JP2008072218A - Digital broadcast wave relay device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital broadcast wave relay device of which the circuit constitution can be made simple and compact. <P>SOLUTION: A received RF signal is converted into an IF signal by a down converter 111 based on a first local oscillation signal, and then digitally converted by an analog-to-digital converting circuit 112 based on a second local oscillation signal. A digital signal processing circuit 113 applies signal processing to the digitally converted IF signal based on the second local oscillation signal. The processed signal is converted by a digital-to-analog converting circuit 114 into an analog IF signal based on the second local oscillation signal, and then converted into an RF signal by an up converter 115 based on the first local oscillation signal. A first local oscillation circuit 117 and a second local oscillation circuit 118 generates the first and second local oscillation signals respectively based on a common reference signal generated by a reference signal generation section 119. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a digital broadcast wave relay apparatus that receives and retransmits a broadcast wave of terrestrial digital broadcast.

In terrestrial digital broadcasting, OFDM (Orthogonal Frequency Division Multiplexing) is adopted. This method is particularly strong against multipath, and has a feature that SFN (Single Frequency Network) is possible. The problem in realizing SFN is that the same frequency signal as the received signal from the transmitting antenna wraps around the receiving antenna in the broadcast wave relay station, causing an oscillation phenomenon, and the sneaking phenomenon due to SFN that makes retransmission impossible. There is. As countermeasures against this wraparound phenomenon, a method of physically separating the reception antenna and the transmission antenna to ensure isolation, or a method of removing a wraparound component called a wraparound canceller from the received signal (see, for example, Patent Document 1) .)
JP-A-11-355160

  However, in the ISDB-T system, which is a standard for terrestrial digital broadcasting, the bandwidth per channel is about 5.572 MHz, and the center frequency is shifted by 1/7 (= 0.142857) MHz. For this reason, in order to accurately convert the frequency to the intermediate frequency, it is necessary to control the local oscillation frequency in the order of mHz (millihertz) in the UHF band, and the circuit configuration is complicated and large, resulting in an increase in cost. There is a problem. In particular, when analog signal processing is performed, the frequency characteristics of the filter are fixed, and therefore a frequency shift may greatly affect the deterioration of the characteristics.

  The present invention has been made paying attention to the above circumstances, and an object of the present invention is to provide a digital broadcast wave relay device that enables simplification and miniaturization of a circuit configuration in broadcast wave relay of digital terrestrial broadcasting. There is.

  In order to achieve the above object, a digital broadcast wave repeater according to the present invention includes a receiving means for receiving a radio frequency (RF) signal of a digital broadcast wave by OFDM, and the received RF signal as a first signal. First frequency conversion means for converting an analog intermediate frequency (IF) signal based on the local oscillation signal, and the analog IF signal converted by the first frequency conversion means based on the second local oscillation signal Analog / digital (A / D) conversion means for converting into a digital IF signal, and signal processing is performed on the digital IF signal digitally converted by the A / D conversion means based on the second local oscillation signal A digital signal processing means for converting the signal-processed digital IF signal into an analog signal based on the second local oscillation signal; A analog (D / A) conversion means; a second frequency conversion means for converting an analog IF signal analog-converted by the D / A conversion means into an RF signal based on the first local oscillation signal; A re-transmission unit for amplifying and re-transmitting the RF signal converted by the frequency conversion unit, a reference signal generation unit for generating a reference signal, and the reference signal generated by the reference signal generation unit based on the reference signal A first local oscillation signal generating means for generating a first local oscillation signal; and a second local oscillation signal for generating the second local oscillation signal based on the reference signal generated by the reference signal generating means. And generating means.

  The second configuration of the digital broadcast wave repeater according to the present invention includes a receiving means for receiving an RF signal of a digital broadcast wave by OFDM, and the received RF signal is analogized based on the first local oscillation signal. First frequency conversion means for converting into an IF signal; A / D conversion means for converting the analog IF signal converted by the first frequency conversion means into a digital IF signal based on a second local oscillation signal; Digital signal processing means for performing signal processing on the digital IF signal digitally converted by the A / D conversion means on the basis of the second local oscillation signal; and the signal processed digital IF signal for the second IF A D / A conversion means for analog conversion based on the local oscillation signal, and an analog IF signal analog-converted by the D / A conversion means as a third local oscillation signal A second frequency converting means for converting the RF signal based on the second frequency converting means, a retransmission means for amplifying and retransmitting the RF signal converted by the second frequency converting means, and a reference signal generating means for generating a reference signal; The first local oscillation signal generating means for generating the first local oscillation signal based on the reference signal generated by the reference signal generating means, and the reference signal generated by the reference signal generating means Second local oscillation signal generating means for generating the second local oscillation signal, and third local oscillation signal generating means for generating the third local oscillation signal based on the reference signal generated by the reference signal generating means. And an oscillation signal generating means.

