Patent Publication Number: US-2005130703-A1

Title: Mobile terminal displaying TV image on both main and sub display units

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a mobile terminal and, more particularly, to a mobile terminal capable of receiving TV signals.  
      2. Description of the Related Art  
      Technologies for mobile terminals have been rapidly developed along with the increased use of mobile terminals. Various features have been added to mobile terminals to meet consumers&#39; demand.  
      Mobile terminals equipped with a camera have gained wide popularity. Recently, mobile terminals equipped with a TV tuner have been also put on the market. As memory capacity available in the mobile terminals increases, such useful features make the mobile terminals almost the same as effective personal multimedia devices.  
      A flip-type TV phone capable of receiving TV signals allows a user to watch TV through a main display unit on the inner surface of the flip. However, when the flip is closed, the user cannot watch TV using the phone. In addition, while the user is watching TV using the phone, the user cannot efficiently take advantage of a sub display unit on the outer surface of the flip.  
      Further, since the TV phone does not allow the user to watch two channels simultaneously, the user stops watching a current channel to tune in to a different channel.  
      Implementing the above-mentioned features incorporated in the mobile terminal require not only the sufficient amount of space available in the mobile terminal but also an efficient system architecture for properly controlling components in the mobile terminal. In addition, designing a new system architecture each time new features are added to the mobile terminal is very inefficient in terms of cost and time.  
     SUMMARY OF THE INVENTION  
      The present invention provides a mobile terminal allowing a user to watch TV when the mobile terminal&#39;s flip is closed.  
      The present invention also provides a mobile terminal allowing a user to watch TV on its main and sub display units.  
      The present invention also provides a mobile terminal allowing a user to watch different channels simultaneously on its main and sub display units.  
      The present invention also provides a system architecture that efficiently operates in a mobile terminal capable of receiving TV signals.  
      The present invention also provides a system architecture that makes it possible to systematically control components in a mobile terminal and is easy to design when adding new modules to the mobile terminal.  
      In accordance with an aspect of the present invention, there is provided a mobile terminal comprising: main and sub display units for displaying operating states; a TV receiver unit for recovering an image signal from a TV signal received over the air; and a signal processor unit for outputting the image signal from the TV receiver unit to the main display unit and the sub display unit selectively or simultaneously.  
      The mobile terminal may further comprise a flip open/close detector for detecting whether a flip is opened or closed and outputting a flip open/close detection signal; and a phone control unit for controlling the signal processor unit to output the image signal to the sub display unit located on the outer surface of the flip when the flip open/close detection signal indicates that the flip is closed.  
      The signal processor unit may comprise an image processor for scaling an image signal output from the TV receiver unit and outputting the scaled image signal to the sub display unit.  
      The TV receiver unit may comprise: a tuner for demodulating a wireless broadcast signal received via an antenna; and a decoder for decoding the demodulated wireless broadcast signal into digital data and outputting the digital data to the signal processor unit.  
      The signal processor unit may control the operation of the TV receiver unit through a serial bus.  
      The TV receiver unit may comprise first and second tuners, and the signal processor unit may comprise a first image output portion for outputting an image signal output from the first tuner to the main display unit, and a second image output portion for outputting an image signal output from the second tuner to the sub display unit.  
      The signal processor unit may further comprise an image processor for scaling an image signal output from the TV receiver unit and outputting the scaled image signal to the second image output portion.  
      The mobile terminal may further comprise a system controller for controlling the signal processor unit to interchange respective images on two channels being currently displayed on the main and sub display units according to an instruction inputted through a keypad.  
      The mobile terminal may further comprise a system controller for controlling the TV receiver unit to tune in to first and second channels in a time division manner so that the TV receiver unit alternately outputs image signals on the first and second channels, wherein the signal processor unit may comprise: a first image output portion for outputting an image signal on the first channel outputted from the TV receiver unit to the main display unit; and a second image output portion for outputting an image signal on the second channel outputted from the TV receiver unit to the sub display unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which:  
       FIG. 1  is a block diagram showing a mobile terminal in accordance with an embodiment of the present invention;  
       FIG. 2  is a more detailed block diagram of the mobile terminal shown in  FIG. 1 ;  
       FIG. 3  is a block diagram showing a main part of the mobile terminal shown in  FIG. 1  in accordance with another embodiment of the present invention;  
       FIG. 4  is a block diagram showing a main part of the mobile terminal shown in  FIG. 1  in accordance with another embodiment of the present invention;  
       FIG. 5  is a block diagram showing the tuner of  FIG. 2  in accordance with the present invention; and  
       FIG. 6  is a flowchart showing a method of controlling the mobile terminal shown in  FIG. 3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand and carry out the present invention.  
       FIG. 1  is a block diagram showing a mobile terminal in accordance with an embodiment of the present invention. The mobile terminal comprises a phone control unit  100  and associated circuits, which are common to the conventional mobile terminal, a camera unit  500 , a TV receiver unit  700 , and a signal processor unit  300 . The camera unit  500  is optional in the present invention.  
      The associated circuits include a keypad  250  for inputting operating instructions, main and sub display units  275  and  277  for displaying menus and operating states, a radio frequency (RF) module  230  for extracting voice and data signals from radio signals transmitted/received via an antenna, and an voice input/output circuit  210  for receiving/outputting a voice communication signal from the RF module  230  via a microphone and a speaker.  
