CN102207550A - Capture engine structure of GPS/Galileo dual-mode receiver - Google Patents

Abstract

The invention discloses a capture engine structure of a GPS/Galileo dual-mode receiver, comprising a band pass filter, a sampling circuit, a band pass filter coefficient register, a carrier stripping circuit, a matching filter, a RAM (Random Access Memory), a capture threshold calculating and judging circuit, a spread spectrum code period counter, a carrier NCO (Numerical Control Oscillator) register, a code NCO register, a code loader, a code initial phase register, a selector, a C/A code generator, and an internal memory and carrier generator, wherein the capture engine structure realizes the capture of GPS L1C/A signals and Galileo E1B/E1C signals with different strengths because the GPSL1 wave section C/A (Acquisition Code) code length and the Galileo E1B/E1C spread spectrum code length are both the integer times of 1023. The capture engine can capture the GPS signals of low to -146 dBm and the Galileo E1B/E1C signals of low to 33 dBHz (the power of equivalent Galileo E1B or E1C signals is -138 dBm). The area of the capture engine under the SMIC 0.18 microns technique is 3.5 mm<2>; the lowest working frequency of the capture engine only needs 12 MHz; and the capture engine can work at random working frequency in a range from 12 MHz to 50 MHz.

Description

Capture engine structure in a kind of GPS/Galileo dual mode receiver

Technical field

The present invention relates to the global positioning system technology field, relate in particular to the capture engine structure in a kind of GPS/Galileo dual mode receiver.

Background technology

GPS global positioning system INVECS Intelligent and Innovation Vehicle Electric Control System is " time service and range measurement navigation system/GPS " (Navigation System Timing and Ranging/Global Positioning System, NAVSTAR GPS), U.S. Department of Defense is that military purposes is set up, and is intended to thoroughly solve the navigation of marine, aerial and land carrying tool and a cover global position system of location.The Aerospace Satellite constellation of GPS is made up of 24 satellites, and these satellite distribution have 4 satellites on each orbital plane in 6 orbital planes.Every satellite has 5 hours more than the local horizon every day approximately, be positioned at simultaneously the above number of satellite in local horizon in time with the place and different, minimum is 4, can reach 11 at most.The gps signal that each gps satellite sent all is a Direct Sequence Spread Spectrum Signal.The signal of commercial use is relevant with standard setting service (SPS), is called the direct sequence two-phase spread-spectrum signal of thick sign indicating number (C/A sign indicating number), under the carrier wave of 1575.42MHz, has the speed of per second 1.023 million chips.Pseudo noise (PN) sequence length is 1023 chips, corresponding to 1 millisecond time cycle.The PN sign indicating number that each satellites transmits is different (Gold sign indicating number) makes signal to send simultaneously from several satellites, and received simultaneously by a receiver, and is almost noiseless each other.

European Union had announced the Galileo plan in 1999, and the Galileo system constitutes so-called fertile gram (Walker) constellation by 30 satellites, and being distributed in specified inclination angle is on three orbital planes of 56 degree.Each orbital plane is evenly laid 9 work satellites, and 40 spend at interval, and other establishes 1 backup satellite, in order to substitute the work satellite that lost efficacy.First Galileo test satellite GIOVE-A launched in Dec, 2005, and second Galileo test satellite GIOVE-B launched in April, 2008.For reducing the interference to gps signal, the Galileo signal adopts and splits the spectrum modulation system, just the binary offset carrier modulation system (Binary Offset Carrier, BOC).Wherein Galileo E1B/E1C signal adopts CBOC (6,1,1/11) modulation system, comprises two sub-carrier frequencies, and wherein the power of BOC (1,1) signal accounts for 10/11 of general power, and the power of BOC (6,1) signal accounts for 1/11 of general power.The spreading code length of GalileoE1B/E1C signal is 4092, and bit rate is 1.023MHz, and the sign indicating number cycle is 4ms.

The co-located of Galileo and GPS constellation systems can provide better bearing accuracy, and the guarantee aspect availability, continuity and integrity also will be good more than single GPS.Such as, Galileo and GPS are used the availability that can significantly improve Navsat, for example end under the urban environment of elevation angle at 30 °, the availability of GPS receiver is 80% (3 satellites is visual), and the availability of Galileo/GPS compatible receiver can reach 95% (7 satellites are visual).Can predict that the dual mode receiver receiver will the occuping market main flow after the Galileo constellation improves.

