Patent Publication Number: US-11652295-B2

Title: Antenna with uniform radiation for ultra-wide bandwidth

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure generally relates to antennas. More particularly, the present disclosure relates to systems and methods for antennas with a uniform radiation pattern for Ultra-Wide Bandwidth (“UWB”). 
     BACKGROUND OF THE DISCLOSURE 
     Ultra-Wide Bandwidth (“UWB”) technology can be used effectively for determining a distance between two devices, often referred to as ranging, by measuring a time it takes for the pulse to travel directly between the devices. As the speed of the pulse is known, the distance can be calculated by multiplying the speed and the measured time. 
     However, there are limitations to the UWB ranging. First, UWB ranging requires a direct path for the pulse sent between the two devices as a distance calculated for an indirect path would give a length of the indirect path rather than a distance between the devices. Second, the angular position between the two devices is typically unknown (although this can be determined using multiple antennas). 
     Due to the above limitations of UWB ranging, a non-uniform radiation pattern of an antenna used for UWB can significantly affect the efficacy of a UWB device.  FIG.  1    is a schematic illustration of a first UWB device  10 , positioned relative to a second UWB device  20  and a third UWB device  40 , with a polar plot  50  illustrating a typical radiation pattern  51  relative to the first antenna  11  of the first UWB device  10 . 
     As shown in  FIG.  1   , the typical radiation pattern  51  of the first antenna is non-uniform at varying angular positions relative to the first UWB device  10 . In typical wireless products, there is a desire for a low profile, small, and internally positioned antennas. Often, Inverted F Antennas (IFAs) and Planar Inverted F Antennas (PIFAs) are used and positioned within the wireless product/device. The shape and positioning of the IFAs/PIFAs can degrade the uniformity of the radiation pattern  51 , such that there is a significant delta between a maximum radiation  52  at a first angular position and a minimum radiation  53  and a second angular position. In the example shown in  FIG.  1   , there is approximately 20 dB (decibel) difference between the maximum radiation  52  and the minimum radiation  53 . Since antennas are reciprocal in nature, the same is true for the maximum and the minimum in a receive sensitivity pattern. 
     As a result of this non-uniformity in the antenna signal strength at certain angular positions, some devices (positioned at similar distances from the first UWB device  10 ) will effectively communicate with the first device  10 , while others cannot. For example, UWB device  20  is at an angular position at or near where the maximum radiation  52  of the first antenna  11  occurs and UWB device  30  is at an angular position at or near where the minimum radiation  53  of the first antenna  11  occurs. Thus, the pulse  22  sent by the second antenna  21  is easily received by the first antenna  11 , while the pulse  32  of the third antenna  31  might not be received by the first antenna  11  as the minimum radiation  53  may be below the receive sensitivity of the first device  10 . 
     While non-uniformity does not critically affect other wireless technologies, such as cellular and Wi-Fi due to the leveraging of multi-path propagation, as discussed above, UWB ranging requires a direct path to accurately determine a distance between two devices.  FIG.  2    is a schematic illustration of a first UWB device  10 , positioned relative to a second UWB device  20  and a third UWB device  40 , with a polar plot  60  illustrating an optimal radiation pattern  61  relative to the first antenna  11  of the first UWB device  10 . As such, antennas with more uniform radiation patterns, particularly for UWB applications, are desirable. As can be seen in  FIG.  2   , by maintaining uniformity in the radiation pattern of the antenna  11  of the first UWB device  10 , the angular positions of the second UWB device  20  and the third UWB device  30  do not matter with regards to whether the pulses  22  and  32  will be received by the first UWB device  10 . 
     BRIEF SUMMARY OF THE DISCLOSURE 
     In an embodiment, an antenna element is disclosed. The antenna element includes an outer conductor and an inner conductor. The outer conductor forms a perimeter of the antenna element. The inner conductor is physically and electrically connected to the outer conductor only at an intermediate connection at an inner portion of the outer conductor. The outer conductor and the inner conductor are arranged to form a slot therebetween. The slot extends around the inner conductor such that each end of the slot is adjacent to the intermediate connection. 
