JP2007189420A - Reception processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reception processor capable of deciding a modulation format with a high probability even if a signal obtained from a sensor is an interference signal, when a center frequency cannot correctly be found, or when a signal-to-noise ratio is small. <P>SOLUTION: The reception processor includes sensors 1<SB>1</SB>to 1<SB>n</SB>which receive external signals, a signal power detection and narrow-band extraction unit 3 which detects a region where signal power appears in a predetermined band of a signal sent from a sensor, extracts a narrow band from the signal of the detected region, and outputs it as a narrow-band signal, a modulation format decision unit 5 which decides the modulation format of the narrow-band signal outputted from the signal power detection and narrow-band extraction unit independently of the center frequency of the narrow-band signal by using the integration of the narrow-band signal, and a demodulation unit 6 which demodulates the signal sent from the sensor according to the modulation format decided by the modulation format decision unit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reception processing apparatus that receives a modulated signal, determines a modulation format, demodulates based on the determination result, and performs automatic reception or monitoring of a target signal.

  In a reception processing apparatus that performs automatic signal reception and automatic monitoring, reception processing is generally performed according to the following procedures (1) to (6).

(1) The reception or monitoring target band of the signal obtained from the sensor is converted into data on the frequency axis by fast Fourier transform or the like, and the appearance of signal power is detected based on the data obtained by this conversion. As the sensor, for example, an antenna is used for wireless, and a receiver is used for wired. In this signal power detection, unnecessary signals are eliminated in consideration of the duration and bandwidth of the received or monitored signal.
(2) The center frequency of the part where the signal detected in (1) is present is estimated.
(3) A target signal is extracted using a bandpass filter based on the center frequency estimated in (2) above.
(4) The frequency spectrum distribution, the amplitude feature and the phase feature of the signal extracted in (3) above are examined, and the communication speed is estimated and the clock is regenerated.
(5) Based on the information obtained in (4) above, the modulation format, for example, PSK, FSK, ASK, etc. is determined.
(6) Demodulate using the modulation format determined in (5) above, and convert to character information as necessary.

  As a related technique, Patent Document 1 discloses an automatic modulation scheme identification device that automatically identifies a modulation scheme of a received signal of unknown communication specifications. This automatic modulation system identification device has an analog / digital modulation system identification circuit for identifying whether a received signal is an analog modulation system, a linear modulation system based on a digital modulation system, or a nonlinear modulation system, and an analog modulation system. When identified, an analog modulation scheme identifying circuit for identifying which one of the analog modulation schemes is AM or FM, and when identified as a linear modulation scheme based on the digital modulation scheme, Of linear modulation systems, BPSK, QPSK, π / 4-shot QPSK, 8-PSK, multi-level M-ary PSK exceeding 8 levels, 16QAM, multi-level M-ary QAM exceeding 16 levels When a linear modulation type identification circuit for identifying a non-linear modulation type by a digital modulation type is identified, M-ary FSK, 2-FSK of the non-linear modulation type by Tal modulation scheme, and includes MSK, and a non-linear modulation type discrimination circuit for identifying which of GMSK.

As a result, it is possible to identify the modulation schemes of received signals of unknown communication specifications with a single identification device without having known communication specifications in advance for a plurality of modulation schemes.
JP 2001-86171 A

  However, in the conventional reception processing described above, when an interference signal in which a plurality of signals are mixed is obtained from the sensor, the appearance of signal power can be detected, but the processing after the above (2) is not performed normally and is modulated. There is a problem of incorrect format judgment. In the process (2), it may be difficult to determine the center frequency correctly depending on the modulation format. If the center frequency is not correct, the process (3) is not performed properly. As a result, (4) In this process, phase characteristics, communication speed estimation or clock reproduction is incorrect, and a correct modulation format determination result cannot be obtained. There is also a problem that erroneous determination of the modulation format increases when the signal-to-noise ratio is small.

  The present invention has been made to solve the above-described problems, and the problem is that the signal obtained from the sensor is an interference signal, the center frequency is not correctly obtained, or the signal-to-noise ratio is An object of the present invention is to provide a reception processing apparatus capable of determining a modulation format with a high probability even in a small case.

