JP2006157362A - Digital modulated signal analyzing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital modulated signal analyzing device capable of easily specifying the case of a decrease in transmission quality of a digital modulated signal. <P>SOLUTION: The digital modulated signal analyzing device 1 analyzes the digital modulated signal modulated by a designated modulation system, and displays the analysis result. The device includes an orthogonal modulating means 10 for orthogonally demodulating the digital modulated signal into an I signal and a Q signal, an amplitude extracting means 20 for extracting signal components of the I signal and Q signal output by the orthogonal modulating means 10, and a synchronism adding means 30 for adding a synchronizing signal to the amplitude components extracted by the amplitude extracting means 20 and outputs resulting signals to a display means 40. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention shows the state at the reception point of a digital modulation signal modulated by a modulation scheme such as QPSK, QAM, OFDM, etc. in the broadcasting field for displaying the state of a digital modulation signal at a shooting site using a digital FPU. The present invention relates to a digital modulation signal analyzing apparatus for analyzing the digital modulation signal in order to display.

  Conventionally, in the broadcasting field, when program material is transmitted wirelessly, it is analog and is used at the shooting site via FPU (Field Pick-up Unit: Broadcast Program Material Wireless Transmission Device) and TSL (Transmitter to Studio Link). The video was transmitted to the broadcasting station (studio). In recent years, wireless transmission between a shooting site, a broadcasting station, and a transmitting station has been changed from analog to digital as digital FPU, digital TSL, digital STL (Studio to Transmitter Link), and digital TTL (Transmitter to Transmitter Link), respectively. Transitioning. Also, in domestic terrestrial digital broadcasting, an ISDB-T (Integrated Services of Digital Broadcasting Terrestrial) system based on a modulation system called OFDM (Orthogonal Frequency Division Multiplexing) system has been adopted. There is a need for technology that can achieve high quality.

  In these FPU, OFDM, and the like, digitally modulated signals that are wirelessly transmitted are subject to various disturbances along the propagation path (transmission path). For example, in the FPU, there are interferences such as interference of digital waves of the same channel, interference of analog FM modulation, interference from communication radio (hereinafter collectively referred to as interference waves), and pulse noise such as radar pulses. Therefore, a measuring apparatus that monitors the state of the digital modulation signal at the reception point is known (for example, see Patent Document 1).

  Examples of such a measuring device include a bit error rate measuring device, a constellation display device, a spectrum analyzer, and a delay profile measuring device. Here, the function of these measuring devices will be briefly described. The bit error rate measuring device displays how much the error rate of the data has occurred compared with the transmission data after the received signal is converted back to a digital signal. The constellation display device monitors the quality of the digital modulation signal by displaying the digital modulation signal on a complex plane and monitoring the size of the displayed signal points and distortion of the signal arrangement. The spectrum analyzer monitors the digital modulation signal directly in the frequency domain, thereby monitoring the frequency distortion, the state of mixing of interference waves, and the like. The delay profile measuring device obtains a delay profile indicating the statistical properties of the transmission line based on the transmission line response.

Further, in the conventional analog FM modulation type FPU, the state at the reception point of the modulation signal can be easily monitored by using an attached video monitor. That is, when the program material is monitored on the video monitor, if a disturbance occurs in the transmission path, noise is generated on the screen of the video monitor. For example, when the interference wave is the cause of the interference, a beat is generated in the video monitor, and when the pulse noise is the cause of the interference, a pulse is generated in the video monitor. As a result, the cause of the interference could be identified by monitoring the video monitor.
JP 2002-335226 A (0025-0047, FIG. 1)

  However, in recent years, digitalization of FPU has progressed, and it has been widely performed that HDTV (High Definition TV) signals are band-compressed by an MPEG encoder and the signals are transmitted by a digital FPU. When using this digital FPU to monitor program material on the attached video monitor, if interference in the propagation path (interference wave, pulse noise, etc.) occurs, on the screen of the video monitor, The image stops (freezes). Therefore, since it is impossible to specify whether the cause of the freeze is due to interference waves or pulse noise, there is no way to deal with it. Therefore, when trying to identify the cause of interference, a plurality of special measuring devices such as the bit error rate measuring device, the constellation display device, the spectrum analyzer, and the delay profile measuring device described above must be used.

  However, it is difficult to always have these plural types of measuring devices on site where wireless transmission of broadcast program material is performed due to problems such as space. Also, when observing the quality of digital terrestrial broadcasting radio waves at a reception point, it is difficult to carry many measurement devices when heading to a point where reception failure (interference) occurs. Therefore, there is a problem that it is difficult to specify the cause when interference in the propagation path occurs.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a digital modulation signal analyzing apparatus capable of easily specifying the cause of reducing the transmission quality of a digital modulation signal. To do.

  The present invention was devised to achieve the above object. First, the digital modulation signal analyzing apparatus according to claim 1 analyzes and analyzes a digital modulation signal modulated by a predetermined modulation method. The digital modulation signal analyzing apparatus for displaying the result is configured to include orthogonal demodulation means, amplitude extraction means, and synchronization adding means. Here, QPSK (Quadrature Phase Shift Keying), QAM (Quadrature Amplitude Modulation), OFDM (Orthogonal Frequency Division Multiplexing), and the like are assumed as modulation schemes.

