KR20190082546A - A method and an apparatus for estimating symbol rate of frequency shift based modulation signals - Google Patents

Abstract

According to some embodiments of the present invention, disclosed is a method for estimating a symbol rate of a frequency shifted digitally modulated signal comprising the steps of: receiving a frequency shifted digitally modulated signal; obtaining in-phase/quadrature (I/Q) data from the frequency shifted digitally modulated signal; estimating a bandwidth of the frequency shifted digitally modulated signal using the obtained I/Q data; oversampling a sampling rate of the obtained I/Q data to a value of at least eight times the estimated bandwidth; and estimating a symbol rate of the frequency shifted digitally modulated signal using the oversampled I/Q data.

Description

[0001] The present invention relates to a method and an apparatus for estimating a symbol rate of a frequency-shifted digital modulated signal,

The present disclosure relates to a method and apparatus for estimating the symbol rate of a frequency-shifted digitally modulated signal.

A blind receiver that detects a received signal in a blind environment without prior information on the received signal and analyzes and / or restores the specification of the signal is used in various fields such as radio wave monitoring and interference signal identification. For example, a blind receiver may be classified into a communication intelligence field for generating information to be transmitted and transmitted in an unknown communication signal, a passive monitoring field for signal surveillance, Software-Defined Radio and Cognitive Radio fields that improve spectral efficiency. In order to demodulate a signal with high quality, a blind receiver used in various fields as described above may require a technique for estimating an accurate symbol rate.

Various embodiments are directed to a method and apparatus for estimating the symbol rate of a frequency-shifted digitally modulated signal. The technical problem to be solved by the present invention is not limited to the above-mentioned technical problems, and other technical problems can be deduced from the following embodiments.

According to an aspect of the present invention, there is provided a method of estimating a symbol rate of a frequency-shifted digital modulation signal according to an aspect, comprising: receiving the frequency-shifted digital modulation signal; Obtaining I / Q (In-phase / Quadrature) data from the frequency shifted digital modulated signal; Estimating a bandwidth of the frequency-shifted digital modulation signal using the obtained I / Q data; Oversampling the sampling rate of the obtained I / Q data to a value of 8 times or more of the estimated bandwidth; And estimating the symbol rate of the frequency shifted digital modulated signal using the oversampled I / Q data.

According to some embodiments, the frequency-shifted digital modulated signal may be a signal modulated by FSK (Frequency-Shift Keying) or MSK (Minimum-Shift Keying) method.

The step of acquiring the I / Q data may include converting the frequency-shifted digital modulation signal, which is a radio frequency (RF) signal, into an intermediate frequency (IF) signal; Obtaining ADC (Analog-Digital Converter) data by performing sampling and quantization on the intermediate frequency signal; And obtaining the I / Q data from the obtained ADC data using a DDC (Digital Down Converter) function.

Estimating the bandwidth comprises: configuring I / Q data frames having a certain length based on the I / Q data; Generating a plurality of instantaneous power spectra by performing Fast Fourier Transform (FFT) on each of the I / Q data frames; Calculating an average power spectrum based on the plurality of instantaneous power spectra; Determining a minimum frequency and a maximum frequency from frequencies corresponding to points where the average power spectrum intersects with a predetermined comparison value; And estimating a difference between the maximum frequency and the minimum frequency as the bandwidth.

On the other hand, the method may further include storing the I / Q data for a time required to estimate the bandwidth of the frequency-shifted digital modulated signal.

Estimating the symbol rate comprises estimating an instantaneous symbol rate of the frequency-shifted digital modulated signal using the oversampled I / Q data; Estimating the instantaneous symbol rate by repeating a predetermined number of times to obtain a plurality of instantaneous symbol rates; Extracting a mode from the plurality of instantaneous symbol rates; And determining the extracted mode as the symbol rate of the frequency shifted digital modulated signal.

The step of estimating the symbol rate may further include determining the largest value among the plurality of modes as the symbol rate of the frequency-shifted digital modulated signal when the extracted mode values are plural.

