JP2007228342A - Receiver and transmitter-receiver using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of always obtaining satisfactory reception quality in both cases of the existence and the absence of an interference wave such as adjacent channel interference by adaptively making the characteristic of an analog filter variable in accordance with a receiving state. <P>SOLUTION: The receiver for receiving a high frequency signal used in a communication or broadcast system and frequency-converting the high frequency signal into a baseband signal is provided with filters 11 and 12 for performing band limitation of an analog baseband signal, AD converters 13 and 14 for converting analog signals outputted from the filters 11 and 12 into digital signals, and a demodulating part 27 for demodulating digital signals output from the AD converters 13 and 14, and varies the characteristics of the filters 11 and 12 by a control signal that corresponds to reception quality outputted from the demodulating part 27. Concretely, a BER (Bit Error Rate) or an EVM (Error Vector Magnitude) after demodulating a received signal is detected, and the characteristics of the filters are controlled so as to make the BER or EVM the best. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a receiving device that receives a high-frequency signal used in a communication or broadcasting system and converts the frequency into a baseband signal, and more particularly to a receiving device that receives a digitally modulated high-frequency signal, such as a portable terminal, and the like. The present invention relates to a technique that is effective when applied to a conventional transmission / reception apparatus.

  For example, the GSM system is used mainly in Europe and the like for mobile phones, and the WCDMA system (2 GHz band with transmission and reception bands of 1920-1980 MHz and 2110-2170 MHz: hereinafter WCDMA2000) has been started as the third generation system in Japan. It was. In the WCDMA system, 3GPP (3rd generation partnership project) formulates transmission / reception standards.

As shown in Non-Patent Document 1 and Patent Document 1, a direct conversion system that directly converts a received RF signal into an IQ signal in a baseband is used for a receiving circuit of a GSM or WCDMA mobile phone. The direct conversion method has an advantage that an intermediate frequency filter is not necessary because an intermediate frequency signal is not used. It is necessary to configure a frequency filter (hereinafter referred to as an analog filter). The IQ signal in the baseband is converted into a digital signal by an AD converter and then shaped by a FIR filter (hereinafter referred to as a digital filter). For example, Patent Documents 2 to 5 are examples of techniques for changing the characteristics of an analog filter.
US Pat. No. 5,483,691 JP-A-6-3104040 JP-A-11-205170 Japanese Patent Laid-Open No. 2003-8684 JP 2004-260528 A “A Single-Chip Quad-Band Direct-Conversion GSM / GPRS RF Transceiver with Integrated VCOs and Fractional-N Synthesizer”, ISSCC 2002, 14.2.

  By the way, according to the above-mentioned 3GPP receiver standard, the bandwidth of one channel of the WCDMA system is 5 MHz and the transmission chip rate is 3.84 MHz. The reception band varies depending on the region, band 1 (2.11 to 2.17 GHz), band 2 (2.11 to 2.17 GHz), band 3 (2.11 to 2.17 GHz), band 4 (2.11). To 2.17 GHz), band 5 (2.11 to 2.17 GHz), and band 6 (2.11 to 2.17 GHz) are allocated.

  In the 3GPP standard, adjacent channel interference is defined for all these bands. This is an interference wave received in the adjacent channel 5 +/− 3.84 MHz, and needs to be suppressed by the receiver. Further, since band 2, band 3, and band 5 overlap with the GSM band, the 3GPP receiver standard includes a “Narrow band blocking” item in which a GSM signal is an interference wave. This assumes an interference wave very close to the desired signal such as an offset frequency of 2.7 MHz from the center of the WCDMA signal. On the other hand, band 1, band 4, and band 6 are specified for adjacent channel interference with an offset frequency of 5 MHz, but there is no specification for adjacent interference waves such as narrow band blocking.

  In addition, the high-speed data communication method HSDPA (High Speed Data Packet Access) is defined in the 3GPP receiver standard. This is a multi-level modulation method using 16QAM or a method for obtaining a data transmission rate up to 14.4 Mbps by reducing the error correction coding rate.

  When configuring a receiving unit corresponding to the 3GPP receiving unit standard, it is necessary to suppress adjacent channel blocking and narrow band blocking with a baseband analog filter in the direct conversion receiving method. In the conventional general receiver, the characteristic of the analog filter is designed so that the maximum interference signal can be sufficiently suppressed regardless of whether or not the interference signal is received. For this reason, there is a problem that even when no interfering wave is received, EVM (Error Vector Magnitude) deteriorates due to the analog filter characteristics. When EVM deteriorates, it is conceivable that the reception sensitivity at the time of HSDPA reception may be reduced or reception may not be possible.

