High-frequency signal acquisition and spectrum analysis system and method based on AD9361 chip

Abstract

The invention discloses a high-frequency signal acquisition and spectrum analysis system based on an AD9361 chip, and relates to the technical field of signal measurement and spectrum analysis, and the system comprises the steps: firstly, selecting an antenna for receiving a radio signal in an environment; then, according to the band-pass range, a band-pass filter is selected to filter out signals outside a pass band, and signals within the pass band range are reserved; furthermore, the band-pass signal passes through a power amplifier with the gain of 30bBm, so that the power of the band-pass signal is improved. Finally, an AD9361 chip is developed, analog-to-digital conversion and down-conversion of input signals are achieved, and baseband signals are obtained. The envelope spectrum of the baseband signal is taken out, and the positive peak value and the negative peak value of the baseband signal can be obtained. And solving the weighted effective value average power of the baseband signal. The invention further discloses a high-frequency signal acquisition and spectrum analysis method based on the AD9361 chip, and the high-frequency signal acquisition and spectrum analysis method based on the AD9361 chip has the advantages of being portable and flexible and has the advantages of being low in cost, easy to implement, good in real-time performance, high in universality and easy to operate.

Description

Technical Field

[0001] The invention relates to the technical field of signal measurement and spectrum analysis, in particular to a high-frequency signal acquisition and spectrum analysis system and method based on an AD9361 chip. Background Art

[0002] In industrial control, environmental spectrum analysis can help us better understand the source, frequency distribution and intensity distribution of sounds in the environment, thus helping us evaluate the noise level, environmental quality and ecological balance of the environment. At the same time, environmental spectrum analysis can also be used to monitor the pollution and noise sources in the environment, helping us find the problems in the environment and the direction of improvement. By analyzing the environmental spectrum, we can provide a scientific basis for environmental protection and management, helping us better protect the environment and ecosystem.

[0003] At present, the existing spectrum analysis solutions mainly use dedicated spectrum analyzers to convert the time domain signal of the input signal into a frequency domain signal by performing Fourier transform or fast Fourier transform on the input signal, thereby obtaining the spectrum characteristics of the signal. However, in the existing spectrum analysis solutions, the singleness of the equipment and the limitations of the measurement environment have led to a series of problems in spectrum analysis, such as high cost and low measurement accuracy. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a high-frequency signal acquisition and spectrum analysis system and method based on the AD9361 chip. The system is easy to operate, low in cost, and suitable for the diverse needs of environmental spectrum analysis; it has a series of advantages such as high precision, low cost, and portable equipment.

[0005] The present invention adopts the following technical solutions to solve the above technical problems:

[0006] According to the present invention, a high-frequency signal acquisition and spectrum analysis system based on AD9361 chip includes a Yagi antenna, a bandpass filter, a power amplifier, an AD9361 module and a terminal, wherein:

[0007] A Yagi antenna is used to output the collected radio signals in the environment to a bandpass filter;

[0008] The bandpass filter is used to isolate and filter out the signal outside the target frequency band according to the frequency characteristics of the radio signal, obtain the isolated and filtered radio signal and output it to the power amplifier;

[0009] A power amplifier is used to pre-process the radio signal after isolation and filtering, obtain the pre-processed radio signal and output it to the AD9361 module;

[0010] AD9361 module, used to perform AD sampling, automatic gain control, DC offset correction, orthogonal correction and digital filtering on the pre-processed radio signal, obtain the baseband digital signal and output it to the terminal;

[0011] The terminal is used to calculate the weighted effective value average power of the baseband digital signal according to the amplitude of the baseband digital signal, draw the weighted effective value average power curve of the baseband digital signal according to the weighted effective value average power of the baseband digital signal, and further use it for spectrum analysis of the digital baseband signal.

[0012] As a further optimization scheme of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip described in the present invention, a feeder is used to connect the output end of the Yagi antenna and the input end of the bandpass filter.

[0013] As a further optimization solution of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip described in the present invention, the AD9361 has a built-in SD memory card for mounting the Linux operating system and driving the AD9361 module.

