JP2006339868A - Terrestrial digital broadcast reception tuner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve compactification by decreasing the circuit scale, and also to select a station with a simple operation. <P>SOLUTION: A tuner includes: first mixers 26, 27 for applying orthogonal transform to a digital television signal with a UHF band into a first intermediate frequency signal; and a second mixer 30 for applying frequency conversion to a digital television signal with a VHF band into a signal with the UHF band, the television signal with the VHF band converted into the signal with the UHF band is given to the mixers 26, 27, the first mixers 26, 27 applies orthogonal transform to the signal into the first intermediate frequency signal so that the tuner employs only one orthogonal transform system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a terrestrial digital broadcast receiving tuner.

  A conventional digital terrestrial broadcast receiving tuner is shown in FIG. In FIG. 3, the VHF band digital television signal and the UHF band digital television signal received by the antenna 1 are separated by the duplexer 2, and the VHF band digital television signal is selected by the VHF bandpass filter 3. Then, it is input to the two mixers 5 and 6 in the subsequent stage via the VHF amplifier 4.

  The mixers 5 and 6 are supplied with local oscillation signals LO / I and LO / Q whose phases are orthogonal to each other. The VHF band digital television signals input to the mixers 5 and 6 are orthogonally transformed to output baseband signals (I signal and Q signal) having orthogonal phases. Each baseband signal is converted into a digital signal by A / D converters 9 and 10 via IF bandpass filters 7 and 8, respectively.

  Similarly, the UHF band digital television signal separated by the duplexer 2 is selected by the UHF bandpass filter 11 and input to the two mixers 13 and 14 via the UHF amplifier 12. The mixers 13 and 14 are respectively supplied with local oscillation signals LO / I and LO / Q whose phases are orthogonal. The digital television signals in the UHF band input to the mixers 13 and 14 are orthogonally transformed, and baseband signals (I signal and Q signal) whose phases are orthogonal are output. Each baseband signal is converted into a digital signal by A / D converters 17 and 18 via IF bandpass filters 15 and 16, respectively.

  The I signal output from the A / D converter 9 and the I signal output from the A / D converter 17 are input to the first switching circuit 19 and the Q signal output from the A / D converter 10. The Q signal output from the A / D converter 18 is input to the second switching circuit 20. The first and second switching circuits 19 and 20 are interlocked by a band switching signal BS output from the local oscillator 21, and output an I signal and a Q signal based on the VHF signal or an I signal and a Q based on the UHF signal. It is switched to output a signal (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2005-064764 (FIG. 1)

  In a conventional digital broadcast receiving tuner, a configuration up to orthogonal conversion and A / D conversion of a UHF band digital television signal, and a configuration up to orthogonal conversion and A / D conversion of a VHF band digital television signal, Since the circuit was independent, the entire circuit scale was large and it was not suitable for use in a mobile phone or the like.

  It is an object of the present invention to reduce the circuit scale and reduce the size.

  As a first solution, a first mixer for orthogonally converting a UHF band digital television signal to a first intermediate frequency signal, and a second mixer for converting a VHF band digital television signal to a UHF band. The VHF band television signal converted to the UHF band is input to the first mixer and orthogonally converted to the first intermediate frequency signal.

  As a second solution, the digital television signal in the VHF band is converted into a band adjacent to the lower end side of the UHF broadcast band.

  Further, as a third solving means, an oscillator for supplying a local oscillation signal to the first mixer is provided, and a first for dividing the oscillation signal output from the oscillator by 1/2 Via a second divider for supplying the first mixer via a frequency divider and further dividing the oscillation signal divided by the first frequency divider by half. Feeded to the second mixer.

  As a fourth solution, a demultiplexer for inputting the UHF band digital television signal and the VHF band digital television signal is provided, and the demultiplexed UHF band digital television signal is received. The VHF band digital television signal input to the first mixer and demultiplexed was input to the second mixer.

  As a fifth solution, a variable tuning circuit is provided between the duplexer and the first mixer, and the VHF band output from the second mixer after being converted to the UHF band is output. A digital television signal was input to the first mixer via the variable tuning circuit.

  As a sixth solution, the VHF band digital television signal is arranged in a specific channel, and a band-pass filter that passes the specific channel between the duplexer and the second mixer Was provided.

  As a seventh solution, a third mixer for orthogonally transforming the first intermediate frequency signal into a second intermediate frequency signal, a PLL circuit for controlling the oscillator, and a reference signal for the PLL circuit A reference oscillator to be supplied was provided, and the reference signal was divided by half and supplied to the third mixer.

  According to the first solving means, the first mixer for orthogonally converting the UHF band digital television signal to the first intermediate frequency signal, and the second for frequency converting the VHF band digital television signal to the UHF band. The VHF band television signal converted into the UHF band is input to the first mixer and orthogonally converted into the first intermediate frequency signal, so that the UHF band digital television signal and the VHF are mixed. The band digital television signal can be orthogonally converted to an intermediate frequency signal by the same mixer, the configuration is simplified, and the circuit scale can be reduced.