In order to improve the start-up time of acquisition sensitivity and receiver, most of satellite navigation receiver chip internal all contains powerful capture engine, and capture engine generally all can occupy more than 1/4 of entire chip area.For the GPS/Galileo dual mode receiver, if two capture engines of design are caught gps signal for one, catch the Galileo signal for one, obviously can cause the remarkable lifting of chip cost, the bimodulus capture engine that therefore designs compatible with GPS/Galileo signal is more reasonably to select.How to select the acquisition algorithm of compatible with GPS/Galileo signal and guarantee that hardware size is a core technology of GPS/Galileo dual mode receiver in the acceptable scope.The present invention does not hereinafter refer in particular to as having, and gps signal is promptly represented GPS L1C/A signal, and the Galileo signal is promptly represented Galileo E1B/E1C signal.

Summary of the invention

(1) technical matters that will solve

In view of this, fundamental purpose of the present invention is to provide the capture engine structure in a kind of GPS/Galileo dual mode receiver, with to the GPS L1C/A signal of varying strength and catching of Galileo E1B/E1C signal.

(2) technical scheme

For achieving the above object, the invention provides the capture engine structure in a kind of GPS/Galileo dual mode receiver, this capture engine structure comprises bandpass filter 101, sampling circuit 102, bandpass filter coefficient register 103, carrier wave stripper circuit 104, matched filter 105, RAM106, detection threshold calculates and decision circuit 107, spreading code period counter 108, carrier wave NCO register 109, sign indicating number NCO register 110, sign indicating number loading bin 111, sign indicating number first phase register 112, selector switch 113, C/A code generator 114, internal memory 115 and carrier generator 116, wherein, it all is 1023 integral multiple that this capture engine structure is utilized GPS L1 wave band C/A code length and Galileo E1B/E1C spreading code length, realizes the GPS L1C/A signal of varying strength and catching of Galileo E1B/E1C signal.

In the such scheme, described bandpass filter 101 is used to receive the digital medium-frequency signal of outside input, and the digital medium-frequency signal that receives carried out bandpass filtering treatment, and obtain GPS or Galileo signal, then the GPS or the Galileo signal that obtain are exported to sampling circuit 102.

In the such scheme, described sampling circuit 102 is used for the GPS or the Galileo signal of bandpass filter 101 input are carried out half chip samples, and is the signal of 2.046MHz to carrier wave stripper circuit 104 output speeds.

In the such scheme, described bandpass filter coefficient register 103 is used to dispose the bandwidth and the centre frequency of bandpass filter 101, and wherein, the filter coefficient of catching GPS of configuration is different with the filter coefficient of catching the Galileo signal.

In the such scheme, described carrier wave stripper circuit 104 is used for that the signal that sampling circuit 102 is imported is carried out carrier wave to be peeled off, and is divided into I, Q two-way, exports to shift register.

In the such scheme, described matched filter 105 is used for the data of shift register storage are separated spread spectrum and added up, and accumulation result is stored among the RAM106.

In the such scheme, described RAM106 is used to store the accumulation result of matched filter 105 outputs.

In the such scheme, described detection threshold calculates the maximal value that is used for searching RAM106 with decision circuit 107, and calculate detection threshold according to the accumulated value of all code phases of preserving among the RAM106, and this maximal value and this decision threshold compared, when maximal value surpasses decision threshold, acquisition success; Otherwise catch failure.

In the such scheme, described spreading code period counter 108 is used to calculate the cycle of spreading code, whether works with controlled sampling circuit 102, and when catching gps satellite, this sampling circuit is being worked always; When catching the Galileo satellite, this spreading code period counter counting region is 0 to 3, counter meter to 1,2 and 3 o'clock sampling circuits all do not work.

In the such scheme, described carrier wave NCO register 109 is used to receive the carrier frequency of dsp processor configuration, to change the frequency operation.

In the such scheme, described sign indicating number NCO register 110 is used to receive the code frequency of dsp processor configuration, to carry out the operation of escape frequency.

In the such scheme, described sign indicating number loading bin 111 is used to receive and store the sign indicating number of exporting from selector switch 113, and matched filter 105 will be used the sign indicating number of 111 storages in yard loading bin in separating the spread spectrum process.

In the such scheme, described sign indicating number first phase register 112 is used to dispose C/A code generator 114 to generate the PN sign indicating number of the corresponding satellite that will catch, exports to yard loading bin 111 behind selector switch 113.

In the such scheme, described selector switch 113 is used to select the PN sign indicating number of gps satellite or the Memory Code sign indicating number of Galileo satellite, and catching gps satellite still is that the Galileo satellite is determined by dsp software.Dsp software is analyzed as the case may be, and configuration control word control selector switch is to select the PN sign indicating number of gps satellite or the Memory Code sign indicating number of Galileo satellite on earth.

In the such scheme, described C/A code generator 114 is used for generating according to the output result of sign indicating number first phase register 112 the PN sign indicating number of corresponding gps satellite.

In the such scheme, described internal memory 115 is used to preserve the PN sign indicating number of the Galileo satellite of dsp processor configuration.

