Abstract:
A communication apparatus having a transmission section and a reception section that are selectively attached or detached from one another. The transmission section is operable to modulate an information signal to generate a high frequency signal and to wirelessly transmit the high frequency signal to the reception section, or to output the information signal to the reception section via a non-wireless coupling. The reception section is operable to receive the high frequency signal transmitted from the transmission section and to demodulate the high frequency signal to recover the information signal, or to receive the information signal outputted from the transmission section. Further, an attached condition is sensed, indicating whether the transmission section and the reception section are connected/attached to each other or disconnected/detached from each other, and switching between wireless transmission and non-wireless transmission is performed in accordance with the indicated condition.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a radio communication apparatus which includes a transmission section for transmitting an information signal and a reception section for receiving the information signal transmitted from the transmission section. 
   SUMMARY OF THE INVENTION 
   It has been recognized that a conventional radio communication apparatus is not designed so that a transmission section and a reception section are used as a unitary member, but is configured in such a manner as shown in  FIG. 1  wherein a radio AV transmitter  102  and a radio AV receiver  110  are formed separately from each other. The radio AV transmitter  102  is formed in order that an audio-video signal (hereinafter referred to as AV signal) reproduced by a video cassette recorder VCR  101  for domestic use may be outputted to a television set  116  for domestic use located at a place spaced away from the VCR  101  for domestic use. In the following, the conventional radio communication apparatus is described with reference to  FIG. 1 . 
   The VCR  101  for domestic use plays back information recorded on an information recording medium and outputs the played back information as an AV signal to an AV signal processing section  103  in the radio AV transmitter  102 . 
   The AV signal processing section  103  is composed of a buffer amplifier, a filter and other elements and converts an AV signal outputted from the VCR  101  for domestic use into a signal of an amplitude value optimum for modulation. The AV signal processing section  103  outputs the AV signal obtained by the conversion to a modulation section  104 . 
   The modulation section  104  modulates the AV signal inputted thereto from the AV signal processing section  103  with a carrier of an IF (intermediate frequency) frequency inputted thereto from a frequency synthesizer  105  which can produce a particular frequency, and outputs the signal obtained by the modulation as an IF signal to a frequency conversion section  106 . 
   The frequency conversion section  106  mixes the IF signal inputted thereto from the modulation section  104  and a local oscillation frequency inputted thereto from the frequency synthesizer  105  to obtain a high frequency signal, that is, a radio frequency (RF) signal and outputs the RF frequency signal to a power amplifier  107 . 
   The power amplifier  107  amplifies the RF signal inputted thereto from the frequency conversion section  106  to a signal of a prescribed power and outputs the amplified RF signal to a transmission antenna  108 . 
   The transmission antenna  108  radiates the RF signal inputted thereto from the power amplifier  107  as radio waves into the space. 
   Then, a reception antenna  109  connected to the radio AV receiver  110  outputs the radio waves outputted from the transmission antenna  108  as an RF signal to a low noise amplifier  111 . 
   The low noise amplifier  111  amplifies the RF signal inputted thereto from the reception antenna  109  and outputs the amplified RF signal to a frequency conversion section  112 . 
   The frequency conversion section  112  mixes a local oscillation frequency inputted from a frequency synthesizer  113  with the RF signal inputted thereto from the low noise amplifier  111  to obtain an IF signal and outputs the IF signal to a demodulation section  114 . 
   The demodulation section  114  demodulates the IF signal inputted thereto from the frequency conversion section  112  with a carrier of an IF frequency inputted thereto from the frequency synthesizer  113  to obtain an AV signal and outputs the AV signal to an AV signal processing section  115 . 
   The AV signal processing section  115  removes noise from the AV signal inputted thereto from the demodulation section  114  and amplifies and outputs the signal free from noise to the television set  116  for domestic use. 
   The television set  116  for domestic use reproduces the AV signal inputted thereto from the AV signal processing section  115  to obtain an image and/or sound. 
   In the conventional radio communication apparatus having the configuration described above, an AV signal outputted from the VCR  101  for domestic use is converted into an RF signal and the RF signal is transmitted by radio transmission, and then an image and/or sound are reproduced from the RF signal by the television set  116  for domestic use. 
   The conventional radio communication apparatus described above is susceptible to radio interference. For example, when an electric apparatus such as a microwave oven which generates radio waves is located in the proximity of the radio communication apparatus, the waves generated by the electric apparatus may be erroneously received by the communication apparatus, thereby degrading performance of the communication apparatus. Such interference can occur even when the transmission antenna and the reception antenna are positioned near to each other. The level of the interfering radio waves is sometimes so high that the image and/or sound reproduced by the radio communication apparatus is unintelligible. 
