KR100686756B1 - Automatic channel search apparatus and method - Google Patents

Abstract

An automatic channel search apparatus and a method therefor are provided to perform AFT(Auto Fine Tuning) by using different information by comparing an image frequency separated from a tuner unit with an image frequency of a frequency table stored in a CPU and transmitting difference between the image frequencies to the CPU by using frequency counting. A PLL(Phase Locked Loop) module(60) outputs a clock frequency according to a channel frequency map table by channel search. A clock comparator(71) compares the clock frequency with an image IF(Intermediate Frequency) signal, obtains frequency difference, and outputs the obtained frequency difference information. A clock counter(72) counts the frequency difference information outputted from the clock comparator(71), and outputs the counted value. A CPU(80) controls AFT by using frequency difference information corresponding to the counted value outputted from the clock counter(72).

Description

Automatic channel search apparatus and method

1 is a system configuration diagram for automatic channel discovery.

FIG. 2 is a detailed configuration diagram of the tuner unit of FIG. 1. FIG.

3 is a detailed configuration diagram of a conventional video detection unit.

4 is a diagram illustrating an AFT process using a conventional ADC value.

5 to 7 is a flow chart showing a conventional automatic channel search method.

8 is a detailed configuration diagram of a video detection unit in the automatic channel search apparatus according to the present invention.

9 to 11 are flowcharts illustrating an automatic channel searching method according to the present invention.

The present invention relates to an automatic channel search apparatus and method using a difference between a channel frequency and an image frequency of a tuner.

In general, a television that reproduces a broadcast signal including a video signal and an audio signal wirelessly transmitted from a plurality of broadcast stations is a means for designating a broadcast station that transmits a specific broadcast program to enable viewing of a desired broadcast signal. A tuner is essential. Tuning data uniquely set for each broadcasting station is applied to this tuner, thereby enabling selective tuning of a desired broadcasting signal among a plurality of broadcasting channels.

In addition to a channel of a broadcasting station that delivers a broadcast signal through a wireless channel, in a situation where a cable broadcasting that delivers a broadcast signal to a specific receiver is performed by a wired channel, as the bandwidth of a viewable channel increases, In addition to the more cumbersome work of tuning, relatively long time is required for tuning of a desired broadcast channel.

In a television, a tuner for tuning a broadcast channel is sequentially applied to specific tuner data to automatically search for a broadcast channel that can be viewed, and the auto-detected tuner data is sequentially stored as a memory means. The automatic channel search method is applied to simplify the tuning of the desired channel by automatically searching the memory means by operating the channel up / down buttons provided on the panel or the control panel of the remote control device. to be.

1 is a block diagram for automatic channel search in a television.

A tuner unit 10 for tuning a broadcast signal received through an ANT and a cable channel and converting the tuned broadcast channel signal to an intermediate frequency to output the video and audio signals; It is configured to include a central processing unit (CPU) 20 connected to the tuner unit 10 by serial communication (SCL, SDA) to control the tuning and gain, and to output the tuning data for channel searching.

FIG. 2 is a detailed configuration diagram of the tuner unit of FIG. 1.

Referring to FIG. 2, the RF unit amplifies an input unit 31 for receiving an antenna signal and a signal received by the input unit 31, and outputs the RF signal by tuning to a local oscillation frequency of a local oscillator 32 corresponding to preset data. An RF unit 30 including an amplifying unit 33 and a mixing unit 34 for mixing the signal amplified by the RF amplifying unit 33 and outputting at an intermediate frequency; SAW (surface acoustic wave) filter 41 which passes only the required frequency band from the output signal of the mixing section 34, and a video and sound detection section that demodulates video and audio signals from the signal passing through the SAW filter 41. And a demodulator 40 including an RF gain control unit (RF AGC) 44 for automatic gain control of the RF amplification unit 33.

The automatic channel search operation will be described with reference to FIGS. 1 and 2 as follows. The central processing unit 20 outputs tuning data for the automatic channel to the tuner unit 10 connected by serial communication when the automatic channel searching command is received, so that the tuner unit 10 performs the automatic tuning operation based on the tuning data. do. At this time, the tuner 10 is composed of an RF unit 30 and a demodulator 40, as shown in Figure 2 to perform channel tuning and demodulation.

The input unit 31 of the RF unit 30 receives and outputs a broadcast signal, and the RF amplifying unit 33 performs channel tuning using the oscillation frequency of the local oscillator 33 which is RF amplified and oscillated by tuning data. Will print. The tuned signal output by the RF amplifier 33 is mixed by the local oscillation frequency in the mixer 34 and output at an intermediate frequency.

