JP2003258681A - Matched filter, correlation detecting method and receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a matched filter capable of correctly and easily detecting the peak of correlation of a spread code in a spread spectrum signal by eliminating the influence of noises due to a certain hardware device or the like provided in the outside or the inside. <P>SOLUTION: The digital matched filter 100 applied to a synchronism acquiring section in a GPS (global positioning system) receiver has an FFT (fast- Fourier transformation) processing section 103 for reading an IF (intermediate frequency) signal buffered by a memory 102 and applying FFT processing to the signal, a limiter 104 for removing spectrum components indicating the strength exceeding a prescribed threshold in frequency band signals obtained by applying the FFT processing by the section 103, a spread code generator 106 for generating the same spread code as that in an RF (radio frequency) signal from a GPS satellite, and an FFT processing section 107 for applying FFT processing to the spread code generated by the generator 106. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, in demodulating a spread spectrum signal, detects the phase of the spread code in the spread spectrum signal and detects the correlation between the spread code and the spread code generated by itself. A filter device and a correlation detection method, and a receiver to which the matched filter device and the correlation detection method are applied, which is a so-called GNSS (Global Navigation Satellites System)
In regard to the receiving device for receiving the signal from the satellite in and calculating the position and velocity of the self.

[0002]

2. Description of the Related Art In recent years, a GNSS system for measuring the position of a moving body on the ground by using an artificial satellite has become popular. As this GNSS system, for example, Global Positioning System (hereinafter, GP)
It is called S. ). In this GPS system, G
A GPS receiver that receives signals from PS satellites receives signals from at least four or more GPS satellites, calculates the position of the GPS receiver based on the received signals,
Notifying the user is a basic function.

That is, the GPS receiver demodulates the signal from each GPS satellite to obtain the orbit information of each GPS satellite, and based on the orbit and time information of each GPS satellite and the delay time of the received signal, The three-dimensional position of the GPS receiver is derived by simultaneous equations. In the GPS system, it is necessary to have at least four GPS satellites to obtain a reception signal because there is an error between the internal time set by the clock of the GPS receiver and the time set by the atomic clock of the GPS satellite. This is because the pseudo distances from at least four GPS satellites are required to calculate the four unknown parameters of the three-dimensional position from which the influence of 1 is removed and the accurate time.

In the GPS system, a GP for consumer use
When the S receiver is used, positioning calculation is performed by receiving a spread spectrum signal radio wave called the C / A (Clear and Acquisition) code in the L1 band from the GPS satellite (Navstar).

The transmission signal called the C / A code in the L1 band has a transmission signal speed, that is, a chip rate of 1.
023 MHz, for example, a so-called Gold code or the like having a code length of 1023 is pseudo-random noise (Pseudo-rando).
m Noise; PN) sequence spreading code, the frequency of which is 1575.42 due to a signal obtained by directly spreading data of 50 bps.
2 for MHz carrier (hereinafter referred to as carrier)
Binary Phase Shift Keying;
This is called the BPSK modulation method. ) Is applied to the signal. In this case, since the code length is 1023,
As shown in the first row in FIG. 12, the C / A code repeats with the spreading code having 1023 chips as one cycle, that is, one cycle = 1 millisecond (msec).

The spread code of the C / A code is different for each GPS satellite, but which GPS satellite uses which spread code can be detected in advance by a GPS receiver. In addition, the GPS receiver can recognize which GPS satellite from which signal can be received at that point and at that point in time by a navigation message described later. Therefore, the GPS receiver
For example, in the case of three-dimensional positioning, by receiving radio waves from at least four or more GPS satellites that can be acquired at that point and at that point, despreading the spectrum and performing positioning calculation, the position of one's own can be determined. calculate.

Further, one bit of the signal data from the GPS satellite is transmitted in units of 20 cycles of the spread code, that is, in units of 20 milliseconds, as shown in the second row in FIG. That is, the data transmission rate is 50b as described above.
ps. Further, 1023 chips for one cycle of the spread code are inverted when the bit is "1" and "0".

Further, the signal from the GPS satellite forms one word in 30 bits, that is, 600 milliseconds, as shown in the third row in FIG. Furthermore, the signal from the GPS satellite is, as shown in the fourth row in the figure, 10 words,
That is, one subframe is formed in 6 seconds. And
In the signal from the GPS satellite, as shown in the fifth row in the figure, the preamble that is always the specified bit pattern is inserted in the first word of one subframe even when the data is updated. Data is transmitted following this preamble.

Further, the signal from the GPS satellite is 5
A subframe, that is, one frame is formed in 30 seconds. Then, in the signal from the GPS satellite, the navigation message described above is transmitted in the data unit of this one frame.

The first 3 of the 1 frame data
Each subframe is information unique to the GPS satellite called Ephemeris information. This ephemeris information includes a parameter for determining the orbit of the GPS satellite and the time at which the signal from the GPS satellite is transmitted.

Since all GPS satellites are equipped with atomic clocks, they use common time information, and the time at which the signals from the GPS satellites contained in the ephemeris information are sent out is in units of 1 second of the atomic clocks. The spread code of the GPS satellite is generated as being synchronized with the atomic clock.

The orbit information included in the ephemeris information is
The information is updated every few hours, but the same information remains until the update is performed. Therefore, the GPS receiver can accurately use the same orbit information for several hours by holding the orbit information included in the ephemeris information in the memory. The time when the signal is transmitted from the GPS satellite is updated every 6 seconds as TOW (Time Of Week) information.

On the other hand, the navigation messages of the remaining two subframes of the data of one frame are information called Almanac information commonly transmitted from all GPS satellites. This almanac information requires 25 frames to acquire all the information, and the approximate position information of each GPS satellite and which GP
It is composed of information and the like indicating whether the S satellite can be used. This almanac information is updated every few days,
The same information remains until the update. Therefore, the GPS receiver can accurately use the same information for several days by holding the almanac information in the memory. However, GPS receivers can also use the same almanac information for several months, albeit with some loss of accuracy.

The GPS receiver receives a signal from a GPS satellite and obtains the above-described data. First, after removing the carrier, the same C / A code as that used by the GPS satellite to be received is used. Using the spreading code, the GP
With respect to the signal from the S satellite, the signal from the GPS satellite is captured by performing the phase synchronization of the C / A code, and the spectrum inverse spread is performed. When the GPS receiver performs spectrum despreading in phase synchronization with the C / A code, bits are detected and it is possible to acquire a navigation message including time information based on the signal from the GPS satellite. Become.

The GPS receiver captures signals from GPS satellites by phase synchronization search of C / A code. As the phase synchronization search, the spread code and GP generated by itself are used.
The correlation between the received signal from the S satellite and the spread code is detected. For example, when the correlation value of the correlation detection result is larger than a predetermined value, it is determined that the two are synchronized. When the GPS receiver determines that the synchronization is not achieved, it uses some synchronization method to control the phase of the spreading code generated by itself and synchronize with the spreading code of the received signal. There is.

By the way, the signal from the GPS satellite is a signal obtained by modulating the carrier based on the BPSK modulation method by the signal obtained by spreading the data with the spreading code as described above. Therefore, the GPS receiver needs to synchronize not only the spread code but also the carrier and the data in order to receive the signal from the GPS satellite, but the spread code and the carrier cannot be synchronized independently.

In addition, the GPS receiver usually has an intermediate frequency (Intermed) within a few MHz of the carrier frequency of the received signal.
iate Frequency; hereinafter referred to as IF. ) To convert the received signal into an IF signal, and the above-described synchronization detection processing is performed with this IF signal. The carrier in this IF signal (hereinafter referred to as the IF carrier) is mainly G
Frequency error due to Doppler shift according to the moving speed of the PS satellite and GPS when converting the received signal to an IF signal
The frequency error component of the local oscillator generated inside the receiver is included.

Therefore, in the GPS receiver, since the IF carrier frequency is unknown due to these frequency error factors, it is necessary to search for that frequency.
Further, the synchronization point (synchronization phase) within one cycle of the spread code is
Since it is unknown because it depends on the positional relationship between the GPS receiver and the GPS satellites, the GPS receiver needs some synchronization method as described above.

The conventional GPS receiver uses a synchronization method that combines frequency search for carriers, synchronization acquisition by a sliding correlator, and synchronization holding by a DLL (Delay Locked Loop) and Costas loop. Hereinafter, this synchronization method will be described.

As a clock for driving a spread code generator of a GPS receiver, a clock obtained by dividing a reference frequency oscillator prepared in the GPS receiver is generally used. A high-precision crystal oscillator is used as the reference frequency oscillator, and the GPS receiver uses a local oscillation signal used to convert a reception signal from a GPS satellite into an IF signal based on the output of the reference frequency oscillator. To generate.

Here, FIG. 13 shows the processing contents of the frequency search. The GPS receiver performs a phase synchronization search for the spread code when the frequency of the clock signal that drives the spread code generator is a certain frequency f1. That is, the GPS receiver sequentially shifts the phase of the spread code by one chip to obtain G at each chip phase.
Detects the correlation between the received signal from the PS satellite and the spread code,
By detecting the peak of correlation, the phase in which synchronization can be achieved is detected. Further, when the frequency of the clock signal is f1, the GPS receiver changes, for example, the frequency division ratio for the reference frequency oscillator when there is no synchronized phase in all of the 1023 chip phase searches. Change the frequency of the signal to another frequency f2
A phase search for 023 chips is performed. The GPS receiver realizes a frequency search by changing the frequency of the clock signal stepwise and repeating such an operation.

When the GPS receiver detects the frequency of the clock signal that can be synchronized by performing such frequency search, the GPS receiver performs final phase synchronization of the spread code with the frequency of the clock signal. This makes G
The PS receiver can capture the signal from the GPS satellite even if the oscillation frequency of the crystal oscillator has a deviation.