  In order to solve the above-mentioned problem, the invention according to claim 1 detects a part receiving signal from the outside and a part where signal power appears in a predetermined band of a signal sent from the sensor, and the detected part The signal power detection / narrowband extraction unit that extracts a narrowband from the signal and outputs it as a narrowband signal, and the modulation format of the narrowband signal output from the signal power detection / narrowband extraction unit is the center of the narrowband signal. A modulation type determination unit that is determined by using integration with respect to a narrowband signal independently of the frequency, and a demodulation unit that demodulates a signal transmitted from the sensor according to the modulation type determined by the modulation type determination unit. It is characterized by having.

  According to a second aspect of the present invention, in the first aspect of the invention, the signal power detection / narrow band extraction unit creates a time-frequency map by performing a short-time Fourier transform on a predetermined band of the signal transmitted from the sensor. However, if there are multiple ranges where the signal exists in the created time-frequency map, the narrow band of the range where each signal exists is extracted separately and output as a plurality of narrow band signals. Features.

  According to the third aspect of the present invention, the sensor includes a plurality of sensors, and whether or not the narrowband signal output from the signal power detection / narrowband extraction unit is an interference signal obtained by mixing a plurality of signals is transmitted from the plurality of sensors. An interference determination unit that uses a received signal to determine whether the signal is an interference signal, and interference separation that separates the signal into a plurality of narrowband signals by beam formation, NULL formation, or independent component analysis. The modulation format determination unit determines the modulation format of the narrowband signal separated by the interference separation unit independently of the center frequency of the separated narrowband signal.

  Further, the invention according to claim 4 creates a time-frequency map by short-time Fourier transforming a sensor that receives an external signal and a predetermined band of the signal sent from the sensor, and the created time- When there are a plurality of ranges in which a signal exists in the frequency map, a narrow band extraction unit is provided that extracts a narrow band in a range in which each signal exists and separately outputs it as a plurality of narrow band signals. It is characterized by that.

  Further, the invention according to claim 5 is the signal power detector according to claim 4, wherein the sensor comprises a plurality of signals, and detects a portion where signal power appears in a predetermined band of signals sent from the plurality of sensors. And an interference determination unit that determines whether or not the signal of the part detected by the signal power detection unit is an interference signal in which a plurality of signals are mixed using signals sent from a plurality of sensors, and interference determination And an interference separation unit that separates the signal into a plurality of narrowband signals by beam formation, NULL formation, or independent component analysis.

  According to the first aspect of the present invention, since the modulation format of the extracted narrowband signal is determined independently of the center frequency of the narrowband signal, even if there is an error in the estimation of the center frequency, the modulation format is determined. Can be determined. In addition, since the modulation format is determined using integration for narrowband signals, the effects of waveform distortion and noise can be reduced, and even if the signal-to-noise ratio is small, the modulation format is highly probable. Can be determined.

  According to the second aspect of the present invention, when there are a plurality of ranges in which the signal exists in the time-frequency map, a plurality of narrow bands in the range in which each signal exists is separated and extracted separately. Since it is output as a narrowband signal, even if there is only one sensor, it is possible to reduce errors in the determination of the modulation format for the interfering signal.

  According to the third aspect of the present invention, it is determined whether or not the signal is a mixed interference signal based on the outputs of the plurality of sensors. Further, since it is configured so as to be separated into a plurality of narrowband signals by NULL formation or independent component analysis, it is possible to reduce an error in determining the modulation format with respect to the interference signal.

  According to the fourth aspect of the present invention, when there are a plurality of ranges in which a signal exists in a time-frequency map created based on an external signal, a narrow band of the range in which each signal exists is extracted separately. Thus, the separated signals are output as a plurality of narrowband signals, so that even if there is only one sensor, it is possible to separate the interfering signals.

  Further, according to the fifth aspect of the present invention, it is determined based on the outputs of the plurality of sensors whether the plurality of signals are mixed interference signals, and when it is determined that the signals are interference signals, beam forming is performed. Since the signal is separated into a plurality of narrowband signals by NULL formation or independent component analysis, the interfering signal can be accurately separated.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the reception processing apparatus according to the embodiment of the present invention described below, an antenna that receives radio waves is used as a sensor. As a sensor, a receiver that receives a signal transmitted by wire can be used in addition to an antenna that receives radio waves.

