JP2006166009A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To excellently receive desired broadcasting waves at all times by eliminating the influence of interference waves or the like in a receiver provided with the reception antenna of a variable resonance frequency. <P>SOLUTION: The receiver 10 receives desired transmission signals as reception signals, the resonance frequency of the reception antenna 11 is adjustable, and the resonance frequency of the reception antenna 11 is adjusted by a DC control voltage outputted from a DC control voltage generation part 16c. As a result, a reception electric field condition identification part 16b controls the DC control voltage generation part corresponding to the reception electric field level of the reception signals received by the reception antenna. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiving apparatus including a receiving antenna having a variable resonance frequency, and more particularly to a receiving apparatus capable of controlling the resonance frequency of the receiving antenna.

  In general, a receiving antenna used in a mobile receiver is composed of a single element. In such a receiving antenna, a so-called unimodal VSWR (voltage standing wave ratio) that resonates only at a center frequency. It has characteristics. For this reason, in the frequency band excluding the vicinity of the center frequency, the reception sensitivity is greatly reduced. That is, in the vicinity of the lower limit frequency and the vicinity of the upper limit frequency, the VSWR is remarkably deteriorated, and the reception sensitivity is greatly reduced in the frequency band excluding the vicinity of the center frequency.

  In order to prevent such inconvenience, improve the sensitivity drop in the reception frequency band, and obtain the best VSWR according to the reception frequency, between the base end of the receiving antenna and the antenna input end of the receiver There is one in which a control voltage corresponding to a reception frequency is applied to the LC series resonance circuit via an LC series resonance circuit, and series resonance is generated based on a capacitance value corresponding to the reception frequency. That is, there is one in which a control voltage is applied to a variable capacitance element to control the resonance frequency of the receiving antenna (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 10-209897 (pages 3 to 6, FIGS. 1 to 6)

  Since the conventional receiving apparatus is configured as described above, the control voltage corresponding to the reception frequency is applied to the variable capacitance element to obtain a good VSWR characteristic in the reception frequency band (in other words, a single If the interference wave exists adjacent to the desired broadcast wave in the reception frequency band of the reception antenna, the VSWR characteristic is good in the reception frequency band. In spite of this, there is a problem that a desired broadcast wave cannot be received satisfactorily when the received electric field strength of the disturbing wave is high.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a receiving apparatus capable of always receiving a desired broadcast wave satisfactorily by removing the influence of an interference wave. .

  A receiving apparatus according to the present invention receives a desired transmission signal as a reception signal, a reception antenna whose resonance frequency can be adjusted, a frequency adjustment means for adjusting the resonance frequency, and a reception signal received by the reception antenna. Control means for controlling the frequency adjusting means in accordance with the received electric field level.

  According to the present invention, since the resonance frequency of the reception antenna is changed based on the reception electric field level of the reception signal received by the reception antenna, the desired transmission signal can be received satisfactorily without the influence of the interference wave. There is an effect that it can be received as a signal.

Embodiment 1 FIG.
First, referring to FIG. 1, a description will be given of a receiving device that receives a terrestrial digital TV broadcast wave (hereinafter simply referred to as a digital broadcast wave) as a broadcast wave. Can be applied. A receiving apparatus 10 shown in FIG. 1 is mounted on a moving body such as a vehicle, and receives a digital broadcast wave (transmission signal) as a reception signal as described later. The receiving device 10 includes a single element receiving antenna 11, and the receiving antenna 11 is connected to a receiver 12.

  As shown in FIG. 2, the receiving antenna 11 has a unimodal VSWR characteristic that resonates at the center frequency f0, and the VSWR deteriorates in the vicinity of the lower limit frequency fL and the upper limit frequency fH. For this reason, the receiving antenna 11 is provided with a variable reactance element 11a, and a DC control voltage is applied to the variable reactance element 11a to control the resonance frequency of the receiving antenna 11 as described later. That is, as shown in FIG. 3, a DC control voltage is applied to the variable reactance element 11a to move the center frequency (resonance frequency) along the frequency axis, as if widening the reception frequency band to improve the VSWR characteristics. I have to.

  By the way, the domestic terrestrial digital TV broadcast ISDB-T (Integrated Service Digital Broadcasting-Terrestrial) is in a transition period from the current domestic terrestrial analog broadcast, and until 2011, both digital broadcast and analog broadcast will be broadcast. Yes (simal broadcast). At present, it is specified that analog broadcasting uses frequencies from 90 MHz to 108 MHz, 170 MHz to 194 MHz, 192 MHz to 222 MHz, 470 MHz to 770 MHz, and digital broadcasting uses frequencies from 470 MHz to 770 MHz.

