JP2011114783A - Television receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a television receiver that allows the device side to automatically perform processing for reducing effect of an interference signal. <P>SOLUTION: The television receiver, which generates an intermediate frequency (IF) signal from a received signal and uses the IF signal to output video or audio, has a first IF generator for generating an IF signal from a first local oscillation frequency; a second IF generator for generating an IF signal from a second local oscillation frequency different from the first local oscillation frequency; a receiving status determinator for determining receiving statuses of the IF signals output from the first IF generator and the second IF generator; and a selective output unit for selecting one of the first and second IF generators, which has a better receiving status, and causing the selected IF generator to output the IF signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a television receiver, and more particularly to a television receiver that modulates a channel signal into an intermediate frequency signal.

  2. Description of the Related Art Conventionally, television receivers that receive digital broadcasts and BS broadcasts with an antenna and extract digital data from the broadcast radio waves are known. The television receiver includes a channel selection unit corresponding to each of the broadcasts. After the channel selection unit extracts a predetermined frequency band of the broadcast signal and modulates the extracted signal into an intermediate frequency signal, To convert to digital data and output as video.

  In addition, there is known one that modulates a channel signal into an intermediate frequency signal by the heterodyne method in the channel selection unit. In the frequency modulation by the heterodyne method, the amplified channel signal is combined with a local oscillation frequency having a predetermined frequency to perform frequency modulation, and the modulated signal is extracted through a bandpass filter.

  In the above-described television receiver, when an interfering signal exists in the same frequency band as the modulated signal, the video output by the subsequent circuit may not be performed correctly due to the interfering signal. For this reason, a tuning unit that reduces the influence of an interference signal by changing the local oscillation frequency is disclosed (for example, see Patent Documents 1-3).

JP 2005-31965 A JP 2006-128757 A JP 2008-160660 A

  As described above, in the conventional tuning unit, the local oscillation frequency is changed in order to reduce the influence of the interference signal, but this frequency change is performed manually and is automatically executed under some conditions. It wasn't. As a result, the user is burdened.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a television receiver that can automatically execute processing when the apparatus side reduces the influence of an interference signal.

  In order to solve the above problems, in the present invention, in a television receiver that generates an intermediate frequency signal from a received signal and outputs video or audio using the intermediate frequency signal, the intermediate frequency is generated by the first local oscillation frequency. A first intermediate frequency generation unit that generates a signal; a second intermediate frequency generation unit that generates an intermediate frequency signal at a second local oscillation frequency different from the first local oscillation frequency; and the first intermediate frequency generation unit The reception state determination unit that determines the reception state of the intermediate frequency signal output from the second intermediate frequency generation unit, and the reception state that is better among the first intermediate frequency generation unit or the second intermediate frequency generation unit And a selection output unit for outputting the intermediate frequency.

In the invention configured as described above, the television receiver includes a first intermediate frequency generation unit that generates an intermediate frequency signal using a first local oscillation frequency, and a second intermediate frequency different from the first local oscillation frequency. A second intermediate frequency generation unit that generates an intermediate frequency signal based on the local oscillation frequency, and the reception state determination unit is configured to output the intermediate frequency signal output from the first intermediate frequency generation unit and the second intermediate frequency generation unit. The reception state is determined, and the selection output unit selects one of the first intermediate frequency generation unit or the second intermediate frequency generation unit that has the determined reception state and outputs the intermediate frequency.
Therefore, when the interfering signal affects either the intermediate frequency generated by the first intermediate frequency generator or the second intermediate frequency generator, the intermediate frequency signal is compared and the better reception state is obtained. Since the intermediate frequency signal is selected, the influence of the interference signal can be automatically reduced on the television receiver side.

Further, as an example of a configuration for determining the reception state of the intermediate frequency signal, the reception state determination unit may determine the reception state based on a carrier / noise ratio of the intermediate frequency signal.
In the invention configured as described above, since the determination is made based on the carrier / noise ratio, it is possible to determine the reception state according to the signal state of the intermediate frequency signal.

