KR20060083656A - Apparatus for digital automatic fine tuning - Google Patents

Abstract

The present invention relates to an automatic fine tuning (AFT) apparatus applied to an analog broadcast reception tuner. The present invention provides a microprocessor for generating a broadcast selection signal for determining whether a received broadcast signal is NTSC or PAL. A frequency counting unit counting a frequency of an input intermediate frequency signal at a predetermined reference counting count during a predetermined counting period; A window generator for generating a window signal for setting a reference counting frequency and a counting period of the frequency counting unit according to a nominal frequency of a broadcast method selected according to a broadcast selection signal of the microprocessor and a preset detection resolution; A controller configured to reset and / or preset control the frequency counting unit based on the window signal generated from the window generator; A latch unit operating according to a window signal output from the window generator to detect a counting value of the frequency counting unit at the end of the window signal and to maintain a predetermined time; In accordance with the broadcast selection signal of the microprocessor, the frequency counting value output from the latch unit is checked to determine whether the input intermediate frequency signal is within the automatic fine tuning range or outside the automatic fine tuning range. An automatic fine tuning determination / selection unit; A digital automatic including an output unit for outputting a frequency counting value output from the latch unit as automatic fine adjustment data indicating a deviation from a nominal frequency when within the automatic fine adjustment range according to the output signal of the fine adjustment determination / selection unit. Provide a fine adjustment device.

Digital Auto Fine Tuning, AFT, NTSC. PAL

Description

Digital automatic fine tuning device {APPARATUS FOR DIGITAL AUTOMATIC FINE TUNING}             

1 is a block diagram showing the configuration of a general tuner.

2 is a block diagram showing the configuration of a digital automatic fine tuning apparatus according to the present invention.

3A and 3B are tables showing an example of digital automatic fine tuning data according to the present invention.

4 is a detailed block diagram of the fine adjustment determination / selection unit of the present invention.

5 is a table showing an example of digital automatic fine tuning results according to the NTSC method of the present invention.

6 is a table showing an example of a digital automatic fine adjustment result according to the PAL method of the present invention.

* Description of the symbols for the main parts of the drawings *

20: digital automatic fine adjustment device 21: window generator

22: frequency counting unit 23: latching unit

24: control unit 25: fine adjustment judgment / selection unit

26 output unit 27 digital-to-analog converter

28 microprocessor

The present invention relates to an automatic fine tuning (AFT) device applied to an analog broadcast reception tuner, and more specifically, to detect a frequency difference from a nominal frequency by detecting an intermediate frequency generated from an analog broadcast reception tuner. The present invention relates to a digital automatic fine tuning device that can be detected simply by using a counter and can be applied to both NTSC and PAL analog broadcast reception.

In general, a device that processes a broadcast signal to receive an analog broadcast such as a television or a VTR or a set-top box includes a tuner for receiving a high frequency broadcast signal of a selected channel.

1 is a block diagram showing a schematic configuration of such an analog broadcast reception tuner. Referring to FIG. 1, a conventional analog broadcast reception tuner receives an RF source through an RF amplifier 11 and selects and amplifies an RF signal corresponding to a channel selected by a user. Here, the RF source is a high frequency broadcast signal of multiple channels including a modulated image, color, and voice carrier. Subsequently, the selected RF signal SRF is mixed with the local oscillation signal having a frequency corresponding to the selected channel by the synthesis unit 12 to convert the frequency into an intermediate frequency signal SIF. Subsequently, the intermediate frequency signal SIF is applied to the video and audio processor 14 at the rear stage as an output signal of the tuner, and is processed into a video signal and an audio signal.

In such an analog broadcast reception tuner, the RF amplifier 11 is amplified by tuning to the RF signal of the channel selected by the user, and the synthesizer 12 to a predetermined intermediate frequency of the frequency of the channel selected by the user In order to generate the local oscillation frequency required for the conversion, when the user selects a channel through the operation unit 19, the microprocessor 18 informs the tuning voltage generator 16 of the selected channel, and the tuning voltage generator 16 In Fig. 3), the tuning voltage corresponding to the selected channel is applied to the RF amplifier 11 and the local oscillator 15, so that the tuning frequency of the RF amplifier 11 and the oscillation frequency of the local oscillator 15 are varied. It is composed.