  Therefore, the present invention solves the above-mentioned problems and adaptively varies the characteristics of the analog filter according to the reception state, so that it is always good whether or not there is an interference wave such as adjacent channel interference. It is an object of the present invention to provide a reception technique that can obtain reception quality.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  For example, when no interference wave is received in an adjacent channel or the like, good values of BER and EVM can be obtained if the cutoff frequency of the analog filter is sufficiently higher than the modulation band. On the other hand, when adjacent channel interference or narrow band blocking is received, if the cutoff of the analog filter is high, the BER or EVM characteristics deteriorate due to the interference wave. For this reason, when there is interference in the adjacent channel, it is desirable to set the cutoff frequency of the analog filter low.

  Therefore, in the present invention, the bit error rate (BER) or EVM after demodulating the received signal is detected by the demodulation unit, and the filter characteristic of the analog unit is adaptively controlled so that the BER or EVM is the best. If the detected values of BER and EVM are better than the reference value, for example, the cutoff frequency of the analog filter is set high. On the other hand, if the detected values of BER and EVM are worse than the reference value, the cutoff frequency of the analog filter is set low. By setting in this way, BER and EVM higher than the reference value can be obtained. It is also possible to set the cut-off characteristics of the analog filter so as to optimize the detection values of BER and EVM.

  As another means, the analog filter is provided with different types of filters having different pole positions, such as a Butterworth filter and a notch filter. In this case, when no interference wave is received in the adjacent channel or the like, good values can be obtained for BER and EVM by using a Butterworth filter as the analog filter. On the other hand, when adjacent channel interference or narrow band blocking is received, a Butterworth filter and a notch filter are used for the analog filter, and the influence of the interference wave is removed to improve the BER or EVM characteristics.

  Therefore, in the present invention, the demodulation unit detects the BER or EVM after demodulating the received signal, and adaptively switches the filter characteristics of the analog unit so that the BER or EVM is the best. If the detected values of BER and EVM are better than the reference value, for example, a setting is made to turn on the notch filter in the analog portion. Conversely, if the detected values of BER and EVM are worse than the reference value, the analog section notch filter is set to be turned off. By setting in this way, BER and EVM higher than the reference value can be obtained. It is also possible to compare the BER, EVM, etc., when the notch filter is used and when not used, and to select the better BER, EVM.

  In addition to detection of reception quality by BER and EVM, filter characteristics may be controlled based on a CQI (Channel Quality Indicator) signal so that the CQI detection value becomes the best.

  In addition to the detection of reception quality by BER and EVM, when a dual mode receiver of WCDMA and GSM is used as a detection means of narrow band blocking, the GSM receiver is operated by a compressed mode or the like at the time of WCDMA reception. , It detects whether there is a disturbing GSM signal in the vicinity of the WCDMA reception signal. Good reception quality can be obtained by changing the cut-off frequency of the analog filter or turning on / off the notch filter using the detection result.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  According to the present invention, it is possible to adaptively vary the characteristics of an analog filter according to the reception state, and always obtain good reception quality whether or not there is an interference wave such as adjacent channel interference.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

(First embodiment)
FIG. 1 shows a block diagram of a receiving apparatus according to the first embodiment of the present invention. FIG. 1 shows a receiving apparatus that receives a digitally modulated signal. The receiving apparatus includes an antenna 1, a duplexer (DPX) 2, a low noise amplifier (LNA) 3, mixers 4, 5, and a 90 degree phase. Shifter (π / 2) 6, VCO 7, AGC amplifiers 8 and 9, filters (LPF: first filter) 11 and 12 for limiting the band of the analog baseband signal, and analog signals output from these filters 11 and 12 A / D converters 13 and 14 for converting into digital signals, a level detector (Det) 23, FIR filters 15 and 16, and the digital signals output from the AD converters 13 and 14 via the FIR filters 15 and 16 are demodulated. The demodulator 27 includes a control unit 17 that varies the characteristics of the filters 11 and 12 according to a control signal corresponding to the reception quality output from the demodulator 27. Various signals are inputted and outputted between configuration circuit.