      A flip-type mobile terminal has two displays: a large main display unit  275  facing inwards and a smaller sub display unit  277  that faces outwards and is used to display basic information when the phone is closed. Each of these displays typically consists of a glass liquid crystal display (LCD) panel on which the image is shown. The display units  275  and  277  are driven by display drivers  271  and  273 , respectively. The RF module  230  includes an antenna and an RF circuit to communicate with base stations. In the present invention, the RF module  230  is designed to be available in all types of cellular systems such as TDMA, CDMA, PDC, and GSM. The voice I/O circuit  210 , which comprises well-known circuits such as an audio amplifier and a filter, converts digital into analog voice signals and vice versa.  
      A baseband circuit in the RF module  230  and most circuits in the phone control unit  100  are integrated into a commercially available single chip.  
      This IC chip, which is usually called a mobile station modem (MSM) chip, includes a hardware dedicated for communication processing, a digital signal processor, and a general-purpose microprocessor. Logically, the IC chip includes a communication processor  110  for processing voice and data communications, and a system controller  130  for controlling the overall system according to operating states or signals inputted from the keypad  250 .  
      In accordance with a preferred embodiment of the present invention, the mobile terminal includes the TV receiver unit  700  for recovering an image signal from a TV signal received over the air, and the signal processor unit  300  for transferring the image signal output from the TV receiver unit  700  to the main display unit  275 , the sub display unit  277 , or both of the display units  275  and  277 . A flip-type mobile terminal displays a received image signal on the main display unit  275  when it is opened, and displays on the sub display unit  277  when it is closed. Alternatively, when it is opened, the flip-type mobile terminal displays a received image signal on both main and sub display units  275  and  277 .  
      In addition, an audio signal of the TV signal demodulated by the TV receiver unit  700  may be directly output through an audio output unit  220 . The audio output unit  220  outputs various audio signals, such as a bell sound signal and a sound source signal, separately or in a mixed manner.  
      In accordance with another preferred embodiment of the present invention, the mobile terminal may further include the camera unit  500  for converting an optical signal received from a lens system into an electric signal and outputting the electric signal to the signal processor unit  300 . The TV receiver unit  700  and the camera unit  500  are configured to output an image signal of the same format, i.e., data of 8-bit YUV format, which is in turn processed selectively in the signal processor unit  300 .  
      In accordance with another preferred embodiment of the present invention, the mobile terminal further includes a flip open/close detector  279  for detecting whether the flip is closed or opened and outputting a signal indicating whether the flip is opened or closed, and the phone control unit  100  for controlling the signal processor unit  300  to output image signals to the sub display unit  277  when the flip open/close signal indicates that the flip is closed. The flip open/close detector  279  uses a well-known mechanical, magnetic, or optical contact. Consequently, the flip-type mobile terminal can display the received image signal on the main display unit  275  when the flip is opened, and on the sub display unit  277  when the flip is closed.  
      In accordance with another preferred embodiment of the present invention, the TV receiver unit  700  includes two tuners. The signal processor unit  300  outputs one of two image signals received through the tuners to the main display unit  275  and outputs the other to the sub display unit  277 .  
      In accordance with another preferred embodiment of the present invention, the TV receiver unit  700  includes a single tuner. The system controller  130  allows the tuner to tune in to two different channels in a time division manner, thereby acquiring image signals from the time-divided channels. The signal processor unit  300  outputs one of the acquired image signals to the main display unit  275  and outputs the other to the sub display unit  277 . The above-mentioned embodiments of the present invention will now be described in detail with reference to  FIG. 2 .  
       FIG. 2  is a more detailed block diagram of the mobile terminal shown in  FIG. 1 . The camera unit  500  converts an optical signal received through a lens system into an electrical signal. The TV receiver unit  700  extracts an image signal from a TV signal received over the air.  
      The signal processor unit  300 , which was developed for signal processing in a camera phone by the present applicant, can also be applied to the TV receiver unit  700  without alteration. In addition, the signal processor unit  300  used for the camera unit  500  can be shared by the TV receiver unit  700  without the need to provide an additional signal processing module to be used for the TV receiver unit  700 . The signal processor unit  300  selectively processes a first image signal outputted from the camera unit  500  and a second image signal outputted from the TV receiver unit  700 , and outputs the processed image signal to the main display unit  275  or the sub display unit  277 .  
      In accordance with another preferred embodiment of the present invention, the signal processor unit  300  selectively activates the camera unit  500  and the TV receiver unit  700  using chip select logic. The system controller  130  provided in the phone control unit  100  instructs the signal processor unit  300  to capture an image through the camera unit  500  or to receive a TV signal through the TV receiver unit  700 . In response to this instruction, the signal processor unit  300  selectively controls the camera unit  500  and the TV receiver unit  700 .  
      In accordance with another preferred embodiment of the present invention, the signal processor unit  300  controls the operations of the camera unit  500  and the TV receiver unit  700  through a serial bus. An I 2 C bus is an example of the serial bus. The I 2 C bus, also called an “Inter-IC bus”, is a serial bus developed by Philips Electronics and a two-wire, bidirectional serial bus that provides a serial data line and a serial clock line interface to exchange information between devices.  
      In accordance with another preferred embodiment, the camera unit  500  includes a lens system  590 , an image pickup portion  510  for converting an optical signal received from the lens system  590  into an analog electric signal, a converter  530  for converting the analog signal outputted from the image pickup portion  510  into a digital signal and outputting the digital signal in a format suitable for the signal processor unit  300 , and a camera controller  550  for controlling the overall operation of the camera unit  500 .  