[0014] As a further optimization scheme of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip described in the present invention, the weighted effective value average power of the baseband digital signal is obtained by the following method, which is as follows:

[0015] First, find the amplitude of the complex baseband digital signal:

[0016]

[0017] in, is the real part of the baseband digital signal collected at the mth sampling frequency, is the imaginary part of the baseband digital signal collected at the mth sampling frequency, y m is the amplitude of the complex baseband digital signal at the mth sampling frequency, where m ranges from 1 to n, n is the total number of sampling frequencies, and j is the imaginary unit in the complex number;

[0018] Then, the amplitude of the complex baseband digital signal is subjected to variational mode decomposition (VMD) to obtain the corresponding analytical signal.

[0019]

[0020] in, is the in-phase component, are orthogonal components, H{·} is the Hilbert transform;

[0021] At the mth sampling frequency, the analytical signal The instantaneous amplitude a m , Phase and frequency f m Features:

[0022]

[0023] in, When the sampling frequency is m, the analytical signal The phase in When the sampling frequency is m-1, the analytical signal The phase in; Δm is the time interval, that is, the time difference between two adjacent sampling points;

[0024] Obtain the weighted effective average power of the complex baseband digital signal after frequency characteristic weighting:

[0025]

[0026] Wherein, P is the weighted effective value average power of the baseband digital signal;

[0027] Then, convert the unit of weighted effective average power obtained by formula (6) into dBm:

[0028]

[0029] Among them, P W is the weighted effective average power in dBm;

[0030] The P obtained by formula (7) W Subtract the thermal noise power and add the system noise factor to get the final weighted effective value average power P f :

[0031] P f =P W -174+N f (8)

[0032] Among them, N f is the total noise factor of the radio signal acquisition system.

[0033] A method for high-frequency signal acquisition and spectrum analysis system based on AD9361 chip, comprising the following steps:

[0034] Step S1, according to actual measurement requirements, adjusting the pitch angle and azimuth angle of the Yagi antenna to collect radio signals at a preset angle in the environment;

[0035] Step S2: according to the frequency characteristics of the collected radio signal, a bandpass filter is used to suppress the amplitude of the signal outside the passband range, so as to isolate and filter out the signal outside the target frequency band, and obtain the radio signal after isolation and filtering; further, a power amplifier that conforms to the frequency characteristics of the high-frequency signal is used to increase the power of the radio signal after isolation and filtering, and obtain the preprocessed radio signal;

[0036] Step S3, developing an AD9361 module for collecting and storing signals, burning a Linux operating system into an SD memory card in the AD9361 module, and using the burned Linux operating system to drive the AD sampling unit, automatic gain control module, DC offset correction module, orthogonal correction module and digital filter module in the AD9361 module;

[0037] Step S4, install data processing software and libraries in the Linux system of the SD memory card, compile the open source libraries gr-iio and pyadi-iio; set the sampling rate, sampling rate, sampling interval and sampling frequency of signal reception, scan the target frequency band of interest, and use the gr-iio and pyadi-iio library functions to digitize and down-convert the pre-processed radio signal to obtain a baseband digital signal;

[0038] Step S5, reading the baseband digital signal, calculating the weighted effective value average power of the baseband digital signal according to the amplitude of the baseband digital signal, drawing the weighted effective value average power curve of the baseband digital signal according to the weighted effective value average power of the baseband digital signal, and further using it for spectrum analysis of the digital baseband signal.

[0039] As a further optimization scheme of the method of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip described in the present invention, the steps of acquiring the radio signal at a preset angle in the environment are as follows:

[0040] A coaxial cable with an impedance of 50 ohms is used as a feeder to connect a Yagi antenna with a beam radiation angle of 45 degrees. The Yagi antenna includes a first active vibrator with a length of 80 cm and a width of 10 cm, a second active vibrator with a length of 30 cm and a width of 10 cm, two first to second reflectors with a width of 30 cm and a length of 30 cm, and six first to sixth directors with a length of 20 cm.

