CN112748689A - Burst signal automatic acquisition system - Google Patents
Burst signal automatic acquisition system Download PDFInfo
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- CN112748689A CN112748689A CN202011625439.5A CN202011625439A CN112748689A CN 112748689 A CN112748689 A CN 112748689A CN 202011625439 A CN202011625439 A CN 202011625439A CN 112748689 A CN112748689 A CN 112748689A
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- G05B19/00—Programme-control systems
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- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
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Abstract
The invention discloses an automatic burst signal acquisition system which comprises a software radio platform for acquiring burst signals, wherein the software radio platform comprises a down converter, a filter and an AD sampler which are used for receiving the burst signals in sequence, the software radio platform is divided into two paths behind the AD sampler, one path is a burst signal detection branch, the other path is a burst signal acquisition branch, and when the burst signal detection branch detects the burst signals, the burst signal acquisition branch is switched on and started to work, so that the burst signals are acquired. The burst signal automatic acquisition system can discriminate and acquire burst signals in real time, and simultaneously performs frequency difference compensation to reduce the frequency deviation of acquired signals.
Description
Technical Field
The invention belongs to the field of signal acquisition systems, and particularly relates to an automatic burst signal acquisition system.
Background
The existing burst signal is continuously collected for a long time, the collected data is stored in a computer or a storage medium, when the sampling rate is high, the collection time is long, the stored data volume can be greatly increased, the computer or the storage medium can bear great burden, the waste of storage resources can be undoubtedly caused, meanwhile, the time for processing the data is prolonged, the efficiency is reduced, and the situation that the collection of a new burst signal cannot be carried out due to the overflow of a storage space can exist, so that the burst signal is missed to be collected.
In addition, when the frequency difference between the acquisition device and the burst modulation signal is large, the energy and information of the acquired signal are lost, and the processing and analysis of the subsequent signal are affected.
Therefore, how to discriminate and collect burst signals, adjust the local oscillator of the down-conversion in real time, perform frequency difference compensation, and reduce the frequency offset of the collected signals is a technical problem to be solved by technical personnel in the technical field.
Disclosure of Invention
The invention mainly solves the technical problem of providing an automatic burst signal acquisition system, and solves the problems that in the prior art, burst signals cannot be discriminated and acquired in real time, frequency difference compensation cannot be carried out in real time, and the frequency offset of the acquired signals cannot be reduced.
In order to solve the technical problem, the technical scheme adopted by the invention is to provide an automatic burst signal acquisition system, which comprises a software radio platform for acquiring burst signals, wherein the software radio platform comprises a down converter, a filter and an AD sampler which are used for receiving the burst signals in sequence, the software radio platform is divided into two paths behind the AD sampler, one path is a burst signal detection branch, the other path is a burst signal acquisition branch, and when the burst signal detection branch detects the burst signals, the burst signal acquisition branch is switched on and started to work, so that the acquisition of the burst signals is realized.
Preferably, the burst signal acquisition device further comprises an upper computer in communication connection with the burst signal acquisition branch, and is used for storing data output by the burst signal acquisition branch to the upper computer and receiving a parameter configuration instruction from the upper computer to the burst signal acquisition branch.
Preferably, the burst signal detection branch comprises a burst frame detection circuit electrically connected with the AD sampler, and the burst frame detection circuit performs frequency difference estimation while detecting burst signals, and comprises an acquisition start control output terminal and a frequency difference estimation output terminal, which are respectively electrically connected with the burst signal acquisition branch and correspondingly and respectively output an acquisition start control signal and a frequency difference estimation value to the burst signal acquisition branch.
Preferably, the burst frame detection circuit includes a first frequency domain detection circuit, and the sampling data sampled by the AD sampler is serially input to the first frequency domain detection circuit to perform signal spectrum detection.
Preferably, the burst signal detection circuit includes two first frequency domain detection circuits and two second frequency domain detection circuits which are arranged in series, and the sampling data sampled by the AD sampler is serially input to the two frequency domain detection circuits to perform signal spectrum detection, respectively.
