JP2005333528A - Jamming wave remover - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a jamming wave remover for detecting a jamming wave correctly even under multipath interference environment or AWGN environment and removing the jamming wave thus detected. <P>SOLUTION: Difference between the power of a received signal and the power of a signal filtered by a jamming wave removing filter is operated and then the average value of power difference is calculated and compared with some threshold. If the average value is not lower than the threshold, a decision is made that a jamming wave exists and a signal subjected to three-stage notch filtering is selected. If the average value is lower than the threshold, a decision is made that a jamming wave does not exist and the output signal from a delay element is selected. Since the power of output signal from the delay element and the power of a filtered signal are subjected to identical multipath interference and AWGN, the average value of difference signal of both powers is not affected by the multipath interference and AWGN. Consequently, erroneous detection of jamming wave is suppressed even under multipath interference environment or AWGN environment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an interference wave removing apparatus.

  In wireless communication, a transmission side performs modulation and encoding with a transmission format determined for a determined frequency band, and performs transmission, and a reception side performs demodulation and decoding based on the received data. At this time, if another radio wave is mixed in the frequency band used by this wireless communication system, the receiving side cannot correctly demodulate and decode. As an example, the following explanation is based on terrestrial digital broadcasting.

  In the United States, in November 1998, terrestrial digital broadcasting using the Advanced Television System Committee (ATSC) system was started in 10 major cities. The ATSC system is a standard that is not compatible with the NTSC (National Television System Committee) system, which is the current analog broadcast wave. The ATSC system is gradually shifted to the ATSC system, and the NTSC system is finally scheduled to be abolished. . In order to shift to the ATSC system step by step, the services of the ATSC system, which is digital terrestrial broadcasting, and the NTSC system, which is analog broadcasting, are currently performed in parallel. At this time, depending on the region, NTSC radio waves may be mixed in the same ATSC 6 MHz channel. When NTSC radio waves coexist, the ATSC system and the NTSC system interfere with each other. Therefore, if the NTSC radio waves are strong, the signal reproduction capability of the receiver that receives the ATSC transmission format is deteriorated. Therefore, it is necessary to remove the NTSC interference when receiving the ATSC transmission format. An NTSC signal is composed of three components: a video carrier, a color subcarrier, and an audio carrier. As a means for removing NTSC interference, the NTSC signal includes a video carrier, a color subcarrier, and an audio carrier as introduced in Patent Document 1. There are three-stage notch filters and comb filters that remove three components. FIG. 18 shows a spectrum of a received signal when an NTSC system signal and an ATSC system signal coexist, and FIG. 19 shows a spectrum of a signal filtered by a three-stage notch filter. As shown in FIG. 19, the NTSC interference wave removal filter removes NTSC interference and at the same time removes part of the ATSC broadcast signal. Will deteriorate the reception performance. Therefore, it is necessary to detect the presence / absence of NTSC radio waves in the reception band, and filter and remove the received signal by the NTSC system elimination filter only when NTSC interference waves exist.

  As a conventional technique, a first error signal between a received signal and a data field synchronization reference signal inserted into a transmission signal is calculated, a first energy is calculated from the first error signal, and an NTSC signal is further calculated. Calculating a second error signal of the filtered signal by the three-stage notch filter and the filtered data field synchronization reference signal, calculating a second energy from the second error signal, By comparing the first energy and the second energy, it is detected whether or not the NTSC signal is present. When the first energy is large, the reception data subjected to the three-stage notch filtering is used as an output signal, If the energy of the signal is large, the received data before the three-step notch filtering is used as the output signal, so that the NTSC signal can be detected. And there is one for removing (see Patent Document 1). FIG. 25 is a block diagram showing the structure of the interference wave detection and removal apparatus described in Patent Document 1.

  The interference wave detection and removal apparatus shown in FIG. 25 includes an NTSC removal unit 232, a first energy calculation unit 216, a second energy calculation unit 226, a minimum energy detector 233, and a multiplexer 234.

  The NTSC removal unit 232 includes two three-stage notch filters. The three-stage notch filter 230 filters the received signal and the three-stage notch filter 231 filters the data field synchronization reference signal.

The first energy calculation unit 216 includes a first adder 210, a first squarer 212, and a first integrator 214. The first adder 210 generates the error signal 211 of the data signal before filtering and the data field synchronization reference signal, the square calculation is performed by the first squarer 212, and then the first integrator 214. The integration calculation is performed to calculate the first energy 215. The second energy calculation unit 226 includes a second adder 220, a second squarer 222, and a second integrator 224. The second adder 220 generates an error signal 221 of the filtered data signal and the filtered data field synchronization reference signal, the square calculation is performed by the second squarer 222, and the second The integration operation is performed by the second integrator 224, and the second energy 225 is calculated. The minimum energy detector 233 receives the first energy 215 and the second energy 225 as input signals, compares the magnitudes thereof, and if the first energy 215 is larger than the second energy 225, the NTSC interference wave. When the first energy 215 is smaller than the second energy 225, it is determined that there is no NTSC interference wave, and a selection control signal is output to the multiplexer 234 based on the result. The multiplexer 234 outputs the output 205 of the first three-stage notch filter 230 when it is determined that the NTSC interference wave is present, and the first three-stage notch filter when it is determined that the NTSC interference wave is not present. Each signal 203 before passing through 230 is selected as a data output. The above configuration realizes detection and removal of NTSC interference waves.
JP-A-11-75133 (pages 5 to 6, FIG. 3)

  However, in the conventional method, since the error is calculated using the received signal and the data field synchronization reference signal that is a known signal, and the first energy and the second energy are calculated, multipath interference, AWGN ( If Additive White Gaussian Noise) is present in the transmission path, the received signal is affected by the transmission path characteristics. Therefore, the first error signal 211 and the second error signal 221 remain affected by the transmission path characteristics, and the NTSC interference wave In some cases, the presence or absence was falsely detected. Furthermore, since the data field synchronization reference signal is used, it is impossible to detect the interference wave until synchronization is established, and it can only be detected in the time zone in which the data field synchronization reference signal appears in the received signal. there were.

