Patent Application
20130171950
Embodiments relate to antennas, and more particularly to planar inverted-F antennas, and modules and systems within which they are incorporated.
Planar inverted-F antennas (PIFAs) are commonly used in portable electronic systems (e.g., cellular telephones) due to their relatively small size, when compared with other antenna options. For example
In order to use PIFA 100 to radiate or receive radio frequency (RF) signals, the PIFA 100 is interconnected with a signal source and/or load (e.g., a transceiver, not illustrated). More particularly, an input (or distal) end 112 of the feed arm 108 is electrically connected with a signal input transmission line (e.g., a 50-Ohm microstrip transmission line, not illustrated), which in turn is connected with the signal source/load. Generally, the impedance of the PIFA 100 and the impedance of the signal source/load are not matched. Accordingly, the input end 112 of the feed arm 108 may be tapered to compensate for the abrupt step transition between the input transmission line and the PIFA 100.
In conventional PIFAs, a solid ground plane (or a solid ground plane with small, narrow slots) having a certain size (e.g., typically >λ/4) is required to achieve antenna performance. Because the ground plane 120 consumes a substantial portion of the area of the layer in which it is included, conductive routing (e.g., the signal input transmission line and other routing) typically is printed on a different metal layer (e.g., the top metal layer or some other layer, not illustrated). Accordingly, conventional PIFAs typically include three or more metal layers. Alternatively, in a design that includes only two metal layers, routing is restricted to the top metal layer.
Embodiments include planar inverted-F antennas (PIFAs) with unique radiation structures that replace conventional, solid ground plane structures, and systems and modules within which such inverted-F antennas are incorporated. More particularly, an embodiment includes a PIFA with a frame-shaped radiation structure (i.e., a closed radiation structure having a central opening or such a structure with a gap), as opposed to a solid ground structure used in conventional PIFAs. When included in an RF module, conductive structures (e.g., routing) and/or electrical components (e.g., transceivers and other RF components) may be included in the central opening of the frame-shaped radiation structure. This allows for more compact RF modules (with PIFAs and ground structures) than those that include conventional PIFAs and solid ground structures.
Substrate 202 has a top surface 204, an opposed, bottom surface 206, and at least one dielectric layer between the top and bottom surfaces 204, 206. For example, substrate 202 may be a printed circuit board (PCB) or other dielectric substrate. In the embodiments described in detail below, substrate 202 consists of a single dielectric layer. In alternate embodiments, substrate 202 may include two or more dielectric layers and a metal layer between each of the dielectric layers. Substrate 202 has a thickness in a range of about 0.05 millimeters (mm) to about 5 mm, with a thickness in a range of about 0.1 mm to about 0.2 mm being preferred. According to a specific embodiment, substrate 202 has a thickness of about 0.1 mm. In addition, substrate 202 has a length (horizontal dimension in
PIFA 210 forms a portion of a PIFA metal layer (e.g., layer 410,
PIFA 210 includes an antenna arm 212, a shorting arm 214, and a feed arm 216. The antenna arm 212 has a proximal end 232 and a distal end 234. Similarly, the shorting arm 214 has a proximal end 236 and a distal end 238, and the feed arm 216 has a proximal end 240 and a distal end 242. The proximal end 236 of the shorting arm 214 is coupled with the proximal end 232 of the antenna arm 212 to define an open end at the distal end 234 of the antenna arm 212. The distal end 238 of the shorting arm 214 is coupled with the radiation frame 220 through one or more conductive structures (e.g., via 502,
Excitation of currents in the PIFA 200 causes excitation of currents in the radiation frame 220. The resulting electromagnetic field is formed by the interaction of the PIFA 200 and an image of itself below the radiation frame 220. Essentially, the combination of the PIFA 200 and the radiation frame 220 operate as an asymmetric dipole. As is known by those of skill in the art, the various dimensions of the antenna arm 212, shorting arm 214, and feed arm 216, as well as the distance between the shorting arm 214 and the feed arm 216, among other things, can be adjusted to achieve a desired center of resonant frequency and bandwidth of the PIFA 200. According to an embodiment, antenna arm 212, shorting arm 214, and feed arm 216 are sized and arranged to have a center of resonant frequency within an ISM band (Industrial, Scientific, and Medical radio band). For example, according to a particular embodiment, antenna arm 212, shorting arm 214, and feed arm 216 are sized and arranged to have a center of resonant frequency within a frequency band spanning from about 2.400 gigahertz (GHz) to about 2.500 GHz, although antenna arm 212, shorting arm 214, and feed arm 216 may be sized and arranged to have a center of resonant frequency within other bands, as well.
