JP2013106112A - Interference wave detection circuit, receiver, and interference wave detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect from among reception signals an interference wave at a lower level than a target radio wave, in radio communication based on a digital modulation system.SOLUTION: An interference wave detection circuit comprises: a convergent point estimation unit which estimates a convergent point with respect to a signal point at each time point of a time series signal obtained by digital demodulation of a received analog signal; an error calculation unit which calculates as an error signal a difference between the time series signal and the convergent point at each time point; a conversion unit which converts the error signal from a time area to a frequency area; and a detection unit which detects the component of the interference wave contained in the time series signal, on the basis of the error signal converted to the frequency area.

Description

  The present invention relates to an interference wave detection circuit, a receiver, and an interference wave detection method for detecting an interference wave in wireless communication, and in particular, a single carrier type communication / broadcast QAM (Quadrature Amplitude Modulation) demodulation method, The present invention relates to an interference wave detection circuit for detecting an interference wave in a PSK (Phase Shift Keying) demodulation method, a receiver provided with the interference wave detection circuit, and an interference wave detection method.

  The demand for demodulation performance of digital broadcast receivers is becoming stricter year by year, and for example, resistance to disturbances such as noise is also required. In the demodulation of a received signal in a QAM modulation system or a PSK modulation system for communication using a single carrier, continuous wave (CW: Continus Wave) interference greatly affects reception performance. Even with low-level CW interference, the characteristics are greatly degraded as the modulation scheme becomes higher order. Therefore, it is necessary to improve reception performance by accurately detecting and removing low-level CW interference.

  The receiving apparatus described in Patent Document 1 aims to detect and remove CW interference by spectrum analysis. This receiving apparatus performs Fast Fourier Transform (FFT) on the demodulated signal itself, and detects the maximum of its power spectrum as CW interference.

  FIG. 9 is a block diagram illustrating a configuration of the receiving device described in Patent Document 1. In FIG. A signal received by the antenna unit 100 selects a predetermined channel by the tuner unit 101 and is A / D converted by an A / D (Analog to Digital) converter 102. Thereafter, the quadrature detection circuit 103 performs quadrature detection, and the multiplier 104 performs frequency shift to remove the frequency error. The FFT circuit 105 converts the time domain signal into a frequency domain signal. The signal after the FFT is equalized by the equalization circuit 106, and then error correction processing is performed by the error correction circuit 107.

  The signal after the FFT is detected by a carrier frequency error in a broadband AFC (Automatic Frequency Control) circuit 108 and added to the time axis processing circuit 109.

  Further, the signal after the FFT is branched and input to the interference detection circuit 110, and the interference detection circuit 110 detects CW interference. The notch of the variable notch filter 111 is controlled by the output of the interference detection circuit 110 to be set at the interference presence position. The variable notch filter 111 is applied to the signal branched from the output of the multiplier 104, and the signal from which the interference is removed by the variable notch filter 111 is used in the time axis processing circuit 109 to perform symbol synchronization, narrow band AFC, clock recovery. I do.

  FIG. 10 is a schematic diagram for explaining the CW interference detection operation by the receiving apparatus described in Patent Document 1. The interference detection circuit 110 sets a predetermined threshold (threshold value) on the assumption that the CW interference is a narrow band and extremely high power, determines that a portion of the spectrum where the power is higher than the threshold is CW interference, Specify the frequency.

Japanese Patent Laying-Open No. 2006-174218 (6th and 7th pages, FIG. 1 and FIG. 4)

  The following analysis was made by the present inventors.

  The receiving apparatus described in Patent Document 1 cannot detect CW interference when the level of CW interference is relatively low compared to the level of the target radio wave including transmission data, and reception performance deteriorates. There is a problem of doing.

  The reason is that since FFT is performed on a signal in which transmission data and CW components are mixed, if the level of CW interference is low, it is buried in surrounding frequency components and cannot be determined as CW interference. At this time, even if CW interference is present, it cannot be removed, and reception performance is degraded.

  Therefore, in wireless communication based on the digital modulation method, it becomes a problem to be able to detect a lower level interference wave from the received signal compared to the target radio wave.