  In the present invention, the power of the received signal after filtering by the interference wave elimination filter is subtracted from the power of the reception signal before being filtered by the interference wave elimination filter, the average value of the differences is calculated, and the average value is set to a certain threshold value. It is an object of the present invention to provide a jamming wave detection apparatus that does not cause false detection even in a multipath interference environment or an AWGN environment by detecting a jamming wave by comparing with. Furthermore, by determining the presence or absence of multipath interference by a multipath interference detector and controlling the threshold based on the determination, it was possible to ignore when multipath interference was present when multipath interference was present. An object of the present invention is to provide a jamming wave detection device capable of suppressing the occurrence of errors due to the combined environment of multipath interference and jamming waves by detecting weak jamming waves.

  In order to solve the conventional problem, an interference wave removing device according to claim 1 of the present invention includes an interference wave removing filter for removing an interference wave, first power calculation means for calculating the power of a received signal, The difference between the output signal of the second power calculation means, the second power calculation means for calculating the power of the signal obtained by filtering the received signal by the interference wave elimination filter, and the output signal of the second power calculation means is calculated. A power difference calculating means for calculating; a first average calculating means for calculating an average of output signals of the power difference calculating means; and a first for comparing an output signal of the first average calculating means with a first threshold value. The first comparison determination means determines that an interference wave exists if the output signal of the first average calculation means is equal to or greater than the first threshold, and removes the interference wave. By filter An output path selection signal for controlling to select the filtered signal, and if the output signal of the first average calculation means is smaller than the first threshold, it is determined that there is no interference wave, An output path that outputs an output path selection signal that is controlled so as to select a received signal, and that selects one of the received signal and the signal filtered by the interference wave elimination filter as an output path by the output path selection signal The output path selection means selects the signal filtered by the interference wave removal filter when the first comparison / determination means determines that the interference wave exists, and there is no interference wave. When it is determined that the received signal is selected, the interference signal is detected and removed.

  According to a second aspect of the present invention, there is provided an interference wave canceling device according to a second aspect of the present invention, wherein the interference wave canceling filter for canceling the interference wave and the second power calculation for calculating the power of the signal obtained by filtering the received signal by the interference wave canceling filter And a first average calculating means for calculating an average of output signals of the second power calculating means, and a first comparison determining means for comparing the output signal of the first average calculating means with a first threshold value. And the first comparison / determination means determines that an interference wave exists if the output signal of the first average calculation means is equal to or less than the first threshold value, and is filtered by the interference wave removal filter. If the output signal of the first average calculation means is greater than the first threshold, it is determined that no interfering wave exists, and the received signal is output. Output path selection means for controlling the output path selection signal to be selected, and output path selection means for selecting, as the output path, one of the received signal and the signal filtered by the interference wave elimination filter by the output path selection signal And the output path selection means selects the signal filtered by the interference wave elimination filter when the first comparison and determination means determines that the interference wave exists, and determines that the interference wave does not exist. When the received signal is received, the received signal is selected to detect and remove the interference wave.

  According to a third aspect of the present invention, there is provided the interference wave canceling apparatus according to the first or second aspect, wherein the first threshold value is controlled according to a transmission path environment. .

  According to a fourth aspect of the present invention, there is provided an interference wave canceling apparatus according to the third aspect, wherein the interference wave canceling apparatus according to the third aspect detects a multipath interference in the transmission path in order to estimate the transmission path environment. Path interference detection means is provided, and the first threshold value is controlled by detecting the presence or absence of multipath interference by the multipath interference detection means.

  The interference wave canceling device according to claim 5 of the present invention is the interference wave canceling device according to claim 4, wherein the multipath interference detecting means is calculated from a known signal inserted into a transmission signal and a reception signal. And a second comparison / determination means for comparing any one of the first largest value to the Nth largest value as an input signal and comparing the input signal with a second threshold value. Thus, the presence or absence of multipath interference is determined by the comparison determination in the second comparison determination means.

  According to a sixth aspect of the present invention, there is provided the interference wave canceling apparatus according to the fourth aspect, wherein the multipath interference detecting means is calculated from a known signal inserted into a transmission signal and a received signal. A computing means for performing computation using at least one of the first largest value to the Nth largest value among the absolute values of the correlation values, and a second threshold value for comparing the output signal from the computing means with a second threshold value. And a second comparison / determination unit that determines the presence / absence of multipath interference by the comparison / determination in the second comparison / determination unit.

  According to claim 7 of the present invention, in the interference wave canceling apparatus according to claim 4, the multipath interference detecting means is calculated from a known signal inserted into a transmission signal and a received signal. A second average value calculating means for calculating an average value of the input signal using any one of the absolute value of the correlation value as an input signal from the first largest value to the Nth largest value; The second average determination unit includes a second comparison determination unit that compares the second average calculation unit with a second threshold value, and determines whether or not there is multipath interference by the comparison determination in the second comparison determination unit.

  An interference wave canceling device according to claim 8 of the present invention is the interference wave canceling device according to claim 4, wherein the multipath interference detecting means is calculated from a known signal inserted into a transmission signal and a reception signal. Calculating means for calculating using at least one of the first largest value to the Nth largest value among the absolute values of the correlation values, and a second value for calculating an average value of the output signals from the computing means An average value calculating unit; and a second comparison determining unit that compares an output signal of the second average calculating unit with a second threshold value. It is configured to determine whether or not there is interference.

  The interference wave detection device of the present invention subtracts the power of the reception signal after filtering by the interference wave elimination filter from the power of the reception signal before being filtered by the interference wave elimination filter, calculates an average, Interference waves are detected by comparison. Multipath interference and AWGN are added to both the received signal power and the filtered signal power, so the average value of the difference signal between the two is not affected by multipath interference and AWGN. It is possible to prevent erroneous detection of interference waves even in an environment or an AWGN environment. Furthermore, the presence or absence of multipath interference is determined by the multipath interference detector, and the threshold value is controlled by the determination, so that when multipath interference exists, it can be ignored when multipath interference does not exist. By detecting and removing the interference wave, it is possible to suppress the occurrence of an error due to the combined environment of the multipath interference and the interference wave.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
Embodiment 1 of an interference wave removing apparatus according to the present invention will be described with reference to FIGS. 1 and 17 to 22.