The reception state determination unit may determine that the reception state is bad when the amplitude of the intermediate frequency signal is greater than a predetermined value.
When the intermediate frequency is combined with the interference signal and output, the signal level is often detected as the interference signal level. Therefore, the reception state of the intermediate frequency signal can be more easily determined by detecting the reception state based on the signal level.

Further, the first intermediate frequency generation unit and the second intermediate frequency generation unit can change the first and second local oscillation frequencies, and the reception state determination unit is not good in the reception state. In this case, the first and second local oscillation frequencies may be changed to generate an intermediate frequency signal again, and a determination may be made using the newly generated intermediate frequency signal.
In the invention configured as described above, the intermediate frequency is generated by the optimum local oscillation frequency even in an environment where the reception state is bad, so that it is possible to provide a television receiver having a high resistance to an interference signal.

  As another aspect of the present invention, the first intermediate frequency generation unit and the second intermediate frequency generation unit can change the first and second local oscillation frequencies, and the reception state determination unit The reception state is determined based on the carrier / noise ratio of the intermediate frequency signal. If both of the reception states are not good, the intermediate frequency signal is generated again by changing the first and second local oscillation frequencies. However, the determination may be made using the newly generated intermediate frequency signal.

As described above, according to the present invention, the influence of the interference signal can be automatically reduced on the television receiver side.
According to the second aspect of the present invention, it is possible to determine the reception state according to the signal state of the intermediate frequency signal.
According to the third aspect of the invention, it is possible to more easily determine the reception state of the intermediate frequency signal.
Furthermore, according to the invention concerning Claim 4, the television receiver with the strong tolerance with respect to a disturbance signal can be provided.

1 is a block configuration diagram illustrating a configuration of a television receiver 100. FIG. 3 is a block diagram illustrating a configuration of a front end unit 92. FIG. It is a figure explaining the frequency modulation of the channel signal performed by the front end part 92. FIG. 5 is a flowchart illustrating an oscillation frequency setting process executed by a front end unit 92. It is a figure for demonstrating the constellation display which shows the relationship between the phase of an intermediate frequency signal, and the value represented by this phase. It is a flowchart explaining the process performed by step S4 of FIG. 4 in 2nd Embodiment.

Embodiments of the present invention will be described below in the following order with reference to the drawings.
(1) First embodiment:
(2) Second embodiment:
(3) Other embodiments:

(1) First embodiment:
Hereinafter, a television receiver as a first embodiment according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating the configuration of the television receiver 90. A television receiver 90 shown in FIG. 1 extracts digital data based on a television broadcast received by an antenna (not shown) and outputs an image.

=== Configuration of Television Receiver ===
The television receiver 90 includes the following main parts. Reference numeral 91 denotes a control unit that controls driving of the television receiver 90. Reference numeral 92 denotes a front-end unit that extracts digital data of a channel selected through a remote control device from broadcast radio waves received by an antenna (not shown). Reference numeral 93 denotes a back-end unit, which decodes and outputs a video signal and an audio signal from selected digital data. Reference numeral 94 denotes a display, which outputs a video based on the decoded video signal. Reference numeral 95 denotes a speaker, which outputs audio based on the decoded audio signal. Reference numeral 96 denotes a remote control receiving unit that receives an infrared signal output from the remote control device and outputs a control command to the control unit 91.

  The control unit 91 controls driving of the television receiver 90 according to a control command input via the remote control receiving unit 96 or a stored program. The control unit 91 includes a CPU (not shown), a ROM that stores programs and data for driving the CPU, and a RAM that functions as a work area for the CPU. The control unit 91 and each unit constituting the television receiver 90 are connected via a bus, and control is performed via this bus.

  FIG. 2 is a block diagram illustrating the configuration of the front end unit 92. The front end unit 92 modulates the selected channel signal into an intermediate frequency signal, and a BPF (band pass filter) 80 that selects the channel signal selected by the user from the broadcast radio waves received by the various antennas by the remote control device. The first intermediate frequency generation unit 70 and the second intermediate frequency generation unit 60 that output the selected intermediate frequency signal, the demodulation circuit 50 that converts the selected intermediate frequency signal into digital data, and an arbitrary frequency according to the control of the control unit 91 The signal output part 40 which outputs the signal provided with is comprised.