  Under such circumstances, there is a channel that transmits an analog broadcast wave adjacent to a channel that transmits a digital broadcast wave. For example, as shown in FIG. The analog broadcast wave A1 (analog video wave AV1 and analog audio wave AS1) exists on the lower frequency side than the wave D, and the analog broadcast wave A2 (analog video wave AV2 and analog audio wave) on the higher frequency side than the digital broadcast wave D. AS2) may be present.

  At present, the transmission output (transmission power) of the digital broadcast wave is set lower than the transmission power of the analog broadcast wave so as not to hinder the reception of the analog broadcast wave. When the analog broadcast waves A1 and A2 exist, if the digital broadcast wave D is received, the analog broadcast wave A1 or A2 becomes an interference wave and the digital broadcast wave D cannot be received satisfactorily.

  Therefore, in order to receive the digital broadcast wave D satisfactorily even if the analog broadcast wave A1 or A2 exists as an interference wave, the illustrated receiving apparatus 10 has the following configuration. In FIG. 1, a receiver 12 includes an electronic tuning circuit 13, a signal processing circuit (demodulation means) 14, an error detection unit (error detection means) 15, and a control circuit 16. The electronic tuning circuit 13 has a high frequency automatic gain. A control circuit (RF-AGC: high frequency gain means) 13a, a first mixer (mixer) 13b, a SAW (surface acoustic wave) filter 13c, an intermediate frequency automatic gain circuit (IF-AGC: intermediate frequency gain means) 13d, and A second mixer 13e is provided. The signal processing circuit 14 includes an A / D (analog / digital) conversion unit 14a and a signal processing unit 14b. The control circuit 16 includes a reception frequency control unit 16a, a reception electric field condition identification unit (control means) 16b, and A DC control voltage generator (frequency adjusting means) 16c is provided.

  In the illustrated receiving apparatus 10, the signal level of a digital broadcast wave (that is, an RF signal) received by the receiving antenna 11 is adjusted by the RF-AGC 13 a, and then the first intermediate frequency ( IF) signal. In the first IF signal, the interference wave is removed by the SAW filter 13c, and the signal level is adjusted again by the IF-AGC 13d. The output of the IF-AGC 13 d is converted into a second IF signal by the second mixer 13 e, and this second IF signal is input to the signal processing circuit 14.

  In the signal processing circuit 14, the A / D converter 14a first A / D converts the second IF signal into a digital signal, and the signal processor 14b performs predetermined signal processing on the digital signal to generate a video signal and An audio signal (demodulated signal) is obtained, and the video signal is output to the CRT 17 and displayed as a video. On the other hand, the audio signal is output to the speaker 18 and output from the speaker 18 as audio.

  The signal processing unit 14 b performs error detection and error correction in signal processing, and the number of errors is given to the error detection unit 15. When the error detection unit 15 detects the number of errors, an error detection signal corresponding to the number of errors is given to the reception electric field state identification unit 16b. The reception electric field condition identification unit 16b receives an RF level signal and an IF level signal representing the RF level and IF level from the RF-AGC 13a and IF-AGC 13d, respectively. In 16b, the received electric field state signal indicating the received electric field state is output to the DC control voltage generating unit 16c in accordance with the error detection signal, the RF level signal, and the IF level signal.

  On the other hand, in the reception frequency control unit 16a, when the user performs a reception frequency selection operation, the first and second mixers 13b are selected to select a reception frequency (that is, a channel) selected according to the reception frequency selection operation. And 13e, and a reception frequency selection signal is given to the DC control voltage generator 16c. Then, the DC control voltage generator 16c generates a DC control voltage based on the received electric field state signal and the received frequency selection signal, and supplies the DC control voltage to the variable reactance element 11a.

Next, the operation will be described.
Referring to FIGS. 1 and 5, when receiving apparatus 10 is turned on and the user selects a desired reception frequency (that is, a channel) by a reception frequency selection operation, reception frequency control unit 16a responds to the reception frequency selection operation. The first and second mixers 13b and 13e are controlled, and a reception frequency selection signal is given to the DC control voltage generator 16c. The DC control voltage generator 16c applies a DC control voltage corresponding to the reception frequency selection signal to the variable reactance element 11a to adjust the resonance frequency of the reception antenna 11.

  FIG. 5 is a diagram showing the reception frequency band of the reception antenna 11 when the resonance frequency is adjusted by the reception frequency selection operation. In the illustrated example, in addition to the digital broadcast wave D which is a desired channel within the reception frequency band, FIG. In addition, the analog audio wave AS1 of the analog broadcast wave A1 exists as an interference channel (that is, an interference wave) in the low frequency side channel.

