JP2008236414A - Digital signal receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the degradation of received signals over a wide range of electric field strength, starting from low electric field strength to strong electric field strength, at low cost. <P>SOLUTION: A digital signal receiver 1 has a weak electric field strength signal receiving system A, and a strong electric field strength signal receiving system B. In addition, the digital sinal receiver 1 also has receiving processors 5 and 6, which perform diversity synthetic processing by using output signals transmitted from the weak electric field strength signal receiving system A and the strong electric field strength signal receiving system B, if digital signals that have an electric field strength weaker than a specified threshold; meanwhile, it dose not perform diversity synthetic processings, if digital signals that have electric field strength stronger than the specified threshold. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a digital signal receiver that receives a digital signal.

  In recent years, digital signal receiving technology has been used in various fields such as in-vehicle digital broadcasting, mobile communication, wireless LAN, and Bluetooth (registered trademark), as well as receiving digital broadcasting for stationary television.

  Among these, in mobile digital broadcast reception such as in-vehicle digital broadcast and mobile communication, the electric field strength of the received signal (radio wave) varies greatly depending on the situation, so it is difficult to always maintain good reception characteristics. .

  For example, in the case of in-vehicle digital broadcasting, digital broadcasting signals in places with extremely high electric field strength, such as directly under Tokyo Tower, and digital broadcasting signals in places with extremely low electric field strength, such as areas far from radio wave sources. There is a need to solve the difficult technical problem of receiving both of these.

  In general, in-vehicle digital broadcasting is often specialized so that only a weak electric field strength signal can be received satisfactorily at the expense of reception characteristics of a strong electric field strength signal.

  With reference to FIG. 13, a configuration of a digital signal receiver generally used in in-vehicle digital broadcasting will be described.

  Normally, in order to support reception of OFDM (Orthogonal Frequency Division Multiplexing) signals, the digital signal receiver 1 has a diversity configuration having a plurality of antennas 41 as shown in FIG.

  Further, the digital signal receiver 1 includes a tuner 43 configured to perform frequency conversion processing, channel selection processing, amplification processing, and filtering processing on the signal received by the antenna 41, and an output from the tuner 43. A demodulation unit 45 configured to perform demodulation processing on the signal, a baseband processing unit 46 configured to extract digital information (baseband signal) from an output signal from the demodulation unit 45, and demodulation And a control unit 44 configured to output to the tuner 43 a control signal for keeping the electric field strength of an input signal (output signal from the tuner 43) to the unit 45 constant.

  Normally, in such a digital signal receiver 1, when a diversity configuration using four antennas is used, four sets of reception systems including the same antenna 41 and tuner 43 are used.

  In the digital signal receiver 1, four control signals are used as control signals fed back from the control unit 44 to the tuner 43 in order to control each tuner 43 separately.

  For example, the control unit 44 transmits a different control signal to each tuner 43 to automatically control the amplification factor of an intermediate frequency (IF) amplifier in each tuner 43, thereby An attempt is made to keep the electric field strength of the output signal from the tuner 43 (input signal to the demodulator 45) constant.

  However, there is a problem with the general digital signal receiver 1 in that the input signal to the demodulator 45 cannot be completely controlled only by automatic gain control based on the control signal transmitted from the controller 44.

  Normally, as shown in FIG. 14, when the electric field strength of the input signal to the intermediate frequency amplifier used in the tuner 43 is increased to some extent, the intermediate frequency amplifier exhibits nonlinear output characteristics.

  Therefore, when the electric field strength of the input signal to the tuner 43 increases to some extent, the control of the amplification factor by the control signal cannot fully control the intermediate frequency amplifier, and the output signal is distorted.

  That is, the conventional general digital signal receiver 1 has a problem in that the reception characteristic of the strong electric field strength signal is sacrificed when the reception system is specialized for receiving the low electric field strength signal. Several proposals have been made to remedy such problems.

  For example, in Patent Document 1, a proposal for a portable terminal that performs two-way communication has been made. However, in the technique according to such a proposal, when a strong electric field strength signal is received, the antenna switch is set in a direction in which the isolation is high (there is a problem). The invention is characterized by switching to the transmission side.

Other than this, a method of switching between a plurality of amplifiers having various amplification factors so that the output signal is not distorted regardless of the input signal of any electric field strength, or when receiving a strong electric field strength signal, A method of stopping the diversity operation and inserting an antenna attenuator into the reception path is known.
JP 2002-76956 A

  However, the conventional method described above has the following drawbacks.

