KR20110068128A - Signal detection apparatus and method, and parameter setting method of the signal detection apparatus - Google Patents

Abstract

PURPOSE: An apparatus and a method for acquiring signals and a method for setting the parameter of the apparatus are provided to reduce the processing amount of a correlation operation by controlling the frequency resolution of a signal acquired from a satellite navigation receiver. CONSTITUTION: A sampling module(110) samples a signal, received from a satellite, and a pre-set PRN code according to pre-set signal acquiring frequency. A correlation operator(120) implements a correlation operation with respect to the signal and the PRN code. A Fourier transformer(140) implements a Fourier transformation operation with respect to the frequency resolution of the correlation operated result according to a pre-set Fourier transformation point. A peak detector(170) detects the peak of an energy value based on the Fourier transformed result.

Description

Signal Detection Apparatus and Method, and Parameter Setting Method of the Signal Detection Apparatus}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite navigation receiver, and more particularly, to a signal acquisition apparatus and method capable of changing a frequency resolution of a signal obtained from a satellite navigation receiver, and a parameter setting method thereof.

The present invention is derived from the research conducted as part of the satellite navigation ground station system and search rescue terminal development project of the Ministry of Knowledge Economy. [Task management number: 2007-S-301-03, Title: Satellite navigation ground station system and search rescue terminal] Technology development].

In general, a satellite navigation receiver uses a signal acquisition device for calculating the Doppler frequency of an input signal.

In the conventional satellite navigation receiver, the frequency resolution of the Doppler frequency of the signal acquisition apparatus has units of length and reciprocal of input data. Therefore, the conventional signal acquisition apparatus has a problem in that when the Doppler resolution is high, the length of the input data increases, thereby increasing the size of the memory storing the input data and the throughput for signal acquisition.

In order to solve the above problems, it is an object of the present invention to provide a signal acquisition apparatus and method and a parameter setting method thereof that can change the frequency resolution of the signal obtained from the satellite navigation receiver.

According to an aspect of the present invention, there is provided a signal obtaining apparatus comprising: a sampling module for sampling a signal obtained from a satellite and a preset PRN code according to a preset signal acquisition frequency; A correlation calculator for correlating the obtained signals with the PRN code; A Fourier transformer for Fourier transforming the frequency resolution of the result of the correlation operation according to a predetermined Fourier transform point; And a peak detector that detects a peak of the energy value from the Fourier transformed result and determines that the signal acquisition is successful when the peak of the energy value is greater than a predetermined threshold value.

According to another aspect of the present invention, there is provided a signal acquisition method, comprising: sampling a signal obtained from a satellite and a predetermined pseudo random noise (PRN) code according to a predetermined signal acquisition frequency; Correlating the obtained signals with the PRN code; Fourier transforming the frequency resolution of the correlation result according to a predetermined Fourier transform point; Detecting a peak of an energy value from the Fourier transformed result; And determining that the signal acquisition is successful when the peak of the energy value is larger than a preset threshold.

According to another aspect of the present invention, there is provided a parameter setting method of a signal obtaining apparatus, the method including: determining a sampling frequency for a signal obtained from a satellite and a PRN code according to a signal acquisition frequency; Determining a size of a matched filter to correlate the obtained signal and the PRN code; Determining a Doppler resolution and a Fourier transform point of the obtained signal.

According to the present invention, unlike the sampling frequency or correlation operation frequency of the signal obtained from the satellite navigation receiver, the frequency resolution of the obtained signal can be adjusted to reduce the throughput of the correlation operation, and the Doppler frequency of the desired resolution can be obtained. It works.

In this way, the present invention can obtain the Doppler resolution more precisely than the size of the sampled data, can reduce the size of the memory used for the correlation operation and the throughput of the correlation operation, thereby improving the efficiency of the satellite navigation receiver.

