Patent Description:
According to a first aspect, a direction-finding antenna according to claim <NUM> is disclosed.

In some embodiments of the direction-finding antenna, the direction-finding antenna further includes a third set of radiating elements configured to radiate at a third wavelength (λ<NUM>) that is shorter than the second wavelength (λ<NUM>). The third set of radiating elements may define a third circle having a third radius with a third phase center distance between about <NUM>. 15λ<NUM> and <NUM>. In embodiments, the third radius of the third circle may be smaller than the second radius of the second circle, and the third set of radiating elements may include smaller radiating elements than the second set of radiating elements.

In some embodiments of the direction-finding antenna, the transmission line-based multiplexer is further coupled to the third set of radiating elements, and the transmission line-based multiplexer is configured to selectively couple the first set of radiating elements, the second set of radiating elements, or the third set of radiating elements to the RF feed line.

In some embodiments of the direction-finding antenna, the direction-finding antenna further includes at least one additional set of radiating elements configured to radiate at an additional wavelength (λn) that is shorter than the third wavelength (λ<NUM>). The additional set of radiating elements may define an additional circle having an additional radius with an additional phase center distance between about <NUM>. 15λn and <NUM>. The additional radius of the additional circle may be smaller than the third radius of the third circle, and the additional set of radiating elements may include smaller radiating elements than the third set of radiating elements. In embodiments, the number of additional sets (n) may be limited by the size and type/geometry of the direction-finding antenna.

In some embodiments of the direction-finding antenna, the transmission line-based multiplexer is further coupled to the additional set of radiating elements, and the transmission line-based multiplexer is configured to selectively couple the first set of radiating elements, the second set of radiating elements, the third set of radiating elements, or the additional set of radiating elements to the RF feed line.

In some embodiments of the direction-finding antenna, the radiating elements may be circular disk (C-disk) antenna elements.

In some embodiments of the direction-finding antenna, the radiating elements may be monopole or monopole-like antenna elements.

In some embodiments of the directions finding-antenna, the radiating element may be dielectric resonator antennas.

In some embodiments of the direction-finding antenna, the first set of radiating elements are a first type of antenna element, and the second set of radiating elements are a second type of antenna element different from the first type of antenna element.

In some embodiments of the direction-finding antenna, the direction-finding antenna is a communications antenna.

In some embodiments of the direction-finding antenna, the direction-finding antenna is a multi-function antenna that is reconfigurable between omnidirectional mode and a commutated quadrant sectored North (N)/South (s)/East (E)/West (W) mode.

According to a second aspect, a direction-finding antenna according to claim <NUM> is also disclosed.

In some embodiments of the direction-finding antenna of the second aspect, the direction-finding antenna further includes a third set of radiating elements configured to radiate at a third wavelength (λ<NUM>) that is shorter than the second wavelength (λ<NUM>). The third set of radiating elements may define a third circle having a third radius with a third phase center distance between about <NUM>. 15λ<NUM> and <NUM>. In embodiments, the third radius of the third circle may be smaller than the second radius of the second circle, and the third set of radiating elements may include smaller radiating elements than the second set of radiating elements.

In some embodiments of the direction-finding antenna of the second aspect, the switches are further coupled to respective radiating elements of the third set of radiating elements, and the switches are configured to selectively couple selected radiating elements of the first set of radiating elements, the second set of radiating elements, or the third set of radiating elements to the RF feed line.

In some embodiments of the direction-finding antenna of the second aspect, the direction-finding antenna further includes at least one additional set of radiating elements configured to radiate at an additional wavelength (λn) that is shorter than the third wavelength (λ<NUM>). The additional set of radiating elements may define an additional circle having an additional radius with an additional phase center distance between about <NUM>. 15λn and <NUM>. The additional radius of the additional circle may be smaller than the third radius of the third circle, and the additional set of radiating elements may include smaller radiating elements than the third set of radiating elements.

