JP4693808B2 - Relay device - Google Patents

Description

  The present invention relates to a relay apparatus having a wraparound canceller, for example, a relay apparatus that detects loop oscillation caused by signal wraparound between transmitting and receiving antennas of a digital broadcast wave relay station.

  There is a wraparound canceller device that cancels a sneak wave by estimating characteristics of a transmission path such as multipath and sneaking from an OFDM (Orthogonal Frequency Division Multiplexing) signal. When this wraparound canceller apparatus is applied to a relay broadcaster for broadcast wave relay SFN (Single Frequency Network), loop oscillation may occur in the relay broadcast station when the level of the wraparound wave is large. Loop oscillation becomes a problem particularly in digital broadcasting or digital transmission using an OFDM signal, when broadcast waves are relayed by re-transmission at the same frequency at a relay station constituting the SFN.

  The sneak canceller is an oscillation detection function that detects sneaking loop oscillations as a safety function to prevent damage to the subsequent PA (Power-Amplifier) due to oscillation operation under abnormal circumstances. Is installed. When the feedback system in the wraparound canceller enters an oscillating state due to an abnormal signal or a sneak condition exceeding the specification, the output of the device is immediately stopped, and it works to suppress damage to the PA and leakage to the adjacent channel.

  In Patent Document 1, as a sneak canceller device incorporating a loop oscillation detection circuit for detecting loop oscillation, oscillation occurs when the ratio between the maximum value and the minimum value in the frequency amplitude characteristic of a received OFDM signal exceeds a predetermined value. Therefore, a wraparound canceller that stops the output of the relay device or reduces the output level is disclosed.

Patent Document 2 focuses on the fact that a large autocorrelation can be obtained continuously when loop oscillation occurs, and performs a correlation operation between an input signal and a delayed one, and exceeds a predetermined value. Discloses a wraparound canceller for detecting oscillation.
JP 2001-160794 A JP 2002-185427 A

  However, the received signal in the actual environment has a large level fluctuation, and if there is an instantaneous level change or instantaneous interruption, the signal level change is regarded as a loop oscillation, or the signal disturbance due to the instantaneous fluctuation wraps around. Increasing the wave estimation error may cause loop oscillation.

  The present invention has been made in view of the above, and a wraparound canceller capable of avoiding loop oscillation caused by a sudden level fluctuation of an input signal or an influence of a momentary interruption and performing a stable operation in a severe propagation environment. It is an object of the present invention to provide a relay device having the same.

The relay device of the present invention uses a sneak canceller that removes a sneak wave from a received signal based on a sneak estimation result, and a cancellation residual that is a difference between the sneak transfer function and the transfer function of the sneak canceller as the sneak estimation result. A sneak wave estimation means to output, a storage means for storing a sneak estimation result estimated by the sneak wave estimation means, a sneak estimation result stored in the storage means, and a sneak estimation result estimated by the sneak wave estimation means; And a control means for supplying the sneak estimation result stored in the storage means to the sneak canceller when the level fluctuation is greater than or equal to a predetermined level. take.

  According to this configuration, there is an effect that it is possible to avoid a loop oscillation that occurs due to the effect of a sudden level fluctuation or instantaneous interruption of the input signal. As a result, it is possible to improve the stable operation in a harsh propagation environment and the resistance against instantaneous level fluctuation.

  In the relay device according to the present invention, in the configuration described above, the determination unit compares a ratio between a sneak estimation result stored in the storage unit and a sneak estimation result estimated by the sneak wave estimation unit with a predetermined threshold value to change a level. The structure which determines the presence or absence of is taken.

  According to this configuration, the ratio between the sneak estimation result stored in the memory and the estimated sneak estimation result only has to be compared with a predetermined threshold value, and therefore, a relatively simple circuit configuration avoids loop oscillation due to level fluctuation and instantaneous interruption. can do.

  The relay apparatus according to the present invention employs a configuration in which, in the above configuration, the control means prohibits the use of the sneak estimation result estimated by the sneak wave estimation means when the level fluctuation is greater than or equal to a predetermined value.

  According to this configuration, when the level fluctuation is greater than or equal to the predetermined value, by prohibiting the use of the estimated sneak estimation result, an abrupt level fluctuation can be reliably avoided and stable operation can be realized. Have

  In the above configuration, the relay apparatus of the present invention further comprises level detection means for detecting a decrease in the level of the received signal, and the control means stores in the storage means when a decrease in the level of the received signal is detected. A configuration is adopted in which control is performed to supply the wraparound estimation result to the wraparound canceller.

  According to this configuration, it is possible to avoid a sudden level fluctuation that occurs after the level of the received signal is lowered and a loop oscillation due to a momentary interruption, thereby realizing a stable operation.

  The relay apparatus according to the present invention employs a configuration in which the level detection means detects a level drop, an instantaneous level change, or an instantaneous interruption as a level fluctuation in the above configuration.

  According to this configuration, it is possible to avoid loop oscillation due to sudden level fluctuations and instantaneous interruptions, and to achieve stable operation.

  The relay apparatus according to the present invention employs a configuration in which, in the above configuration, the level detection means outputs a level decrease detection signal until a predetermined time elapses after the level decrease is detected after the level decrease is detected.

  According to this configuration, by masking from the time when the level drop is detected until a predetermined time has elapsed after returning from the level drop, it is possible to avoid abrupt level fluctuations and loop oscillation due to instantaneous interruptions, realizing stable operation Has the effect of

  In the relay apparatus according to the present invention, in the configuration described above, the wraparound canceller includes an FIR filter that replicates a sneak wave from a received signal, a subtracting unit that subtracts an output signal of the FIR filter from the received signal, and a coefficient of the FIR filter. And a filter coefficient updating means for updating, and removing the sneak wave from the received signal and outputting it.

  According to this configuration, in a specific wraparound canceller, it is possible to avoid a loop oscillation due to abrupt level fluctuations and instantaneous interruption, and to achieve a stable operation.

  According to the present invention, by not using the sneak estimation result in the section with a large estimation error, it is possible to avoid a loop oscillation due to abrupt level fluctuation and instantaneous interruption, and to realize a stable operation of the sneak canceller. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a relay apparatus having a wraparound canceller according to Embodiment 1 of the present invention, and is a configuration until a master station wave received by receiving antenna 101 is transmitted from transmitting antenna 121 as a relay signal. Indicates.

  In FIG. 1, a relay apparatus 100 includes a reception antenna 101, a reception conversion unit 102, a subtraction unit 103, a transmission conversion unit 104, a transmission antenna 121, a synchronization unit 105, an FFT (Fast Fourier Transform) 106, and a sneak wave estimation. Unit 107, IFFT (Inverse Fast Fourier Transform) 108, memory 109, sneak wave abnormality determination unit 110, coefficient update unit 111, and FIR (Finite Impulse Response) filter 112. The

  The subtraction unit 103, synchronization unit 105, FFT 106, sneak wave estimation unit 107, IFFT 108, coefficient update unit 111, and FIR filter 112 constitute a sneak canceller 120. The sneak canceller 120 and the sneak wave abnormality determination unit 110 are configured by, for example, a DSP (Digital Signal Processor).