Preferably, the burst signal acquisition branch comprises an FIFO buffer circuit electrically connected to the AD sampler and a signal acquisition circuit, a control switch is disposed between the FIFO buffer circuit and the signal acquisition circuit, a control end of the control switch is electrically connected to an acquisition start control output end of the burst frame detection circuit, the control switch is turned on when receiving an acquisition start control signal output from the burst frame detection circuit, otherwise, the control switch is turned off.
Preferably, the burst signal acquisition branch further includes a framing and parameter control circuit electrically connected to the output end of the signal acquisition circuit, the frequency difference estimation output end of the burst frame detection circuit is electrically connected to the framing and parameter control circuit, the frequency difference estimation value is input to the framing and parameter control circuit, and the framing and parameter control circuit is further electrically connected to the down converter for inputting the frequency difference estimation value to the down converter for frequency difference compensation.
Preferably, the software radio platform further comprises a navigation positioning circuit, and the navigation positioning circuit is electrically connected with the framing and parameter control circuit and is used for inputting time and position information to the framing and parameter control circuit.
Preferably, the framing and parameter control circuit is in communication connection with the upper computer through a network interface or a USB interface.
Preferably, the upper computer comprises a waveform spectrum display module, a file storage module and a parameter configuration module.
The invention has the beneficial effects that: the invention discloses an automatic burst signal acquisition system which comprises a software radio platform for acquiring burst signals, wherein the software radio platform comprises a down converter, a filter and an AD sampler which are used for receiving the burst signals in sequence, the software radio platform is divided into two paths behind the AD sampler, one path is a burst signal detection branch, the other path is a burst signal acquisition branch, and when the burst signal detection branch detects the burst signals, the burst signal acquisition branch is switched on and started to work, so that the burst signals are acquired. The burst signal automatic acquisition system can discriminate and acquire burst signals in real time, and simultaneously performs frequency difference compensation to reduce the frequency deviation of acquired signals.
Drawings
FIG. 1 is a block diagram of an embodiment of an automatic burst signal acquisition system according to the present invention;
fig. 2 is a schematic diagram of the detection principle of the first frequency domain detection circuit and the second frequency domain detection circuit in another embodiment of the burst signal automatic acquisition system of the present invention;
FIG. 3 is a schematic diagram of the initial detection spectrum of the burst signal in another embodiment of the burst signal automatic acquisition system of the present invention;
fig. 4 is a schematic diagram of a burst end detection spectrum in another embodiment of the burst automatic acquisition system of the present invention;
fig. 5 is a schematic diagram of a carrier tracking loop in another embodiment of the burst signal automatic acquisition system of the present invention;
fig. 6 is a schematic diagram of the loop filter in another embodiment of the burst signal automatic acquisition system of the present invention;
fig. 7 is a flow chart of an embodiment of a burst signal automatic acquisition method.
Detailed Description
In order to facilitate an understanding of the invention, the invention is described in more detail below with reference to the accompanying drawings and specific examples. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It is to be noted that, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
As shown in fig. 1, the burst signal automatic acquisition system comprises a software radio platform 1 for acquiring burst signals, wherein the software radio platform 1 comprises a down converter 11 for receiving burst signals in sequence, a filter 12 and an AD sampler 13, and is divided into two paths after the AD sampler 13, wherein one path is a burst signal detection branch, and the other path is a burst signal acquisition branch, and when the burst signal detection branch detects a burst signal, the burst signal acquisition branch is switched on and started to operate, so that the acquisition of the burst signal is realized.
In fig. 1, a down-converter 11 down-converts a received burst signal by using a local carrier, and down-converts the carrier of the burst signal from a radio frequency band to an intermediate frequency band or a baseband. Here, since the actual frequency value of the carrier of the burst signal may have a frequency offset and therefore is not equal to the local carrier frequency, which may cause the carrier obtained by the down-conversion to deviate from the theoretical value, it is also necessary to perform frequency offset estimation on the burst signal after the down-conversion, which is beneficial to further adjusting the frequency of the local carrier according to the estimated frequency offset value, and finally, the frequency of the local carrier is made to be consistent with the carrier frequency of the burst signal. By the frequency offset correction mode, the frequency spectrum of the burst signal obtained during subsequent sampling is mainly concentrated in an effective bandwidth with the carrier frequency as the center, otherwise, if frequency offset exists, the frequency spectrum component of the signal deviates from the carrier frequency, and a larger bandwidth is needed to include the frequency spectrum component of the signal with the frequency offset during sampling.
