JP2007266811A - Receiver and electronic apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the reception sensitivity and the interference immunity of a receiver compatible with each other at a first frequency band being a desired frequency band by selecting an optimum filter circuit depending on an existing state of a disturbance signal. <P>SOLUTION: The receiver 5 for attaining the purpose above includes: a detection section 28 for detecting a reception level of the disturbance signal from a second filter circuit 11; and a control section 32 that connects an output of a switch circuit 8 to a position of a first filter circuit 9 when the reception level of the disturbance signal detected by the detection section 28 is a predetermined value or over, and connects the output of the switch circuit 8 to a position of the second filter circuit 11 when the reception level of the disturbance signal detected by the detection section 28 is less than the predetermined value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a receiving device that receives a high-frequency signal and an electronic apparatus using the receiving device.

  Hereinafter, a conventional receiving apparatus will be described with reference to FIG. In FIG. 7, a conventional receiving apparatus 1 includes a filter circuit 3 that is connected to the output side of the antenna 2 and passes a signal in the first frequency band, and a receiving circuit 4 that is connected to the output side of the filter circuit 3. Have As this filter circuit 3, a SAW (Surface Acoustic Wave) filter having a steep filter characteristic is used in order to sufficiently attenuate an interference signal that is present in a frequency band near the first frequency band and exceeds a predetermined value. It was.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2005-130279 A

  In the conventional receiving apparatus 1, since the filter circuit 3 needs to abruptly attenuate the interference wave very close to the desired waveband, the insertion loss (loss) of the first frequency, which is the desired signal, increases. Since the reception sensitivity of the device 1 deteriorates, it is difficult to achieve both anti-jamming performance and reception sensitivity.

  SUMMARY OF THE INVENTION Accordingly, the present invention aims to achieve both the reception sensitivity and the anti-jamming performance of the receiving apparatus in the first frequency band, which is the desired frequency band, by selecting an optimum filter circuit according to the presence state of the interfering signal. To do.

  In order to achieve the above object, a receiving apparatus according to the present invention includes an antenna terminal, a switch circuit connected to the antenna terminal, one of the switch circuits connected to the output side, and passes a signal in the first frequency band. And a first receiving circuit connected to the output side of the first filter circuit. Further, the receiving apparatus of the present invention is connected to the other output side of the switch circuit and passes a second frequency band signal including the first frequency band and wider than the first frequency band. And a second receiving circuit connected to the output side of the second filter circuit. Furthermore, the receiving apparatus according to the present invention includes a detector that detects the reception level of the interference signal from the second filter circuit, and a switch when the reception level of the interference signal detected by the detection unit is greater than or equal to a predetermined value. A control unit that connects the output of the circuit to the first filter circuit side and connects the output of the switch circuit to the second filter circuit side when the reception level of the interference signal detected by the detection unit is less than a predetermined value; Have.

  With the above configuration, the receiving apparatus of the present invention has a large insertion loss in the desired wave band but a large amount of attenuation in the disturbing wave band when there is an interference signal of a predetermined value or more in a frequency band near the first frequency band. By using the first filter circuit having a large value, this interference signal can be sufficiently suppressed. On the other hand, when there is no interference signal exceeding a predetermined value in the frequency band near the first frequency band, a second filter circuit is used which has a small attenuation amount in the interference wave band but a small insertion loss in the desired wave band. Thus, it is possible to improve the receiving sensitivity of the receiving device in the desired frequency band.

(Embodiment 1)
Embodiment 1 of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram of a receiving apparatus according to the first embodiment.

  The antenna 6 receives, for example, a television / radio broadcast wave having a frequency of 90 MHz to 770 MHz (used as an example of a high-frequency signal). The television / radio broadcast wave received by the antenna 6 is input to the antenna terminal 7 of the receiving device 5. This receiving device 5 selects only a desired channel from the input television / radio broadcast waves, converts it to a 500 kHz intermediate frequency signal, and outputs it to the demodulation circuit 13, as a video data and audio data, Output to the audio output unit.

