Systems and methods for automatic direction finding

Abstract

SOLUTION: A method includes receiving a first signal from a first loop antenna, and receiving a second signal from a second loop antenna. The method includes sampling the first signal and the second signal at a sampling rate high enough to capture an entire frequency range associated with a plurality of radio sources to generate a first digital signal and a second digital signal. The method includes converting the first digital signal and the second digital signal to a frequency domain representation. The method also includes generating, based on the frequency domain representation, a first bearing estimate for a radio source of the plurality of radio sources by comparing the relative amplitudes and phases of the first digital signal and the second digital signal represented in the frequency domain.EFFECT: The systems and methods provide a redundant navigation tool that can be used in the case of failures in other navigation systems like GPS or inertial navigation systems.SELECTED DRAWING: None

Description

[Technical Field]

[0001]

[0001] The present disclosure relates generally to systems and methods for automatic direction finding. [Background technology]

[0002]

[0002] An automatic direction finder (ADF) is a navigational device used in aviation. The ADF provides the pilot with information about the direction of radio transmitters at known positions relative to the aircraft by measuring the relative strength of signals received from radio transmitter stations on the aircraft by one or more loop antennas.

[0003]

[0003] In certain operational situations, the use of ADFs has declined as other navigation systems, such as the Global Positioning System (GPS), have replaced them. The transition to GPS has been spurred by, among other reasons, the superior performance and global coverage offered by GPS, the ability of GPS to be more easily integrated into other avionics systems, and the smaller form factor available for GPS systems as opposed to traditional ADFs. However, ADFs remain aboard many aircraft, particularly in areas where other navigation systems are unavailable or function less effectively as a backup to GPS. ADFs are also used on smaller and older aircraft where transitioning to more advanced navigation methods is not cost-effective. Summary of the Invention

[0004] In one particular embodiment, an automatic direction finder includes a first loop antenna, a second loop antenna, and one or more processors coupled to the first and second loop antennas. The one or more processors are configured to receive a first signal from the first loop antenna and a second signal from the second loop antenna. The one or more processors are configured to sample the first and second signals over a frequency range high enough to capture the entire frequency range associated with the plurality of wireless sources to generate a first digital signal and a second digital signal. The one or more processors are configured to convert the first and second digital signals to frequency-domain representations. The one or more processors are also configured to generate a first bearing estimate for a wireless source of the plurality of wireless sources based on the frequency-domain representations by comparing the relative amplitudes and phases of the first and second digital signals represented in the frequency domain.

[0005] In another particular embodiment, a non-transitory computer-readable medium includes instructions that, when executed by one or more processors, cause the one or more processors to receive a first signal from a first loop antenna and a second signal from a second loop antenna. When executed by the one or more processors, the instructions cause the one or more processors to sample the first and second signals over a frequency range high enough to capture the entire frequency range associated with a plurality of wireless sources to generate first and second digital signals. When executed by the one or more processors, the instructions cause the one or more processors to convert the first and second digital signals to frequency-domain representations. When executed by the one or more processors, the instructions cause the one or more processors to generate a first bearing estimate for a wireless source of the plurality of wireless sources based on the frequency-domain representations by comparing the relative amplitudes and phases of the first and second digital signals represented in the frequency domain.

[0006] In another particular embodiment, a method includes receiving a first signal from a first loop antenna and a second signal from a second loop antenna. The method includes sampling the first signal and the second signal over a frequency range high enough to capture the entire frequency range associated with a plurality of wireless sources to generate first and second digital signals. The method includes converting the first and second digital signals to frequency-domain representations. The method includes generating a first bearing estimate for a wireless source of the plurality of wireless sources based on the frequency-domain representations by comparing relative amplitudes and phases of the first and second digital signals represented in the frequency domain.

[0007] In another particular embodiment, a device includes means for receiving a first signal from a first loop antenna and a second signal from a second loop antenna. The device includes means for sampling the first signal and the second signal over a frequency range high enough to capture the entire frequency range associated with a plurality of wireless sources to generate a first digital signal and a second digital signal. The device includes means for converting the first digital signal and the second digital signal to a frequency-domain representation. The device includes means for generating a first bearing estimate for a wireless source of the plurality of wireless sources based on the frequency-domain representation by comparing the relative amplitudes and phases of the first digital signal and the second digital signal represented in the frequency domain.

[0008] In another particular embodiment, a system includes one or more processors configured to receive, from an automatic direction finder, a first bearing estimate associated with a first orientation relative to a first wireless source. The first bearing estimate is based on a first plurality of bearing measurements. A first portion of the first plurality of bearing measurements is based on a first signal from a first loop antenna, and a second portion of the first plurality of bearing measurements is based on a second signal from a second loop antenna. The one or more processors are configured to receive, from the automatic direction finder, a second bearing estimate associated with a second orientation relative to a second wireless source. The second bearing estimate is based on the second plurality of bearing measurements. A first portion of the second plurality of bearing measurements is based on the first signal from the first loop antenna, and a second portion of the second plurality of bearing measurements is based on a second signal from the second loop antenna. The one or more processors are also configured to determine a location based at least on the first bearing estimate and the second bearing estimate.

[0009] In another particular embodiment, a non-transitory computer-readable medium includes instructions that, when executed by one or more processors, cause the one or more processors to receive, from the automatic direction finder, a first bearing estimate associated with a first orientation relative to a first wireless source. The first bearing estimate is based on a first plurality of bearing measurements. A first portion of the first plurality of bearing measurements is based on a first signal from a first loop antenna, and a second portion of the first plurality of bearing measurements is based on a second signal from a second loop antenna. When executed by the one or more processors, the instructions cause the one or more processors to receive, from the automatic direction finder, a second bearing estimate associated with a second orientation relative to a second wireless source. The second bearing estimate is based on the second plurality of bearing measurements. A first portion of the second plurality of bearing measurements is based on a first signal from the first loop antenna and a second portion of the second plurality of bearing measurements is based on a second signal from the second loop antenna. The instructions, when executed by the one or more processors, also cause the one or more processors to determine a location based at least on the first bearing estimate and the second bearing estimate.

[0010] In another particular embodiment, a method includes receiving, from an automatic direction finder, a first bearing estimate associated with a first orientation relative to a first wireless source. The first bearing estimate is based on a first plurality of bearing measurements. A first portion of the first plurality of bearing measurements is generated by one or more processors based on a first signal from a first loop antenna, and a second portion of the first plurality of bearing measurements is generated by one or more processors based on a second signal from a second loop antenna. The method includes receiving, from the automatic direction finder, a second bearing estimate associated with a second orientation relative to a second wireless source. The second bearing estimate is based on the second plurality of bearing measurements. The first portion of the second plurality of bearing measurements is generated by the one or more processors based on the first signal from the first loop antenna, and the second portion of the second plurality of bearing measurements is generated by the one or more processors based on the second signal from the second loop antenna. The method also includes determining a location based at least on the first orientation estimate and the second orientation estimate.

[0011] In another particular embodiment, a device includes means for receiving, from an automatic direction finder, a first bearing estimate associated with a first orientation relative to a first wireless source. The first bearing estimate is based on a first plurality of bearing measurements. A first portion of the first plurality of bearing measurements is generated by one or more processors based on a first signal from a first loop antenna, and a second portion of the first plurality of bearing measurements is generated by one or more processors based on a second signal from a second loop antenna. The device includes means for receiving, from the automatic direction finder, a second bearing estimate associated with a second orientation relative to a second wireless source. The second bearing estimate is based on the second plurality of bearing measurements. The first portion of the second plurality of bearing measurements is generated by the one or more processors based on the first signal from the first loop antenna, and the second portion of the second plurality of bearing measurements is generated by the one or more processors based on the second signal from the second loop antenna. The device also includes means for determining a location based at least on the first orientation estimate and the second orientation estimate.

[0012] In another particular embodiment, an antenna includes a core. The antenna includes a first loop antenna including a first plurality of conductive loops formed around the core. The antenna includes a second loop antenna including a second plurality of conductive loops formed around the core at a first angle relative to the first plurality of conductive loops. The antenna also includes a third loop antenna including a third plurality of conductive loops formed around the core at a second angle relative to the first plurality of conductive loops.

[0013] In another particular embodiment, a device includes an antenna and an electronics unit coupled to the antenna. The antenna includes a core. The antenna also includes a first loop antenna including a first plurality of conductive loops formed around the core, a second loop antenna including a second plurality of conductive loops formed around the core at a first angle relative to the first plurality of conductive loops, and a third loop antenna including a third plurality of conductive loops formed around the core at a second angle relative to the first plurality of conductive loops. The electronics unit includes a receiver configured to receive a first signal from the first loop antenna, receive a second signal from the second loop antenna, and receive a third signal from the third loop antenna. The electronics unit also includes a software-defined radio component configured to process signals associated with the first signal, the second signal, and the third signal.

