JP2006067283A - Electronic tuner and portable device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic tuner for injecting entry of a high power interference signal adjacent to a receiving frequency band, and also to provide a portable device using the same tuner. <P>SOLUTION: The electronic tuner comprises an input terminal 1 to which the television broadcast signal is inputted, an input filter 3 receiving an input signal to this input terminal 1 and allowing the signals of the television broadcast frequency bands 15, 16 to pass, a mixer 5 receiving the output of the input filter 3 with one input thereof and connecting to the output of an local oscillator 7 with the other input thereof, an intermediate frequency filter 8 connected to the output of the mixer 5, and an output terminal 10 receiving the output of the intermediate frequency filter 8. A notch filter 2 provided adjacently to the input terminal 1 for rejecting passing of the interference signal is inserted between the input terminal 1 and the input filter 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electronic tuner that receives a high-frequency signal that is close to a television broadcast wave band and includes an interference signal that is input at a higher level than any other television broadcast wave in the television broadcast wave band, and a portable device using the same It is about.

  Hereinafter, a conventional electronic tuner will be described. In a conventional electronic tuner, a metal case is provided with an input terminal for receiving a television broadcast wave, and an input filter for supplying a signal input to the input terminal and passing the signal of the television broadcast wave band. A mixer in which the output of the input filter is supplied to one input and the output of the local oscillator is connected to the other input, an intermediate frequency filter to which the output of the mixer is connected, and the intermediate frequency filter And an output terminal to which the output is supplied.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2000-13357 A

  However, in such a conventional electronic tuner, if a high-power interference signal (for example, a transmission signal of a mobile phone) is present in the vicinity of the television broadcast wave band received by the electronic tuner, the television broadcast wave is received due to the interference signal. There was a problem that it was difficult. That is, although an input filter that allows the reception band to pass is inserted in the electronic tuner, if there is a high-power interference signal in the vicinity of the television broadcast wave band, the attenuation characteristic of this input filter cannot be prevented.

  Accordingly, the present invention has been made to solve this problem, and an object of the present invention is to provide an electronic tuner capable of blocking the input of a large power interference signal close to the reception band and a portable device using the electronic tuner. .

  In order to achieve this object, the electronic tuner of the present invention and a portable device using the electronic tuner are provided with a notch filter inserted in the vicinity of the input so as to prevent passage of interference signals. Thereby, the initial purpose can be achieved.

  As described above, according to the present invention, a notch filter for preventing the passage of an interference signal is inserted in the vicinity of the input, so that the interference signal is input to the electronic tuner and a portable device using the notch filter by this notch filter. Can be blocked.

  Further, since the notch filter is inserted in the vicinity of the input, the interference signal is not transmitted to the notch filter and the subsequent parts. Therefore, it is possible to enjoy clear audio and beautiful video.

(Embodiment 1)
Hereinafter, the electronic tuner according to the present embodiment will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes an input terminal to which a television broadcast wave (VHF broadcast wave, UHF broadcast wave) is input. The input terminal 1 allows one of a notch filter (also referred to as a trap filter or an absorption filter) 2 to pass a television broadcast wave and block a passage of an interference wave signal (for example, a signal of a transmission unit of an 830 MHz mobile phone). Connected to the terminal. The other terminal of the notch filter 2 is connected to one terminal of the input filter 3 that allows the television broadcast wave band to pass therethrough. The input filter 3 uses a low-pass filter in the present embodiment. However, this is not limited to the low-pass filter, and may be a band-pass filter.

  The other terminal of the input filter 3 is connected to one input of the mixer 5 via the high frequency amplifier 4. The other input of the mixer 5 is connected to the output of the local oscillator 7 controlled by the PLL circuit 6.

  The output of the mixer 5 is connected to an output terminal 10 via an intermediate frequency filter 8 and an intermediate frequency amplifier 9. A data input terminal 11 is connected to the PLL circuit 6. These circuits are housed in a metal case 12.

  Here, what is important is that the notch filter 2 is provided close to the input terminal 1 (at least 1/8 wavelength or less of the reception frequency). That is, the wiring distance between the input terminal 1 and the notch filter 2 is made shorter than the wiring distance connecting the notch filter 2 and the next circuit (the input filter 3 in this embodiment) connected to the notch filter 2. It is important to keep This is because the notch filter 2 is set to at least one-eighth wavelength of the maximum reception frequency from the input terminal 1, and the wiring from the notch filter 2 to the input terminal 1 becomes an antenna at any reception frequency. This is to prevent the interference signal from being radiated to the circuit.

