JP2022136738A - Fm relay device - Google Patents

Abstract

To provide a technology of suppressing an unnecessary wave such as a sneak wave at a relay station of an FM broadcasting system that constitutes a single frequency network.SOLUTION: A first profile generation section generates a first delay profile from a result obtained by calculating temporal axis correlation between a transmission signal generated by a signal reproduction section and a reception signal received in a sneak wave survey period. A second profile generation section generates a second delay profile from a result obtained by calculating temporal axis correlation between a master station signal extracted by a master station wave extraction section and a reception signal received in a multipath wave survey period. A first suppression section and a second suppression section generate replica signals of a sneak wave and a multipath wave according to the delay profiles and subtracts the replica signals from a reception signal input to a signal generation section.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to technology for relaying broadcast waves of an FM broadcasting system.

FM synchronous broadcasting is known in which frequency-modulated audio broadcast waves of the same frequency and the same program are transmitted from a plurality of transmitting stations. FM is an abbreviation for frequency modulation. Broadcasting systems are generally provided with repeaters in order to expand the reception area. Existing repeater stations used in FM broadcasting build a multi-frequency network (MFN). That is, each relay station belonging to the MFN retransmits a broadcast wave (hereinafter referred to as relay wave) having a frequency different from that of the broadcast wave received from the transmission station serving as the master station (hereinafter referred to as master station wave).

On the other hand, a relay station used for FM synchronous broadcasting constructs a single frequency network (hereinafter referred to as SFN) using relay waves having the same frequency as the master station wave. That is, each relay station belonging to the SFN retransmits a relay wave having the same frequency as the master station wave. In a repeater station belonging to SFN, when a repeater wave of a level stronger than that of a parent station wave enters the receiving antenna, that is, in a so-called minus D/U state, loop loop oscillation occurs, and countermeasures against loop loop oscillation are required.

Japanese Patent Laid-Open No. 2002-200001 describes a technique for canceling a loop interference wave generated at a repeater station in a terrestrial digital broadcasting system that employs SFN.

JP 2009-105834 A

However, the technology described in Patent Document 1 is based on terrestrial digital broadcasting using OFDM signals, and has the problem that it cannot be applied to analog modulation FM broadcasting, which uses a completely different broadcasting signal format. there were.

One aspect of the present disclosure provides a technology for suppressing unwanted waves such as loop interference waves at a repeater station of an FM broadcasting system that configures a single frequency network.

One aspect of the present disclosure is an FM relay device comprising a receiver (3, 3A, 3B), a signal reproducer (41), a transmitter (5), a first profile generator (432), It comprises a first suppression unit (433, 434), a master station wave extraction unit (441), a second profile generation unit (442), and a second suppression unit (443, 444).

The receiving section is configured to receive broadcast waves of FM broadcasting via receiving antennas (2, 2A, 2B). The signal regenerator is configured to demodulate the received signal from the receiver and remodulate the demodulated signal to generate a transmission signal. The transmitting section is configured to transmit, via a transmitting antenna (7), a relay wave obtained by reproducing a broadcast wave using the transmission signal generated by the signal reproducing section.

The first profile generation unit calculates a time axis correlation using the transmission signal generated by the signal reproduction unit and the reception signal received during the loop interference wave search period, and calculates the maximum correlation, which is the maximum value of the time axis correlation. and a delay time of the transmitted signal with respect to the received signal when the maximum correlation value is obtained. The first suppressing unit delays the transmission signal generated by the signal reproducing unit by a delay time according to the first delay profile and adjusts the intensity and phase according to the maximum correlation value to generate the first replica signal. and the first replica signal is subtracted from the received signal input to the signal regenerator.

The parent station wave extracting unit is configured to extract a parent station signal, which is a signal component based on the parent station wave, from the received signal, using the direct wave from the parent station, which is the transmission source of the broadcast wave, as the parent station wave. The second profile generation unit calculates the time axis correlation using the master station signal extracted by the master station wave extraction unit and the received signal received during the multipath wave search period, and finds the maximum value of the time axis correlation. and a second delay profile that is information including the delay time of the transmission signal with respect to the master station signal when the maximum correlation value is obtained. The second suppressing unit delays the master station signal extracted by the master station wave extracting unit by the delay time according to the second delay profile and adjusts the intensity and phase according to the maximum correlation value to obtain the second replica. It is configured to generate a signal and subtract the second replica signal from the received signal that is input to the signal regenerator.

In the loopback wave search period, the loopback set time (ΔTr) is set based on the time required for the relay wave transmitted from the transmitting antenna to be received by the receiving antenna as a loopback wave. is set to the period from when the transmission signal is generated until the wrap-around set time elapses. During the multipath wave search period, the master station signal is detected by the master station wave extractor using the retransmission delay time (Tr) required for the broadcast wave received by the receiver to be transmitted as a relay wave from the transmitter. It is set to a period from extraction to elapse of the retransmission delay time.

According to the FM repeater configured in this way, the received signal is divided in terms of time, and in the first search period, a loop interference wave having the same waveform as the transmitted signal (that is, the relay wave) is extracted, and in the second search period, In the search period, multipath waves having the same waveform as the parent station signal (that is, broadcast waves) are extracted. Therefore, both the loop interference wave and the multipath wave can be accurately extracted.

In the FM repeater, since the first replica signal has the same waveform as the loop interference wave, it is possible to appropriately suppress signal components based on the loop interference wave that cause oscillation.
In the FM repeater, the processing for suppressing the effects of loop interference waves and multipath waves is performed at the analog waveform level. can be processed at the same time without being separated into two, and the device configuration can be simplified.

In the FM repeater, by repeating the processing, all the loop interference waves and multipath waves are processed in order from the one with the largest intensity, regardless of the number of the loop interference waves and the number of the multipath waves. can deal with

1 is an explanatory diagram showing an outline of a same-frequency FM broadcasting system; FIG. 1 is a block diagram showing the configuration of an FM relay device according to a first embodiment; FIG. FIG. 3 is an explanatory diagram showing the relationship between a master station wave, a relay wave, a sneak wave, and a multipath wave in an FM repeater; FIG. 4 is an explanatory diagram showing the spectrum of a stereo composite signal; 4 is a flow chart showing the details of processing in a correlation analysis unit; FIG. 2 is an explanatory diagram showing an outline of a delay profile and parameters used to generate the delay profile; FIG. FIG. 4 is an explanatory diagram showing output level control of a relay wave that is performed at the time of startup and oscillation detection; It is a block diagram which shows the structure of the FM relay apparatus of 2nd Embodiment. 4 is a block diagram showing the configuration of a signal synthesizing unit; FIG. 5 is a graph illustrating a signal quality detection result; FIG. 3 is an explanatory diagram showing, in vectors, parent station wave components and loop interference wave components contained in the first and second received IQ signals and the composite IQ signal; It is the graph which showed the detection result of the signal quality detected by processing block B5 on the complex plane. FIG. 2 is an explanatory diagram showing an outline of a delay profile and parameters used to generate the delay profile; FIG. FIG. 10 is an explanatory diagram showing received IQ signals on a complex plane when there is no interference due to loop interference and when there is interference;

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Same frequency FM broadcasting system]
First, a same-frequency FM broadcasting system 100 to which the FM repeater 1 according to the present disclosure is applied will be described.

The same-frequency FM broadcasting system 100 comprises a distribution station 101, one or more transmitting stations 102, 103, and one or more repeating stations 105, as shown in FIG. Distribution station 101 distributes the same audio signal to transmission stations 102 and 103 via a predetermined transmission network 104 . The transmitting stations 102 and 103 are arranged so that at least a part of their respective broadcast areas A1 and A2 overlap each other. The overlapping broadcast areas are hereinafter referred to as overlapping areas Ad. Transmitting stations 102 and 103 use the same audio signal received from distribution station 101 via transmission network 104 to transmit broadcast waves obtained by frequency-modulating carrier waves of the same frequency, thereby performing FM synchronous broadcasting (hereinafter simply referred to as synchronous broadcasting). )I do. Further, at the transmitting stations 102 and 103, FM modulation characteristics including timing of FM modulation using a clock synchronized with a one-second pulse signal (hereinafter referred to as 1 pps) obtained using GPS are the same between both transmitting stations. is controlled to be GPS is an abbreviation for Global Positioning System.