, 상기 주파수 인덱스 지점을 m이라고 할 때, 다음과 같은 수학식

에 따라 상기 순시 심볼율

를 결정하는 단계를 포함할 수 있다.Estimating the instantaneous symbol rate comprises: constructing I / Q data frames having a predetermined length based on the I / Q data; Normalizing the I / Q data frames; Calculating an instantaneous frequency from the normalized I / Q data frames; Calculating a magnitude spectrum of the instantaneous frequency based on a result of fast Fourier transform having a length N with respect to the calculated instantaneous frequency; Searching for a frequency index point having a maximum magnitude value in a positive frequency region of the calculated magnitude spectrum; And a final sampling rate of the I / Q data

, And the frequency index point is m, the following equation

The instantaneous symbol rate

Based on the result of the determination.

Wherein the calculating the instantaneous frequency comprises: calculating instantaneous phases by performing a four-quadrant inverse tangent operation on the normalized I / Q data frames; Performing moving average filtering on the calculated instantaneous phases; And calculating the instantaneous frequency from a difference between consecutive ones of the instantaneous phases in which the moving average filtering is performed.

Wherein the step of calculating the magnitude spectrum of the instantaneous frequency comprises: performing fast Fourier transform of length N with respect to the calculated instantaneous frequency; Shifting the frequency index axis such that a zero frequency component is centered in the fast Fourier transformed result; And determining the absolute value of the fast Fourier transformed result of the frequency index axis as the magnitude spectrum of the instantaneous frequency.

Further, a computer-readable recording medium according to another aspect may include a recording medium having recorded thereon one or more programs including instructions for executing the above-described method.

According to another aspect of the present invention, there is provided an apparatus for estimating a symbol rate of a frequency-shifted digitally modulated signal, comprising: a high-frequency receiver for receiving the frequency-shifted digitally modulated signal; A baseband converter for obtaining I / Q data from the frequency shifted digitally modulated signal; A bandwidth estimator for estimating a bandwidth of the frequency-shifted digital modulation signal using the obtained I / Q data; A resampler for oversampling the sampling rate of the obtained I / Q data to a value of 8 times or more of the estimated bandwidth; And a symbol rate estimator for estimating the symbol rate of the frequency shifted digital modulation signal using the oversampled I / Q data.

The present disclosure can provide a method and apparatus for estimating the symbol rate of a frequency-shifted digitally modulated signal. Specifically, the method and apparatus according to the present disclosure estimate the bandwidth of a frequency-shifted digital modulated signal using I / Q data obtained from a frequency-shifted digital modulated signal and estimate the sampling rate of the I / Q data to 8 The sampling rate of the I / Q data can be made to be four times or more the symbol rate of the frequency shift digital modulation signal. As the sampling rate of the I / Q data is more than four times the symbol rate of the frequency-shifted digital modulation signal, the cyclostationarity characteristic can be obtained. As a result, the frequency index search having the maximum size value in the magnitude spectrum of the I / A sufficient characteristic can be secured.

The method and apparatus according to the present disclosure may further include estimating an instantaneous symbol rate by repeating a predetermined number of times to obtain a plurality of instantaneous symbol rates and setting a mode among the plurality of instantaneous symbol rates as a final symbol of a frequency- The accuracy of the symbol rate estimation can be improved by using a statistical method determined by the rate.

1 is a block diagram showing a configuration of a symbol rate estimation apparatus according to some embodiments.
2 is a flowchart illustrating a method for estimating a symbol rate by a symbol rate estimator according to some embodiments.
3 is a diagram illustrating an example of a magnitude spectrum for an instantaneous frequency according to some embodiments.
4 is a diagram showing simulation results of a symbol rate estimation apparatus according to some embodiments.
5 is a flow chart illustrating a method for estimating the symbol rate of a frequency-shifted digitally modulated signal according to some embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the following description is intended to illustrate the embodiments and not to limit or limit the scope of the invention. Those skilled in the art can easily deduce from the detailed description and examples that the scope of the present invention falls within the scope of the right.

As used herein, the terms " comprising " or " comprising " and the like should not be construed as necessarily including the various elements or steps described in the specification, May not be included, or may be interpreted to include additional components or steps.

As used herein, the terminology used herein is intended to encompass all commonly used generic terms that may be considered while considering the functionality of the present invention, but this may vary depending upon the intent or circumstance of the skilled artisan, the emergence of new technology, and the like. Also, in certain cases, there may be a term selected arbitrarily by the applicant, in which case the meaning thereof will be described in detail in the description of the corresponding invention. Therefore, the term used in the present invention should be defined based on the meaning of the term, not on the name of a simple term, but on the entire contents of the present invention.

