JP3979739B2 - Modulation analysis apparatus and modulation analysis result display method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a modulation analysis apparatus and a modulation analysis result display method for analyzing a modulation signal and displaying a signal point arrangement diagram.
[0002]
[Prior art]
A digital cellular system based on a code division multiple access (CDMA) system is excellent in terms of call quality and has been put into practical use in Japan. In this digital cellular system, for example, the QPSK modulation method is used in the downlink for transmitting data from the base station to the mobile station, and the offset QPSK modulation method is used in the uplink for transmitting data from the mobile station to the base station. Is used. In this digital cellular system, in order to maintain good call quality, it is necessary to measure and analyze the actually received signal.
[0003]
FIG. 4 is a diagram showing a display example of a signal point arrangement diagram of a baseband signal of QPSK modulation obtained by a conventional analysis device. Only the chip points are plotted in the signal point arrangement diagram shown in FIG. The chip point indicates a baseband signal corresponding to a transmitted symbol (2-bit data in the case of the QPSK modulation method), and sampling processing is generally performed at a sampling frequency several times the symbol rate. Therefore, there are a plurality of sample points between continuously inputted chip points.
[0004]
FIG. 5 is a diagram showing another display example of a signal point arrangement diagram of a baseband signal of QPSK modulation obtained by a conventional analyzer. The signal point arrangement diagram shown in the figure shows a trajectory obtained by interpolating the sample points between the chip points.
[0005]
[Problems to be solved by the invention]
By the way, in the above-described conventional analysis apparatus, when only each chip point is displayed as shown in FIG. 4, it is impossible to observe the trajectory of the signal connecting each sample point existing between each chip point. As shown in FIG. 5, when the signal trajectory is displayed by interpolating between the sample points, the trajectory is concentrated near the chip points, so that the chip points are hidden and cannot be observed. Thus, in the conventional analysis device, when the signal points of the phase-modulated signal are displayed on the signal point arrangement diagram, it is not possible to observe both the chip points and the trajectory between them. There was a problem with sex.
[0006]
The present invention was created in view of such points, and its purpose is to improve the visibility when observing each signal point on the signal point arrangement diagram corresponding to the modulated signal. An object of the present invention is to provide a modulation analysis apparatus and a modulation analysis result display method that can be used.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problem, in the present invention, when frequency conversion is performed on a modulated signal, an in-phase component and a quadrature component are extracted and a signal point arrangement diagram is displayed. The display is performed in a state where the sample point can be identified. In particular, since only the sample points are displayed without displaying the trajectory connecting the sample points, both the sample points and the tip points are displayed on the same screen even when the tip points are displayed at the same time. In addition, even when these points are mixed in the same screen, they can be distinguished from each other so that the user can observe each signal point with good visibility. can do.
[0008]
In particular, by assigning different colors to the chip points and the sample points or using different shapes, the user can identify the points as different from each other. In addition, a tracking unit is provided to track the sample points and chip points included in the signal point arrangement map described above in the order of signal input, so that a trace connecting the sample points and chip points can be displayed on the screen. It is possible to easily know the input order of these points scattered in the area, and the input signal analysis operation becomes easy.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a modulation analyzing apparatus according to an embodiment. For example, a configuration for displaying a signal point arrangement diagram for a received signal subjected to QPSK modulation is illustrated.
[0010]
1 includes a local oscillator 10, a frequency converter 12, a bandpass filter (BPF) 14, an analog-digital (A / D) converter 16, a signal analysis unit 20, a display unit 30, and an operation unit 40. It is comprised including.
[0011]
The local oscillator 10 generates a predetermined local signal used for frequency conversion. The frequency converter 12 mixes the local signal output from the local oscillator 10 and the input QPSK modulation signal, and outputs an analog intermediate frequency (IF) signal that is a difference between them. The frequency of the IF signal is a frequency that can be converted into digital data by the A / D converter 16 in the subsequent stage, and needs to include the band of the QPSK modulation signal. The bandpass filter 14 performs a band limiting process on the IF signal output from the frequency converter 12 and removes an aliasing component included in the IF signal. The A / D converter 16 converts the input IF signal into digital data in order to perform various processes in the signal analysis unit 20 at the subsequent stage.
[0012]
The signal analysis unit 20 obtains an in-phase component and a quadrature component of the QPSK modulation signal based on the IF signal after being converted into digital data by the A / D converter 16 and is necessary for creating a signal point arrangement diagram. Sample points and tip points are extracted. The signal analysis unit 20 includes an in-phase component extraction unit 21, a quadrature component extraction unit 22, and a chip point determination unit 23.