  Although not shown, an AGC (Automatic Gain Controller) and an analog / digital (A / D) conversion unit are provided between the reception conversion unit 102 and the subtraction unit 103 and transmitted from the subtraction unit 103. A digital / analog (D / A) conversion unit is provided between the conversion units 104.

  The receiving antenna 101 receives a signal in which the relay signal from the own station is superimposed on the base station wave as a sneak wave.

  The reception conversion unit 102 performs low noise amplification, channel filtering, frequency conversion, and the like on the reception antenna output using an LNA (Low Noise Amplifier). The output level of the reception conversion unit 102 is controlled so that the signal is not saturated in the A / D conversion unit by keeping the signal level of the reception signal constant by AGC (not shown).

  The sneak canceller 120 cancels a duplicate signal of a sneak wave generated by a sneak current between the transmitting and receiving antennas (the transmitting antenna 121 and the receiving antenna 101) of the broadcast wave relay station (relay apparatus 100). The sneak canceller 120 includes a subtractor 103 that subtracts a sneak path duplication signal from the A / D converted signal, an FIR filter 112 that outputs a sneak path duplication signal, and a coefficient updating unit 111 that determines a filter coefficient of the FIR filter 112. . The digital signal from which the replica (replica) of the sneak wave is reduced by the sneak canceller 120 is sent to the transmission conversion unit 104 via a D / A conversion unit (not shown). It is also possible to prevent oscillation due to frequency components outside the OFDM signal band by interposing a band pass filter between the subtractor 103 and a D / A converter (not shown).

  The transmission conversion unit 104 converts the D / A converted output of the subtraction unit 103 to the same frequency channel as that of the master station, and performs processing such as gain adjustment to generate a relay signal, and the generated output Is supplied to the transmitting antenna 121.

  The transmission antenna 121 radiates the output of the transmission conversion unit 104. A part of the output radiated from the transmission antenna 121 passes through the wraparound transmission path, and then wraps around the reception antenna 101 as a sneak wave.

  The configuration of the wraparound canceller 120 will be described in detail.

  The synchronization unit 105 in the wraparound canceller 120 synchronizes the output of the subtraction unit 103 that is a time domain signal.

  The FFT 106 converts the output of the synchronization unit 105 into a frequency domain signal.

  The sneak wave estimation unit 107 estimates a sneak wave of the propagation path from the conversion result of the FFT 106 and the propagation path frequency characteristic. The sneak wave estimation unit 107 obtains, for example, a cancellation residual that is an error from the conversion result of the FFT 106 and the ideal channel frequency characteristic, and cancels the difference between the sneaking transfer function and the transfer function of the FIR filter 112. The feedback control operates so that the residual converges to 0, and only the main wave component is output to the output of the wraparound canceller 120 (subtraction unit 105), thereby estimating the frequency characteristic of the propagation path.

  IFFT 108 converts the sneak estimation result estimated by sneak wave estimation unit 107 into a signal in the time domain, and outputs the result to memory 109 and sneak wave abnormality determination unit 110 as the sum Pb of IFFT output and output power.

  The memory 109 stores the previously calculated IFFT 108 output and power sum Pb, which is the previous wraparound estimation result.

  The sneak wave abnormality determination unit 110 determines the sneak wave abnormality from the fluctuation of the sneak wave estimation result due to the instantaneous level fluctuation. The sneak wave abnormality determination unit 110 compares the IFFT output power sum Pa, which is a sneak estimation result by the sneak wave estimation unit 107, with the IFFT output power sum Pb calculated last time which is the previous sneak estimation result stored in the memory 109, and If the rate of change between the IFFT output power sum Pb, which is the previous wraparound estimation result, and the IFFT output power sum Pa, which is the current wraparound estimation result, is greater than the determination threshold α for abnormality estimation, it is affected by instantaneous level fluctuations, etc. And by continuously reflecting the previous wraparound estimation result calculated in the past, the section where the estimation error is large is not used. If an instantaneous level fluctuation occurs in the received signal and a case where a sneak wave is estimated in the fluctuation zone occurs, a sneak wave estimation error increases, which causes a loop oscillation. The sneak wave abnormality determination unit 110 determines an increase in sneak wave estimation error due to instantaneous level fluctuations, and uses the previous sneak estimation result stored in the memory 109 to suppress a factor that causes loop oscillation.

  The coefficient updating unit 111 updates the coefficient from the output of the sneak wave abnormality determining unit 110 by a predetermined coefficient updating formula, and outputs the updated filter coefficient to the second input of the FIR filter 112.

  The FIR filter 112 performs a convolution operation based on the output of the coefficient updating unit 111 on the output of the subtracting unit 103 to generate a replica (replica) of the wraparound signal. The generated replica is supplied to the second input of the subtraction unit 103.

  The subtraction unit 103 is a subtraction circuit for a wraparound replica. The subtraction unit 103 subtracts the output of the FIR filter 112 from the output of the reception conversion unit 102, outputs the output to the first input and synchronization unit 105 of the FIR filter 112, and outputs the output as a wraparound canceller 120 as a transmission conversion unit To 104.

  In this manner, the sneak canceller 120 generates a sneak wave replica by digital signal processing, and subtracts this replica from the input signal including the sneak wave signal component. That is, the feedback control operates so that the cancellation residual that is the difference between the wraparound transfer function and the transfer function of the FIR filter 112 converges to 0, and the output of the subtractor 103 of the wraparound canceller 120 includes the main wave component. Is output only. As a result, highly accurate and stable sneak cancellation that follows fluctuations in the propagation path and the like can be realized.

  Hereinafter, the operation of the relay apparatus 100 having the wraparound canceller configured as described above will be described.

  If an instantaneous level fluctuation occurs in the received signal and a case where a sneak wave is estimated in the fluctuation zone occurs, a sneak wave estimation error increases, which causes a loop oscillation.

  In the present embodiment, the estimation result estimated in the past is stored in the memory 109, and the ratio between the previous estimation result and the estimation result this time is compared with a predetermined threshold value to determine the estimation error. However, exception processing is performed as an erroneous estimation for a section in which the estimation error of the wraparound estimation result is larger than a predetermined value. In the exception processing, the use of the sneak estimation result estimated this time is prohibited, and the sneak estimation result stored in the memory 109 is controlled to be used.