The embodiments are directed to a method and apparatus for estimating the symbol rate of a frequency-shifted digital modulated signal, and a detailed description thereof will be omitted with respect to matters widely known to those skilled in the art to which the following embodiments belong .

1 is a block diagram showing a configuration of a symbol rate estimation apparatus according to some embodiments.

The symbol rate estimation apparatus 10 may be an apparatus for estimating a symbol rate of a frequency-shifted digital modulation signal received in a blind environment in which there is no prior information such as a bandwidth, a frequency shift, a tone interval, a signal specification of a frequency, For example, the symbol rate estimation apparatus 10 may be included in a blind receiver.

1, the symbol rate estimation apparatus 10 includes a high frequency receiver 110, an analog-to-digital converter (ADC) 120, a baseband converter 130, a bandwidth estimator 140, a delay buffer 150, A resampler 160 and a symbol rate estimator 170. [ Meanwhile, the symbol rate estimation apparatus 10 shown in FIG. 1 only shows the configurations related to the present embodiment. Therefore, it will be understood by those skilled in the art that other general components other than the components shown in FIG. 1 may be further included in the symbol rate estimation apparatus 10.

For example, the symbol rate estimation apparatus 10 may further include a memory (not shown). The memory is hardware for storing various data to be processed in the symbol rate estimation apparatus 10. For example, the memory may store data processed in the symbol rate estimation apparatus 10 and data to be processed. In addition, the memory may store applications, drivers, and the like to be driven by the symbol rate estimation apparatus 10. [

The memory may be a random access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM) such as a dynamic random access memory (DRAM), a static random access memory (SRAM) Ray or other optical disk storage, a hard disk drive (HDD), a solid state drive (SSD), or flash memory and further includes an external storage device that can be accessed by the symbol rate estimation device 10 .

The high-frequency receiver 110 may receive a frequency-shifted digital modulated signal. The frequency-shifted digital modulated signal may be a signal modulated by FSK (Frequency-Shift Keying) or MSK (Minimum-Shift Keying) method. When a signal to be transmitted such as an image or a voice is transmitted in a carrier wave, a method of containing a digital signal in a carrier wave may be an FSK or MSK method.

The high-frequency receiver 110 may convert a frequency-shifted digital modulated signal, which is a radio frequency (RF) signal, into an intermediate frequency (IF) signal.

The ADC 120 can acquire ADC (Analog-Digital Converter) data by performing sampling and quantization on the intermediate frequency signal.

The baseband converter 130 may obtain I / Q (In-phase / Quadrature) data from ADC data obtained by using a DDC (Digital Down Converter) function. The I / Q data may include data corresponding to the I channel and data corresponding to the Q channel.

Meanwhile, the bandwidth estimator 140 may estimate the bandwidth of the frequency-shifted digital modulated signal using the I / Q data. The bandwidth estimator 140 constructs I / Q data frames having a predetermined length based on the I / Q data and performs Fast Fourier Transform (FFT) on each of the I / Q data frames, Instantaneous power spectra can be generated.

The bandwidth estimator 140 may calculate the average power spectrum based on the plurality of instantaneous power spectra and determine the minimum frequency and the maximum frequency from the frequencies corresponding to the points where the average power spectrum intersects the predetermined comparison value . Also, the bandwidth estimator 140 may estimate the difference between the maximum frequency and the minimum frequency as the bandwidth of the frequency-shifted digital modulation signal. The bandwidth estimator 140 may deliver the estimated bandwidth to the resampler 160. [

Meanwhile, the delay buffer 150 may store and delay the I / Q data for a time required to estimate the bandwidth of the frequency-shifted digital modulation signal. Accordingly, the I / Q data and the estimated bandwidth can be transmitted to the resampler 160 at the same time.

The resampler 160 may oversamplify the sampling rate of the obtained I / Q data to a value of 8 times or more of the estimated bandwidth. Since the sampling rate of the I / Q data is oversampled to a value 8 times or more of the estimated bandwidth because the bandwidth of the frequency-shifted digital modulation signal is larger than the symbol rate, the sampling rate of the I / Of the symbol rate. As the sampling rate of the I / Q data is more than four times the symbol rate of the frequency-shifted digital modulation signal, the cyclostationarity characteristic can be obtained. As a result, the frequency index search having the maximum size value in the magnitude spectrum of the I / A sufficient characteristic can be secured.

