Abstract:
An apparatus and related method for matching antenna pattern to the mobile phone. The mobile phone includes an antenna, at least one radio frequency (RF) circuit and a diplexer for relaying signals of the RF circuits to the antenna. Each RF circuit has its own matching circuit, such that the antenna performance for receiving and transmitting signals can be independently adjusted without affecting each other.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a new antenna architecture used in a mobile phone for adjusting the antenna matching circuits operating in different function modes in different frequency bands. More specifically, a mobile phone having independent matching circuits corresponding to different RF circuits, which is capable of individually adjusting the matching circuits to optimize the mobile phone performance.  
           [0003]    2. Description of the Prior Art  
           [0004]    Owing to the rapid development of wireless communication systems, people can access resources, exchange information, and share experiences via a mobile phone or other wireless communication devices anytime and anywhere. Modern mobile phones with dual-band or multi-band capabilities have allowed users to access various wireless network resources and expand access capability for convenience. How to promote the dual-band mobile phones becomes a key point for modern information industry. In a typical multimode, multi-band wireless communication system, the same identical antenna and matching circuit are used to transceive various electromagnetic waves with different frequencies which may have completely different field patterns. Therefore, it has become an important issue to efficiently unify various access capabilities associated with various bands into one single antenna which will not interfere the operation of the antenna in one band with the other. In the following description, we will focus on dual band mobile phones to illustrate the idea. However, the same idea can be applied to any multi-band wireless communication device using a single antenna port to transmit/receive radiation signals.  
           [0005]    Please refer to FIG. 1 and FIG. 2, where FIG. 1 shows a conventional dual-band mobile phone  10  and FIG. 2 is a block diagram of the conventional dual-band mobile phone  10 . Mobile phone  10  includes a baseband circuit  18 , a radio frequency circuit  40 , an antenna  20 , an input device  12 , a monitor  14 , a microphone  36  and a speaker  38 . The baseband circuit  18  includes a processor  16  for controlling the operation of the mobile phone  10 . The input device  12  can be a button or other trigger devices for receiving control commands from a user and for transmitting them to the processor  16  which controls the mobile phone  10  according to the user&#39;s manipulation. A graphic operation status with respect to the mobile phone  10  can be shown on the monitor  14  through the processor  16 . The monitor  14  can be a liquid crystal device (LCD) or a touch panel with the input device  12 . The microphone  36  is used to receive sound waves from the user, to generate a corresponding audio signal  42  and to send the audio signal  42  to the baseband circuit  18 . The speaker  38  can transform a sound signal  43  into sound waves, and let the user hear the corresponding sound.  
           [0006]    In a dual-band mobile phone, the radio frequency circuit  40  within the mobile phone  10  includes two radio frequency (RF) signal circuits  22 A and  22 B for accessing different wireless communication networks with different frequency bands. For instance, the radio frequency circuit signal  22 A can be used for processing CDMA (Code Division Multiple Access) signals associated with a PCS (Personal Communication Services) band, where its frequency range is roughly 1900 MHz; the other radio frequency circuit signal  22 B can be used for processing AMPS (Advanced Mobile Phone System) signals associated with a Cellular band, where its frequency range is roughly 900 MHz. The RF circuits  22 A,  22 B respectively include power controllers  28 A,  28 B, isolators  30 A,  30 B, duplexers  32 A,  32 B, and receiving circuits  34 A,  34 B. Within the conventional mobile phone  10 , both the RF circuits  22 A,  22 B are electrically connected to a matching circuit  26  by way of the diplexer  24 , and then are electrically connected to the antenna  20 . While one band of the dual-band mobile phone  10  is in use, the RF circuit corresponding to that band is switched on; meanwhile, the other RF circuit operated in the other band within the mobile phone  10  is turned off because the mobile phone  10  temporarily cuts off power supply to it.  