In the such scheme, described carrier generator 116 is used for the phase value of carrier wave NCO register 109 is carried out sine and cosine mapping, and the output result of its output result and sampling circuit 102 multiplies each other.

In the such scheme, when this capture engine structures capture gps signal, dsp processor calculates bandpass filter 101 coefficients according to the carrier frequency and the sampling rate of digital intermediate frequency, disposes bandpass filter coefficient register 103 then, makes that bandpass filter 101 pass band widths are 2MHz; Dsp processor configuration spreading code period counter 108 and sign indicating number NCO register 110 make sampling circuit 102 carry out down-sampling according to the speed of 2.046MHz; Signal is divided into I, Q two-way through carrier wave stripper circuit 104, enters matched filter 105; The carrier frequency of carrier generator 116 is by 109 controls of carrier wave NCO register; Dsp processor is selected into yard loading bin 111 by configuration code first phase register 112 configuration C/A code generators 114 by selector switch 113; The intermediate structure of catching deposits RAM106 in; Detection threshold calculates with decision circuit 107 and calculates detection threshold and provide the judgement that whether captures signal by the accumulated value that statistics RAM preserves.

In the such scheme, when this capture engine structures capture Galileo signal, dsp processor calculates the bandpass filter coefficient according to the carrier frequency and the sampling rate of digital intermediate frequency, disposes bandpass filter coefficient register 103 then; Dsp processor configuration spreading code period counter 108 and sign indicating number NCO register 110, make sampling circuit 102 carry out down-sampling according to the speed of 2.046MHz, it is the spreading code phase information of Galileo signal that spreading code period counter 108 can also provide current catching, and guarantees to have traveled through all Galileo spreading code phase places; Signal is divided into I, Q two-way through carrier wave stripper circuit 104, enters matched filter 105; The carrier frequency of carrier generator is by 109 controls of carrier wave NCO register; Because the Galileo spreading code do not provide code generator, dsp processor is selected into yard loading bin 111 with the Galileo spreading code internal memory 115 that writes direct by selector switch 113; The intermediate structure of catching deposits RAM106 in; Detection threshold calculates with decision circuit 107 and calculates detection threshold and provide the judgement that whether captures signal by the accumulated value that statistics RAM preserves.

(3) beneficial effect

From technique scheme as can be seen, the present invention has following beneficial effect:

1, the capture engine structure in this GPS/Galileo dual mode receiver provided by the invention can realize the GPS L1C/A signal of varying strength and catching of Galileo E1B/E1C signal by software arrangements.Experimental results show that this capture engine can realize being low to moderate-the GPS L1C/A signal capture of 147dBm and to the parallel capture of the Galileo E1B/E1C signal (the GalileoE1B/E1C signal power of equivalence-138dBm) of 33dBHz.

2, the capture engine structure in this GPS/Galileo dual mode receiver provided by the invention has been used the variable coefficient bandpass filter.When catching gps signal, configuration bandpass filter centre frequency is the digital intermediate frequency frequency, and bandwidth is 2MHz; When catching the Galileo signal, configuration bandpass filter centre frequency makes wave filter aim at a sideband of Galileo signal for the digital intermediate frequency frequency adds 1.023MHz, and bandwidth is 2MHz.This makes and can both obtain filtering result preferably when catching gps signal and Galileo signal, to promote acquisition performance.

3, the capture engine structure in this GPS/Galileo dual mode receiver provided by the invention, be based on that matched filter unit realizes, having utilized GPS L1 wave band C/A code length and GalileoE1B/E1C spreading code length all is the characteristics of 1023 integral multiple, can realize the sign indicating number territory parallel capture of gps signal and 1/4 parallel capture in Galileo signal code territory, avoid the FFT operation.

4, the capture engine structure in this GPS/Galileo dual mode receiver provided by the invention, can utilize the noncoherent accumulation RAM statistical noise variance of matched filter unit, calculate detection threshold with the thresholding multiplication of software setting, and then carrying out prize judgment, this thresholding can guarantee the constant false alarm rate of system.

5, the capture engine structure in this GPS/Galileo dual mode receiver provided by the invention, described capture engine minimum clock frequency only is 12MHz, the comprehensive area under SMIC0.18 micron technology is 3.5mm ², be the bimodulus capture engine of a low-cost low-power consumption.

Description of drawings

Below by for example and the accompanying drawing that is not construed as limiting the present invention is described, the identical represented same meaning of label among the figure.

Fig. 1 is the synoptic diagram according to the capture engine structure in the GPS/Galileo dual mode receiver of the embodiment of the invention;

Fig. 2 is according to the synoptic diagram of detection threshold calculating in the capture engine structure in the GPS/Galileo dual mode receiver of the embodiment of the invention with decision circuit.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.