FIG. 1 is a block diagram illustrating the configuration of the reception processing apparatus according to the first embodiment of the present invention. The reception processing apparatus includes a plurality of sensors 1 ₁ to 1 _n , a sampling unit 2, a signal power detection / narrowband extraction unit 3, an interference determination / interference separation unit 4, a modulation format determination unit 5, and a demodulation / decoding unit 6. Has been. The narrowband extraction unit of the present invention is configured by the signal power detection / narrowband extraction unit 3, and the demodulation unit of the present invention is configured by the demodulation / decoding unit 6.

Each of the sensors 1 ₁ to 1 _n receives incident signals S 1 to Sm coming from a plurality of directions. Incident signals received by the sensors 1 ₁ to 1 _n include incident signals S2 to Sm from outside the target in addition to the incident signal S1 from the target. The number n of sensors is “2” or more when interference separation is performed in the interference determination / interference separation unit 4 described later. In addition, when separating the interference signal in which three or more signals interfere, the number of sensors equal to or more than the number of the interference signals is required. Signals obtained by receiving the incident signals S1 to Sm by the sensors 1 ₁ to 1 _n are sent to the sampling unit 2.

The sampling unit 2 samples high-frequency analog signals sent from the sensors 1 ₁ to 1 _n to convert them into digital signals, and sends them to the signal power detection / narrow band extraction unit 3.

  The signal power detection / narrow band extraction unit 3 receives the entire band to be received or monitored from the signal sent from the sampling unit 2 by a fast Fourier transform (hereinafter referred to as “FFT: Fast Fourier Transform”) or the like. The data is converted into data on the frequency axis with resolution, and a map of the time change (time-frequency map) is generated. In other words, a time-frequency map is generated by performing a short time Fourier transform (STFT) on the entire reception or monitoring target band. FIG. 2 shows an example of a time-frequency map when the signal of frequency f1 and the signal of frequency f1 + Δ are in interference.

  Then, the existence range of signals having a predetermined bandwidth and time length is specified from the generated time-frequency map. In the example shown in FIG. 2, the signal S1 exists near the frequency f1, and the signal S2 exists near the frequency f1 + Δ. Then, in the range where the specified signal S1 and signal S2 exist, the center frequencies of the signal S1 and the signal S2 are estimated, and the bandpass filter BPF is applied around the estimated center frequency, so that the signals S1 and S2 A narrow band in a range where the signal S2 exists is extracted. The narrowband signal extracted by the signal power detection / narrowband extraction unit 3 is sent to the interference determination / interference separation unit 4.

  The interference determination / interference separation unit 4 receives a signal of a part detected by the signal power detection / narrowband extraction unit 3, more specifically, a narrowband signal transmitted from the signal power detection / narrowband extraction unit 3. An interference determination unit that determines whether the signal is a single signal or a mixture (interference) of a plurality of signals, and an interference separation unit that separates the signals into a plurality of signals when the interference determination unit determines that interference occurs. It is configured.

  The interference determination unit determines the presence or absence of interference, for example, by performing eigenvalue analysis or the like using a plurality of sensor outputs. In the eigenvalue analysis, the number of signals is obtained by obtaining eigenvalues of a plurality of sensor outputs. That is, in the eigenvalue analysis, the number of eigenvalues corresponding to the number of sensors is obtained, and the number of eigenvalues having a larger value among the plurality of eigenvalues corresponds to the number of signals that are interfering. Therefore, the interference determination unit determines the presence / absence of interference and the number of interfering signals based on the presence / absence and number of eigenvalues having a large value, and sends the determination result to the interference separation unit.

  When the interference determination unit determines that there is interference, the interference separation unit separates the signals into a plurality of signals using well-known beam formation, NULL formation, independent component analysis, or the like. In beam forming, a desired signal is received by outputting an antenna pattern (beam pattern) having directivity in a desired direction.

  In NULL formation, a desired signal is received by providing a point with low sensitivity (gain) in addition to a desired direction. Independent component analysis obtains a desired signal using an algorithm that separates up to the same number of incident signals as the number of sensors without prior knowledge of sensor responsiveness, signal characteristics, and incident signals. The signal obtained by the interference separation unit is sent to the modulation format determination unit 5 as a narrowband signal.