  Since the method shown in Patent Document 1 switches the antenna switch to the transmission side when receiving a strong electric field strength signal, it effectively has no antenna for reception, and when receiving a strong electric field strength signal, There was a problem that sufficient reception sensitivity could not be obtained.

  Furthermore, since the method disclosed in Patent Document 1 does not have a diversity configuration, there is a problem that sufficient reception sensitivity cannot be obtained even when a low electric field strength signal is received.

  In other methods, the antenna system, the amplifier system, and the control system are complicated, so that the design is difficult and the manufacturing cost increases.

  Therefore, the present invention has been made in view of the above points, and is capable of reducing deterioration of a received signal in a wide electric field strength range from a low electric field strength signal to a strong electric field strength signal, and is relatively low. An object is to provide a digital signal receiver that can be realized at low cost.

  A first feature of the present invention is a digital signal receiver for receiving a digital signal, which is a medium / weak electric field strength signal receiving system, a strong electric field strength signal receiving system, and a digital signal having an electric field strength weaker than a predetermined threshold. Is received, diversity combining processing is performed using an output signal from the medium / weak electric field strength signal receiving system and an output signal from the strong electric field strength signal receiving system, and an electric field strength stronger than the predetermined threshold is obtained. The gist of the present invention is that the diversity combining process is not performed when a digital signal is received.

  In the first aspect of the present invention, it may be configured to determine whether to perform the diversity combining process based on a result of an analog-digital conversion process for the received digital signal.

  In the first aspect of the present invention, it may be configured to determine whether to perform the diversity combining process based on a result of a maximum ratio combining process for the received digital signal.

  According to this invention, when receiving a medium / weak electric field strength signal, the medium / weak electric field strength signal receiving system specialized for receiving the medium / weak electric field strength signal can receive a digital signal with high sensitivity. When receiving a strong electric field strength signal, the medium / weak electric field strength signal receiving system can be disconnected and a digital signal with little deterioration can be received only by the strong electric field strength signal receiving system specialized for receiving the strong electric field strength signal. .

  In the first feature of the present invention, a switch for switching connection and disconnection between the medium / weak electric field strength signal receiving system and the reception processing unit, and a digital signal having an electric field strength stronger than the predetermined threshold value are received The control unit may be configured to transmit a control signal instructing the switch to disconnect the medium / weak electric field strength signal receiving system.

  According to this invention, when receiving the strong electric field strength signal, the medium / weak electric field strength signal receiving system can be disconnected by switching the switch, so that the strong electric field strength signal receiving system specialized for receiving the strong electric field strength signal is provided. It is possible to receive a digital signal with little deterioration.

  In the first feature of the present invention, the medium / weak electric field strength signal receiving system includes a first tuner, and the strong electric field strength signal receiving system includes a second tuner, A control unit configured to transmit an amplification factor control signal for controlling the amplification factor of the second tuner so that the output level of the second tuner falls within a linear region in the input / output characteristics of the second tuner; You may have.

  According to this invention, even when a strong electric field strength signal is received, a signal of an appropriate level can be output from the second tuner.

  In the first feature of the present invention, the first tuner includes a first high frequency amplifier capable of controlling an amplification factor by the amplification factor control signal and a first intermediate frequency amplifier connected to a subsequent stage of the first high frequency amplifier. The second tuner includes a second high frequency amplifier capable of controlling an amplification factor by the amplification factor control signal and a second intermediate frequency amplifier connected to a subsequent stage of the second high frequency amplifier; The amplification factor of the high frequency amplifier may be larger than the amplification factor of the second high frequency amplifier.

  In the first feature of the present invention, the first tuner includes a first high frequency amplifier capable of controlling an amplification factor by the amplification factor control signal and a first intermediate frequency amplifier connected to a subsequent stage of the first high frequency amplifier. The second tuner includes a second high frequency amplifier capable of controlling an amplification factor by the amplification factor control signal and a second intermediate frequency amplifier connected to a subsequent stage of the second high frequency amplifier; The amplification factor of the intermediate frequency amplifier may be larger than the amplification factor of the second intermediate frequency amplifier.

  As described above, according to the present invention, it is possible to reduce deterioration of a received signal in a wide field strength range from a low field strength signal to a strong field strength signal, and it can be realized at a relatively low cost. A digital signal receiver can be provided.

