KR100296751B1 - Digital TV with AFT Control - Google Patents
Digital TV with AFT Control Download PDFInfo
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- KR100296751B1 KR100296751B1 KR1019980053698A KR19980053698A KR100296751B1 KR 100296751 B1 KR100296751 B1 KR 100296751B1 KR 1019980053698 A KR1019980053698 A KR 1019980053698A KR 19980053698 A KR19980053698 A KR 19980053698A KR 100296751 B1 KR100296751 B1 KR 100296751B1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
- H04N5/50—Tuning indicators; Automatic tuning control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/41—Structure of client; Structure of client peripherals
- H04N21/426—Internal components of the client ; Characteristics thereof
- H04N21/42607—Internal components of the client ; Characteristics thereof for processing the incoming bitstream
- H04N21/4263—Internal components of the client ; Characteristics thereof for processing the incoming bitstream involving specific tuning arrangements, e.g. two tuners
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/015—High-definition television systems
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- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Television Receiver Circuits (AREA)
- Channel Selection Circuits, Automatic Tuning Circuits (AREA)
Abstract
AFT(Automatic Fine Tuning)제어기능을 갖는 디지털 TV는 수신되는 RF 방송신호의 반송주파수 및 중간주파처리를 위한 발진주파수의 변동으로 인한 IF신호의 주파수변화를 보정하기 위한 것이다. 본 발명의 디지털 TV는 IF신호의 주파수 변화에 따른 전압 변화곡선을 미리 저장하고 수신되는 RF신호로부터 변환된 IF신호의 주파수에 대응하여 저장된 곡선의 해당 전압을 AFT전압으로 검파 출력하는 AFT검파기, 그 전압에 따라서 발진주파수를 제어하는 마이콤, 및 마이콤의 제어하에 발진주파수가 조정되며 수신되는 RF신호를 조정된 발진주파수와 혼합하여 IF신호로 변환하여 출력하는 튜너로 구성된다. 따라서, 본 발명은 방송국에서 송출되는 RF신호의 반송주파수나 수신되는 RF신호를 발진주파수와 혼합하여 IF신호로 변환하여 출력하는 튜너의 발진주파수가 변동하더라도 IF신호를 정확하게 만들어 출력하므로, 화면왜곡없는 양호한 수신을 할 수 있는 효과를 제공한다.Digital TV with AFT (Automatic Fine Tuning) control function is to compensate for the frequency change of the IF signal due to the variation of the oscillation frequency for the carrier frequency and intermediate frequency processing of the received RF broadcast signal. The digital TV of the present invention stores an voltage change curve according to a frequency change of an IF signal in advance and detects and outputs a corresponding voltage of a stored curve as an AFT voltage corresponding to a frequency of an IF signal converted from a received RF signal, The microcomputer controls the oscillation frequency according to the voltage, and the oscillation frequency is controlled under the control of the microcomputer, and the tuner converts the received RF signal with the adjusted oscillation frequency and converts it into an IF signal. Therefore, the present invention accurately produces and outputs the IF signal even if the oscillation frequency of the tuner converting and outputting the IF signal by mixing the carrier frequency or the received RF signal of the RF signal transmitted from the broadcasting station with the oscillation frequency, without distortion It provides an effect that allows good reception.
Description
본 발명은 디지털(Digital) TV에 관한 것으로, 보다 상세하게는, 수신되는 RF 방송신호의 반송주파수나 RF신호의 IF변환시 사용되는 발진주파수의 변동으로 인한 IF신호의 주파수 변화를 보정하여 항상 일정한 주파수의 IF신호를 얻어낼 수 있도록 한 AFT제어기능을 갖는 디지털 TV에 관한 것이다.The present invention relates to a digital TV, and more particularly, to correct a frequency change of an IF signal due to a change in a carrier frequency of a received RF broadcast signal or an oscillation frequency used in the IF conversion of an RF signal. The present invention relates to a digital TV having an AFT control function capable of obtaining an IF signal.