  According to such a configuration, the digital modulation signal analyzing apparatus orthogonally demodulates the digital modulation signal by the orthogonal demodulation means and converts it into an I signal and a Q signal. Here, the I signal is a real axis component of a symbol (carrier symbol), and the Q signal is an imaginary axis component of the symbol. Then, the digital modulation signal analyzing apparatus extracts the amplitude component of the predetermined time axis signal by the amplitude extracting unit based on the I signal and the Q signal output from the quadrature demodulating unit. Here, the time axis signal is a complex signal, and the amplitude component thereof includes, for example, the square root of the square sum of the real number component and the imaginary number component, or the real number portion of the result of the predetermined complex division. Further, the digital modulation signal analyzing apparatus adds the synchronization signal to the amplitude component extracted by the amplitude extracting means by the synchronization adding means and outputs the same to the display means. Thereby, the amplitude component of the time axis signal is displayed on the display means. The display of the amplitude component can reflect the cause of the interference when interference occurs in the propagation path or reception point of the digital modulation signal.

  The digital modulation signal analysis apparatus according to claim 2 is the digital modulation signal analysis apparatus according to claim 1, wherein the time-axis signals are an I signal and a Q signal output by the orthogonal demodulation means. And By doing in this way, the structure of a digital modulation signal analyzer can be simplified.

  According to a third aspect of the present invention, there is provided a digital modulation signal analyzing apparatus according to the first aspect, wherein the digital modulation signal analyzing apparatus according to the first aspect cancels a modulation component included in the I signal and the Q signal output by the orthogonal demodulation means. It further comprises signal processing means for performing processing to generate a time axis signal. According to such a configuration, since the time axis signal is subjected to signal processing for canceling the modulation component, the modulation component is also canceled from the amplitude component. As a result, random noise is suppressed when this amplitude component is displayed on the display means.

  The digital modulation signal analyzing apparatus according to claim 4 is the digital modulation signal analyzing apparatus according to claim 3, wherein the signal processing means includes synchronous detection means, hard decision means, and complex division means. It was.

  According to this configuration, the signal processing means performs phase synchronization and frequency synchronization on the I signal and the Q signal output from the orthogonal demodulation means by the synchronous detection means. Thereby, the modulation component included in the I signal and the Q signal is canceled. The signal processing means makes a hard decision on the carrier symbol in the signal output from the synchronous detection means by the hard decision means. Thereby, the influence of multipath etc. can be removed. Further, the signal processing means complex-divides the signal output from the synchronous detection means by the signal output from the hard decision means by the complex division means. As a result, a complex signal from which influences such as modulation and multipath are removed can be generated. A signal output from the complex division means is used as a time axis signal. According to this, noise can be reduced when the amplitude component of the time axis signal is displayed on the display means.

  The digital modulation signal analyzing apparatus according to claim 5 is the digital modulation signal analyzing apparatus according to claim 3, wherein the signal processing means includes a reference signal generating means, a fast Fourier transform means, a reference signal extracting means, And complex division means.

  According to this configuration, the signal processing means generates the waveform equalization reference signal for equalizing the waveform of the digital modulation signal by the reference signal generation means, and is output from the quadrature demodulation means by the fast Fourier transform means. The signal and the Q signal are converted to frequency domain carrier data by fast Fourier transform. Here, the waveform equalization reference signal is the same as that previously inserted in the transmission modulation signal on the transmission side, and for example, an OFDM SP (Scattered Pilot) signal or a CP (Continual pilot) signal. That is. The signal processing means extracts the reference signal corresponding to the waveform equalization reference signal inserted in advance on the transmission side from the carrier data output from the fast Fourier transform means by the reference signal extraction means. Further, the signal processing means performs complex division on the reference signal extracted by the reference signal extracting means by the complex dividing means by the reference signal for waveform equalization generated by the reference signal generating means. A signal output from the complex division means is used as a time axis signal. According to this, since only a part of carrier data is used for calculation, it can be processed at high speed.

  The digital modulation signal analyzing apparatus according to claim 6 is the digital modulation signal analyzing apparatus according to claim 3, wherein the signal processing means includes equalization means, hard decision means, switching means, and complex division means. And prepared.

  According to this configuration, the signal processing means is based on the waveform equalization reference signal for equalizing the waveform of the digital modulation signal by the equalization means, and the I signal and the Q signal output from the orthogonal demodulation means. The transmission path characteristics of the transmission path through which the digital modulation signal is transmitted are estimated. As a result, transmission path characteristics are also estimated for symbols that do not include a reference signal. Note that the waveform equalization reference signal may be generated inside the equalization means. Then, the signal processing means makes a hard decision on the carrier symbol in the transmission path characteristic output from the equalization means by the hard decision means. Thereby, the influence of multipath can be removed. The signal processing means switches the waveform equalization reference signal and the hard decision output outputted from the hard decision means at a predetermined timing by the switching means. Here, the switching timing is such that the waveform equalization reference signal side is in the reference signal section of the digital modulation signal, and the hard decision output side is in the data section. Further, the signal processing means performs complex division on the transmission path characteristic estimated by the equalization means by the signal switched by the switching means by the complex division means. The signal output from the complex division means is used as a time axis signal. According to this, since all carrier data is used, the accuracy of the amplitude component displayed on the display means is improved.

  According to a seventh aspect of the present invention, there is provided a digital modulation signal analyzing apparatus that analyzes a digital modulation signal modulated by a predetermined modulation method and displays an analysis result. Means and synchronization adding means.

  According to such a configuration, the digital modulation signal analyzing apparatus orthogonally demodulates the digital modulation signal by the orthogonal demodulation means and converts it into an I signal and a Q signal. Then, the digital modulation signal analyzing apparatus generates a time axis signal by performing signal processing for canceling the modulation component included in the I signal and the Q signal output by the quadrature demodulation means by the signal processing means. Extract the amplitude component of the axis signal. Further, the digital modulation signal analyzing apparatus adds the synchronization signal to the amplitude component extracted by the signal processing means by the synchronization adding means, and outputs it to the display means. Thereby, the amplitude component of the time axis signal in which the modulation component is canceled is displayed on the display means. The display of the amplitude component can reflect the cause of the interference when interference occurs in the propagation path or reception point of the digital modulation signal.