     In embodiments, the inner conductor includes a feed point adapted to receive an electrical connection distal to the intermediate connection. In some embodiments, the perimeter of the outer conductor includes a cylindrical shape. In some embodiments, the perimeter of the cylindrical shape is within ten percent of half of a wavelength that the antenna element is adapted to receive. In some embodiments, the slot meanders on each side of the inner conductor such that the slot includes a length that is within ten percent of half of a wavelength that the antenna element is adapted to receive. 
     In embodiments, the antenna element further includes a planar portion that at least forms the perimeter of the antenna element, and a protruding section that protrudes from the planar portion. Optionally, the protruding section includes a dome shape, the inner conductor includes a feed point adapted to receive an electrical connection distal to the intermediate connection, and the intermediate portion is adapted to be angled towards a ground plane due to the dome shape of the protruding section. 
     In another embodiment, a slotted patch antenna is disclosed. The slotted patch antenna includes an antenna element and short walls. The antenna element includes an outer conductor and an inner conductor. The outer conductor forms a perimeter of the antenna element. The inner conductor is physically and electrically connected to the outer conductor only at an intermediate connection at an inner portion of the outer conductor. The inner conductor is adapted to approximate an electric monopole. The outer conductor and the inner conductor are arranged to form a slot therebetween. The outer conductor and the inner conductor are adapted to generate a voltage across the slot that approximates a magnetic dipole that is orthogonal to the approximated electric monopole. The short walls are adapted to physically and electrically connect the antenna element to a ground plane. Each short wall connects to an end of the outer conductor on a side of the antenna element opposite to the intermediate connection. 
     In embodiments, the inner conductor includes a feed point adapted to receive an electrical connection distal to the intermediate connection, the feed point being between the ends of the outer conductor, and the electric monopole is approximated by an electric current flowing from the feed point to the intermediate connection. Optionally, the electric monopole is further approximated by an electric current flowing along the perimeter of the outer conductor from the short walls towards the intermediate connector. Optionally, the magnetic dipole is approximated by the voltage across the slot resulting from the electric current flowing along the perimeter of the outer conductor from the short walls towards the intermediate connector, which is also flowing along the slot, and the electric current flowing across the intermediate connector and along the slot on the inner conductor towards the feed point. 
     In embodiments, the perimeter of the cylindrical shape is within ten percent of half of a wavelength that the antenna element is adapted to receive, and the slot meanders on each side of the inner conductor such that the slot includes a length that is within ten percent of half of the wavelength that the antenna element is adapted to receive. 
     In embodiments, the antenna element further includes a planar portion that at least forms the perimeter of the antenna element, and a protruding section that protrudes from the planar portion. Optionally, the protruding section includes a dome shape, the inner conductor includes a feed point adapted to receive an electrical connection distal to the intermediate connection, and the intermediate connection is adapted to be angled towards a ground plane due to the dome shape of the protruding section. 
     In a further embodiment, an antenna system is disclosed. The antenna system includes an antenna element, a mounting bracket, and short walls. The antenna element includes an outer conductor and an inner conductor. The outer conductor forms a perimeter of the antenna element. The inner conductor is physically and electrically connected to the outer conductor only at an intermediate connection at an inner portion of the outer conductor. The inner conductor extends from the intermediate connection to a feed point adapted to receive an electrical connection distal to the intermediate connection. The outer conductor and the inner conductor are arranged to form a slot therebetween. The slot extends around the inner conductor such that each end of the slot is adjacent to the intermediate connection. The mounting bracket is adapted to be a ground plane. The short walls physically and electrically connect the outer conductor to the mounting bracket. Each short wall connects to an end of the outer conductor adjacent to the feed point. 
     In embodiments, the inner conductor is adapted to approximate an electric monopole, and the outer conductor and the inner conductor are adapted to generate a voltage across the slot that approximates a magnetic dipole that is orthogonal to the approximated electric monopole. 