Hereinafter, a signal acquisition apparatus of a satellite navigation receiver according to an embodiment of the present invention will be described with reference to FIG. 1. 1 is a block diagram illustrating a signal acquisition apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the signal acquisition apparatus 10 according to an exemplary embodiment of the present invention may include a sampling module 110, a correlation operator 120, a first memory 130, a Fourier transformer 140, and a power detector ( 150, a second memory 160, and a peak detector 170.

The sampling module 110 samples the received signal and the preset pseudo random noise (PRN) code obtained from the satellite according to the preset signal acquisition frequency, respectively, and includes a sampling unit 111, a carrier removing unit 112, and a down sampling unit. 113, a code generator 114, and an oversampling unit 115. Here, the signal acquisition frequency may be an operation unit of the signal acquisition device 10, and it will be described on the assumption that FIG. 1 is a 0.5 chip unit (2.046 [MHz]).

The sampling unit 111 converts a received signal (that is, a satellite navigation signal) obtained from a GPS satellite into an intermediate frequency (IF) band, and then digitally converts and outputs sampling data. In this case, the sampling unit 111 may receive the received signal converted into the intermediate frequency band and perform only digital conversion to output sampling data.

The carrier removing unit 112 removes the carrier from the sampling data and outputs sampling data from which the carrier is removed.

The down sampling unit 113 down-samples the sampling data from which the carrier is removed to a signal acquisition frequency and outputs block data. That is, if the sampling data is sampled at the sampling frequency of 112 MHz, the down sampling unit 113 merges the sampling frequency of the sampling data by the number divided by the signal acquisition frequency (for example, 112000/2046 = 54.7) to determine the signal acquisition frequency. Output block data.

The code generator 114 generates a predetermined pseudo random noise (PRN) code in units of one chip (for example, 1.023 MHz).

The oversampling unit 115 oversamples the PRN code of one chip unit to the signal acquisition frequency of the signal acquisition device 10. That is, if the signal acquisition frequency is 0.5 chip unit, the oversampling unit 115 oversamples the PRN code twice, and if the signal acquisition frequency is 0.25 chip unit, the oversampling unit 115 oversamples the PRN code 4 times. do.

The correlation calculator 120 receives a block data and an oversampled PRN code in units of a length of 1 ms and performs a correlation operation, and includes a data buffer 121, a code buffer 122, and a correlation unit 123.

The data buffer 121 temporarily stores down-sampled block data in units of 1 ms in length, and the code buffer 122 temporarily stores oversampled PRN code in units of 1 ms in length.

The correlator 123 uses the matched filter or fast fourier transform / inverse fast fourier transform (FFT / IFFT) to block data stored in the data buffer 121 and the PRN code stored in the code buffer 122. By correlating, a correlation sample corresponding to the block data of 1 ms length is output.

The first memory 130 sequentially stores the 1 ms correlation sample outputted from the correlation calculator 120, and transfers the 1 ms correlation sample stored in the Fourier transformer 140 if it corresponds to the operation unit of the Fourier transformer 140. . In this case, the first memory 130 may be a coherent memory.

The Fourier transformer 140 performs zero padding on the correlation sample received from the first memory 130 to change the frequency resolution, and then performs a Fourier transform. The zero padding unit 141 and the Fourier transform unit ( 142).

The zero padding unit 141 changes the frequency resolution of the correlation sample by performing zero padding to correspond to the number of points (N, constant) of the Fourier transform unit 142.

The Fourier transform unit 142 outputs a correlation sample of a frequency band by performing a Four-point Fourier transform on a correlation sample whose frequency resolution is changed.

The power detector 150 calculates an energy value Power of a correlation sample of a frequency band and stores the energy value Power in the second memory 160.

When the peak of the energy value of the correlation sample stored in the second memory 160 exceeds a preset threshold, the peak detector 170 determines that the signal acquisition is successful and detects the Doppler frequency and the code phase of the obtained signal. The second memory 160 may be a non-coherent memory.

 In this case, the threshold value may be set by an experimental value or a simulation result, and the power detector 150 and the peak detector 170 may be configured as one component.