[0041] The azimuth angle of the antenna is adjusted according to a fixed increment to obtain a radio signal in the target frequency band with an azimuth of 0° to 360° when the elevation angle is fixed.

[0042] As a further optimization scheme of the method of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip described in the present invention, the parameters of the bandpass filter and the power amplifier are as follows:

[0043] The bandpass range of the bandpass filter is 240MHz to 280MHz, and the transition band of the bandpass filter is 235MHz to 240MHz and 280MHz to 285MHz;

[0044] The power amplifier has a frequency selection range of 20MHz to 3.5GHz and a noise figure of less than or equal to 0.4dBm.

[0045] As a further optimization scheme of the method of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip described in the present invention, the weighted effective value average power of the baseband digital signal is as follows:

[0046] First, find the amplitude of the complex baseband digital signal:

[0047]

[0048] in, is the real part of the baseband digital signal collected at the mth sampling frequency, is the imaginary part of the baseband digital signal collected at the mth sampling frequency, y m is the amplitude of the complex baseband digital signal at the mth sampling frequency, where m ranges from 1 to n, n is the total number of sampling frequencies, and j is the imaginary unit in the complex number;

[0049] Then, the amplitude of the complex baseband digital signal is subjected to variational mode decomposition (VMD) to obtain the corresponding analytical signal.

[0050]

[0051] in, is the in-phase component, are orthogonal components, H{·} is the Hilbert transform;

[0052] At the mth sampling frequency, the analytical signal The instantaneous amplitude a m , Phase and frequency f m Features:

[0053]

[0054]

[0055] in, When the sampling frequency is m, the analytical signal The phase in When the sampling frequency is m-1, the analytical signal The phase in; Δm is the time interval, that is, the time difference between two adjacent sampling points;

[0056] Obtain the weighted effective average power of the complex baseband digital signal after frequency characteristic weighting:

[0057]

[0058] Wherein, P is the weighted effective value average power of the baseband digital signal;

[0059] Then, convert the unit of weighted effective average power obtained by formula (14) into dBm:

[0060]

[0061] Among them, P W is the weighted effective average power in dBm;

[0062] The P obtained by formula (15) W Subtract the thermal noise power and add the system noise factor to get the final weighted effective value average power P f :

[0063] P f =P W -174+N f (16)

[0064] Among them, N f is the total noise factor of the radio signal acquisition system.

[0065] As a further optimization scheme of the method of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip described in the present invention, a weighted effective value average power curve of the baseband digital signal is drawn, and further used for spectrum analysis of the digital baseband signal; it means: by drawing P f The curve that changes with frequency f performs spectrum analysis on the collected radio signal.

[0066] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0067] (1) In actual measurement, the present invention records the effective value average power of the signal with high accuracy and the result is reliable;

[0068] (2) The present invention can accurately record and calculate the effective value average power of the signal at different azimuth angles, and has good azimuth resolution capability;

[0069] (3) The present invention can accurately complete signal acquisition and spectrum analysis at the same measurement angle and in different time periods, and obtain a true and reliable average power curve with a high level of accuracy;

[0070] (4) This system is easy to operate, low-cost, and suitable for the diverse needs of environmental spectrum analysis; it has a series of advantages such as high accuracy, low cost, and portable equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 The following are the physical pictures of the high-frequency signal acquisition system based on the AD9361 chip and the physical pictures of each module; (a) is the diagram of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip, (b) is a Yagi antenna for UAV-mounted VHF signal acquisition, (c) is a bandpass filter with a passband of 240MHZ-280MHZ, (d) is a broadband low-noise amplifier, (e) is the AD9361 chip, and (f) is a laptop computer for drawing power curves;

[0072] Figure 2 This is a signal processing flow chart in the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip;

[0073] Figure 3 This is the structural diagram of the signal A / D sampling in the AD9361 chip;

[0074] Figure 4a This is a curve showing the change of the effective value average power of the signal with the frequency obtained by measuring the signal in the city using the Agilent spectrum analyzer;

