Patent Publication Number: US-2002004413-A1

Title: Radio communication apparatus and radio communication method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-204100, filed Jul. 5, 2000, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The present invention relates to a radio communication apparatus having a TV-phone function, and particularly, to a radio communication apparatus having a TV-phone function capable of controlling an image on a display unit.  
       [0004] 2. Description of the Related Art  
       [0005] In recent years, in the field of the radio communication apparatus each of which comprises a display unit composed of liquid crystal or the like, developments have been made in a so-called TV-phone that displays not only texts and still pictures but also has a TV-phone function capable of displaying moving pictures such as videos, animations, and the like along conversation. Improvements have rapidly come to be made in this function.  
       [0006] In a radio communication apparatus having this kind of the TV-phone function, a lot of modes are considered without being limiting to a voice conversation mode in which speech signals are transmitted/received like a conventional radio communication apparatus. That is, the apparatus is expected to be used in a short-mail mode in which character strings including a relatively small number of characters are transmitted/received, a mail communication transfer mode in which text mails including a large number of characters are transmitted/received, a still picture communication mode in which still pictures are transmitted/received, and a video communication mode in which video data having a large data volume is transmitted/received.  
       [0007] In a radio communication apparatus that is thus expected to be used in various modes, a battery capacity as its power source must be enhanced. In order to enhance the battery capacity, the size of the battery is also enlarged so that its portability is deteriorated. To solve this problem, improvements of the battery have been promoted. This improvement requires that the portability should not be hindered and the expandability should be maintained. That is, it is demanded that the radio communication apparatus should constantly be driven with least necessary power.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008] The present invention has an object of providing a radio communication apparatus having a TV-phone function capable of reducing the current consumption of the display unit by letting the display unit display least necessary images, in accordance with data to be displayed.  
       [0009] The present invention has another object of providing a radio communication apparatus having a TV-phone function, in which a mode of data to be displayed can be specified and the data can be displayed on the display unit.  
       [0010] According to the present invention, there is provided a radio communication apparatus comprising:  
       [0011] receiving means for receiving a signal including a speech signal and a data signal, and separating the speech signal and the data signal from the signal;  
       [0012] voice outputting means for converting the speech signal into a voice, and outputting the voice;  
       [0013] converting means for converting the data signal into a display signal;  
       [0014] a display displaying data in accordance with the display signal at a display speed; and  
       [0015] display controlling means for setting the display speed for displaying an image on the display, the display speed being selected from values of display speeds.  
       [0016] Moreover, according to the present invention, there is provided a radio communication method comprising:  
       [0017] receiving a signal including a speech signal and a data signal;  
       [0018] converting the data signal separated from the signal into a display signal;  
       [0019] setting a display speed selected from values of display speeds for displaying data; and  
       [0020] displaying the data as an image based on the display signal at the set display speed.  
       [0021] Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
     [0022] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
     [0023]FIG. 1A is a front view showing the front surface of a radio communication apparatus having a TV-phone function, according to the fist embodiment of the present invention;  
     [0024]FIG. 1B is cross-sectional views of a display unit of the radio communication apparatus, cut along the line A-B shown in FIG. 1A, according to methods for displaying an image and the like on the display unit, using a back light (upper diagram) and a front light (lower diagram);  
     [0025]FIG. 1C is a side view showing the side surface of the radio communication apparatus shown in FIG. 1A;  
     [0026]FIG. 2 is a functional block diagram showing an electrical internal structure of the radio communication apparatus shown in FIG. 1A;  
     [0027]FIG. 3 is a flowchart indicating the process that receiving a radio-frequency signal, outputting a voice and displaying an image at a preset display speed by the electrical internal structure shown in FIG. 2;  
