WO2002082809A1

WO2002082809A1 - Combination tuner for earth and satellite broadcasting

Info

Publication number: WO2002082809A1
Application number: PCT/KR2002/000581
Authority: WO
Inventors: Soek-Dong Choi
Original assignee: Lg Innotek Co., Ltd.
Priority date: 2001-04-03
Filing date: 2002-04-02
Publication date: 2002-10-17
Also published as: EP1380163A4; KR100365359B1; KR20020078482A; CN1284365C; EP1380163A1; CN1528086A

Abstract

Combination-tuner for receiving Ground wave and satellite wave, the tuner comprising: A satellite frequency output part for receiving satellite wave, a ground frequency output part for receiving ground wave, first switching means to input selectively the RF signals which are output through the satellite frequency output part or ground frequency output part by control signals, IF signal forming means for forming IF signals, second switching means to input selectively the IF signals, low pass filters to filter selectively ground wave or satellite wave out of second IF signals which is output though the second switching means.

Description

COMBINATION TUNER FOR EARTH AND SATELLITE BROADCASTING

Technical Field

The present invention relates to a tuner, and more particularly, to a combination tuner for earth and satellite broadcasting, which allows watcher to selectively receive either a ground broadcasting or a satellite broadcasting using a single device.

Background Art Generally, tuner is driven in two conversion types, e.g., single conversion type and double conversion type. Single conversion type tuner outputs an intermediate frequency (IF) signal. Double conversion type tuner amplifies and mixes a first IF signal to convert the first IF signal into a secondary IF signal, and thus detection is carried out. These double conversion type tuners are again classified into ground wave tuner and satellite wave tuner.

Meanwhile, to convert a broadcasting signal into an IF signal and then to perform detection process of the converted IF signal is a way generally adopted so as to enhance the selectivity of frequency. FIG. 1 is a block diagram of a conventional double conversion type ground tuner.

Referring to FIG. 1, a double conversion type ground tuner 1 includes an AGC (Automatic Gain Controller) 2, a tracking filter 3, an RF amplifier 4, an RF filter 5, a first mixer 6, a first local oscillator 7, a first PLL 8, a first IF filter 9, a first IF amplifier 10, a secondary mixer 11 , a secondary local oscillator 12, a secondary PLL 13 and a secondary IF filter 14.

In detail, AGC 2 automatically controls gain such that output of an image signal is always maintained at a constant level even though a radio frequency (RF) signal having a frequency range of 44 to 860 MHz that is induced and inputted from the antenna (ANT) is changed in size.

Tracking filter 3 eliminates noise contained in the RF signal received at the antenna, and passes only an RF signal corresponding to a wanted frequency band.

RF amplifier 4 amplifies the RF signal passing through the tracking filter 3. RF filter 5 selects a wanted RF component out of the signal amplified by the RF amplifier 4.

First mixer 6 mixes the RF component selected in the RF filter 5 with oscillation frequency generated by the first local oscillator 7, thereby outputting a first IF signal. While a channel is selected, the first local oscillator 7 generates a predetermined oscillation frequency according to control voltage of the first PLL 8 and outputs the generated oscillation frequency to the first mixer 6. The first PLL (Phase Locked Loop) 8 outputs a control voltage to the first local oscillator 7 according to an external control if there is a stored channel data therein. First IF filter 9 passes only a wanted IF component among the first

IF signal outputted from the first mixer 6.

First IF amplifier 10 amplifies the first IF signal outputted from the first IF filter 9.

Secondary mixer 11 mixes the first IF signal amplified by the first IF amplifier 10 with oscillation frequency signal generated in the secondary local oscillator 12, thereby outputting a secondary IF signal. When a channel is selected, the secondary local oscillator 12 generates a predetermined oscillation frequency depending on control voltage of the secondary PLL 13, and outputs the generated oscillation frequency to the second mixer 11. The second PLL outputs control voltage to the second local oscillator 12 depending on an external control if there is a stored channel data therein.

Secondary IF filter 14 passes only a signal having a wanted bandwidth out of the secondary IF signal outputted from the secondary mixer 11.

