JP2004214817A - Radio identification system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To identify a transmitting radio in a illegal radio station even when a received radio wave contains a noise. <P>SOLUTION: The radio identification system for identifying a source radio using a received radio wave comprises a means 100B for determining a trigger position from a received radio wave, means 11 and 15 for starting read out of the received radio wave at the trigger position and capturing the rising waveform thereof, a means 24 for operating a spectrogram pattern from the rising waveform, a reference information storage means 22 for storing a spectrogram pattern predetermined for each manufacturer and model of the radio as a reference spectrogram pattern, and means 6, 24 and 22 for identifying the model of a source radio of the radio wave received currently by comparing a spectrogram pattern operated from the rising waveform of the radio wave received currently with the reference spectrogram pattern. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radio device identification device that captures radio waves transmitted by an illegal radio station and identifies a model (model) and an individual of a radio device of a transmission source.
[0002]
[Prior art]
Illegal radio stations cause interference and interference with important radio communications and general business radio, and illegally increase the output to interfere with televisions and radios along roads. In recent years, the number of illegal radio stations has been increasing and appropriate measures for eradication have been strongly demanded. As a method for controlling an illegal radio station, a method of finding a source of an illegal radio wave by using a direction finder has been generally known.
[0003]
However, what is obtained by this direction finder is the place where radio waves are emitted, not the radio itself. For example, when there are a plurality of wireless devices in the same frequency band, it was not possible to specify which wireless device emitted the radio wave. Therefore, there is a need for a method of identifying a wireless device that is the source of the received radio wave.For example, a database is created for radio waves emitted from individual wireless devices, and when an illegal radio wave is received, a fingerprint is collated. A wireless device identification device that can identify a wireless device by collating with reference data stored in advance is being developed (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-2002-26826 [0005]
[Problems to be solved by the invention]
However, in the case of the wireless device identification device disclosed in Patent Document 1, if noise is included in the received radio wave, the rising time of the received radio wave may not be able to be accurately captured. In some cases, it was not possible to perform the matching with high accuracy, and it was not possible to identify the wireless device that transmitted the illegal radio wave.
[0006]
The present invention has been proposed in view of the above, and an object of the present invention is to provide a wireless device identification device capable of specifying from which wireless device of an illegal wireless station a signal is transmitted even when a received radio wave includes noise. Aim.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an apparatus for identifying a transmission source radio device using a received radio wave, wherein a trigger position determination for determining a trigger position from the received radio wave is performed. Means, starting reading of the received radio wave at a trigger position, rising waveform capturing means for capturing a rising waveform of the received radio wave, spectrogram pattern calculating means for calculating a spectrogram pattern from the rising waveform, Reference information storage means for storing a spectrogram pattern obtained in advance for each manufacturer and model as a reference spectrogram pattern, and comparing the reference spectrogram pattern with the spectrogram pattern calculated from the rising waveform of the received radio wave this time. , Of the wireless device that It is characterized by comprising the identifying means for identifying a Dell, a.
[0008]
According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the trigger position determining means determines that a spectrum obtained by converting a received radio wave is equal to or higher than a predetermined level. The first point is a trigger position.
[0009]
According to a third aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the rising waveform capturing means converts the received radio wave into an intermediate frequency band signal, and then converts the received radio wave to a predetermined bandwidth. In this case, the rising waveform is captured.
[0010]
Further, in the invention according to claim 4, in addition to the configuration of the invention described in claim 1, the spectrogram pattern is obtained by further connecting the signal levels of the spectrogram calculated from the rising waveform by contour lines. It is a pattern unique to the wireless device.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1 is a configuration diagram of a wireless device identification device of the present invention. In the figure, the wireless device identification device of the present invention includes a device main unit 100A and a trigger position determination unit 100B. The antenna 2 of the device main unit 100A receives a radio wave from the wireless device 1 and captures its rising state. In the following description, it is assumed that an illegal radio wave is transmitted from the wireless device 1. The antenna 2 can be rotated in an arbitrary direction by a driving unit 3. The direction finder 4 has a function of automatically tracking the antenna 2 in the direction of the illegal radio wave by controlling the drive unit 3. The receiving unit 5 receives the illegal radio wave captured by the antenna 2. The radio wave analyzer 7 analyzes the radio waves received by the receiver 5 to determine whether the radio waves are similar to illegal radio waves. The setting unit 8 is a keyboard and a mouse that can be set by an operator from the outside. The display unit 6 is used for displaying a spectrum, a waveform, and the like of the captured illegal radio wave, and displaying a model of a wireless device that generates the illegal radio wave described later, an individual number, and the like.
