In-Band Full-Duplex Antenna With Direction Finding Capability

Abstract

Described is an in-band full-duplex (IBFD) antenna having direction finding capability. The IBFD antenna includes a transmit antenna having an omnidirectional radiation pattern and a receive antenna configured to provide a plurality of difference beams. The IBFD antenna may be disposed on a moving platform to cover all angles around the moving platform.

Claims

1. A transceiver system comprising: an antenna; a transmit/receive (TX/RX) circuit configured to couple transmit (TX) signals for transmission to the antenna and receive incoming (RX) signals from the antenna, wherein transmission of the TX signals and reception of the RX signals occurs concurrently within a single frequency band; and a bidirectional frequency converter (BDFC) circuit to separate the TX signals from the RX signals by converting the frequency of the TX signals, the RX signals, or both, the BDFC circuit comprising a plurality of signal paths, each signal path including a modulator circuit; wherein at least N1 of the plurality of signal paths includes a circuit that shifts a phase of the signal on the respective signal path relative to a signal on at least one other signal path of the plurality of signal paths, where N is the number of signal paths in the plurality of signal paths.

2. The transceiver system of claim 1 wherein the BDFC circuit is configured to shift the frequency of the RX signal in one direction in a frequency spectrum and shift the frequency of the TX signal in another direction in the frequency spectrum.

3. The transceiver of claim 2 wherein the frequency converter circuit is configured to shift the frequency of the RX signal to a frequency that is lower than the single frequency band and shift the frequency of the TX signal to a frequency that is higher than the single frequency band.

4. The transceiver system of claim 1 further comprising a first filter to filter the TX signals and a second filter to filter the RX signals.

5. The transceiver system of claim 1 wherein the plurality of signal paths comprises parallel signal paths.

6. The transceiver system of claim 1 wherein the plurality of signal paths comprises four signal paths.

7-8. (canceled)

9. The transceiver system of claim 1 wherein the phase shifter circuit in each path of the plurality of signal paths is configured to shift the phase of the TX signal and the RX signal by a different degree value.

10. The transceiver system of claim 5 wherein the plurality of parallel signal paths are differential signal paths.

11. The transceiver system of claim 10 wherein the differential modulation switch and the phase shifter circuit is a differential phase shifter circuit.

12. A transceiver system comprising: an antenna; a transmit/receive (TX/RX) circuit configured to couple transmit (TX) signals for transmission to the antenna and receive incoming (RX) signals from the antenna, wherein transmission of the TX signals and reception of the RX signals occurs concurrently within a single frequency band; and a bidirectional frequency converter (BDFC) circuit having: a plurality of signal paths that convert a frequency of the TX signals to a first frequency and convert a frequency of the RX signals second frequency, wherein the first frequency and the second frequency are in separate frequency bands; a first port coupled to the antenna and configured to receive the RX signals and transmit the TX signals within the single frequency band; and a second port coupled to the message circuit to: receive the TX signals having the first frequency from the TX/RX circuit; and transmit the RX signals having the second frequency to the RX/RX circuit, where each of the signal paths of the plurality of signal paths includes a modulator circuit; and wherein at least N1 of the plurality of signal paths includes a circuit that shifts a phase of the signal on the respective signal path relative to a signal on at least one other signal path of the plurality of signal paths, where N is the number of signal paths in the plurality of signal paths.

13. The transceiver system of claim 12 wherein the BDFC circuit is configured to shift the frequency of the RX signal to frequency that is lower than the single frequency band and shift the frequency of the TX signal to a frequency that is higher than the single frequency band.

14. The transceiver system of claim 12 further comprising a first filter to pass the TX signals having the first frequency and a second filter to pass the RX signals having the second frequency.

15. The transceiver system of claim 12 wherein the plurality of signal paths comprises four signal paths.

16-17. (canceled)

18. The transceiver system of claim 12 wherein the one or more parallel signal paths are differential signal paths.

19. The transceiver system of claim 18 wherein at least one of the plurality of parallel signal paths includes a differential modulation switch and a differential phase shift circuit.