  The digital modulation signal analyzing apparatus according to claim 8 is the digital modulation signal analyzing apparatus according to claim 7, wherein the signal processing means includes synchronous detection means, hard decision means, and complex division means. It was.

  According to this configuration, the signal processing means performs phase synchronization and frequency synchronization on the I signal and the Q signal output from the orthogonal demodulation means by the synchronous detection means. The signal processing means makes a hard decision on the carrier symbol in the signal output from the synchronous detection means by the hard decision means. Further, the signal processing means complex-divides the signal output from the synchronous detection means by the signal output from the hard decision means by the complex division means to generate a time axis signal, and the real part is converted to the time axis. Extracted as the amplitude component of the signal. According to this, when the amplitude component is displayed on the display means, noise can be reduced.

  The digital modulation signal analysis apparatus according to claim 9 is the digital modulation signal analysis apparatus according to claim 8, wherein the signal processing means generates a waveform equalization reference signal for equalizing the waveform of the digital modulation signal. Further comprising: a reference signal generating means for switching, a waveform equalizing reference signal generated by the reference signal generating means, and a switching means for switching the signal output from the hard decision means at a predetermined timing; However, the signal output from the synchronous detection means is complex-divided by the signal switched by the switching means.

  According to such a configuration, the signal input to the complex division means is switched at a predetermined timing. Here, as the switching timing, the waveform equalization reference signal side is set in the reference signal section of the digital modulation signal, and the hard decision output side is set in the data section. According to this, the influence of the determination error by the hard determination means can be reduced.

  According to the first aspect of the present invention, the amplitude component of the time axis signal extracted by the amplitude extracting unit is displayed on the display unit. The display of the amplitude component can reflect the cause of the interference when interference occurs in the propagation path or reception point of the digital modulation signal. As a result, the cause of the interference of the digital modulation signal can be specified by monitoring the display means. Therefore, it is possible to quickly take appropriate measures according to the identified cause of disturbance.

  According to the second aspect of the present invention, the configuration of the digital modulation signal analyzing apparatus can be simplified. As a result, it is possible to reduce the size of the apparatus and the manufacturing cost.

  According to the third aspect of the present invention, the modulation component is canceled from the amplitude component of the time axis signal, and when this amplitude component is displayed on the display means, random noise is suppressed on the screen. Is done. This makes it easy to determine the cause of interference when monitoring the display means.

  According to the fourth aspect of the present invention, the modulation components included in the I signal and the Q signal are canceled, and the influence of multipath or the like can be removed. As a result, noise can be reduced when displayed on the display means, so that the display becomes relatively bright and the cause of the interference can be easily identified.

  According to the fifth aspect of the present invention, since only the reference signal is extracted from the digital modulation signal and the time axis signal is generated, the arithmetic processing can be performed at high speed with a simple configuration.

  According to the sixth aspect of the present invention, since the time axis signal is generated based on all carrier data including symbols that do not include the reference signal, the accuracy of the amplitude component displayed on the display means is improved.

  According to the seventh aspect of the present invention, the amplitude component of the time axis signal is extracted in the signal processing means for canceling the modulation component included in the I signal and the Q signal, so that the configuration is simplified. Can do. Further, when the amplitude component of the time axis signal in which the modulation component is canceled is displayed on the display unit, random noise is suppressed on the screen. This makes it easy to determine the cause of interference when monitoring the display means.

  According to the eighth aspect of the invention, with a simple configuration, the modulation component included in the I signal and the Q signal can be canceled and the influence of multipath or the like can be removed. Thereby, noise is reduced when the amplitude component of the time axis signal is displayed on the display means.

  According to the ninth aspect of the present invention, since the signal input to the complex division means is switched between the reference signal section and the data section, errors in hard decision can be reduced.

  In the following, first, the basic configuration of the digital modulation signal analyzing apparatus will be described, and various variations based on the basic configuration will be sequentially described as first to sixth embodiments.

[Basic configuration]
FIG. 1 is a block diagram showing a basic configuration of a digital modulation signal analyzing apparatus. The digital modulation signal analyzing apparatus 1 analyzes a digital modulation signal (hereinafter simply referred to as a digital modulation signal) modulated by a modulation method such as QPSK, QAM, or OFDM, and displays the analysis result. For this purpose, as shown in FIG. 1, the digital modulation signal analyzing apparatus 1 includes an orthogonal demodulation unit 10, an amplitude extraction unit 20, a synchronization adding unit 30, and a display unit 40.

The quadrature demodulating unit 10 performs quadrature demodulation on the input digital modulation signal, converts it into an I signal and a Q signal, and outputs the signal to the amplitude extracting unit 20. Here, the I signal is a real axis component of a symbol (carrier symbol), and the Q signal is an imaginary axis component of the symbol. The digital modulation signal input to the quadrature demodulation means 10 is a complex digital IF signal input from an antenna (not shown), frequency-converted to an intermediate frequency (IF), and AD converted.
The amplitude extracting means 20 extracts the amplitude component of the input signal (time axis signal) based on the I signal and Q signal output from the quadrature demodulating means 10, and outputs the extracted amplitude component to the synchronization adding means 30. It is.

The synchronization adding unit 30 includes a synchronization signal generating unit (not shown). In order to display the amplitude component extracted by the amplitude extracting unit 20 on the display unit 40, a synchronization signal (horizontal synchronization signal and vertical synchronization) is displayed on the amplitude component. Signal) and output to the display means 40.
The display means 40 displays the amplitude component to which the synchronization signal is added by the synchronization adding means 30 on the screen.

