JP2011137802A - Received signal integrating method and receiving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an appropriate received signal integrating method in consideration of periodic deviation. <P>SOLUTION: A received signal of GPS satellite signal is sampled for each one clock as sampling time interval to acquire a plurality pieces of sampling data. Then, using sampling data sets with different code periods when the received signal is time-divided by an assumed period of CA code as diffusion sign of the GPS satellite signal, a periodic deviation coefficient representing a periodic deviation between a true period of CA code and the assumed period is calculated for each code period. Then the received signals are integrated using the periodic deviation coefficient. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a received signal integration method and a receiving apparatus.

  A GPS (Global Positioning System) is widely known as a positioning system using positioning signals, and is used in a GPS receiver built in a mobile phone or a car navigation device. The GPS receiver performs position calculation processing for obtaining a three-dimensional coordinate value indicating the position of the receiver and a clock error based on information such as the positions of a plurality of GPS satellites and pseudo distances from each GPS satellite to the receiver. .

  A GPS satellite signal is a type of communication signal that is spread-modulated by a CDMA (Code Division Multiple Access) method that has long been known as a spread spectrum modulation method. When capturing a GPS satellite signal from a received signal, correlation processing between the received signal and a CA (Coarse and Acquisition) code replica signal, which is a spread code of the GPS satellite signal, is performed while changing the frequency and code phase. (So-called correlation calculation in frequency direction and phase direction, also called frequency search or phase search) is generally determined (for example, Patent Document 1).

JP 2007-256111 A

  Since the received signal is weak in an environment where the received signal of the GPS satellite signal is a weak electric field (for example, indoor environment, hereinafter referred to as “weak electric field environment”), a difference appears in the correlation value obtained by performing correlation processing. In some cases, the correlation value peak may be buried. Therefore, in a weak electric field environment or the like, a technique is used that makes it easy to determine the peak of the correlation value by integrating received signals over a predetermined period and performing correlation processing on the integrated signals.

  By the way, the carrier wave frequency of the GPS satellite signal is 1.57542 [GHz]. The CA code, which is a spreading code for GPS satellite signals, is a pseudo-random noise code with a repetition period of 1 ms using a code length of 1023 chips as a 1PN frame, and the chip rate is 1.023 [MHz]. Therefore, theoretically, the number of carrier wave cycles per chip is 1540 cycles, and 1540 × 1023 = 1,575,420 cycles per CA code cycle.

  However, the reception frequency when the GPS satellite signal is actually received includes a so-called Doppler frequency and a frequency error caused by a local clock error (clock error). Due to the presence of these frequency errors, a code cycle (hereinafter, this cycle is referred to as an “assumed cycle”) in which one CA code cycle, which should originally be a repetition cycle of 1 ms, is estimated from the true cycle. It will shift. Each time the carrier wave is 1,575,420 cycles, the CA code becomes one code cycle, and this cycle becomes the “true cycle”. However, the receiver does not determine the code period by counting the period of the carrier wave. The code period is determined on the assumption without counting the period of the carrier wave. More specifically, instead of directly assuming the code period, the code period is equivalently assumed by determining the frequency.

  For this reason, when the received signal is time-divided at the assumed period, the carrier wave is not always time-divided at the 1,575,420 period, and some phase shift occurs. In other words, since time division is performed assuming a code period, there is a difference between the phase of the carrier at the start of a certain code period and the phase of the carrier at the start of the next code period (hereinafter referred to as this The deviation is referred to as “periodic deviation”.) The period deviation is equivalent to a deviation between the true period of the CA code and the assumed period. As described above, it can be said that the assumption of the code period is to obtain the reception frequency. The frequency deviation is included in the reception frequency, resulting in a period shift.

  In a weak electric field environment, even if you try to integrate received signals to make it easier to determine the correlation value peak, if the received signals are integrated with a period shift, the amplitude of the received signal will be smaller There is. This is because if the period is accumulated without accurately grasping the period, the phase of the signal to be accumulated is shifted, and a signal in which the amplitude is changed may be accumulated. In addition, when the received signals are integrated and correlation processing is performed in a state where a period shift has occurred, the peak of the determined correlation value may not be a correct result.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to propose an appropriate received signal integration method in consideration of a period shift.

  The first mode for solving the above problems is when the received signal of the satellite signal is time-divided with an assumed period in which the code period time of the spreading code of the satellite signal is estimated when the satellite signal is received. The first received signal portion and the first received signal portion of the received signal have a second received signal portion having a different assumed cycle, and the period deviation between the true cycle of the spread code and the assumed cycle is changed. A received signal integration method comprising: calculating a periodic shift coefficient to be expressed; and integrating the received signal using the periodic shift coefficient.

  According to the first aspect, when the satellite signal reception signal is time-divided in the assumed cycle of the satellite signal spreading code, the second received signal is different from the first received signal portion in the received signal. Is used to calculate a period deviation coefficient representing a period deviation between the true period of the spread code and the assumed period. Then, the received signals are integrated using a period shift coefficient.

  The period shift is a difference between the true period of the spread code of the satellite signal and the assumed period. Although details will be described later, the inventor of the present application uses a received signal portion having a different assumed cycle among received signal portions obtained by time-division of a received signal of a satellite signal with an assumed cycle of a spread code, thereby causing a period shift. It was discovered that a coefficient (index) representing can be calculated. By integrating the reception signals using this period deviation coefficient, it is possible to obtain an appropriate integrated reception signal in consideration of the period deviation.

  Further, as a second mode, in the received signal integration method according to the first mode, the integration of the received signals includes the first received signal portion, the second received signal portion, and the period deviation coefficient. You may comprise the received signal integration method which is producing | generating the signal which integrated | accumulated the said received signal by multiply-adding.

  According to the second aspect, the sum of the received signals is generated by multiplying and summing the first received signal portion and the second received signal portion and the period shift coefficient. By multiplying the received signal portion by a period deviation coefficient, an error component due to the period deviation can be removed. For this reason, the signal obtained by integrating the received signals is a high-quality signal in which no signal deterioration due to the period shift occurs.

