JPH09298567A - Method for discriminating and displaying digital phase modulating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly discriminate the digital phase modulating system of an input signal from unknown radio equipment by finding an estimated carrier frequency from the frequency area data of an unknown digital phase modulated signal, detecting that frequency, operating it, finding the symbol point of phase modulation and displaying data provided by detecting and operating that frequency again. SOLUTION: A down converter 12 converts the radio wave of unknown radio equipment received by an antenna 10 to an intermediate frequency signal and a data spectrum analyzer 14 converts that signal to digital frequency component data and stores them in a memory. Afterwards, a computer 16 finds the estimated carrier frequency from the digital frequency component data in the memory and finds an orthogonal coordinate by detecting and operating time area data based on this frequency. Further, the symbol point of phase modulation is found at the respective points of these coordinate data and a true carrier frequency is found from this symbol point. Then, the time area data are detected and operated again based on the found carrier frequency and the provided symbol point is displayed on a coordinate plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. 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 received signal from an unknown radio device.

[0002]

2. Description of the Related Art PSK, QPSK, π are used as digital phase modulation systems for radio equipment.
There are various digital phase modulation schemes such as / 4 shift QPSK, 16QAM and 256QAM. 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 displayed graphically for easy confirmation. be able to. That is, a unique symbol pattern corresponding to the 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 an accurate carrier frequency and phase by analyzing an input signal whose digital phase modulation method is known.

However, in the case of an input signal from an unknown radio device, 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 the carrier signal from the input signal, the digital phase modulation method must be known, and for the input signal of the unknown digital phase modulation method, a large number of circuits corresponding to all possible methods, respectively. However, there is only a method of switching and using it until proper synchronous detection is performed, but such a trial-and-error analysis method has a drawback that it is extremely complicated and costly. Therefore, it is difficult to accurately synchronously detect the input signal from the unknown radio and display it in a graph, and it is also possible to determine the digital phase modulation method of the unknown radio from the received signal from the unknown radio. It was extremely difficult.

Therefore, an object of the present invention is to provide a digital phase modulation method determination display method capable of accurately and easily determining the digital phase modulation method of an input signal from an unknown radio device.

[0005]

SUMMARY OF THE INVENTION The present invention provides a digital phase modulation method determination display method for automatically determining the digital phase modulation method of an input signal from an unknown radio device. As a premise, when the in-phase component (I component) and the quadrature component (Q component) of the received signal are displayed on the orthogonal coordinate plane or the polar coordinate plane, the fact that the symbol patterns differ depending on the digital phase modulation method is used. . Therefore, in order to perform the display for determining the digital phase modulation method from the input signal from the unknown wireless device, the following procedure is adopted. 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 this frequency domain data. Next, the time domain data of the unknown digital phase modulation signal is detected and calculated based on this estimated carrier frequency to obtain the Cartesian coordinate data of the time domain, and at either point of this Cartesian coordinate data, one of the coordinates is the extreme value. To find the symbol point
Estimate a series of operations of plotting only these symbol points on a coordinate plane composed of a plurality of divided areas and counting the number of divided areas in which the symbol points are not plotted in the plurality of divided areas. This is repeatedly executed while changing the carrier frequency. As a result, the estimated carrier frequency when the number of divided regions where the symbol points are not plotted becomes the maximum is obtained as the true carrier frequency. Based on this carrier frequency, the time domain data of the unknown digital phase modulation signal is detected and calculated, and the resulting data is displayed on the display screen.

According to the present invention, since the detection calculation for obtaining the orthogonal 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 orthogonal coordinate data is converted into polar coordinate data, and the data corresponding to the previously obtained symbol points is extracted from the polar coordinate data. As a result, the calculation load for directly obtaining the symbol points from the orthogonal coordinate data is significantly reduced, and the processing speed can be increased.