[0014] In another specific embodiment, a device includes a housing, an antenna contained within the housing, an electronics unit contained within the housing and coupled to the antenna, and an interface contained within the housing and coupled to the electronics unit, the interface configured to enable data transfer from the electronics unit to a second device external to the housing. The antenna includes a core, a first loop antenna including a first conductive loop formed around the core, a second loop antenna including a second plurality of conductive loops formed around the core at a first angle relative to the first conductive loop, and a third loop antenna including a third conductive loop formed around the core at a second angle relative to the first loop antenna. The electronics unit includes a receiver configured to receive a first signal from the first loop antenna, a second signal from the second loop antenna, and a third signal from the third loop antenna. The electronics unit also includes a software-defined radio component configured to process signals associated with the first signal, the second signal, and the third signal. [Brief explanation of the drawings]

[0015] [Figure 1] 1 illustrates an exemplary system for automatic direction finding, according to some embodiments of the present disclosure. [Figure 2]

[0016] 1 illustrates another exemplary system for automatic direction finding, according to some embodiments of the present disclosure. [Figure 3]

[0017] 1 illustrates another exemplary system for automatic direction finding, according to some embodiments of the present disclosure. [Figure 4]

[0018] 1 illustrates another exemplary system for automatic direction finding, according to some embodiments of the present disclosure. [Figure 5]

[0019] 1 illustrates an exemplary antenna, according to some embodiments of the present disclosure. [Figure 6]

[0020] 1 illustrates an exemplary device for automatic direction finding, according to some embodiments of the present disclosure. [Figure 7]

[0021] 1 illustrates an exemplary determination of the location of an ADF, according to some embodiments of the present disclosure. [Figure 8]

[0022] 1 is a flowchart illustrating an example method for automatic direction finding, according to some embodiments of the present disclosure. [Figure 9]

[0023] 10 illustrates another example flowchart for automatic direction finding, according to some embodiments of the present disclosure. [Figure 10]

[0024] 1 is a flowchart of an example method for location estimation, according to some embodiments of the present disclosure. [Figure 11]

[0025] FIG. 1 is a block diagram of a computing environment including a computing device configured to support aspects of computer-implemented methods and computer-executable program instructions (or code) according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016]

[0026] For efficient and safe aircraft operation, aircraft are often equipped with automatic direction finders (ADFs). In recent years, many aircraft have transitioned to using global positioning systems (GPSs) for navigation instead of or in addition to ADFs. However, ADFs remain a valuable tool for aircraft navigation, especially in situations where GPS equipment fails, GPS signals are unavailable (e.g., in geographic areas where GPS signals are blocked), GPS signals are spoofed, etc. The ADFs described herein can be used as independent and / or alternative navigation devices.

[0017]

[0027] A technical advantage of the present disclosure is that it provides GPS-independent navigation redundancy. The systems and methods disclosed herein provide a redundant navigation tool that can be used in the event of a failure in a GPS or other navigation system, such as an inertial navigation system.

[0018]

[0028] Another technical advantage of the present disclosure is that it provides wider navigation coverage: the systems and methods disclosed herein may operate in areas where other navigation systems may be less effective or non-existent, such as remote or underdeveloped regions of the world.

[0019]

[0029] Another technical advantage of the present disclosure is that it provides a navigation tool upgrade for older aircraft that do not incorporate the latest navigation technology due to the costs associated with the latest navigation technology.

[0020]

[0030] Another technical advantage of the present disclosure is that it helps aircraft operators meet regulatory requirements while improving the efficiency and capabilities of the ADF. For example, certain regulatory authorities may have specific requirements regarding the types of navigation equipment that must be installed on aircraft. The ADF has historically been, and may continue to be, required by certain regulatory frameworks.

[0021]

[0031] Another technical advantage of the present disclosure is the improved capabilities of ADFs installed on aircraft of most major aircraft operators. For example, as described in more detail below, the systems and methods disclosed herein may provide multiple orientation estimates that may be used to employ fault detection and rejection operations to improve the accuracy of the aircraft's orientation, and that may be used to provide an estimate of the aircraft's position.

[0022]

[0032] Another technical advantage of the present disclosure is reducing the overall size required for the ADF, thereby increasing the space available on the aircraft for other equipment. The systems and methods disclosed herein may also reduce the complexity required to accommodate certain legacy ADFs, such as by reducing the amount and / or extent of cabling and other electronics used to connect the ADF to other avionics on the aircraft.

[0023]

[0033] This disclosure describes systems and methods for automatic direction finding, such as ADFs that have reduced size, reduced weight, and additional capabilities compared to certain widely used legacy ADFs.

[0024]

[0034] In one particular example, the ADF can be a drop-in replacement for an ARINC 712 form factor ADF, eliminating significant portions of the system. (The Airlines Electronic Engineering Committee (AEEC), Aviation Maintenance Conference (AMC), and Flight Simulator Engineering and Maintenance Conference (FSEMC) are aviation industry activities sponsored by ARINC Industry Activities, an industry program of the SAE Industry Technologies Consortia (ITC). "ARINC" is a registered trademark of ARINC, Inc., Annapolis, Maryland.) In this particular example, the ADF can include the same interface and controls while performing the same functions as, and beyond, conventional ADFs, allowing it to be easily integrated into aircraft using ARINC 712-style ADFs without requiring modifications to other systems on the aircraft other than the functionality of conventional ADFs and potentially the removal of wiring and physical equipment racks. Specifically, the systems and methods disclosed herein can enable simultaneous bearing determination to multiple non-directional beacons (NDBs) or amplitude-modulated (AM) radio stations operating in the 190 kHz to 1.75 MHz band. High-frequency transmissions in the 2 MHz to 20 MHz band can also be used as a source of bearing measurements. Conventional ADFs can only track one transmitter at a time and can only provide bearing measurements for one transmitter at a time. As a result, two separate ADFs are required to obtain the two bearing estimates necessary for position determination. In the ADF of the present disclosure, multiple software-based receiver chains can operate in parallel to track multiple signals and derive bearings for multiple sources. The number of bearing measurements can be limited only by the available signal sources and the processing power of the system.

[0025]

[0035] In one particular embodiment, the systems and methods disclosed herein may include an arrangement of four crossed loops rather than the two crossed loops used by some conventional ADFs. The use of four loops improves the accuracy of the orientation measurement and enables fault detection and isolation for potential failures in one of the loop antennas. In general, any number of loops greater than two may be used. The use of three loops may enable some fault detection. The use of four or more loops may enable fault detection and isolation. The more observations (i.e., loops) used, the greater the degree of fault detection and isolation, improving the accuracy of the final measurement.

[0026]

[0036] The drawings and the following description illustrate several specific, exemplary embodiments. Those skilled in the art will recognize that, even if not explicitly described or shown herein, they may devise various configurations that embody the principles described herein and are within the scope of the claims that follow. Furthermore, any examples described herein are intended to aid in the understanding of the principles of the disclosure and are not intended to be limiting. Consequently, the disclosure is not limited to the specific embodiments or examples described below, but is limited by the claims and their equivalents.

[0027]

[0037] Certain embodiments are described herein with reference to the drawings. In the description, common features are given common reference numbers throughout the drawings. In some drawings, multiple instances of a particular type of feature are used. Although these features are physically and / or logically different, the same reference number is used for each, and different instances are distinguished by adding a letter to the reference number. When features as a group or type are referred to herein (e.g., when no specific one of the features is referenced), the reference number is used without a distinguishing letter. However, when one specific feature of multiple features of the same type is referred to herein, the reference number is used with a distinguishing letter. For example, with reference to FIG. 3, multiple loop antennas are shown and associated with reference numbers 302A, 302B, 302C, and 302D. When referring to a specific one of these loop antennas, such as loop antenna 302A, the distinguishing letter "A" is used. However, when referring to any one of these loop antennas, the reference number 302 is used without a distinguishing letter.

[0028]

[0038] As used herein, various terms are used only for the purpose of describing particular embodiments and are not intended to be limiting. For example, the singular forms "a" and "an" and "the" are intended to include the plural (unless the context clearly dictates otherwise). Furthermore, some features described herein may exist in the singular in some embodiments and in the plural in other embodiments. To illustrate, FIG. 1 depicts a system 100 including one or more processors ("(one or more) processors 106" in FIG. 1), indicating that in some embodiments, the system 100 includes a single processor 106 and in other embodiments, the system 100 includes multiple processors 106. For ease of reference herein, such features are generally introduced as "one or more" features, followed by a single or optionally multiple features (typically indicated by "s"), unless it is clearly stated that multiple aspects relate to multiple features.

[0029]

[0039] Furthermore, the terms "comprise," "comprises," and "comprising" are used interchangeably with "include," "includes," and "including." Furthermore, the term "wherein" is used interchangeably with the term "where." As used herein, "exemplary" indicates an example, an implementation, and / or an aspect and should not be construed as limiting or as indicating a preferred or preferred implementation. As used herein, ordinal terms (e.g., "first," "second," "third," etc.) modifying elements such as structures, components, acts, etc. do not in themselves indicate a priority or order of one element over another, but merely distinguish one element from another element having the same name (apart from its use as an ordinal term). As used herein, the term "set" refers to a grouping of one or more elements, and the term "plurality" refers to a plurality of elements.

[0030]

[0040] As used herein, "generating," "calculating," "using," "selecting," "accessing," and "determining" are interchangeable unless the context indicates otherwise. For example, "generating," "calculating," or "determining" a parameter (or signal) can refer to actively generating, calculating, or determining a parameter (or signal), or can refer to using, selecting, or accessing a parameter (or signal) that has already been generated, for example, by another component or device. As used herein, "coupled" may include "communicatively coupled," "electrically coupled," or "physically coupled," or may also (or alternatively) include any combination thereof. Two devices (or components) can be directly or indirectly coupled (communicatively coupled, electrically coupled, or physically coupled) via one or more other devices, components, wires, buses, networks (wired networks, wireless networks, or combinations thereof), etc. Two devices (or components) that are electrically coupled can be included in the same device or different devices and can be connected via electronics, one or more connectors, or inductive coupling, as illustrative, non-limiting examples. In some implementations, two devices (or components) that are communicatively coupled, such as via electrical communication, can send and receive electrical signals (digital signals or analog signals) directly or indirectly via one or more wires, buses, networks, etc. As used herein, "directly coupled" is used to describe two devices that are coupled (e.g., communicatively coupled, electrically coupled, or physically coupled) without any intervening components.