In some embodiments of the direction-finding antenna of the second aspect, the switches are further coupled to respective radiating elements of the additional set of radiating elements, and the switches are configured to selectively couple selected radiating elements of the first set of radiating elements, the second set of radiating elements, the third set of radiating elements, or the additional set of radiating elements to the RF feed line.

In some embodiments of the direction-finding antenna of the second aspect, the radiating elements may be circular disk (C-disk) antenna elements.

In some embodiments of the direction-finding antenna of the second aspect, the radiating elements may be monopole or monopole-like antenna elements.

In some embodiments of the direction-finding antenna of the second aspect, the radiating elements may be dielectric resonator antennas.

In some embodiments of the direction-finding antenna of the second aspect, the switches may be or may include micro-electromechanical system (MEMS) switches, p-i-n junction (PIN) diodes, and/or transistors.

An interferometric direction-finding antenna with multiplexed/switched monopole or monopole-like radiating elements (e.g., circular disk (c-Disk) antenna elements, or the like) is disclosed. Direction-finding antennas may be utilized for navigation in GPS-denied situations. Interferometry is a desirable technique for direction finding because it employs simple antenna structures. However, interferometry direct-finding techniques require omni-directional antennas, typically resulting in the use of high-profile dipole antennas that can be easily targeted by adversaries and have limited bandwidth (e.g., <<NUM>%). To overcome these shortfalls of the current systems, the interferometric direction-finding antenna disclosed herein employs a network of switched/multiplexed monopole or monopole-like radiating elements (e.g., circular disk (c-Disk) antenna elements, or the like) in order to maintain a low-profile structure for a broadband, omni-directional antenna that can change its phase center with frequency.

<FIG> illustrates an embodiment of a direction-finding antenna <NUM> including multiple sets radiating elements in an omni-directional configuration. In some embodiments, the radiating elements (e.g., radiating elements <NUM>, <NUM>, <NUM>, etc.) may be circular disk (c-Disk) antenna elements, such as the radiating elements described in <CIT>. Alternatively, the radiating elements (e.g., radiating elements <NUM>, <NUM>, <NUM>, etc.) may include any other monopole or monopole-like antenna elements having a low-profile structure. For example, other types of radiating elements that may be utilized are described in <CIT>. Examples of other monopole or monopole-like antenna elements having a low-profile structure include, but are not limited to, inverted F antennas, inverted F antennas in a puck, layered c-Disk or printed circuit board (PCB) elements, serpentine or distorted log periodic (LP) elements, serpentine c-Disk elements, local cavity antennas, or the like. Dielectric resonator antennas are also attractive since they are volumetrically small as a function of wavelength.

In embodiments, the direction-finding antenna <NUM> includes at least a first set of radiating elements <NUM> (e.g., elements 102A, 102B, 102C, and 102D) configured to radiate at a first wavelength (λ<NUM>) and a second set of radiating elements <NUM> (e.g., elements 104A, 104B, 104C, and 104D) configured to radiate at a second wavelength (λ<NUM>) that is shorter than the first wavelength (λ<NUM>). The first set of radiating elements <NUM> may define a first circle having a first radius with a first phase center distance between about <NUM>. 15λ<NUM> and <NUM>. For example, radiating elements 102A, 102B, 102C, and 102D may be distributed along an outermost circle, equidistantly from one another. The second set of radiating elements <NUM> may define a second circle having a second radius with a second phase center distance between about <NUM>. 15λ<NUM> and <NUM>. In embodiments, the second radius of the second circle may be smaller than the first radius of the first circle. For example, radiating elements 104A, 104B, 104C, and 104D may be distributed, equidistantly from one another, along another circular path that is inside the outermost circle formed by the first set of radiating elements <NUM>. In addition, the second set of radiating elements <NUM> may include smaller radiating elements (e.g., c-Disk antenna elements having smaller diameters) than the first set of radiating elements <NUM>.