  The digital modulation signal analyzing apparatus 1 is configured by electrically connecting a commercially available video monitor as the display means 40 to a single device including the quadrature demodulating means 10, the amplitude extracting means 20, and the synchronization adding means 30. can do. Note that a digital modulation signal analyzing apparatus integrally including the display unit 40 can be configured, but in the following description, the display unit 40 is assumed to be a separate video monitor.

[First Embodiment]
A configuration example of the orthogonal demodulation means 10 and the amplitude extraction means 20 in the digital modulation signal analyzing apparatus 1 shown in FIG. 1 will be described as a first embodiment with reference to FIG. FIG. 2 is a configuration diagram of the digital modulation signal analyzing apparatus according to the first embodiment. As shown in FIG. 2, since this digital modulation signal analyzing apparatus 1A has the same configuration as that of the digital modulation signal analyzing apparatus 1 shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted.

The quadrature demodulating means 10 includes a sine wave oscillator 11, a 90 degree phase shifter 12, and multipliers 13a and 13b.
The sine wave oscillator 11 is an oscillator that generates a sine wave signal having a predetermined frequency and amplitude, and outputs the generated sine wave signal to the multiplier 13 a and the 90-degree phase shifter 12.
The 90-degree phase shifter 12 shifts the phase of the sine wave signal generated by the sine wave oscillator 11 by 90 degrees, and outputs the shifted sine wave signal to the multiplier 13b.

The multiplier 13a multiplies the digital modulation signal (complex digital IF signal) input to the quadrature demodulator 10 by the sine wave signal output from the sine wave oscillator 11, so that the real axis component ( I signal) is generated and output to the amplitude extracting means 20.
The multiplier 13b multiplies the digital modulation signal (complex digital IF signal) input to the quadrature demodulation means 10 by the 90-degree shifted sine wave signal output from the 90-degree phase shifter 12 to thereby calculate the complex digital IF. An imaginary axis component (Q signal) of the signal is generated and output to the amplitude extracting means 20.

The amplitude extraction means 20 inputs an I signal and a Q signal as time axis signals and extracts amplitude components of the time axis signals. The square calculators 21a and 21b, an adder 22, and a square root calculator 23.
The square calculator 21 a squares the I signal output from the multiplier 13 a and outputs it to the adder 22.
The square calculator 21b squares the Q signal output from the multiplier 13b and outputs it to the adder 22.
The adder 22 adds the square value of the I signal output from the square calculator 21a and the square value of the Q signal output from the square calculator 21b, and adds this value (power value). Is output to the square root calculator 23.
The square root calculator 23 calculates the square root of the added value output from the adder 22 and outputs the calculated square root value to the synchronization adding means 30.

  The digital modulation signal analyzing apparatus 1A including the quadrature demodulating unit 10 and the amplitude extracting unit 20 having the above configuration performs quadrature demodulation on the input digital modulated signal by the quadrature demodulating unit 10 and performs orthogonal demodulation on the signal (time axis). The amplitude component of the signal is extracted by the amplitude extracting means 20. Then, the digital modulation signal analyzing apparatus 1A adds a synchronization signal to the amplitude component by the synchronization adding means 30 and displays the same on the display means 40 (video monitor).

  Here, a display example of amplitude components displayed on the video monitor by the digital modulation signal analyzing apparatus 1A will be described with reference to FIG. FIG. 8 is a diagram for explaining a display example of the video monitor. When the digital modulation signal input to the digital modulation signal analyzing apparatus 1A is not disturbed, uniform noise (sandstorm) is displayed on the screen (normal) as shown in FIG. Here, examples of the interference include digital wave interference of the same channel, analog FM modulation interference, interference from communication radio (interference wave), and pulse noise such as radar pulses.

  On the other hand, when the digital modulation signal input to the digital modulation signal analyzing apparatus 1A is affected by an interference wave, a uniform noise is displayed on the screen as shown in FIG. A diagonal stripe pattern is displayed on (beat). Further, when the digital modulation signal input to the digital modulation signal analyzing apparatus 1A is affected by pulse noise, as shown in FIG. Multiple scratches that appear to have been scratched are displayed (pulse).

  According to this digital modulation signal analyzing apparatus 1A, when the digital modulation signal is disturbed, the image displayed on the screen changes according to the type of the disturbance. Therefore, by monitoring the video monitor of the digital modulation signal analyzing apparatus 1A, it is possible to easily identify the cause of the interference generated in the propagation path (transmission path) without using a plurality of measurement apparatuses. As a result, it is possible to quickly cope with the interference generated in the propagation path.

  Note that the square root calculator 23 may be removed from the amplitude extraction unit 20 of the digital modulation signal analysis apparatus 1A. In this case, the added value (power value) output from the adder 22 is output to the synchronization adding means 30 as it is, and the power value is displayed on the video monitor instead of the amplitude component. The screen display at this time is the same as that shown in FIG.

  Here, in addition to the interference (interference wave, pulse noise) that occurs in the propagation path, the cause of lowering the transmission quality of the digital modulation signal is an increase in random noise due to a decrease in received power (hereinafter referred to as a decrease in received power). Are known. However, in the digital modulation signal analyzing apparatus 1A of the first embodiment, there is a problem that it is difficult to discriminate between the screen display displayed on the video monitor when the reception power is low and the normal (non-interfering) screen display. is there. Therefore, embodiments in which the screen display of the reception power reduction is improved will be described as second to sixth embodiments below.