The present invention has provided a kind of based on matched filter unit (Matched Filter Unit, MFU) the capture engine structure in the GPS/Galileo dual mode receiver, bimodulus GNSS signal be can catch, GPS L1C/A signal and Galileo E1B/E1C signal comprised.MFU catches the spreading code phase place at time-domain parallel, has avoided the FFT operation.The spreading code length of GPS L1C/A signal and Galileo E1B/E1C signal all is 1023 integral multiple, and the search precision of code phase is half chip normally.The MFU of the present invention's design is an elementary cell with the shift register of two group of 2046 length.MFU can be directly used in and catch GPS L1C/A signal, and when catching Galileo E1B/E1C signal, MFU is configured to search for 1023 code phases at every turn, until having searched for 4092 code phases.

Suppose that the road gps satellite signal that receiver receives is:

r(t)＝AD(t)c(t)cos(2πf _ct)+n(t)(1)

The satellite message of D (t) expression herein data, c (t) expression C/A sign indicating number, f _cExpression intermediate frequency carrier frequency, A represents signal amplitude.

Suppose that the road Galileo satellite-signal that receiver receives is:

r(t)＝AD(t)BOC(t)cos(2πf _ct)+n(t)(2)

Herein

BOC(t)＝c(t)sign(sin(2πf _sct))(3)

Here c (t) expression spreading code, sign (.) represents sign function, f _ScThe expression sub-carrier frequencies.Sign (.) is carried out Fourier expansion can be obtained

$\mathrm{sign}\left(\sin \left(2\mathrm{\&pi;}{f}_{\mathrm{sc}}t\right)\right)=\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{n\&pi;}}{\sin }^2\frac{\mathrm{n\&pi;}}{2}\sin \left(2\mathrm{\&pi;n}{f}_{\mathrm{sc}}t\right)---\left(4\right)$

Only getting (4) formula low frequency component substitution (3) formula obtains

$\mathrm{BOC}\left(t\right)\&ap;c\left(t\right)\&times;\frac{4}{\mathrm{\&pi;}}\sin \left(2\mathrm{\&pi;n}{f}_{\mathrm{sc}}t\right)---\left(5\right)$

(5) formula substitution (2) formula can be obtained

$r\left(t\right)=\mathrm{AD}\left(t\right)c\left(t\right)\&times;\frac{4}{\mathrm{\&pi;}}\sin \left(2\mathrm{\&pi;n}{f}_{\mathrm{sc}}t\right)\cos \left(2\mathrm{\&pi;}{f}_{c}t\right)+n\left(t\right)$

$=\frac{2A}{\mathrm{\&pi;}}D\left(t\right)c\left(t\right)[\sin \left(2\mathrm{\&pi;}(f_{\mathrm{sc}}+f_c)t\right)+\sin \left(2\mathrm{\&pi;}(f_{\mathrm{sc}}-f_c)t\right)]+n\left(t\right)---\left(6\right)$

(6) it is consistent with (1) formula that formula is only got the representation of a sideband, this for GPS L1C/A signal and Galileo E1B/E1C signal adopt identical acquisition algorithm to create may.Difference only is that the spread spectrum code length of GPS L1C/A signal is 1023, and the spread spectrum code length of Galileo E1B/E1C signal is 4092.

The capture engine based on matched filter unit of the present invention's design, its structure as shown in Figure 1, comprise variable coefficient bandpass filter, sampling circuit, carrier generator, shift register, matched filter, relevant and incoherent RAM, decision circuit, red module is represented the circuit with the ASIC realization, and the grey module is represented the module of available processors configuration.

Bandpass filter can change centre frequency to realize the filtering to gps signal and Galileo signal by configuration coefficients.Sampling circuit makes that the sampled point speed that enters shift register is 2.046MHz, to realize catching of half chip precision.The length of I, Q two-way shift register is 2046.When carrying out gps signal when catching, pack into the sign indicating number loading bin of matched filter of the spreading code that selector switch generates the C/A code generator; When carrying out the Galileo signal capture, pack into the sign indicating number loading bin of matched filter of the Galileo spreading code that selector switch will deposit Memory in.The length of sign indicating number loading bin is 1023, therefore, only loads 1/4 of Galileo spreading code when catching the Galileo signal.

When catching gps signal, can realize catching by disposing incoherent and coherent accumulation number of times to the gps signal of varying strength.When catching the Galileo signal, because shift register length is limit, every millisecond can only obtain 2046 half chip phase, travel through and obtain 8192 half chip phase, need capture engine to catch four times, the capture time of the Galileo signal of therefore same intensity increases to some extent than the capture time of gps signal.The Galileo signal can only be realized the coherent accumulation of 4ms, and the noncoherent accumulation number of times can be configured by processor.