The filter 12 can filter the frequency spectrum occupied by the burst signal, so that the signal frequency spectrum except the frequency spectrum of the burst signal is filtered, and only the frequency spectrum occupied by the burst signal is reserved, thereby being beneficial to subsequent sampling only by sampling the frequency spectrum occupied by the burst signal, being beneficial to improving the accuracy of sampling treatment, being capable of carrying out undersampling treatment, and ensuring that the sampling of the frequency spectrum of the burst signal is obtained while the sampling rate is reduced.
Preferably, because a software radio platform architecture is adopted, the filter 12 is implemented as a digital filter, and the configuration and parameters of the filter can be set, so that the invention can be suitable for filtering burst signals with different bandwidths and different carrier frequencies, and is enhanced to be suitable for various conditions. Therefore, the working parameters of the filter 12 can be set through the upper computer and the framing and parameter control circuit.
Through the two-path processing of the burst signals, the burst signal detection branch is used for finding the burst signals, and the burst signal acquisition branch is started only after the burst signals are found, so that the situation that the burst signal acquisition branch does not have targeted signal acquisition can be avoided, storage resources are saved, waste is avoided, and the missing rate of the burst signals can be effectively reduced on the basis of distinguishing the burst signals and carrying out screening acquisition.
Preferably, as shown in fig. 1, the system further includes an upper computer 2 connected in communication with the burst signal acquisition branch, and configured to store data output by the burst signal acquisition branch, including acquired burst signal sampling data or burst information data demodulated from a burst signal, to the upper computer 2, and receive a parameter configuration instruction from the upper computer 2. The remote data acquisition of burst signals is realized by the arrangement of the upper computer 2, and due to the fact that data are automatically acquired, manual operation is reduced, and efficiency is improved.
Further preferably, the upper computer 2 includes a waveform spectrum display module 21, a file storage module 22 and a parameter configuration module 23, and after receiving the collected signal, the upper computer 2 displays the signal through the waveform spectrum display module 21 and stores the signal through the file storage module 22, and meanwhile, the parameter configuration module 23, in combination with various values set by the user, can send a command to the software radio platform 1 and perform autonomous setting of parameters such as receiving frequency, bandwidth and gain control.
Therefore, by arranging the upper computer and being in communication connection with the burst signal acquisition branch, the defect of storage space when data are acquired on the software radio platform can be effectively overcome, the functions of the software radio platform in the aspects of detection and demodulation are mainly exerted, the acquired useful data are stored in the upper computer for display observation, and the separation of detection, storage and display is effectively realized.
Preferably, as shown in fig. 1, the burst signal detection branch comprises a burst frame detection circuit 14 electrically connected to the AD sampler 13, and the burst frame detection circuit 14 performs frequency difference estimation while detecting the burst signal, and comprises an acquisition start control output terminal and a frequency difference estimation output terminal, which are respectively electrically connected to the burst signal acquisition branch and correspondingly respectively output an acquisition start control signal and a frequency difference estimation value to the burst signal acquisition branch.
Preferably, as shown in fig. 1, the burst signal acquisition branch comprises a FIFO buffer circuit 15 electrically connected to the AD sampler 13, and a signal acquisition circuit 16, wherein a control switch is disposed between the FIFO buffer circuit 15 and the signal acquisition circuit 16, a control end of the control switch is electrically connected to an acquisition start control output end of the burst frame detection circuit 14, the control switch is turned on when receiving an acquisition start control signal output from the burst frame detection circuit 14, and otherwise, the control switch is turned off. The FIFO buffer circuit 15 is configured to buffer a continuous data stream, so as to prevent data loss during a storage operation, and particularly, when a burst signal is found in an initial stage and an end stage, data at the head and tail of the burst signal can be stored, so as to avoid loss and ensure data integrity. The signal acquisition circuit 16 is arranged to further demodulate the sampled data from the FIFO buffer circuit 15 to obtain burst information data in the burst signal, so that the signal acquisition circuit 16 here mainly demodulates the sampled data of the burst signal digitally, thereby completing the burst information recovery in the burst signal.
