JPH066693A - Channel selecting device - Google Patents

Abstract

PURPOSE:To prevent the capacity of a memory(ROM) for a frequency synthesizer system which is applicable to a multi-reception system from increasing and to shorten a channel search time. CONSTITUTION:This channel selecting device consists of a PLL frequency synthesizer system tuner 4, a detecting circuit 5 which detects the intermediate frequency signal from this tuner 4, a key circuit 7 which designates an automatic search at the time of channel presetting, a channel selecting microcomputer 6 which makes a search by supplying frequency data to the tuner 4 one after another at the time of the channel presetting according to the AFT output and synchronism detection signal from the detecting circuit 5 and frequency data from the frequency data memory 8 which has specific step width and then makes a next search with specific width based upon a channel interval frequency on the basis of frequency data obtained when a signal presence channel can be searched for, and a position memory 9 which stores frequency data on the signal presence channel determined by the automatic search by the microcomputer 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency synthesizer type channel selecting device in a television signal receiving device.

[0002]

2. Description of the Related Art A channel synthesizer of a frequency synthesizer type used in a television signal receiver has an automatic search function.

FIG. 3 shows a conventional channel synthesizer of a frequency synthesizer system.

In FIG. 3, a television signal induced in the antenna 11 is selected by the electronic tuning tuner 12 as a desired band channel. Electronic tuning tuner 12
The electronic tuning tuner 12 includes a high-frequency amplifier for amplifying received high-frequency waves, a local oscillator, and a frequency mixer for mixing the received high-frequency from the high-frequency amplifier and the local oscillation frequency from the local oscillator. The applied tuning voltage and band voltage are PLLIC (Phase Locked Loop Integ
rated circuit 13). PLL I
C13 is composed of a prescaler, a variable frequency divider, a phase comparator, a reference oscillator, a low pass filter, and a band switching circuit. The PLL IC 13 frequency compares the local oscillation frequency from the electronic tuning tuner 12 with the frequency data (frequency division ratio data) from the microcomputer 16 and compares the phase with a reference frequency, smooths the comparison data, and uses the electronic tuning tuner as a tuning voltage. Supply to 12. Also, PLL
The IC 13 creates a band voltage based on the band data from the microcomputer 16 and supplies it to the electronic tuning tuner 12. The electronic tuning tuner 12 and the PLL IC 13 have P
The tuner 14 of the LL frequency synthesizer system is configured. The frequency-converted video intermediate frequency output (hereinafter referred to as PIF output) from the electronic tuning tuner 12 is supplied to a video intermediate frequency detection circuit (hereinafter referred to as PIF detection circuit) 15 to perform video detection and synchronization detection.

The electronic tuning tuner 12 is controlled by a channel tuning microcomputer 16. The tuning microcomputer 16 is coupled to the key input circuit 17 and is also connected to a channel frequency data memory 18 in which frequency data and band data for receiving a television channel are written. The channel frequency data memory 18 is a ROM (Read
Only Memory). The tuning microcomputer 16 receives the memory (ROM) data of the desired channel in response to a channel selection command from the key input circuit 17 and outputs the data to the PLL IC in the tuner 14 of the PLL frequency synthesizer system.
Send to 13. The PLL IC 13 compares the local oscillation frequency from the tuner 12 with the channel data to generate a desired tuning voltage, and switches the band according to the band data.

The tuning microcomputer 16 is also supplied with the synchronization detection signal output from the PIF detection circuit 15 and an automatic frequency fine adjustment output (hereinafter referred to as AFT output). The sync detection signal is a signal indicating the presence or absence of the video sync signal in the PIF detection output. The AFT output is a signal indicating a deviation of the video intermediate frequency signal (PIF) from the specified value. With these two signals, the tuning microcomputer 16 can detect the presence or absence of the broadcast signal of the channel received by the electronic tuning tuner 12 and the frequency of the broadcast signal.