However, such a conventional synchronization method is not suitable for high-speed synchronization in principle. In the GPS receiver, if it takes time to synchronize the spread code and the IF carrier, the reaction becomes slow, which causes inconvenience in use. Therefore, in an actual GPS receiver, in order to compensate for this drawback, the number of channels is increased and parallel processing is performed to shorten the time until synchronization acquisition.

On the other hand, a matched filter is used as a method for performing synchronous acquisition of a spread spectrum signal at high speed, instead of the method using the sliding correlation described above. The matched filter can be realized digitally by a so-called transversal filter. Also,
As a matched filter, recent DSP (Digital Si
Fast Fourier Transform (Fast Fourier Transfor
m; hereinafter referred to as FFT. ) Has been used to implement a method for synchronizing spread codes at high speed with a digital matched filter. The latter is based on a long-known method for speeding up correlation calculation.

By using these matched filters, the GPS receiver detects a correlation peak when there is a correlation, for example, as shown in FIG. 14 for one cycle of the output waveform. The position of this peak indicates the beginning of the spread code. By detecting this peak, the GPS receiver can capture synchronization, that is, detect the phase of the spread code in the received signal. Also, GPS
The receiver can detect the IF carrier frequency together with the phase of the spread code by operating the FFT in the frequency domain using, for example, the above-described digital matched filter using the FFT. Then, the GPS receiver can convert the phase of the spread code into a pseudorange, calculate the position of the GPS receiver when at least four GPS satellites are detected, and calculate the IF carrier frequency. Based on this, the speed of the GPS receiver can be calculated.

[0026]

By the way, in the GPS receiver, as described above, a digital matched filter using an FFT may be used to perform synchronization acquisition.

Specifically, as shown in FIG. 15, the digital matched filter 300 is obtained by an antenna 401 that receives an RF signal transmitted from a GPS satellite and a frequency converter 402 that converts the RF signal into an IF signal. The IF signal to be sampled is sampled by a sampler 301 which samples the input signal at a predetermined sampling frequency, and is then input. Digital matched filter 3
00 is the I sampled by the sampler 301.
A memory 302 that buffers the F signal, an FFT processing unit 303 that reads the IF signal buffered by the memory 302 and performs the FFT processing,
Memory 304 for buffering the frequency domain signal obtained by the FFT processing by the FT processing unit 303
A spread code generator 305 that generates the same spread code as the spread code in the RF signal from the GPS satellite; an FFT processing unit 306 that performs FFT processing on the spread code generated by the spread code generator 305; A memory 307 that buffers the frequency domain signal obtained by performing the FFT processing by the FFT processing unit 306, a frequency domain signal buffered in the memory 304, and a frequency domain signal buffered in the memory 307. A multiplier 308 that multiplies one of the complex conjugates with the other, and an inverse FFT (Inversed Fast Four) for the frequency domain signal multiplied by the multiplier 308.
ier Transform; hereinafter referred to as IFFT. ) The IFFT processing unit 309 that performs the processing, and the spreading code and the spreading code generator 305 in the RF signal from the GPS satellite based on the cross-correlation function obtained by performing the IFFT processing by the IFFT processing unit 309. A peak detector 310 that detects a peak of correlation with the spread code.

Such a digital matched filter 3
00 is actually an FFT processing unit 303, 306, a spreading code generator 305, a multiplier 308, an IFFT processing unit 30.
9 and each part of the peak detector 310 are implemented as software executed by the DSP.

Such a digital matched filter 3
00 is capable of detecting the peak of correlation in the phase synchronized with the spreading code and discriminating the synchronization point of the spreading code by performing the processing by the DSP having high computing ability.

However, although high-performance hardware such as DSP enables high-speed signal processing, the hardware itself may become a noise source and adversely affect peripheral equipment. Moreover, such hardware may act as a noise source not only in the surroundings but also in itself. This effect is particularly remarkable in the case of a GPS receiver that receives an analog signal.

For example, as shown in FIG. 16, the spectrum function of the frequency domain signal obtained by performing the FFT processing on the IF signal received by the GPS receiver equipped with the digital matched filter 300 implemented by the DSP is as shown in FIG. The noise generated by the GPS receiver itself appears as a peak of a specific frequency.

In a GPS receiver, if an RF signal affected by such noise is processed as it is, it is often affected by noise and accurate positioning is often difficult. Specifically, when the phase of the spread code is detected using the digital matched filter 300 for the IF signal having the spectrum function shown in FIG. 16 obtained by converting the RF signal, the IFFT processing unit 309 performs the IFFT processing. The output waveform showing the cross-correlation function obtained by applying the S to N (Signal to Noise rati) is shown in FIG.
o) is extremely low. It is obvious that the GPS receiver cannot detect the peak of the correlation which should be represented by n _p in the figure when the output waveform showing such a cross-correlation function is obtained.

A method for removing such noise is described in Japanese Patent No. 2937578. In this method, FFT processing is applied to the received spread spectrum signal to detect a noise component, a noise waveform is formed based on the detection result, and further spread spectrum is performed in the time domain based on the noise waveform. The noise component is removed from the signal.

However, this method is intended to remove the noise superimposed on the received spread spectrum signal during transmission and reception, and copes with the noise caused by specific hardware such as a digital matched filter. I can't. In addition, this method requires a separate means for performing processing such as FFT processing and formation of noise waveforms in order to remove noise, and therefore, the scale is significantly increased. When realizing the means, as described above,
It is also possible that it itself becomes a noise source.

Therefore, as a GPS receiver, a measure for removing the influence of noise caused by specific hardware provided externally or internally and accurately detecting the peak of the spread code correlation is desired. It was

This problem is not limited to GPS receivers, but is common to all mobile communications that employ a direct spread modulation method with the same spread spectrum as GPS signals.

The present invention has been made in view of such a situation, removes the influence of noise caused by specific hardware or the like provided externally or internally, and determines the correlation of the spread code in the spread spectrum signal. An object of the present invention is to provide a matched filter device and a correlation detection method capable of accurately and easily detecting peaks. It is another object of the present invention to provide a receiving device that can improve sensitivity and accuracy by applying these matched filter devices and correlation detection methods.

[0038]

A matched filter device according to the present invention, which achieves the above-mentioned object, detects a phase of a spread code in an input spread spectrum signal in order to detect a spread code and a spread code generated by itself. A matched filter device for detecting a correlation with the first spread spectrum signal, wherein the spread spectrum signal is sampled at a predetermined sampling frequency, and the received data is subjected to fast Fourier transform processing. Spreading code generating means for generating the same spreading code as the spreading code in the signal, second fast Fourier transform processing means for performing fast Fourier transform processing on the spreading code generated by this spreading code generating means, and at least the first Fast Fourier transform processing means of It is characterized in that it comprises a limiting means for removing spectral components representing the intensity exceeding a predetermined threshold value among the frequency-domain signal.

In such a matched filter device according to the present invention, the intensity exceeding the predetermined threshold value in the frequency domain signal obtained by performing the fast Fourier transform processing by at least the first fast Fourier transform processing means by the limiting means. Is removed.

Further, the correlation detecting method according to the present invention which achieves the above-mentioned object, in order to detect the phase of the spread code in the input spread spectrum signal, detects the correlation between the spread code and the spread code generated by itself. A correlation detection method for detecting, wherein a spread spectrum signal is sampled at a predetermined sampling frequency and a fast Fourier transform process is applied to input data, and a spread code same as the spread code in the spread spectrum signal is generated. A step of performing a fast Fourier transform process on the generated spread code, and at least an intensity exceeding a predetermined threshold value in the frequency domain signal obtained by performing the fast Fourier transform process on the input data And a step of removing spectral components.

In the correlation detecting method according to the present invention as described above, at least the spectral component showing the intensity exceeding the predetermined threshold value is removed from the frequency domain signal obtained by performing the fast Fourier transform process on the input data. .

Further, the receiving device according to the present invention which achieves the above-mentioned object is a receiving device for receiving a signal from a satellite and calculating its own position and velocity, and a receiving means for receiving a signal from the satellite. A frequency conversion means for converting the frequency of the reception signal received by the reception means into a predetermined intermediate frequency, and a synchronous acquisition and intermediate frequency signal for detecting the phase of the spread code in the intermediate frequency signal obtained by the frequency conversion means. And a carrier frequency detected by the synchronization acquisition means, the phase of the spread code detected by the synchronization acquisition means, and the carrier frequency detected by the synchronization acquisition means Assigned to each satellite for each channel and set, and set the spread code phase and carrier frequency as initial values. In order to detect the phase of the spread code in the intermediate frequency signal which is a spread spectrum signal, the synchronization code holding means for holding the spread code and the carrier and demodulating the message included in the intermediate frequency signal is provided. The synchronization acquisition means for detecting the correlation between the spread code and the spread code generated by itself is the first high speed for performing the fast Fourier transform processing on the input data obtained by sampling the intermediate frequency signal at the predetermined sampling frequency. Fourier transform processing means, spreading code generating means for generating the same spreading code as the spreading code in the intermediate frequency signal,
A second fast Fourier transform processing means for subjecting the spread code generated by the spread code generating means to a fast Fourier transform processing and a fast Fourier transform processing by at least the first fast Fourier transform processing means are obtained. It is characterized in that it is configured by using a matched filter having a limiting means for removing a spectral component showing an intensity exceeding a predetermined threshold value in the frequency domain signal.

In such a receiving apparatus according to the present invention, the limiting means in the synchronization acquisition means performs at least the fast Fourier transform processing by the first fast Fourier transform processing means to obtain a predetermined threshold value in the frequency domain signal. Spectral components exhibiting intensities above are removed.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings.

This embodiment is a so-called GNSS in which the position of a moving body on the ground is measured using an artificial satellite.
(Global Navigation Satellites System) Global Positioning System
ystem; hereinafter referred to as GPS. ) Is applied, and signals from at least four or more GPS satellites are received, and the position of itself is calculated based on the received signals.
It is a PS receiver. This GPS receiver is L1 band, C /
A spread spectrum signal radio wave called A (Clear and Acquisition) code is received as a reception signal, and when performing synchronous acquisition of a spread spectrum signal using a digital matched filter, the generated noise is appropriately removed, The correlation peak can be accurately detected.