[0013]
The receiver 5 receives the radio waves propagating in the air, but does not capture the radio waves propagating in the air for the test of the radio itself, but receives the radio waves directly from the transmission terminal of the radio. It may be configured to acquire a signal.
[0014]
The receiving unit 5 outputs the reception signal S1 as an FM wave (for example, 30 to 3000 MHz) and inputs the reception signal S1 to the down converter 10. The received signal S1 is sampled at, for example, 20.48 MHz in the down-converter 10, converted into an intermediate frequency band signal (IF signal), and then output to the A / D converter 11.
[0015]
A part of the IF signal is branched and input to the trigger position determining unit 100B. The trigger position determination unit 100B determines a trigger position for a received radio wave by performing a predetermined calculation process on the IF signal, and outputs the trigger position Tr to the A / D converter 11. The details will be described later.
[0016]
The A / D converter 11 starts reading the current received radio wave from the trigger position Tr received from the trigger position determination unit 100B, digitizes the read signal, and outputs it as a digital IF signal S2.
[0017]
The digital IF signal S2 is input to the digital quadrature detection unit 15, and is converted into a pre-processing I signal S3 and a pre-processing Q signal S4 in the preceding stage. The pre-processing I signal S3 and the pre-processing Q signal S4 are decimated by the decimating unit 16, and the bandwidth is limited if necessary, and then buffered once in the memory 17. That is, the digital IF signal S2 is detected by the digital quadrature detection unit 15, and finally outputted from the memory 17 as an I signal S5 as amplitude information of a rising waveform and a Q signal S6 as phase information.
[0018]
FIG. 2 is a diagram illustrating a received radio wave waveform via an antenna, and FIG. 3 is a diagram illustrating a received radio wave waveform when a reception signal from the same wireless device is directly acquired by a receiving unit on a test basis by wire. The received radio wave waveform is displayed on an amplitude-phase display unit (not shown in FIG. 1). In each figure, the upper part shows the amplitude (I signal S5) and the lower part shows the phase (Q signal S6).
[0019]
As can be seen from the comparison between FIG. 2 and FIG. 3, the measurement data (FIG. 2) via the antenna is distorted so that the noise is totally superimposed and the characteristics of the rising waveform cannot be identified. It can be seen (see the upper part of FIG. 2). Then, it is difficult to capture the rising waveform of the received radio wave on which such noise is superimposed. On the other hand, the identification (identification) of a wireless device has conventionally been performed based on a rising waveform. Therefore, the function cannot be sufficiently exerted on a received radio wave including noise, and the identification of the wireless device is extremely difficult. It was difficult.
[0020]
On the other hand, in the present invention, (1) the rising point of the received radio wave is grasped with high accuracy, and the rising point is triggered to capture the received radio wave; and (2) the rising waveform of the received radio wave is Identifies a wireless device even in a noisy situation by performing arithmetic processing peculiar to the present invention so that a spectrogram pattern unique to each wireless device can be extracted with high accuracy. I can do it.
[0021]
In the following description, (2) spectrogram pattern extraction will be described first with reference to FIGS. 4 to 10, and (1) a trigger position determination technique will be described with reference to FIG. 11.
[0022]
As described above, in the present invention, the acquired data is converted into a spectrogram, and further converted into a spectrogram pattern that appropriately represents the characteristics of the wireless device. In order to efficiently perform pattern matching, an appropriate spectrogram pattern display method is important. Therefore, as a tool for quickly grasping the entire image of the spectrogram pattern, a predetermined software process was attempted. This software processing is executed by the time-frequency spectrum analyzer 24 in FIG. 1 and is performed on the I signal S5 and the Q signal S6 obtained by the digital quadrature detector 15. The resulting spectrogram pattern is displayed on the display. On the other hand, the radio identification data section 22 stores a spectrogram pattern obtained in advance for each manufacturer and model of the radio as a reference spectrogram pattern, which is calculated from a rising waveform such as the I signal S5 of the current reception radio wave. By comparing the obtained spectrogram pattern with the reference spectrogram pattern, the model of the wireless device that is the source of the current received radio wave is identified.