  In FIG. 1, the receiving device 5 includes an antenna terminal 7 that connects the antenna 6 and the receiving device 5, a first switch circuit 8 that is connected to the antenna terminal 7, and one output side of the first switch circuit 8. And a first receiving circuit 10 connected to the output side of the first filter circuit 9. The receiving device 5 further includes a second filter circuit 11 connected to the other output side of the switch circuit 8 and a second receiving circuit 12 connected to the output side of the second filter circuit 11. Further, a demodulation circuit 13 is connected to the output sides of the first receiving circuit 10 and the second receiving circuit 12. An electronic device (not shown) on which the receiving device 5 is mounted is connected to a signal processing circuit (not shown) connected to the output side of the demodulation circuit 13 and to the output side of the signal processing circuit. A display unit (not shown) and an audio output unit (not shown).

  1, the first switch circuit 8 has an antenna 6 connected to the input terminal side, a first filter circuit 9 connected to one output terminal side, and a second filter circuit 11 connected to the other output terminal side. ing. The first switch circuit 8 is, for example, an SPDT (1-input 2-output) type gallium / arsenic switch.

  The first filter circuit 9 passes signals in the first frequency band. This first frequency band is, for example, the VHF band 7 channel or the VHF band 8 channel. The first filter circuit 9 includes, for example, a second switch circuit 14 connected to one output side of the first switch circuit 8, a third switch circuit 15 connected to the input side of the first receiving circuit 10, The second switch circuit 14 and the third switch circuit 15 are connected in parallel, and have a filter 16 for passing a 7-channel VHF band signal and a filter 17 for passing a 8-channel VHF band signal. The filter 16 and the filter 17 are provided in order to prevent unnecessary disturbing waves that are close to the desired channel from being supplied to the first receiving circuit 10. It includes several types of filters, such as a SAW filter that attenuates.

  The first receiving circuit 10 amplifies the signal from the first filter circuit 9 and frequency-converts the signal from the first gain control amplifier 18 using the signal from the first local oscillator 19. The first mixer 20, the first low-pass filter 21 for attenuating high-frequency noise contained in the signal from the first mixer 20, and the third gain control amplifier 22 for amplifying the signal from the first low-pass filter 21. And have.

  The second filter circuit 11 passes a signal in a second frequency band that includes the first frequency band and is wider than the first frequency band. For example, the second frequency band signals of the VHF band 6 channel, the VHF band 7 channel, the VHF band 8 channel, and the VHF band 9 channel are passed. The second filter circuit 11 is an LTCC (Low Temperature Co-fired Ceramics) filter, a dielectric filter, a discrete filter, etc. for attenuating an interference wave (for example, a cellular interference wave) having a frequency relationship away from a desired channel. Includes several types of filters. Compared with the first filter circuit 9, the second filter circuit 11 has a frequency band to be attenuated away from the desired frequency band and has a gentle filter characteristic, but has a small insertion loss of the desired wave band, and therefore has a low reception sensitivity. Can be reduced.

  Similarly to the first receiving circuit 10, the second receiving circuit 12 also amplifies the signal from the second filter circuit 11, and the signal from the second gain control amplifier 23 is second local. A second mixer 25 that performs frequency conversion using a signal from the oscillator 24, a second low-pass filter 26 that attenuates high-frequency noise contained in the signal from the second mixer 25, and a second low-pass filter 26 And a fourth gain control amplifier 27 for amplifying the signal. Further, the second reception circuit 12 includes a detection unit 28 that is connected between the second mixer 25 and the second low-pass filter 26 and detects the reception level of the signal from the second mixer 25. The detector 28 is connected to the output of the second mixer 25 and outputs a DC voltage corresponding to the signal level output from the second mixer 25. The control unit 32 controls the output of the first switch circuit to be connected to the first filter circuit side when the voltage output from the detection unit 28 is greater than a predetermined threshold voltage.

  The demodulator circuit 13 includes a first demodulator 29 that demodulates a signal from the first receiver circuit 10, a second demodulator 30 that demodulates a signal from the second receiver circuit 12, and a signal from the first demodulator 29. And a synthesizing unit 31 that synthesizes the signal from the second demodulating unit 30. Further, the demodulation circuit 13 has a control unit 32 connected to the output side of the detection unit 28.