[0075] Figure 4b It is a curve diagram showing the change of the weighted effective value average power of the signal obtained by measuring the signal in the city using the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip proposed by the present invention as a function of frequency;

[0076] Figure 5 The invention provides a high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip, which is a graph showing the weighted effective value average power of the acquired signal changing with frequency at the same location and the same time period and at different azimuth angles; wherein (a) is a weighted effective value average power curve of the signal recorded when the Yagi antenna signal measurement angle is 0°, (b) is a weighted effective value average power curve of the signal recorded when the Yagi antenna signal measurement angle is 90°, (c) is a weighted effective value average power curve of the signal recorded when the Yagi antenna signal measurement angle is 180°, and (d) is a weighted effective value average power curve of the signal recorded when the Yagi antenna signal measurement angle is 270°;

[0077] Figure 6The high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip provided by the present invention is a curve diagram of the weighted effective value average power of the collected signal changing with the frequency at the same location and the same azimuth and in different time periods; wherein (a) is a curve diagram of the weighted effective value average power of the signal from 6 am to 8 am, (b) is a curve diagram of the weighted effective value average power of the signal from 12 noon to 13 pm, and (c) is a curve diagram of the weighted effective value average power of the signal from 11 pm to 12 am. DETAILED DESCRIPTION

[0078] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0079] A method for high-frequency signal acquisition and spectrum analysis system based on AD9361 chip, comprising the following steps:

[0080] Step S1, according to actual measurement requirements, adjusting the pitch angle and azimuth angle of the Yagi antenna to collect radio signals at a preset angle in the environment;

[0081] Step S2: according to the frequency characteristics of the collected radio signal, a bandpass filter is used to suppress the amplitude of the signal outside the passband range, so as to isolate and filter out the signal outside the target frequency band, and obtain the radio signal after isolation and filtering; further, a power amplifier that conforms to the frequency characteristics of the high-frequency signal is used to increase the power of the radio signal after isolation and filtering, and obtain the preprocessed radio signal;

[0082] Step S3, developing an AD9361 module for collecting and storing signals, burning a Linux operating system into an SD memory card in the AD9361 module, and using the burned Linux operating system to drive the AD sampling unit, automatic gain control module, DC offset correction module, orthogonal correction module and digital filter module in the AD9361 module;

[0083] Step S4, install data processing software and libraries in the Linux system of the SD memory card, compile the open source libraries gr-iio and pyadi-iio; set the sampling rate, sampling rate, sampling interval and sampling frequency of signal reception, scan the target frequency band of interest, and use the gr-iio and pyadi-iio library functions to digitize and down-convert the pre-processed radio signal to obtain a baseband digital signal;

[0084] Step S5: read the processed baseband digital signal, calculate the effective value average power of the baseband digital signal according to the amplitude of the baseband digital signal, draw a weighted effective value average power curve of the baseband digital signal according to the weighted effective value average power of the baseband digital signal, and further use it for spectrum analysis of the digital baseband signal.

[0085] The steps for collecting radio signals at a preset angle in the environment are as follows:

[0086] A coaxial cable with an impedance of 50 ohms is used as a feeder to connect a Yagi antenna with a beam radiation angle of 45 degrees. The Yagi antenna includes a first active vibrator with a length of 80 cm and a width of 10 cm, a second active vibrator with a length of 30 cm and a width of 10 cm, two first to second reflectors with a width of 30 cm and a length of 30 cm, and six first to sixth directors with a length of 20 cm.

[0087] The azimuth angle of the antenna is adjusted according to a fixed increment to obtain a radio signal in the target frequency band with an azimuth of 0° to 360° when the elevation angle is fixed.

[0088] The parameters of the bandpass filter and power amplifier are as follows:

[0089] The bandpass range of the bandpass filter is 240MHz to 280MHz, and the transition band of the bandpass filter is 235MHz to 240MHz and 280MHz to 285MHz;

[0090] The power amplifier has a frequency selection range of 20MHz to 3.5GHz and a noise figure of less than or equal to 0.4dBm.

