JP2011244115A - Tuner for receiving digital broadcast, mobile receiver using the same, and channel search method used for the receiver - Google Patents

Abstract

An object of the present invention is to provide a digital broadcast receiving tuner in which reception quality is unlikely to deteriorate even when a search is being performed.
In order to solve this problem, the present invention provides an input terminal 2a connected to an antenna 3a, a low noise amplifier 8a, a gain control amplifier 9a supplied with the output of the low noise amplifier 8a, and a mixer. 10a, a full-segment tuner 7a having a filter 12a and an output terminal 13a, and a one-segment tuner 18 for receiving only one segment of a digital broadcast signal while receiving the output of the low-noise amplifier 8a. It is provided. Thereby, when the search operation is performed by the one-segment tuner 18, the level of the broadcast signal supplied to the mixer 10a can be supplemented by the low noise amplifier 8a and the gain control amplifier 9a.
[Selection] Figure 1

Description

  The present invention relates to a tuner for receiving a digital broadcast and a mobile receiving apparatus using the tuner.

  Hereinafter, a conventional digital broadcast receiving apparatus (used as an example of a mobile receiving apparatus) will be described. A conventional receiving apparatus is for viewing a 12-segment terrestrial digital broadcast (also referred to as a full segment), an antenna, a tuner to which the antenna is connected, and a demodulation to which the output of the tuner is connected. A circuit, a signal processing circuit to which an output of the demodulation circuit is connected, and an output terminal to which an output signal output from the signal processing circuit is supplied.

  In such a receiving apparatus, a broadcast signal wave of 12-segment terrestrial digital broadcast received by the antenna is input to the tuner. The tuner to which this signal is input converts the broadcast signal of the desired channel into an intermediate frequency and outputs it to the demodulation circuit. The demodulation circuit to which the tuner output is input demodulates the signal input from the tuner and outputs a transport stream signal (hereinafter referred to as a TS signal). Then, the signal processing circuit decodes the TS signal, reproduces the video signal and the audio signal, and outputs them to a display device and a speaker connected to the output terminal.

  Such a receiving device is mounted on a moving means such as a car and views a digital broadcast while moving, but may move across a broadcasting area due to movement. When approaching the boundary of the broadcast area, the video and audio are disturbed, and the reception quality deteriorates. In such a case, the receiving apparatus is searched for a receivable broadcast channel.

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

JP 2005-184548 A

  In such a conventional receiving apparatus, since there is one tuner, it cannot be received at the time of searching. In view of this, a method has been proposed in which a plurality of antennas and tuners are prepared in a receiving apparatus, and this problem is solved by using a receiving apparatus based on a combined diversity method. In other words, in this case, it is possible to continue watching the desired program by performing the search operation with one tuner and receiving the broadcast of the desired channel with the remaining tuners. However, while the search operation is being performed by the tuner, the number of tuners to be combined is reduced, resulting in a problem that reception quality is deteriorated.

  Accordingly, the present invention has been made to solve this problem, and an object of the present invention is to provide a tuner for receiving a digital broadcast in which reception quality is unlikely to deteriorate even when a search is being performed.

  In order to achieve this object, an input signal is branched between a low noise amplifier and a gain control amplifier of a tuner for receiving a 12-segment broadcast. One of the branched signals is supplied to the mixer via the gain control amplifier, and the other of the branched signals is supplied to the tuner for receiving one segment broadcast. As a result, the intended purpose can be achieved.