  The various signals include the control signal 19 of the AGC amplifiers 8 and 9, the control signal 10 of the filters 11 and 12, the I / Q signal 28 to the level detector 23, the output signal 30 of the level detector 23, and the FIR filters 15 and 16. Control signal 25, demodulator 27 control signal 20, transmission signal 22 from the transmission system, and the like.

  Hereinafter, the operation of the receiving apparatus according to the present embodiment will be described. A radio high-frequency signal (hereinafter referred to as an RF signal) input from the antenna 1 is demultiplexed from the transmission signal 22 by the duplexer 2 and input to the circuit of the reception system 56. In the circuit of the reception system 56, the signal is amplified by the low noise amplifier 3, and is orthogonally detected by the oscillation signals from the VCO 7 and the 90-degree phase shifter 6 by the mixers 4 and 5, and I (In-phase) / Q (Quadrature-phase) Converted to a signal. The I / Q signals are gain-controlled by AGC amplifiers 8 and 9, respectively, unnecessary waves are removed by filters 11 and 12, and then converted to digital signals by AD converters 13 and 14, respectively. The digital I / Q signal 28 is input to the level detector 23, unnecessary waves are removed and waveform shaping is performed by the FIR filters 15 and 16, and demodulated by the demodulator 27.

  The demodulator 27 calculates BER, EVM, and the like corresponding to the quality of the received signal. When the calculation result is equal to or less than the reference value compared with the reference value, the control signal 20 is updated and transmitted to the control unit 17, and the control signal 10 for changing the characteristics of the filters 11 and 12 from the control unit 17. Update. If the quality of the received signal exceeds the reference value by these updates, the update of the control signals 20 and 10 is stopped, and the values finally obtained by the control signals 20 and 10 are set as the set values of the filters 11 and 12. . If the reference value is not reached, the setting values of the control signals 20 and 10 for obtaining the best received signal quality (BER and EVM) and the filters 11 and 12 given by the control signal are set.

  As another method, the reference signals are not set, and the control signals 20 and 10 can be varied within a predetermined range, and the best received signal quality can be obtained. The settings of the filters 11 and 12 may be set values.

  In the present embodiment, low-pass filters (LPF) such as Butterworth filters and Chebyshev filters can be used as the filters 11 and 12.

  According to this configuration, since the characteristics of the filters 11 and 12 are optimized based on the quality of the received signal such as BER or EVM, it is possible to always receive the signal with the optimum received signal quality.

  FIG. 2 shows a flowchart for setting filter characteristics in the present embodiment. After the start of reception (S101), the characteristics (cutoff frequency, etc.) of the filters 11 and 12 are set to default values (S102). Next, EVM, BER, etc. are measured by the demodulator 27 (S103) and compared with a reference value (S104). As a result of the comparison, when EVM, BER, etc. are below the reference value (low), the set value of the filter is updated, and EVM, BER, etc. are measured again by the demodulator 27. When this operation is repeated and EVM, BER, etc. become higher than the reference value (high), the setting of the filter ends (S105). Even if it does not exceed the reference value, when N trials set in advance are completed (S106), the setting value of the filter with the best EVM and BER is selected and the setting is completed (S107).

  In the present embodiment, as an example of adaptively varying the cutoff frequency such as a Butterworth filter as the characteristics of the filters 11 and 12, an effect in the case where there is an interference wave in the received signal and there is no interference wave will be described.

  FIG. 3 shows a characteristic diagram of the amplitude with respect to the frequency of the filter. A signal bandwidth 45 indicates a modulation bandwidth of a desired reception signal. In the WCDMA system, the signal bandwidth 45 is 1.92 MHz in the baseband (3.84 MHz in the RF band). The characteristics of the broken lines 46 and 47 are the frequency characteristics of the filters 11 and 12, the broken line 46 is the setting with the highest cutoff frequency, and the broken line 47 is the setting with the lowest cutoff frequency. A solid line 49 represents the interference wave of the adjacent channel. In the WCDMA system, adjacent channel interference exists at 5 MHz +/− 1.92 MHz.