The transmission network 104 used for distributing the voice signal may be different for each of the transmitting stations 102 and 103, or may be the same. Also, the transmission network 104 is composed of, for example, a wireless transmission network, an IP transmission network, or the like, but is not limited to these.

The relay station 105 is provided to enable program listening in an area (hereafter referred to as a hearing-impaired area) A3 that cannot be covered by the transmitting stations 102 and 103 due to topographical influences. relay broadcasting is realized by receiving from and retransmitting on the same frequency.

[1-2. Configuration of FM relay device]
The FM relay device 1 that constitutes the relay station 105 will be described.
As shown in FIG. 2, the FM relay device 1 includes a receiving antenna 2, a receiving section 3, a relay processing section 4, a transmitting section 5, a power amplifier 6, and a transmitting antenna 7.

In the following, as shown in FIG. 3, the broadcast wave directly arriving at the receiving antenna 2 from the transmitting station 102 serving as the master station is referred to as the master station wave D, and the reproduced broadcast wave transmitted from the transmitting antenna 7 is referred to as the relay wave Dr. . Multipath waves M0 to Mm are the master station waves D transmitted from the master station and reflected by some object and indirectly reach the receiving antenna 2, and the loopback wave U0 is the repeater wave Dr that goes around from the transmitting antenna 7 to the receiving antenna 2. ~Un. The loop interference waves U0 to Un are assigned numbers in descending order of reception strength at the receiving antenna 2. FIG. Normally, the loop interference wave U<b>0 with the maximum reception intensity is a direct wave that directly reaches the reception antenna 2 from the transmission antenna 7 . Other wraparound waves U1 to Un are reflected waves that reach indirectly after being reflected by some object. All of the loop interference waves U0 to Un have waveforms obtained by attenuating and delaying the repeater wave Dr.

The FM repeater 1 is designed so that the relay wave Dr is delayed from the master station wave D by the retransmission delay time Tr. The retransmission delay time Tr is set to one cycle (that is, 52.6 μs) of the pilot signal in order to reduce distortion of the 19 kHz pilot signal in the stereo composite signal Sc described later due to interference between the master station wave D and the relay wave Dr. Set to integer multiples. Specifically, for example, it is set to 6 times the period of the pilot signal, that is, Tr=315.8 μs. However, it is not necessary to limit the period to an integer multiple of the pilot signal period because the distortion of the pilot signal due to interference is also reduced under operating conditions in which interference waves can be sufficiently removed.

Returning to FIG. 2, the receiving antenna 2 is arranged to receive at least the master station wave D. As shown in FIG. The receiving antenna 2 may be an omnidirectional antenna or a directional antenna. The master station wave D is an FM modulated wave, and its center frequency is fc.

The receiver 3 includes an amplifier 31 , a local signal generator 32 , a mixer 33 , an A/D converter 34 , a quadrature demodulator 35 and a band-limiting filter 36 .
Amplifier 31 amplifies the received signal from receiving antenna 2 .

A local signal generator 32 generates a local signal LO for down-converting the frequency of the received signal supplied from the receiving antenna 2 . In the following, the frequency of the local signal LO is assumed to be fl.

The mixer 33 mixes the received signal amplified by the amplifier 31 with the local signal LO supplied from the local signal generator 32, thereby down-converting the frequency of the received signal to fc-fl.

The A/D converter 34 samples the received signal down-converted by the mixer 33 at a preset sampling frequency Fad. In the description of the processing upstream from the A/D converter 34, the "signal" means an analog signal, and in the description of the processing downstream of the A/D converter 34, the "signal" means a series of digital values. do. The sampling frequency Fad of the A/D converter 34 is several tens of It is set to about MHz. Specifically, it is set to an integral multiple of the sampling frequency for signal processing, eg, 49.152 MHz. Further, by setting the sampling frequency to an integral multiple of the sampling frequency for signal processing, downsampling, which will be described later, can be performed simply.

The quadrature demodulator 35 complexes the received signal by obtaining an in-phase component and a quadrature component for each sample value of the received signal by applying a Hilbert transform to the received signal. Specifically, the received signal is multiplied by two carrier signals that are orthogonal to each other (that is, the phases are different by 90°) to generate an I signal representing an in-phase component and a Q signal representing a quadrature component. The I and Q signals are baseband signals. The I signal and the Q signal may be down-sampled to a frequency covering a band more than twice that of the FM modulation signal, for example, 768 kHz, thereby reducing the number of data and reducing the subsequent calculation load in the relay processing unit 4 . The sampling frequency Fs for signal processing may be set to a frequency other than 768 kHz as long as it can sufficiently cover the band of the FM modulated signal.

A band-limiting filter 36 extracts a signal in the frequency range that the FM-modulated carrier wave can take from the I signal and the Q signal generated by the quadrature demodulator 35 .
Hereinafter, the I signal and the Q signal generated by the receiver 3 are collectively referred to as received IQ signals.

The relay processing unit 4 FM-demodulates the received IQ signal generated by the receiving unit 3, and FM-modulates it again to reproduce an I signal and a Q signal having constant amplitudes. Details of the relay processing unit 4 will be described later. Hereinafter, the I signal and the Q signal reproduced by the relay processing unit 4 are collectively referred to as transmission IQ signals.

The transmitter 5 includes a quadrature modulator 51 , a D/A converter 52 , a local signal generator 53 , a mixer 54 and an amplifier 55 .
The quadrature modulator 51 generates an FM-modulated transmission signal by multiplying and adding the transmission IQ signal regenerated by the relay processing unit 4 by two mutually orthogonal carrier signals.

The D/A converter 52 converts a transmission signal represented by a series of digital values into an analog signal. In the discussion of processing downstream from the D/A converter 52, "signal" means an analog signal.

A local signal generator 53 generates a local signal LO for up-converting the frequency of the transmission signal. The local signal generator 53 may be a device shared with the local signal generator 32 of the receiver 3 .

The mixer 54 mixes the transmission signal generated by the D/A converter 52 and the local signal LO generated by the local signal generator 53, and up-converts the frequency of the transmission signal. The center frequency of the up-converted transmission signal is the same as the center frequency fc of the master station wave D. FIG.

The amplifier 55 amplifies the transmission signal up-converted by the mixer 54 . This amplified transmission signal is called a relay signal.
The power amplifier 6 further amplifies the relay signal generated by the transmission section 5 and supplies it to the transmission antenna 7 . The power amplifier 6 is an amplifier that is set according to the size of the relay area covered by the relay station 105, and may be connected in multiple stages or may be omitted.

The transmitting antenna 7 transmits a relay wave Dr corresponding to the relay signal toward the relay area.
[1-3. Relay processing section]
The relay processing unit 4 includes a signal reproduction unit 41 , an oscillation detection unit 42 , a loop interference wave removal unit 43 , a multipath wave removal unit 44 , and a silence detection unit 45 .

All the functions of the relay processing unit 4 may be realized by hardware, or at least part of them may be realized by processing executed by a microcomputer having a processor and a memory that is a non-transitional substantive recording medium. . In this case, various functions implemented by the microcomputer are implemented by the processor executing programs stored in the memory.

[1-3-1. Signal reproduction section]
The signal reproducing section 41 includes a band limiting filter 411 , an FM demodulating section 412 , a composite filter 413 and an FM modulating section 414 .

The band-limiting filter 411 extracts a signal in the frequency range that the FM-modulated carrier wave can take from the received IQ signal supplied from the receiving section 3 via the loop interference removing section 43 and the multipath wave removing section 44 . Band-limiting filter 411 is a filter similar to band-limiting filter 36 described above.