     [0028]FIG. 4 is a functional block diagram showing an electrical internal structure of an LCD control unit provided in a baseband unit and an LCD unit provided in an input/output unit shown in FIG. 2;  
     [0029]FIG. 5A is a timing chart showing timings of an image control signal and image data in case one line of one frame is output from the LCD control unit to the LCD unit shown in FIG. 2;  
     [0030]FIG. 5B is a timing chart showing timings of an image control signal and image data in case one frame is output from the LCD control unit to the LCD unit shown in FIG. 2;  
     [0031]FIG. 6A is a timing chart showing timings of an image control signal and image data in case one line of one frame is output from the MM processing unit shown in FIG. 2 to the MPEG-4 IF in the LCD control unit shown in FIG. 4;  
     [0032]FIG. 6B is a timing chart showing timings of an image control signal and image data in case one frame is output from the MM processing unit shown in FIG. 2 to the MPEG-4 IF in the LCD control unit shown in FIG. 4;  
     [0033]FIG. 7 is a schematic view showing the LCD panel shown in FIG. 4, pixels (composed of transparent electrodes and liquid crystal layer) constructing the LCD panel, and a simplified diagram of circuits connected with the pixels;  
     [0034]FIG. 8 is a schematic view showing input/output of the operation-mode storing unit shown in FIG. 2 and correspondence between the operation modes (input) and ID numbers (output);  
     [0035]FIG. 9 is a schematic view showing input/output of the display-speed storing unit shown in FIG. 2 and correspondence between ID numbers (input) and display speeds (output);  
     [0036]FIG. 10A is a timing chart showing an example of a data transfer timing from the LCD IF in the LCD control unit to the driver in the LCD unit shown in FIG. 4;  
     [0037]FIG. 10B is a timing chart showing an example of a data transfer timing based on the data transfer timing shown in FIG. 10A, where the CLK frequency is reduced;  
     [0038]FIG. 11 is a flowchart indicating that the display speed of an image displayed in the LCD unit may be variable based on variation of frequency of the base clock signal in the clock generator shown in FIG. 4;  
     [0039]FIG. 12 is a functional block diagram showing an electrical internal structure of an LCD control unit provided in a baseband unit and an LCD unit provided in an input/output unit in a radio communication apparatus according to the second embodiment of the present invention, corresponding to FIG. 4;  
     [0040]FIG. 13A is a timing chart showing an example of a data transfer timing from the LCD IF in the LCD control unit shown in FIG. 12 to the driver in the LCD unit shown in FIG. 2;  
     [0041]FIG. 13B is a timing chart showing an example of a data transfer timing based on the data transfer timing shown in FIG. 13A, where the number of falls of the VSYNC signal is reduced; and  
     [0042]FIG. 14 is a flowchart indicating that the display speed of an image displayed in the LCD unit may be variable based on variation of an interval of the VSYNC in the clock generator shown in FIG. 12, and variation of a transfer timing of transferring the RGB pixel data. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0043] In the following, a radio communication apparatus according to the embodiment of the present invention will be explained with reference to the drawings.  
     [0044] In the embodiment, an image displayed on the display screen can be changed automatically according to the type of data or a predetermined key pressed by a user. Images that can be changed are set to four types from videos which most consume the electric power of the portable phone up to images such as a small number of texts, still figures, and the like (showing a residual amount of the battery, receiving status of a radio wave, and the like and called a stand-by hereinafter). Specifically, there are prepared four types of operation modes, i.e., a moving picture display mode (also called a video communication mode), a high-speed text display mode (also called a mail communication/transfer mode), a text display mode (also called a short mail communication mode), and a stand-by mode (also called a voice communication mode). For example, the image display speeds in these modes are respectively 30 f/s (frame numbers per second) in the moving picture display mode, 20 f/s in the high-speed text display mode, 10 f/s in the text display mode, and 2 f/s in the stand-by display mode.  
     [0045] A specific example of a radio communication apparatus and method according to the first embodiment of the present invention is shown in FIGS. 1A to  11 . FIGS. 1A, 1B, and  1 C respectively show a front view showing the front surface of the radio communication apparatus, a cross-sectional view cut along a cross-section A-B in the display unit  34  shown in FIG. 1A, and a side view showing a side surface of the radio communication apparatus. Note that the upper diagram of FIG. 1B is a cross-sectional view of the display unit  34  for displaying an image by means of a back light  341 . The lower diagram of FIG. 1B is a cross-sectional view of the display unit  34  for displaying an image by means of a front light  344 .  