  FIG. 2 is a flowchart showing the sneak wave abnormality determination process, which is executed by the DSP constituting the sneak canceller 120 and the sneak wave abnormality determination unit 110. In this flow, in order to prevent occurrence of erroneous estimation due to instantaneous interruption, instantaneous fluctuation, etc., it is determined whether or not erroneous estimation has occurred in the sneak wave estimation, and when erroneous estimation is determined, the process proceeds to exception processing.

  In step S <b> 1, the output of IFFT 108 is taken into the memory 109 and the sneak wave abnormality determination unit 110.

  In step S <b> 2, the sneak current abnormality determination unit 110 calculates the sum Pa of the output power of the IFFT 108.

  In step S <b> 3, the sneak current abnormality determination unit 110 reads the sum Pb of the output power of the IFFT 108 calculated last time from the memory 109. Here, at the first time when there is no previous IFFT output power total Pb, a predetermined default value is read.

  In step S4, the sneak current abnormality determination unit 110 compares the total IF Pa of the IFFT output power with a value (Pb × α) obtained by multiplying the IFFT output power total Pb calculated last time by the abnormality estimation determination threshold α. If the total IFFT output power Pa is equal to or less than the value (Pb × α) (Pa ≦ (Pb × α)) obtained by multiplying the previously calculated IFFT output power total Pb by the abnormality estimation threshold value α (Pa ≦ (Pb × α)), there is no sneak wave abnormality. And the process proceeds to step S5. If the total IFFT output power Pa is equal to or less than the value (Pb × α) obtained by multiplying the previously calculated IFFT output power total Pb by the abnormality estimation threshold value α (Pb × α), the previous IFFT output power level calculated previously is calculated. This is a case where the IFFT output power level is within the abnormality estimation determination threshold value α. In this case, it is determined that there is no influence due to instantaneous level fluctuation or the like. When instantaneous level fluctuations occur in the received signal, if the sneak wave is estimated in the fluctuation section, the estimation error of the sneak wave increases, causing a loop oscillation. In this embodiment, the sneak wave estimation error due to the instantaneous level fluctuation is determined by comparing the total IF Pa of the IFFT output power with a value (Pb × α) obtained by multiplying the IFFT output power total Pb calculated last time by the threshold value α. .

  In step S <b> 5, the sneak current abnormality determination unit 110 transfers the total IF Pa of the IFFT output power to the coefficient update unit 111 when there is no instantaneous level fluctuation. The coefficient updating unit 111 updates the coefficient from the total IF Pa of the IFFT output power of the sneak wave abnormality determining unit 110 by a predetermined coefficient updating formula, and outputs the updated filter coefficient to the FIR filter 112. The FIR filter 112 performs a convolution operation based on the output of the coefficient updating unit 111 on the output of the subtracting unit 103 to generate a replica (replica) of the wraparound signal. The subtraction unit 103 subtracts the output of the FIR filter 112 from the output of the reception conversion unit 102, outputs the output to the first input and synchronization unit 105 of the FIR filter 112, and outputs the output as a wraparound canceller 120 as a transmission conversion unit To 104.

  In step S6, the total IF Pa of IFFT output power transferred to the coefficient updating unit 111 is stored in the memory 109 for the next calculation (Pb = Pa).

  In step S7, it is determined whether or not the IFFT output power total Pb calculated last time is larger than the startup determination threshold value β of the apparatus. When the IFFT output power total Pb calculated last time is larger than the startup determination threshold value β of the apparatus (Pb> β), the IFFT output power total Pb previously calculated in step S8 is set to a predetermined value γ (Pb = γ). When the IFFT output power total Pb calculated last time is equal to or less than the rise determination threshold value β (Pb ≦ β), the flow ends.

  When the relay device 100 starts up, the level variation of the received signal is larger than when the relay device 100 is in steady operation. In the present embodiment, the sneak wave abnormality determination unit 110 is prevented from using the previous sneak estimation result due to the level fluctuation of the received signal at the time of rising. That is, even if the rate of change between the previous wraparound estimation result and the current wraparound estimation result is equal to or less than the abnormality estimation determination threshold value α, the IFFT output power total Pb calculated last time is larger than the startup determination threshold value β (Pb> β), if Pb> β, it is determined that it is a rising time, and the IFFT output power total Pb calculated last time is clipped to a predetermined value γ (Pb = γ). Thus, by determining the instantaneous level fluctuation including the rise time, the IFFT output power sum Pb calculated last time is first set as the current IFFT output power sum Pa (step S6), and then the IFFT calculated last time. By comparing the total output power Pb with the rising determination threshold value β, the rising Pb is set to a predetermined value γ, so that the rising Pb is set (step S8).

  On the other hand, when the total IFFT output power Pa in step S4 is larger than the value (Pb × α) obtained by multiplying the previously calculated IFFT output power total Pb by the abnormality estimation determination threshold value α (Pa> (Pb × α)). Then, it is determined that there is a wraparound wave abnormality, and the process proceeds to step S9.

  In step S9, the sneak current abnormality determination unit 110 reads the IFFT output power total Pb calculated last time from the memory 109, transfers it to the coefficient update unit 111, and ends this flow. When Pa> (Pb × α), there is an instantaneous level fluctuation and the sneak wave estimation error increases. In this case, instead of using the total IF Pa of IFFT output power, which is the current wraparound estimation result, the IFFT output power total Pb calculated last time from the memory 109 is transferred to the coefficient updating unit 111 and used. Further, at the first time when there is no previous IFFT output power total Pb, a predetermined default value is transferred to the coefficient updating unit 111. The coefficient updating unit 111 updates the coefficient from the total IF Pa of the IFFT output power of the sneak wave abnormality determining unit 110 by a predetermined coefficient updating formula, and outputs the updated filter coefficient to the FIR filter 112. The FIR filter 112 performs a convolution operation based on the output of the coefficient updating unit 111 on the output of the subtracting unit 103 to generate a replica (replica) of the wraparound signal. The subtraction unit 103 subtracts the output of the FIR filter 112 from the output of the reception conversion unit 102, outputs the output to the first input and synchronization unit 105 of the FIR filter 112, and outputs the output as a wraparound canceller 120 as a transmission conversion unit To 104.

  As described above in detail, according to relay apparatus 100 of the present embodiment, the previously calculated IFFT output and power total sum Pb, which are estimation results of sneaking estimated in the past, are stored in memory 109 and sneak waves The abnormality determination unit 110 compares the ratio of the IFFT output power sum Pb, which is the previous wraparound estimation result, and the IFFT output power sum Pa, which is the currently estimated wraparound estimation result, with the abnormality estimation determination threshold value α, If there is no instantaneous level fluctuation, the IFFT output power total Pa is transferred to the coefficient updating unit 111, and the previous rounding estimation stored in the memory 109 for the section where the level fluctuation becomes larger than a predetermined value. Since the resulting IFFT output power total Pb is transferred to the coefficient updating unit 111, the section where the estimation error is large is not used. Unishi Te, a loop oscillation which occurs under the influence due to rapid level variation and instantaneous interruption of the input signal can be avoided in advance, it is possible to perform a stable wraparound canceller in harsh propagation environment.