FM demodulation section 412 uses the received IQ signal from which unnecessary components have been removed by band-limiting filter 411 to calculate the phase of the received signal for each preset unit period Δt, and calculates the phase for the immediately preceding unit period Δt. The instantaneous phase change amount Δθ, which is the difference from the calculated phase, is calculated. Note that the unit period Δt is set to a sampling period Ts=1/Fs, which is the reciprocal of the sampling period Fs for signal processing, or an integral multiple thereof. Then, an audio signal is generated by performing Δf detection in which the calculated instantaneous phase change Δθ is replaced with the degree of FM modulation using a conversion table or conversion formula prepared in advance. The FM modulation index is zero when there is no modulation, and takes values having positive and negative signs. The audio signal is a stereo composite signal Sc in the case of stereo broadcasting, and a monaural audio signal in the case of monaural broadcasting.

The stereo composite signal Sc, as shown in FIG. 4, has a pilot signal of 19 kHz, an L+R signal having frequency components of 15 kHz or less, and an LR signal having frequency components of ±15 kHz around 38 kHz. Note that the L+R signal is a signal obtained by adding the L signal and the R signal representing the stereo audio signal. The LR signal is a signal obtained by AM-modulating a carrier having a frequency twice that of the pilot signal (that is, 38 kHz) with a signal obtained by subtracting the R signal from the L signal. A monaural audio signal is a signal having frequency components of 15 kHz or less.

Returning to FIG. 2, the composite filter 413 removes unnecessary components other than the pilot signal, the L+R signal, and the LR signal from the stereo composite signal Sc demodulated by the FM demodulator 412 in the case of stereo broadcasting. The composite filter 413 may be composed of three bandpass filters that individually extract each signal, or may be composed of one bandpass filter that collectively extracts each signal. Composite filter 413 is composed of a band-pass filter that passes a monaural audio signal in the case of monaural broadcasting. If there is an effective signal centered at 57 kHz or 76 kHz in the composite signal, the band of the filter may be changed as required.

FM modulation section 414 re-modulates the signal demodulated by FM demodulation section 412 . Specifically, the FM modulation unit 414 calculates the FM modulation degree Δf for each unit period Δt for the audio signal (that is, the stereo composite signal Sc or the monaural audio signal) that has passed through the composite filter 413, and the FM demodulation unit 412 Using the same conversion table used, the instantaneous phase change Δθ is calculated from the FM modulation degree Δf. Then, FM modulation section 414 generates an I signal representing the in-phase component of the transmission signal and a Q signal representing the quadrature component, that is, a transmission IQ signal, from this instantaneous phase change Δθ.

The FM modulation section 414 is configured to control the output level of the generated transmission IQ signal in multiple stages. When the FM repeater 1 is activated or when the oscillation detection signal So output from the oscillation detection section 42 becomes active level, the output level of the FM modulation section 414 is initially set to the minimum level. The active level of the oscillation detection signal So indicates that the wraparound oscillation has been detected. After that, the FM modulation section 414 gradually increases the output level to the maximum level while sequentially removing the loop interference wave U over a preset start-up time. The minimum level is set so that the reception strength of the loop interference wave UO from the transmission antenna 7 directly received by the reception antenna 2 is sufficiently lower than the reception strength of the parent station wave D. FIG. The maximum level is set to a magnitude that does not cause signal saturation due to the processing in the transmitting section 5 .

[1-3-2. Oscillation detector/Silence detector]
The oscillation detection unit 42 monitors the amplitude of the received IQ signal, and outputs an oscillation detection signal So set to an active level when the fluctuation of the amplitude exceeds a preset threshold or is saturated. . In other words, in the oscillation detection unit 42, the received IQ signal representing the FM-modulated wave ideally has a constant amplitude, but the FM-modulated wave is superimposed with signals with different delays (that is, loop interference waves U0 to Un). Oscillation is detected by utilizing the fact that the amplitude fluctuates. Note that it is difficult to correctly demodulate an FM-modulated wave whose amplitude fluctuation range exceeds a certain value. Also, the received IQ signal to be monitored may be either the signal on the input side of the band-limiting filter 411 or the signal on the output side. The silence detection signal Ss is input to the correlation analysis section 432 of the loop interference wave removal section 43, the correlation analysis section 442 of the multipath wave removal section 44, and the FM modulation section 414, which will be described later.

The silence detector 45 monitors the instantaneous phase change Δθ generated by the FM demodulator 412, and when the absolute value of the instantaneous phase change Δθ continues below the threshold for a certain period of time or longer, it is set to the active level. Then, the silence detection signal Ss is output. In other words, the silence detector 45 detects the silence state by utilizing the fact that the instantaneous phase change Δθ of signals other than the pilot signal becomes zero during silence. The threshold is set to a size that is approximately equal to the detection error included in Δθ. The silence detection signal Ss is input to the correlation analysis section 432 of the loop interference removing section 43, which will be described later.

[1-3-3. Loop Wave Eliminator]
The interference wave removal section 43 includes a band-limiting filter 431 , a correlation analysis section 432 , an adaptive filter 433 and a subtractor 434 .

The band-limiting filter 431 extracts from the transmission IQ signal regenerated by the signal regenerator 41 a signal within a frequency range that the FM-modulated carrier wave can take. Band-limiting filter 431 is a filter similar to band-limiting filters 36 and 411 described above.

The correlation analysis unit 432 calculates the time axis correlation between the received IQ signal output from the loop interference removing unit 43 and the transmission IQ signal supplied from the band-limiting filter 431 during the loop interference search period. The wraparound search period is a period in which the delay time with respect to the transmission IQ signal is 0 to ΔTr. .DELTA.Tr is a turnaround setting time set to a value larger than the maximum value of the time required for the relay wave Dr transmitted from the transmitting antenna 7 to be received by the receiving antenna 2 as the turnaround wave U. FIG. The wrap setting time ΔTr is set by adjusting the number of taps of the adaptive filter 433, and is set to about 45 μs, for example. However, in FIG. 6, the description is based on the reception timing of the master station wave D (that is, the received IQ signal), and the relay wave Dr (that is, the transmitted IQ signal) is retransmitted with respect to the master station wave D. Since it is delayed by Tr, the loop interference wave search period is represented by Tr to Tr+ΔTr.

Specifically, the correlation analysis unit 432 cuts the received IQ signal and the transmitted IQ signal for each convolution operation time To (<ΔTr) set in advance. Then, in the loop interference wave search period Tr to Tr+ΔTr, while sequentially delaying the transmission IQ signal by the time of the sampling period Ts, the reception IQ signal for the convolution operation time To and the complex conjugate signal of the transmission IQ signal are multiplied and the convolution operation is performed. I do. The convolution operation time To is set to a time sufficient to identify the waveform of the signal, for example, about 10 ms for identifying an audio signal mainly having a frequency of 100 Hz to several kHz.

The correlation analysis unit 432 calculates the maximum correlation value, which is the maximum value of the correlation coefficient, and the delay time DL (where DL≠0) at which the maximum correlation value is obtained, based on the time-axis correlation that is the result of the convolution operation. Extract. Then, the correlation analysis unit 432 stores the signal strength A, the phase θ, and the delay time DL of the delayed wave estimated from the extraction result as a delay profile. The delay profile is stored in a rewritable memory. The delay profile generated by the correlation analysis unit 432 is hereinafter referred to as a loop interference wave delay profile.

Here, the flow of processing in the correlation analysis unit 432 will be described along the flowchart shown in FIG.
Processing in the correlation analysis unit 432 is started when the FM repeater 1 is activated.

In S110, the correlation analysis unit 432 initializes (for example, clears to zero) the stored content of the loop interference wave delay profile.
In S120, the correlation analysis section 432 determines whether or not the oscillation detection section 42 has detected oscillation, that is, whether or not the oscillation detection signal So has reached the active level. If the correlation analysis unit 432 determines that oscillation has been detected, the process proceeds to S130, and if it determines that the oscillation has not been detected, the process proceeds to S140.