(Digital signal receiver according to the first embodiment of the present invention)
The configuration of the digital signal receiver 1 according to the first embodiment of the present invention will be described with reference to FIGS. Hereinafter, a configuration using four antennas will be described as a configuration of the digital signal receiver 1 according to the present embodiment, but the present invention is not limited to such a configuration.

  Note that the term “(signal) electric field strength” in this specification includes the meaning of “(signal) received power”.

  As shown in FIG. 1, a digital signal receiver 1 according to the present embodiment includes a medium / low electric field strength signal receiving system A specialized for medium / low electric field strength signal (digital signal) reception, and a strong electric field strength signal. (Digital signal) A strong electric field strength signal receiving system B specialized for reception is provided.

  Furthermore, the digital signal receiver 1 according to the present embodiment includes demodulation units 5 a and 5 b, a baseband processing unit 6, and a control unit 4.

  The medium / low electric field strength signal receiving system A includes three sets of receiving paths, and each receiving path includes an antenna 1a, a switch 8, and a tuner (first tuner) 3a.

  The strong electric field strength signal receiving system B is composed of a pair of reception paths, and the reception path includes an antenna 1b and a tuner (second tuner) 3b.

  The antenna 1a and the antenna 1b are configured to receive a digital signal. The antenna 1a and the antenna 1b may be the same antenna or different antennas.

  The switch 8 switches the connection (ON) and disconnection (OFF) between the antenna 1a and the tuner 3a in the medium / weak electric field strength signal receiving system A in accordance with the control signal from the control unit, thereby The signal receiving system A is configured to be switched according to whether it is disconnected (OFF) or connected (ON).

  The digital signal receiver 1 according to the present embodiment receives an output signal and a strong electric field strength signal from the medium / weak electric field strength signal receiving system A when a digital signal having an electric field strength weaker than a predetermined threshold is received. The diversity combining process is performed using the output signal from the system B, and the diversity combining process is not performed when a digital signal having an electric field strength stronger than the predetermined threshold is received.

  The tuner 3a is configured to perform frequency conversion processing, channel selection processing, and amplification processing on the digital signal (medium / low electric field strength signal) received by the antenna 1a.

  Specifically, as shown in FIG. 2A, the tuner 3a includes a first-stage high-frequency amplifier (LNA: Low Noise Amplifier) 31a1 that does not include an automatic gain control circuit (AGC). A second-stage high-frequency amplifier (LNA / RF-AGC: Radio Frequency-AGC) 31a2, an automatic gain control circuit (AGC) 31a2, a BPF (Band Pass Filter) 32a, a channel selection circuit 33a, a BPF 34a, and an intermediate A frequency amplifier (IF AMP / IF-AGC) 35a and an LPF (Low Pass Filter) 36a are provided.

  The first-stage high-frequency amplifier 31a1 is configured to amplify the high-frequency signal from the antenna 1a.

  The second-stage high-frequency amplifier 31a2 performs amplification processing on the high-frequency signal amplified by the first-stage high-frequency amplifier 31a1 based on the high-frequency gain control signal transmitted from the control unit 4 (RF-AGC 41). It is configured.

  Here, the high-frequency amplifier 31a2 at the second stage may be any amplifier that can control the amplification factor by the high-frequency amplification factor control signal transmitted from the control unit 4 (RF-AGC 41), and is an automatic amplification factor control circuit (AGC). May not be included.

  The intermediate frequency amplifier 35a includes amplification processing (amplification rate control) for the output signal (intermediate frequency signal) from the BPF 34a based on the intermediate frequency amplification rate control signal transmitted from the control unit 4 (IF-AGC42). ). Here, the output signal from the tuner 3a in the medium / low electric field strength signal receiving system A is input to the baseband processing unit 6 through the demodulation unit 5a.

  The tuner 3b is configured to perform frequency conversion processing, channel selection processing, and amplification processing of a digital signal (medium / low electric field strength signal or strong electric field strength signal) received by the antenna 1b.

  Specifically, as shown in FIG. 2B, the tuner 3b includes a high-frequency amplifier (LNA) 31b1 that does not have an automatic gain control circuit (AGC), a BPF 32b, a channel selection circuit 33b, a BPF 34b, An intermediate frequency amplifier (IF AMP / IF-AGC) 35b and an LPF 36b are provided. In the present embodiment, the tuner 3b does not include a high-frequency amplifier having an automatic gain control circuit (AGC).

  The high frequency amplifier 31b1 is configured to amplify the high frequency signal from the antenna 1b.