     [0046] The radio communication apparatus shown in FIG. 1A, i.e., the portable phone  5  has an antenna  11  for transmitting/receiving radio waves to and from the outside, and signals processed by the portable phone  5  are transmitted/received by the antenna  11 . A signal received by the antenna  11  is processed in the portable phone  5 , and a voice is output from a speaker  32  through which users can listen to the voice. Meanwhile, a microphone  31  is provided as a voice inputting means for inputting words as a voice given from a user to a receiver. In case the portable phone  5  is used as a TV-phone, a camera  33  as a video image obtaining means of obtaining an actual video image is turned on, and the video image is obtained by the camera  33 . The video image thus obtained by the camera  33  is encoded as image data and transmitted. In addition, received image data is decoded by a circuit in the portable phone  5 , and video signals are output to the display unit  34 , thereby displaying video images on the display unit  34 . Here, the term of a video image includes moving pictures, still pictures, texts, and the like, which are displayed as images. These operations are implemented through a key input unit  35  comprised of a plurality of keys. For example, there are numeric keys for inputting phone numbers, a key for displaying an operation menu, a key for switching a displayed image to a moving picture or still picture (that is an extracted frame from texts or a moving picture), and the like.  
     [0047] The display unit  34  adopts a method using a back light  341  and another method using a front light  344 . The upper diagram of FIG. 1B shows the case of the back light method. In this case, an LCD (liquid crystal display panel)  342  is sandwiched between the back light  341  and the protection cover  343 . Light is emitted in the direction toward a protection cover  343  from the back light  341 . Therefore, users watch the display screen from the side of the front cover  343 . The lower diagram of FIG. 1B shows the case of the front light method. In this case, the front light  344  is sandwiched between the protection cover  343  and the LCD panel  342 . Light is emitted in the direction toward the protection cover  343  from the LCD panel  342 . Like the case of the back light  341 , users watch the display screen from the side of the protection cover  343 . In case of the back light method, video images are displayed by transmitted light. In the case of the front light method, video images are displayed by reflected light.  
     [0048]FIG. 1C is a side view showing the side surface of the casing of the portable phone. A battery such as a Lithium ion battery is provided in the casing. Circuits in the portable phone are supplied with a power by the battery.  
     [0049] According to FIG. 2, the portable phone  5  is constructed by a radio unit  1 , a baseband unit  2 , an input/output unit  3 , and a power source unit  4 . FIG. 2 is a block diagram showing the electrical internal structure of the portable phone  5 .  
     [0050] In FIG. 2, a radio-frequency signal transmitted over a radio channel for a movable communication system from a base station is received by the antenna  11  and is then input to a receiver circuit (RX)  13  through an antenna duplexer (DUP)  12 . The receiving circuit  13  comprises a high-frequency wave amplifier, a frequency converter, and a demodulator. Further, the radio-frequency signal is subjected to low-noise amplification by a low-noise amplifier, and is mixed with a receiving local-oscillation signal generated by a frequency synthesizer (SYN)  14  in the frequency converter, thus being subjected to frequency conversion into a receiving middle-frequency signal or a receiving baseband signal. The output signal thereof is subjected to digital demodulation by the demodulator. For example, as a demodulation method, an orthogonal demodulation method corresponding to a QPSK (quadrature phase shift keying) method is used. Note that the frequency of the receiving local-oscillation signal generated from the frequency synthesizer  4  is operated from a total control unit  21 .  
     [0051] The demodulated signal output from the demodulator is input to the baseband unit  2 . The baseband unit  2  comprises a total control unit  21 , a multiple separation unit  22 , a speech coding-encoding unit (that will be hereinafter abbreviated as a speech codec)  23 , a multi-media processing unit (hereinafter abbreviated as an MM processing unit)  24 , an LCD control unit  25 , an operation-mode storing unit  26 , and a display-speed storing unit  27 .  
     [0052] With reference to FIG. 3, a flow of receiving the radio-frequency signal, outputting a voice and displaying an image is explained.  