The Doppler frequency and code phase can then be used for earth Doppler estimation, Doppler search range prediction, or code search range prediction.

On the other hand, when the peak detector 170 has a peak value of the energy value of the correlation sample stored in the second memory 160 is smaller than the threshold value, the peak detector 170 determines that the signal acquisition has failed, and the received signal obtained from the satellite and another preset PRN code Perform signal acquisition such as sampling, correlation, and Fourier transform.

Meanwhile, the signal acquisition apparatus 10 may set a plurality of PRN codes by receiving a plurality of PRN codes from satellites or other devices, and in this case, perform a signal acquisition process on the plurality of PRN codes to adjust the Doppler frequency and the code phase. Calculate.

As such, the signal acquisition device of the present invention can adjust the frequency resolution of the acquired signal, unlike the sampling frequency or correlation operation frequency of the signal obtained from the satellite navigation receiver, thereby reducing the throughput of the correlation operation, and the Doppler of the desired resolution. Frequency can be obtained.

Hereinafter, a parameter setting method of the signal acquisition apparatus 10 according to an exemplary embodiment of the present invention will be described with reference to FIG. 2. 2 is a flowchart illustrating a parameter setting method of the signal acquisition apparatus 10 according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the signal acquisition apparatus 10 determines a sampling frequency (S210). Here, the sampling frequency may be a reference frequency for digitally converting a received signal received from a GPS satellite.

Subsequently, the signal acquisition apparatus 10 determines a down sampling frequency corresponding to the signal acquisition frequency (S220). That is, if the signal acquisition frequency is 0.5 chip unit, the signal acquisition apparatus 10 may determine the down sampling frequency as 2.046 MHz in the case of GPS L1 and 20.46 MHz in the case of GPS L5.

The signal acquisition apparatus 10 determines a range of Doppler frequencies to be searched and determines the size of the matched filter accordingly (S230). For example, if the matching filter size is determined to be 128 in GPS L1, the Doppler frequency range is determined to be approximately 16 kHz (# 2046/128).

The signal acquisition apparatus 10 determines a point of Fourier transform (S240), and thus the frequency resolution of the Doppler frequency is determined.

Hereinafter, the process of FIG. 2 will be described, for example, in Table 1 below.

Sampling frequency 50 MHz Down sampling frequency 50 MHz Matched filter size 2500 Doppler Search Range 20 kHz

That is, if each parameter of the signal acquisition apparatus 10 is set as shown in Table 1 through the steps S210 to S230, 20, which is a value obtained by dividing the down sampling frequency by the Doppler search range, is the number and minimum of correlation samples. It becomes a point of Fourier transform, and the point of Fourier transform may be determined to be 20 or more.

That is, if the point of Fourier transform is determined to be 40 in step S240, the frequency resolution of the Doppler frequency is determined to be 500 Hz, and if it is determined to be 200, it may be determined to be 100 Hz.

3 illustrates a calculation process of the Fourier transformer 140 and the peak detector 170 according to an exemplary embodiment of the present invention. 3 is a diagram illustrating a Fourier transform process of the Fourier transformer 140. In FIG. 3, an example in which 20 correlation samples are input to the Fourier transformer 140 and the Fourier transformer 140 performs an N point Fourier transform will be described as an example.

As shown in FIG. 3, the Fourier transformer 140 receives 20 first correlation samples from the first memory 130 (S310).

The Fourier transformer 140 performs N-point Fourier transformation while performing zero padding on the first correlation sample (S320). That is, the Fourier transformer 140 performs (N-20) zero padding on 20 correlation samples, and then performs an N point Fourier transform on the first padded correlation sample.

Next, the power detector 150 calculates an energy value from the N point Fourier transform result (S340), and the peak detector 170 compares the peak and the threshold of the energy value to determine whether the signal acquisition is successful. (S350). At this time, if the signal acquisition apparatus 10 succeeds in acquiring the signal, the signal acquisition apparatus 10 detects the Doppler frequency and the code phase from the acquired signal.