[0091] In the development of the AD9361 chip, the Linux operating system is first burned into the SD memory card. The burned Linux operating system is used to drive the analog digital sampling unit, automatic gain control (AutoGain Control), DC offset correction, orthogonal correction and digital filtering modules in the AD9361 chip to obtain the processed baseband signal. The input signal will also use a high dynamic range analog-to-digital converter to digitize the received signal and pass it through a configurable decimation filter and 128-tap limited sampling.

[0092] In the signal acquisition process based on the AD9361 chip, commonly used data processing software and libraries are further installed in the SD memory card Linux system, and dedicated open source libraries gr-iio and pyadi-iio are compiled. The sampling rate, sampling rate, sampling interval and sampling frequency of the signal reception are set, the frequency band of interest is scanned, and the received signal is digitized and down-converted using the gr-iio and pyadi-iio library functions to obtain a baseband digital signal.

[0093] In the baseband digital signal analysis process, the weighted effective value average power of the baseband digital signal is calculated.

[0094] First, find the amplitude of the complex baseband digital signal:

[0095]

[0096] in, is the real part of the baseband digital signal collected at the mth sampling frequency, is the imaginary part of the baseband digital signal collected at the mth sampling frequency, y m is the amplitude of the complex baseband digital signal at the mth sampling frequency, where m ranges from 1 to n, and there are n sampling frequencies in total, and j is the imaginary unit in the complex number;

[0097] Then, VMD operation is performed on the complex baseband digital signal amplitude to obtain the corresponding analytical signal

[0098]

[0099] in is the in-phase component and are orthogonal components. H{·} is the Hilbert transform.

[0100] At the mth sampling frequency, the analytical signal The instantaneous amplitude a m , Phase and frequency f m Features:

[0101]

[0102] The frequency characteristics are retained for subsequent calculations. When the sampling frequency is m, the analytical signal The phase in When the sampling frequency is m-1, the analytical signal The phase in; Δm is the time interval, that is, the time difference between two adjacent sampling points;

[0103] Obtain the weighted effective average power of the complex baseband digital signal after frequency characteristic weighting:

[0104]

[0105] Wherein, P is the weighted effective average power of the baseband digital signal;

[0106] Then, convert the unit of weighted effective average power obtained by formula (6) into dBm:

[0107]

[0108] Among them, PW is the weighted effective average power in dBm;

[0109] The P obtained by formula (7) W Subtract the thermal noise power and add the system noise factor to get the final weighted effective value average power P f :

[0110] P f =P W -174+N f (8) Where N f is the total noise factor of the radio signal acquisition system.

[0111] By drawing P f The curve that changes with frequency f performs spectrum analysis on the collected radio signal.

[0112] The advantages of this system include easy operation, low cost, and suitability for diverse needs of environmental spectrum analysis.

[0113] In a specific embodiment, the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip is shown in FIG. Figure 1 As shown in (a) in . Figure 1 (b) is a Yagi antenna for collecting VHF signals on a drone. Figure 1 (c) is a bandpass filter with a passband of 240MHZ-280MHZ. Figure 1 (d) is a broadband low noise amplifier, Figure 1 (e) is the AD9361 chip. Figure 1 (f) in FIG. 1 is a laptop computer for drawing a power curve. The overall flow chart of the signal processing part of the present invention is as follows: Figure 2 As shown in the figure, the radio signal in the environment collected by the Yagi antenna. After passing through the bandpass filter, the power amplifier performs signal preprocessing. After a series of processing by the AD9361 chip, the processed signal is obtained through the computer terminal as a digital baseband signal for subsequent signal component analysis and drawing of the signal weighted effective value average power curve.