     [0053] The radio-frequency signal is input as a receiving signal to receiving circuit  13  through an antenna duplexer (DUP)  12  (ST-A1). Whether the demodulated signal in this receiving circuit  13  is control information or multi-media information is distinguished by the total control unit  21 . If the demodulated signal is multi-media information, it is supplied to the multiple separation unit  22 , and then in the unit  22  voice data and image data are separated (ST-A2, ST-A3). The image data is compressed data, e.g., MPEG-4 format data. Further, the image data is supplied to the MM processing unit  24 , and subjected to an image decoding process. An image signal thus reproduced is output to the LCD control unit  25 . In the MM processing unit  24 , the image data is expanded (ST-A4). An operation-mode indicating signal that indicates an operation mode is input from the total control unit  21  to the operation-mode storing unit  26  (ST-A5). One of operation modes (operation modes include above-mentioned four modes) indicated by the operation-mode indication signal is stored in the operation-mode storing unit  26  (ST-A6). Next, in the display-speed storing unit  27 , the display speed (frame numbers per unit time) corresponding to the operation mode is set (ST-A7). A displaying speed signal that indicates the display speed is output to the LCD control unit  25 . The displaying speed is stored in the display-speed storing unit (ST-A8). Thereafter, the image signal that includes data of the image displayed in LCD unit  34  is supplied to an LCD unit  34  of the input/output unit  3  and displayed in the LCD unit  34  (ST-A9). Meanwhile, the voice data is supplied to the speech codec  23  and subjected to speech decoding (ST-A10). A speech signal thus reproduced is enhanced and output as a voice by the speaker  32  of the input/output unit  3  (ST-A11).  
     [0054] Received image data is stored into a RAM (random access memory; not shown) in the total control unit  21  for the occasion that has arisen. The LCD unit  34  displays various information indicating operation status of the device itself, such as a telephone directory, a receiving electric-field-strength detection value, a residual amount of the battery, and the like, which is output from the total control unit  21 .  
     [0055] Meanwhile, a speech signal of a user output from the microphone  31  in the input/output unit  3  is input to the speech codec  23  in the baseband unit  2 , being encoded by the speech codec  23 , and then being input to the multiple separation unit  22 . In addition, the image signals output from the camera (CAM)  33  is input to the MM processing unit  24  in the baseband unit  2 , being subjected to an image encoding process, and then being input to the multiple separation unit  22 . In the multiple separation unit  22 , the voice data and image data encoded as described above are duplexed in a predetermined format. The duplexed data is input from the total control unit  21  to the transmitting circuit (TX)  15  in the radio unit  1 .  
     [0056] The transmitting circuit  15  comprises a modulator, a frequency converter, and a transmission power amplifier. The transmission data is subjected to digital modulation by the modulator, and is thereafter mixed with a transmission local-oscillation signal generated from the frequency synthesizer by the frequency converter, thus frequency being converted into a radio-frequency signal. The QPSK method is used as a modulation method. Further, a transmission radio-frequency signal thus generated is amplified to a predetermined transmission level by the transmission power amplifier, and is thereafter supplied to the antenna  11  through the antenna duplexer  12 . Thus, the signal is transmitted from the antenna  11  to a base station not shown.  
     [0057] The power source unit  4  is provided with a battery  41  such as a Lithium ion battery or the like, a charger (CHG)  42  for charging the battery  41 , and a power supply (PS)  43 . The power supply  43  is constructed by, for example, a DC/DC converter and generates a predetermined power source voltage Vcc based on the output voltage of the battery  41 .  
     [0058] In addition, the input/output unit  3  is provided with an illuminator  36  for illuminating the LCD unit  34  and the key input unit  35  during operation and communication. This illuminator  36  is, for example, called a backlight or an illumination.  
     [0059] The structure and the operation of the LCD control unit  25  will be explained in details with reference to FIGS.  4  to  6 .  
     [0060]FIG. 4 is a block diagram showing the LCD control unit  25  and the LCD unit  34 .  