      The lens system  590 , composed of one or more small lenses, focuses and provides light to the image pickup portion  510 . The image pickup portion  510 , which typically includes a complementary metal-oxide-semiconductor (CMOS) or charge coupled device (CCD) image sensor, is a well-known component used for converting light into electric signals in each pixel and sequentially outputting the converted electric signals in synchronization with clocks. The converter  530  converts a current or voltage value proportional to the brightness of an image, which is output from the image pickup portion  510 , into a digital signal, which is in turn transformed into a YUV format. Alternatively, the converter  530  may further include a codec for compressing the pickup image into a Joint Photographic Experts Group (JPEG) or Motion Picture Experts Group (MPEG) format.  
      In the present invention, an image signal processed in the mobile terminal has a single format, e.g., YUV format in an embodiment. That is, image processing modules transform signals into a YUV format. The camera controller  550  controls the operation of the camera unit  500  according to instructions from the external devices. The camera controller  550  may be implemented with a microprocessor or digital logic circuit. An interface with the external devices will be described in detail later.  
      In an embodiment, the TV receiver unit  700  includes an antenna for receiving radio signals, a tuner  710  for demodulating broadcast signals received via the antenna, a decoder  730  for decoding the demodulated broadcast signals into digital data, and a TV controller  750  for controlling the operation of the TV receiver unit  700  according to control instruction signals from the external devices. The antenna may be provided separately from an antenna for mobile communications. Alternatively, a micro-strip patch antenna may be shared for both TV reception and mobile communications.  
      The tuner  710  may be a typical tuner which supports National Television System Committee (NTSC) broadcast system or Phase Alternation by Line (PAL) broadcast system, or a tuner commonly available in all of them. In another embodiment, the tuner  710  may be a tuner which supports multimedia broadcast for mobile communications, such as wireless local area network (LAN) based multimedia broadcast or satellite based digital multimedia broadcast (DMB).  
       FIG. 5  is a block diagram showing the tuner  710  in accordance with the present invention. A wireless broadcast signal received from the antenna is divided into an ultra high frequency (UHF) band signal and a very high frequency (VHF) band signal by means of a UHF filter  718  and a VHF filter  719 . The UHF and VHF band signals are filtered through low noise amplifiers (LNAs)  728  and  729 , respectively. The filtered signals are sent to a phase-locked loop (PLL)  717  to be mixed with local oscillation frequencies, whereby the signals are demodulated. The PLL  717  receives an intermediate frequency (IF) for each of the band signals from each of UHF and VHF voltage-controlled oscillators (VCOs)  715  and  716 . The oscillation frequency of each of the UHF VCO and VHF VCO  715  and  716  is controlled by the TV controller  750  shown in  FIG. 2 . The demodulated signal is demodulated once again by an IF signal processor  725  into analog image and audio signals, which are in turn outputted to image and voice output units  726  and  727 , respectively. The IF signal processor  725  is controlled by the TV controller  750  shown in  FIG. 2 . An output level (i.e., volume) of the voice output unit  727  is also controlled by the TV controller  750  shown in  FIG. 2 .  
      In an embodiment, the decoder  730  transforms an analog image signal outputted from the image output portion  726  into a digital YUV signal. The operation of the decoder  730  is controlled by the TV controller  750 .  
      In an embodiment, the signal processor unit  300  includes a media interface portion  355  for selectively receiving first and second image signals, an image processor  321  for processing an image signal received from the media interface portion  355 , a image output portion  323  for converting the image signal processed by the image processor  321  into display data and outputting the display data, a bus interface portion  353  for controlling the operations of the camera unit  500  and the TV receiver unit  700 , and a controller  310  for controlling the overall operation of the signal processor unit  300  and the external devices.  
      The media interface portion  355  receives and buffers 8-bit YUV format image data into an internal memory. The image processor  321  converts an interlaced-scan signal into a progressive scan signal, which is in turn scaled through interpolation and/or decimation to suit the resolution of the display  275  or  277 . The image processor  321  further includes a codec for storing image data or decompressing the image data. In an embodiment, the codec includes an MPEG encoder/decoder, and a JPEG encoder/decoder for compressing a captured image frame into a still image, storing and reading the still image. The MPEG encoder/decoder and the JPEG encoder/decoder are implemented with a DSP and a core. The image processor  321  may further include circuits for enhancing definition and adjusting brightness/contrast. In addition, the image processor  321  may include filters for providing graphic effects.  
      In an embodiment, the image output portion  323  receives image data from the image processor  321  or directly from the media interface portion  355 , and outputs the image data in 16-bit RGB format to the display  275  or  277 .  
      A detailed description will now be given of how the signal processor unit  300  controls the camera unit  500  and TV receiver unit  700  in media signal processing with reference to  FIG. 2 .  
      In accordance with another preferred embodiment of the present invention, the camera unit  500  includes a bus interface portion  573  for receiving a serial bus control signal from the signal processor unit  300 , and a camera controller  550  for controlling the overall operation of the camera unit  500  according to control signals received from the bus interface portion  573 .  
      In accordance with another preferred embodiment of the present invention, the TV receiver unit  700  includes a bus interface portion  773  for receiving a serial bus control signal from the signal processor unit  300 , and a TV controller  750  for controlling the overall operation of the TV receiver unit  700  according to control signals received from the bus interface portion  773 .  
      In accordance with another preferred embodiment of the present invention, the signal processor unit  300  includes a media interface portion  355  for selectively receiving a first image signal from the camera unit  500  and a second image signal from the TV receiver unit  700 , a bus interface portion  353  for controlling the operations of the camera unit  500  and the TV receiver unit  700 , and a controller  310  for controlling external devices through the bus interface portion  353 .  