  In the digital broadcast wave repeater having the above configuration, the first local oscillation signal generator generates the first local oscillation signal by using the common reference signal source for the first local oscillation signal generator and the second local oscillation signal generator. The phase noise of the first local oscillation signal can be reduced. For this reason, the frequency control of the first local oscillation signal generating means can be simplified and the circuit configuration can be miniaturized.

  Therefore, according to the present invention, it is possible to provide a digital broadcast wave relay device that enables simplification and miniaturization of the circuit configuration in relay of terrestrial digital broadcasting.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a digital broadcast relay device according to the present invention. In FIG. 1, the digital broadcast wave relay device 1 includes a reception antenna 10, a signal processing unit 11, and a transmission antenna 12. The radio frequency (RF) signal of the terrestrial digital broadcast wave received by the receiving antenna 10 according to the OFDM method is input to the signal processing unit 11. The signal processing unit 11 removes adjacent channel signals other than the broadcast signal to be retransmitted from the input RF signal, noise components existing in the same channel, and the like, and then retransmits from the transmission antenna 12.

  The signal processing unit 11 includes a down converter 111, an analog / digital conversion circuit 112, a digital signal processing circuit 113, a digital / analog conversion circuit 114, an up converter 115, a power amplifier (PA) 116, a first amplifier A local oscillation circuit 117, a second local oscillation circuit 118, and a reference signal generation unit 119 are provided. In the signal processing unit 11, the signal received by the receiving antenna 10 is frequency-converted to an intermediate frequency by the down converter 111 and then converted to a digital signal by the analog / digital conversion circuit 112. The digital signal processing circuit 113 removes unnecessary signals such as adjacent channel signals other than the signal to be retransmitted from the digital signal.

  Here, the analog / digital conversion circuit 112 and the digital / analog conversion circuit 114 are operated with a clock that is an integral multiple of 512/63 (= 8.1698) MHz output from the second local oscillation circuit 118. In addition, the digital signal processing circuit 113 also operates with the same clock, performs FFT or IFFT processing on the signal, and enables digital signal processing for each subcarrier. The signal converted back to an analog signal by the digital / analog conversion circuit 114 is frequency-converted to a radio frequency by the up-converter 115, amplified by the power amplifier 116, and retransmitted from the transmission antenna 12.

  At this time, in the frequency conversion in the down converter 111 and the up converter 115, the local oscillation signal distributed by the first local oscillation circuit 117 is used. Further, the first local oscillation circuit 117 and the second local oscillation circuit 118 generate a local oscillation signal based on a common reference signal supplied from the reference signal generation unit 119. For this reason, the accuracy of the first local oscillation circuit 117 and the second local oscillation circuit 118 can be matched. Thereby, it is possible to reliably return to the original frequency at the time of retransmission, and it is possible to form an SFN.

  As described above, in the above-described embodiment, the received RF signal is converted into the IF signal based on the first local oscillation signal by the down converter 111, and converted into the second local oscillation signal by the analog / digital conversion circuit 112. Based on the digital conversion. The digital signal processing circuit 113 performs signal processing on the digitally converted IF signal based on the second local oscillation signal. The signal-processed signal is converted into an analog IF signal based on the second local oscillation signal by the digital / analog conversion circuit 114, and then converted into an RF signal based on the first local oscillation signal in the up-converter 115. The The first local oscillation circuit 117 and the second local oscillation circuit 118 generate the first and second local oscillation signals based on the common reference signal generated by the reference signal generation unit 119, respectively.

  With this configuration, the digital signal processing circuit 113 forms a similar circuit using an analog signal processing circuit such as a SAW device in order to remove unnecessary signals such as adjacent channel signals other than the signal to be retransmitted. Compared to, it is possible to achieve a high degree of adjacent channel suppression at a small size and at a low price. In addition, by using a rewritable circuit such as FPGA or DSP, the function of the digital signal processing circuit 113 can be changed as necessary.