[0114] In a specific embodiment, a Yagi antenna needs to be prepared. After adjusting the target azimuth and elevation angle of the antenna, a feeder is used to connect the output end of the antenna and the input end of the bandpass filter respectively. The analog signal collected by the antenna will be filtered to greatly weaken the amplitude of the signal outside the passband range, thereby isolating and filtering out the signal outside the target frequency band. After the above work is completed, the output signal of the bandpass filter is input into the power amplifier. A stable 5V DC current is externally connected to the power supply interface of the power amplifier. After the analog signal passes through the power amplifier, a power amplification gain of about 30dBm will be obtained to prevent the target signal with lower power from being submerged by noise. After completing the preprocessing of the signal, the analog signal will be injected from the output end of the power amplifier into the RX input end of the AD9361 chip. The module equipped with the AD9361 chip communicates with the computer terminal, accesses the AD9361 chip, and completes the A / D operation of the signal.

[0115] In a specific embodiment, the analog signal will be converted into an analog signal after preprocessing. Figure 3 As shown in the figure, the analog signal will enter the RX input and undergo independent automatic gain control, DC offset correction, orthogonal correction and digital filtering. This eliminates the need for these functions in the digital baseband. In addition, the input signal will also use a high dynamic range analog-to-digital converter to digitize the received signal, and pass it through a configurable decimation filter and 128-tap limited sampling to output a digital signal.

[0116] In a specific embodiment, the collected signal can be processed in a series of processes in the AD9361 chip and then the signal data can be obtained through a computer terminal. Due to different numbers of collection points and sampling rates, the acquisition time of the signal data file is different. By setting the sampling parameters, signal data of different frequency bands can be obtained. By calculating the power value of the signal, a series of spectrum analysis graphs such as the average power curve and the maximum power curve of the signal can be drawn, thereby mastering the acquisition accuracy of the present invention. According to the radio signal spectrum analysis criteria, it can be observed that the present invention, which is about a high-frequency offline signal acquisition and spectrum analysis system based on the AD9361 chip, has a series of advantages such as high accuracy, low cost, and portable equipment.

[0117] In a specific embodiment, two locations are selected to actually verify the performance of the equipment, namely, near Youhao Park at the Jinkui Bridge on Taihu Avenue in Liangxi District, Wuxi City, and near Jinkui Park on Gonghu Avenue in Binhu District, Wuxi City, which meets the urban standard for high-frequency signal measurement.

[0118] Figure 4a , Figure 4b The weighted effective value average power curve of the signal obtained by the N9020A spectrum analyzer and the signal acquisition and analysis system of the present invention during the period from 13:00 to 14:00 noon in Youhao Park when the directional antenna acquisition angle is 0° is given. Figure 4aThis is the signal weighted RMS average power curve recorded by the N9020A spectrum analyzer. Figure 4b This is a signal weighted effective value average power curve recorded by the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip. Figure 4a As shown in the figure, within the frequency range of 235MHz to 285MHz, the weighted effective value average power of each frequency point can be distinguished, which shows that the system proposed in the present invention has the ability of high-frequency signal acquisition and spectrum analysis under actual measurement. Figure 4a and Figure 4b It can be seen that in the range of 235MHz to 285MHz, the weighted effective value average power curve recorded by the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip is almost consistent with the weighted effective value average power curve recorded by the N9020A spectrum analyzer. This further illustrates that under actual measurement conditions, the weighted effective value average power result of the signal recorded by the present invention is highly accurate and the result is credible.

[0119] Figure 5 The weighted effective value average power curve of the radio signal recorded by the system of the present invention under different azimuth angles collected by the Yagi antenna in the time range of 13:00 to 14:00 noon in Youhao Park is given. Figure 5 (a), (b), (c), and (d) are the weighted effective average power curves of the signal recorded when the Yagi antenna signal measurement angles are 0°, 90°, 180°, and 270°, respectively. Figure 5 It can be seen that at different angles, the weighted effective value average power curves are different, and at some specific angles, the noise activity distribution is more closely concentrated. This shows that the present invention can accurately record and calculate the weighted effective value average power of the signal at different azimuth angles, and has good azimuth resolution.