      In accordance with another preferred embodiment of the present invention, the controller  310  provided in the signal processor unit  300  controls the bus interface portion  353  to individually access the tuner  710  and the decoder  730  provided in the TV receiver unit  700  by assigning a plurality of addresses.  
      When the signal processor unit  300  selects the camera unit  500  or the TV receiver unit  700  through chip select logic, the controller  310  controls the operation of the camera unit  300  or TV receiver unit  700  through the bus interface portion  353 . In an embodiment, the bus interface portions  353 ,  573  and  773  use an I 2 C bus for communications. In an embodiment, addresses are individually allocated to each of the operations of the camera unit  500  such as image capturing, brightness adjusting, and resolution setting operations. Addresses are individually allocated to each of the operations of the TV receiver unit  700  such as channel selecting, audio output level adjusting, and decoding operations. The controller  310  controls the operations of the camera unit  500 , such as image capturing, brightness adjusting, and resolution setting operations, by writing control instructions into the addresses allocated to the operations of the camera unit  500  through the bus interface portion  353 . In addition, the controller  310  can control the operations of the TV receiver unit  700 , such as TV channel changing, volume adjusting, and image format changing operations, by writing control instructions into the addresses allocated to the operations of the TV receiver unit  700  through the bus interface portion  353 .  
      Image signals outputted from the camera unit  500  through the converter  530  and from the TV receiver unit  700  through the decoder  730  have 8-bit YUV format in common. Thus, the image signals input to the signal processor unit  300  through the media interface portion  355  can be processed by the image processor  321  and the image output portion  323 .  
      In accordance with another preferred embodiment of the present invention, the mobile terminal outputs an image signal from the TV receiver unit  700  to the main display unit  275  and the sub display unit  277  selectively or simultaneously. A more detailed description will be given of how the signal processor unit  300  operates according to this embodiment of the present invention.  
      In accordance with another preferred embodiment of the present invention, the mobile terminal further includes a flip open/close detector  279  for detecting whether the flip is opened or closed and outputting a flip open/close detection signal, and the phone control unit  100  for controlling the signal processor unit  300  to output image signals to the sub display unit  277  when the flip open/close detection signal indicates that the flip is closed. When a user selects a TV mode and a desired TV channel with the flip opened, the system controller  130  instructs, through the I 2 C bus, the signal processor unit  300  to allow the selected channel to be viewed. The signal processor unit  300  receives the instruction through the bus interface portion  353  and the controller  310  operates according to the instruction. On the other hand, the controller  310  switches the bus interface portion  353  from I 2 C slave mode to I 2 C host mode, and then instructs the TV receiver unit  700  to tune in to the selected channel. The TV receiver unit  700  receives this instruction through the bus interface portion  773 . The TV controller  750  controls, according to the instruction, the UHF and VHF VCOs  715  and  716  and the IF signal processor  725  provided in the tuner  710  to tune in to the selected channel and demodulate a TV broadcast signal on the selected channel into an image signal. The decoder  730  decodes the demodulated image signal into a digital YUV signal.  
      The digital YUV signal is input to the media interface portion  355  in the signal processor unit  300 . The image processor  321  converts an interlaced-scan image signal inputted under the control of the controller  310  into a progressive scan image signal, which is in turn scaled through interpolation and/or decimation to suit the resolution of the main display unit  275 . The scaled image signal is selectively subjected to brightness/contrast adjustment, image quality enhancement, etc., and is output from the image processor  321  to the image output portion  323 . The image output portion  323  converts the image signal received from the image processor  321  into an image signal with 16-bit RGB format suitable for input to the main display unit  275 , and provides the 16-bit RGB image signal to the main display unit  275 . The image output portion  323  sequentially records display data in a display memory provided in the display driver  271  through a 16-bit parallel bus, thereby allowing the image to be displayed on the main display unit  275 .  
      On the other hand, when the flip is closed, the system controller  130  instructs the signal processor unit  300 , via the I 2 C bus, to output the display data to the sub display unit  277 . The signal processor unit  300  receives this instruction through the bus interface portion  353 , and the controller  310  operates according to the instruction. The TV receiver unit  700  performs the subsequent operations in the same manner as described above.  
      A signal output from the TV receiver unit  700  is input to the media interface portion  355  in the signal processor unit  300  through the bus. The image processor  321  converts an interlaced-scan image signal inputted under the control of the controller  310  into a progressive scan image signal, which is in turn scaled through interpolation and/or decimation to suit the resolution of the sub display unit  277 . The scaled image signal is selectively subjected to brightness/contrast adjustment, image quality enhancement, etc. and then output from the image processor  321  to the image output portion  323 . The image processor  321  includes a frame memory for storing one or more frames. This image processing technique is well-known in the art and a detailed description thereof is thus omitted herein.  
      The image output portion  323  converts the image signal received from the image processor  321  into 16-bit RGB format suitable for input to the sub display unit  277 , and provides the 16-bit RGB image signal to the sub display unit  277 . The image output portion  323  sequentially records display data in a display memory provided in the display driver  273  through a 16-bit parallel bus, thereby allowing the image to be displayed on the sub display unit  277 .  
      The image output portion  323  can distinguish the display drivers  271  and  273  from each other through a memory map, or can distinguish the main and sub display units from each other through chip select logic.  
      Another embodiment of the present invention will now be described with reference to  FIG. 2 , in which an image is simultaneously displayed on both main and sub display units  275  and  277  regardless of whether the flip is opened or closed.  
