JP3605229B2 - Digital phase modulation method display method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital phase modulation method determination display method for determining a digital phase modulation method of a signal received from an unknown wireless device.
[0002]
Problems to be solved by the prior art and the invention
Various digital phase modulation methods such as PSK, QPSK, π / 4 shift QPSK, 16 QAM, and 256 QAM are available as digital phase modulation methods for wireless devices. In such a digital phase modulation method, if the carrier frequency and phase of the received signal are known, the received signal is synchronously detected at the accurate frequency and phase, and the detected data is easily confirmed by displaying the data graphically. be able to. That is, a unique symbol pattern corresponding to a phase change point is determined according to each digital phase modulation method. As described above, in the conventional signal analysis system, an appropriate synchronous detection can be performed based on a precise carrier frequency and phase by analyzing an input signal whose digital phase modulation method is known.
[0003]
However, in the case of an input signal from an unknown radio, the digital phase modulation method is unknown, and the carrier frequency and phase of the signal are also unknown, so that the input signal cannot be properly synchronously detected. In order to extract a carrier signal from an input signal, the digital phase modulation method must be known, and for an unknown digital phase modulation input signal, a large number of circuits corresponding to all conceivable methods respectively. There is only a method of switching and using until a proper synchronous detection can be performed, but such a trial-and-error analysis method has a drawback that it is extremely complicated and increases the cost. Therefore, it is difficult to accurately detect an input signal from an unknown wireless device by synchronous detection and display the graph, and it is also possible to determine the digital phase modulation method of the unknown wireless device from a received signal from the unknown wireless device. It was extremely difficult.
[0004]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a digital phase modulation method determination and display method capable of accurately and easily determining a digital phase modulation method of an input signal from an unknown wireless device.
[0005]
[Means for solving the problem]
The present invention provides a digital phase modulation method determination display method for automatically determining a digital phase modulation method of an input signal from an unknown wireless device. As a premise, when the in-phase component (I component) and the quadrature component (Q component) of the received signal are displayed on a quadrature coordinate plane or a polar coordinate plane, the fact that the symbol pattern differs depending on the digital phase modulation method is used. . Therefore, in order to perform display for determining a digital phase modulation method from an input signal from an unknown wireless device, the following procedure is employed. First, frequency domain data of an unknown digital phase modulation signal is generated, and an estimated carrier frequency of the unknown digital phase modulation signal is obtained from the frequency domain data. Next, the time domain data of the unknown digital phase modulation signal is detected and calculated based on the estimated carrier frequency to obtain rectangular coordinate data in the time domain. At each point of the rectangular coordinate data, one of the coordinates is an extreme value. Are determined, and only these symbol points are plotted on a coordinate plane composed of a plurality of divided areas, and the number of divided areas in which the symbol points are not plotted among the plurality of divided areas is counted. Are sequentially repeated while changing the estimated carrier frequency. As a result, the estimated carrier frequency when the number of divided regions in which the symbol points are not plotted becomes the maximum is obtained as the true carrier frequency. Based on this carrier frequency, time domain data of the unknown digital phase modulation signal is detected and calculated, and the resulting data is displayed on a display screen.
[0006]
According to the present invention, since the detection calculation for obtaining the rectangular coordinate data in the time domain has a relatively heavy calculation load, a method of reducing the calculation load can also be adopted. That is, not all the symbol points are obtained from the rectangular coordinate data, but the rectangular coordinate data is converted into polar coordinate data, and data corresponding to the previously obtained symbol point is extracted from the polar coordinate data. As a result, the calculation load for directly finding the symbol points from the orthogonal coordinate data is significantly reduced, and the processing speed is increased.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 4 is a block diagram showing an example of the configuration of an analysis system suitable for using the digital phase modulation system determination display method of the present invention. The antenna 10 receives an output signal of an unknown or known radio device. The signal received by the antenna 10 is supplied to a down converter 12 functioning as a receiver and a frequency converter, and is converted into an intermediate frequency signal. This intermediate frequency signal is supplied to the digital spectrum analyzer 14, converted into a digital data sequence (time domain), further converted into digital frequency component data by FFT processing, and stored in a memory (not shown). . Thereafter, the digital frequency component data in the memory is sent to the computer 16. The computer 16 has a display screen 18 and displays information necessary for controlling the entire system such as a measurement result, an analysis result, and a setting state of the system. As the downconverter 12, for example, a 2784 type spectrum analyzer manufactured by Sony Tektronix is suitable, and as the digital spectrum analyzer 14, a 3055 type real time spectrum analyzer manufactured by Sony Tektronix is suitable. It is. However, of course, other suitable measuring instruments can be used. However, it is desirable that the digital spectrum analyzer 14 has a real-time analysis function because it is desirable to analyze data without a break in time in order to improve analysis accuracy. The real-time analysis function of the digital spectrum analyzer is well known to those skilled in the art, and is not directly related to the present invention, so that the description is omitted.