[0120] Figure 6 A weighted effective value average power curve of the signal recorded by the present invention at the Jinkui Park location, the same measurement angle, and different time periods is given. Figure 6 (a), (b) and (c) are the weighted effective average power curves of the signal from 6:00 to 8:00 in the morning, from 12:00 to 1:00 noon and from 23:00 to 24:00 at night respectively. Figure 6 It can be seen from (a), (b), and (c) that during the period from 12 noon to 13 o'clock, the noise is more densely distributed and active than in the morning and evening, and the average power value of the noise is higher. It is relatively quiet at night, and the activities that generate noise are reduced. This shows that the present invention can accurately complete the signal acquisition and spectrum analysis work at the same measurement angle and different time periods, and obtain a real and reliable weighted effective value average power curve with a high level of accuracy.

[0121] The above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A high-frequency signal acquisition and spectrum analysis system based on AD9361 chip, characterized in that: It includes Yagi antenna, bandpass filter, power amplifier, AD9361 module and terminal, among which, A Yagi antenna is used to output the collected radio signals in the environment to a bandpass filter; The bandpass filter is used to isolate and filter out the signal outside the target frequency band according to the frequency characteristics of the radio signal, obtain the isolated and filtered radio signal and output it to the power amplifier; A power amplifier is used to pre-process the radio signal after isolation and filtering, obtain the pre-processed radio signal and output it to the AD9361 module; AD9361 module, used to perform AD sampling, automatic gain control, DC offset correction, orthogonal correction and digital filtering on the pre-processed radio signal, obtain the baseband digital signal and output it to the terminal; The terminal is used to calculate the weighted effective value average power of the baseband digital signal according to the amplitude of the baseband digital signal, draw the weighted effective value average power curve of the baseband digital signal according to the weighted effective value average power of the baseband digital signal, and further use it for spectrum analysis of the digital baseband signal.

2. According to claim 1, a high-frequency signal acquisition and spectrum analysis system based on AD9361 chip is characterized in that: A feed line is used to connect the output of the Yagi antenna and the input of the bandpass filter.

3. The high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip according to claim 1, characterized in that: AD9361 has a built-in SD memory card, which is used to mount the Linux operating system and drive the AD9361 module.

4. The high-frequency signal acquisition and spectrum analysis system based on AD9361 chip according to claim 1 is characterized in that: The weighted effective value average power of the baseband digital signal is obtained by the following method, as follows: First, find the amplitude of the complex baseband digital signal: in, is the real part of the baseband digital signal collected at the mth sampling frequency, is the imaginary part of the baseband digital signal collected at the mth sampling frequency, y m is the amplitude of the complex baseband digital signal at the mth sampling frequency, where m ranges from 1 to n, n is the total number of sampling frequencies, and j is the imaginary unit in the complex number; Then, the amplitude of the complex baseband digital signal is subjected to variational mode decomposition (VMD) to obtain the corresponding analytical signal. in, is the in-phase component, are orthogonal components, H{·} is the Hilbert transform; At the mth sampling frequency, the analytical signal The instantaneous amplitude a m , Phase and frequency f m Features: in, When the sampling frequency is m, the analytical signal The phase in When the sampling frequency is m-1, the analytical signal The phase in; Δm is the time interval, that is, the time difference between two adjacent sampling points; Obtain the weighted effective average power of the complex baseband digital signal after frequency characteristic weighting: Wherein, P is the weighted effective value average power of the baseband digital signal; Then, convert the unit of weighted effective average power obtained by formula (6) into dBm: Among them, P W is the weighted effective average power in dBm; The P obtained by formula (7) W Subtract the thermal noise power and add the system noise factor to get the final weighted effective value average power P f : P f =P W -174+N f (8) Where N f is the total noise factor of the radio signal acquisition system.