  Hereinafter, a specific operation of the receiving device 5 will be described with reference to a flowchart shown in FIG.

  When the user selects the channel 7 of the VHF band, which is the first frequency band (S1), first, the output of the switch circuit 8 is detected by the control unit 32 in order to detect the level of the disturbing wave close to the desired wave channel. Is connected to the second filter circuit 11 side (S2). Then, the output of the second switch circuit 14 and the input of the third switch circuit 15 are connected to the side of the filter 16 that passes the signal of the VHF band 7 channel (S3). Next, the 2nd receiving circuit 12 selects the VHF band 8 channel which is an analog upper adjacent interference frequency among the signals which passed the 2nd filter circuit 11 (S4). Specifically, the second local oscillator 24 is controlled by serial data from the control unit 32 and set to a frequency corresponding to the selected channel. Then, the detection unit 28 outputs a voltage corresponding to the level of the VHF band 8-channel interference signal (S5). That is, the detector 28 detects the reception level of the interference signal in the frequency band adjacent to the high frequency side of the desired frequency band. Further, the control unit 32 compares the reception level of the VHF band 8-channel interference signal indicated by the output voltage from the detection unit 28 with a predetermined threshold (S6). As a result of the comparison in the control unit 32, when the reception level of the VHF band 8-channel interference signal is less than a predetermined threshold, the second reception circuit 12 outputs the analog lower side of the signal that has passed through the second filter circuit 11. Channel 6 of the VHF band, which is an adjacent interference frequency band, is selected (S7). Then, the detection unit 28 outputs a voltage corresponding to the level of the VHF band 6-channel interference signal (S8). That is, the detector 28 detects the reception level of the interference signal in the frequency band adjacent to the lower side of the desired frequency band. Further, the control unit 32 compares the reception level of the VHF band 6-channel interference signal indicated by the output voltage from the detection unit 28 with a predetermined threshold value (S9). As a result of the comparison in the control unit 32, when the reception level of the VHF band 6-channel interference signal is less than a predetermined threshold, the second reception circuit 12 uses the desired frequency band among the signals that have passed through the second filter circuit 11. The VHF band 7 channel is selected (S10), and the VHF band 7 channel signal is sent from the second receiving circuit 12 to the display unit via the signal processing circuit, and the VHF band 7 channel is displayed on the display unit. (S11).

  On the other hand, as a result of the comparison in the control unit 32 in step S6 or step S10, if the reception level of the disturbing signal is equal to or higher than a predetermined threshold value, or out of synchronization or BER (Bit Error Rate) degradation has occurred in step S11. In the case (S12), the output of the first switch circuit 8 is connected to the first filter circuit 9 side under the control of the control unit 32 (S13). Then, the first receiving circuit 10 selects the VHF band 7 channel, which is the desired frequency band that has passed through the first filter circuit 9 (S14), and the signal of the VHF band 7 channel is subjected to signal processing from the first receiving circuit 10. It is sent to the display unit through the circuit, and the VHF band 7 channel is displayed on the display unit (S15). If out-of-synchronization or BER (Bit Error Rate) degradation occurs in this step S15 (S16), the output of the switch circuit 8 is connected to the second filter circuit 11 side under the control of the control unit 32 (S17). ). And it returns to step S10 and the channel selection process of the 2nd receiving circuit 12 is repeated.

  As described above, the receiving device 5 of the present invention has a large insertion loss of the desired wave band when there is an interference signal of a predetermined value or more in a frequency band near the first frequency band, but the interference wave band By using the first filter circuit 9 having a large attenuation, this interference signal can be sufficiently suppressed. On the other hand, when there is no interference signal exceeding a predetermined value in the frequency band near the first frequency band, a second filter circuit is used which has a small attenuation amount in the interference wave band but a small insertion loss in the desired wave band. Thus, it is possible to improve the receiving sensitivity of the receiving device in the desired frequency band.