The capture engine lowest operating frequency only needs 12MHz, can be operated in any frequency of operation in the 12MHz-50MHz scope.Altera EP3C120FPGA synthesis result, logic unit numbers are 40900, and the Memory resource consumption is 55k bit.Under SMIC0.18 micron technology, Design Compiler synthesis result is 3.514231mm ²

Fig. 1 is the synoptic diagram according to the capture engine structure in the GPS/Galileo dual mode receiver of the embodiment of the invention, and this capture engine structure comprises that bandpass filter 101, sampling circuit 102, bandpass filter coefficient register 103, carrier wave stripper circuit 104, matched filter 105, RAM106, detection threshold calculate and decision circuit 107, spreading code period counter 108, carrier wave NCO register 109, sign indicating number NCO register 110, sign indicating number loading bin 111, sign indicating number first phase register 112, selector switch 113, C/A code generator 114, internal memory 115 and carrier generator 116.Wherein:

Bandpass filter 101 is used to receive the outside digital medium-frequency signal of importing, and the digital medium-frequency signal that receives is carried out bandpass filtering treatment, obtains GPS or Galileo signal, then the GPS or the Galileo signal that obtain is exported to sampling circuit 102.Sampling circuit 102 is used for the GPS or the Galileo signal of bandpass filter 101 input are carried out half chip samples, and is the signal of 2.046MHz to carrier wave stripper circuit 104 output speeds.Bandpass filter coefficient register 103 is used to dispose the bandwidth and the centre frequency of bandpass filter 101, and wherein, the filter coefficient of catching GPS of configuration is different with the filter coefficient of catching the Galileo signal.Carrier wave stripper circuit 104 is used for that the signal that sampling circuit 102 is imported is carried out carrier wave and peels off, and is divided into I, Q two-way, exports to shift register.Matched filter 105 is used for the data of shift register storage are separated spread spectrum and added up, and accumulation result is stored among the RAM106.RAM106 is used to store the accumulation result of matched filter 105 outputs.Detection threshold calculates and decision circuit 107, the maximal value that is used for searching RAM106, and calculate detection threshold according to the accumulated value of all code phases of preserving among the RAM106, and this maximal value and this decision threshold are compared, whether successfully to catch with judgement.Whether spreading code period counter 108 in the cycle that is used to calculate spreading code, works with controlled sampling circuit 102.Carrier wave NCO register 109 is used to receive the carrier frequency that dsp processor disposes, to change the frequency operation.Sign indicating number NCO register 110 is used to receive the code frequency that dsp processor disposes, to carry out the operation of escape frequency.Sign indicating number loading bin 111 is used to receive and store the sign indicating number of exporting from selector switch 113, and matched filter 105 will be used the sign indicating number of 111 storages in yard loading bin in separating the spread spectrum process.Sign indicating number first phase register 112 is used to dispose C/A code generator 114 to generate the PN sign indicating number of the corresponding satellite that will catch, exports to yard loading bin 111 behind selector switch 113.Selector switch 113 is used to select the PN sign indicating number of gps satellite or the Memory Code sign indicating number of Galileo satellite.C/A code generator 114 generates the PN sign indicating number of corresponding gps satellite according to the output result of sign indicating number first phase register 112.Internal memory 115 is used to preserve the PN sign indicating number of the Galileo satellite of dsp processor configuration.Carrier generator 116 carries out sine and cosine mapping with the phase value of carrier wave NCO register 109, and output result of its output result and sampling circuit 102 multiplies each other.

When this capture engine structures capture gps signal, dsp processor calculates bandpass filter 101 coefficients according to the carrier frequency and the sampling rate of digital intermediate frequency, disposes bandpass filter coefficient register 103 then, makes that bandpass filter 101 pass band widths are 2MHz; Dsp processor configuration spreading code period counter 108 and sign indicating number NCO register 110 make sampling circuit 102 carry out down-sampling according to the speed of 2.046MHz; Signal is divided into I, Q two-way through carrier wave stripper circuit 104, enters matched filter 105; The carrier frequency of carrier generator 116 is by 109 controls of carrier wave NCO register; Dsp processor is selected into yard loading bin 111 by configuration code first phase register 112 configuration C/A code generators 114 by selector switch 113; The intermediate structure of catching deposits RAM106 in; Detection threshold calculates with decision circuit 107 and calculates detection threshold and provide the judgement that whether captures signal by the accumulated value that statistics RAM preserves.