As shown in FIG. 1, this GPS receiver 10 generates pseudo-random noise (P) when it demodulates a received signal received.
N) By separating the function of capturing the synchronization between the spreading code of the sequence and the spreading code in the received signal and the function of maintaining the synchronization between the spreading code and the carrier (hereinafter referred to as carrier), a small circuit scale can be achieved. Originally, it is possible to speed up the synchronization acquisition.

In the following, first, the overall configuration of the GPS receiver 10 in which the synchronization acquisition function and the synchronization holding function are separated will be described, and then the synchronization acquisition unit 24 and the synchronization holding unit 2 will be described.
5 will be described in detail, and then the specific configuration of the synchronization acquisition unit 24 will be described in detail.

First, the overall structure of the GPS receiver will be described.

The GPS receiver 10 is, as shown in FIG.
A crystal oscillator (X'tal Oscillator; hereinafter referred to as XO) 11 that generates an oscillation signal D1 having a predetermined oscillation frequency.
And a predetermined oscillation frequency F _OSC different from this XO11
Compensated X'tal Oscillator (Temperature Compensated X'tal Oscillator) for generating an oscillation signal D2 having
It is called TCXO. ) 12 and a multiplier / divider 13 for multiplying and / or dividing the oscillation signal D2 supplied from the TCXO 12.

The XO 11 generates an oscillation signal D1 having a predetermined oscillation frequency of, for example, 32.768 kHz. The XO 11 uses the generated oscillation signal D1 for RT described later.
Supply to C (Real Time Clock) 27.

The TCXO12 is different from the XO11 and has a predetermined oscillation frequency F _OSC of, for example, about 18.414 MHz.
Generate an oscillating signal D2. The TCXO 12 supplies the generated oscillation signal D2 to the multiplier / divider 13 and the frequency synthesizer 18 described later.

The multiplier / divider 13 is a CPU (Ce
The oscillation signal D2 supplied from the TCXO 12 is multiplied by a predetermined multiplication rate and / or divided by a predetermined division ratio based on the control signal D3 supplied from the ntral processing unit 26. The multiplication / frequency divider 13 includes a synchronization acquisition unit 24, which will be described later, a synchronization holding unit 25, which will be described later, a CPU 26, a timer 28, which will be described later, and an oscillation signal D4 that has been multiplied and / or divided.
And to a memory 29 described later.

The GPS receiver 10 also includes an antenna 14 for receiving an RF (Radio Frequency) signal transmitted from a GPS satellite and a low noise amplifier (Low) for amplifying a received RF signal D5 received by the antenna 14. Noise Amplifier; hereinafter referred to as LNA.) 15
And the amplified RF signal D amplified by this LNA 15.
Band pass filter (hereinafter referred to as BPF) 1 that passes a predetermined frequency band component out of 6
6, an amplifier 17 for further amplifying the amplified RF signal D7 passed by the BPF 16, and a predetermined frequency F _LO based on the oscillation signal D2 supplied from the TCXO 12.
And a mixer 19 for multiplying the amplified RF signal D8 having the predetermined frequency F _RF amplified by the amplifier 17 by the local oscillation signal D10 supplied from the frequency synthesizer 18. And a predetermined frequency F down-converted by being multiplied by the mixer 19.
An intermediate frequency having a _IF (Intermediate Frequency;. Hereinafter referred IF) amplifier 20 for amplifying the signal D11
And the amplified IF signal D amplified by this amplifier 20
Low pass filter (hereinafter, referred to as LPF) that passes a predetermined frequency band component out of 12.
21 and an analog / digital converter (Anal for converting the analog amplified IF signal D13 passed by the LPF 21 into a digital amplified IF signal D14).
og / Digital Converter; hereinafter referred to as A / D. ) 22 and.

The antenna 14 receives the RF signal transmitted from the GPS satellite and having the carrier of the frequency 1575.42 MHz spread. The received RF signal D5 received by the antenna 14 is supplied to the LNA 15.

The LNA 15 amplifies the received RF signal D5 received by the antenna 14. The LNA 15 supplies the amplified amplified RF signal D6 to the BPF 16.

The BPF 16 is a so-called SAW (Surface).
Acoustic wave) filter, and passes a predetermined frequency band component of the amplified RF signal D6 amplified by the LNA 15. The amplified RF signal D7 passed by the BPF 16 is supplied to the amplifier 17.

The amplifier 17 further amplifies the amplified RF signal D7 passed by the BPF 16. Amplifier 17
Is the amplified predetermined frequency F _RF , that is, 157
The amplified RF signal D8 of 5.42 MHz is supplied to the mixer 19.

The frequency synthesizer 18 controls the TCX under the control of the control signal D9 supplied from the CPU 26.
A local oscillation signal D10 having a predetermined frequency F _LO is generated based on the oscillation signal D2 supplied from O12. The frequency synthesizer 18 uses the generated local oscillation signal D10.
Is supplied to the mixer 19.

The mixer 19 down-converts the amplified RF signal D8 by multiplying the amplified RF signal D8 having the predetermined frequency F _RF amplified by the amplifier 17 by the local oscillation signal D10 supplied from the frequency synthesizer 18. Then, the IF signal D11 having a predetermined frequency F _IF of, for example, about 1.023 MHz is generated. The IF signal D11 generated by the mixer 19 is supplied to the amplifier 20.

The amplifier 20 amplifies the IF signal D11 down-converted by the mixer 19. Amplifier 2
0 supplies the amplified amplified IF signal D12 to the LPF 21.

The LPF 21 passes a low frequency component of the amplified IF signal D12 amplified by the amplifier 20 that is lower than a predetermined frequency. The amplified IF signal D13 passed by the LPF 21 is supplied to the A / D 22.

The A / D 22 converts the analog amplified IF signal D13 passed by the LPF 21 into a digital amplified IF signal D14. The amplified IF signal D14 converted by the A / D 22 is supplied to the synchronization acquisition unit 2
4 and the synchronization holding unit 25.

In the GPS receiver 10, among these units, the LNA 15, the BPF 16, the amplifier 1
7, 20, frequency synthesizer 18, mixer 19, LP
The F21 and the A / D 22 amplify the received RF signal D5 having a high frequency of 1575.42 MHz received by the antenna 14 and having a low frequency F _IF of, for example, about 1.023 MHz so as to facilitate digital signal processing. The frequency conversion unit 23 down-converts the IF signal D14.

Further, the GPS receiver 10 synchronously acquires the spread code generated by itself and the spread code in the amplified IF signal D14 supplied from the A / D 22 and detects the carrier frequency in the amplified IF signal D14. The unit 24 and the amplified IF signal D14 supplied from the A / D 22
The synchronization holding unit 25 that holds the synchronization between the spreading code and the carrier and demodulates the message, the CPU 26 that collectively controls each unit to perform various arithmetic processes, and the time based on the oscillation signal D1 supplied from XO11. RTC to measure
27, a timer 28 as an internal clock of the CPU 26,
RAM (Random Access Memory) and ROM (Read Only M)
a memory 29 including an emory) and the like.

The synchronization acquisition unit 24 will be described in detail later, but it is
Under the control of the PU 26, based on the frequency-multiplied and / or frequency-divided oscillation signal D4 supplied from the frequency multiplier / frequency divider 13, synchronization acquisition of the spread code in the amplified IF signal D14 supplied from the A / D 22 is performed. And the carrier frequency in the amplified IF signal D14 is detected. At this time, the synchronization acquisition unit 24 performs synchronization acquisition with coarse accuracy, as will be described later. The synchronization acquisition unit 24 supplies the satellite number for identifying the detected GPS satellite, the phase of the spread code, and the carrier frequency to the synchronization holding unit 25 and the CPU 26.

The synchronization holding unit 25, which will be described in detail later, is C
Under the control of the PU 26, based on the multiplied and / or divided oscillation signal D4 supplied from the multiplier / divider 13, the spread code and carrier in the amplified IF signal D14 supplied from the A / D 22 While keeping the synchronization of
The navigation message included in the amplified IF signal D14 is demodulated. At this time, the synchronization holding unit 25, as described later,
The operation is started with the satellite number, the phase of the spread code, and the carrier frequency supplied from the synchronization acquisition unit 24 as initial values. The synchronization holding unit 25 uses the amplification I from a plurality of GPS satellites.
The F signal D14 is held in synchronism in parallel, and the detected spread code phase, carrier frequency, and navigation message are supplied to the CPU 26.

The CPU 26 acquires the phase of the spread code, the carrier frequency, and the navigation message supplied from the synchronization holding unit 25, and based on these various information, the GP concerned.
The position and speed of the S receiver 10 are calculated, and various arithmetic processing related to GPS, such as correcting the time information of the GPS receiver 10 based on accurate time information of GPS satellites obtained from the navigation message, is performed. Also, C
The PU 26 centrally controls each unit of the GPS receiver 10, various peripherals, and input / output with the outside.

The RTC 27 measures time based on the oscillation signal D1 supplied from the XO 11. This RTC2
The time information measured by 7 is used until the accurate time information of the GPS satellite is obtained.
It is appropriately corrected by controlling O11.

The timer 28 functions as an internal clock of the CPU 26, and is used for generating various timing signals necessary for the operation of each section and for time reference. For example, in the GPS receiver 10, the timer 28 refers to the timing at which the synchronization holding unit 25 starts the operation of the spreading code generator described later in synchronization with the phase of the spreading code acquired by the synchronization acquisition unit 24.

The memory 29 is composed of RAM, ROM and the like. In the memory 29, a RAM is used as a work area when various processes are performed by the CPU 26 and the like, when buffering various input data, and when storing intermediate data and calculation result data generated in the calculation process. Also RAM is used. Further, in the memory 29, a ROM is used as a means for storing various programs and fixed data.

In the GPS receiver 10, these synchronization acquisition unit 24, synchronization holding unit 25, CPU 26, R
The TC 27, the timer 28, and the memory 29 are configured as a baseband processing unit.