[0031]

[0041] FIG. 1 illustrates an exemplary system 100 for automatic direction finding in accordance with some embodiments of the present disclosure. In some implementations, the system 100 includes a computing device 102 configured to receive a first signal 132 via a first loop antenna 126 and a second signal 134 via a second loop antenna 128. In some aspects, the computing device 102 may also be configured to receive a third signal 136 from a third loop antenna 130 and a fourth signal 137 from a fourth loop antenna 131. The loop antennas 126-131 have different orientations relative to one another. The loop antennas 126-131 may be wound around a common core. For example, the loop antennas 126-130 may be wound around opposing flats of an octagonal core, as described in more detail below with reference to FIG. 5. The first signal 132, the second signal 134, the third signal 136, and / or the fourth signal 137 are associated with radio frequency signals from one or more wireless sources 138, 140. For example, the wireless source(s) 138, 140 may include an NDB, an AM radio station tower, etc.

[0032]

[0042] In some implementations, first loop antenna 126, second loop antenna 128, third loop antenna 130, fourth loop antenna 131, or some combination thereof, may include, correspond to, or be included in an ADF, another suitable computing device, or some combination thereof. In the same or alternative implementations, first loop antenna 126, second loop antenna 128, third loop antenna 130, fourth loop antenna 131, or some combination thereof, may be external to and / or remote from computing device 102 and may communicate first signal 132, second signal 134, third signal 136, fourth signal 137, or some combination thereof, to computing device 102 via a communications link, such as a coaxial cable.

[0033]

[0043] In some implementations, computing device 102 includes one or more processors 106 coupled to memory 108. The one or more processors 106 may be configured to receive a first signal 132 from first loop antenna 126, a second signal 134 from second loop antenna 128, a third loop signal 136 from third loop antenna 130, and a fourth signal 137 from fourth loop antenna 131.

[0034]

[0044] The processor(s) 106 may include one or more signal samplers 104, one or more signal converters 142, one or more heading estimate generators 112, or some combination thereof. In some implementations, the signal sampler(s) 104 samples the first signal 132 to generate a first digital signal 114, the second signal 134 to generate a second digital signal 116, the third signal 136 to generate a third digital signal 118, the fourth signal 137 to generate a fourth digital signal 119, or some combination thereof, across a frequency range associated with the wireless sources 138, 140. The signal sampler(s) 104 may include, for example, one or more analog-to-digital converters configured to convert the received wireless signals to digital signals. For example, if the wireless sources 138, 140 are NDB or AM radio stations operating in the 190 kHz to 1.75 MHz band, the signal sampler(s) 104 may be configured to sample the entire 190 kHz to 1.75 MHz band at a sampling rate at least twice the bandwidth of interest. For example, in the 190 kHz to 1.75 MHz band, the signal sampler(s) 104 may be configured to have a sampling rate of at least twice 1.75 MHz (i.e., 3.5 MHz). The sampling of the digital signal may include the first digital signal 114, the second digital signal 116, the third digital signal 118, the fourth digital signal 119, or a combination thereof, within a single sampled signal. The first digital signal 114, the second digital signal 116, the third digital signal 118, the fourth digital signal 119, or a combination thereof, may be separated in digital signal processing performed in one or more processing chains 422, as described in more detail below with reference to FIG. 4.

[0035]

[0045] In some implementations, the signal converter(s) 142 may be configured to convert the first digital signal 114, the second digital signal 116, the third digital signal 118, the fourth digital signal 119, or a combination thereof, into a frequency-domain representation. For example, the signal converter(s) 142 may be configured to perform a fast Fourier transform on the digital signals 114-119. In one particular aspect, the signal sampler(s) 104 are configured to sample the signals 132-137 using a sampling rate high enough to capture the entire bandwidth of interest (which may be referred to as the Nyquist frequency). The signal converter(s) 142 may then convert the digital signals 114-119 one at a time to generate the frequency-domain representation 144. In one particular example, the bandwidth of interest may be related to the operating frequency range (e.g., 0.19-1.75 MHz) of the wireless sources 138, 140. The source transmitter frequency data 124 may be included in a database stored in the memory 108. This database may also include the known locations of the wireless sources 138, 140.

[0036]

[0046] In some implementations, the bearing estimate generator(s) 112 may be configured to generate an bearing estimate for each wireless source 138, 140 based on the frequency-domain representation 144. As described in more detail below with reference to Figures 3 and 4, the bearing estimate generator(s) 112 may include one or more components for generating a first bearing estimate 120 associated with the first wireless source 138 and a second bearing estimate 122 associated with the second wireless source 140 based on the frequency-domain representation 144. In one particular aspect, the processor(s) 106 may be configured to generate the multiple bearing estimates 122 for each of the wireless sources 138, 140 in parallel processing operations.

[0037]

[0047] In some embodiments, system 100 may also include a sense antenna coupled to processor(s) 106. The sense antenna may be an omnidirectional antenna with sufficient sensitivity to be able to distinguish the relative phase of loop antennas 126-130. Processor(s) 106 may be configured to receive signals from the sense antenna and determine the relative phase between first signal 132, second signal 134, third signal 136, and fourth signal 137 received by the sense antenna, as well as the phase of first signal 132, second signal 134, third signal 136, and fourth signal 137 received by the loop antenna.

[0038]

[0048] In some implementations, the processor(s) 106 are also configured to generate an overall orientation estimate for one or more of the wireless sources 138, 140. In some aspects, the overall orientation estimate may be derived by averaging the first orientation estimate 120 and the second orientation estimate 122 for one or more of the wireless sources 138, 140. In the same or alternative aspects, the processor(s) 106 may be configured to employ other means for generating the overall orientation estimate. For example, the first orientation estimate 120 and the second orientation estimate 122 may be used to perform a best fit of a sine wave corresponding to an expected distribution of amplitude and phase of a wave arriving from a given angle. The phase of the best-fit sine wave may indicate the angle of arrival. If a particular loop antenna fails, the system 100 can detect and isolate the faulty measurement and still continue to generate orientation measurements.

[0039]

[0049] In some aspects, the processor(s) 106 may also be configured to apply fault detection operations, fault exclusion operations, or some combination thereof to the multiple bearing estimates 120, 122 of the wireless sources 138, 140. For example, a fault detection operation may be based on comparing two different measurements made using two different pairs of loop antennas. The resulting comparison may be compared to a fault detection threshold to detect a fault. If the comparison exceeds the fault detection threshold, there is a potential fault in one of the loop antennas (one or more of the first loop antenna 126, the second loop antenna 128, and the third loop antenna 130) that is causing the inconsistent measurements.

[0040]

[0050] In some aspects, system 100 may be an integrated unit, as described in more detail below with reference to Figure 6. In one particular aspect, the integrated unit may be a system-on-chip.

[0041]

[0051] While FIG. 1 illustrates certain components of system 100, more, fewer, and / or different components may be present without departing from the scope of this disclosure. For example, while four loop antennas 126-131 are illustrated, there may be two, three, or more than four loop antennas. A particular example of implementing four loop antennas is described in more detail below with reference to FIGS. 3-5, 7, and 8. As another example, as described above, computing device 102 and loop antennas 126-131 may be an integrated unit. As a further example, memory 108 may include a database containing known locations of wireless sources 138, 140.

[0042]

[0052] In operation, the processor(s) 106 may receive a first signal 132, a second signal 134, a third signal 136, and a fourth signal 137 from wireless sources 138, 140. The amplitude of a particular signal received from a first source depends on the angle of arrival of the particular signal received. For example, for a simple sinusoidal source signal, the amplitude S(t) may be calculated using the following equation: where θ is the angle of arrival measured from the plane of the antenna loop, ω is the frequency of the carrier, and φ is an arbitrary phase of the carrier. S(t)=A·sin(θ)sin(ωt+φ) In such a configuration, two crossed loops positioned at 90 degrees can be used to determine the angle of arrival θ. The amplitudes S1(t) and S2(t) of the two crossed loops can be calculated using the following equations: S1(t)=A·sin(θ)sin(ωt+φ) S2(t)=A·sin(θ+π / 2)sin(ωt+φ)=A·cos(θ)sin(ωt+φ)

[0043]

[0053] The processor(s) 106 may be configured to measure the amplitude of each signal and calculate the ratio of one signal to another, as shown in the following equation: |S1(t)| / |S2(t)|=Asinθ / Acosθ=tanθ The processor(s) 106 may then be configured to calculate the angle B associated with the angle of arrival θ using the following equation: B=tan -1 (|S1(t)| / |S2(t)|) Angle B will always be between 0 and 180 degrees due to the absolute value of the division part of the equation. The angle of arrival θ will either be angle B or B+180 degrees. The determination of whether the angle of arrival θ is B or B+180 degrees can be determined based on the phase difference between the signal received from the first source by the sensing antenna and the signal received from the first source by the loop antennas 126-130.

