JP2007166257A - Channel-select searching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of taking time in obtaining channel-select search information. <P>SOLUTION: This channel-select searching device is provided with an input terminal 12 for receiving a high frequency signal, a mixer 16, wherein the signal inputted to the input terminal 12 is supplied to one input and an output of an oscillator 17 is connected to the other input, a filter 18 connected to an output of the mixer 16, a discriminator 19 with an output of the filter 18 connected thereto, and a memory 20 with an output of the discriminator 19 connected thereto. A center frequency of the filter 18 is set narrower than the band of an intermediate frequency outputted from the mixer 16, and the discriminator 19 decides the type of the high frequency signal inputted from the input terminal 12 on the basis of an output level from the filter 18 while making the inside of the band of the intermediate frequency variable to thereby be able to attain the expected target. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a channel selection search device that searches for a high-frequency signal.

  Hereinafter, a conventional channel selection search apparatus will be described. As shown in FIG. 6, the conventional channel search device includes an electronic tuner 1 that selects an input high-frequency signal, a demodulator 2 connected to the output of the electronic tuner 1, and an output of the demodulator 2. And a channel selection control unit 3 that controls the electronic tuner 1 based on the above. The demodulator 2 includes an error corrector 4 for correcting an error in the digital broadcast signal and an error detector 5 connected to the output of the error corrector 4. Based on the output, a digital broadcast wave and an analog broadcast wave included in the input high-frequency signal are discriminated.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2003-333441 A

  However, such a conventional channel selection search device determines whether a digital broadcast wave or an analog broadcast wave based on the output of the error detector 5 when performing a channel search. For this reason, the error rate must be calculated every time a channel is selected, and there is a problem that it takes time to make a determination.

  Accordingly, the present invention has been made to solve this problem, and an object of the present invention is to provide a channel selection search device that can obtain channel selection search information in a short time.

  In order to achieve this object, the channel selection search apparatus of the present invention has an input terminal to which a high-frequency signal is input, a signal input to the input terminal supplied to one input, and the other input has an oscillator. A mixer connected to the output; a first filter connected to the output of the mixer; a determiner connected to the output of the first filter; a memory connected to the output of the determiner; The center frequency of the first filter is set to be narrower than the intermediate frequency band output from the mixer, the inside of the intermediate frequency band is variable, and based on the output level from the first filter The determination unit determines the type of the high-frequency signal input from the input terminal. Thereby, the intended purpose can be achieved.

  According to the present invention, the center frequency of the first filter connected to the output of the mixer that performs the channel selection operation is set to be narrower than the band of the intermediate frequency output from the mixer, and the band of the intermediate frequency is set. The inside is variable, and the type of the high-frequency signal input from the input terminal is determined by the determiner based on the output level from the first filter.

  Therefore, since the determination is made based on the output level output from the first filter, the error is corrected by the error corrector and the input is made in a shorter time than the case where the determination is made based on the error rate as in the conventional case. The type of the high-frequency signal input to the terminal can be determined.

  In addition, since an error corrector is not required, it is possible to realize a small size and a low price.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram of a channel selection search apparatus 10 according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 11 denotes an antenna to which a high frequency signal such as a digital broadcast wave or an analog broadcast wave is input. The antenna 11 is connected to an input terminal 12.

  The input terminal 12 is connected to an input of a filter 13 that allows both analog broadcast waves and digital broadcast waves to pass therethrough. The output of the filter 13 is connected to the input of an AGC (automatic gain control) amplifier 14. The output of the AGC amplifier 14 is connected to the input of a second filter 15 (hereinafter referred to as filter 15) that passes the frequency of the selected channel. The output of the filter 15 is connected to one of the mixers 16. Connected to the input. The other input of the mixer 16 is connected to the output of an oscillator 17 that outputs a variable frequency for channel selection.

  The output of the mixer 16 is a first filter 18 (hereinafter referred to as a filter 18) having a variable center frequency and a narrower bandwidth than the intermediate frequency within the intermediate frequency output from the mixer 16. The output of the filter 18 is connected to the input of a determination unit 19 that determines the type of the high-frequency signal input from the input terminal 12.