Further, by using a common reference signal source for the first local oscillation circuit 117 and the second local oscillation circuit 118, the phase jitter of the frequency conversion signal generated by the first local oscillation circuit 117 is allowed. be able to. For this reason, the frequency control of the first local oscillation circuit 117 can be simplified, and the circuit configuration can be reduced in size.
Therefore, according to the above embodiment, the circuit configuration can be simplified and miniaturized in the relay of digital terrestrial broadcasting, and the manufacturing cost of the relay device can be reduced.

(Another embodiment)
FIG. 2 is a diagram showing another embodiment of the digital broadcast wave relay apparatus according to the present invention. In FIG. 2, the difference from the digital broadcast wave repeater 1 shown in FIG. 1 is that a third local oscillation circuit 120 is added. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the digital broadcast wave repeater 1 shown in FIG. 1, the same local oscillation signal distributed by the first local oscillation circuit 117 is used for frequency conversion in the down converter 111 and the up converter 115. The first local oscillation circuit 117 and the second local oscillation circuit 118 generate a local oscillation signal based on a common reference signal supplied from the reference signal generation unit 119. Therefore, the accuracy of the first local oscillation circuit 117 and the second local oscillation circuit 118 can be matched. Thereby, it is possible to reliably return to the original frequency at the time of retransmission, and it is possible to form an SFN.

On the other hand, in the digital broadcast wave repeater 1 shown in FIG. 2, the local oscillation signal of the first local oscillation circuit 117 is used for frequency conversion in the down converter 111, but the first local oscillation circuit 117 is used for frequency conversion in the up converter 115. The local oscillation signal of the third local oscillation circuit 120 different from the local oscillation signal is used. However, both the local oscillation signal of the first local oscillation circuit 117 and the local oscillation signal of the third local oscillation circuit 120 generate the local oscillation signal based on the common reference signal supplied from the reference signal generation unit 119. The accuracy is the same.
By adopting the configuration as described above, it is possible to provide a digital broadcast wave repeater 1 that can also support MFN (Multi Frequency Network) having different reception frequencies and transmission frequencies.

(First configuration example)
FIG. 3 shows a first configuration example of the digital signal processing circuit 113 of the digital broadcast relay apparatus shown in FIGS. In FIG. 3, the digital intermediate frequency (IF) signal supplied from the analog / digital conversion circuit 112 is frequency-converted to a predetermined digital IF frequency through a digital down converter 1131 and a low-pass filter (LPF) 1132. Further, the band pass filter (BPF) 1133 removes unnecessary signals such as adjacent channel signals from the frequency-converted signal and distributes them to the digital up-converter 1134 and the frequency monitoring unit 1138. The signal distributed from the BPF 1133 is frequency-converted by the digital up-converter 1134 and the LPF 1135 to the same frequency as the output signal of the analog-digital conversion circuit 112 and supplied to the digital-analog conversion circuit 114. The supplied digital signal is converted back to an analog signal in the digital / analog conversion circuit 114.

  On the other hand, the frequency monitoring unit 1138 detects a difference between the signal distributed from the BPF 1133 and a desired frequency, and outputs the difference to the frequency control unit 1139 as a frequency error. The frequency control unit 1139 generates a control signal for correcting the frequency error output from the frequency monitoring unit 1138 and supplies the control signal to the fourth local oscillation circuit 1136. The fourth local oscillation circuit 1136 oscillates at a predetermined frequency in accordance with this control signal.

  Here, since the fourth local oscillation circuit 1136 distributes the common local oscillation signal to the digital down converter 1131 and the digital up converter 1134, the fourth local oscillation circuit 1136 can surely return to the original frequency.

  By matching the pass band of the BPF 1133 and the band of the received signal, unnecessary signals such as adjacent channel signals can be removed. At this time, in order to adjust the pass band only by the first local oscillation circuit 117, it is necessary to set a very fine frequency. On the other hand, in the above configuration, since the first local oscillation circuit 117 and the fourth local oscillation circuit 1136 are combined, complicated frequency setting is not necessary.

  That is, in the first local oscillation circuit 117 of the digitel broadcast wave repeater of FIG. 3, it is sufficient if there is an accuracy corresponding to the adjacent channel interval, and if the fourth local oscillation circuit 1136 performs high-accuracy frequency setting. Good. By adopting this method, the frequency division ratio of the PLL (phase synchronization circuit) can be set small, so that the phase noise that is a problem in the first local oscillation circuit 117 can be reduced. Further, since the oscillation frequency is kept low in the fourth local oscillation circuit 1136, it is possible to set the frequency with high accuracy without increasing the frequency division ratio.