A GPS receiver 10 including each of the above components
In the above, at least each of the units except the XO 11, the TCXO 12, the antenna 14, the LNA 15, and the BPF 16 can be configured as a demodulation circuit 30 that is formed of one integrated chip.

The GPS receiver 10 receives RF signals from at least four or more GPS satellites, converts the RF signals into IF signals by the frequency conversion unit 23, and then synchronizes the spread codes by the synchronization acquisition unit 24. The acquisition and the carrier frequency are detected, and the synchronization holding unit 25 holds the synchronization between the spread code and the carrier and demodulates the navigation message. Then, the GPS receiver 10 determines the CPU based on the phase of the spread code, the carrier frequency, and the navigation message.
The position and speed of the GPS receiver 10 are calculated by 26.

Now, the processing by the synchronization acquisition section 24 and the synchronization holding section 25 in the GPS receiver 10 will be described in detail below. As described above, the GPS receiver 10 has the synchronization acquisition function and the synchronization holding function separated into the synchronization acquisition unit 24 and the synchronization holding unit 25. Here, the reason why the functions are separated in this way will also be described.

The synchronization acquisition unit 24 uses a matched filter in order to acquire the synchronization of the spread code at high speed. Specifically, the synchronization acquisition unit 24, as a matched filter, will be described in detail later, but the fast Fourier transform (Fast Fourier Transform) is used.
nsform; hereinafter referred to as FFT. ) Can be used for the digital matched filter. This digital matched filter is actually implemented as software in which processing such as FFT processing and peak detection is executed by a DSP (Digital Signal Processor).

The synchronization acquisition section 24 is configured as a digital matched filter to detect the peak of the correlation in the phase synchronized with the spreading code and determine the synchronization point of the spreading code. The synchronization acquisition unit 24 is, for example, 1.023M
IF signal of Hz is sampled at 4.096 MHz,
By performing an operation equivalent to a digital matched filter by the DSP, the synchronization of the spread code, that is,
It is possible to detect the phase of the spread code in the IF signal with an accuracy of 1/4 chip. In addition, the synchronization acquisition unit 24
Is an RA for buffering the input IF signal.
Assuming that the capacity of M is 16 milliseconds, by operating the FFT in the frequency domain by the DSP,
It is possible to detect a carrier (hereinafter referred to as an IF carrier) frequency in an IF signal with an accuracy of 1/16 kHz (± 1/32 kHz). The synchronization acquisition unit 24 uses the RA
Since the IF signal stored in M includes signals from a plurality of GPS satellites, a plurality of GPS satellites can be detected by calculating the correlation with the spread code of each GPS satellite.

The GPS receiver 10 has the synchronization acquisition unit 24.
The position and speed of the GPS receiver 10 can be calculated based on the phase of the spread code and the carrier frequency for at least four GPS satellites detected by.

However, in the GPS receiver 10, the above-mentioned ¼ chip as the spread code phase detection accuracy,
And 1/16 kHz as detection accuracy of carrier frequency
It is hard to say that the calculation result of the position and speed of the GPS receiver 10 obtained based on the above is sufficiently accurate. GP
In the S receiver 10, in order to improve accuracy,
Processing such as increasing the sampling frequency of the IF signal and lengthening the time length for storing the IF signal is required. Along with this, the capacity of the memory such as RAM increases, and the phase and carrier of the spread code are also increased. It is assumed that the processing time until the frequency is detected becomes long. Also,
In the GPS receiver 10, if the synchronization acquisition unit 24 does not receive a navigation message from the outside, the navigation message from at least four or more GPS satellites will be transmitted.
Due to the need to demodulate every millisecond, the DSP must always detect synchronization and demodulate navigation messages very fast. These problems bring about an increase in cost and power consumption due to the enormous size of hardware.

Therefore, in the GPS receiver 10, the synchronization acquisition is performed by the synchronization acquisition unit 24 with coarse accuracy, and the synchronization retention unit 25 retains the synchronization of a plurality of GPS satellites and demodulates the navigation message.

The synchronization acquisition unit 24 supplies the satellite number of the detected GPS satellite, the phase of the spread code, and the carrier frequency to the synchronization holding unit 25. On the other hand, the synchronization holding unit 25
The operation is started with these various kinds of information supplied from the synchronization acquisition unit 24 as initial values. The synchronization holding unit 25, based on the phase of the spread code, uses a DLL (Delay Locked Loo) described later.
Match the start timing of the spreading code generated by the circuit in p). The GPS receiver 10 sets the spreading code corresponding to the satellite number of the detected GPS satellite as the spreading code to be generated. At this time, the GPS receiver 10 is affected by the Doppler shift and the error in the oscillation frequency of the oscillation signal generated by the oscillator such as the TCXO 12, but the spread code is basically repeated at a cycle of 1 millisecond. Therefore, the start timing of the spreading code generated by the DLL circuit may be shifted by an integral multiple of 1 millisecond.

Since the IF carrier frequency includes the error of the TCXO 12 which generates the sampling clock for fetching the IF signal into the memory such as the RAM described above, it is accurate even if the above problem of resolution is eliminated. Value, that is, the sum of the carrier frequency and the Doppler shift amount. However, in the GPS receiver 10, when the synchronization acquisition unit 24 and the synchronization holding unit 25 are operating with the same oscillator, that is, a clock whose oscillation source is the TCXO 12, both have the same frequency error. Therefore, there is no problem for the synchronization holding unit 25 to start the operation with the IF carrier frequency detected by the synchronization acquisition unit 24 as the initial value.

Since the synchronization holding unit 25 holds the synchronization of a plurality of GPS satellites in parallel, as shown in FIG. 2, for example, a plurality of independent channel circuits 51 ₁ , 51 ₂ ,
..., having 51 _N. Channel circuit 51 ₁ , 51
₂ , ..., 51 _N are respectively assigned to the individual detection results by the synchronization acquisition unit 24 according to the setting of the control register 52.

Channel circuits 51 ₁ , 51 ₂ , ...,
As shown in FIG. 3, each 51 _N is a conventional GPS.
The circuit basically has the same configuration as that in which a Costas loop 61 for IF carrier synchronization and a DLL 62 for spreading code synchronization, which realizes both synchronization acquisition and synchronization holding in a receiver, are combined.

That is, the channel circuits 51 ₁ , 5
In 1 ₂ , ..., 51 _N , as shown in the figure, in the Costas loop 61, with respect to the IF signal corresponding to the amplified IF signal D14 obtained by the antenna 14 and the frequency conversion unit 23 described above, Then, a spread code generator (PN Generator; hereinafter referred to as PNG) 88 described later.
A signal obtained by multiplying the spread code, which has the phase generated by P (Prompt) by the multiplier 63, is input.
On the other hand, the channel circuits 51 ₁ , 51 ₂ , ..., 51 _N
In the DLL 62, the amplification I obtained by the antenna 14 and the frequency conversion unit 23 described above is provided.
The IF signal corresponding to the F signal D14 is input.

In the Costas loop 61, an NCO (Numeric Controlled Oscillat) is applied to the input signal.
or) 64 the sine component (in-phase component) of the reproduced carrier generated by the multiplier 64 is multiplied by the multiplier 65, while the cosine component (quadrature component) of the reproduced carrier generated by the NCO 64 is multiplied by the multiplier 66. To be done. In the Costas loop 61, a predetermined frequency band component of the signal of the in-phase component obtained by the multiplier 65 is passed by the LPF 67, and this signal is detected by the phase detector 70, the binarization circuit 71, and the sum of squares calculation circuit 72. Is supplied to. On the other hand, in the Costas loop 61, a predetermined frequency band component of the quadrature component signal obtained by the multiplier 66 is passed by the LPF 68, and this signal is supplied to the phase detector 70 and the sum of squares calculation circuit 72. . In the Costas loop 61, the LPF 67, 68
Phase detector 7 based on the signals output from the respective
The phase information detected by 0 is supplied to the NCO 64 via the loop filter 69. In the Costas loop 61, the signals output from the LPFs 67 and 68 are supplied to the square sum calculation circuit 72, and the square sum (I ² +) calculated by the square sum calculation circuit 72 is supplied.
Q ² ) is output as the correlation value (P) for the spreading code whose phase is P. In addition, Costas Loop 61
In, the signal output from the LPF 67 is supplied to the binarization circuit 71, and the information obtained by binarization is output as a navigation message.

On the other hand, in the DLL 62, the input IF signal is multiplied by the spreading code, which is E (Early), in which the phase generated by the PNG 88 leads the P, and is multiplied by the multiplier 73. The multiplier 74 multiplies the spread code, which is L (Late) in which the phase generated by is delayed from P. DLL62
, The sign component of the reproduced carrier generated by the NCO 64 in the Costas loop 61 is added to the signal obtained by the multiplier 73.
And the cosine component of the reproduced carrier generated by the NCO 64 is multiplied by
Is multiplied by. And in the DLL 62,
A predetermined frequency band component of the in-phase component signal obtained by the multiplier 75 is passed by the LPF 77, and this signal is supplied to the square sum calculation circuit 79. On the other hand, DLL
In 62, a predetermined frequency band component of the quadrature component signal obtained by the multiplier 76 is passed by the LPF 78, and this signal is supplied to the sum of squares calculation circuit 79. Further, in the DLL 62, with respect to the signal obtained by the multiplier 74,
The sine component of the reproduced carrier generated by the CO 64 is multiplied by the multiplier 80, and NC
The multiplier 81 multiplies the cosine component of the reproduction carrier generated by O64. And DL
In L62, a predetermined frequency band component of the signal of the in-phase component obtained by the multiplier 80 is passed by the LPF 82, and this signal is supplied to the square sum calculation circuit 84. On the other hand, in the DLL 62, a predetermined frequency band component of the orthogonal component signal obtained by the multiplier 81 is passed by the LPF 83, and this signal is supplied to the square sum calculation circuit 84.