  The intermediate frequency amplifier 35b includes amplification processing (amplification rate control) for the output signal (intermediate frequency signal) from the BPF 34a based on the intermediate frequency amplification rate control signal transmitted from the control unit 4 (IF-AGC42). ).

  Here, the output signal from the tuner 3b in the strong electric field strength signal receiving system B is input to the baseband processing unit 6 through the demodulation unit 5b.

The demodulating units 5a and 5b are configured to perform demodulation processing on output signals from the tuner 3a and the tuner 3b, respectively. As shown in FIG. 3, the demodulating units 5a and 5b are ADCs (Analog Digital Converter). ) Circuit 51, average electric field strength calculation unit 52, ADC maximum value detection unit 53, FFT (Fast Fourier Transform) circuit 54, pilot signal detection unit 55, and equalizer 56. ing.

  The average electric field strength calculation unit 52 calculates an average electric field strength within a predetermined period for a signal after analog / digital conversion (A / D conversion) is performed on the input signals from the tuners 3a and 3b, and the control unit 4 to transmit to.

  The ADC maximum value detection unit 53 calculates an output maximum value (ADC maximum value) within a predetermined period for a signal after analog / digital conversion (A / D conversion) is performed on the input signals from the tuners 3a and 3b. It is configured to detect and transmit to the control unit 4.

  The pilot signal detection unit 55 is configured to detect the electric field strength of the pilot signal from the output signal of the FFT circuit 54 and transmit it to the control unit 4.

  The baseband processing unit 6 is configured to extract digital information (baseband signal) from the output signals from the demodulation units 5a and 5b.

  As shown in FIG. 4, the baseband processing unit 6 includes an MPC (Maximum Ratio Combining) circuit 61 and a baseband processing circuit 62.

  The MPC circuit 61 performs maximum ratio combining processing on the output signals of the plurality of demodulation units 5a and 5b, calculates the combining ratio of each output signal used in the maximum ratio combining processing, and transmits it to the control unit 4. It is configured as follows.

  Specifically, when a digital signal having an electric field strength weaker than a predetermined threshold is received, the switch 8 is ON, and the medium / weak electric field strength signal receiving system is connected to the MPC circuit 61 of the baseband processing unit 6. Since the output signal from A is input, the MPC circuit 61 performs diversity combining processing using the output signal from the medium / weak electric field strength signal receiving system A and the output signal from the strong electric field strength signal receiving system B. Configured to do.

  On the other hand, when a digital signal having an electric field strength stronger than a predetermined threshold is received, the switch is turned OFF, and the output from the medium / weak electric field strength signal receiving system A is sent to the MPC circuit 61 of the baseband processing unit 6. Since no signal is input, the MPC circuit 61 is configured not to perform diversity combining processing.

  As shown in FIG. 5, the control unit 4 includes a switch control unit 4a and an automatic gain control unit 4b including an RF-AGC 41 and an IF-AGC.

  The switch control unit 4a turns on / off the switch 8 based on whether it receives a digital signal having an electric field strength weaker than a predetermined threshold or a digital signal having an electric field strength stronger than the predetermined threshold. It is configured to transmit a control signal for controlling OFF.

  That is, when a digital signal having an electric field strength stronger than a predetermined threshold is received, the switch control unit 4a transmits a control signal instructing the switch 8 to disconnect the medium / weak electric field strength signal receiving system A. To do.

  Specifically, the switch control unit 4a is configured to output the analog / digital conversion processing result in the ADC circuit 51 of the demodulation unit 5 (for example, the average electric field strength from the average electric field strength calculation unit 52 or the ADC maximum value detection unit 53). A control signal for controlling ON / OFF of the switch 8 is transmitted based on the ADC maximum value, the electric field strength of the pilot signal from the pilot signal detection unit 55, and the like. The switch control unit 4a is configured to transmit a control signal for controlling ON / OFF of the switch 8 based on the result of the maximum ratio combining process in the MRC circuit 61 of the baseband processing unit 6. .

  The automatic gain control unit 4b transmits to the tuner 3a an gain control signal for controlling the gain of the tuner 3a so that the output level of the tuner 3a falls within the linear region in the input / output characteristics of the tuner 3a. It is configured.

  The automatic gain control unit 4b transmits to the tuner 3b an gain control signal for controlling the gain of the tuner 3b so that the output level of the tuner 3b falls within the linear region in the input / output characteristics of the tuner 3b. It is configured as follows.