  Further, as a third mode, in the received signal integration method according to the first or second mode, the calculation of the period deviation coefficient may include n assumption cycles of the received signal (n is (Natural number) calculating the period deviation coefficient for each of the different second received signal parts, and integrating the received signals integrates the second received signal parts having n different assumed periods. In this case, a reception signal integration method including integration using the corresponding period deviation coefficient may be configured.

  According to the third embodiment, the period deviation coefficient is calculated for each of the second received signal portions having n different spread code assumption periods. Then, when integrating each of the second received signal portions having different assumed periods by n, the corresponding period deviation coefficients are used for integration. By integrating a plurality of received signal portions using a period shift coefficient, an integrated signal with higher quality can be obtained.

  Further, as a fourth mode, in the received signal integration method according to any one of the first to third modes, the calculation of the period shift coefficient may be performed in the first and second received signal portions. You may comprise the received signal integration method including calculating the said period shift coefficient using the signal part which becomes the same timing within an assumption period.

  According to this 4th form, a period shift coefficient is calculated using the signal part which becomes the same timing within an assumption period in a 1st and 2nd received signal part. By using a signal portion having the same timing within the assumed period, the period deviation coefficient can be calculated appropriately.

  Further, as a fifth mode, in the received signal integration method according to any one of the first to fourth modes, calculating the period deviation coefficient includes the first received signal portion and the second received signal. You may comprise the received signal integration method including calculating the said period shift coefficient by multiplying with the complex conjugate of a part.

  According to the fifth embodiment, the period deviation coefficient can be calculated by a simple calculation such as multiplying the first received signal portion by the complex conjugate of the second received signal portion.

  Further, as a sixth aspect, in the received signal integration method according to the fourth aspect, the calculation of the period deviation coefficient is a signal having a different timing within the assumed period of the first received signal portion. Multiplying the portion by the complex conjugate of the corresponding signal portion of the nth (n is a natural number) second received signal portion and the nth second received signal portion. The average of the obtained multiplication results of the respective timings is used as a period shift coefficient between the first received signal portion and the nth second received signal portion, and a received signal integrating method is configured. May be.

  According to the sixth aspect, the signal portion having the different timing within the assumed period in the first received signal portion and the corresponding signal portion in the nth second received signal portion having the same timing. Multiply by complex conjugate. Then, the average of the multiplication results at the respective timings obtained for the nth second received signal portion is taken as the period shift coefficient between the first received signal portion and the nth second received signal portion. By performing such processing, a more accurate periodic deviation coefficient can be calculated.

  Further, as a seventh aspect, the reception signal integration method according to any one of the first to sixth aspects, wherein the integration of the reception signals is a reception signal in a state where a carrier wave of the satellite signal is not removed. May be configured to integrate the received signal using the period deviation coefficient.

  According to the seventh aspect, the received signals in a state where the carrier wave of the satellite signal is not removed are integrated using the period shift coefficient. Since it is not necessary to remove the carrier wave of the satellite signal from the received signal, simplification of the satellite signal receiving circuit is realized.

  Further, as an eighth aspect, when the satellite signal reception signal is time-divided with an assumed period in which the code period time of the spreading code of the satellite signal is estimated when the satellite signal is received, The first received signal portion and the first received signal portion use a second received signal portion having a different assumed period, and a period deviation coefficient representing a period deviation between the true period of the spread code and the assumed period A periodic deviation coefficient calculating unit to calculate, a received signal integrating unit that integrates the received signal using the periodic deviation coefficient, a correlation processing unit that performs correlation processing on the signal integrated by the received signal integrating unit, and the correlation You may comprise the receiver provided with the acquisition part which acquires the said satellite signal based on the result of a process.

  According to the eighth embodiment, the period deviation coefficient calculating unit calculates a period deviation coefficient representing the period deviation between the true period of the spread code and the assumed period. Then, the received signal is integrated by the received signal integrating unit using the period shift coefficient, and the correlation processing for the integrated signal is performed by the correlation processing unit. Then, the capturing unit captures the satellite signal based on the correlation processing result. With this configuration, the same effect as that of the first embodiment is exhibited, and the correlation value for capturing the satellite signal can be appropriately obtained by performing the correlation process on the accumulated reception signal in consideration of the period shift. .

Explanatory drawing of the principle of reception signal integration. The flowchart which shows the flow of a received signal integration process. Explanatory drawing of the principle of period shift coefficient calculation. Explanatory drawing of the principle of reception signal integration. The block diagram which shows the function structure of a portable telephone. The figure which shows an example of the circuit structure of a baseband process circuit part. The flowchart which shows the flow of a period shift coefficient calculation process. The flowchart which shows the flow of a received signal integration process. The flowchart which shows the flow of a baseband process. The flowchart which shows the flow of a code phase detection process.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Below, the case where this invention is applied to the GPS receiver which receives and captures the GPS satellite signal transmitted from the GPS (Global Positioning System) satellite is demonstrated. Of course, embodiments to which the present invention is applicable are not limited to the embodiments described below.

1. Principle First, the principle of received signal integration in this embodiment will be described.
GPS satellites are a kind of positioning satellites, and four or more satellites are arranged on each of the six orbiting surfaces of the earth. In principle, four or more satellites are always observed from anywhere on the earth in a geometrical arrangement. It is operated as possible.

  GPS satellites transmit navigation messages such as almanac and ephemeris in GPS satellite signals that are a type of positioning signals. The GPS satellite signal is a 1.57542 [GHz] communication signal modulated by a CDMA (Code Division Multiple Access) system known as a spread spectrum system by a CA (Coarse and Acquisition) code which is a kind of spreading code. The CA code is a pseudo-random noise code having a repetition period of 1 ms with a code length of 1023 chips as 1 PN frame, and is different for each GPS satellite.

  The frequency (carrier frequency) at which a GPS satellite transmits a GPS satellite signal is specified in advance as 1.57542 [GHz]. However, GPS reception is possible due to the influence of Doppler caused by the movement of the GPS satellite and the GPS receiver. The frequency at which the device receives GPS satellite signals does not necessarily match the carrier frequency. Therefore, a conventional GPS receiver captures a GPS satellite signal by performing a frequency search that is a correlation calculation in the frequency direction and a phase search that is a correlation calculation in the phase direction for capturing the GPS satellite signal from the received signal. .