[0023]
FIG. 4 is a diagram showing an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from the wireless device a of Company A. The absolute value of the amplitude is displayed in the upper part. The lower spectrogram pattern is obtained by performing a fast Fourier transform (FFT) with a data length Nfft = 1024, calculating a spectrogram, and further connecting the signal levels by contour lines. That is, 95% to 10% of the maximum signal level Pmax is displayed in a pattern of 0.05 step contours over the entire data acquisition time. In the case of the decibel display selection, the display is performed from 1 dB of Pmax to -22 dB in 2 dB steps. The reason why the data length Nfft = 1024 was adopted was determined based on the frequency resolution, the time resolution, and the spread of the spectrum density. The vertical axis indicates the frequency deviation from the center frequency in this case in the range of ± 15 kHz, and the horizontal axis indicates the elapsed time from the trigger start point in a pattern over 102 ms. This tool is run interactively, the display can be selected linear or decibel, and the frequency range etc. is devised to obtain a pattern of appropriate size.
[0024]
In this way, by connecting the signal levels of the spectrogram pattern with the contour lines, it is possible to grasp the pattern unique to the wireless device. In the spectrogram pattern in the lower part of FIG. 4, the contour line pattern unique to the wireless device a is just Perfectly captured like a fingerprint.
[0025]
FIG. 5 is a diagram showing an absolute value of an amplitude waveform and a spectrogram pattern when a radio wave from the wireless device a receives strong interference. The vertical axis (frequency deviation) in the lower spectrogram pattern is scaled down and displayed. Comparing the amplitude waveforms of FIG. 4 and FIG. 5, in the former (FIG. 4), it can be seen that the amplitude waveform is slightly affected by noise and is receiving interference from an adjacent station. However, in the case of the latter amplitude waveform (FIG. 5), the influence of the interference wave and the noise becomes dominant, and the signal waveform is deteriorated to the extent that the prototype cannot be confirmed.
[0026]
Comparing the spectrogram patterns, focusing on the point where a step occurs in the frequency, the entire pattern rises apparently earlier in FIG. 5 by about 4 μs. This seems to be due to a change in the trigger setting and a change in the S / N ratio. As a result of superimposing the spectrogram patterns of FIGS. 4 and 5 and examining the degree of coincidence, the influence of the deformation of the spectrogram pattern, etc. There were few and good matches between the two patterns. That is, it was found that the spectrogram pattern was hardly affected by noise and could maintain a pattern unique to the wireless device.
[0027]
FIGS. 6 and 7 are diagrams showing an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from the wireless device b of Company B. The wireless device b has such a characteristic that the frequency change at the rising time vibrates vigorously from 0 to 30 ms and thereafter converges to the set frequency. In order to clearly show the fluctuation at the start of each measurement, the measurement is performed ten times in succession, and the maximum and the minimum measurement examples of the frequency change are selected and shown. FIG. 6 shows the minimum case, and FIG. 7 shows the maximum case.
[0028]
As described above, when the fluctuation at the rise of each measurement is large, the frequency of the rise is certainly large, but as a whole, both patterns show a good match, and the frequency change at the rise is drastic. It has been found that the present invention can be sufficiently applied to the identification of a wireless device.
[0029]
FIG. 8 is a diagram showing an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from a wireless device c of Company C. In the case of the wireless device c, the frequency tends to greatly vibrate at first and then tends to attenuate. According to the results obtained by using another wireless device, the pattern of the damped vibration is complicated, but the pattern to be shown differs depending on the device, and the wireless device can be identified.
[0030]
The measurement examples shown in FIGS. 4 to 8 are all obtained by setting the IF bandwidth to 250 kHz, performing measurements, and displaying the absolute value of the amplitude waveform and processing the spectrogram pattern through a 40 kHz low-pass filter. However, the effect of the IF bandwidth and the low-pass filter in the processing on the spectrogram pattern will be described. The bandwidth limitation is performed by the thinning unit 16 in FIG.