Meanwhile, the numeral 8 is merely an example, but is not limited thereto. For example, the resampler 160 may oversample the sampling rate of I / Q data by any suitable multiple such that the sampling rate of the I / Q data is at least four times the symbol rate of the frequency-shifted digital modulation signal have.

The symbol rate estimator 170 may estimate the symbol rate of the frequency-shifted digital modulated signal using the oversampled I / Q data. Hereinafter, a method for estimating the symbol rate of the frequency-shifted digital modulation signal will be described in detail with reference to FIG.

2 is a flowchart illustrating a method for estimating a symbol rate by a symbol rate estimator according to some embodiments.

In step 210, the symbol rate estimator 170 may construct I / Q data frames with a certain length based on the I / Q data and normalize the configured I / Q data frames. For example, the symbol rate estimator 170 may collect I / Q data and construct I / Q data frames of length N based on the collected I / Q data.

The symbol rate estimator 170 may normalize the I / Q data frames by calculating the maximum value among the configured I / Q data frames and dividing the values included in the I / Q data frame by the calculated maximum value.

을 계산할 수 있다.In step 220, the symbol rate estimator 170 may calculate the instantaneous phase using the normalized I / Q data frames. The symbol rate estimator 170 performs four-quadrant inverse tangent operations on the normalized I / Q data frames according to Equation (1) to obtain instantaneous phases

Can be calculated.

의 결과값은

범위이고,

및

은 각각 I 데이터 및 Q 데이터를 의미하고, n은 시간 인덱스일 수 있다.In Equation (1)

The result of

Range,

And

Respectively denote I data and Q data, and n may be a time index.

에 대해

를 기준으로 언랩(Unwrap) 연산을 수행함으로써 연속된 순시위상들인

의 천이를 최소화시킬 수 있다.The symbol rate estimator 170 estimates the instantaneous phases calculated by Equation (1)

About

By performing an unwrap operation on the basis of

Can be minimized.

In step 230, the symbol rate estimator 170 may perform moving average filtering on the calculated instantaneous phases. For example, the symbol rate estimator 170 may obtain a smoothing effect by performing moving average filtering with a window size W for the calculated instantaneous phases. The moving average filtering can be performed by the following Equation (2).

In step 240, the symbol rate estimator 170 may calculate the instantaneous frequency from the difference between successive ones of the instantaneous phases for which moving average filtering has been performed. In the process of calculating the instantaneous frequency, the initial value of the instantaneous phases may be set to zero.

In step 250, the symbol rate estimator 170 may calculate the magnitude spectrum of the instantaneous frequency based on the result of performing fast Fourier transform of length N with respect to the calculated instantaneous frequency.

Specifically, the symbol rate estimator 170 may perform fast Fourier transform with length N for the calculated instantaneous frequency and move the frequency index axis such that the zero frequency component is located at the center in the fast Fourier transformed result. Also, the symbol rate estimator 170 may determine the absolute value of the fast Fourier transformed result in which the frequency index axis is shifted, as the magnitude spectrum of the instantaneous frequency. Hereinafter, an example of a magnitude spectrum with respect to an instantaneous frequency will be described with reference to FIG.

3 is a diagram illustrating an example of a magnitude spectrum for an instantaneous frequency according to some embodiments. Referring to FIG. 3, an example of the result of calculating the magnitude spectrum for a 4-FSK frequency-shifted digitally modulated signal with a symbol rate of 10 kHz is shown in the symbol rate estimator 170. In this example, the length N of the FFT is 4096 and the final sampling rate of the used I / Q data is 80 ksps.

Returning to FIG. 2, at step 260, the symbol rate estimator 170 may estimate the instantaneous symbol rate of the frequency-shifted digital modulated signal. In particular, the symbol rate estimator 170 may search for a frequency index point having a maximum magnitude value in the positive frequency range of the calculated magnitude spectrum. On the other hand, the zero frequency component may be excluded in the positive frequency region.

를 결정할 수 있다.The symbol rate estimator 170 calculates an instantaneous symbol rate

Can be determined.

는 I/Q 데이터의 최종 샘플링율을 의미하고, m은 최대 크기 값을 갖는 주파수 인덱스 지점을 의미하며, N은 순시주파수에 대해 수행된 고속푸리에변환의 길이를 의미할 수 있다.In Equation 3,

Denotes a final sampling rate of I / Q data, m denotes a frequency index point having a maximum magnitude value, and N denotes a length of a fast Fourier transform performed on the instantaneous frequency.