   In the system of  FIG. 1 , to obtain a good image and/or sound in the presence of interference, it is necessary to move the television set  116  to a place near to the VCR  101 , or conversely, to move the VCR  101  to a place near to the television set  116 , remove the radio AV transmitter  102  and the radio AV receiver  110 ; and connect the television set  116  and the VCR  101  directly to each other by an AV cable or the like. In this manner, the image information and/or sound information is communicated between the television set  116  and the VCR  101  via the cable, which is less susceptible to interference than a wireless link. 
   The present invention overcomes drawbacks of conventional radio communication systems. 
   The invention includes a transmission section and a reception section that are selectively attached or detached from one another. The transmission section is operable to modulate an information signal to generate a high frequency signal and to wirelessly transmit the high frequency signal to the reception section, or to output the information signal to the reception section via a non-wireless coupling. The reception section is operable to receive the high frequency signal transmitted from the transmission section and to demodulate the high frequency signal to recover the information signal, or to receive the information signal outputted from the transmission section. Further, an attached condition is sensed, indicating whether the transmission section and the reception section are connected/attached to each other or disconnected/detached from each other, and switching between wireless transmission and non-wireless transmission is performed in accordance with the indicated condition. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following detailed description, given by way of example and not intended to limit the present invention solely thereto, will best be appreciated in conjunction with the accompanying drawings, wherein like reference numerals denote like elements and parts, in which: 
       FIG. 1  is a block diagram showing a conventional radio communication apparatus; 
       FIG. 2  is a block diagram showing a configuration of an illustrative radio communication apparatus to which the present invention is applied; and 
       FIG. 3  is a circuit diagram showing a detailed configuration of the radio communication apparatus of  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 2 , there is shown an illustrative radio communication apparatus to which the present invention is applied. In the apparatus of  FIG. 2  an AV signal outputted from a VCR  3  is displayed on a liquid crystal display (LCD)  14 . 
   The radio communication apparatus includes a transmission section  1  for transmitting an information signal which is a signal of image information and/or sound information, and a reception section  2  for receiving the information signal. 
   The transmission section  1  and the reception section  2  of the radio communication apparatus can be operated in a detached configuration, wherein communication between the sections is through a wireless link. Or, the transmission section and reception section can be operated as a unitary apparatus, wherein the sections are in physical contact with each other (“attached”) and communication is carried out through a non-wireless link. 
   The transmission section  1  includes an apparatus which outputs an information signal as an AV signal such as, for example, a VCR  3  which outputs an AV signal. The transmission section  1  can convert the AV signal into a high frequency signal, that is, an RF signal and transmit the RF signal to the reception section  2  by radio transmission or by wire transmission. 
   The VCR  3  can record and play back an information signal onto and from a video cassette tape which is a kind of information recording medium and can output a played back information signal as an AV signal. 
   The transmission section  1  includes a radio AV transmitter  4  for converting an AV signal inputted thereto from the VCR  3  into an RF signal and outputting the RF signal, an antenna switch  5  serving as a selection means, a sensor  6  serving as a detection means for detecting a connection/attached condition between the transmission section  1  and the reception section  2 , a transmission antenna  7  for outputting the RF signal by radio transmission, and an output terminal  8  adapted to be connected/attached to the reception section  2  for outputting the RF signal by non-wireless (e.g. wire) transmission. 
   The radio AV transmitter  4  is connected to the VCR  3  and the antenna switch  5 , and converts an AV signal inputted thereto from the VCR  3  into an RF signal and outputs the RF signal to the antenna switch  5 . The radio AV transmitter  4  is substantially similar to the radio AV transmitter  102  described hereinabove with reference to  FIG. 1 , and therefore overlapping description of an internal configuration and operation of the radio AV transmitter  4  is omitted to avoid redundancy. 
   The sensor  6  is connected to the antenna switch  5 , and detects a connection condition between the transmission section  1  and the reception section  2 , for example, when the reception section  2  is located at a predetermined position at an upper portion of the transmission section  1 , and sends connection information to the antenna switch  5 . 