  Here, the filter 18 may be composed of a plurality of fixed filters, or may be composed of a single filter whose center frequency can be varied. In any case, the bandwidth is about 500 KHz, and any bandwidth can be used as long as the pass frequency can be varied within the intermediate frequency.

  The output of the determiner 19 is connected to the memory 20. Reference numeral 21 denotes a controller, and the output of the controller 21 is connected to a filter 18, a determiner 19, and a PLL (phase lock loop) circuit 22. The output of the PLL circuit 22 is connected to the input of the oscillator 17. Reference numeral 23 denotes a data input terminal to which channel selection data is input, and is connected to an input of the controller 21.

  The output of the mixer 16 is connected to the control terminal 14 a of the AGC amplifier 14 via the gain controller 24.

  The operation of the channel selection search apparatus 10 configured as described above will be described below. First, when a search command is input from the data input terminal 23, the controller 21 sequentially outputs channel selection data to the PLL circuit 22. The PLL circuit 22 controls the oscillation frequency output from the oscillator 17 based on the input search command.

  On the other hand, high-frequency signals (including digital broadcast waves and analog broadcast waves) that arrive at the antenna 11 (which may be a cable) are input to the input terminal 12. The high-frequency signal input to the input terminal 12 suppresses frequencies other than the digital broadcast wave and the analog broadcast wave by the filter 13 that passes the band of the digital broadcast wave and the analog broadcast wave. The output of the filter 13 is controlled by the AGC amplifier 14, and the output is input to the mixer 16 via the filter 15 that mainly passes the channel specified by the channel selection data.

  In the mixer 16, the channel is selected by the output of the AGC amplifier 14 and the output of the oscillator 17 and converted to an intermediate frequency. The gain of the AGC amplifier 14 is controlled by the gain controller 24 in accordance with the intermediate frequency level. Therefore, the level output from the mixer 16 is controlled so that the level of the high-frequency signal input to the input terminal 12 is substantially constant from the weak electric field to the strong electric field.

  As shown in FIG. 2, the output of the mixer 16 has a different waveform depending on the type of the high-frequency signal input to the input terminal 12. That is, 31 is a digital broadcast wave, and 32 is an analog broadcast wave. Reference numeral 34 denotes an unnecessary interference signal in the vicinity of these broadcast waves.

  Here, the horizontal axis 35 is the frequency (MHz), and 35 c is the center frequency of the digital broadcast wave 31 and the analog broadcast wave 32. The center frequency 35c is, for example, 50 MHz. Reference numeral 35d denotes a bandwidth of a high-frequency signal input from the input terminal 12, which has a bandwidth of 6 MHz. The vertical axis 36 is the level of the signal output from the mixer 16.

  As shown in FIG. 2, the high-frequency signal input from the input terminal 12 has the following characteristics. That is, the digital broadcast wave 31 exists at substantially the same level throughout the bandwidth 35d. The analog broadcast wave 32 has a video carrier 32a in a low frequency region with a bandwidth 35d, and an audio carrier 32b in a high frequency region with a bandwidth 35d. The level of the audio carrier 32b is smaller than the level of the video carrier 32a. Reference numeral 34 denotes a waveform of an interference signal input from the input terminal 12, and the location of the interference signal 34 is indefinite.

  As described above, since a characteristic waveform is formed depending on the type of the high-frequency signal, the type of the high-frequency signal input to the input terminal 12 can be determined by selecting and focusing on this waveform.

  In order to realize this, three filters 18 having a bandwidth of, for example, about 500 KHz are prepared at the output of the mixer 16. The center frequency of one of the filters 18 a is set substantially equal to the video carrier 32 a of the analog broadcast wave 32. The center frequency of the second filter 18b is substantially equal to the center frequency 35c of the digital broadcast wave 31 and the analog broadcast wave 32. The center frequency of the third filter 18c is made substantially equal to the frequency of the audio carrier wave 32b of the analog broadcast wave 32.

  The filter 18 may not be a fixed filter but a filter whose center frequency can be varied. Further, the digital broadcast wave 31 and the analog broadcast wave 32 can be discriminated even if the filter 18 is two filters of the filter 18a and the filter 18b or two filters of the filter 18b and the filter 18c. In the present embodiment, in order to improve the determination accuracy, the high frequency signal is determined using the three filters 18a, 18b, and 18c.