[0031]
FIG. 9 is a diagram showing an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from the wireless device b of Company B. 9 is different from FIGS. 6 and 7 in that the measurement is performed with an IF bandwidth of 50 kHz and the measured IQ data is processed through a low-pass filter having a cutoff frequency of 20 kHz. Compare FIG. 9 with FIGS. 6 and 7, which are measurement examples at an IF bandwidth of 250 kHz. First, in the comparison of the amplitude waveforms on the upper side of each figure, both figures in FIGS. 6 and 7 first overshoot, and then settle down to a certain level. In FIG. 9, distortion occurs in the amplitude waveform in the overshoot section. The cause of this distortion is due to the influence of the low-pass filter used for noise removal. This is because frequency components exceeding the characteristics of the low-pass filter have been removed from the data in this section. However, no effect that impairs the effectiveness of the pattern has been observed.
[0032]
FIG. 10 is a diagram showing an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from the radio device b of Company B. The measurement is performed with an IF bandwidth of 12 kHz, and the measured IQ data is cut off. The result of processing through a low-pass filter with a frequency of 10 kHz is shown. The distortion of the amplitude waveform in FIG. 10 is even more severe, and in the section where the overshoot is shown in FIGS. 6 and 7, the frequency component exceeding the band limit is cut off by the characteristics of the filter, and the amplitude waveform is greatly depressed. If this phenomenon is related to the pattern below, it is clear that the frequency component in this portion has been removed. However, it can be seen that the tendency of the pattern in the entire lower spectrogram pattern is preserved as it is and the wireless device can be identified.
That is, the following results were obtained from FIG. 9 and FIG. That is, the relationship between the spectrogram pattern and the bandwidth can be expected to have the effect of suppressing the noise and improving the S / N ratio as the bandwidth becomes narrower. However, on the other hand, there is a possibility that necessary signal information is lost. The influence of the amplitude waveform in the time domain is large, and the characteristics of the amplitude waveform are degraded. In contrast, the affected portion can be clearly seen in the frequency domain spectrogram pattern. It was found that in the case of identifying a wireless device under a situation where the influence of noise is large, even a pattern obtained by performing signal processing of a narrow band for noise removal can be effectively used.
[0033]
Next, a method of determining the trigger position will be described. As shown in the upper part of FIG. 2, the received radio wave via the antenna is distorted so that noise is superimposed entirely and the characteristics of the rising waveform cannot be identified. For this reason, it has conventionally been extremely difficult to detect the rising point of the radio wave even when the radio wave is received. On the other hand, in the present invention, the received radio wave is converted into an IF signal by the down-converter 10, branched, input to the trigger position determining unit 100B, and subjected to predetermined data processing to determine the trigger position.
[0034]
The trigger position determination unit 100B includes an A / D converter 110 and a digital quadrature detection unit 150, similarly to the device main unit 100A. The IF signal output from the down converter 10 is applied to the A / D converter 110 at a sample rate of 10.24 MHz, and is converted into a digital IF signal S20 in the A / D converter 110. Subsequently, the signal is converted into an I signal S30 before processing and a Q signal S40 before processing by the digital quadrature detection unit 15 and further thinned by the thinning unit 160, and the bandwidth is set to 31.25 kHz, 15.63 kHz and 7.81 kHz, for example. After being limited to one of the types, it is temporarily buffered in the memory 170. Thereafter, an I signal S50 as amplitude information and a Q signal S60 as phase information are output. Then, spectrum calculation section 180 provided at the subsequent stage of quadrature detection section 150 converts I signal S50 and Q signal S60 into a spectrum, and the spectrum is input to trigger detection section 190.
[0035]
FIG. 11 is a diagram showing a free-run spectrum obtained by the spectrum calculation unit. As shown in this figure, the trigger detection unit 190 compares the calculated maximum value of the spectrum with the trigger level T0 set by the setting unit 8, and determines the first point at which the spectrum becomes equal to or higher than the preset level. An instruction is sent to the A / D converter 11 of the apparatus main unit 100A so as to set the trigger position Tr and take in the trigger position information.
[0036]
As described above, in the present invention, when determining the trigger position, the bandwidth is limited, and after converting the spectrum to a spectrum, the first point at which the spectrum is equal to or higher than a predetermined level is set as the trigger position. Even when the rise time cannot be grasped due to white noise or the like, the reading start position for the received radio wave can be accurately detected.