  As described above, according to the present invention, the first input terminal to which the digital broadcasting signal is input and the first low noise amplifier to which the first input terminal is connected are connected to the first antenna. A first gain control amplifier to which the output of the first low noise amplifier is supplied, an output of the first gain control amplifier is supplied to one input, and a first input to the other input A first mixer to which an output of the oscillator is supplied; a first filter connected to the output of the first mixer and passing a 12-segment broadcast signal of the digital broadcast signal; A first 12-segment broadcast receiving tuner having an output terminal for outputting an output signal of the filter to a first demodulating circuit for demodulating the 12-segment broadcast signal, and an output of the low-noise amplifier. , Digital broadcast reception tuner provided with a one-segment broadcast reception tuner for receiving only one segment broadcast signal of the total broadcast signal, and thereby the first 12-segment broadcast reception tuner Since the signal branched from between the low noise amplifier and the first gain control amplifier is supplied to the tuner for receiving one segment broadcast, the first low noise is obtained even if the search operation is performed by the tuner for receiving one segment broadcast. Digital broadcast reception that can compensate for the level of the broadcast signal input to the first mixer by the amplifier and the first gain control amplifier, and the reception quality of the broadcast to be viewed is difficult to deteriorate during the search. A tuner can be realized.

Circuit block diagram of receiving apparatus in this embodiment The circuit block diagram of the receiving apparatus in the second example

  Hereinafter, a receiving apparatus using the tuner in this embodiment will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a circuit block diagram of a receiving apparatus according to the present embodiment. In FIG. 1, a receiving apparatus 1 receives terrestrial digital broadcasting. An antenna 3a is connected to the input terminal 2a of the receiving device 1, and a terrestrial digital broadcast signal received by the antenna 3a is supplied. A display device 5 is connected to the output terminal 4a of the receiving device 1, and a speaker 6 is connected to the output terminal 4b. In the receiving device 1, the terrestrial digital broadcast signal received by the antenna 3 a is converted into a video and audio signal and output to the display device 5 and the speaker 6. Thereby, it is possible to view the broadcast program of the channel that the user wants to view.

  Next, details of the receiving apparatus 1 will be described. A 12-segment broadcast receiving tuner (hereinafter referred to as a full-segment tuner 7a) includes a low noise amplifier 8a, a gain control amplifier 9a, a mixer 10a, an oscillator 11a, a filter 12a, and an output terminal 13a. The input terminal 2a is shared by the receiving device 1 and the full segment tuner 7a.

  The low noise amplifier 8a is supplied with a terrestrial digital broadcast signal input to the input terminal 2a and amplifies the signal. The gain control amplifier 9a is supplied with the output of the low noise amplifier 8a and amplifies the signal. However, in the gain control amplifier 9a, the gain is controlled so that the level of the output signal from the gain control amplifier 9a is a constant value. The output of the gain control amplifier 9a is supplied to one input of the mixer 10a, and the output of the oscillator 11a is supplied to the other input. As a result, the mixer 10a mixes the signals from the gain control amplifier 9a and the oscillator 11a and converts them to an intermediate frequency signal. The filter 12a is supplied with the output of the mixer 10a and passes the intermediate frequency signal. For this purpose, the filter 12a passes a 12-segment broadcast band (in practice, a signal band including 12 segments + 1 segment) and has a pass band of about 6 MHz. As a result, the full-segment tuner 7a converts the terrestrial digital broadcast signal received by the antenna 3a into an intermediate frequency signal and outputs it from the output terminal 13a.

  The intermediate frequency signal output from the output terminal 13a of the full-segment tuner 7a is supplied to the demodulation circuit 14 that demodulates the 12-segment broadcast signal. The demodulation circuit 14 demodulates the intermediate frequency signal and outputs a transport stream signal (hereinafter referred to as a TS signal). The signal processing circuit 15 is supplied with the output of the demodulation circuit 14, decodes and expands the TS signal, and converts it into a video signal and an audio signal.

  Here, the full segment tuner 7a includes a distribution signal terminal 16a and a data input terminal 17a. The distribution signal terminal 16a is connected by distributing the output of the low noise amplifier 8a. On the other hand, the data input terminal 17a is connected to a PLL circuit loop-connected to the oscillator 11a, and the oscillator 11a oscillates a signal having a frequency corresponding to the channel data input to the data input terminal 17a and receives a desired channel. To do.

  Next, the one-segment broadcast receiving tuner (hereinafter referred to as the one-segment tuner 18) receives one-segment broadcast from the terrestrial digital broadcast received by the antenna 3a.