      When a user sequentially selects a TV mode and a desired TV channel with the flip opened, the system controller  130  instructs, through the I 2 C bus, the signal processor unit  300  to allow the selected channel to be viewed. The signal processor unit  300  operates according to this instruction. On the other hand, the controller  310  switches the bus interface portion  353  from I 2 C slave mode to I 2 C host mode, and then instructs the TV receiver unit  700  to tune in to the selected channel. Next, the TV receiver unit  700  operates in the same manner as in the above-mentioned embodiment. The decoder  730  decodes the demodulated image signal into a digital YUV signal.  
      The digital YUV signal is input to the image processor  310  in the signal processor unit  300  through the bus. The image processor  321  converts an interlaced-scan image signal inputted under the control of the controller  310  into a progressive scan image signal, which is subjected to brightness/contrast and definition adjustments, etc. Subsequently, the image signal is scaled by the image processor  321  to suit the resolution of the main display unit  275  and is output to the display driver  271 . Next, the image signal is scaled by the image processor  321  to suit the resolution of the sub display unit  277  and is output to the display driver  273 . For instance, in the case when the resolution of the main display unit  275  is a multiple of the resolution of the sub display unit  277 , the above-mentioned scaling operation can be implemented simply by skipping addresses in reading data from the memory.  
      In accordance with another preferred embodiment of the present invention, an image signal received from the TV receiver unit  700  is buffered into the media interface portion  355 , and the image processor  321  controls the image output portion  323  to display the same frame once on each of the main display unit  275  and the sub display unit  277 . Displaying the same frame once on each of the display units  275  and  277  is performed within a time corresponding to one frame, e.g., within {fraction (1/30)} second in the NTSC system, whereby images are naturally displayed on both main and sub display units  275  and  277 .  
      The present invention is not limited to this embodiment. For instance, images may be displayed on both the main and sub display units  275  and  277  by allocating more frames to the main display unit  275  than the sub display unit  277 .  
      In a preferred embodiment of the present invention where an image is simultaneously displayed on the main and sub display units  275  and  277 , in response to an instruction from the keypad  250 , the system controller  130  controls the image processor  321  to perform a vertical image reversal process on an image outputted to the sub display unit  277  so that a vertically reversed image is displayed on the sub display unit  277 . Accordingly, a user can view an image through the main display unit  275 , while another user can view the image through the sub display unit  277 .  
      The TV receiver unit  700  performs the subsequent operations in the same manner as described above. The image output portion  323  converts the image signal received from the image processor  321  into 16-bit RGB format suitable for input to the main and display units  275  and  277 , and sequentially writes the 16-bit RGB image signals into the display memories in the display drivers  271  and  273 .  
      The image output portion  323  can distinguish the display drivers  271  and  273  from each other through a memory map, or can distinguish the main and sub display units  275  and  277  from each other through chip select logic.  
       FIG. 3  is a block diagram showing a main part of the mobile terminal shown in  FIG. 1  in accordance with another embodiment of the present invention. Although some of components shown in  FIG. 1  have not been shown in  FIG. 3 , a description thereof is not deemed necessary for an understanding of the present embodiment.  
      The system controller  130  tunes the TV receiver unit  700  to two channels in a time division manner so that the TV receiver unit  700  alternately outputs image signals in the channels. The image output portion  323  includes a first image output portion  3231  for transferring the image signal in the first channel output from the TV receiver unit  700  to the main display unit  275 , and a second image output portion  3233  for transferring the image signal in the second channel output from the TV receiver unit  700  to the sub display unit  277 .  
      In accordance with another preferred embodiment of the present invention, the signal processor unit  300  further includes an image processor  321  for scaling an image signal output from the TV receiver unit  700  and transferring the scaled image signal to the second image output portion  3233 .  
      In accordance with another preferred embodiment of the present invention, the system controller  130  controls the signal processor unit  300  to interchange images on the channels currently displayed on the main and sub display units  275  and  277  according to an instruction inputted through the keypad.  
      In accordance with another preferred embodiment of the present invention, the signal processor unit  300  controls the operation of the TV receiver unit  700  via a serial bus.  
      A more detailed description will now be given of how the signal processor unit  300  operates according to an embodiment of the present invention.  FIG. 6  is a flowchart showing how the mobile terminal shown in  FIG. 3  operates to play a plurality of channels.  
      First, when a user selects a TV mode and two channels to view on the main and sub display units  275  and  277  while the flip is opened, the system controller  130  instructs the signal processor unit  300  through the I 2 C bus to play the selected channels. The signal processor unit  300  receives this instruction through the bus interface portion  353 , and the controller  310  operates according to the instruction.  
      After switching to I 2 C host mode, the controller  310  instructs the TV receiver unit  700  to tune in to the channel selected to display on the main display unit  275 . The TV controller  750  in the TV receiver unit  700  controls, according to the instruction, the UHF and VHF VCOs  715  and  716  and the IF signal processor  725  provided in the tuner  710  to tune in to the channel selected to display on the main display unit  275  and demodulate a TV broadcast signal on the selected channel into an image signal (S 110 ). The decoder  730  decodes the demodulated image signal into a digital YUV signal.  
      The digital YUV signal is input to a signal converter  3211  in the signal processor unit  300  through the bus. The signal converter  3211  converts an interlaced-scan image signal inputted under the control of the controller  310  into a progressive scan image signal. A scaler  3213  in the signal processor unit  300  scales the converted image signal through interpolation and/or decimation to suit the resolution of the main display unit  275  (S 120 ).  