In S130, the correlation analysis unit 432 resets (for example, clears to zero) the stored contents of the loop interference wave delay profile, and returns the process to S120.
In S140, the correlation analysis unit 432 determines whether or not the silence detection unit 45 has detected a silence state, that is, whether or not the silence detection signal Ss has reached the active level. If the correlation analysis unit 432 determines that the silence state has been detected, the processing returns to S120, and if it determines that the silence state has not been detected, the processing proceeds to S150.

In S150, the correlation analysis unit 432 calculates the time axis correlation by executing a convolution operation of the transmission IQ signal and the reception IQ signal. Both the transmission IQ signal and the reception IQ signal are treated as a vector on the complex plane represented by the I signal and the Q signal, and the convolution operation is performed using the complex conjugate signal of the transmission IQ signal and the complex signal of the reception IQ signal. This is done by multiplying the

In subsequent S160, the correlation analysis unit 432 creates a delay profile for loop interference wave based on the time axis correlation that is the result of the convolution operation. Hereinafter, the delay profile for loop interference wave generated for each convolution operation time To in S160 will be referred to as a generated profile, and the delay profile for loop interference wave that has already been stored will be referred to as an existing profile.

In subsequent S170, the correlation analysis unit 432 determines whether or not there is an existing profile whose delay time DL matches the generated profile. If the correlation analysis unit 432 determines that no matching existing profile exists, the process proceeds to S180, and if it determines that the matching existing profile exists, the process proceeds to S190.

In S180, the correlation analysis unit 432 additionally stores the generated profile in the memory, and returns the process to S120.
In S190, the correlation analysis unit 432 updates the content of the existing profile by adding the signal strength A and phase θ of the generated profile to the signal strength A and phase θ stored for the matching existing profile, and performs the process. Return to S120.

As a result of the processing in the correlation analysis unit 432, a delay profile is generated for each convolution operation time To in the loop interference wave search period Tr to Tr+ΔTr, and the delay profile for the loop interference wave is stored in the memory storing the delay profile as shown in FIG. A plurality of delay profiles for loop interference waves with different times DL are accumulated. The loop interference wave delay profile is information representing the state of the loop interference waves U 0 to Un received by the receiving antenna 2 .

Returning to FIG. 2, the adaptive filter 433 generates a replica IQ signal based on each loop interference wave delay profile generated by the correlation analysis section 432 and stored in the memory. The replica IQ signal delays the transmission IQ signal by the delay time DL based on the delay time DL, the signal strength A, and the phase θ shown in the delay profile for loop interference wave, adjusts the amplitude based on the signal strength A, and adjusts the phase It is a signal whose phase is adjusted based on θ. A replica IQ signal is a general term for a replica I signal and a replica Q signal having a phase different from that of the replica I signal by 90°. Hereinafter, the replica IQ signal generated by the adaptive filter 433 is referred to as a loop interference wave replica IQ signal. The adaptive filter 433 generates the same number of loop interference wave replica IQ signals as the number of loop interference wave delay profiles.

The subtractor 434 supplies the result of subtracting the loop interference wave replica IQ signal generated by the adaptive filter 433 from the received IQ signal supplied from the receiver 3 to the multipath wave remover 44 .

[1-3-4. Multipath wave removal section]
The multipath wave removal unit 44 includes a parent station wave extraction unit 441 , a correlation analysis unit 442 , an adaptive filter 443 and a subtractor 444 .

The parent station wave extraction unit 441 extracts the parent station wave, which is the direct wave from the parent station, from the received IQ signal output by the multipath wave removal unit 44 (that is, input to the signal reproduction unit 41). The extraction of the master station wave utilizes the characteristic that the amplitude of the FM-modulated wave not receiving interference is constant and the amplitude of the FM-modulating wave receiving interference fluctuates. That is, it is estimated that the signal of constant amplitude is the signal based on the master station wave (hereinafter referred to as the master station signal).

The correlation analysis unit 442 calculates the time axis correlation between the received IQ signal output from the multipath wave removal unit 44 and the parent station signal extracted by the parent station wave extraction unit 441 during the multipath search period. The multipath wave search period is, as shown in FIG. 6, a period in which the delay time with respect to the parent station signal is 0 to Tr.

Specifically, the correlation analysis unit 442 cuts out the received IQ signal and the parent station signal for each convolution operation time To. Then, in the multipath wave search period 0 to Tr, while sequentially delaying the parent station signal by the time of the sampling period Ts, the received IQ signal for the convolution operation time To is multiplied by the complex conjugate signal of the parent station signal and convoluted. perform calculations.

Correlation analysis section 442 creates and stores a delay profile based on the time axis correlation, which is the result of the convolution operation, in the same manner as in the processing of correlation analysis section 432 . The delay profile generated by the correlation analysis unit 442 is hereinafter referred to as a multipath wave delay profile.

The flow of processing in the correlation analysis unit 442 is the same as the flow of processing in the correlation analysis unit 432 described using the flowchart shown in FIG. In the explanation of the processing, "multipath wave" is replaced with "multipath wave", and "transmission IQ signal" is replaced with "master station signal".

As a result of the processing in the correlation analysis unit 442, a multipath wave delay profile is generated for each convolution operation time To within the multipath wave search period, and the memory for storing the multipath wave delay profile shown in FIG. , a plurality of delay profiles for multipath waves with different delay times DL are accumulated. The multipath wave delay profile is information representing the state of the multipath waves M0 to Mm received by the receiving antenna 2. FIG.

Returning to FIG. 2, the adaptive filter 443 generates replica IQ signals based on each of the multipath wave delay profiles generated by the correlation analysis unit 442 and stored in the memory. The replica IQ signal delays the parent station signal by the delay time DL based on the delay time DL, signal strength A, and phase θ shown in the delay profile for multipath waves, adjusts the amplitude based on the signal strength A, It is a signal whose phase is adjusted based on the phase θ. Hereinafter, the replica IQ signal generated by the adaptive filter 443 will be referred to as a replica IQ signal for multipath waves. The adaptive filter 443 generates the same number of replica IQ signals for multipath waves as the number of delay profiles for multipath waves.

The subtractor 444 supplies the result of subtracting the replica IQ signal for multipath waves generated by the adaptive filter 443 from the received IQ signal supplied from the loop interference removing unit 43 to the signal reproducing unit 41 .

[1-4. motion]
The operation of the system will be explained.
Immediately after the FM repeater 1 is activated, the transmission IQ signal reproduced by the repeater 4 is output with the lowest intensity. As a result, the intensity of the loop interference waves U0-Un received by the receiving antenna 2 is sufficiently reduced, so that the oscillation due to the loop interference waves U0-Un is suppressed.

In the loop interference removing unit 43, the correlation analysis unit 432 determines the delay profile (i.e., delay profile for loop interference wave). Therefore, first, a loop interference delay profile for the direct wave U0 is generated and stored in the memory. The adaptive filter 433 generates a loop interference wave replica IQ signal for the direct wave U0 according to the loop interference wave delay profile stored in the memory. The subtractor 434 subtracts the loop interference wave replica IQ signal from the received IQ signal, thereby removing the signal component based on the direct wave U0 from the received IQ signal.

Subsequently, in the loop interference removing unit 43, the same processing is performed on the received IQ signal from which the influence of the direct wave U0 has been removed. A new delay profile is generated, and the contents of the loop interference wave delay profile stored in the memory are updated. The adaptive filter 433 generates a loop interference replica IQ signal for the direct wave U0 and the reflected wave U1 according to the loop interference delay profile stored in the memory. The subtractor 434 subtracts the loop interference wave replica IQ signal from the received IQ signal, thereby removing signal components based on the direct wave U0 and the reflected wave U1 from the received IQ signal.

By repeating the same processing, the signal components based on the loop interference waves U0 to Un are sequentially removed from the received IQ signal in descending order of received strength. Also, at the time of start-up, etc., the output level of the transmission IQ signal (and thus the relay wave Dr) gradually increases as the process of removing the loop interference waves U0 to Un described above progresses.