[0008]
The data analysis is executed by the computer 16 according to the software. 1 and 2 are an example of a flowchart of a process executed by the computer 16 in accordance with the digital phase modulation method determination display method of the present invention. First, frequency domain data of a signal from an unknown wireless device input to the digital spectrum analyzer 14 via the antenna 10 and the down converter 12 is generated (step 100). Specifically, time domain data is generated by digitizing the input signal, and FFT (fast Fourier transform) processing is executed to generate frequency domain data. Next, an estimated carrier frequency is calculated based on the generated frequency domain data (step 102). In the estimation calculation of the carrier frequency, a frequency value corresponding to a half value of the total accumulated value of the amplitude of the frequency domain data is employed. The value of the estimated carrier frequency obtained by such an estimation calculation does not necessarily match the actual carrier frequency of the input signal, but can be gradually approximated to the true value by the processing described later. .
[0009]
Next, detection processing is performed on the time domain data of the input signal based on the estimated carrier frequency to obtain rectangular coordinate data in the time domain (step 104). As the time domain data of the input signal used in this case, the data used in the digital spectrum analyzer 14 may be used as it is, or the frequency domain data generated in step 100 may be subjected to an inverse FFT calculation process. You may ask. The detection calculation means that a process similar to the detection by hardware is performed by the calculation of the computer 16. That is, the rectangular coordinate data in the time domain is represented on a rectangular coordinate plane of the I (in-phase) axis and the Q (quadrature) axis. If the digital phase modulation method of the input signal is known and the carrier frequency and phase are also known, accurate rectangular detection can be performed on the rectangular coordinate data. If the data is plotted on the IQ coordinate plane, Although a symbol pattern corresponding to the phase modulation method is displayed, in the present invention, neither the digital phase modulation method nor the carrier frequency is unknown at this time, and only an approximate detection operation is performed. . Specifically, the detection calculation is executed based on the following Expressions 1 and 2.
[0010]
(Equation 1)
a = cosωx
b = sin ωx
ω = 2πFT
F: Difference between the center frequency of the frequency domain width and the estimated carrier frequency T: Sampling period x: Data variable
I (x) = a · i (x) + b · q (x)
Q (x) = a · q (x) −bi · (x)
i (x): In-phase component data in time domain q (x): Quadrature component data in time domain I (x): I-axis component data of quadrature coordinate data Q (x): Q-axis component data of quadrature coordinate data By performing the detection operation, the rectangular coordinate data I (x) and Q (x) in the time domain are obtained. Note that the orthogonal coordinate data obtained here is not obtained by accurate synchronous detection, but is the result of an approximate estimation calculation.
[0011]
Next, for each point of the orthogonal coordinate data, a symbol point at which any one of the coordinates has an extreme value is determined (step 106). The symbol point is a point considered to correspond to the phase change point in the phase modulation. At the phase change point, one of the in-phase component coordinate I (x) and the quadrature component data Q (x) is an extreme value (maximum value). Value or local minimum value).
[0012]
Next, the symbol points obtained in step 106 are plotted on a coordinate plane composed of a plurality of divided areas (step 108). In this case, the coordinate plane may be a rectangular coordinate plane or a polar coordinate plane. Whatever the coordinate plane, it is only necessary to be divided by a plurality of small divided areas. In addition, since the shape of each divided area does not need to be particularly limited, a divided area that is convenient for the adopted coordinate plane can be adopted. Further, the process of “plot” here does not need to be performed at all by actually displaying the coordinate plane on the screen. It is sufficient to record the coordinate data on the coordinate plane. That is, it is sufficient that the computer 16 can determine whether or not a symbol point exists in each of the plurality of regions on the coordinate plane, and the observer does not need to determine.