  It should be noted that it is not possible to specify which of the separated signals is a desired signal at the stage of processing by the interference separation unit. However, when the rough azimuth is known in advance, the desired wave can be specified using the information on the arrival azimuth of the signal obtained by the azimuth measurement performed in the process of the interference separation process. If the rough azimuth is not known, a desired signal is determined based on the determination result in the subsequent modulation format determination unit 5. The processing result (narrowband signal) by the interference determination / interference separation unit 4 is sent to the modulation format determination unit 5.

  The modulation format determination unit 5 determines the modulation format based on the narrowband signal sent from the interference determination / interference separation unit 4, and sends the determination result to the demodulation / decoding unit 6. When there is interference in the signal received from the outside and a plurality of signals are separated, the modulation format is determined for each signal, and signals other than the desired signal are excluded here.

  Next, details of processing performed in the modulation format determination unit 5 will be described. Even if the center frequency estimated by the signal power detection / narrowband extraction unit 3 is incorrect, the modulation format determination unit 5 uses the data that has less influence, that is, modulates independently of the center frequency of the narrowband signal. Determine the format. Examples of specifications include amplitude standard deviation, input waveform, input waveform squared and input waveform squared feature extraction, presence / absence of carrier component, FM demodulated spectrum, voice feature as modulation component And the like.

  FIG. 3 is a diagram illustrating processing performed by the modulation format determination unit 5. The modulation format determination unit 5 inputs the narrowband signal transmitted from the interference determination / interference separation unit 4 and executes the following processing. First, in the process of obtaining the amplitude standard deviation, the absolute value of the amplitude of the input narrowband signal is obtained (step ST11). Next, a standard deviation is obtained from the absolute value of the amplitude (step ST12). The standard deviation obtained in step ST12 is sent to the determination process (step ST71) as an amplitude standard deviation.

  In the feature extraction process of the spectrum of the input waveform, the input narrowband signal is subjected to FFT (step ST21). Next, the values are integrated (added) (step ST22) and sent to the determination process (step ST71).

  In the feature extraction process of the square spectrum of the input waveform, first, the input narrowband signal is doubled (squared) (step ST31). Next, the doubled signal is subjected to FFT (step ST32). Next, the value is integrated (added) (step ST33) and sent to the determination process (step ST71).

  In the feature extraction process for the fourth power spectrum of the input waveform, first, the input narrowband signal is multiplied by four (fourth power) (step ST41). Next, the signal multiplied by 4 is subjected to FFT (step ST42). Next, the values are integrated (added) (step ST43) and sent to the determination process (step ST71).

  In the feature extraction process of the eighth power spectrum of the input waveform, first, the input narrowband signal is multiplied by eight (8th power) (step ST51). Next, the signal multiplied by 8 is subjected to FFT (step ST52). Next, the values are integrated (added) (step ST53) and sent to the determination process (step ST71).

  In the process of obtaining the spectrum after the FM demodulation process, first, the input narrowband signal is FM detected (step ST61). Next, the absolute value of the amplitude of the FM detected signal is obtained (step ST62). Next, the absolute value of the obtained amplitude is integrated (added) (step ST63) and sent to the determination process (step ST71).

  In the determination process (step ST71), ASK, FSK, PSK (BPSK, QPSK, 8PSK) is determined for each combination of values obtained in step ST12, step ST22, step ST33, step ST43, step ST53, step ST63. The correspondence between each value combination and each modulation method is as follows. First, when a known narrowband signal corresponding to each modulation method is input, step ST12, step ST22, step ST33, step ST43, step ST53, It is obtained by measuring the value of each output in step ST63. Here, the value obtained by the measurement is held and used as an internal threshold value.

  In the process of analog modulation wave (AM, FM, SSB) determination and digital modulation wave (ASK, FSK, PSK) determination (step ST72), the modulation format of the input narrowband signal is, for example, shown in Patent Document 1 Thus, the determination result is sent to the comprehensive determination process (step ST73).