20. A transceiver system comprising: an antenna; a transmit/receive (TX/RX) circuit configured to couple transmit (TX) signals for transmission to the antenna and receive incoming (RX) signals from the antenna, wherein transmission of the TX signals and reception of the RX signals occurs concurrently within a single frequency band; and means for modulating the TX signal and the RX signal by a modulation frequency; and means for shifting a frequency of the TX signal to a first frequency and shifting the RX signal to a second frequency, wherein the first and second frequencies are in different frequency bands; where the means for shifting the frequency comprises a circuit with a plurality of signal paths, each signal path having a modulator circuit; and wherein at least N1 of the plurality of signal paths includes a circuit that shifts a phase of the signal on the respective signal path relative to a signal on at least one other signal path of the plurality of signal paths, where N is the number of signal paths in the plurality of signal paths.

21. The transceiver system of claim 1 wherein each circuit that shifts the phase is configured to shift the phase of the respective by a different phase offset relative to a phase offset other circuits that shift the phases.

22. The transceiver system of claim 1 wherein each circuit that shifts the phase is configured to shift the phase of the respective by a different phase offset relative to a phase offset of other circuits that shift the phases.

23. A transceiver system comprising: an antenna; a transmit/receive (TX/RX) circuit configured to couple transmit (TX) signals for transmission to the antenna and receive incoming (RX) signals from the antenna, wherein transmission of the TX signals and reception of the RX signals occurs concurrently within a single frequency band; and a bidirectional frequency converter (BDFC) circuit to separate the TX signals from the RX signals by converting the frequency of the TX signals, the RX signals, or both, the BDFC circuit comprising a plurality of signal paths, each signal path including a modulator circuit and a phase shifter circuit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The manner and process of making and using the disclosed embodiments may be appreciated by reference to the figures of the accompanying drawings which form a part this application, and which show, by way of illustration, specific example implementations and are referred to in the following Detailed Description. Other implementations may be made without departing from the scope of the disclosure. It should thus be appreciated that like reference numerals designate corresponding parts throughout the different views and components and structures illustrated in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principals of the concepts described herein. Furthermore, embodiments are illustrated by way of example and not limitation in the figures, in which:

[0018] FIG. 1 is a block diagram of a vehicle-mounted in-band full-duplex (IBFD) antenna having an omnidirectional transmit pattern and four receive patterns used for beamforming;

[0019] FIG. 2 is a block diagram of an IBFD antenna having a single transmit antenna element and eight (8) receive antenna elements;

[0020] FIG. 3A is an isometric view of an IBFD antenna having a single monopole antenna which may be used in an antenna transmit mode of operation and eight (8) wide-angle short horns which may be used in an antenna receive mode of operation;

[0021] FIG. 3B is a side view of the IBFD antenna of FIG. 3A having the radome removed;

[0022] FIG. 3C is a plot of gain (dBi) vs. azimuth angle (degrees) of an IBFD antenna which may be the same as or similar to the IBFD antenna of FIG. 3A;

[0023] FIG. 4 is a block diagram of an IBFD system capable of performing adaptive beam forming and direction finding;

[0024] FIG. 5 is a three-dimensional (3D) polar plot of antenna gain pattern for an IBFD monopole antenna;

[0025] FIG. 6 is a three-dimensional (3D) polar plot of antenna gain patterns a receive wide-angle short horn;

[0026] FIG. 7 is a block diagram of an IBFD antenna having a single transmit antenna element and four (4) receive antenna elements; and

[0027] FIG. 8 is a block diagram of an IBFD antenna having a single transmit antenna element and eight (8) receive antenna elements.

DETAILED DESCRIPTION

[0028] Described is an in-band full-duplex (IBFD) array antenna and system. IBFD antennas and systems provided in accordance with the concepts described herein provide omnidirectional phasing using circular modes and integrating a unique receive adaptive beamforming functionality (which provides direction-finding capability on receive) applicable for use in wireless communications and other applications.

