Patent Application
20130171951
Embodiments relate to antennas, and modules and systems within which they are incorporated.
A typical antenna includes at least one conductive antenna arm connected through a transmission line to a receiver, transmitter or transceiver. To transmit a radio frequency (RF) signal, a transmitter (or the transmitter portion of a transceiver) applies an oscillating RF current to the antenna arm, and the antenna arm radiates the energy from the oscillating current onto the “air interface” as electromagnetic waves. To receive a signal, the antenna arm converts electromagnetic waves that impinge upon the antenna arm from the air interface into voltages, which are provided to a receiver (or the receiver portion of a transceiver).
Half-wave dipole antennas and quarter-wave vertical antennas are among the most commonly implemented types of antennas, and they may be designed to operate within a desired bandwidth with a specific center frequency. Often, influences external to the antenna may cause the operating bandwidth of the antenna to shift. For example, when the antenna is incorporated into a system, the proximity of other system components to the antenna may affect the center frequency of the operating band. When those influences are predictable, they may be accounted for in the antenna design. However, when those influences are not predictable, they may cause the center frequency of the operating band to shift in an undesirable manner when the antenna is incorporated into a system.
Embodiments include antennas configured to enable the electrical length of their antenna arms to be extended, and systems and modules within which such antennas are incorporated. More particularly, embodiments of antennas includes a substrate, one or more antenna arms coupled to the substrate, and one or more conductive structures between distal end(s) of the antenna arm(s) and a bottom surface of the substrate. According to further embodiments, the conductive structures may be coupled to tuning structure(s) on a separate substrate in order to extend the electrical length of the antenna arm(s). The use of the tuning structure(s) allows for adjustments to center frequencies of operating bands of antennas after the antennas have been fabricated. Although specific microstrip antennas, such as planar inverted-F antennas and dipole antennas, are discussed in detail below according to certain embodiments, it is to be understood that alternate embodiments may include differently configured half-wave dipole antennas, differently configured quarter-wave vertical antennas, Yagi-Uda antennas, and other types of antennas in which the electrical length of the antenna arm(s) affect the performance (e.g., the center frequency of the operating band) of the antenna. Accordingly, such alternate embodiments are intended to be included within the scope of the inventive subject matter.
Substrate 102 has a top surface 104, an opposed, bottom surface 106, and at least one dielectric layer between the top and bottom surfaces 104, 106. For example, substrate 102 may be a printed circuit board (PCB) or other dielectric substrate. In the embodiments described in detail below, substrate 102 consists of a single dielectric layer. In alternate embodiments, substrate 102 may include two or more dielectric layers and a metal layer between each of the dielectric layers. Substrate 102 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 102 has a thickness of about 0.1 mm. In addition, substrate 102 has a length 190 and a width 192 each in a range of about 15 mm to about 30 mm, with a length and a width in a range of about 20 mm to about 25 mm being preferred. According to a specific embodiment, substrate 102 has a length of about 20 mm and a width of about 25 mm. In other embodiments, substrate 102 may be thicker or thinner than the above-given ranges, and/or may have a length and/or width that are larger or smaller than the above-given ranges.
PIFA 110 forms a portion of a PIFA metal layer (e.g., layer 310,
PIFA 110 includes an antenna arm 112, a shorting arm 114, and a feed arm 116. The antenna arm 112 has a proximal end 132 and a distal end 134. Similarly, the shorting arm 114 has a proximal end 136 and a distal end 138, and the feed arm 116 has a proximal end 140 and a distal end 142. The proximal end 136 of the shorting arm 114 is coupled with the proximal end 132 of the antenna arm 112 to define an open end at the distal end 134 of the antenna arm 112. The distal end 138 of the shorting arm 114 is coupled with the ground plane 120 through one or more conductive structures (not illustrated) that extend between the top and bottom surfaces 104, 106 of substrate 102 (i.e., the shorting arm 114 and the ground plane 120 are conductively or electrically coupled). The proximal end 140 of the feed arm 116 is coupled to the antenna arm 112 between the shorting arm 114 and the distal end 134 of the antenna arm 112. The distal end 142 of the feed arm 116 is coupled to a transmission line 163 (e.g., a 50-Ohm microstrip transmission line), which carries an RF signal to be radiated onto the air interface by the PIFA 110. A taper at the distal end 142 of the feed arm 116 is configured to compensate for the abrupt step transition encountered between the transmission line 163 and the PIFA 110. The input impedance of the PIFA 110 can be designed to have an appropriate value to match the load impedance, which may or may not be 50 Ohms.