  In frequency search and phase search, the correlation value is acquired by performing correlation processing between the received signal and the generated signal of the replica code that is a replica of the spread code of the GPS satellite signal, and the frequency and phase at which the correlation value is maximized are detected. To do. In an environment where the received signal of the GPS satellite signal is a strong electric field signal (for example, an outdoor environment, hereinafter referred to as “strong electric field environment”), there is a clear difference in the correlation value when correlation processing is performed on the received signal. Since it appears easily, the peak detection of the correlation value is relatively easy.

  However, in an environment where the received signal of the GPS satellite signal is a weak electric field signal (for example, indoor environment, hereinafter referred to as “weak electric field environment”), the correlation value is clear when the correlation processing is performed on the received signal. In many cases, the difference does not appear and it is not easy to determine the peak of the correlation value. Therefore, in a weak electric field environment or the like, there is a technique for accumulating received signals over a predetermined period and performing correlation processing on the accumulated received signals (hereinafter referred to as “integrated received signals”) to obtain a correlation value. Used.

  FIG. 1 is an explanatory diagram of the concept of conventional received signal integration. The CA code, which is a spreading code for GPS satellite signals, has periodicity. Specifically, it is repeatedly transmitted from a GPS satellite with a code length of 1023 chips as a 1PN frame and a repetition period of 1 ms. Therefore, if the received signal of the GPS satellite signal is added at the CA code cycle time interval, an integrated signal with a large amplitude (power) should be obtained.

  More specifically, sampling data of the received signal is acquired by sampling the received signal of the GPS satellite signal at a predetermined sampling time interval. In this embodiment, the sampling unit of the received signal is referred to as “clock”, and the elapsed time of one clock is represented by “T”. The sampling time interval (that is, time T) may be a time interval for one chip of the CA code, or may be a time interval obtained by finely subdividing one chip.

式（１）において、「Ｉ（ｔ）」と「Ｑ（ｔ）」はそれぞれ受信信号「ｒ（ｔ）」のＩＱ成分を示している。すなわち「Ｉ（ｔ）」は受信信号「ｒ（ｔ）」の同相成分（実部）を示し、「Ｑ（ｔ）」は「ｒ（ｔ）」の直交成分（虚部）を示す。「ＣＡ（ｔ）」はＧＰＳ衛星信号のＣＡコードを示しており、「＋１」と「−１」の何れかの値である。また、「ｅｘｐ（ｉωｔ）」は、ＧＰＳ衛星信号の搬送波を表す項である。 Here, the received signal “r (t)” at time “t” can be expressed as the following equation (1).

In Expression (1), “I (t)” and “Q (t)” indicate IQ components of the received signal “r (t)”, respectively. That is, “I (t)” represents the in-phase component (real part) of the received signal “r (t)”, and “Q (t)” represents the quadrature component (imaginary part) of “r (t)”. “CA (t)” indicates a CA code of the GPS satellite signal, and is a value of “+1” or “−1”. “Exp (iωt)” is a term representing a carrier wave of a GPS satellite signal.

但し、「ω_c」はＧＰＳ衛星信号の搬送波周波数であり、「ω_d」は周波数誤差（例えば、ドップラー周波数やローカルクロックの誤差（時計誤差））である。 In equation (1), “ω” is the frequency of the received signal, and is represented by the following equation (2).

However, “ω _c ” is the carrier frequency of the GPS satellite signal, and “ω _d ” is a frequency error (for example, an error of the Doppler frequency or a local clock (clock error)).

  The received signal “r (t)” is sampled every clock and, for example, M + 1 (m = 0, 1, 2,..., M) sampling data is acquired for each CA code period. . For example, if sampling is performed for N + 1 (n = 0, 1, 2,..., N) periods, a total of (M + 1) × (N + 1) sampling data is obtained.

  It should be noted that the CA code period mentioned here is a period (assumed period) in which the GPS receiver estimates the period time of the CA code, and is different from the true period of the CA code. . As described above, the GPS receiver determines the frequency of the GPS satellite signal to determine the CA code period equivalently. However, the frequency at which the GPS receiver receives a GPS satellite signal does not completely match the carrier frequency due to the influence of Doppler. For this reason, the apparent CA code period may deviate from the true period of the CA code.

  In addition, due to an error (clock error) of the local clock in the GPS receiver, the 1 ms period internally measured by the GPS receiver may not be accurate, and the assumed period may deviate from the true period. Therefore, normally, a “period shift” occurs between the true period and the assumed period. As described above, this period deviation is equivalent to a deviation between the phase of the carrier at the start of a certain code period and the phase of the carrier at the start of another code period.

In the present embodiment, the number “n” of each assumed period when the received signal “r (t)” of the GPS satellite signal is time-divided by the assumed period “T _CA ” of the _CA code is referred to as “code period number”. The sampling number “m” of the received signal in each code period is referred to as “sampling number”. However, “n” and “m” are both natural numbers.

The sampling data of the sampling number “m” in the code cycle number “n” is expressed as “r _{n, m} (t)”. That is, the code cycle number and the sampling number are represented by subscripts in this order, and the corresponding time is represented by parentheses. The corresponding CA code is expressed as “CA _{n, m} (t)”.

In FIG. 1, for the 0th code period (n = 0), {r _0,0 (t), r _0,1 (t + T), r _0,2 (t + 2T),..., R _{0, M} (t + MT )} “M + 1” sampling data is obtained. Similarly, for the first code period (n = 1), {r _1,0 (t + T _CA ), r _1,1 (t + T + T _CA ), r _1,2 (t + 2T + T _CA ),..., R _{1, M} (T + MT + T _CA )}, for the Nth code period (n = N), {r _{N, 0} (t + NT _CA ), r _{N, 1} (t + T + NT _CA ), r _{N, 2} (t + 2T + NT _CA ), .., R _{N, M} (t + MT + NT _CA )} sampling data is obtained. That is, “M + 1” sampling data is obtained for each code period “n”.