[Second Embodiment]
A digital modulation signal analyzer for analyzing and displaying a QAM digital modulation signal will be described with reference to FIG. FIG. 3 is a configuration diagram of the digital modulation signal analyzing apparatus according to the second embodiment. As shown in FIG. 3, this digital modulation signal analyzing apparatus 1B is basically the same as the digital modulation signal analyzing apparatus 1A shown in FIG. 2 except that a signal processing means 50 (50B) is provided after the orthogonal demodulation means 10. In general. Therefore, the same components are denoted by the same reference numerals, and description thereof is omitted.

  The signal processing unit 50B cancels the modulation component included in the digital modulation signal (QAM system) input from the quadrature demodulation unit 10. The signal processing unit 50B includes a synchronous detection unit 51, a hard decision unit 52, and a complex division unit 53.

The synchronous detection means 51 performs phase synchronization and frequency synchronization on the I signal and Q signal input from the quadrature demodulation means 10, and uses the signal S (= S _I + jS _Q ) in which phase synchronization and frequency synchronization are established as hard decision means. 52 and the complex division means 53.
The synchronous detection means 51 includes a decision feedback type PLL (Phase Locked Loop) including a phase comparator, a loop filter, and a VCO (Voltage Controlled Oscillator). Establish signal phase synchronization.
The synchronous detection means 51 includes a carrier (carrier wave) recovery circuit including a frequency doubler circuit (square law circuit), a BPF (bandpass filter), and a 1/2 frequency division circuit. Establish frequency synchronization of signals.

The hard decision means 52 receives the signal S output from the synchronous detection means 51 and estimates a transmission signal point that is considered to have been transmitted on the transmission side by making a hard decision on a symbol (carrier symbol) in the input signal S. The hard decision output signal S ′ (= S _I ′ + jS _Q ′) is output to the complex division means 53. By this hard decision means 52, even if the digital modulation signal includes the influence of multipath or noise, these can be removed.
The complex division means 53 divides the signal S output from the synchronous detection means 51 by the hard decision output signal S ′, and outputs the time axis signal D, which is the quotient thereof, to the amplitude extraction means 20. This time axis signal D is expressed by equation (1).

  Here, as shown in the equation (1), the real component of the time-axis signal D calculated by the complex division means 53 is defined as a, and the imaginary component is defined as b. The real number component a and the imaginary number component b are output to the square calculators 21a and 21b of the amplitude extracting means 20, respectively. Then, the adder 22 adds the square value of the real component a output from the square calculator 21a and the square value of the imaginary component b output from the square calculator 21b, and adds this value. (Power value) is output to the square root calculator 23. Further, the square root calculator 23 calculates the square root value Amp of the addition value output from the adder 22 and outputs it to the synchronization adding means 30. At this time, Amp is expressed by equation (2).

  The digital modulation signal analyzing apparatus 1B having such a configuration orthogonally demodulates the input digital modulation signal (QAM method) by the orthogonal demodulation means 10 and converts the modulation components included in the generated I signal and Q signal. The amplitude extraction means 20 extracts the amplitude component of the time axis signal D that has been canceled by the signal processing means 50B and the modulation component has been canceled. Then, the digital modulation signal analyzing apparatus 1B adds the synchronization signal to the amplitude component by the synchronization adding means 30 and displays the same on the display means 40 (video monitor).

  Here, a display example of amplitude components displayed on the video monitor by the digital modulation signal analyzing apparatus 1B will be described with reference to FIG. FIG. 9 is a diagram for explaining a display example of the video monitor. When the digital modulation signal input to the digital modulation signal analyzer 1B is not affected by interference or the like in the propagation path, uniform noise (sandstorm) is displayed on the screen as shown in FIG. Is done. The noise at this time is lighter than the noise shown in (a) of FIG. 8 with a reduced feeling of roughness (the grain of the noise is finer).

  On the other hand, when the digital modulation signal input to the digital modulation signal analyzing apparatus 1B is affected by the interference wave, as shown in FIG. When a striped pattern is displayed (beat) and is affected by pulse noise, as shown in FIG. 9 (c), a plurality of scratches such as those scratched horizontally on uniform noise on the screen. Is displayed (pulse). The noise that is the background at this time is brighter with a less rough feeling compared to the noise shown in FIGS. 8B and 8C (the grain of the noise is finer). .

  When the beats and pulses respectively shown in FIGS. 8B and 8C are generated and the digital modulation signal analyzing apparatus 1B further causes a reduction in received power, As shown in (d) and (e), the background noise is increased and darkened (the grain of noise is rough). However, it is possible to visually distinguish diagonal stripes (beats) and a plurality of scratches (pulses).

  Therefore, according to this digital modulation signal analyzing apparatus 1B, by providing the signal processing means 50 (50B), the video monitor is monitored not only when receiving interference in the propagation path but also when receiving power is reduced. By doing so, the cause of the interference can be easily identified. As a result, it is possible to quickly cope with the disturbance.

[Third Embodiment]
A second example of a digital modulation signal analyzing apparatus that analyzes and displays a QAM digital modulation signal will be described with reference to FIG. FIG. 4 is a configuration diagram of the digital modulation signal analyzing apparatus according to the third embodiment. As shown in FIG. 4, this digital modulation signal analyzing apparatus 1C has basically the same configuration as the digital modulation signal analyzing apparatus 1B shown in FIG. 3 with the main difference being that the amplitude extracting means 20 is omitted. is there. Therefore, the same components are denoted by the same reference numerals, and description thereof is omitted.