Excitation of currents in the PIFA 100 causes excitation of currents in the ground plane 120. The resulting electromagnetic field is formed by the interaction of the PIFA 100 and an image of itself below the ground plane 120. Essentially, the combination of the PIFA 100 and the ground plane 120 operate as an asymmetric dipole. As is known by those of skill in the art, the various dimensions of the antenna arm 112, shorting arm 114, and feed arm 116, as well as the distance between the shorting arm 114 and the feed arm 116, among other things, can be adjusted to achieve a desired resonant frequency and bandwidth of the PIFA 100. According to an embodiment, antenna arm 112, shorting arm 114, and feed arm 116 are sized and arranged to have a resonant frequency within an ISM band (Industrial, Scientific, and Medical radio band). For example, according to a particular embodiment, antenna arm 112, shorting arm 114, and feed arm 116 are sized and arranged to have a resonant frequency within a frequency band spanning from about 2.400 gigahertz (GHz) to about 2.500 GHz, although antenna arm 112, shorting arm 114, and feed arm 116 may be sized and arranged to have a resonant frequency within other bands, as well.
Ground plane 120 has a length (horizontal dimension) and a height (vertical dimension), which define a total area occupied by the ground plane. The length of the ground plane 120 is less than about one quarter of the operating wavelength (i.e., λ/4). According to an embodiment, ground plane 120 has a length in a range of about 8 mm to about 15 mm, with a length in a range of about 10 mm to about 13 mm being preferred. According to a specific embodiment, ground plane 120 has a length of about 12 mm. Ground plane frame has a height in a range of about 15 mm to about 25 mm, with a height in a range of about 18 mm to about 22 mm being preferred. According to a specific embodiment, ground plane 120 has a height of about 20 mm. In other embodiments, the length and/or height of ground plane 120 may be larger or smaller than the above-given ranges.
According to an embodiment, RF module 100 also includes one or more electrical components 150, 151, 152, 153 which, in conjunction with PIFA 110 and ground plane 120 form an RF module configured to function as a transmitter, receiver, or transceiver. For example, but not by way of limitation, electrical components 150-153 may include one or more transceivers, transmitters, receivers, crystal oscillators, Baluns, or other components. In particular, for example, electrical component 150 may be a transceiver, Balun, or other component that supplies an RF signal to transmission line 163, which in turn, is coupled to the distal (input) end 142 of feed arm 116.
Some of the electrical components 150, 151 are coupled to a portion 170 of the substrate 102 that overlies the ground plane 120, and others of the electrical components 152, 153 are coupled to a portion 172 of the substrate 102 that does not overlie the ground plane 120 or coincide with PIFA 110. Although
RF module 100 also may include conductive interconnects 160, 161, 162, 163, 164 and other conductive structures 165, 166 (e.g., input/output pads and mechanical connection pads), in an embodiment. Some of the conductive interconnects 160-163 are coupled to the top surface 104 of substrate 102, and may provide routing (e.g., signal, ground, and so on) between electrical components 150-153 on the top surface 104. For example, as discussed previously, conductive interconnect 163 may be a transmission line (e.g., a 50 Ohm microstrip transmission line), which is coupled between component 150 and the distal (input) end 142 of feed arm 116. Other ones of the conductive interconnects 160-162 may provide top-surface routing between the various electrical components 150-153. According to an embodiment, conductive interconnects 160-163 form portions of the PIFA metal layer (or M1).