(Second configuration example)
FIG. 4 shows a second configuration example of the digital signal processing circuit 113 of the digital broadcast relay apparatus shown in FIGS. 4, the same parts as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.
The digital intermediate frequency (IF) signal supplied from the analog / digital conversion circuit 112 is supplied to the mixers 1131a and 1131b. The IF signal supplied to the mixer 1131a is mixed with the local oscillation signal output from the fourth local oscillation circuit 1136, and converted into a digital baseband I signal via a low-pass filter (LPF) 1132a. The IF signal supplied to the mixer 1131b is mixed with the local oscillation signal obtained by phase-converting the local oscillation signal by the 90 ° phase shifter 1137a, and converted into a digital baseband Q signal through the LPF 1132b.

  Here, by making the filter characteristics of the LPF 1132a and the LPF 1132b steep, unnecessary signals such as adjacent channel signals can be removed. The converted digital baseband IQ signal is converted into a digital intermediate frequency by a quadrature modulation circuit constituted by mixers 1134a and 1134b and LPFs 1135a and 1135b, and then returned to an original analog signal in a digital / analog conversion circuit 114.

  In the second configuration example of the digital signal processing circuit 113 shown in FIG. 4, since the digitized IF signal is orthogonally demodulated and converted into a digital baseband IQ signal, the received signal itself is unbalanced or the down converter 111 is used. In addition, it is possible to correct the imbalance of the I signal Q signal generated in the analog / digital conversion circuit 112. For this reason, it is possible to create a transmission signal with higher quality than the first configuration example of the digital signal processing circuit 113 shown in FIG.

(Third configuration example)
FIG. 5 shows a third configuration example of the digital signal processing circuit 113 of the digital broadcast relay apparatus shown in FIGS. In FIG. 5, the difference from the second configuration example of the digital signal processing circuit 113 shown in FIG. 4 is that an FFT circuit 1138a and a subcarrier peak detection unit 1138b are added. In this figure, the same parts as those in FIG.

  The FFT circuit 1138a performs FFT processing on the digital baseband IQ signal that is the output of the quadrature demodulation circuit configured by the mixers 1131a and 1131b and the LPFs 1132a and 1132b, and divides the signal into signals for each subcarrier. At this time, when the digital baseband IQ signal to be FFT-processed has a desired frequency characteristic, the peak of each subcarrier appears at the output of the FFT circuit as shown in FIG. The relationship is orthogonal. However, when the digital baseband IQ signal to be FFT-processed does not have a desired frequency characteristic, since the peaks of the subcarriers are shifted as shown in FIG.

  Therefore, the subcarrier peak detector 1138b detects the frequency shift of the digital baseband IQ signal by detecting the peak of each subcarrier signal. The detected frequency shift is supplied to the frequency control unit 1139, and the frequency control unit 1139 generates a control signal for correcting the frequency shift. The generated control signal is supplied to the fourth local oscillation circuit 1136, and the fourth local oscillation circuit 1136 oscillates at a predetermined frequency in accordance with this control signal.

  As described above, the third configuration example further includes the FFT circuit 1138a and the subcarrier peak detection unit 1138b, and detects the peak of each subcarrier signal divided by the FFT processing, thereby enabling the digital baseband IQ. Signal frequency deviation is detected with high accuracy. With this configuration, the fourth local oscillation circuit 1136 can be finely adjusted. Therefore, it is possible to realize broadcast wave relay that takes into account the Doppler shift and frequency offset of the received wave.

(Fourth configuration example)
FIG. 7 shows a fourth configuration example of the digital signal processing circuit 113 of the digital broadcast wave repeater shown in FIGS. 7 is different from the third configuration example of the digital signal processing circuit 113 shown in FIG. 5 in that a CP (Continual Pilot) extraction unit 1138c is provided instead of the subcarrier peak detection unit 1138b. . In the figure, the same parts as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The FFT circuit 1138a performs FFT processing on the digital baseband IQ signal that is the output of the quadrature demodulation circuit configured by the mixers 1131a and 1131b and the LPFs 1132a and 1132b, and divides the signal into signals for each subcarrier. As shown in FIG. 8, CP extraction section 1138c extracts a CP signal from the signal divided for each subcarrier, and detects the frequency shift of the extracted CP signal. The detected frequency shift is supplied to the frequency control unit 1139, and the frequency control unit 1139 generates a control signal for correcting the frequency shift. The generated control signal is supplied to the fourth local oscillation circuit 1136, and the fourth local oscillation circuit 1136 oscillates at a predetermined frequency in accordance with this control signal.