     [0061] The LCD control unit  25  has a clock generator  201  that generates a base clock signal (CLK) for controlling image signals and synchronization signals that are output to the LCD unit  34 . The clock generator  201  inputs a frequency control signal for controlling the frequency of the base clock signal generated by the clock generator  201  from the displayspeed storing unit  27 . In response to the frequency control signal, the clock generator  201  outputs a base clock signal having a desired frequency to an LCD interface (LCD IF)  202 . The LCD IF  202  is an interface that connects the LCD control unit  25  and the LCD unit  34 , thereby displaying an image signal or the like for displaying an image. Further, the LCD control unit  25  inputs an image control signal for controlling images from the total control unit  21  through a BUS interface (BUS IF). The image control signal input through the BUS IF is input to circuits of a configuration register  203 , a frame memory  204 , and a look-up table  205 . In these circuits, the image signal, which is input from the MM processing unit  24  to the LCD control unit  25  and expanded, is input to these circuits through the LCD IF  202 . Based on the image signal, the three circuits ( 203 ,  204 , and  205 ) control the image signal, and a desired image signal is output to a driver  207  in the LCD unit  34  through the LCD IF  202 .  
     [0062] The configuration register  203  controls the layout and size of an image that are determined by the screen size of the LCD panel  342 . In addition, the configuration register  203  specifies, for example, where on the screen of the LCD panel  342  an image should be positioned, and where on the screen a text should be positioned. In this manner, it is possible to control the layout of the image displayed on the display screen.  
     [0063] The look-up table  205  is a controlling means for adding a large number of colors including transparence to the displayed image. The number of colors is determined by the bit number of image data. For example, the color of transparence is selected at a position on the display screen. At the position, an image based on the image signal is directly output to the screen based on an image signal input from the MM processing unit  24  and expanded. In case of another example the red color is specified to another position on the display screen, the image in red is only displayed at this position. That is, the image based on the MM processing unit  24  is not displayed at this position on the display screen. Thus, the look-up table  205  can color the image displayed on the LCD panel  342 .  
     [0064] The frame memory  204  inputs and temporarily stores an image signal input from the MM processing unit  24  and expanded. The color as described above is supplied to every pixel of the LCD panel  342  that performs display by referring to a color information of the look-up table  205 . In addition, the position of each of the pixels constructing the LCD panel  342  is specified in the configuration register  203 . Further, image data is written into a line buffer every one line of an image, and simultaneously, image data is output to the LCD IF  202  from the line buffer for every one line.  
     [0065] Based on the base clock signal generated by the clock generator  201 , a horizontal synchronization signal (HSYNC) and a vertical synchronization signal (VSYNC) are generated by the LCD IF  202 . The HSYNC and VSYNC are synchronized with the base clock signal. The frequency of the HSYNC indicates the number of scanning lines per unit time. The frequency of the VSYNC indicates the number of times for which one frame is updated per unit time (refresh rate). Further, to display an image on the LCD display screen, an enable signal (ENAB) by which the RGB signal output to the driver  207  of the LCD is rendered effective is generated also by LCD IF  202 .  
     [0066] These CLK, HSYNC, and VSYNC are output to the MM processing unit  24  through an MPEG-4 interface (IF)  206 . The MM processing unit  24  outputs an image signal according to these three image control signals, to the MPEG-4 IF  206 . Image data is input, in the format of YUV422, to the MPEG-4 IF  206  from the MM processing unit  24 . The image data of this YUV422 is converted into RGB pixel data by the MPEG-4 IF  206  and is stored in the frame memory  204 . The RGB pixel data stored in the frame memory  204  is output to the driver  207  of the LCD, by referring to the configuration register  203  and look-up table  205 , based on the synchronization signal depending on the base clock.  
     [0067] In this manner, the RGB pixel data synchronized with the CLK, HSYNC, and VSYNC can be obtained. As a result of this, the RGB pixel data stored in the frame memory  204  is output to pixels on the LCD panel  342 , and thus, an image is displayed on the LCD panel  342 .  
     [0068] With reference to FIGS. 5A and 5B, timings of signals to be input to the driver  207  of the LCD will be explained. FIGS. 5A and 5B are timing charts showing image data and image control signals output from the LCD control unit  25  to the LCD unit  34 .  
     [0069]FIG. 5A is a timing chart showing timings of the image control signal and image data in case one line of one frame is output.  