  Thus, even if an interference signal is input to the input terminal 1, it is first removed by the notch filter 2 so that the interference signal is not transmitted to the input filter 3 and thereafter. If this notch filter 2 is surrounded by a metal partition plate 13, it is possible to further block the input of interference signals (to the input filter 3 and subsequent parts).

  Here, the relationship between the television broadcast wave band and the interference signal in a portable device in which an electronic tuner of a television broadcast receiver is incorporated in a mobile phone will be described with reference to FIG. In FIG. 2, 15 is an example of a broadcast wave band of VHF broadcast waves, and has a band of 90 MHz to 220 MHz. 16 is an example of a broadcast wave band of UHF broadcast waves, and has a band of 470 MHz to 770 MHz.

  Reference numeral 17 is an example of a signal from the transmitter of the mobile phone, and the electric field strength may be 14 dBm or higher at the input terminal 1 at a frequency of 830 MHz. The signal 17 is very close to the highest channel (62ch) of the UHF broadcast wave band 16, and has a very large level as compared to this highest channel. That is, the signal 17 becomes a disturbing signal that is difficult to remove for the reception of the television broadcast.

  If such a large interference signal is present close to the television broadcast wave, it is difficult for the input filter 3 to remove all of it. That is, there is only a 60 MHz interval 20 between the highest channel of the UHF broadcast wave band 16 and the signal 17, and the attenuation characteristic 3 a of the input filter 3 cannot completely remove it. That is, as shown in FIG. 2, only an attenuation of about 3b can be obtained for the signal 17. Therefore, when such a large disturbance signal is input to the high frequency amplifier 4 or the mixer 5 of the electronic tuner, the high frequency amplifier 4 or the mixer 5 is distorted, and the desired signal is linearly amplified without distortion. It cannot be mixed.

  When the signal is input to an AGC circuit or the like, the AGC operation is governed by the large input interference signal, and the amplification level of the original signal becomes very small. That is, in the reception of a television broadcast wave or the like, if this disturbing signal exists, it becomes impossible to enjoy clear audio and beautiful video.

  18 and 19 are also examples of signals output from the transmitters of different types of mobile phones, and the electric field strength at the input terminal 1 is 14 dBm or higher at frequencies of 1.5 GHz and 1.9 GHz, respectively. There is also. These signals 18 and 19 are also interference signals with respect to television broadcast waves. However, since these signals 18 and 19 are farther away from the television broadcast wave band than the signal 17, the influence thereof is small. In other words, the removal may be possible if the input filter 3 having good performance is used.

  As described above, in a portable device in which a television receiver is built in a mobile phone, a signal from a transmission unit of the mobile phone becomes an interference signal for reception of a television broadcast. The level of the interference signal may be as large as 1000 times or more of the television broadcast wave because an electronic tuner exists in the vicinity of the transmission unit of the mobile phone. In other words, the strength of the radio wave is inversely proportional to the square of the distance, so if the distance is close, even a small output cannot be ignored. In FIG. 2, the horizontal axis 21 is frequency (MHz) and the vertical axis 22 is level (dB).

  Next, a description will be given of the notch filter 2 that removes the signal 17 that becomes an interference signal in a portable device in which a television receiver is built in a cellular phone. In FIG. 3, 2 a is one terminal (input) of the notch filter 2, and 2 b is the other terminal (output) of the notch filter 2. A first notch filter 25 and a second notch filter 26 that prevent passage of interference signals are connected in series between the one terminal 2a and the other terminal 2b.

  Further, between the input (2a) of the first notch filter 25 and the ground, the connection point (2c) of the first notch filter 25 and the second notch filter 26, and the output of the second notch filter 26 ( Between each of 2b) and the ground, a third notch filter 27, a fourth notch filter 28, and a fifth notch filter 29 for attenuating the interference signal are respectively connected.

  Here, the first notch filter 25 is configured such that a 1.2 nH inductor 25a and a 30pF capacitor 25b are connected in parallel to prevent passage of a frequency of 839 MHz. Similarly, the second notch filter 26 is configured such that a 1.2 nH inductor 26 a and a 27 pF capacitor 26 b are connected to block passage of a frequency of 885 MHz.

  The third notch filter 27 is configured such that an 82 nH inductor 27 a and a 0.4 pF capacitor 27 b are connected in series to attenuate the frequency of 879 MHz. Similarly, the fourth notch filter 28 is configured such that a 47 nH inductor 28a and a 0.75 pF capacitor 28b are connected in series to attenuate the frequency of 848 MHz. The fifth notch filter 29 is configured such that a 47 nH inductor 29a and a 0.75 pF capacitor 29b are connected in series to attenuate the frequency of 848 MHz.