  Specifically, it is possible to avoid a loop oscillation that occurs due to an abrupt level fluctuation of the input signal or an instantaneous interruption, and a stable operation can be realized in a severe propagation environment. As a result, it is possible to improve the stable operation in a harsh propagation environment and the resistance against instantaneous level fluctuation.

(Embodiment 2)
In the first embodiment, the previous sneak wave estimation result is stored, and an abnormality estimation determination threshold value α is set as a ratio to the current sneak wave estimation result, thereby determining an increase in sneak wave estimation error due to instantaneous level fluctuation. In addition, the possibility of loop oscillation is prevented in advance by using the previous wraparound estimation result. In the second embodiment, a decrease in level is detected, and at the time of the level decrease, the “estimation error determination of sneak wave” in the first embodiment is validated to suppress an increase in sneak wave estimation error.

  FIG. 3 is a block diagram showing a configuration of a relay apparatus having a wraparound canceller according to Embodiment 2 of the present invention. In the description of the present embodiment, the same components as those in FIG.

  3, the relay device 200 includes a reception antenna 101, a reception conversion unit 102, a level detection unit 201, a subtraction unit 103, a transmission conversion unit 104, a transmission antenna 121, a synchronization unit 105, an FFT 106, a sneak wave estimation unit 107, an IFFT 108, A memory 109, a sneak wave abnormality determination unit 210, a coefficient update unit 111, and an FIR filter 112 are provided.

  The subtraction unit 103, synchronization unit 105, FFT 106, sneak wave estimation unit 107, IFFT 108, coefficient update unit 111, and FIR filter 112 constitute a sneak canceller 120. The sneak canceller 120 and the sneak wave abnormality determination unit 210 are configured by, for example, a DSP.

  Although not shown, an AGC and A / D converter is provided between the level detector 201 and the subtractor 103, and a D / A converter is provided between the subtractor 103 and the transmission converter 104. ing.

  The reception conversion unit 102 performs low noise amplification, channel filtering, frequency conversion, and the like on the reception antenna output. The output level of the reception conversion unit 102 is controlled through the level detection unit 201 so that the signal level of the reception signal is kept constant by the AGC (not shown) so that the signal is not saturated in the A / D conversion unit. The

  The level detection unit 201 detects a decrease in the signal level of the output of the reception conversion unit 102 and outputs the detection result to the sneak wave abnormality determination unit 210. For example, when the signal level becomes equal to or lower than a predetermined level (for example, −7 dB), the level detection unit 201 outputs a level decrease detection signal to the sneak wave abnormality determination unit 210.

  FIG. 4 is a diagram illustrating a level decrease detection signal output from the level detection unit 201. FIG. 4A shows an output signal waveform of the reception conversion unit 102, for example, an OFDM signal. FIG. 4B shows a level decrease detection signal output from the reception conversion unit 102 to the sneak wave abnormality determination unit 210.

  As shown in FIG. 4A, the level detection unit 201 detects a level drop in the OFDM output signal of the reception conversion unit 102, and sends the level drop detection signal shown in FIG. 4B to the sneak wave abnormality determination unit 210. Output. When the level detection unit 201 detects the instantaneous level reduction section shown in FIG. 4A, the level detection unit 201 falls from the level reduction detection time, and the predetermined level extension process shown in FIG. The level decrease detection signal that rises after time is output to the sneak wave abnormality determination unit 210. Here, the level detection unit 201 immediately outputs a level decrease detection signal upon detection of a level decrease, and the processing delay of the subtraction unit 103 → synchronization unit 105 → FFT 106 → wraparound wave estimation unit 107 → IFFT 108 from the recovery of the level decrease. The signal extended for the time is output to the sneak wave abnormality determination unit 210.

  The sneak canceller 120 cancels a duplicate signal of a sneak wave generated by a sneak current between the transmitting and receiving antennas (the transmitting antenna 121 and the receiving antenna 101) of the broadcast wave relay station (relay apparatus 200). The sneak canceller 120 includes a subtractor 103 that subtracts a sneak path duplication signal from the A / D converted signal, an FIR filter 112 that outputs a sneak path duplication signal, and a coefficient updating unit 111 that determines a filter coefficient of the FIR filter 112. . The digital signal from which the replica (replica) of the sneak wave is reduced by the sneak canceller 120 is sent to the transmission conversion unit 104 via a D / A conversion unit (not shown).

  The transmission conversion unit 104 converts the D / A converted output of the subtraction unit 103 into the same frequency channel as that of the master station, performs a process such as gain adjustment, generates a relay signal, and outputs the generated output. The signal is supplied to the transmission antenna 121.

  The transmission antenna 121 radiates the output of the transmission conversion unit 104. A part of the output radiated from the transmission antenna 121 passes through the wraparound transmission path, and then wraps around the reception antenna 101 as a sneak wave.

  The configuration of the wraparound canceller 120 will be described in detail.

  The synchronization unit 105 in the wraparound canceller 120 synchronizes the output of the subtraction unit 103 that is a time domain signal.

  The FFT 106 converts the output of the subtraction unit 103, which is a time domain signal, into a frequency domain signal.

  The sneak wave estimation unit 107 estimates the frequency characteristic of the propagation path from the conversion result of the FFT 106. The wraparound estimation result estimated by the wraparound wave estimation unit 107 is output to the IFFT 108.

  IFFT 108 converts the sneak estimation result estimated by sneak wave estimation unit 107 into a signal in the time domain, and outputs the result to memory 109 and sneak wave abnormality determination unit 210 as the sum Pb of IFFT output power.

  The memory 109 stores the sum total Pb of the output power of the IFFT 108 calculated last time, which is the previous wraparound estimation result.

  Similar to the sneak wave abnormality determination unit 110 of FIG. 1, the sneak wave abnormality determination unit 210 determines the sneak wave abnormality from the fluctuation of the sneak wave estimation result due to the instantaneous level fluctuation. The sneak wave abnormality determination unit 210 compares the sneak estimation result by the sneak wave estimation unit 107 with the previous sneak estimation result stored in the memory 109, and the rate of change between the previous sneak estimation result and the current sneak estimation result is abnormal. If it is greater than the estimation threshold value α, it is determined that instantaneous level fluctuation is detected, and when a level decrease is detected by the level detection unit 201, the previous wraparound estimation result calculated in the past is continuously reflected to estimate. Avoid using intervals with large errors. In the present embodiment, the sneak wave abnormality determination unit 210 determines an increase in the sneak wave estimation error due to the instantaneous level fluctuation, and uses the previous sneak estimation result stored in the memory 109 when the level decreases, thereby generating a loop oscillation. To suppress the factors that cause Here, the sneak wave abnormality determination unit 210 compares the sneak estimation result by the sneak wave estimation unit 107 with the previous sneak estimation result stored in the memory 109 when the level is lowered, and increases the sneak wave estimation error due to the instantaneous level fluctuation. It may be a mode of determining.