Since the signal processing means 50 (50C) is the same as the signal processing means 50B shown in FIG. 3 except that the function of the complex division means 54 is different, description of the other components is omitted.
Complex division unit 54, and outputs as well as dividing a signal S output from the synchronous detection means 51 in the hard decision output signal S ', a real part D _I of the time domain signal is the quotient to synchronous adding means 30 is there. This real part D _I is expressed by equation (3). The complex division means 54 corresponds to the amplitude extraction means 20 shown in FIG.

  The digital modulation signal analyzing apparatus 1C having such a configuration orthogonally demodulates the input digital modulation signal (QAM method) by the orthogonal demodulation means 10 and converts the modulation components included in the generated I signal and Q signal. The signal processing means 50C cancels out and extracts the amplitude component of the time axis signal. Then, the digital modulation signal analyzing apparatus 1C adds the synchronization signal to the amplitude component by the synchronization adding means 30, and displays the same on the display means 40 (video monitor). A display example of the amplitude component displayed on the video monitor by the digital modulation signal analyzing apparatus 1C is the same as that shown in FIG. According to the present embodiment, it is possible to realize a monitoring apparatus that can cope with a case of a decrease in received power with a simple configuration.

[Fourth Embodiment]
A third example of a digital modulation signal analyzing apparatus for analyzing and displaying a QAM digital modulation signal will be described with reference to FIG. FIG. 5 is a configuration diagram of a digital modulation signal analyzing apparatus according to the fourth embodiment. As shown in FIG. 5, this digital modulation signal analyzing apparatus 1D is basically the same as the digital modulation signal analyzing apparatus 1C shown in FIG. 4 except that the signal processing means 50 (50D) includes a reference signal generating means 55. The same configuration. Therefore, the same components are denoted by the same reference numerals, and description thereof is omitted.

The reference signal generation means 55 of the signal processing means 50D generates a waveform equalization reference signal that equalizes the waveform of the digital modulation signal in accordance with the signal format used in the QAM FPU, STL, TTL, and TSL. The reference signal for waveform equalization stored in a memory (not shown) is output to the complex division means 54 under a predetermined condition.
The signal format of the waveform equalization reference signal is as follows: reference signal length 256 symbols, block length 19200 symbols, rate 178.1 [kHz], insertion period 695.5 [Hz], occupation rate 1/75, information transmission symbol rate 13 .18 [Mbaud] and a maximum transmission rate of 79.056 [Mbit / s] (in the case of 64QAM). Alternatively, when an auxiliary signal is included, the block length is 20096 symbols, the occupation ratio is 2/157, the maximum information rate is 13.18 [Mbaud], and the auxiliary signal rate is 623 [kbaud].

The switches (switching means) SW1 and SW2 are configured to apply a signal (divisor signal) to be input to the complex division means 54 based on the digital modulation signal input to the digital modulation signal analyzing apparatus 1D at a predetermined timing. The output signal from 52 or the output signal from the reference signal generating means 55 can be switched. That is, at the reception timing of the reference signal section (256 symbols) of the digital modulation signal input to the digital modulation signal analyzing apparatus 1D, the waveform equalization reference signal output from the reference signal generating means 55 is the above-mentioned ( Input as signal S ′ (= S _I ′ + jS _Q ′) in equation 3). Further, at the reception timing of the digital modulation signal in the FPU data section, the hard decision output signal output from the hard decision means 52 is the signal S ′ (= S _I ′ + jS _Q ′) in the above equation (3). input. The switches SW1 and SW2 correspond to the real axis component and the imaginary axis component, respectively.

  A display example of the amplitude component displayed on the video monitor by the digital modulation signal analyzing apparatus 1D having such a configuration is the same as that shown in FIG. According to this embodiment, at the time of amplitude extraction, the complex division means 54 depends entirely on the hard decision output by the hard decision means 52 by using the waveform equalization reference signal as the head reference signal of the digital modulation signal. Can be avoided. According to this, the influence of the determination error by the hard determination means 52 can be reduced, and the amplitude extraction can be executed with high accuracy.

[Fifth Embodiment]
As an example applied to terrestrial digital broadcasting, a digital modulation signal analyzing apparatus for analyzing and displaying an OFDM digital modulation signal will be described with reference to FIG. FIG. 6 is a configuration diagram of the digital modulation signal analyzing apparatus of the fifth embodiment. As shown in FIG. 6, this digital modulation signal analyzing apparatus 1E has basically the same configuration as the digital modulation signal analyzing apparatus 1B shown in FIG. 3 except that the configuration of the signal processing means 50 (50E) is different. It is. Therefore, the same components are denoted by the same reference numerals, and description thereof is omitted.

The signal processing unit 50E includes a reference signal generation unit 55, an FFT (Fast Fourier Transform) 56, a reference signal extraction unit 57, and a complex division unit 54a.
The reference signal generation means 55 is the same as that shown in FIG. 5, and outputs a waveform equalization reference signal read from a memory (not shown) to the complex division means 54a. The reference signal for waveform equalization read out here is the same as the SP signal (known) inserted on the transmission side, and here it is described as SP signal _Xsp .

The FFT 56 extracts an effective symbol period signal from the I signal and Q signal output from the quadrature demodulating means 10, converts the signal into carrier data in the frequency domain by fast Fourier transform (FFT), and converts the spectrum signal S into the reference signal. This is output to the extraction means 57.
The reference signal extraction means 57 extracts the reference signal (SP signal) inserted on the transmission side from the FFTed spectrum signal S as a position on the complex plane of the symbol signal arrangement diagram, and actually extracts the SP signal S. _sp is output to the complex division means 54a.