[0044]

[0054] While the bearing estimate from the loop antenna can be used to generate an overall bearing estimate, adding additional bearing estimates from additional antennas enables further functionality of the ADF. For example, the four-antenna embodiment shown in FIG. 1 and the four-antenna embodiment shown in FIGS. 3-5 may enable over-specification of the overall bearing estimate, thereby enabling fault detection, fault exclusion, further functionality, or some combination thereof. Further functionality may also be enabled by sampling the incoming radio signal across the entire frequency band of the radio sources 138, 140.

[0045]

[0055] In one particular embodiment using four loop antennas A, B, C, and D arranged at increasing 45 degree angles from each other (e.g., as shown in FIG. 5), the signal amplitude (i.e., S A (t), S B (t), S C (t), and S D (t)) can be written using the following equation: S A (t)=A·sin(θ)sin(ωt+φ) S B (t)=A·sin(θ-π / 4)sin(ωt+φ) S C (t)=A·sin(θ-π / 2)sin(ωt+φ)=A·cos(θ)sin(ωt+φ) S D (t)=A·sin(θ-3π / 4)sin(ωt+φ)=A·cos(θ-π / 4)sin(ωt+φ)

[0046]

[0056] The A and C loops form a first pair of perpendicularly crossed loops, and the B and D loops form a second pair of perpendicularly crossed loops, so that measurements from four antennas can be taken, and the processor(s) 106 can be configured to average the overall heading estimate provided by the two sets of perpendicularly crossed loops, as shown in the following equation: where B ACis the θ of the pair of loops A to C AC is the angle associated with B BD is the arrival angle θ of the pair of B to D loops BD is the angle associated with TIFF2025160118000001.tif5170 is angle B AC and B BD is the average. B AC =tan -1 (|S A (t)| / |S C (t)|) B BD =tan -1 (|S B (t)| / |S D (t)|) TIFF2025160118000002.tif10170

[0047]

[0057] The values ​​of the various angles B in the above three equations will always be between 0 and 180 degrees due to the absolute values ​​in the division parts of the equations. The angle θ corresponding to one of the various angles B will be either angle B or B+180 degrees. The determination of whether the angle of arrival θ is B or B+180 degrees may be determined based on the phase difference between the signal received from the first source by the sensing antenna and the signal received from the first source by the loop antennas 126-130.

[0048]

[0058] Using multiple sets of orientation estimates from multiple crossed pairs of loop antennas, the processor(s) 106 may generate a detection statistic d based on a comparison of multiple measurements, as shown in the following equation: If d exceeds a fault detection threshold, the processor(s) 106 may be configured to generate an alert, for example, that there is a potential fault in one of the loops and the measurements are inconsistent. As noted above, other means of fault detection may also be used without departing from the scope of this disclosure. d=|θ AC -θ BD |

[0049]

[0059] In some aspects, system 100 may include multiple software-based receiver chains. In such aspects, computing device 102 may include a larger number of receivers in a smaller physical package. In certain configurations, the number of orientation measurements may be limited only by the processing and other computing resources of computing device 102.

[0050]

[0060] In some implementations, computing device 102 may be associated with, integrated with, or otherwise included in an aircraft, a portable electronic device such as a portable ADF, or the like. System 100 may also include components not shown in FIG. 1 . For example, computing device 102 may also include a receiver configured to receive first signal 132, second signal 134, third signal 136, or some combination thereof. The receiver may be configured to receive data via a data bus, such as an ARINC 429 bus. As a further example, system 100 may also include one or more input / output interfaces, one or more network interfaces, etc. Additionally, while FIG. 1 illustrates memory 108 of system 100 as storing particular data, more, less, and / or different data may be present in memory 108 without departing from the scope of the present disclosure.

[0051]

[0061] 1 illustrates certain operations occurring within computing device 102, these operations may be performed by other components of system 100 without departing from the scope of the present disclosure. For example, one or more components external to computing device 102 may be configured to host or otherwise incorporate some or all of the components of signal sampler(s) 104, signal converter(s) 142, heading estimate generator(s) 112, or some combination thereof. Such component(s) may be located remotely from computing device 102 and accessed via a modem of computing device 102.

[0052]

[0062] 1 depicts the processor(s) 106 and memory 108 as being integrated within a single computing device 102, other configurations are possible without departing from the scope of this disclosure. For example, the memory 108 may be stored as a separate data store and integrated within the navigation computer, while the processor(s) 106 may be integrated within an ADF located remotely from the navigation computer. As a further example, one or more components of the computing device 102 may be distributed across multiple computing devices (e.g., a group of processor cores).

[0053]

[0063] In addition to using two or more loop antennas as part of an ADF, the systems and methods disclosed herein may also be implemented as part of a multi-bearing position solution that may enable an aircraft to determine its geographic location based on multiple radio signals received from each of multiple radio sources 138, 140, as described in more detail below.

[0054]

[0064] 2 illustrates another exemplary system 200 for automatic direction finding, according to some embodiments of the present disclosure. In some implementations, the system 200 includes a computing device 202 configured to receive a first bearing estimate 242 and a second bearing estimate 244 from an automatic direction finder 204 based on at least one wireless signal received from a wireless source 138, 140.

[0055]

[0065] In some implementations, the automatic direction finder 204 may include one or more processors 210 coupled to a memory 212. In some aspects, the automatic direction finder 204 may also include multiple loop antennas, including the first loop antenna 126 and the second loop antenna 128, where each loop antenna is configured to receive wireless signals from multiple wireless sources 138, 140. As described above with reference to FIG. 1, in some implementations, the automatic direction finder 204 may include three or more loop antennas. In one particular aspect, the automatic direction finder 204 generally corresponds to the computing device 102 of FIG. 1.

[0056]

[0066] The processor(s) 210 may be configured to receive a first signal 236 from the first loop antenna 126 and a second signal 238 from the second loop antenna 128. The processor(s) 210 may also be configured to generate a first plurality of bearing measurements 228 for the first signal 236 and a second plurality of bearing measurements 230 for the second signal 238. In one particular aspect, the first plurality of bearing measurements 228 and the second plurality of bearing measurements 230 may be stored in the memory 212.

[0057]

[0067] In some aspects, the processor(s) 210 may be configured to generate a first portion 232 of a first plurality of bearing measurements 228 associated with wireless signals received by the first loop antenna 126 from the first wireless source 138, a second portion 234 of the first plurality of bearing measurements 228 associated with wireless signals received by the first loop antenna 126 from the second wireless source 140, a first portion 233 of a second plurality of bearing measurements 230 associated with wireless signals received by the second loop antenna 128 from the first wireless source 138, and a second portion 235 of the second plurality of bearing measurements 230 associated with wireless signals received by the second loop antenna 128 from the second wireless source 140.

[0058]

[0068] In some implementations, the processor(s) 210 may be configured to generate a first bearing estimate 242 associated with a first orientation of the automatic direction finder 204 relative to the first wireless source 138 and to communicate the first bearing estimate 242 to the computing device 202. The processor(s) 210 may also be configured to generate a second bearing estimate 244 associated with a second orientation of the automatic direction finder 204 relative to the second wireless source 140 and to communicate the second bearing estimate 244 to the computing device 202.

[0059]

[0069] In some implementations, computing device 202 includes one or more processors 206 coupled to memory 208. The processor(s) 206 may be configured to receive a first bearing estimate 242 and a second bearing estimate 244 from the automatic direction finder 204.

[0060]

[0070] In some implementations, computing device 202 may include a location determination system 214 configured to determine location 216 based at least on first orientation estimate 242 and second orientation estimate 244, as described in more detail below with reference to FIGS. 8 and 9.

[0061]

[0071] In some aspects, system 200 may also include aircraft control system 220 configured to communicate one or more aircraft control signals 224 to computing device 202. For example, aircraft control system 220 may include, be integrated into, or otherwise be a part of an aircraft control system configured to generate aircraft control signal(s) 224 associated with the aircraft's flight state, aircraft control configuration, etc. As one particular example, aircraft control signal(s) 224 may include one or more signals indicating the pilot's intent to switch to ADF 204 for navigation instead of or in addition to an alternative navigation tool, such as a GPS. In some implementations, processor(s) 206 may be configured to determine position 216 responsive to aircraft control system 220 of the aircraft.

[0062]

[0072] In the same or alternative aspects, system 200 may also include a positioning system 222 communicatively coupled to computing device 202. Positioning system 222 may include, for example, a GPS unit, an inertial navigation device, or some combination thereof. In one particular aspect, positioning system 222 may be configured to communicate a positioning system failure indication signal 226 associated with a failure of positioning system 222. For example, positioning system failure indication signal 226 may include one or more signals indicative of a loss of satellite signals, a power failure, a computing failure, etc. associated with positioning system 222. In some implementations, processor(s) 206 may be configured to determine location 216 in response to positioning system failure indication signal 226 indicative of a failure associated with positioning system 222.

[0063]

[0073] In some implementations, the wireless sources 138, 140 may be NDBs, AM radio stations, etc., as described in more detail above with reference to FIG. 1. In some aspects, the processor(s) 206 may be configured to determine the location 216 based at least on the known location of the first wireless source 138 and the known location of the second wireless source 140. In a particular aspect, the known locations of the wireless sources 138, 140 may be stored as part of a known location dataset 218 stored in the memory 208. In a particular aspect, the known location of the first wireless source 138 is a measurement of the location of the first wireless source 138 relative to the center of the Earth, the known location of the second wireless source 140 is a measurement of the location of the second wireless source 140 relative to the center of the Earth, or some combination thereof, as described in more detail below with reference to FIG. 9.