  FIG. 1 is a block diagram of an interference wave canceling apparatus according to Embodiment 1 of the present invention. The jamming wave removing apparatus shown in FIG. 1 is a jamming wave removing apparatus conforming to the ATSC system of US terrestrial digital broadcasting, and detects and removes an NTSC system signal. Here, as shown in FIG. 22B, a three-stage notch filter having frequency characteristics for removing the frequency components of the video carrier, color subcarrier, and audio carrier of the NTSC signal is used as the interference wave removal filter. As shown in FIG. 22A, the three-stage notch filter includes a notch filter for removing the video carrier component, a notch filter for removing the color subcarrier component, and a notch filter for removing the audio carrier in series in three stages. doing.

  As shown in FIG. 1, the interference rejection apparatus according to Embodiment 1 of the present invention includes a three-stage notch filter 1, a first squarer 2, a second squarer 3, a subtractor 4, and a first average. It comprises a calculator 5, a first comparison / determination unit 6, a multiplexer 7, and a delay element 71.

  The received signal is sent to the delay element 71 and the three-stage notch filter 1. Here, the delay element 71 is an element that delays the received signal by the delay generated by the three-stage notch filter 1. The output signal of the delay element 71 is sent to the first squarer 2 and the multiplexer 7. The power signal of the output signal of the delay element 71 is calculated by the first squarer 2. On the other hand, the signal filtered by the three-stage notch filter 1 is sent to the second squarer 3 and the multiplexer 7. The second squarer 3 calculates the power signal of the signal subjected to the three-stage notch filtering, and the subtractor 4 calculates the difference between the power signal of the output signal of the delay element 71 and the power signal of the signal subjected to the three-stage notch filtering. Is done. An average value is calculated by the first average calculator 5 from the calculated difference signal of the power signal.

  The calculated average value is compared with the first threshold value 8 in the first comparison / determination unit 6. The first comparison / determination unit 6 compares the average value with the first threshold value 8. If the average value is equal to or greater than the first threshold value 8, it is determined that the NTSC interference wave exists, and the multiplexer 7 has a three-stage notch filtering. The output path selection signal for selecting the selected signal is output. If the average value is smaller than the first threshold value 8, it is determined that there is no NTSC interference wave, and the output path for selecting the output signal of the delay element 71 to the multiplexer 7 is output. Outputs a selection signal. The multiplexer 7 selects one of the output signal of the delay element 71 and the signal subjected to the three-stage notch filtering based on the output path selection signal, and sets it as the output signal of the interference wave removing device. FIG. 17 shows the spectrum of the ATSC system signal, and FIG. 18 shows the spectrum of the received signal when the NTSC system signal and the ATSC system signal coexist. FIG. 19 shows a spectrum of a signal filtered by the three-stage notch filter 1. FIG. 20 is a diagram showing the difference between the spectrum of the output signal of the delay element 71 (FIG. 18) and the spectrum of the signal subjected to three-stage notch filtering (FIG. 19) in the presence of an NTSC interference wave, and FIG. It is a figure showing the difference of the spectrum (FIG. 17) of the output signal of the delay element 71, and the spectrum (FIG. 19) of the signal which carried out the 3 step | paragraph notch filter when an interference wave does not exist. As shown in FIG. 20, if an NTSC interference wave exists in the transmission line, a part of the ATSC system signal and the NTSC interference wave are attenuated by the three-stage notch filter 1, and therefore the strength of the mixed NTSC interference wave is present. Depending on, the calculated average value increases. As shown in FIG. 21, if the NTSC interference wave does not exist in the transmission line, the three-stage notch filter 1 only attenuates part of the signal component of the ATSC system, so the average value is when the NTSC interference wave exists. Compared to By comparing the average of the power differences with a threshold value, it is possible to detect NTSC interference waves. Further, since the power of the output signal of the delay element 71 and the power of the filtered signal have the same multipath interference and AWGN, the average value of the differential signals of both powers is affected by the multipath interference and AWGN. Absent. Therefore, according to this configuration, since the average value compared with the first threshold value 8 is not affected by AWGN or multipath interference, it is possible to detect and remove the NTSC interference wave with less stable false detection. In addition, in this configuration, since a known signal inserted into the transmission signal is not used, it is possible to detect the presence or absence of an interfering wave without waiting for establishment of synchronization, and even in a time zone where no known signal appears. Detection is possible at any time.

  Further, in a small amount of NTSC interference wave that does not generate an error, it is better not to remove the ATSC signal by performing three-stage notch filtering, so that the reception performance is degraded. By providing the value, the minimum NTSC interference wave intensity that can be detected as having an interference wave can be adjusted by the set value of the first threshold value 8.

  Although the NTSC removal filter is a three-stage notch filter here, any filter that removes the frequency components of the video carrier, color subcarrier, and audio carrier of the NTSC signal may be applied. Further, the interference wave canceling apparatus according to the first embodiment is configured to cancel the NTSC system signal in relation to the US terrestrial digital broadcasting. However, regardless of the NTSC interference wave, the interference wave canceling filter is in the reception band. Any filter may be used to remove the interference wave existing in. At this time, the input signal may be a complex signal or a real axis signal according to a desired transmission format.

  The first average calculator 5 is arranged not to be subsequent to the subtracter 4 but to input the output signal of the first squarer and the output signal of the second squarer 3 as shown in FIG. May be.

  Further, as shown in FIG. 15, a protection unit 91 may be used instead of the first average calculator 5. When the determination result of the first comparison / determination unit 6 changes, the protection unit 91 continues to output the determination result before the change until the changed determination appears several times in succession, and the changed determination When there is a certain number of consecutive occurrences, the changed judgment result is output.

(Embodiment 2)
Embodiment 2 of the interference wave removing apparatus of the present invention will be described with reference to FIGS. 3, 20, and 21. FIG.

  FIG. 3 is a block diagram showing an interference wave removing apparatus according to Embodiment 2 of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  The present embodiment is different from the first embodiment in that the first power calculation is not performed and the output signal of the second squarer 3 is input to the first average calculator 5.

