Abstract:
Disclosed herein are techniques, systems, and methods relating to minimizing mutual coupling between a first antenna and a second antenna.

Description:
BACKGROUND 
       [0001]    The mobile communication industry is facing the demand of high data rate (and applications, e.g. video applications) on mobile phones to compete with the data rate on wired systems. To meet the increasing demand, standards such as High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA) are being developed within the Universal Mobile Telecommunications System (UMTS) standard. However, higher date rates may necessitate better signal quality at both a mobile terminal (the mobile phone) and a base station. 
         [0002]    For a mobile terminal at an edge of a mobile communications cell, the signal quality may be limited by thermal noise, noise figure of the mobile terminal, noise figure of the base station, as well as a channel quality (fading), limiting a reliable data transfer. Further, feasible high data rates may be obtained only closer to the base station. 
         [0003]    To that end, a method to facilitate high data rates is to expand an active area for the mobile terminal. More specifically, a quantity of base stations is increased to minimize the distance between the mobile terminal and the base station. Another method to facilitate high data rates is to increase the signal quality at the mobile terminal. More specifically, a second receiver chain (diversity receiver) is employed at the mobile terminal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items. 
           [0005]      FIG. 1  is a block diagram of a tunable mutual antenna decoupling system, in a first embodiment. 
           [0006]      FIG. 2  is a block diagram of tunable mutual antenna decoupling system, in a second embodiment. 
           [0007]      FIGS. 3   a - 3   b  is a block diagram of tunable mutual antenna decoupling system, in a third and a fourth embodiment. 
           [0008]      FIG. 4  is a block diagram of tunable mutual antenna decoupling system, in a fourth embodiment. 
           [0009]      FIG. 5  is a flowchart of employing the system of  FIG. 1 , in a first implementation. 
           [0010]      FIG. 6  is a flowchart employing system of  FIG. 1 , in a further implementation. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The present application describes a tunable mutual antenna decoupling system. Many specific details are set forth in the following description and in  FIGS. 1-5  to provide a thorough understanding of various implementations. One skilled in the art will understand, however, that the subject matter described herein may have additional implementations, or that the concepts set forth may be practiced without several of the details described in the following description. More specifically, a mobile terminal may comprise at least two antennas coupled together via a tuning circuit, with the tuning circuit altering a phase and an amplitude of a signal between the two antennas by control of a control unit. 
         [0012]    System  100   
         [0013]      FIG. 1  shows an overview of a tunable mutual antenna decoupling system  100  that may be employed within a mobile terminal. System  100  comprises a receiving portion  102 , a transceiving portion  104 , a control portion  106 , and a baseband module  108 . 
         [0014]    Receiving Potion  102   
         [0015]    Receiving portion  102  of system  100  receives a signal, i.e. a radio signal via a mobile communications network. Receiving portion  102  comprises an antenna  110 , a detector module  112 , a receiver (RX) front end filter  114 , and a receiver low noise amplifier (LNA)  116 . 
         [0016]    Antenna  110  may be a planar inverted-F antenna (PIFA), however, antenna  110  may be any antenna desired. Antenna  110  may receive a signal S radio  from any mobile communications network, including but not limited to 1G, 2G, 3G, 4G, LTE, WiMax, or any future mobile communications network. Antenna  110  is connected to an input terminal  118   a  of detector module  112 . 
         [0017]    Detector module  112  receives signal S radio  and converts S radio  from a RF signal to a DC voltage signal. Detector module  112  comprises a 4 port coupler  120 , a diode  122 , and a resistor  124 . Diode  122  is connected to terminal  118   b  of coupler  120  and resistor  124  is connected to terminal  118   c  of coupler  120 . A reflected signal S 1  may be input to control portion  106  via path  126 . Diode  122  measures a reflected voltage from antenna  110  to RX front end filter  114  and produces signal S 2 . An output terminal  118   d  of detector module  112  is connected to an input terminal  128  of RX front end filter  114 . 