  The input terminal 18a of the one-segment tuner 18 is connected to the distribution signal terminal 16a of the full-segment tuner 7a, and a broadcast signal to which the output of the low noise amplifier 8a is distributed is supplied. The gain control amplifier 18b is supplied with the broadcast signal input to the input terminal 18a, and its gain is controlled so that the output level becomes a specified value. The output of the gain control amplifier 18b is supplied to one input of the mixer 18c, and the output of the oscillator 18d is supplied to the other input, and the outputs of the gain control amplifier 18b and the oscillator 18d are mixed to obtain an intermediate frequency. Convert frequency to signal. The filter 18e is supplied with the output of the mixer 18c and passes the intermediate frequency signal. For this purpose, the filter 18e passes the band of one segment broadcast and has a pass band of about 462 KHz. Then, the intermediate frequency signal output through the filter 18e is output from the output terminal 18f. The data input terminal 18g is connected to a PLL circuit loop-connected to the oscillator 18d. The oscillator 18d oscillates a signal having a frequency corresponding to the channel data input to the data input terminal 18g and receives a desired channel. Is.

  The demodulating circuit 19 demodulates the one-segment broadcasting signal, and is supplied with the intermediate frequency signal output from the output terminal 18f and demodulates the intermediate frequency signal. The control circuit 20 is supplied with the output of the demodulation circuit 19. In the present embodiment, the demodulation circuit 19 outputs a TS signal and a C / N ratio value to the control circuit 20. The control circuit 20 includes a circuit that determines program information, a reception channel, reception quality, and the like from the signal demodulated by the demodulation circuit 19. The value of the C / N ratio is given as a representative physical property value indicating the reception quality. Besides this, the S / N ratio of the received signal and the AGC voltage (gain control amplifier) used in the one-segment tuner 18 are also shown. 9a and the value of the control voltage to the gain control amplifier provided between the filter 12a and the output terminal 13a) are selected appropriately from the demodulation circuit 19 and the optimum value for specifying the reception quality is appropriately selected. It may be supplied to the circuit 20.

  The control circuit 20 is supplied with a signal indicating the reception quality of the full-segment tuner 7 a from the demodulation circuit 14 and the signal processing circuit 15. The control circuit 20 includes a circuit for determining program information, a reception channel, reception quality, and the like based on an output from the demodulation circuit 14 and a signal from the signal processing circuit 15. In the present embodiment, the BER of the full-segment tuner 7a is supplied as a signal indicating reception quality. In addition, the program information of the program received by the full-segment tuner 7 a is also supplied from the signal processing circuit 15 to the control circuit 20. Further, the output of the control circuit 20 is also connected to the data input terminal 17a and the data input terminal 18g, and the control unit generates a channel data signal for the full-segment tuner 7a and the one-segment tuner 18, thereby broadcasting the desired channel. Receive a signal. Note that the BER value is given as a representative physical property value representing the reception quality. Besides this, the C / N ratio value, the S / N ratio of the received signal, and the AGC voltage used in the one-segment tuner 18 From the values of (the control voltage to the gain control amplifier 18b and the gain control amplifier provided between the filter 18e and the output terminal 18f), the optimum value for specifying the reception quality is appropriately selected and demodulated. What is necessary is just to make it supply to the control circuit 20 from the circuit 14. FIG. Such C / N ratio values, S / N ratio values, AGC voltage values, and the like have a faster response to changes in response to changes in the level of broadcast signals than BER. Therefore, the reception quality can be quickly determined.

  With the above configuration, the broadcast signal supplied to the one-segment tuner 18 is distributed from between the low noise amplifier 8a and the gain control amplifier 9a. As a result, even if the level of the broadcast signal input to the gain control amplifier 9a becomes small due to the distribution, the level of the signal input to the mixer 10a is controlled to a specified level by controlling the gain of the gain control amplifier 9a. can do. Therefore, even if the output signal of the low noise amplifier 8a is distributed and supplied to the one-segment tuner 18, the reception quality of the full-segment tuner 7a can be hardly deteriorated. Therefore, both the full-segment tuner 7a and the one-segment tuner 18 can Even if reception is performed, the reception quality of the full-segment tuner 7a can be hardly deteriorated.