  The coefficient update unit 111 updates the coefficient from the output of the sneak wave abnormality determination unit 120 by a predetermined coefficient update formula, and outputs the updated filter coefficient to the second input of the FIR filter 112.

  The FIR filter 112 performs a convolution operation based on the output of the coefficient updating unit 111 on the output of the subtracting unit 103 to generate a replica (replica) of the wraparound signal. The generated replica is supplied to the second input of the subtraction unit 103.

  The subtraction unit 103 subtracts the output of the FIR filter 112 from the output of the reception conversion unit 102, outputs the output to the first input and synchronization unit 105 of the FIR filter 112, and outputs the output as a wraparound canceller 120 as a transmission conversion unit To 104.

  In this manner, the sneak canceller 120 generates a sneak wave replica by digital signal processing, and subtracts this replica from the input signal including the sneak wave signal component. As a result, highly accurate and stable sneak cancellation that follows fluctuations in the propagation path and the like can be realized.

  Hereinafter, the operation of the relay apparatus 200 having the wraparound canceller configured as described above will be described.

  First, the possibility of loop oscillation due to instantaneous level fluctuation will be described.

  FIG. 5 is a diagram illustrating the time change of the output signal of the subtracting unit 103 of the wraparound canceller 120, where the horizontal axis represents time and the vertical axis represents the signal level. FIG. 5A shows the output signal waveform of the subtractor 103 when a level drop of −3 dB occurs in the 1 ms section, and FIG. 5B shows the case where a level drop of −5 dB occurs in the 1 ms section. The output signal waveform of the subtraction unit 103, FIG. 5C shows the output signal waveform of the subtraction unit 103 when a level decrease of −7 dB occurs in the 1 ms interval, and FIG. 5D shows the output signal waveform of −8 dB in the 1 ms interval. FIG. 5E shows an output signal waveform of the subtraction unit 103 when a level decrease of −9 dB is generated in a 1 ms section. The wraparound D / U is ∞ (no wraparound wave).

  A. In FIG. When the level drop of −3 dB to −9 dB is generated in the 1 ms section at the position shown in FIG. 2, it has been found that the following two patterns of oscillation detection are made depending on the instantaneous drop level.

(1) Oscillation detection by erroneous estimation In the case of −3 dB to −8 dB shown in FIGS. 5 (a) to (d), the maximum 6.2. After the elapse of ms, an increase in output after replica subtraction (output of the subtraction unit 103) due to erroneous estimation occurred, and loop oscillation was detected. This loop oscillation is caused by b. Shown in

(2) Oscillation detection by recovery from instantaneous decrease As shown in FIG. 5E, at −9 dB, the level change rate of the output after replica subtraction (output of the subtraction unit 103) becomes large when recovery from the instantaneous decrease is made. The oscillation detection threshold value due to the fluctuation rate is reached.

  As described above, it has been found that when an instantaneous level drop occurs for 1 ms, loop oscillation is detected regardless of the level drop.

  Therefore, in the present embodiment, a level detection unit 201 that detects a level drop is provided, and at the time of the level drop, an increase in the sneak wave estimation error is suppressed by enabling the sneak wave abnormality determination unit 210.

  FIG. 6 is a flowchart showing a sneak wave abnormality determination process. Steps in which the same processing as the flow shown in FIG. 2 is performed are denoted by the same step numbers and description of overlapping portions is omitted.

  If the total IFFT output power Pa in step S4 is equal to or less than the value (Pb × α) (Pa ≦ (Pb × α)) obtained by multiplying the previously calculated IFFT output power total Pb by the abnormality estimation determination threshold value α, step S11. Proceed to

  In step S11, the level detection unit 201 detects a decrease in the signal level of the output of the reception conversion unit 102. If the signal level falls below a predetermined level (for example, −7 dB), the level detection unit 201 determines that the level has been detected and proceeds to step S9. . That is, even if it is determined in step S4 that there is no sneak wave abnormality by comparing the previous and current estimation result fluctuation level threshold value α, if the signal level is reduced in step S11, the sneak wave It is determined that there is a possibility that the reliability of the estimation is low, and the wraparound wave estimation exception process is performed. In step S9, when the total IFFT output power Pa in step S4 is larger than the value (Pb × α) obtained by multiplying the IFFT output power total Pb calculated last time by the abnormality estimation determination threshold α (Pa> (Pb × α )) Alternatively, when the signal level is reduced in step S11, the sneak current abnormality determination unit 210 reads the IFFT output power total Pb calculated last time from the memory 109, transfers it to the coefficient update unit 111, and this flow. Exit.

  If no signal level decrease is detected in step S11, it is determined that there is no sneak wave abnormality and there is no signal level decrease, and the process proceeds to step S5. In step S <b> 5, the sneak current abnormality determination unit 210 transfers the IFFT output power total Pa when there is no instantaneous level fluctuation to the coefficient update unit 111.

  In step S7, it is determined whether or not the IFFT output power total Pb calculated last time is larger than the startup determination threshold value β of the apparatus. When the IFFT output power total Pb calculated last time is larger than the startup determination threshold value β of the apparatus (Pb> β), the IFFT output power total Pb previously calculated in step S8 is set to a predetermined value γ (Pb = γ). When the IFFT output power total Pb calculated last time is equal to or less than the rise determination threshold value β (Pb ≦ β), the flow ends.

  As described above, according to relay apparatus 200 of the present embodiment, sneak current abnormality determination unit 210 has a low signal level and the sneak wave estimation itself performed under a low signal level is not reliable. In this case, the effect of the first embodiment can be effectively achieved by promptly shifting to exception processing. That is, it is possible to avoid a loop oscillation that occurs due to a sudden level fluctuation of the input signal or an instantaneous interruption, and it is possible to more reliably realize a stable operation in a severe propagation environment. As a result, it is possible to improve the stable operation in a harsh propagation environment and the resistance against instantaneous level fluctuation.

(Embodiment 3)
FIG. 7 is a block diagram showing a configuration of a relay apparatus having a wraparound canceller according to Embodiment 3 of the present invention. In the description of this embodiment, the same components as those in FIG.