The broadcast signal receiving apparatus as described above has an auto search mode for automatically searching for a signal channel by searching for the presence or absence of a broadcast signal in addition to the normal channel selection mode. The automatic search mode is switched when a predetermined key is pressed by the key input circuit 17. In the auto search mode, the channel selection microcomputer 16 searches the table of the channel frequency data memory 18 in order of channel number. In the determination of the signal channel, the presence or absence of the signal and the frequency are determined by the synchronization detection and the AFT output, and when the signal is determined to be the signal, the search is stopped.

The contents of the two channel frequency data memories 18 of the North American M system and the European B / G system are shown in Table 1 below. Since there are many channels, U here
The table is only HF, and the video intermediate frequency (PIF) is 38.
0 MHz.

[0009]

[Table 1] In this table, the mode distinguishes the North American channel from the European channel, and the frequency data is the frequency data =
(Image carrier frequency) + (Image intermediate frequency). In addition, U of band data indicates UHF.

As shown in Table 1, for example, the North American channel 21 has unique frequency data of 551.25 MHz. In addition, the frequency data of European channel 21 is 509.25 MHz, and the frequency data does not match the same channel of the North American channel. Therefore, it is necessary to distinguish between modes 1 and 2. This means that the more multi-reception systems are supported, the more frequency data must be increased. Therefore, since the memory (ROM) capacity is increased and the number of channels is increased, the search time is further increased.

[0011]

As described above, in the frequency synthesizer channel selection method for the multi-reception system, since the frequency data peculiar to the channel is provided, the more the corresponding systems increase, the more the natural frequency data becomes. Since the number of channels is increased, the memory (ROM) capacity is increased and the number of channels is increased, so that there is a problem that the search time is further increased.

Therefore, the present invention is for eliminating the above-mentioned problems, and it is possible to prevent the increase of the memory (ROM) capacity in the frequency synthesizer system corresponding to the multi-reception system and to realize the shortening of the channel search time. An object of the present invention is to provide a synthesizer type channel selection device.

[0013]

A channel selection apparatus according to the present invention is a tuner for mixing a received broadcast signal with a local oscillation signal corresponding to a desired channel, converting the signal into a signal of a predetermined intermediate frequency, and outputting the signal. Then, the PLL frequency synthesizer that matches the local oscillation frequency of the tuner with the specified channel frequency by phase-comparing the frequency obtained by dividing the local oscillation frequency of the tuner with the reference frequency using frequency data according to the channel. System tuner, detection means for detecting the presence or absence of a broadcast signal by detecting the intermediate frequency signal output from this tuner, key input means for specifying the automatic search during channel presetting, and a specific value for the channel frequency. Constant frequency stepped first frequency data and a constant interval determined from the channel interval frequency. A first storage means for storing second frequency data of a step-up width and an automatic search by supplying frequency data to the tuner, when the automatic search is designated by the key input means. , The search is started from a predetermined specific frequency, the search is carried out at the interval of the first frequency data defined by the first storage means, and the first signal channel is detected using the detection result of the detection means. , The tuning control means for performing the next search at the interval of the second frequency data defined by the first storage means with reference to the frequency data of the channel, and the tuning control. Second storage means for holding the frequency data of the signal channel which has been selected and confirmed by the automatic search by the means in correspondence with the channel position. It is intended to.

[0014]

In the present invention, the automatic search at the time of channel preset starts the search from an arbitrary predetermined frequency, the television signal channel can be searched first, and after the frequency data of the channel is confirmed, the next In the automatic channel search, a channel search is performed based on predetermined channel frequency data with reference to the determined channel frequency data. For this reason, since only the basic frequency data is stored in the first storage means for storing the search frequency data, the eigenchannel data does not increase even in the multi-reception system, and the search speed is increased. It becomes possible.

[0015]

EXAMPLES Examples will be described with reference to the drawings. FIG. 1 is a block diagram showing a channel selection device according to an embodiment of the present invention.