   The antenna switch  5  is connected to the transmission antenna  7  and the output terminal  8  and receives the connection information from the sensor  6 . Based on the connection information, the antenna switch  5  switches between the outputting methods of radio transmission and wire transmission. Further, if the connection information indicates that the transmission section  1  and the reception section  2  are not connected to each other (“detached” from each other), the antenna switch  5  changes over the circuit to the transmission antenna  7  side in order that the inputted RF signal may be outputted by radio transmission. Then, the antenna switch  5  outputs an RF signal sent thereto from the radio AV transmitter  4  to the transmission antenna  7  so that the RF signal is radiated as radio waves from the transmission antenna  7 . 
   On the other hand, if the antenna switch  5  receives from the sensor  6  connection information indicating that the transmission section  1  and the reception section  2  are connected to each other, it changes over the circuit to the output terminal  8  side so that the inputted RF signal may be transmitted by non-wireless (e.g. wire) transmission. Then, the antenna switch  5  outputs an RF signal sent thereto from the radio AV transmitter  4  to the output terminal  8  so that the RF signal is transmitted from the output terminal  8  to the reception section  2 . 
   The transmission antenna  7  is provided, for example, external to the transmission section  1  and outputs an RF signal inputted thereto from the antenna switch  5  as radio waves into the space. 
   Further, the transmission section  1  is connected, for example, to a power supply (not shown) for energizing the entire transmission section  1 . For the power supply, a commercial power supply of a voltage of 100 V, 110 V, 200 V or 220 V or the like may be used. 
   The reception section  2  includes a sensor  9  serving as a detection means for detecting that the transmission section  1  and the reception section  2  are connected/attached to each other, an antenna switch  10  serving as a selection means, a reception antenna  11  for receiving an RF signal transmitted by radio waves from the transmission antenna  7 , and an input terminal  12  adapted to be connected to the output terminal  8  for allowing non-wireless (e.g. wire) transmission. 
   The sensor  9  is connected to the antenna switch  10 , and similar to the sensor  6 , detects a connection condition between the transmission section  1  and the reception section  2  when the reception section  2  is located, for example, at a predetermined position of the upper portion of the transmission section  1 . The sensor  9  sends connection information indicative of the connection condition to the antenna switch  10 . 
   The antenna switch  10  is connected to the reception antenna  11  and the input terminal  12 , and changes over the circuit to the reception antenna  11  or the input terminal  12  in response to the connection information from the sensor  9 . 
   When the transmission section  1  and the reception section  2  are not connected to each other, the antenna switch  10  changes over the circuit to the reception antenna  11  in response to the connection information from the sensor  9  so that an RF signal transmitted by radio waves from the transmission antenna  7  is received. 
   On the other hand, when the transmission section  1  and the reception section  2  are connected to each other, the antenna switch  10  changes over the circuit to the input terminal  12  in response to the connection information from the sensor  9  so that an RF signal transmitted via output terminal  8  is received. 
   When the transmission section  1  and the reception section  2  are connected to each other, the output terminal  8  and the input terminal  12  may be moved into a connected state, for example, by biasing forces of respective spring elements, or may be projected into a connected state in response to the connection information sent from the sensors  6  and  9 . In the latter case, the sensors  6  and  9  and the output terminal  8  and input terminal  12  are connected to each other, respectively, and the output terminal  8  and the input terminal  12  require projection elements for individually projecting them. 
   The reception section  2  further includes a radio AV receiver  13  for converting an RF signal into an AV signal. The radio AV receiver  13  is connected to the antenna switch  10  such that the antenna switch  10  sends an RF signal inputted from the reception antenna  11  or the input terminal  12  to the radio AV receiver  13 . It is to be noted that the radio AV receiver  13  is substantially similar to the radio AV receiver  110  described hereinabove with reference to  FIG. 1 , and therefore overlapping description of an internal configuration and operation of the radio AV receiver  13  is omitted to avoid redundancy. 
   The reception section  2  further includes, for example, an LCD display section  14  which can reproduce image information and a speaker  15  which can reproduce sound information. 
   The radio AV receiver  13  is connected to the LCD display section  14  and the speaker  15 , and converts an RF signal inputted thereto from the antenna switch  10  into an AV signal and outputs the AV signal to the LCD display section  14  and the speaker  15 . It is to be noted that the signal to be outputted to the LCD display section  14  is an analog composite signal, which is an image signal included in the AV signal, and the signal to be outputted to the speaker  15  is an audio signal. 
   Thus, in the reception section  2 , an information signal, originally played back by the VCR  3 , is reproduced by the LCD display section  14  and/or the speaker  15 . 
