Patent Publication Number: US-9893426-B2

Title: PCB embedded radiator antenna with exposed tuning stub

Description:
BACKGROUND 
     Printed Planar Inverted-F antennas (PIFAs) are antennas that resemble an inverted letter “F” formed on a printed circuit board (PCB). A PIFA has a ground trace and a feed trace formed in a single plane with a resonant antenna radiator conductive trace on the PCB. The antenna radiator conductive trace of the PIFA has a certain length that determines the resonant frequency of the antenna. A position of the feed trace on the antenna radiator conductive trace can be used to control the input impedance of the PIFA antenna. Typically, the PIFA is placed on the edge of the PCB, with the area on the PCB surrounding the PIFA being copper-free to prevent any impact on the frequency response of the PIFA. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an “exploded” three dimensional view of a multilayer PCB antenna; 
         FIGS. 2A, 2B and 2C  depict a two-dimensional “overhead” view of each layer of the multilayer PCB antenna of  FIG. 1 ; 
         FIG. 3A  depicts an “exploded” two-dimensional side view of the multilayer PCB antenna of  FIG. 1 ; 
         FIG. 3B  depicts a two-dimensional side view of the multiplayer PCB antenna of  FIG. 1 , where the multiple layers are depicted as affixed to one another; 
         FIGS. 4-6  depict dimensional parameters associated with the various components of the PCB antenna of  FIG. 1 ; 
         FIG. 7  depicts a tuning plot of the PCB antenna of  FIG. 1  according to an exemplary implementation in which the antenna is a Bluetooth antenna; and 
         FIG. 8  depicts a further implementation of the multilayer PCB antenna of  FIG. 1  in which additional intermediate layers are contained within the PCB antenna between the top layer and the intermediate layer, or between the intermediate layer and the bottom layer. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. The following detailed description does not limit the invention. 
     A multilayered printed circuit board (PCB) antenna, as described herein, includes a main antenna radiator trace embedded within the layers of the multilayered PCB and formed on, or within, a separate substrate layer of the multilayered PCB from the antenna ground trace and the antenna feed trace, and on, or within, a separate substrate layer from the antenna tuning stub trace. The PCB antenna is formed on, or within, multiple different layers of a PCB, with one PCB layer including the antenna feed trace and the antenna ground trace formed on, or within, a first substrate layer comprising a dielectric material, and another PCB layer including the main antenna radiator trace formed on, or within, a different, second substrate layer comprising a dielectric material. In one embodiment, the antenna tuning stub trace may be formed on, or within, the same PCB substrate layer as the antenna ground trace and the antenna feed trace. In another embodiment, the antenna tuning stub trace may be formed on, or within, a substrate layer of the multi-layer PCB that is different than the substrate layer containing the antenna radiator trace, or different than the substrate layer containing the antenna ground trace and the antenna feed trace. The multiple layers of the PCB may be affixed to one another using known techniques for forming multi-layered PCBs. The effect of the main antenna radiator trace being embedded within, and sandwiched between, the dielectric PCB substrate layers of the multi-layered PCB is a reduction in the length of the main antenna radiator trace needed for a particular desired resonant frequency, as compared to a conventional antenna. Therefore, embedding the antenna radiator within substrate layers of a multi-layered PCB, on a separate PCB layer from the antenna ground trace and the antenna feed trace or on a same PCB layer, as described herein, reduces the space required for the antenna for a given resonant frequency. In one implementation described herein, the antenna tuning stub trace may be formed on, or within, an outside substrate layer of the multilayer PCB to facilitate the fine tuning of the antenna via adjustment of the length of the antenna tuning stub. When the antenna tuning stub is formed on the outside substrate layer (e.g., on substrate  116  in  FIG. 1 ), the conductive trace of the antenna tuning stub may be formed on an underside of the substrate layer (i.e., facing downwards on the underside of substrate  116  in  FIG. 1 ) and exposed to air to allow easy access to the antenna tuning stub. 