At the time of processing, the correlation analysis unit 442 in the multipath wave removing unit 44 determines the delay profile (i.e., , multipath wave delay profile) are generated and sequentially stored in the memory. That is, first, a multipath wave delay profile for the multipath wave M0 is generated. The adaptive filter 443 generates a multipath wave replica IQ signal for the multipath wave M0 according to the multipath wave delay profile stored in the memory. The subtractor 444 subtracts the multipath wave replica IQ signal from the received IQ signal, thereby removing the signal component based on the multipath wave M0 from the received IQ signal.

Subsequently, the multipath wave removing unit 44 performs similar processing on the received IQ signal from which the influence of the multipath wave M0 has been removed. That is, a new multipath wave delay profile is generated for the multipath wave M1 having the maximum intensity except for the multipath wave M0, and the content of the multipath wave delay profile stored in the memory is updated. The adaptive filter 443 generates multipath wave replica IQ signals for the multipath waves M0 and M1 according to the multipath wave delay profile stored in the memory. The subtractor 444 subtracts the multipath wave replica IQ signal from the received IQ signal, thereby removing the signal components based on the multipath waves M0 and M1 from the received IQ signal.

By repeating the same processing, the signal components based on the multipath waves M0 to Mm are sequentially removed from the received IQ signal in descending order of received strength.
[1-5. Correspondence of terms]
In this embodiment, the correlation analysis unit 432 corresponds to the first profile generation unit, the adaptive filter 433 and the subtractor 434 correspond to the first suppression unit, the correlation analysis unit 442 corresponds to the second profile generation unit, and the adaptive The filter 443 and subtractor 444 correspond to the second suppression unit. The configuration for realizing the function of adjusting the output level in the FM modulation section 414 corresponds to the output adjustment section, and the processing in S140 corresponds to the resetting processing. The loop interference wave delay profile corresponds to the first delay profile, and the loop interference wave replica signal corresponds to the first replica signal. The multipath wave search period corresponds to the multipath wave search period, the multipath wave delay profile corresponds to the second delay profile, and the multipath wave replica signal corresponds to the second replica signal.
[1-6. effect]
According to the embodiment detailed above, the following effects are obtained.

(1a) In the FM repeater 1, the period from when the master station wave D is received until the retransmission delay time Tr elapses is defined as the multipath wave search period, and a predetermined time ΔTr elapses after the relay wave Dr is transmitted. Using the period up to this time as a loop interference wave search period, the multipath waves M0 to Mm and the loop interference waves U0 to Un are extracted separately. Therefore, both multipath waves and loop interference waves can be accurately extracted.

That is, the FM broadcast wave is an analog modulation signal that converts the change in the audio signal into a frequency shift from the center frequency and transmits it. It has not been. In the FM relay device 1, by searching the loop interference wave U and the multipath wave M by dividing the period, the loop interference wave U and the multipath wave M having the same frequency as the parent station wave D can be obtained without superimposing a special signal on the FM broadcast wave. Multipath waves M can be estimated.

(1b) In the FM repeater 1, the loop interference replica IQ signal used to remove the signal components based on the loop interference waves U0 to Un from the received IQ signal is the transmission IQ signal used to generate the repeater wave Dr, that is, the loop interference Waves U0 to Un are generated from the original signals. Therefore, according to the FM repeater 1, the components based on the loop interference waves U0 to Un, which cause oscillation, can be suppressed accurately.

(1c) In the FM repeater 1, the multipath wave replica IQ signal used to remove the signal components based on the multipath waves M0 to Mm from the received IQ signal is the parent station signal extracted from the received IQ signal, that is, , are generated from the original signals of the multipath waves M0 to Mm. Therefore, according to the FM repeater 1, the components based on the multipath waves M0 to Mm can be suppressed appropriately.

(1d) In the FM repeater 1, both the loop interference wave removing unit 43 and the multipath wave removing unit 44 select the loop interference wave U and the multipath wave M that have the highest reception strength contained in the received IQ signal at the time of processing. Generate a delay profile for Therefore, each time the processing is repeated, the effects of both the loop interference wave U and the multipath wave M are suppressed in descending order of signal strength. Therefore, as long as the maximum number of replica IQ signals that can be generated by the adaptive filters 433 and 443 is not exceeded, any number of loop interference waves U and multipath waves M can be handled.

(1e) The FM repeater 1 sets the output level of the relay wave Dr to the minimum level at the time of startup and oscillation detection, and with the passage of time (that is, the progress of the processing for removing the loop interference waves U0 to Un), , gradually increasing the output level. Therefore, according to the FM repeater 1, as shown in FIG. 7, the final output signal of the repeater wave Dr, which is the source of the loop interference waves U0 to Un, reaches the receiving antenna 2 at a level higher than the parent station wave D. Even if it wraps around, it is possible to suppress the occurrence of wraparound oscillation. The progress of the processing for removing the loop interference waves U0 to Un may be determined based on the generation status of the delay profile, etc., instead of based on the passage of time.

(1f) The FM repeater 1 stops updating the delay profile when a silent state is detected. Therefore, it is possible to prevent deterioration of accuracy of the delay profile due to the influence of the silent state, and thus deterioration of accuracy of suppressing the loop interference wave U and the multipath wave M by the replica IQ signal.

(1g) In the FM repeater 1, the replica IQ signal is subtracted from the received IQ signal generated by Hilbert transforming the received signal, that is, the effects of the wraparound wave U and the multipath wave M at the analog waveform level. is suppressed. Therefore, according to the FM relay device 1, the information about the delay time DL of the loop interference wave U and the multipath wave M and the information about the intensity A and the phase θ can be processed simultaneously without separating them separately. Configuration can be simplified.

[2. Second Embodiment]
[2-1. Differences from First Embodiment]
Since the basic configuration of the second embodiment is the same as that of the first embodiment, differences will be described below. Note that the same reference numerals as in the first embodiment indicate the same configurations, and refer to the preceding description.

In the first embodiment described above, processing is performed based on the signal received by one receiving antenna 2 . In contrast, the second embodiment differs from the first embodiment in that processing is performed based on signals received by two receiving antennas 2A and 2B.

[2-2. Constitution]
As shown in FIG. 8, the FM repeater 1A of the second embodiment includes two receiving antennas 2A and 2B, two receiving sections 3A and 3B, a relay processing section 4A, a transmitting section 5, and a power amplifier 6. and a transmitting antenna 7.

Receiving antennas 2A and 2B are ideally arranged so that the master station wave D is received in phase and the loopback wave U0 is received in opposite phase (that is, a phase difference of 180°). Actually, the phase difference between the master station wave D and the loop interference wave U0 received by the receiving antennas 2A and 2B does not have to be exactly opposite in phase, and the loop interference wave U0 is synthesized at the same level and in opposite phase. It suffices if it is set so that the parent station wave D remains. That is, the receiving antennas 2A and 2B add the master station wave component, which is a signal component based on the master station wave D, to the signal generated by the signal synthesizing unit 40, which will be described later. is arranged to be contained in

Specifically, the receiving antennas 2A and 2B may be arranged so as to satisfy at least one of the formulas (1) and (2). However, let Δθp be the phase difference and ΔPp be the phase difference and ΔPp of the master station wave D received by the receiving antennas 2A and 2B, and Δθr and ΔPr be the phase difference and level difference of the loopback wave U0. THθ and THP are lower thresholds set according to the signal strength required for processing in the signal reproducing unit 41, and are set to THθ=10° and THP=3 dB, for example.

|Δθp−Δθr|≧THθ (1)
ΔPp−ΔPr≧THP (2)
The receiving antennas 2A and 2B may be omnidirectional antennas or directional antennas. The master station wave D is an FM modulated wave, and its center frequency is fc.

The receiving section 3A is connected to the receiving antenna 2A, and the receiving section 3B is connected to the receiving antenna 2B.
Both of the receivers 3A and 3B are configured in the same manner as the receiver 3 of the first embodiment. Note that the local signal generator 32 may have a common configuration for the receiving units 3A and 3B.

Hereinafter, the I signal and the Q signal generated by the receiving section 3A are collectively referred to as the first received IQ signal, and the I signal and the Q signal generated by the receiving section 3B are collectively referred to as the second received signal. It is called an IQ signal.