  When the output of the first switch circuit 8 is on the first filter circuit 9 side, the control unit 32 shuts off the power supply of the second receiving circuit, and the output of the first switch circuit 8 is on the second filter circuit 11 side. In some cases, it is desirable to shut off the power supply of the first receiving circuit. Thereby, the power consumption of the receiving device 5 can be reduced, and the electronic device in which the receiving device 5 is mounted can be used for a long time.

  Further, as shown in FIGS. 3A and 3B, the input level (P2) at the antenna terminal 7 at which the gain of the second gain control amplifier 23 starts the suppression operation, the gain of the first gain control amplifier 18 is suppressed. It is desirable to be lower than the input level (P1) at the starting antenna terminal 7. In other words, in the second receiving circuit 12 that performs reception level detection of the interference signal, the gain of the second gain control amplifier 23 is set to be low by setting the input level (P2) at the antenna terminal 7 at which the suppression operation starts to be low. When a level interference signal is input, the gain of the gain control amplifier 23 is suppressed, and the first mixer 20 is prevented from being distorted by the interference signal output from the second gain control amplifier 23. As a result, the level of the interference signal can be accurately detected in the detector.

  Furthermore, the detector 28 may detect the level of the interference signal based on the output signal of the second mixer 25 as shown in FIG. 4, or the second gain control amplifier 23 as shown in FIG. The level of the interference signal may be detected based on the output signal. As shown in FIG. 4, when the level of the interference signal is detected on the basis of the output signal of the second mixer 25, the detection circuit converts it into an intermediate frequency signal of 500 kHz, and detects the low frequency signal to handle the low frequency signal. Electricity becomes possible. As shown in FIG. 5, when the level of the interference signal is detected based on the output signal of the second gain control amplifier 23, detection is performed before conversion to the intermediate frequency signal, so that only the interference signal at the selected channel frequency is detected. In addition, since the total level of all the signals that have passed through the second filter circuit 11 can be detected, the time required for detecting the level of the interference signal can be shortened.

  The maximum gain (G2) of the second gain control amplifier 23 is preferably smaller than the maximum gain (G1) of the first gain control amplifier 15. That is, the distortion of the signal output from the second gain control amplifier 23 due to the interference signal is suppressed by reducing the amplification degree of the second gain control amplifier 23 in the second reception circuit that performs reception level detection of the interference signal. Can do.

  Further, it is desirable that the second gain control amplifier can be switched so that the maximum gain when detecting the interference signal is set small and the maximum gain when receiving the desired wave signal is set large. That is, when the detection unit 28 determines that the interference signal level is low, the reception sensitivity can be improved by switching the maximum gain of the second gain control amplifier 23 to be large.

  Furthermore, the receiving device 5 includes a third receiving circuit (not shown), and a first frequency band that is a desired frequency band using the third receiving circuit and the second receiving circuit 12 when an interference signal is detected. It is also possible to receive jamming signals existing in two frequency bands adjacent above and below and detect the reception levels of the jamming signals existing in these two frequency bands substantially simultaneously. Thereby, the interference signal detection time can be shortened.

  The receiving device 5 has a desired signal detection unit (not shown) that detects the reception level of the desired signal from the first filter circuit 9, and the control unit 32 detects the desired signal detected by the desired signal detection unit. The output of the switch circuit 8 may be connected to the first filter circuit 9 side or the second filter circuit 11 side based on the ratio between the received level and the received level of the interference signal detected by the detector 28. Thereby, the receiving device 5 can select a more optimal filter circuit according to the S / N (Signal to Noise ratio) ratio.

  The receiving device 5 has a second antenna terminal 33 connected between the switch circuit 8 and the second receiving circuit 12, as indicated by a broken line in FIG. 1, and the output of the switch circuit 8 is the first filter. In the case of the circuit 9 side, diversity reception may be performed using the signal received by the first receiving circuit 10 from the antenna terminal 7 and the signal received by the second receiving circuit 12 from the second antenna terminal 33. Thereby, the reception quality of the receiver 5 can be improved. Note that diversity combining methods such as carrier combining diversity and switching diversity can be considered.