  Considering the case where there is no (or very small) adjacent channel interference of the solid line 49, in order to pass the signal bandwidth 45 of the desired signal without signal loss, the characteristics of the filters 11 and 12 are reduced within the signal band. The characteristic of the broken line 46 may be used. The characteristics of the filters 11 and 12 can be set to the characteristics of the broken line 46 based on the algorithm shown in FIG. If the signal bandwidth 45 of the desired signal is passed without signal loss as indicated by the broken line 46 in FIG. 3, no distortion occurs in the amplitude characteristic and phase characteristic of the desired signal, so that the demodulator 27 has good EVM and BER characteristics. Can be obtained. Accordingly, it is possible to improve the reception sensitivity particularly in the HSDPA method using the 16QAM modulation method and the like and to receive at a high data rate up to 14.4 Mbps.

  Next, consider a case where a strong interference signal (solid line 49) is present in the adjacent channel. In this case, in order to sufficiently suppress the adjacent channel interference signal (solid line 49), the cut-off frequency of the filters 11 and 12 is lowered and set to a characteristic as shown by the broken line 47. The characteristics of the filters 11 and 12 can be set to the characteristics indicated by the broken line 47 based on the algorithm shown in FIG. If the filter characteristic indicated by the broken line 47 is used, the interference signal can be sufficiently suppressed, saturation of the AD converters 13 and 14 shown in FIG. 1 can be prevented, and the EVM and BER characteristics in the demodulator 27. Can be improved, and the minimum reception sensitivity at the time of normal call or HSDPA reception can be improved.

  Further, when the interference signal (solid line 49) is relatively low, the cutoff frequency of the filters 11 and 12 is broken from the broken line 47 to the broken line so that the EVM and BER of the demodulator 27 are best by the algorithm shown in FIG. 46 is set. Also in this case, it is possible to improve the minimum reception sensitivity at the time of normal call or HSDPA reception.

(Second Embodiment)
FIG. 4 is a block diagram of a receiving apparatus according to the second embodiment of the present invention. FIG. 4 shows a receiving apparatus that receives a digitally modulated signal. The receiving apparatus includes an antenna 1, a duplexer (DPX) 2, a low noise amplifier (LNA) 3, mixers 4, 5, and a 90 degree phase. Shifter (π / 2) 6, VCO 7, AGC amplifiers 8 and 9, filters (LPF: first filter) 11, 12 for limiting the band of the analog baseband signal, and filters (NF: second filter) 21, 24, AD converters 13, 14 for converting analog signals output from the filters 11, 12, 21, 24 to digital signals, level detectors (Det) 23, FIR filters 15, 16, and FIRs 15, 16 The demodulator 27 demodulates the digital signals output from the AD converters 13 and 14, and the filter 11 using a control signal corresponding to the reception quality output from the demodulator 27. Consists a control unit 17 for switching the 12,21,24, various signals are input and output between each component circuits.

  The various signals include the control signal 19 of the AGC amplifiers 8 and 9, the control signal 10 of the filters 11 and 12, the control signal 18 of the filters 21 and 24, the I / Q signal 28 to the level detector 23, and the level detector 23. There are an output signal 30, a control signal 25 of the FIR filters 15 and 16, a control signal 20 of the demodulator 27, a transmission signal 22 from the transmission system, and the like.

  Hereinafter, the operation of the receiving apparatus according to the present embodiment will be described. A radio high-frequency signal (hereinafter referred to as an RF signal) input from the antenna 1 is demultiplexed from the transmission signal 22 by the duplexer 2 and input to the circuit of the reception system 56. In the circuit of the reception system 56, the signal is amplified by the low noise amplifier 3, and is orthogonally detected by the oscillation signals from the VCO 7 and the 90-degree phase shifter 6 by the mixers 4 and 5, and I (In-phase) / Q (Quadrature-phase) Converted to a signal. The I / Q signals are gain-controlled by the AGC amplifiers 8 and 9, respectively, and unnecessary waves are removed by the filters 11 and 12 and the filters 21 and 24, and then converted into digital signals by the AD converters 13 and 14. The digital I / Q signal 28 is input to the level detector 23, unnecessary waves are removed and waveform shaping is performed by the FIR filters 15 and 16, and demodulated by the demodulator 27.

  The demodulator 27 calculates BER and EVM corresponding to the quality of the received signal. When the calculation result is equal to or less than the reference value compared with the reference value, the control signal 20 is updated and transmitted to the control unit 17, and the control signal 10 that changes the characteristics of the filter 11 is updated from the control unit 17. If the quality of the received signal exceeds the reference value due to these updates, the update of the control signals 20, 10, 18 is stopped, and the filters 11, 12 and the filters 21, 24 obtained by the control signals 20, 10, 18 are set. Is the set value. If the reference is not reached, the setting of the control signals 20, 10, and 18 for obtaining the best received signal quality and the filters 11, 12 and the filters 21, 24 given by the control signal are set.