In some embodiments, the direction-finding antenna <NUM> may further include a third set of radiating elements <NUM> (e.g., elements 106A, 106B, 106C, and 106D) configured to radiate at a third wavelength (λ<NUM>) that is shorter than the second wavelength (λ<NUM>). The third set of radiating elements <NUM> may define a third circle having a third radius with a third phase center distance between about <NUM>. 15λ<NUM> and <NUM>. In embodiments, the third radius of the third circle may be smaller than the second radius of the second circle. For example, radiating elements 106A, 106B, 106C, and 106D may be distributed, equidistantly from one another, along another circular path that is inside the circle formed by the second set of radiating elements <NUM>. In addition, the third set of radiating elements <NUM> may include smaller radiating elements (e.g., c-Disk antenna elements having smaller diameters) than the second set of radiating elements <NUM>.

The direction-finding antenna <NUM> may include any number of radiating elements that are configured in a similar fashion to the radiating elements <NUM>, <NUM>, and <NUM> described above. For example, in embodiments, the direction-finding antenna <NUM> may further include at least one additional (e.g., fourth, fifth,. , nth) set of radiating elements configured to radiate at an additional wavelength (e.g., λ<NUM>, λ<NUM>,. , λn) that is shorter than the third wavelength (λ<NUM>), and so forth. The additional set of radiating elements may define an additional (e.g., fourth, fifth,. , nth) circle having an additional radius with an additional phase center distance between about <NUM>. 15λn and <NUM>. In embodiments, the radius of the additional (e.g., fourth, fifth,. , nth) circle may be smaller than the third radius of the third circle. For example, radiating elements of the additional (e.g., fourth, fifth,. , nth) set of radiating elements may be distributed, equidistantly from one another, along another circular path that is inside the circle formed by the third set of radiating elements <NUM>, and so forth. In addition, the additional (e.g., fourth, fifth,. , nth) set of radiating elements may include smaller radiating elements (e.g., c-Disk antenna elements having smaller diameters) than the third set of radiating elements <NUM>. The number of additional sets (n) may be limited by the size and type/geometry of the direction-finding antenna. Higher frequency monopole variants can help; however, the ring radius may eventually become too small at upper microwave/millimeter wave frequencies.

The foregoing embodiments illustrate the general structure of the direction-finding antenna <NUM>, where sets of radiating elements making up the direction-finding antenna <NUM> define a plurality of circles, ellipses, or other loop structures that decrease in size from the outermost loop defined by the outermost set of radiating elements to the innermost loop defined by the innermost set of radiating elements. In embodiments, the respective sizes of the radiating elements also decrease in size from the outermost loop defined by the outermost set of radiating elements to the innermost loop defined by the innermost set of radiating elements. The radiating wavelength also decreases from the outermost loop defined by the outermost set of radiating elements to the innermost loop defined by the innermost set of radiating elements. Meanwhile, the operating frequency or frequency band increases from the outermost loop defined by the outermost set of radiating elements to the innermost loop defined by the innermost set of radiating elements.

<FIG> is graphical plot illustrating an example of the impedance matching at selected operating frequencies of the direction-finding antenna <NUM>. For an arbitrary number of frequencies (e.g., f<NUM>, f<NUM>,. , fn), the spacing between sets of radiating elements (e.g., radiating elements <NUM>. etc.) may be sufficient to prevent crosstalk/interference between the different sets. For example, the spacing may be at least λ/<NUM> (e.g., at least (λ<NUM>)/<NUM> spacing between radiating elements <NUM> and <NUM>, and may be at least (λ<NUM>)/<NUM> spacing between radiating elements <NUM> and <NUM>, and so on). The radiating elements (e.g., radiating elements <NUM>, <NUM>, <NUM>, etc.) of the different sets may also be offset from one another. For example, <FIG> illustrates radiating elements 104A, 104B, 104C, and 104D having both x and y offsets from respective ones of radiating elements 102A, 102B, 102C, and 102D. Similarly, radiating elements 106A, 106B, 106C, and 106D may have x and y offsets from respective ones of radiating elements 104A, 104B, 104C, and 104D, and so forth. In some embodiments, with meander interconnect structures, the radiating center can maintain a phase center of above <NUM>. 15λ to <NUM>. Band-stop filter structures may also be introduced/included in the direction-finding antenna <NUM> (e.g., between the sets of radiating elements <NUM>, <NUM>, <NUM>, etc.).