According to an embodiment, other ones of the conductive interconnects 164 and the other conductive structures 165, 166 are coupled to the bottom surface 106 of substrate 102. Conductive interconnects 164 also may provide routing between the electrical components on the top surface 104. More specifically, conductive interconnects 164 may provide bottom-surface routing between electrical components 152, 153 within portion 172 of substrate 102, in addition to the top-surface routing provided by conductive interconnects 162. Conductive structures 165 include I/O pads (or other structures), which may be electrically coupled with corresponding I/O pads (or other structures) on another substrate (e.g., substrate 402,
As depicted in
Desirably, conductive structure 180 is configured to have approximately the same characteristic impedance as antenna arm 112, in order to minimize reflections. Conductive structure 180 may be a single via, as shown in
According to an embodiment, and as depicted in
In the above description, PIFA 110 and its corresponding ground plane 120 are included in different metal layers of a module. In alternate embodiments (not illustrated), a PIFA and its corresponding ground plane 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 100 with two metal layers (e.g., layers 310, 320,
Further, although various electrical components 150-153, conductive interconnects 160-164, and conductive structures 165, 166 are illustrated in
As mentioned above, embodiments of RF modules, such as RF module 100, may be incorporated into systems in which there is a desire to communicate information wirelessly. For example,
As discussed previously, RF module 100 includes a PIFA 110, a ground plane 120, and various electrical components (e.g., components 150-154,
RF module 100, tuning structure 410, and non-RF component 420 are mechanically coupled to substrate 402. For example, RF module 100 may be mechanically coupled to substrate 402 using at least one conductive structure (e.g., conductive structures 166, such as floating pads), which may be soldered to at least one corresponding conductive structure 430 (e.g., other floating pads) on substrate 402. Non-RF component 420 may be similarly mechanically coupled to substrate 402. Alternatively, RF module 100 and/or non-RF component 420 may be mechanically coupled to substrate 402 using pins, glues, or other means. In addition, RF module 100 and non-RF component 420 may be electrically coupled to substrate 402 and to each other using various pads (not illustrated), vias (not illustrated), and conductive interconnects (not illustrated) on and/or through substrate 402. In this manner, RF module 100 and non-RF component 420 may exchange electrical signals.
The dielectric constant (or relative permittivity, Er) and thickness of substrate 402 may affect the resonant frequency of PIFA 110. For example, commonly-used substrates may have dielectric constants in a range of about 2.0 to 4.7, although substrates may have lower or higher dielectric constants, as well. In addition, the thicknesses of various PCBs may vary significantly. According to an embodiment, RF module 100 is designed to have a particular resonant frequency and bandwidth. In order to ensure that the desired resonant frequency is not shifted significantly due to the dielectric constant and thickness of substrate 402, tuning structure 410 is provided on substrate 402 to increase the electrical length of antenna arm 112, according to an embodiment. The configuration of the tuning structure 410 may be different on substrates having different dielectric constants and/or thicknesses, to ensure that the desired resonant frequency is achieved regardless of the dielectric constant and/or thickness of the substrate to which RF module 100 is coupled.
According to an embodiment, tuning structure 410 includes a patterned, planar conductive structure (e.g., a portion of a conductive layer) on a top surface 404 of substrate 402. In other embodiments, tuning structure 410 may be a conductive structure other than a patterned conductive structure. For example, tuning structure 410 alternatively may be a conductive bump, ball, plate, or via (e.g., a via into and/or through substrate 402). As discussed previously, tuning structure 410 is configured to increase an electrical length of antenna arm 112 when tuning structure 410 is electrically coupled (e.g., using conductive structure 180 and optional pad 304) to the distal end 134 of antenna arm 112. As shown in
The configuration of tuning structure 410 defines the percentage increase in the electrical length of antenna arm 112 that tuning structure 410 provides. For example, the relative difference between the physical length 430 of antenna arm 112 and the physical length 432 of tuning structure 410 may relate to the percentage increase in the electrical length of antenna arm 112 that tuning structure 410 provides. Those of skill in the art would understand, based on the description herein, however, that the physical length 432 of tuning structure 410 would not be the only factor in determining the percentage increase in the electrical length of antenna arm 112 that tuning structure 410 provides.
The resonant frequency of system 400 relates to the electrical length of the entire combination of antenna arm 112, conductive structure 180, and tuning structure 410. According to an embodiment, tuning structure 410 accounts for about 10 percent or less of the electrical length of the entire combination of antenna arm 112, conductive structure 180, and tuning structure 410. According to another embodiment, tuning structure 410 accounts for up to 50 percent of the electrical length of the entire combination of antenna arm 112, conductive structure 180, and tuning structure 410. In still other embodiments, tuning structure 410 may account for more than 50 percent of the entire electrical length of each combination.