         [0018]    RX front end filter  114  is configured to receive signal S 2  from detector module  112 . Signal S 2  may comprises a receive portion and a transmit portion. To that end, RX front end filter  114  isolates signal S 2  such that signal S 2  comprises the receive portion. Further, RX front end filter  114  may minimize, if not prevent, interference between the receive portion and the transmit portion of signal S 2 . RX front end filter  114  filters signal S 2  such that signal S 2  may comprise a desired frequency band, defining signal S 3 . The desired frequency band of signal S 3  comprises substantially only reception signals to be received from the mobile communications network. An output terminal  130  of RX front end filter  114  is connected to an input terminal  132  of receiver LNA  116 . 
         [0019]    Receiver LNA  116  is configured to receive signal S 3  from RX front end filter  114 . Receiver LNA  116  amplifies signal S 3 , creating and outputting signal S 4 . An output terminal  134  of receiver LNA  116  is connected to an input terminal  136  of baseband module  108  and an input terminal  137  of control portion  106 , described further below. 
         [0020]    Transceiving Portion  104   
         [0021]    Transceiving portion  104  of system  100  also receives the aforementioned radio signal via the mobile communications network, and further transmits an additional signal via the mobile communications network. Transceiving portion  104  comprises an antenna  138 , duplex filters  140  and  142 , a transmitter power amplifier (PA)  144 , and a receiver LNA  146 . 
         [0022]    Analogous to antenna  110  of receiving portion  102 , antenna  138  may be a planar inverted-F antenna (PIFA), however, antenna  138  may be any antenna desired. Antenna  138  may receive the signal S radio  from any mobile communications network. In a further implementation, antenna  138  may receive a differing signal from the mobile communications network. Antenna  138  may also transmit a signal S transmit , described further below. Antenna  138  is connected to input terminal  147  of duplex filter  142 . 
         [0023]    Analogous to RX front end filter  114 , duplex filter  140  is configured to receive signal S radio  from antenna  138 . Signal S radio  may comprise a receive portion and a transmit portion. To that end, duplex filter  140  isolates signal S radio  such that signal S radio  comprises the receive portion. Further, duplex filter  140  may minimize, if not prevent, interference between the receive portion and the transmit portion of signal S radio . Duplex filter  140  filters signal S radio  such that signal S radio  may comprise a desired frequency band, defining signal S 4 . The desired frequency band of signal S 4  comprises substantially only reception signals to be received from the mobile communications network. An output terminal  148  of duplex filter  140  is connected to an input terminal  150  of receiver LNA  146 . 
         [0024]    Receiver LNA  146  is configured to receive signal S 4  from duplex filter  140 . Receiver LNA  146  amplifies signal S 4 , creating and outputting signal S 5 . An output terminal  152  of receiver LNA  146  is connected to an input terminal  154  of baseband module  108  and an input terminal  156  of control portion  106 , described further below. 
         [0025]    An input terminal  158  of transmitter PA  144  is connected to an output terminal  160  of baseband module  108 . Transmitter PA  144  is configured to receive a signal S 6  from baseband module  108  and amplify the same, creating and outputting a signal S 7 . An output terminal  162  of transmitter PA  144  is connected to an input terminal  164  of duplex filter  142 . 
         [0026]    Duplex filter  142  is configured to receive signal S 7  from transmitter PA  144 . Signal S 7  may comprise a receive portion and a transmit portion. To that end, duplex filter  142  isolates signal S 7  such that signal S 7  comprises the receive portion. Further, duplex filter  142  may minimize, if not prevent, interference between the receive portion and the transmit portion of signal S 7 . Duplex filter  142  filters signal S 7  such that signal S 7  may comprise a desired frequency band, defining signal S transmit . The desired frequency band of signal S transmit  comprises substantially only transmission signals to be transmitted to the mobile communications network. An output terminal  166  of duplex filter  142  is connected to antenna  138 . Antenna  138  may transmit signal S transmit  to the mobile communications network. 