Meanwhile, when a broadcast station transmits a broadcast signal, a change may occur in a carrier frequency of the broadcast signal, and a change may occur in the oscillation frequency of the local oscillator 15 in the tuner. In this case, a change occurs in the intermediate frequency converted by the combining unit 12 to cause distortion of the image.

Accordingly, by reducing the deviation between the frequency of the signal which is frequency-converted and output by the combining unit 12 and the nominal frequency (meaning a predetermined intermediate frequency, for example, 45.75MHz in the NTSC method, 38.9MHz in the PAL method) In order to correct to the correct center frequency, the analog broadcast reception tuner detects a signal of an intermediate frequency applied to the video / audio processing unit 14 and calculates a deviation between the detected intermediate frequency and a set nominal frequency and thus the microprocessor 18. It is further provided with an automatic fine adjustment unit 17 to deliver. The microprocessor 18 transmits the automatic fine adjustment value transmitted from the automatic fine adjustment unit 17 to the tuning voltage generation unit 16, and thereby corrects the tuning voltage by the deviation in the tuning voltage generation unit 16. For example, ensure that the intermediate frequency signal exactly matches the center frequency of the preset nominal frequency.

The automatic fine adjustment unit 17 conventionally uses an output frequency of a voltage controlled oscillator (VCO) having an LC tank circuit as an input and an analog circuit for tuning the size of the variable coil (L of the LC tank circuit) outside the IC. Although implemented as, there is a problem in that the tank circuit is not integrated. In addition, when the signal level is low, frequency detection may be incorrectly executed, and if the signal is not input cleanly in the surrounding environment of the electric field, detection may not be performed. In addition, since the nominal frequency used in the NTSC and PAL broadcast is different, the conventional automatic fine tuning unit 17 has a problem that can not be applied to the two broadcasts at the same time.

The present invention has been proposed to solve the above problems of the prior art, the object of which is to detect the intermediate frequency generated in the analog broadcast receiving tuner can easily detect the frequency deviation from the nominal frequency by using a counter The present invention provides a digital automatic fine tuning apparatus that can be applied to both NTSC and PAL analog broadcast reception.

In order to achieve the above object, the present invention provides a microprocessor for generating a broadcast selection signal for determining whether a received broadcast signal is NTSC or PAL; A frequency counting unit counting a frequency of an input intermediate frequency signal at a predetermined reference counting count during a predetermined counting period; A window generator for generating a window signal for setting a reference counting frequency and a counting period of the frequency counting unit according to a nominal frequency of a broadcast method selected according to a broadcast selection signal of the microprocessor and a preset detection resolution; A controller configured to reset and / or preset control the frequency counting unit based on the window signal generated from the window generator; A latch unit operating according to a window signal output from the window generator to detect a counting value of the frequency counting unit at the end of the window signal and to maintain a predetermined time; In accordance with the broadcast selection signal of the microprocessor, the frequency counting value output from the latch unit is checked to determine whether the input intermediate frequency signal is within the automatic fine tuning range or outside the automatic fine tuning range. An automatic fine tuning determination / selection unit; A digital automatic including an output unit for outputting a frequency counting value output from the latch unit as automatic fine adjustment data indicating a deviation from a nominal frequency when within the automatic fine adjustment range according to the output signal of the fine adjustment determination / selection unit. Provide fine tuning device.

The window generating unit may calculate the reference counting frequency (X) and the counting period (b) of the frequency counting unit according to the nominal frequency f0 and the preset detection resolution (a) of the broadcasting method selected according to the broadcast selection signal. It is characterized by determining according to equation (2).

[Equation 1]

X = f0 / a

[Equation 2]

b = 1 / a

The window generator may further include a crystal oscillator for generating a predetermined reference frequency; And a window counting unit configured to divide the reference frequency generated by the crystal oscillator to generate a window signal corresponding to a counting period required to count the reference count.