  As another method, the control signals 20, 10, and 18 that can obtain the best received signal quality by changing the control signals 20, 10, and 18 within a predetermined range without setting a reference value and the control thereof. The settings of the filters 11 and 12 and the filters 21 and 24 given by signals may be set as set values.

  In this embodiment, an example in which the filters 21 and 24 are turned on and off by the control signal 18 is also possible. For example, a notch filter is used for the filters 21 and 24, and when the EVM and BER of the demodulator 27 are deteriorated by an adjacent channel interference wave, the adjacent interference signal is removed by turning on the filters 21 and 24. This configuration improves EVM and BER. When there is no adjacent interfering signal and the EVM and BER of the demodulator 27 are good, the filters 21 and 24 are turned off by the control signal 18 and the through mode is set. In this embodiment, the filters 11 and 12 are low-pass filters (LPF) such as Butterworth filters and Chebyshev filters, and the filters 21 and 24 are LPFs or filters whose pole positions are different from those of the filters 11 and 12 (for example, notch filters). Can be used.

  According to this configuration, the characteristics of the filters 11 and 12 and the filters 21 and 24 are optimized based on the quality of the received signal such as BER and EVM, so that the signal can always be received with the optimum received signal quality.

  FIG. 5 shows a flowchart for setting filter characteristics in the present embodiment. After starting reception (S201), the filters 21 and 24 are set to OFF (S202), and the EVM, BER, etc. are measured by the demodulator 27 (S203). Next, the filters 21 and 24 are set to ON (S204), and the EVM, BER, etc. are measured by the demodulator 27 (S205). Comparing EVM and BER when the filter is ON and OFF (S206), and setting the better one as the filter setting value (if ON, the filters 21, 24 are set to ON: S207, OFF is good In this case, the filters 21 and 24 are set to OFF (S208), and the filter setting is completed (S209).

  In the present embodiment, an example in which a notch filter is assumed as the characteristics of the filters 21 and 24 and the notch filter is turned ON / OFF by the control signal 18 will be described in the case where there is an interference wave in the received signal and none.

  FIG. 6 shows a characteristic diagram of the amplitude with respect to the frequency of the filter. A signal bandwidth 45 indicates a modulation bandwidth of a desired reception signal. In the WCDMA system, the signal bandwidth 45 is 1.92 MHz in the baseband (3.84 MHz in the RF band). The characteristic of the broken line 46 is the frequency characteristic of the filters 11 and 12, and the characteristic of the dotted line 48 is the frequency characteristic of the filters 21 and 24. A solid line 49 represents the interference wave of the adjacent channel. In the WCDMA system, adjacent channel interference exists at 5 MHz +/− 1.92 MHz.

  Considering the case where there is no (or very small) adjacent channel interference of the solid line 49, the characteristics of the filters 11 and 12 can be changed to the characteristics of the broken line 46 in order to pass the signal bandwidth 45 of the desired signal without signal loss. good. The characteristic of the filters 11 and 12 can be set to the characteristic of the broken line 46 based on the algorithm shown in FIG. When the signal bandwidth 45 of the desired signal is passed without signal loss as shown by the broken line 46 in FIG. 6, the amplitude and phase characteristics of the desired signal are not distorted, so that the demodulator 27 has good EVM and BER characteristics. Can be obtained. Accordingly, it is possible to improve the reception sensitivity particularly in the HSDPA method using the 16QAM modulation method and the like and to receive at a high data rate up to 14.4 Mbps.

  Next, consider a case where a strong interference signal (solid line 49) is present in the adjacent channel. In this case, in order to sufficiently suppress the adjacent channel interference signal (solid line 49), the filters 21 and 24 are turned on, and a characteristic such as a dotted line 48 is added. The characteristics of the filters 21 and 24 can be turned on based on the algorithm shown in FIG. If the filter characteristic indicated by the dotted line 48 is used, the interference signal can be sufficiently suppressed, saturation of the AD converters 13 and 14 shown in FIG. 4 can be prevented, and the EVM and BER characteristics in the demodulator 27. Can be improved, and the minimum reception sensitivity at the time of normal call or HSDPA reception can be improved.