  Here, in the present embodiment, the switch 21 is inserted between the distribution signal terminal 16a and the input terminal 18a. The switch 21 is turned on / off according to a command from the control circuit 20. Here, the switch 21 is preferably an emitter follower type or a source follower type. This is because these types of switches have high input impedance, so that the influence of the level of the signal supplied to the gain control amplifier 18b depending on whether or not the one-segment tuner 18 is connected can be reduced. That is, even if the output signal of the low noise amplifier 8a is distributed and supplied to the gain control amplifier 9a and the one-segment tuner 18, the level of the signal supplied to the gain control amplifier 9a of the full-segment tuner 7a is unlikely to decrease. Become. Therefore, even if both the full-segment tuner 7a and the one-segment tuner 18 perform reception, the reception quality of the full-segment tuner 7a can be hardly deteriorated.

  In this embodiment, the signal is distributed by the switch 21, but this may be resistance distribution. At this time, the distribution signal terminal 16a and the input terminal 18a are directly connected without providing the switch 21. However, resistors are inserted between the signal branch point 22 where the signal output from the low noise amplifier 8a branches and the gain control amplifier 9a, and between the signal branch point 22 and the input terminal 18a. At this time, these resistance values are preferably selected so that the reception limit levels of the full-segment tuner 7a and the one-segment tuner 18 are substantially equal. Thereby, the comparison of the reception quality in the control circuit 20 can be performed with high accuracy.

  Now, the operation of the receiving apparatus 1 configured as described above will be described. First, an operation for selecting a program to be viewed will be described. A viewer (also an operator of the receiving apparatus 1) presses a button (not shown) for determining a desired channel and instructs the control circuit 20 of a channel (referred to as channel A) of a program to be viewed. The control circuit 20 to which this instruction is input outputs channel data corresponding to the desired channel to the data input terminal 17a. As a result, the full-segment tuner 7a can receive the desired channel and view the broadcast program of the desired channel. At this time, the control circuit 20 evaluates the reception quality of the reception channel. In the present embodiment, the control circuit 20 continuously observes the BER value and evaluates the quality by comparing it with a threshold value stored in advance in a memory (not shown).

  Here, the receiving apparatus 1 is mounted on a car or the like and moves. At this time, if the distance from the broadcasting station is increased due to movement, the level of the broadcast wave is reduced (weak electric field), and the reception quality is deteriorated. Therefore, in the receiving apparatus 1 according to the present invention, when the reception quality of the full-segment tuner 7a is deteriorated (weak electric field), it is automatically determined whether there is any other receivable channel using the one-segment tuner 18. It is detected (channel search) and the receivable channels are stored. Specifically, when the control circuit 20 evaluates the reception quality and determines that the reception quality is viewable, it is stored as a receivable channel. As a result, a receivable broadcast channel can be searched while the viewer is watching the program.

  By using the configuration according to the present invention, the reception quality of the full-segment tuner 7a can be hardly deteriorated while the channel search is performed by the one-segment tuner 18, so that the viewer can watch the program and not notice it. Channel search can be performed.

  In the present embodiment, when the broadcast wave level decreases, the BER value increases and the C / N ratio value decreases. Therefore, when the control circuit 20 determines that the BER value has become worse than a predetermined threshold value, the control circuit 20 operates the one-seg tuner 18 and causes the one-seg tuner 18 to perform a channel search. The control circuit 20 determines the reception quality based on the C / N ratio for the channel detected by the one-segment tuner 18. Specifically, by comparing the acquired C / N ratio value with a threshold value, it is determined whether or not reception is possible in the full-segment tuner 7a.