       FIGS. 1, 2A-2C, 3A and 3B  are diagrams that depict a multilayered PCB antenna in which a main radiator element of the antenna is formed on, or within, a separate substrate layer of the multilayered PCB from the antenna tuning stub, and from the feed and ground traces of the antenna.  FIG. 1  depicts an “exploded” three dimensional view of multilayer PCB antenna  100 ,  FIGS. 2A, 2B and 2C  depict a two-dimensional “overhead” view of each layer of multilayer PCB antenna  100 ,  FIG. 3A  depicts an “exploded” two-dimensional side view of multilayer PCB antenna  100 , and  FIG. 3B  depicts a two-dimensional side view of multiplayer PCB antenna  100  where the multiple layers are depicted as affixed to one another. A “layer” or “PCB layer,” as referred to herein, includes a single layer of substrate material, and the conductive traces of components of an antenna formed upon, or within, that layer of substrate material. A “substrate” or “substrate layer,” as referred to herein, includes a single layer of substrate material, comprising a dielectric material, but does not include the conductive traces, or other circuit components, formed on or within the layer of substrate material. 
     As shown in  FIG. 1 , multilayer PCB antenna  100  includes multiple PCB layers affixed to one another in a stack of PCB layers, such as bottom layer  105 , intermediate layer  110  and top layer  115 . Each of layers  105 ,  110  and  115  includes a copper-free area  120  that is free of conductive traces including copper or other conductive elements, or other circuit components, except conductive traces of the antenna itself. On each of layers  105 ,  110  and  115 , the regions surrounding copper-free area  120  include conductive traces associated with other circuitry (not shown), and components (not shown) of other circuitry connected to, or in the vicinity of, the antenna of multilayer PCB  100 . As shown in  FIG. 1 , PCB layer  105  may include a substrate  116 , PCB layer  110  may include a substrate  117 , and PCB layer  115  may include a substrate  118 . Substrate layers  116 ,  117  and  118  may be formed, using known techniques, from dielectric materials such as, for example, fiberglass (e.g., FR4), plastic, epoxy, or phenolics. Bottom layer  105 , depicted in  FIG. 1 , may be optional such that multilayer PCB antenna  100  only includes top layer  115  and intermediate layer  110 , where top layer  115  includes the antenna tuning stub. Alternatively, the antenna tuning stub formed on, or within, bottom layer  105  (described below) may be optional, with bottom layer  105  existing within the multiple PCB layers but not including the antenna tuning stub. In the particular embodiment depicted in  FIG. 1 , bottom layer  105  represents an outside layer of antenna  100 , such that the underside is exposed (e.g., to air) and no further PCB layers are affixed to, and beneath, bottom layer  105 . 
     As depicted in  FIGS. 1 and 2A , copper-free area  120  of top layer  115  of PCB antenna  100  includes a feed/ground trace conductive pattern  125  and, optionally, an antenna tuning stub  135 . The view of top layer  115  in  FIG. 2A  corresponds to a downward view from above top layer  115  in  FIG. 1  (i.e., looking downwards, in  FIG. 1 , from the top of  FIG. 1  towards the bottom of  FIG. 1 ). Feed/ground trace conductive pattern  125  further includes an antenna ground trace  127  and an antenna feed trace  130  and, as shown, includes a via  155 -T formed to extend through feed/ground trace  125 , and through substrate  118  of top layer  115  to intermediate layer  110 . Via  155 -T includes, for example, a circular hole formed through substrate  118  of top layer  115  such that feed/ground trace  125  can be connected to antenna radiator  140  of intermediate layer  110  by a wire, or by conductive solder. Antenna ground trace  127  includes a conductive trace pattern that connects to electrical ground through the circuitry in the regions surrounding copper-free area  120 . Antenna feed trace  130  includes a conductive trace pattern that connects to other circuitry components (not shown), in the regions surrounding copper-free area  120 , that provide the output radio-frequency (RF) signals to be transmitted via the PCB antenna  100 , or which process input RF signals received via the PCB antenna  100 . Optional antenna tuning stub  135  includes a conductive trace pattern having a tuning length (described further with respect to  FIGS. 4-6  below) that may be adjusted to change the frequency response (e.g., the resonant frequency) of PCB antenna  100 . Antenna tuning stub  135  additionally includes a via  150 -T that extends through tuning stub  135  and through substrate  118  of top layer  115  to intermediate layer  110 . Via  150 -T includes, for example, a circular hole formed through substrate  118  of top layer  115  such that antenna tuning stub  135  can be connected to antenna radiator  140  of intermediate layer  110  by a wire, or by conductive solder. The configuration and dimensions of antenna tuning stub  135 , vias  150 -T and  155 -T, and feed/ground trace conductive pattern  125  are described in further detail below with respect to  FIG. 4 . 