When the double conversion type tuner 1 as aforementioned, selects a wanted channel among ground wave signals induced from the antenna (ANT), the wanted channel is selected by the control of the first PLL 8, a signal corresponding to the wanted channel passes through the first mixer 6 and the first IF filter 9 to be up-converted to an IF of 1038 MHz by the oscillation frequency, and again passes through the secondary mixer 11 and the secondary IF filter 14 to be down-converted to a final IF of 44 MHz by the oscillation frequency.

Meanwhile, the double conversion type satellite wave tuner has the same structure as the conventional ground wave tuner, but is different from the conventional earth wave tuner in frequency conversion way and target frequency for down-conversion.

However, in case these conventional double conversion type ground tuner and satellite tuner are applied to a single device, it is requested to separately apply respective tuners suitable for the ground wave tuner and the satellite wave tuner, so that there occurs a drawback in that manufacturing costs increase.

Also, since the ground wave tuner and the satellite wave tuner are respectively used in electronic wave receiver markets orienting continuous miniaturization, volume increases, which acts as a considerable problem.

Disclosure of the Invention

The present invention is to solve the aforesaid problems, and it is an object to provide a combination tuner for earth and satellite broadcasting capable of receiving both of ground (or earth) wave and satellite wave.

To achieve the above object and other advantages, there is provided a combination tuner for earth and satellite broadcasting, comprising-^' a double conversion tuner including a first antenna, an AGC, a first amplifier, a first low pass filter, a first mixer, a first local oscillator, a first PLL, a band pass filter, a secondary amplifier, a secondary mixer, a secondary local oscillator and a secondary PLL; a satellite frequency output part for receiving a satellite wave and outputting a predetermined frequency signal; a first switching means, which is switched by a control signal inputted from an outside to select and output an RF signal inputted from the first antenna or an RF signal outputted from the satellite frequency output part using the AGC; a second switching means, which is switched along with the first switching means, to selectively supply a second IF signal outputted from the second mixer; a second low pass filter for passing only a frequency corresponding to earth wave band out of the second IF outputted from the second switching means; and a third low pass filter for passing only a frequency corresponding to satellite wave band out of the second IF outputted from the second switching means.

According to another aspect of the invention, there is provided a combination tuner for earth and satellite broadcasting, comprising: a double conversion tuner including a first antenna, an AGC, a first amplifier, a first low pass filter, a first mixer, a first local oscillator, a first PLL, a band pass filter, a second amplifier, a second mixer, a second local oscillator and a second PLL; a satellite frequency output part for receiving a satellite wave and outputting a predetermined frequency signal; a first switching means for selectively outputting a secondary IF signal inputted from the second mixer or an RF signal outputted from the satellite frequency output part by an external control signal; a second switching means operating in combination with the first switching means and selectively supplying the second IF signal outputted from the first switching means; a second low pass filter for passing only a frequency corresponding to earth wave band out of the second IF outputted from the second switching means; and a third low pass filter for passing only a frequency corresponding to satellite wave band out of the second IF outputted from the second switching means. According to further another aspect of the invention, there is provided a combination tuner for earth and satellite broadcasting, comprising: an earth frequency output part essentially including an earth wave antenna for receiving an earth wave; a satellite frequency output part essentially including a satellite wave antenna for receiving a satellite wave; a first switching means for selectively supplying a frequency outputted from the earth wave output part or the satellite frequency output part; and a second switching means formed at a rear end of the first switching means, for selectively supplying a signal that has passed through the first switching means to a low pass filter suitable for the earth wave and the satellite wave.

Brief Description of the drawings

FIG. 1 is a block diagram for illustrating a conventional double conversion type earth tuner;

FIG. 2 is a block diagram for illustrating a combination type tuner for earth and satellite broadcasting in accordance with one preferred embodiment of the present invention; and

FIG. 3 is a block diagram for illustrating a combination type tuner for earth and satellite broadcasting in accordance with another preferred embodiment of the present invention.

Best Mode for Carrying Out the Invention

Hereinafter, there is described a combination tuner for earth and satellite broadcasting in accordance with one preferred embodiment of the present invention with reference to FIG. 2.

FIG. 2 is a block diagram for illustrating a combination type tuner for earth and satellite broadcasting in accordance with one preferred embodiment of the present invention.