但し、ＣＡコードの周期性から「ＣＡ_n,m（ｔ）＝ＣＡ_n,m（ｔ＋ｎＴ_CA）」となる性質を利用している。 Next, for each sampling number “m”, the sampling data of each code period (n = 0 to N) is added to obtain integrated sampling data “R _m ”. Specifically, the integrated sampling data “R _m (t)” is calculated according to the following equation (3).

However, the property of “CA _{n, m} (t) = CA _{n, m} (t + nT _CA )” is used from the periodicity of the CA code.

For example, the description will be given focusing on the sampling number “m = 1”. As shown in FIG. 1, sampling data “r _0,1 (t + T)” in the 0th code period, sampling data “r _1,1 (t + T + T _CA )” in the first code period, and sampling in the second code period The data “r _2,1 (t + T + 2T _CA )”,..., The sampling data “r _{N, 1} (t + T + NT _CA )” of the Nth code period are added together, and the integrated sampling data “R ₁ (t + T)” Is calculated.

Here, looking at equation (3), the integrated sampling data “R _m (t)” includes a term represented by “Σexp (iωnT _CA )”. The absolute value of this term is a term that is “N + 1” at the maximum and “0” at the minimum, as represented by the following equation (4).

Therefore, if the value of the term represented by “Σexp (iωnT _CA )” is smaller than “1”, the integrated sampling data “R _m (t)” is converted into the original sampling data “r _{n, m} (t)”. The value is smaller than

Consider this meaning. “Exp (iωnT _CA )” in Expression (4) is a shift between the phase of the carrier at the start of the 0th code period and the phase of the carrier at the start of the nth code period, that is, a period shift in the nth code period. It is thought that it represents. Therefore, depending on the magnitude of the period deviation in each code period, it means that the amplitude (power) of the accumulated signal may be reduced when the received signal is accumulated.

  As can be seen from the above calculation formula, the cause of such a problem is due to the presence of the carrier wave “exp (iωt)”. That is, if the received signal is integrated without removing the carrier wave “exp (iωt)” from the received signal “r (t)”, the signal may be weakened rather than strengthened due to the presence of a period shift. That's what it means.

  In order to solve this problem, the inventor of the present application calculates a coefficient called “period deviation coefficient” as an index representing the period deviation in each code period, and uses this period deviation coefficient to integrate the received signals. We have devised an integration method.

FIG. 2 is a flowchart showing the received signal integration process in this embodiment.
First, a sampling process and an accumulation process of the received signal are performed (step A1). Specifically, the received signal is sampled at a predetermined sampling time interval (timing for each clock), and the sampling data “r _{n, m} (t)” is accumulated in the storage unit.

但し、「ＣＡ_0,m（ｔ）×ＣＡ_n,m（ｔ＋ｎＴ_CA）＝１」となる性質を利用している。また、上付きの添え字の「＊」は複素共役を示している。 Next, a period deviation coefficient calculation process is performed (step A3). In the period deviation coefficient calculation process, for each code period (n = 0 to N), a period deviation coefficient representing the period deviation is calculated using the received signal portions having different code periods. Specifically, for example, when the 0th code period (n = 0) is set as the reference code period, the period deviation coefficient “S _n ” of other code periods (n = 1 to N) is _expressed by the following equation (5). Calculate according to

However, the property of “CA _{0, m} (t) × CA _{n, m} (t + nT _CA ) = 1” is used. The superscript “*” indicates a complex conjugate.

FIG. 3 is an explanatory diagram of the principle of calculating the period deviation coefficient. A period deviation coefficient is calculated using sampling data (first received signal portion) of a reference code cycle (0th code cycle) and sampling data (second received signal portion) of another code cycle (nth code cycle). To do. Specifically, as shown in FIG. 3, signal portions having different timings in the 0th code period, that is, sampling data “r _{0, m} ” of each sampling number “m” (m = 0 to M), A signal portion corresponding to the same timing within the n code period, that is, a complex conjugate “{r _{n, m} } ^* ” of the sampling data corresponding to the sampling number “m” (m = 0 to M) is set to the sampling number “ m ”are aligned and multiplied.

Then, the average of the multiplication results “r _{0, m} · {r _{n, m} } ^* ” obtained for each of the M + 1 pieces of sampling data is calculated as the period deviation between the reference code period (0th code period) and the nth code period. The coefficient is “S _n ”. That is, among the sets of sampling data as the received signal portion in each code period in the received signal, the period deviation coefficient is calculated for each code period using sampling data having the same timing within the code period.

但し、「ＣＡ_n,m（ｔ＋ｎＴ_CA）＝ＣＡ_n,m（ｔ）」となる性質を利用している。 Returning to the reception signal integration process of FIG. 2, after performing the period deviation coefficient calculation process, the reception signal integration process is performed (step A5). In the received signal integration process, the integrated sampling data “r _{n, m} ” and the period deviation coefficient “S _n ” calculated in the period deviation coefficient calculation process are used according to the following equation (6). to calculate the R _m ".

However, the property of “CA _{n, m} (t + nT _CA ) = CA _{n, m} (t)” is used.

FIG. 4 is an explanatory diagram of the principle of reception signal integration. The integrated sampling data “R _m ” is calculated by multiplying the sampling data “r _{n, m} ” in each code period by the period deviation coefficient “S _n ” of the corresponding code period. Specifically, as shown in FIG. 4, for each sampling number “m” (m = 0 to M), sampling data “rn _{, m} ” in the nth code period and a period shift in the nth code period The product “r _{n, m} · S _n ” is calculated by multiplying the coefficient “S _n ”. Then, the integrated sampling data “R _m ” is calculated for each sampling number “m” by adding the multiplication values “r _{n, m} · S _n ” obtained for each of the N + 1 code periods. Finally, a set of integrated sampling data “R _m ” for one period obtained for each sampling number “m” becomes an integrated received signal (hereinafter referred to as “integrated received signal”).