(Third embodiment)
FIG. 7 shows a block diagram of a receiving apparatus according to the third embodiment of the present invention. FIG. 7 shows a receiving apparatus that receives a digitally modulated signal. The same reference numerals are assigned to the same blocks as those in the first embodiment (FIG. 1), and description thereof is omitted.

  The present embodiment is an example in which the FIR filters 15 and 16 are removed from the configuration of the first embodiment. In this embodiment, since there is no FIR filter, all the interference signals such as adjacent channel interference are removed by the filters 11 and 12. Other operations and effects are the same as those of the first embodiment.

  In the present embodiment, the performance of the filters 11 and 12 can always be fixed without using the control signals 10 and 20. In this case, for example, the filters 11 and 12 use LPFs such as Butterworth filters.

(Fourth embodiment)
FIG. 8 is a block diagram of a receiving apparatus according to the fourth embodiment of the present invention. FIG. 8 shows a receiving apparatus that receives a digitally modulated signal. The same blocks as those in the second embodiment (FIG. 4) are assigned the same reference numerals and explanations thereof are omitted.

  The present embodiment is an example in which the FIR filters 15 and 16 are removed from the configuration of the second embodiment. In this embodiment, since there is no FIR filter, the filters 11 and 12 and the filters 21 and 24 remove all interference signals such as adjacent channel interference. Other operations and effects are the same as those of the second embodiment.

  In the present embodiment, the performance of the filters 11 and 12 can always be fixed without using the control signals 10, 18, and 20, and the filters 21 and 22 can always be turned on for use. In this case, for example, the filters 11 and 12 use LPFs such as Butterworth filters, and the filters 21 and 24 use LPFs or filters having a pole position different from the filters 11 and 12 (for example, notch filters).

(Fifth embodiment)
FIG. 9 shows a block diagram of a receiving apparatus according to the fifth embodiment of the present invention. In FIG. 9, the same blocks as those in the second embodiment (FIG. 4) are assigned the same numbers, and description thereof is omitted.

  The present embodiment is an example provided with two receiving systems, a receiving system 56 and a receiving system 57. The receiving system 56 has the same configuration as that of the second embodiment. The reception system 57 includes a low-noise amplifier 63, direct conversion type mixers 64 and 65, a 90-degree phase shifter 66, a VCO 67, AGC amplifiers 68 and 69, filters 71 and 72, AD converters 73 and 74, a demodulation unit 77, and the like. Composed.

  The reception system 56 and the reception system 57 are reception systems that receive signals from different systems. For example, the reception system 56 receives the WCDMA system and the reception system 57 receives the GSM system. When the interference wave in the vicinity of the desired signal in the WCDMA reception system 56 is the GSM signal in the reception system 57, the reception system 57 is used to determine whether there is an interference wave in the vicinity of the desired signal in the reception system 56. can do.

  The determination is made based on a control signal 78 from the demodulator 77, for example. Based on this determination, when the control unit 17 determines that there is an interference wave in the vicinity of the received signal, the WCDMA reception system 56 turns on the filters 21 and 24 to remove the nearby interference wave. Further, the band characteristics can be compensated by changing the tap coefficients of the FIR filters 15 and 16 at the subsequent stage. On the other hand, if it is determined that there is no interference wave in the vicinity of the received signal, the filters 21 and 24 are turned off.

  According to the present embodiment, since it is determined using other reception systems whether or not nearby interference such as narrow band blocking interference has been received, accurate determination is possible. Also, if a nearby interference wave is received as a result of the determination, the filters 21 and 24 are turned on to eliminate the interference so that the input level of the AD converters 13 and 14 can be optimized and good reception characteristics can be obtained. There is an effect that can be realized.

(Sixth embodiment)
FIG. 10 shows a block diagram of a transmission / reception apparatus according to the sixth embodiment of the present invention. FIG. 10 shows a transmission / reception apparatus using a WCDMA terminal. This transmission / reception apparatus includes an antenna 1, a duplexer 2, a reception system 56, a control unit 17, a digital signal processing unit (baseband signal processing unit) 58, a transmission. The system 59, PA61, etc. are comprised. The configuration of the first to fourth embodiments is used for the reception system 56.