Referring to FIG. 2, a combination tuner 100 for earth and satellite broadcasting, includes a first antenna (ANT 1), a second antenna (ANT 2), an AGC 101, a first amplifier 102, a first low pass filter 103, a first mixer 104, a first local oscillator 105, a first PLL 106, a band pass filter 107, a second amplifier 108, a second mixer 109, a second local oscillator 110, a second PLL 111 , a third mixer 112, a third local oscillator 113, a third PLL 114, a first switch 115, a second switch 116, a second low pass filter 117, and a third low pass filter 118. In more detail, first antenna (ANT 1) receives an earth wave corresponding to a frequency band ranged from 44 to 860 MHz, and the second antenna (ANT 2) receives a satellite wave corresponding to a frequency band ranged from 950 to 2150 MHz.

The third mixer 112 mixes an RF signal as the satellite wave, inputted from the second antenna (ANT 2) with an oscillation frequency inputted from the third local oscillator 113, to output a predetermined intermediate frequency (IF) signal. The IF signal outputted from the third mixer 112 preferably has a frequency of 479.5 MHz.

The third local oscillator 113 generates a predetermined oscillation frequency using a control voltage inputted from the third PLL 114 in which channel data is stored, and outputs the generated oscillation frequency to the third mixer 112. The third PLL 114 receives a fed-back voltage of the third local oscillator 113, and thereby outputs a control voltage to the third local oscillator 113.

The first switch 115 has a fixed terminal "a" connected to the output terminal of the first antenna (ANT 1), a fixed terminal "b" connected to the output terminal of the third mixer 112, and an operation terminal. The operation terminal of the first switch 115 is switched by an external control signal, to thereby select an IF signal outputted from the third mixer 112 and to output the selected IF signal to the AGC 101. Meanwhile, the first switch 115 is switched by the control of QAM or QPSK of the system, and the operation terminal thereof is changed in combination with the second switch 116.

The AGC 101 is connected to the operation terminal of the first switch 115 to automatically control gain so as to maintain the output of a signal at a constant level even through size of the RF signal inputted through the first switch 115 is varied. The first amplifier 102 amplifies the RF signal passing through the AGC 101. The low pass filter 103 passes only an RF signal component of 860 MHz or less out of the RF signal amplified by the first amplifier 102.

The first mixer 104 mixes the RF signal selected by the first low pass filter 103 with the oscillation frequency inputted from the first local oscillator 105, to up-convert the RF signal to a first IF signal having a frequency of 1038 MHz and output the converted IF signal. While a channel is selected, the first local oscillator 105 generates the oscillation frequency according to a control voltage supplied from the first PLL 106, to output the oscillation frequency to the first mixer 104. The first PLL 106 receives the output voltage fed-back from the first local oscillator 105 to supply and output a control voltage to the first local oscillator 105 according to the size of the output voltage.

The band pass filter 107 passes only a frequency corresponding to a wanted band out of the first intermediate frequencies outputted from the first mixer 104. The second amplifier 108 is connected to an output terminal of the band pass filter 107 to amplify the signal outputted from the band pass filter 107.

The second mixer mixes the first IF signal amplified by the second amplifier 108 with an oscillation frequency inputted from the second local oscillator 110, to output a secondary IF signal having a frequency of 45 MHz. The second local oscillator 110 generates the oscillation frequency according to a control voltage of the second PLL 111 when a channel is selected, to output the generated oscillation frequency to the second mixer 109. The second PLL 111 receives the output voltage fed-back from the second local oscillator 110 to output the control voltage to the second local oscillator 110 according to the size of the output voltage.

The second switch 116 has an operation terminal connected to an output terminal of the second mixer 109, a fixed terminal "a" connected to an input terminal of the second low pass filter 117, and a fixed terminal "b" connected to an input terminal of the third low pass filter 118. The second switch is switched according to an external control signal to selectively supply a secondary IF signal outputted from the second mixer 109 to the second low pass filter 117 or the third low pass filter 118. Here, the second switch 116 is switched according to control of QAM or QPSK of the system.

The second low pass filter 117 passes only a frequency having a bandwidth suitable for receiving earth wave out of the secondary intermediate frequencies outputted from the second switch 116, while the third low pass filter 118 passes only a frequency having a band suitable for receiving satellite wave out of the secondary intermediate frequencies outputted from the second switch 116.