5. A method for high-frequency signal acquisition and spectrum analysis system based on AD9361 chip, characterized in that: The following steps are involved: Step S1, according to actual measurement requirements, adjusting the pitch angle and azimuth angle of the Yagi antenna to collect radio signals at a preset angle in the environment; Step S2: according to the frequency characteristics of the collected radio signal, a bandpass filter is used to suppress the amplitude of the signal outside the passband range, so as to isolate and filter out the signal outside the target frequency band, and obtain the radio signal after isolation and filtering; further, a power amplifier that conforms to the frequency characteristics of the high-frequency signal is used to increase the power of the radio signal after isolation and filtering, and obtain the preprocessed radio signal; Step S3, developing an AD9361 module for collecting and storing signals, burning a Linux operating system into an SD memory card in the AD9361 module, and using the burned Linux operating system to drive the AD sampling unit, automatic gain control module, DC offset correction module, orthogonal correction module and digital filter module in the AD9361 module; Step S4, install data processing software and libraries in the Linux system of the SD memory card, compile the open source libraries gr-iio and pyadi-iio; set the sampling rate, sampling rate, sampling interval and sampling frequency of signal reception, scan the target frequency band of interest, and use the gr-iio and pyadi-iio library functions to digitize and down-convert the pre-processed radio signal to obtain a baseband digital signal; Step S5, reading the baseband digital signal, calculating the weighted effective value average power of the baseband digital signal according to the amplitude of the baseband digital signal, drawing the weighted effective value average power curve of the baseband digital signal according to the weighted effective value average power of the baseband digital signal, and further using it for spectrum analysis of the digital baseband signal.

6. The method of a high-frequency signal acquisition and spectrum analysis system based on AD9361 chip according to claim 5, characterized in that: The steps for collecting radio signals at a preset angle in the environment are as follows: A coaxial cable with an impedance of 50 ohms is used as a feeder to connect a Yagi antenna with a beam radiation angle of 45 degrees. The Yagi antenna includes a first active vibrator with a length of 80 cm and a width of 10 cm, a second active vibrator with a length of 30 cm and a width of 10 cm, two first to second reflectors with a width of 30 cm and a length of 30 cm, and six first to sixth directors with a length of 20 cm. The azimuth angle of the antenna is adjusted according to a fixed increment to obtain a radio signal in the target frequency band with an azimuth of 0° to 360° when the elevation angle is fixed.

7. The method of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip according to claim 5 is characterized in that: The parameters of the bandpass filter and power amplifier are as follows: The bandpass range of the bandpass filter is 240MHz to 280MHz, and the transition band of the bandpass filter is 235MHz to 240MHz and 280MHz to 285MHz; The power amplifier has a frequency selection range of 20MHz to 3.5GHz and a noise figure of less than or equal to 0.4dBm.

8. The method of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip according to claim 5 is characterized in that: The weighted effective average power of the baseband digital signal is as follows: First, find the amplitude of the complex baseband digital signal: in, is the real part of the baseband digital signal collected at the mth sampling frequency, is the imaginary part of the baseband digital signal collected at the mth sampling frequency, y m is the amplitude of the complex baseband digital signal at the mth sampling frequency, where m ranges from 1 to n, n is the total number of sampling frequencies, and j is the imaginary unit in the complex number; Then, the amplitude of the complex baseband digital signal is subjected to variational mode decomposition (VMD) to obtain the corresponding analytical signal. in, is the in-phase component, are orthogonal components, H{·} is the Hilbert transform; At the mth sampling frequency, the analytical signal The instantaneous amplitude a m , Phase and frequency f m Features: in, When the sampling frequency is m, the analytical signal The phase in When the sampling frequency is m-1, the analytical signal The phase in; Δm is the time interval, that is, the time difference between two adjacent sampling points; Obtain the weighted effective average power of the complex baseband digital signal after frequency characteristic weighting: Wherein, P is the weighted effective value average power of the baseband digital signal; Then, convert the unit of weighted effective average power obtained by formula (14) into dBm: Among them, P W is the weighted effective average power in dBm; The P obtained by formula (15) W Subtract the thermal noise power and add the system noise factor to get the final weighted effective value average power P f : P f =P W -174+N f (16) Where N f is the total noise factor of the radio signal acquisition system.

9. The method of the high-frequency signal acquisition and spectrum analysis system based on the AD9361 chip according to claim 8, characterized in that: Draw the weighted effective value average power curve of the baseband digital signal, and further use it for spectrum analysis of the digital baseband signal; it means: by drawing P f The curve that changes with frequency f performs spectrum analysis on the collected radio signal.

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