Abstract:
The combined TV receiver can receive and process an analog broadcasting signal as well as a digital broadcasting signal, and includes a controller determining whether a channel selected by a user is a digital broadcast or an analog broadcast. The controller generates station selection data on the selected channel and a control signal pertinent to the determination. A tuner receives the station selection data and tunes to a broadcasting signal associated with the selected channel, out of signals received through an antenna. A switch unit forwards the broadcasting signal tuned at the tuner, in response to the control signal, to either an analog broadcasting processor or a digital broadcasting processor. An AGC (auto-gain controller) receives a gain signal either from the analog broadcasting processor or from the digital broadcasting processor, and adjusts a signal gain of the broadcasting signal tuned at the tuner, thereby allowing reception of both analog and digital signals.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a TV, and more particularly, to a combined TV receiver which can receive and process an analog broadcasting signal as well as a digital broadcasting signal. 
     2. Background of the Related Art 
     The TV receiver is an appliance for decoding a broadcasting signal transmitted from a broadcasting station into an image signal and presenting image information to TV watchers. There are different standards of TV systems depending on scanning lines, frames per second, modulation type, channel bandwidth, video signal bandwidth, and audio channel modulation of a broadcasting signal transmitted from the broadcasting station, inclusive of the NTSC(National Television System Committee), PAL(Phase Alternation by Line), SECAM(Sequential Couleur a Memoire). The NTSC system is a standard system of a broadcasting signal having 525 scanning lines and transmitting 30 frames per second used in the north America, Japan and Korea. The NTSC system is compatible with black and white TV and has a simple driving circuit compared to other systems. The PAL system is a standard system of a broadcasting signal used in most European countries except some eastern European countries starting from France, in which a phase of one of two color difference signals are inverted at every scanning line in modulation. Though the PAL system has a somewhat poor compatibility with a black and white TV, a video signal of the PAL system is less influenced by a phase distortion caused by recording or transmission. The SECAM system is a standard system of a broadcasting signal developed in France and used in France, the old soviet union, east Europe and some African countries, in which a color subcarrier is frequency modulated and overlapped with a luminance signal while the two color difference signals are cut off in a sequence before transmission. Though the SECAM system is advantageous in small amplitude and phase distortions during transmission, a vertical resolution is poor. 
     FIG. 1 illustrates a block diagram of a related art analog TV receiver circuit schematically, of which operation will be explained. A tuning data is received at a tuner  1 . Then, a VIF(Video Intermediate Frequency)  2  provides a video signal, of which synchronizing signal is detected by a synchronizing signal detector  3 . If a synchronizing signal is contained in the signal received from the antenna, the signal is an analog signal, if there is no synchronizing signal, the signal is not an analog signal. An analog broadcasting receiver determines the presence of a broadcasting signal according to existence of a synchronizing signal, and stores a channel number having a broadcasting signal in a memory. 
     In the meantime, there have been research and other efforts for replacing a related art analog transmission type TV system with a digital transmission type TV gradually as digital technologies and video and audio data compression and restoring technologies are developed. In such a digital terrestrial TV broadcasting transmission system, there is a system of the USA and a system of Europe. The USA system is a VSB transmission system in which a single carrier is used and the European system is a COFDM(Coded Orthogonal Frequency Division Multiplexing) transmission system in which multi carriers are used. Particularly, because the multi carriers are used, the COFDM system is strong against interference and ghost in multiple path channel and allows to construct an SFN(Single Frequency Network) which can make a wide band transmission in a signal frequency. Because the present carrier condition is sensed in the COFDM system for making a Viterbi decoding with reference to the channel condition, an interference between channels or a selective fading of a frequency affect system performance, seriously. Therefore, as shown in FIG. 2, in the COFDM system, a signal called pilot  5  having a predictable value is added at every fixed intervals both in frequency axis Nf and time axis Nt directions between carriers of data at a transmitter side before transmission, which is used in synchronization or equalizing required in reception for restoring data at a receiver side. Together with this, the related art COFDM transmitter side transmits TPS(Transmission Parameter Signaling) including information on various transmission modes, and the receiver side decodes the TPS for use in demodulation. That is, the COFDM system is characterized in the use of multi carrier intransmission as well as the addition of pilots before transmission for use at the receiver side. 