Meanwhile, in step 270, the symbol rate estimator 170 may determine whether the instantaneous symbol rate estimation operation described above is repeated. The symbol rate estimator 170 may obtain a plurality of instantaneous symbol rates by repeating the instantaneous symbol rate estimation operation described above a predetermined number of times. For example, the symbol rate estimator 170 may repeat the instantaneous symbol rate estimation operation L times to obtain L instantaneous symbol rates. The symbol rate estimator 170 may again perform step 210 to obtain a new instantaneous symbol rate if the instantaneous symbol rate estimation operation is not repeated L times. The symbol rate estimator 170 may perform step 280 if the instantaneous symbol rate estimation operation is repeated L times.

At step 280, the symbol rate estimator 170 may estimate the final symbol rate based on the plurality of instantaneous symbol rates. In particular, the symbol rate estimator 170 may extract a mode from a plurality of instantaneous symbol rates. Mode extraction can be performed by a mode operation. The symbol rate estimator 170 may determine the extracted mode as the symbol rate of the frequency shifted digital modulation signal. On the other hand, when there are a plurality of extracted modes, the symbol rate estimator 170 may determine the largest value among the plurality of modes as the symbol rate of the frequency-shifted digital modulation signal.

As described above, the symbol rate estimator 170 obtains a plurality of instantaneous symbol rates by repeating the step of estimating the instantaneous symbol rate a predetermined number of times, and calculates a mode of the plurality of instantaneous symbol rates as a frequency shift digital modulated signal The accuracy of the symbol rate estimation can be improved by using a statistical method that determines the symbol rate. Hereinafter, the effect of improving the accuracy of the symbol rate estimation apparatus 10 according to some embodiments of the present disclosure will be described in detail with reference to FIG.

4 is a diagram showing simulation results of a symbol rate estimation apparatus according to some embodiments.

Referring to FIG. 4, when the frequency shift digital modulation method is 2/4/8-FSK and MSK, the symbol rate of the actual frequency shift digital modulation signal is 10 kHz, the final sampling rate of I / Q data is 80 kps, The symbol rate estimation mean error rate of the symbol rate estimation apparatus 10 is shown when the frame length N of the Q data, the window size W, and the instantaneous symbol rate estimate times L are 4096, 5, and 10, respectively. Referring to FIG. 4, it can be seen that the symbol rate estimation average error rate is considerably low under conditions of SNR (Signal-to-Noise Ratio) of 6 dB or more. As a result, the symbols of the symbol rate estimation apparatus 10 according to some embodiments of the present disclosure The accuracy of the estimation method is considerably high.

1, the baseband converter 130, the bandwidth estimator 140, the delay buffer 150, the resampler 160, and the symbol rate estimator 170 included in the symbol rate estimation apparatus 10 may be one or more, And may be implemented by a plurality of processors. For example, the baseband converter 130, the bandwidth estimator 140, the delay buffer 150, the resampler 160, and the symbol rate estimator 170 may be implemented as an array of multiple logic gates, The microprocessor and the program that can be executed in the microprocessor may be implemented as a combination of stored memories.

5 is a flow chart illustrating a method for estimating the symbol rate of a frequency-shifted digitally modulated signal according to some embodiments.

Referring to FIG. 5, a method of estimating a symbol rate of a frequency-shifted digital modulated signal is comprised of steps that are processed in a time-series manner in the symbol rate estimation apparatus 10 shown in FIG. Therefore, even if omitted from the following description, it can be understood that the above description of the symbol rate estimation apparatus 10 of FIG. 1 also applies to the method of estimating the symbol rate of the frequency-shifted digital modulation signal of FIG.

In step 510, the symbol rate estimation device may receive a frequency shifted digital modulation signal. The frequency-shifted digital modulated signal may be a signal modulated by the FSK or MSK scheme.

In step 520, the symbol rate estimation device may obtain I / Q data from the frequency shifted digital modulation signal. Specifically, the symbol rate estimation apparatus can acquire ADC data by converting a frequency-shifted digital modulation signal, which is a radio frequency signal, into an intermediate frequency signal, and performing sampling and quantization on the intermediate frequency signal. The symbol rate estimator may obtain I / Q data from the ADC data obtained using the DDC function.