  As described above, in the fourth configuration example of the digital signal processing circuit 113, FFT processing is performed on the quadrature demodulated digital baseband IQ signal, and the CP signal among the subcarrier signals is observed. Fine adjustment by the fourth local oscillation circuit 1136 is possible without observing a plurality of subcarrier signals and strictly setting the frequency of the first local oscillation circuit 117. This makes it possible to obtain accurate information such as when demodulation processing and propagation path estimation are performed by each compensation circuit. Therefore, the circuit scale can be simplified and reduced in size.

  Further, the modulation method of the CP signal is determined to be BPSK (Binary Phase Shift Keying), which is more accurate than data having a different modulation method depending on the subcarrier number or broadcast mode, and is provided in the data. Since there is no need to extract the SP from the time / subcarrier number like a SP (Scattered Pilot) signal, it is possible to detect the frequency deviation with high accuracy. In addition, since the frequency can be finely adjusted by the fourth local oscillation circuit 1136, it is possible to perform broadcast wave relay in consideration of the Doppler shift and frequency offset of the received wave.

(Fifth configuration example)
FIG. 9 shows a fifth configuration example of the digital signal processing circuit 113 of the digital broadcast relay apparatus shown in FIGS. In FIG. 9, the difference from the third or fourth embodiment of the digital signal processing circuit 113 shown in FIG. 5 or 7 is that a compensation circuit 113C is added. In this figure, the same parts as those in FIG. 5 or FIG.

  The frequency monitoring unit 1138 detects a frequency shift from the digital baseband IQ signal that is an output of the quadrature demodulation circuit configured by the mixers 1131a and 1131b and the LPFs 1132a and 1132b, and supplies the detected frequency shift to the frequency control unit 1139. The frequency control unit 1139 transmits to the fourth local oscillation circuit 1136 a control signal that corrects the frequency so that the operation of the compensation circuit 113C is optimized based on the detected frequency deviation, and the fourth local oscillation circuit 1136. Controls the oscillation frequency.

  Here, as described above with reference to FIG. 6, since the orthogonality of each subcarrier is maintained when the digital baseband IQ signal has a desired frequency component, the accuracy of channel estimation of the compensation circuit 113C described later is increased. Thus, a compensation circuit with higher compensation capability can be realized.

FIG. 10 is a diagram illustrating a configuration example of a compensation circuit 113 </ b> C having a multipath interference cancellation function provided in the fifth configuration example of the digital signal processing circuit 113.
The digital baseband IQ signal input to the compensation circuit 113C is compensated for delayed wave components in the FIR filters 113C1 and 113C2, and only the desired wave is output. Some of the outputs of the FIR filters 113C1 and 113C2 are distributed to the channel estimation unit 113C3, and the channel response is estimated to determine whether the delayed wave or the like is suppressed. The filter coefficient control unit 113C4 calculates the filter coefficients of the FIR filters 113C1 and 113C2 so as to suppress the delayed wave (multipath wave) based on the channel response estimated by the channel estimation unit 113C3, and sends the filter coefficients to the FIR filters 113C1 and 113C2. Output. At this time, if the frequency of the digital baseband IQ signal is adjusted to a desired frequency, the accuracy of channel estimation in the channel estimation unit 113C3 is improved, so that it is possible to efficiently suppress delay waves (multipath waves). It becomes possible.

  FIG. 11 is a diagram illustrating a configuration example of a compensation circuit 113 </ b> C having a sneak wave removal function provided in the fifth configuration example of the digital signal processing circuit 113.

  In FIG. 11, the digital baseband IQ signal input to the compensation circuit 113C is reduced in the number of replicas (replicas) of the transmission signal generated by the compensation circuit 113C to the receiving device, and received from the desired upper station. Only signal. Thereafter, the band is limited to a signal of only a desired channel through the BPF 113C7 and 113C8 and output.