     In embodiments, the antenna element, including the outer conductor and the inner conductor, the short walls, and the mounting bracket are formed of a unitary structure by one of stamping and casting. 
     In embodiments, the antenna system further includes a second antenna element physically and electrically connected to the mounting bracket by the second short walls. Optionally, wherein the antenna element, the short walls, the mounting bracket and the second antenna element form a unitary structure by one of stamping and casting. 
     In embodiments, the antenna element further includes a planar portion and a protruding section. The planar portion at least forms the perimeter of the antenna element. The protruding section protrudes from the planar portion. The feed point is adapted to be angled towards a ground plane due to the shape of the protruding section. 
     In embodiments, the antenna element is planar and printed on a Printed Circuit Board (PCB). Optionally, the slot and the perimeter are defined by printed shapes on the surface of the PCB. Optionally, the short walls are vias extending through the PCB to a ground. 
     In embodiments, the antenna system includes a plurality of the antenna element positioned within a device with known distances and angles therebetween for finding relative phases and angles of incoming signals from other devices. 
     In embodiments, the antenna element is printed using metalized plastic on a carrier, and wherein the antenna element and the carrier are mounted as a unit to a device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is illustrated and described herein with reference to the various drawings, in which like reference numbers are used to denote like system components/method steps, as appropriate, and in which: 
         FIG.  1    is a schematic illustration of a first UWB device, positioned relative to a second UWB device and a third UWB device, with a polar plot illustrating a typical radiation pattern relative to the first antenna of the first UWB device; 
         FIG.  2    is a schematic illustration of a first UWB device, positioned relative to a second UWB device and a third UWB device, with a polar plot illustrating an optimal radiation pattern relative to the first antenna of the first UWB device; 
         FIG.  3    is a perspective diagram of a slotted patch antenna; 
         FIG.  4    is a perspective diagram of the slotted patch antenna of  FIG.  3    from an alternate view; 
         FIG.  5    is a side perspective diagram of the slotted patch antenna of  FIGS.  3 - 4   ; 
         FIG.  6    is a top perspective diagram of the slotted patch antenna of  FIGS.  3 - 5   ; 
         FIG.  7    is a perspective diagram of an embodiment of a single slotted patch antenna of  FIGS.  3 - 6    connected to a mounting bracket; 
         FIG.  8    is a perspective diagram of an embodiment of two slotted patch antenna of  FIGS.  3 - 6    connected to a mounting bracket; 
         FIG.  9    is a schematic illustration and representation of the currents flowing in the slotted patch antenna of  FIGS.  3 - 6   ; 
         FIG.  10    is a schematic illustration and representation of the voltages of the slotted patch antenna of  FIGS.  3 - 6   ; 
         FIG.  11    is a schematic illustration and representation of the currents flowing, the voltages across the slot, and the equivalent magnetic currents of the slotted patch antenna of  FIGS.  3 - 6   ; 
         FIG.  12    is a schematic illustration and representation of the resulting radiation patterns from the currents and voltages of the slotted patch antenna of  FIGS.  3 - 6   ; 
         FIG.  13    is a polar plot illustrating a comparison of a radiation pattern for an embodiment of the slotted patch antenna and a radiation pattern for a classical IFA antenna; and 
         FIG.  14    is a Cartesian plot of the comparison of  FIG.  13   . 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     In various embodiments, the present disclosure relates to systems and methods for generating a uniform radiation pattern with a slotted patch antenna. The slotted patch antenna includes vertical short walls that position the slotted patch antenna above the ground plane and mechanically support the antenna element. The antenna element includes a long slot that separates an outer conducting element from an inner conducting element except at an intermediate connection between the outer and inner conducting elements that is distal to a feed point on the inner conductor. The outer and inner conducting elements and the slot therebetween are adapted to generate two complementary radiation sources that are orthogonal to each other such that the two radiation sources compensate for dips in the radiation pattern of the other radiation source, which results in a more uniform overall radiation pattern of the slotted patch antenna. 