In one embodiment of the present invention, the control unit, based on the reference counting count, the state value of a predetermined bit in the counting value at the end of the counting period when counting the frequency of the intermediate frequency signal of the same frequency as the air frequency It is preferable that all of the preset values become " 0 " are set, the window generating unit and the frequency counting unit are reset in synchronization, the operation of the frequency counting unit is checked, and the frequency counting unit is preset at a preset preset period.

Further, in one embodiment of the present invention, the automatic fine adjustment determination / selection unit checks the frequency counting value output from the latch unit to determine whether the input intermediate frequency signal is within the automatic fine adjustment range of the NTSC method. An NTSC fine adjustment determining unit determining whether the fine adjustment range is out of range; A PAL fine adjustment determining unit which checks the frequency counting value output from the latch unit and determines whether the input intermediate frequency signal is within an automatic fine adjustment range of the PAL method or outside an automatic fine adjustment range; In accordance with the broadcast selection signal received from the microprocessor, it is preferable to include a selection unit for selecting and outputting one of the determination results of the NTSC fine adjustment determination unit and the PAL fine adjustment determination unit.

In addition, an embodiment of the present invention may further include a digital / analog converter for converting the automatic fine tuning data output from the output unit into an analog signal according to the automatic fine tuning frequency-voltage curve.

Hereinafter, with reference to the accompanying drawings will be described in more detail the configuration and operation of the digital automatic fine tuning apparatus according to the present invention.

2 is a block diagram showing the configuration of a digital automatic fine tuning apparatus according to the present invention. 2, the digital automatic fine tuning device 20 according to the present invention includes a microprocessor 28 for generating a broadcast selection signal for determining whether a received broadcast signal is NTSC or PAL; A frequency counting unit 22 counting a frequency of an input intermediate frequency signal at a predetermined reference counting count during a predetermined counting period; The frequency counting unit according to the nominal frequency of the broadcast method selected according to the broadcast selection signal of the microprocessor 28 (for example, a reference frequency of IF, for example, 45.75 MHz in the NTSC method, 38.9 MHz in the PAL method) and a preset detection resolution. A window generator 21 for generating a window signal for setting a reference counting count and a counting period of (22); A controller (24) for resetting and / or preset controlling the frequency counting unit based on the window signal generated from the window generator (21); A latch unit 23 operating according to a window signal output from the window generator 21 to detect a counting value of the frequency counting unit at the end of the window signal and to maintain a predetermined time; The frequency counting value output from the latch unit 23 is checked according to the broadcast method selected by the broadcast selection signal of the microprocessor 28 to determine whether the input intermediate frequency signal is within an automatic fine tuning range. An automatic fine adjustment determining / selecting unit 25 for determining whether it is outside the fine adjustment range; When within the automatic fine adjustment range according to the output signal of the fine adjustment determination / selection unit 25, the frequency counting value output from the latch unit 23 is output as automatic fine adjustment data indicating a deviation from the nominal frequency. It is configured to include an output unit 26 to.

The microprocessor 28 of the present invention determines whether the received broadcast signal is NTSC or PAL and generates a broadcast selection signal accordingly.

The frequency counting unit 22 of the present invention counts the frequency of the input intermediate frequency signal at a predetermined counting period (counting time interval). The frequency counting unit 22 may be implemented as an up / down counter that receives an input of an intermediate frequency signal to a clock stage and counts up or down, and more preferably, it is implemented as a down counter.

The counting period of the counting unit 22 is determined according to the nominal frequency and the counting resolution in the window generator 21 described below.

The window generator 21 of the present invention sets the counting period of the frequency counting unit 22 according to the broadcast selection signal according to the broadcast selection signal of the microprocessor 28. When the broadcast selection signal of the microprocessor 28 is NTSC, the window generator 21 sets a period for counting a nominal frequency of 45.75MHz. On the other hand, when the broadcast selection signal of the microprocessor 28 is the PAL method, the window generator 21 sets a period for counting the nominal frequency of 38.9MHz.