The various embodiments discussed above include an RF module 100 that includes a PIFA 110. In other embodiments, an RF module may include a different type of antenna. For example,
Except for the antennas 110, 610 themselves (and the lack of a ground plane in RF module 600, although one could be included), modules 100, 600 may have certain substantially common elements. For conciseness, all of the elements of module 100 have not been included in the illustrations of module 600, although module 600 may have many of the elements illustrated and discussed in conjunction with module 100. For example, only a few electronic components 650, 651, 652 and simple routing therebetween are illustrated in
Substrate 602 has a top surface 604, an opposed, bottom surface 606, and at least one dielectric layer between the top and bottom surfaces 604, 606. For example, substrate 602 may be a printed circuit board (PCB) or other dielectric substrate. In the embodiments described in detail below, substrate 602 consists of a single dielectric layer. In alternate embodiments, substrate 602 may include two or more dielectric layers and a metal layer between each of the dielectric layers. Substrate 602 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 602 has a thickness of about 0.1 mm. In addition, substrate 602 has a length 690 in a range of about 20 mm to about 60 mm, with a length 690 in a range of about 30 mm to about 50 mm being preferred. Substrate 602 has a width 692 in a range of about 5 mm to about 20 mm, with a width 692 in a range of about 8 mm to about 12 mm being preferred. According to a specific embodiment, substrate 602 has a length of about 40 mm and a width of about 10 mm. In other embodiments, substrate 602 may be thicker or thinner than the above-given ranges, and/or may have a length and/or width that are larger or smaller than the above-given ranges.
Dipole antenna 610 forms a portion of an antenna metal layer (e.g., layer 810,
Dipole antenna 610 includes symmetrical antenna arms 612, 613 coupled at their proximal ends 632, 633 to parallel feed arms 616, 617 (i.e., the dipole antenna 610 is center fed). Antenna arms 612, 613 may include a single bend, as shown, or antenna arms 612, 613 may be differently shaped. For example, in other embodiments, antenna arms 612, 613 may be straight or curved, or may include multiple bends. Parallel feed arms 616, 617 transition to a coaxial unbalanced feed point 614 using linear tapers. An end launch connector (e.g., a 50-Ohm connector) is connected at the feed point 614. At the feed point 614, an RF signal is provided to the dipole antenna 610 from an electrical component 650 (e.g., a transmitter or transceiver) for radiation onto the air interface, or an RF signal intercepted by the dipole antenna 610 is provided to the electrical component 650 (e.g., a receiver or transceiver). According to an embodiment, antenna arms 662, 613 and feed arms 616, 617 are sized and arranged to have a resonant frequency within an ISM band, although antenna arms 662, 613 and feed arms 616, 617 may be sized and arranged to have a resonant frequency within other bands, as well.
According to an embodiment, RF module 600 also includes one or more electrical components 650, 651, 652 which, in conjunction with dipole antenna 610 form an RF module configured to function as a transmitter, receiver, or transceiver. For example, but not by way of limitation, electrical components 650-652 may include one or more transceivers, transmitters, receivers, crystal oscillators, or other components (a Balun may not be needed in antenna 610, but may be included). In particular, for example, electrical component 650 may be a transceiver or other component that supplies an RF signal to feed point 614, which in turn, is coupled to the input ends of feed arms 616, 617. Although
RF module 600 also may include conductive interconnects (not numbered) forming portions of the M1 and/or M2 layers to provide routing (e.g., signal, ground, and so on) between the electrical components 650-652. In addition, RF module 660 includes conductive structures 660, 662 (e.g., I/O pads and/or other structures), which may be electrically coupled with corresponding I/O pads (or other structures) on another substrate (e.g., substrate 902,
As depicted in
Desirably, conductive structures 680, 681 are configured to have approximately the same characteristic impedances as antenna arms 612, 613, in order to minimize reflections. Conductive structures 680, 681 each may be a single via, as shown in
Although the various embodiments discussed herein describe an RF module 600 with two metal layers (e.g., layers 810, 820,
Further, although various electrical components 650-652, conductive interconnects, and conductive structures 660, 662 are illustrated in
As mentioned above, embodiments of RF modules, such as RF module 600, may be incorporated into systems in which there is a desire to communicate information wirelessly. For example,
As discussed previously, RF module 600 includes a dipole antenna 610 and various electrical components (e.g., components 650-652,
RF module 600, tuning structures 910, 911, and non-RF component 920 are mechanically coupled to substrate 902. For example, RF module 600 may be mechanically coupled to substrate 902 using at least one conductive structure (e.g., conductive structures 662, such as floating pads), which may be soldered to at least one corresponding conductive structure (e.g., other floating pads, not illustrated) on substrate 902. Non-RF component 920 may be similarly mechanically coupled to substrate 902. Alternatively, RF module 600 and/or non-RF component 920 may be mechanically coupled to substrate 902 using pins, glues, or other means. In addition, RF module 600 and non-RF component 920 may be electrically coupled to substrate 902 and to each other using various pads (not illustrated), vias (not illustrated), and conductive interconnects (not illustrated) on and/or through substrate 902. In this manner, RF module 600 and non-RF component 920 may exchange electrical signals.