     FIGS. 3 a  and  3   b  illustrate reception blocks in a COFDM system. As shows, signals (t) received through an antenna is amplified as necessary through a transmission channel  11  and the amplification terminal  12 . An amplification gain is controlled through an AGC(Auto Gain Controller)  16 . The amplified signal is digitized at an A/D converter  13 , provided to an I &amp; Q demodulator  14 , and converted into of an I signal and a Q signal. The I signal and Q signal are subjected to adjustment of frequencies and powers as they pass through an FFT(Fast Fourier Transformer) block  15  and an equalizer  31 , and are restored into an original data as they pass through a demapper  32 , deinterleavers  33  and  36  and FEC(Forward Error Corrector)(not shown). At first, the received data is provided to a course timing block  17  for being divided into an effective data interval and a guard interval. The course timing block  17  shifts data by one interval to obtain correlation between data, and provides the correlation to an FFT start window generator  18  for establishing an interval of the data appropriate for subjecting to FFT. After the I &amp; Q composite signals are converted at the FFT block  15 , TPS information is demodulated. The TPS demodulator  19  analyzes the pilot signals, and corrects frequency and time basis distortions of the received data using a result of the analysis, to decode a correct TPS signal. The pilot signals are detected from the signal subjected FFT at a scattered pilot extractor  20  and analyzed at an IFFT block  21  and a narrow &amp; fine frequency controller  22  for obtaining a correct frequency band of the signal. The signal subjected to FFT is provided to a continual pilot extractor  23  for being frequency synchronized by which an error in a received frequency is corrected. And, the fine timing block  24  receives the data subjected to FFT and decodes a pilot signal in the data, for finding an exact timing of conversion of the FFT. The signal having frequency synchronized and frequency band corrected through the IFFT block  21 , the narrow &amp; fine frequency controller  22 , and the fine timing block  24  is provided to the FFT block  15 , again. The signal provided to the FFT block  24  is corrected for an error in a data carrier by hard or soft decision. The FFT  15  should be provided in a COFDM demodulating system for receiving an I signal and a Q signal and transform into frequency components. The signal transformed into the frequency components at the FFT is provided to a TPS(Transmission Parameter Signalling) decoder  19 . 
     A memory  2  stores a signal from the FFT block  15  and provides the stored signal to the equalizer  31 , and the equalizer  31  compensates for a distortion in a frequency response signal caused in a transmission channel. The demapper  32  receives both the signal having distortion compensated at the equalizer  31  and a TPS signal from the TPS decoder  19 , and analyzes a mapped signal. The internal deinterleaver  33  subjects the signal analyzed at the demapper  32  to internal deinterleave, and provides the result to a Viterbi decoder  34 . The Viterbi decoder  34  receives both  20  a signal from the internal deinterleaver  33  and the TPS signal, and subjects to viterbi decoding. An external deinterleaver  36  subjects the signal subjected to internal interleave to external interleave with reference to a synchronizing signal detected at a synchronizing signal detector  35 . RS decoder  37  and a derandomizer  38  process the signal subjected to external interleave, for extracting a broadcasting signal of the channel the user selected. Also, the TPS decoder  19  receives a frequency component from the FFT block  15 , analyzes a modulation type of the signal, and provides a result of the analysis to a processor(not shown). In this instance, different parameters are provided to the TPS decoder in succession until a right modulation type of the signal is analyzed. Accordingly, when the right modulation type of the signal is analyzed, the processor stores a channel of the signal having analyzed by the TPS decoder in an internal memory. If the TPS decoder can not detect the modulation type of the signal, the digital tuner receives information on a new channel number, and the aforementioned process is repeated. The TPS decoder is adapted to provide a right result only when the entire COFDM demodulator in the digital broadcasting receiver is operative regularly. 
     Most of the digital broadcasting signals provided to such digital TV receivers are based on the MPEG standards. Particularly, the MPEG-3 which is an MPEG standard for broadcasting and has all standards for system, audio and video established therein. For reference, the system standard No. in the MPEG-2 is ISO/IEC 13818-1, the video standard No. is ISO/WEC 13818-2, and the audio standard No. is ISO/IEC 13818-3. 