  Specifically, the RF-AGC 41 in the automatic gain control unit 4b refers to the average electric field strength from the average electric field strength calculation unit 52 to control the gain of the second-stage high-frequency amplifier 31a2 in the tuner 3a. The high frequency amplification factor control signal is transmitted.

  Also, the IF-AGC 42 in the automatic gain control unit 4b refers to the average electric field strength from the average electric field strength calculation unit 52, and controls the gain of the intermediate frequency amplifier 35a in the tuner 3a and the intermediate frequency amplifier 35b in the tuner 3b. For transmitting the intermediate frequency gain control signal.

  Hereinafter, an operation at the time of receiving a medium / low electric field strength signal and an operation at the time of receiving a strong electric field strength signal in the digital signal receiver 1 according to the present embodiment will be described.

  First, the operation at the time of receiving a medium / low electric field strength signal in the digital signal receiver 1 according to the present embodiment will be described.

  In such a case, since the switch 8 is ON, the digital signal receiver 1 according to the present embodiment uses the four antennas including the medium / low electric field strength signal receiving system A and the strong electric field strength signal receiving system B. Works as a configuration.

  Here, the medium / low electric field strength signal is a signal of an input level (electric field strength) that enters the linear region X1 of the input / output characteristics of the tuner 3a (intermediate frequency amplifier 35a) shown in FIG.

  In the middle / low electric field signal receiving system A, the middle / low electric field strength signal received by the antenna 1a is amplified by the first-stage high-frequency amplifier 31a1 and the second-stage high-frequency amplifier 31a2 of the tuner 3a. An appropriate level signal can be input to the frequency amplifier 35a.

  Further, by inputting an intermediate frequency amplification factor control signal to the intermediate frequency amplifier 35a of the tuner 3a and adjusting the amplification factor of the intermediate frequency amplifier 35a, the demodulation unit 5a has an appropriate level with little deterioration due to distortion. A signal can be input.

  Here, as shown in FIG. 7, in the strong electric field strength signal receiving system B, the input level in the tuner 3b (intermediate frequency amplifier 35b) is small, but this input level is the amplification characteristic of the tuner 3b (intermediate frequency amplifier 35b). Since it is located in the linear region of (input / output characteristics), although the input level in the demodulator 5b is small, the distortion of the output signal from the tuner 3b is small.

  Therefore, the digital signal receiver 1 according to the present embodiment, when receiving a medium / low electric field strength signal, the above-described four sets of receiving systems, that is, three sets of medium / low electric field strength signal receiving systems A and one set. By diversity combining the output signal from the strong electric field strength signal receiving system B, a digital signal with little deterioration can be received with high sensitivity.

  Secondly, an operation at the time of receiving a strong electric field strength signal in the digital signal receiver 1 according to the present embodiment will be described.

  Here, the strong electric field strength signal is a signal having an input level (electric field strength) that enters the saturation region Y1 of the input / output characteristics of the tuner 3a (intermediate frequency amplifier 35a) shown in FIG.

  When the input signal to the medium / low electric field strength receiving system A is increased to some extent and the control unit 4 performs the automatic gain control processing for the intermediate frequency amplifier 35a of the tuner 3a, the output level from the tuner 3a is shown in FIG. When it is determined to enter the saturation region Y1 shown, the control unit 4 transmits a control signal to the switch 8 to turn off the switch 8 and disconnect the reception paths in the three sets of medium / low electric field strength signal reception systems A. .

  As shown in FIG. 7, the strong electric field strength signal receiving system A uses the high frequency gain control signal from the control unit 4 so that the output level of the intermediate frequency amplifier 35b of the tuner 3b falls within the linear region X2. By controlling the amplification factor of the intermediate frequency amplifier 35b of the tuner 3b, it is possible to input an appropriate level signal with little distortion to the demodulator 5b.

  Therefore, the digital signal receiver 1 according to the present embodiment operates with a configuration using one antenna of the strong electric field strength signal receiving system B when receiving a strong electric field strength signal, and receives a digital signal with little deterioration. Can do.

  At this time, the switch control unit 4a of the control unit 4 is configured to determine that a strong electric field strength signal is received, for example, when the following conditions (1) to (5) are satisfied. It is also possible (see FIG. 8).

(1) The automatic gain control unit 4b provided in the control unit 4 minimizes the gain of the tuner 3a (the high frequency amplifier 31a and the intermediate frequency amplifier 35a) in the medium / low electric field strength signal receiving system A. .