  The average value of the output signal of the second squarer 3 is calculated by the first average calculator 5 and compared with the first threshold value 8 by the first comparison / determination unit 6. If the first average value is equal to or less than the threshold value 8, the first comparison / determination unit 6 determines that there is an NTSC interference wave, and outputs to the multiplexer 7 an output path selection signal for selecting the signal subjected to the three-stage notch filtering. If the average value is larger than the first threshold value 8, it is determined that there is no NTSC interference wave, and an output path selection signal for selecting the output signal of the delay element 71 is output to the multiplexer 7.

  As shown in FIGS. 20 and 21, the greater the mixed NTSC interference wave power is, the more power is removed by the three-stage notch filter. On the other hand, the received signal of the interference wave canceling apparatus is maintained at a constant power by an AGC (Auto Gain Control) (not shown), and the ATSC system signal and the NTSC signal are used regardless of the power of the NTSC interference wave. The total power of is constant. For this reason, the stronger the power of the mixed NTSC interference wave, the smaller the output of the first average calculator calculated from the signal cut by the three-stage notch filter 1. Therefore, the NTSC interference wave can be detected by comparing the average value with the threshold value. Even in a multipath interference environment or an AWGN environment, the power of the received signal of the interference canceller is kept constant by AGC, so the average value is reduced by the amount of power removed by the three-stage notch filter 1. And is not affected by multipath interference or AWGN. Therefore, by adopting this configuration, it is possible to suppress erroneous detection of NTSC interference waves even in a multipath interference environment or an AWGN environment. Further, in this configuration, the first squarer 2 and the subtracter 4 are not used as compared with the first embodiment, so that the circuit scale is smaller than that in the first embodiment.

  Although the NTSC removal filter is a three-stage notch filter here, any filter that removes the frequency components of the video carrier, color subcarrier, and audio carrier of the NTSC signal may be applied. Further, the interference wave canceling apparatus according to the second embodiment is configured to cancel the NTSC system signal in relation to the US terrestrial digital broadcasting. However, regardless of the NTSC interference wave, the interference wave canceling filter is in the reception band. Any filter may be used to remove the interference wave existing in. At this time, the input signal may be a complex signal or a real axis signal according to a desired transmission format.

  Further, as described with respect to the protection unit 91 in the first embodiment in FIG. 15, also in the present embodiment, between the second comparison / determination unit 9 and the multiplexer 7 instead of the first average calculator 5. The protection unit 91 may be used.

(Embodiment 3)
Embodiment 3 of the interference wave canceling apparatus of the present invention will be described with reference to FIGS. 4, 5, and 23. FIG. FIG. 4 is a block diagram showing an interference wave removing apparatus according to Embodiment 3 of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. The jamming wave removing unit 50 in FIG. 4 is the jamming wave removing unit 50 shown in the first embodiment in FIG.

  Compared with the first embodiment, this embodiment has a multipath interference detection unit 80 that detects the presence or absence of multipath interference in the transmission path, and the threshold value input to the first comparison / determination unit 6 in FIG. The difference is that the multiplexer 13 selects from the first threshold value A11 or the first threshold value B12 based on the determination result of the multipath interference detection unit 80.

  FIG. 5 is a block diagram showing the multipath interference detection unit 80. The multipath interference detection unit 80 includes a second comparison / determination unit 23. The multipath interference detection unit 80 receives the largest value 14 among the absolute values of the correlation values calculated from the correlation calculation unit (not shown) that calculates the correlation value between the received signal and the data field synchronization reference signal that is a known signal. (Hereinafter referred to as the first correlation value 14). A first comparison value 14 and a second threshold value 16 are input to the second comparison / determination unit 23 to perform comparison / determination. The second comparison / determination unit 23 determines that multipath interference does not exist if the first correlation value 14 is equal to or greater than the second threshold value 16, and selects the first threshold value A11 for the multiplexer 13 in FIG. If the average value is smaller than the second threshold 16, it is determined that multipath interference exists, and a threshold selection signal for selecting the first threshold B12 is output to the multiplexer 13 in FIG. .

  4 selects the first threshold value A11 and the first threshold value B according to the threshold selection signal that is the determination result of the multipath interference detection unit 80, and the first comparison / determination unit 6 in FIG. To enter.

  As an example, FIG. 23 shows the distribution of the first correlation value under an AWGN environment (C / N = 15 dB) and a multipath interference environment (delay 0.1 us, Doppler frequency 1 Hz, D / U = 2 dB) ( Number of data: 2500). From FIG. 23, it can be said that in the multipath interference environment, the frequency becomes a smaller value than in the AWGN environment, and the distribution is different. From this, it is possible to determine the presence or absence of multipath interference by setting the second threshold 16 to 0.9 and comparing the first correlation value 14 with the second threshold 16. As described in the first embodiment, even if an NTSC interference wave exists, if it is a weak radio wave that does not cause an error, it is better not to perform filtering. However, when multipath interference exists, even such a weak radio wave causes an error due to the combination of multipath interference and NTSC interference. For this reason, the presence or absence of multipath interference is detected, and in a multipath interference environment, the first threshold value B12, which is a threshold value for the multipath interference environment, is input to the first comparison / determination unit 6. When there is no path interference, it is possible to detect and remove the NTSC interference wave having a strength that does not need to be detected and removed.

  Note that the second comparison / determination unit 23 of the multipath interference detection unit 80 may input N second threshold values 16 instead of one, and determine the degree of multipath interference in N + 1 stages. At this time, the second comparison / determination unit 23 outputs a threshold selection signal, which is a determination result, to the multiplexer 13 in FIG. 4. In the multiplexer 13, the first threshold A 11 and the first threshold B 12 are used. Instead, N + 1 threshold values are input, one of the N + 1 threshold values is selected according to the threshold selection signal, and is input to the first comparison / determination unit 6 in FIG.

  Further, in the correlation calculation in the correlation calculation unit, the signal to be used may be any known signal inserted into the transmission signal, not the data field synchronization reference signal.

  Further, in the present embodiment, the interference wave removing unit has been described as the interference wave removing unit 50 in the first embodiment. However, the interference wave removing unit 51 in FIG. 2, the interference wave removing unit 53 in FIG. The interference wave removing unit 52 of the second embodiment may be used.