The complex division means 54a acquires the SP signal _Ssp extracted by the reference signal extraction means 57 and the regular SP signal _Xsp read by the reference signal generation means 55 at the same timing, and is based on the equation (4). Te, extracted signal S _sp complex division at nominal SP signal X _sp, and outputs the time domain signal H _sp is the quotient of the amplitude extraction means 20. The time axis signal H _sp acts on the regular SP signal X _sp and indicates the transmission path characteristic of the transmission path through which the digital modulation signal is transmitted.

The amplitude extraction unit 20 calculates a square root value Amp of the square sum of the real number component and the imaginary number component of the time axis signal _Hsp based on the equation (2), and outputs it to the synchronization addition unit 30.

A display example of the amplitude component displayed on the video monitor by the digital modulation signal analyzing apparatus 1E having such a configuration is the same as that shown in FIG. According to the present embodiment, in the digital modulation signal transmitted to the digital modulation signal analyzing apparatus 1E, the insertion ratio of the SP signal with respect to all the OFDM carriers is relatively high at about 8%. Therefore, the amplitude component based on this SP signal The cause of the interference can be specified with a simple configuration in which only the message is displayed.
Although this embodiment has been described as an example applied to terrestrial digital broadcasting, for example, when applied to an FPU or the like, a waveform equalization reference signal may be a CP (Continual Pilot) signal instead of an SP signal. Similar effects can be achieved.

[Sixth Embodiment]
As a second example applied to terrestrial digital broadcasting, a digital modulation signal analyzing apparatus for analyzing and displaying an OFDM digital modulation signal will be described with reference to FIG. FIG. 7 is a configuration diagram of a digital modulation signal analyzing apparatus according to the sixth embodiment. As shown in FIG. 7, this digital modulation signal analyzing apparatus 1F has basically the same configuration as the digital modulation signal analyzing apparatus 1E shown in FIG. 6 except that the configuration of the signal processing means 50 (50F) is different. It is. Therefore, the same components are denoted by the same reference numerals, and description thereof is omitted.

The signal processing means 50F includes a reference signal generation means 55a, an FFT 56a, a reference signal extraction means 57, complex division means 54b, 54c and 54d, a hard decision means 52a, an interpolation means 58, and switches SW1 and SW2. I have.
The reference signal generating means 55a outputs a normal SP signal _Xsp read from a memory (not shown ₎ to the complex division means 54b and 54d.

The FFT 56a outputs the carrier data converted into the frequency domain by the fast Fourier transform to the reference signal extraction unit 57 and the complex division unit 54c.
The reference signal extraction means 57 extracts the reference signal (SP signal) inserted on the transmission side from the FFT spectrum signal S and outputs the actually extracted SP signal _Ssp to the complex division means 54b. is there.
Complex division unit 54b, based on the equation (4), a reference signal extraction means 57 signals S _sp extracted, in the reference signal generating means of the read regular in 55 SP signal X _sp complex division, the The quotient transmission path characteristic H _sp (acting on the regular SP signal X _sp and the transmission path characteristic of the transmission path on which the digital modulation signal is transmitted) is output to the interpolation means 58.

The interpolating means 58 interpolates the transmission path characteristics for the carrier in which no SP signal is inserted, based on the transmission path characteristics H _sp output from the complex division means 54b, and is generated by the interpolation (estimated). ) The transmission path characteristics H _isp for all carriers are output to the complex division means 54c. For this purpose, the interpolation means 58 includes a symbol filter G _s and a carrier filter G _{c (} not shown). The symbol filter G _s is arranged on the complex division means 54b side and performs interpolation in the symbol direction (time direction). The carrier filter G _c is disposed complex division unit 54c side, and performs interpolation in the frequency direction. The transmission path characteristic H _isp estimated by the symbol filter G _s and the carrier filter G _c is expressed by equation (5).

Based on the equation (6), the complex division means 54c performs complex division on the spectrum signal S output from the FFT 56a by the transmission path characteristic H _isp output from the interpolation means 58, and the determination signal SH that is the quotient thereof is obtained. This is output to the hard decision means 52a and the complex division means 54d. The signal processing means 50F so far, that is, the reference signal generation means 55a, the reference signal extraction means 57, the complex division means 54b and 54c, and the interpolation means 58 constitute an equalization means. .

The hard decision means 52a receives the determination signal SH output from the complex division means 54c, makes a hard decision on a symbol (carrier symbol) in the input determination signal SH, and converts the hard decision output signal _Xd into the complex division means. 54d.
As shown in the equation (7), the switches SW1 and SW2 receive a signal X (divisor signal) input to the complex division means 54d based on the digital modulation signal input to the digital modulation signal analyzing apparatus 1F. At the timing, the hard decision output signal _Xd or the output signal _Xsp (regular SP signal) from the reference signal generating means 55 can be switched. That is, in the reception timing of the reference signal interval of the digital modulation signal to be inputted to the digital modulation signal analyzer 1F, input as signal X to enter the nominal SP signal X _sp to the complex division section 54d. Further, in a section (data section) in which arbitrary data of the digital modulation signal is transmitted, the hard decision output signal _Xd is input as a signal X input to the complex division means 54d. That is, this input signal X (divisor signal) is used as an estimated value of the transmission signal. The switches SW1 and SW2 correspond to the real axis component and the imaginary axis component, respectively.

Based on the equation (8), the complex division means 54d performs complex division by one of the input signal X (divisor signal) of the hard decision output signal _Xd or the normal SP signal _Xsp , and the time that is the quotient thereof The axis signal H is output to the amplitude extracting means 20. Note that the time axis signal H in the equation (8) indicates the transmission path characteristic in which the modulation component is canceled.