Preferably, as shown in fig. 1, the burst signal acquisition branch further comprises a framing and parameter control circuit 17 electrically connected to the output of the signal acquisition circuit 16. On one hand, the frequency difference estimation output end of the burst frame detection circuit 14 is electrically connected with the framing and parameter control circuit 17, the frequency difference estimation value is input into the framing and parameter control circuit 17, and the framing and parameter control circuit 17 is also electrically connected with the down converter 11 and used for inputting the frequency difference estimation value into the down converter 11 for frequency difference compensation; on the other hand, by setting the framing and parameter control circuit 17, the collected burst information data and the frequency difference estimation value can be framed and packed and sent to the upper computer 2 for processing.
In addition, because the framing and parameter control circuit 17 is also connected to the down converter 11, that is, according to the frequency difference estimated value obtained by the framing and parameter control circuit 17, the frequency of the local carrier wave generated by the local oscillator circuit in the down converter 11 can be adjusted in real time, so as to complete frequency difference compensation, reduce the frequency deviation of the acquired signal, and reduce the loss of the acquired signal energy and information.
Preferably, as shown in fig. 1, the software defined radio platform 1 further comprises a navigation positioning circuit 18, and the navigation positioning circuit 18 is electrically connected to the framing and parameter control circuit 17 for inputting time and location information to the framing and parameter control circuit 17. Further preferably, the navigation positioning circuit 18 is a GPS module, and the framing and parameter control circuit 17 may frame and package the collected time information and position information to the upper computer 2. Therefore, when the corresponding information data form the data frame, time information and position information can be obtained, and analysis and use of the later data are facilitated.
Preferably, as shown in fig. 1, the framing and parameter control circuit 17 is communicatively connected to the upper computer 2 through a network interface or a USB interface.
Further preferably, in the burst signal detection branch, the burst frame detection circuit 14 includes a first frequency domain detection circuit, and the sampling data sampled by the AD sampler is serially input to the first frequency domain detection circuit to perform signal spectrum detection.
Preferably, the sample data is represented by X (1), X (2), X (3), … X (N), …, where N represents the serial number of the sample data, and the data length of the spectrum conversion processing of the sample data by the first frequency domain detection circuit is L1And the spectrum conversion process is performed every time a new sample data is entered. For example, the current first frequency domain detection circuit is to sample data X (1), X (2), X (3), … X (L)1) The next sample data X (L) is processed by spectrum conversion1+1) comes in, the first sample data X (1) is dropped, and the sample data X (2), X (3), X (4), … X (L)1+1) the spectral conversion process and so on. It can be seen that this serial processing of the sampled data by the first frequency domain detection circuit facilitates the detection and detection of burst signals in time, since the presence of a burst signal is uncertain and the duration of the burst signal is short, preferably 0.5-2 seconds. This is equivalent to the first frequency domain detection circuit being a slidable window that continuously and uninterruptedly detects the sample data serially input to the detection window, and when a burst signal occurs, it can be found in time and locate the position and time when the corresponding sample data occurs when the burst signal occurs.
Preferably, the data length L of the spectrum conversion process1The sliding length of the window corresponding to the first frequency domain detection circuit can be reasonably set as required, and is generally the longer the window is selected under the conditions that the duration time of the burst signal is shorter and the signal-to-noise ratio is lower, because the burst signal is difficult to be found, the burst signal is beneficial to capturing the burst signal, and the shorter the window is selected under the conditions that the duration time of the burst signal is longer and the signal-to-noise ratio is higher, because the burst signal is easy to be captured, the hardware resources of the first frequency domain detection circuit are beneficial to being reduced through the short window, and meanwhile, the sensitivity and the accuracy of burst signal discovery are not reduced.
Preferably, the FIFO buffer circuit in the burst signal acquisition branch is used to buffer the sampled data, and since the first frequency domain detection circuit and the FIFO buffer circuit are both sampled data from the AD sampler, when the first frequency domain detection circuit obtains the position and time at which the sampled data corresponding to the burst signal appears, the corresponding sampled data can also be accurately located from the FIFO buffer circuit, so that the initial sampled data of the burst signal can be accurately found during subsequent data demodulation and data storage. Also, when the first frequency domain detection circuit detects the end of the burst signal, the end sample data of the burst signal can be accurately located in the FIFO buffer circuit. Therefore, the FIFO buffer circuit is beneficial to keeping synchronization with the first frequency domain detection circuit, accurately determining the positions of the initial sampling data and the ending sampling data corresponding to the burst signal, and accurately acquiring and storing the burst signal.