      The scaled image signal is selectively subjected to brightness/contrast adjustment, image quality enhancement, etc., and is output from the image processor  321  to the first image output portion  3231  in the image output portion  323 . In an embodiment, the image processor  321  writes completely processed image data into a frame memory area for the main display unit  275 , and the first image output portion  3231  accesses the frame memory area to acquire data for display on the main display unit  275 . The first image output portion  3231  then converts the image signal received from the image processor  321  into 16-bit RGB format suitable for input to the main display unit  275 , and provides the 16-bit RGB image signal to the main display unit  275 . The first image output portion  3231  sequentially writes display data into a display memory provided in the display driver  271  through a 16-bit parallel bus, thereby allowing the image to be displayed on the main display unit  275  (S 130 ).  
      After switching to I 2 C host mode, the controller  310  instructs the TV receiver unit  700  to tune in to the channel selected to display on the sub display unit  277 . Alternatively, once the controller  310  sets a mode, the controller  310  or the TV controller  750  can control the TV receiver unit  700  to tune in to the selected channels in a time division manner. In this case, since the first setting of a mode for the tuning based on time division is made in the system controller  130 , the claims of the present invention are intended to cover this modification.  
      The TV controller  750  in the TV receiver unit  700  controls, according to the instruction, the UHF and VHF VCOs  715  and  716  and the IF signal processor  725  in the tuner  710  to tune in to the channel selected to display on the sub display unit  277  and demodulate a TV broadcast signal on the selected channel into an image signal (S 140 ). The decoder  730  decodes the demodulated image signal into a digital YUV signal.  
      The digital YUV signal is input to the signal converter  3211  in the signal processor unit  300  through the bus. The signal converter  3211  converts an interlaced-scan image signal inputted under the control of the controller  310  into a progressive scan image signal. The scaler  3213  in the signal processor unit  300  scales the converted image signal through interpolation and/or decimation to suit the resolution of the sub display unit  277 . Further, the scaled image signal is subjected to a vertical image reversal process in an image reversal portion  3215  provided in the signal processor unit  300  so that a vertically reversed image is displayed on the sub display unit  277  (S 150 ). Accordingly, a user can view an image through the main display unit  275 , while another user can view the image through the sub display unit  277 .  
      After the image signal is selectively subjected to brightness/contrast adjustment, image quality enhancement, etc., it is output from the image processor  321  to the second image output portion  3233  in the image output portion  323 . In an embodiment, the image processor  321  writes completely processed image data into a frame memory area for the sub display unit  277 , and the second image output portion  3233  accesses the frame memory area to acquire data for display on the sub display unit  277 . The second image output portion  3233  then converts the image signal received from the image processor  321  into 16-bit RGB format suitable for input to the sub display unit  277 , and provides the 16-bit RGB image signal to the sub display unit  277 . The second image output portion  3233  sequentially writes display data into a display memory provided in the display driver  273  through a 16-bit parallel bus, thereby allowing the image to be displayed on the sub display unit  277  (S 160 ).  
      The image output portions  3231  and  3233  in the image output portion  323  can distinguish the display drivers  271  and  273  from each other through a memory map. Alternatively, the image output portions  3231  and  3233  can discriminate data for display on the display units  275  and  277  by selecting the corresponding individual memory chips through chip select logic.  
      An NTSC TV signal typically carries 60 fields or 30 frames per second. However, in the case of LCDs, a frame rate of about 24 frames per second is enough to appear as a continuous image to naked eyes. In a tuning method based on time division, during the first 24 frames, the controller  310  in the signal processor unit  300  controls the tuner  710  in the TV receiver unit  700  to tune in to a main display channel selected to display on the main display unit  275 , and controls the image processor  321  and the image output portion  323  to display a TV image received through the main display channel on the main display unit  275 . During the next 6 frames, the controller  310  in the signal processor unit  300  controls the tuner  710  in the TV receiver unit  700  to tune in to a sub display channel selected to display on the sub display unit  277 , and controls the image processor  321  and the image output portion  323  to display a TV image received through the sub display channel on the sub display unit  277 .  
      In another tuning method based on time division, during the first 4 of 5 consecutive frames, the controller  310  in the signal processor unit  300  controls the tuner  710  in the TV receiver unit  700  to tune in to a main display channel selected to display on the main display unit  275 , and controls the image processor  321  and the image output portion  323  to display a TV image received through the main display channel on the main display unit  275 . During the next 1 frame, the controller  310  in the signal processor unit  300  controls the tuner  710  in the TV receiver unit  700  to tune in to a sub display channel selected to display on the sub display unit  277 , and controls the image processor  321  and the image output portion  323  to display a TV image received through the sub display channel on the sub display unit  277 . The tuning method based on time division is advantageous over the previous tuning method based on time division in that voice signals demodulated in the main display channel are reproduced more smoothly.  
      In accordance with another preferred embodiment of the present invention, the phone control unit  100  further includes a display interchange unit (not shown) for controlling the signal processor unit  300  to interchange images on the channels currently displayed on the main and sub display units  275  and  277  according to an instruction inputted through the keypad  250 . This instruction is preferably input through a hotkey.  
      In a channel interchange method, the controller  310  in the signal processor unit  300  adjusts the times to tune the TV receiver unit  700  to two channels in a time division manner so as to interchange the channels currently displayed on the main and sub display units  275  and  277 . In another channel interchange method, the controller  310  controls the tuning duration of each of the channels, during which the TV receiver unit  700  is tuned to two channels, and the image processor  321  performs operations required to interchange the channels currently displayed on the main and sub display units  275  and  277 .  