In FIG. 1, the television signal induced in the antenna 1 is selected by the electronic tuning tuner 2 in a desired band. The electronic tuning tuner 2 includes a high frequency amplifier for amplifying a received signal, a local oscillator, and a frequency mixer for mixing the received signal from the high frequency amplifier with the local oscillation frequency from the local oscillator. The tuning voltage and band voltage applied to the tuning tuner 2 are supplied by the PLL IC 3. PLL IC3
Is composed of a prescaler, a variable frequency divider, a phase comparator, a reference oscillator, a low pass filter, and a band switching circuit. The PLL IC 3 frequency-divides the local oscillation frequency from the electronic tuning tuner 2 with frequency data (frequency division ratio data) from the microcomputer 6, and compares the phase with a reference frequency.
The comparison data is smoothed and supplied as a tuning voltage to the electronic tuning tuner 2. Further, the PLL IC 3 creates a band voltage based on the band data from the microcomputer 6 and supplies it to the electronic tuning tuner 2. The electronic tuning tuner 2 and the PLL IC 3 constitute a tuner 4 of a PLL frequency synthesizer system. The frequency-converted PIF output from the electronic tuning tuner 2 is supplied to the PIF detection circuit 5
The video signal is detected and the synchronization is detected.

The electronic tuning tuner 2 is controlled by a channel tuning microcomputer 6. Channel tuning microcomputer 6
Has an automatic search function for channel presets in addition to the normal tuning function. The tuning microcomputer 6 is coupled to the key input circuit 7 and is also connected to a frequency data memory 8 in which frequency data and band data for receiving a television channel are written. The frequency data memory 8 is composed of a ROM (Read Only Memory). In this ROM, not the fixed channel frequency data but the data of a constant step width determined from the upper and lower limit frequencies of the channel frequency of the corresponding system
Data having a constant step width determined from the channel interval frequency is written as the second frequency data. Further, the channel tuning microcomputer 6 is connected to a position memory 9 which holds frequency data of a signal channel which is detected when a search is performed using the frequency data of the frequency data memory 8 in an automatic search during channel presetting. There is. The position memory 9 is a RAM (Ramdom Acces
s Memory). In this RAM, the frequency data determined by the auto-search at the time of channel preset is stored in correspondence with the channel position, and when the channel position is designated by the key input circuit 7 at the time of normal channel selection, RA is designated.
Channel frequency data is read from M, and tuning is performed.

At the time of normal channel selection, the channel selection microcomputer 6 sends the memory (RAM) data of the desired channel to the PLL IC 3 in the tuner 4 of the PLL frequency synthesizer system in response to a channel selection command from the key input circuit 7. P
The LLIC 3 compares the local oscillation frequency from the tuner 2 with the channel frequency data from the position memory 9 to generate a desired tuning voltage, and performs band switching according to the band data.

Channel presetting microcomputer 6 at the time of channel presetting
Sends the memory (ROM) data to the PLL IC 3 in the PLL frequency synthesizer type tuner 4 in response to an auto search command from the key input circuit 7. PLL IC3
Performs a search operation by sequentially comparing the local oscillation frequency from the tuner 2 with the frequency data of a predetermined step from the frequency data memory 8 and generating a tuning voltage.

The tuning microcomputer 6 is also supplied with the synchronization detection signal output from the PIF detection circuit 5 and an automatic frequency fine adjustment output (hereinafter referred to as AFT output). The sync detection signal is a signal indicating the presence or absence of the video sync signal in the PIF detection output. The AFT output is a signal indicating a deviation of the video intermediate frequency signal (PIF) from the specified value. Based on these two signals, the tuning microcomputer 6 can detect the presence or absence of the broadcast signal of the channel received by the electronic tuning tuner 2 and the frequency of the broadcast signal.

As described above, in the broadcast signal receiving apparatus described above, in addition to the normal channel selection mode, the presence or absence of a broadcast signal is automatically searched during channel presetting, and the channel frequency data of the signal channel is set in the position memory 9. Has a preset function. The automatic search mode at the time of channel preset is switched when a predetermined key is pressed by the key input circuit 7.