     [0070] During a period from a low level of HSYNC to a next low level thereof, one line is output from the LCD control unit  25  to the LCD unit  34 . That is, ENAB is rendered high during a preset duration between the low level and the next low level as shown in FIG. 5A. By the high ENAB, the RGB pixel data is output to the driver  207  of the LCD. The RGB pixel data is varied at a fall timing (i.e. timing when a pulse changes from high level to low level) of CLK and is transferred to the driver  207  of the LCD at a rise timing (i.e. timing when a pulse changes from low level to high level) thereof. Further, the amount of transfer data of the RGB pixel data corresponds to the length of one line, which is the lateral length of the screen.  
     [0071]FIG. 5B is a timing chart showing timings of the image control signal and image data in case one frame is output.  
     [0072] One frame is output from the LCD control unit  25  to the LCD unit  34  during a period from a low level of VSYNC to a next low level thereof. That is, between these low levels, there are rectangular signals for the number of lines included in one frame. Further, during the period when the ENAB is high, the RGB pixel data is output to the driver  207  of the LCD. The period when the ENAB is high, i.e., the unit surrounded by a rectangular broken line part shown in FIG. 5B, corresponds to FIG. 5A. In addition, the number of rectangular wave signals corresponds to the number of lines existing in one frame.  
     [0073] With reference to FIGS. 6A and 6B, explanation will be made of timings of image data based on YUV422, which is input from the MM processing unit  24  to the MPEG-4 IF  206  in the LCD control unit  25 , and timings of CLK, HSYNC, and VSYNC output from the MPEG-4 IF  206  to the MM processing unit  24 . FIGS. 6A and 6B are timing charts showing timings of image data and image control signals, which are output from the MM processing unit  24  to the MPEG-4 IF  206  in the LCD control unit  25 .  
     [0074]FIG. 6A is a timing chart showing timings of an image control signal in case one line of one frame is output like FIG. 5A. FIG. 6B is a timing chart showing timings of the image control signal in case one frame is output like FIG. 5B. The rectangular part surrounded by a broken line in FIG. 6B corresponds to FIG. 6A. These figures are different from FIGS. 5A and 5B in the point that the direction of the image data is an input direction to the LCD control unit  25 , and that the image data is not RGB pixel data but image data based on the YUV422 format. The YUV422 is a format that is a series of Cr, Y, Cb, Y, Cr, Y, Cb or the like. In the LCD control unit  25 , image data based on the input signal YUV422 output from the MM processing unit  24  and the RGB pixel data as output data to the LCD driver  207  are synchronized with each other in some cases and are not synchronized in other cases.  
     [0075] The RGB pixel data described above drives the driver  207  in the LCD unit  34  and thereby displays an image on the LCD panel  342 . The LCD unit  34  comprising the driver  207  and the LCD panel  342  is shown in FIG. 7. FIG. 7 is a schematic view showing an LCD panel  342 , pixels (made of transparent electrodes and liquid crystal layer) constructing the LCD panel  342 , and a simplified diagram of circuits connected with the pixels.  
     [0076] In the LCD unit  34 , in order to adjust directions of liquid crystal every time when the screen is updated, alternating current driving is executed. With respect to each pixel of the LCD panel  342 , a liquid crystal layer is provided between transparent electrodes opposed to each other, and the electrodes are driven by an alternating current. If the alternating current driving is thus executed, the opposed electrodes repeat charging and discharging. Therefore, electric power is consumed by the charging and discharging. In addition, circuits of the display unit except for those of the LCD unit  34  increase their power consumption.  
     [0077] With reference to FIGS. 8 and 9, explanation will be made of the operation-mode storing unit  26  and the display-speed storing unit  27 . FIG. 8 shows input/output of the operation-mode storing unit  26  and correspondence between operation modes and ID numbers. FIG. 9 shows input/output of the display-speed storing unit  27  and correspondence between ID numbers and display speeds.  
     [0078] If a signal for specifying an operation mode is output from the total control unit  21 , the operation-mode storing unit  26  shown in FIG. 8 outputs an ID signal assigned with an ID number corresponding to the operation mode. In response to a trigger signal for storing information on the mode, the ID signal is stored in the operation-mode storing unit  26 . The operation-mode storing unit  26  is a register. There is one-to-one correspondence between the operation modes and the ID numbers, so the ID numbers are determined uniquely. That is, the stand-by corresponds to 0, the text display to 1, the high-speed text display to 2, as well as the moving picture display to 3.  