The interference wave detection circuit according to the first aspect of the present invention is:
A convergence point estimation unit for estimating a convergence point for a signal point at each time point of a time-series signal obtained by digital demodulation of a received analog signal;
An error calculating unit that calculates a difference at each time point between the time series signal and the convergence point as an error signal;
A converter for converting the error signal from a time domain to a frequency domain;
A detection unit configured to detect a component of an interference wave included in the time series signal based on the error signal converted into the frequency domain.

The receiving apparatus according to the second aspect of the present invention is:
A convergence point estimation unit for estimating a convergence point for a signal point at each time point of a time-series signal obtained by digital demodulation of a received analog signal;
An error calculating unit that calculates a difference at each time point between the time series signal and the convergence point as an error signal;
A converter for converting the error signal from a time domain to a frequency domain;
A detection unit that analyzes a spectrum of the error signal converted into a frequency domain and extracts an amplitude and a frequency of a continuous wave (CW: Continuous Wave) as a component of an interference wave included in the time-series signal;
An interference wave removing unit that removes the CW component from the time series signal based on at least the amplitude and frequency of the CW.

The interference wave detection method according to the third aspect of the present invention is:
An estimation step for estimating a convergence point with respect to a signal point at each time point of a time-series signal obtained by digital demodulation of a received analog signal;
Calculating a difference at each time point between the time series signal and the convergence point as an error signal;
Converting the error signal from a time domain to a frequency domain;
And a detection step of detecting an interference wave component included in the time-series signal based on the error signal converted into the frequency domain.

  According to the jamming wave detection circuit, the receiving device, and the jamming wave detection method according to the present invention, it is possible to detect a jamming wave having a lower level than a target radio wave from a received signal in wireless communication based on a digital modulation method. It becomes.

It is a block diagram which shows the structure of the receiver which concerns on 1st Embodiment as an example. It is a flowchart which shows operation | movement of the receiver which concerns on 1st Embodiment as an example. It is a figure which shows typically the ideal signal point arrangement | positioning in a QAM modulation system, and the signal point arrangement | sequence influenced by the CW interference. It is a figure which shows typically CW disturbance detection by the receiver which concerns on 1st Embodiment. It is a block diagram which shows the modification of a structure of the receiver which concerns on 1st Embodiment. It is a block diagram which shows the modification of a structure of the receiver which concerns on 1st Embodiment. It is a block diagram which shows the structure of the receiver which concerns on 2nd Embodiment as an example. 6 is a flowchart illustrating an example of an operation of a receiving apparatus according to the second embodiment. 10 is a block diagram illustrating a configuration of a receiving device described in Patent Literature 1. FIG. 10 is a diagram for explaining a CW interference detection operation by a receiving device described in Patent Literature 1. FIG.

  First, the outline of the present invention will be described. Note that the reference numerals of the drawings attached to this summary are merely examples for facilitating understanding, and are not intended to limit the present invention to the illustrated embodiment.

  Referring to FIG. 1, the interference wave detection circuit (20) according to the present invention estimates a convergence point estimation unit for a signal point at each time point of a time-series signal obtained by digital demodulation of a received analog signal. (21), an error calculation unit (22) that calculates a difference at each time point between the time series signal and the convergence point as an error signal, and a conversion unit (FFT unit 23) that converts the error signal from the time domain to the frequency domain. And a detection unit (50) for detecting a component of the interference wave included in the time series signal based on the error signal converted into the frequency domain.

  Here, the convergence point estimation unit (21) estimates the signal point having the shortest distance from the signal point at each time point among the ideal signal points determined according to the digital demodulation method as the convergence point. You may do it.

  Further, the detection unit (50) may analyze the spectrum of the error signal converted into the frequency domain and extract the amplitude and frequency of a continuous wave (CW: Continuous Wave) as an interference wave component.

  Referring to FIG. 7, the detection unit (60) calculates the phase of the CW at the time when the time series signal is acquired based on the error signal, and starts removing the interference wave included in the time series signal from the time. Based on the period up to the time and the CW frequency, the amount of rotation of the CW phase in the period may be calculated, and the phase of the CW at the start time may be obtained according to the calculated phase and the amount of phase rotation. .