일반적으로, TV 내지 튜너(Tuner)를 내장한 VTR에서는 안테나를 통해 수신되는 다수의 방송신호중 원하는 채널의 방송신호를 선국하고, 그 방송신호(NTSC방식의 경우)의 영상을 45.75㎒, 음성을 41.25㎒의 중간주파수(Intermediate Frequency; IF)신호로 주파수변환한다. 그런데, 방송국에서 방송신호를 송출시 그 방송신호의 반송주파수(carrier frequency)에 변동이 생길 수 있으며, TV내의 튜너측에서 선국된 방송신호를 중간주파수신호로 변환시키기 위해 발진기(Oscillator)에서 발진되는 주파수에 변동이 생길 수 있다. 이럴 경우, 중간주파수가 변화하여 화면왜곡이 유발되는 문제가 있었다. 그래서, 기존의 아날로그(Analog) TV에는 튜너에서 선국되어 방송신호를 영상복조하는 영상복조부내에 AFT(Automatic Fine Tuning)회로를 채용하여 주파수의 변동을 보정할 수 있도록 한다.In general, in a VTR with a built-in TV or tuner, a broadcast signal of a desired channel is tuned among a plurality of broadcast signals received through an antenna, and the video of the broadcast signal (in the NTSC system) is 45.75MHz and the voice is 41.25. Frequency conversion is performed by an intermediate frequency (IF) signal of MHz. However, when a broadcast station transmits a broadcast signal, a change may occur in a carrier frequency of the broadcast signal, and an oscillator is oscillated to convert a broadcast signal tuned at the tuner side into an intermediate frequency signal. Frequency can fluctuate. In this case, there is a problem that the distortion of the screen caused by changing the intermediate frequency. Therefore, the conventional analog TV employs an AFT (Automatic Fine Tuning) circuit in the image demodulation unit which is tuned by the tuner and demodulates the broadcast signal, thereby correcting the frequency variation.
한편, 디지털 추세에 따른 고화질의 디지털 방송을 수신하여 시청할 수 있는 TV시스템이 출시되고 있으며, 현재는 디지털 TV 방송에 관한 표준화가 빠른 속도로 진전되고 있고 그중에는 구체적인 서비스를 시작한 것도 나오고 있다. 방송 서비스는 그 성격상 표준화의 중요성이 매우 높은 응용이다. 서비스면에서는 고화질, 고음질등의 엄격한 요구조건을 만족시키면서도 수상기를 적절한 가격으로 보급할 수 있어야 한다.Meanwhile, a TV system capable of receiving and watching high-definition digital broadcasting according to the digital trend is being released, and now standardization of digital TV broadcasting is rapidly progressing, and among them, specific services have been started. Broadcast service is an application that is very important in standardization. In terms of service, it must be able to supply the water receiver at an appropriate price while satisfying the strict requirements such as high quality and high sound quality.
그런데, 위와 같은 고화질 제공의 특징을 갖는 디지털 TV의 구성블록에는 영상복조의 구성블록이 없기 때문에, 수신되는 방송신호의 주파수나 발진주파수에 변동이 생기면 IF신호의 주파수가 변화되어 화면왜곡을 유발할 여지가 있다. 이로 인하여, 디지털 TV에서도 AFT기능의 구현이 필수적으로 요구되어 졌다.However, since there is no component block for image demodulation in a component block of a digital TV having the above characteristics of providing a high picture quality, if the frequency or oscillation frequency of a broadcast signal is received, the frequency of the IF signal is changed to cause screen distortion. There is. For this reason, the implementation of the AFT function has been required in digital TV.
따라서, 본 발명의 목적은 전술한 점을 감안하여, IF신호의 주파수 변화에 따른 전압 변화곡선을 미리 저장하고, 중간주파처리된 방송신호의 주파수에 대응하는 전압을 검파하여 튜너의 발진주파수를 보정하므로, 주파수변동이 생겨도 항상 일정한 중간주파수신호가 출력되도록 한 AFT제어기능을 갖는 디지털 TV을 제공함에 있다.Accordingly, an object of the present invention is to store the voltage change curve according to the frequency change of the IF signal in advance, and to detect the voltage corresponding to the frequency of the intermediate frequency processed broadcast signal to correct the oscillation frequency of the tuner. Therefore, the present invention provides a digital TV having an AFT control function such that a constant intermediate frequency signal is always output even when a frequency variation occurs.
도 1은 본 발명에 따른 AFT제어기능을 갖는 디지털 TV을 나타내는 구성도,1 is a block diagram showing a digital TV having an AFT control function according to the present invention;
도 2는 도 1 AFT검파기의 동작을 설명하기 위한 주파수-전압 변화곡선 그래프.2 is a graph showing a frequency-voltage change curve for explaining the operation of the AFT detector of FIG.