This is because, when the burst signal detection branch starts to collect and store the burst signal from the discovery of the occurrence of the burst signal to the switching to the burst signal collection branch, and the burst signal detection branch finishes to the burst signal collection branch, both of these two conversion processes have a conversion delay, if the sampling data in this delay is not accurately positioned and stored, it is possible that the head and the tail of the burst signal obtained are incomplete, and the integrity of the burst signal collection data cannot be guaranteed, so by setting the FIFO buffer circuit in the burst signal collection branch and making the FIFO buffer circuit and the first frequency domain detection circuit keep synchronization in data collection, the invention is specifically designed for the characteristics of the head and tail collection of the burst signal, and is favorable for avoiding the problem of "pinching head and tail off" in the burst signal collection process, therefore, the integrity of burst signal acquisition is kept, accurate acquisition is realized, and limited storage resources are prevented from being wasted.
It can also be seen that the frequency spectrum conversion processing speed of the first frequency domain detection circuit is adapted to the sampling speed of the sampled data, and since the frequency spectrum conversion processing needs to be completed once every sampling point comes, the frequency spectrum conversion processing speed and the data size need to be adapted in consideration of the data size L and the data size L1Related to, and each sampleThe number of bits of the data is related, because the difference of the number of bits of the sampled data corresponds to the precision of the sampling quantization, the higher the precision is, the more the corresponding number of bits is, for example, 6 bits of sampled data and 12 bits of sampled data are obtained, and obviously, the precision is different. When the amount of data processed by one spectrum conversion is too large, the processing speed is reduced, and more hardware resources are also occupied.
Preferably, when the sampling rate is high, when the spectrum conversion processing is performed on the sampling data input in series, the spectrum conversion processing performed two adjacent times may be performed at least one sampling data interval, for example, the sampling data currently used is:
X(1),X(2),X(3),…X(L1)，
then the next adjacent sample data is:
X(3),X(4),X(5),…X(L1+2)，
it can be seen that the sample data X (2) is spaced between the start data X (3) and X (1), which is only spaced by one sample data, but also spaced by a plurality of sample data, so as to adapt the speed of the spectrum conversion process to the sampling speed, and to ensure that the burst signal can be found early.
Preferably, when the method for processing at least one sample data at two adjacent intervals of spectrum conversion processing is adopted, it is possible that a burst signal may be present before the current sample data when the burst signal is found, and therefore, when the FIFO buffer circuit determines the sample data corresponding to the burst signal occurrence time, it is possible to forward calculate that more sample data corresponding to the corresponding interval is reserved, so that when the improved method is adopted, the integrity of the sample data of the burst signal can still be ensured through the FIFO buffer circuit.
Preferably, the spectrum conversion process uses a DFT or FFT transform process. Whether the burst signal appears or not can be detected through DFT or FFT conversion processing, and frequency information of the burst signal can also be detected, so that the acquisition starting control signal and the frequency difference estimation value are respectively output to the burst signal acquisition branch through the acquisition starting control output end and the frequency difference estimation output end.
Further preferably, in the burst signal detection branch, the burst frame detection circuit includes two frequency domain detection circuits arranged in series, that is, a first frequency domain detection circuit and a second frequency domain detection circuit, and the sampling data sampled by the AD sampler is serially input to the two frequency domain detection circuits to perform signal spectrum detection, respectively.
Preferably, the spectrum conversion processing in the first frequency domain detection circuit and the second frequency domain detection circuit both adopt DFT or FFT transform processing. Also, the first frequency domain detection circuit and the second frequency domain detection circuit have the same circuit composition, whereby two sliding detection windows in series can be formed.