[0064]

[0074] In the same or alternative certain aspects, processor(s) 206 may be configured to determine the location of the aircraft based on an iterative process between an initial position and established known positions of first wireless source 138 and second wireless source 140. The initial position may include the last known position of the aircraft, a starting position, an arbitrary position, or any combination thereof. As described in more detail below with reference to FIG. 9 , the iterative process may begin with the initial position and determine the location of the aircraft through analysis of first heading estimate 242 and second heading estimate 244.

[0065]

[0075] In some implementations, computing device 202 may be associated with, integrated with, or otherwise included in an aircraft, a portable electronic device such as a portable ADF, or the like. System 200 may also include components not shown in FIG. 2 . For example, computing device 202 may also include a receiver configured to receive first heading estimate 242, second heading estimate 244, or some combination thereof. The receiver may be configured to receive data via a data bus, such as an ARINC 429 bus, for example. As a further example, system 200 may also include one or more input / output interfaces, one or more network interfaces, or the like. Additionally, while FIG. 1 illustrates memory 208 of system 200 as storing particular data, more, less, and / or different data may be present in memory 208 without departing from the scope of the present disclosure.

[0066]

[0076] 2 illustrates certain operations occurring within computing device 202, these operations may be performed by other components of system 200 without departing from the scope of the present disclosure. For example, one or more components external to computing device 202 may be configured to host or otherwise incorporate location system 214. Such component(s) may be located remotely from computing device 202 and accessed via a modem of computing device 202.

[0067]

[0077] 2 depicts processor(s) 206 and memory 208 as being integrated within a single computing device 202, other configurations are possible without departing from the scope of this disclosure. For example, memory 208 may be stored as a separate data store and integrated within the navigation computer, while processor(s) 206 may be integrated within an ADF located remotely from the navigation computer. As a further example, one or more components of computing device 202 may be distributed across multiple computing devices (e.g., a group of processor cores).

[0068]

[0078] 2 illustrates system 200 as using only two loop antennas 126, 128, more loop antennas may be used without departing from the scope of this disclosure. For example, automatic direction finder 204 may include and / or receive radio signals from four loop antennas or any number of loop antennas as shown in FIGS. 1 and 3-5. The use of multiple loop antennas, multiple bearing estimates from each loop antenna, enables functionality of automatic direction finder 204, computing device 202, and system 200, as described further below. In that case, a portion of each of the multiple bearing estimates is associated with a particular radio source.

[0069]

[0079] 3 illustrates another exemplary system 300 for automatic direction finding in accordance with some embodiments of the present disclosure. The exemplary system 300 includes one or more processors 328 coupled to loop antennas 302A, 302B, 302C, and 302D. The loop antennas 302A-D may be wrapped around flat portions of a common octagonal core. The processor(s) 328 are configured to process incoming radio signals from the loop antennas 302A-D. The processor(s) 328 generally correspond to the processor(s) 106 of FIG. 1, the processor(s) 210 of FIG. 2, or some combination thereof.

[0070]

[0080] In some embodiments, each of the loop antennas 302A-D is coupled to a respective matching network 312A-D and a matched amplifier 322A-D. After amplification, the radio signal is communicated to a respective analog-to-digital converter (ADC) 326A-D before being communicated to one or more processors 328. In some aspects, the processor(s) 328 may be configured to provide gain control to the amplifiers 322A-D to provide better conditioning of the incoming radio signal. In some aspects, the processor(s) 328 and the ADCs 326A-D are driven by a common clock 324. The system 300 may also include a sensing antenna 310 coupled to the processor(s) 328 via the matching network 320, the amplifier 334, and the ADC 336. The sensing antenna 310 allows an orientation estimate to be determined in a 360-degree range relative to the orientation associated with the loop antennas 302A-D when the equations described above are utilized.

[0071]

[0081] In some implementations, processor(s) 328 may be configured to provide an output to connector 330 for further communication to other aspects of the automatic direction finding system (e.g., to signal sampler(s) 104, heading estimate generator(s) 112, or some combination thereof, of FIG. 1). System 300 may also include power circuitry 332 configured to provide further signal conditioning, power distribution, other suitable power-related functionality, or some combination thereof, to the output.

[0072]

[0082] In operation, system 300 receives radio signals from four loop antennas 302A-D positioned at increasing 45-degree angles from each other, as described in more detail below with reference to FIG. 4. In one exemplary embodiment of FIG. 3, the frequency range of the ADF receiver is 190 kHz to 1.75 MHz, direct analog-to-digital conversion is used at a moderate sampling rate (e.g., 4 megasamples per second) that is still above the Nyquist sampling rate T, and conversion of the signal to baseband, represented as in-phase and quadrature components, can occur during digital processing. All five channels of digitized RF signals corresponding to the signals received by the four loop antennas 302A-D and sensing antenna 310 are provided to processor(s) 328. System 300 is configured to immediately digitize the incoming radio signals and process the digital signals.

[0073]

[0083] 3 shows certain components in a particular configuration, system 300 may include more, fewer, and / or different components without departing from the scope of this disclosure. For example, processor(s) 328 may include multiple processors for different tasks. A particular configuration may include, for example, a field programmable gate array (FPGA) to support digital signal processing, with a separate processor configured to handle input / output and other maintenance-type functions.

[0074]

[0084] 4 illustrates another exemplary system 400 for automatic direction finding, according to some embodiments of the present disclosure. System 400 may include one or more processors 420 configured to receive a plurality of voltage signals 402 corresponding to respective wireless signals received by an antenna (e.g., loop antennas 302A-D and sensing antenna 310 of FIG. 3).

[0075]

[0085] In some implementations, each of the multiple voltage signals 402 may be converted to a digital signal via a respective ADC 414. As shown in FIG. 4, the voltage signals 402 include all signals received over a frequency range associated with a wireless source (e.g., wireless sources 138, 140 in FIGS. 1 and 2 ), as shown at step 404. The system 400 may be configured to sample signals at the ADC 414 over the entire frequency range of the wireless signals associated with the wireless source(s), as shown at step 406. The system 400 may also be configured to convert the digital signals output from the ADC 414 to the frequency domain. For example, the system 400 may include circuitry 416 configured to perform a fast Fourier transform (FFT) on each of the digital signals output from the ADC 414. In some aspects, the converted digital signals may be separated into one or more data streams for parallel processing, as shown at step 408. In some aspects, the FFT circuit 416 may include one or more components of a processor (e.g., processor(s) 106 of FIG. 1 , processor(s) 206 of FIG. 2 , processor(s) 420, etc.) that executes instructions that cause the one or more components of the processor(s) to transform the digital signal output from the ADC 414 into the frequency domain.

[0076]

[0086] The system 400 may also be configured to apply respective bandpass filters (BPFs) 418 in the frequency domain to the frequency-domain digital signal from the FFT circuit 416. As illustrated in step 410, the BPFs 418 may operate to select one or more channels of interest across a frequency range. For example, a particular BPF 418 may select a portion of a frequency range associated with a known transmission frequency of a wireless source (e.g., wireless sources 138, 140 in FIGS. 1 and 2). As noted in step 408, the converted digital signal may be provided to multiple processing streams for parallel processing. In such a configuration, multiple BPFs 418 may be applied to select multiple portions of the wireless frequency range of interest.

[0077]

[0087] The processor(s) 420 may be configured to receive a signal of interest in the frequency domain, as illustrated at step 412. The processor(s) 420 may be configured to determine the amplitude and phase of radio signals received by the multiple antennas of the ADF, as described in more detail above with reference to FIG. 1. The processor(s) 420 may be configured to estimate a direction of arrival associated with each of the radio signals and generate multiple bearing estimates, as described in more detail above with reference to FIGS. 1 and 2. In some aspects, the processor(s) 420 may also be configured to perform additional functions. For example, the processor(s) 420 may be configured to perform additional processing for a radio source that is an NDB transmitter, such as Morse code demodulation. Similarly, the processor(s) 420 may be configured to perform demodulation of the AM radio signal to recover the acoustic signal.

[0078]

[0088] In some aspects, the processor(s) 420 may be configured to implement multiple processing chains 422. Each of the multiple processing chains may be configured to generate an orientation estimate for a respective channel of interest. For example, processing chain 422A may be configured to generate an orientation estimate associated with a first channel associated with a first wireless source, processing chain 422B may be configured to generate an orientation estimate associated with a second channel associated with a second wireless source, and so on, until processing chain 422C may be configured to generate an orientation estimate associated with an Nth channel associated with an Nth wireless source. For purposes of the present disclosure, a channel may be associated with a particular wireless source (e.g., wireless sources 138, 140 of FIG. 1). For example, the first channel may be associated with the first wireless source and the second channel may be associated with the second wireless source. As described in more detail above with reference to FIG. 2 and below with reference to FIGS. 7-9, the multiple orientation estimates may be used to generate an estimate of the aircraft's current position.

[0079]

[0089] In one exemplary implementation of FIG. 4 , system 400 analyzes voltage signals 402 from four loop antennas and a sensing antenna (e.g., as described in more detail below with reference to FIG. 5 ). The voltage signals are sampled, converted, and filtered into signals in N channels. The number of channels (and the number of associated processing chains 422 and associated components, such as BPFs 418) may depend on the particular implementation of system 400. For example, the number of channels may be selected based on the highest expected number of wireless sources for a given operation, the processing resources available to system 400, the fault detection requirements of a particular configuration, etc., or some combination thereof. Furthermore, while FIG. 4 shows five voltage signals 402, more, fewer, and / or different voltage signals 402 may be present without departing from the scope of the present disclosure. For example, system 400 may be configured to process voltage signals 402 associated with three, five, or more loop antennas.