In the demodulator 40, only the required band is passed from the intermediate frequency by the SAW filter 41, and the signal passing through the SAW filter 41 is a video signal through the video detector 42. The sound signal is output through the sound detector 43. At this time, the AFT (Auto Fine Tuning) voltage corresponding to the image signal frequency is output from the video detector 42 to the central processing unit 20 to perform the AFT tuning operation using this voltage. The sound detection unit 43 then outputs the voice intermediate frequency SIF-out. Here, the RF gain control unit 44 automatically adjusts the gain of the RF amplifier 33.

Conventionally, the AFT voltage curve (graph) detected by the video detector 42 is used during automatic channel search, and the video detector 42 uses the CVBS (Composite Video) of the channel through AFT tuning as shown in FIG. 3. Demodulated and outputted. The video detector 42 includes an AFT detector 51, a VIF processor 52, and a video trap 53. The ATF detection unit 51 detects the AFT voltage from the intermediate frequency signal and outputs it to the central processing unit. The VIF processing unit 52 processes the image intermediate frequency signal and transmits the signal to the video trap 53, and the video trap 53 is a channel. It outputs by demodulating the composite video signal of.

At this time, the central processing unit 20 performs the channel search operation by using the AFT voltage curve by checking the ADC voltage is changed from the AFT voltage to the DC voltage. That is, the AFT locking operation is performed according to the AFT tuning curve.

4 shows an example of a channel search using a conventional AFT voltage, and has a center frequency (Fo, current point), a one-step shift frequency (62.5 KHz), and a shift frequency (± 1.5) when there is no sync signal. MHz, low frequency (Fo-1.5MHz), when the synchronization signal is present and the ADC voltage is 4 (ADC = 4) shows the moving frequency (375KHz).

A conventional automatic channel search method will now be described with reference to FIGS. 5 to 7.

When the automatic channel search starts, the PLL data is set (S101) and waits for a first wait time (for example, 70 ms) (S102). When the first time is over, it is checked whether the synchronization is performed (S103). If there is a synchronization signal, the PLL data is set (S104). If there is no synchronization signal, the current point (Current point) is compared with the upper data of the PLL (S015) and ends when it is larger than the upper data, and the PLL upper data (Upper) data is terminated. If smaller, it is determined whether the current point is equal to the PLL Low data (S106), and then the PLL is moved to the PLL Shift Lower (+1.5 MHz, -1.5 MHz) according to the determination result. . In other words, when there is no synchronization signal, it is shifted by ± 1.5 MHz.

After setting the PLL data in step S104, as shown in FIG. 6, after waiting for a second waiting time (for example, 40 ms) and confirming that the synchronization and the ADC are 4 or less (S110), if both conditions are satisfied, ADC = If the two conditions are not satisfied (S114), and if the two points are not satisfied, the valley point (jump) is set to 8 or less, and then the PLL data is set to the frequency at -375KHz or + 375KHz.

If the ADC = 2, the tuner performs the tuning operation normally, or confirms that the ADC = 3. If ADC = 3, a high layer jump is performed. If ADC ≠ 3, a low layer jump is performed to set PLL data. Then, it moves to item ②.

Subsequently, after waiting for the third waiting time (40 ms) as shown in FIG. 7 (S118) and checking whether there is synchronization (S119), and if there is a synchronization signal after checking whether ADC = 4 (S120), ADC = 4 In this case, it is checked whether ADC = 3 or ADC = 2 (S121, S122) and if it has the corresponding value, normal tuning operation is performed (S123). If the ADC is not equal to the ADC = 3 and the ADC = 2, the count is increased (S124) and the PLL data setting (+62.5 KHz) is performed when the count is less than the threshold (for example, 5) (S125).

Conventionally, the ADC voltage obtained by changing the AFT voltage output from the tuner to a DC voltage is checked by moving a predetermined step (62.5KHz * 12 = 750KHz) to the-side at the channel-specific tuning point (FO). If the ADC voltage is higher than the high reference voltage compared to the reference voltage (ADC = 4), the frequency is moved in the order of 3-2 and 2-3 to check the positive tuning point.

Conventionally, in performing AFT locking according to an AFT tuning curve detected from an image signal detector, an ADC voltage must be changed and checked, and thus an AFT locking operation is complicated. Accordingly, there is a problem that the channel search time is increased.

The present invention provides an automatic channel search apparatus and method for performing AFT locking using difference information of an image frequency.

The present invention compares the image frequency separated by the tuner unit with the image frequency of the frequency table stored in the central processing unit, and transmits the difference to the central processing unit using its frequency count, thereby performing AFT tuning using the difference information. The present invention provides an apparatus and method for automatic channel discovery that can be performed.