(2) The analog / digital conversion (ADC) circuit 51 provided in the demodulator 5a outputs the maximum value (ADC maximum value) that the ADC can take.

(3) The states of (1) and (2) occur continuously.

(4) The output of the ADC circuit 51 provided in the demodulator 5b does not indicate a continuous peak value.

(5) The ratio of the weight of the strong electric field strength signal receiving system B and the weight of the medium / weak electric field strength signal receiving system A (based on the combination ratio from the MRC circuit 61) is larger than a certain threshold.

  Here, in the MRC circuit 61 provided in the baseband processing unit 6, the received signals from the antennas 1a and 1b are combined in accordance with the weight separately calculated for each antenna.

(Operation and effect of the digital signal receiver according to the first embodiment of the present invention)
According to the digital signal receiver 1 according to the first embodiment of the present invention, when receiving a medium / weak electric field strength signal, the medium / weak electric field strength signal receiving system A specialized for receiving the medium / weak electric field strength signal is provided. However, when receiving a strong electric field strength signal, the medium / weak electric field strength signal receiving system A is disconnected to receive a strong electric field strength signal specialized for receiving a strong electric field strength signal. Only the reception system B can receive a digital signal with little deterioration.

  According to the digital signal receiver 1 according to the first embodiment of the present invention, when receiving a strong electric field strength signal, the medium / weak electric field strength signal receiving system A can be disconnected by switching the switch 8. Only a strong electric field strength signal receiving system B specialized for receiving an electric field strength signal can receive a digital signal with little deterioration.

  According to the digital signal receiver 1 according to the first embodiment of the present invention, a signal of an appropriate level can be output from the tuner 3b even when a strong electric field strength signal is received.

(Digital signal receiver according to the second embodiment of the present invention)
With reference to FIGS. 9 and 10, a digital signal receiver according to a second embodiment of the present invention will be described. Hereinafter, the difference between the digital signal receiver 1 according to the second embodiment of the present invention and the digital signal receiver 1 according to the first embodiment will be mainly described.

  The difference between the digital signal receiver 1 according to the second embodiment of the present invention and the digital signal receiver 1 according to the first embodiment described above is that, as shown in FIG. The tuner 3b in FIG. 1 includes a high frequency amplifier 31b2 having an automatic gain control circuit (AGC).

  The high frequency amplifier 31b2 may be any amplifier that can control the amplification factor by the high frequency amplification factor control signal transmitted from the control unit 4 (RF-AGC 41), and does not have an automatic amplification factor control circuit (AGC). May be.

  Here, as shown in FIGS. 10A and 10B, the medium / low electric field strength signal is an input that causes the output level of the intermediate frequency amplifier 35a that falls within the linear region X1 of the input / output characteristics of the intermediate frequency amplifier 35a. This is a signal, that is, an input signal to the high-frequency amplifier 31a1 (or the high-frequency amplifier 31a2) of the input level that falls within the middle / low electric field strength signal region R1.

  In addition, as shown in FIGS. 10A to 10D, the strong electric field strength signal is an input signal that causes an output level of the intermediate frequency amplifier 35a that falls within the saturation region Y1 of the input / output characteristics of the intermediate frequency amplifier 35a (that is, , An input level high-frequency amplifier 31a1 or an input signal to the high-frequency amplifier 31a2 that does not fall within the medium / low electric field strength signal region R1, and an intermediate frequency that falls within the linear region X1 of the input / output characteristics of the intermediate-frequency amplifier 35b This is an input signal that causes an output level of the amplifier 35b (that is, an input signal to the high-frequency amplifier 31b2 having an input level that falls within the strong electric field strength signal region R2).

  As shown in FIGS. 10B and 10D, the digital signal receiver 1 according to the present embodiment includes an intermediate frequency amplifier when receiving a medium / weak electric field strength signal in the medium / weak electric field strength signal receiving system A. In the strong electric field strength signal receiving system A, the amplification factor of the high frequency amplifier 31a2 is set so that the output signal of the intermediate frequency amplifier 35b is not distorted when the strong electric field strength signal is received. )> (Amplification factor of the high-frequency amplifier 31b2).

  In the digital signal receiver 1 according to the present embodiment, as shown in FIGS. 10A and 10C, the intermediate frequency amplifier 35a and the strong electric field strength signal receiving system B in the medium / weak electric field strength signal receiving system A are used. The intermediate frequency amplifier 35b has the same input / output characteristics.