  In FIG. 7, the relay device 300 includes a reception antenna 101, a reception conversion unit 102, a level detection unit 201, an AGC 301, an AGC gain control unit 310, a subtraction unit 103, a transmission conversion unit 104, a transmission antenna 121, a synchronization unit 105, an FFT 106, A wraparound wave estimation unit 107, IFFT 108, coefficient update unit 111, and FIR filter 112 are configured.

  The subtraction unit 103, synchronization unit 105, FFT 106, sneak wave estimation unit 107, IFFT 108, coefficient update unit 111, and FIR filter 112 constitute a sneak canceller 120. Further, the wraparound canceller 120 is constituted by a DSP, for example.

  Although not shown, an A / D conversion unit is provided between the AGC 301 and the subtraction unit 103, and a D / A conversion unit is provided between the subtraction unit 103 and the transmission conversion unit 104.

  The reception conversion unit 102 performs low noise amplification, channel filtering, frequency conversion, and the like on the reception antenna output. The output of the reception conversion unit 102 is input to the wraparound canceller 120 via the level detection unit 201.

  Level detection section 201 detects a decrease in the signal level of reception conversion section 102 output, and outputs the detection result to AGC gain control section 310. For example, the level detection unit 201 outputs a level decrease detection signal to the AGC gain control unit 310 when the signal level is equal to or lower than a predetermined level (for example, −7 dB).

  When the AGC gain control unit 310 receives the level decrease detection signal from the level detection unit 201, the AGC gain control unit 310 performs control to set the amplification factor of the AGC 301 to a constant value.

  The AGC 301 keeps the signal level of the received signal constant according to the gain control signal from the AGC gain control unit 310, thereby controlling the signal level so that the signal is not saturated in the subsequent A / D conversion unit.

  The sneak canceller 120 cancels a duplicate signal of a sneak wave generated by a sneak current between the transmitting and receiving antennas (the transmitting antenna 121 and the receiving antenna 101) of the broadcast wave relay station (relay device 300). The sneak canceller 120 includes a subtractor 103 that subtracts a sneak path duplication signal from the A / D converted signal, an FIR filter 112 that outputs a sneak path duplication signal, and a coefficient updating unit 111 that determines a filter coefficient of the FIR filter 112. . The digital signal from which the replica (replica) of the sneak wave is reduced by the sneak canceller 120 is sent to the transmission conversion unit 104 via a D / A conversion unit (not shown).

  The transmission conversion unit 104 converts the D / A converted output of the subtraction unit 103 into the same frequency channel as that of the master station, performs a process such as gain adjustment, generates a relay signal, and outputs the generated output. The signal is supplied to the transmission antenna 121.

  The transmission antenna 121 radiates the output of the transmission conversion unit 104. A part of the output radiated from the transmission antenna 121 passes through the wraparound transmission path, and then wraps around the reception antenna 101 as a sneak wave.

  Hereinafter, the operation of the relay apparatus 300 having the wraparound canceller configured as described above will be described.

  In FIG. 7, the input signal input from the reception conversion unit 102 to the subtraction unit 103 of the wraparound canceller 120 via the level detection unit 201 and the AGC 301 is a signal in which a base station wave and a sneak wave are superimposed. If the input signal is saturated by an A / D converter (not shown), a desired wraparound cancel characteristic cannot be obtained. Therefore, AGC 301 is controlled to perform A / D conversion at an appropriate signal level.

  At this time, the signal power (U) of the sneak wave coupled at the reception antenna 101 is larger than the reception power (D) from the master station wave, that is, D / U (dB value) expressed in common logarithm is negative. In this case, gain control is performed mainly in accordance with the sneak wave signal power (U). For example, when the propagation path from the master station to the relay apparatus 300 is on the sea or on the coastline, the received power of the master station is attenuated by several tens dB or more than the normal received power assumed by fading or the like especially on a high temperature day. In this case, the D / U (dB value) is a severe condition of −10 dB or less. In such a case, the power of the sneak wave is sufficiently larger than the reception wave of the master station, and the AGC 301 performs control following the signal level of the sneak wave.

  Under such conditions, in the sneak canceller 120, if the sneak wave duplication is reduced after A / D conversion, the master station signal level is significantly reduced. Oscillation detection must be performed on the basis of a signal from which the sneak wave component is removed, and in the case of the severe conditions as described above, the oscillation must be detected from a small level signal. For this reason, although it is not actually oscillating, a false detection that oscillates occurs, and the transmission output level is stopped or reduced, so it is possible to relay SFN broadcast waves. Limit D / U (dB value) is limited.

  The above is the fluctuation of the received signal due to fading or the like, but there may be a momentary interruption / instantaneous fluctuation of the signal level. Instantaneous interruptions and instantaneous level fluctuations occur without prediction due to passage of obstacles such as passenger aircraft. When the instantaneous level decrease continues, due to the characteristics of the AGC 301 arranged in the preceding stage of the subtracting unit 103 of the wraparound canceller 120, noise amplification occurs when the level decreases beyond the time that the AGC 301 follows. When the noise signal is amplified by the AGC 301, the output level of the subtraction unit 103 increases when the level signal recovers from the level decrease, and the oscillation signal is determined to reach the determination threshold value in the oscillation detection circuit.

  FIG. 8 is a diagram illustrating a time change of the output signal of the subtractor 103 of the sneak canceller 120 when the gain control by the AGC gain controller 310 is not performed. The horizontal axis represents time and the vertical axis represents the signal level. The instantaneous fluctuation condition indicates the output signal waveform of the subtraction unit 103 when a level decrease of −7 dB is generated for 10 ms.

  FIG. When a −7 dB level drop occurs for 10 ms at the position shown in FIG. 6, the AGC 301 amplifies a signal having a large noise signal with a lowered signal level. B of FIG. Indicates a signal with a lot of noise signals that the AGC 301 follows and amplifies. The noise signal is amplified by the AGC 301 so that the level is restored from the level drop in FIG. When the output level of the subtracting unit 103 increases and reaches a determination threshold value in the oscillation detection circuit at the position shown in FIG.

  In order to prevent this, in the present embodiment, a level detection unit 201 that detects a level decrease and an AGC gain control unit 310 that controls the amplification factor of the AGC 301 to a constant value are provided, and the AGC gain control unit 310 performs level detection. When the unit 201 detects a level drop, control is performed to set the gain of the AGC 301 to a constant value.

  FIG. 9 is a diagram showing a time change of the output signal of the subtraction unit 103 of the sneak canceller 120 when the gain control by the AGC gain control unit 310 is performed, and the subtraction unit 103 of the condition of instantaneous variation similar to FIG. The output signal waveform is shown.