The relay processing unit 4A FM-demodulates the combined IQ signal obtained by combining the first received IQ signal and the second received IQ signal generated by the receiving units 3A and 3B, and FM-modulates it again to obtain a constant amplitude and reproduce the I and Q signals. Hereinafter, the I signal and the Q signal reproduced by the relay processing unit 4A are collectively referred to as the transmission IQ signal.

The transmitter 5, power amplifier 6, and transmitting antenna 7 are the same as in the first embodiment.
[2-3. Relay processing section]
The relay processing unit 4A includes a signal synthesis unit 40, a signal reproduction unit 41, an oscillation detection unit 42, a loop interference wave removal unit 43, a multipath wave removal unit 44, and a silence detection unit 45.

Like the functions of the relay processing unit 4, the functions of the relay processing unit 4A may all be realized by hardware, or at least part of them may be implemented by a microcomputer having a processor and a memory that is a non-transitional substantive recording medium. may be implemented by a process executed by

In addition, in the relay processing unit 4A, the configuration other than the signal synthesizing unit 40 is the same as that of the relay processing unit 4 of the first embodiment.
[2-3-1. signal synthesizing unit]
The signal synthesis unit 40 includes an interference wave anti-phase synthesis unit 401 , a synthesis error analysis unit 402 , a difference detection unit 403 and a coefficient adjustment unit 404 .

As shown in FIG. 9 , the interference wave anti-phase combining section 401 includes a signal conditioner 81 and an adder 82 . The signal adjuster 81 adjusts the phase and signal strength of the second received IQ signal according to the synthesis coefficient (φ, A) set by the coefficient adjuster 404 . φ is the amount of phase adjustment, and A is the amount of level adjustment. Here, the maximum loop interference wave U0 included in the first received IQ signal is UA0, and the maximum loop interference wave U0 included in the second received IQ signal is UB0. Phase adjustment amount φ of signal adjuster 81 is set by coefficient adjuster 404 such that the phase of loop interference wave UB0 is opposite to the phase of loop interference wave UA0. Further, the level adjustment amount A of the signal adjuster 81 is set so that the signal strength of the loop interference wave UB0 matches the signal strength of the loop interference wave UA0. Here, as the level adjustment amount A, a value obtained by dividing the signal strength of the loop interference wave UA0 by the signal strength of the loop interference wave UB0 and expressed in decibels is used.

The adder 82 adds the second received IQ signal whose phase and signal strength have been adjusted by the signal adjuster 81 and the first received IQ signal to generate a combined IQ signal. As a result, the loop interference waves UA0 and UB0 cancel each other out, and a combined IQ signal is generated in which the parent station waves DA and DB are combined in a state close to the same phase. That is, the loop interference waves UA0 and UB0 correspond to interference wave components, and the parent station waves DA and DB correspond to broadcast wave components.

The synthesis error analysis section 402 has a quality detector 930 that detects the signal quality of the synthesis IQ signal. Signal quality can use, for example, the amount of error. The amount of error can be represented by a variation in amplitude per unit time (for example, variance) in the case of an FM-modulated signal.

The synthetic error analysis unit 402 further has five processing blocks B1 to B5. Each processing block Bi (where i=1 to 5) has a signal conditioner 91i, an adder 92i and a quality detector 93i.

Signal conditioner 91 i is configured similarly to signal conditioner 81 , adder 92 i is configured similarly to adder 82 , and quality detector 93 i is configured similarly to quality detector 930 . However, the synthesis coefficients set in the signal adjusters 911 to 915 by the coefficient adjuster 404 are different.

Specifically, the synthesis coefficient (φ, AdA) is set in the signal adjuster 911 based on the synthesis coefficient (φ, A) set in the signal adjuster 81 . A synthesis coefficient (φ, A+dA) is set in the signal adjuster 912 . A synthesis coefficient (φ−dφ, A) is set in the signal adjuster 913 . A synthesis coefficient (φ+dφ, A) is set in the signal adjuster 914 . A synthesis coefficient (φs, A) is set in the signal adjuster 915 . However, dA represents a minute amount of intensity shift, and dφ represents a minute amount of phase shift. φs means scanning the phase adjustment amount by 360°.

Each processing block Bi adds the second received IQ signal whose phase and signal strength have been adjusted according to the combining coefficient set in the signal adjuster 91i and the first received IQ signal to generate a control combined signal. and detects the signal quality of the generated control synthesized signal.

That is, the synthesis error analysis section 402 detects the signal quality of each of the six types of synthesis signals (that is, the synthesis IQ signal and the five types of control synthesis signals), and supplies the signal quality to the coefficient adjustment section 404 .

The difference detection unit 403 calculates the average value of the phase difference and the average value of the level difference for each preset measurement time for each of the first received IQ signal and the second received IQ signal, and the coefficient adjustment unit 404 supply. The measurement time is, for example, 10 ms (reciprocal of 100 Hz), but is not limited to this.

Based on the signal quality detection results detected by the quality detector 930 and the processing blocks B1 to B4, the coefficient adjustment unit 404 uses the signal quality as an index to optimize the signal quality (that is, minimizes the amount of error). ) to generate a synthesis coefficient (φ, A).

Here, when the synthesis coefficients are (φ, A−dA), (φ, A), and (φ, A+dA), that is, when the phase adjustment amount φ is fixed and the level adjustment amount A is slightly changed. An example of the signal quality detection result of is shown in the upper part of FIG. Further, when the synthesis coefficients are (φ−dφ, A), (φ, A), and (φ+dφ, A), that is, when the level adjustment amount A is fixed and the phase adjustment amount φ is slightly changed, An example of signal quality detection results is shown in the lower part of FIG. With reference to these two graphs, the signal quality of the synthesis coefficients (φ, AdA) and (φ-dφ, A) changed to the negative side with respect to the current synthesis coefficient (φ, A) is good ( That is, if the error amount is small), the adjustment amounts φ and A are finely adjusted to the negative side. If the signal quality of the synthesis coefficients (φ, A + dA) and (φ + dφ, A) changed to the positive side relative to the current synthesis coefficient (φ, A) is good, the adjustment amount φ, A is increased to the positive side. Fine tune. The fine adjustment amount Δφ of the phase adjustment amount φ and the fine adjustment amount ΔA of the level adjustment amount A may be fixed values, or may be set according to the difference or ratio between the signal quality on the minus side and the signal quality on the plus side. It may be a variable value that is set. Then, the signal qualities at the synthesis coefficients (φ, A−d1) and (φ, A+dA) are equal, and the signal qualities at the synthesis coefficients (φ−dφ, A) and (φ+dφ, A) are equal. By repeating the fine adjustment, the synthesis coefficient (φ, A) with the best signal quality is obtained.

However, the coefficient adjustment unit 404, when the reception strength of the loop interference wave U received by the receiving antennas 2A and 2B is higher than the reception strength of the parent station wave D, i.e., the so-called minus D/U, the difference detection unit Using the phase difference φ _AV and the intensity difference A _AV detected in 403, the synthesis coefficient (φ, A) is set so as to satisfy the equations (3) and (4).

φ _AV + φ = 180° (3)
_AAV +A=0dB (4)
The phase difference φ _AV is the result of subtracting the average phase value of the second received IQ signal from the average phase value of the first received IQ signal. The intensity difference A _AV is the result of dividing the average intensity of the first received IQ signal by the average intensity of the second received IQ signal, and the unit is decibel.

That is, in the case of minus D/U, the difference detection unit 403 detects the phase difference φ _AV and the intensity difference A _AV for the loop interference wave U0 with the highest level. ) may be used as

The parent station wave component DA included in the first received IQ signal and the parent station wave component DB included in the second received IQ signal, which are input to the signal combining unit 40 due to the arrangement of the receiving antennas 2A and 2B, are shown in FIG. As shown in 11, they are in substantially the same phase. Moreover, it is desirable that the loop interference wave component UA included in the first received IQ signal and the loop interference wave component UB included in the second received IQ signal have a phase difference close to 180°. It should be different from phase difference. In the signal synthesizing unit 40, the second received IQ signal and the first received IQ signal adjusted by the synthesis coefficients (φ, A) so that the loop interference wave components UA and UB have opposite phases and have the same signal strength are combined. Additive synthesis. As a result, the synthesized loop interference wave components UA and UB cancel each other out, and the parent station wave components UA and UB are synthesized with a phase difference obtained by adding the phase adjustment amount φ to the original phase shift amount. be.