[0037]
In addition, by applying arithmetic processing unique to the present invention to the received radio wave read from the trigger position described above, a spectrogram pattern unique to each wireless device can be extracted with high accuracy, so that a situation with severe noise Even now, the radio can be specified.
[0038]
【The invention's effect】
As described above, in the present invention, when determining the trigger position, the bandwidth is limited, and after conversion into a spectrum, the first point at which the spectrum is equal to or higher than a preset level is set as the trigger position. Even when the rising time of the radio wave cannot be determined due to white noise or the like, the reading start position for the received radio wave can be accurately detected.
[0039]
In addition, by performing an arithmetic process specific to the invention on the received radio wave read from the trigger position, a spectrogram pattern unique to each wireless device can be extracted with high accuracy, and the pattern is referred to as a reference spectrogram pattern. Since the comparison is made, the wireless device can be specified even in a situation where the noise is severe. Therefore, even if the received radio wave includes noise, it is possible to specify from which radio device of the illegal radio station the signal is transmitted, which can greatly contribute to crackdown on the illegal radio station.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a wireless device identification device of the present invention.
FIG. 2 is a diagram showing a waveform of a radio wave received via an antenna.
FIG. 3 is a diagram illustrating a received radio wave when a reception signal from the same wireless device is directly acquired by a reception unit on a trial basis through a cable.
FIG. 4 is a diagram showing an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from a wireless device a of Company A.
FIG. 5 is a diagram showing an absolute value of an amplitude waveform and a spectrogram pattern when a radio wave from a wireless device a receives strong interference.
FIG. 6 is a diagram showing an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from a wireless device b of Company B.
FIG. 7 is a diagram showing an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from a wireless device b of Company B.
FIG. 8 is a diagram showing an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from a wireless device c of Company C.
FIG. 9 shows an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from a wireless device b of Company B, which is measured at an IF bandwidth of 50 kHz. It is a figure showing the result of having processed through a low pass filter.
FIG. 10 shows an amplitude waveform and a spectrogram pattern obtained by applying this software to a radio wave received from a wireless device “b” of Company B. The measurement is performed with an IF bandwidth of 12 kHz, and the measured IQ data has a cutoff frequency of 10 kHz. It is a figure showing the result of having processed through a low pass filter.
FIG. 11 is a diagram illustrating a spectrum in a free run obtained by a spectrum calculation unit.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 radio 2 antenna 3 driving section 4 direction finder 5 reception section 6 display section 7 radio wave analysis section 8 setting section 10 down converter 11 A / D converter 15 digital quadrature detection section 16 thinning section 17 memory 22 radio apparatus identification data section 24 Time-frequency spectrum analyzer 100A Device main unit 100B Trigger position determiner 110 A / D converter 150 Digital quadrature detector 160 Decimator 170 Memory 180 Spectrum calculator 190 Trigger detector S1 Received signal S2 Digital IF signal S3 Before processing I signal S4 Q signal before processing S5 I signal S6 Q signal S20 Digital IF signal S30 I signal before processing S40 Q signal before processing S50 I signal S60 Q signal

Claims (4)

In a wireless device identification device that identifies the source wireless device using the received radio wave,
Trigger position determining means for determining a trigger position from the received radio wave,
A rising waveform capturing unit that starts reading the received radio wave at a trigger position and captures a rising waveform of the received radio wave;
Spectrogram pattern calculating means for calculating a spectrogram pattern from the rising waveform;
Reference information storage means for storing a spectrogram pattern obtained in advance for each manufacturer and model of the wireless device as a reference spectrogram pattern,
Identification means for identifying the model of the wireless device that is the source of the received radio wave by comparing the spectrogram pattern calculated from the rising waveform of the received radio wave this time with the reference spectrogram pattern,
A wireless device identification device comprising: The wireless device identification device according to claim 1, wherein the trigger position determining means sets a first point at which a spectrum obtained by converting from a received radio wave is equal to or higher than a predetermined level as a trigger position. The wireless device identification device according to claim 1, wherein the rising waveform capturing means converts a received radio wave into an intermediate frequency band signal, and thereafter performs a rising waveform capturing process by limiting the received radio wave to a predetermined bandwidth. 2. The wireless device identification device according to claim 1, wherein the spectrogram pattern is a pattern unique to a wireless device obtained by connecting signal levels of a spectrogram calculated from a rising waveform further by contour lines.

Images