KR20000005818U - Digital broadcast tuner - Google Patents

Abstract

The present invention relates to a digital broadcast reception tuner having a wide variable range without affecting the impedance change by placing an automatic gain control circuit at a high frequency input terminal and an output terminal of the first mixer circuit, respectively.

First automatic gain control means for inputting a high frequency signal received from a tuner antenna for receiving digital broadcasts, and a high frequency signal input through the first automatic gain control means and an output from the first local oscillation circuit. A first mixer circuit for mixing the generated oscillation frequency signals, a first band pass filter circuit for passing only a frequency component of a predetermined band among the high frequency signals output from the first mixer circuit, and a high frequency output from the first band pass filter circuit An amplifying circuit for amplifying a signal, a second mixer circuit for mixing a high frequency signal from the amplifying circuit with an oscillation frequency signal output from a second local oscillating circuit, and outputting a baseband signal, and the first bandpass filter circuit And a second automatic gain control means connected between the amplification circuit and the amplification circuit.

Description

Digital broadcast tuner

The present invention relates to a digital broadcast receiving tuner (TUNER), and more particularly, a digital broadcasting having a wide variable range without affecting the impedance change by placing an automatic gain control circuit at each of a high frequency input terminal and an output terminal of the first mixer circuit. A receive tuner.

Generally, a tuner for receiving digital broadcasts is a device that selects only one desired channel from among a plurality of TV channels being broadcast, converts it into an intermediate frequency (IF), and then supplies it to a set of image intermediate amplifiers. .

Hereinafter, a configuration of a conventional general digital broadcast tuner will be briefly described.

1 is a block diagram of a conventional digital broadcast reception tuner, which includes a first tracking filter circuit 12, an amplifier circuit 14, a second tracking filter circuit 16, a first mixer circuit 18, and a band pass. The filter circuit 20, the amplifier circuit 22, the automatic gain control circuit 24, the local oscillation circuit 26, the PLL circuit 70, and the like are shown.

The first tracking filter circuit 12 is composed of a splitter circuit for inputting a signal of a high frequency band received from an antenna to separate a VHF / UHF signal. The first tracking filter circuit 12 removes noise so that a noise component is not supplied when a luminance signal including a synchronization signal is supplied to a next stage.

The automatic gain control (AGC) circuit 24 automatically adjusts gain so that the output of the video signal is always constant even if the magnitude of the high frequency signal induced by the antenna changes.

The amplifying circuit 14 amplifies a signal of a high frequency band received from the antenna, and the second tracking filter circuit 16 removes only a noise component of the high frequency signal from the amplifying circuit 14. It plays the role of passing only the frequency of a certain band.

The local oscillator circuit 26 is linked by a frequency synthesizer controlled by a microcom (not shown) installed outside the tuner to generate an oscillation frequency.

The phase locked loop (PLL) 28 compares an oscillation frequency of the local oscillation circuit 26 with a predetermined reference frequency to determine whether the oscillation frequency of the local oscillation circuit is lowered. In the low case, the height is controlled to obtain the accurate oscillation frequency.

The first mixer circuit 18 outputs an intermediate frequency by mixing the high frequency signal passed through the second tracking filter 16 with the oscillation frequency of the local oscillation circuit 26.

On the other hand, the output signal of the first mixer circuit 18 is input to the second mixer circuit and the third mixer circuit (not shown in this figure) through the band pass filter circuit 20, the amplifier circuit 22 and the like.

The second mixer circuit (not shown) is a demodulated baseband signal mixed with an intermediate frequency passed through the amplifier circuit 22 and a 0 ° phase shifted oscillation frequency generated from a local oscillator circuit (not shown). Output (I)

The third mixer circuit (not shown) is demodulated by mixing the intermediate frequency passed through the amplifier circuit 22 with the 90 ° phase shifted oscillation frequency generated from a local oscillator circuit (not shown). The band signal Q is output.

The first and second tracking filter circuits 12 and 16 are configured as a high pass filter and are band erasing filters for canceling the intermediate frequency in order to eliminate interference by the intermediate frequency signal band.

2 is a block diagram of another conventional digital broadcast receiving tuner, which includes a high pass filter circuit 32, a first automatic gain control circuit 34, an amplifier circuit 36, a low pass filter circuit 38, 2 automatic gain control circuit 40, first mixing circuit 42, local oscillating circuit 44, PLL 46, band pass filter circuit 48, amplifying circuit 50, second mixing circuit 52 And a local oscillation circuit 54, a PLL 56, a band pass filter circuit 58, an amplification circuit 60, and the like.