  At this time, the full-segment tuner 7a and the one-segment tuner 18 have a difference in signal level (reception sensitivity limit) that can be received. In general, one-segment broadcasting (one-segment tuner 18) can receive even a broadcast signal at a level as low as about 10 db as compared to twelve-segment broadcasting (full-segment tuner 7a). Therefore, reception when the channel is received by the full-segment tuner 7a from the C / N ratio value (or S / N ratio value or AGC voltage) with respect to the channel (channel B) received by the one-segment tuner 18. The quality is estimated, and whether or not channel B can be received by the full-segment tuner 7a is determined. For example, in the present embodiment, the estimation is performed by setting a threshold value higher than the value of the C / N ratio when the one-seg tuner 18 reaches the reception limit. In addition, it may be estimated by multiplying by a coefficient.

  It should be noted that the threshold for determining the reception quality of the broadcast received by the full-segment tuner 7a (starting the channel search) may have a margin with respect to the value at which reception is completely impossible. As a result, the search operation is performed before the viewing is completely impossible, so that the viewer is in a state before the viewing of the currently viewed broadcast becomes impossible (disturbance or stillness of the image or block noise). ), You can switch to another channel smoothly.

  Here, the search operation in the one-segment tuner 18 is performed in a weak electric field. In addition, since the reception quality is determined with a margin with respect to the reception limit, the gain of the low noise amplifier 8a is maximized when the one-segment tuner 18 starts a search. Therefore, even if the broadcast signal is distributed, the level of the broadcast signal input to the gain control amplifier 9a does not reach the reception limit level of the full-segment tuner 7a. Therefore, even when the one-segment tuner 18 is performing a search operation, it is possible to reduce deterioration in reception quality in the full-segment tuner 7a.

  In general, adjacent broadcast areas have an overlap. That is, in a place close to the boundary between these broadcast areas, it may be possible to view both broadcasts in adjacent broadcast areas. Such a place near the boundary of the broadcast area is a weak electric field, and the search operation in the one-segment tuner 18 is started. At this time, the one-segment tuner 18 also receives a broadcast signal in an adjacent broadcast area, and determines whether the control circuit 20 has a reception quality that can be received and viewed by the full-segment tuner 7a. When it is determined that it is, it is stored in the memory. By doing in this way, this invention can respond even when there exists an adjacent broadcast area.

  Here, in the present embodiment, the control circuit 20 acquires the program information of the program broadcast on each channel at the current time from the TS signal output from the demodulation circuit 19 by the search operation. Further, the control circuit 20 broadcasts from the program information signal output from the signal processing circuit 15 (or using the TS signal output from the demodulation circuit 14) on the channel (channel A) currently received by the full-segment tuner 7a. Get program information of the program being played. Then, the control circuit 20 compares the program information, and if a channel (referred to as channel B) that broadcasts the same program as channel A is detected among the searched channels, the reception quality of the full segment tuner 7a and the one segment By comparing with the reception quality of the tuner 18, it is determined which broadcasting station has the higher signal level. As a result, if the control circuit 20 determines that the signal level of channel B is higher, the control circuit 20 outputs channel data corresponding to channel B to the data input terminal 17a. As a result, the full-segment tuner 7a receives the channel B. In this way, even when moving across broadcasting areas, the program can be viewed without interruption.

  In this case as well, since the limit of the level of the broadcast signal that can be received differs between the one-segment tuner 18 and the full-segment tuner 7a, the control circuit 20 uses the characteristic value (C indicating the reception quality when the one-seg tuner 18 searches. (N / N ratio, S / N ratio, AGC voltage, etc.) are corrected (or the threshold value to be determined is changed), and the reception quality when the full-seg tuner 7a receives is estimated, and the full-seg tuner 7a It is determined whether or not channel B can be received.

(Embodiment 2)
Hereinafter, the present embodiment will be described with reference to the drawings. FIG. 2 is a circuit block diagram of the receiving apparatus in this embodiment. 2, the same reference numerals are used for the same components as those in FIG. 1, and the description thereof is simplified.

  In FIG. 2, the receiving apparatus 51 in the present embodiment employs a so-called diversity system. That is, in addition to the antenna 3a and the full segment tuner 7a, the antenna 3b and the full segment tuner 7b to which the antenna 3b is connected are provided. Specifically, the antenna 3b is connected to the input terminal 2b of the full-segment tuner 7b, and the terrestrial digital broadcast received by the antenna 3b is input. The full-segment tuner 7b converts the broadcast signal of the channel desired to be received into an intermediate frequency signal, and outputs it to the demodulation circuit 14a from the output terminal 13b, like the full-segment tuner 7a.