(Embodiment 4)
Embodiment 4 of the interference wave removing apparatus of the present invention will be described with reference to FIGS. 6, 7, and 23. FIG. FIG. 6 is a block diagram showing an interference wave removing apparatus according to Embodiment 4 of the present invention. FIG. 7 is a block diagram showing the multipath interference detection unit 81. The same components as those in FIGS. 4 and 5 are denoted by the same reference numerals, and description thereof is omitted.

  The present embodiment is different from the third embodiment in that the multipath interference detection unit 81 has a second average calculator 22.

  The multipath interference detection unit 81 includes a second average calculator 22 and a second comparison / determination unit 23. The multipath interference detection unit 81 receives the first correlation value 14 from a correlation calculation unit (not shown) that calculates the correlation value between the received signal and the data field synchronization reference signal that is a known signal. In the second average calculator 22, the average value of the first correlation value 14 is calculated, the calculated average value and the second threshold 16 are input to the second comparison / determination unit 23, and multipath interference is detected. Detection is performed.

  As can be seen from the distribution of the first correlation value 14 shown in FIG. 23, in the multipath interference environment, the frequency is often smaller than in the AWGN environment, but 0.9 or more in the multipath interference environment. A value equal to or greater than that in the AWGN environment may appear. In this case, the multipath interference detection unit performs erroneous detection. Therefore, by calculating the average of the first correlation value 14 with the second average calculator 22, the calculated average value becomes smaller in the multipath interference environment than in the AWGN environment, thereby suppressing erroneous detection. it can.

  Note that the second comparison / determination unit 23 of the multipath interference detector 81 may input N second threshold values 16 instead of one, and determine the degree of multipath interference in N + 1 stages. At this time, the second comparison / determination unit 23 outputs a threshold selection signal, which is a determination result, to the multiplexer 13 in FIG. 6. In the multiplexer 13, the first threshold A 11 and the first threshold B 12 are used. Instead, N + 1 threshold values are input, one of the N + 1 threshold values is selected according to the threshold selection signal, and is input to the first comparison / determination unit 6 in FIG.

  Further, in the correlation calculation in the correlation calculation unit, the signal to be used may be any known signal inserted into the transmission signal, not the data field synchronization reference signal.

  In the present embodiment, the interference wave removal unit has been described as the interference wave removal unit 50 in the first embodiment. However, the interference wave removal unit 51 in FIG. 2, the interference wave removal unit 53 in FIG. The interference wave removing unit 52 of the second embodiment may be used.

  Further, as described with respect to the protection unit 91 in the first embodiment in FIG. 15, also in the present embodiment, between the second comparison / determination unit 22 and the multiplexer 13 instead of the second average calculator 22. The protection unit 91 may be used.

(Embodiment 5)
Embodiment 5 of the interference wave removing apparatus of the present invention will be described with reference to FIGS. 8, 9, and 23. FIG. FIG. 8 is a block diagram showing an interference wave removing apparatus according to Embodiment 5 of the present invention. FIG. 9 is a block diagram showing the multipath interference detection unit 82. The same components as those in FIGS. 4 and 5 are denoted by the same reference numerals, and description thereof is omitted.

  The present embodiment is different from the third embodiment in that the multipath interference detection unit 82 has a clip calculation unit 33.

  The multipath interference detection unit 82 includes a clip calculation unit 33 and a second comparison / determination unit 23. The multipath interference detection unit 82 inputs the first correlation value 14 from a correlation calculation unit (not shown) that calculates the correlation value between the received signal and the data field synchronization reference signal that is a known signal. The first correlation value 14 and the third threshold 31 are input to the clip calculation unit 33. If the first correlation value 14 is smaller than the third threshold 31, the clip calculation unit 33 outputs the first correlation value 14 as it is, and the first correlation value 14 is equal to or greater than the third threshold 31. If so, the third threshold value 31 is output. In the second comparison / determination unit 23, the output signal of the clip calculation unit 33 and the second threshold value 16 are input to detect the presence or absence of multipath interference.

  Looking at the distribution of the first correlation value 14 shown in FIG. 23, the frequency is often smaller in the multipath interference environment than in the AWGN environment, but 0.9% in the multipath interference environment. A value equal to or greater than that under the AWGN environment may appear, and in this case, the multipath interference detection unit performs erroneous detection. Therefore, the clip calculation unit 33 sets the upper limit value of the first correlation value in the AWGN environment as the third threshold value 31, and clips the first correlation value 14 with this threshold value. Appearance of a large value can be suppressed, and erroneous detection of the presence or absence of multipath interference can be suppressed.

  Note that the second comparison / determination unit 23 of the multipath interference detection unit 82 may input N second threshold values 16 instead of one, and determine the degree of multipath interference in N + 1 stages. At this time, the second comparison / determination unit 23 outputs a threshold selection signal, which is a determination result, to the multiplexer 13 in FIG. 8. In the multiplexer 13, the first threshold A 11 and the first threshold B 12 have two thresholds. Instead, N + 1 threshold values are input, one of the N + 1 threshold values is selected according to the threshold selection signal, and is input to the first comparison / determination unit 6 in FIG.

  Further, in the correlation calculation in the correlation calculation unit, the signal to be used may be any known signal inserted into the transmission signal, not the data field synchronization reference signal.

  In the present embodiment, the interference wave removal unit has been described as the interference wave removal unit 50 in the first embodiment. However, the interference wave removal unit 51 in FIG. 2, the interference wave removal unit 53 in FIG. The interference wave removing unit 52 of the second embodiment may be used.

(Embodiment 6)
Embodiment 6 of the interference wave removing apparatus of the present invention will be described with reference to FIGS. 10, 11, and 24. FIG. FIG. 10 is a block diagram showing an interference wave removing apparatus according to Embodiment 6 of the present invention. FIG. 11 is a block diagram showing the multipath interference detection unit 83. The same components as those in FIG. 10 and FIG.