         [0027]    In a further embodiment, system  100  may comprise more than two antennas. 
         [0028]    Mutual Coupling of Antennas  110  and  138   
         [0029]    Antennas  110  and  138  may be located physically proximate to one another within system  100 . Upon excitation of either (or both) of antennas  110  and  138 , energy may be transferred from antenna  110  to antenna  138  (or from antenna  138  to antenna  110 ). As such, antennas  110  and  138  may be mutually coupled. However, a low mutual coupling between antennas  110  and  132  may be desired, i.e. antenna isolation may be desired. A low mutual coupling may lead to at least 1) optimized diversity gain of antennas  110  and  138 ; 2) low absorption of transmitted power in antennas  110  and  138 ; and 3) optimal filter requirements of signal S transmit . 
         [0030]    Further, the mutual coupling between antennas  110  and  138  may further be altered dynamically as a result of user interference. More specifically, either (or both) of antennas  110  and  138  may be covered (partially or fully) by a user using the mobile terminal, and thus, result in signal loss. Further, a position (free-space, talk, on table, etc.) of system  100 , and specifically antennas  110  and  138 , may alter the mutual coupling thereof. 
         [0031]    To that end, to minimize, if not prevent, the mutual coupling between antennas  110  and  138 , antennas  110  and  138  may be coupled to one another via a tuning strip  168  and a tuning module  170 , described further below. 
         [0032]    Control Portion  106   
         [0033]    Control portion  106  of system  100  controls a mutual coupling between antennas  110  and  138 . Control portion  106  comprises the tuning module  170  and a control module  172 . 
         [0034]    Tuning module  170  is connected to antenna  110  via tuning strip  168   a  and is further connected to antenna  138  via tuning strip  168   b.  More specifically, an output terminal  174  of tuning module  170  is connected to antenna  110  via tuning strip  168   a  and an output terminal  176  of tuning module  160  is connected to antenna  138  via tuning strip  168   b.  In a further implementation, as shown in  FIG. 2 , tuning strips  168  may be connected to metal plates  202  of antennas  110  and  138 . In still a further implementation, as shown in  FIG. 3   a,  tuning strips  168  may be connected to feeding ports  302  of antennas  110  and  138 . In still a further implementation, as shown in  FIG. 3   b,  tuning strips  168  may be connected to a ground plane  304  of antennas  110  and  138 . 
         [0035]    To that end, a signal S 9  may be transmitted between antennas  110  and  138 . At a specific frequency (or frequency band) that antennas  110  and  138  receive signal S radio , signal S 9  may minimize, if not prevent, the mutual coupling between antennas  110  and  138  and further provide an improved antenna isolation in a frequency range (single band) around the specific frequency. 
         [0036]    Furthermore, to minimize, if not prevent, mutual coupling between antennas  110  and  138  for a plurality of frequency bands (multi band) that antennas  110  and  138  may receive signal S radio , tuning module  160  may dynamically alter a phase and an amplitude of signal S 9 , described further below. Also, as mentioned above, user interference may alter the mutual coupling between antennas  110  and  138 . As a result, tuning module  160  also alters the phase and amplitude of signal S 9  in relation to user interference and positional changes of system  100 . 
         [0037]    Control module  172  facilitates minimizing, if not preventing, mutual coupling between antennas  110  and  138  by controlling tuning module  170 . An output terminal  178  of control module  172  is connected to an input terminal  180  of tuning module  170  and is configured to receive a signal S 10  from control module  172 . Control module  172  determines signal S 10  based upon multiple parameters from baseband module  108  and a received signal strength indication (RSSI) parameter from receiver LNAs  116  and  146 , described further below. 