     As further depicted in  FIG. 1  and  FIG. 2B , copper-free area  120  of intermediate layer  110  includes a main antenna radiator conductive trace pattern  140 . The view of intermediate layer  110  in  FIG. 2B  corresponds to a downward view from above intermediate layer  110  in FIG.  1  (i.e., looking downwards, in  FIG. 1 , from the top of  FIG. 1  towards the bottom of  FIG. 1 ). As shown, main antenna radiator  140  includes a rectangular trace pattern that extends along an edge of intermediate layer  110  of PCB antenna  100 . Antenna radiator  140  includes a via  155 -I formed through one end of antenna radiator  140 , and a via  150 -I formed through an opposite end of antenna radiator  140 . Via  155 -I includes, for example, a circular hole formed through substrate  117  of intermediate layer  110  such that the one end of antenna radiator  140  can be connected to feed/ground trace  125  of top layer  115  by a wire, or by conductive solder. Via  150 -I includes, for example, a circular hole formed through substrate  117  of intermediate layer  110  such that the opposite end of antenna radiator  140  can be connected to antenna tuning stub  145  of bottom layer  105 , or to antenna tuning stub  135  of top layer  115  through via  150 -T, by a wire, or by conductive solder. The configuration and dimensions of antenna radiator trace  140 , and vias  150 -I and  155 -I, are described in further detail below with respect to  FIG. 5 . As an alternative to the disposition of feed/ground trace  125 , and antenna radiator  140 , shown in  FIGS. 1, 2A and 2B , antenna feed/ground trace  125  may be formed on an underside of substrate  118  (an underside as shown in  FIG. 1  looking from the top of  FIG. 1  towards a bottom of  FIG. 1 ) and antenna radiator  140  may be formed on an underside of substrate  117  (looking from the top of  FIG. 1  towards a bottom of  FIG. 1 ), with antenna feed/ground trace  125  connecting to antenna radiator  140  through via  155 -I and substrate  117 . 
     As depicted in  FIG. 1  and  FIG. 2C , copper-free area  120  of bottom layer  105  may include an antenna tuning stub  145 . The view of bottom layer  105  in  FIG. 2C  corresponds to an upwards view from below bottom layer  105  in  FIG. 1  (i.e., looking upwards, in  FIG. 1 , from the bottom of  FIG. 1  towards the top of  FIG. 1 ). Antenna tuning stub  145  includes a conductive trace pattern having a length (described further with respect to  FIGS. 4-6  below) that may be adjusted to change the frequency response (e.g., the resonant frequency) of PCB antenna  100 . Antenna tuning stub  145  additionally includes a via  150 -B that extends through tuning stub  145  and through substrate  116  of bottom layer  105 . Via  150 -B includes, for example, a circular hole formed through substrate  116  of bottom layer  105  such that antenna tuning stub  145  can be connected to antenna radiator  140  (through via  150 -I) of intermediate layer  110  by a wire, or by conductive solder. The configuration and dimensions of antenna tuning stub  145 , and via  150 -B, are described in further detail below with respect to  FIG. 6 . As an alternative to the disposition of antenna tuning stub  145  shown in  FIGS. 1 and 2C , antenna tuning stub  145  may be formed upon an underside of substrate  117  of layer  110  (i.e., on an opposite of substrate layer  117  from antenna radiator  140 ) with via  150 -I of layer  110  being used to connect one end of antenna radiator  140  to antenna tuning stub  145  through substrate layer  117 . In such an implementation, layer  105  may not exist in multilayer PCB antenna  100  such that layer  110  is the bottom layer, and antenna tuning stub  145  is exposed on the underside of substrate layer  117 . 