Here, the N point Fourier transform of the signal acquisition device 10, the comparison of the peak and threshold of the energy value, the determination of whether the signal acquisition is successful, and the Doppler frequency and the code phase detection are performed for 20 correlation samples for the same PRN code. Repeatedly performed (S360).

On the other hand, if the signal acquisition apparatus 10 fails to acquire the signal as a result of the determination, the signal acquisition apparatus 10 detects the Doppler frequency and the code phase by performing signal acquisition on another PRN code.

In this way, the present invention can obtain the Doppler resolution more precisely than the size of the sampled data, can reduce the size of the memory used for the correlation operation and the throughput of the correlation operation, thereby improving the efficiency of the satellite navigation receiver.

While the present invention has been described in detail with reference to the accompanying drawings, it is to be understood that the invention is not limited to the above-described embodiments. Those skilled in the art will appreciate that various modifications, Of course, this is possible. Accordingly, the scope of protection of the present invention should not be limited to the above-described embodiments, but should be determined by the description of the following claims.

1 is a block diagram showing a signal acquisition device according to an embodiment of the present invention.

2 is a flowchart illustrating a parameter setting method of a signal acquisition apparatus according to an embodiment of the present invention.

3 is a diagram illustrating a Fourier transform process of a Fourier transformer.

Claims (10)

A sampling module for sampling a signal obtained from a satellite and a predetermined pseudo random noise (PRN) code according to a predetermined signal acquisition frequency; A correlation calculator for correlating the obtained signals with the PRN code; A Fourier transformer for Fourier transforming the frequency resolution of the result of the correlation operation according to a predetermined Fourier transform point; And A peak detector that detects a peak of an energy value from the Fourier transformed result and determines that the signal acquisition is successful when the peak of the energy value is larger than a predetermined threshold value Signal acquisition device comprising a. The method of claim 1, And the sampling module samples each of the obtained signal and a different PRN code. The method of claim 1, wherein the Fourier transformer, And changing the Fourier transform point according to a preset frequency resolution, and performing zero padding on the result of the correlation operation to change the frequency resolution of the result of the correlation operation. The method of claim 1, wherein the sampling module, A down sampling unit for down sampling the acquired signal or the PRN code according to the signal acquisition frequency; And An oversampling unit for oversampling the acquired signal or the PRN code according to the signal acquisition frequency Signal acquisition device comprising a. Sampling a signal obtained from a satellite and a preset pseudo random noise (PRN) code according to a preset signal acquisition frequency; Correlating the obtained signals with the PRN code; Fourier transforming the frequency resolution of the correlation result according to a predetermined Fourier transform point; And Detecting a peak of an energy value from the Fourier transformed result Signal acquisition method comprising a. The method of claim 5, wherein each sampling comprises: Down sampling the acquired signal according to the signal acquisition frequency; And Oversampling the PRN code according to the signal acquisition frequency Signal acquisition method comprising a. The method of claim 5, wherein the Fourier transform step, Determining a frequency resolution of the Doppler frequency; Determining the Fourier transform point according to the determined frequency resolution; Performing the Fourier transform while performing zero padding on the determined Fourier transform point in the correlation result; And a frequency resolution of the result of the correlation is changed according to the number of zero paddings. The method of claim 5, Determining that the signal acquisition is successful when the peak of the energy value is greater than a preset threshold value; And Determining that the signal acquisition fails when the peak of the energy value is less than the threshold value; And if each of the signal acquisition fails, sampling each sample a PRN code different from the acquired signal. The method of claim 8, Detecting the Doppler frequency and the phase code of the acquired signal when the peak of the energy value is greater than the threshold value and determines that the signal is successfully obtained. Signal acquisition method further comprising. Determining a sampling frequency for a signal obtained from a satellite and a PRN code according to the signal acquisition frequency; Determining a size of a matched filter to correlate the obtained signal and the PRN code; Determining a Doppler resolution and a Fourier transform point of the obtained signal Parameter setting method of the signal acquisition device comprising a.

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