In the DLL 62, the square sum calculation circuit 7
The signals output from 9 and 84 are the phase detector 8
5 and the phase detector 85 based on these signals
The phase information detected by the NCO 87 is supplied to the NCO 87 through the loop filter 86, and P based on the signal having the predetermined frequency generated by the NCO 87.
The spreading code of each phase E, P, L is generated by the NG 88. Further, in the DLL 62, the sum of squares (I ² + Q ² ) calculated by the sum of squares calculation circuit 79 is output as the correlation value (E) for the spread code whose phase is E, while the square The sum of squares (I ² + Q ² ) calculated by the sum calculation circuit 84 is output as the correlation value (L) for the spreading code whose phase is L.

In this way, the cost of IF carrier synchronization Costa
A combination of a loop 61 and a spread code synchronization DLL 62
Channel circuit 51 configured in the same manner as the combined circuit₁，
51 _Two, ・ ・ ・, 51_NIn the synchronization holding unit 25 having
Before the operation starts, the satellite number of the GPS satellite and the spread code
, And the carrier frequency are set as initial values.
It The setting of this initial value is performed directly with the synchronization acquisition unit 24.
Communication or the synchronization acquisition unit 24 and the synchronization
By performing via the CPU 26 that controls the holding unit 25
Is done.

The synchronization holding unit 25 as described above synchronizes the spread code with the synchronization as follows. That is, as shown in FIG. 4, the synchronization acquisition unit 24 starts a timer at the timing of loading the IF signal into a memory such as a RAM, and the synchronization acquisition unit 24 sets the phase of the spread code with respect to the IF signal stored in the memory. When h is detected, the synchronization holding unit 25 receives the value of this phase h, and then starts the spreading code generated by the DLL 62 at the time when the same timer shifts by h from an integer multiple of 1 millisecond, thereby receiving Match the phase with the spreading code of the signal. In addition, "
“PN” indicates a PN sequence code, that is, a spreading code.

Here, in the conventional circuit combining the Costas loop and the DLL, since the phase of the spread code in the received signal is unknown, the IF carrier frequency generated by the DLL and the cycle of the spread code are slightly shifted. , In the process of sliding the phase with respect to the spread code of the IF signal, a phase having a significant strength correlation was detected. Therefore, in the conventional circuit, in the case of detecting the phase, in the worst case, the carrier frequency in the range of several kHz and all the phases in the spread code having the code length of 1023 are detected. It took a long time to establish.

On the other hand, in the GPS receiver 10, although the synchronization holding unit 25 has basically the same configuration as the conventional circuit, the phase of the spread code received by the synchronization holding unit 25 and the IF carrier frequency. Since the initial values of and are slightly deviated from the true values, the phases having significant intensity correlation always exist in the vicinity of the initial values even if errors are included.
Therefore, the synchronization holding unit 25, like the conventional circuit,
First, the control of the loop filters 69 and 86 in the Costas loop 61 and the DLL 62 is stopped, and the NCO
The signals generated by 64 and 87 are changed in the vicinity of the initial value to search for a correlation of significant intensity, and after detecting the correlation, the control is switched to that from each of the loop filters 69 and 86. As a result, the synchronization holding unit 2
5, the DLL 62 can establish the synchronization of the phase of the spread code and the Costas loop 61 can establish the synchronization of the phase of the carrier in an extremely short time, and thereafter, the synchronization can be maintained. In the synchronization holding unit 25, the IF
Since the initial value of the frequency of the reproduction carrier generated by the NCO 64 with respect to the carrier frequency can be set within an error range of several tens Hz, the LPF 67, 68, 77, 78,
The bandwidths of the 82, 83 and the loop filters 69, 86 can be narrowed from the beginning, and S / N (Signal to Nois)
It is possible to establish synchronization with a high e ratio).

In the GPS receiver 10, the synchronization holding unit 25 is, for example, 1.023 MHz × 16 = 16.368 M.
If the phase of the spread code is detected with a time resolution of 1 / 16.368 MHz in the DLL 62 by operating with a clock of Hz, the G of the phase of the spread code will be G with an accuracy of 1/16 chip.
Pseudo distance to PS satellite can be calculated, and
If the NCO 64 in the Costas loop 61 can be controlled in units of 1 Hz, the resolution of the IF carrier frequency becomes 1 Hz, and the DLL 62 and the Costas loop 61 can maintain synchronization with these precisions.

As described above, in the GPS receiver 10, when the synchronization holding unit 25 holds the synchronization, D
Based on the phase of the spreading code generated by LL62,
The position of the GPS receiver 10 can be continuously calculated and output, and the speed of the GPS receiver 10 can be continuously calculated and output based on the IF carrier frequency obtained by the Costas loop 61. be able to.

As described above, the synchronization holding unit 25 sets the phase of the spreading code and the IF carrier frequency passed from the synchronization acquisition unit 24 as initial values, so that significant strength is obtained in the vicinity of these initial values. Search for the phase at which the correlation is obtained. This is due in part to the fact that the clock source oscillator on board the GPS receiver 10, the TCXO 12, has an error with respect to the nominal frequency. In the GPS receiver 10, when the synchronization acquisition unit 24 is configured by using a digital matched filter using FFT, the IF signal is stored in the memory and then detected by the synchronization holding unit 25 with a delay of the processing time of the DSP. Since the result is supplied, the error from the nominal frequency F _{OSC of the} oscillator is calculated as ΔF _OSC.
And the processing time of the DSP is T seconds, the synchronization holding unit 2
At the time when the detection result is supplied to 5, T × ΔF _OSC /
An error of F _OSC occurs. For example, in the GPS receiver 10, T = 3 seconds and ΔF _OSC / F _OSC is ± 3.
Within the range of ppm, an error within ± 9 microseconds = about ± 9 chips occurs. In this way, the GPS receiver 10
In, the longer the DSP processing time, the larger the error.

Further, in the GPS receiver 10, the GP
The Doppler shift of the carrier frequency caused by the movement of the S satellite and the GPS receiver 10 also causes an error. In the GPS receiver 10, assuming that the frequency of the carrier, that is, 1575.42 MHz is F _RF, and the Doppler shift of the received signal is ΔF _D , the period of the spreading code due to the Doppler shift, that is, 1 ms is
It is almost (1-ΔF _D / F _{R F} ) times, for example, +5 to +5.
When the Doppler shift in the range of -5 kHz occurs, about -9.5 to 9.5 microseconds in about 3 seconds = about -9.
An error of 5 to 9.5 chips occurs.

These two examples are values that are relatively close to reality, and in the GPS receiver 10, when factors of both the error of the oscillator and the Doppler shift are combined, the error within the range of about ± 20 chips is obtained. Therefore, the correlation may be detected by searching only this range. For example, the synchronization holding unit 25 starts the spreading code generated by the DLL 62 by 20 chips earlier than the phase of the spreading code supplied from the synchronization acquisition unit 24, and the cycle of the spreading code at that time is set to NCO 64 or 87. Set the frequency (1 + 5/157
5.420) If you set it longer than milliseconds, the IF
Search for the presence or absence of correlation when the phase of the spread codes of the signals from the GPS satellites included in the signal is shifted by +20 chips, and the phase of the spread codes slides for an appropriate time. You can

As described above, conventionally, the correlation detection is performed by using the DLL and the Costas loop within the range of 1023 chips and the IF carrier frequency within the range of the error of the oscillator and the Doppler shift amount. Compared to what was done, in the GPS receiver 10,
Since the carrier frequency of the initial value has only a slight error and the range for detecting the correlation is only about several tens of minutes, the time required for establishing synchronization by the synchronization holding unit 25 can be made extremely short. .

As described above, the GPS receiver 10 is configured so that the synchronization acquisition function and the synchronization holding function are separated, so that the G signal included in the IF signal by the synchronization acquisition unit 24.
The phase of the spread code of the signal from the PS satellite and the IF carrier frequency can be detected at high speed, and the synchronization holding unit 25 can quickly shift to the synchronization holding operation based on the detection result. However, in the GPS receiver 10, when the processing sequence increases in order to detect a weak GPS satellite signal included in the IF signal, and the synchronization acquisition unit 24 is operated with a low-speed clock in order to suppress power consumption. In the case where it is set, the processing time in the synchronization acquisition unit 24 becomes long, and accordingly, the range to be searched until the synchronization is established by the synchronization holding unit 25 becomes wide, which is not preferable.

Generally, in a GPS receiver, the frequency
In the local oscillator in the converter and the baseband processor
Common as a source oscillator that generates a clock for signal processing
Using the crystal oscillator of
Similarly, as shown in FIG.
The source oscillator of the local oscillator in the conversion unit 23 and the synchronization acquisition unit 2
4 and the source oscillator of the operation clock of the synchronization holding unit 25,
Common to TCXO12. Then, the synchronization holding unit 25
Is the IF carrier frequency detected by the synchronization acquisition unit 24.
Based on the number and the nominal value of TCXO12, eg 1.023M
Intermediate frequency F of Hz _IFAnd the difference is ΔF_IFAnd 15
Carry of signals from GPS satellites at 75.42 MHz
A frequency is F_RFThen, the synchronization acquisition unit 24 outputs the IF signal.
The time required for the synchronization acquisition processing after being loaded into memory is T seconds
And the phase of the spreading code is h, as shown in FIG.
, The phase h of the spreading code is h + Δh (Δh = −T × ΔF
_IF/ F_{R F}) Is corrected. For example, ΔF_IF=
When +3 kHz and T = 10 seconds, Δh = −19 My
Crosecond = about -19 chips. The synchronization holding unit 25 is
The oscillation frequency of TCXO12
Wave number F_OSCCaused by the error of and the Doppler shift
The phase shift of the spread code can be corrected very accurately.
The synchronization acquisition processing by the synchronization acquisition unit 24 takes several tens of seconds.
Even if it is necessary, search within a range of about 1 chip
You can establish synchronization by searching.

The reason why such a correction is possible is as follows.