Next, the automatic search operation at the time of channel preset will be described with reference to FIG. FIG. 2 shows the relationship between the search time and the search frequency during the automatic search.

The case of the M and B / G UHF described in the prior art will be described. Frequency data memory 8
In the ROM, data having a constant step width determined from the upper and lower limit frequencies of the channel frequency is written as first frequency data, and data having a constant step width determined from the channel interval frequency is written as second frequency data. Has been. Here, the lower limit frequency is 509.25 MHz for North American channel 14 and European channel 21.
And the upper limit frequency is 92 of the North American channel 83.
It is 3.25 MHz. Frequency step width is 250 kHz
The search speed is 30 msec / 1 step with z steps. There are 16 North American signal channels.

At the time of automatic search, first, the channel search is started in 250 kHz steps from the above lower limit frequency. Next, after there is a signal on 16 channels in North America, the detection of the channel frequency f0 is completed, and the channel frequency data is confirmed, the next channel search is based on this first channel frequency data as a basic channel interval. Based on the 6 MHz and 8 MHz steps, the search is performed in the common 2 MHz steps.

As described above, the channel search is performed at 250 kHz / 30 msec until the first channel can be searched during the automatic search, and the next search is 2 MHz / 30 msec.
Done in. Therefore, the channel search can be performed at a speed of 8 times after the one-station search.

By the above automatic search operation, the channel frequency data of a signal is stored in the RAM of the position memory 9.
Since it is stored (preset) in, the normal tuning thereafter can be performed by specifying the channel position.

[0027]

As described above, according to the present invention, it is not necessary to separately hold the data of the fixed channel as in the conventional case, so that the fixed memory capacity can be reduced. For example, it is effective in a channel selection system such as a multi-receiver, and in the automatic search at the time of channel presetting, the next search step width can be set based on the frequency data of the signal channel first selected. , The channel search speed is dramatically improved, and the channel search time can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing a channel selection device according to an embodiment of the present invention.

FIG. 2 is a graph illustrating the auto search operation of FIG.

FIG. 3 is a block diagram showing a conventional channel synthesizer of a frequency synthesizer system.

[Explanation of symbols]

 2 ... Electronic tuning tuner 3 ... PLL IC 4 ... PLL frequency synthesizer system tuner 5 ... Video intermediate frequency detection circuit (detection means) 6 ... Channel selection microcomputer (tuning control means) 7 ... Key input circuit (key input means) 8 ... Frequency data memory (first storage means) 9 ... Position memory (second storage means)

Claims (1)

[Claims] 1. A tuner that mixes a received broadcast signal with a local oscillation signal corresponding to a desired channel, converts the signal into a signal of a predetermined intermediate frequency, and outputs the signal, the tuner using frequency data corresponding to the channel. A PLL frequency synthesizer-type tuner that matches the local oscillation frequency of the tuner with a specified channel frequency by phase-comparing a frequency obtained by dividing the local oscillation frequency with a reference frequency, and an intermediate frequency output from this tuner. Detection means for detecting a signal to detect the presence or absence of a broadcast signal, key input means for specifying an automatic search at the time of channel presetting, first frequency data having a constant step width determined from a specific value of the channel frequency, and The first memory in which the second frequency data having a constant step width determined from the channel interval frequency is stored. Means for supplying frequency data to the tuner to perform an auto-search, and when the auto-search is designated by the key input means, the search is started from a predetermined specific frequency, and the first storage is performed. When the first signaled signal channel can be searched using the detection result of the detecting means, the next search is performed with reference to the frequency data of the channel. Is a channel selection control means for performing a search at an interval of the second frequency data defined by the first storage means, and frequency data of a signal channel having a channel selected and confirmed by an automatic search by the channel selection control means. A channel selection device, comprising: a second storage unit that holds the channel position.