  The time-series signal may be a time-series signal obtained by digitally demodulating a received analog signal and compensating for transmission path characteristics, as shown in FIG.

  Referring to FIG. 1, a receiving apparatus (10) according to the present invention includes a convergence point estimation unit (21) for estimating a convergence point for a signal point at each time point of a time-series signal obtained by digital demodulation of a received analog signal. ), An error calculation unit (22) that calculates a difference at each time point between the time series signal and the convergence point as an error signal, a conversion unit (FFT unit 23) that converts the error signal from the time domain to the frequency domain, and a frequency Analyzing the spectrum of the error signal converted into a region and extracting the amplitude and frequency of a continuous wave (CW: Continuous Wave) as an interference wave component included in the time-series signal; and at least CW An interference wave removing unit (17) that removes a CW component from the time-series signal based on the amplitude and the frequency.

  Referring to FIG. 7, the interference wave removing unit (37) may remove the CW component from the time series signal based on the amplitude, frequency, and phase at the start time of the CW. In particular, the jamming wave detection circuit (40) generates a signal having a phase opposite to that of CW based on the amplitude and frequency of CW and the phase at the start time, and adds the signal to the time series signal, thereby adding the time signal. The CW component may be removed from the series signal.

  As a more specific configuration, referring to FIG. 1, the receiving device (10) according to the present invention is a single carrier type communication / broadcast QAM demodulation or PSK demodulating device, which is a CW (Continus Wave). In detection of interference noise, a convergence point estimator (21) for estimating convergence point information from a signal after transmission path characteristic compensation, and a convergence point information from the signal after the transmission path characteristic compensation and convergence point estimation section (21) ( 28), an error calculation unit (22) that calculates an error signal (27), an FFT unit (23) that generates a spectrum of an error signal after FFT from the calculated error signal (27), and an error signal A spectrum analysis unit (24) that performs spectrum analysis and obtains the intensity, frequency, phase, and the like of the CW interference and passes the information to the interference wave removal unit (17).

  The jamming wave detection circuit and the receiving device according to the present invention estimate a convergence point with respect to a signal point at each time point of a time series signal obtained by digital demodulation of a received analog signal, and each of the time series signal and the convergence point. The difference at the time is calculated as an error signal. According to such a configuration, it is possible to separate the transmission data component and the interference wave component included in the received signal and extract only the interference wave component. Furthermore, the interference wave caused by CW interference can be detected by converting the interference wave component obtained in the time domain into the frequency domain. Therefore, according to the interfering wave detection circuit and the receiving device according to the present invention, even when the level of the interfering wave included in the received signal is lower than the level of the transmission data in the wireless communication based on the digital modulation scheme, Interference waves can be detected.

(Embodiment 1)
A receiving apparatus according to the first embodiment will be described with reference to the drawings. FIG. 1 is a block diagram illustrating an example of the configuration of the receiving apparatus 10 according to the present embodiment.

  Referring to FIG. 1, a receiving device 10 includes an antenna unit 11, a mixer 12 that lowers a frequency, an oscillator 13, a band-pass filter (BPF: Band-Pass Filter) 14 that attenuates a band other than a desired band, an analog, and the like. An A / D converter 15 that converts a signal into a digital signal, a digital demodulation unit 16 that performs clock synchronization and frequency synchronization, an interference wave detection circuit 20 that detects CW interference, and an interference wave removal unit 17 that removes CW interference A transmission path characteristic compensation unit 18 that compensates transmission path characteristics by waveform equalization and the like, and a decoding unit 19 that decodes the encoded signal.

  The interference wave detection circuit 20 estimates the convergence point and outputs the convergence point information 28 as the convergence point information 28, the error calculation unit 22 that calculates an error based on the convergence point information 28, and the error signal 27. An FFT unit 23 that performs an FFT operation and a spectrum analysis unit 24 that analyzes the spectrum 29 of the error signal and detects the presence / absence of CW interference and its frequency and intensity as CW interference strength / frequency 26 are provided.

  The antenna unit 11 receives an RF (Radio Frequency) signal and outputs the RF signal to the mixer 12.