  Furthermore, an electronic device (not shown) on which the receiving device 5 is mounted has a time measuring unit (not shown) for measuring time, and based on a signal indicating the time from the time measuring unit, a control unit 32 may be controlled so that the output of the switch circuit 8 is connected to the second filter circuit 11 side. For example, the control unit 32 controls so that the output of the switch circuit 8 is always connected to the second filter circuit 11 when analog broadcasting is abolished in 2011. As a result, for example, when there is no analog jamming signal, reception is always performed using the second receiving circuit 12, and it is not necessary to detect the analog jamming signal by the detection unit 28, and the control is simplified. At the same time, the reception sensitivity can be improved.

  The detection level of the interference signal in the detection unit is not performed every time a desired channel is selected, but it is possible to reduce the time required for detection of the interference signal by performing in advance during channel search.

  As shown in FIG. 6, the receiving device 5 has an input connected to the antenna terminal 7 and outputs SAW filter 16, SAW filter 17, and second filter circuit 11 instead of the switch circuit 8 and switch circuit 14. And a 1-input 3-output switch circuit 34 that is selectively connected to each other. As a result, the number of switch circuits connected between the antenna terminal 7 and the first receiving circuit 10 is reduced by one. Therefore, when the receiving device 5 receives a signal using the first receiving circuit 10, It can suppress that reception sensitivity deteriorates.

  In the present embodiment, a receiving apparatus that receives television / radio broadcast waves has been described as an example. However, the present invention can also be applied to a radio apparatus for mobile phones, a high-frequency signal receiving apparatus such as GPS, WLAN, and Bluetooth.

  The receiving device of the present invention can improve the receiving sensitivity of the receiving device in the first frequency band, which is the desired frequency band, by selecting an optimum filter circuit according to the presence state of the interference signal. It can be used for electronic devices such as TVs and mobile terminals.

Block diagram of receiving apparatus in embodiment 1 of the present invention Operation flowchart of receiving apparatus in embodiment 1 of the present invention Both (a) and (b) are relationship diagrams between the input level and gain of the gain amplifier according to the first embodiment of the present invention. The figure which shows arrangement | positioning of the detection part in Embodiment 1 of this invention Another figure which shows arrangement | positioning of the detection part in Embodiment 1 of this invention Another block diagram of the receiving apparatus in Embodiment 1 of the present invention Block diagram of conventional receiver

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Receiver 6 Antenna 7 Antenna terminal 8 Switch circuit 9 1st filter circuit 10 1st receiver circuit 11 2nd filter circuit 12 2nd receiver circuit 28 Detection part 32 Control part

Claims (18)