       FIGS. 3A and 3B  depict side views of multilayer PCB antenna  100  that show the alignment between the vias of the different layers of PCB antenna  100 . Referring to the “exploded” side view of PCB antenna  100  shown in  FIG. 3A , top layer  115  includes feed/ground trace  125  and antenna tuning stub  135  formed on substrate layer  118 . Feed/ground trace  125  and antenna tuning stub  135  may each include a pattern of conductive material (e.g., copper) formed on an upper surface of substrate layer  118 . Substrate layer  118  may have a thickness t 1  ranging from about 0.25 mm to about 1.0 mm, and may be composed of a substrate material having a dielectric constant ranging from about 2.6 to about 6.2. In one exemplary implementation, the dielectric constant of substrate layer  118  may be 4.6. However, in other implementations, any value for the dielectric constant of substrate layer  118  may be used (i.e., less than 2.6, or greater than 6.2). The substrate material of substrate layer  118  may include, for example, fiberglass (e.g., FR4), plastic, epoxy, or phenolics. 
     Intermediate layer  110  includes antenna radiator trace  140  formed on substrate layer  117 . Antenna radiator  140  includes a pattern of conductive material (e.g., copper) formed on an upper surface of substrate layer  117 , where substrate layer  117  may have a thickness t 2  ranging from about 0.25 mm to about 1.0 mm, and may be composed of a substrate material having a dielectric constant ranging from about 2.6 to about 6.2. In one exemplary implementation, the dielectric constant of substrate layer  117  may be 4.6. However, in other implementations, any value for the dielectric constant of substrate layer  117  may be used (i.e., less than 2.6, or greater than 6.2). The substrate material of substrate layer  117  may include, for example, fiberglass (e.g., FR4), plastic, epoxy, or phenolics. 
     Bottom layer  105  may include optional antenna tuning stub  145  formed on substrate layer  116 . Antenna tuning stub  145  includes a pattern of conductive material (e.g., copper) formed on a lower surface of substrate layer  116 , where substrate layer  116  may have a thickness t 3  ranging from about 0.25 mm to about 1.0 mm, and may be composed of a substrate material having a dielectric constant ranging from about 2.6 to about 6.2. Formation of antenna tuning stub  145  on the lower surface of substrate layer  116 , thus, exposes antenna tuning stub  145  for adjustment of a length of the tuning stub. In one exemplary implementation, the dielectric constant of substrate layer  116  may be 4.6. However, in other implementations, any value for the dielectric constant of substrate layer  116  may be used (i.e., less than 2.6, or greater than 6.2). The substrate material of substrate layer  116  may include, for example, fiberglass (e.g., FR4), plastic, epoxy, or phenolics. Other types of substrate material, than those described, may be used for substrate layers  116 ,  117  and  118 . The substrate material of the different substrate layers  116 ,  117  and  118  may be composed of the same, or of different, substrate materials (e.g., the substrate material of substrate layer  116  may be different than the substrate material of substrate layer  117 , etc.). Additionally, different types of conductive material, other than copper, may be used for forming the conductive traces on the substrate layers of PCB layers  105 ,  110  and/or  115  of multilayer PCB antenna  100 . The respective thicknesses t 1 , t 2  and t 3  of substrate layers  116 ,  117  and  118  may, in some implementations, be approximately at least ten times the thickness of the conductive traces that form antenna ground trace  127 , antenna feed trace  130 , antenna radiator  140 , antenna tubing stub  135  and antenna tuning stub  145 . 