       FIG. 4  is a block diagram showing a main part of the mobile terminal shown in  FIG. 1  in accordance with another embodiment of the present invention. Although some of components shown in  FIG. 1  have not been shown in  FIG. 4 , a description thereof is not deemed necessary for an understanding of the present embodiment. A TV receiver unit  700  includes first and second tuners  711  and  713 . An image output portion  323  in a signal processor unit  300  includes a first image output portion  3231  for transferring an image signal outputted from the first tuner  711  to a main display unit  275 , and a second image output portion  3233  for transferring an image signal outputted from the second tuner  713  to a sub display unit  277 .  
      In accordance with another preferred embodiment of the present invention, the signal processor unit  300  further includes an image processor  321  for scaling an image signal outputted from the TV receiver unit  700  and transferring the scaled image signal to the second image output portion  3233 .  
      In accordance with another preferred embodiment of the present invention, the system controller  130  controls the signal processor unit  300  to interchange images on the channels currently displayed on the main and sub display units  275  and  277  according to an instruction inputted through a keypad  250 . In addition, the signal processor unit  300  controls the operation of the TV receiver unit  700  through a serial bus.  
      The configuration and operation of the mobile terminal in accordance with this embodiment will now be described in more detail with reference to  FIG. 4 .  
      The TV receiver unit  700  includes an antenna for receiving radio signals, a tuner  710  for demodulating wireless broadcast signals received through the antenna, a decoder  730  for decoding the demodulated broadcast signals into digital data, and a TV controller  750  for controlling the operation of the TV receiver unit  700  according to control instructions from the external devices. Here, the tuner  710  includes first and second tuners  711  and  713 , and the decoder  730  includes first and second decoders  731  and  733 . The decoder  730  may alternately receive and decode the demodulated signals from the first and second tuners  711  and  713 , and sequentially output the decoded signals. The antenna of the TV receiver unit  700  may be provided separately from an antenna for mobile communications. Alternatively, a micro-strip patch antenna may be used for both TV reception and mobile communications.  
      The system controller  130  controls the first tuner  711  in the TV receiver unit  700  to tune in to a first channel, and controls the signal processor unit  300  to display an image on the first channel outputted from the first tuner  711  on the main display unit  275 . The system controller  130  controls the second tuner  713  in the TV receiver unit  700  to tune in to a second channel, and controls the signal processor unit  300  to display an image on the second channel outputted from the second tuner  713  on the sub display unit  277 .  
      Each of the first and second tuners  711  and  713  may be a conventional analog broadcast tuner which supports NTSC or PAL broadcast system, or a tuner commonly available in all of them. In another embodiment, each of the first and second tuners  711  and  713  may be a tuner which supports multimedia broadcast for mobile communications, such as wireless LAN based multimedia broadcast or satellite based DMB.  
      The signal processor unit  300  includes first and second signal converters  3212  and  3213 , first and second scalers  3216  and  3217 , an image reversal portion  3215 , and first and second image output portions  3231  and  3233 . The first signal converter  3212  converts an interlaced-scan image signal on the first channel, which is decoded by the first decoder  731 , into a progressive scan image signal. The second signal converter  3213  converts an interlaced-scan image signal on the second channel, which is decoded by the second decoder  733 , into a progressive scan image signal. The first scaler  3216  scales the image signal on the first channel converted by the first signal converter  3212  through interpolation and/or decimation to suit the resolution of the main display unit  275 . The second scaler  3217  scales the image signal on the second channel converted by the second signal converter  3213  through interpolation and/or decimation to suit the resolution of the sub display unit  277 . The image reversal portion  3215  performs a vertical image reversal process on the image signal scaled by the second scaler  3217 . The first image output portion  3231  transfers the image signal on the first channel outputted from the first scaler  3216  to the display driver  271  used for the main display unit  275 . The second image output portion  3233  transfers the image signal on the second channel processed by the image reversal portion  3215  to the display driver  273  used for the sub display unit  277 .  
      The signal converters  3212  and  3213 , the scalers  3216  and  3217 , the image reversal portion  3215 , and the image output portions  3231  and  3233  can be implemented with some memories and dedicated hardware or firmware known in the art, and various changes thereof in form and details may be made without departing from the scope and spirit of the present invention. For instance, it will be understood by those skilled in the art that the same process as described above can be performed by switching a converter and a scaler at high speed in synchronization with a field synchronization signal.  
      A detailed description will now be given of the operation of the mobile terminal in accordance with the embodiment of  FIG. 4 . First, when a user selects a TV mode and channels to view on the main and sub display units  275  and  277 , the system controller  130  transfers the selected information to the signal processor unit  300  through the I 2 C bus. The controller  310  in the signal processor unit  300  receives the instruction, and controls the operations of the image processor  321 , the image output portion  323  and the TV receiver unit  700  according to the received instruction.  
      On the other hand, the controller  310  switches the bus interface portion  353  from I 2 C slave mode to I 2 C host mode, and then instructs the TV receiver unit  700  to tune in to the selected channels. The TV controller  750  in the TV receiver unit  700  receives this instruction through a serial bus. The TV controller  750  controls the voltage-controlled oscillators and the IF signal processor in the first tuner  711  to tune in to the main display channel selected to display on the main display unit  275  and demodulate a TV broadcast signal on the main display channel into an image signal. In addition, the TV controller  750  controls the voltage-controlled oscillators and the IF signal processor in the second tuner  713  to tune in to the sub display channel selected to display on the sub display unit  277  and demodulate a TV broadcast signal on the sub display channel into an image signal.  