  The mixer 12 receives an RF signal from the antenna unit 11 and an oscillation signal from the oscillator 13, and outputs a signal after frequency down-conversion to the BPF 14.

  The BPF 14 receives the down-converted signal from the mixer 12 and outputs the filtered signal to the A / D converter 15.

  The A / D converter 15 receives the filtered analog signal from the BPF 14 and outputs the digital signal after A / D conversion to the digital demodulator 16.

  The digital demodulator 16 receives the digital signal after A / D conversion from the A / D converter 15 and separates the in-phase and quadrature phase components, synchronizes the carrier frequency and timing, and the like. Is output to the interference wave removing unit 17.

  The interference wave removal unit 17 receives the digital demodulated signal 25 from the digital demodulation unit 16 and also receives the CW interference strength / frequency 26 from the spectrum analysis unit 24. When there is CW interference, the interference wave removal unit 17 outputs the signal after CW interference removal to the transmission line characteristic compensation unit 18. On the other hand, when there is no CW interference, the interference wave removal unit 17 outputs the digital demodulated signal 25 to the transmission line characteristic compensation unit 18 as it is.

  The method for removing CW interference in this embodiment is not particularly limited. As an example of CW interference removal, there is a method of attenuating the magnitude of the CW frequency detected by a notch filter or the like.

  When CW interference is detected, the transmission path characteristic compensation unit 18 receives the signal after removing the CW interference from the post-digital demodulation signal 25 from the interference wave removal unit 17. On the other hand, when no CW interference is detected, the transmission path characteristic compensation unit 18 receives a signal that has passed through the signal of the digital demodulation unit 16 from the interference wave removal unit 17. The transmission path characteristic compensation unit 18 performs a decoding unit 19, a convergence point estimation unit 21, and an error calculation on the received signal after performing compensation such as waveform equalization according to the transmission path characteristic. To the unit 22.

  The decoding unit 19 receives the signal after the channel characteristic compensation from the channel characteristic compensation unit 18 and outputs the signal after the decoding.

  The convergence point estimation unit 21 receives the signal after the transmission line characteristic compensation from the transmission line characteristic compensation unit 18, and outputs the estimated convergence point information 28 to the error calculation unit 22. As an example, the convergence point estimation unit 21 compares the signal point of the input signal after compensation of the transmission path characteristics with the convergence point determined by the modulation method, and the convergence point of the transmitted signal is the most likely convergence point. It is estimated that.

  The error calculation unit 22 receives the signal after the transmission line characteristic compensation from the transmission line characteristic compensation unit 18 and receives the convergence point information from the convergence point estimation unit 21, obtains an error signal 27, and outputs the error signal 27 to the FFT unit 23. . As an example, the error calculation unit 22 calculates the error signal 27 by subtracting the values of the respective axes of the signal point and the convergence point of the signal after the transmission path characteristic compensation.

  The FFT unit 23 receives the error signal 27 from the error calculation unit 22 and outputs a spectrum 29 of the error signal after the FFT to the spectrum analysis unit 24.

  The spectrum analysis unit 24 receives the error signal spectrum 29 from the FFT unit 23, and outputs the CW interference strength / frequency 26 to the interference wave removal unit 17. As an example, the spectrum analysis unit 24 detects information on the frequency and strength of CW interference that appears as a frequency component stronger than the other from the spectrum 29 of the input error signal.

  FIG. 2 is a flowchart showing an example of the operation of the receiving apparatus according to this embodiment. FIG. 2 specifically shows the operation of CW disturbance detection in detail. With reference to FIG. 2, the operation of the receiving apparatus 10 (FIG. 1) according to the present embodiment will be described.

  The antenna unit 11 receives the RF signal (step S1).

  The mixer 12 and the oscillator 13 down-convert the RF frequency to IF (Intermediate Frequency) or baseband, attenuate the unnecessary band by the BPF 14, and convert it to a digital value by the A / D converter 15 (step S2).

  The digital demodulator 16 corrects the frequency and phase shift of the clock and signal (step S3).

  The convergence point estimation unit 21 compares the signal point of the signal after transmission path compensation with a plurality of convergence points determined by the modulation method, and converges at the closest distance to the signal point of the signal after transmission path compensation on the coordinates. The point is estimated to be the convergence point of the transmitted signal (step S4).