  Next, the determination of the high frequency signal performed by the determination unit 19 will be described with reference to FIG. The digital broadcast wave 31 has outputs from all of the filters 18a, 18b, and 18c. In this case, it is determined that the digital broadcast wave 31 has been input. The analog broadcast wave 32 is output when the filter 18a and the filter 18c output, and the filter 18b does not output. In this case, it is determined that the analog broadcast wave 32 is input. In the case of the analog broadcast wave 32, the analog broadcast wave 32 can be more accurately determined by including a condition that the level output from the filter 18a is greater than the level output from the filter 18c.

  In the case of other combinations, it is determined that all are interference signals and not broadcast waves. In the case of this interference signal, the following three patterns exist. That is, as shown in the interference signal 34a, there is an output only in the filter 18a and there is no output in the other filters 18b and 18c, and when there is an output only in the filter 18b as shown in the interference signal 34b, the other filters 18a The case where there is no output in the filter 18c and the case where there is an output only in the filter 18c and there is no output in the other filters 18a and 18b as shown in the interference signal 34c.

  As described above, in the present embodiment, since the type of the high frequency signal is determined based on the logical product condition of the three filters 18a, 18b, and 18c, the type of the high frequency signal can be determined accurately at high speed. .

  Next, determination using the two filters 18a and 18b will be described. The digital broadcast wave 31 is a case where there is an output from both the filters 18a and 18b, and it is determined that the digital broadcast wave 31 has been input. The analog broadcast wave 32 is output when the filter 18a is output and is not output by the filter 18b, and it is determined that the analog broadcast wave 32 is input.

  When the two filters 18a and 18b are used, the interference signal 34a cannot be determined.

  The digital broadcast wave 31 and the analog broadcast wave 32 can also be determined using the two filters 18b and 18c. That is, the digital broadcast wave 31 is output from both the filters 18b and 18c, and it is determined that the digital broadcast wave 31 has been input. The analog broadcast wave 32 is output when the filter 18c is output and is not output by the filter 18b, and it is determined that the analog broadcast wave 32 is input.

  When the two filters 18b and 18c are used, the interference signal 34c cannot be determined.

  As described above, since the type of the high frequency signal can be determined based on the logical product condition of the two filters 18a and 18b or the filters 18b and 18c, compared to the case where the three filters 18a, 18b, and 18c are used. Miniaturization and price reduction can be achieved.

  FIG. 4 shows a block diagram of the filter 18 that uses three fixed filters or a variable center frequency filter and can also determine the interference signals 34a to 34c. FIG. 4A shows a filter 18 formed by fixed filters 18a, 18b, and 18c. Electronic changeover switches 41a and 41b are used to connect the changeover switches 41a and 41b to the inputs of the filters 18a, 18b, and 18c. The filters 18a, 18b, and 18c are electronically switched by inserting them into the outputs. Control of the electronic switches 41 a and 41 b is controlled by the controller 21. In this case, since the pass frequency is fixed, stable performance can be obtained.

  FIG. 4B shows an example of a filter 18d that can vary the center frequency using a varicap diode. In this filter 18d, three stages of voltages are sequentially applied to realize a filter 18d having filter characteristics corresponding to the filters 18a, 18b, and 18c, respectively. In this case, it can be divided into three or more stages. Reference numeral 18e denotes a control terminal for changing the center frequency, which is controlled by the controller 21. In this case, since only one filter 18 is required, downsizing can be realized. In this manner, the filter 18a, 18b, 18c or filter 18d is used to determine the type of the high frequency signal input from the input terminal 12 by the determiner 19 based on the output level as shown in FIG. .

  The high-frequency signal determined in this way is stored in the memory 20 for each type of high-frequency signal. That is, the controller 21 scans the entire band of the high-frequency signal, and sequentially stores the frequencies of the digital broadcast wave 31 and the analog broadcast wave 32 that can be received in the area together with the channel number.

  As described above, since the determination is made based on the output level output from the filter 18, the error correction unit 4 corrects the error by using the error corrector 4 and makes a determination based on the error rate as in the prior art. The type of high frequency signal can be determined in time.