  FIG. When the level decrease of −7 dB occurs at the position shown in FIG. 5, the level detection unit 201 detects this level decrease and outputs a level decrease detection signal to the AGC gain control unit 310. The AGC gain control unit 310 receives the level decrease detection signal from the level detection unit 201 and performs control to set the amplification factor of the AGC 301 to a constant value. B of FIG. These show operations of the AGC 301 in which the amplification factor is controlled to a constant value by the AGC gain control unit 310. When the signal level decreases, the AGC 301 performs an AGC operation with a constant amplification factor. Therefore, in FIG. In the level reduction section shown in FIG. 9, the AGC 301 does not amplify a signal having a lot of noise signals whose signal level is reduced, and c. The output level of the subtracting unit 103 does not increase at the position shown in FIG. As a result, the determination threshold in the oscillation detection circuit is not reached, so that unnecessary loop oscillation can be prevented.

  Thus, according to relay apparatus 300 of the present embodiment, when the signal level decrease of the received signal is detected, AGC gain control section 310 increases the gain of AGC 301 for the period during which the level decrease is detected. Since it is limited to a certain value, it is possible to suppress the noise amplification in the level reduction section and to prevent the level of the subtraction unit 103 from increasing and causing loop oscillation when returning from the level reduction. .

(Embodiment 4)
FIG. 10 is a block diagram showing a configuration of a relay apparatus having a wraparound canceller according to Embodiment 4 of the present invention. In the description of this embodiment, the same components as those in FIG.

  10, the relay device 400 includes a reception antenna 101, a reception conversion unit 102, a level detection unit 201, a subtraction unit 103, a level control unit 401, a transmission conversion unit 104, a transmission antenna 121, an amplitude determination unit 411, and a change rate determination unit. 412, a synchronization unit 105, an FFT 106, a sneak wave estimation unit 107, an IFFT 108, a coefficient update unit 111, and an FIR filter 112.

  The subtraction unit 103, the synchronization unit 105, the FFT 106, the sneak wave estimation unit 107, the IFFT 108, the coefficient update unit 111, and the FIR filter 112 constitute a sneak canceller 120, and the amplitude determination unit 411 and change rate determination unit 412. Constitutes the oscillation detection circuit 410. The wraparound canceller 120 is configured by a DSP, for example.

  Although not shown, an AGC and A / D conversion unit is provided between the reception conversion unit 102 and the subtraction unit 103, and a D / A conversion unit is provided between the subtraction unit 103 and the level control unit 401. ing.

  The reception conversion unit 102 performs low noise amplification, channel filtering, frequency conversion, and the like on the reception antenna output. The output of the reception conversion unit 102 is input to the wraparound canceller 120 via the level detection unit 201 under AGC control by an AGC (not shown).

  The level detection unit 201 detects a decrease in the signal level of the output of the reception conversion unit 102 and outputs the detection result to the oscillation detection circuit 410. For example, the level detection unit 201 outputs a level decrease detection signal to the change rate determination unit 412 of the oscillation detection circuit 410 when the signal level becomes a predetermined level (for example, −7 dB) or less.

  The level control unit 401 controls the transmission power and controls to stop or reduce the relay signal to be transmitted based on the oscillation detection signal from the oscillation detection circuit 410.

  The oscillation detection circuit 410 detects a loop oscillation caused by a signal wraparound between the transmission / reception antennas (the transmission antenna 121 and the reception antenna 101) of the broadcast wave relay station. When the loop oscillation is detected, the level control unit 401 Stop or reduce the transmission by.

  The amplitude determination unit 411 determines the amplitude of the input signal.

  The change rate determination unit 412 determines the change rate of the level of the received signal and masks the result of oscillation detection when the level is lowered or when the level is restored.

  The sneak canceller 120 cancels a duplicate signal of a sneak wave generated by a sneak current between the transmitting and receiving antennas (the transmitting antenna 121 and the receiving antenna 101) of the broadcast wave relay station (relay apparatus 400). The sneak canceller 120 includes a subtractor 103 that subtracts a sneak path duplication signal from the A / D converted signal, an FIR filter 112 that outputs a sneak path duplication signal, and a coefficient updating unit 111 that determines a filter coefficient of the FIR filter 112. . The digital signal from which the wraparound wave replica (replica) is reduced by the wraparound canceller 120 is sent to the transmission conversion section 104 via the level control section 401 and a D / A conversion section (not shown).

  The transmission conversion unit 104 converts the D / A converted output of the subtraction unit 103 into the same frequency channel as that of the master station, performs a process such as gain adjustment, generates a relay signal, and outputs the generated output. The signal is supplied to the transmission antenna 121.

  The transmission antenna 121 radiates the output of the transmission conversion unit 104. A part of the output radiated from the transmission antenna 121 passes through the wraparound transmission path, and then wraps around the reception antenna 101 as a sneak wave.

  Hereinafter, the operation of the relay apparatus 400 having the wraparound canceller configured as described above will be described.

  When the level fluctuation of the received signal is large, it may be detected as loop oscillation. In particular, when returning from an instantaneous interruption, the rate of change in the signal level increases rapidly, and there is a possibility of erroneous detection as loop oscillation. The effect of false detection of loop oscillation is enormous. Taking the case where the relay device 400 is a broadcast wave relay station as an example, when loop oscillation occurs, the output of the device is temporarily stopped for the purpose of suppressing damage to the PA and leakage to the adjacent channel by the oscillation operation. . Since broadcasting stops when transmission stops, it becomes a big problem.

  In order to avoid this, in the present embodiment, a level detection unit 201 that detects a level drop and an oscillation detection circuit 410 that stops or reduces transmission by the level control unit 401 when loop oscillation is detected are provided. The change rate determination unit 412 determines the rate of change in the level of the received signal, and the oscillation detection circuit 410 masks the oscillation detection signal output to the level control unit 401 when a level drop occurs.

  FIG. 11 is a diagram illustrating a level decrease detection signal output from the level detection unit 201. 11A shows an output signal waveform of the reception conversion unit 102, and FIG. 11B shows a level decrease detection signal output from the reception conversion unit 102 to the wraparound rate determination unit 412.

  As illustrated in FIG. 11A, the level detection unit 201 detects a level decrease in the OFDM output signal of the reception conversion unit 102 and outputs the level decrease detection signal illustrated in FIG. 11B to the change rate determination unit 412. To do. When the level detection unit 201 detects the instantaneous level decrease section shown in FIG. 11A, the level detection unit 201 falls from the level decrease detection time, and the predetermined level extension process shown in FIG. The level decrease detection signal that rises after time is output to the change rate determination unit 412. Here, the level detection unit 201 immediately outputs a level decrease detection signal at the time of detecting the level decrease, and also outputs a signal extended by the processing delay time of the oscillation detection by the subtraction unit 103 → the oscillation detection circuit 410 from the recovery from the level decrease. Output to the oscillation detection circuit 410. The oscillation detection circuit 410 masks the result of oscillation detection when the level is lowered or when the level is restored. Thereby, a. Of FIG. As shown in FIG. 6, exception processing is performed so that the return from the return from the level drop is not regarded as loop oscillation even when the rate of change is large.