  The error calculator 22 generates an error signal 27 by calculating an error from the signal after the transmission path characteristic compensation and the convergence point information 28 after the convergence point estimation (step S5).

  The FFT unit 23 performs an FFT operation on the error signal output from the error calculation unit 22, and generates an error signal spectrum 29 representing the strength of each frequency component of the error signal (step S6).

  The spectrum analysis unit 24 calculates information such as the difference between the strength and average of each frequency component and the level of the frequency components before and after from the spectrum 29 of the input error signal (step S7).

  Based on the analysis result, the spectrum analysis unit 24 determines whether there is a high (strong) frequency component among the frequency components in the spectrum (step S8).

  If there is a high-level frequency component (Yes in step S8), the spectrum analysis unit 24 detects the strength and frequency information of the high-level frequency component (step S9).

  Next, the interference wave removing unit 17 performs CW interference removal based on the CW interference intensity / frequency 26 output from the spectrum analysis unit 24 of the error signal (step S10).

  On the other hand, when there is no high-level frequency component (No in step S8), the process proceeds to step S11.

  The transmission path characteristic compensation unit 18 compensates for disturbance factors in the transmission path other than CW interference such as multipath by waveform equalization or the like (step S11).

  The decoding unit 19 receives the signal after the transmission path compensation and performs decoding (step S12).

  FIG. 3 is a diagram showing signal point arrangement in the QAM modulation method. FIG. 3A shows an ideal signal point arrangement in the QAM modulation system. On the other hand, FIG. 3B shows the signal point arrangement affected by the CW interference. FIG. 4 is a diagram schematically illustrating a CW interference detection operation by the receiving device 10 according to the present embodiment. With reference to FIG. 3 and FIG. 4, the detection mechanism of the interference wave by the receiving apparatus 10 of this embodiment is demonstrated.

  Here, the unit of data of the modulation scheme is “symbol”, the point plotted on the complex plane of the in-phase I-axis and quadrature Q-axis is the “signal point”, The arrangement of signal points is referred to as “constellation (signal point arrangement diagram)”.

  FIG. 3A shows a case where 16QAM is used as a modulation method from P-14 of DVB-C (Digital Video Broadcasting-Cable, European CATV digital method) document EN 300 429 V1.2.1 (1998-04). An example of constellation is shown. FIG. 3A shows an arrangement relationship between the orthogonal I-axis and Q-axis and 16 signal points, and the ideal arrangement is uniquely determined by the standard and modulation method used for broadcasting. Each signal point in an ideal signal point arrangement is defined as a “convergence point”.

  As indicated by “1011” in FIG. 3A, information is assigned to each convergence point, and information on the convergence point closest to the signal point is used as information transmitted by the transmission side.

  FIG. 3B shows a constellation when the ideal constellation in FIG. 3A is affected by CW interference in the transmission path. In an actual transmission path, a deviation occurs from the ideal arrangement as shown in FIG. White circles in FIG. 3B indicate convergence points in FIG. On the other hand, black circles in FIG. 3 (b) indicate signal points affected by CW interference. When receiving the influence of CW interference, the signal point circulates in a circular manner at a certain distance from the convergence point as shown in FIG. 3B according to the level and frequency of the CW interference. Referring to FIG. 3B, the signal points (black circles) are arranged so as to circulate around a certain distance from the convergence point (white circles) in a circular shape.

  FIG. 4 is a diagram schematically illustrating a CW interference detection operation by the receiving device 10 according to the present embodiment.

  FIG. 4A shows a signal point arrangement for four symbols of a post-digital demodulation signal affected by CW interference. Referring to FIG. 4 (a), the signal points are arranged at locations away from the convergence point by a certain distance. Times t1 to t4 exemplify times when signal points are arranged. In the case shown in FIG. 4A, signal points are arranged in the order of times t1 to t4.

  FIG. 4B shows a spectrum obtained as a result of performing FFT on the digital demodulated signal affected by the CW interference as shown in FIG. The horizontal axis of FIG.4 (b) shows a frequency and a vertical axis | shaft shows a level. In the signal after digital demodulation, a large movement of the signal point occurs like the signal point at time t1 to t4 in FIG. Since the movement of the signal point becomes a frequency component and appears as a large level in the spectrum, the spectrum of the CW interference component is buried in other frequency components as shown in FIG.