  Referring also to FIG. 6, in the state shown in FIG. 5, when the RF-AGC 13 a receives a reception output (RF signal) from the reception antenna 11, even if the reception electric field level of the digital broadcast wave D is optimal, it is an interference wave. Since the received electric field level of a certain analog broadcast wave A1 (analog audio wave AS1) is high (see FIG. 6A), the received electric field level is assumed to be a strong received electric field level when the received electric field level of the analog broadcast wave A1 is added. As a result, the reception electric field level of the RF signal is lowered (see FIG. 6B).

  The output of the RF-AGC 13a is converted into a first IF signal by the first mixer 13b and applied to the SAW filter 13c, where the interference wave component is removed and the digital broadcast wave component is converted to IF-AGC 13d. Given to. The IF-AGC 13d acts to increase the received electric field level of the digital broadcast wave component, assuming that the received electric field level of the digital broadcast wave component is too low due to the level suppression of the RF-AGC 13a (FIG. 6 (c). )reference). However, when the received electric field level of the digital broadcast wave component is increased by adjusting the gain of the IF-AGC 13d, the noise component N is unavoidably amplified as shown in FIG. Noise ratio) decreases, and errors generated when signal processing is performed by the signal processing circuit 14 increase, resulting in a situation in which a desired digital broadcast wave cannot be received satisfactorily.

  On the other hand, as shown in FIG. 7, the channels adjacent to the desired digital broadcast wave (desired channel) D1 may be digital broadcast waves D2 and D3 (in the illustrated example, the low frequency side of the digital broadcast wave D1). If there is an adjacent digital wave D2 and an adjacent digital wave D3 is present on the high frequency side) and the digital broadcast wave D1 is received, if the reception frequency band is wide, the noise component is suppressed as described later. This makes it difficult to receive a desired digital broadcast wave satisfactorily.

  Referring to FIG. 8, in the state shown in FIG. 7, that is, assuming that the digital broadcast waves D1, D2 and D3 shown in FIG. 8A are input to the RF-AGC 13a, the RF-AGC 13a is digital. If the reception electric field level of the broadcast wave D1 is sufficiently high, the reception electric field levels of the adjacent digital broadcast waves (that is, the interference waves here) D2 and D3 are added, so that the total reception electric field level is the saturation electric field level of the RF-AGC 13a. Thus, when the total received electric field level is equal to or higher than the saturation electric field level, the noise component N due to the saturation state is added when the gain adjustment is performed by the RF-AGC 13a ( (Refer FIG.8 (b)).

  The output of the RF-AGC 13a is converted into a first IF signal by the first mixer 13b and applied to the SAW filter 13c, where adjacent digital broadcast waves D2 and D3 which are interference wave components are removed, Broadcast wave D1 is applied to IF-AGC 13d. In the IF-AGC 13d, gain adjustment is performed, for example, to further reduce the reception electric field level of the digital broadcast wave D1 (see FIG. 8C). Then, for example, an output having a reception electric field level shown in FIG. 8D is transmitted from the IF-AGC 13d.

  However, when the RF-AGC 13a is saturated, the noise component N cannot be removed (see FIG. 8D), and as a result, the C / N ratio (carrier-to-noise ratio) decreases, and the signal Errors that occur when signal processing is performed in the processing circuit 14 increase, and as a result, a situation in which the desired digital broadcast wave D1 cannot be satisfactorily received occurs.

  Therefore, as described later, the received electric field state identification unit 16b controls the DC control voltage generation unit 16c to adjust the DC control voltage according to the RF level signal, the IF signal, and the error detection signal, as described later. (By changing), the resonance frequency of the reception antenna 11 is changed, the reception frequency band is shifted along the frequency axis, and the influence of the interference wave is removed.

  Referring to FIG. 9, the received electric field state identification unit 16b includes an error determination unit 21, first and second comparison units (comparison means) 22 and 23, an electric field determination unit (first and second adjustment unit) 24, and An output necessity determination unit (output determination means) 25 is provided, the error determination unit 21 is connected to the above-described error detection unit 15, and the output necessity determination unit 25 is connected to the DC control voltage generation unit 16c. .

  Referring also to FIG. 10, the RF level signal and the IF level signal are given to the first and second comparison units 22 and 23, respectively. In the first comparison unit 22, the RF level signal and a preset RF level threshold value are provided. Compared with Th1, when RF level> Th1, a high level signal is output as the first comparison result signal (when RF level ≦ Th1, the first comparison is performed) A low level signal is output as a result signal). On the other hand, the second comparison unit 23 compares the IF level signal with a preset IF level threshold Th2, and if IF level> Th2, outputs a high level signal as a second comparison result signal, and IF If level ≦ Th2, a low level signal is output as the second comparison result signal.