     A system and operation of a related art digital TV receiver based on the MPEG-2 standard will be explained with reference to FIG.  4 . 
     Referring to FIG. 4, the related art digital TV receiver is provided with a tuner  100  for receiving a digital broadcasting signal, an IF converter  110  for subjecting the digital broadcasting signal received from the tuner  100  to frequency conversion to provide an intermediate frequency signal, a channel decoder  120  for detecting a pilot signal from the IF signal and decoding a lower frequency broadcasting signal, a TP parser  130  for parsing a TP signal from the lower frequency broadcasting signal to detect audio/video signals, audio/video decoders  140  and  150  for decoding the audio/video signals parsed at the TP parser, respectively, an audio signal converter  170  for converting a digital audio signal decoded at the audio decoder, a TV microprocessor  200  for controlling a TV system, a ROM  210  storing channels, programs, and the like, a RAM  220  for storing temporary data following operation of the TV microcomputer  200 , an OSD processor  190  for processing OSD text, a switch unit  160  for selective forwarding the digital video signal decoded at the video decoder and the OSD text from the OSD processor  190 , and a video signal encoder  180  for converting a video signal from the switch unit  160  into an image signal displayable on a TV or a monitor. 
     The tuner  100  receives and detects a QPSK(Quadrature Phase Shift Keying) signal or a QAM(Quadrature Amplitude Modulation) signal. The IF converter  110  receives a signal detected at the tuner and converts it into a signal of IF band, because the high frequency signal in a very high frequency band detected at the tuner can not be processed by a driving circuit of the digital TV, directly. The channel decoder, identical to the COFDM receiver block shown in FIGS. 3 a  and  3   b , detects a pilot signal from the IF signal, decodes a baseband signal, converts the baseband signal into a digital signal, restores timing appropriate for the symbol rate, thereby correcting errors. The signal from the channel decoder  120  is a signal stream in the form of a transport stream packet in byte units. A transport signal stream as in MPEG-2 is a time-multiplexed signal stream named as a transport stream packet. The transport stream packet has a header at a beginning portion of the packet having a PID(Packet Identifier) number recorded therein. The PID number can be used as information which can demultiplex a time multiplexed signal. And, the PID number denotes a kind of the present packet, and, by analyzing the PID number, the present packet can be known as either a video packet, an audio packet, or program specific information. The video and audio standards in the MPEG-2 are standards on compressed video and audio signal streams. According to the MPEG-2 standards, all video signals, audio signals and program specific information signals are time-multiplexed, and transported as plural transport stream packets which can be identified with PID numbers. 
     The TP parser  130  parses a signal stream of such a transport stream packet form based on the PID number, and provides the result to respective decoders  140  and  150 . That is, the TP parser  130  receives a transport signal stream through the tuner  100  and detects a PID number at a header of the signal stream. Thereby, the TP parser  130  parses a video signal stream, an audio signal stream and program specific information stream according to the PID numbers. Then, the TP parser  130  provides the video signal stream to the video decoder  150 , the audio signal stream to the audio decoder  140 , and the program specific information signal stream to the microcomputer  200 . 
     The video decoder  150  decodes the video signal stream from the TP parser  130 , and provides the result to the NTSC encoder  180 . The video signal stream from the TP parser  130  is data compressed according to the MPEG-2 standards. According to this, the video decoder decompresses the compressed video signal stream, to restore an original digital video data. The audio decoder  140  decodes the audio signal stream from the TP parser  130 , and provides to an audio digital to analog converter  170 . The audio signal stream from the TP parser  130  is a data compressed according to the MPEG-1 standards. Therefore, the audio decoder  140  decompresses the compressed audio signal stream, to restore an original digital audio data. The audio digital to analog converter  170  converts digital audio data from the audio decoder  140  into an analog audio signal an amplifier or a speaker can process. The analog audio signal is presented as voice or sound by stereo speakers(not shown). 