  In the comprehensive determination process (step ST74), the determination process (step ST71), the analog modulation wave (AM, FM, SSB) determination, and the digital modulation wave (ASK, FSK, PSK) determination process (step ST72) are sent. Based on the result, the modulation format is finally determined, and the determination result is sent to the demodulation / decoding unit 6.

  The demodulation / decoding unit 6 demodulates based on the modulation format determined by the modulation format determination unit 5, and converts binary (1 or 0) data obtained by the demodulation into characters or the like according to a predetermined procedure.

  Although digitally modulated PSK, FSK, ASK, etc. need to generate a recovered clock, the modulation format determination unit 5 can obtain a modulation format as look-ahead information, so that clock recovery can be performed by a method suitable for each modulation format. Done.

  As described above, according to the reception processing apparatus according to the first embodiment, even if the center frequency estimated in the signal power detection / narrowband extraction unit 3 is incorrect, the specifications that have little influence are used, that is, the narrowness. Since the modulation format is determined independently of the center frequency of the band signal, the modulation format can be determined even if there is an error in the estimation of the center frequency.

  Also, as shown in steps ST23, ST33, ST44, and ST54 in FIG. 3, the modulation type is determined by using a large amount of integration with respect to the narrowband signal, so that the influence of waveform distortion and noise can be reduced. Even when the signal-to-noise ratio is small, the modulation format can be determined with high probability.

  Further, it is determined based on the outputs of a plurality of sensors whether or not a plurality of signals are mixed interference signals. When it is determined that the signals are interference signals, a plurality of signals are obtained by beam forming, NULL forming, or independent component analysis. Since it is configured so as to be separated into narrowband signals, it is possible to reduce errors in the determination of the modulation format for the interfering signals.

The reception processing apparatus according to the first embodiment described above includes a plurality of sensors 1 ₁ to 1 _n and is configured to determine the presence or absence of interference by eigenvalue analysis or the like using a plurality of sensor outputs. Such a reception processing device includes one sensor and determines the presence or absence of interference based on one sensor output.

  FIG. 4 is a block diagram illustrating the configuration of the reception processing apparatus according to the second embodiment of the present invention. In the following description, the same or equivalent components as those of the reception processing apparatus according to the first embodiment are denoted by the same reference numerals as those used in the first embodiment, and the description is simplified.

  The reception processing apparatus includes a sensor 1, a sampling unit 2, a signal power detection / narrowband extraction unit 7, a modulation format determination unit 5, and a demodulation / decoding unit 6.

  The sensor 1 receives incident signals S1 to Sm coming from a plurality of directions. The incident signal received by the sensor 1 includes incident signals S2 to Sm from outside the target in addition to the incident signal S1 from the target. A signal obtained by receiving the incident signals S <b> 1 to Sm by the sensor 1 is sent to the sampling unit 2.

  The sampling unit 2 samples the high-frequency analog signal sent from the sensor 1 to convert it into a digital signal and sends it to the signal power detection / narrowband extraction unit 7.

  Similarly to the signal power detection / narrow band extraction unit 3 of the first embodiment, the signal power detection / narrow band extraction unit 7 receives the entire band to be received or monitored among the signals sent from the sampling unit 2 by FFT or the like. The data is converted into data on the frequency axis with a predetermined frequency resolution, and a time-frequency map is generated. Then, the existence range of signals having a predetermined bandwidth and time length is specified from the generated time-frequency map.

  In an example in which two signals are interfering as shown in FIG. 2, the signal power detection / narrowband extraction unit 3 receives a signal S1 existing in the vicinity of the frequency f1 and a signal S2 existing in the vicinity of the frequency f1 + Δ. Identify. Then, in the range where the specified signal S1 exists, the center frequency of the signal S1 is estimated, and by applying the band pass filter BPF1 around the estimated center frequency, the narrow band of the range where the signal S1 exists is reduced. Extracted and sent to the modulation format determination unit 5 as a narrowband signal.

  Similarly, the signal power detection / narrowband extraction unit 7 estimates the center frequency of the signal S2 in the range where the other specified signal S2 exists, and applies the bandpass filter BPF2 around the estimated center frequency. As a result, a narrow band in a range where the signal S2 exists is extracted and sent to the modulation format determination unit 5 as a narrow band signal. In this way, the signal power detection / narrowband extraction unit 7 simultaneously performs narrowband signal extraction and interference signal separation.