<도면의 주요부분에 대한 부호의 설명><Description of the symbols for the main parts of the drawings>
11 : 튜너 16 : AFT검파기11: tuner 16: AFT detector
17 : 마이콤17: micom
이와 같은 목적을 달성하기 위한 본 발명의 AFT제어기능을 갖는 디지털 TV는, 디지털 TV에 있어서, 중간주파수(IF)신호의 주파수 변화에 따른 전압 변화곡선을 미리 저장하고, 입력되는 IF신호의 주파수에 대응하여 저장된 곡선의 해당 전압을 AFT전압으로 검파 출력하는 AFT검파기와, 상기 AFT검파기에서 출력되는 AFT전압에 따라서 발진주파수를 제어하는 마이콤, 및 상기 마이콤의 제어하에 발진주파수가 조정되며, 수신되는 RF 방송신호를 조정되는 발진주파수신호에 따라 중간주파처리하여 IF신호로 출력하는 튜너를 포함한다.A digital TV having the AFT control function of the present invention for achieving the above object, in the digital TV, the voltage change curve according to the frequency change of the intermediate frequency (IF) signal is stored in advance, and the frequency of the input IF signal An AFT detector that detects and outputs a corresponding voltage of a correspondingly stored curve as an AFT voltage, a micom that controls an oscillation frequency according to the AFT voltage output from the AFT detector, and an oscillation frequency is controlled under the control of the micom, and the received RF And a tuner which outputs an IF signal by processing an intermediate frequency according to the oscillation frequency signal to be adjusted.
이하, 첨부한 도면들을 참조하여 본 발명의 바람직한 실시예를 상세히 기술하기로 한다.Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.
도 1은 본 발명에 따른 AFT제어기능을 갖는 디지털 TV의 구성도를 나타낸다. 도 1에 나타낸 디지털 TV는 일반적인 디지털 TV의 수신구성블록에, IF신호의 주파수 변화에 따른 전압 변화곡선을 미리 저장하여 중간주파처리된 방송신호의 주파수에 대응하는 전압을 AFT전압으로 검파하여 출력하는 AFT검파기(16)와, 검파된 AFT전압에 따라 튜너(11)의 발진주파수를 가변조정하여 튜너(11)에서 항상 일정한 주파수의 IF신호가 정확하게 만들어져 출력되도록 하는 마이콤(17)을 더 포함하도록 구성된다. 이러한 구성을 갖는 도 1의 AFT제어기능을 갖는 디지털 TV에 대한 동작을 도 2를 통해 좀더 구체적으로 설명한다.1 is a block diagram of a digital TV having an AFT control function according to the present invention. In the digital TV shown in FIG. 1, a voltage change curve according to a frequency change of an IF signal is stored in advance in a reception configuration block of a general digital TV, and a voltage corresponding to a frequency of an intermediate frequency processed broadcast signal is detected and output as an AFT voltage. It further comprises an AFT detector 16 and a microcomputer 17 to variably adjust the oscillation frequency of the tuner 11 according to the detected AFT voltage so that the IF signal of a constant frequency is always made and outputted from the tuner 11 at all times. do. An operation of the digital TV having the AFT control function of FIG. 1 having such a configuration will be described in more detail with reference to FIG. 2.