  The first intermediate frequency generation unit 70 generates an intermediate frequency signal from the channel signal selected by the BPF 80 and outputs the intermediate frequency signal, and includes the following main part. Reference numeral 71 denotes an amplifier that amplifies the extracted channel signal. Reference numeral 72 denotes a mixer, which modulates the frequency of the amplified channel signal using the local oscillation frequency (first local oscillation frequency) FA output from the local oscillator 73. Reference numeral 74 denotes a PLL circuit that varies the period of the local oscillation frequency FA output from the local oscillator 73 in accordance with a control signal from the control unit 91. Reference numeral 75 denotes an AGC circuit that feedback-controls the gain of the amplifier 71. Reference numeral 76 denotes a BPF, which filters a signal having a predetermined frequency among the signals output from the mixer 72. Reference numeral 77 denotes an I / F amplifier that amplifies the signal output from the BPF 76.

  When the selected channel signal is input by the configuration of the first intermediate frequency generation unit 70, the mixer 72 modulates the frequency of the channel signal to a predetermined cycle by adding or subtracting the local oscillation frequency FA to the frequency of the channel signal. . The modulated channel signal is filtered by the BPF 76 for high frequency components or low frequency components, then amplified by the I / F amplifier 77 and output to the demodulation circuit 50 as an intermediate frequency signal.

  Similar to the first intermediate frequency generation unit 70, the second intermediate frequency generation unit 60 includes an amplifier 61, a mixer 62, a local oscillator 63, a PLL circuit 64, an AGC circuit 65, a BPF 66, and an I / F amplifier 67. ing. The frequency of the local oscillation frequency (second local oscillation frequency) FB output from the local oscillator 63 is set to be different from the frequency of the local oscillation frequency FA output from the local oscillator 73.

  The demodulating circuit 50 demodulates the intermediate frequency signal and includes the following main part. Reference numeral 51 denotes an AGC circuit that performs feedback control on the gains of the I / F amplifiers 67 and 77. Reference numeral 52 denotes a determination unit (reception state determination unit) that determines the reception state of the intermediate frequency signal output from the first intermediate frequency generation unit 70 and the second intermediate frequency generation unit 60. Reference numeral 53 denotes a switching circuit (selection output unit) that selects and outputs the intermediate frequency signal output from the first intermediate frequency generation unit 70 or the second intermediate frequency generation unit 60 according to the control signal from the control unit 91. . Reference numeral 54 denotes an A / D conversion circuit that performs analog / digital conversion on the intermediate frequency signal and outputs digital data. In addition, each part which comprises the above-mentioned demodulation circuit 50 is connected to the control part 91, and performs a process according to the control signal from the control part 91. FIG.

  The signal output unit 40 outputs a signal having an arbitrary frequency in response to an instruction from the control unit 91. The signal output unit 40 can output a signal having the same frequency as a plurality of channel signals that can be selected by the television receiver 90 as an inspection signal. The inspection signal is set to be converted into a predetermined digital value in advance when demodulated by the demodulation circuit 50.

  The back-end unit 93 includes a descrambling unit that unscrambles the acquired digital data, an MPEG demultiplexing unit that extracts an MPEG video / audio signal and TS signal from the descrambled digital data, The video / audio decoding unit is configured to decode the video / audio signal.

  With the above configuration, the television receiver 90 extracts digital data from the selected channel signal and outputs it as video or audio. Further, the television receiver 90 according to the present embodiment generates an intermediate frequency signal from the channel signal by the first intermediate frequency generation unit 70 and the second intermediate frequency generation unit 60 having different local oscillation frequencies (FA, FB). And output to the demodulator circuit 50 in the subsequent stage. Further, the demodulating circuit 50 can automatically demodulate a digital signal by automatically selecting the better received state among the input intermediate frequency signals (hereinafter, such processing is referred to as oscillation frequency setting processing). .