  FIG. 4 is a characteristic curve 31 of the notch filter 2 configured as described above. As shown in FIG. 4, up to the frequency of 770 MHz (point 32 indicates 770 MHz) of the highest channel of the UHF broadcast wave band 16 shows a substantially flat characteristic. Then, at a frequency of 830 MHz (point 33 indicates 830 MHz) in which the signal 17 as an interference signal exists, an abrupt attenuation characteristic of about 100 dB is shown.

  Therefore, by using such a notch filter 2, it is possible to pass through the uppermost channel of the UHF broadcast wave band 16 without substantial attenuation and to attenuate the signal 17 (interference signal) by about 100 dB. .

  What is important here is that the notch filter 2 is provided close to the input (in this embodiment, the input terminal 1). As a result, the interference signal can be removed. In FIG. 4, the horizontal axis 34 is the frequency (MHz), and the vertical axis 35 is the attenuation (dB).

(Embodiment 2)
FIG. 5 is a block diagram of a portable device in the second embodiment, in which a television receiver using the electronic tuner of the present invention is housed in the same case in a cellular phone. In addition, the same code | symbol is attached | subjected about the same thing and description is simplified.

  In FIG. 5, reference numeral 41 denotes a television receiving antenna. The television receiving antenna 41 constitutes a television receiver and is connected to an input terminal 43 of an electronic tuner 42 housed in a metal case 42a. The input terminal 43 is connected to the notch filter 2 of the present invention. Here, what is important is that the notch filter 2 is arranged close to the input terminal 43 (at least 1/8 or less of the reception frequency). As a result, it is possible to efficiently prevent an interference signal from being input to another circuit of the electronic tuner 42. In addition, when this notch filter 2 is enclosed with a metal partition plate, the effect is improved more and more.

  The output of the notch filter 2 is connected to one input of a mixer 44 through an input filter 3 constituted by a low-pass filter and a high frequency amplifier 4. The other input of the mixer 44 is connected to the output of the local oscillator 46 controlled by the PLL circuit 45. The output of the mixer 44 is connected to one input of a mixer 48 through a band pass filter 47, and the output of a local oscillator 49 controlled by the PLL circuit 45 is connected to the other input. . The output of the mixer 48 is connected to the output terminal 51 of the electronic tuner 42 via the band pass filter 50.

  The output terminal 51 is connected to a video display unit 54 composed of liquid crystal via a television demodulating circuit 52 and a decoding circuit 53. The output of the decoding circuit 53 is also connected to an audio output unit 55 configured with a speaker or an earphone.

  The television receiver unit is configured as described above. Note that the decoding circuit 53, the video display unit 54, and the audio output unit 55 are shared with a mobile phone unit described later. 56 is also a control unit shared with the portable receiver unit, and this control unit 56 is connected to the PLL circuit 45 and performs a channel selection operation. The mixer 48 performs direct conversion.

  Reference numeral 61 denotes a mobile phone antenna, and the mobile phone antenna 61 is connected to an input / output terminal 63 of a telephone transmission / reception unit 62 constituting a mobile receiver. The input / output terminal 63 is connected to a common terminal of the antenna switch 64. One terminal of the antenna switch 64 is connected to one input of a mixer 66 through a low noise amplifier 65, and the other input is connected to the output of a local oscillator 68 controlled by a PLL circuit 67. Yes.

  The output of the mixer 66 is connected to one input of the mixer 70 via the band pass filter 69, and the output of the local oscillator 71 controlled by the PLL circuit 67 is connected to the other input. Yes. The output of the mixer 70 is connected to the output terminal 73 of the transmission / reception unit 62 via the telephone demodulation circuit 72. The output terminal 73 is connected to the video display unit 54 and the audio output unit 55 via the decoding circuit 53.

  Reference numeral 74 denotes an audio / data input unit composed of a keyboard and a microphone. The output of the audio / data input unit 74 is connected to the input terminal 76 of the transmission / reception unit 62 via the encoding circuit 75. The input terminal 76 is connected to one input of the modulation circuit 77, and the output of the local oscillator 79 controlled by the PLL circuit 78 is connected to the other input. The output of the modulation circuit 77 is connected to one input of the mixer 80, and the output of the local oscillator 68 controlled by the PLL circuit 67 is connected to the other input. The output of the mixer 80 is connected to the other terminal of the antenna switch 64 via the power amplifier 81. The output of the control unit 56 is connected to PLL circuits 67 and 78, and the reception frequency and transmission frequency of the mobile phone unit are determined by signals output from the control unit 56.