도 1에서, 튜너(11)는 마이콤(17)으로부터 수신하고자 하는 채널정보가 공급되면, 안테나를 통해 수신되는 RF(Radio Frequency)형태의 TV방송신호중 원하는 채널의 방송신호를 선국한다. 튜너(11)는 선국된 채널의 RF신호를 발진기(미도시)로부터의 발진주파수에 의하여 IF신호로 변환하여 출력한다. 디지털 TV에서 IF신호의 주파수는 49.58119㎒로 정해져 있다. 튜너(11)에서 출력되는 IF신호는 프리앰프(AMPPRE)(12)와 AFT검파기(16)로 각각 입력된다. 프리앰프(12)는 인가되는 IF신호를 일정크기로 증폭하고, 증폭된 IF신호는 SAW(Surface Acoustic Wave; 표면강성파)필터(13)를 통해 필요한 주파수특성을 얻는다. SAW필터(13)를 통과한 IF신호는 다운컨버터(Down Convter) 및 FEC(Forward Error Corredtion)를 차례로 거치면서 다운컨버팅 및 전송에러 정정이 이루어진다. 한편, AFT검파기(16)는 도 2에 보여진 바와 같은 특성 그래프를 미리 저장한다. 도 2를 보면, 가로축은 주파수(f)를, 세로축은 전압(V)을 각각 나타내며, fo는 45.58119㎒의 중간주파수가 정확하게 만들어지는 튜닝포인트이다. AFT검파기(16)는 입력되는 IF신호의 주파수에 대응하는 전압을 AFT전압으로 검파하여 마이콤(17)으로 출력한다. 즉, AFT검파기(16)는 IF주파수가 fo보다 높으면 fo에 대응하는 전압보다 낮은 전압을, 반대로 fo보다 낮으면 높은 전압을 출력한다. 마이콤(17)은 인가되는 AFT전압에 따라서 I2C버스를 통해 튜너(11)의 발진주파수를 가변조정시킨다. 그래서, 튜너(11)는 입력 RF신호의 반송주파수가 변동하거나 발진주파수가 변동하더라도 IF신호의 주파수 변화에 따라 발진주파수가 재조정되어 항상 일정주파수의 IF신호를 출력한다. 여기서, AFT검파기(16)는 다운컨버터(14) 전단에 마련된 구성블록에서 출력되는 IF신호 즉, 프리앰프(12)나 SAW필터(13)에서 출력되는 IF신호를 입력받아 AFT전압 검파를 수행할 수도 있다.In FIG. 1, when the channel information to be received from the microcomputer 17 is supplied, the tuner 11 tunes a broadcast signal of a desired channel among TV broadcast signals in the form of RF (Radio Frequency) received through an antenna. The tuner 11 converts an RF signal of a tuned channel into an IF signal by an oscillation frequency from an oscillator (not shown) and outputs the IF signal. In digital TV, the frequency of the IF signal is set at 49.58119 MHz. The IF signal output from the tuner 11 is input to the AMP PRE 12 and the AFT detector 16, respectively. The preamplifier 12 amplifies the applied IF signal to a predetermined size, and the amplified IF signal obtains the required frequency characteristics through a surface acoustic wave (SAW) filter 13. The IF signal passing through the SAW filter 13 passes through a downconverter and a forward error corretion (FEC), and downconverting and transmission error correction are performed. On the other hand, the AFT detector 16 stores the characteristic graph as shown in FIG. 2 in advance. 2, the horizontal axis represents frequency f, the vertical axis represents voltage V, and fo is a tuning point at which an intermediate frequency of 45.58119 MHz is accurately made. The AFT detector 16 detects a voltage corresponding to the frequency of the input IF signal as an AFT voltage and outputs it to the microcomputer 17. That is, the AFT detector 16 outputs a voltage lower than the voltage corresponding to fo if the IF frequency is higher than fo, and high voltage if lower than fo. The microcomputer 17 variably adjusts the oscillation frequency of the tuner 11 through the I 2 C bus according to the applied AFT voltage. Thus, even if the carrier frequency of the input RF signal fluctuates or the oscillation frequency fluctuates, the tuner 11 always adjusts the oscillation frequency according to the frequency change of the IF signal and always outputs an IF signal having a constant frequency. Here, the AFT detector 16 receives an IF signal output from a component block provided in front of the down converter 14, that is, an IF signal output from the preamplifier 12 or the SAW filter 13 to perform AFT voltage detection. It may be.
상술한 바와 같이, 본 발명의 AFT제어기능을 갖는 디지털 TV는, 수신되는 RF신호의 반송주파수가 변동하거나 튜너의 발진주파수가 변동하더라도 이를 보정하여 항상 일정주파수 즉, 49.58119㎒의 IF신호로 변환시켜 출력할 수 있는 AFT제어기능을 수행하므로, 화면왜곡없는 양호한 수신을 할 수 있는 효과를 갖는다.As described above, the digital TV having the AFT control function of the present invention always compensates for a change in the carrier frequency of the received RF signal or the oscillation frequency of the tuner and converts it into an IF signal of a constant frequency, that is, 49.58119 MHz. Since the AFT control function can be performed, it has the effect of good reception without distortion.
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| KR1019980053698A KR100296751B1 (en) | 1998-12-08 | 1998-12-08 | Digital TV with AFT Control |
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| KR1019980053698A KR100296751B1 (en) | 1998-12-08 | 1998-12-08 | Digital TV with AFT Control |
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