       FIG.  3    is a perspective diagram of a slotted patch antenna  100 .  FIG.  4    is a perspective diagram of the slotted patch antenna  100  of  FIG.  3    from an alternate view.  FIG.  5    is a side perspective diagram of the slotted patch antenna  100  of  FIGS.  3 - 4   .  FIG.  6    is a top perspective diagram of the slotted patch antenna  100  of  FIGS.  3 - 5   . Referring to  FIGS.  3 - 6   , the slotted patch antenna  100  includes short walls  110  and an antenna element  120 . The short walls  110  are adapted to physically and electronically connect the antenna element  120  to a ground plane  105  and are adapted to act as vertical grounding walls/pins. The short walls  110  provide matching vias adding shunt inductance to the ground. As shown in  FIG.  4   , the short walls  110  are adapted to maintain a gap  115  between the antenna element  120  and the ground plane  105 . In embodiments, the short walls  110  are adapted such that the gap  115  is smaller than at least one of a length, width, and height of the antenna element  120  so that the slotted patch antenna  100  has a low profile relative to the ground plane  105 . In the embodiment illustrated, the slotted patch antenna  100  includes two short walls  110  positioned on the same side of the antenna element  120  and are spaced apart. In some embodiments, the gap  115  is from 1-2 millimeters. 
     In some embodiments, the short walls  110  are vias that extend through a Printed Circuit Board (“PCB”) to the ground plane  105  at the bottom of the PCB, allowing the antenna element  120  to rest on the dielectric material. 
     The antenna element  120  includes an outer conductor  122 , an inner conductor  124 , and a slot  125 . The outer conductor  122  is adapted to form a perimeter of the antenna element  120  (this length is the fully enclosed perimeter, including across the slot, between the short walls  110 ). In embodiments, the perimeter has a length of approximately half of the wavelength that the antenna element  120  is configured to receive. 
     In some embodiments, the perimeter of the antenna element  120  is within ten percent of the wavelength from half of the wavelength, such as from forty percent to 60 percent of the wavelength. For example, a UWB channel is centered at 6.5 GHz, where the wavelength in free space is approximately 46 millimeters. In these embodiments, the perimeter is within ten percent of half of 46 millimeters, or in other words, within plus or minus 4.6 millimeters of 23 millimeters. In one embodiment, the perimeter is 27 millimeters. 
     In some embodiments, the perimeter is within 5 millimeters of half of the wavelength. In the embodiment illustrated, the perimeter includes a circular shape, such as a cylindrical shape. In some embodiments, the cylindrical shape includes a radius from 3 millimeters to 4.5 millimeters. 
     The outer conductor  122  connects to the short walls  110 . In embodiments, the outer conductor  122  includes two adjacent ends on the same side of the antenna element  120 , each connected to a short wall  110 . The outer conductor  122  then extends around the inner conductor  124 , forming the perimeter of the antenna element, while maintaining a gap directly between the two adjacent ends. In embodiments with the circular/cylindrical shape, the circular/cylindrical shape is formed with an opening opposite the intermediate connection  123 . 
     The inner conductor  124  physically and electrically connects to the outer conductor  122  at an intermediate connection  123  that is at an inner portion of the outer conductor  122  and a side of the antenna element  120  opposite the short walls  110 . The inner conductor  124  extends from the intermediate connection  123  generally toward the short walls to a feed point  126  that is proximal to the short walls  110  and distal to the intermediate connection  123 . In embodiments, the feed point  126  is positioned between the ends of the outer conductor  122  that are connected to the short walls  110 . In embodiments with the circular/cylindrical shape, the feed point  126  is positioned between the ends defining the opening therein. 
     The inner conductor  124  and the outer conductor  122  are adapted to form a slot  125  therebetween. Referring to  FIG.  6   , the ends of the slot  125  are each adjacent to the intermediate connection  123 , and the slot  125  extends from one end of the slot  125 , along the inner conductor  124 , around the feed point  126 , and back along the inner conductor  124  to the other end of the slot  125 . While the slot  125  appears to be open between the ends of the outer conductor  122  and the short walls  110 , the slot  125  can be considered enclosed by short walls  110  and the ground plane  105  at that end of the antenna element  120 , which provides continuity of conductive material, such as metal, around the entire slot structure. 