         [0038]    Baseband Module  108   
         [0039]    Baseband module  108  determines a plurality of parameters that control module  172  employs to determine signal S 10  (and ultimately, signal S 9 ). More specifically, baseband module  108  comprises parameters modules  182 , such as a bit error rate (BER) module  182   a,  a power control module  182   b,  a forward power module  182   c,  a reflected power module  182   d,  a use module  182   e,  a sensor module  182   f,  and a current consumption module  182   g.    
         [0040]    The details of parameter modules  182  of baseband module  108  are as follows:
       BER module  182   a  determines a lowest possible BER.   The power level required to obtain a desired performance in the uplink by the mobile terminal is sent by the mobile communications network. As such, power control module  182   b  determines a minimum power control level feedback from the mobile communications network.   The decoupling of antennas  110  and  138  may be optimized for minimum transmission power at either antenna  110  or  138  (or both). If power at a detector is coming from the transmission or other sources, the forward power may be measured with a directional coupler and a detector at forward power module  182   c.      The reflected power module  182   d  detects if either antenna  110  or  138  (or both) is detuned. The reflected power module  182   d  may comprise a directional coupler (not shown) and a detector (not shown).   The use module  182   e  determines an influence of user interaction and provides statistical data such as a position of the user&#39;s hands and/or head.   The sensor module  182   f  provides data via sensors on a casing of the mobile terminal of user interaction.   The current consumption module  182   g  minimizes the current consumption, and in particular, the current consumption of receiver LNA  116  and  146  and transmitter PA  144 . The current consumption of transmitter PA  144  is dependent upon the load at transmitter PA  144 .       
 
         [0048]    Each of modules  182   a - g  comprise an output terminal  184   a - g,  respectively. Further, an input terminal  186   a - g  of control module  172  is connected to an output terminal  184   a - g,  respectively, of modules  182   a - g.  As a result, the control parameters determined by modules  182   a - g  are communicated to control module  172 . For simplicity of illustration, only output terminal  184   e  and input terminal  186   e  are labeled. 
         [0049]    RSSI Signal 
         [0050]    As mentioned above, control module  172  also determines signal S 10  based upon a received signal strength indication (RSSI) parameter from receiver LNAs  116  and  146 . Also, as mentioned, the output terminal  134  of receiver LNA  116  is connected to the input terminal  138  of control portion  106  (i.e. control module  172 ) and the output terminal  152  of receiver LNA  146  is connected to an input terminal  156  of control portion  106  (i.e. control module  172 ). 
         [0051]    The RSSI parameter is optimized if a magnitude of S radio  is below a certain threshold. This control parameter is communicated to control module  164 . 
         [0052]    Tuning of Tuning Module  170   
         [0053]    As mentioned above, control module  172  determines signal S 10  based upon multiple parameters from parameter modules  182  of baseband module  108  and a received signal strength indication (RSSI) parameter from receivers  116  and  146 . Based upon these parameters, control module  172  tunes tuning module  170  via signal S 10  such that signal S 9  communicated to antennas  110  and  138  via tuning module  170  results in minimizing, if not preventing, a mutual coupling between antennas  110  and  138 . More specifically, control module  172  tunes tuning module  170  via signal S 10  to alter phase and amplitude of signal S 9  such that the phase and the amplitude of signal S 9  communicated to antennas  110  and  138  via tuning module  170  results in minimizing, if not preventing, a mutual coupling between antennas  110  and  138 . 
         [0054]    The tuning of tuning module  170  may be done iteratively for each parameter, wherein each parameter may be weighted according to an importance, depending on the application desired. Further, signal S 10  may comprise a product of the weighted parameters. 
         [0055]    System  400   
         [0056]      FIG. 4  shows an additional implementation of a tunable mutual antenna system  400 . System  400  comprises transceiving portions  402  and  404 , control portion  406 , and baseband module  408 . 