[0029] In particular, IBFD systems provided in accordance with the concepts described herein have a direction-finding (DF) capability. Thus, IBFD systems provided in accordance with the concepts described herein provide information indicative of a direction from which signals are received. Such DF information can be used to improve communications links. For example, DF information can be used by one or both of receive and/or transmit systems of an IBDF system. For example, DF information can be used by one or more components of IBDF receive systems (e.g., components in an IBDF receive system such as RF and/or IF receivers and processors) to reduce (and ideally minimize) intentional/unintentional interference from external sources. DF information can also be used by one or more components in an IBDF transmit systems to increase antenna gain in a direction of interest.

[0030] Referring now to FIG. 1, an example in-band, full-duplex (IBFD) array antenna 10 comprises a first antenna 11 having a substantially omnidirectional antenna pattern 12 which may be used, for example, in a transmit mode of operation of IBFD array antenna 10. Antenna 11 may comprise one or more antenna elements. For example, Antenna 11 may comprise one or more monopole, horn or monocone antenna elements. Any arrangement or type of antenna elements which provide a substantially omnidirectional antenna pattern may be used.

[0031] IBFD antenna array further comprises a second antenna generally denoted 14. In this example embodiment, antenna 14 comprises one or more sets of four wide-angle short horn antennas 16a-16d fed by respective ones of feed elements (or circuits) 18a-18d. In embodiments, feed elements 18a-18d are provided as probe feeds. Thus, wide-angle short horn antennas are sometimes referred to herein as probe-fed wide-angle short horn antennas.

[0032] The probe-fed wide-angle short horn antennas are disposed or otherwise configured to generate difference patterns having pattern segments 19a, 19b, 19c, 19d, which form difference pattern nulls 20a-20d.

[0033] In embodiments, the probe feeds 18a-18d (and thus the associated antenna elements) are oriented (both physically and electrically) at 180 degrees from the opposing sets. That is, the antenna elements/probes on opposing sides are fed 180-degrees out of phase. Thus, in the example embodiment of FIG. 1, antenna elements, 18a and 18c have a 180-degree phase difference and antenna elements 18b and 18d have a 180-degree phase difference (e.g., probe 18a is 180 out of phase from probe 18c and probe 18b is 180 out of phase from probe 18d).

[0034] The difference patterns 19a-19d are achieved using a combination of the physical horn arrangement and the above-described phasing. While DF could be achieved with the physical arrangement alone, the addition of the above-described phasing enables full-duplex capability.

[0035] Furthermore, orienting probe feeds at 180 degrees for opposing sets avoids the need for a balun which may otherwise be required to generate difference patterns. Thus, the arrangement of antenna elements and feeds described herein avoids the need for a balun to generate difference patterns.

[0036] In the example embodiment of FIG. 1, IBFD array antenna 10 is disposed on a moving platform 16 (with moving platform 16 shown in phantom since it is not properly a part of antenna 10) with antenna 10 having a radiation patter which covers all angles around the moving platform (i.e., 360-degree field of view coverage around the moving platform). Moving platform 16 may be provided as any type of ground-vehicle, water-vehicle or air-vehicle.

[0037] Omnidirectional antenna 11 may achieve relatively high amounts of isolation between transmit and receive signal paths using circular mode phasing for designs with monopole, horn and monocone elements.

[0038] Thus, antenna 10 integrates the use of a circular mode phasing technique with the ability to perform adaptive beamforming on receive.

[0039] This added benefit provides an IBFD system comprising such an IBFD antenna with the capability of estimating a signal's direction of arrival, which can improve communication-link performance for vehicle communication systems (e.g., vehicle-to-everything communication systems such as V2X, V2V and V2I systems) and other applications.

[0040] Referring now to FIG. 2, an IBFD antenna 22 comprises a single transmit antenna element 24 and eight (8) receive antenna elements 26a-26h. The receive antenna elements are disposed in two spaced apart planes. In this example, four (4) receive antenna elements 26a-26h are disposed in a first plane and four (4) receive antenna elements 26a-26h are disposed in a second, different plane. In this example embodiment, the receive antenna elements are disposed in each plane are disposed in a circular pattern. The receive antenna elements may be the same as or similar to the probe-fed wide-angle short horn antennas described below in conjunction with FIGS. 3A, 3B. As can be seen in FIG. 2, the transmit antenna is disposed at or about a center point of the receive antenna elements (e.g. along a central longitudinal axis 25 of antenna 22). In embodiments, the transmit antenna is disposed in a plane which is different than the plane in which the receive antenna elements are disposed. In embodiments, transmit antenna may be disposed in a plane which is either in, above or below a plane in which receive antenna elements are disposed.