[0007]

FIG. 4 is a block diagram showing an example of the configuration of an analysis system suitable for using the digital phase modulation method determination display method of the present invention. Antenna 10
Is to receive radio waves of an output signal of an unknown or known radio device. The signal received by the antenna 10 is supplied to a down converter 12 that functions 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 string (time domain), further converted into digital frequency component data by FFT processing, and stored in a memory (not shown). . After that, the digital frequency component data in the memory is
Sent to computer 16. This computer 16
Has a display screen 18 for measuring, analyzing,
Displays information necessary for controlling the entire system, such as system settings. As the down converter 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. Is. However, it goes without saying that other suitable measuring instruments can be used. However, digital
It is preferable that the 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. Note that 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 the description thereof will be omitted.

The data analysis is performed by the computer 16 according to software. 1 and 2 are an example of a flowchart of processing 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 radio which is input to the digital spectrum analyzer 14 via the antenna 10 and the down converter 12 is generated (step 100). Specifically, the input signal is digitized to generate time domain data, 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). This carrier frequency estimation calculation is 2 times the total accumulated value of the amplitudes of the frequency domain data.
The frequency value corresponding to the fractional value is adopted. Although the value of the estimated carrier frequency obtained by such an estimation calculation does not always match the actual carrier frequency of the input signal, it can be gradually approximated to the true value by the processing described later. .

Next, the time domain data of the input signal is detected and calculated based on the estimated carrier frequency to obtain the time domain orthogonal coordinate data (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 inverse FFT calculation process may be performed on the frequency domain data generated in step 100. You may ask. The detection calculation means that the computer 16 performs a process similar to the detection by hardware. That is, the Cartesian coordinate data in the time domain is represented on the Cartesian coordinate plane of the I (in-phase) axis and the Q (orthogonal) axis. This Cartesian coordinate data can be accurately detected synchronously if the digital phase modulation method of the input signal is known and the carrier frequency and phase are also known. When the data is plotted on the IQ coordinate plane, Although the 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 point, and only an approximate detection calculation is performed. . Specifically, the detection calculation is executed based on the following formulas 1 and 2.

[0010]

## EQU1 ## a = cos ωx b = sin ωx ω = 2πFT F: difference between center frequency of frequency domain width and estimated carrier frequency T: sampling period x: data variable

## EQU00002 ## I (x) = a.i (x) + b.q (x) Q (x) = a.q (x) -b.i (x) i (x): In-phase component data in the time domain q (x): Quadrature component data in the time domain I (x): I-axis component data of the Cartesian coordinate data Q (x): Q-axis component data of the Cartesian coordinate data Cartesian coordinate data I (x) and Q (x) are obtained. It should be noted that the Cartesian coordinate data obtained here is not the one obtained by accurate synchronous detection but the result of approximate estimation calculation.

Next, at each point of the Cartesian coordinate data, a symbol point in which one of the coordinates has an extreme value is obtained (step 106). A symbol point is a point that is considered to correspond to a phase change time point in phase modulation, and at the phase change time point, either the in-phase component coordinate I (x) or the quadrature component data Q (x) has an extreme value (maximum value). Value or minimum value)
It is considered that

Next, the symbol points obtained in step 106 are plotted on a coordinate plane composed of a plurality of divided areas (step 108). The coordinate plane in this case may be a rectangular coordinate plane or a polar coordinate plane. Any coordinate plane may be divided into a plurality of small divided areas. Further, since it is not necessary to limit the shape of each divided area, it is possible to adopt a divided area that is convenient for the coordinate plane to be used. Further, the process of "plot" here does not need to be performed by actually displaying the coordinate plane on the screen. It is sufficient to record the coordinate data on the coordinate plane. In other words, it is sufficient if 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.