When this capture engine structures capture Galileo signal, dsp processor calculates the bandpass filter coefficient according to the carrier frequency and the sampling rate of digital intermediate frequency, disposes bandpass filter coefficient register 103 then; Dsp processor configuration spreading code period counter 108 and sign indicating number NCO register 110, make sampling circuit 102 carry out down-sampling according to the speed of 2.046MHz, it is the spreading code phase information of Galileo signal that spreading code period counter 108 can also provide current catching, and guarantees to have traveled through all Galileo spreading code phase places; Signal is divided into I, Q two-way through carrier wave stripper circuit 104, enters matched filter 105; The carrier frequency of carrier generator is by 109 controls of carrier wave NCO register; Because the Galileo spreading code do not provide code generator, dsp processor is selected into yard loading bin 111 with the Galileo spreading code internal memory 115 that writes direct by selector switch 113; The intermediate structure of catching deposits RAM106 in; Detection threshold calculates with decision circuit 107 and calculates detection threshold and provide the judgement that whether captures signal by the accumulated value that statistics RAM preserves.

Fig. 2 has described the workflow of detection threshold calculating with decision circuit 107, is that example describes to catch gps signal below.

Suppose that the road satellite-signal that the GPS receiver receives is:

r(t)＝AD(t)c(t)cos(ω _ct)+n(t)(1)

The satellite message of D (t) expression herein data, c (t) expression C/A sign indicating number, ω _cThe expression intermediate frequency carrier, A represents signal amplitude, σ ²Be the power of noise n (t), snr is a signal to noise ratio (S/N ratio), and

I, Q two-way multiply by cos (ω respectively _LT) and sin (ω _LT), carry out relevantly with this locality reproduction C/A sign indicating number again, be a C/A sign indicating number cycle correlation time, ω _LThe local reproduction of expression carrier frequency.The accumulation result on the I road of k 1ms is:

$I_k=\underset{i=\mathrm{kN}}{\overset{\mathrm{kN}+N-1}{\mathrm{\&Sigma;}}}r\left(\mathrm{iT}\right)c_L\left(\mathrm{iT}\right)\&CenterDot;\cos \left({\mathrm{\&omega;}}_L\mathrm{iT}\right)---\left(2\right)$

C herein _L(iT) the local reproduction sign indicating number of expression, N represents the sampling number of 1ms, T represents sampling interval, NT=1ms.

Suppose satellite telegraph text data D (t)=1 in sign indicating number alignment and the sign indicating number correlated process, then formula this moment (2) can be reduced to:

$I_k=\underset{i=\mathrm{kN}}{\overset{\mathrm{kN}+N-1}{\mathrm{\&Sigma;}}}[A\&times;\cos \left({\mathrm{\&omega;}}_c\mathrm{iT}\right)\&CenterDot;\cos \left({\mathrm{\&omega;}}_L\mathrm{iT}\right)+n\left(\mathrm{iT}\right)c_L\left(\mathrm{iT}\right)\&CenterDot;\cos \left({\mathrm{\&omega;}}_L\mathrm{iT}\right)]$

$=\frac{A}{2}\frac{\sin \left(\frac{\mathrm{\&Delta;\&omega;TN}}{2}\right)}{\sin \left(\frac{\mathrm{\&Delta;\&omega;T}}{2}\right)}\cos (\frac{\mathrm{\&Delta;\&omega;T}(N-1)}{2}+\mathrm{\&Delta;\&omega;TkN})+N_{I_k}---\left(3\right)$

Δ ω=ω herein _c-ω _L

$N_{I_k}=\underset{i=\mathrm{kN}}{\overset{\mathrm{kN}+N-1}{\mathrm{\&Sigma;}}}n\left(\mathrm{iT}\right)c_L\left(\mathrm{iT}\right)\&CenterDot;\cos \left({\mathrm{\&omega;}}_L\mathrm{iT}\right)---\left(4\right)$

Calculate according to formula (4) this moment

Probability distribution.N (t) is that average is zero, and variance is σ ²This noise of band limit for height,

Variance be N stochastic variable n (iT) c _L(iT) cos (ω _LIT) variance and, promptly

Probability distribution be:

To sum up can get:

In like manner can get the accumulation result of k 1ms of Q branch road:

Here

Probability distribution be:

Test statistics adopts

$Y=\underset{i=0}{\overset{L-1}{\mathrm{\&Sigma;}}}(I_i^2+Q_i^2)---\left(8\right)$

Set up test of hypothesis:

H1: capture signal (sign indicating number alignment and frequency alignment);

H0: do not capture signal (sign indicating number is unjustified).