[0041] To generate difference patterns and implement adaptive beamforming, this example antenna embodiment requires zero (0) analog splitters, four (4) analog combiners and has zero (0) pattern ambiguities. This configuration allows for the combination of opposing pairs with the resulting channel count of four. It should be noted the self-interference (SI) is the same for elements on the first ring (numbers 1-4) and then the second ring (numbers 5-8).

[0042] Referring now to FIGS. 3A and 3B in which like elements are provided having like reference designations, an example embodiment of an IBFD array antenna 28 comprises a plurality of horn antenna elements, here eight antenna elements 30a-30h (with horn antenna elements 30d, 30h not visible in this view). Horn antenna elements 30a-30h may be the same as or similar to probe-fed wide-angle short horn antenna elements 21a-21d described above in conjunction with FIG. 1. The elements in FIGS. 3A, 3B that are 180-degrees out of phase are fed from the top/bottom of the horn (e.g., probe 34a is fed from the top of horn 30a and probe 34b is fed from the bottom of horn 30e). This arrangement eliminates the need for a balun.

[0043] In this example embodiment, the horn antenna elements 30a-30h comprise wide-angle short horn antennas 32 fed by respective ones of probe feed elements 34. The plurality of horn antenna elements 30a-30h are arranged as two sets of four probe-fed wide-angle short horn antenna elements with antenna elements 30a-30d comprising a first set and antenna elements 30e-30h comprising a second set. A first one of the two sets of horn antenna elements is disposed above a second one of the two sets of horn antenna elements.

[0044] In this example embodiment, one set of four probe-fed wide-angle short horn antenna elements are physically disposed above a second set of four probe-fed wide-angle short horn antenna elements.

[0045] Opposing sets of probe feeds 34 are oriented at 180 degrees to avoid the need for a balun in generating a difference patterns (e.g., such as difference pattern 14 in FIG. 1). Thus, each set of four probe-fed wide-angle short horn antenna elements generate a total of four difference patterns in azimuth on receive. It is noted each set of our (4) horn antennas generates two (2) difference patterns, so two sets of four (4) horn antenna elements are required to generate the four (4) difference patterns illustrated in FIG. 3C.

[0046] As can be seen in FIG. 3A, antenna elements 30a-30h are disposed to provide array 28 as a cylindrical array 28. Array 28 further comprises an omnidirectional monopole antenna 36 having a substantially omnidirectional antenna pattern. Omnidirectional monopole antenna 36 may be used, for example, in a transmit mode of operation of IBFD array antenna 28. Omnidirectional monopole antenna 36 is disposed over a ground plane 37 and is disposed above at least one of the two sets of probe-fed wide-angle short horn antenna elements

[0047] In embodiments, a radome 38 may be disposed over antenna 28. In the example of FIG. 2, radome 38 and antenna 30 may be coupled to a base 40.

[0048] In embodiments, commercial off-the-shelf (COTS) power combiners may be used to combine the feeds that are on the opposing sides of cylindrical array 28.

[0049] In one example embodiment, antenna elements 30 are tuned for operation at 1.88 GHz and radome 38 is provided from a plastic material having a relative dielectric constant of about 3.0. In embodiments, plastic radome may have a thickness of about -inch. In embodiments for operation at 1.88 GHz, the overall assembly shown in FIG. 2 may be about 10.5 inches tall with an outer diameter of about 5.7 inches.

[0050] It should, of course, be appreciated that antenna 28 may be scaled for operation over a wide range of frequencies. The general principle of combining in-band full-duplex and direction-of-arrival estimation is scalable to other frequency bands. Additionally, increasing a number of antenna elements within the receive array would improve resolution of angle-of-arrival information.