That is, the window generation unit, based on the nominal frequency f0 of the broadcast method selected according to the broadcast selection signal of the microprocessor 28 and the preset detection resolution (a), the reference counting number (X) and counting of the frequency counting unit Period (b) is determined according to the following equations (1) and (2).

[Equation 1]

X = f0 / a

[Equation 2]

b = 1 / a

For example, when the detection resolution is set to 25 kHz in the NTSC method with a nominal frequency of 45.75 MHz, the reference counting count is 1830 and the counting period is 40 Hz. Here, the detection resolution of 25 kHz means that the frequency deviation can be detected by a multiple of 4 kHz based on the nominal frequency 45.75 MHz. For example, when the detection resolution is set to 25 kHz in the PAL method having a nominal frequency of 38.9 MHz, the reference counting frequency is 1556, and the counting period is 40 Hz.

The window generator 21 includes a crystal oscillator for generating a predetermined reference frequency; And a window counting unit configured to divide a reference frequency generated by the crystal oscillator and generate a window signal corresponding to a counting period required to count the reference count. For example, when a 25 kHz clock signal having a counting period of 40 kHz is to be generated, the window generator 40 divides the 4 MHz crystal oscillator and the 4 MHz oscillation signal of the crystal oscillator into 160 to divide the clock at 25 kHz. It is implemented as a counter (window counting unit) that generates a signal. The window signal output from the window generator 40 is transmitted to the control unit 43 and the latch unit 42.

The latch unit 23 of the present invention is a means for temporarily storing counting data output from the frequency counting unit 22. The latching unit 23 counts the counting value during the window period in synchronization with the window signal applied from the window generating unit 21. Is maintained until the count of the next window cycle occurs. That is, the stored data is updated at the window period (counting period).

The control unit 24 of the present invention simultaneously resets the window generating unit 21 and the frequency counting unit to be synchronized. In addition, the control unit 24 controls the preset of the frequency counting unit 22 so that counting data (counting value) can be symmetrical for each frequency deviation. That is, when the counting value of the frequency counting unit 22 is input, when the counting value reaches the preset setting value, the preset signal is applied to the frequency counting unit 22 to count again from the initial value.

3A and 3B are tables showing an example of digital automatic fine tuning data according to the present invention. 22 shows an example of using the down counter. 3A and 3B illustrate an example of the NTSC scheme, it will be apparent to those skilled in the art that the PAL scheme can detect the intermediate frequency signal using the same technique, although there are only differences in the nominal frequency and the reference counting frequency.

FIG. 3A illustrates a case where an intermediate frequency signal of 45.75 MHz corresponding to a nominal frequency is input, and FIG. 3B illustrates a case where an intermediate frequency signal of 45.775 MHz having a frequency deviation of 25 kHz and a nominal frequency is input. At the same time, the frequency counting unit (22 in FIG. 2) receives each intermediate frequency signal into the clock stage and starts down counting from 1818 by the intermediate frequency signal. When the counting unit 22 counts down and the counting value becomes 0, the frequency counting unit 22 (22 of FIG. 2) is preset again by the controller (24 of FIG. 2) to perform the counting operation from 1818. In FIGS. 3A and 3B, the portion indicated by the counting value 1818 indicates a time point at which each preset operation is started. After the preset operation as described above, when the counting operation is performed again, the frequency counting unit is reached when the window period 40 ms indicated by the window generating unit 21 (see FIG. 2) (1830 as the window counting value) is reached. Looking at the data of the lower 4 bits (2 ³ , 2 ² , 2 ¹ , 2 ⁰ ) of (Fig. 2), when the intermediate frequency signal is 45.75 MHz, it becomes [0 0 0 0] as shown in FIG. When the frequency signal is 45.775MHz, it becomes [1 1 1 1] as shown in FIG. 3B.

Referring back to FIG. 2, the output unit 26 of the present invention extracts the data of the lower predetermined bit from the frequency counting data output from the latch unit 23 as described with reference to FIGS. 3A and 3B to decode the frequency. Output as automatic fine adjustment data.

By the way, in the tuner, in general, the frequency deviation range that can be adjusted by the automatic fine tuning unit is approximately 200 kHz, and the frequency adjustment for the above range is meaningless. Should be done. Therefore, the present invention includes a fine adjustment determining / selecting section 25 to determine such fine adjustment range.