  Here, the decoding circuit 53 and the encoding circuit 75 form a signal processing unit 82, and the low noise amplifier 65, the mixers 66 and 70, the bandpass filter 69, and the telephone demodulation circuit 72 form a receiving unit 83. is doing. The modulation circuit 77, the mixer 80, and the power amplifier 81 form a transmission unit 84.

  In the portable device configured as described above, the signal input from the voice / data input unit 74 is encoded by the encoding circuit 75. The encoded signal is modulated by the modulation circuit 77, mixed by the mixer 80 to be a carrier wave, power amplified by the power amplifier 81, and then radiated from the cellular phone antenna 61 as a radio wave.

  The output level of this radio wave is extremely small compared to the output level of the radio wave radiated from a television broadcast station. However, the television receiving antenna 41 is arranged very close to the cellular phone antenna 61 with respect to the antenna of the television station, and becomes a high-power interference signal for the electronic tuner 42. Moreover, since the frequency of the radio wave radiated from the cellular phone antenna 61 is extremely close to the highest channel of the UHF broadcast wave band 16 as described in the first embodiment, it is extremely difficult for the electronic tuner 42. It becomes a big disturbance signal. However, in the present embodiment, since the notch filter 2 for removing the interference signal is provided in the vicinity of the input terminal 43, the influence of the interference signal on the electronic tuner 42 is extremely small and is accommodated in the same case. TV reception can be enjoyed without being affected by the mobile phone unit.

(Embodiment 3)
FIG. 6 is a block diagram of a portable device according to the third embodiment. This portable device is a portable phone unit in which a television receiver unit using the electronic tuner of the present invention is housed in the same case. In addition, the same code | symbol is attached | subjected about the same thing and description is simplified.

  Therefore, in FIG. 6, only the differences from the second embodiment will be described. That is, in FIG. 6, a notch filter 85 whose removal frequency can be controlled by voltage is provided, and the output of the PLL circuit 67 is connected to the control terminal of the notch filter 85 by a connection line 86. This notch filter 85 is a capacitor (capacitor 27b in the first embodiment) constituting a first-stage filter constituted by a varicap diode. This is because the frequency of the interference signal is accurately attenuated by the first filter (the filter formed by the series connection body of the inductor 27a and the capacitor 27b in the first embodiment), and is prevented from being transmitted thereafter. .

  Therefore, when the control unit 56 controls the PLL circuit 67 to change the frequency output from the transmission unit 84, the attenuation frequency of the notch filter 85 changes in conjunction with this frequency. That is, even if the frequency output from the transmission unit 84 changes, the attenuation frequency of the notch filter 85 changes in conjunction with it, so that the electronic tuner 87 can receive a good television broadcast. Reference numeral 87a denotes a metal case in which the electronic tuner 87 is accommodated.

(Embodiment 4)
FIG. 7 is a block diagram of a portable device according to the fourth embodiment. This portable device is a portable telephone unit in which a television receiver unit using the electronic tuner of the present invention is housed in the same case. In addition, the same code | symbol is attached | subjected about the same thing and description is simplified.

  Therefore, in FIG. 7, only the differences from the second embodiment will be described. That is, in FIG. 7, reference numeral 90 is the one obtained by removing the notch filter 2 from the electronic tuner 42 in the second embodiment. That is, the input terminal 43 of the electronic tuner 90 is directly connected to the input filter 3. Others are the same as those of the electronic tuner 42.

  The notch filter 2 according to the fourth embodiment is connected in proximity to the television receiving antenna 41, and its output is connected to the input terminal 43 of the electronic tuner 90 via the high frequency amplifier 91. The notch filter 2 and the high frequency amplifier 91 are housed in a metal shield case 93a to form an active antenna block 93. The active antenna block 93 is disposed in the vicinity of the input terminal 43.

  Even in this case, it is important that the distance between the television antenna 41 and the notch filter 2 is shorter than the distance between the notch filter 2 and the input terminal 43. By arranging in this way, it is possible to prevent the input of a signal radiated from the cellular phone antenna 61 and enjoy good television reception.

  The electronic tuner 90 is housed in a metal case 90a. And the ferrite is inserted between the shield case 93a of the active antenna block 93 and the television receiving antenna 41, so that the sensitivity of the television receiving antenna 41 is improved.

(Embodiment 5)
FIG. 8 is a block diagram of a portable device according to the fifth embodiment. This portable device is a portable telephone device unit in which a television receiver unit using the electronic tuner of the present invention is housed in the same case. In addition, the same code | symbol is attached | subjected about the same thing and description is simplified.