[0080]

[0090] The systems 300, 400 described above illustrate exemplary operation using voltage signals output from four loop antennas positioned at increasing 45 degree angles from one another. One exemplary implementation of this arrangement of four loop antennas is described in more detail below with reference to FIG. 5.

[0081]

[0091] 5 illustrates an exemplary antenna 500 according to some embodiments of the present disclosure. Antenna 500 includes a core 502, a first loop antenna 504A including a first conductive loop 506 around core 502, a second loop antenna 504C including a second conductive loop 510 formed around core 502 at a first angle relative to first conductive loop 506, a third loop antenna 504B including a third conductive loop 514 around core 502 at a second angle relative to first loop antenna 504A, and a fourth loop antenna 504D including a fourth conductive loop 518 formed around core 502 at a third angle relative to third loop antenna 504B.

[0082]

[0092] In one example of FIG. 5 , the first angle is substantially 90 degrees, the second angle is substantially 45 degrees, and the third angle is substantially 90 degrees. The angles between the loop antennas may also be described with respect to the y-axis 503 at the center of the core 502. For example, the first loop antenna 504A may be positioned at a zero-degree angle with respect to the y-axis 503, the third loop antenna 504B may be positioned at a 45-degree angle in a clockwise direction with respect to the y-axis 503, the second loop antenna 504C may be positioned at a 90-degree angle in a clockwise direction with respect to the y-axis 503, and the fourth loop antenna 504D may be positioned at a 135-degree angle in a clockwise direction with respect to the y-axis 503. While FIG. 5 shows four loop antennas 504A-504D, other configurations of three or more loop antennas are possible without departing from the scope of the present disclosure. For example, the antenna 500 may include three loop antennas 504A-504C positioned at a 60-degree angle with respect to each other.

[0083]

[0093] In some embodiments, core 502 of antenna 500 may be substantially octagonal to accommodate two pairs of crossed loop antennas (i.e., a total of four loop antennas). Loop antennas 504A-D may be wound around the core. The core may include ferrite to increase the effective electrical size of loop antennas 504A-D. For example, core 502 may include ferrite to increase the effective electrical size of antenna 500.

[0084]

[0094] In some embodiments, antenna 500 may also include a sensing antenna, as described in more detail above with reference to Figures 1-4 and shown below with reference to Figure 6. In some aspects, antenna 500 may also include a first matching network coupled to first loop antenna 504A, a second matching network coupled to second loop antenna 504C, a third matching network coupled to third loop antenna 504B, a fourth matching network coupled to fourth loop antenna 504D, or some combination thereof, as described in more detail above with reference to Figures 4 and 5.

[0085]

[0095] 1-5, the system may be configured to estimate the angle of arrival 520 of a radio signal 522 entering the antenna 500. The two crossed loop pairs of loop antennas shown in FIG. 5 (e.g., crossed loop antenna pair 504A, 504C and crossed loop antenna pair 504B, 504D) may enable further ADF functions such as fault detection and correction.

[0086]

[0096] Although antenna 500 includes two crossed loop antenna pairs, any number of crossed loop antenna pairs greater than or equal to two may be included without departing from the scope of this disclosure. Any number of loops greater than or equal to three may generate redundant measurements that may be used for noise reduction and fault detection.

[0087]

[0097] Additionally, although antenna 500 illustrates a substantially octagonal core 502, other shapes are possible without departing from the scope of this disclosure. For example, if antenna 500 includes three loop antennas, core 502 may be substantially hexagonal. Generally, core 502 is a regular polygon having 2*N sides, where N is the number of loop antennas.

[0088]

[0098] In some implementations, antenna 500 may be included in, integrated with, or otherwise associated with the ADF device. Figure 6 shows another exemplary device 600 for automatic direction finding, according to some embodiments of the present disclosure. Device 600 includes a housing 602, an antenna 500 housed within housing 602, an electronics unit 604 housed within housing 602 and coupled to antenna 500, and an interface 606 housed within housing 602 and coupled to electronics unit 604.

[0089]

[0099] 5. The electronic unit 604 may also include one or more software-defined radio components 610 configured to process signals associated with the first loop and the second loop. The software-defined radio components 610 may include some or all of the functionality described in more detail above with reference to FIGS. 3 and 4. In some aspects, the device 600 may also include a sensing antenna 614 coupled to the electronic unit 604.

[0090]

[0100] Interface 606 may be configured to enable data transfer from electronics unit 604 to a second device external to housing 602. For example, interface 606 may be configured to enable data transfer of first orientation estimate 242 and second orientation estimate 244 of Figure 2 to computing device 202 for further processing, display by a display device, or both. In one particular aspect, interface 606 includes an ARINC 429 interface.

[0091]

[0101] In some implementations, device 600 may be integrated, embedded, or otherwise installed within portion 612 of the aircraft. For example, device 600 may be mounted on the exterior of the aircraft to facilitate reception of wireless signals from a wireless source (e.g., wireless sources 138, 140 in FIG. 1 ). In certain configurations, device 600 may be installed so that loop antenna 504A faces a forward direction associated with the normal forward direction of the aircraft.

[0092]

[0102] 7 illustrates an example determination 700 of the position of an ADF, according to some embodiments of the present disclosure. Certain conventional methods for solving for a position fix in multiple orientations are performed in two-dimensional space (e.g., latitude / longitude) with corrections and compensations to account for the non-flat Earth. The systems and methods disclosed herein enable an alternative three-dimensional, vector-based approach. Certain other approaches, such as those based on spherical geometry, may be more complex than vector-based approaches and may involve approximations that may limit performance in certain situations (e.g., at very high latitudes).

[0093]

[0103] The exemplary image 700 shows an unknown position 702 of an aircraft relative to a known position 706 of a first wireless source, a known position 704 of a second wireless source, and a known position of the center of the Earth 708. The image 700 includes unit vectors 710, 713 that point from the unknown position 702 to the known positions 706, 704, respectively.

[0094]

[0104] As described above with reference to Figures 1-6, the system can perform bearing measurements from multiple loop antennas. One or more processors (e.g., processor(s) 106 of Figure 1, processor(s) 206 of Figure 2, or some combination thereof) calculate the unit vectors 710, 713 relative to an unknown position 702 (P u =[xyz]) to known positions 706, 704 (P i), the vectors 722, 718 from the known location 708 of the center of the Earth to the known locations 706, 704, respectively, may be known. For example, the known locations 704, 706, 708 may be stored in memory (e.g., memory 108 of FIG. 1) as latitude and longitude values.

[0095]

[0105] As a simplified example, assuming the altitudes of known locations 704, 706 are the same as the altitude of unknown location 702, the unknown location 702 in an Earth-centered, Earth-fixed (ECEF) coordinate system can be expressed as vector 720( TIFF2025160118000003.tif5170). The vector 720 can be expressed as the ith wireless source ( TIFF2025160118000004.tif5170), where TIFF2025160118000005.tif6170 is a vector (e.g., vectors 714, 716) from unknown location 702 to known locations 706, 704, TIFF2025160118000006.tif5170 is a vector (e.g., vectors 722, 718) from known location 708 to known locations 706, 704. That is, TIFF2025160118000007.tif6170

[0096]

[0106] The processor(s) may be configured to estimate the direction of the vector 720 by measuring the direction of arrival of the wireless signal from the wireless source as known locations 704, 706. Taking into account the direction of arrival of the wireless signal from the known location 706, the unit vector 710 ( TIFF2025160118000008.tif5170) is a unit vector pointing from unknown location 702 to known location 706, and considering the direction of the wireless signal from known location 704, unit vector 713 ( TIFF2025160118000009.tif5170) is a unit vector pointing from unknown location 702 to known location 704, then vector 720 may be expressed by the following equation: where R i is the magnitude of vector 720 and is unknown. That is, TIFF2025160118000010.tif6170

[0097]

[0107] In any observation, TIFF2025160118000011.tif5170. Expanding this relationship into the individual x, y, and z coordinate components gives us the following three equations: TIFF2025160118000012.tif18170

[0098]

[0108] The above equation contains four unknowns: three unknown user position states and an unknown vector magnitude. Each orientation measurement adds an additional unknown. Two orientation measurements, for example, can give the following six equations: TIFF2025160118000013.tif37170

[0099]

[0109] The unknowns can be collected and rearranged into a matrix as shown below: TIFF2025160118000014.tif30170

[0100]

[0110] With six equations and five unknowns, the system can be solved using a generalized pseudoinverse: TIFF2025160118000015.tif5170. The above formulation can be expanded to accommodate additional orientation estimates. Each new orientation estimate adds three rows and one column to the H matrix. The first three columns of the added row are always the identity matrix. The added columns are all zero except for the three rows containing the components of the unit vector. All other rows and columns are set to zero. The system is solvable as long as there are at least as many equations as there are unknowns. Those skilled in the art will recognize how to expand the matrix representation of the system of linear equations to accommodate additional orientation measurements. For example, if three orientation estimates are available, the matrix representation of the system of equations can be as follows: TIFF2025160118000016.tif45170

[0101]

[0111] In some implementations, angle-of-arrival measurements are actually generated in the aircraft body coordinate frame, and the processor(s) can convert these measurements to ECEF coordinates. The conversion can be performed from the aircraft frame of reference to a local-level frame of reference using the aircraft's pitch, roll, and heading. The vectors can then be converted from the local-level to ECEF. To perform this conversion, the conversion requires an estimate of the latitude, longitude, and altitude of the origin of the local-level body frame. The processor(s) can be configured to perform a calculation using the best available estimate of the aircraft's position to obtain a new estimate of position. This process can be repeated until the difference between the new estimate and the last estimate meets a position estimate accuracy threshold.