In detail, the second low pass filter 117 passes only the frequencies having a bandwidth of 10 MHz, while the third low pass filter passes only the frequencies having a bandwidth of 45 MHz.

Meanwhile, more precisely, the bandwidth is a width of a frequency band for carrying data provided by a transmittal side provider. It is preferably to use SPS (Symbol rate Per Second) in more precise definition instead of the bandwidth, but since SPS and the bandwidth are similar to each other, the bandwidth is used for the convenience of description, which is identically applied to the below description.

Hereinafter, operation of the combination type tuner for earth and satellite broadcasting in accordance with one preferred embodiment of the present invention is described in detail with reference to FIG. 2. First, when it is requested to receive a broadcasting signal for earth wave, QAM or QPSK of a system connects respective operation terminals of the first switch 115 and the second switch 116 with the fixed terminals "a" of them.

Meanwhile, it can be allowed that the initial state of the first and second switches 115 and 116 is made as a state in which the operation terminals of the first and second switches 115 and 116 are connected with the fixed terminals "a" of the first and second switches 115 and 116.

An RF signal introduced through the first antenna (ANT 1) is made in a tuned waveform while passing through the first switch 115, the AGC 101, the first amplifier 102 and the first low pass filter 103. Afterward, the RF signal is up-converted to a first intermediate frequency (1038 MHz) while passing the first mixer 104. By the band pass filter 107, only a frequency having a wanted bandwidth out of the first intermediate frequencies outputted from the first mixer 104 passes through the band pass filter 107. Then, this signal is amplified while passing through the second amplifier 108, and is down-converted to the secondary intermediate frequency (45 MHz) while passing through the second mixer 109. Afterwards, only a frequency having the bandwidth of 10 MHz passes through the second switch 116 and the second low pass filter 117.

On the contrary, when it is requested to receive a broadcasting signal for satellite wave, QAM or QPSK of the system connects the operation terminals of the first and second switches 115 and 116 with the fixed terminals "b" of the first and second switches 115 and 116.

Then, an RF signal introduced through the second antenna (ANT 2) is destroyed while passing through the third mixer 112, so that only a signal having a frequency of 479.5 MHz is inputted to the AGC 101 through the operation terminal and the fixed terminal of "b" of the first switch 115. Thereafter, after this signal undergoes up-converting step and down-converting step, only a frequency having a bandwidth of 45 MHz suitable for the satellite wave is outputted through the third low pass filter 117 while the second switch 116 is switched. Thus, by applying a plurality of switches to a single tuner structure and switching the switches, earth and satellite wave signals inputted through respective antennas are selectively introduced into the circuit, and are detection-processed by the single structure. Bandwidths of the earth and satellite waves are selected by different low pass filters 117 and 118 through the second mixer 109. According to the aforementioned structure and operation applying a pair of switches to a single tuner structure, there is generated an effect capable of receiving earth wave and satellite wave at the same time.

Referring to FIG. 3, a combination tuner 200 for earth and satellite broadcasting, includes a tenth antenna (ANT 1), an AGC 201, a tenth amplifier 202, a tenth low pass filter 203, a tenth mixer 204, a tenth local oscillator 205, a tenth PLL 206, a band pass filter 207, a twentieth amplifier 208, a twentieth mixer 209, a twentieth local oscillator 210, a twentieth PLL 211, a twentieth antenna (ANT 2), a thirtieth mixer 212, a thirtieth local oscillator 213, a thirtieth PLL 214, a tenth switch 215, a twentieth switch 216, a twentieth low pass filter 217, and a thirtieth low pass filter 218.

In more detail, the tenth antenna (ANT 1) receives an earth wave corresponding to a frequency band ranged from 44 to 860 MHz.

The AGC 201 is connected to an operation terminal of the tenth switch 115 to control gain automatically so as to maintain the output of an image signal at a constant level even through size of an RF signal inputted from the tenth antenna (ANT 1) is varied. The tenth amplifier 202 amplifies the RF signal passing through the AGC 201. The tenth low pass filter 203 passes only an RF signal having frequencies of 860 MHz or less out of the RF signal amplified by the tenth amplifier 202.

