier comparison unit 330, etc. It includes. Here, the structure of the carrier tracking loop performed by the carrier tracking loop control unit 340 has a phase locked loop (PLL) structure or a frequency locked loop (FLL) structure, which is a code tracking loop. The structure of the code tracking loop performed by the controller 240 is different from that of the delayed locked loop (DLL) structure. Due to this difference, the carrier tracking loop control performed by the carrier tracking loop control unit 340 is performed by an algorithm different from the code tracking loop control.

Meanwhile, the GPS / Galileo receiver including the satellite signal tracking device 200 according to the present invention further includes a navigation data modulator and a navigation performer.

4 is a view illustrating in more detail the apparatus 200 for tracking satellite signals of the GPS / Galileo receiver described above with reference to FIGS. 2 and 3.

Referring to FIG. 4, the carrier oscillator 342 adjusts a frequency of a clock output by adjusting a register value, and the carrier generator 310 receives a clock (square wave) of the adjusted frequency so as to determine a resolution of a predetermined bit ( It generates an estimated carrier of the sinusoidal signal having a resolution and can be implemented by a frequency synthesizer (Frequency Synthesizer). The estimated carrier of the sinusoidal signal generated by the carrier generator 310 is multiplied by the in-phase (I) component and the quadrature (Q) component of the received satellite signal by the two carrier mixers 221 and 222, respectively.

Referring to FIG. 4, a signal in which an in-phase phase (I) component of a satellite signal is mixed in an estimated carrier and a carrier mixer 221 may include a VE code, an E code, a P code, an L code, generated by the code generator 210. Estimated PRN code including VL code and 5 code mixers 2211, 2212, 2213, 2214, 2215 in in phase (I) portion, multiplied by 5 code mixers 2211, 2212, 2213, 2214, 2215 The mixed signal in is used to calculate the correlation values for each of the five integrators. The correlation values calculated for the five integrators are the In-phase Very Early (IVE) correlation, the In-phase Early correlation, the In-phase Prompt correlation, the In-phase Late correlation, In-phase Very Late (IVL) correlation.

Referring to FIG. 4, a signal in which a quadrature phase (Q) component of a satellite signal is mixed in the estimated carrier and the carrier mixer 222 may be a VE code, an E code, a P code, or an L code generated by the code generator 210. And the five code mixers 2221, 2222, 2223, 2224, and 2225 in quadrature (Q) portions with the estimated PRN code including the VL code, and five code mixers (2221, 2222, 2223, 2224, 2225). The mixed signal in) is used to calculate the correlation values for each of the five integrators. The correlation values calculated for these five integrators are Quadrature-phase Very Early (QVE), Quadrature-phase Early (QE), Quadrature-phase Prompt (QP), and Quadrature-phase Late (QL) And Quadrature-phase Very Late (QVL) correlation values.

10 correlation values (IVE correlation value, IE correlation value, IP correlation value, IL correlation value, IVL correlation value, QVE correlation value, QE correlation value, QP correlation value, QL correlation value and QVL) IP correlation value and QP correlation value are input to the carrier comparison unit 330 to detect the frequency difference (frequency error) between the estimated carrier and the satellite signal, and the carrier tracking loop control unit 340 according to the detection result. The tracking loop is controlled. The carrier tracking loop controller 340 may include a carrier oscillator 342 and a carrier loop filter 341. The carrier loop filter 341 removes a noise component that may occur when the carrier frequency and the estimated carrier frequency of the satellite signal are different, and in a feedback control system to compensate for a frequency error that changes according to a dynamically changing signal characteristic. Can act as a compensator.