  Part of the outputs of the BPFs 113C7 and 113C8 are input to the channel estimation unit 113C3. The channel estimation unit 113C3 that estimates the channel response estimates the channel response of the output signal, detects a wraparound component or multipath component of the output signal included in the output signal, and outputs it to the filter coefficient control unit 113C4. The filter coefficient control unit 113C4 calculates filter coefficients that suppress the wraparound component and the multipath component estimated by the channel estimation unit 113C3, generates replicas of the wraparound component and the multipath component, and supplies them to the FIR filters 113C9 and 113C10. Output.

  As described above, the FIR filters 113C9 and 113C10 generate and output replicas of the wraparound component and the multipath component by using a part of the outputs of the BPFs 113C7 and 113C8 as input signals. In this wraparound canceller, similarly to the multipath removal means, if the baseband IQ signal is adjusted to have a desired frequency component, the channel estimation accuracy is improved and the wraparound component and the multipath component are suppressed more efficiently. It becomes possible to do.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The block diagram which shows one Embodiment of the digital broadcast relay apparatus which concerns on this invention. The block diagram which shows another embodiment of the digital broadcast relay apparatus based on this invention. The figure which shows the 1st structural example of the digital signal processing circuit provided in the digital broadcast wave relay apparatus shown in FIG. The figure which shows the 2nd structural example of the digital signal processing circuit provided in the digital broadcast wave relay apparatus shown in FIG. The figure which shows the 3rd structural example of the digital signal processing circuit provided in the digital broadcast wave relay apparatus shown in FIG. The figure which shows the relationship between the peak of a subcarrier and the peak of FFT. The figure which shows the 4th structural example of the digital signal processing circuit provided in the digital broadcast wave relay apparatus shown in FIG. The figure which shows the example of extraction of CP subcarrier. The figure which shows the 5th structural example of the digital signal processing circuit provided in the digital broadcast wave relay apparatus shown in FIG. The figure which shows the structural example of the compensation circuit which has a multipath wave removal function. The figure which shows the structural example of the compensation circuit which has a wraparound wave removal function.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Digital broadcast wave relay apparatus, 10 ... Reception antenna, 11 ... Digital broadcast wave relay apparatus, 12 ... Transmission antenna, 111 ... Down converter, 112 ... Analog-digital conversion circuit, 113 ... Digital signal processing circuit, 114 ... Digital Analog conversion circuit, 115 ... up converter, 116 ... power amplifier (PA), 117 ... first local oscillation circuit, 118 ... second local oscillation circuit, 119 ... reference signal generation unit, 120 ... third local oscillation circuit DESCRIPTION OF SYMBOLS 1131 ... Digital down converter, 1132 ... Low pass filter (LPF), 1133 ... Band pass filter (BPF), 1134 ... Digital up converter, 1135 ... LPF, 1136 ... Fourth local oscillation circuit, 1138 ... Frequency Monitoring unit, 1139 ... frequency control unit, 1131a, 1131b ... mixer 1132a, 1132b... LPF, 1134a, 1134b... Mixer, 1135a, 1135b... LPF, 1137a, 1137b... 90 ° phase shifter, 1138a. 113C ... compensation circuit, 113C1, 113C2 ... FIR filter, 113C3 ... channel estimation unit, 113C4 ... filter coefficient control unit, 113C5, 113C6 ... mixer, 113C7, 113C8 ... BPF, 113C9, 113C10 ... FIR filter.

Claims (11)