In the GPS receiver 10, frequency conversion
By the unit 23, the known signal of the GPS satellite is known.
Rear frequency F_RFKnown intermediate frequency F_IFConversion to
In order to_OSCOn the TCXO12
Based on the local oscillator frequency by the frequency synthesizer 18.
Number F_LO= N × F_OSC(N is a constant number, N >> 1)
Made, F_IF= F_RF-F_LOSo that here
Therefore, the signal from the GPS satellite actually received is
Wave number F_IFWith respect to the oscillation frequency F of TCXO12_OSC
Error ΔF caused by the error of_IF
Is added. That is, the GPS receiver 10
In addition, the Doppler shift amount is ΔF_DAnd TCXO1
The error from the nominal oscillation frequency due to 2 is ΔF_OSCTo
When, F_IF+ ΔF_IF= F_RF+ ΔF_D-F_LO= F_RF+
ΔF_D-Nx (F_{OS C}+ ΔF_OSC) Becomes Therefore, in the GPS receiver 10,
The IF carrier frequency detected by the period acquisition unit 24 is F_IF+ ΔF_IF, ΔF_IF= ΔF_D−N × ΔF_OSC Becomes What is important here is that the synchronization acquisition unit 24 detects
Can be ΔF_IFAnd only ΔF_D, Δ
F_OSCIs unknown at the initial acquisition stage
That is.

Here, the spreading code of TCXO12
The timer operates at the nominal oscillation frequency for 1 millisecond, which is one cycle length.
If it does, the error ΔF_OSCTo be real
In case of 1 millisecond x F_OSC/ (F_OSC+ Δ
F_OSC) ≈ (1-ΔF_OSC/ F_{O SC}) Milliseconds
It On the other hand, one cycle length of the spread code in the received signal is
Doppler shift amount ΔF_D1 ms × F_RF/
(F_RF+ ΔF_D) ≈ (1-ΔF _D/ F_RF) With milliseconds
Become. Therefore, one cycle of the spread code in the received signal
Counted by length and nominal oscillation frequency by TCXO12
The ratio to 1 millisecond is (1-ΔF_D/ F_RF) / (1-ΔF_OSC/
F_OSC) ≈1-ΔF_D/ F_{R F}+ ΔF_OSC/ F
_OSC Becomes Furthermore, if the right side of this equation is transformed, 1-ΔF_IF/ F_RF+ (ΔF_OSC/ F_OSC) ×
(F_IF/ (N × F_{OS C})) ≈ 1-ΔF_IF/ F_RF Becomes Thus, in the GPS receiver 10, the same
ΔF which is an unknown parameter for the period capturing unit 24_D，
ΔF_OSCMake a fairly good approximation without
You can

As a result, in the GPS receiver 10, the synchronization acquisition processing is performed from the time when the synchronization acquisition unit 24 acquires the IF signal into the memory, and the detected phase h of the spread code is supplied to the synchronization holding unit 25. If it takes T seconds to reach, the phase of the spread code detected by the synchronization acquisition unit 24 during this T seconds is shifted by −T × ΔF _IF / F _RF . Therefore, as shown in FIG. 5, the synchronization holding unit 25 generates by the DLL 62 by h + Δh obtained by adding the correction value Δh = −T × ΔF _IF / F _RF to the phase h of the spread code supplied from the synchronization acquisition unit 24. By adjusting the start timing of the spreading code to be used, it is possible to correct the phase shift of the spreading code that has occurred during the synchronization acquisition processing time, and this makes it possible to detect the correlation within a range of about 1 chip. Synchronization can be established in a short time. In the GPS receiver 10, for example, the CPU 26 calculates a correction value, supplies the calculation result to the synchronization holding unit 25, corrects the phase by the synchronization holding unit 25, and then starts the synchronization acquisition process by the synchronization acquisition unit 24. Good.

The information necessary for such a method of correcting the phase of the spread code is only the IF carrier frequency detected by the synchronization acquisition unit 24. In the GPS receiver 10, the error of the oscillation frequency F _OSC of the TCXO 12 is detected. Neither the Doppler shift amount is necessary as information. Also, GP
In the S receiver 10, even if the local oscillation frequency F _LO is set so that F _IF = F _RO −F _LO does not depend on the IF carrier frequency, it is only necessary to change the sign of ΔF _IF. I'm done.

Now, the specific configuration of the above-described synchronization acquisition unit 24 will be described below.

As described above, the synchronization acquisition unit 24 is configured by implementing a digital matched filter using FFT as software executed by the DSP in order to perform synchronization acquisition of the spread code at high speed. Here, in the GPS receiver 10, the received I
Since the approximate intensity of the F signal can be theoretically obtained in advance, a component exceeding this intensity can be regarded as a noise component. for that reason,
The synchronization acquisition unit 24 is provided with a limiter for removing a spectrum component having an intensity exceeding a predetermined threshold value from the data in the frequency domain obtained by performing the FFT processing on the sampled IF signal.

Specifically, as shown in FIG. 6, the digital matched filter 100 has the amplified IF signal D1 obtained by the antenna 14 and the frequency conversion section 23 described above.
The IF signal corresponding to No. 4 is sampled by the sampler 101 that samples the input signal at a predetermined sampling frequency based on the oscillation signal D2 generated by the TCXO 12 described above, and then input. The digital matched filter 100 includes a memory 102 that buffers an IF signal sampled by the sampler 101 and having a constant time length, and an F signal that performs FFT processing by reading the IF signal buffered by the memory 102.
An FT processing unit 103, a limiter 104 that removes a spectrum component having an intensity exceeding a predetermined threshold value from the frequency domain signal obtained by the FFT processing performed by the FFT processing unit 103, and the limiter 104 that is obtained via the limiter 104. Memory 105 for buffering the captured frequency domain signal
A spread code generator 106 that generates the same spread code as the spread code in the RF signal from the GPS satellite; an FFT processing unit 107 that performs FFT processing on the spread code generated by the spread code generator 106; A memory 108 that buffers a frequency domain signal obtained by performing the FFT processing by the FFT processing unit 107, a frequency domain signal buffered in the memory 105, and a frequency domain signal buffered in the memory 108. A multiplier 109 that multiplies one of the complex conjugates and the other, and an inverse FFT (Inversed Fast Four) for the frequency domain signal multiplied by the multiplier 109.
ier Transform; hereinafter referred to as IFFT. ) The IFFT processing unit 110 that performs the processing, and the spreading code and the spreading code generator 106 in the RF signal from the GPS satellite based on the cross-correlation function obtained by performing the IFFT processing by the IFFT processing unit 110. A peak detector 111 for detecting the peak of the correlation with the spread code.

Such a digital matched filter 1
00 is actually an FFT processing unit 103, 107, a limiter 104, a spread code generator 106, a multiplier 109, I
The FFT processing unit 110 and each unit of the peak detector 111 are implemented as software executed by the DSP. That is, the synchronization acquisition unit 24 to which the digital matched filter 100 is applied includes, for example, as shown in FIG. 7, a sampler 121 corresponding to the above-mentioned sampler 101, a RAM 122 corresponding to the above-mentioned memory 102, and the above-mentioned memories 105 and 108. RAM / ROM 123 including the DSP program area and the work area, the FFT processing units 103 and 107, and the spread code generator 10 described above.
6, a multiplier 109, an IFFT processing unit 110, and a DSP 124 that executes the processing of the peak detector 111. The DSP 124 may be a CPU.

The sampler 121 is the TCXO12 described above.
The IF signal input at a predetermined sampling frequency based on the oscillation signal D2 generated by is sampled. At this time, the sampler 121 uses the DSP 124 or a CPU that replaces the DSP 124, or the main CPU 2 described above.
The sampling of the IF signal is started in response to the sampling start instruction of 6. The IF signal sampled by the sampler 121 is written in the RAM 122 and buffered.

The RAM 122 stores the IF signal of a fixed time length sampled and written by the sampler 121. The IF signal stored in the RAM 122 is read by the DSP 124 or a CPU instead of the DSP 124 and is used for the correlation detection processing with the spread code.

The RAM / ROM 123 stores various information. RAM of RAM / ROM 123
Is an area for storing the detected correlation value and the DSP 12
4 or a work area of a CPU which replaces the above. Further, of the RAM / ROM 123, the ROM is
It is used as a program area executed by the DSP 124 or a CPU instead of the DSP 124 and an area for storing necessary data. Note that the RAM of the RAM / ROM 123 may be physically shared with the RAM 122,
In the figure, it is merely shown as a logically different storage element.

The DSP 124 or the CPU as an alternative thereto is
The spread code corresponding to the GPS satellite designated by the CPU 26 is generated, and the digital matched filter 100 is generated.
The correlation value for each phase of the spread code with respect to the IF signal stored in the RAM 122 is detected by performing an operation equivalent to. DSP124 or CPU as an alternative
Indicates the detected correlation value as R in the RAM / ROM 123.
Store in a part of AM.

The digital matched filter 100 applied to the synchronization acquisition unit 24 having the DSP 124 as described above.
When the FFT processing unit 103 performs FFT processing on the IF signal sampled by the sampler 101, the limiter 104 removes a spectrum component having an intensity exceeding a predetermined threshold value from the obtained frequency domain signal. For example, the limiter 104 removes noise by changing the same value as the threshold value or changing the value to “0” for the spectral component exceeding the threshold value,
The obtained frequency domain signal is written in the memory 105. For example, as shown in FIG. 8, the spectral function of the frequency domain signal obtained by the limiter 104 that changes the value of the spectral component exceeding the threshold value to “0” is determined by the GPS receiver 10 itself which appears as a peak of a specific frequency. The spectrum component indicating the generated noise is removed. As a result, the GPS receiver 10 can significantly reduce noise.

As the synchronization acquisition section 24, a digital matched filter 150 as shown in FIG. 9 may be applied.