[0013]
The in-phase component extraction unit 21 extracts only the in-phase component included in the QPSK modulation signal by multiplying the data of the input QPSK modulation signal by data of a sine wave waveform having the same frequency as the IF signal. Further, the quadrature component extraction unit 22 has a waveform having the same frequency as that of the IF signal and having a phase that is 90 ° different from the phase of the sine wave waveform used for extracting the in-phase component described above with respect to the input QPSK modulation signal data. By multiplying the data, only the orthogonal component included in the QPSK modulation signal is extracted. By the way, the data output from the in-phase component extraction unit 21 and the quadrature component extraction unit 22 correspond to the sample points sampled at a predetermined frequency by the A / D converter 16, but are transmitted therein. The one corresponding to the chip point as a symbol is included. For example, when a frequency that is eight times the chip rate, which is a repetition period of chip points, is set as the sample rate, the interval between adjacent chip points is equally divided into eight, and there are seven sample points therebetween. The chip point determination unit 23 receives in-phase component data included in the QPSK modulation signal from the in-phase component extraction unit 21, and quadrature component data included in the QPSK modulation signal from the quadrature component extraction unit 22, respectively. It is determined whether the data corresponds to a chip point or a sample point other than the chip point. When it is determined that each of the input in-phase component and quadrature component data corresponds to the chip point, determination data indicating that is output from the chip point determination unit 23 toward the display unit 30. .
[0014]
Based on the in-phase component and quadrature component data of the QPSK modulation signal extracted by the signal analysis unit 20, the display unit 30 displays the signal point arrangement diagram in a state where the chip points and other sample points can be distinguished from each other. Display. For example, a signal point arrangement diagram in which the chip points are colored yellow and the sample points are colored green is displayed.
[0015]
FIG. 2 is a diagram showing a detailed configuration of the display unit 30 shown in FIG. As shown in the figure, the display unit 30 includes a data storage unit 31, a display color setting unit 32, a drawing unit 33, a VRAM (video RAM) 34, a display driver 35, and a CRT (cathode ray tube) 36. ing.
[0016]
The data storage unit 31 receives the in-phase and quadrature component data of the QPSK modulation signal extracted by the in-phase component extraction unit 21 and the quadrature component extraction unit 22 in the signal analysis unit 20, and inputs these data. Accumulate in order. The data storage unit 31 also receives determination data sent from the chip point determination unit 23 in the signal analysis unit 20, and each data corresponds to a chip point when the data is stored. Identification data indicating whether there is a sample point other than the chip point is stored at the same time.
[0017]
Based on the identification data corresponding to the in-phase component and quadrature component data of the QPSK modulation signal accumulated in the data accumulation unit 31, the display color setting unit 32 includes each chip point and each sample included in the signal point arrangement diagram. Set the dot display color. For example, as described above, the tip point is set to yellow and the sample point is set to green.
[0018]
The drawing unit 33 reads out in-phase component and quadrature component data of the QPSK modulation signal stored in the data storage unit 31, and the signal point arrangement corresponding to the in-phase component I on the horizontal axis and the quadrature component Q on the vertical axis, respectively. A predetermined mark figure indicating each signal point corresponding to a chip point or a sample point is drawn at a corresponding position in the figure and written in an area corresponding to one screen of the VRAM 34. In this drawing process, the color of each mark image is set to the color set by the display color setting unit 32, that is, a set of data (in-phase component data and quadrature component data) read from the data storage unit 31. A mark image colored yellow is drawn when it corresponds to a chip point, and a mark image colored green is drawn when it corresponds to a sample point other than that. The display driver 35 reads the image data stored in the VRAM 34 in the scanning direction to generate a video signal for display, and a predetermined signal point arrangement diagram is displayed on the screen of the CRT 36.
[0019]
The operation unit 40 has a predetermined operation key that is pointed to track the chip point and the sample point in the order of input. Each time the operation key is pressed, the chip point or the sample point is highlighted in the order of input. . For example, assuming that the cursor key has a function as the operation key, the drawing process in the drawing unit 33 is performed so that the chip point or the sample point with increased brightness is moved one by one each time the cursor key is pressed. Done. Thus, by highlighting the chip points or sample points in the order of input, the transition state of the input QPSK modulation signal can be clearly understood. In the above description, highlighting is performed by increasing the brightness of each chip point or sample point. However, the color or shape of the chip point or sample point pointed to by the operation of the cursor key is temporarily changed for emphasis. A pointer having a predetermined shape such as an arrow or the like may be displayed and highlighted near the tip point or sample point to be displayed.
[0020]
FIG. 3 is a diagram showing a display example of a signal point arrangement diagram. In the signal point arrangement diagram shown in the figure, the horizontal axis corresponds to the in-phase component I, and the vertical axis corresponds to the quadrature component Q, and is extracted by the in-phase component extraction unit 21 and the quadrature component extraction unit 22 in the signal analysis unit 20. A predetermined mark image is displayed at a position specified by the set of in-phase component data and quadrature component data. In the figure, a circle indicates a yellow tip point, and a circle indicates a green sample point.