A receiving means for receiving a radio frequency (RF: Ratio Frequency) signal of a digital broadcast wave by orthogonal frequency division multiplexing (OFDM);
First frequency conversion means for converting the received RF signal into an analog intermediate frequency (IF) signal based on a first local oscillation signal;
Analog / digital (A / D) conversion means for converting the analog IF signal converted by the first frequency conversion means into a digital IF signal based on the second local oscillation signal;
Digital signal processing means for performing signal processing on the digital IF signal digitally converted by the A / D conversion means based on the second local oscillation signal;
Digital / analog (D / A) conversion means for analog-converting the signal-processed digital IF signal based on the second local oscillation signal;
Second frequency conversion means for converting the analog IF signal analog-converted by the D / A conversion means into an RF signal based on the first local oscillation signal;
Re-transmission means for amplifying and re-transmitting the RF signal converted by the second frequency conversion means;
A reference signal generating means for generating a reference signal;
First local oscillation signal generating means for generating the first local oscillation signal based on the reference signal generated by the reference signal generating means;
And a second local oscillation signal generating means for generating the second local oscillation signal based on the reference signal generated by the reference signal generating means. Receiving means for receiving an RF signal of a digital broadcast wave by OFDM;
First frequency converting means for converting the received RF signal into an analog IF signal based on a first local oscillation signal;
A / D conversion means for converting the analog IF signal converted by the first frequency conversion means into a digital IF signal based on the second local oscillation signal;
Digital signal processing means for performing signal processing on the digital IF signal digitally converted by the A / D conversion means based on the second local oscillation signal;
D / A conversion means for analog-converting the signal-processed digital IF signal based on the second local oscillation signal;
Second frequency conversion means for converting the analog IF signal analog-converted by the D / A conversion means into an RF signal based on a third local oscillation signal;
Re-transmission means for amplifying and re-transmitting the RF signal converted by the second frequency conversion means;
A reference signal generating means for generating a reference signal;
First local oscillation signal generating means for generating the first local oscillation signal based on the reference signal generated by the reference signal generating means;
Second local oscillation signal generating means for generating the second local oscillation signal based on the reference signal generated by the reference signal generating means;
3. A digital broadcast wave repeater comprising: third local oscillation signal generating means for generating the third local oscillation signal based on the reference signal generated by the reference signal generating means. The first local oscillation signal generating means includes:
Controlling the output frequency of the first local oscillation signal to correspond to the channel interval of the digital broadcast wave;
2. The second local oscillation signal generating means controls the output frequency of the second local oscillation signal to an integral multiple of about 8.1698 (= 512/63) MHz. Digital broadcast wave relay device. The first and third local oscillation signal generating means are:
Controlling the output frequency of the first and third local oscillation signals to correspond to the channel interval of the digital broadcast wave;
3. The second local oscillation signal generating means controls the output frequency of the second local oscillation signal to an integer multiple of about 8.1698 (= 512/63) MHz. Digital broadcast wave relay device. The digital signal processing means includes
First digital frequency conversion means for converting a digital IF signal output from the A / D conversion means into a digital baseband signal based on a fourth local oscillation signal;
Filter means for generating a signal to be retransmitted from the digital baseband signal converted by the first digital frequency conversion means;
Second digital frequency conversion means for converting a signal to be retransmitted generated by the filter means into a digital IF signal based on the fourth local oscillation signal;
Frequency monitoring means for monitoring frequency characteristics of a signal to be retransmitted generated by the filter means;
3. The digital broadcast wave repeater according to claim 1, further comprising: a fourth local oscillation signal generating unit that generates the fourth local oscillation signal based on a monitoring result by the frequency monitoring unit. . The digital signal processing means includes
Orthogonal demodulation means for converting a digital IF signal output from the D / A conversion means into a digital baseband IQ signal based on a fourth local oscillation signal;
Orthogonal modulation means for converting the digital baseband IQ signal into a digital IF signal based on the fourth local oscillation signal;
Frequency monitoring means for monitoring frequency characteristics of the digital baseband IQ signal converted by the orthogonal demodulation means;
3. The digital broadcast wave repeater according to claim 1, further comprising: a fourth local oscillation signal generating unit that generates the fourth local oscillation signal based on a monitoring result by the frequency monitoring unit. . The frequency monitoring means includes
Fast digital Fourier transform (FFT) processing is performed on the digital baseband IQ signal converted by the orthogonal demodulating means to divide it into signals for each subcarrier, and a peak is detected for each of the divided subcarriers. 7. The digital broadcast wave repeater according to claim 6, wherein a deviation from a desired frequency is detected by using the digital broadcast wave repeater. The frequency monitoring means includes
The digital baseband IQ signal converted by the orthogonal demodulation means is subjected to FFT processing and divided into subcarrier signals, and a continuous pilot (CP) signal is extracted from the divided subcarrier signals. 7. The digital broadcast wave repeater according to claim 6, wherein a deviation from a desired frequency is detected.   7. The digital broadcast wave repeater according to claim 6, wherein the digital signal processing means further comprises compensation means for compensating the digital IF signal output from the quadrature demodulation means.   10. The digital broadcast wave repeater according to claim 9, wherein the compensation unit removes a multipath interference wave from the digital IF signal output from the quadrature demodulation unit.   10. The digital broadcast wave repeater according to claim 9, wherein the compensation unit removes a sneak wave from the digital IF signal output from the quadrature demodulation unit.

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