     In embodiments, the slot  125  meanders to increase a length of the slot  125 , such that each half of the slot, extending along each side of the inner conductor  124 , has a length longer than at least one of a length and a width of the antenna element  120 . In the embodiment illustrated, each half of the slot  125  is longer than a diameter of the cylindrical shape of the perimeter of the outer conductor  122 . In some embodiments, the length of the slot  125 , measured from one end of the slot  125  adjacent to the intermediate connection around the inner conductor to the other end of the slot  125  adjacent to the intermediate connection  123 , is approximately half of the wavelength that the antenna element  120  is configured to receive. 
     In some embodiments, the length of the slot  125  of the antenna element  120  is within ten percent of the wavelength from half of the wavelength, such as from forty percent to 60 percent of the wavelength. For example, a UWB channel is centered at 6.5 GHz, where the wavelength in free space is approximately 46 millimeters. In these embodiments, the length of the slot  125  is within ten percent of half of 46 millimeters, or in other words, within plus or minus 4.6 millimeters of 23 millimeters. In one embodiment, the length of the slot is 20 millimeters. In some embodiments, the length of the slot  125  is within 5 millimeters of half the wavelength. 
     In embodiments, the meandering path is in the form of one or more curves that benefit the radiation pattern. In the embodiment illustrated, the slot  125  is symmetrical, with each half of the slot  125  circumferentially diverging from the intermediate connection  123  before converging towards the other half of the slot  125 , after which each half of the slot  125  extends parallel to the other towards the feed point  126  and the short walls  110 . This meandering results in an inner conductor with a thicker, semicircular/wedge-like shape adjoining the intermediate connection with a stem-like shape extending therefrom and to the feed point  126 . As discussed in greater detail below, the meandering slot  125  produces an approximate of a magnetic dipole that is orthogonal to an approximate electric monopole produced by the antenna element  120 . 
     A width of the slot  125  is selected to control a voltage across the slot  125 . In embodiments, a width of the slot  125  is less than a width of the portion of the inner conductor  124  with the stem-like shape. In embodiments, the slot  125  is narrow relative to the length and width of the antenna element  120 . In some embodiments, the slot is approximately 1 millimeter, such as within a predetermined tolerance of 1 millimeter. However, other widths are also contemplated. As the slot  125  is relatively narrow, the bandwidth resulting therefrom is sufficient, the mechanical integrity of the antenna element  120  is maintained, and the resulting volume of the antenna element  120  is minimized. 
     The antenna element  120  includes a plate-like shape. In embodiments, the plate-like shape is one of a flat plate and a planar portion  128  with a protruding section  129  therein. In some embodiments, the protruding section  129  raises away from the ground plane  105 , and in other embodiments, the protruding section  129  lowers towards the ground plane  105 . In the embodiment illustrated in  FIGS.  3 - 6   , the protruding section  129  includes a dome shape, such as a hollow spherical cap and hollow hemisphere, with the planar portion  128  at the base thereof, where the planar portion  128  includes an annular shape, such as a hollow right circular cylinder. As a minimum portion section of the radiation pattern can result due to the direction that the protruding section  129  extends, the direction of the protruding section  129  extending away from or towards the ground plane  105  may be selected based off of a direction in which a dip in the radiation pattern can be tolerated the most. 
     In some embodiments, a maximum height  127  of the protruding section  129  relative to the planar portion  128  is from 1/15 to 1/10 of the wavelength, such as from 3 millimeters to 5 millimeters. 
     In embodiments, the slot  125  extends primarily within the protruding section  129 , such that the outer conductor  122  includes the planar portion  128  and outer portions of the protruding section  129 , while the inner conductor  124  primarily includes an inner portion of the protruding section  129 . 