The fine adjustment determination / selection unit 25 checks the frequency counting value output from the latch unit 23 according to the broadcast method selected according to the broadcast selection signal of the microprocessor 28, and inputs the received intermediate value. Determine if the frequency signal is within the automatic fine tuning range or outside the automatic fine tuning range. The result determined by the fine adjustment determination / selection unit 25 is transmitted to the output unit 46, and the output unit 46 outputs automatic fine adjustment data corresponding to the frequency deviation when the automatic fine adjustment is within the range. do.

As shown in FIG. 4, the fine adjustment determination / selection unit 25 may include an NTSC fine adjustment determination unit 251, a PAL fine adjustment determination unit 252, and a selection unit 253. The present invention is characterized by providing a digital automatic fine tuning device that can be used in both NTSC and PAL. According to this feature, in the present invention, the fine tuning determination unit 251 in the fine tuning determination / selection unit 25 determines the fine tuning range according to the NTSC method, and the PAL fine tuning determination unit 252 determines the PAL. Judgment of the fine tuning range is made according to the method. The fine tuning determination result made by the NTSC fine tuning determination unit 251 and the PAL fine tuning determination unit 252 is selected by the broadcast selection signal of the microprocessor 28 and is output by the selection unit.

As described above, the fine tuning range is determined by dividing into the NTSC fine tuning determining unit 251 and the PAL fine tuning determining unit 252 because the counting value outputted according to each broadcasting method may be different. That is, the range determination of the fine adjustment is based on the bit data output from the latch unit. The output bit data, as described above, the lower 4 bits can be used for frequency detection, and the remaining higher bits can be used to determine whether it is within the fine tuning range, which is different depending on the NTSC and PAL scheme. Because it can.

5 and 6 show examples of the output of the automatic fine tuning signal of the automatic fine tuning apparatus applied to the NTSC system and the PAL system. 5 and 6 show the results applied to the NTSC method because the counting times (NTSC 1830, PAL 1556) and the down counting start value differ, but the principles used for detecting the intermediate frequencies are the same. This will be described in detail, and a detailed description of FIG. 6 will be omitted.

5 is a frequency voltage graph for automatic fine tuning when the nominal frequency of the NTSC system is 45.75 MHz, the frequency range of 45.58 MHz to 45.95 MHz, which is the automatic fine tuning range, is the interval B, and among the other frequency ranges. An example of output of an automatic fine adjustment signal when a frequency section of 45.95 MHz or more is set to section A and a frequency section of 45.57 MHz or less is set to section C is shown.

In FIG. 5, the 11-bit frequency counting data displayed in the upper portion represents counting data that appears during counting for the window period for the intermediate frequency signal of each corresponding frequency, and the counting value represented by the data is expressed in decimal numbers. In the lower part of the table, the frequency-voltage curve of the automatic fine adjustment unit is indicated.

In FIG. 5, when the lower 4 bits of the frequency counting data of the section B, which is the automatic fine tuning section, are repeated, the lower 4 bits of the nominal frequency section A and the section C may be repeated, but the data of the upper bit may be repeated. Different values are shown in the sections A, B, and C. Therefore, the value of the lower 4 bits is used to detect the frequency deviation, and the upper bits are used to determine the interval of automatic fine tuning. That is, the NTSC fine adjustment determining unit and the PAL fine adjustment determining unit (252 in FIG. 4) in the fine adjustment determining / selecting unit (251 in FIG. 4) use the higher bit data as shown in FIG. , C is determined.

In FIG. 5, when the frequency counting value belongs to 1815 to 1800 corresponding to the automatic fine tuning frequency range (45.58 MHz to 45.95 MHz), the output value S1 is outputted as 1, and when it does not belong to the above, S1 is outputted as 0. do. When the value is 1815 or more, 0 is output as the output value S2, and when the value is 1800 or less, 1 is output by the S2.