  FIG. 3 is a diagram for explaining the frequency modulation of the channel signal executed by the front end unit 92. As shown in FIG. 3A, when a disturbing signal is generated in a band close to the intermediate frequency signal, an error may occur in the demodulated digital signal. On the other hand, in the present invention, since the channel signal modulated by either the first intermediate frequency generation unit 70 or the second intermediate frequency generation unit 60 having a different local oscillation frequency is used, the band of the intermediate frequency signal is separated from the interference signal. The band can be set, and the video signal can be output satisfactorily while reducing the influence of the interference signal (FIG. 3B). Hereinafter, the function of the front end unit 92 according to the present invention will be described in more detail.

=== Description of Oscillation Frequency Setting Processing ===
FIG. 4 is a flowchart for explaining the oscillation frequency setting process executed by the front end unit 92. When the user operates the remote controller to select a desired channel, in step S1, the control unit 91 receives this channel selection signal and outputs an inspection signal having the same frequency as the selected channel signal to the BPF 40. Here, the frequency of each channel is set in the channel map stored in the memory (not shown), and the control unit 91 determines the frequency corresponding to the selected channel with reference to the channel map, and outputs the signal. The unit 40 is caused to output an inspection signal.

  In step S <b> 2, the control unit 91 causes the first intermediate frequency generation unit 70 to generate an intermediate frequency signal from the extracted channel signal. That is, the control unit 91 modulates the frequency of the inspection signal with respect to the first intermediate frequency generation unit 70 using the local oscillation frequency FA output from the local oscillator 73, and amplifies the modulated inspection signal with an amplifier. And generating an intermediate frequency signal.

  In step S <b> 3, the control unit 91 causes the second intermediate frequency generation unit 60 to generate an intermediate frequency signal from the extracted inspection signal. That is, the control unit 91 modulates the frequency of the inspection signal with respect to the second intermediate frequency generation unit 60 using the local oscillation frequency FB output from the local oscillator 63, and amplifies the modulated channel signal by an amplifier. Then, an intermediate frequency signal is generated.

  In step S4, the demodulation circuit 50 determines the reception state of the intermediate frequency signal output from the first intermediate frequency generation unit 70 and the second intermediate frequency generation unit 60. As an example, the determination unit 52 determines the reception state based on the carrier / noise ratio of the intermediate frequency signal output from the first intermediate frequency generation unit 70 and the second intermediate frequency generation unit 60. When the intermediate frequency signal is affected by the interference signal, the intermediate frequency signal is not generated correctly, and the carrier / noise ratio becomes high. Therefore, the determination unit 52 can determine the influence (reception state) of the interference signal by detecting the carrier / noise ratio of the intermediate frequency signal.

  As a specific example in which the determination unit 52 determines the carrier / noise ratio, the determination unit 52 determines the channel based on the relationship between the phase of the intermediate frequency signal and the digital value (1, 0, or a combination thereof) expressed by this phase. Determine the carrier / noise ratio of the signal. For example, in the DPSK system adopted in Japanese terrestrial digital broadcasting, predetermined data is transferred by changing the phase of a signal in accordance with the change of data. Therefore, the determination unit 52 determines the carrier / noise ratio of the intermediate frequency signal by comparing the phase change of the intermediate frequency signal with a value preset by the inspection signal that is the basis of the intermediate frequency signal.

  FIG. 5 is a diagram for explaining the constellation display showing the relationship between the phase of the intermediate frequency signal and the value represented by this phase. In this constellation display, the phase relationship of the intermediate frequency signal and the digital value corresponding to this phase are expressed on coordinates defined by the I axis (horizontal axis) and the Q axis (vertical axis). Therefore, in FIG. 5, the digital value “00” is expressed by an analog signal having a phase θ, and the digital value “11” is expressed by an analog signal whose phase is shifted by 90 degrees with respect to the digital value “00”. . On the other hand, a signal whose phase deviates from a predetermined coordinate increases the probability that an error will occur because the digital value cannot be accurately determined. Therefore, the determination unit 52 compares each phase shift of the intermediate frequency signal with a threshold value, and determines a noise / error rate in the intermediate frequency signal by determining a phase in which the shift is equal to or greater than the threshold value as an error.