[0051] It is also appreciated that incorporation of additional receive arrays in a similar manner would provide for the ability to also discriminate an elevation angle of incoming signals (as opposed to the azimuth-angle information already provided).

[0052] In embodiments antenna 28 may be pole-mounted on top of a vehicle. In such embodiments, it would be desirable to provide antenna 28 as compact in size and low in weight.

[0053] Referring now to FIG. 4 an IBDF system 42 includes transmit and receive signal paths 43, 44. Transmit signal path 43 comprises a transmitter 45 which provides a transmit signal to a transmit antenna 48 via a transmit feed circuit 46. In embodiments, transmit antenna 46 may be provided, for example, as one or more monopole, horn or monocone antenna elements.

[0054] Receive signal path 44 comprises a receive antenna 50 comprising an array of N antenna elements (where N is an integer greater than or equal to 2) with this example embodiment comprising eight (8) antenna element 52a-52h. Receive Antenna 50 is configured to receive (or intercept) RF signals and provide the RF signals to a combiner network 54.

[0055] Combiner network 54 combines the RF (analog) signals provided thereto and provides a set of analog signals (here four analog signals corresponding to receive signals Rx 1-Rx 4) to an M channel receiver 56 where M is an integer greater than or equal to 2. In this example embodiment, receiver 56 is illustrated as a four (4) channel receiver having four inputs and four outputs. Receive 56 comprises an appropriate combination of one or more filter circuits, one or more amplifiers (e.g., low noise amplifiers), one or more downconverter circuits (e.g. RF mixers) and one or more analog to digital converter circuits (DACs) and provides a digital signal (e.g. a stream of digital bits) via one or more digital signal paths 58 (e.g. a bus such as a parallel or serial bus) to an adaptive beamformer network 59 (or more simply, adaptive beamformer 59).

[0056] Adaptive beamformer 59 implements an adaptive beamforming process to form a plurality of difference beams such as those shown in FIG. 3C. The particular difference patterns produced by adaptive beamforming network 59 will depend upon a variety of factors including but not limited to: the number, type and configuration of receive antenna elements, the combining characteristics of the combiner network and the number of channels in the receiver.

[0057] In embodiments, adaptive beamforming network 59 utilizes a process to (ideally) maximize signal-to-interference-plus-noise ratio (SINR) in a manner which may be the same as or similar to a Minimum Variance Distortionless Response (MVDR) process. It should, however, be appreciated that unlike MVDR, the adaptive beamforming process does not assume knowledge of the array response in a known signal of interest (SOI) direction. Rather, the adaptive beamforming process uses a known training sequence embedded in the SOI, first by detecting and synchronizing to training data, then estimating the SDI's unknown array response. Those results are used to estimate MVDR-type array weights. The adaptive beamforming process used herein is thus sometimes referred to as Minimum Variance Distortionless Response (MVDR) for Uncalibrated Arrays (MUA). The output of adaptive beamformer network may then be provided to one or more processors (not shown in FIG. 4) for further processing (e.g., to utilize DF information).

[0058] Referring now to FIG. 5, a three-dimensional (3D) polar plot of an antenna gain pattern for an IBFD monopole antenna which may be the same as or similar to the transmit monopole antennas described above in conjunction with FIGS. 1, 2, 3A, 3B and 4-8 shows the transmit antenna has substantially omnidirectional gain pattern. Thus, it can be seen that a transmit monopole element on top of the antenna (e.g., as shown in FIGS. 2, 3A, 3B and 7) provides a good omnidirectional radiation pattern.

[0059] Referring now to FIG. 6, a three-dimensional (3D) polar plot of antenna gain pattern illustrates the directional nature of a wide-angle short horn antenna element which may be the same as or similar to one of the wide-angle short horn antenna elements shown in FIG. 3A

[0060] Referring now to FIG. 7, an example IBFD antenna comprises a single transmit antenna element 62 and four (4) receive antenna elements 64a-64d. The receive antenna elements are disposed in a single plane. In this example embodiment, the receive antenna elements are disposed in a circular pattern in a single plane. The receive antenna elements may be the same as or similar to the probe-fed wide-angle short horn antennas described above in conjunction with FIGS. 3A and 3B. As can be seen in FIG. 6, the transmit antenna is disposed at or about a center point of the four (4) receive antenna elements. In embodiments, transmit antenna is disposed in a plane which is different than the plane in which the receive antenna elements are disposed. In embodiments, transmit antenna may be disposed in a plane which is either above or below the plane in which the receive antenna elements are disposed.