As can be seen from the equation (5), the period deviation coefficient “S _n ” is the complex conjugate of the sampling data “r _{0, m} (t)” of the 0th code period and the sampling data of the nth code period (imaginary complex number). It is calculated by multiplying by “{r _{n, m} (t + nT)} ^* ” and represented by “S _n = exp (−iωnT _CA )”. From this, it can be seen that the period deviation coefficient “S _n ” is a complex conjugate of the part of “exp (iωnT _CA )” that is a problem in the equations (3) and (4). Therefore, the portion of “exp (iωnT _CA )” can be eliminated by multiplying the sampling data “r _{n, m} ” by the period shift coefficient “S _n ”.

In this way, the part of “exp (iωnT _CA )” is deleted for each code period “n”, and then the multiplication value “r _{n, m} · S _n ” obtained for each code period n is added. By increasing the value, an integrated reception signal that does not include the term “Σexp (iωnT _CA )” can be obtained.

Comparing equation (3) with equation (6), the term “Σexp (iωnT _CA )” in the equation of accumulated sampling data “R _m ” is replaced with “N + 1”, which is the total number of code periods. I understand. “N + 1” is a constant and the value does not change. Therefore, the integrated sampling data “R _m ” calculated according to the equation (6) is a strong signal with an increased gain.

  As described above, the gain is increased without removing the carrier wave “exp (iωt)” from the received signal of the GPS satellite signal by integrating the received signal “r (t)” using the period shift coefficient “S”. A high-quality integrated reception signal can be obtained.

In addition, although “ω _d ” in Expression (2) is a frequency error caused by an error (clock error) of the Doppler frequency and the local clock in the GPS receiver, other frequency errors can be considered. Regardless of the value of “ω _d ”, a signal suitable for correlation processing can be obtained by the received signal integration method.

2. Embodiment Next, an embodiment of a GPS receiver to which the above-described principle is applied will be described. Here, a mobile phone 1 which is a kind of electronic device equipped with a GPS receiver will be described as a specific example.

2-1. Configuration FIG. 5 is a block diagram showing a functional configuration of the mobile phone 1. The mobile phone 1 includes a GPS antenna 9, a GPS receiving unit 10, a host CPU (Central Processing Unit) 30, an operation unit 40, a display unit 50, a mobile phone antenna 60, and a mobile phone radio communication circuit. Unit 70 and storage unit 80.

  The GPS antenna 9 is an antenna that receives an RF (Radio Frequency) signal including a GPS satellite signal transmitted from a GPS satellite, and outputs a received signal to the GPS receiver 10.

  The GPS receiver 10 is a position calculation circuit that measures the position of the mobile phone 1 based on a signal output from the GPS antenna 9, and is a functional block corresponding to a so-called GPS receiver. The GPS receiving unit 10 includes an RF (Radio Frequency) receiving circuit unit 11 and a baseband processing circuit unit 20. The RF receiving circuit unit 11 and the baseband processing circuit unit 20 can be manufactured as separate LSIs (Large Scale Integration) or can be manufactured as one chip.

  The RF receiving circuit unit 11 is an RF signal processing circuit block, and generates an oscillation signal for RF signal multiplication by dividing or multiplying a predetermined oscillation signal. Then, by multiplying the generated oscillation signal by the RF signal output from the GPS antenna 9, the RF signal is down-converted to an intermediate frequency signal (hereinafter referred to as an "IF (Intermediate Frequency) signal"), After the IF signal is amplified, it is converted into a digital signal by an A / D converter and output to the baseband processing circuit unit 20.

  The baseband processing circuit unit 20 performs correlation calculation processing or the like on the IF signal output from the RF receiving circuit unit 11 to acquire and extract GPS satellite signals, decodes the data, and displays navigation messages, time information, and the like. It is a circuit part to take out.

  FIG. 6 is a diagram illustrating an example of a circuit configuration of the baseband processing circuit unit 20. The baseband processing circuit unit 20 includes a satellite signal capturing unit 21, a CPU 25, and a storage unit 27.

  The satellite signal capturing unit 21 is a circuit unit that captures a GPS satellite signal from a reception signal that is an IF signal output from the RF reception circuit unit 11, and includes a reception signal integration processing circuit unit 211, a replica signal generation unit 213, And a correlation processing unit 215.

  The reception signal integration processing circuit unit 211 is a circuit unit that performs processing to integrate the reception signal “r (t)” that is an IF signal output from the RF reception circuit unit 11, and the integration reception signal “R (t)”. Is output to the correlation processing unit 215. In this embodiment, the received signal integration processing circuit unit 211 includes a processor such as a digital signal processor (DSP) and a memory, and performs the received signal integration processing according to the flowchart described in FIG. Will be described as being executed.

  The reception signal integration processing circuit unit 211 includes a storage unit 212 as a memory for storing various data. In the storage unit 212, for example, received signal sampling data 2121 obtained by sampling the received signal, period deviation coefficient data 2122 which is data of the period deviation coefficient calculated for each code period, and the integrated reception The accumulated reception signal data 2123 which is signal data is stored.

  The reception signal integration processing circuit unit 211 functions as a period deviation coefficient calculation unit that calculates a period deviation coefficient using the sampling data 2121 of the reception signal, and receives the sampling data 2121 of the reception signal using the period deviation coefficient. Functions as a signal integration unit.

  In the conventional GPS receiver, it is necessary to integrate the received signal “r (t)” after removing the carrier wave “exp (iωt)” from the received signal “r (t)”. It is necessary to provide a detection unit (carrier reproduction unit) for removing the carrier wave in the unit 211. However, in the present embodiment, as described in the principle, the reception signals are integrated using the period shift coefficient, so that it is not necessary to provide a detection unit in the reception signal integration processing circuit unit 211.

The replica signal generation unit 213 is a circuit unit that generates a replica signal that is a generation signal of a spread code replica of a CA code of a GPS satellite signal. The replica signal generation unit 213 generates a replica signal “CA _R (t)” according to the CA code instruction signal (capture target satellite instruction signal) output from the CPU 25 and outputs the replica signal “CA _R (t)” to the correlation processing unit 215.