At step 530, the symbol rate estimation device may estimate the bandwidth of the frequency-shifted digital modulated signal using the acquired I / Q data. Specifically, the symbol rate estimation apparatus generates a plurality of instantaneous power spectrums by constructing I / Q data frames having a predetermined length based on I / Q data, and performing fast Fourier transform on each of I / Q data frames can do.

Further, the symbol rate estimation apparatus calculates the average power spectrum based on the plurality of instantaneous power spectra, determines the minimum frequency and the maximum frequency from the frequencies corresponding to the points where the average power spectrum intersects with the predetermined comparison value , The difference between the maximum frequency and the minimum frequency can be estimated as the bandwidth of the frequency-shifted digital modulation signal.

On the other hand, the symbol rate estimator may store and delay I / Q data for a time required to estimate the bandwidth of the frequency-shifted digital modulated signal.

At step 540, the symbol rate estimation device may oversample the sampling rate of the acquired I / Q data to a value that is at least eight times the estimated bandwidth. Since the sampling rate of the I / Q data is oversampled to a value 8 times or more of the estimated bandwidth because the bandwidth of the frequency-shifted digital modulation signal is larger than the symbol rate, the sampling rate of the I / Of the symbol rate. As the sampling rate of the I / Q data is more than four times the symbol rate of the frequency-shifted digital modulation signal, the cyclostationarity characteristic can be obtained. As a result, the frequency index search having the maximum size value in the magnitude spectrum of the I / A sufficient characteristic can be secured.

In step 550, the symbol rate estimation device may estimate the symbol rate of the frequency-shifted digital modulated signal using the oversampled I / Q data.

Specifically, the symbol rate estimation apparatus can estimate the instantaneous symbol rate of the frequency-shifted digital modulation signal using the oversampled I / Q data. The symbol rate estimation apparatus can construct I / Q data frames having a certain length based on I / Q data, normalize I / Q data frames, and calculate an instantaneous frequency from normalized I / Q data frames .

Further, the symbol rate estimation apparatus calculates instantaneous phases by performing a quadrant inverse tangent operation according to Equation (1) described above on the normalized I / Q data frames, and calculates the instantaneous phases using Equation (2) To perform a moving average filtering. The symbol rate estimation apparatus can calculate the instantaneous frequency from the difference between consecutive values among the instantaneous phases in which the moving average filtering is performed.

The symbol rate estimation apparatus can calculate the magnitude spectrum of the instantaneous frequency based on the result of performing fast Fourier transform with length N for the calculated instantaneous frequency. Specifically, the symbol rate estimator may perform fast Fourier transform with length N for the calculated instantaneous frequency, and move the frequency index axis such that the zero frequency component is centered in the fast Fourier transformed result. The symbol rate estimating apparatus can determine the absolute value of the fast Fourier transformed result in which the frequency index axis is shifted as the magnitude spectrum of the instantaneous frequency.

, 주파수 인덱스 지점을 m이라고 할 때, 앞서 설명한 수학식 3에 따라 순시 심볼율

를 결정할 수 있다. Further, the symbol rate estimation apparatus searches for a frequency index point having a maximum magnitude value in the positive frequency region of the calculated magnitude spectrum, and calculates a final sampling rate of I / Q data

, And the frequency index point is m, the instantaneous symbol rate

Can be determined.

The symbol rate estimation apparatus repeats the step of estimating the instantaneous symbol rate by a predetermined number of times to obtain a plurality of instantaneous symbol rates, extracts a mode from a plurality of instantaneous symbol rates, and outputs the extracted mode to a frequency- The symbol rate can be determined. The symbol rate estimation apparatus may determine the largest value among the plurality of modes when the extracted mode is a plurality of symbols, as the symbol rate of the frequency-shifted digital modulation signal. Thus, the symbol rate estimating apparatus can improve the symbol rate estimation accuracy by using a statistical method.

On the other hand, a method for estimating the symbol rate of a frequency-shifted digital modulation signal may be recorded in a computer-readable recording medium on which one or more programs including instructions for executing the method are recorded. Examples of the computer-readable recording medium include magnetic media such as a hard disk, a floppy disk and a magnetic tape, optical media such as CD-ROM and DVD, optical disks such as a floppy disk, And hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, .