     In the embodiment illustrated in  FIGS.  3 - 6   , the slotted patch antenna  100 , including the short walls  110  and the antenna element  120 , is a unitary structure that is a single structurally formed entity. In embodiments, the slotted patch antenna  100  is stamped sheet metal. In other embodiments, the slotted patch antenna  100  is cast. 
     In further embodiments, the slotted patch antenna  100  is integrated into a PCB. In particular, the antenna element  120  is planar and printed on a PCB. In some embodiments, the antenna element  120  is formed using traces on top of the PCB. With ground at a backside of the PCB, the short walls  110  are vias extending through the PCB to the ground. In some embodiments, the slot  125  and the perimeter are defined by printed shapes on the surface of the PCB. In some embodiments, multiple antenna elements  120  are printed on the PCB, each being connected to the ground by short walls  110  that are vias. 
     In yet further embodiments, the slotted patch antenna  100  is printed on a carrier with metalized plastic, such as LDS, printed metal on plastic, and a metal pattern on a flex material. The antenna element  120  and the carrier are mounted as a unit to a device. 
       FIG.  7    is a perspective diagram of an embodiment of a single slotted patch antenna  100  of  FIGS.  3 - 6    connected to a mounting bracket.  FIG.  8    is a perspective diagram of an embodiment of two slotted patch antennas  100  of  FIGS.  3 - 6    connected to a mounting bracket. Referring to  FIGS.  7  and  8   , one or more single slotted patch antennas  100  can be connected to a mounting bracket, where the mounting bracket is a ground plane  105 . 
     In the embodiments illustrated in  FIGS.  7  and  8   , the mounting bracket includes bracket arms  104  that connect the short walls  110  to the mounting bracket. The mounting bracket also includes first bores  106  and second bores  108  for securing the mounting bracket within an electronic device. The first and second bores  106  and  108  can be formed in a body of the mounting bracket, separate bracket supports  107 , and the like. In some embodiments, the mounting bracket also includes clips  109  for securing the slotted patch antennas  100  in place within the electronic device. 
     In embodiments with two or more slotted patch antennas  100 , an angle of arrival and relative phases can be determined, and in embodiments with at least three slotted patch antennas  100 , a position of an electronic device sending the signal can be determined using triangulation. The spacing between the multiple slotted patch antennas  100  is selected to work across a full range of UWB frequencies. In some embodiments, the spacing between multiple slotted patch antennas  100  is different such that good spacing for varying UWB frequencies is achieved. In embodiments with multiple slotted patch antennas  100 , the antenna elements  120  are positioned within a device with known distances and angles therebetween for finding relative phases and angles of incoming signals from other devices. 
     Again, the structure of the slotted patch antenna  100  is formed such that two complimentary radiation sources are generated. The two complimentary radiation sources are orthogonal to each other such that the two radiation sources compensate for dips in the radiation pattern of the other radiation source to generate a more uniform overall radiation pattern of the slotted patch antenna  100 . 
       FIG.  9    is a schematic illustration and representation of the currents  93 ,  94  flowing in the slotted patch antenna  100  of  FIGS.  3 - 6   . The current flows in  FIG.  9    are illustrated with arrows where the larger arrows are the stronger electric currents. Referring to  FIG.  9   , most of the electric currents and the strongest electric currents flow from the electric feed  91  and ground  92  towards an opposing end of the slotted patch antenna, the opposing end including the intermediate connection  123 . The strong electric currents across the inner conductor  124  and around an edge of the outer conductor  122  are a first source of radiation. As illustrated in  FIG.  9   , the first source of radiation flowing in a direction from the electric feed  91  and ground  92  have a similar flow to that of an electric monopole  80 . Furthermore, in embodiments with a protruding section  129 , such as with a domed shape, currents at the end of the inner conductor  124  and traversing the intermediate connection  123  are moving at least partially towards the ground plate  105 . As the radiation patterns of monopoles and dipoles can be weak in the direction of the current flow, bending the current towards the ground tilts a weak portion of the radiation towards the ground, which results in a more uniform pattern of the overall radiation pattern. 