     The NTSC encoder  180  converts the digital video data from the video decoder  150  into a luminance signal Y and a color difference signal C which can be displayed on a related art TV or a monitor. The luminance signal Y and the color difference signal C can be displayed by a CRT. 
     The microcomputer  200  controls operation of the digital TV receiver. And, programs and OSD information required for controlling the microcomputer  200  are stored in the ROM(Read Only Memory)  210 , and temporary information required for the microcomputer control operation is stored in the RAM  220 (Random Access Memory). That is, the microcomputer  200  processes the program specific information signal stream from the TP parser  130  and provides a program specific information data to the OSD processor  190  in response to control signals provided through a user input device  230 , such as a remote controller or a key pad. Though OSD information is stored in the ROM  210 , when a control signal is provided from the input device, the microcomputer  200  draws out OSD information corresponding to the control signal from the ROM  210  and provides it to the OSD processor  190 . The OSD processor  190  converts the OSD information transmitted by the microcomputer  200  into a video signal that the NTSC encoder  180  can process. The switch unit  160  selects the OSD information converted into the video signal at the OSD processor  190  and the video signal converted at the video decoder  150  and provides the selection to the NTSC encoder  180 . If no OSD information is provided according to the user input device, the switch unit  160  provides the video signal provided from the video decoder  150  to the NTSC encoder  180 . And, if the OSD information is provided according to the user input device, the switch unit  160  provides the OSD information provided from the OSD processor  190  to the NTSC encoder  180 . 
     However, the related art digital TV receiver can not receive an analog broadcasting signal, and the related art analog TV receiver can not receive a digital broadcasting signal. Therefore, if the user intends to watch both the analog broadcasting signal and the digital broadcasting signal, the user must provide two separate TV receivers, which is a substantial burden to the user. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a combined TV receiver which can receive and process an analog broadcasting signal as well as a digital broadcasting signal that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the digital/analog TV receiver includes a controller for determining a channel of user&#39;s selection of being of a digital broadcasting or an analog broadcasting, and generating a station selection data on the channel and a control signal pertinent to the determination, a tuner for receiving the station selection data and tuning to a broadcasting signal pertinent to the channel out of signals received through an antenna, an IF switch unit for selecting a direction of forwarding the broadcasting signal tuned at the tuner in response to the control signal, an analog broadcasting processor for demodulating the broadcasting signal selected at the IF switch unit into an audio signal and a video signal, a digital broadcasting processor for decoding the broadcasting signal selected at the IF switch unit into digital broadcasting information, and an AGC(auto-gain controller) for receiving a gain signal either from the analog broadcasting processor or from the digital broadcasting processor and adjusting a signal gain of the broadcasting signal tuned at the tuner. 
     It is foreseen that the digital TV broadcasting systems will use channels the present analog broadcasting systems do not use, frequently. Therefore, the digital TV broadcasting signals can be received by an existing analog TV antenna. Moreover, an output frequency band of a digital tuner is also similar to an output frequency band of a tuner of an existing analog TV receiver. 
     However, a digital TV broadcasting signal has program specific information in addition to video and audio information. The program specific information allows a digital TV receiver to provide more information than an analog TV receiver. The present invention utilizes the very feature of frequency common use between a digital TV receiver and an analog TV receiver and the distinctive feature of the digital TV receiver of having the program specific information, for providing a combined TV receiver which can receive and process both the analog broadcasting signal and the digital broadcasting signal. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention: 
     In the drawings: 
     FIG. 1 illustrates a block diagram of a related art analog TV receiver circuit, schematically; 
     FIG. 2 illustrates a data of a related art digital TV COFDM added with pilots; 
     FIGS. 3 a  and  3   b  illustrate a reception block in a COFDM system; 
     FIG. 4 illustrates a block diagram of a related art digital TV receiver circuit, schematically; and, 
     FIG. 5 schematically illustrates a block diagram of a combined TV receiver circuit in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. FIG. 5 schematically illustrates a block diagram of a combined TV receiver circuit in accordance with a preferred embodiment of the present invention. 