Correlation processing unit 215 performs the cumulative received signal input from reception signal integration processing circuit unit 211 "R (t)", the correlation between the replica signal input from the replica signal generation unit 213 "CA _R (t)" It is a circuit part. Correlation processing unit 215, according to the phase instruction signal input from the CPU 25, to calculate the correlation while changing the replica signal phase "Delta] t" and "R (t)" and "CA _R (t + Δt)", the correlation value “P (Δt)” is output to the CPU 25.

  The CPU 25 is a processor that comprehensively controls each unit of the baseband processing circuit unit 20 according to various programs such as a system program stored in the storage unit 27. The CPU 25 performs a process of detecting the code phase for each capture target satellite based on the correlation value “P (Δt)” output from the correlation processing unit 215. Then, a pseudo distance between the capture target satellite and the mobile phone 1 is calculated using the detected code phase, and a position calculation calculation using the calculated pseudo distance is performed to calculate the position of the mobile phone 1.

CPU25 outputs a CA code instruction signal for instructing the CA code acquisition target satellite (PRN number of the acquisition target satellite) to the replica signal generation unit 213, a replica signal of the acquisition target satellite "CA _R (t)" The replica signal generator 213 generates the signal. Also it outputs a phase instruction signal for instructing the phase "Δt" of the replica signal "CA _R (t)" to the correlation processing unit 215, a correlation processing unit 215, the phase of the replica signal "CA _R (t)" Correlation processing is executed while changing “Δt”.

  The storage unit 27 is configured by a storage device such as a ROM (Read Only Memory), a flash ROM, or a RAM (Random Access Memory), and has a system program for the CPU 25 to control the baseband processing circuit unit 20 and a position calculation function. Various programs, data, etc. for realizing are stored. In addition, a work area for temporarily storing a system program executed by the CPU 25, various processing programs, data being processed in various processing, processing results, and the like is formed.

  The host CPU 30 is a processor that comprehensively controls each unit of the mobile phone 1 according to various programs such as a system program stored in the storage unit 80. The host CPU 30 performs processing for displaying the position information input from the baseband processing circuit unit 20 on the display unit 50, and performs various application processes using the position information.

  The operation unit 40 is an input device configured by, for example, a touch panel, a button switch, or the like, and outputs a pressed key or button signal to the host CPU 30. By operating the operation unit 40, various instructions such as a call request, a mail transmission / reception request, and a position calculation request are input.

  The display unit 50 is configured by an LCD (Liquid Crystal Display) or the like, and is a display device that performs various displays based on display signals input from the host CPU 30. The display unit 50 displays a position display screen, time information, and the like.

  The cellular phone antenna 60 is an antenna that transmits and receives cellular phone radio signals to and from a radio base station installed by a communication service provider of the cellular phone 1.

  The cellular phone wireless communication circuit unit 70 is a cellular phone communication circuit unit configured by an RF conversion circuit, a baseband processing circuit, and the like, and performs modulation and demodulation of the cellular phone radio signal, thereby enabling communication and mailing. Realize transmission / reception and so on.

  The storage unit 80 is a storage device that stores a system program for the host CPU 30 to control the mobile phone 1 and various programs and data for realizing a position calculation function.

2-2. Processing Flow (1) Processing of Received Signal Integration Processing Circuit Unit 211 FIG. 7 shows a flow of periodic shift coefficient calculation processing executed by the received signal integration processing circuit unit 211 in step A3 of the received signal integration processing of FIG. It is a flowchart. Although not specifically described, during reception signal integration processing, reception of an RF signal received by the GPS antenna 9 or down-conversion of the RF signal to an IF signal by the RF reception circuit unit 11 is performed and converted into an IF signal. It is assumed that the signal “r (t)” is being output to the baseband processing circuit unit 20 as needed.

First, the reception signal integration processing circuit unit 211 samples the reception signal “r (t)” output from the RF reception circuit unit 11 at a predetermined sampling time interval to obtain the sampling data “r _{n, m} ” of the reception signal. Acquired and stored in the storage unit 212 as sampling data 2121 (step B1).

Next, the reception signal integration processing circuit unit 211 sets the period deviation coefficient “S ₀ ” of the 0th code period (n = 0), which is the reference code period, to “1”, and the period deviation coefficient data stored in the storage unit 212. 2122 (step B3).

  Thereafter, the reception signal integration processing circuit unit 211 executes the process of loop A for each of the other code cycle numbers (n = 1 to N) excluding the reference code cycle (steps B5 to B19). In the loop A process, the loop B process is executed for each sampling number “m” (m = 0 to M) (steps B7 to B13).

In the process of loop B, the received signal integration processing circuit unit 211 calculates the complex conjugate “{r _{n, m} } ^* ” of the sampling data “r _{n, m} ” (step B9). Then, the sampling data “r _{0, m} ” of the reference code period is multiplied by the calculated complex conjugate “{r _{n, m} } ^* ” (step B11). Then, the processing shifts to the next sampling number.

After performing the processing of steps B9 and B11 for all the sampling numbers “m”, the received signal integration processing circuit unit 211 ends the processing of loop B (step B13). Then, the multiplication values “r _{0, m} · {r _{n, m} } ^* ” obtained for each sampling number “m” are added together (step B15).

The received signal integration processing circuit unit 211 then calculates the period deviation coefficient “S _n ” of the nth code period by dividing the sum by the total number of sampling numbers M + 1, and the period deviation coefficient data 2122 in the storage unit 212. (Step B17). Then, the processing shifts to the next code cycle number.

When the processing of steps B7 to B17 is performed for all the code cycle numbers “n” to calculate the cycle shift coefficient “S _n ”, the received signal integration processing circuit unit 211 ends the processing of loop A (step B19). Then, the period deviation coefficient calculation process is terminated.

  FIG. 8 is a flowchart showing the flow of the reception signal integration process executed by the reception signal integration processing circuit unit 211 in step A5 of the reception signal integration process of FIG.

  First, the received signal integration processing circuit unit 211 executes processing of loop C for each sampling number (m = 0 to M) (steps C1 to C11). In the process of loop C, the process of loop D is executed for each code cycle number (n = 0 to N) (steps C3 to C7).