Further, as shown in fig. 2, the serially entered sample data sequentially enters the first frequency domain detection circuit and the second frequency domain detection circuit for detection, and the identification of the arrival and the end of the burst signal under the noise condition is improved by setting a relative threshold between the two detection circuits in consideration of the influence of noise. This is because, because noise exists and the noise also shows fluctuation, if the magnitude of the modulus of the spectrum data obtained after the spectrum conversion processing is merely detected, the magnitude of the modulus of the spectrum data changes with the change in the noise, and in the case where the noise is large and the signal-to-noise ratio is small, a problem that a burst signal is not detected easily occurs, and a problem that it is difficult to identify the end timing of the burst signal easily occurs after the burst signal is detected.
Preferably, in the frequency spectrum data obtained by the frequency spectrum conversion processing of the first frequency domain detection circuit, the maximum value of the modulus value therein is called as a first maximum detection modulus value; in the spectrum data obtained by the second frequency domain detection circuit after the spectrum conversion processing, the maximum value of the modulus value is called as the second maximum detection modulus value, the relative threshold value is the value obtained by comparing the larger value of the two maximum detection modulus values with the smaller value, if the relative threshold value is close to 1, the difference degree of the two maximum modulus values is not large, the situation is usually met when no burst signal exists, and the noise is not influenced, namely, the relative threshold value is close to 1 when the noise is large or small. When a burst signal occurs, the value of the relative threshold value is obviously larger than 1, which is beneficial to timely finding the burst signal.
As shown in fig. 2, the data length of the spectrum conversion process of the first frequency domain detection circuit and the second frequency domain detection circuit is the same, i.e., both have the same window length. Preferably, the window lengths of the two detection circuits can be flexibly selected according to requirements, that is, the two detection circuits can be sliding windows, and the two detection circuits can also be different window lengths. In fig. 2, m (n) is a ratio of maximum frequency point amplitudes after the first frequency domain detection circuit and the second frequency domain detection circuit perform the frequency spectrum conversion processing, when there is only noise, a difference between maximum frequency points of the two frequency domain detection circuits after the frequency spectrum conversion processing is very small, and m (n) is relatively flat, as shown by a first detection curve T1; when the burst signal arrives, the ratio m (n) will rise sharply, as shown by the first detection curve T2, and when the set relative threshold is reached, the burst signal is determined to arrive. Therefore, the arrival and the end of the signal can be accurately determined if the relative threshold is set in advance.
Preferably, the second frequency domain detection circuit is located behind the first frequency domain detection circuit, and when the first frequency domain detection circuit continuously detects new input sample data, the second frequency domain detection circuit performs spectrum conversion processing on the previous sample data, when a burst signal occurs, a relatively obvious maximum value of a modulus value occurs in the first frequency domain detection circuit, the maximum value of the modulus value which currently occurs in the first frequency domain detection circuit can be compared with the maximum value of the modulus value which currently occurs in the second frequency domain detection circuit, and if the maximum value of the modulus value is greater than a set relative threshold value, the occurrence of the burst signal can be timely judged. Under the influence of noise, if the signal-to-noise ratio is better, the relative threshold value can be set to be larger, and if the signal-to-noise ratio is poorer, the relative threshold value can be set to be smaller, so that the detection accuracy can be improved, and the false alarm rate and the omission factor can be reduced. As shown in fig. 3, a spectrum diagram is shown detected in the presence of a burst signal.
Similarly, when the burst signal is ended, the maximum value of the modulus value currently appearing in the second frequency domain detection circuit is compared with the maximum value of the modulus value currently appearing in the first frequency domain detection circuit, and if the maximum value of the modulus value currently appearing in the second frequency domain detection circuit is larger than the set relative threshold value, the end of the burst signal is judged in time.
The same relative threshold may be used in both the beginning and end of the burst signal described above, with the difference that the ratio of the first detected maximum modulus to the second detected maximum modulus is used at the time of arrival of the detected burst signal, and the ratio of the second detected maximum modulus to the first detected maximum modulus is used at the end of the detected burst signal. As shown in fig. 4, the detected spectrum at the end of the burst is shown on the basis of fig. 3.
Preferably, the frequency band of the signal sampled by the AD sampler is in the range of 300MHz-3000MHz, and the length of the sampled data converted by DFT or FFT, i.e. the length of the sliding window, may be selected to include 2048, 1024, 512, 256, 128, 64 and/or 32.