     A controller  2300  determines a channel of a user&#39;s selection, either a digital broadcasting or an analog broadcasting, channel, and provides a station selection data of the selected channel to a tuner  1000 . The tuner  1000  is provided with the station selection data from the controller  2300 , and selects a channel of a digital broadcasting signal and an analog broadcasting signal received through an antenna with reference to the station selection data. In this instance, the antenna is, for example, a combined antenna capable of receiving both the digital broadcasting signal and the analog broadcasting signal. 
     An IF switch unit  1100  is also provided with a control signal from the control unit  2300 . In response to the control signal, either an analog broadcasting processor or a digital broadcasting processor is selected, and the broadcasting signal received through the antenna presently is provided thereto. That is, the IF switch unit  1100  provides the digital broadcasting signal and the analog broadcasting signal to different broadcasting processors. The analog broadcasting processor includes a second IF modulator  1200  for extracting an IF audio signal and an IF video signal from the analog broadcasting signal, an audio detector  1300  for demodulating the audio signal extracted at the second IF modulator  1200  into a baseband audio signal, and a video detector  1400  for demodulating the video signal extracted at the second IF modulator  1300  into a baseband video signal. Thus, if the broadcasting signal received presently is the analog broadcasting signal, the IF switch unit  1100  provides the analog broadcasting signal to the second IF modulator  1200  in the analog broadcasting processor. And, if the broadcasting signal received presently is the digital broadcasting signal, the IF switch unit  1100  provides the digital broadcasting signal to a first IF modulator  2000  in the digital broadcasting processor. In this instance, the broadcasting signal received presently is tuned by the control signal determined and provided by the controller  2300 . As an example, the IF switch unit  1100  provides the broadcasting signal received presently to the digital broadcasting processor if the control signal from the controller  2300  is at high, and provides to the analog broadcasting processor if the control signal is at low. The determination by the IF switch unit  1100  in response to the control signal may be set to be opposite to the aforementioned explanation. That is, the broadcasting signal received presently may be provided to the analog broadcasting processor if the control signal from the controller  2300  is at high, and the broadcasting signal received presently may be provided to the digital broadcasting processor if the control signal from the controller  2300  is at low. 
     The second IF modulator  1200  receives the analog broadcasting signal from the IF switch unit  1100  and extracts an IF audio signal and an IF video signal. The first IF modulator  2000  receives the digital broadcasting signal from the switch unit  1100  and modulates  15  into an IF broadcasting signal. The audio detector  1300  demodulates the audio signal extracted at the second IF modulator  1200  into a low frequency band audio signal, to restore the IF audio signal into an original voice. The video detector  1400  demodulates the video signal extracted at the second IF modulator  1200  into a low frequency band video signal, to restore the luminance signal Y and the color difference signal C. Though not shown in the drawings, the luminance signal and the color difference signal are processed by an image processing circuit for displaying on a CRT. 
     In the digital processor, a channel decoder  2100  receives the station selection data from the controller  2300 , and decodes the broadcasting signal modulated at the second IF modulator  2000  into a digital signal. System and operation of the channel decoder are almost identical to the COFDM decoder in FIGS. 3 a  and  3   b , and explanation of which will be omitted. As explained in the related art, the digital signal from the channel decoder is a transport bit stream signal stream. A TP(Transport Packet) parser  2200  reads the PID signals contained in a header portion of the transport bit signal stream from the channel decoder  2100 , and parses the signal stream into an audio packet, a video packet, and a program specific information packet. The audio decoder  1600  decodes the audio packet from the TP parser  2200  into a digital audio signal. And, the video decoder  1800  decodes the video packet from the TP parser  2200  into a digital video signal. An audio digital-to-analog converter (DAC)  1700  converts the digital audio signal into an analog audio signal, and the video processor  1900  converts the digital video signal into a luminance signal Y and a color difference signal C. The audio DAC  1700  has a digital to analog converter, and the video processor  1900  has an encoder according to a broadcasting signal standard. As broadcasting signals of Korea, Japan and the USA are based on the NTSC standard, the video processor  1900  has an NTSC encoder. 