     [0079] The display-speed storing unit  27  shown in FIG. 9 is a memory that stores a display speed corresponding to a mode. ID signals are input from the operation-mode storing unit  26 , and display speed signals indicating display speeds are output to the LCD control unit  25 . The relationship between the ID number and the display speed is as follows. That is, stand-by: 0 corresponds to 2 f/s, text display: 1 to 10 f/s, high-speed text display: 2 to 20 f/s, as well as moving picture display: 3 to 30 f/s.  
     [0080]FIGS. 10A and 10B are timing charts showing examples of data transfer timings to the LCD unit  34  in the present embodiment. A base clock signal supplied to the LCD control unit  25  is rendered variable by the clock generator  201 , and the speed of CLK itself is increased or decreased. In this case, the CLK frequency remains unchanged in the moving picture display mode. In the high-speed text display mode, the CLK frequency is reduced to ⅔ of an initial frequency. In the text display mode, the CLK frequency is reduced to ⅓ of the initial frequency. In the stand-by mode, the CLK frequency is reduced to {fraction (1/15)} of the initial frequency. As the CLK frequency is thus reduced, an amount of the image data is also reduced. Therefore, the power consumption in the LCD panel  342  is reduced. This method needs only to add a clock change circuit to the LCD control unit  25 , and thus, a portable phone  5  having a TV-phone function with low power consumption is obtained easily and simply.  
     [0081] With reference to FIG. 11, a flow indicating that the display speed of an image displaying in LCD unit  34  may be variable based on variation of frequency of the base clock signal in the clock generator  201  is explained.  
     [0082] An operation-mode indicating signal that indicates an operation mode is input from the total control unit  21  to the operation-mode storing unit  26 . One of operation modes indicated by the operation-mode indication signal is stored in the display-speed storing unit  27 . In the display-speed storing unit  27 , the display speed corresponding to the operation mode is set. A signal corresponding to this display speed set above is output to the clock generator  201  (ST-B1). A frequency of the base clock is varied based on the signal (ST-B2). This frequency corresponds to the display speed. In the clock generator  201 , a base clock signal for controlling an image signal and a synchronization signal that are output to the LCD unit  34  is generated. In the LCD IF  202  synchronization signals (HSYNC and VSYNC) is generated based on the base clock signal (ST-B3). The image data signal is input from MM processing unit  24  to the LCD control unit  25 , and then the image data extracted from the image data signal is output to the LCD unit  34  based on the synchronization signal (ST-B4). In the LCD unit  34 , an image is reproduced from the image data. The image extracted from this image data displays at a speed of the display speed corresponding to the clock frequency (ST-B5). In this way, the display speed is set to a preset speed.  
     [0083] With reference to FIGS. 12, 13A,  13 B, and  14  explanation will be made of a radio communication apparatus having a TV-phone function, and a radio communication method according to the second embodiment of the present invention. FIG. 12 is a block diagram showing an LCD control unit  25  and an LCD unit  34  in the radio communication apparatus having the TV-phone function according to the second embodiment.  
     [0084] In the first embodiment described above, the LCD panel  342  may not be operated well when the base clock frequency for transferring image data is extremely low, in some cases. If such an LCD panel  342  is used, there may not be a possibility that the display speed can be set very low.  
     [0085] Hence, the present embodiment shows a portable phone having a TV-phone function in which image data is reduced with the CLK frequency unchanged, so that very low power consumption is realized.  
     [0086] Specifically, timing information of VSYNC is generated by a VSYNC timing generator  209  based on a signal from a clock generator  201 . Further, transfer timings of RGB pixel data are generated by an RGB transfer data timing generator  210  based on a signal from the clock generator  201 .  
     [0087]FIGS. 13A and 13B show that the transfer speed of the RGB pixel data is set constant and the interval of VSYNC is rendered variable. In this case, the period of the CLK is set constant. In addition, the RGB pixel data is transferred at the rise timing of the CLK. If the period of the CLK is constant, the transfer speed of the RGB pixel data is constant.  
     [0088] In this method, the VSYNC and the CLK are controlled separately. That is, the timing information of VSYNC and the transfer timing information of the RGB pixel data are controlled respectively.  