The high pass filter circuit 32 is composed of a splitter circuit that inputs a signal of a high frequency band received from an antenna and separates the VHF / UHF signal, and is synchronized with the first automatic gain control circuit 34 of the next stage. When supplying a luminance signal containing a signal serves to remove the noise so that the noise component is not supplied.

The first automatic gain control (AGC) circuit 34 automatically adjusts gain so that the output of the video signal is always constant even if the magnitude of the high frequency signal induced by the antenna changes.

The amplifying circuit 36 serves to amplify a signal of a high frequency band received from the antenna, and the low pass filter circuit 38 is fixed to remove only noise components of the high frequency signal from the amplifying circuit 36. It only passes the frequency of the band.

The local oscillation circuit 44 is interlocked by a frequency synthesizer controlled by a microcom (not shown) installed outside the tuner to generate an oscillation frequency, and the PLL 46 generates the oscillation frequency. The oscillation frequency of the local oscillation circuit 44 is compared to determine whether the oscillation frequency is higher or lower than the reference frequency. If the oscillation frequency is high, the oscillation frequency of the local oscillation circuit is lowered. do.

The first mixer circuit 18 mixes the high frequency signal passed through the second automatic gain control circuit 40 and the oscillation frequency of the local oscillation circuit 44 to output an intermediate frequency.

On the other hand, the output signal of the first mixer circuit 42 is input to the second mixer circuit 52 through the band pass filter circuit 48, the amplifier circuit 50, and the like.

The second mixer circuit 52 mixes the demodulated baseband signal I by mixing the intermediate frequency passed through the amplifier circuit 50 with the 0 ° phase shifted oscillation frequency generated from the local oscillator circuit 54. Outputs through the band pass filter circuit 58 and the amplification circuit (60).

However, in the conventional digital broadcast reception tuner configured as described above, since the automatic gain control circuit 24 of one stage is used in the case of FIG. 1, a wide variable range automatic gain required by a terrestrial digital TV tuner is required. The control (AGC) side characteristics could not be obtained. In addition, in the conventional tuner using the two stage automatic gain control circuits 34 and 40 as shown in Fig. 2, two automatic gain control circuits 34 and 40 are provided in front of the first mixer circuit 42. ), It is necessary to obtain a wide variable range over the entire high frequency frequency (50 to 800 MHz). Therefore, there is a problem in that the automatic gain control (AGC) sub-characteristic of the wide variable range is obtained over the wide frequency range of the high frequency frequency. .

Therefore, the present invention was devised to solve the above problems, and an object of the present invention is to place an automatic gain control circuit at each of a high frequency input terminal and an output terminal of the first mixer circuit, thereby providing a wide variable range without affecting the impedance change. It is to provide a tuner for receiving digital broadcast.

1 is a block diagram of a conventional digital broadcast tuner

2 is a block diagram of another conventional digital broadcast receiving tuner

3 is a block diagram of a tuner for receiving digital broadcasts according to the present invention.

4A and 4B are graphs of gain characteristics according to the present invention

* Explanation of symbols for the main parts of the drawings

12: first tracking filter circuit 14: amplification circuit

16. 2nd tracking filter circuit 18: 1st mixer circuit

20: band pass filter circuit 22: amplification circuit

24: automatic gain control circuit 26: local oscillation circuit

28: Phase Locked Loop (PLL)

32: high pass filter circuit 34: first automatic gain control circuit

36: amplification circuit 38: low pass filter circuit

40: second automatic gain control circuit 42: first mixed circuit

44: local oscillation circuit 46: PLL

48: band pass filter circuit 50: amplification circuit

52: second mixed circuit 54: local oscillation circuit

56: PLL 58: Bandpass Filter Circuit

60: amplification circuit 72: automatic gain control circuit

74: tracking filter 76: amplification circuit

78 band filter 80 first mixer circuit

82: local oscillation circuit 84: PLL

86: band pass filter circuit 88: automatic gain control circuit

90 amplification circuit 92 second mixing circuit

94: local oscillation circuit 96: PLL

98: band pass filter circuit 100: amplification circuit

In order to achieve the above object, the digital broadcast reception tuner according to the present invention,

First automatic gain control means for inputting a high frequency signal received from the antenna;

A first mixer circuit for mixing the high frequency signal input through the first automatic gain control means and the oscillation frequency signal output from the first local oscillation circuit;

A first band pass filter circuit for passing only a frequency component of a predetermined band among the high frequency signals output from the first mixer circuit;

An amplifier circuit for amplifying a high frequency signal output from the first band pass filter circuit;

A second mixer circuit for mixing a high frequency signal from the amplifying circuit and an oscillation frequency signal output from a second local oscillating circuit and outputting a baseband signal;

And a second automatic gain control means connected between the first band pass filter circuit and the amplification circuit.