         [0057]    Transceiving Portion  402   
         [0058]    Portions of transceiving portion  402  are analogous to receiving portion  102  mentioned above with respect to  FIG. 1 . More specifically, antenna  410 , detector module  412 , duplex filter  414 , and receiver PA  416  are analogous to antenna  110 , detector module  112 , RX front end filter  114 , and receiver LNA  116 , respectively, of  FIG. 1 . As such, any reference to any portion of the analogous portions of receiving portion  102  may be applied analogous to the corresponding portion of transceiving portion  402 . However, detector module  412  differs slightly from detector module  112 . More specifically, detector module  412  comprises an additional diode  416  in place of resistor  124 . Further, an additional reflected signal S 1 , may be input to control portion  106  via path  418 . 
         [0059]    Further, transceiving portion  402  comprises a tuning module  420 , an additional duplex filter  422 , and a transmitter PA  424 . 
         [0060]    Transmitter PA  424  and Additional Duplex Filter  422   
         [0061]    An input terminal  426  of transmitter PA  424  is connected to an output terminal  428  of baseband module  408 . Transmitter PA  424  is configured to receive a signal S 11  from baseband module  408  and amplify the same, creating and outputting a signal S 12 . An output terminal  430  of transmitter PA  424  is connected to an input terminal  432  of duplex filter  422 . 
         [0062]    Analogous to duplex filters  414 , duplex filter  422  is configured to receive signal S 11  from transmitter PA  424 . Signal S 11  may comprise a receive portion and a transmit portion. To that end, duplex filter  422  isolates signal S 11  such that signal S 11  comprises the transmit portion. Further, duplex filter  422  may minimize, if not prevent, interference between the receive portion and the transmit portion of signal S 11 . Duplex filter  422  filters signal S 11  such that signal S 11  may comprise a desired frequency band, defining signal S 12 . The desired frequency band of signal S 12  comprises substantially only transmission signals to be transmitted to the mobile communications network. An output terminal  434  of duplex filter  422  is connected to detector module  412 . 
         [0063]    Tuning Module  420   
         [0064]    Tuning module  420  tunes a frequency band that antenna  410  may receive signals via the mobile communications network. An input terminal  436  of tuning module  420  is connected to an output terminal  438  of control portion  406 . Tuning module  420  is configured to receive a signal S 13  from control portion  406 , described further below. 
         [0065]    In an implementation, tuning module  420  comprises switches combined with a single or multiple capacitors and/or inductors (e.g. a capacitor bank, an inductor bank, and a capacitor &amp; inductor bank). By employing RF switches, the tuning of tuning module  420  is in discrete steps (e.g. 4 elements in the bank allow 4 bit control). The types of switches include, but are not limited to, RF MEMS (ohmic and/or capacitive), pin diodes, transistor, silicon on sapphire, PHEMT, and MESFET. The capacitors may be discrete SMD type capacitors and/or a combination of thin film capacitors. The values of the capacitors may be controlled by an analog voltage, i.e. controlled by a diode, varactor, dielectric based material, RF MEMS based capacitors. 
         [0066]    Transceiving Portion  404   
         [0067]    Transceiving portion  404  is analogous to transceiving portion  402 . As such, any reference to any portion of transceiving portion  402  may be applied analogous to the corresponding portion of transceiving portion  404 . In an example, antenna  440 , tuning circuit  442 , detector module  444 , duplex filters  446  and  448 , receiver PA  450 , and transmitter PA  452  is analogous to antenna  410 , tuning circuit  420 , detector module  412 , duplex filters  414  and  422 , receiver PA  424 , and transmitter  416 , respectively. 
         [0068]    Control Portion  406   
         [0069]    Control portion  406  is analogous to control portion  106  of  FIG. 1 . More specifically, control module  454  and tuning module  456  are analogous to control module  172  and tuning module  170  of  FIG. 1 , respectively. 