   Further, the reception section  2  has an internal power supply (not shown), which may be, for example, a re-chargeable secondary battery. The secondary battery can receive supply of power from the transmission section  1  and be charged thereby while the transmission section  1  and the reception section  2  are connected to each other. 
   When the sensor  9  detects that the transmission section  1  and the reception section  2  are connected to each other, the reception section  2  does not use the internal power supply but receives supply of power for the components thereof, such as the LCD display section  14 , from the transmission section  1  to allow the components to operate. It is to be noted that also the reception section  2  may be configured such that it can be connected to an external commercial power supply of 100 V, 110 V, 200 V or 220 V or the like. 
   When the sensor  9  detects that the transmission section  1  and the reception section  2  are not connected, the secondary battery is used to power the components of the reception section  2 . 
     FIG. 3  is a circuit diagram showing a detailed configuration of the radio communication apparatus of  FIG. 2 .  FIG. 3  shows a preferred configuration for implementing switching between radio communication and wire communication of an information signal in response to the existing connection condition between the transmission section  1  and the reception section  2 . 
   The sensor  6  in the transmission section  1  is formed from, for example, an electric circuit and detects the connection condition between the transmission section  1  and the reception section  2  from flow of current through the electric circuit. The sensor  6  includes four terminals C 1 , D 1 , E 1  and F 1 . 
   The sensor  9  in the reception section  2  detects a connection condition between the transmission section  1  and the reception section  2  in the same fashion as sensor  6 . The sensor  9  includes four terminals C 2 , D 2 , E 2  and F 2 . 
   If the reception section  2  is placed at the predetermined position at the upper portion of the transmission section  1 , then the terminals C 1  and C 2 , D 1  and D 2 , E 1  and E 2 , and F 1  and F 2  are respectively connected to each other, and the voltage applied in the electric circuit of each of the sensors  6  and  9  changes. The sensors  6  and  9  interpret such changes in current and voltage as connection information and respectively forward the information to the antenna switches  5  and  10 . In response to the connection information, the antenna switches  5  and  10  change over the communication method to radio communication or to wire communication. 
   Here, the voltages to be applied in the electric circuits of the sensors  6  and  9  when the transmission section  1  and the reception section  2  are not connected to each other are described. 
   A voltage Vcc 1  is applied to a point P 1  in the transmission section  1 , and a voltage Vcc 2  is applied to a point P 2  in the reception section  2 . 
   The terminals C 1 , D 1 , E 1  and F 1  on the transmission section  1  side are not connected to the terminals C 2 , D 2 , E 2  and F 2  on the reception section  2  side. Thus, the voltage Vcc 1  applied to the point P 1  is applied to a resistor R 1 , and a voltage equal to Vcc 1  minus the voltage drop across resistor R 1  is applied to a terminal A 1  of the antenna switch  5 . Meanwhile, the voltage Vcc 2  applied to the point P 2  is applied to a resistor R 3 , and a voltage equal to Vcc 2  minus the voltage drop across resistor R 3  is applied to a terminal A 2  of the antenna switch  10 . 
   In short, when the sensors  6  and  9  do not detect that the transmission section  1  and the reception section  2  are connected/attached to each other, predetermined voltages are applied to the terminals Al and A 2  of the antenna switches  5  and  10 . The voltages are used as connection information, and the antenna switch  5  and the antenna switch  10  change over the circuits to the transmission antenna  7  and the reception antenna  11 , respectively, in response to the connection information. 
   Next, the voltages applied in the electric circuits of the sensors  6  and  9  when the transmission section  1  and the reception section  2  are connected to each other are described. 
   In this instance, the terminals C 1 , D 1 , E 1  and F 1  on the transmission section  1  side are respectively connected to the terminals C 2 , D 2 , E 2  and F 2  on the reception section  2  side. Thus, the voltage Vcc 1  applied to the point P 1  is applied through the terminals E 1  and E 2  connected to each other to a terminal B 2  of the antenna switch  10  in the reception section  2 . Meanwhile, the voltage Vcc 2  applied to the point P 2  is applied through the terminals C 1  and C 2  connected to each other to a terminal B 1  of the antenna switch  5  in the transmission section  1 . 
   In short, the sensors  6  and  9  detect that the transmission section  1  and the reception section  2  are connected to each other when the voltage Vcc 1  is applied to the terminal B 2  of the antenna switch  10  and the voltage Vcc 2  is applied to the terminal B 1  of the antenna switch  5 . The voltages Vcc 1  and Vcc 2  are used as connection information, and the antenna switch  5  and the antenna switch  10  change over the circuits to the output terminal  8  and the input terminal  12 , respectively, in response to the connection information. 