  Here, the demodulation circuit 14a synthesizes and demodulates the output of the full-segment tuner 7a and the output of the full-segment tuner 7b. Therefore, it is possible to receive well particularly for fading due to movement. In the present embodiment, the full seg tuner 7b is the same as the full seg tuner 7a. This eliminates the need to prepare two different types of tuners and makes management very easy.

  In the present embodiment, the output of the control circuit 20 is connected to the data input terminal 17b of the full-segment tuner 7b. Further, the demodulating circuit 14a outputs a signal synthesis ratio value between the full-segment tuner 7a and the full-segment tuner 7b, a BER value after synthesizing these signals, and the full-segment tuner 7a and the full-segment tuner 7b. The value of each C / N ratio is also input.

  In the demodulation circuit 14a according to the present embodiment, the output of the full-segment tuner 7a and the output of the full-segment tuner 7b are combined. This is a method of selecting one of the outputs and demodulating (selection diversity). You can use it. However, in this case, in the demodulation circuit 14a, the C / N ratio values of the full-segment tuner 7a and the full-segment tuner 7b are compared, and the signal received by the tuner having the better C / N ratio value is demodulated. In this case, the demodulation circuit 14 a outputs to the control circuit 20 the value of the C / N ratio of the demodulating tuner to the control circuit 20.

  Further, either the signal output from the distribution signal terminal 16a of the full segment tuner 7a or the signal output from the distribution signal terminal 16b of the full segment tuner 7b is selectively supplied to the input terminal 18a. ing. Therefore, in the present embodiment, a changeover switch 21a is provided in which one terminal is connected to the distribution signal terminal 16a of the full-segment tuner 7a and the other terminal is connected to the distribution signal terminal 16b of the full-segment tuner 7b. ing. An input terminal 18a is connected to the common terminal of the changeover switch 21a, and the changeover switch 21a connects either the full segment tuner 7a or the full segment tuner 7b to the input terminal 18a. Here, the change-over switch 21a may be an emitter follower type or source follower type switch as in the first embodiment.

  Further, since the changeover switch 21a may selectively supply the signal output from the distribution signal terminal 16a and the signal output from the distribution signal terminal 16b to the input terminal 18a, the distribution signal terminal 16a and the input terminal 18a. And the distribution signal terminal 16b and the input terminal 18a are connected. The switches 21 may be inserted between the distribution signal terminal 16a and the input terminal 18a and between the distribution signal terminal 16b and the input terminal 18a. In this case, each switch 21 is turned ON / OFF in an exclusive relationship (when one is ON, the other is OFF).

  Now, the operation of the receiving apparatus 51 configured as described above will be described. Here, differences from the first embodiment will be mainly described, and descriptions of elements that perform the same operations are simplified. When an instruction for a channel of a program to be viewed is input, the control circuit 20 outputs channel data corresponding to the desired channel to the data input terminal 17a and the data input terminal 17b. As a result, both the full-segment tuner 7a and the full-segment tuner 7b receive the same channel, and each output an intermediate frequency signal to the demodulation circuit 14a. The demodulation circuit 14a to which the intermediate frequency signal is input can receive a desired channel by outputting a TS signal from a signal obtained by synthesizing these intermediate frequency signals. At this time, the control circuit 20 continuously observes the BER value, the synthesis ratio, and the respective C / N values (or the respective AGC voltage values). The control circuit 20 evaluates the reception quality by comparing the input BER value with a threshold value stored in advance in a memory (not shown). In this embodiment, the evaluation is performed by the BER. However, when the reception quality is determined using the C / N ratio value (AGC voltage), for example, the average value of each value is used, or each value is determined by the combination ratio. Use a weighted average.