         [0070]    Further, control module  454  controls a tuning of tuning module modules  436  and  442  via signal S 13 . More specifically, control module  454  controls tuning modules  420  and  442  such that tuning modules  420  and  442  alter a frequency band which antennas  410  and  440  receive signals from the mobile communications network. In an example, control modules  454  controls tuning modules  420  and  442  such that tuning modules  420  and  442  alter the frequency band of antennas  410  and  440  such that antennas  410  and  442  receive a signal at substantially the same frequency. 
         [0071]    Baseband Module  408   
         [0072]    Baseband Module  408  is analogous to baseband module  108  of  FIG. 1 . More specifically, parameter modules  458  are analogous to parameter modules  182  of  FIG. 1 . 
         [0073]    Process Model  500   
         [0074]      FIG. 5  shows a method  500  of employing system  100 . The process  500  is illustrated as a collection of referenced acts arranged in a logical flow graph, which represent a sequence that can be implemented in hardware, software, or a combination thereof. The order in which the acts are described is not intended to be construed as a limitation, and any number of the described acts can be combined in other orders and/or in parallel to implement the process. 
         [0075]    At step  502 , BER module  182   a  determines a lowest possible BER. 
         [0076]    At step  504 , power control module  182   b  determines a minimum power control level feedback from the mobile communications network 
         [0077]    At step  506 , forward power module  182   c  measures the forward power. 
         [0078]    At step  508 , reflected module  182   d  detects if either antenna  110  or  138  (or both) is detuned. 
         [0079]    At step  510 , use module  182   e  determines an influence of user interaction and provides statistical data such as a position of the user&#39;s hands and/or head. 
         [0080]    At step  512 , sensor module  182   f  provides data via sensors on a casing of the mobile terminal of user interaction. 
         [0081]    At step  514 , current consumption module  182   g  minimizes the current consumption, and in particular, the current consumption of receiver LNA  116  and  146  and transmitter PA  144 . 
         [0082]    At step  516 , a received signal strength of S radio  is determined. 
         [0083]    At step  518 , parameter modules  182  communicate the control parameters to control module  172 . 
         [0084]    At step  520 , control module  172  determines signal S 10  based upon the multiple parameters from parameter modules  182  of baseband module  108  and a received signal strength indication (RSSI) parameter from receiver PAs  116  and  146 . 
         [0085]    At step  522 , control module  172  tunes tuning module  170  via signal S 10  such that the phase and the amplitude of signal S 9  communicated to antennas  110  and  138  via tuning module  170  result in minimizing, if not preventing, a mutual coupling between antennas  110  and  138 . 
         [0086]    At step  524 , it is determined if a coupling level between antennas  110  and  138  is acceptable and/or desirable. If the coupling level between antennas  110  and  138  is acceptable and/or desirable, the process is ended at step  526 . If the coupling level between antennas  110  and  138  is not acceptable and/or desirable, process  500  is repeated iteratively until the coupling level between antennas  110  and  138  is acceptable and/or desirable. 
         [0087]    Process Model  600   
         [0088]      FIG. 6  shows a method  600  of employing system  100 . The process  600  is illustrated as a collection of referenced acts arranged in a logical flow graph, which represent a sequence that can be implemented in hardware, software, or a combination thereof. The order in which the acts are described is not intended to be construed as a limitation, and any number of the described acts can be combined in other orders and/or in parallel to implement the process. Further,  FIG. 6  references elements of  FIG. 1 . 
         [0089]    At step  602 , antenna  110  is coupled to antenna  138 . 
         [0090]    At step  604 , antenna  110  receives signal S radio . 
         [0091]    At step  606 , a phase and an amplitude of signal S 9  (control signal) is altered. 
         [0092]    At step  608 , a plurality of parameters from parameter modules  182  is determined to affect the phase and the amplitude of signal S 9  such that a mutual coupling between antenna  110  and antenna  138  is minimized. 
       CONCLUSION 
       [0093]    Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claims.