[0013]
Next, the number of divided regions in which no symbol point is plotted among a plurality of divided regions constituting the coordinate plane is counted (step 110). Thereafter, the estimated carrier frequency is changed by a predetermined value (step 112). The above steps 104 to 112 are sequentially and repeatedly executed over the search range of the estimated carrier frequency. When all the processes in the search range are completed (step 114), an estimated carrier frequency at which the number of divided regions where no symbol points are plotted is maximized is determined, and this is regarded as a true carrier frequency (step 116). The detection operation of the time-domain data of the input signal is performed again based on (118). The data obtained as a result is graphically displayed on a coordinate plane (I-Q coordinate plane) on the display screen (step 120). As a result, a symbol pattern corresponding to the digital phase modulation method of the input signal is displayed, so that those skilled in the art having ordinary knowledge can determine the digital phase modulation method of the unknown input signal at a glance.
[0014]
The search range of the estimated carrier frequency is a predetermined frequency range centered on the first estimated carrier frequency. For example, when the frequency domain data width is 200 kHz, the search range is 6.25 kHz. The search step of the estimated carrier frequency in the search process is, for example, about 4 Hz. These values are merely examples, and can be executed in other search ranges and search steps.
[0015]
In the above-described processing, the processing of the detection calculation performed in step 104 includes the calculation of the trigonometric function, and thus takes a relatively long time. Therefore, it is not always appropriate to execute the calculations of Expressions 1 and 2 for each search step within all search ranges. Of course, it is theoretically sufficient to perform the detection operation in step 104, but a method of performing the calculation at a higher speed without substantially sacrificing accuracy may be adopted.
[0016]
In other words, the detection operation is not performed for each search step over the entire search range, but the search range is divided into a plurality of equal parts, for example, and the detection calculation is performed once for each search divided region, and the result is obtained. Using the data of the obtained symbol points, the calculation of the remaining search steps in each search divided area can be simplified. As an example, a case will be described in which 20 search division regions are set around the estimated carrier wave frequency calculated first, and 80 search steps are executed for each search division region. In this case, the detection calculation in step 104 is performed only 20 times in total (once for each search divided region), and the remaining 79 times for each search divided region perform approximate calculation. The processing procedure in this case is shown in the flowchart of FIG.
[0017]
The flowchart of FIG. 3 replaces the processing of steps 108 to 110 of FIG. 1, and is a processing for reducing the calculation load. Note that the processing in FIG. 2 shows processing in each of the 20 divided regions, and the processing in FIG. 3 is repeated 20 times while changing the search range over the entire search range.
[0018]
In FIG. 2, the orthogonal coordinate data obtained in step 104 of FIG. 1 is coordinate-converted into polar coordinate data (r, φ) (step 200). Next, data points corresponding to the symbol points of the orthogonal coordinate data are extracted from the polar coordinate data (step 202). This process simply extracts, from the polar coordinate data, data points at the same position as the symbol point of the orthogonal coordinate data, so that the complicated detection operation and the search process of the symbol point are omitted as in the related art. It is a calculation. Next, data points corresponding to the symbol points extracted from the polar coordinate data are plotted on a coordinate plane constituted by a plurality of divided areas (step 204). Next, the number of symbol points and the number of divided areas in which data points corresponding to the symbol points are not plotted are counted (step 206). Further, polar coordinate data (r, φ + Δφ) is generated by changing only the argument component φ of the polar coordinate data (r, φ) by a predetermined angle (step 208). In the case of FIG. 1, this processing corresponds to the processing of step 104 of executing the complicated detection operation to generate the orthogonal coordinate data, and changes the radial component r of the polar coordinate data (r, φ). Instead, only the declination component φ is slightly changed, thereby greatly reducing the load of calculation processing without lowering the search accuracy.
[0019]
The processing of the above steps 200 to 208 is repeatedly executed until the processing of one search divided area is completed in the determination step 210. That is, in this example, the processing of one search divided area is repeated 80 times. Since the processing of the search divided area is repeated 20 times, the processing is performed 80 × 20 = 1600 times in total. In this process, the detection calculation (step 104) of FIG. 1 is performed only 20 times, and the process of FIG. 3 is repeated 79 × 20 = 1580 times. As a result, the calculation load is remarkably reduced, and the processing can be speeded up. It should be noted that the number of executions of the above-described calculation processing is arbitrary, and is not limited to this case.
[0020]
5 to 8 show examples of hard copy output of the display result on the display screen 18 of the computer 16 obtained according to the present invention. In the coordinate plane display indicated as “IQ”, a set portion of points with high density (dark) indicates a symbol point or a data point corresponding to the symbol point. The linear display other than the symbol points is a display based on the data other than the symbol points, and indicates the state of the phase change. However, for the determination of the digital phase modulation method, the symbol display corresponds to the symbol points or the symbol points. Displaying data points is sufficient. FIG. 5 clearly shows the symbol pattern display of “QPSK”, FIG. 6 clearly shows the symbol pattern of “16 QAM”, and FIG. 7 clearly shows the symbol pattern display of “64 QAM”. In FIG. 8, the symbol pattern display of “1 / π shift QPSK” is clearly shown. From the above display, those skilled in the art can clearly determine the digital phase modulation method of the unknown input signal.