Coefficient adjustment section 404 performs phase combining as shown in FIG. Generate a pattern graph. The phase synthesis pattern graph shows the signal strength of the loopback wave U0 detected at each phase when the phase of the master station wave D is set to 0° and the phase adjustment amount added during synthesis is varied from 0° to 360°. be. The phase corresponding to the dent in the phase synthesis pattern graph represents the phase difference of the loop interference wave U0 with respect to the parent station wave D. FIG. In other words, coefficient adjustment section 404 removes loop interference wave U0 by forming an antenna synthesis null in the direction of arrival of the signal having this phase difference (that is, loop interference wave U0). Therefore, the initial value of the synthesis coefficient may be set using the phase difference read from the phase synthesis pattern flag.

[2-4. motion]
The operation of the system will be explained.
Immediately after the FM repeater 1A is activated, the transmission IQ signal reproduced by the repeater 4 is output with the lowest strength. As a result, the intensity of the loop interference waves U0-Un received by the receiving antennas 2A and 2B is sufficiently reduced, so that the oscillation due to the loop interference waves U0-Un is suppressed.

The signal synthesizing unit 40 adjusts the phase difference and level between the first received IQ signal and the second received IQ signal so that the loop interference waves U0 received by the receiving antennas 2A and 2B have opposite phases and have the same signal strength. Synthesize by adjusting the difference. Therefore, as shown in FIG. 13, the maximum loop interference wave U0 is suppressed in the synthesized IQ signal.

The loop interference wave removing unit 43 removes the loop interference waves U1 to Un that cannot be removed by the signal synthesizing unit 40 in descending order of reception strength using the delay profile. If the suppression of the coupling loop interference wave U0 is insufficient in the signal synthesizing unit 40, a delay profile is generated when the intensity of the suppressed coupling loop interference wave U0 reaches the maximum intensity in the synthesized IQ signal. be. As a result, the loop interference wave U0 that is left unremoved by the signal synthesizing section 40 is also removed from the synthetic IQ signal.

The multipath wave removal unit 44 removes the multipath waves M0 to Mm in descending order of reception intensity using the delay profile.
Also, at the time of start-up, etc., the output level of the transmission IQ signal (and thus the relay wave Dr) gradually increases as the process of removing the loop interference waves U0 to Un described above progresses.

[2-5. Correspondence of terms]
In this embodiment, the synthetic error analysis unit 402 and the coefficient adjustment unit 404 correspond to the coefficient setting unit.

[2-6. effect]
According to the second embodiment described in detail above, the effects (1a) to (1g) of the first embodiment described above are obtained, and the following effects are also obtained.

(2a) In the FM repeater 1A, the interference wave of maximum intensity (for example, the loopback wave U0) is removed by synthesizing the signals obtained from the two receiving antennas 2A and 2B. can be lowered. As a result, the oscillation due to the sneak wave U is suppressed, and the stability of the operation can be improved.

(2b) In the FM relay device 1A, the signal synthesizing unit 40 eliminates interference waves by synthesizing the signals obtained from the two receiving antennas 2A and 2B. can effectively remove this interference wave even if they have different waveforms. For example, even when different kinds of program broadcasts interfere with each other on the same channel, the phase difference between the different kinds of program broadcasts is controlled to be the opposite phase by synthesizing the antennas, so that the interference can be eliminated. In this case, the maximum intensity loop interference wave U0 is removed by processing using the delay profile.

(2c) In the FM repeater 1A, the coupling interference wave U is removed using the delay profile from the combined IQ signal in which the maximum interference wave is suppressed. It can be narrowed, and the configuration of the loop interference wave removing section 43 can be simplified.

[3. Other embodiments]
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be implemented in various modifications.

(3a) In the present disclosure, the delay profile stored in the memory is initialized (that is, S110) when the FM repeater 1 or 1A is activated, and is reset (that is, S140) when oscillation is detected. Although the memory contents are cleared to zero at the time of initialization and resetting, the present disclosure is not limited to this. For example, the update history of the delay profile is stored in a memory, and when oscillation is detected, the correlation analysis units 432 and 442, instead of clearing the storage contents of the memory in which the delay profile is stored, based on the update history, calculate the delay profile. may be returned to the state before oscillation detection. According to such a configuration, it is possible to quickly return to a state in which the effects of the sneak waves U0 to Un are sufficiently suppressed after the oscillation is detected.

(3b) In the present disclosure, the control of the output level of the relay wave Dr at startup and at the time of oscillation detection is performed by the FM modulation unit 414, but it is performed by changing the amplification factors of the amplifier 55 and the power amplifier 6. Alternatively, a separately provided attenuator may be used.

(3c) In the present disclosure, the FM relay devices 1 and 1A have been exemplified in the case of expanding the broadcasting area in the FM synchronous broadcasting system using SFN, but the present disclosure is not limited to this, and normal broadcasting that is not FM synchronous broadcasting It may be applied to extend the broadcasting area in the FM broadcasting system.

(3d) The FM relay devices 1 and 1A determine the state of the received IQ signal (in the case of the FM relay device 1A, at least one of the first received IQ signal, the second received IQ signal, and the combined IQ signal), and the combined A configuration for displaying the detection result of the signal quality by the error analysis unit 402 (only in the case of the FM repeater 1A) may be provided. Specifically, the FM relay devices 1 and 1A generate an image signal representing an image obtained by plotting the received IQ signal on a complex plane and an image obtained by graphing the signal quality (only in the case of the FM relay device 1A). A generator and an image output terminal for outputting an image signal may be provided. Furthermore, a display device connected to the image output terminal and a wireless communication device for transmitting image signals to an external display device (for example, a mobile phone) may be provided.

The image obtained by plotting the received IQ signal on the complex plane, as shown in FIG. 14, is different depending on whether there is interference due to loop interference waves, multipath waves, or heterogeneous program interference waves, and when there is interference. Therefore, the presence or absence of interference can be visually confirmed. An image (see, for example, FIGS. 10 and 12) in which the signal quality is graphed is displayed with the synthesis coefficient fixed to (φ=180°, A=1), for example, so that the receiving antennas 2A and 2B You can proceed with the work while checking the status at the time of installation.

(3e) In the FM repeaters 1 and 1A, the center frequency of the carrier wave is set to be the same for the reception IQ signal used for the master station wave D and the relay wave Dr (and thus the transmission IQ signal). is not limited to this. For example, the center frequency of the carrier wave of the relay wave Dr may be different from the center frequency of the carrier wave of the master station wave D by an offset frequency Δfo. In this case, the offset frequency Δfo is set within the allowable center frequency deviation (20 ppm) in the FM broadcast wave, for example, it may be set to about 100 Hz (1.25 ppm if the frequency of the carrier signal is 80 MHz). .

Also, in this case, when calculating the time-axis correlation between the received IQ signal or combined IQ signal and the transmitted IQ signal, the length of the section for performing the convolution operation is set to the offset time To, which is the reciprocal of the offset frequency Δfo. You may As a result, the signal component based on the parent station wave D contained in the received IQ signal or combined IQ signal has a weak correlation with the transmitted IQ signal, and is detected as a kind of noise in the calculation of the correlation analysis section 432 . Therefore, it is possible to prevent the signal component based on the parent station wave D from interfering with the detection of the looping wave U. That is, by making the center frequencies of the carrier waves of the relay wave Dr and the parent station wave D different by the offset frequency Δfo, it is possible to estimate the loop interference wave without superimposing a special signal on the FM broadcast wave.