The radiating elements (e.g., elements <NUM>, <NUM>, <NUM>, etc.) may be coupled to a common radio frequency (RF) feed line <NUM> using one or more multiplexers, switches, or the like. For example, <FIG> and <FIG> illustrate embodiments of the direction-finding antenna <NUM> including at least one transmission line-based multiplexer <NUM> (<FIG>) and/or switches <NUM> (<FIG>) that are configured to selectively connect the RF feed line <NUM> with at least one selected set of radiating elements (e.g., elements <NUM>, <NUM>, and/or <NUM>) and/or at least one selected radiating element (e.g., element 102A, 102B, 102C, 102D, 104A, 104B, 104C, 104D, 106A, 106B, 106C, and/or 106D). In embodiments, the feed line <NUM> junction may be broadband matched. Alternatively, the direction-finding antenna <NUM> can have <NUM> parallel transceiver channels. Furthermore, each of the North (N)/South (S)/East (E)/West (W) legs may be commutated with a <NUM>-way RF switch network. It is possible to have <NUM> or more individual transceiver channels to process the signal of each of the four quadrants of the antenna simultaneously.

As the frequency goes up, monopole and monopole-like elements become attractive as the ½ wave resonant length becomes smaller in terms of absolute dimension. In some embodiments, the different sets of radiating elements may include different types of radiating elements (per set). For example, the first set of radiating elements <NUM> can be a first type of antenna element, and the second set of radiating elements <NUM> can be a second type of antenna element different from the first type of antenna element. In this regard, the radiating elements may be mixed and matched different types of radiating elements for each concentric ring/loop of the direction-finding antenna <NUM> array, each for a specific frequency. In embodiments, the different types of antennas may include, but are not limited to, pure monopole (for higher frequency), printed monopole-like variants, ½ loops that can be ground-plain driven, dielectric resonator antennas, and/or microstrip type radiating elements.

It is noted that the discussion, thus far, implies vertical polarizations. However, horizontal polarization and elliptical/circular polarizations are also potentially applicable, depending on system needs and frequency ranges of interest.

As shown in <FIG>, the transmission line-based multiplexer <NUM> may be coupled to the first set of radiating elements <NUM>, the second set of radiating elements <NUM>, the third set of radiating elements <NUM>, and any additional sets of radiating elements. In embodiments, the transmission line-based multiplexer <NUM> is configured to selectively couple the first set of radiating elements <NUM>, the second set of radiating elements <NUM>, the third set of radiating elements <NUM>, or any additional sets of radiating elements to the RF feed line <NUM>. For example, the transmission line-based multiplexer <NUM> may be configured to sample all the radiating elements in a selected set simultaneously. In some embodiments, time-division multiplexing (TDM) is used to sample multiple frequency bands simultaneously, substantially simultaneously, or at least partially in parallel. For example, the transmission line-based multiplexer <NUM> can be configured to sample the first set of radiating elements <NUM> at a first time slot, the second set of radiating elements <NUM> at a second time slot, the third set of radiating elements <NUM> at a third time slot, and so forth. A receiver may then receive the signals from the different sets of radiating elements (via the RF feed line <NUM>) and process each set of signals individually based on the dedicated time slots.