  According to the second solution, since the digital television signal in the VHF band is converted into a band adjacent to the lower end side of the UHF broadcast band, the digital television signal in the UHF band and the digital television signal in the VHF band Can be received without switching.

  Further, according to the third solution means, an oscillator for supplying a local oscillation signal to the first mixer is provided, and a first frequency for dividing the oscillation signal output from the oscillator by 1/2 is provided. The second signal is supplied to the first mixer via the frequency divider and the second frequency divider is used to divide the oscillation signal frequency-divided by the first frequency divider by a factor of two. Thus, the UHF band digital television signal and the VHF band digital television signal can be received using a common oscillator.

  According to the fourth solution, a demultiplexer for inputting a UHF band digital television signal and a VHF band digital television signal is provided, and the demultiplexed UHF band digital television signal is recorded. Since the VHF band digital television signal input to the first mixer and demultiplexed is input to the second mixer, the number of input systems can be reduced to one.

  Further, according to the fifth solution, a VHF band digital television which is provided with a variable tuning circuit between the duplexer and the first mixer and is converted to the UHF band and output from the second mixer. Since the John signal is input to the first mixer via the variable tuning circuit, the UHF band digital television signal and the VHF band digital television signal can be selected by the variable tuning circuit.

  According to the sixth solution, the digital television signal in the VHF band is arranged in a specific channel, and a band pass filter that passes the specific channel is provided between the duplexer and the second mixer. Therefore, signals other than digital television signals in the VHF band can be removed.

  According to the seventh solution, the third mixer for orthogonally transforming the first intermediate frequency signal to the second intermediate frequency signal, the PLL circuit for controlling the oscillator, and the reference signal to the PLL circuit are supplied. And the reference signal is divided by half and supplied to the third mixer, so that the local oscillator signal source supplied to the third mixer can be shared by the reference oscillator.

  FIG. 1 shows the configuration of a digital terrestrial broadcast receiving tuner according to the present invention. In FIG. 1, a VHF band digital television signal and a UHF band digital television signal received by an antenna 21 are demultiplexed by a demultiplexer 22.

  Here, the digital television signal handled in the present invention will be described. Currently planned digital television broadcast channels are VHF band high channels (channels 7 to 8 of channels 4 to 12) and UHF band channels 13 to 36. is there. These broadcast channels are divided into 13 segments (the bandwidth of each segment is 3/7 MHz), and an OFDM-modulated digital television signal is broadcast using one central segment or three adjacent segments. . Broadcast content is mainly music, but video broadcasting is also planned, and it is expected that it will be used in mobile phones and the like in the future. In addition, the number of broadcast channels is expected to increase.

  Returning to the description of FIG. The digital television signal in the UHF band output from the duplexer 22 is connected to the first mixer 26 for orthogonal transform through the first amplifier 23, the variable tuning circuit 24, and the second amplifier 25 that are connected in cascade. , 27. The variable tuning circuit 24 is configured to tune to a UHF band reception channel.

  On the other hand, the digital television signal in the VHF band output from the duplexer 22 is input to the second mixer 30 for frequency conversion via the bandpass filter 28 and the third amplifier 29. The band-pass filter passes through the band of the channel on which the digital television signal in the VHF band is broadcast (for example, the entire band of channel 7 and channel 8). The VHF band digital television signal is converted into the UHF band by the second mixer 30. The digital television signal in the VHF band converted into the UHF band is selected by the variable tuning circuit 24 and input to the first mixers 26 and 27 through the second amplifier 25.

  A local oscillation signal for orthogonal conversion supplied to the two first mixers 26 and 27 and a local oscillation signal for frequency conversion supplied to the second mixer 30 are generated from the oscillation circuit 31. The oscillator 31 is controlled by a PLL circuit 32 and oscillates between approximately 800 MHz and 1550 MHz corresponding to the frequency of the digital television signal input to the first mixers 26 and 27. Note that channel data for channel selection is input to the PLL circuit 32, and a reference signal (16 MHz) for phase comparison is supplied from the reference oscillator 33. The tuning frequency of the variable tuning circuit 24 is also controlled by the PLL circuit 32.

  The oscillation signal output from the oscillator 31 is divided by ½ by the first frequency divider 34. For example, as shown in FIG. 2, the first frequency divider 34 includes master / slave F / F circuits 34a and 34b and an inverter 34c. The oscillation signal is input to the master F / F circuit 34a and the slave F / F circuit 34b, but is input to the slave F / F circuit 34b via the inverter 34c. This first frequency divider 34 is called a Johnson counter, and the Q output of the slave F / F circuit 34b is delayed in phase by 90 ° from the Q output of the master F / F circuit 34a. The signals having different phases by 90 ° are supplied to the first mixers 25 and 26 as local oscillation signals (Lo / I, Lo / Q), respectively.

  The oscillation signal divided by the first frequency divider 34 is divided by half by the second frequency divider 35 and supplied to the second mixer 30 as a local oscillation signal. The second frequency divider 35 may have the configuration shown in FIG.