           [0007]    The wireless communication operation of the mobile phone  10  describes as follows. If the band corresponding to the RF circuit  22 A is in use, the RF circuit  22 B is turned off. Sound from the user is received by the microphone  36 , transformed into audio signal  42 , and then transmitted to the baseband circuit  18 . The baseband circuit  18  encodes, modulates the audio signal  42 , and performs other necessary signal processes, so as to generate a communication signal  44 A. Then the signal  44 A is transmitted to a power controller  28 A where it is up converted to the correct frequency and the power level is adjusted to meet the communication requirement. The adjusted communication signal  46 A is sent to the duplexer  32 A by way of the isolator  30 A for ensuring the power from the power controller  28 A to the duplexer  32 A rather than from the duplexer  32 A, where the isolator  30 A can greatly reduce the power reflected from the duplexer  32 A for preventing from breaking the power controller  28 A. The communication signal  46 A is transmitted to the matching circuit  26 A, and then to the antenna  20 , where it is wirelessly broadcasted. In this way, the owner can broadcast desired message to a wireless network through the mobile phone  10 . Similarly, messages from the wireless network can be received by the antenna  20  of the mobile phone  10 , and then be passed through the matching circuit  26  and the diplexer  24  to the RF circuit  40 . The diplexer  24  functions similarly as a filter, capable of filtering of various RF band signals, and delivering these signals to corresponding RF circuits. For instance, suppose that the RF circuits  22 A,  22 B are respectively operated in 1900 MHz, 900 MHz, after receiving the signal from the antenna  20  by way of the matching circuit  26 , the diplexer  24  filters off the signals within 1900 MHz and sends them to the RF circuit  22 A. Meanwhile, the duplexer  24  filters off the signals within 900 MHz and sends them to the RF circuit  22 B. A signal received by the RF circuit  22 A is passed to the receiving circuit  34 A through the duplexer  32 A, and then transmitted to the baseband circuit  18  for modulating, decoding, or signal processing so as to generate the corresponding sound signal  43  capable of being transformed into sound waves which can be played by the speaker  38 . In this way, the mobile phone  10  can receive messages from network. Note that the duplexer  32 A is similarly functioned as a filter as well. Although the RF circuit  22 A is operated under the band of 1900 MHz, the signal emitted from the antenna  20  to the wireless network is substantially in the range of 1850 MHz and 1910 MHz. The signal sent back from the wireless network and received by the antenna  20  is substantially in the range of 1930 MHz and 1990 MHz. Hence, the 1930 MHz-to-1990 MHz signal can be filtered off by the duplexer  32 A as the received signal  49 A and be passed to the receiving circuit  34 A.  
           [0008]    Similarly, if the RF circuit  22 B is operated under the corresponding band, the RF circuit  22 A stops operating. The user&#39;s message will pass the microphone  36 , the baseband circuit  18 , the RF circuit  22 B, the power controller  28 B, the isolator  30 B, the duplexer  32 B, the diplexer  24 , the matching circuit  26 , and the antenna  20 , and is wirelessly sent to the network. The received signal from the wireless network with the corresponding band, received by the antenna  20 , will pass the matching circuit  26 , the diplexer  24 , the duplexer  32 B, the receiving circuit  34 B, and the baseband circuit  18 , and will be played by the microphone  36 . Although the RF circuit  22 B is operated under the band of 900 MHz, the signal emitted from the antenna  20  to the wireless network is substantially in the range of 824 MHz to 849 MHz. The signal sent back from the wireless network and received by the antenna  20  is substantially in the range of 869 MHz to 894 MHz. Hence, the 869 MHz-to-894 MHz signal can be filtered off by the duplexer  32 B as the received signal  49 A and be passed to the receiving circuit  34 B.  
           [0009]    For the RF circuit  40  of the conventional mobile phone  10 , in general, the matching circuit  26  is composed of passive components such as resistors, capacitors, and inductors. The phase between voltage and current can be changed and the output power is likely to be reduced when the signal is passing through the matching circuit  26 . The field pattern of the transmitting signal, especially the near field, emitted from the antenna  20  changes as the phase between the voltage and the current changes. For this reason, the field pattern of the transmitting signal from the antenna  20  changes with the component parameters (e.g. a resistance, a capacitance, an inductance) of the matching circuit  26 . From FIG. 2 and the above description, no matter which band is in use, the signal has to pass the same matching circuit  26 . In other words, the same matching circuit need to be optimized for all frequency bands in use. However, different frequencies may require different matching circuits for optimal performance. This will result in a trouble of the design of antenna matching circuit. For example, while the RF circuit  22 A is operating, the gain of the antenna pattern is probably so large that the power of the wireless signal transmitting from the antenna  20  is too strong. Modifying the matching circuit  26  to reduce the antenna gain pattern for RF circuit  22 A may result in a lower or higher than expected gain pattern for RF circuit  22 B. Too lower gain may degrade the quality communication, and too higher gain may lead to a violation of government regulations (eg. FCC regulations). Similarly, for the conventional mobile phone  10 , no matter which band is in use, the received or the transmitted signal has to pass the same matching circuit  26  and the antenna gain pattern of the received and transmitted signals may be affected simultaneously.  