  In step S5, the determination unit 52 compares the intermediate frequency signals based on the determination result in step S4. That is, the control unit 91 determines that the reception state of the intermediate frequency signal with a small carrier / noise ratio detected in step S4 is good.

  In step S6, the control unit 91 performs switching so that the intermediate frequency generation unit determined to have a good reception state in step S5 is used in the selected channel thereafter. Specifically, the control unit 91 causes the switching circuit 53 to establish a connection with either the first intermediate frequency generation unit 70 or the second intermediate frequency generation unit 60 according to the determination result of step S5. Therefore, thereafter, the intermediate frequency signal output from the intermediate frequency generator selected by the switching circuit 53 is output to the back end unit 93 through the A / D converter 54.

  As described above, the television receiver 90 includes the first intermediate frequency generation unit 70 and the second intermediate frequency generation unit 60 having different local oscillation frequencies, and according to the reception state of the channel signal output from each unit. The intermediate frequency signal can be automatically switched.

(2) Second embodiment:
The local oscillation frequency used by the first intermediate frequency generation unit 70 and the second intermediate frequency generation unit 60 may be configured to be variable by PLL control. That is, when the reception state is bad in both of the intermediate frequency signals output from the first intermediate frequency generation unit 70 and the second intermediate frequency generation unit 60, after changing the local oscillation frequency, the changed local oscillation frequency is used. The reception state may be determined again. By adopting the above configuration, an optimum local oscillation frequency can be selected even in an environment where the reception state is bad, and the resistance against an interference signal can be increased.

  FIG. 6 is a flowchart illustrating the process executed in step S4 of FIG. 4 in the second embodiment. Note that the configuration of the television receiver 90 according to the second embodiment is the same as that of the first embodiment, and will not be described.

  In the process in which the control unit 91 determines the reception state of the intermediate frequency signal in step S4 in FIG. 4, the control unit 91 outputs the intermediate signal output from the first intermediate frequency generation unit 70 to the determination unit 52 in step S11 in FIG. The reception state of the frequency signal is determined. In step S <b> 12, the control unit 91 causes the determination unit 52 to determine the reception state of the intermediate frequency signal output from the second intermediate frequency generation unit 60.

  Here, in step S11 and step S12, the determination unit 52 may determine the reception state of the intermediate frequency signal based on the signal level. That is, in FIG. 3A, when the intermediate frequency signal is combined with the interference signal, it is known that the signal level increases. It may be judged as “bad”. If the reception state is determined based on the signal level, it is not necessary to detect the phase of the intermediate frequency signal, so that the processing can be simplified. Of course, as a method of determining the reception state, it may be determined using the phase of the signal as in the first embodiment.

  If both of the reception states of the intermediate frequency signal determined in step S11 and step S12 are “bad” (step S13: YES), the control unit 81 outputs the local oscillators 63 and 73 to the PLL circuits 64 and 74 in step S15. The values of the local oscillation frequencies FA and FB are changed.

  In step S16, the control unit 91 reacquires the inspection signal, generates an intermediate frequency signal (steps S1 to S3 in FIG. 4), and executes the processes from steps S11 to S13 in FIG. The processing from step S11 to step S13 is performed until it is determined that one of the reception states of the intermediate frequency signals output from the first intermediate frequency generation unit 70 or the second intermediate frequency generation unit 60 is “good” ( Step S13: NO) Repeatedly.

  On the other hand, if the number of reception state determinations exceeds N in step S14 (YES), the control unit 91 determines that the environment in which the television receiver 90 is installed is bad, and ends the oscillation frequency setting process. (Step S18).