(Digital signal receiver according to the third embodiment of the present invention)
A digital signal receiver according to a third embodiment of the present invention will be described with reference to FIG. Hereinafter, the difference between the digital signal receiver 1 according to the third embodiment of the present invention and the digital signal receiver 1 according to the first embodiment will be mainly described.

  The difference between the digital signal receiver 1 according to the third embodiment of the present invention and the digital signal receiver 1 according to the first embodiment described above is that the tuner 3b in the strong electrolysis signal receiving system B is automatically amplified. A high frequency amplifier 31b2 having a control circuit (AGC), and an intermediate frequency amplifier 35a in the tuner a in the medium / weak electric field strength signal receiving system A and a tuner b in the strong electric field strength signal receiving system B. The intermediate frequency amplifier 35b has different input / output characteristics.

  The high frequency amplifier 31b2 may be any amplifier that can control the amplification factor by the high frequency amplification factor control signal transmitted from the control unit 4 (RF-AGC 41), and does not have an automatic amplification factor control circuit (AGC). May be.

  Here, as shown in FIGS. 11A and 11B, the medium / low electric field strength signal is an input that causes the output level of the intermediate frequency amplifier 35a that falls within the linear region X1 of the input / output characteristics of the intermediate frequency amplifier 35a. This is a signal, that is, an input signal to the high-frequency amplifier 31a1 (or the high-frequency amplifier 31a2) of the input level that falls within the middle / low electric field strength signal region R1.

  Further, as shown in FIGS. 11A and 11B, the strong electric field strength signal is an input signal (that is, an input signal that causes an output level of the intermediate frequency amplifier 35a that falls within the saturation region Y1 of the input / output characteristics of the intermediate frequency amplifier 35a). , An input level high-frequency amplifier 31a1 or an input signal to the high-frequency amplifier 31a2 that does not fall within the middle / low electric field strength signal region R1, and an intermediate frequency that falls within the linear region X2 of the input / output characteristics of the intermediate-frequency amplifier 35b This is an input signal that causes an output level of the amplifier 35b (that is, an input signal to the high-frequency amplifier 31b2 having an input level that falls within the strong electric field strength signal region R2).

  As shown in FIGS. 11B and 11D, the digital signal receiver 1 according to the present embodiment includes an intermediate frequency amplifier when receiving a medium / weak electric field strength signal in the medium / weak electric field strength signal receiving system A. In the strong electric field strength signal receiving system A, when the strong electric field strength signal is received, the output signal of the intermediate frequency amplifier 35b is not distorted (amplification of the intermediate frequency amplifier 35a). Rate)> (amplification rate of the intermediate frequency amplifier 35b).

  In the digital signal receiver 1 according to the present embodiment, as shown in FIGS. 11B and 11D, the high-frequency amplifier 31a2 in the medium / weak electric field strength signal receiving system A and the strong electric field strength signal receiving system B are used. The high frequency amplifier 31b2 has the same input / output characteristics.

(Digital signal receiver according to the fourth embodiment of the present invention)
A digital signal receiver according to the fourth embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 12, the digital signal receiver 1 according to the present embodiment includes a GPS (Global Positioning System) antenna 1c and GPS signal processing in the configuration of the digital signal receiver 1 according to the first embodiment described above. A part 101 and a car navigation system 100 including a decoder part and a display part are incorporated.

  The configuration of the digital signal receiver 1 according to the first embodiment included in the digital signal receiver 1 according to this embodiment shown in FIG. 12 is the same as that of the digital signal according to the second or third embodiment described above. It may be replaced with the signal receiver 1.

  Although the present invention has been described in detail using the above-described embodiments, it is obvious to those skilled in the art that the present invention is not limited to the embodiments described in this specification. The present invention can be implemented as modified and changed modes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Accordingly, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention.