Radiation frame 220 is a planar conductive structure defined by an outer boundary 224 and an inner boundary 226. A central opening 222 (i.e., non-conductive) is defined by the inner boundary 226. Although
Radiation frame 220 has a length 290 and a height 291, which define a total area occupied by the radiation frame (including the central opening 222). A dimension or multiple dimensions (e.g., the length 290 and/or height 291 and/or some other dimension) of the radiation frame 220 is less than about one quarter of the operating wavelength (i.e., λ/4). According to an embodiment, radiation frame 220 has a length 290 in a range of about 8 mm to about 15 mm, with a length 290 in a range of about 10 mm to about 13 mm being preferred. According to a specific embodiment, radiation frame 220 has a length 290 of about 12 mm. Radiation frame has a height 291 in a range of about 15 mm to about 25 mm, with a height 291 in a range of about 18 mm to about 22 mm being preferred. According to a specific embodiment, radiation frame 220 has a height 291 of about 20 mm. In other embodiments, length 290 and/or height 291 may be larger or smaller than the above-given ranges.
Central opening 222 has a length 293 and a height 294, which define an area of the central opening 222 (referred to herein as the “central opening area.” According to an embodiment, the central opening area is in a range of about 20 percent to about 90 percent of the total area occupied by the radiation frame (including the central opening 222). According to another embodiment, the central opening area is in a range of about 60 percent to about 80 percent of the total area occupied by the radiation frame (including the central opening 222). In other embodiments, the central opening area may be greater or smaller than the above-given ranges.
The distance between the outer and inner boundaries 224, 226 defines the frame width 292. Although the embodiments illustrated in
According to an embodiment, RF module 200 also includes one or more electrical components 250, 251, 252, 253, 254 which, in conjunction with PIFA 210 and radiation frame 220 form an RF module configured to function as a transmitter, receiver, or transceiver. For example, but not by way of limitation, electrical components 250-254 may include one or more transceivers, transmitters, receivers, crystal oscillators, Baluns, or other components. In particular, for example, electrical component 250 may be a transceiver, Balun, or other component that supplies an RF signal to transmission line 263, which in turn, is coupled to the distal (input) end 242 of feed arm 216.
As shown in
In addition to the electrical components 250-252 coupled to a portion of the substrate 202 that coincides with the central opening 222, RF module 200 also may include one or more additional electrical components 253, 254 that are coupled to a portion of the substrate 202 that does not coincide with the radiation frame 220 or the central opening 222. For example, the additional electrical components 253, 254 may be coupled to a portion 270 of the top surface 204 that does not include conductive portions of PIFA 210 and that does not overlie the radiation frame 220 or its central opening 222. Again, although
RF module 200 also may include conductive interconnects 260, 261, 262, 263, 264, 265, 266 and other conductive structures 267, 268 (e.g., input/output pads and mechanical connection pads), in an embodiment. Some of the conductive interconnects 260-263 are coupled to the top surface 204 of substrate 202, and may provide routing (e.g., signal, ground, and so on) between electrical components 250-254 on the top surface 204. For example, as discussed previously, conductive interconnect 263 may be a transmission line (e.g., a 50 Ohm microstrip transmission line), which is coupled between component 250 and the distal (input) end 242 of feed arm 216. Other ones of the conductive interconnects 260-262 may provide top-surface routing between the various electrical components 250-254. According to an embodiment, conductive interconnects 260-263 form portions of the PIFA metal layer (or M1).
According to an embodiment, other ones of the conductive interconnects 264-266 and the other conductive structures 267, 268, 269 are coupled to the bottom surface 206 of substrate 202. Conductive interconnects 264-266 also may provide routing between the electrical components 250-254 on the top surface 204, as will be explained in more detail in conjunction with
Conductive interconnect 266 and conductive structure 268 are coupled to a portion of the bottom surface 206 of substrate 202 that does not coincide with the radiation frame 220 or the central opening 222. According to an embodiment, the central opening 222 also provides an area on the radiation frame metal layer (or M2) for routing between electrical components 250-254 and interconnection with other substrates (e.g., substrate 802,
In the above description, PIFA 210 and its corresponding radiation frame 220 are included in different metal layers of a module. In alternate embodiments (not illustrated), a PIFA and its corresponding radiation frame may be in the same metal layer of a module (e.g., both a PIFA and a ground plane could be printed on the same surface of the substrate). In addition, although the various embodiments discussed herein describe an RF module 200 with two metal layers (e.g., layers 410, 420,
Further, although various electrical components 250-254, conductive interconnects 260-266, and conductive structures 267-269, 402-404, 502 are illustrated in
Embodiments of RF modules with radiation frames, such as those described above, may be incorporated into systems in which there is a desire to communicate information wirelessly. For example,
As discussed previously, RF module 200 includes a PIFA 210, a radiation frame 220, and various electrical components (e.g., component 250), which enable PIFA 210 to transmit RF signals over an air interface, receive RF signals from an air interface, or both. According to an embodiment, non-RF component 804 is configured to produce signals for transmission by RF module 200 and/or to consume signals produced by RF module 200 (based on RF signals that RF module 200 received from the air interface). RF module 200 and non-RF component 804 may be electrically coupled to substrate 802 and to each other using various pads (e.g., pads 810, 812), vias (e.g., vias 814, 816), and conductive interconnects (e.g., conductive interconnect 818) on and through substrate 802. In this manner, RF module 200 and non-RF component 804 may exchange electrical signals.