  FIG. 4C shows signal points of the error signal of FIG. The convergence point estimation unit 21 estimates the white circle closest to the signal point at the time t1 in FIG. 4A as a convergence point (step S4 in FIG. 2). The error calculation unit 22 subtracts the convergence point for the signal point at time t1 from the coordinates of the signal point at time t1 in FIG. 4A to obtain an error for the signal point at time t1 in FIG. 4C (step S5). ). The error calculation unit 22 repeats this for each symbol in order from time t1 to time t4. Then, an error signal shown in FIG. 4C is obtained. Thus, the error signal is a signal obtained from the error of the received signal and the convergence point, and corresponds to a signal component obtained by removing information on the transmission side from the digital demodulated signal. At this time, the error signal includes only the interference component.

  The FFT unit 23 performs FFT on the error signal in FIG. 4C (step S6). FIG. 4D shows a spectrum obtained as a result of FFT. Here, as an example, only four symbols from time t1 to time t4 are illustrated, but in practice, a sufficient number of symbols are required to perform FFT.

  FIG. 4D shows the spectrum of only the disturbing component. In particular, since CW interference is single frequency interference, it occurs as a strong peak in the spectrum compared to other interference waves. Therefore, the spectrum analysis unit 24 can easily detect CW interference by searching for a high-level frequency from the spectrum of FIG. 4D (steps S7 to S9).

  According to the receiving apparatus 10 of this embodiment, the convergence point is estimated from the signal point of the received signal and the modulation method before the FFT analysis, the error signal of the signal point and the estimated convergence point is calculated, and only the error signal is analyzed. Therefore, it is possible to detect low-level CW with high accuracy.

  Various modifications can be made to the receiving device 10 according to the present embodiment. 5 and 6 are block diagrams illustrating modifications of the configuration of the receiving device 10 according to the embodiment. In the present embodiment, as shown in FIG. 1, the interference wave detection circuit 20 receives a signal compensated for the transmission path characteristic from the transmission path characteristic compensation unit 18. On the other hand, as shown in FIG. 5, the interference wave detection circuit 20 a may receive the signal output from the interference wave removal unit 17. Further, as illustrated in FIG. 6, the interference wave detection circuit 20 b may receive the digital demodulated signal 25 output from the digital demodulation unit 16. As shown in FIG. 1, when the interference wave detection circuit 20 receives a signal after compensating the transmission path characteristics, it is compared with the case where the signal before compensation (FIGS. 5 and 6) is received. And the peak of the CW component becomes clear in the spectrum after FFT.

(Embodiment 2)
A receiving apparatus according to the second embodiment will be described with reference to the drawings. FIG. 7 is a block diagram illustrating an example of the configuration of the receiving device 30 according to the present embodiment.

  Referring to FIG. 7, the receiving device 30 includes an antenna unit 11, a mixer 12, an oscillator 13, a band pass filter (BPF) 14, an A / D converter 15, a digital demodulation unit 16, an interference wave detection circuit 40, and interference wave removal. Unit 37, transmission line characteristic compensation unit 18, and decoding unit 19.

  The receiving device 30 of this embodiment is different from the receiving device 10 (FIG. 1) of the first embodiment in the configurations of the interference wave removing unit 37 and the interference wave detecting circuit 40. Of the elements of the receiving device 30 (FIG. 7), the elements denoted by the same reference numerals as those included in the receiving device 10 (FIG. 1) have the same configuration as in the first embodiment. The description is omitted.

  The interference wave removing unit 37 receives the digital demodulated signal 25 from the digital demodulating unit 16 and receives the CW interference intensity / frequency / phase 35 from the CW interference phase calculating unit 34. When CW interference exists, the interference wave removal unit 37 outputs the signal after CW interference removal to the transmission line characteristic compensation unit 18. The interference wave removing unit 37 creates a signal having a phase opposite to that of the CW interference according to the strength, frequency and phase of the CW interference, and adds the signal to the post-digital demodulation signal 25 so as to attenuate the CW interference. Also good. On the other hand, when there is no CW interference, the interference wave removal unit 37 outputs the post-digital demodulation signal 25 to the transmission line characteristic compensation unit 18 as it is.