In addition, 10 correlation values (IVE correlation value, IE correlation value, IP correlation value, IL correlation value, IVL correlation value, QVE correlation value, QE correlation value, QP correlation value, QL correlation value) And 8 correlation values excluding the IP correlation value and the QP correlation value among the QVL correlation values) are input to the code comparison unit 230 to detect a phase difference (phase error) between the estimated PRN code and the PRN code of the satellite signal. The code tracking loop is controlled by the code tracking loop controller 240 according to the detection result. The code tracking loop controller 240 may include a code oscillator 242 and a code loop filter 241. The code loop filter 341 removes noise components that may occur due to the phase difference between the PRN code of the satellite signal and the phase of the estimated PRN code, and a feedback control system for compensating for a phase error that changes according to a dynamically changing signal characteristic. It can act as a compensator in a control system.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the scope of the present invention but to limit the scope of the technical idea of the present invention. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

1 is a diagram showing an autocorrelation function of a BOC modulated signal;

2 is a schematic block diagram of an apparatus for tracking satellite signals of a GPS / Galileo receiver according to the present invention;

3 is a schematic block diagram of a satellite signal tracking apparatus including a carrier tracking loop structure according to the present invention;

4 is a detailed block diagram of an apparatus for tracking satellite signals of a GPS / Galileo receiver according to the present invention;

5 is a graph showing a code phase error output from a code comparator in a satellite signal tracking device of a GPS / Galileo receiver according to the present invention;

6 is a graph for comparing satellite signal tracking performance.

<Description of Symbols for Main Parts of Drawings>

200: satellite signal tracking device

210: code generation unit

220: correlator

230: code comparison unit

240: code tracking loop control

Claims (7)

A satellite signal tracking device of a GPS / Galileo receiver for receiving and obtaining a satellite signal, which is a BOC (1,1) signal modulated by a BOC (Binary Offset Carrier) (1,1) modulation technique, P (Prompt) code having a specific phase and receiving a clock of a specific phase, an L (Late) code that is delayed by a predetermined delay value based on the specific phase, and a VL (Very Late) code that is further behind the specific delay value. A code generator for generating and outputting an estimated PRN code including an E (Early) code preceding the specific delay value and a VE (Very Early) code earlier than the specific delay value; The satellite signal is input to the estimated PRN code, the satellite signal is separated into an in-phase phase component and a quadrature phase component, and a correlation value is output by correlating the PRN code included in the separated satellite signal and the estimated PRN code, respectively. Correlator; A code comparison unit configured to calculate and output a code phase error using the output correlation value, the autocorrelation function of the BOC (1,1) signal, and two weights; And The code tracking loop control unit controls the specific phase of the clock to be changed to input the code generation unit to track the satellite signal transmitted from the satellite while the output code phase error is within a preset satellite signal tracking range. Satellite signal tracking device of the GPS / Galileo receiver comprising a. The method of claim 1, The correlation unit, Correlating the in-phase (I) component of the satellite signal with the estimated PRN code to generate an IVE correlation value, an IE correlation value, an IP correlation value, an IL correlation value, and an IVL correlation value; The quadrature-phase (Q) component is correlated with the estimated PRN code to generate a QVE correlation value, a QE correlation value, a QP correlation value, a QL correlation value, and a QVL correlation value, wherein the IVE correlation value and the IE correlation value are generated. Outputting a value, the IL correlation value, the IVL correlation value, the QVE correlation value, the QE correlation value, the QL correlation value, and the QVL correlation value. 3. The method of claim 2, The code comparison unit, The IVE correlation value, the IE correlation value, the IL correlation value, the IVL correlation value, the QVE correlation value, the QE correlation value, the QL correlation value, and the QVL correlation value output from the correlation part are received. And calculating the code phase error using the following weights.

The method of claim 3, wherein The code comparison unit, And setting the two weights such that the slope code of the output code phase error is always equal to or greater than zero. The method of claim 1, The code tracking loop control unit, GPS, characterized in that it is determined that the satellite signal is acquired when the output code phase error falls within the preset satellite signal tracking range, and that the satellite signal is missed when it is out of the preset satellite signal tracking range. Satellite signal tracking device for Galileo receiver. The method of claim 1, The code generator, And setting the specific delay value in units of chips, wherein the specific delay value is changeable according to an acquisition rate of the satellite signal. The method of claim 1, The code generator, And additionally generating, as the estimated PRN code, at least one code that is later than the phase of the VL code and at least one code that is earlier than the phase of the VE code as the estimated PRN code.

Images