Next, among the plurality of divided areas forming the coordinate plane, the number of divided areas in which no symbol point is plotted is counted (step 110). Then, the estimated carrier frequency is changed by a predetermined value (step 11).
2). The above steps 104 to 112 are sequentially repeated over the search range of the estimated carrier frequency. When all the processing in the search range is completed (step 11
4) Obtain an estimated carrier frequency that maximizes the number of divided regions in which symbol points are not plotted, consider this as the true carrier frequency (step 116), and re-calculate the time domain data of the input signal based on that frequency. The detection calculation is performed (118). The data obtained as a result is graphically displayed on the coordinate plane (I-Q coordinate plane) on the display screen (step 120). As a result, since the symbol pattern corresponding to the digital phase modulation method of the input signal is displayed, a person having ordinary skill in the art can easily determine the unknown digital phase modulation method of the input signal.

The estimated carrier frequency search range is a predetermined frequency range centered on the initially determined estimated carrier frequency, and is 6.25 kHz when the frequency domain data width is 200 kHz, for example. The search step for the estimated carrier frequency in the search process is, for example, about 4 Hz. It is needless to say that these values are examples and can be executed in other search ranges and search steps.

In the above-mentioned processing, since the processing of the detection calculation executed in step 104 includes the calculation of trigonometric functions, it takes a relatively long time. Therefore, it is not always appropriate to execute the calculation of Expression 1 and Expression 2 for each search step within the entire search range. Of course, theoretically, all the detection calculation of step 104 should be performed, but a method of performing the calculation at a higher speed without sacrificing the accuracy may be adopted.

That is, the detection operation is not executed for each search step over the entire search range, but the search range is divided into, for example, a plurality of equal parts, and the detection operation is executed once for each search divided area. The data of the resulting symbol points can be used to simplify the calculation of the remaining search steps within each search segment. As an example, a case will be described in which 20 search divided areas are set around the estimated carrier frequency calculated first and 80 search steps are executed for each search divided area. In this case, step 104
The detection calculation is performed only 20 times in total (once for each search divided area), and the remaining 79 times for each search divided area are approximated. The processing procedure in this case is shown in FIG.
Is shown in the flowchart.

The flow chart of FIG. 3 includes steps 108 to 108 of FIG.
It replaces the processing up to 110 and is processing for reducing the calculation load. Note that the process of FIG. 2 shows the process in each of the 20 divided areas, and for the entire search range, the process of FIG.
It will be repeated times.

In FIG. 2, the Cartesian coordinate data obtained in step 104 of FIG. 1 is converted into polar coordinate data (r, φ) (step 200). Next, data points corresponding to the symbol points of the rectangular coordinate data are extracted from the polar coordinate data (step 202). This process simply extracts the data points whose polarities are the same as the symbol points of the Cartesian coordinate data from the polar coordinate data, so it is extremely easy to perform without the cumbersome detection calculation and symbol point search processing. It is a simple calculation. Next, the data points corresponding to the symbol points extracted from the polar coordinate data are plotted on the coordinate plane composed of a plurality of divided areas (step 204).
Next, the number of divided areas in which the symbol points and the data points corresponding to the symbol points are not plotted is counted (step 206). Furthermore, polar coordinate data (r, φ) obtained by changing only the angle component φ of the polar coordinate data (r, φ) by a predetermined angle.
+ Δφ) is generated (step 208). This process
The case of FIG. 1 corresponds to the process of step 104 of performing a cumbersome detection calculation to generate Cartesian coordinate data, and does not change the radial component r of the polar coordinate data (r, φ), and the declination angle By only slightly changing the component φ, the calculation accuracy is greatly reduced without lowering the search accuracy.

The processing in steps 200 to 208 described above is
The determination step 210 is repeatedly executed until the processing of one search division area is completed. That is, in this example, the processing for one search division area is repeated 80 times. Since the processing of the search division area is repeated 20 times, the processing is performed 80 × 20 = 1600 times in total. In this process, the detection calculation of FIG. 1 (step 10
4) is executed only 20 times, and the processing of FIG. 3 is repeated 79 × 20 = 1580 times. As a result, the calculation load is remarkably reduced, and the processing speed can be increased. It should be noted that the number of executions of the above-described calculation process is arbitrary and is not limited to this case.