  When the value indicating the reception quality is worse than a predetermined threshold value, the changeover switch 21a is connected to one of the channels, a search operation is performed by the one-segment tuner 18, and a channel that can be received by the full-segment tuner 7b. Store in memory.

  Now, an example of switching of the changeover switch 21a will be described. The normal control circuit 20 switches the changeover switch 21a so as to be connected to the tuner side having the larger value of the synthesis ratio (the side with good reception quality). As a result, since the branch is from the tuner on the side with good reception quality, the influence on the reception quality can be further reduced.

  However, when the synthesis ratio of the full-segment tuner 7a and the full-segment tuner 7b in the demodulation circuit 14a is 1 to 0, the output signal of the full-segment tuner 7b is not used for demodulation. . Therefore, in such a case, the control circuit 20 checks the value of the C / N ratio of the full-segment tuner 7b. Then, from the value of the C / N ratio, it is determined whether the level of the broadcast signal input to the antenna 3b is a signal level that can be received by the one-segment tuner 18. If it is determined that the one-segment tuner 18 can receive, the changeover switch 21a is connected to the full-segment tuner 7b side. However, when the one-segment tuner 18 determines that reception is impossible, the selector switch 21a is connected to the full-segment tuner 7a side.

  In this embodiment, the combined diversity method using two antennas and two tuners is used, but this may be further increased. The present invention can obtain the same effect even when applied to a receiving apparatus 51 by combining diversity using four or more tuners, such as a receiving apparatus 51 mounted on an automobile or the like.

  The digital broadcast receiving tuner according to the present invention has an effect that there is little deterioration in the reception quality of a program viewed during channel search, and is particularly useful when used for a digital broadcast receiving television mounted in a car or the like.

2a input terminal 3a antenna 7a full segment tuner 8a low noise amplifier 9a gain control amplifier 10a mixer 11a oscillator 12a filter 14 demodulation circuit 18 one segment tuner

Claims (9)