Automatic channel search apparatus according to the present invention for achieving the above object,

In the automatic channel search apparatus of a broadcast receiver,

A PLL module for outputting a clock frequency according to a channel frequency map table according to channel searching;

A clock comparator for comparing the clock frequency with an image intermediate frequency signal to obtain a frequency difference and outputting the frequency difference;

A clock counter for counting and outputting frequency difference information output from the clock comparator;

And a central processing unit controlling AFT (Auto Fine Tuning) tuning by using frequency difference information corresponding to the count output from the clock counter.

The image intermediate frequency processor may further include separating the image intermediate frequency signal and outputting the same to the clock comparator.

An automatic channel discovery method according to another embodiment of the present invention,

(a) determining whether a synchronization signal is present after the first waiting time when the PLL data is set;

(b) storing PLL data settings if there is a synchronization signal, and if there is no synchronization signal, calculating the current point to shift the PLL frequency in the positive or negative direction and re-determining whether there is a synchronization signal;

(c) After setting the PLL data, determine the two conditions for the presence of the synchronization signal and whether the AFC level is within a certain range after the second waiting time, and if the two conditions are met, perform the tuning after confirming whether the AFC level is minimum or maximum. And if the two conditions are not satisfied, setting the PLL data again through the valley jump using the valley counter.

Preferably, the method further comprises: (d) setting the PLL data through a high or low layer jump if the AFC level is at a value between maximum / minimum unless it is maximum or minimum.

Preferably, (e) after setting the PLL data in step (d), checking whether there is a synchronization signal after a third waiting time, and performing a tuning operation when the AFC level is maximum or minimum when there is a synchronization signal; (f) if the AFC level is not the maximum or the minimum, further increasing the count, and then adjusting the direct frequency according to the range of the AFC value within the reference count, and then setting the PLL data.

Hereinafter, with reference to the accompanying drawings as follows.

8 is a block diagram illustrating an automatic channel discovery apparatus according to an exemplary embodiment of the present invention. FIG. 8 is a detailed configuration diagram of the video detector, and the same parts will be described with the same reference numerals with reference to FIGS. 1 and 2.

A clock comparator 71 which receives the PLL data from the PLL module 60 and compares the image frequency of the pre-stored frequency table with the image intermediate frequency output from the tuner unit; and the clock comparator 71 A clock counter 72 for counting the frequency difference information of the video signal, an image intermediate frequency (VIF) processor 73 for receiving an intermediate frequency signal and processing a video signal, and a video trap 74 for outputting only a CVBS signal; A video detector 70,

The central processing unit 80 performs AFT tuning using the count value input from the clock counter 72.

Referring to the operation, in Figure 1, the broadcast signal input to the tuner unit 10 by cable or wireless is tuned to the intermediate frequency (A / V) and passed through the SAW filter, the video signal in the intermediate frequency signal The demodulated and outputted CVBS signal is output through the VIF processor 73 and the video trap of the video detector 70 of FIG. 8, and the sound signal is demodulated and output by the sound detector.

At this time, when the automatic channel search command is transmitted, the central processing unit 80 outputs the tuning data, and the tuner 10 performs channel tuning using the local oscillation frequency of the local oscillator oscillated by the tuning data. .

In this case, as shown in FIG. 8, the central processing unit 80 outputs channel selection data corresponding to a frequency table pre-stored in the PLL module 60 to perform a channel search, and the PLL module 60 outputs the channel selection data. The clock frequency is outputted to the video detection unit 70 by the operation.

The clock comparator 71 of the video detector 70 compares the difference between the clock frequency and the image frequency input by the VIF processor 73, and compares the difference frequency according to the comparison result with the clock counter 72. The clock counter 72 transmits the difference information to the central processing unit 80 through serial communication (SCL, SDA) using the difference frequency count.

Accordingly, the central processing unit 80 controls the automatic channel search operation to compensate for the difference by using the clock frequency and image frequency difference information. That is, the frequency difference is calculated using the clock comparison unit 71 and the clock counter 72 using the channel frequency map table (that is, AFC), which is the center frequency fosc of the tuner unit, and the pilot carrier frequency of the received broadcast signal. By transmitting the bit (eg, 16-bit) data to the CPU 80, the CPU 80 performs AFT tuning using the difference information. That is, AFT tuning is performed through frequency compensation using actual frequency difference information, not ADC voltage.

In addition, the central processing unit 80 may output data to compensate the frequency difference information to the PLL module in order to control the tuning operation of the tuner.

The automatic channel searching method according to the present invention will be described with reference to FIGS. 9 to 11 as follows.

If the PLL data is set by the automatic channel search command (S201), after waiting for the first waiting time (for example, 70ms), it is checked whether the signals are synchronized (S203). If there is a synchronization signal in the video signal, the PLL setting operation is performed (S204). If there is no synchronization signal, it is checked whether the current point (Current point, Fo) is less than or equal to the PLL UPPER data (S205). If it is not less than the upper PLL data, compare whether the current pointer is PLL LOWER data (S206), and if it is low data, shift the PLL data forward (+ 1.5MHz) (S207). -1.5MHz) is moved (S208). After that, the presence or absence of the synchronization signal is determined again using the changed PLL data.

