Abstract:
An antenna with proximity sensor function is disclosed, the antenna includes at least one parasitic element coupled to a filter circuit and a proximity sensing circuit for sensing a load on the parasitic element to determine load capacitive loading characteristics for sensing user leading of the device. By sensing the user loading or mode of the device, the antenna can be reconfigured with beam steering or frequency shifting adjustments.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of priority with U.S. Provisional Ser. No. 61/682,145, filed Aug. 10, 2012. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to antennas for use in wireless communications; and more particularly, to an antenna with proximity sensor function. 
         [0004]    2. Description of the Related Art 
         [0005]    Proximity sensors are in use in commercial wireless devices as well as other product groups, and are used for a wide variety of applications. For example, it is common for a proximity sensor to be integrated into a cell phone, with the proximity sensor used to sense when the display region of the cell phone is in close proximity to an object. This sensing of an object close to the display is used to reduce battery power consumption by turning off or down the brightness of the display when the display is in close proximity to a user&#39;s head or the display is covered by an object. Another application of a proximity sensor is to integrate the sensor into a Tablet computing device and use the sensor to sense proximity of the user&#39;s body to the Tablet. When the user&#39;s body is close to the Tablet, the transmit power of the cellular transceiver is reduced to allow the Tablet to meet requirements for specific absorption rate (SAR). 
         [0006]    One implementation of a proximity sensor is a capacitive sensor, and is effectively a parallel plate capacitor. A dielectric material is positioned between the two plates to provide support and maintain a set separation distance between the plates. Two conductors are used to connect the two plates to a circuit that monitors capacitance. As objects are placed in proximity to the capacitor the objects interact with the fringing electric field emanating from the region between and external to the plates. This interference with the fringing fields of the capacitor translates into a change in capacitance. 
         [0007]    Multiple proximity sensors can be integrated into a device and used to provide more information on the environment and changes to the environment. Multiple problems arise in integrating proximity sensors into a device such as finding volume for the proximity sensors, incurring the cost of the sensors, and positioning the sensors at locations that are desirable, such as close to the antenna system. 
       SUMMARY OF THE INVENTION 
       [0008]    An antenna with proximity sensor function is disclosed, the antenna includes at least one parasitic element coupled to a filter circuit and a proximity sensing circuit for sensing a load on the parasitic element to determine capacitive loading characteristics for sensing user loading of the device. By sensing the user loading, or mode of the device, the antenna can be reconfigured with beam steering or frequency shifting adjustments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows an antenna with proximity sensor function in accordance with an embodiment. 
           [0010]      FIG. 2  shows an active modal antenna with n parasitic elements and proximity sensors in accordance with another embodiment. 
           [0011]      FIG. 3  shows an antenna with proximity sensor function in accordance with another embodiment. 
           [0012]      FIG. 4  shows an antenna with proximity sensor function, the antenna includes a parasitic element positioned within the antenna volume and configured for frequency shifting, and capacitors implemented to isolate the parasitic element at frequencies from the ground plane. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    A proximity sensor can be positioned beside or beneath an antenna and the antenna can be re-tuned to compensate for the effect of placing the metal conductors near the antenna. A more efficient method in terms of maintaining antenna performance, reducing volume required, and saving cost is to design the proximity sensor into the antenna structure. This combination antenna and proximity sensor provides a more optimized and cost effective solution for devices that require antennas and proximity sensing systems. More importantly, by designing the proximity sensor, or multiple proximity sensors into the antenna, the ability to detect changes to the environment in the region of the antenna can be improved. Sensing when objects are in close proximity to an antenna can be used to assist in re-tuning the antenna and keeping the antenna impedance optimized. 
         [0014]    In certain embodiments a parasitic element is positioned beneath a radiating antenna element, with this parasitic element used to shift the frequency response of the antenna. A second active antenna topology developed consists of a parasitic element positioned in close proximity but outside of the volume of the main antenna, with this “offset” parasitic element used to alter the radiation mode, and in turn the pattern characteristics of the main antenna. These modal antennas are capable of beam-steering and band-switching and are further described in U.S. Ser. No. 13/726,477, filed Dec. 24, 2012; which is related to U.S. Pat. No. 8,362,962, issued Jan. 29, 2013; and U.S. Pat. No. 7,911,402, issued Mar. 22, 2011; each of which are commonly owned and their contents are hereby incorporated by reference. The parasitic elements described in these examples can also be used as a proximity sensor. The parasitic element can be coupled using a filter circuit to separate the high frequency RF component at the frequency of operation of the antenna from the low frequency signal required for the proximity sensing function. The parasitic element can be designed to operate as a proximity sensor by using blocking capacitors to isolate the parasitic element from ground at DC and present a high impedance at the lower frequencies used for proximity sensing. 
         [0015]    In one embodiment, an antenna element is coupled to a ground plane with a parasitic element beneath the antenna element. The parasitic element is configured to shift the frequency response of the antenna when a reactive load or change in reactance is applied to the parasitic element at the junction of the parasitic element and the ground plane, or at locations along the parasitic element. A filtering circuit is coupled to the parasitic element, with the filtering circuit connecting the parasitic element to a proximity sensing circuit. 