[0102]

[0112] 8 is a flowchart of an example method 800 for automatic direction finding, according to some embodiments of the present disclosure. Method 800 may be initiated, performed, or controlled by one or more processors executing instructions, such as by processor(s) 106 of FIG. 1 executing instructions from memory 108, processor(s) 206 of FIG. 2 executing instructions from memory 208, processor(s) 210 executing instructions from memory 212, or any combination thereof.

[0103]

[0113] In some implementations, the method 800 includes receiving a first signal from a first loop antenna and a second signal from a second loop antenna, at block 802. For example, the processor(s) 106 of FIG. 1 may receive the first signal 132 from the first loop antenna 126 and the second signal 134 from the second loop antenna 128.

[0104]

[0114] Method 800 also includes sampling the first signal and the second signal at a sampling rate high enough to capture the entire frequency range associated with the multiple wireless sources to generate the first digital signal and the second digital signal, at block 804. For example, processor(s) 106 of FIG. 1 may sample second signal 132 and first signal 134 to generate first digital signal 114 and second digital signal 116.

[0105]

[0115] The method 800 also includes converting the first digital signal and the second digital signal to a frequency domain representation at block 806. For example, the processor(s) 106 of FIG. 1 may convert the first digital signal 114 and the second digital signal 116 to a frequency domain representation 144.

[0106]

[0116] Method 800 also includes generating a first bearing estimate for a wireless source of the plurality of wireless sources based on the frequency domain representation by comparing the relative amplitudes and phases of the signals represented in the frequency domain, at block 808. For example, processor(s) 106 of FIG. 1 may generate bearing estimate 120 of wireless source 138 based on comparing the relative amplitudes and phases of frequency domain representation 144.

[0107]

[0117] In some implementations, method 800 may include more, fewer, and / or different steps without departing from the scope of this disclosure. For example, method 800 may apply fault detection operations, fault exclusion operations, or both to the multiple bearing estimates 120, 122 of FIG. 1 . As another example, method 800 may also include generating an overall bearing estimate for the wireless source(s) of the one or more wireless sources. In this case, the overall bearing estimate includes an average of the first bearing estimate 120 and the second bearing estimate 122 of the wireless source(s) 138, 140.

[0108]

[0118] 9 is a flowchart of an example method 900 for automatic direction finding, according to some embodiments of the present disclosure. Method 900 may be initiated, performed, or controlled by one or more processors executing instructions, such as by processor(s) 106 of FIG. 1 executing instructions from memory 108, processor(s) 206 of FIG. 2 executing instructions from memory 208, processor(s) 210 executing instructions from memory 212, or any combination thereof.

[0109]

[0119] In some embodiments, the method 900 includes, at block 902, receiving from the automatic direction finder a first bearing estimate associated with a first orientation relative to the first wireless source, the first bearing estimate being based on a first plurality of bearing measurements. In this case, a first portion of the first plurality of bearing measurements is generated by one or more processors based on a first signal from the first loop antenna. A second portion of the first plurality of bearing measurements is generated by one or more processors based on a second signal from the second loop antenna. For example, the processor(s) 206 of FIG. 2 may receive from the automatic direction finder 204 a first bearing estimate 242 associated with a first orientation relative to the first wireless source 138, the first bearing estimate 242 being based on the first plurality of bearing measurements 228. In this case, a first portion 232 of the first plurality of bearing measurements 228 is generated by the processor(s) 210 based on a first signal 236 from the first loop antenna 126. A second portion 234 of the first plurality of azimuth measurements 228 is generated by the processor(s) 210 based on a second signal 238 from the second loop antenna 128 .

[0110]

[0120] In one embodiment of FIG. 9 , method 900 also includes, at block 904, receiving from the automatic direction finder a second bearing estimate associated with a second orientation relative to the second wireless source, the second bearing estimate being based on the second plurality of bearing measurements. In this case, a first portion of the second plurality of bearing measurements is generated by one or more processors based on a first signal from the first loop antenna. A second portion of the second plurality of bearing measurements is generated by one or more processors based on a second signal from the second loop antenna. For example, processor(s) 206 of FIG. 2 may receive from automatic direction finder 204 a second bearing estimate 244 associated with a second orientation relative to second wireless source 140, the second bearing estimate 244 being based on the second plurality of bearing measurements 230. In this case, first portion 233 of second plurality of bearing measurements 230 is generated by processor(s) 210 based on a first signal 236 from first loop antenna 126. A second portion 235 of the second plurality of bearing measurements 230 is generated by the processor(s) 210 based on a second signal 238 from the second loop antenna 128 .

[0111]

[0121] 9, method 900 also includes determining a location based at least on the first orientation estimate and the second orientation estimate, at block 906. For example, processor(s) 206 of FIG. 2 may determine location 216 based at least on first orientation estimate 242 and second orientation estimate 244.

[0112]

[0122] In some implementations, method 900 may include more, fewer, and / or different steps without departing from the scope of this disclosure. For example, method 900 may also receive a third bearing estimate from the automatic direction finder, the third bearing estimate being associated with a third orientation relative to a third wireless source, and determine a location based at least on the first bearing estimate, the second bearing estimate, and the third bearing estimate.

[0113]

[0123] 10 is a flowchart of an example method 1000 for position estimation, according to some embodiments of the present disclosure. Method 1000 may be initiated, performed, or controlled by one or more processors executing instructions, such as by processor(s) 106 of FIG. 1 executing instructions from memory 108, processor(s) 206 of FIG. 2 executing instructions from memory 208, processor(s) 210 executing instructions from memory 212, or a combination thereof. In one particular aspect, method 1000 illustrates example block 700 of FIG. 7. In some implementations, method 1000 may be initiated, performed, or controlled at block 1001.

[0114]

[0124] In some embodiments, the method 1000 measures orientation relative to the transmitter locations at block 1002. For example, as described in more detail above with reference to Figures 1 and 2, the processor(s) 106, 206 may generate orientation measurements relative to the wireless sources 138, 140 of Figure 1 (e.g., the first plurality of orientation measurements 228 and / or the second plurality of orientation measurements 230 of Figure 2). In some aspects, the orientation measurements may be calculated based on the angle θ from the nose of the aircraft in which the ADF is installed to each emitter. i This can be done in

[0115]

[0125] In some implementations, the method 1000 includes forming a unit vector in the aircraft's frame of reference for each orientation measurement at block 1004. For example, as described above with reference to Figure 7, the processor(s) 106, 206 of Figures 1 and 2 may be configured to form the unit vectors 710, 713 in the aircraft's frame of reference.

[0116]

[0126] In some implementations, the method 1000 includes transforming the unit vectors in the aircraft's frame of reference to the ECEF frame of reference using the best estimate of the user's position at block 1006. For example, the processor(s) 106, 206 of Figures 1 and 2 may be configured to transform the unit vectors 710, 713 of Figure 7 to the ECEF frame of reference using the best estimate of the aircraft's position.

[0117]

[0127] In some implementations, method 1000 includes populating the H matrix with the components of the unit vectors at block 1008. For example, as described in more detail above with reference to FIG. 7, the processor(s) 106, 206 of FIGS. 1 and 2 may populate the H matrix with the components of the unit vectors. Method 1000 also includes calculating a new estimate of position at 1010. For example, as described in more detail above with reference to FIG. 7, the processor(s) 106, 206 of FIGS. 1 and 2 may calculate the new estimate of position.

[0118]

[0128] In some implementations, method 1000 includes comparing the new position estimate to the last position estimate at block 1012. For example, processor(s) 106, 206 of Figures 1 and 2 may compare the new position estimate to the last position estimate. In some aspects, method 1000 may be an iterative process, as described above with reference to Figure 7.

[0119]

[0129] In some implementations, the method 1000 includes determining whether the new position estimate matches the last position estimate within a tolerance, at block 1014. For example, as described in more detail above with reference to FIG. 7, the processor(s) 106, 206 of FIGS. 1 and 2 may determine whether the new position estimate matches the last position estimate within a position estimate accuracy threshold.

[0120]

[0130] If the positions match within the tolerance, method 1000 includes outputting a new position estimate at block 1016. For example, processor(s) 106, 206 of FIGS. 1 and 2 may output the position estimate. Method 1000 may then include determining whether another measurement is needed at block 1018. For example, processor(s) 106, 206 of FIGS. 1 and 2 may determine whether another measurement is needed. If another measurement is needed, method 1000 may return to block 1002. Method 1000 may then continue to find a new position estimate. If another measurement is not needed, method 1000 may proceed to block 1020. There, in some implementations, method 1000 may end. Referring again to block 1014, if the positions do not match within the tolerance, method 1000 may return to block 1006. The method 1000 may then continue to iterate to identify acceptable position estimates.

[0121]

[0131] In some implementations, method 1000 may include more, fewer, and / or different steps without departing from the scope of the present disclosure. For example, method 1000 may combine steps of method 1000 (e.g., blocks 1008, 1010) without departing from the scope of the present disclosure.

[0122]

[0132] 1-10 may be implemented to achieve one or more of the technical advantages described in more detail above. For example, methods 800, 900, and 1000 may enable an automatic direction finder with improved capabilities (e.g., fault detection) in a smaller physical size than certain conventional ADFs.