     The controller  2300  may receive, and subject the program specific information packet to OSD processing, or generate the station selection data on the channel of the user&#39;s selection and provide to the tuner  1000  and the channel decoder  2100  for selection of a broadcasting signal. And, the controller  2300  provides a control signal according to the station selection data to the switch unit  1100  and an audio/video switch unit  1500 , for realizing the broadcasting signal to an image and voice. In this instance, the channel of the user&#39;s selection is applied by any one of a remote controller and a key input pad. An AGC  3000  selects one of gain signals from the analog broadcasting processor and the digital broadcasting processor in response to a control signal from the controller  2300  for adjusting a gain of the broadcasting signal tuned at the tuner. That is, when the controller  2300  determines the channel of the user&#39;s selection as an analog broadcasting signal and provides a control signal accordingly, the AGC  3000  is provided with a gain signal from the second IF modulator  1200  in the analog broadcasting processor for adjusting a gain (e.g., amplifier AMP) of the broadcasting signal tuned at the tuner  1000  presently. And, when the controller  2300  determines the channel of the user&#39;s selection as a digital broadcasting signal and provides a control signal accordingly, the AGC  3000  is provided with a gain signal from the first IF modulator  2000  in the digital broadcasting processor for adjusting a gain (e.g., amplifier AMP) of the broadcasting signal tuned at the tuner  1000  presently. The controller  2300  includes a ROM  2320  having a processing program of the program specific information packet, a system control program, and channel information on digital broadcasting systems stored therein, a microcomputer  2310  for conducting a program stored in the ROM  2320 , reading channel information to generate a station selection ID data of the channel of user&#39;s selection, and determining the channel of user&#39;s selection of being the analog broadcasting or a digital broadcasting to generate a control signal accordingly, and RAM  2330  for storing additional data required for operation of the microcomputer  2310 . 
     The controller  2300  is operative as follows. 
     Upon turning on a power to the TV receiver, if there is channel information already set, the microcomputer  2310  provides a station selection data of the channel to the tuner  1000  via an I 2 C bus, so that the tuner  1000  receives a digital broadcasting signal pertinent to the station selection data. If there is no channel information in the microcomputer  2310  of the TV receiver, that is, there is no channel information set up in the TV receiver, the microcomputer  2310  provides the station selection data of a channel set up as an initial value of a digital broadcasting to the tuner  1000  so that the tuner  1000  selects the channel set up as the initial value of a digital broadcasting. For example, if channel No. 1 is set up as the initial value, the microcomputer  2310  provides the station selection data on the channel No. 1, so that the tuner  1000  selects a broadcasting signal of the channel No. 1. If the broadcasting signal received in the channel No. 1 is not restored into a digital signal stream, i.e., a transport bit stream by the channel decoder  2100 , it implies that there is no broadcasting signal in the channel No. 1. Then, the microcomputer  2310  provides a station selection data of another channel to the tuner  1000  for selecting a broadcasting signal of another channel. The microcomputer  2310  repeats the foregoing station selection process many times, for storing the program specific information of the channels of which digital signal streams are received in the RAM  2330  in a form of a table, so that, when the user selects an arbitrary channel later, the microcomputer  2310  refers to the table for determining a kind of the broadcasting signal of the user&#39;s selection. That is, if the broadcasting signal of the channel of user&#39;s selection is contained in the table stored in the RAM  2330 , the microcomputer  2310  determines the broadcasting signal as a digital broadcasting signal, and, if not, as an analog broadcasting signal, to control the switch unit  1100  and the audio/video switch unit  1500 . 
     Like the IF switch unit  1100 , the audio/video switch unit  1500  selects a signal source in response to a control signal from the microcomputer  2310 . First, if the microcomputer  2310  controls the IF switch unit  1100  so that the IF switch unit  1100  provides a broadcasting signal to the second IF modulator  1200 , the audio/video switch unit  1500  processes an audio signal and a video signal from the audio detector  1300  and the video detector  1400 . And, if the microcomputer  2310  controls the switch unit  1100  to provide a broadcasting signal to the IF modulator  2000 , the audio/video switch unit  1500  processes the audio signal and the video signal converted into analog signals by the audio processor  1700  and the video processor  1900  respectively. Thus, the microcomputer  2310  in the digital/analog TV receiver of the present invention refers to the already stored station selection data on digital broadcasting signal for tuning to the broadcasting signal of the channel of user&#39;s selection. The station selection data on the digital broadcasting signal is stored in a separate memory  2325 , preferably, an EEPROM, or flash memory. 