This digital matched filter 150
In addition to the sampler 101, the memory 102, the FFT processing units 103 and 107, the spreading code generator 106, the memory 108, the IFFT processing unit 110, and the peak detector 111, as shown in FIG. A memory 151 that buffers a frequency domain signal obtained by performing FFT processing by 103, and a limiter that removes a spectrum component having an intensity exceeding a predetermined threshold value from the frequency domain signal buffered in the memory 151. 152, and a multiplier 153 that multiplies either the complex conjugate of the frequency domain signal obtained through the limiter 152 or the frequency domain signal buffered in the memory 108 by the other.

That is, the digital matched filter 1
In the digital matched filter 100, the limiter 104 is provided as a limiter 152 immediately after the memory 151 corresponding to the memory 105, not immediately after the FFT processing unit 103.

Such a digital matched filter 1
50 is the same as the digital matched filter 100,
The DSP 124 in the synchronization acquisition unit 24 shown in FIG.
Can be implemented using. The digital matched filter 150 applies an F signal by the FFT processing unit 103 to the IF signal sampled by the sampler 101.
The frequency domain signal obtained by performing the FT process is stored in the memory 15
After being temporarily stored in 1, the frequency component of the frequency domain signal stored in the memory 151 is removed by the limiter 152 with a spectral component having an intensity exceeding a predetermined threshold value.
At this time, similarly to the limiter 104, the limiter 152 removes noise with respect to the spectrum component exceeding the threshold value by changing the value to the same value as the threshold value or changing the value to “0”, for example. The frequency domain signal is supplied to the multiplier 153.

Further, as the synchronization acquisition unit 24, FIG.
The digital matched filter 200 as shown in FIG.

This digital matched filter 200
Is a multiplier in addition to the sampler 101, the memories 102 and 151, the FFT processing units 103 and 107, the spreading code generator 106, the memory 108, the multiplier 109, and the peak detector 111, as shown in FIG. A limiter 201 that removes a spectrum component having an intensity exceeding a predetermined threshold value from the frequency domain signal multiplied by 109, and an IFFT processing unit 202 that performs IFFT processing on the frequency domain signal obtained through this limiter 201. Have and.

That is, the digital matched filter 2
Reference numeral 00 denotes the limiter 104 provided in the digital matched filter 100 described above as the limiter 201 immediately after the multiplier 109, not immediately after the FFT processing unit 103.

Such a digital matched filter 2
00 is the DS in the synchronization acquisition unit 24 shown in FIG. 7 similarly to the digital matched filters 100 and 150.
It can be implemented using P124. The digital matched filter 200 temporarily stores, in the memory 151, the frequency domain signal obtained by performing the FFT processing by the FFT processing unit 103 on the IF signal sampled by the sampler 101, and the frequency stored in the memory 151. After multiplying the complex conjugate of either one of the domain signal and the frequency domain signal stored in the memory 108 by the multiplier 109, the multiplier 10
The limiter 201 removes the spectrum component showing the intensity exceeding the predetermined threshold value from the frequency domain signal obtained by the step 9. At this time, similarly to the limiters 104 and 152, the limiter 201 removes noise from the spectral components exceeding the threshold value by, for example, changing the value to the same value as the threshold value or changing the value to "0" to obtain the noise. The obtained frequency domain signal is supplied to the IFFT processing unit 202.

The synchronization acquisition unit 24 can apply such digital matched filters 100, 150 and 200. That is, the synchronization acquisition unit 24 may provide a limiter at any position between the FFT processing of the sampled IF signal and the IFFT processing of the frequency domain signal. The feature is that noise is removed in a region. The GPS receiver 10 has the digital matched filter 1 as described above.
By including the synchronization acquisition unit 24 using 00, 150, and 200, the influence of noise caused by specific hardware such as a DSP provided outside or inside is removed and spread without increasing the circuit scale. The peak of code correlation can be detected accurately and easily.

When the phase of the spread code is detected by using one of the digital matched filters 100, 150 and 200 for the frequency domain signal after noise removal by the limiter whose spectrum function is shown in FIG.
The output waveform showing the cross-correlation function obtained by performing the IFFT processing by the FT processing units 110 and 202 is, for example, as shown in FIG.
As shown in FIG. 1, S / N in which noise is significantly reduced without superimposing a specific frequency component due to the influence of noise
Will be high. Therefore, the GPS receiver 10
Based on the output waveform showing such a cross-correlation function, the peak detector 111 can accurately and easily detect the peak of the correlation represented by n _p in the figure.

As the synchronization acquisition unit 24, it is most preferable to limit the strength of the frequency domain signal immediately after the FFT processing of the IF signal by the limiter, like the digital matched filter 100. This is because the number of bits representing the value of the spectrum function of the frequency domain signal can be reduced in advance based on the threshold value in the limiter by limiting the intensity to the frequency domain signal immediately after the FFT processing. With this, it is possible to reduce the capacity of the memory that stores the frequency domain signal.

As described above, the GPS receiver 10
Is the IF sampled when the synchronization acquisition unit 24 detects the correlation value for searching the phase of the spreading code.
S / N is improved even in a noisy environment by removing spectral components showing an intensity exceeding a predetermined threshold value from data in the frequency domain obtained by performing FFT processing on the signal. The obtained signal can be obtained, and the correlation peak can be detected accurately and easily.
Therefore, the GPS receiver 10 can achieve higher sensitivity and higher accuracy.

In particular, even when the GPS receiver 10 itself becomes a noise source and adversely affects the received signal, the GPS receiver 10 can reduce the noise without making a large-scale hardware change. Therefore, the development cost can be reduced.

Further, when the GPS receiver 10 is constructed as an integrated circuit, it usually overcomes the fact that the density of the integrated circuit could not be increased in view of the influence of noise, and the GPS receiver 10 is obsessed with noise. Since the degree of integration can be increased without doing so, downsizing and cost reduction can be achieved.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the GPS receiver 10 is used for explanation, but the present invention is
Any receiver that receives and demodulates a spread spectrum signal can be applied.

Further, according to the present invention, the function of the limiter may be switched to an on state or an off state according to various states such as a reception state.

Further, in the above-mentioned embodiment, the GPS
Although the receiver 10 is used for the description, the present invention is applicable to any positioning system using a satellite, that is, any electronic device incorporating the function of the receiver to which the GNSS system is applied. be able to. GNSS
As the system, in addition to the above-mentioned GPS system in the United States, GLONASS (Global Nav
igation Satellites System) and GALILEO which are being developed mainly in Europe, but the present invention can be applied to all of these GNSS systems.

As described above, it goes without saying that the present invention can be appropriately modified without departing from the spirit thereof.

[0132]

As described in detail above, the matched filter device according to the present invention detects the phase of the spread code in the input spread spectrum signal, and therefore the spread code and the spread code generated by itself are used. A matched filter device for detecting a correlation, wherein the spread spectrum signal is sampled at a predetermined sampling frequency and is subjected to a fast Fourier transform process on the inputted data. Spreading code generating means for generating the same spreading code as the spreading code, second fast Fourier transform processing means for performing fast Fourier transform processing on the spreading code generated by this spreading code generating means, and at least a first high speed The frequency range obtained by performing the fast Fourier transform processing by the Fourier transform processing means. And a limiting means for removing spectral components representing the intensity exceeding a predetermined threshold value among the signals.

Therefore, in the matched filter device according to the present invention, the intensity exceeding the predetermined threshold in the frequency domain signal obtained by performing the fast Fourier transform processing by at least the first fast Fourier transform processing means by the limiting means. By removing the indicated spectrum component, the peak of the correlation of the spread code in the spread spectrum signal can be detected accurately and easily.

Further, the correlation detection method according to the present invention is a correlation detection method for detecting the correlation between the spread code and the spread code generated by itself in order to detect the phase of the spread code in the input spread spectrum signal. Then, the spread spectrum signal is sampled at a predetermined sampling frequency, the fast Fourier transform process is performed on the input data, and the same spread code as the spread code in the spread spectrum signal is generated. A step of performing a fast Fourier transform process on the spread code, and a step of removing at least a spectrum component showing an intensity exceeding a predetermined threshold value in the frequency domain signal obtained by performing the fast Fourier transform process on the input data With.

Therefore, the correlation detecting method according to the present invention removes at least the spectrum component showing the intensity exceeding the predetermined threshold value from the frequency domain signal obtained by subjecting the input data to the fast Fourier transform process. Thereby, it becomes possible to accurately and easily detect the peak of the correlation of the spread code in the spread spectrum signal.

Further, the receiving device according to the present invention is a receiving device for receiving a signal from a satellite to calculate its own position and velocity, and a receiving means for receiving a signal from the satellite and this receiving means. Frequency conversion means for converting the frequency of the received signal received to a predetermined intermediate frequency, synchronous acquisition for detecting the phase of the spreading code in the intermediate frequency signal obtained by this frequency conversion means, and detection of the carrier frequency in the intermediate frequency signal Synchronization acquisition means for performing
The phase of the spread code detected by this synchronization acquisition means and the carrier frequency detected by the synchronization acquisition means are
It is set by allocating each satellite to each of multiple channels provided independently corresponding to multiple satellites, and the synchronization of the spreading code and carrier is maintained with the set spreading code phase and carrier frequency as initial values. Along with
A synchronization holding means for demodulating a message included in the intermediate frequency signal is provided, and in order to detect the phase of the spreading code in the intermediate frequency signal which is a spread spectrum signal, the correlation between the spreading code and the spreading code generated by itself is determined. The synchronization acquisition means for detection is the same as the first fast Fourier transform processing means for performing fast Fourier transform processing on the input data obtained by sampling the intermediate frequency signal at the predetermined sampling frequency, and the spreading code for the intermediate frequency signal. Spreading code generating means for generating a spreading code, second fast Fourier transform processing means for performing fast Fourier transform processing on the spread code generated by the spreading code generating means, and at least first fast Fourier transform processing means. Of the frequency domain signals obtained by the fast Fourier transform processing by It constructed using a matched filter and a limiting means for removing spectral components indicating the that intensity.