  Referring to FIG. 7, the interference wave detection circuit 40 includes a convergence point estimation unit 21, an error calculation unit 22, an FFT unit 23, a spectrum analysis unit 24, an error phase calculation unit 33, and a CW interference phase calculation unit 34. The jamming wave detection circuit 40 is different from the jamming wave detection circuit 20 (FIG. 1) in the receiving apparatus 10 of the first embodiment in that it further includes an error phase calculation unit 33 and a CW jamming phase calculation unit 34. Of the elements of the interference wave detection circuit 40 (FIG. 7), elements having the same reference numerals as those included in the interference wave detection circuit 20 (FIG. 1) are configured in the same manner as in the first embodiment. Therefore, the description is omitted.

  The error phase calculation unit 33 receives the error signal 27 from the error calculation unit 22 and outputs phase information 36 of the error signal to the CW interference phase calculation unit 34. As an example, the error phase calculation unit 33 performs, for example, an approximate calculation of Arctan (Q / I) from the values of the I axis and the Q axis of the error signal 27 in order to calculate the phase information 36 of the error signal. May be.

  The CW interference phase calculation unit 34 receives the CW interference strength / frequency information from the error signal spectrum analysis unit 24 and also receives the error signal phase information 36 from the error phase calculation unit 33, so that the CW interference strength is increased. Information on the length, frequency, and phase 35 is output to the interference wave removing unit 37. As an example, the CW interference phase calculation unit 34 calculates the phase of the CW interference in the interference wave removal unit 37 based on the frequency of the CW interference and the delay time from the interference wave removal unit 37 to the CW interference phase calculation unit 34. can do. The CW interference phase calculation unit 34 can calculate the amount of rotation of the phase of the CW interference in the delay time by multiplying the frequency of the CW interference by the delay time. The CW interference phase calculation unit 34 can obtain the current phase of the CW interference by adding the rotation amount of the calculated phase to the phase of the CW interference received from the error phase calculation unit 33.

  FIG. 8 is a flowchart showing an example of the operation of the receiving apparatus 30 (FIG. 7) according to the present embodiment. Since steps S1 to S9 and steps S11 and S12 in FIG. 8 are the same as the operation (FIG. 2) of the receiving apparatus 10 (FIG. 1) according to the first embodiment, the description thereof is omitted.

  The error phase calculation unit 33 calculates the phase of the error signal (step S21).

  The CW interference phase calculation unit 34 calculates the current phase of the CW interference in the interference wave removal unit 37 from the frequency of the CW interference and the error signal phase (step S22).

  The jamming wave removing unit 17 removes CW jamming based on the input information on the strength, frequency, and phase 35 of the CW jamming (step S23).

  Unlike the receiving device 10 of the first embodiment, the receiving device 30 of this embodiment calculates the phase of the CW interference that cannot be determined by the FFT calculation by calculating the phase from the error signal. At this time, the interference wave removing unit 37 can remove the CW interference by creating a signal having a phase opposite to that of the CW interference signal and adding the signal to the post-digital demodulation signal 25 affected by the CW interference signal. Become.

  It should be noted that the disclosures of prior art documents such as the above patent documents are incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiment can be changed and adjusted based on the basic technical concept. Various disclosed elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) can be combined or selected within the scope of the claims of the present invention. . That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

10, 30 Receiving device 11 Antenna unit 12 Mixer 13 Oscillator 14 Band pass filter (BPF)
15 A / D converter 16 Digital demodulation unit 17, 37 Interference wave removal unit 18 Transmission path characteristic compensation unit 19 Decoding unit 20, 20a, 20b, 40 Interference wave detection circuit 21 Convergence point estimation unit 22 Error calculation unit 23 FFT unit 24 Spectrum analysis unit 25 Digital demodulated signal 26 CW interference strength / frequency 27 Error signal 28 Convergence point information 29 Error signal spectrum 33 Error phase calculation unit 34 CW interference phase calculation unit 35 CW interference intensity / frequency / phase 36 Error Signal phase information 50, 60 Detection unit 100 Antenna unit 101 Tuner unit 102 A / D conversion unit 103 Quadrature detection circuit 104 Multiplier 105 FFT circuit 106 Equalization circuit 107 Error correction circuit 108 Broadband AFC circuit 109 Time axis processing circuit 110 Interference Detection circuit 111 Variable notch filter t1 to t4 Time