  In the operation of the transmission / reception apparatus according to the present embodiment, the reception signal received by the antenna 1 is demultiplexed from the transmission signal 22 by the duplexer 2 and input to the reception system 56. The output of the reception system 56 is input to the digital signal processing unit 58. On the other hand, transmission data output from the digital processing unit 58 is input to the transmission system 59. The output of the transmission system 59 is transmitted via the PA 61, the duplexer 2, and the antenna 1. In the present embodiment, it is obvious that the same effect as described in the first to fifth embodiments can be obtained.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention relates to a receiving device that receives a high-frequency signal used in a communication or broadcasting system and converts the frequency into a baseband signal, and more particularly to a receiving device that receives a digitally modulated high-frequency signal, such as a portable terminal, and the like. It is effective when applied to a conventional transmission / reception apparatus.

It is a block diagram which shows the receiver of 1st Embodiment in this invention. It is a flowchart which shows the case where the characteristic of a filter is set in the receiver of 1st Embodiment in this invention. In the receiving apparatus of 1st Embodiment in this invention, it is a characteristic view which shows the amplitude with respect to the frequency of a filter. It is a block diagram which shows the receiver of 2nd Embodiment in this invention. It is a flowchart which shows the case where the characteristic of a filter is set in the receiver of 2nd Embodiment in this invention. In the receiving apparatus of 2nd Embodiment in this invention, it is a characteristic view which shows the amplitude with respect to the frequency of a filter. It is a block diagram which shows the receiver of 3rd Embodiment in this invention. It is a block diagram which shows the receiver of 4th Embodiment in this invention. It is a block diagram which shows the receiver of 5th Embodiment in this invention. It is a block diagram which shows the transmission / reception apparatus of 6th Embodiment in this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Splitter, 3,63 ... Low noise amplifier, 4, 5, 64, 65 ... Mixer, 6, 66 ... 90 degree phase shifter, 7, 67 ... VCO, 8, 9, 68, 69 ... AGC amplifier 11, 12, 21, 24, 71, 72 ... filter, 13, 14, 73, 74 ... AD converter, 15, 16 ... FIR filter, 17 ... control unit, 23 ... level detector, 27, 77: Demodulator 10, 18, 19, 20, 25, 78 ... Control signal, 22 ... Transmission signal, 28 ... I / Q signal, 30 ... Output signal, 56, 57 ... Reception system, 58 ... Digital signal processor 59 ... transmission system, 61 ... PA.

Claims (6)

A receiving device that receives a high-frequency signal used in a communication or broadcasting system and converts the frequency into a baseband signal,
A first filter that limits the bandwidth of the analog baseband signal;
An AD converter that converts an analog signal output from the first filter into a digital signal;
A demodulator that demodulates the digital signal output from the AD converter,
A receiving apparatus, wherein the characteristic of the first filter is varied by a control signal corresponding to the reception quality output from the demodulator. A receiving device that receives a high-frequency signal used in a communication or broadcasting system and converts the frequency into a baseband signal,
A first filter and a second filter for performing band limitation of the analog baseband signal;
An AD converter that converts an analog signal output from the first filter and the second filter into a digital signal;
A demodulator that demodulates the digital signal output from the AD converter,
A receiving apparatus, wherein the second filter is switched using a control signal corresponding to reception quality output from the demodulator. A receiving device that receives a high-frequency signal used in a communication or broadcasting system and converts the frequency into a baseband signal,
Two reception systems are provided,
A first reception system that receives a signal of the first communication or broadcasting system includes a first filter and a second filter that limit a band of an analog baseband signal, and the first filter and the second filter. An AD converter that converts an analog signal output from the digital signal into a digital signal, and a demodulator that demodulates the digital signal output from the AD converter,
A second reception system that receives a signal of the second communication or broadcasting system can receive a signal that becomes an interference signal of the first reception system, and receives a signal that becomes an interference signal of the first reception system. When the signal cannot be received, it is determined that there is no interfering signal, the second filter of the first receiving system is set to OFF, and when a signal that becomes an interfering signal of the first receiving system is received, there is an interfering signal. A receiving apparatus that determines and sets the second filter of the first receiving system to ON. The receiving device according to claim 1, 2, or 3,
A receiving apparatus using a low-pass filter as the first filter. The receiving device according to claim 2 or 3,
A receiving apparatus using a notch filter as the second filter.   6. A transmission / reception apparatus using the receiving apparatus according to claim 1 and using a CDMA system as a communication system.

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