  The modulation format determination unit 5 determines the modulation format based on the narrowband signal sent from the signal power detection / narrowband extraction unit 7 and sends the determination result to the demodulation / decoding unit 6. When there is interference in the signal received from the outside and a plurality of signals are separated, the modulation format is determined for each signal, and signals other than the desired signal are excluded here.

  The demodulation / decoding unit 6 demodulates based on the modulation format determined by the modulation format determination unit 5, and converts binary (1 or 0) data obtained by the demodulation into characters or the like according to a predetermined procedure. Although digitally modulated PSK, FSK, ASK, etc. need to generate a recovered clock, the modulation format determination unit 5 can obtain a modulation format as look-ahead information, so that clock recovery can be performed by a method suitable for each modulation format. Done.

  As described above, according to the reception processing apparatus according to the second embodiment, when there are a plurality of ranges in which a signal exists in the time-frequency map, the narrow band of the range in which each signal exists is extracted separately. Therefore, even if there is only one sensor, it is possible to reduce an error in determining the modulation format for a signal that has been interfered.

  The reception processing device according to the present invention can be applied to an automatic receiving device that automatically receives a signal coming from the outside and an automatic monitoring device that constantly monitors a signal coming from the outside.

It is a block diagram which shows the structure of the reception processing apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating the process performed in the signal power detection and narrowband extraction part of the reception processing apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating the process performed in the modulation | alteration format determination part of the reception processing apparatus which concerns on Example 1 of this invention. It is a block diagram which shows the structure of the reception processing apparatus which concerns on Example 2 of this invention.

Explanation of symbols

1, 1 ₁ to 1 _n sensor 2 sampling unit 3, 7 signal power detection / narrow band extraction unit 4 interference determination / interference separation unit 5 modulation format determination unit 6 demodulation / decoding unit

Claims (5)

A sensor that receives an external signal;
A signal power detection / narrow band extraction unit that detects a part where signal power appears in a predetermined band of the signal sent from the sensor, extracts a narrow band from the signal of the detected part, and outputs it as a narrow band signal;
A modulation format determination unit that determines the modulation format of the narrowband signal output from the signal power detection / narrowband extraction unit independently of the center frequency of the narrowband signal and using integration with respect to the narrowband signal;
A demodulator that demodulates a signal transmitted from the sensor according to the modulation format determined by the modulation format determination unit;
A reception processing apparatus comprising:   The signal power detection / narrow band extraction unit creates a time-frequency map by performing a short-time Fourier transform on a predetermined band of the signal transmitted from the sensor, and a range in which the signal exists in the created time-frequency map 2. The reception processing apparatus according to claim 1, wherein when there are a plurality of signals, a narrowband in a range in which each signal exists is extracted separately and output as a plurality of narrowband signals. The sensor comprises a plurality of
Interference determination unit that determines whether a narrowband signal output from the signal power detection / narrowband extraction unit is an interference signal in which a plurality of signals are mixed, using signals sent from the plurality of sensors When,
An interference separation unit that separates into a plurality of narrowband signals by beam forming, NULL formation or independent component analysis when the interference determination unit determines that the signal is an interference signal,
The modulation format determination unit
The reception processing apparatus according to claim 1, wherein the modulation format of the narrowband signal separated by the interference separation unit is determined independently of the center frequency of the separated narrowband signal. A sensor that receives an external signal;
A time-frequency map is created by short-time Fourier transform of a predetermined band of the signal sent from the sensor, and if there are multiple ranges where the signal exists in the created time-frequency map, each signal exists. A narrowband extraction unit that separates and outputs a plurality of narrowband signals by extracting a narrowband of a range to be separately,
A reception processing apparatus comprising: The sensor comprises a plurality of
A signal power detection unit for detecting a portion where signal power appears in a predetermined band of signals sent from the plurality of sensors;
An interference determination unit that determines whether the signal of the part detected by the signal power detection unit is an interference signal in which a plurality of signals are mixed, using signals sent from the plurality of sensors,
5. An interference separating unit that separates into a plurality of narrowband signals by beam forming, NULL forming or independent component analysis when the interference determining unit determines that the signal is an interference signal. Reception processing device.

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