Here, the present invention is a second band pass filter circuit for outputting only a frequency component of a predetermined band of the baseband signal output from the second mixer circuit,

A third automatic gain control means connected between the second band pass filter circuit and the base band signal output terminal may be further provided.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In addition, in all the drawings for demonstrating an embodiment, the thing with the same function uses the same code | symbol, and the repeated description is abbreviate | omitted.

3 is a block diagram of a tuner for receiving digital broadcasts according to the present invention, and FIGS. 4a and 4b show graphs of gain characteristics according to the present invention.

In the figure, the tuner for receiving digital broadcasting according to the present invention includes a first automatic gain control circuit 72, a tracking filter 74, an amplification circuit 76, a band pass filter (BPF) 78, and a first tuner. 1 mixer circuit 80, local oscillation circuit 82, PLL circuit 84, band pass filter circuit 86, second automatic gain control circuit 88, amplification circuit 90, second mixing circuit 92 ), A local oscillation circuit 94, a PLL 96, a band pass filter circuit 98, an amplification circuit 100, and the like.

According to the above configuration, the tuner according to the present invention has a first automatic gain control circuit 72 connected to the high frequency input stage so as to obtain a primary variable range in the entire high frequency frequency, and an automatic gain control for the high frequency output frequency. A second automatic gain connected between the bandpass filter circuit 86 at the rear end of the first mixer circuit 80 and the amplification circuit 90 at the front end of the second mixer circuit 92 so as to obtain AGC characteristics. The control circuit 88 is configured differently in a conventional tuner.

According to the present invention, the AGC circuit 72 of one stage is placed in the high frequency input unit to obtain AGC sub-characteristics in the entire high frequency frequency (50 to 800 MHz), and the second automatic gain control (AGC) circuit 1 was placed at the rear end of the bandpass filter circuit 86 via the mixer circuit 80 to obtain AGC sub-characteristics at a single frequency.

The first automatic gain control circuit 72 automatically adjusts the gain so that the output of the video signal is always constant even if the magnitude of the high frequency signal induced by the antenna changes, and the high frequency frequency (50 to 800 MHz) Obtain AGC sub-characteristics throughout

The first automatic gain control circuit 88 is disposed between the band pass filter circuit 86 connected to the output terminal of the first mixer circuit 80 and the amplification circuit 90 connected to the input terminal of the second mixer circuit 92. By positioning it, the AGC characteristic is obtained for the output of the first high frequency signal (920MHz), which effectively enables a wide range of AGC sub-characteristics.

The present invention focuses on the fact that the second automatic gain control circuit 88 connected to the rear end of the bandpass filter circuit 86 effectively controls gain at a single frequency. The third automatic gain control circuit (not shown) may be connected to the rear of the band pass filter circuit 98 (final output: 44 MHz) of the second stage to control gain at a low frequency (44 MHz) at a single frequency.

As described above, according to the digital broadcast reception tuner according to the present invention, the first automatic gain control circuit 72 is placed at the high frequency input terminal to obtain a first variable range in the entire high frequency frequency. A second automatic gain control circuit 88 is placed between the bandpass filter circuit 86 at the rear end of the circuit 80 and the amplification circuit 90 at the front of the second mixer circuit 92 to output a high frequency output single frequency. The automatic gain control (AGC) characteristic can be obtained and the wide range automatic gain control (AGC) characteristic can be obtained more easily. In addition, the present invention uses the automatic gain control circuit 88 at the rear end of the first band pass filter circuit 86, thereby easily coping with the impedance matching noise feedback phenomenon.

In addition, preferred embodiments of the present invention are disclosed for the purpose of illustration, those skilled in the art will be possible to various modifications, changes, substitutions and additions through the spirit and scope of the present invention disclosed in the appended utility model registration claims.

Claims (2)

In the tuner for digital broadcast reception, First automatic gain control means for inputting a high frequency signal received from the antenna; A first mixer circuit for mixing the high frequency signal input through the first automatic gain control means and the oscillation frequency signal output from the first local oscillation circuit; A first band pass filter circuit for passing only a frequency component of a predetermined band among the high frequency signals output from the first mixer circuit; An amplifier circuit for amplifying a high frequency signal output from the first band pass filter circuit; A second mixer circuit for mixing a high frequency signal from the amplifying circuit and an oscillation frequency signal output from a second local oscillating circuit and outputting a baseband signal; And a second automatic gain control means connected between the first band pass filter circuit and the amplification circuit. The method of claim 1, A second band pass filter circuit for outputting only a frequency component of a predetermined band among the baseband signals output from the second mixer circuit; And a third automatic gain control means connected between said second band pass filter circuit and a base band signal output terminal.