     [0089] With reference to FIG. 14 a flow indicating that the display speed of an image displaying in LCD unit  34  may be variable based on variation of a generating interval of the VSYNC in the clock generator  201 , and variation of a transfer timing of transferring the RGB pixel data is explained.  
     [0090] An operation-mode indicating signal that indicates an operation mode is input from the total control unit  21  to the operation-mode storing unit  26 . One of operation modes indicated by the operation-mode indication signal is stored in the display-speed storing unit  27 . In the display-speed storing unit  27 , the display speed corresponding to the operation mode is set. A signal corresponding to the display speed set above is output to the clock generator  201 . The base clock having a constant frequency is generated based on the signal (ST-C1). The base clock controls the image signal and the synchronization signal that are output to the LCD unit  34 . The generating interval of the VSYNC and the transfer timing of the RGB pixel data are varied in a VSYNC timing generator  209  and a RGB transfer timing generator  210  respectively based on the display speed signal (ST-C2). Based on the base clock signal, the synchronization signals (HSYNC and VSYNC) are generated in the LCD IF  202  (ST-C3). The image data signal is input from an MM processing unit  24  to an LCD control unit  25 , and then a transfer signal that the image data extracted from the image data signal based on the synchronization signals is transferred to the LCD unit  34  is generated (ST-C4). The image data is output to the LCD unit  34  based on the transfer signal (ST-C5). In the LCD unit  34 , an image is reproduced from the image data. The image extracted from the image data is displayed at a speed of the display speed corresponding to the CLK frequency (ST-C6). In this way, the display speed is set to a preset speed.  
     [0091] In the VSYNC timing generator  209 , the number of falls of a signal is reduced at a predetermined ratio per unit time. According to the timing chart of the present embodiment shown in FIG. 13B, the number of falls of the VSYNC signal is reduced at a ratio of 3:1 per unit time. The ratio 3 to 1 is non-varied VSYNC fall interval to varied VSYNC fall interval. More specifically in the present embodiment, the VSYNC signal falls only once as shown in FIG. 13B during a period in which the VSYNC signal falls three times as shown in FIG. 13A.  
     [0092] Meanwhile, the RGB transfer data timing generator  210  controls the time when the RGB pixel data is transferred to the driver  207 . As described above, the transfer speed at which the RGB pixel data is transferred to the driver  207  is the same as that of the transfer speed in case of conventional RGB transfer data. The present embodiment differs from the above one in that a period in which the RGB pixel data is not transferred is provided at a constant ratio in the present embodiment. Referring to FIGS. 13A and 13B, the data amount of the RGB pixel data that is transferred in a predetermined time period is reduced at a ratio of 3:1. That is, the present embodiment displays only one screen within a time period in which three screens are displayed in the moving picture display mode in the above embodiment. In addition, since the transfer timing of the RGB pixel data to the LCD unit  34  is constant, there is not possibility that the LCD panel  342  does not work and no image is displayed.  
     [0093] Meanwhile, in the RGB transfer data timing generator  210 , the rise and fall timings of HSYNC are determined, based on the CLK. The rise and fall timings of ENAB are determined by the fall timing of HSYNC. As a result of this, timings of varying and transferring the RGB pixel data are determined.  
     [0094] By thus making the display speed of the display changeable according to the operation mode, it is possible to make changes such that 10 frames are displayed for every second in case of displaying a phone number, 30 frames are displayed for every second in the moving picture display mode, and several frames are displayed in the standby mode. Accordingly, the power consumption of the LCD panel  342  can be reduced.  
     [0095] The present invention is not limited to the embodiments described above but may be modified appropriately. For example, there may be provided a function of reducing power consumption of the operation of the LCD control unit  25  by repeatedly displaying one same screen stored in the RAM of the driver  207  of the LCD in case the screen does not change. The CLK frequency may be controlled depending on the operation mode, so that the power consumption is much more reduced.  
     [0096] As has been explained above, according to the radio communication apparatus having the TV-phone function of the present invention, the display speed at which the display panel is driven is changeable, so that a display speed corresponding to the operation mode is set, thereby realizing power saving.  
     [0097] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.