         [0016]    In an embodiment, two or more parasitic elements are positioned beneath the antenna element, and one or more of the parasitic elements is connected to a filtering circuit which in turn is connected to a proximity sensing circuit. 
         [0017]    In another embodiment, an antenna element is coupled to a ground plane with a parasitic element positioned in close proximity to the antenna element. The parasitic element is configured to alter the radiation mode of the antenna, which in turn will alter the radiation pattern characteristics of the antenna. The radiation mode is altered when a reactive load or change in reactance is applied to the parasitic element at the junction of the parasitic element and the ground plane, or at locations along the parasitic element. A filtering circuit is coupled to the parasitic element, with the filtering circuit connecting the parasitic element to a proximity sensing circuit. 
         [0018]    In another embodiment, an antenna is positioned in proximity to a ground plane wherein the antenna is not connected to the ground plane. A filtering circuit is coupled to the antenna, with the filtering circuit connecting the antenna to a proximity sensing circuit. The antenna can be used for transmission and/or receiving RF signals and the antenna structure acts as a proximity sensor. 
         [0019]    In yet another embodiment, an antenna is provided wherein conductors are attached at multiple locations; with these conductors coupled to one or more filter circuits to couple the conductors to a proximity sensing circuit. 
         [0020]    Now turning to the drawings,  FIG. 1  shows an antenna with proximity sensor function in accordance with an embodiment. The antenna is implemented as an active modal antenna described above, having an antenna radiator  102  positioned above a ground plane  101  forming an antenna volume therebetween. A parasitic element  103  is positioned within the antenna volume. The parasitic element  103  is coupled to an antenna tuning module (ATM)  108  and a filter circuit  105 . The ATM  108  comprises a switch  109  and one or more tunable components including tunable capacitors  110 , tunable inductors, or tunable phase shifters. The ATM is further coupled to a baseband processor  111  or a separate processor with an algorithm  112  for controlling the parasitic element  103 . The filter circuit  105  is coupled to a proximity sensing circuit  106  and algorithm  107  for sensing capacitive load on the parasitic element as a mechanism for sensing proximity of user extremities. 
         [0021]      FIG. 2  shows an active modal antenna with n parasitic elements and proximity sensors in accordance with another embodiment. This embodiment is similar to  FIG. 1  having an antenna radiator  202  positioned above a ground plane  201 , and first parasitic element  203   a  adjacent to the antenna radiator, but with the additional parasitic elements  203   b;    203   c;  and  203   n , respectively. One parasitic element is shown within the antenna volume, and three additional parasitic elements are shown as positioned outside of the antenna volume. Each parasitic element is coupled to a distinct ATM  208   a;    208   b;    208   c;  and  208   n,  and each of the ATM&#39;s are further coupled to the baseband  211  or other processor having an algorithm  212  for controlling the parasitic element function. Each ATM is further coupled to the filter circuit  205 , which incorporates a proximity sensing circuit  206  and an algorithm  207  for sensing capacitive load on the parasitic element as a mechanism for sensing proximity of user extremities. As in the example of  FIG.1 , each of the ATMs  208 ( a, b, c . . . n ) individually comprises a switch  209 ( a, b, c . . . n ) and one or more tunable components including tunable capacitors  210 ( a, b, c . . . n ), tunable inductors, or tunable phase shifters. The tunable components and baseband control signals are coupled to a parasitic element through a respective switch within the ATM. 
         [0022]      FIG. 3  shows an antenna with proximity sensor function in accordance with another embodiment. Here, first parasitic element  303  and ATM  308  are positioned beneath an antenna element  302  and within the antenna volume, as above, and a second parasitic element is positioned outside of the antenna volume. The second parasitic element comprises a plurality of portions, including a first portion  316  and a second portion  318 , the first portion  316  is coupled to the ground plane at a first switch  317   a,  and the second portion  318  is isolated from the ground plane. Multiple portions can be integrated into the second parasitic for additional control; however, three portions are shown here, each portion coupled to the ground plane at a distinct switch ( 317   a;    317   b;    317   c ), and the terminal end of the second parasitic element  318  is isolated from the ground plane  301 . Each of the switches is further coupled to a corresponding tunable component  319 ( a - c ), and the tunable components are coupled to the filter circuit  305 , which is further coupled to a proximity sensing circuit  306  and algorithm  307  as above. 
         [0023]      FIG. 4  shows an antenna with proximity sensor function, the antenna includes a parasitic element  403  positioned beneath an antenna radiating element  402  within the antenna volume for frequency shifting, and further includes capacitors  404  implemented to isolate the parasitic element at frequencies from the ground plane. 
         [0024]    In the illustrated embodiments, the antenna components inherently provide the proximity sensor function, thereby eliminating the cost for additional capacitive sensors. Moreover, less energy is consumed by the system with less components for distributing power. Smaller antenna device form is achieved by reduced size due to reduced componentry requirements.