  Therefore, in FIG. 8, only the differences from the third and fourth embodiments will be described. The fifth embodiment is substantially the same as the fourth embodiment except that a notch filter 85 capable of varying the notch frequency is used for the active antenna block 95. That is, in FIG. 8, a notch filter 85 capable of controlling the attenuation frequency by voltage is provided, and is connected from the PLL circuit 67 to the control terminal of the notch filter 85 by a connection line 86.

  Therefore, when the control unit 56 controls the PLL circuit 67 to change the frequency output from the transmission unit 84, the attenuation frequency of the notch filter 85 changes in conjunction with this frequency. That is, when the frequency output from the transmitter 84 is changed, the frequency of the notch filter 85 of the active antenna block 95 is changed in conjunction with the change, so that a good television broadcast can be received.

  The electronic tuner 90 is housed in a metal case 90a. Further, by inserting ferrite between the shield case 95a of the active antenna block 95 and the television receiving antenna 41, the sensitivity of the television receiving antenna 41 can be improved.

  The electronic tuner according to the present invention is useful as an electronic tuner built in a mobile phone or the like because it can remove a high-power interference wave signal close to the reception band.

Block diagram of electronic tuner in Embodiment 1 of the present invention Same as above, relationship between TV broadcast wave band and jamming signal Same notch filter circuit diagram Same characteristic curve The block diagram of the portable apparatus using the electronic tuner of the present invention in the second embodiment Block diagram of portable device in Embodiment 3 Block diagram of portable device according to Embodiment 4 Block diagram of portable device according to Embodiment 5

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input terminal 2 Notch filter 3 Input filter 5 Mixer 7 Local oscillator 8 Intermediate frequency filter 10 Output terminal 12 Case 15 VHF broadcast wave band 16 UHF broadcast wave band 17 Signal 18 Signal 19 Signal

Claims (12)

In an electronic tuner that receives a high-frequency signal that is close to a television broadcast wave band and includes an interference signal that is input at a higher level than any television broadcast wave in the television broadcast wave band, the electronic tuner is a metal case. An input terminal to which the high-frequency signal is input, an input filter that is supplied with the signal input to the input terminal and passes the signal of the television broadcast wave band, and an output of the input filter A mixer to which the output of the local oscillator is connected to the other input, an intermediate frequency filter to which the output of the mixer is connected, and an output terminal to which the output of the intermediate frequency filter is supplied A notch filter between the input terminal and the input filter, for blocking the passage of the interfering signal in the vicinity of the input terminal. Electronic tuner but that has been inserted. The electronic tuner according to claim 1, wherein the notch filter is surrounded by a metal partition plate. In the notch filter, a first notch filter and a second notch filter are connected in series to a signal passage, and an input of the first notch filter and a connection point of the first notch filter and the second notch filter. A third notch filter, a fourth notch filter, and a fifth notch filter are respectively connected between the output of the second notch filter and the ground, and the first notch filter and the first notch filter. In the second notch filter, an inductor and a capacitor are connected in parallel to prevent passage of interference signals, and in the third notch filter, the fourth notch filter, and the fifth notch filter, an inductor and a capacitor are connected in series. The electronic tuner according to claim 1, wherein the electronic tuner is connected to attenuate the interference signal. 2. The electronic tuner according to claim 1, wherein the length of the wiring between the input terminal and the notch filter is at least one-eighth or less of the wavelength of the highest frequency of the television broadcast wave. A portable device provided with a transmission / reception unit of a cellular phone that outputs an interference signal to the electronic tuner in the vicinity of the electronic tuner according to claim 1. The portable device according to claim 5, wherein the notch frequency of the notch filter is controlled in conjunction with the transmission frequency of the transmission unit constituting the transmission / reception unit. The portable device according to claim 6, wherein the capacitor forming the first stage of the notch filter is configured by a varicap diode. A mobile device in which a mobile phone and a television receiver are housed in a case, the proximity of the television receiving antenna between the television receiving antenna and an input terminal of an electronic tuner constituting the television receiver And the portable apparatus in which the notch filter which prevents passage of the signal output from the transmission / reception part which comprises the said mobile telephone was inserted. The portable device according to claim 8, wherein the notch filter is covered with a shield case. The portable device according to claim 9, wherein ferrite is inserted between the television receiving antenna and the shield case. The portable device according to claim 8, wherein a distance between the television receiving antenna and the notch filter is shorter than a distance between the notch filter and an input terminal of the electronic tuner. The portable device according to claim 8, wherein the notch frequency of the notch filter is controlled in conjunction with a transmission frequency of a transmission unit constituting a telephone transmission / reception unit.

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