[0061] To generate difference patterns and implement adaptive beamforming, this example antenna embodiment requires four (4) analog splitters, four (4) analog combiners (which may, for example, be provided as part of a combiner network such as combiner network 54 in FIG. 4) and has zero (0) pattern ambiguities. It should be appreciated that the designs described herein assume the use of four (4) receive channels, (which is a common number in state of the art systems). Since this example antenna structure only has four elements, it is possible to provide the 180-dgree combinations in such a way that it doesn't create the ambiguities.

[0062] Referring now to FIG. 8, an example IBFD antenna 66 comprises a single transmit antenna element 68 and eight (8) receive antenna elements 70a-70h. In this example embodiment, the receive antenna elements are disposed in a circular pattern in a single plane. Other embodiments are of course, also possible. The receive antenna elements may be the same as or similar to the probe-fed wide-angle short horn antennas described above in conjunction with FIGS. 3A and 3B. As can be seen in FIG. 8, the transmit antenna is disposed at or about a center point of the eight (8) receive antenna elements. In embodiments, transmit antenna is disposed in a plane which is different than the plane in which the receive antenna elements are disposed. In embodiments, transmit antenna may be disposed in a plane which is either above or below the plane in which the receive antenna elements are disposed.

[0063] It should be noted that to generate difference patterns, and implement adaptive beamforming this example antenna embodiment requires zero analog splitters, four analog combiners (which may, for example, be provided as part of a combiner network such as combiner network 54 in FIG. 4) and has 4 pattern ambiguities. This is because when the opposing elements are combined 180-degrees out of phase, the resulting patterns are figure-eight shaped with the same radiation coverage in both the front and back. This makes it difficult to determine if the signals are arriving from the front or back, which creates an ambiguity (for the four (4) pairs, four (4) ambiguities exist).

[0064] It is noted that the above assumes the use of four (4) receive channels (hence the reason for ambiguities), As will be appreciated by one of ordinary skill in the art, if a sufficient number of receive channels are used, then it is possible to utilize the configuration of FIG. 8 without creating ambiguities.

[0065] IBFD antennas provided in accordance with the concepts described herein find application in a wide variety of applications including but not limited to wireless networking applications, wireless communication applications and other applications. It is noted that wireless networking specifications may contain provisions related to vehicle-to-everything (e.g., V2X) operation that can enable advanced driving functions, such as collision avoidance, cooperative lane change and remote driving options. In addition to these driving aides, vehicle-to-everything nodes (e.g., V2X nodes) may be tasked with performing multiple simultaneous functions, such as radar, communications and spectral sensing, which can be demanding for a wireless device operating in a traditional time-division duplex mode.

[0066] IBFD technology implemented in accordance with the concepts described herein can alleviate challenges such as the aforementioned challenges by providing a mechanism to access frequency spectrums more efficiently as well as host multiple functions at the same time. One fundamental concept/principle described herein is based on the fact that IBFD techniques enable wireless systems to simultaneously utilize the same frequency band for transmit and receive operation. This concept can help propel the adoption of vehicle-to-everything systems by allowing platforms to not only connect to multiple networks concurrently, but also do so in such a way that the spectral utilization is minimized.

[0067] This may be accomplished using tailored antenna designs, including those for vehicles, that offer the initial opportunity to combat the resulting self-interference (SI), and often focus on the direct path coupling of the transmitter to the receiver. Omnidirectional IBFD antennas have demonstrated high amounts of isolation using circular mode phasing for designs with monopole, horn and monocone elements.

[0068] While these antennas effectively suppress the SI, they do not provide any insight into the direction from which the signals are received, which can be used to improve communications links. For such a capability, IBFD directional phased arrays have been investigated, but tend to be expensive and complex to operate.