  As described above, according to relay apparatus 400 of the present embodiment, oscillation detection circuit 410, when the level fluctuation of the received signal is detected, sends the level reduction section and a certain time thereafter to level control section 401. Since the oscillation detection signal is masked, it is possible to prevent the level of the output of the subtractor 103 from increasing and erroneously determining loop oscillation when returning from the level drop.

  Further, since the oscillation detection circuit 410 can detect the loop oscillation at an earlier stage than the conventional method, it is possible to protect the PA in the subsequent stage and to block the adjacent channel leakage.

  The above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this.

  For example, as a threshold value to be set, an optimum value obtained by an experiment or the like can be set in advance, or can be changed according to D / U (Desired to Undesired Ratio) (dB value) or the like. It is.

  In the first and second embodiments, the rate of change between the IFFT output power sum Pb, which is the previous wraparound estimation result stored in the memory 109, and the IFFT output power sum Pa, which is the current wraparound estimation result, is the determination threshold for abnormality estimation. The presence or absence of level fluctuation is determined by comparison with α, but any method can be used as long as the presence or absence of level fluctuation can be determined. For example, the difference between the IFFT output power total Pb and the IFFT output power total Pa It may be an absolute value comparison.

  Further, the value stored in the memory includes not only the sum of the previous IFFT outputs but also the previous IFFT output. The total IFFT output is a determination value for determining whether or not an abrupt estimation error has occurred in the wraparound estimation error distributed in each delay time, and no coefficient of the FIR filter is generated from the total IFFT output. The sum of the IFFT outputs is used only for abnormality determination, and if there is no abnormality as a result, the current IFFT output is subjected to coefficient update processing to be a filter coefficient. If there is an abnormality, the coefficient is updated from the previous IFFT output stored in the memory to obtain a filter coefficient.

  In addition, each of the above embodiments is an example applied to a relay device that performs a television relay. However, the present invention can be mounted on any device as long as the relay device has a wraparound canceller.

  In each of the above embodiments, the name of the relay device having the wraparound canceller is used. However, this is for convenience of explanation, and it is needless to say that the relay broadcaster and the wraparound canceller may be used.

  Furthermore, each circuit unit constituting the relay device, for example, the type of filter, the number of taps and the connection method, and the type of coefficient updating unit / memory are not limited to the above-described embodiments.

  In the relay apparatus according to the present invention, D (master station wave) / U (wraparound wave) generates loop oscillation caused by signal wraparound between transmission / reception antennas of a broadcast wave relay station that performs retransmission at the same frequency constituting the SFN. Even when the true value is 1 or less (the common logarithm is negative), it is possible to provide a relay apparatus having a wraparound canceller that can accurately detect without erroneous detection. Severe SFN broadcast wave relay with a sneak wave signal level greater than the master station wave is possible, and effective use of the frequency can be realized at low cost.

The block diagram which shows the structure of the relay apparatus which concerns on Embodiment 1 of this invention. The flowchart which shows the sneak wave abnormality determination process of the relay apparatus which concerns on this Embodiment 1. The block diagram which shows the structure of the relay apparatus which concerns on Embodiment 2 of this invention. The figure which shows the level fall detection signal output from the level detection part of the relay apparatus which concerns on this Embodiment 2. FIG. The figure which shows the time change of the output signal of the subtraction part of the wraparound canceller of the relay apparatus which concerns on this Embodiment 2. FIG. The flowchart which shows the sneak wave abnormality determination process of the relay apparatus which concerns on this Embodiment 2. The block diagram which shows the structure of the relay apparatus which concerns on Embodiment 3 of this invention. The figure which shows the time change of the output signal of the subtraction part of a wraparound canceller in case the gain control by the AGC gain control part of the relay apparatus which concerns on this Embodiment 3 is not performed. The figure which shows the time change of the output signal of the subtraction part of a wraparound canceller in the case of performing gain control by the AGC gain control part of the relay apparatus which concerns on this Embodiment 3. The block diagram which shows the structure of the relay apparatus which concerns on Embodiment 4 of this invention. The figure which shows the level fall detection signal output from the level detection part of the relay apparatus which concerns on this Embodiment 4. FIG.

Explanation of symbols

100, 200, 300, 400 Relay device 101 Reception antenna 102 Reception conversion unit 103 Subtraction unit 104 Transmission conversion unit 105 Synchronization unit 106 FFT
107 wraparound wave estimation unit 108 IFFT
109 memory 110, 210 sneak wave abnormality determination unit 111 coefficient update unit 112 FIR filter 120 sneak canceller 121 transmission antenna 201 level detection unit 210 sneak wave abnormality determination unit 301 AGC
310 AGC gain control unit 401 Level control unit 411 Amplitude determination unit 412 Change rate determination unit

Claims (7)

A sneak canceller that removes a sneak wave from the received signal based on the sneak estimation result;
A sneak wave estimation means for outputting a cancellation residual that is a difference between a sneak path transfer function and a sneak canceller transfer function as the sneak estimation result ;
Storage means for storing a sneak estimation result estimated by the sneak wave estimation means;
Determining means for determining the presence or absence of level fluctuations of the received signal based on the sneak estimation result stored in the storage means and the sneak estimation result estimated by the sneak wave estimation means;
And a control unit that supplies the sneak estimation result stored in the storage unit to the sneak canceller when the level fluctuation is equal to or greater than a predetermined level.   The determination unit compares the ratio of the sneak estimation result stored in the storage unit and the sneak estimation result estimated by the sneak wave estimation unit with a predetermined threshold value to determine the presence or absence of level fluctuation. Item 4. The relay device according to Item 1.   2. The relay apparatus according to claim 1, wherein the control unit prohibits the use of a sneak estimation result estimated by the sneak wave estimation unit when the level fluctuation is greater than or equal to a predetermined value. Further comprising level detection means for detecting a decrease in level of the received signal;
The control means includes
2. The relay apparatus according to claim 1, wherein when a decrease in level of the received signal is detected, control is performed to supply a sneak estimation result stored in the storage unit to the sneak canceller.   The relay apparatus according to claim 4, wherein the level detection means detects a level drop, an instantaneous level change, or an instantaneous interruption as a level fluctuation.   5. The relay apparatus according to claim 4, wherein the level detection means outputs a level decrease detection signal until a predetermined time elapses after the level decrease is detected after the level decrease is detected. The wraparound canceller is
An FIR filter that replicates a sneak wave from the received signal;
Subtracting means for subtracting the output signal of the FIR filter from the received signal;
Filter coefficient updating means for updating the coefficient of the FIR filter,
2. The relay apparatus according to claim 1, wherein a sneak wave is removed from the received signal and output.

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