It is a block diagram of the digital signal receiver which concerns on the 1st Embodiment of this invention. It is a functional block diagram of a tuner in the digital signal receiver according to the first embodiment of the present invention. It is a functional block diagram of a demodulator in the digital signal receiver according to the first embodiment of the present invention. It is a functional block diagram of a baseband processing unit in the digital signal receiver according to the first embodiment of the present invention. It is a functional block diagram of a control part in a digital signal receiver concerning a 1st embodiment of the present invention. It is a figure which shows an example of the input / output characteristic of the tuner contained in the medium / low electric field strength signal receiving system in the digital signal receiver which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the input / output characteristic of the tuner contained in the strong electric field strength signal receiving system in the digital signal receiver which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating an example of the switch control method in the digital signal receiver which concerns on the 1st Embodiment of this invention. It is a functional block diagram of a tuner (strong electric field strength signal receiving system) in a digital signal receiver according to a second embodiment of the present invention. It is a figure which shows an example of the input / output characteristic of the tuner in the digital signal receiver which concerns on the 2nd Embodiment of this invention. It is a figure which shows an example of the input / output characteristic of the tuner in the digital signal receiver which concerns on the 3rd Embodiment of this invention. It is a block diagram of the digital signal receiver which concerns on the 4th Embodiment of this invention. It is a block diagram of the digital signal receiver which concerns on a prior art. It is a figure which shows an example of the input / output characteristic of the tuner in the digital signal receiver concerning a prior art.

Explanation of symbols

10: Digital signal receivers 1a, 1b, 41 ... Antennas 3a, 3b ... Tuners 31a1, 31a2, 31b1, 31b2 ... High frequency amplifiers 32a, 34a, 32b, 34b ... BPF
33a, 33b ... tuning circuits 35a, 35b ... intermediate frequency circuits 36a, 36b ... LPF
4 ... Control unit 4a ... Switch control unit 4b ... Automatic gain control unit 41 ... RF-AGC
42 ... IF-AGC
5a, 5b ... demodulator 51 ... ADC circuit 52 ... average electric field strength calculator 53 ... ADC maximum value detector 54 ... FFT circuit 55 ... pilot signal detector 56 ... equalizer 6 ... baseband processor 61 ... MRC circuit 62 ... Baseband processing circuit 8 ... Switch 1c ... GPS antenna 100 ... Car navigation system 101 ... GPS signal processing unit

Claims (7)

A digital signal receiver for receiving a digital signal,
Medium / weak electric field strength signal receiving system,
A strong electric field strength signal receiving system,
When a digital signal having an electric field strength weaker than a predetermined threshold is received, diversity combining processing is performed using the output signal from the medium / weak electric field strength signal receiving system and the output signal from the strong electric field strength signal receiving system. The digital signal receiver is configured not to perform the diversity combining process when a digital signal having an electric field strength stronger than the predetermined threshold is received.   2. The digital signal receiver according to claim 1, wherein the digital signal receiver is configured to determine whether or not to perform the diversity combining process based on a result of an analog-digital conversion process on the received digital signal. .   The digital signal receiver according to claim 1, wherein the digital signal receiver is configured to determine whether or not to perform the diversity combining process based on a result of a maximum ratio combining process for the received digital signal. A switch for switching connection and disconnection between the medium / weak electric field strength signal receiving system and the reception processing unit;
When a digital signal having an electric field strength stronger than the predetermined threshold is received, the switch is configured to transmit a control signal instructing the switch to disconnect the medium / weak electric field strength signal receiving system. The digital signal receiver according to claim 1, further comprising a control unit. The medium / weak electric field strength signal receiving system includes a first tuner,
The strong electric field strength signal receiving system includes a second tuner,
An amplification factor control signal for controlling the amplification factor of the second tuner is transmitted to the second tuner so that the output level of the second tuner falls within a linear region in the input / output characteristics of the second tuner. The digital signal receiver according to claim 1, further comprising a configured control unit. The first tuner includes a first high frequency amplifier capable of controlling an amplification factor by the amplification factor control signal and a first intermediate frequency amplifier connected to a subsequent stage of the first high frequency amplifier,
The second tuner includes a second high frequency amplifier capable of controlling an amplification factor by the amplification factor control signal and a second intermediate frequency amplifier connected to a subsequent stage of the second high frequency amplifier,
6. The digital signal receiver according to claim 5, wherein an amplification factor of the first high frequency amplifier is larger than an amplification factor of the second high frequency amplifier. The first tuner includes a first high frequency amplifier capable of controlling an amplification factor by the amplification factor control signal and a first intermediate frequency amplifier connected to a subsequent stage of the first high frequency amplifier,
The second tuner includes a second high frequency amplifier capable of controlling an amplification factor by the amplification factor control signal and a second intermediate frequency amplifier connected to a subsequent stage of the second high frequency amplifier,
6. The digital signal receiver according to claim 5, wherein an amplification factor of the first intermediate frequency amplifier is larger than an amplification factor of the second intermediate frequency amplifier.

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