  In step S13, if any of the intermediate frequency signals output from the first intermediate frequency generation unit 70 or the second intermediate frequency generation unit 60 is determined to be “good” (NO), In S17, the control unit 91 stores the values of the local oscillation frequencies FA and FB changed in Step S14 in the memory. And it transfers to step 5 of FIG. 4, and a process is continued. The second embodiment has been described above.

(3) Other embodiments:
In the process of setting the local oscillation frequency, the use of the inspection signal is an example, and the present invention is not limited to this. That is, when the noise / error rate in the broadcast signal is set in advance, the reception state may be determined using the normal broadcast signal without using the inspection signal.

  Further, any timing can be assumed as the timing for executing the oscillation frequency setting process. In other words, it may be configured to be executed every time the user selects a channel, or may be configured to be executed automatically every predetermined period.

Needless to say, the present invention is not limited to the above embodiments. It goes without saying for those skilled in the art,
・ Applying mutually interchangeable members and configurations disclosed in the above embodiments by appropriately changing the combination thereof.− Although not disclosed in the above embodiments, it is a publicly known technique and the above embodiments. The members and configurations that can be mutually replaced with the members and configurations disclosed in the above are appropriately replaced, and the combination is changed and applied. It is an embodiment of the present invention that a person skilled in the art can appropriately replace the members and configurations that can be assumed as substitutes for the members and configurations disclosed in the above-described embodiments, and change the combinations and apply them. It is disclosed as.

  DESCRIPTION OF SYMBOLS 40 ... Signal output part, 50 ... Demodulation circuit, 51 ... AGC circuit, 52 ... Judgment part, 53 ... Switching circuit, 54 ... A / D conversion part, 60 ... 2nd intermediate frequency generation part, 61 ... Amplifier, 62 ... Mixer 63 ... Local oscillator, 64 ... PLL circuit, 65 ... AGC circuit, 66 ... BPF, 67 ... I / F amplifier, 70 ... first intermediate frequency generator, 71 ... amplifier, 72 ... mixer, 73 ... local oscillator, 74 ... PLL circuit, 75 ... AGC circuit, 76 ... BPF, 77 ... I / F amplifier, 80 ... BPF, 81 ... Control unit, 90 ... TV receiver, 91 ... Control unit, 92 ... Front end unit, 93 ... Back End part, 96 ... Remote control receiving part

Claims (5)

In a television receiver that generates an intermediate frequency signal from a received signal and outputs video or audio using the intermediate frequency signal,
A first intermediate frequency generation unit that generates an intermediate frequency signal using a first local oscillation frequency;
A second intermediate frequency generation unit that generates an intermediate frequency signal with a second local oscillation frequency different from the first local oscillation frequency;
A reception state determination unit for determining a reception state of the intermediate frequency signal output from the first intermediate frequency generation unit and the second intermediate frequency generation unit;
And a selection output unit that selects the first intermediate frequency generation unit or the second intermediate frequency generation unit that has a better reception state and outputs the intermediate frequency signal. Receiver.   The television receiver according to claim 1, wherein the reception state determination unit determines a reception state based on a carrier / noise ratio of the intermediate frequency signal.   The television receiver according to claim 1, wherein the reception state determination unit determines that the reception state is bad when the amplitude of the intermediate frequency signal is greater than a predetermined value. The first intermediate frequency generation unit and the second intermediate frequency generation unit can change the first and second local oscillation frequencies,
The reception state determination unit generates the intermediate frequency signal again by changing the first and second local oscillation frequencies when both of the reception states are not good, and uses the newly generated intermediate frequency signal. The television receiver according to any one of claims 1 to 3, wherein a determination is made. The first intermediate frequency generator and the second intermediate frequency generator can change the first and second local oscillation frequencies,
The reception state determination unit determines a reception state based on a carrier / noise ratio of the intermediate frequency signal,
When both of the reception states are not good, the intermediate frequency signal is generated again by changing the first and second local oscillation frequencies, and the determination is performed using the newly generated intermediate frequency signal. The television receiver according to claim 1.

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