The tenth mixer 204 mixes the RF signal selected by the tenth low pass filter 203 with the oscillation frequency inputted from the tenth local oscillator 105, to up-convert the RF signal to a first IF of 1038 MHz and to output the up-converted IF signal. The tenth local oscillator 205 generates the oscillation frequency according to a control voltage supplied from the tenth PLL 206 when a channel is selected, to output the oscillation frequency to the tenth mixer 204. The tenth PLL 206 receives the output voltage fed-back from the tenth local oscillator 205 to output the control voltage according to the size of the output voltage.

The band pass filter 207 passes only a frequency corresponding to a wanted band out of the first intermediate frequencies outputted from the tenth mixer 204. The twentieth amplifier 208 is connected to an output terminal of the band pass filter 207 to amplify the signal outputted from the twentieth amplifier 208.

The twentieth mixer 209 mixes the first IF signal amplified by the twentieth amplifier 208 with an oscillation frequency inputted from the twentieth local oscillator 210, to output a secondary IF of 45 MHz. The twentieth local oscillator 210 generates the oscillation frequency according to a control voltage of the twentieth PLL 211 when a channel is selected, to output the generated oscillation frequency to the twentieth mixer 209. The twentieth PLL 211 receives the output voltage fed-back from the twentieth local oscillator 210 to output the control voltage to the twentieth local oscillator 210 according to the size of the output voltage.

Meanwhile, the twentieth antenna (ANT 2) receives a satellite wave corresponding to a frequency ranged from 950 to 2150 MHz.

The thirtieth mixer 213 mixes an RF signal inputted from the twentieth antenna (ANT 2) with an oscillation frequency inputted from the thirtieth local oscillator 213, to output an intermediate frequency (IF) of 45 MHz. The thirtieth local oscillator 213 generates the oscillation frequency according to a control voltage inputted from the thirtieth PLL 214, to output the generated oscillation frequency to the thirtieth mixer 212. The thirtieth PLL 214 receives the output voltage fed-back from the thirtieth local oscillator 213 to output the control voltage to the thirtieth local oscillator 213.

The tenth switch 215 has a fixed terminal "a" connected to the output terminal of the twentieth mixer 209, and a fixed terminal "b" connected to the output terminal of the thirtieth mixer 212. By the above structure of the tenth switch 215, operation terminal of the tenth switch 215 is switched by an external control signal, so that a secondary IF outputted from the twentieth mixer 209 or an IF outputted from the thirtieth mixer 312 is selected and the selected IF is outputted to the twentieth switch 216. Here, the tenth switch 215 is switched by the control of QAM or QPSK of the system, and the operation terminal thereof is changed in combination with the twentieth switch 216.

The twentieth switch 216 has a fixed terminal "a" connected to the operation terminal of the tenth switch 215, a fixed terminal "a" connected to the input terminal of the twentieth low pass filter 217, and a fixed terminal "b" connected to the input terminal of the thirtieth low pass filter 218. The twentieth switch 216 is switched depending on an external control signal to selectively supply a secondary IF signal outputted from the twentieth mixer 209 or an IF signal outputted from the thirtieth mixer 212 to the twentieth low pass filter 217 or the thirtieth low pass filter 218. Here, the twentieth switch 216 is switched according to the control of QAM or QPSK of the system. In particular, the tenth switch 215 operates in combination with the twentieth switch 216. The twentieth low pass filter 217 passes only a frequency having a bandwidth (BW) of 10 MHz out of the secondary intermediate frequencies outputted from the twentieth switch 216, while the thirtieth low pass filter 218 passes only a frequency having a bandwidth of 45 MHz of the intermediate frequencies outputted from the twentieth switch 216. Hereinafter, operation of the combination type tuner for earth and satellite broadcasting in accordance with another preferred embodiment of the present invention is described in detail with reference to FIG. 3.

First, when it is requested to receive a broadcasting signal for earth wave, QAM or QPSK of the system connects respective operation terminals of the tenth switch 215 and the twentieth switch 216 with the fixed terminals "a" of them. At this time, it is allowed that the initial state of the tenth and twentieth switches 215 and 216 is made as a state in which the operation terminals of the tenth and twentieth switches 215 and 216 are connected with the fixed terminals "a" of the tenth and twentieth switches 215 and 216.