A first input terminal to which a digital broadcasting signal is input, a first low noise amplifier to which the first input terminal is connected, and a first low noise amplifier connected to the first antenna; A first gain control amplifier to which an output is supplied, and an output of the first gain control amplifier is supplied to one input, and a first oscillator to which the output of the first oscillator is supplied to the other input A mixer, a first filter connected to an output of the first mixer and passing a 12-segment broadcast signal of the digital broadcast signal; and an output signal of the first filter for the 12-segment broadcast signal. A first 12-segment broadcast receiving tuner having an output terminal for outputting to a first demodulation circuit for demodulating a broadcast signal, and an output of the low noise amplifier are supplied, and one segment of the digital broadcast signal Cement digital broadcast receiving tuner and a tuner for 1 segment broadcasting reception for reception is provided only broadcast signals. A tuner for receiving one-segment broadcasting has a second input terminal to which the output of the first low-noise amplifier is supplied, and a second gain control to which a signal input to the second input terminal is supplied. An amplifier, a second mixer whose one input is supplied with the output of the second low-noise amplifier and whose other input is supplied with the output of the oscillator, and connected to the output of the second mixer A second filter that passes a one-segment broadcast signal of the digital broadcast signal, and an output terminal that outputs an output signal of the second filter to a second demodulation circuit that demodulates the one-segment broadcast signal The digital broadcast receiving tuner according to claim 1, further comprising: 3. The digital broadcast receiving tuner according to claim 2, wherein a first switch is inserted between the first low noise amplifier and the second input terminal, and the first switch is of an emitter follower type or a source follower type. . A second 12-segment broadcast receiving tuner connected to the second antenna is provided, and in the first demodulation circuit, output signals from the first 12-segment broadcast receiving tuner and the second 12-segment broadcast receiving tuner Or a process of either selecting the output signal of either the first 12-segment broadcast receiving tuner or the second 12-segment broadcast receiving tuner. The digital broadcast receiving tuner according to claim 2. The second tuner has a third input terminal to which the digital broadcast signal input to the second antenna is input, a second low-noise amplifier to which the third input terminal is connected, and the second tuner The third gain control amplifier supplied with the output of the low noise amplifier, the output of the third gain control amplifier supplied to one input, and the output of the third oscillator supplied to the other input And a third filter connected to the output of the third mixer for passing a 12-segment broadcast signal of the digital broadcast signal, and an output signal of the third filter Is provided to the first demodulating circuit, a first switch is inserted between the first low noise amplifier and the second input terminal, and the second low noise amplifier. And a second switch between the second input terminal Input to the first and second switches digital broadcast receiving tuner according to claim 4 in which both the emitter follower or source-follower. A first input terminal to which a digital broadcasting signal is input, a first low noise amplifier to which the first input terminal is connected, and a first low noise amplifier connected to the first antenna; A first gain control amplifier to which an output is supplied, and an output of the first gain control amplifier is supplied to one input, and a first oscillator to which the output of the first oscillator is supplied to the other input A mixer, a first filter connected to the output of the first mixer and passing a 12-segment broadcast signal of the digital broadcast signal, and an output supplied with an output signal of the first filter A first 12-segment broadcast receiving tuner having a terminal, a first demodulator circuit connected to the output terminal and demodulating the 12-segment broadcast signal, and an output of the first demodulator circuit Audio signal And a signal processing circuit for converting the signal into a video signal and an output terminal from which the audio or video signal is output. The output of the low noise amplifier is supplied, and one segment of the digital broadcast signal is supplied. A one-segment broadcast receiving tuner that receives only broadcast signals, a second demodulator circuit connected to the output terminal of the one-segment broadcast receiver tuner, and an output of the second demodulator circuit are connected and the 1 A receiving apparatus provided with a control circuit for causing a segment broadcast receiving tuner to perform a search operation. The control circuit obtains program information of the currently received program from the signal output from the first demodulation circuit or signal processing circuit, and at the current time from the signal output from the second demodulation circuit by the search operation. The receiving apparatus according to claim 6, wherein program information of a broadcast program is acquired, and program information of the currently received program is compared with program information of the receivable program. A tuner for receiving 12-segment broadcast, an output of the tuner for receiving 12-segment broadcast, a first demodulating circuit for demodulating a 12-segment broadcast signal, a tuner for receiving 1-segment broadcast, and for this one-segment broadcast A control circuit to which a tuner output is supplied and a second demodulation circuit for demodulating a one-segment broadcast signal; and a control circuit to which the output of the second demodulation circuit and the first demodulation circuit is supplied. Is used for a receiving device to which a first value indicating the reception quality of the broadcast received by the 12-segment broadcast tuner and a second value indicating the reception quality of the broadcast received by the 1-segment broadcast tuner are input. In the search method, the step of receiving the first channel by the tuner for receiving the 12-segment broadcast, and this step After the step, the control circuit obtains the first value, after this step the control circuit compares the first value with a predetermined first threshold, and in this step When the control circuit determines that the first value has exceeded the threshold value and has changed in a direction in which the reception quality deteriorates, search for a receivable channel in the one-segment broadcast reception tuner after the comparison step. The step of searching includes the step of receiving a second channel by the tuner for receiving one-segment broadcasting, the step of acquiring the second value by the control circuit after this step, After the step, based on a second value, the reception quality when the second channel is received by the 12-segment broadcast tuner is estimated, Search method of a receiving apparatus having a step of determining reception possibility in two channels. A signal processing circuit to which the output of the first demodulation circuit is supplied, and after the step of receiving the first channel, the control circuit receives a first signal from either the first demodulation circuit or the signal processing circuit; The control circuit is configured to acquire the first program information broadcasted at the current time on the channel and to determine whether or not reception is possible in the step of determining whether or not reception is possible. Obtaining the second program information broadcasted at the current time on the second channel from the output of the second demodulation circuit, and after this step, the second program information and the first program information A reception quality estimated from the second value after the step of comparing and the step of comparing the program information when the first and second broadcast information match in this step; And the control circuit determines that the reception quality estimated from the second value in this step is better than the reception quality based on the first value. The receiving device search method according to claim 8, wherein the second channel is received by a 12-segment broadcasting tuner.

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