      In an embodiment, the decoder  730  decodes the demodulated image signal into a digital YUV signal in a time division manner. Since the decoder  730  performs a decoding operation using a matrix circuit after analog-to-digital conversion, it can decode received signals in a time division manner through a high-speed sampling operation. In another embodiment, each of the demodulated image signals can be decoded through the corresponding decoders  731  and  733 .  
      The image signals outputted from the decoder  730  are transferred to the image processor  321  in the signal processor unit  300  through the bus. The first signal converter  3212  in the image processor  321  receives and converts an interlaced-scan image signal outputted from the first decoder  731  into a progressive scan image signal. The second signal converter  3213  in the image processor  321  receives and converts an interlaced-scan image signal outputted from the second decoder  733  into a progressive scan image signal. The first scaler  3216  in the image processor  321  scales the signal outputted from the first signal converter  3212  through interpolation and/or decimation to suit the resolution of the main display unit  275 . The second scaler  3217  in the image processor  321  scales the signal outputted from the second signal converter  3213  through interpolation and/or decimation to suit the resolution of the sub display unit  277 . The image reversal portion  3215  operates to perform a vertical image reversal process on the image signal outputted from the second scaler  3217  so that the image can be properly displayed on the sub display unit  277  with the flip opened.  
      The scaled image signals are output from the image processor  321  to the image output portion  323  after being subjected to brightness/contrast adjustment, image quality enhancement, etc.  
      In an embodiment, the image processor  321  writes image data for display on the main display unit  275  into a frame memory area allocated to the main display unit  275 , and writes image data for display on the sub display unit  277  into a frame memory area allocated to the sub display unit  277 . Here, the frame memory areas are distinguished from each other on a memory map. In another embodiment, a frame memory is allocated to each of the display units  275  and  277 . The image processor  321  alternately accesses the frame memories through chip select logic.  
      The first image output portion  3231  in the image output portion  323  accesses the memory area allocated to the main display unit  275  to acquire image data for display on the main display unit  275 . The first image output portion  3231  then converts the acquired image data into 16-bit RGB format suitable for input to the main display unit  275 , and provides the 16-bit RGB image signal to the main display unit  275 . The first image output portion  3231  sequentially writes display data into a display memory provided in the display driver  271  through a 16-bit parallel bus, thereby allowing the image to be displayed on the main display unit  275 .  
      The second image output portion  3233  in the image output portion  323  accesses the memory area allocated to the sub display unit  277  to acquire image data for display on the sub display unit  277 . The second image output portion  3233  then converts the acquired image data into 16-bit RGB format suitable for input to the sub display unit  277 , and provides the 16-bit RGB image signal to the sub display unit  277 . The second image output portion  3233  sequentially writes display data into a display memory provided in the display driver  273  through a 16-bit parallel bus, thereby allowing the image to be displayed on the sub display unit  277 .  
      The image output portions  3231  and  3233  in the image output portion  323  can distinguish the display drivers  271  and  273  from each other through the memory map. Alternatively, the image output portions  3231  and  3233  can distinguish data for display on the display units  275  and  277  by selecting the corresponding individual memory chips through chip select logic.  
      In the embodiment of  FIG. 4 , since the TV receiver unit  700  includes a plurality of tuners (i.e., the first and second tuners  711  and  713  in the example of  FIG. 4 ), the signal processor unit  300  can process the demodulated image signals in a time division manner to reproduce the demodulated image signals on the main and sub display units  275  and  277 .  
      According to the present embodiment, the mobile terminal outputs voice signals demodulated by the first and second tuners  711  and  713  through different output means. That is, the mobile terminal outputs a voice signal demodulated by the first tuner  711  through a speaker, and outputs a voice signal demodulated by the second tuner  713  through a voice output circuit used for telephone communications.  
      The voice input/output circuit  210  includes an audio output circuit for outputting communication voice recovered by the RF module  230  under the control of the communication processor  110 . The audio output circuit includes an earphone and a speaker for telephone communications. Audio signals outputted from the second tuner  713 , which is responsible for demodulating an image signal for display on the sub display unit  277 , are output from the voice input/output circuit  210  through the speaker or earphone. On the other hand, audio signals outputted from the first tuner  711 , which is responsible for demodulating an image signal for display on the main display unit  275 , are output from the audio output unit  220  which is responsible for outputting acoustic signals such as bell sounds.  
      In accordance with another preferred embodiment of the present invention, the phone control unit  100  further includes a display interchange unit (not shown) for controlling the signal processor unit  300  to interchange images on the channels currently displayed on the main and sub display units  275  and  277  according to an instruction inputted through the keypad  250 . This instruction is preferably input through a hotkey. The channel interchange is performed under the control of the TV controller  750 .  
      As apparent from the above description, the present invention provides a mobile terminal capable of receiving TV broadcasts, which has the following features and advantages.  
      The mobile terminal can display a received TV image on both main and sub display units.  
      The mobile terminal also allows users to watch different channels on the main and sub display units.  
      The mobile terminal also allows users to watch different channels on the main and sub display units with a single tuner, thereby simplifying hardware required for the mobile terminal and reducing manufacturing costs.  
      Furthermore, the mobile terminal includes a bus used for operation control in addition to a bus used for image processing. This makes it possible to systematically is control the mobile terminal and thus facilitates system design.  
      While the present invention has been described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the present invention as defined by the following claims.