     The operation of the digital/analog TV receiver of the present invention will be explained following flow of a signal. 
     First, a user selects a channel number by an input device  2400 , such as a remote controller. On reception of the channel number of the user&#39;s selection, the microcomputer  2310  determines of the channel number of being contained in the table of digital broadcasting signals stored in the RAM  2330  or the separate EEPROM  2325 . If the channel number is a number contained in the table, the microcomputer  2310  determines the channel number of the user&#39;s selection as a digital broadcasting signal, and controls the switch unit  1100  and the audio/video switch unit  1500  to process the digital broadcasting signal. At the same time, the microcomputer  2310  provides the station selection data on the channel number of the user&#39;s selection to the tuner  1000  and the channel decoder unit  2100 , so that the right broadcasting signal of the channel number is selected and processed. The tuner  1000  selects a broadcasting signal of the channel pertinent to the station selection data provided by the microcomputer  2310  and provides it to the IF switch unit  1100 . The broadcasting signal provided to the IF switch unit  1100  is provided to the first IF modulator  2000  under the control of the microcomputer  2310 , and modulated into a broadcasting signal of IF band. The broadcasting signal modulated into the broadcasting signal of IF band is provided to the channel decoder  2100 , and decoded into a digital broadcasting signal of the channel pertinent to the station selection data provided from the microcomputer  2310 . The digital broadcasting signal is parsed into an audio signal the video signal by the TP parser  2200 , and audio signal is provided to the audio decoder  1600 , and the video signal is provided to the video decoder  1800 . The audio signal provided to the audio decoder  1600  is converted into an original digital audio data, and the video signal provided to the video decoder  1800  is converted into an original digital video data. The digital audio data is converted into an analog signal at the audio DAC  1700 , and the digital video data is restored into a video signal having a luminance signal and a color difference signal. The audio signal from the audio DAC  1700  and the video signal from the video processor  1900  are presented to a speaker and a CRT by the audio/video switching unit  1500 , respectively. 
     In the meantime, in a case when the channel number selected by the user is not contained in the table stored in the RAM  2330  or the separate EEPROM  2325 , the microcomputer  2310  determines the channel number as an analog broadcasting signal. The microcomputer  2310  then controls the IF switch unit  1100  and the audio/video switch unit  1500  to process the analog broadcasting signal. At the same time, the microcomputer  2310  provides a station selection data pertinent to the channel number of the user&#39;s selection to the tuner  1000 , so that the right broadcasting signal pertinent to the channel number is selected and processed. The tuner  1000  selects a broadcasting signal pertinent to the channel number provided by the microcomputer  2310  and provides it to the switch unit  1100 . The broadcasting signal provided to the switch unit  1100  is applied to the second IF modulator  1200  under the control of the microcomputer  2310 , and separated into an audio signal and a video signal. The audio signal of IF band is provided to the audio detector  1300 , and the video signal of IF band is provided to the video detector  1400 . The audio signal provided to the audio detector  1300  is restored into an audio signal of baseband frequency, and the video signal provided to the video detector  1400  is converted into an original video signal having a luminance signal and a color difference signal. The audio signal from the audio detector  1300  and the video signal from the video detector  1400  are presented to the speaker and the CRT, respectively by the audio/video switch unit  1500 . 
     Thus, since the microcomputer  2310  determines a broadcasting signal of being of analog or digital with reference to the channel number table, the digital/analog TV receiver of the present invention allows the user to watch both broadcasting signals. 
     The combined functions of watching a digital TV signal and an analog TV signal of the digital/analog TV receiver of the present invention provides the user both with the digital broadcasting signal and the analog broadcasting signal. Particularly, by allowing users to watch both broadcasting signals even if the user does not purchase two kinds of TV receivers in a time transition when the digital TV and the analog TV are coexistent, an economic burden on the user is reduced. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the combined TV receiver of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.