Although a particular system configuration is illustrated in
Thus, various embodiments of inverted-F antennas, and modules and systems in which they are incorporated have been described above. An embodiment of an antenna includes a radiation frame and a planar inverted-F antenna (PIFA). The radiation frame has a frame shape that defines a central opening. The PIFA includes an antenna arm, a feed arm, and a shorting arm. A distal end of the shorting arm is conductively coupled with the radiation frame.
An embodiment of an RF module includes a substrate and an antenna coupled to the substrate. The antenna includes a radiation frame and a planar inverted-F antenna. The radiation frame has a frame shape that defines a central opening. The radiation frame forms a first portion of a first metal layer of the module. The PIFA includes an antenna arm, a feed arm, and a shorting arm. A distal end of the shorting arm is conductively coupled with the radiation frame.
An embodiment of a system includes a non-RF component that produces a signal for transmission, and an RF module electrically coupled to but physically distinct from the non-RF component. The module is configured to receive the signal, convert the signal to an RF signal, and radiate the RF signal over an air interface. The module includes a substrate and an antenna coupled to the substrate. The antenna includes a radiation frame and a PIFA. The radiation frame has a frame shape that defines a central opening. The radiation frame forms a first portion of a first metal layer of the module. The PIFA includes an antenna arm, a feed arm, and a shorting arm. A distal end of the shorting arm is conductively coupled with the radiation frame.
As used herein, the term “pad” means a conductive connection between circuitry external to a package and circuitry internal to the package. A “pad” should be interpreted to include a pin, a pad, a bump, a ball, and any other conductive connection. The term “interconnect” means an input (I) conductor for a particular IC, an output (O) conductor for a particular IC, or a conductor serving a dual I/O purpose for a particular IC. In some cases, an interconnect may be directly coupled with a package pin, and in other cases, an interconnect may be coupled with an interconnect of another IC.
The terms “first,” “second,” “third,” “fourth” and the like in the description and the claims, if any, may be used for distinguishing between similar elements or steps and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments described herein are, for example, capable of operation or fabrication in sequences or arrangements other than those illustrated or otherwise described herein. In addition, the sequence of processes, blocks or steps depicted in and described in conjunction with any flowchart is for example purposes only, and it is to be understood that various processes, blocks or steps may be performed in other sequences and/or in parallel, in other embodiments, and/or that certain ones of the processes, blocks or steps may be combined, deleted or broken into multiple processes, blocks or steps, and/or that additional or different processes, blocks or steps may be performed in conjunction with the embodiments. Furthermore, the terms “comprise,” “include,” “have” and any variations thereof, are intended to cover non-exclusive inclusions, such that a process, method, article, or apparatus that comprises a list of elements or steps is not necessarily limited to those elements or steps, but may include other elements or steps not expressly listed or inherent to such process, method, article, or apparatus.
It is to be understood that various modifications may be made to the above-described embodiments without departing from the scope of the inventive subject matter. While the principles of the inventive subject matter have been described above in connection with specific systems, apparatus, and methods, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the inventive subject matter. The various functions or processing blocks discussed herein and illustrated in the Figures may be implemented in hardware, firmware, software or any combination thereof. Further, the phraseology or terminology employed herein is for the purpose of description and not of limitation.
The foregoing description of specific embodiments reveals the general nature of the inventive subject matter sufficiently that others can, by applying current knowledge, readily modify and/or adapt it for various applications without departing from the general concept. Therefore, such adaptations and modifications are within the meaning and range of equivalents of the disclosed embodiments. The inventive subject matter embraces all such alternatives, modifications, equivalents, and variations as fall within the spirit and broad scope of the appended claims.