           [0010]    [0010]FIG. 3 shows a block diagram of another conventional mobile phone  50 . The mobile phone  50  can be a typical GSM (Global System for Mobile communication)/DCS dual-band mobile phone, which is operated at the GSM 900 MHz and DCS 1800 MHz. For simplicity, the identical labeled components of the mobile phone  50  and those of the mobile phone  10  have the same function. The mobile phone  50  also comprises a microphone  36 , a baseband circuit  18 , a processor  16 , an input device  12 , a monitor  14 , an antenna  20 , and a matching circuit  26 . The RF portion  45  comprises two RF circuits,  52 A and  52 B. Each circuit can transceive RF signals in different frequency bands. The two RF circuits also have power controllers  28 A,  28 B and receiving circuits  34 A,  34 B. The switch  56  is similar to the diplexer  24  shown in FIG. 2, which is used for transmitting and receiving signals from the antenna  20  to either the RF circuit  52 A or the RF circuit  52 B based on the band selected. The switches  54 A,  54 B within RF circuit  52 A,  52 B are similar to the duplexers  32 A,  32 B shown in FIG. 2. In the case of transmitting signals, sound waves are transformed into electrical signals by the microphone  36 , and then the electrical signal is coded, modulated, and processed by the baseband circuit  18 . If operated at the frequency band corresponding to the RF circuit  52 B, the processed signal will pass through the power controller  28 B, the switch  54 B, the switch  56 , the matching circuit  26  and then finally be transmitted to the wireless network via the antenna  20 . Alternately, in the case of receiving signal, the signal received by the antenna  20  will pass through the matching circuit  26 , the switch  56 , the switch  54 B, the receiving circuit  34 B, baseband circuit  18  and is finally played by the speaker  38 . However, the different transceived signals in different bands have to pass the identical matching circuit  26 . Thus the field pattern for each transceived signal can not be individually adjusted and this phone will have the same disadvantage as the mobile phone  10 .  
         SUMMARY OF INVENTION  
         [0011]    It is therefore a primary objective of the present invention to provide a mobile phone and a related method to solve the problem mentioned above.  
           [0012]    To summarize briefly, the claimed invention provides a mobile phone comprising of independent matching circuits to individually adjust the antenna gain patterns of the transceived signals in different frequency bands. In this way, the mobile phone can be optimized to meet various requirements, which can not only keep good communication quality, but also reduce unwanted transmitted electromagnetic power.  
           [0013]    These claimed inventions will become obvious after reading the following detailed description of the invention, which is illustrated in various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0014]    [0014]FIG. 1 is a schematic diagram of a conventional dual-band mobile phone according to a prior art.  
         [0015]    [0015]FIG. 2 is a block diagram of the conventional dual-band mobile phone.  
         [0016]    [0016]FIG. 3 shows a block diagram of another conventional mobile phone.  
         [0017]    [0017]FIG. 4 shows a block diagram of a first embodiment of dual-band mobile phone according to the present invention.  
         [0018]    [0018]FIG. 5 shows a block diagram of a second embodiment of dual-band mobile phone according to the present invention.  