  The present embodiment is different from the third embodiment in that the multipath interference detection unit 83 has a subtracter 21 and a second average calculator 22. The multipath interference detection unit 83 includes a subtracter 21, a second average calculator 22, and a second comparison / determination unit 23. The multipath interference detection unit 83 calculates the correlation value between the received signal and the data field synchronization reference signal, which is a known signal, from the correlation calculation unit (not shown). A certain first correlation value 14 and a second largest value 15 (hereinafter referred to as a second correlation value 15) are input. The subtractor 21 subtracts the second correlation value 15 from the first correlation value 14. The calculated difference signal between the first correlation value 14 and the second correlation value 15 and the second threshold value are input to the second comparison / determination unit 23 to detect the presence or absence of multipath interference.

  FIG. 24 shows the distribution of the second highest correlation value (data number: 2500). From FIG. 24, it can be said that there is a greater frequency in the multipath interference environment than in the AWGN environment, and there is a difference in distribution. As described above, since the distribution of the first largest value among the absolute values of the correlation values is more frequent in the AWGN environment than in the multipath interference environment, the subtractor 21 By calculating the difference between the first largest value and the second largest value, the difference between the correlation value calculation results in the multipath interference environment and the AWGN interference environment can be reduced as compared with the case where only one correlation value is used. Therefore, it is possible to suppress erroneous detection of the presence or absence of multipath interference.

  Note that the second comparison / determination unit 23 of the multipath interference detection unit 83 may input N second threshold values 16 instead of one, and determine the degree of multipath interference in N + 1 stages. At this time, the second comparison / determination unit 23 outputs a threshold selection signal, which is a determination result, to the multiplexer 13 in FIG. 10. In the multiplexer 13, the first threshold A 11 and the first threshold B 12 are used. Instead, N + 1 threshold values are input, one of the N + 1 threshold values is selected according to the threshold selection signal, and is input to the first comparison / determination unit 6 in FIG.

  Further, in the correlation calculation in the correlation calculation unit, the signal to be used may be any known signal inserted into the transmission signal, not the data field synchronization reference signal.

  In the present embodiment, the interference wave removal unit has been described as the interference wave removal unit 50 in the first embodiment. However, the interference wave removal unit 51 in FIG. 2, the interference wave removal unit 53 in FIG. The interference wave removing unit 52 of the second embodiment may be used.

  Furthermore, the second average calculator 22 in FIG. 11 is not in the subsequent stage of the subtracter 21 but in the previous stage of the subtractor 21, as described with respect to the position of the first average calculator 5 in the first embodiment in FIG. The average value of the first correlation value and the average value of the second correlation value are calculated, and the average value of the first correlation value and the average value of the second correlation value are input to the subtractor 21. You may do it.

  In addition, as described with respect to the protection unit 91 in the first embodiment in FIG. 15, also in the present embodiment, instead of the second average calculator 22, a gap between the second comparison / determination unit 22 and the multiplexer 13 is used. The protection unit 91 may be used.

(Embodiment 7)
Embodiment 7 of the interference wave removing apparatus of the present invention will be described with reference to FIGS. 12, 13, 23, and 24. FIG. The same components as those in FIGS. 10 and 11 are denoted by the same reference numerals, and description thereof is omitted. FIG. 12 is a block diagram showing an interference wave canceling apparatus according to the seventh embodiment of the present invention, and FIG. 13 is a block diagram showing a multipath interference detecting unit 84 in the interference wave canceling apparatus according to the seventh embodiment. Compared with the sixth embodiment, in the present embodiment, the multipath interference detection unit 84 performs a clip process and a mask process on the first correlation value 14 and the second correlation value 15, respectively. The difference is that a mask calculation unit 34 is provided.

  The multipath interference detection unit 84 includes a subtracter 21, an average calculator 22, a comparison / determination unit 23, a clip calculation unit 33, and a mask calculation unit 34. The multipath interference detection unit 84 obtains a first correlation value 14 and a second correlation value 15 from a correlation calculation unit (not shown) that calculates a correlation value between a received signal and a data field synchronization reference signal that is a known signal. input. The clip calculation unit 33 receives the first correlation value 14 and the third threshold 31. If the first correlation value 14 is smaller than the third threshold 31, the clip calculation unit 33 outputs the first correlation value 14 as it is, and the first correlation value 14 is equal to or greater than the third threshold 31. If so, the third threshold value 31 is output. The mask calculation unit 34 receives the second highest correlation value 15 output from the correlation calculation unit and the fourth threshold 32. If the second-order correlation value 15 is greater than or equal to the fourth threshold value 32, the mask calculation unit 34 outputs the second-order correlation value 15 as it is, and the second-order correlation value 15 is greater than the fourth threshold value 32. If it is smaller, 0 is output.

  The subtracter 21 receives the output signal from the clip calculation unit 33 and the output signal from the mask calculation unit 34 and performs subtraction. An average value of the output signal of the subtracter 21 is calculated by the second average calculator 22 and input to the second comparison / determination unit 23. Then, the second comparison / determination unit 23 compares with the second threshold 16 to detect the presence or absence of multipath interference.

  Looking at the distribution of the first correlation value 14 in FIG. 23, it can be seen that a value larger than the upper limit value of the distribution in the AWGN environment appears in the multipath interference environment. When the average value is calculated by the second average calculator 22, the average value may be equivalent to that in the AWGN environment due to this large value. By clipping the first correlation value 14 with the third threshold value 31 set to 0.9, for example, in the clip calculation unit 33, it is possible to suppress the average value from being equivalent to AWGN.

  Looking at the distribution of the second highest correlation value 15 in FIG. 24, the second highest correlation value 15 is 0.25 or less in the AWGN environment, and 0.25 in the multipath interference environment. The above values appear frequently. Here, in the mask calculation unit 34, by masking the second highest correlation value 15 with 0.25 as the fourth threshold value 32, the output signal of the mask calculation unit 34 is almost 0 in the AWGN environment. When a value larger than the value of the fourth threshold value 32 is obtained in a multipath interference environment, the value is larger and affects the difference between the average values in the multipath interference environment and the AWGN environment. Since the difference between the two is increased, the accuracy of multipath interference detection is improved.