After the PLL data is set, the process moves to step ⓐ and the process moves to step S209 shown in FIG. 10. In step S209, the second waiting time is waited, and when the second waiting time passes, it is checked whether the synchronization and AFC levels are within a predetermined range (187.5 <AFC, +187.5> AFC) (S210).

If the AFC frequency value is within the predetermined range, check whether the AFC level is the minimum (0) or the maximum (15 (= 187.5 / 12.5)) value, and at the minimum / maximum level, output the tuning data according to the AFT information to perform normal tuning. Will be performed. If there is no sync signal or not in the AFC range, check whether the valley counter value is below a certain value (eg, 8) (S211), and if the valley counter value is below a certain value, move the frequency through the valley jump (S212) (-375 KHz, +375 KHz) to set the PLL data (S213).

If the AFC level is not the minimum or maximum, the intermediate value checks whether the AFC is 8 levels (+ 187.5K IN) (S215), if it is 8 or more levels, performs the high layer jump operation (S216), and if it is less than 8 steps, the low layer The jump operation is performed (S217) to set the PLL data.

After performing the high / low layer jump operation, move to ⓑ, and if the waiting time is greater than or equal to the third waiting time (for example, 40 ms) as shown in FIG. 11, check whether or not the synchronization signal is performed (S219). If it is confirmed that the AFC is 8 levels or less (S220). If the AFC exceeds 8 levels, the process ends. If the AFC is 8 levels or less, it is checked whether the AFC is 0 or 15 levels (S221, S222). If AFC = 0 or 15 levels (or step range), perform the tuning operation normally (S223) .If AFC = 0 (-12.5Khz) or 15 (+ 12.5Khz), increase the counter and then increase the reference count (for example, 5). If the AFC range is greater than level 0 or less than level 8 (-Freq.Khz) (S226), the PLL setting is performed with the increased frequency (Direct + Freq) at the direct frequency (S225, S226, S228). Otherwise, the PLL setting operation is performed at the frequency reduced to the direct frequency (Direct-Freq) (S225, S227, S228). That is, the PLL data is set by adding or subtracting the direct frequency.

As described above, the present invention can perform tuning and PLL setting operation while shifting a frequency while performing AFT tuning using a pre-stored AFC table. In addition, the PLL data setting can be performed more smoothly by compensating the frequency per channel. This solves the time delay problem that occurs when performing AFT tuning with the ADC voltage.

So far, the present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be implemented. Here, the essential technical scope of the present invention is shown in the claims, and all differences within the equivalent range will be construed as being included in the present invention.

The present invention compares the image frequency separated from the tuner and the image frequency of the frequency table stored in the central processing unit, and transmits the frequency to the central processing unit using the frequency count corresponding to the difference, and the central processing unit uses the frequency difference information. By performing AFT tuning, the automatic channel search time can be shortened.

Claims (5)

In the automatic channel search apparatus of a broadcast receiver, A PLL module for outputting a clock frequency according to a channel frequency map table according to channel searching; A clock comparator for comparing the clock frequency with an image intermediate frequency signal to obtain a frequency difference and outputting the frequency difference; A clock counter for counting and outputting frequency difference information output from the clock comparator; And a central processing unit for controlling AFT (Auto Fine Tuning) tuning by using frequency difference information corresponding to the count output from the clock counter. The method of claim 1, And an image intermediate frequency processor which separates the image intermediate frequency signal and outputs the image intermediate frequency signal to the clock comparator. (a) determining whether a synchronization signal is present after the first waiting time when the PLL data is set; (b) storing PLL data settings if there is a synchronization signal, and if there is no synchronization signal, calculating the current point to shift the PLL frequency in the positive or negative direction and re-determining whether there is a synchronization signal; (c) After setting the PLL data, determine the two conditions for the presence of the synchronization signal and whether the AFC level is within a certain range after the second waiting time, and if the two conditions are met, perform the tuning after confirming whether the AFC level is minimum or maximum. And if the two conditions are not satisfied, resetting the PLL data through the valley jump using the valley counter. The method of claim 3, and (d) setting the PLL data through a high or low layer jump if the AFC level is at a value between maximum / minimum unless it is maximum or minimum. The method of claim 4, wherein (e) after setting the PLL data in step (d), checking whether there is a synchronization signal after a third waiting time, and performing a tuning operation when the AFC level is maximum or minimum when there is a synchronization signal; (f) if the AFC level is not the maximum or minimum, increasing the count, and then compensating by adjusting the direct frequency according to the range of the AFC value within the reference count, and then setting the PLL data. How to navigate your channel.

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