<FIG> illustrates another embodiment, where instead of or in addition to the transmission line-based multiplexer <NUM>, the radiating elements (e.g., element 102A, 102B, 102C, 102D, 104A, 104B, 104C, 104D, 106A, 106B, 106C, 106D, etc.) may be coupled to switches <NUM> that are configured to selectively couple selected ones of the radiating elements to the RF feed line <NUM>. For example, the switches <NUM> coupling radiating elements 102A, 102B, 102C, and 102D may be closed to connect the first set of radiating elements <NUM> to the RF feed line <NUM>. Similarly, the switches <NUM> coupling radiating elements 104A, 104B, 104C, and 104D may be closed to connect the second set of radiating elements <NUM> to the RF feed line <NUM>, or the switches <NUM> coupling radiating elements 106A, 106B, 106C, and 106D may be closed to connect the third set of radiating elements <NUM> to the RF feed line <NUM>, and so forth. The switches may be <NUM>-way switches, where the "off" elements are switched to a terminating load. In embodiments, the switches <NUM> may be or may include, but are not limited to, micro-electromechanical system (MEMS) switches, p-i-n junction (PIN) diodes, transistors (e.g., field-effect transistors (FETs)), or any combination thereof.

Having a switch <NUM> associated with each of the radiating elements (e.g., element 102A, 102B, 102C, 102D, 104A, 104B, 104C, 104D, 106A, 106B, 106C, 106D, etc.) also allows for individual connection of a radiating element or any selected group of the radiating elements to the RF feed line <NUM>. For example, any of the radiating elements (e.g., element 102A, 102B, 102C, 102D, 104A, 104B, 104C, 104D, 106A, 106B, 106C, 106D, etc.) can be individually sampled, a set of elements (e.g., elements <NUM>, <NUM>, <NUM>, etc.) can be sampled together, or any other grouping of elements may be sampled. In some embodiments, a timing scheme is used to sample multiple frequency bands simultaneously, substantially simultaneously, or at least partially in parallel. For example, the switches <NUM> can be configured to sample the first set of radiating elements <NUM> at a first time slot, the second set of radiating elements <NUM> at a second time slot, the third set of radiating elements <NUM> at a third time slot, and so forth. A receiver may then receive the signals from the different sets of radiating elements (via the RF feed line <NUM>) and process each set of signals individually based on the dedicated time slots. Alternatively, or additionally, in the switched configuration, selected elements (e.g., element 102A, 102B, 102C, 102D, 104A, 104B, 104C, 104D, 106A, 106B, 106C, 106D, etc.) can be sampled at dedicated time slots and processed individually.

In some embodiments of the direction-finding antenna, the direction-finding antenna is a dielectric resonator antenna and/or a communications antenna. Furthermore, the direction-finding antenna may be a multi-function antenna that is reconfigurable between an omnidirectional mode and a commutated quadrant sectored N/S/E/W mode.

As shown in <FIG> and <FIG>, the direction-finding antenna <NUM> includes at least one controller <NUM> communicatively coupled to the one or more multiplexers <NUM> and/or the plurality of switches <NUM>. As shown in <FIG>, the controller <NUM> may be configured to generate one or more control signals that cause the transmission line-based multiplexer <NUM> to selectively couple the first set of radiating elements <NUM>, the second set of radiating elements <NUM>, the third set of radiating elements <NUM>, and/or one or more additional sets of radiating elements to the RF feed line <NUM>. As shown in <FIG>, the controller is configured to generate one or more control signals that cause the switches <NUM> to selectively couple selected sets and/or individual radiating elements of the first set of radiating elements <NUM>, the second set of radiating elements <NUM>, the third set of radiating elements <NUM>, and/or one or more additional sets of radiating elements to the RF feed line <NUM>.

<FIG> illustrates an embodiment of the controller <NUM>, which may include, but is not limited to, at least one processor <NUM>, memory <NUM>, and communication interface <NUM>. The processor <NUM> provides processing functionality for at least the controller <NUM> and can include any number of processors, micro-controllers, circuitry, field programmable gate array (FPGA) or other processing systems, and resident or external memory for storing data, executable code, and other information accessed or generated by the controller <NUM>. The processor <NUM> can execute one or more software programs embodied in a non-transitory computer readable medium (e.g., memory <NUM>) that implement techniques described herein. The processor <NUM> is not limited by the materials from which it is formed, or the processing mechanisms employed therein and, as such, can be implemented via semiconductor(s) and/or transistors (e.g., using electronic integrated circuit (IC) components), and so forth.