  Further, since the error corrector 4 and the error detector 5 are not required, it is possible to realize a small size and a low price.

(Embodiment 2)
FIG. 5 is a block diagram of an electronic tuner 45 using the channel selection search apparatus 10 described in the first embodiment. In FIG. 5, the same components as those in the first embodiment are denoted by the same reference numerals, and the description is simplified.

  The electronic tuner 45 according to the second embodiment includes a third filter 46 (hereinafter referred to as an intermediate frequency filter 46) connected to the output of the mixer 16, and an output terminal 47 connected to the output of the intermediate frequency filter 46. It consists of The intermediate frequency filter 46 has a center frequency of 50 MHz and a bandwidth of 6 MHz.

  Reference numeral 19a denotes a determiner, and the output of the intermediate frequency filter 46 is connected to one input of the determiner 19a. This is different from the determiner 19 described in the first embodiment. 21a is a controller, and this controller 21a is different from the controller 21 described in the first embodiment in that it controls the determiner 19a.

  The operation of the electronic tuner 45 configured as described above will be described below. Also in this electronic tuner 45, a channel selection search is performed in the same manner as in the first embodiment, and the result of the channel selection search is stored in the memory 20. Further, since the output of the intermediate frequency filter 46 is input to the determination unit 19a during the channel selection search, the channel selection search time can be shortened as described below.

  That is, the oscillation frequency of the oscillator 17 is scanned by the controller 21a, and the scan is stopped when the output of the intermediate frequency filter 46 exists. Then, at this frequency, the type of the high-frequency signal input to the input terminal 12 is determined based on the same reference as in the first embodiment. By using the intermediate frequency output from the intermediate frequency filter 46 as described above, a channel where the output of the intermediate frequency filter 46 does not exist can be skipped. Therefore, the time required for the channel selection search can be shortened.

  In the second embodiment, since the output of the mixer 16 is connected to the output terminal 47 via the intermediate frequency filter 46, it can be used as the electronic tuner 45.

  That is, the operator inputs the channel number to be viewed from the data input terminal 23. Then, the controller 21a controls the oscillation frequency of the oscillator 17 to the corresponding oscillation frequency via the PLL circuit 22. Thus, the high frequency signal input from the input terminal 12 is selected by the mixer 16 and the intermediate frequency filter 46 and output from the output terminal 47.

  As described above, the electronic tuner 45 according to the present embodiment also includes a channel selection search device, so that only channels that can be received in that area can be efficiently viewed.

  Since the channel selection search apparatus of the present invention can obtain channel selection search information in a short time, it can be applied to a portable device using an electronic tuner.

Block diagram of a channel selection search apparatus according to Embodiment 1 of the present invention Same as above, high-frequency signal waveform diagram Same as above FIG. 2 is a block diagram of the filter, (a) is a block diagram of the fixed filter, and (b) is a block diagram of the variable filter. Block diagram of electronic tuner in the second embodiment Block diagram of a conventional channel selection search device and an electronic tuner using the same

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Channel selection search apparatus 12 Input terminal 16 Mixer 17 Oscillator 18 Filter 19 Judgment device 20 Memory 21 Controller

Claims (5)

An input terminal to which a high-frequency signal is input, a mixer in which the signal input to this input terminal is supplied to one input and the output of the oscillator is connected to the other input, and the output of this mixer is connected A first filter, a determiner connected to the output of the first filter, and a memory connected to the output of the determiner, and the center frequency of the first filter is derived from the mixer. It is set to be narrower than the output intermediate frequency band, the inside of the intermediate frequency band is variable, and the high-frequency signal input from the input terminal in the determiner based on the output level from the first filter. Tuning search device that determines the type. The channel selection search device according to claim 1, wherein the first filter includes a plurality of fixed filters. The channel selection search device according to claim 1, wherein the first filter is a filter whose center frequency is variable. An AGC amplifier and a second filter are inserted in this order between the input terminal and one input of the mixer, and connected from the output of the mixer to the control terminal of the AGC amplifier via a gain controller. 1. The channel selection search device according to 1. The channel selection search device according to claim 1, wherein a third filter that passes an intermediate frequency is connected to an output of the mixer according to claim 1, and an output of the third filter is connected to an input of a determiner.

Images