Under the H1 condition, Y obeys the non-central χ of 2L degree of freedom ²Distribute non-centrality parameter

$s^2=\frac{A^2{N}^{2}L}{4}---\left(9\right)$

Then the probability density function of statistic Y is:

$f\left(y\right|H_1)=\frac{1}{N{\mathrm{\&sigma;}}^2}{\left(\frac{y}{s^2}\right)}^{(L-1)/2}{e}^{-\frac{y+s^2}{N{\mathrm{\&sigma;}}^2}}{I}_{(L-1)}\left(\frac{2\sqrt{y}\&CenterDot;s}{N{\mathrm{\&sigma;}}^2}\right)---\left(10\right)$

The average of statistic Y is

m ₁＝E(Y)＝LNσ ²(1+N·snr/2)(11)

The variance of statistic Y is

${\mathrm{\&sigma;}}_1^2={\mathrm{\&sigma;}}_y^2={\mathrm{LN}}^2{\mathrm{\&sigma;}}^4(1+N\&CenterDot;\mathrm{snr})---\left(12\right)$

Under the H0 condition, statistic Y obeys the center χ of 2L degree of freedom ²Distribute, then the probability density function of statistic Y is:

$f\left(y\right|H_0)=\frac{1}{2^L\&CenterDot;{(N{\mathrm{\&sigma;}}^2/2)}^L\mathrm{\&Gamma;}\left(L\right)}{y}^{L-1}{e}^{-\frac{y}{N{\mathrm{\&sigma;}}^2}}---\left(13\right)$

The average of statistic Y is

m ₀＝E(Y)＝LNσ ²(14)

The variance of statistic Y is

${\mathrm{\&sigma;}}_0^2={\mathrm{\&sigma;}}_y^2={\mathrm{LN}}^2{\mathrm{\&sigma;}}^4---\left(15\right)$

Because to χ ²Calculate comparatively complexity when distribution is quadratured, use here and χ ²Distribution substitutes χ with the homoscedastic Gaussian distribution of average ²Distribute.

Substitute χ with Gaussian distribution ²After the distribution, under H0 and the H1 condition, the probability distribution of statistic Y can be rewritten as

$f\left(y\right|H_0)=\frac{1}{\sqrt{2\mathrm{\&pi;}\&CenterDot;{\mathrm{\&sigma;}}_0^2}}\exp (-\frac{{(y-m_0)}^2}{2\&CenterDot;{\mathrm{\&sigma;}}_0^2})---\left(16\right)$

$f\left(y\right|H_1)=\frac{1}{\sqrt{2\mathrm{\&pi;}\&CenterDot;{\mathrm{\&sigma;}}_1^2}}\exp (-\frac{{(y-m_1)}^2}{2\&CenterDot;{\mathrm{\&sigma;}}_1^2})---\left(17\right)$

Like this based on the thresholding V of false alarm rate _tCan be expressed as

$P_{\mathrm{fa}}={\&Integral;}_{V_t}^{+\&infin;}f\left(y\right|H_0)\mathrm{dy}---\left(18\right)$

Here V _tExpression prize judgment thresholding can get according to formula (17) (18):

$V_t={\mathrm{\&sigma;}}_0{Q}^{-1}\left(P_{\mathrm{fa}}\right)+m_0=\sqrt{L}N{\mathrm{\&sigma;}}^2{Q}^{-1}\left(P_{\mathrm{fa}}\right)+\mathrm{LN}{\mathrm{\&sigma;}}^2=\mathrm{LN}{\mathrm{\&sigma;}}^2(Q^{-1}\left(P_{\mathrm{fa}}\right)/\sqrt{L}+1)---\left(19\right)$

Here Q ^-1(x) inverse function of expression Q (x),

By (19) formula as seen, thresholding is by LN σ ²With

Multiplying each other obtains, wherein LN σ ²Can obtain by the accumulated value of all address rams among Fig. 2,

Write configuration register by processor calculating.This thresholding has guaranteed the constant false alarm rate of system.

Catch peak value and then relatively obtain by 2045 times of Fig. 2 right part, when peak value surpassed thresholding, the expression capture engine captured signal; If peak value does not surpass thresholding, then expression does not capture signal.

Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (19)

1. the capture engine structure in the GPS/Galileo dual mode receiver, it is characterized in that, this capture engine structure comprises bandpass filter (101), sampling circuit (102), bandpass filter coefficient register (103), carrier wave stripper circuit (104), matched filter (105), RAM (106), detection threshold calculates and decision circuit (107), spreading code period counter (108), carrier wave NCO register (109), sign indicating number NCO register (110), sign indicating number loading bin (111), sign indicating number first phase register (112), selector switch (113), C/A code generator (114), internal memory (115) and carrier generator (116), wherein, it all is 1023 integral multiple that this capture engine structure is utilized GPS L1 wave band C/A code length and GalileoE1B/E1C spreading code length, realizes the GPS L1C/A signal of varying strength and catching of Galileo E1B/E1C signal.

2. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, described bandpass filter (101) is used to receive the digital medium-frequency signal of outside input, and the digital medium-frequency signal that receives carried out bandpass filtering treatment, obtain GPS or Galileo signal, then the GPS or the Galileo signal that obtain are exported to sampling circuit (102).

3. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, described sampling circuit (102) is used for the GPS or the Galileo signal of bandpass filter (101) input are carried out half chip samples, and is the signal of 2.046MHz to carrier wave stripper circuit (104) output speed.

4. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, described bandpass filter coefficient register (103) is used to dispose the bandwidth and the centre frequency of bandpass filter (101), wherein, the filter coefficient of catching GPS of configuration is different with the filter coefficient of catching the Galileo signal.

5. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, described carrier wave stripper circuit (104) is used for that the signal that sampling circuit (102) is imported is carried out carrier wave to be peeled off, and is divided into I, Q two-way, exports to shift register.

6. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, described matched filter (105) is used for the data of shift register storage are separated spread spectrum and added up, and accumulation result is stored among the RAM (106).

7. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1 is characterized in that, described RAM (106) is used to store the accumulation result of matched filter (105) output.

8. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, described detection threshold calculates the maximal value that is used for searching RAM (106) with decision circuit (107), and calculate detection threshold according to the accumulated value of all code phases of preserving among the RAM (106), and this maximal value and this decision threshold compared, when maximal value surpasses decision threshold, acquisition success; Otherwise catch failure.

9. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, the cycle that described spreading code period counter (108) is used to calculate spreading code, whether work with controlled sampling circuit (102), when catching gps satellite, this sampling circuit is being worked always; When catching the Galileo satellite, this spreading code period counter counting region is 0 to 3, counter meter to 1,2 and 3 o'clock sampling circuits all do not work.

10. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1 is characterized in that, described carrier wave NCO register (109) is used to receive the carrier frequency of dsp processor configuration, to change the frequency operation.

11. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1 is characterized in that, described sign indicating number NCO register (110) is used to receive the code frequency of dsp processor configuration, to carry out the operation of escape frequency.

12. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, described sign indicating number loading bin (111) is used for receiving and storing the sign indicating number of exporting from selector switch (113), and matched filter (105) will be used the sign indicating number of (111) storage in yard loading bin in separating the spread spectrum process.

13. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, described sign indicating number first phase register (112) is used to dispose C/A code generator (114) to generate the PN sign indicating number of the corresponding satellite that will catch, exports to a yard loading bin (111) behind selector switch (113).

14. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1 is characterized in that, described selector switch (113) is used to select the PN sign indicating number of gps satellite or the Memory Code sign indicating number of Galileo satellite.

15. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1 is characterized in that, described C/A code generator (114) is used for generating according to the output result of sign indicating number first phase register (112) the PN sign indicating number of corresponding gps satellite.

16. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1 is characterized in that, described internal memory (115) is used to preserve the PN sign indicating number of the Galileo satellite of dsp processor configuration.

17. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, described carrier generator (116) is used for the phase value of carrier wave NCO register (109) is carried out sine and cosine mapping, and the output result of its output result and sampling circuit (102) multiplies each other.

18. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, when this capture engine structures capture gps signal, dsp processor calculates bandpass filter (101) coefficient according to the carrier frequency and the sampling rate of digital intermediate frequency, dispose bandpass filter coefficient register (103) then, make that bandpass filter (101) pass band width is 2MHz; Dsp processor configuration spreading code period counter (108) and sign indicating number NCO register (110) make sampling circuit (102) carry out down-sampling according to the speed of 2.046MHz; Signal is divided into I, Q two-way through carrier wave stripper circuit (104), enters matched filter (105); The carrier frequency of carrier generator (116) is controlled by carrier wave NCO register (109); Dsp processor is selected into a yard loading bin (111) by configuration code first phase register (112) configuration C/A code generator (114) by selector switch (113); The intermediate structure of catching deposits RAM (106) in; Detection threshold calculates with decision circuit (107) and calculates detection threshold and provide the judgement that whether captures signal by the accumulated value that statistics RAM preserves.

19. the capture engine structure in the GPS/Galileo dual mode receiver according to claim 1, it is characterized in that, when this capture engine structures capture Galileo signal, dsp processor calculates the bandpass filter coefficient according to the carrier frequency and the sampling rate of digital intermediate frequency, disposes bandpass filter coefficient register (103) then; Dsp processor configuration spreading code period counter (108) and sign indicating number NCO register (110), make sampling circuit (102) carry out down-sampling according to the speed of 2.046MHz, it is the spreading code phase information of Galileo signal that spreading code period counter (108) can also provide current catching, and guarantees to have traveled through all Galileo spreading code phase places; Signal is divided into I, Q two-way through carrier wave stripper circuit (104), enters matched filter (105); The carrier frequency of carrier generator is controlled by carrier wave NCO register (109); Because the Galileo spreading code do not provide code generator, dsp processor is selected into a yard loading bin (111) with the Galileo spreading code internal memory (115) that writes direct by selector switch (113); The intermediate structure of catching deposits RAM (106) in; Detection threshold calculates with decision circuit (107) and calculates detection threshold and provide the judgement that whether captures signal by the accumulated value that statistics RAM preserves.

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