   It should be noted that antenna switches  5  and  10  of  FIG. 3  are static switches. They are not powered, and therefore they each require two terminals for control. For example, with respect to antenna switch  5 , when terminal A 1  is high (pull-up), terminal B 1  is low (pull-down), and the switch changes over to the transmission antenna  7 . When terminal A 1  is low (pull-down), terminal B 1  is high (pull-up), and the switch changes over to the output terminal  8 . 
   The invention is not limited to employing static switches. Upon study of the description provided herein, one of ordinary skill in the art will recognize many switch types that may be employed. 
   In any event, the output terminal  8  is formed from the terminals H 1  and G 1 , and the input terminal  12  is formed from the terminals H 2  and G 2 . 
   When the transmission section  1  and the reception section  2  are connected to each other, the sensors  6  and  9  detect the connection, and the antenna switches  5  and  10  are changed over to the output terminal  8  and the input terminal  12 , respectively. Then, an RF signal is transmitted through the terminals H 1  and H 2 . At this time, the terminals G 1  and G 2  are grounded to shield the RF signal transmitted through the terminals H 1  and H 2  and to connect the grounds of the transmission section  1  and the reception section  2  to each other. 
   By such operations as described above, the radio communication apparatus of the present embodiment can convert an AV signal outputted from the VCR  3  into an RF signal, switch between radio transmission and non-wireless transmission of communications from the transmission section  1  to the reception section  2 , and output an information signal using the LCD display section  14  and/or the speaker  15 . 
   Consequently, the transmission section  1  and the reception section  2  can be used at places spaced away from each other. Yet, when the information signal transmitted by radio from the transmission section  1  to the reception section  2  is subject to undue interference, the reception section  2  can be placed at the predetermined position at the upper portion of the transmission section  1  and the communication is changed over to non-wireless communication immediately. Thereby, eliminating or reducing the effect of the interference upon the communication. 
   Further, when an RF signal is used upon transmission by wire transmission as described above, only one line is required for transmission of a signal. Consequently, an information signal can be transmitted by wire transmission using a smaller number of lines than when compared with an alternative case wherein an AV signal is outputted. It is to be noted that a coaxial cable may be used as the transmission line for an RF signal. 
   It is to be noted that the radio communication apparatus according to the present invention is not limited to using a VCR  3  for producing an AV signal, but may alternatively use a tuner (not shown) for receiving image information and/or sound information transmitted from a transmitting station. Where a tuner is used, radio transmission and wire transmission, as well as the switching between them, may be performed in the same manner that they are performed in the VCR embodiment, and therefore, overlapping description of transmission and switching in the tuner embodiment is omitted to avoid redundancy. 
   Further, the AV signal generation apparatus of the transmission section  1  is not limited to a VCR or a tuner, but may be some other apparatus which has a function of outputting an AV signal. Also, the AV signal generation apparatus may be externally connected to the transmission section  1 . 
   It is to be noted that the radio communication apparatus may be modified such that the antenna switches  5  and  10  are changed over manually. In this instance, a mechanism for such manual switching needs to be provided for the transmission section  1  and/or the reception section  2 . The implementation of such a mechanism will be readily apparent to one skilled in the art after study of the description provided herein. 
   For non-wireless communication, an AV signal may be communicated in lieu of an RF signal. In such an implementation, the antenna switches  5  and  10  are not required, and the sensor  6  is connected to the radio AV transmitter  4  and sends connection information to the radio AV transmitter  4  while the sensor  9  is connected to the radio AV receiver  13  and sends connection information to the radio AV receiver  13 . The AV signal is communicated directly between the radio AV transmitter  4  and the radio AV receiver  13  without converting it into an RF signal. In this instance, a greater number of connection terminals than that of the output terminal  8  and the input terminal  12  are prepared for each of the radio AV transmitter  4  and the radio AV receiver  13  and couplings for interconnecting the connection terminals are prepared to communicate the AV signal. 
   Although a greater number of communication terminals are required when an AV signal is used for non-wireless communication, the configuration can be simplified because the antenna switches  5  and  10  and so forth are not required. 
   While the present invention has been particularly shown and described in conjunction with preferred embodiments thereof, it will be readily appreciated by those of ordinary skill in the art that various changes may be made without departing from the spirit and scope of the invention. 
   Therefore, it is intended that the appended claims be interpreted as including the embodiments described herein as well as all equivalents thereto.