Abstract:
A ABSTRACT electronic device having multiple antennas and capable of operating in a wireless communication system, where interference between the multiple antennas is minimized using a detuning circuit activated by one or more antennas and resulting in detuning of at least one of the antennas. Activation of the detuning circuit can be accomplished by positioning an antenna to complete the detuning circuit and thereby activate the detuning circuit.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an electronic device having multiple antennas and, more particularly to an electronic device for reducing interference between the multiple antennas by engaging a decoupling electronic circuit for the electronic device operable in a wireless communication system.  
         BACKGROUND OF THE INVENTION  
         [0002]    A communication system is operable to communicate information between a transmitting station, also referred to as a calling party, and a receiving station, also referred to as a receiving or called party, by way of a communication network. Operation of a wireless communication system transfers information between the transmitting and receiving stations via one or more base stations. These transmitting and receiving stations are also known as wireless communication devices, cell phones or mobile phones, Personal Digital Assistants (PDA&#39;s), or portable computers. As the capability and sophistication of the wireless communication system has increased, the demand for mobile communication devices having at least two antennas has proliferated. Previous mobile communication devices having multiple antennas utilize an electrical or mechanical switch to provide an RF signal to one of the multiple antennas, thereby providing an active antenna. However, the non-active antennas on the mobile communication device can degrade the performance of the active antenna. Among the concerns for locating multiple antennas within a limited space of a mobile communication device is the interference, or coupling between the antennas. Typical solutions include greater separation between the antennas to minimize the interference. Consequently, the relatively small dimensions of the mobile communication device restricts the available separation of the antennas. It would be useful to provide decoupling, also called detuning, or changing resonant frequency, of multiple antennas of a mobile communication device, while achieving sufficient gain and impedance matching of the antennas.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention encompasses an electronic device having multiple antennas detuned to minimize interference and operable in a wireless communication system, where the electronic device can comprise a mobile station, a personal digital assistant (PDA) or a portable computer. The apparatus of the present invention comprises an internal antenna, an exterior antenna, and a detuning circuit to alter resonant frequency of the inactive antenna and thereby minimize interference between the antennas. Detuning circuitry may cooperate with either the interior antenna or the exterior antenna to minimize interference during operation of the electronic device. In addition, activation of the detuning circuit can be by achieved by positioning the exterior antenna to cooperate with the detuning circuit.  
           [0004]    A more complete appreciation of all the advantages and scope of the present invention can be obtained from the accompanying drawings, the following detailed description of the invention and the appended claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is an illustration of a mobile station block diagram representing an embodiment of the present invention.  
         [0006]    [0006]FIG. 2 is a detuning circuit illustrating an embodiment of the present invention.  
         [0007]    [0007]FIG. 3 is a detuning circuit illustrating an alternative embodiment of the present invention.  
         [0008]    [0008]FIG. 4 is a detuning circuit illustrating an alternative embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0009]    [0009]FIG. 1 is a block diagram representing an electronic device of the present invention where a mobile station  10  can be used in conjunction with an embodiment of the present invention. Generally, the mobile station  10  includes a receiver  20 , a transmitter  22  and a controller or processor  24  that is coupled to the receiver  20  and the transmitter  22 . The receiver  20  sends incoming messages to the processor  24  for analysis, whereas outgoing or originating messages are sent from the processor  24  to the transmitter  22 . These incoming and originating messages can be in the form of a voice message, a data message or a combination of voice and data messages.  
         [0010]    User interface with the mobile station  10  can be accomplished via an input device  26  which may comprise: a Liquid Crystal Display (LCD)  28  which can contain a touch-screen display (not shown), or a Light Emitting Diode (LED) (not shown); a tone generator  30 ; a speaker  32 ; a vibrating device  34 ; and a data entry device  36 . The data entry device  36  can be an alpha-numeric keypad (not shown) and the input device  26  further contains a microphone  38  capable of capturing a voice message. In addition, a timer  40 , also known as a clock chip, can be used for synchronizing the operations of the processor  24  and tracking time, a term well known to those of ordinary skill in the art of mobile stations. The mobile station  10  also includes a storage location, illustrated in the embodiment of FIG. 1 as a memory  41 , where the memory  41  is capable of storing a plurality of constants and variables used by processor  24  in the operation of the mobile station  10 . Communication between the input device  26 , the tone generator  30  and the vibrating device  34  is assured by coupling these devices to the processor  24 .  
         [0011]    In an embodiment according to the invention, the mobile station  10  contains a first antenna  42 , a second antenna  44  and a detuning circuit  46 . The detuning circuit  46  in accordance with the invention minimizes interference between the first and second antennas,  42  and  44  respectively. The first antenna  42  and the second antenna  44  are capable of transmitting and receiving communication signals in any number of communication frequencies, for example: Global System for Mobile Communication (GSM), Personal Communication System (PCS), Global Positioning System (GPS), Bluetooth, Code Division Multiple Access (CDMA) and W-CDMA. Antennas  42  and  44  can also function as dual-band (i.e. CELL/PCS), tri-banded, quad-banded etc. antennas. An embodiment of the present invention includes the antennas  42  and  44  used as transceivers for data, voice and GPS applications.  