In the process of loop D, the received signal integration processing circuit unit 211 multiplies the sampling data “r _{n, m} ” by the period deviation coefficient “S _n ” (step C5). Then, the processing shifts to the next code cycle number.

After performing the process of step C5 for all code cycle numbers “n”, the received signal integration processing circuit unit 211 ends the process of loop D (step C7). After that, by multiplying the multiplication results “r _{n, m} · S _n ” obtained for each code cycle number “n”, the portion of the sampling number “m” in the integrated received signal “R” is calculated. Then, the accumulated reception signal data 2123 of the storage unit 212 is stored (step C9). Then, the processing shifts to the next sampling number.

  After calculating the integrated reception signal “R (t)” by performing the processing of steps C3 to C9 for all sampling numbers “m”, the reception signal integration processing circuit unit 211 ends the processing of the loop C ( Step C11), the received signal integration process is terminated.

(2) Processing of CPU 25 FIG. 9 is a flowchart showing a flow of baseband processing executed by the CPU 25 of the baseband processing circuit unit 20.

  First, the CPU 25 performs capture target satellite determination processing (step D1). Specifically, at the current time measured by a clock unit (not shown), a GPS satellite located in the sky at a given reference position is determined using satellite orbit data such as an almanac or an ephemeris, and is captured. Satellite. The reference position is, for example, the position acquired from the base station of the mobile phone 1 by so-called server assist in the case of the first position calculation after power-on, and in the case of the second or subsequent position calculation, It can be set by a method such as obtaining the latest calculated GPS position.

  Next, the CPU 25 executes a process of loop E for each capture target satellite determined in step D1 (steps D3 to D11). In the process of loop E, the CPU 25 calculates satellite information such as the satellite position, satellite moving speed, and satellite moving direction of the capture target satellite based on the navigation message included in the GPS satellite signal (step D5). Then, the CPU 25 performs code phase detection processing (step D7).

FIG. 10 is a flowchart showing the flow of the code phase detection process.
First, the CPU 25 outputs an instruction signal of the CA code of the capture target satellite to the replica signal generator 213 (step E1). Then, the CPU 25 sets a search range and a search interval for the phase, and determines a search phase to be used for the phase search (step E3).

  Next, the CPU 25 executes loop F processing for each search phase set in step E3 (steps E5 to E11). In the process of loop F, the CPU 25 outputs an instruction signal of the search phase “Δt” to the correlation processing unit 215 (step E7).

When step E7 is executed, as described above, the correlation processing unit 215 determines that the reception signal integration processing circuit unit 211 calculates the integrated reception signal “R (t)” calculated based on the principle described with reference to FIGS. performs correlation processing with the replica signal input from the replica signal generation unit 213 "CA _R (t)". Correlation processing unit 215, according to the phase instruction signal input from the CPU 25, to calculate the correlation while changing the replica signal phase "Delta] t" and "R (t)" and "CA _R (t + Δt)", the correlation value “P (Δt)” is output to the CPU 25.

  When the correlation value “P (Δt)” is input from the correlation processing unit 215, the CPU 25 stores the correlation value “P (Δt)” in the storage unit 27 (step E9). Then, the CPU 25 shifts the processing to the next search phase.

  After performing the processing of steps E7 and E9 for all search phases, the CPU 25 ends the processing of loop F (step E11). Then, the CPU 25 determines the search phase “Δt” at which the correlation value “P (Δt)” stored in the storage unit 27 is maximized as the code phase (step E13). Then, the CPU 25 ends the code phase detection process.

  Returning to the baseband process of FIG. 9, after the code phase detection process is completed, the CPU 25 uses the satellite information calculated in step D5 and the code phase detected in step D7 to determine the acquisition target satellite and the portable type. The pseudo distance between the telephones 1 is calculated (step D9). The integer part of the pseudorange can be calculated using, for example, the latest GPS calculation position and the satellite position, and the fractional part of the pseudorange can be calculated using the code phase. After calculating the pseudorange, the CPU 25 shifts the processing to the next capture target satellite.

  After performing the processing of steps D5 to D9 for all the capture target satellites, the CPU 25 ends the processing of loop E (step D11). Thereafter, the CPU 25 calculates the position of the mobile phone 1 by performing GPS position calculation processing using the pseudorange calculated for each capture target satellite in step D9 (step D13). The details of the position calculation calculation using the pseudo distance are well known in the art and will not be described in detail.

  Next, the CPU 25 outputs the position calculated by the GPS position calculation process to the host CPU 30 (step D15). Then, the CPU 25 determines whether or not to end the position calculation (step D17). When it is determined that the position calculation has not ended yet (step D17; No), the CPU 25 returns to step D1. If it is determined that the position calculation is to be ended (step D17; Yes), the baseband processing is ended.

2-3. Action In the satellite signal acquisition unit 21 of the baseband processing circuit unit 20, the reception signal output from the RF reception circuit unit 11 is integrated by the reception signal integration processing circuit unit 211. That is, the received signal is sampled every clock that is a sampling time interval, and a plurality of sampling data is acquired. Then, using a sampling data set having different code periods when the received signal is time-divided with an assumed period of the CA code that is a spreading code of the GPS satellite signal, a period deviation between the true period of the CA code and the assumed period Is calculated. Then, the received signal is integrated using a period shift coefficient.

  The period shift is a difference between the true period of the CA code and the assumed period. A coefficient representing a period shift is calculated by using a sampling data set having a different assumed period from among a set of sampling data obtained by time-division of the received signal of the GPS satellite signal with an assumed period of the CA code. be able to. Then, by integrating the reception signals using this period deviation coefficient, it is possible to obtain an appropriate integrated reception signal considering the period deviation.

  That is, the received signal is sampled every clock that is a sampling time interval, and M + 1 pieces of sampling data are acquired for one code period. Then, for example, using the 0th code period as a reference code period, using sampling data (first received signal part) of the reference code period and sampling data (second received signal part) of other N code periods, A period deviation coefficient is calculated for each code period. Then, when sampling data of N + 1 code periods of the reference code period and the other code periods are integrated, they are integrated using the period deviation coefficient of the corresponding code period.