Claims (12)

A method for estimating a symbol rate of a frequency-shifted digital modulation signal,
Receiving the frequency shifted digitally modulated signal;
Obtaining I / Q (In-phase / Quadrature) data from the frequency shifted digital modulated signal;
Estimating a bandwidth of the frequency-shifted digital modulation signal using the obtained I / Q data;
Oversampling the sampling rate of the obtained I / Q data to a value of 8 times or more of the estimated bandwidth; And
And estimating the symbol rate of the frequency-shifted digitally modulated signal using the oversampled I / Q data. The method according to claim 1,
Wherein the frequency shifted digital modulated signal is a signal modulated by a Frequency Shift Keying (FSK) or a Minimum-Shift Keying (MSK) scheme. The method according to claim 1,
The step of acquiring the I / Q data comprises:
Converting the frequency-shifted digital modulated signal into an intermediate frequency (IF) signal, which is a radio frequency (RF) signal;
Obtaining ADC (Analog-Digital Converter) data by performing sampling and quantization on the intermediate frequency signal; And
And obtaining the I / Q data from the obtained ADC data using a DDC (Digital Down Converter) function. The method according to claim 1,
Estimating the bandwidth comprises:
Configuring I / Q data frames having a predetermined length based on the I / Q data;
Generating a plurality of instantaneous power spectra by performing Fast Fourier Transform (FFT) on each of the I / Q data frames;
Calculating an average power spectrum based on the plurality of instantaneous power spectra;
Determining a minimum frequency and a maximum frequency from frequencies corresponding to points where the average power spectrum intersects with a predetermined comparison value; And
Estimating a difference between the maximum frequency and the minimum frequency as the bandwidth. The method according to claim 1,
The method comprises:
Further comprising storing the I / Q data for a time required to estimate the bandwidth of the frequency shifted digital modulated signal. The method according to claim 1,
Wherein estimating the symbol rate comprises:
Estimating an instantaneous symbol rate of the frequency-shifted digital modulated signal using the oversampled I / Q data;
Estimating the instantaneous symbol rate by repeating a predetermined number of times to obtain a plurality of instantaneous symbol rates;
Extracting a mode from the plurality of instantaneous symbol rates; And
And determining the extracted mode as the symbol rate of the frequency shifted digital modulated signal. The method according to claim 6,
Wherein estimating the symbol rate comprises:
Further comprising determining the largest of the plurality of modes as the symbol rate of the frequency shifted digital modulated signal when there is a plurality of extracted modes. The method according to claim 6,
Estimating the instantaneous symbol rate,
Configuring I / Q data frames having a predetermined length based on the I / Q data;
Normalizing the I / Q data frames;
Calculating an instantaneous frequency from the normalized I / Q data frames;
Calculating a magnitude spectrum of the instantaneous frequency based on a result of fast Fourier transform having a length N with respect to the calculated instantaneous frequency;
Searching for a frequency index point having a maximum magnitude value in a positive frequency region of the calculated magnitude spectrum; And
The final sampling rate of the I / Q data is

, And the frequency index point is m, the following equation

The instantaneous symbol rate

The method comprising the steps of: 9. The method of claim 8,
Wherein the step of calculating the instantaneous frequency comprises:
Calculating instantaneous phases by performing a four-quadrant inverse tangent operation on the normalized I / Q data frames;
Performing moving average filtering on the calculated instantaneous phases; And
And calculating the instantaneous frequency from a difference between consecutive ones of the instantaneous phases in which the moving average filtering is performed. 9. The method of claim 8,
Wherein the step of calculating the magnitude spectrum of the instantaneous frequency comprises:
Performing fast Fourier transform of length N with respect to the calculated instantaneous frequency;
Shifting the frequency index axis such that a zero frequency component is centered in the fast Fourier transformed result; And
And determining the absolute value of the fast Fourier transformed result of the frequency index axis as the magnitude spectrum of the instantaneous frequency. A computer-readable recording medium having recorded thereon one or more programs comprising instructions for executing the method of claim 1. A computer- An apparatus for estimating a symbol rate of a frequency-shifted digital modulation signal,
A high frequency receiver for receiving the frequency shifted digitally modulated signal;
A baseband converter for obtaining I / Q data from the frequency shifted digitally modulated signal;
A bandwidth estimator for estimating a bandwidth of the frequency-shifted digital modulation signal using the obtained I / Q data;
A resampler for oversampling the sampling rate of the obtained I / Q data to a value of 8 times or more of the estimated bandwidth; And
And a symbol rate estimator for estimating the symbol rate of the frequency shifted digital modulated signal using the oversampled I / Q data.

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