[0069] The IBFD antenna concepts described herein provide omnidirectional phasing using the circular modes and integrating a unique receive beamforming functionality suitable for use in wireless communications and other applications.

[0070] Although reference is sometimes made herein to particular types of antenna elements, it is appreciated that other antenna elements having similar functional and/or structural properties may be substituted where appropriate, and that a person having ordinary skill in the art would understand how to select such antenna elements and incorporate them into embodiments of the concepts, techniques, and structures set forth herein without deviating from the scope of those teachings.

[0071] Various embodiments of the concepts, systems, devices, structures and techniques sought to be protected are described herein with reference to the related drawings. Alternative embodiments can be devised without departing from the scope of the concepts, systems, devices, structures and techniques described herein. It is noted that various connections and positional relationships (e.g., over, below, adjacent, etc.) are set forth between elements in the following description and in the drawings. These connections and/or positional relationships, unless specified otherwise, can be direct or indirect, and the described concepts, systems, devices, structures and techniques are not intended to be limiting in this respect. Accordingly, a coupling of entities can refer to either a direct or an indirect coupling, and a positional relationship between entities can be a direct or indirect positional relationship.

[0072] As an example of an indirect positional relationship, references in the present description to providing element A over element B include situations in which one or more intermediate elements (e.g., element C) is between element A and element B as long as the relevant characteristics and functionalities of element A and element B are not substantially changed by the intermediate element(s).

[0073] The following definitions and abbreviations are to be used for the interpretation of the claims and the specification. As used herein, the terms comprises, comprising, includes, including, has, having, contains or containing, or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, a mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus.

[0074] Additionally, the term exemplary is used herein to mean serving as an example, instance, or illustration. Any embodiment or design described herein as exemplary is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms one or more and one or more are understood to include any integer number greater than or equal to one, i.e. one, two, three, four, etc. The terms a plurality are understood to include any integer number greater than or equal to two, i.e. two, three, four, five, etc. The term connection can include an indirect connection and a direct connection.

[0075] References in the specification to one embodiment, an embodiment, an example embodiment, etc., indicate that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment can include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0076] For purposes of the description hereinafter, the terms upper, lower, right, left, vertical, horizontal, top, bottom, and derivatives thereof shall relate to the described structures and methods, as oriented in the drawing figures. The terms overlying, atop, on top, positioned on or positioned atop mean that a first element, such as a first structure, is present on a second element, such as a second structure, where intervening elements such as an interface structure can be present between the first element and the second element. The term direct contact means that a first element, such as a first structure, and a second element, such as a second structure, are connected without any intermediary elements.

[0077] Use of ordinal terms such as first, second, third, etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0078] The terms approximately and about may be used to mean within 20% of a target value in some embodiments, within 10% of a target value in some embodiments, within 5% of a target value in some embodiments, and yet within 2% of a target value in some embodiments. The terms approximately and about may include the target value. The term substantially equal may be used to refer to values that are within 20% of one another in some embodiments, within 10% of one another in some embodiments, within 5% of one another in some embodiments, and yet within 2% of one another in some embodiments.

[0079] The term substantially may be used to refer to values that are within 20% of a comparative measure in some embodiments, within 10% in some embodiments, within 5% in some embodiments, and yet within 2% in some embodiments. For example, a first direction that is substantially perpendicular to a second direction may refer to a first direction that is within 20% of making a 90 angle with the second direction in some embodiments, within 10% of making a 90 angle with the second direction in some embodiments, within 5% of making a 90 angle with the second direction in some embodiments, and yet within 2% of making a 90 angle with the second direction in some embodiments.

[0080] It is to be understood that the disclosed subject matter is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The disclosed subject matter is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the several purposes of the disclosed subject matter. Therefore, the claims should be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the disclosed subject matter.

[0081] Although the disclosed subject matter has been described and illustrated in the foregoing exemplary embodiments, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the details of implementation of the disclosed subject matter may be made without departing from the spirit and scope of the disclosed subject matter.

[0082] Accordingly, it should be understood that subject matter defined in the appended claims is not necessarily limited to the specific implementations described above. The specific implementations described above are disclosed as examples only.