Therefore, the receiving apparatus according to the present invention is
At least a first by the limiting means in the synchronization acquisition means
By removing the spectrum component showing the intensity exceeding a predetermined threshold value from the frequency domain signal obtained by performing the fast Fourier transform processing means of the fast Fourier transform processing means, the peak of the correlation of the spread code in the spread spectrum signal is It can be detected accurately and easily, and high sensitivity and high accuracy can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a GPS receiver shown as an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a synchronization holding unit included in the GPS receiver.

FIG. 3 is a block diagram illustrating a configuration of a channel circuit included in a synchronization holding unit included in the GPS receiver.

FIG. 4 is a diagram for explaining phase matching of spread codes in a synchronization holding unit included in the GPS receiver.

FIG. 5 is a diagram for explaining phase correction of a spread code in a synchronization holding unit included in the GPS receiver.

FIG. 6 is a block diagram illustrating a configuration of a digital matched filter using an FFT that can be applied as a synchronization acquisition unit included in the GPS receiver.

FIG. 7 shows a synchronization acquisition unit included in the GPS receiver shown in FIG.
FIG. 11 is a block diagram illustrating an actual implementation example when the digital matched filter shown in FIG.

FIG. 8 is a diagram illustrating an example of a spectrum function of a frequency domain signal from which noise has been removed by a digital matched filter applied as a synchronization acquisition unit included in the GPS receiver.

FIG. 9 is a block diagram illustrating the configuration of another digital matched filter using an FFT that can be applied as a synchronization acquisition unit included in the GPS receiver.

FIG. 10 is a block diagram illustrating a configuration of still another digital matched filter using an FFT that can be applied as a synchronization acquisition unit included in the GPS receiver.

FIG. 11 is a diagram illustrating an example of an output waveform showing a temporal change of a correlation value detected by a synchronization acquisition unit included in the GPS receiver.

FIG. 12 is a diagram illustrating a configuration of a signal from a GPS satellite.

FIG. 13 is a diagram for explaining a conventional spreading code and carrier synchronization process, and is a diagram for explaining a frequency search.

FIG. 14 is a diagram illustrating an example of an output waveform showing a temporal change of a correlation value detected by using a digital matched filter.

FIG. 15 is a block diagram illustrating a configuration of a digital matched filter using an FFT applied to a conventional GPS receiver.

FIG. 16 is a diagram illustrating an example of a spectrum function of a frequency domain signal obtained by performing FFT processing on an IF signal.

FIG. 17 is a diagram illustrating an example of an output waveform showing a temporal change of a correlation value detected by using a conventional digital matched filter.

[Explanation of symbols]

10 GPS receiver, 11 XO, 12 TCX
O, 13 multiplier / divider, 14 antenna, 15
LNA, 16 BPF, 17, 20 amplifier,
18 frequency synthesizer, 19 mixer, 21,
67, 68, 77, 78, 82, 83 LPF, 22
A / D, 23 frequency conversion unit, 24 synchronization acquisition unit,
25 synchronization holding unit, 26 CPU, 27 RT
C, 28 timer, 29, 102, 105, 108,
151 memory, 30 demodulation circuit, 51, 51 ₁ ,
51 ₂ , ..., 51 _N- channel circuit, 52 control register, 61 Costas loop, 6
2 DLLs, 63, 65, 66, 73, 74, 75,
76, 80, 81, 109, 153 multiplier, 64,
87 NCO, 69,86 loop filter, 7
0,85 Phase detector, 71 Binarization circuit, 72,
79,84 Sum of squares calculation circuit, 88,106 Spread code generator, 100,150,200 Digital matched filter, 101,121 sampler, 103,1
07 FFT processing unit, 104, 152, 201 limiter, 110, 202 IFFT processing unit, 111
Peak detector, 122 RAM, 123 RAM /
ROM, 124 DSP

Claims (12)

[Claims] 1. A matched filter device for detecting the correlation between a spread code and a spread code generated by itself in order to detect the phase of the spread code in an input spread spectrum signal, wherein the spread spectrum signal is First fast Fourier transform processing means for performing fast Fourier transform processing on the data sampled at a predetermined sampling frequency and input, and spread code generating means for generating the same spread code as the spread code in the spread spectrum signal. Second fast Fourier transform processing means for performing fast Fourier transform processing on the spread code generated by the spread code generating means, and fast Fourier transform processing for at least the first fast Fourier transform processing means A spectrum showing the intensity of the obtained frequency domain signal that exceeds a predetermined threshold. Matched filter device, characterized in that it comprises a limiting means for removing Le component. 2. The limiting means removes a spectral component having an intensity exceeding a predetermined threshold value from the frequency domain signal obtained by performing the fast Fourier transform processing by the first fast Fourier transform processing means. The matched filter device according to claim 1, wherein: 3. Fast Fourier transform processing by the storage means for storing the frequency domain signal obtained through the limiting means, the frequency domain signal stored in the storage means, and the second fast Fourier transform processing means. Multiplication means for multiplying one of the complex conjugates of the frequency domain signal obtained by performing the above with the other, and inverse fast Fourier transform processing for the frequency domain signal multiplied by the multiplication means. Based on the cross-correlation function obtained by the fast Fourier transform processing means and the inverse fast Fourier transform processing by the inverse fast Fourier transform processing means, the spread code in the spread spectrum signal and the spread code generated by the spread code generating means. 3. The matched signal according to claim 2, further comprising peak detection means for detecting a peak of correlation with the spread code. Filter device. 4. A storage means for storing a frequency domain signal obtained by performing the fast Fourier transform processing by the first fast Fourier transform processing means, and the limiting means is stored in the storage means. The matched filter device according to claim 1, wherein a spectral component showing an intensity exceeding a predetermined threshold value is removed from the frequency domain signal. 5. A complex of either one of the frequency domain signal obtained through the limiting means and the frequency domain signal obtained by performing the fast Fourier transform processing by the second fast Fourier transform processing means. Multiplication means for multiplying the conjugate by the other; inverse fast Fourier transform processing means for performing inverse fast Fourier transform processing on the frequency domain signal multiplied by the multiplying means; and inverse fast Fourier transform processing means for inverse fast Fourier transform processing means. Peak detection means for detecting the peak of the correlation between the spread code in the spread spectrum signal and the spread code generated by the spread code generation means based on the cross-correlation function obtained by the conversion processing The matched filter device according to claim 4, wherein 6. Storage means for storing a frequency domain signal obtained by performing the fast Fourier transform processing by the first fast Fourier transform processing means, frequency domain signals stored in the storage means, and the first frequency domain signal stored in the storage means. 2 is provided with multiplication means for multiplying the complex conjugate of one of the frequency domain signals obtained by performing the fast Fourier transform processing by the fast Fourier transform processing means 2 and the other, and the limiting means is the multiplication 2. The matched filter device according to claim 1, wherein spectral components showing an intensity exceeding a predetermined threshold value are removed from the frequency domain signal multiplied by the means. 7. An inverse fast Fourier transform processing means for subjecting the frequency domain signal obtained through the limiting means to an inverse fast Fourier transform processing, and an inverse fast Fourier transform processing by the inverse fast Fourier transform processing means. Based on the cross-correlation function obtained by the above, it is characterized by comprising peak detection means for detecting a peak of the correlation between the spread code in the spread spectrum signal and the spread code generated by the spread code generating means. The matched filter device according to claim 6. 8. A storage means for storing data obtained by sampling the spread spectrum signal at a predetermined sampling frequency, wherein the first fast Fourier transform processing means reads out the data stored in the storage means. 2. The matched filter device according to claim 1, wherein a fast Fourier transform process is performed. 9. The matched filter device according to claim 1, further comprising storage means for buffering a frequency domain signal obtained by performing the fast Fourier transform processing by the second fast Fourier transform processing means. . 10. A synchronous acquisition for detecting the phase of a spread code in the spread spectrum signal when calculating the position and velocity of the self by receiving a signal from a satellite. 1. The matched filter device according to 1. 11. A correlation detection method for detecting a correlation between a spread code and a spread code generated by itself to detect the phase of the spread code in an input spread spectrum signal, wherein the spread spectrum signal is A step of performing a fast Fourier transform process on the input data sampled at a predetermined sampling frequency, a step of generating the same spread code as the spread code in the above spread spectrum signal, and a high speed for the generated spread code. A step of performing a Fourier transform process, and a step of removing at least a spectral component having an intensity exceeding a predetermined threshold value in the frequency domain signal obtained by performing the fast Fourier transform process on the input data. A characteristic correlation detection method. 12. A receiving device for receiving a signal from a satellite to calculate its own position and velocity, comprising: receiving means for receiving the signal from the satellite; and frequency of a received signal received by the receiving means. Frequency conversion means for converting to a predetermined intermediate frequency; synchronization acquisition means for detecting the phase of the spread code in the intermediate frequency signal obtained by the frequency conversion means and for detecting the carrier frequency in the intermediate frequency signal; , The phase of the spread code detected by the synchronization acquisition means and the carrier frequency detected by the synchronization acquisition means for each of a plurality of channels independently provided corresponding to the plurality of satellites. Set by allocating and setting for each satellite, and using the set spreading code phase and carrier frequency as initial values, the spreading In order to detect the phase of the spread code in the intermediate frequency signal, which is a spread spectrum signal, with synchronization holding means for performing synchronization holding between the signal and the carrier and demodulating the message included in the intermediate frequency signal, The synchronization acquisition means for detecting the correlation between the spreading code and the spreading code generated by itself, is a first Fourier transform processing for the data input by sampling the intermediate frequency signal at a predetermined sampling frequency. Fast Fourier transform processing means, spread code generating means for generating the same spread code as the spread code in the intermediate frequency signal, and fast Fourier transform processing for the spread code generated by the spread code generating means. By means of at least the first fast Fourier transform processing means Receiver characterized in that it is constructed using the matched filter and a limiting means for removing spectral components representing the intensity exceeding a predetermined threshold value among the frequency-domain signal obtained is subjected fast Fourier transform processing.