         [0019]    [0019]FIG. 6 shows a block diagram of a third embodiment of dual-band mobile phone according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]    Please refer to FIG. 4, which shows a block diagram of a first embodiment of dual-band mobile phone  60 . The mobile phone  60  can be a CDMA/AMPS/PCS dual-band, tri-mode mobile phone. The mobile phone  60  comprises a baseband circuit  68 , an RF circuit  90 , an antenna  70 , a microphone  86 , a speaker  88 , an input device  62 , and a monitor  64 . The baseband circuit  68  has a processor  66  for controlling operation of the mobile phone  60 . The user inputs control instruments to the processor  66 , which is displayed on the monitor  64  such as an LCD for showing the operation state of the mobile phone  60 . The mobile phone  60  has an RF circuit  72 A for cellular CDMA/AMPS mode and an RF circuit  72 B for PCS mode. Within the RF circuit  72 A,  72 B, power controllers  78 A,  78 B, isolators  80 A,  80 B, receiving circuits  84 A,  84 B, a diplexer  74 , and duplexers  82 A,  82 B are identically functioned as the power controllers  28 A,  28 B, the isolators  30 A,  30 B, the receiving circuits  34 A,  34 B, the diplexer  24 , and the duplexers  32 A,  32 B.  
         [0021]    The difference between the present invention and the prior art is that independent matching circuits are individually implemented to adjust the field patterns of the corresponding transceived signals. As shown in FIG. 4, within the RF circuits  72 A,  72 B, the matching circuits  77 A,  76 A, 77 B, and  76 B are implemented to adjust field patterns of signals in cellular Rx, cellular Tx, PCS Rx, and PCS Tx bands, respectively. For example, when operating under the frequency band corresponding to the RF circuit  72 A, the microphone  86  transforms the received sound sent out by the user into audio signal  92 . The audio signal  92  is transformed into communication signal  94 A through the baseband circuit  68 . Meanwhile, the RF circuit  72 B is suspended. The power controller  78 A will adjust the power of the communication signal  94 A into communication signal  96 A. The matching circuit  76 A adjusts the phase and amplitude of the current and voltage of the communication signal  96 A to generate transmitting signal  98 A. Finally, the transmitting signal  98 A is wirelessly sent to a wireless network by the antenna  70  through the duplexer  82 A and the diplexer  74 .  
         [0022]    Alternately, wireless signal from the wireless network is received by the antenna  70  of the mobile phone  60 , and is transformed into receiving signal  99 A by way of diplexer  74 , and duplexer  82 A. The matching circuit  77 A adjusts the phase and amplitude of the current and voltage of the receiving signal  99 A to form receiving signal  99 B. The signal  99 B through the receiving circuit  84 A is processed by the baseband circuit  68  to generate audio signal  93 A that is transformed into sound waves and is played by the speaker  88 . The amplitude and phase between current and voltage are the key parameters in determining the radiation efficiency as well as the near field radiation pattern. The purpose of the matching circuit is to alter these parameters so as to optimize the antenna performance. In conventional phone designs, this matching circuit is placed between the antenna and the diplexer which can change the current and voltage at the antenna feeding point directly. However, the same purpose can be achieved with different matching circuits placed at different locations. As shown in FIG. 4, the matching circuit  76 A can be used to adjust the phase and amplitude of the transmitting current and voltage at the antenna port  70  while the matching circuit  77 A can be used to adjust the same parameters of the received signal. Because the transmitted and received signals are in different frequency bands, each signal path will have very different signal characteristics. Unlike the conventional design where single matching circuit is used to match the antenna to all frequency bands, in this invention, different matching circuits can be used to optimize the performance of the corresponding band. The same principle is suitable to the RF circuit  72 B of the mobile phone  60 .  
         [0023]    From above description, the individual matching circuits implemented on different transceiving loops are capable of adjusting the field pattern without interfering with each other. Because the matching circuit  76 A is located between the duplexer  82 A and the power controller  78 A, the equivalent impedance along the receiving loop (i.e. the loop from the duplexer  82 A to the receiving circuit  84 A) is not changed. Equivalently, the field pattern gain of the receiving loop is also not changed. In this way, on one hand, the field pattern of the transmitting loop is capable of being properly controlled for reducing the transmitting power of electromagnetic wave, on the other hand, the field pattern of the receiving loop of the antenna  70  remains to ensure the quality of signal-receiving.  