  When integrating sampling data, an error component due to the period deviation can be removed by multiplying the sampling data by a period deviation coefficient in advance. Then, by integrating the signals from which the error component due to the period deviation is removed, a signal suitable for correlation processing in which the amplitude (power) is multiplied by a constant can be obtained. In other words, a high-quality integrated received signal that does not include an error component due to the period deviation is obtained by integrating the GPS satellite signal reception signals from which carrier waves have not been removed using the period deviation coefficient. Means that you can. Since it is unnecessary to remove the carrier wave, it is not necessary to provide a carrier reproducing unit in the baseband processing circuit unit 20, and the GPS receiving circuit can be simplified.

3. Modification 3-1. Application System In the above-described embodiment, the acquisition of a GPS satellite signal has been described as an example. However, the present invention can be similarly applied to a receiving apparatus that receives a signal other than a GPS satellite signal. In other words, the present invention can be applied to any receiving apparatus that integrates received signals of satellite signals that have been spread-modulated with spreading codes, and performs correlation processing on the integrated signals to capture satellite signals.

3-2. In the above-described embodiment, the case where the present invention is applied to a mobile phone that is a kind of electronic device has been described as an example. However, electronic devices to which the present invention can be applied are not limited thereto. Absent. For example, the present invention can be similarly applied to other electronic devices such as a car navigation device, a portable navigation device, a personal computer, a PDA (Personal Digital Assistant), and a wristwatch.

3-3. In the above-described embodiment, the GPS is described as an example of the satellite position calculation system, but WAAS (Wide Area Augmentation System), QZSS (Quasi Zenith Satellite System), GLONASS (GLObal NAvigation Satellite System), GALILEO Other satellite position calculation systems may be used.

3-4. In the embodiment described above, the sampling data “r _{0, m} ” and the complex conjugate “{r _{n, m} } ^* ” of the sampling data are multiplied by the sampling numbers “m = 0 to M”, respectively. In the above description, M + 1 multiplication results “r _{0, m} · {r _{n, m} } ^* ” are acquired and averaged to obtain a period deviation coefficient “S _n ” of the nth code period. The period deviation coefficient may be calculated as follows. That is, instead of using a set of all sampling data for each code period, the period deviation coefficient “S _n ” is calculated using sampling data as one or more received signal portions arbitrarily selected for each code period. To do.

In the case of using sampling data with arbitrarily selected L (1 ≦ L ≦ M + 1) sampling numbers, the multiplication result for each of the selected sampling numbers is averaged with L to obtain the period deviation coefficient “S _n ”. It can be calculated similarly. For example, when sampling data of one sampling number “m” arbitrarily selected is used, the period deviation coefficient “S _n ” may be calculated according to the following equation (7).

3-5. Reception signal integration processing In the above-described embodiments, the reception signal integration processing circuit unit 211 has been described as performing software integration of reception signals as digital signal processing. However, it is also possible to configure with a digital circuit using circuit elements such as a logic circuit instead of using software.

1 mobile phone, 10 GPS receiver, 11 RF receiver,
20 baseband processing circuit section, 21 satellite signal capturing section, 25 CPU,
27 storage unit, 30 host CPU, 40 operation unit, 50 display unit,
60 cellular phone antenna, 70 wireless communication circuit unit for cellular phone, 80 storage unit,
211 reception signal integration processing circuit unit, 213 replica signal generation unit,
215 Correlation processing unit

Claims (8)

When the satellite signal reception signal is time-divided with an assumed period in which the code period time of the spread code of the satellite signal is estimated when the satellite signal is received, the first reception signal portion of the reception signal and the first Calculating a period deviation coefficient representing a period deviation between the true period of the spreading code and the assumed period using a second received signal part having a different assumed period from the one received signal part;
Integrating the received signal using the periodic shift coefficient;
A received signal integrating method including: The integration of the reception signals is to generate a signal obtained by integrating the reception signals by multiplying and summing the first reception signal portion and the second reception signal portion and the period deviation coefficient.
The received signal integration method according to claim 1. Calculating the period deviation coefficient includes calculating the period deviation coefficient for each of the second received signal portions of the received signal, the assumption period being different by n (n is a natural number);
Accumulating the received signals includes integrating using the corresponding period deviation coefficients when integrating each of the second received signal parts having different n assumed periods.
The received signal integration method according to claim 1 or 2. Calculating the period deviation coefficient includes calculating the period deviation coefficient using a signal part having the same timing within the assumed period in the first and second received signal parts.
The received signal integration method according to any one of claims 1 to 3. Calculating the period deviation coefficient includes calculating the period deviation coefficient by multiplying the first received signal portion by a complex conjugate of the second received signal part.
The received signal integration method according to any one of claims 1 to 4. Calculating the period deviation coefficient is
A complex of a signal portion having a different timing within the assumed period of the first received signal portion and a corresponding signal portion of the nth (n is a natural number) second received signal portion corresponding to the same timing. Multiplying with the conjugate,
An average of the multiplication results of the respective timings obtained for the nth second received signal portion is used as a period shift coefficient between the first received signal portion and the nth second received signal portion. When,
including,
The received signal integration method according to claim 4. Accumulating the received signal is to integrate the received signal in a state in which the carrier wave of the satellite signal is not removed, using the period deviation coefficient.
The received signal integration method according to any one of claims 1 to 6. When the satellite signal reception signal is time-divided with an assumed period in which the code period time of the spread code of the satellite signal is estimated when the satellite signal is received, the first reception signal portion of the reception signal and the first A period deviation coefficient calculating unit that calculates a period deviation coefficient representing a period deviation between a true period of the spread code and the assumed period using a second received signal part having a different assumed period from the one received signal part; ,
A received signal integrating unit that integrates the received signal using the periodic deviation coefficient;
A correlation processing unit that performs correlation processing on the signal integrated by the received signal integration unit;
A capturing unit that captures the satellite signal based on a result of the correlation processing;
A receiving device.

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