According to an embodiment, RF module 600 is designed to have a particular resonant frequency and bandwidth. In order to ensure that the desired resonant frequency is not shifted significantly due to the dielectric constant and thickness of substrate 902, tuning structures 910, 911 are provided on substrate 902 to increase the electrical length of antenna arms 612, 613, according to an embodiment. The configuration of the tuning structures 910, 911 may be different on substrates having different dielectric constants and/or thicknesses, to ensure that the desired resonant frequency is achieved regardless of the dielectric constant and/or thickness of the substrate to which RF module 600 is coupled.
According to an embodiment, tuning structures 910, 911 each include a patterned, planar conductive structure (e.g., a portion of a conductive layer) on a top surface 904 of substrate 902. In other embodiments, tuning structures 910, 911 may be conductive structures other than patterned conductive structures. For example, tuning structures 910, 911 alternatively may be conductive bumps, balls, plates, or vias (e.g., vias into and/or through substrate 902). As discussed previously, tuning structures 910, 911 are configured to increase an electrical length of antenna arms 612, 613 when tuning structures 910, 911 are electrically coupled (e.g., using conductive structures 680, 681 and optional pads 804, 805) to the distal ends 634, 635 of antenna arms 612, 613. As shown in
The configuration of tuning structures 910, 911 define the percentage increase in the electrical lengths of antenna arms 612, 613 that tuning structures 910, 911 provide. For example, the relative differences between the physical lengths 930, 931 of antenna arms 612, 613 and the physical lengths 932, 933 of tuning structures 910, 911 may relate to the percentage increase in the electrical lengths of antenna arms 612, 613 that tuning structures 910, 911 provide. Those of skill in the art would understand, based on the description herein, however, that the physical lengths 932, 933 of tuning structures 910, 911 would not be the only factor in determining the percentage increase in the electrical lengths of antenna arms 612, 613 that tuning structures 910, 911 provide.
The resonant frequency of system 900 relates to the electrical length of the entire combination of antenna arms 612, 613, conductive structures 680, 681, and tuning structures 910, 911. According to an embodiment, tuning structures 910, 911 account for about 10 percent or less of the electrical lengths of each entire combination of antenna arms 612, 613, conductive structures 680, 681, and tuning structures 910, 911. According to another embodiment, tuning structures 910, 911 account for up to 50 percent of the electrical length of each entire combination of antenna arms 612, 613, conductive structures 680, 681, and tuning structures 910, 911. In still other embodiments, tuning structures 910, 911 may account for more than 50 percent of the entire electrical length of each combination.
According to an embodiment, and as depicted in
To further illustrate the various embodiments,
In the various embodiments discussed above, an RF module (e.g., module 100, 600,
In an alternate embodiment, an RF module may be assembled with another substrate so that the side of the module substrate with the antenna is facing the other substrate (i.e., the RF module is flipped, with respect to the previously described embodiments. For example,
Although particular system configurations are illustrated in
Thus, various embodiments of antennas configured to enable the electrical length of their antenna arms to be extended, and modules and systems in which they are incorporated have been described above. An embodiment of an antenna includes a substrate, a first antenna arm coupled to the substrate, and a first conductive structure between a distal end of the first antenna arm and a bottom surface of the substrate.
An embodiment of an RF module includes a substrate, an antenna including a first antenna arm coupled to the substrate, and a first conductive structure between a distal end of the first antenna arm and a bottom surface of the substrate. Another embodiment of an RF module includes a first substrate, an antenna coupled to the first substrate, and a set of electrical components coupled to the first substrate and to the antenna. The set of electrical components is configured to receive a signal for transmission from a non-RF component that is separately packaged from the module, to convert the signal to an RF signal, and to provide the RF signal to the antenna for radiation over an air interface.
An embodiment of a system includes a first substrate, a first conductive structure on a top surface of the first substrate, and an antenna coupled to the top surface of the first substrate. The antenna includes a second substrate, a first antenna arm coupled to the second substrate, and a second conductive structure having a proximal end and a distal end. The proximal end of the second conductive structure is coupled to a distal end of the first antenna arm, and the distal end of the second conductive structure extends to a bottom surface of the second substrate and is coupled to the first conductive structure on the first substrate. Another embodiment of a system includes an antenna having a first substrate, a first antenna arm coupled to the first substrate, and a dielectric layer covering the first antenna arm and having a first opening at a distal end of the first antenna arm.
As used herein, the term “conductive structure” means a planar conductive structure, a pad, a via, a plurality of vias, a bump, a ball, a wire, or any combination thereof. 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.