The memory <NUM> can be an example of tangible, computer-readable storage medium that provides storage functionality to store various data and/or program code associated with operation of the controller <NUM>/processor <NUM>, such as software programs and/or code segments, or other data to instruct the processor <NUM>, and possibly other components of the controller <NUM>, to perform the functionality described herein. Thus, the memory <NUM> can store data, such as a program of instructions for operating the controller <NUM>, including its components (e.g., processor <NUM>, communication interface <NUM>, etc.), and so forth. It should be noted that while a single memory <NUM> is described, a wide variety of types and combinations of memory (e.g., tangible, non-transitory memory) can be employed. The memory <NUM> can be integral with the processor <NUM>, can comprise stand-alone memory, or can be a combination of both. Some examples of the memory <NUM> can include removable and non-removable memory components, such as randomaccess memory (RAM), read-only memory (ROM), flash memory (e.g., a secure digital (SD) memory card, a mini-SD memory card, and/or a micro-SD memory card), solid-state drive (SSD) memory, magnetic memory, optical memory, universal serial bus (USB) memory devices, hard disk memory, external memory, and so forth.

The communication interface <NUM> can be operatively configured to communicate with components of the controller <NUM>. For example, the communication interface <NUM> can be configured to retrieve data from the processor <NUM> or other devices, transmit data for storage in the memory <NUM>, retrieve data from storage in the memory <NUM>, and so forth. The communication interface <NUM> can also be communicatively coupled with the processor <NUM> to facilitate data transfer between components of the controller <NUM> and the processor <NUM>. It should be noted that while the communication interface <NUM> is described as a component of the controller <NUM>, one or more components of the communication interface <NUM> can be implemented as external components communicatively coupled to the controller <NUM> via a wired and/or wireless connection. The controller <NUM> may be connected to one or more input/output (I/O) devices, system components (e.g., multiplexer <NUM>, switches <NUM>, etc.), and so forth via the communication interface <NUM>. In embodiments, the communication interface <NUM> may include a transmitter, receiver, transceiver, physical connection interface, or any combination thereof.

Various embodiments of a direction-finding antenna <NUM> have been described with reference to <FIG>. However, in other embodiments, the direction-finding antenna <NUM> may be modified without deviating from the scope of this disclosure. For example, any of the components (e.g., radiating elements <NUM>/<NUM>/<NUM>/etc., multiplexer <NUM>, switches <NUM>, controller <NUM>, etc.) described herein may be implemented by a plurality of components. In this regard, any reference to "a" or "the" component should be understood as a reference to "one or more" of the same component.

Claim 1:
A direction-finding antenna (<NUM>), comprising:
a first set of radiating elements (102A-D) configured to radiate at a first wavelength, λ<NUM>, wherein the first set of radiating elements defines a first circle having a first radius with a first phase center distance between about <NUM>.15λ<NUM> and <NUM>.20λ<NUM>;
a second set of radiating elements (104A-D) configured to radiate at a second wavelength, λ<NUM>, that is shorter than the first wavelength, λ<NUM>, wherein the second set of radiating elements defines a second circle having a second radius with a second phase center distance between about <NUM>.15λ<NUM> and <NUM>.20λ<NUM>, the second radius of the second circle is smaller than the first radius of the first circle, and the second set of radiating elements includes smaller radiating elements than the first set of radiating elements, wherein the first circle and the second circle are concentric;
a transmission line-based multiplexer (<NUM>) coupled to the first set of radiating elements and the second set of radiating elements, the transmission line-based multiplexer configured to selectively couple the first set of radiating elements or the second set of radiating elements to a radio frequency, RF,
feed line (<NUM>),
wherein the transmission line-based multiplexer is configured to sample all the radiating elements in a selected set simultaneously or at least partially in parallel.