         [0012]    In a preferred embodiment, the first antenna  42  is a whip antenna, and the second antenna  44  is an internal antenna. An increase in performance of the antennas  42  and  44 , specifically gain and impedance matching, results when using the detuning circuit  46  to alter the resonant frequency of the antenna  42  or  44 , connected to the detuning circuit  46 .  
         [0013]    [0013]FIG. 2 illustrates an embodiment of the present invention wherein the second antenna  44  comprises an internal antenna acted upon by the detuning circuit  46 . A first digital signal  48 , also designated as control  1 , an RF feed  50  and a second digital signal  52 , also designated as control  2 , provide inputs to the detuning circuit  46 . In an embodiment of the present invention, the second digital signal  52  is the inverse of the first digital signal  48 . The detuning circuit  46  further contains a first capacitor  54 , a second capacitor  56 , a third capacitor  58 , a fourth capacitor  60 , an inductor  62 , a first switch  64 , a second switch  66  and first ground  68 . In a preferred embodiment, capacitors  54 ,  56  and  60  are DC decoupling capacitors and switches  64  and  66  can be either an FET (Field Effect Transistors) switch or a MEMS RF (Micro Electromechanical System) switch. Activation of the second antenna  44  entails closing the first switch  64 , and opening the second switch  66 . Deactivation of the second antenna  44  entails opening the first switch  64  and closing the second switch  66 , thereby engaging the inductor  62  in cooperation with the third capacitor  58  to detune the second antenna  44  by changing the resonance of the second antenna  44 .  
         [0014]    Use of the detuning circuit  46  acts to minimize interference between the first antenna  42  and the second antenna  44 .  
         [0015]    [0015]FIG. 3 illustrates another embodiment of the present invention wherein the second antenna  44  comprises an internal antenna acted upon by the detuning circuit  146 . A first digital signal  148 , also designated as control  1 , an RF feed  150  and a second digital signal  152 , also designated as control  2 , provide inputs to the detuning circuit  146 . In an embodiment of the present invention, the second digital signal  152  is the inverse of the first digital signal  148 . The detuning circuit  146  further contains a fifth capacitor  154 , a sixth capacitor  156 , a seventh capacitor  158 , an eighth capacitor  160 , a third switch  164 , a fourth switch  166  and a second ground  168 . In a preferred embodiment, capacitors  154 ,  156 ,  158  and  160  are DC decoupling capacitors and switches  164  and  166  can be either an FET (Field Effect Transistors) switch or a MEMS RF (Micro Electromechanical System) switch. Activation of the second antenna  44  entails closing the third switch  164 , and closing the fourth switch  166 . Deactivation of the second antenna  44  entails opening the third switch  164  and opening the fourth switch  166 , thereby removing the connection of the second ground  168  to the second antenna  44 . By removing the connection of the second antenna  44  to the second ground  168  the antenna  44  is described as “floating”, and thereby detuned. This detuning acts to minimize interference between the first antenna  42  and the second antenna  44 .  
         [0016]    Note that the embodiments described in FIG. 2 and FIG. 3 describe a detuning circuit,  46  and  146  respectively, acting upon the second antenna  44 , wherein switches  64  and  66  must oppose one another (i.e. when switch  64  is closed switch  66  must be open) in embodiment of FIG. 2. However, switches  164  and  166  must act in tandem (i.e. when switch  164  is closed switch  166  must be closed) in embodiment of FIG. 3. In a preferred embodiment the detuning circuits  46  and  146  are activated when the antenna  42  is manipulated to a pre-set position, such as extension of a whip antenna. In distinction to the above embodiments, FIG. 4, described below, involves decoupling the first antenna  42  to minimize interference between the first antenna  42  and the second antenna  44 .  
         [0017]    [0017]FIG. 4 illustrates another embodiment of the present invention wherein the first antenna  42  comprises an extendible whip antenna acted upon by a third detuning circuit  208 . A PCB (Printed Circuit Board)  202  contains the first antenna  42 , the second antenna  44 , a connector  204  attached to the first antenna  42 , a clip  206 , the third detuning circuit  208  and conduit  210  to connect the third detuning circuit  208  to the clip  206 . Operation of the first antenna  42  to a retracted position causes the connector  204  to communicate with the conduit  210  and engage the third detuning circuit  208 . A shunt inductor circuit forms the third detuning circuit  208  to detune the first antenna  42  and minimize interference between the first antenna  42  and the second antenna  44 .  
         [0018]    It is understood that various modifications can be made to the mobile station apparatus and method of operation and remain within the scope of the present invention. For example, the protective enclosure may comprise an external or internal antenna to assist transmission and reception of wireless signals.  
         [0019]    While preferred embodiments have been discussed and illustrated above, the present invention is not limited to these descriptions or illustrations, and includes all such modifications, which fall within the scope of the invention and claim language presented below.