Then, an RF signal introduced through the tenth antenna (ANT 1) is made in a tuned waveform while sequentially passing through the AGC 201, the tenth amplifier 202 and the tenth low pass filter 203. Afterward, the turned RF signal is up-converted to a first intermediate frequency (1038 MHz) while passing the tenth mixer 204. Then, the band pass filter 207 passes through only a frequency having a wanted bandwidth among the tenth intermediate frequencies outputted from the tenth mixer 204.

Thereafter, this signal is amplified while passing through the twentieth amplifier 208, and is then down-converted to an intermediate frequency (45 MHz) while passing through the twentieth mixer 209. Afterwards, only a frequency having the bandwidth of 10 MHz corresponding to the earth wave passes through the twentieth switch 216 and the twentieth low pass filter 217.

On the contrary, when it is requested to receive a broadcasting signal for satellite wave, QAM or QPSK of the system connects the operation terminals of the tenth and twentieth switches 215 and 216 with the fixed terminals "b" of the tenth and twentieth switches 215 and 216.

Then, an RF signal introduced through the twentieth antenna (ANT 2) is destroyed while passing through the thirtieth mixer 212, so that only a signal having a frequency of 45 MHz is outputted to the twentieth switch 216 through the operation terminal and the fixed terminal of "b" of the tenth switch 215.

Due to the above operation, the IF signal passing through the twentieth switch 216 is filtered by the thirtieth low pass filter 218, so that only a frequency having the bandwidth of 45 MHz corresponding to the satellite wave passes through the thirtieth low pass filter 217. Thus, by applying a plurality of switches to a single tuner structure and switching the switches, earth and satellite wave signals inputted through respective antennas are selectively introduced into the circuit, and the tuner allows secondary IF outputted from twentieth mixer or If outputted from thirtieth mixer to pass through different low pass filters, so that both of earth wave and satellite wave can be received.

Meanwhile, the above embodiments can be reviewed from another aspect. In other words, a tuner includes an earth frequency output part that is a set of elements for receiving earth wave and outputting the received earth wave, and a satellite frequency output part that is a set of elements for receiving satellite wave and outputting the received satellite wave. Also, first and second switching means are included in the tuner such that received signals outputted from the earth frequency output part and the satellite frequency output part are filtered by respective low pass filters and filtered signals are outputted, thereby capable of grossly describing the tuner structure.

As described previously, according to a combination tuner for earth and satellite broadcasting of the present invention, earth wave and satellite wave can be received by a single tuner, so that manufacturing costs and volume of products can decrease.

Industrial Applicability As provided previously, a combination tuner for earth and satellite broadcasting adds a pair of simple switches to a single tuner structure, thereby providing an effect capable of receiving earth wave and satellite wave at the same time.

Also, the circuit structure of the tuner is simplified to thus decrease volume of electro wave receiver, so that the tuner of the invention allows for more near approach on the miniaturization of the electronic wave receiver.

Further, the tuner of the invention allows earth wave and satellite wave to be received at the same time by a single electronic wave receiver, so that manufacturing cost decreases.

Claims

1. A combination tuner for earth and satellite broadcasting, comprising: a double conversion tuner including a first antenna, an AGC, a first amplifier, a first low pass filter, a first mixer, a first local oscillator, a first PLL, a band pass filter, a second amplifier, a second mixer, a second local oscillator and a second PLL; a satellite frequency output part for receiving a satellite wave and outputting a predetermined frequency signal; first switching means switched by a control signal inputted from an outside to select and output an RF signal inputted from the first antenna or an RF signal outputted from the satellite frequency output part using the AGC; second switching means switched along with the first switching means, to selectively supply a second IF signal outputted from the second mixer; a second low pass filter for passing only a frequency corresponding to earth wave band out of the second IF outputted from the second switching means; and a third low pass filter for passing only a frequency corresponding to satellite wave band out of the second IF outputted from the second switching means.

2. The combination tuner as claimed in claim 1, wherein the second low pass filter passes only a frequency of 10 MHz in bandwidth.

3. The combination tuner as claimed in claim 1, wherein the third low pass filter passes only a frequency of 45 MHz in bandwidth.