Claims (12)

A convergence point estimation unit for estimating a convergence point for a signal point at each time point of a time-series signal obtained by digital demodulation of a received analog signal;
An error calculating unit that calculates a difference at each time point between the time series signal and the convergence point as an error signal;
A converter for converting the error signal from a time domain to a frequency domain;
A jamming wave detection circuit comprising: a detection unit that detects a jamming wave component included in the time series signal based on the error signal converted into the frequency domain.   The convergence point estimation unit estimates a signal point having the shortest distance from the signal point at each time point among the ideal signal points determined according to the digital demodulation method as the convergence point. The interference wave detection circuit according to claim 1.   The said detection part analyzes the spectrum of the said error signal converted into the frequency domain, The amplitude and frequency of a continuous wave (CW: Continuous Wave) are extracted as a component of the said interference wave, It is characterized by the above-mentioned. The interference wave detection circuit according to 1 or 2.   The detection unit calculates the phase of the CW at the time when the time series signal is acquired based on the error signal, and a period from the time to the time when the removal of the interference wave included in the time series signal is started And calculating the amount of rotation of the phase of the CW in the period based on the frequency of the CW, and obtaining the phase of the CW at the start time according to the calculated phase and the amount of rotation of the phase. The interference wave detection circuit according to claim 3.   5. The interference according to claim 1, wherein the time-series signal is a time-series signal obtained by digitally demodulating a received analog signal and compensating for transmission path characteristics. Wave detection circuit. A convergence point estimation unit for estimating a convergence point for a signal point at each time point of a time-series signal obtained by digital demodulation of a received analog signal;
An error calculating unit that calculates a difference at each time point between the time series signal and the convergence point as an error signal;
A converter for converting the error signal from a time domain to a frequency domain;
A detection unit that analyzes a spectrum of the error signal converted into a frequency domain and extracts an amplitude and a frequency of a continuous wave (CW: Continuous Wave) as a component of an interference wave included in the time-series signal;
A receiving apparatus comprising: an interference wave removing unit that removes the CW component from the time-series signal based on at least the amplitude and frequency of the CW.   The reception according to claim 6, wherein the interference wave removing unit removes the CW component from the time-series signal based on the amplitude, frequency, and phase at the start time of the CW. apparatus.   The interference wave removing unit generates a signal having an opposite phase to the CW based on the amplitude, frequency, and phase at the start time of the CW, and adds the signal to the time series signal, thereby adding the time series signal. The receiving apparatus according to claim 7, wherein the CW component is removed from the receiver. An estimation step for estimating a convergence point with respect to a signal point at each time point of a time-series signal obtained by digital demodulation of a received analog signal;
Calculating a difference at each time point between the time series signal and the convergence point as an error signal;
Converting the error signal from a time domain to a frequency domain;
A detection step of detecting a component of the interference wave included in the time-series signal based on the error signal converted into the frequency domain.   In the estimating step, a signal point having the shortest distance from the signal point at each time point among ideal signal points determined according to the digital demodulation method is estimated as the convergence point. The interference wave detection method according to claim 9.   The detection step includes analyzing a spectrum of the error signal converted into a frequency domain, and extracting an amplitude and a frequency of a continuous wave (CW: Continuous Wave) as a component of the interference wave. The interference wave detection method according to 9 or 10.   In the detection step, the phase of the CW at the time when the time-series signal is acquired is calculated based on the error signal, and a period from the time to the time when removal of the interference wave included in the time-series signal is started And calculating the amount of rotation of the phase of the CW in the period based on the frequency of the CW, and obtaining the phase of the CW at the start time according to the calculated phase and the amount of rotation of the phase. The interference wave detection method according to claim 11.

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