Preferably, based on fig. 1, the down converter receives parameter settings from the framing and parameter control circuit, the parameter settings mainly adjust the frequency of the local carrier generated by the carrier tracking loop in the down converter in real time to complete frequency offset compensation, and the frequency offset parameters include an initial frequency offset value obtained when the burst signal is detected by the burst frame detection circuit and a tracking frequency offset value obtained when the burst signal is acquired by demodulation and tracking.
As shown in fig. 5, the carrier tracking loop includes a frequency discriminator, a loop filter, and a voltage controlled oscillator, an input end of the discriminator receives an input signal, the input signal refers to a signal after frequency offset correction, the discriminator performs frequency discrimination on a current output signal, that is, a local carrier signal, and then connects to an input end of the loop filter through an output end, after the loop filter performs loop filtering, an error value of the loop filtering is used to control the voltage controlled oscillator to generate a local carrier as an output signal, and the output end of the voltage controlled oscillator outputs the signal, and meanwhile, the voltage controlled oscillator is further connected to the discriminator and is used to perform frequency discrimination on the output carrier signal.
Preferably, the input end of the discriminator receives an input signal and corresponds to two frequency offset values, wherein an initial NCO value of the carrier tracking loop is assigned with an initial frequency offset value, a third-order loop filter is used for tracking a signal containing doppler dynamics, and meanwhile, in order to accelerate convergence speed, a loop for updating sampling data is used, and after the loop filter converges, the carrier loop is switched to a carrier loop for updating symbol data. Specifically, as shown in fig. 6, the third-order loop filter includes an upper branch and a lower branch, where the third-order loop filter corresponding to the upper first branch is used for receiving the sampling data and updating the carrier phase input error to implement the loop filtering, where K1, K2, and K3 are coefficients of the third-order loop filter; the third-order loop filter corresponding to the lower second branch is used for receiving the sign data and updating the carrier phase input error to realize loop filtering, wherein K4, K5 and K6 are coefficients of the third-order loop filter; the two third order loop filters share two delays 1/S and two adders. As mentioned above, when a burst signal occurs initially, a third-order loop filter is used to track a signal containing doppler dynamics, and in order to accelerate convergence speed, a loop for updating sampling data is used, that is, a third-order loop filter corresponding to the first branch above is used; and when the loop filter is converged, switching to a carrier ring for symbol data updating, namely switching to a third-order loop filter corresponding to the second branch. The three-order loop filter with the two branches can realize rapid tracking and convergence when a burst signal is initially found, and can realize tracking and demodulation of symbol data by switching to a tracking loop after large carrier frequency difference is eliminated.
Preferably, based on the same concept, the present invention further provides an automatic burst signal acquisition method, as shown in fig. 7, the method comprising the steps of:
sampling processing S1, receiving the burst signal, and sequentially performing down-conversion processing, filtering processing and AD sampling processing to obtain sampling data;
a detection process S2, which detects the sampled data, and starts an acquisition process when a burst signal is detected;
the acquisition process S3 is to receive the sampled data, demodulate the data to obtain burst information in the burst signal, and store the information.
Further preferably, in the acquisition processing step S3, the method further includes remote monitoring, transmitting the burst information to an upper computer, and receiving a parameter configuration instruction from the upper computer.
Preferably, in the detection processing step S2, frequency difference estimation is performed simultaneously with burst signal detection, and then the acquisition start control signal and the frequency difference estimation value are output to the acquisition processing S3, respectively.
Preferably, the acquiring step S3 includes performing FIFO buffer processing and signal acquiring processing on the sampled data, and a control switch is further disposed between the FIFO buffer processing and the signal acquiring processing, and when receiving the acquisition start control signal output from the detecting step S2, the control switch is turned on, otherwise, the control switch is turned off
Preferably, in the acquisition processing step S3, framing and parameter control processing is performed after the signal acquisition processing, burst information is framed and transmitted to an upper computer, the frequency offset estimation value output in the detection processing step S2 is received, and the frequency offset estimation value is further fed back to down-conversion processing in the sampling processing step, and is used for frequency offset compensation.
Preferably, in the acquisition processing step S3, the framing and parameter control processing further includes navigation positioning processing, and the time and position information after the navigation positioning processing and the burst information are framed and transmitted to an upper computer.