  Note that the second comparison / determination unit 23 of the multipath interference detector 84 may input N second threshold values 16 instead of one, and determine the degree of multipath interference in N + 1 stages. At this time, the second comparison / determination unit 23 outputs a threshold selection signal as a determination result to the multiplexer 13 in FIG. 12, and the multiplexer 13 uses the first threshold A11 and the first threshold B12 for the two thresholds. Instead, N + 1 threshold values are input, one of the N + 1 threshold values is selected according to the threshold selection signal, and is input to the first comparison / determination unit 6 in FIG.

  Further, in the correlation calculation in the correlation calculation unit, the signal to be used may be any known signal inserted into the transmission signal, not the data field synchronization reference signal.

  In the present embodiment, the interference wave removal unit has been described as the interference wave removal unit 50 in the first embodiment. However, the interference wave removal unit 51 in FIG. 2, the interference wave removal unit 53 in FIG. The interference wave removing unit 52 of the second embodiment may be used.

  Further, the second average calculator 22 in FIG. 13 is not in the subsequent stage of the subtracter 21 but in the previous stage of the subtractor 21 as described with respect to the position of the first average calculator 5 in the first embodiment in FIG. The average value of the output signal of the clip calculation unit 33 and the output signal of the mask calculation unit 34 is calculated, and the average value of the output signal of the clip calculation unit 33 and the output signal of the mask calculation unit 34 is input to the subtractor 21. You may make it do.

  Further, as described with respect to the protection unit 91 in the first embodiment of FIG. 15, also in the present embodiment, instead of the second average calculator 22, a gap between the second comparison / determination unit 23 and the multiplexer 13 is used. The protection unit 91 may be used.

(Embodiment 8)
Embodiment 8 of the interference wave removing apparatus of the present invention will be described with reference to FIG. FIG. 14 is a block diagram showing an interference wave canceller in Embodiment 8 of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. An interference wave removing unit 50 in FIG. 14 is the interference wave removing unit shown in the first embodiment in FIG.

  Compared to the first embodiment, the present embodiment is based on the estimated noise amount signal 61 from the noise amount estimation unit that estimates the noise amount in the transmission path (not shown), and is sent to the first comparison / determination unit 6 in FIG. The difference is that the input threshold value is selected from the first threshold value A11 or the first threshold value B12 in the multiplexer 13.

  The estimated noise amount signal 61 and the fifth threshold value 62 from the noise amount estimation unit are input to the third comparison / determination unit 63. In the third comparison / determination unit 63, if the estimated noise amount signal 61 is smaller than the fifth threshold 62, a threshold selection signal for selecting the first threshold A11 is output to the multiplexer 13, and the average value is the fifth threshold 62. If so, a threshold selection signal for selecting the first threshold B12 is output to the multiplexer 13.

  As described in the first embodiment, even if an NTSC interference wave exists, if it is a weak radio wave that does not cause an error, it is better not to perform filtering. However, if the C / N of the received signal is low, an error occurs due to the combination of AWGN and NTSC interference even with such a weak radio wave. For this reason, in a low C / N environment, the first threshold value B12, which is a threshold value for a low C / N environment, is input to the first comparison / determination unit 6 to detect in a high C / N environment. In addition, it is possible to detect and remove the NTSC interference wave having a strength that did not need to be removed.

  Note that the third comparison / determination unit 63 may input N fifth threshold values 62 instead of one, and determine the degree of the estimated noise amount in N + 1 stages. At this time, the third comparison / determination unit 63 outputs a threshold selection signal, which is a determination result, to the multiplexer 13 in FIG. 14. In the multiplexer 13, the first threshold A 11 and the first threshold B 12 are used. Instead, N + 1 threshold values are input, one of the N + 1 threshold values is selected according to the threshold selection signal, and is input to the first comparison / determination unit 6 in FIG.

  Further, as a method of controlling the first threshold value 8 based on the estimated noise amount, the third comparison / determination unit 63, the multiplexer 13, the first threshold value A11, and the first threshold value B12 are not used, as shown in FIG. The estimated noise amount signal 61 may be input to the ROM 64, and the output signal of the ROM 64 may be used as the first threshold value 8 to be input to the first comparison / determination unit 6 in FIG.

  Further, an estimated bit error rate signal 65 from a bit error rate estimator for estimating the bit error rate of demodulated data, not shown, is input instead of the estimated noise amount signal 61 input to the third comparison / determination unit 63. The threshold value input to the first comparison / determination unit 6 of FIG. 1 may be controlled according to the estimated bit error rate.

  Further, in the present embodiment, the interference wave removing unit has been described as the interference wave removing unit 50 in the first embodiment. However, the interference wave removing unit 51 in FIG. 2, the interference wave removing unit 53 in FIG. The interference wave removing unit 52 of the second embodiment may be used.

  The interference elimination device according to the present invention is useful in a wide range of communication devices that need to eliminate interference waves.

Block diagram of interference wave canceller in Embodiment 1 of the present invention The block diagram of the interference wave removal apparatus from which the position of the average calculator in Embodiment 1 of this invention differs Block diagram of interference wave removing apparatus in Embodiment 2 of the present invention Block diagram of interference wave removing apparatus in Embodiment 3 of the present invention The block diagram of the multipath interference detection part in Embodiment 3 of this invention Block diagram of interference wave removing apparatus in Embodiment 4 of the present invention The block diagram of the multipath interference detection part in Embodiment 4 of this invention Block diagram of interference wave removing apparatus in Embodiment 5 of the present invention The block diagram of the multipath interference detection part in Embodiment 5 of this invention Block diagram of interference wave removing apparatus in Embodiment 6 of the present invention The block diagram of the multipath interference detection part in Embodiment 6 of this invention Block diagram of interference wave removing apparatus in Embodiment 7 of the present invention The block diagram of the multipath interference detection part in Embodiment 7 of this invention Block diagram of interference wave canceller in Embodiment 8 of the present invention The block diagram showing the jamming wave removal apparatus which uses the protection part 91 in Embodiment 1 of this invention The block diagram showing the jamming wave removal apparatus which uses ROM64 in Embodiment 8 of this invention ATSC signal spectrum diagram Spectrum diagram when NTSC and ATSC signals are mixed Spectrum diagram of the received signal filtered by a three-stage notch filter The figure showing the power difference of the output signal of the delay element 71 when a NTSC interference wave exists, and the signal which carried out 3 step | paragraph notch filtering The figure showing the power difference between the output signal of the delay element 71 and the signal subjected to three-stage notch filtering when no NTSC interference wave is present The figure showing the frequency characteristic of three stage notch filter 1 Diagram showing the appearance frequency of the first correlation value Diagram showing the appearance frequency of the second highest correlation value Block diagram of a conventional interference wave canceling device that detects and removes NTSC interference waves