Therefore, the output unit 26 of FIG. 2 checks the output signals S1 and S2 of the fine adjustment determination / selection unit 25 of FIG. 2 and if S1 is 0 regardless of the S2 value, The lower 4 bits of data are output as automatic fine adjustment data. If S1 is 1, 0111 or 1000 is output according to S2.

As described above, the automatic fine adjustment data output from the output unit 26 of FIG. 2 may be applied to the microprocessor as it is, and from the output unit 26 of FIG. 2 in the digital / analog conversion unit 27 of FIG. 2. The output automatic fine tuning data may be converted into an analog signal according to the frequency-voltage curve for automatic fine tuning and output.

The present invention is not limited by the above-described embodiment and the accompanying drawings, but is intended to be limited by the appended claims, and various forms of substitution, modification, and within the scope not departing from the technical spirit of the present invention described in the claims. It will be apparent to those skilled in the art that changes are possible.

As described above, according to the present invention, the intermediate frequency generated by the analog broadcast reception tuner can be detected to easily detect a frequency deviation from the nominal frequency by using a counter. In addition, there is an effect that can be applied to both NTSC and PAL analog broadcast reception.

Claims (6)

A microprocessor for generating a broadcast selection signal for determining whether the received broadcast signal is NTSC or PAL; A frequency counting unit counting a frequency of an input intermediate frequency signal at a predetermined reference counting count during a predetermined counting period; A window generator for generating a window signal for setting a reference counting frequency and a counting period of the frequency counting unit according to a nominal frequency of a broadcast method selected according to a broadcast selection signal of the microprocessor and a preset detection resolution; A controller configured to reset and / or preset control the frequency counting unit based on the window signal generated from the window generator; A latch unit operating according to a window signal output from the window generator to detect a counting value of the frequency counting unit at the end of the window signal and to maintain a predetermined time; In accordance with the broadcast selection signal of the microprocessor, the frequency counting value output from the latch unit is checked to determine whether the input intermediate frequency signal is within the automatic fine tuning range or outside the automatic fine tuning range. An automatic fine tuning determination / selection unit; A digital output unit for outputting the frequency counting value output from the latch unit as automatic fine adjustment data indicating a deviation from the nominal frequency when the fine adjustment determination / selection unit is within the automatic fine adjustment range according to the output signal. Automatic fine tuning device. The method of claim 1, wherein the window generating unit, The reference counting count (X) and the counting period (b) of the frequency counting unit are determined according to the following equations 1 and 2 according to the nominal frequency f0 and the preset detection resolution (a) of the broadcast method selected according to the broadcast selection signal. Digital automatic fine adjustment device characterized in that. [Equation 1] X = f0 / a [Equation 2] b = 1 / a The method of claim 1, wherein the window generating unit, A crystal oscillator for generating a predetermined reference frequency; And And a window counting unit configured to divide the reference frequency generated by the crystal oscillator and generate a window signal corresponding to a counting period required to count the reference count. The method of claim 1, wherein the control unit, On the basis of the reference counting frequency, when the frequency of the intermediate frequency signal of the same frequency as the aerial frequency is counted, a preset value is set such that all the state values of the predetermined bits in the counting value become "0" at the end of the counting period. And synchronously resetting the window generating unit and the frequency counting unit, checking the operation of the frequency counting unit, and presetting the frequency counting unit at a preset preset period. The method of claim 1, wherein the automatic fine adjustment determination / selection unit, An NTSC fine adjustment determining unit which checks the frequency counting value output from the latch unit and determines whether the input intermediate frequency signal is within the NTSC automatic fine tuning range or outside the automatic fine tuning range; A PAL fine adjustment determining unit which checks the frequency counting value output from the latch unit and determines whether the input intermediate frequency signal is within an automatic fine adjustment range of the PAL method or outside an automatic fine adjustment range; And a selection unit for selecting and outputting one of the determination results of the NTSC fine adjustment determination unit and the PAL fine adjustment determination unit according to the broadcast selection signal received from the microprocessor. The method of claim 1, And a digital / analog converter for converting the automatic fine tuning data output from the output unit into an analog signal according to the frequency fine voltage curve for automatic fine tuning and outputting the analog signal.

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