5 to 8 show examples of hard copy output of display results on the display screen 18 of the computer 16 obtained by the present invention. In the coordinate plane display labeled "I-Q", a set of high-density (dark) points represents symbol points or data points corresponding to the symbol points. The linear display other than the symbol points is a display based on the data other than the symbol points and represents the state of the phase change, but corresponds to the symbol points or the symbol points for the determination of the digital phase modulation method. Display of data points is sufficient. In FIG. 5, the symbol pattern display of “QPSK” is clearly shown, and in FIG.
The symbol pattern of “6QAM” is clearly displayed, the symbol pattern display of “64QAM” is clearly shown in FIG. 7, and the symbol pattern display of “1 / π shift QPSK” is clearly shown in FIG. ing. From the above display, those skilled in the art can easily determine the digital phase modulation method of an unknown input signal.

The preferred embodiment of the present invention has been described above.
It will be apparent to those skilled in the art that the present invention is not limited to only the above-described embodiments, and that various changes and modifications can be made without departing from the spirit of the present invention.

[Brief description of drawings]

1 is a portion of a flow chart illustrating the method of the present invention.

2 is a flow chart of the method of the present invention except for the portion of FIG.

FIG. 3 is a flow chart 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 in accordance with 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 in accordance with the present invention.

[Explanation of symbols]

 10 antenna 12 down converter 14 digital spectrum analyzer 16 computer 18 display screen

Claims (8)

[Claims] 1. (a) generating frequency domain data of an unknown digital phase modulation signal, (b) obtaining an estimated carrier frequency of the unknown digital phase modulation signal from the frequency domain data, and (c) the estimated carrier frequency. The time domain data of the unknown digital phase modulation signal is detected and calculated based on the frequency to obtain the Cartesian coordinate data in the time domain, and (d) a symbol in which any one of the coordinates of the Cartesian coordinate data has an extreme value. Points are obtained, (e) only these symbol points are plotted on a coordinate plane composed of a plurality of divided areas, and (f) of the divided areas in which the symbol points are not plotted among the plurality of divided areas. Counting the number, (g) changing the estimated carrier frequency, (h) the steps (c) to (g)
By repeating the above, the time domain data of the unknown digital phase modulation signal is detected and calculated based on the estimated carrier frequency when the number of divided areas in which the symbol points are not plotted is the maximum, and (i) this result A method for determining and displaying a digital phase modulation method, characterized by displaying the obtained data on a display screen. 2. The step (a), wherein the time domain data of the unknown digital phase modulation signal is generated, and the frequency domain data is generated by performing an FFT operation on the time domain data. Item 2. A digital phase modulation method determination display method according to item 1. 3. The digital phase modulation method determination display 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. 4. 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. Item 2. A digital phase modulation method determination display method according to item 1. 5. (a) frequency domain data of an unknown digital phase modulation signal is generated, (b) an estimated carrier frequency of the unknown digital phase modulation signal is obtained from the frequency domain data, and (c) the estimated carrier frequency. The time domain data of the unknown digital phase modulation signal is detected and calculated based on the frequency to obtain the Cartesian coordinate data in the time domain, and (d) a symbol in which any one of the coordinates of the Cartesian coordinate data has an extreme value. Obtaining points, (e) coordinate conversion of the rectangular coordinate data into polar coordinate data, (f) extracting data points corresponding to the symbol points from the polar coordinate data, and (g) only a plurality of these extracted data points. Plotting on a polar coordinate plane composed of the divided areas, and (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 steps (c) to (i) above, and based on the estimated carrier frequency when the number of divided regions in which the data points are not plotted is the maximum Then, the time domain data of the unknown digital phase modulation signal is detected and calculated, and (k) the resulting data is displayed on a display screen. 6. The step (a), wherein the frequency domain data of the unknown digital phase modulation signal is generated, and the frequency domain data is generated by performing an FFT operation on the time domain data. Item 5. A digital phase modulation method determination display method according to Item 5. 7. The digital phase modulation method determination display 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. 8. 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. Item 5. A digital phase modulation method determination display method according to Item 5.