[0021]
As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to only the above-described embodiments, and various changes and modifications can be made without departing from the gist of the present invention. It will be clear to those skilled in the art.
[Brief description of the drawings]
FIG. 1 is a part of a flow chart illustrating the method of the present invention.
FIG. 2 is a flowchart other than the part of FIG. 1 illustrating the method of the present invention.
FIG. 3 is a flowchart showing an example of another embodiment of the method of the present invention.
FIG. 4 is a block diagram showing a configuration of a system suitable for applying the present invention.
FIG. 5 is a halftone image showing an example of a computer display display according to the present invention.
FIG. 6 is a halftone image showing another example of a computer display display according to the present invention.
FIG. 7 is a halftone image showing another example of a computer display display according to the present invention.
FIG. 8 is a halftone image showing yet another example of a computer display display according to the present invention.
[Explanation of symbols]
Reference Signs List 10 antenna 12 down converter 14 digital spectrum analyzer 16 computer 18 display screen

Claims (8)

(A) generating frequency domain data of an unknown digital phase modulation signal,
(B) determining an estimated carrier frequency of the unknown digital phase modulation signal from the frequency domain data;
(C) detecting and calculating time domain data of the unknown digital phase modulation signal based on the estimated carrier frequency to obtain rectangular coordinate data in the time domain;
(D) finding a symbol point at which one of the coordinates is an extreme value at each point of the rectangular coordinate data;
(E) plotting only these symbol points on a coordinate plane composed of a plurality of divided areas,
(F) counting the number of divided areas in which the symbol points are not plotted among the plurality of divided areas;
(G) changing the estimated carrier frequency,
(H) repeating the above steps (c) to (g) to determine the time of the unknown digital phase modulation signal based on the estimated carrier frequency when the number of divided areas where the symbol points are not plotted is maximized. Detect and calculate the area data,
(I) A digital phase modulation method determination display method, wherein the data obtained as a result is displayed on a display screen. In the step (a), time domain data of the unknown digital phase modulation signal is generated,
2. The method according to claim 1, wherein the frequency domain data is generated by performing an FFT operation on the time domain data. 2. The method according to claim 1, wherein in the step (c), the time domain data is obtained by performing an inverse FFT operation on the frequency domain data. 2. The digital signal according to claim 1, wherein in the step (c), the time domain data is detected and calculated by a difference between a center frequency of the frequency domain data of the unknown digital phase modulation signal and the estimated carrier frequency. Phase modulation method determination display method. (A) generating frequency domain data of an unknown digital phase modulation signal,
(B) determining an estimated carrier frequency of the unknown digital phase modulation signal from the frequency domain data;
(C) detecting and calculating time domain data of the unknown digital phase modulation signal based on the estimated carrier frequency to obtain rectangular coordinate data in the time domain;
(D) finding a symbol point at which one of the coordinates is an extreme value at each point of the rectangular coordinate data;
(E) converting the rectangular coordinate data into polar coordinate data,
(F) extracting a data point corresponding to the symbol point from the polar coordinate data;
(G) plotting only these extracted data points on a polar coordinate plane composed of a plurality of divided areas,
(H) counting the number of divided areas in which data points are not plotted among the plurality of divided areas;
(I) changing the estimated carrier frequency,
(J) repeating the above steps (c) to (i) to determine the time of the unknown digital phase modulation signal based on the estimated carrier frequency when the number of divided areas where the data points are not plotted is at a maximum. Detect and calculate the area data,
(K) A digital phase modulation method determination display method, wherein the data obtained as a result is displayed on a display screen. In the step (a), time domain data of the unknown digital phase modulation signal is generated,
6. The method according to claim 5, wherein the frequency domain data is generated by performing an FFT operation on the time domain data. 6. The method according to claim 5, wherein in the step (c), the time domain data is obtained by performing an inverse FFT operation on the frequency domain data. 6. The digital signal according to claim 5, wherein in the step (c), the time domain data is detected by a difference between a center frequency of the frequency domain data of the unknown digital phase modulation signal and the estimated carrier frequency. Phase modulation method determination display method.

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