[0021]
As shown in FIG. 3, in the constellation diagram of the QPSK modulation signal, four types of chip points corresponding to four phases (45 °, 135 °, −45 °, −135 °) and each chip point are shown. Each sample point arranged on the connected locus is included, and each of these chip points and each sample point are represented by different colors. Moreover, since the sample points are displayed without displaying the locus connecting the sample points, the tip points are not hidden by the dense locus around the tip points as in the prior art, and displayed on the CRT 36. When the user views the signal arrangement map, the chip point colored yellow and the sample point colored green can be identified in one screen, and the baseband signal subjected to QPSK modulation is observed. The visibility at the time can be improved.
[0022]
Further, by operating the operation unit 40, chip points or sample points can be highlighted and tracked in the order of signal input, so that the input order of each chip point and each sample point can be easily known, and QPSK Analyzing the modulated signal is facilitated.
[0023]
In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention. In the modulation analyzing apparatus of the present embodiment, each chip point and each sample point are displayed with different colors so that they can be distinguished from each other, but mark images having different shapes are associated and identified. It may be. For example, each chip point is indicated by a circle, and each other sample point is indicated by a cross. In this case, the display color setting unit 32 included in the display unit 30 is replaced with a display shape setting unit, and mark images having different shapes are drawn at the chip points and other sample points. Further, the display may be performed by changing both the shape and the color of the mark image.
[0024]
In the above-described embodiment, the case where the signal point arrangement diagram is displayed for the signal subjected to QPSK modulation has been described. The present invention can be similarly applied to the case where a layout diagram is displayed. Alternatively, the present invention can also be applied to a case where a signal point arrangement diagram corresponding to an amplitude phase modulation signal or an FSK modulation signal is displayed.
[0025]
In the above-described embodiment, the case where the signal point arrangement diagram is displayed using the CRT 36 capable of color display has been described. In addition to displaying each of the chip points and the sample points in a shape that can be distinguished from each other, they may be displayed in a brightness and shade that are distinguishable from each other.
[0026]
【The invention's effect】
As described above, according to the present invention, after the frequency conversion is performed on the modulated signal, the in-phase component and the quadrature component are extracted, and the signal point arrangement diagram is displayed so that these points can be identified. Since the trajectory connecting the sample points is not displayed, even if the chip points and sample points are displayed at the same time, each can be identified well, and the signal points corresponding to the modulated signal Visibility when observing signal points on the layout drawing can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a modulation analysis apparatus according to an embodiment.
FIG. 2 is a diagram illustrating a detailed configuration of a display unit illustrated in FIG.
FIG. 3 is a diagram showing a display example of a signal point arrangement diagram.
FIG. 4 is a diagram showing a display example of a signal point arrangement diagram of a baseband signal of QPSK modulation obtained by a conventional analysis device.
FIG. 5 is a diagram showing another display example of a signal point arrangement diagram of a baseband signal of QPSK modulation obtained by a conventional analysis device.
[Explanation of symbols]
20 Signal analysis unit 21 In-phase component extraction unit 22 Quadrature component extraction unit 23 Chip point determination unit 30 Display unit 31 Data storage unit 32 Display color setting unit 33 Drawing unit 34 VRAM
35 Display driver 36 CRT
40 Operation unit

Claims (5)

A frequency conversion means for inputting a modulated signal and converting the input signal into an intermediate frequency signal;
First component extraction means for extracting either the in-phase component or the quadrature component by multiplying the intermediate frequency signal by a sine wave waveform equal to the frequency of the intermediate frequency signal;
A second component extracting means for extracting either the in-phase component or the quadrature component by multiplying the intermediate frequency signal by a waveform whose phase is 90 ° different from the sine wave waveform;
The in-phase component and the quadrature component extracted by the first and second component extracting means correspond to two axes, respectively, and sample points and chip points specified by the in-phase component and the quadrature component are determined. Display means for displaying a signal point arrangement diagram in an identifiable state;
A modulation analysis apparatus comprising: In claim 1,
The modulation analysis apparatus characterized in that the display means displays the sample points and the chip points in different colors or different shapes. In claim 1 or 2,
The modulation analysis apparatus further comprising tracking means for tracking the sample points and the chip points included in the signal point arrangement diagram in the order of signal input. A modulation analysis result display method for displaying a signal point arrangement diagram in a state where sample points and chip points can be identified by associating each of an in-phase component and a quadrature component of a modulated signal with two axis lines . In claim 4,
A modulation analysis result display method, wherein the sample points and the chip points are displayed in different colors or different shapes.

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