An antenna terminal;
A switch circuit connected to the antenna terminal;
A first filter circuit connected to one output side of the switch circuit and having a first frequency band as a passband;
A first receiving circuit connected to the output side of the first filter circuit;
A second filter circuit connected to the other output side of the switch circuit and having a second frequency band including the first frequency band and wider than the first frequency band as a pass band;
A second receiving circuit connected to the output side of the second filter circuit;
A detector for detecting a reception level of an interference signal from the second filter circuit;
When the reception level of the interference signal detected by the detection unit is greater than or equal to a predetermined value, the output of the switch circuit is connected to the first filter circuit side, and the reception level of the interference signal detected by the detection unit And a control unit that connects the output of the switch circuit to the second filter circuit when the value is less than a predetermined value. The receiving apparatus according to claim 1, wherein the second frequency band includes the first frequency band and a frequency band close to the first frequency band. When the output of the switch circuit is on the first filter circuit side, the control unit shuts off the power supply of the second reception circuit, and when the output of the switch circuit is on the second filter circuit side, The receiving device according to claim 1, wherein the receiving device is controlled so as to cut off a power source of the one receiving circuit. The first receiving circuit has a first gain control amplifier for amplifying a signal from the first filter circuit;
The second receiving circuit has a second gain control amplifier for amplifying a signal from the second filter circuit;
2. The receiving device according to claim 1, wherein an input level at the antenna terminal at which a gain of the first gain control amplifier starts a suppression operation is greater than an input level at the antenna terminal at which a gain of the second gain control amplifier starts a suppression operation. . The receiving device according to claim 1, wherein the detection unit detects a reception level of an interference signal based on an output signal of the second mixer. The receiving device according to claim 1, wherein the detection unit detects a reception level of an interference signal based on an output signal of the second gain control amplifier. The first receiving circuit has a first gain control amplifier for amplifying a signal from the first filter circuit;
The second receiving circuit has a second gain control amplifier for amplifying a signal from the second filter circuit;
The receiving device according to claim 1, wherein a maximum gain of the first gain control amplifier is larger than a maximum gain of the second gain control amplifier. 2. The receiving apparatus according to claim 1, wherein the second gain control amplifier is controlled by the control of the control unit such that a maximum gain when an interference signal is detected is different from a maximum gain when a desired signal is received. The first filter circuit includes a plurality of filter circuits connected in parallel, and an output of the switch circuit is selectively connected to an input of the plurality of filter circuits and an input of the second filter circuit. Item 4. The receiving device according to Item 1. A third receiving circuit, and using the third receiving circuit and the second receiving circuit to receive an interfering signal existing in two adjacent frequency bands above and below the first frequency band; The control unit detects the reception level of the interference signal present in the band substantially simultaneously, and the control unit connects the output of the switch circuit to the first filter circuit side or the second filter circuit side based on the detection result The receiving device according to claim 1. A desired signal detector for detecting a reception level of the desired signal from the first filter circuit;
The control unit, based on the reception level of the desired signal detected by the control desired signal detection unit and the reception level of the interference signal detected by the detection unit, the output of the switch circuit, the first filter circuit side, Alternatively, the receiving apparatus according to claim 1, wherein the receiving apparatus is connected to the second filter circuit side. Having a second antenna terminal connected between the switch circuit and the second receiving circuit, and controlling the output of the switch circuit to be connected to the first filter circuit side by the control unit; The receiving apparatus according to claim 1, wherein diversity reception is performed using a signal received by the first receiving circuit from the antenna terminal and a signal received by the second receiving circuit from the second antenna terminal. The receiving apparatus according to claim 1, wherein the control unit controls the output of the switch circuit to be connected to the second filter side based on a signal indicating time. The receiving apparatus according to claim 1, wherein the detection level detection of the interference signal in the detection unit is executed in advance during channel search. The receiving apparatus according to claim 1, wherein the first filter circuit is configured by a SAW filter, and the second filter circuit is configured by an LTCC filter or a discrete filter. An antenna terminal;
A switch circuit connected to the antenna terminal;
A first filter circuit connected to one output side of the switch circuit and having a signal in the first frequency band as a pass band;
A first receiving circuit connected to the output side of the first filter circuit;
A second filter circuit connected to the other output side of the switch circuit and having a signal in a second frequency band including the first frequency band and wider than the first frequency band as a pass band;
A second receiving circuit connected to the output side of the second filter circuit;
A detector for detecting a reception level of an interference signal from the second filter circuit;
When the reception level of the interference signal detected by the detection unit is greater than or equal to a predetermined value, the output of the switch circuit is connected to the first filter circuit side, and the reception level of the interference signal detected by the detection unit Is less than a predetermined value, a control unit for connecting the output of the switch circuit to the second filter circuit side,
A demodulation circuit connected to an output side of the first receiving circuit and the second receiving circuit;
A signal processing circuit connected to the output side of the demodulation circuit;
An electronic device having a display unit connected to the output side of the signal processing circuit. The demodulator circuit includes a demodulator to which outputs of the first receiver circuit and the second receiver circuit are supplied, an error corrector connected to one output side of the demodulator, and the other output of the demodulator And a detection unit inserted between the control unit and the control unit, and the control unit outputs the output of the switch circuit when the level of the output signal of the detector is equal to or higher than a predetermined value. The electronic device according to claim 16, wherein the electronic device is controlled to be connected to the second filter circuit side. The demodulator circuit includes a demodulator to which outputs of the first receiver circuit and the second receiver circuit are supplied, an error corrector connected to one output side of the demodulator, and an output of the error corrector; An error rate determiner inserted between the controller and the control unit, when the error rate determiner determines that the error rate determiner is greater than or equal to a predetermined value, the output of the switch circuit The electronic device according to claim 16, wherein the electronic device is controlled to be connected to the second filter circuit side.

Images