4. The combination tuner as claimed in claim 1, wherein the satellite frequency output part comprises: a second antenna for receiving the satellite wave; a third mixer for mixing an RF signal inputted from the second antenna with an oscillation frequency to output a predetermined frequency; a third local oscillator for generating a predetermined oscillation frequency according to a control voltage inputted from an outside and outputting the generated oscillation frequency to the third mixer; and a third PLL for outputting a control voltage to the third local oscillator.

5. The combination tuner as claimed in claim 1, wherein the satellite frequency output part outputs a signal having a frequency of 479.5 MHz.

6. The combination tuner as claimed in claim 1, wherein the first low pass filter passes only an RF signal of 860 MHz or less.

7. The combination tuner as claimed in claim 1, wherein the first switching means has a first fixed terminal formed at an output terminal of the first antenna, a second fixed terminal formed at an output terminal of the satellite frequency output part, and an operation terminal connected to the AGC according to a control signal from an outside.

8. The combination tuner as claimed in claim 1 , wherein the second switching means has an operation terminal formed at an output terminal of the second mixer, a first fixed terminal formed at the second low pass filter, and a second fixed terminal connected to the third low pass filter, the second switching means being switched according to a control signal from an outside to selectively supply a secondary IF signal outputted from the second mixer to the second low pass filter or the third low pass filter.

9. The combination tuner as claimed in claim 1, wherein the first switching means and the second switching means are switched according to a control of QAM or QPSK of a system.

10. A combination tuner for earth and satellite broadcasting, comprising: a double conversion tuner including a first antenna, an AGC, a first amplifier, a first low pass filter, a first mixer, a first local oscillator, a first PLL, a band pass filter, a second amplifier, a second mixer, a second local oscillator and a second PLL; a satellite frequency output part for receiving a satellite wave and outputting a predetermined frequency signal; first switching means for selectively outputting a secondary IF signal inputted from the second mixer or an RF signal outputted from the satellite frequency output part by an external control signal; second switching means operating in combination with the first switching means and selectively supplying the second IF signal outputted from the first switching means; a second low pass filter for passing only a frequency corresponding to earth wave band out of the second IF outputted from the second switching means; and a third low pass filter for passing only a frequency corresponding to satellite wave band out of the second IF outputted from the second switching means.

11. The combination tuner as claimed in claim 10, wherein the second low pass filter passes only a frequency of 10 MHz in bandwidth.

12. The combination tuner as claimed in claim 10, wherein the third low pass filter passes only a frequency of 45 MHz in bandwidth.

13. The combination tuner as claimed in claim 10, wherein the satellite frequency output part comprises: a second antenna for receiving the satellite wave; a third mixer for mixing an RF signal inputted from the second antenna with an oscillation frequency to output a predetermined frequency; a third local oscillator for creating a predetermined oscillation frequency according to an external control voltage and outputting the generated oscillation frequency to the third mixer; and a third PLL for outputting the control voltage to the third local oscillator.

14. The combination tuner as claimed in claim 10, wherein the satellite frequency output part outputs an IF of 45 MHz.

15. The combination tuner as claimed in claim 10, wherein the first low pass filter passes only an RF signal having a frequency of 860 MHz or less.

16. The combination tuner as claimed in claim 10, wherein the first switching means has a first fixed terminal formed at an output terminal of the second mixer, a second fixed terminal formed at an output terminal of the satellite frequency output part, and an operation terminal formed at an output terminal of the second switching means.

17. The combination tuner as claimed in claim 10, wherein the second switching means has an operation terminal formed at the first switching means, a first fixed terminal formed at the second low pass filter, and a second fixed terminal formed at the third low pass filter, the second switching means being switched according to an external control signal to selectively supply a secondary IF signal outputted from the second mixer or an IF signal outputted from the satellite frequency output part to the second low pass filter or the third low pass filter.

18. The combination tuner as claimed in claim 10, wherein the first switching means and the second switching means are switched according to a control of QAM or QPSK of a system.

19. A combination tuner for earth and satellite broadcasting, comprising: an earth frequency output part essentially including an earth wave antenna for receiving an earth wave; a satellite frequency output part essentially including a satellite wave antenna for receiving a satellite wave; a first switching means for selectively supplying a frequency outputted from the earth wave output part or the satellite frequency output part; and a second switching means formed at a rear end of the first switching means, for selectively supplying a signal that has passed through the first switching means to a low pass filter suitable for the earth wave and the satellite wave.