     As depicted with a dashed alignment line (left side,  FIG. 3A ) extending between layers  115  and  110 , and a dashed alignment line (right side,  FIG. 3A ) extending between layers  115 ,  110  and  105 , the layers of PCB antenna  100  are affixed to one another such that certain vias of the different layers “line-up” with another in a vertical direction. For example, via  155 -T of top layer  115  lines up with via  155 -I of intermediate layer  110  such that a conductive wire, or conductive solder, may be placed, or formed, through the vias to interconnect feed/ground trace  125  with antenna radiator trace  140 . As another example, via  150 -T of top layer  115  lines up with via  150 -I of intermediate layer  110 , and via  150 -I lines up with via  150 -B of bottom layer  105  such a conductive wire, or conductive solder, may be placed, or formed, through the vias to interconnect antenna tuning stub  135  to antenna radiator trace  140 , or antenna radiator  140  to antenna tuning stub  145 . 
       FIG. 3B  depicts layers  105 ,  110  and  115  of PCB antenna  100  affixed to one another in a completely formed multilayer PCB antenna assembly. As shown with a dashed alignment line (left side,  FIG. 3B ), vias  155 -T and  155 -I of respective layers  115  and  110  line up to permit an electrical interconnection between feed/ground trace  125  and one end of antenna radiator trace  140 . As further shown with a dashed alignment line (right side,  FIG. 3B ), vias  150 -T,  150 -I and  150 -B line up to permit an electrical interconnection between antenna tuning stub trace  135 , and an opposite end of antenna radiator trace  140 , or optionally between antenna radiator trace  140  and antenna tuning stub trace  145 . 
       FIGS. 4-6  depict exemplary dimensional parameters associated with the various components of multi-layered PCB antenna  100 . In one exemplary implementation, PCB antenna  100  may be used as a Bluetooth antenna having a resonant frequency of approximately 2.45 Gigahertz (GHz) and a bandwidth of at least 100 Megahertz (MHz). In other implementations, PCB antenna  100  may have different dimensional parameters than those described below with respect to  FIGS. 4-6  for other, different wireless applications than Bluetooth. 
       FIG. 4  shows dimensional parameters of top layer  115  which, as described above, includes feed/ground conductive trace pattern  125  and, optionally, antenna tuning stub  135 . The view of top layer  115  in  FIG. 4  corresponds to a downward view (i.e., from the top of  FIG. 1 ) from above top layer  115  in  FIG. 1 . In an implementation in which the antenna tuning stub is formed on top layer  115 , instead of bottom layer  105 , antenna tuning stub  135  may include a rectangular shape having a trace width (w 1 ) and a length (stub length 1 ). The rectangular shape of antenna tuning stub  135  may reside at an edge of the circuit board and extend inwards perpendicular to the circuit board edge. Width w 1  of antenna tuning stub  135  may range from about 0.5 mm to about 1.0 mm. In an exemplary implementation where multilayer PCB antenna  100  is used as a Bluetooth antenna, width w 1  of antenna tuning stub  135  may be 0.96 mm. The length, stub length 1 , of antenna tuning stub  135  may range from about 2.0 mm to about 3.5 mm. In an exemplary implementation where multilayer PCB antenna  100  is used as a Bluetooth antenna, stub length 1  may be 2.98 mm. Via  150 -T may have a diameter approximately one half of width w 1 , and may be located at a location upon antenna tuning stub  135  to align precisely with via  150 -I of antenna radiator trace  140  of intermediate layer  110 . As further shown in  FIG. 4 , antenna tuning stub  135  may be located an offset distance (offset 1 ) from a pad  400  of feed/ground trace  125 , wherein offset 1  may range from about 10.0 mm to about 12.0 mm. In an exemplary implementation where multilayer PCB antenna  100  is used as a Bluetooth antenna, offset 1  may be 10.8 mm. 