It is the block diagram which showed the basic composition of the digital modulation signal analyzer. It is a block diagram of the digital modulation signal analyzer of 1st Embodiment. It is a block diagram of the digital modulation signal analyzer of 2nd Embodiment. It is a block diagram of the digital modulation signal analyzer of 3rd Embodiment. It is a block diagram of the digital modulation signal analyzer of 4th Embodiment. It is a block diagram of the digital modulation signal analyzer of 5th Embodiment. It is a block diagram of the digital modulation signal analyzer of 6th Embodiment. It is a figure for demonstrating the example of a display of an image | video monitor, Comprising: (a) is normal, (b) has shown the beat, (c) has each shown the pulse. It is a figure for demonstrating the example of a display of a video monitor, (a) is normal, (b) is a beat, (c) is a pulse, (d) is a beat (electric field fall), (e) is a pulse (electric field Respectively).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A-1F Digital modulation signal analyzer 10 Quadrature demodulation means 11 Sine wave oscillator 12 90 degree phase shifter 13a, 13b Multiplier 20 Amplitude extraction means 21a, 21b Square calculator 22 Adder 23 Square root calculator 30 Synchronous addition Means 40 Display means 50, 50B-50F Signal processing means 51 Synchronous detection means 52, 52a Hard decision means 53, 54, 54a-54d Complex division means 55, 55a Reference signal generation means 56, 56a FFT (fast Fourier transform means)
57 Reference signal extraction means 58 Interpolation means

Claims (9)

In a digital modulation signal analyzer that analyzes a digital modulation signal modulated by a predetermined modulation method and displays an analysis result,
Orthogonal demodulation means for orthogonally demodulating the digital modulation signal to convert it into an I signal and a Q signal;
An amplitude extraction means for extracting an amplitude component of a predetermined time axis signal based on the I signal and the Q signal output by the orthogonal demodulation means;
Synchronization adding means for adding a synchronizing signal to the amplitude component extracted by the amplitude extracting means and outputting it to the display means;
A digital modulation signal analyzing apparatus comprising:   2. The digital modulation signal analyzing apparatus according to claim 1, wherein the time axis signal is an I signal and a Q signal output by the orthogonal demodulation unit.   2. The signal processing unit according to claim 1, further comprising a signal processing unit configured to perform signal processing for canceling a modulation component included in the I signal and the Q signal output by the quadrature demodulation unit to generate the time axis signal. Digital modulation signal analyzer. The signal processing means includes
Synchronous detection means for performing phase synchronization and frequency synchronization for the I and Q signals output by the orthogonal demodulation means;
Hard decision means for making a hard decision on the carrier symbol in the signal output from the synchronous detection means;
Complex division means for complex dividing the signal output from the synchronous detection means by the signal output from the hard decision means;
With
4. The digital modulation signal analyzing apparatus according to claim 3, wherein a signal output from the complex division means is the time axis signal. The signal processing means includes
Reference signal generating means for generating a waveform equalization reference signal for equalizing the waveform of the digital modulation signal;
Fast Fourier transform means for transforming the I signal and Q signal output from the orthogonal demodulation means into carrier data in the frequency domain by fast Fourier transform;
Reference signal extraction means for extracting a reference signal corresponding to the waveform equalization reference signal inserted in advance on the transmission side from carrier data output from the fast Fourier transform means;
Complex division means for complex dividing the reference signal extracted by the reference signal extraction means by the waveform equalization reference signal generated by the reference signal generation means;
With
4. The digital modulation signal analyzing apparatus according to claim 3, wherein a signal output from the complex division means is the time axis signal. The signal processing means includes
Transmission path characteristics of a transmission path on which the digital modulation signal is transmitted based on a waveform equalization reference signal for equalizing the waveform of the digital modulation signal and the I signal and the Q signal output from the orthogonal demodulation means An equalization means for estimating
Hard decision means for making a hard decision on the carrier symbol in the transmission path characteristics output from the equalization means;
Switching means for switching the waveform equalization reference signal and the hard decision output output from the hard decision means at a predetermined timing;
Complex division means for performing complex division on the transmission path characteristic estimated by the equalization means by the signal switched by the switching means;
With
4. The digital modulation signal analyzing apparatus according to claim 3, wherein a signal output from the complex division means is the time axis signal. In a digital modulation signal analyzer that analyzes a digital modulation signal modulated by a predetermined modulation method and displays an analysis result,
Orthogonal demodulation means for orthogonally demodulating the digital modulation signal to convert it into an I signal and a Q signal;
A signal processing means for generating a time axis signal by performing signal processing for canceling the modulation component included in the I signal and the Q signal output by the orthogonal demodulation means, and extracting an amplitude component of the time axis signal;
Synchronization adding means for adding a synchronization signal to the amplitude component extracted by the signal processing means and outputting it to the display means;
A digital modulation signal analyzing apparatus comprising: The signal processing means includes
Synchronous detection means for performing phase synchronization and frequency synchronization for the I and Q signals output by the orthogonal demodulation means;
Hard decision means for making a hard decision on the carrier symbol in the signal output from the synchronous detection means;
Complex division of the signal output from the synchronous detection means with the signal output from the hard decision means to generate the time axis signal and extract the real part as the amplitude component of the time axis signal Means,
The digital modulation signal analyzing apparatus according to claim 7, comprising: The signal processing means includes
Reference signal generating means for generating a waveform equalization reference signal for equalizing the waveform of the digital modulation signal;
Switching means for switching between a waveform equalization reference signal generated by the reference signal generation means and a signal output from the hard decision means at a predetermined timing;
Further comprising
9. The digital modulation signal analyzing apparatus according to claim 8, wherein the complex division means performs complex division on the signal output from the synchronous detection means by the signal switched by the switching means.

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