  Third mixers 38 and 39 are connected to the next stage of the first mixers 26 and 27 via bandpass filter filters 36 and 37, respectively. The outputs of the third mixers 38 and 39 are connected to the synthesizer 40. The local oscillation signal supplied to the third mixers 38 and 39 is generated by the third frequency divider 41. Since the third frequency divider 41 divides the reference oscillation signal by half to generate a local oscillation signal having a phase difference of 90 °, the configuration is the same as that of the first frequency divider 34. Therefore, the frequency of this local oscillation signal is 8 MHz.

  In the above configuration, the UHF band digital television signal and the VHF band digital television signal converted into the UHF band are selected by the variable tuning circuit 24 and the first mixers 26 and 27 select the channel to be received. Entered.

  For example, when the UHF band channel 13 is received, the center frequency of the seventh segment arranged in the center of the band is 471.1429 MHz. When the center frequency of the first intermediate frequency signal (I / Q) output from the first mixer is 8.4286 MHz, the local oscillation signal supplied to the first mixer is 481.5715 MHz. Accordingly, the oscillation frequency of the oscillator 31 at this time is 963.143 MHz. The frequency of the second intermediate frequency signal (I / Q) output from the third mixers 38 and 39 is 0.4286 MHz.

  When receiving the channel 7 of the VHF band, the center frequency of the seventh segment arranged at the center of the band is 191.1429 MHz. A digital television signal in the VHF band is converted to a position adjacent to the lower end of the UHF broadcast band. Therefore, in this case, the frequency of the local oscillation signal supplied to the second mixer 30 is 199.5715. MHz. As a result, the television signal in the VHF band is converted to 390.7144 MHz (= 191.1429 + 199.715). Since the first mixers 26 and 27 are supplied with a local oscillation signal of 399.143 MHz (= 199.5715 × 2), the first intermediate frequency signal is 8.4286 MHz. The oscillator 31 oscillates at 798.286 MHz.

  As described above, the VHF band digital television signal is converted to a band lower than the lower end (lower band edge) of the UHF broadcast band and is input to the first mixers 26 and 27. Therefore, the UHF band and VHF There is no need to switch reception with the band.

It is a circuit diagram which shows the structure of the terrestrial digital broadcast receiving tuner of this invention. It is a circuit diagram of the frequency divider used for the terrestrial digital broadcast receiving tuner of the present invention. It is a circuit diagram which shows the structure of the conventional digital terrestrial broadcast receiving tuner.

Explanation of symbols

21: antenna 22: duplexer 23: first amplifier 24: variable tuning circuit 25: second amplifier 26, 27: first mixer 28: bandpass filter 29: third amplifier 30: second Mixer 31: Oscillator 32: PLL circuit 33: Reference oscillator 34: First frequency divider 35: Second frequency divider 36, 37: Band pass filter 38, 39: Third mixer 40: Synthesizer 41 : Third frequency divider

Claims (7)

A first mixer for orthogonally converting a UHF band digital television signal to a first intermediate frequency signal; and a second mixer for converting a VHF band digital television signal to a UHF band. A digital terrestrial broadcast receiving tuner characterized in that the VHF band television signal converted into the above is input to the first mixer and is orthogonally converted to the first intermediate frequency signal. 2. The terrestrial digital broadcast receiving tuner according to claim 1, wherein the VHF band digital television signal is converted into a band adjacent to a lower end side of the UHF broadcast band. An oscillator for supplying a local oscillation signal to the first mixer is provided, and the first divider is used to divide the oscillation signal output from the oscillator by 1/2. And the oscillation signal divided by the first divider is supplied to the second mixer via a second divider for further dividing the oscillation signal by half. The terrestrial digital broadcast receiving tuner according to claim 1 or 2. A demultiplexer for inputting the UHF band digital television signal and the VHF band digital television signal is provided, and the demultiplexed UHF band digital television signal is input to the first mixer. 4. The terrestrial digital broadcast receiving tuner according to claim 1, wherein the demultiplexed VHF band digital television signal is input to the second mixer. A variable tuning circuit is provided between the branching filter and the first mixer, and the VHF band digital television signal output from the second mixer after being converted to the UHF band is converted into the variable tuning circuit. The terrestrial digital broadcast receiving tuner according to claim 4, wherein the terrestrial digital broadcast receiving tuner is input to the first mixer via The digital television signal in the VHF band is arranged in a specific channel, and a band pass filter that passes through the specific channel is provided between the duplexer and the second mixer. Item 6. The digital terrestrial broadcast receiving tuner according to Item 4 or 5. A third mixer for orthogonally transforming the first intermediate frequency signal into a second intermediate frequency signal, a PLL circuit for controlling the oscillator, and a reference oscillator for supplying a reference signal to the PLL circuit, 7. The digital terrestrial broadcast receiving tuner according to claim 3, wherein the reference signal is divided into ½ and supplied to the third mixer.

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