     As also shown, pad  400  of conductive trace pattern  125  may include a rectangular shape that has a width w 2 , and a length l 3  that extends perpendicularly inwards from the edge of the circuit board to connect with antenna ground trace  127  and antenna feed trace  130 . w 2  may range from about 0.8 mm to about 1.2 mm, and l 3  may range from about 1.6 mm to about 2.0 mm. In an exemplary implementation where multilayer PCB antenna  100  is used as a Bluetooth antenna, w 2  may equal 1.0 mm and l 3  may equal 1.76 mm. Via  155 -T may have a diameter approximately one half of width w 2 , and may be located at a location upon pad  400  to align precisely with via  155 -I of antenna radiator trace  140  of intermediate layer  110 . 
     Antenna ground trace  127  and antenna feed trace  130  include, together, an L-shaped conductive trace pattern, with the “base” of the L shape having a length l 5  and a width w 6 , and the “leg” of the L shape having a width w 4 . l 5  may range from about 3.0 mm to about 3.6 mm, w 6  may range from about 0.8 mm to about 1.2 mm, and w 4  may range from about 1.3 mm to about 1.6 mm. In an exemplary implementation where multilayer PCB antenna  100  is used as a Bluetooth antenna, l 5  may equal 3.36 mm, w 6  may equal 1.0 mm, and w 4  may equal 1.5 mm. 
       FIG. 5  shows dimensional parameters of intermediate layer  110  which, as described above, includes antenna radiator  140 . The view of intermediate layer  110  in  FIG. 5  corresponds to a downward view (i.e., from the top of  FIG. 1 ) from above top layer  115  in  FIG. 1 . Antenna radiator  140  may include a rectangular shape having an antenna trace width (w A ) and an antenna length (L) that runs along an edge of the printed circuit board. The antenna trace width w A  may range from about 0.8 mm to about 1.2 mm, and the antenna length L may range from about 12.0 mm to about 13.3 mm. In an exemplary implementation where multilayer PCB antenna  100  is a Bluetooth antenna, antenna trace width w A  may equal 1.0 mm and antenna length L may equal 12.95 mm. Vias  150 -I and  155 -I may each have a diameter approximately one half of antenna trace width w A , and may be located at appropriate locations at each end of antenna radiator  140  to align precisely with respective vias  150 -T and  155 -T of top layer  115 . 
       FIG. 6  shows dimensional parameters of bottom layer  105  which, as described above, includes antenna tuning stub  145  in an optional implementation in which the antenna tuning stub is formed on bottom layer  105 , instead of top layer  115 . The view of bottom layer  105  in  FIG. 6  corresponds to an upwards view (i.e., from the bottom of  FIG. 1 ) from below bottom layer  105  in  FIG. 1 . Antenna tuning stub  145  may include a rectangular shape having a trace width (w 7 ) and a length (stub length 2 ). The rectangular shape of antenna tuning stub  145  may reside at an edge of the circuit board and extend inwards perpendicular to the circuit board edge. Width w 7  of antenna tuning stub  145  may range from about 0.5 mm to about 1.0 mm. In an exemplary implementation where multilayer PCB antenna  100  is used as a Bluetooth antenna, width w 7  of antenna tuning stub  145  may be 0.96 mm. The length, stub length 2 , of antenna tuning stub  145  may range from about 2.0 mm to about 3.5 mm. In the exemplary implementation where multilayer PCB antenna  100  is used as a Bluetooth antenna, stub length 2  may be 2.98 mm. Via  150 -B may have a diameter approximately one half of width w 7 , and may be located at a location upon antenna tuning stub  145  to align precisely with via  150 -I of antenna radiator trace  140  of intermediate layer  110 . 
       FIG. 7  depicts a tuning plot of multilayer PCB antenna  100  in the exemplary implementation in which antenna  100  is a Bluetooth antenna. As seen in  FIG. 7 , the tuning plot covers a frequency range of 2.0 GHz to 3.0 GHz with a resonant frequency  700  of PCB antenna  100  occurring at 2.4525070 GHz. As can further be seen from  FIG. 7 , PCB antenna  100  has a bandwidth, at the resonant frequency  700 , greater than 100 MHz. 