(3f) A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or a function possessed by one component may be realized by a plurality of components. . Also, a plurality of functions possessed by a plurality of components may be realized by a single component, or a function realized by a plurality of components may be realized by a single component. Also, part of the configuration of the above embodiment may be omitted. Moreover, at least part of the configuration of the above embodiment may be added or replaced with respect to the configuration of the other above embodiment.

(3g) In addition to the FM relay devices 1 and 1A described above, a program for causing a computer to function as the FM relay device 1 and 1A, a non-transitional substantive recording medium such as a semiconductor memory in which this program is recorded, and delay profile generation The present disclosure can also be implemented in various forms, such as a method.

1, 1A... FM repeater, 2, 2A, 2B... receiving antenna, 3, 3A, 3B... receiving section, 4, 4A... relay processing section, 5... transmitting section, 6... power amplifier, 7... transmitting antenna, 40 Signal synthesizing unit 41 Signal reproducing unit 42 Oscillation detecting unit 43 Looping wave removing unit 44 Multipath wave removing unit 45 Silence detecting unit 401 Interference wave reverse phase synthesizing unit 402 Synthesizing unit Error analysis unit 403 Difference detection unit 404 Coefficient adjustment unit 431 Band-limiting filter 432, 442 Correlation analysis unit 433, 443 Adaptive filter 434, 444 Subtractor 441 Parent station wave extraction Department.

Claims (12)

a receiver (3, 3A, 3B) configured to receive an FM broadcast wave via a receiving antenna (2, 2A, 2B);
a signal regeneration unit (41) configured to generate a transmission signal by demodulating the received signal from the receiving unit and re-modulating the demodulated signal;
a transmission unit (5) configured to transmit, through a transmission antenna (7), a relay wave obtained by reproducing the broadcast wave using the transmission signal generated by the signal reproduction unit;
calculating a time-axis correlation using the transmission signal generated by the signal reproduction unit and the reception signal received during a loop interference wave search period, and calculating a maximum correlation value that is the maximum value of the time-axis correlation; a first profile generation unit (432) configured to generate a first delay profile that is information including the delay time of the transmission signal with respect to the reception signal when the maximum correlation value is obtained;
generating a first replica signal by delaying the transmission signal generated by the signal reproduction unit by the delay time according to the first delay profile and adjusting the strength and phase according to the maximum correlation value; , a first suppressing unit (433, 434) configured to subtract the first replica signal from the received signal input to the signal reproducing unit;
A parent station wave extraction unit configured to extract a parent station signal, which is a signal component based on the parent station wave, from the received signal, using a direct wave from the parent station, which is the transmission source of the broadcast wave, as the parent station wave. (441) and
A time-axis correlation is calculated using the master station signal extracted by the master station wave extraction unit and the received signal received during the multipath wave search period, and the maximum value of the time-axis correlation is calculated. A second profile generation unit (442) configured to generate a second delay profile that is information including a correlation value and a delay time of the transmission signal with respect to the master station signal when the maximum correlation value is obtained. When,
a second replica signal by delaying the master station signal extracted by the master station wave extracting unit by the delay time according to the second delay profile and adjusting the strength and phase according to the maximum correlation value; and subtracting the second replica signal from the received signal input to the signal regeneration unit;
with
The loopback wave search period is set based on the time required for the relay wave transmitted from the transmitting antenna to be received by the receiving antenna as a loopback wave, using a wraparound set time (ΔTr), is set to a period from when the transmission signal is generated by the signal reproduction unit until the wrap-around set time elapses,
In the multipath wave search period, the parent station wave extracting unit uses a retransmission delay time (Tr) required for the broadcast wave received by the receiving unit to be transmitted as the relay wave from the transmitting unit. set to a period from the extraction of the parent station signal to the elapse of the retransmission delay time in
FM repeater. The FM relay device according to claim 1,
When the FM repeater is activated, the output level of the relay wave transmitted by the transmitting antenna is set to a preset minimum level, and the output level of the relay wave is set to a preset maximum level to eliminate interference waves. A power adjustment unit (414) configured to adjust step by step according to progress
FM relay device further comprising: The FM relay device according to claim 2,
an oscillation detector (42) configured to detect oscillation of the FM repeater;
further comprising
The first profile generator is configured to store the generated first delay profile, and the second profile generator is configured to store the generated second delay profile,
The first suppressing unit generates the first replica signal according to the first delay profile stored in the first profile generating unit, and the second suppressing unit generates the delay profile stored in the second profile generating unit. configured to generate the second replica signal according to a second delay profile;
The first profile generation unit and the second profile generation unit are configured to perform a resetting process of resetting the stored contents of the first delay profile and the second delay profile when the oscillation is detected by the oscillation detection unit. was
The output adjustment unit is configured to adjust the output level of the relay wave not only at the time of startup but also at the time of oscillation detection by the oscillation detection unit.
FM repeater. The FM relay device according to claim 3,
As the resetting process, the first profile generator erases the stored contents of the first delay profile, and the second profile generator erases the stored contents of the second delay profile. FM relay Device. The FM relay device according to claim 3,
The first profile generator is configured to further store a history of the first delay profile, and the second profile generator is configured to further store a history of the second delay profile,
As the resetting process, the first profile generation unit restores the stored contents of the first delay profile to the state before oscillation detection using the history of the first delay profile, and the second profile generation unit The resetting process is configured to return the stored contents of the second delay profile to the state before oscillation detection using the history of the second delay profile.
FM repeater. The FM relay device according to any one of claims 1 to 5,
Further comprising a silence detection unit (45) for detecting a silence state of the broadcast wave,
The first profile generation unit and the second profile generation unit are configured to stop generating the first delay profile and the second delay profile while the silence detection unit detects the silence state. FM repeater. The FM relay device according to any one of claims 1 to 6,
The receiving unit converts the received signal into an I signal representing an in-phase component and a Q signal representing a quadrature component and outputs the signal;
The FM repeater, wherein the transmission section is configured to orthogonally demodulate the transmission signal represented by the I signal and the Q signal, and transmit the transmission signal. The FM relay device according to any one of claims 1 to 7,
The receiving unit is configured to receive the broadcast wave using two receiving antennas (2A, 2B),
The two received signals obtained from the receiving unit are combined so that the phases of the interference wave components, which are signal components based on the interference waves, are opposite to each other and the signal strengths of the interference wave components match. further comprising a signal synthesizing unit (40),
The signal reproducing unit, the first profile generating unit, the first suppressing unit, the parent station wave extracting unit, the second profile generating unit, and the second suppressing unit, as the received signal to be processed, the signal configured to use the synthesized signal synthesized by the synthesizing unit,
FM repeater. The FM relay device according to claim 8,
The two receiving antennas are arranged so that a broadcast wave component, which is a signal component based on the broadcast wave, is included in the combined signal with signal strength necessary for processing in the signal reproducing unit. The FM relay device according to claim 9,
Δθp is the phase difference of the broadcast waves received by the two receiving antennas, ΔPp is the level difference of the broadcast waves, Δθr is the phase difference of the interference waves, ΔPr is the level difference of the interference waves, and the signal reproduction unit Let THθ and THp be the lower thresholds set according to the signal strength required for the processing of
The two receiving antennas are arranged to satisfy at least one of |Δθp-Δθr|≧THθ and ΔPp-ΔPr≧THP. The FM relay device according to any one of claims 8 to 10,
The signal synthesizing unit
Interference wave anti-phase synthesis configured to generate the synthesized signal by synthesizing the two received signals obtained from the receiving unit with the phase difference and level difference adjusted according to a set synthesis coefficient. a part (401);
a coefficient setting unit (402, 404) configured to set the synthesis coefficient using the signal quality of the synthesized signal as an index;
FM repeater. The FM relay device according to claim 11,
The signal synthesis unit further comprises a difference detection unit (403) configured to calculate the average value of the phase difference and the average value of the level difference between the two received signals for each preset measurement time,
The FM repeater, wherein the coefficient setting unit is configured to set the synthesis coefficient according to the detection result of the difference detection unit when the received intensity of the interference wave is greater than that of the broadcast wave.

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