         [0024]    Similarly, the field patterns under various frequency bands are not interfered with each other. As shown in FIG. 4, the matching circuits for matching the field pattern are located between the diplexer  74  and the baseband circuit  68 . Even if either element parameter of the matching circuits is adjusted, the other matching circuits for the other bands remain the same. For example, if the field pattern of the signal-transmitting through the RF circuit  72 B is changed, due to the element parameter adjustment of the matching circuit  76 B, both the field pattern of the signal-transceiving through the RF circuit  72 A and that of the signal-receiving through the RF circuit  72 B are not changed. Therefore, the field patterns associated with various frequency bands are capable of being individually adjusted, improving the prior art defect that each field pattern of signal-transceiving is changed as the element parameter of the matching circuit is altered. Moreover, within the mobile phone  60 , the matching circuits  76 A,  76 B are located between the duplexers  82 A,  82 B and the isolators  80 A,  80 B, where the isolators  80 A,  80 B are capable of isolating the power from the matching circuit to the power controller. Hence, when the element parameter of the matching circuits  76 A,  76 B is adjusted, the matching circuit does not cause power reflection to the power controller, which probably will damage the power controller.  
         [0025]    Please refer to FIG. 5, which shows a block diagram of a second embodiment of the dual-band mobile phone  100 . For simplicity, elements that have the same function as that described in FIG. 4 are provided the same item numbers used in the above description of the mobile phone  60 . Differing from the mobile phone  60 , the mobile phone  100  constitutes the matching circuits  76 A,  76 B on the signal-transmitting loop, leaving out the matching circuits on the signal-receiving loop. As described above, the different field patterns of the signal-transmitting loops are capable of being respectively adjusted by the matching circuits  76 A,  76 B. When receiving signal under different frequency bands, the antenna  70  passively receives the radio signal and does not actively transmit electromagnetic waves, not threatening users health. Consequently, it is not necessary to adjust the field pattern of the signal-receiving, and the corresponding matching circuit can be omitted. For example, the matching circuit  76 A can consist of capacitors C 1 , C 2  and an inductor L 1 , functioning to adjust the phase and amplitude of the voltage and current. For matching the antenna, the capacitance of the capacitors C 1 , C 2  or the inductance of the inductor L 1  are adjusted.  
         [0026]    Please refer to FIG. 6, which shows a block diagram of a third embodiment of the mobile phone  110 . Similar to the mobile phone  50  shown in FIG. 3, the mobile phone  110  can be a GSM/DCS dual-band mobile phone. For simplicity, elements that have the same function as that described in FIG. 5 are provided the same item numbers used in the above description of the mobile phone  100 . The RF circuit  134  of the mobile phone  110  has two RF circuits  122 A and  122 B corresponding to two frequency bands. The two RF circuits have switches  124 A,  124 B, power controllers  108 A,  108 B, receiving circuits  114 A,  114 B, functioning as the switches  54 A,  54 B, the power controllers  28 A,  28 B, and receiving circuits  34 A,  34 B shown in FIG. 3, respectively. A switch  126  functions as the switch  56  shown in FIG. 3 for distributing signal from the antenna  70  to the two RF circuits  122 A,  122 B. Comparing with FIGS. 3 and 6, individual matching circuits  116 A,  116 B and  117 A,  117 B are constituted so as to independently adjust the field pattern of signal-transceiving, without interfering with each other.  
         [0027]    In contrast to prior art, the present invention mobile phone has independent matching circuits corresponding to different RF circuits, and is capable of individually adjusting the field pattern of the transceived signal of the mobile phone. When adjusting either matching circuit, only the field pattern of transceived signal corresponding to the adjusted matching circuit is changed, but the transceived signal corresponding to the other matching circuits remains the same. Consequently, the designer is capable of adjusting optimal field pattern depending on different transceived signal requirements, which are operated on different frequency bands. So, the mobile phone can not only keep good quality for received signal, but also adjust the transmitted electromagnetic power to the probable level at the same time. According to the present invention, the technique is employed to the single-band mobile phone as well, for adjusting the field pattern of signal-transmitting and that of signal receiving for the same frequency band. Furthermore, the present invention technique is also capable of being applied to other wireless apparatuses, which also belongs to the scope of the present invention.  
         [0028]    Those skilled in the art will readily observe that numerous modifications and alterations of the method and the device may be made while retaining the technique of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.