       FIG. 8  depicts a further implementation of multilayer PCB antenna  100  in which additional intermediate layers are contained within PCB antenna  100  between top layer  115  and intermediate layer  110 , and/or between intermediate layer  110  and bottom layer  105 .  FIG. 8  shows an additional intermediate layer  800 , formed from a substrate  810 , affixed between top layer  115  and intermediate layer  110 , with electrical connections between feed/ground trace  125  and antenna radiator  140 , and between antenna tuning stub  135  and antenna radiator  140 , running through substrate  810  of intermediate layer  800 . An additional intermediate layer(s), not shown in  FIG. 8 , may be affixed between intermediate layer  110  and bottom layer  105 . If the additional intermediate layer(s) is affixed between layers  110  and  105 , an electrical connection may be formed between antenna radiator  140  and antenna tuning stub trace  145  through the substrate of the additional intermediate layer(s). 
     The foregoing description of implementations provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. For example, various antenna patterns have been shown and various exemplary dimensions have been provided. It should be understood that different patterns and/or dimensions may be used than those described herein. Various dimensions associated with the substrate layers (e.g., substrate layers  116 ,  117 ,  118 ) have been provided herein, such as, for example, thicknesses of the substrate layers. It should be understood that different dimensions of the substrate layers, such as different thicknesses, may be used than those described herein. For example, for thickness dimensions described as encompassing an exemplary range of values, substrate layer thicknesses outside of those layers may be used, such as thicknesses greater than that described in the exemplary range of values. In each case, the antenna radiator may be embedded within, or located between, one or more dielectrics layers (e.g., PCBs) to effectively reduce the dimensions of the radiator as compared to conventional antennas. Some implementations have been described herein as using three substrate layers for the various conductive trace patterns of the PCB antenna. In other implementations, other numbers of substrate layers (e.g., 2, 4, 5 or 6 substrate layers) may be used for multilayer PCB antenna  100 . Antenna radiator  140  is described herein (e.g., with respect to  FIG. 1  and  FIGS. 2A-2C ) as formed on an upper surface of substrate layer  117 , with antenna feed/ground trace  125  being formed on an upper surface of an adjacent substrate layer  118 . However, other implementations may include antenna radiator  140  formed on a lower surface of substrate layer  117 , or on an upper or lower surface of yet another substrate layer (not shown in  FIG. 1 ) disposed between layer  110  and layer  105  in  FIG. 1 . In such implementations, a via(s) through the substrate layer(s) may connect antenna radiator  140  with antenna feed/ground trace  125  regardless of which side of the substrate layer antenna radiator  140  is formed upon. 
     In an exemplary embodiment, the tuning stub may be on one side of a given first substrate layer, where the tuning stub material is exposed to air, and the antenna radiator may be on the opposite side of the first substrate. In such an embodiment, another, second substrate layer side may be formed against the radiator side of the first substrate layer. Thus, the radiator is effectively encased, embedded, and/or sandwiched between, or otherwise surrounded by, dielectric material with one or more tuning stubs on a side of either the first or second substrate to expose the stub to enable tuning of the antenna. The feed/ground from the radiator may be formed on either side of the second substrate, or may be formed on the same side of the first substrate as the radiator. 
     In another exemplary embodiment, the thickness of the substrate that surrounds the antenna radiator may vary. For example, a first thickness of substrate may intervene between the radiator and air on one side of the radiator formed on a substrate layer, and a second thickness of dielectric material may intervene between the radiator and air on a second side of the radiator formed on the substrate layer. This may be accomplished by varying thicknesses of an equal number of layers on either side of the radiator, or by constructing different numbers of similar-thickness substrate/dielectric layers on opposite sides of the radiator. Regardless of the thicknesses, or number of layers that surround, or embed within, the radiator, a tuning stub is preferably constructed on an exterior side of an outermost substrate so that the conductive material of the stub is exposed to enable tuning of the antenna. 
     Certain features described above may be implemented as “logic” or a “unit” that performs one or more functions. This logic or unit may include hardware, such as one or more processors, microprocessors, application specific integrated circuits, or field programmable gate arrays, software, or a combination of hardware and software. 
     No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. 
     In the preceding specification, various preferred embodiments have been described with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.