  These first and second comparison result signals are sent to the electric field determination unit 24. When the first comparison result signal is at a high level (that is, when the RF level is at a high level), step ST1. Subsequently, it is determined whether or not the second comparison result signal is at a high level (that is, whether or not the IF level is at a high level: step ST2). Then, in the electric field determination unit 24, when the IF level is the low level (not the high level), it is determined that the adjacent disturbance due to the analog broadcast wave exists (first determination: step ST3). On the other hand, if the IF level is high, it is determined that the received strong electric field level state is generated by the adjacent digital broadcast wave (second determination: step ST4). That is, it is determined that the RF-AGC 13a is in a saturated state. In the electric field determination unit 24, when the first determination is made, a first voltage control signal (first frequency adjustment signal) indicating that the resonance frequency is slightly shifted is sent (step ST5), and the second determination is made. Then, a second voltage control signal (second frequency adjustment signal) indicating that the resonance frequency is largely shifted is transmitted (step ST6).

  When the number of detected errors indicated by the error detection signal provided from the error detection unit 15 exceeds a predetermined number of errors, the error determination unit 21 performs error determination and provides an error determination signal to the output necessity determination unit 25. When the output necessity determination unit 25 receives the error determination signal, the first or second voltage control signal is supplied to the DC control voltage generation unit 16c. Then, the DC control voltage generator 16c generates a DC control voltage corresponding to the first or second voltage control signal, and applies the DC control voltage to the variable reactance element 11a.

  When a DC control voltage corresponding to the first voltage control signal is applied to the variable reactance element 11a, for example, as shown in FIG. 11, the resonance frequency f0 of the receiving antenna 11 is slightly shifted to the high frequency side (for example, FIG. 11 As shown in FIG. 4, when the resonance frequency is shifted to the upper limit of the band of the digital broadcast wave D (the resonance frequency is shifted by the first amount), an interference wave (analog audio wave SA1) is generated in the reception frequency band of the reception antenna 11. Abundance is low.

  As described above, if the resonance frequency of the reception antenna 11 is shifted to the high frequency wave side, the reception electric field level of the digital broadcast wave D is slightly reduced, but the influence of the interference wave is reduced. The number of errors during processing is reduced, and there is no problem in receiving digital broadcast waves.

  As shown in FIG. 12, in addition to the digital broadcast wave D which is a desired channel within the reception frequency band, an analog audio wave of the analog broadcast wave A2 as a disturbing channel (that is, a disturbing wave) in the channel on the higher frequency side. When AS2 exists, the resonance frequency f0 may be shifted to the low frequency side so that the interference wave (analog sound wave SA2) does not exist within the reception frequency band of the reception antenna 11.

  On the other hand, when a DC control voltage corresponding to the second voltage control signal is applied to the variable reactance element 11a, the resonance frequency f0 of the receiving antenna 11 is greatly shifted (for example, as shown in FIG. 13, the band of the digital broadcast wave D1). The resonance frequency is greatly shifted until the lower limit of (the second amount resonance frequency larger than the first amount is shifted), and as a result, the input electric field level of the RF-AGC 13a is lowered, and the RF-AGC 13a The generation of noise components due to the saturation of the signal is suppressed and reception of the desired digital broadcast wave D1 is improved.

  As described above, according to the first embodiment, when the number of errors when the signal processing unit 14a performs signal processing exceeds a predetermined number, the RF level obtained from the RF-AGC 13a and the IF-AGC 13d Since the resonance frequency of the receiving antenna 11 is shifted in accordance with the IF level obtained from the above, there is an effect that a desired digital signal wave can always be received satisfactorily regardless of the presence of an interference wave or the like.

  According to the first embodiment, the comparison unit 22 compares the RF level with the RF level threshold value, and if the RF level exceeds the RF level threshold value, a first comparison result signal having a high level is obtained. If the IF level exceeds the IF level threshold, a high-level second comparison result signal is obtained. If the IF level is equal to or lower than the IF level threshold, the second low-level second signal is obtained. When the first comparison result signal is at a high level and the second comparison result signal is at a low level, the resonance frequency of the receiving antenna 11 is shifted by a first amount, and the first comparison result signal is obtained. Is high level and the second comparison result signal is high level, the resonance frequency of the receiving antenna is shifted by a second amount larger than the first amount. Kill well, there is an effect that it prevents the poor reception due to the saturation of the RF-AGC.