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 3 step | paragraph notch filter 2 1st squarer 3 2nd squarer 4 Subtractor 5 1st average calculator 6 1st comparison determination device 7 Multiplexer 8 1st threshold value 9 2nd comparison determination device 11 1st One threshold A
12 First threshold B
13 Multiplexer 14 First-order correlation value 15 Second-order correlation value 16 Second threshold value 21 Subtractor 22 Second average calculator 23 Second comparison / determination unit 31 Third threshold value 32 Fourth threshold value 33 Clip Calculation unit 34 Mask calculation unit 41 First average calculator 42 Second average calculator 50 Interference wave removal unit 51 Interference wave removal unit 52 Interference wave removal unit 53 Interference wave removal unit 61 Estimated noise amount signal 62 Fifth threshold value 63 Third comparison / determination unit 64 ROM
71 delay element 80 multipath interference detection unit 81 multipath interference detection unit 82 multipath interference detection unit 83 multipath interference detection unit 84 multipath interference detection unit 91 protection unit 210 first adder 212 first squarer 214 first One integrator 216 First energy calculation unit 220 Second adder 222 Second squarer 224 Second integrator 226 Second energy calculation unit 230 First three-stage notch filter 231 Second three-stage Notch filter 232 NTSC removal unit 233 Minimum energy detector 234 Multiplexer

Claims (8)

An interference elimination filter for eliminating the interference,
First power calculation means for calculating the power of the received signal;
The second power calculation means for calculating the power of the signal obtained by filtering the received signal with the interference wave elimination filter, and the difference between the output signal of the first power calculation means and the output signal of the second power calculation means Power difference calculation means for calculating;
First average calculating means for calculating an average of output signals of the power difference calculating means;
Having a first comparison determination means for comparing the output signal of the first average calculation means with a first threshold;
The first comparison / determination unit determines that an interference wave is present if the output signal of the first average calculation unit is equal to or greater than the first threshold value, and outputs the signal filtered by the interference wave removal filter. An output path selection signal that is controlled to be selected is output, and if the output signal of the first average calculating means is smaller than the first threshold value, it is determined that no interfering wave exists, and the received signal is selected. Output the output route selection signal to control
Output path selection means for selecting, as the output path, one of the received signal and the signal filtered by the interference wave removal filter by the output path selection signal,
The output path selection means selects the signal filtered by the interference wave removal filter when the first comparison and determination means determines that the interference wave exists, and when it is determined that the interference wave does not exist, An interference wave removing apparatus that detects and removes an interference wave by selecting the received signal. An interference elimination filter for eliminating the interference,
Second power calculation means for calculating the power of a signal obtained by filtering the received signal by the interference wave removal filter; and first average calculation means for calculating an average of output signals of the second power calculation means;
Having a first comparison determination means for comparing the output signal of the first average calculation means with a first threshold;
The first comparison / determination means determines that an interference wave exists if the output signal of the first average calculation means is equal to or less than the first threshold value, and outputs the signal filtered by the interference wave removal filter. An output path selection signal that is controlled to be selected is output, and if the output signal of the first average calculating means is greater than the first threshold value, it is determined that no interfering wave exists, and the received signal is selected. Output the output route selection signal to control
Output path selection means for selecting, as the output path, one of the received signal and the signal filtered by the interference wave removal filter by the output path selection signal,
The output path selection means selects the signal filtered by the interference wave removal filter when the first comparison and determination means determines that the interference wave exists, and when it is determined that the interference wave does not exist, An interference wave removing apparatus that detects and removes an interference wave by selecting the received signal. 3. The interference wave removing apparatus according to claim 1, wherein the magnitude of the first threshold value is controlled according to a transmission path environment. In order to estimate the transmission path environment, multipath interference detection means for detecting the presence or absence of multipath interference in the transmission path,
4. The interference wave removing apparatus according to claim 3, wherein the magnitude of the first threshold value is controlled by detecting the presence or absence of multipath interference by the multipath interference detecting means. The multipath interference detection unit inputs one of absolute values of correlation values calculated from a known signal inserted into a transmission signal and a received signal, from the first largest value to the Nth largest value. Signal and
A second comparison / determination means for comparing the input signal with a second threshold;
5. The interference wave removing apparatus according to claim 4, wherein the presence / absence of multipath interference is determined by the comparison determination by the second comparison determination means. The multipath interference detection means uses at least one of an absolute value of correlation values calculated from a known signal inserted into a transmission signal and a reception signal, from the first largest value to the Nth largest value. A calculation means for performing a calculation;
Having a second comparison determination means for comparing the output signal from the calculation means with a second threshold;
5. The interference wave removing apparatus according to claim 4, wherein the presence / absence of multipath interference is determined by the comparison determination by the second comparison determination means. The multipath interference detection unit inputs one of absolute values of correlation values calculated from a known signal inserted into a transmission signal and a received signal, from the first largest value to the Nth largest value. Signal and
A second average value calculating means for calculating an average value of the input signal;
Having a second comparison determination means for comparing the second average calculation means with a second threshold;
5. The interference wave removing apparatus according to claim 4, wherein the presence / absence of multipath interference is determined by the comparison determination by the second comparison determination means. The multipath interference detection means uses at least one of an absolute value of correlation values calculated from a known signal inserted into a transmission signal and a reception signal, from the first largest value to the Nth largest value. A calculation means for performing a calculation;
A second average value calculating means for calculating an average value of the output signal from the calculating means;
A second comparison determination means for comparing the output signal of the second average calculation means with a second threshold;
5. The interference wave removing apparatus according to claim 4, wherein the presence / absence of multipath interference is determined by the comparison determination by the second comparison determination means.

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