Preferably, in the remote monitoring, the waveform spectrum display processing, the file storage processing and the parameter configuration processing are carried out on the upper computer
Based on the same concept, the specific implementation embodiment of the burst signal automatic acquisition method refers to the specific description of each circuit in the burst signal automatic acquisition system, and is not described herein again.
Based on the above embodiment, the invention discloses an automatic burst signal acquisition system, which comprises a software radio platform for acquiring burst signals, wherein the software radio platform comprises a down converter, a filter and an AD sampler, the down converter, the filter and the AD sampler are used for receiving burst signals in sequence, the software radio platform is divided into two paths after the AD sampler, one path is a burst signal detection branch, the other path is a burst signal acquisition branch, and when the burst signal detection branch detects the burst signals, the burst signal acquisition branch is switched on and started to work, so that the burst signals are acquired. The burst signal automatic acquisition system can discriminate and acquire burst signals in real time, and simultaneously performs frequency difference compensation to reduce the frequency deviation of acquired signals.
The above description is only an embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or any other related technical fields, are included in the scope of the present invention.
Claims (10)
1. The burst signal automatic acquisition system is characterized by comprising a down converter, a filter and an AD sampler which are used for receiving burst signals in sequence, wherein the down converter, the filter and the AD sampler are divided into two paths behind the AD sampler, one path is a burst signal detection branch, the other path is a burst signal acquisition branch, and when the burst signal detection branch detects the burst signals, the burst signal acquisition branch is switched on and started to work, so that the burst signals are acquired.
2. The burst signal automatic acquisition system according to claim 1, further comprising an upper computer communicatively connected to the burst signal acquisition branch for storing data output by the burst signal acquisition branch to the upper computer and receiving parameter configuration instructions from the upper computer to the burst signal acquisition branch.
3. The burst signal automatic acquisition system according to claim 2, wherein the burst signal detection branch comprises a burst frame detection circuit electrically connected to the AD sampler, and the burst frame detection circuit performs frequency difference estimation while detecting burst signals, and comprises an acquisition start control output terminal and a frequency difference estimation output terminal, which are respectively electrically connected to the burst signal acquisition branch, and correspondingly respectively output an acquisition start control signal and a frequency difference estimation value to the burst signal acquisition branch.
4. The burst signal automatic acquisition system according to claim 3, wherein the burst frame detection circuit comprises a first frequency domain detection circuit to which the sampled data sampled by the AD sampler is serially input for signal spectrum detection.
5. The burst signal automatic acquisition system according to claim 3, wherein the burst signal detection circuit comprises two first frequency domain detection circuits and second frequency domain detection circuits arranged in series, and the sampled data sampled by the AD sampler is serially inputted to the two frequency domain detection circuits for signal spectrum detection, respectively.
6. The burst signal automatic acquisition system according to claim 3, wherein the burst signal acquisition branch comprises a FIFO buffer circuit electrically connected to the AD sampler, and a signal acquisition circuit, a control switch is provided between the FIFO buffer circuit and the signal acquisition circuit, a control terminal of the control switch is electrically connected to the acquisition start control output terminal of the burst frame detection circuit, the control switch is turned on when receiving the acquisition start control signal from the output of the burst frame detection circuit, otherwise, the control switch is turned off.
7. The burst signal automatic acquisition system according to claim 6, wherein said burst signal acquisition branch further comprises a framing and parameter control circuit electrically connected to said signal acquisition circuit output, said burst frame detection circuit frequency difference estimation output being electrically connected to said framing and parameter control circuit, said frequency difference estimation value being input to said framing and parameter control circuit, said framing and parameter control circuit being further electrically connected to said downconverter for inputting said frequency difference estimation value to said downconverter for frequency difference compensation.
8. The burst signal automatic acquisition system according to claim 7, further comprising a navigation positioning circuit electrically connected to the framing and parameter control circuit for inputting time and position information to the framing and parameter control circuit.
9. The burst signal automatic acquisition system according to claim 8, wherein the framing and parameter control circuit is communicatively connected to the host computer through a network interface or a USB interface.
10. The burst signal automatic acquisition system according to claim 9, wherein the upper computer comprises a waveform spectrum display module, a file storage module and a parameter configuration module.
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