It is a block diagram which shows an example of the receiver by Embodiment 1 of this invention. It is a figure which shows the unimodal VSWR characteristic of the receiving antenna shown in FIG. It is a figure for demonstrating the change of the resonant frequency of the receiving antenna shown in FIG. It is a channel spectrum figure which shows the state where a digital broadcast wave and an analog broadcast wave adjoin. It is a figure which shows the analog broadcast wave adjacent to the low frequency side of a digital broadcast wave. 6A and 6B are diagrams for explaining the influence of the analog broadcast wave shown in FIG. 5, where FIG. 5A shows the input level to the RF-AGC shown in FIG. 1, and FIG. 5B shows the input to the SAW filter shown in FIG. FIG. 2C is a diagram showing levels, FIG. 3C is a diagram showing input levels to the IF-AGC shown in FIG. 1, and FIG. 4D is a diagram showing output levels of the IF-AGC. It is a channel spectrum figure which shows the state where mutually different digital broadcast waves adjoin. FIG. 8 is a diagram for explaining the influence of adjacent digital broadcast waves shown in FIG. 7, where (a) shows the input level to the RF-AGC shown in FIG. 1, and (b) shows the output level of the RF-AGC. FIG. 4C is a diagram showing the input level to the IF-AGC shown in FIG. 1, and FIG. 4D is a diagram showing the output level of the IF-AGC. It is a block diagram which shows the structure of the reception electric field condition identification part shown in FIG. It is a flowchart for demonstrating operation | movement of the electric field determination part shown in FIG. It is a figure which shows the state which shifted the position of the resonant frequency shown in FIG. 5 to the high frequency side a little. It is a figure which shows the analog broadcast wave adjacent to the high frequency side of a digital broadcast wave. It is a figure which shows the state which shifted the position of the resonant frequency shown in FIG. 7 largely to the low frequency side.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Receiver, 11 Receive antenna, 11a Variable reactance element, 12 Receiver, 13 Electronic tuning circuit, 13a High frequency automatic gain control circuit (RF-AGC), 13b First mixer (mixer), 13c SAW (surface acoustic wave) ) Filter, 13d intermediate frequency automatic gain circuit (IF-AGC), 13e second mixer, 14 signal processing circuit, 14a A / D (analog / digital) conversion unit, 14b signal processing unit, 15 error detection unit, 16 control Circuit, 16a reception frequency control unit, 16b reception electric field condition identification unit, 16c DC control voltage generation unit, 21 error determination unit, 22 first comparison unit, 23 second comparison unit, 24 electric field determination unit, 25 output necessity Judgment part.

Claims (5)

A receiving antenna capable of adjusting the resonance frequency;
A frequency adjusting means for adjusting the resonance frequency;
A receiving device comprising: control means for controlling the frequency adjusting means in accordance with a received electric field level of a received signal received by the receiving antenna. High frequency gain means connected to the receiving antenna to adjust the received electric field level of the received signal to an RF level;
Intermediate frequency gain means for adjusting the level of the output from the high frequency gain means to IF level,
2. The receiving apparatus according to claim 1, wherein the control unit controls the frequency adjusting unit according to the RF level and the IF level. Demodulation means for demodulating the output from the intermediate frequency gain means to obtain a demodulated signal;
Error detection means for detecting the number of errors during demodulation by the demodulation means and outputting an error detection signal;
3. The receiving apparatus according to claim 2, wherein the control means controls the frequency adjusting means according to the RF level and the IF level when the number of errors indicated by the error detection signal exceeds a predetermined number. The control means compares the RF level with a predetermined RF level threshold value, and outputs a high-level first comparison result signal when the RF level exceeds the RF level threshold value. When,
The IF level is compared with a predetermined IF level threshold, and if the IF level exceeds the IF level threshold, a second comparison result signal having a high level is output, and the IF level is the IF level threshold. Second comparison means for outputting a low-level second comparison result signal if:
First adjusting means for outputting a first frequency adjustment signal when the first comparison result signal is at a high level and the second comparison result signal is at a low level;
Second adjustment means for outputting a second frequency adjustment signal when the first comparison result signal is at a high level and the second comparison result signal is at a high level;
The receiving apparatus according to claim 1, further comprising: an output determination unit that provides the frequency adjustment unit with the first or second frequency adjustment signal according to an error detection signal.   The frequency adjustment means shifts the resonance frequency by a first amount when receiving the first frequency adjustment signal, and a second amount larger than the first amount when receiving the second frequency adjustment signal. 5. The receiving apparatus according to claim 4, wherein the receiving apparatus is shifted.

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