       FIG.  10    is a schematic illustration and representation of the voltages  95 ,  96 ,  97  of the slotted patch antenna of  FIGS.  3 - 6   .  FIG.  11    is a schematic illustration and representation of the currents  93 ,  94  flowing, the voltages  95 ,  96  across the slot, and the equivalent magnetic currents  98  of the slotted patch antenna  100  of  FIGS.  3 - 6   . Referring to  FIGS.  10  and  11   , the currents  93 ,  94  flowing around the slot form a voltage  95 ,  96  across the slot  125  with the maximum voltage  95  adjoining the feed point  126 , while the minimum voltage  96  adjoins the intermediate connection  123 , which produces a second source of radiation. Note that a fringe field voltage  97  is also created between the ground plane  105  and the perimeter of the antenna element  120 , which contributes to the radiation. 
     With the currents  93 ,  94  flowing around the slot  125 , an equivalent magnetic current  98  is produced that is the equivalent to a magnetic dipole  83 .  FIG.  12    is a schematic illustration and representation of the resulting electric fields from the approximations of the electric monopole  80  and the magnetic dipole  83  produced from the currents  93 ,  94  and voltages  95 ,  96 ,  97  of the slotted patch antenna  100  of  FIGS.  3 - 6   . As illustrated in  FIG.  12   , the approximated electric monopole  80  resulting from the electric currents flowing across the slotted patch antenna  100  has a minimum electric field  82  in the direction of the approximated electric monopole  80 , with a maximum electric field orthogonal thereto. Complementarily, the approximated magnetic dipole  83  is orthogonal to the approximated electric monopole  80  and has a minimum electric field  85  in the direction thereof, and a maximum electric field  86  orthogonal thereto. Thus, the two sources are complementary due to the radiation pattern resulting from the combined electric fields that result from the orthogonal nature of the maximum electric fields  81  and  84 , which results in a combined electric field that is more uniform in all angular directions. 
     Thus, since the inner conductor  124 , the edge of the outer conductor  122 , and the slot  125  each radiate, and the resulting patterns are orthogonal, the inner conductor  124  and edge of the outer conductor  122  compensate for the dips in the radiation pattern produced by the slot  125  and vice versa. 
       FIG.  13    is a polar plot  70  illustrating a comparison of a radiation pattern  72  for an embodiment of the slotted patch antenna  100  and a radiation pattern  73  for a classical IFA antenna.  FIG.  14    is a Cartesian plot  71  of the comparison of  FIG.  13   . As shown in  FIGS.  13  and  14   , the radiation pattern  72  for the embodiment of the slotted patch antenna  100  has a generally uniform radiation pattern with a variation range that is only about 6 dB. In contrast, the classical IFA antenna has a non-uniform radiation pattern with a variation range that is significantly larger, at about 20 dB. 
     With a generally uniform pattern in all angular directions, such as the radiation pattern  72  illustrated in  FIGS.  13  and  14   , a more accurate determination of a distance a device is from an electronic device with one or more slotted patch antennas and a more accurate determination of whether a device (and therefore the user) is moving towards or moving away from the electronic device that includes the one or more slotted patch antennas  100 , no matter the angular direction is achievable. Further, with multiple slotted patch antennas  100 , triangulation can be used to track a device within range thereof. Such tracking can be used to track the location of the device, movement of the device, identify devices that are coming/going from the location, and the like. Indeed, the more uniform the radiation pattern, the more accurately each of the above can be determined. Such tracking can be used for wellness, such as ensuring the elderly is moving, not on the floor (such as detecting that the device is on the floor) and still at the location, energy management (based on a number of devices detected and the location of those devices), and security, such as turning alarms on/off, detecting whether an unknown person is approaching, identifying the person approaching, which direction a person is approaching from, and the like. 
     Although the present disclosure has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present disclosure, are contemplated thereby, and are intended to be covered by the following claims.