[0123]

[0133] 11 is a block diagram of a computing environment 1100 including a computing device 1110 configured to support aspects of computer-implemented methods and computer-executable program instructions (or code) according to some embodiments of the present disclosure. For example, the computing device 1110, or portions thereof, are configured to execute instructions to initiate, perform, or control one or more of the operations described in more detail above with reference to FIGS. 1-9. In one particular aspect, the computing device 1110 may include, correspond to, or be included in the computing device 102 of FIG. 1, the computing device 202 of FIG. 2, the automatic direction finder 204 of FIG. 2, a component of the system of FIG. 3, a component of the system 400 of FIG. 4, one or more servers, one or more virtual devices, or a combination thereof.

[0124]

[0134] Computing device 1110 includes one or more processors 1120. In a particular aspect, processor(s) 1120 correspond to processor(s) 106 of Figure 1, processor(s) 206 of Figure 2, processor(s) 210 of Figure 2, or some combination thereof. Processor(s) 1120 are configured to communicate with system memory 1130, one or more storage devices 1150, one or more input / output interfaces 1140, one or more communication interfaces 1160, or any combination thereof. System memory 1130 includes volatile memory devices (e.g., random access memory (RAM) devices), non-volatile memory devices (e.g., read-only memory (ROM) devices, programmable read-only memory, and flash memory), or both. System memory 1130 stores operating system 1132, which may include a basic input / output system for booting computing device 1110 as well as a full operating system for allowing computing device 1110 to interact with users, other programs, and other devices. System memory 1130 stores system (program) data 1138, such as source transmitter frequency data 124 of Figure 1, known position data set 218 of Figure 2, multiple bearing measurements 1105 (e.g., including first multiple bearing measurements 228 and second multiple bearing measurements 230 of Figure 2), or a combination thereof.

[0125]

[0135] The system memory 1130 includes one or more applications 1134 (e.g., sets of instructions) executable by the processor(s) 1120. As one example, the one or more applications 1134 include instructions 1136 executable by the processor(s) 1120 to initiate, control, or perform one or more of the operations described with reference to Figures 1-9. For example, the one or more applications 1134 include instructions 1136 executable by the processor(s) 1120 to initiate, control, or perform one or more of the operations described with reference to receiving a first bearing estimate 242 and a second bearing estimate 244 from the automatic direction finder 204 of Figure 2 and determining a location based at least on the first bearing estimate 242 and the second bearing estimate 244. As another example, the one or more applications 1134 include instructions 1136 executable by the processor(s) 1120 to initiate, control, or perform one or more of the operations described with reference to receiving the first signal 132, the second signal 134, and the third signal 136 of FIG. 1 , converting those signals into respective digital signals 114, 116, 118 into frequency domain representations 120, and generating a first bearing estimate 122 for wireless sources 138, 140 of the plurality of wireless sources based on the frequency domain representations 120.

[0126]

[0136] In one particular implementation, the system memory 1130 includes a non-transitory computer-readable medium (e.g., a computer-readable storage device) having stored thereon instructions 1136 that, when executed by the processor(s) 1120, cause the processor(s) 1120 to initiate, perform, or control operations for automatic direction finding. The operations include receiving a first signal from a first loop antenna, receiving a second signal from a second loop antenna, and receiving a third signal from a third loop antenna. The operations also include converting the first signal to a first digital signal, converting the second signal to a second digital signal, and converting the third signal to a third digital signal. The operations also include processing the first digital signal, the second digital signal, and the third digital signal over frequency bands associated with the one or more wireless sources to generate sampled signals. The operations also include generating a plurality of bearing estimates for each wireless source of the one or more wireless sources based on the sampled signals.

[0127]

[0137] In the same or an alternative embodiment, the system memory 1130 includes a non-transitory computer-readable medium (e.g., a computer-readable storage device) having stored thereon instructions 1136 that, when executed by the processor(s) 1120, cause the processor(s) 1120 to initiate, perform, or control operations for automatic direction finding, including receiving, from the automatic direction finder, a first bearing estimate associated with a first orientation relative to a first wireless source, the first bearing estimate being based on a first plurality of bearing measurements, where a first portion of the first plurality of bearing measurements is generated by the one or more processors based on a first signal from a first loop antenna, and a second portion of the first plurality of bearing measurements is generated by the one or more processors based on a second signal from a second loop antenna. The operations also include receiving, from the automatic direction finder, a second bearing estimate associated with a second orientation relative to the second wireless source, the second bearing estimate being based on a second plurality of bearing measurements, where a first portion of the second plurality of bearing measurements is generated by the one or more processors based on a first signal from the first loop antenna, and a second portion of the second plurality of bearing measurements is generated by the one or more processors based on a second signal from the second loop antenna. The operations also include determining a location based at least on the first bearing estimate and the second bearing estimate.

[0128]

[0138] The one or more storage devices 1150 include non-volatile storage devices such as magnetic disks, optical disks, or flash memory devices. In a particular embodiment, the storage devices 1150 include both removable and non-removable memory devices. The storage devices 1150 are configured to store an operating system, operating system images, applications (e.g., one or more applications 1134), and program data (e.g., program data 1138). In a particular aspect, the system memory 1130, the storage devices 1150, or both, comprise tangible computer-readable media. In a particular aspect, one or more of the storage devices 1150 reside external to the computing device 1110.

[0129]

[0139] The one or more input / output interfaces 1140 enable the computing device 1110 to communicate with one or more input / output devices 1170 to facilitate interaction with a user. For example, the one or more input / output interfaces 1140 may include a display interface, an input interface, or both. For example, the input / output interface 1140 may be adapted to receive input from a user, receive input from another computing device, or a combination thereof. In some embodiments, input / output interface 1140 conforms to one or more standard interface protocols, including a serial interface (e.g., a universal serial bus (USB) interface or (IEEE (Institute of Electrical and Electronics Engineers) interface standard), a parallel interface, a display adapter, an audio adapter, or a custom interface ("IEEE" is a registered trademark of the Institute of Electrical and Electronics Engineers, Inc. of Piscataway, NJ). In some embodiments, input / output device(s) 1170 include one or more user interface devices and displays, including any combination of buttons, keyboards, pointing devices, displays, speakers, microphones, touchscreens, and other devices.

[0130]

[0140] The processor(s) 1120 are configured to communicate with a device or controller 1180 via one or more communication interfaces 1160. For example, the one or more communication interfaces 1160 may include a network interface. The device or controller 1180 may include, for example, the automatic direction finder 204 of FIG. 2.

[0131]

[0141] In some implementations, a non-transitory computer-readable medium (e.g., a computer-readable storage device) stores instructions that, when executed by one or more processors, cause the one or more processors to initiate, perform, or control operations to perform some or all of the functions described above. For example, the instructions may be executable to perform one or more of the operations or methods of FIGS. 1-10. In some implementations, some or all of one or more of the operations or methods of FIGS. 1-10 may be performed by one or more processors (e.g., one or more central processing units (CPUs), one or more graphics processing units (GPUs), one or more digital signal processors (DSPs)), or any combination thereof, that execute instructions using dedicated hardware circuitry.

[0132]

[0142] The illustrations of the various embodiments described herein are intended to provide a general understanding of the structure of various embodiments. These illustrations are not intended to exhaustively describe all elements and features of apparatus and systems that utilize the structures or methods described herein. Many other embodiments may become apparent to those skilled in the art upon review of this disclosure. Other embodiments may be utilized and derived from this disclosure, such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. For example, method actions may be performed in a different order than shown in the figures, or one or more method actions may be omitted. Therefore, the present disclosure and the figures should be considered illustrative rather than restrictive.

[0133]

[0143] Furthermore, while specific examples have been shown and described herein, any subsequent configurations designed to achieve the same or similar results may be substituted for the specific embodiment shown. The present disclosure is intended to include any and all subsequent adaptations or variations of the various embodiments. Combinations of the above-described embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon review of this specification.

[0134]

[0144] The Abstract of the Disclosure is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Additionally, in the above Detailed Description, various features may be grouped together or described within a single embodiment for the purpose of conciseness of the disclosure. The above examples are illustrative of the disclosure, not limiting. Furthermore, many modifications and variations are possible in accordance with the principles of the disclosure. As reflected in the following claims, claimed subject matter may not be directed to all features of any disclosed embodiment. Accordingly, the scope of the disclosure is defined by the following claims and their equivalents.

[0135]

[0145] Furthermore, the present disclosure includes embodiments according to the following examples.

[0136]

[0146] According to Example 1, an automatic direction finder includes a first loop antenna, a second loop antenna, and one or more processors coupled to the first loop antenna and the second loop antenna, wherein the one or more processors are configured to perform the following: receive a first signal from the first loop antenna and receive a second signal from the second loop antenna; sample the first signal and the second signal at a sampling rate high enough to capture an entire frequency range associated with a plurality of wireless sources to generate a first digital signal and a second digital signal; convert the first digital signal and the second digital signal to a frequency domain representation; and generate a first bearing estimate for a wireless source of the plurality of wireless sources based on the frequency domain representation by comparing the relative amplitudes and phases of the signals represented in the frequency domain.

[0137]

[0147] Example 2 includes the automatic direction finder of example 1, wherein the one or more processors are configured to: generate an estimate of the first bearing of the wireless source by generating the estimate of the first bearing of the wireless source in parallel processing operations.

[0138]

[0148] Example 3 includes the automatic direction finder of example 1 or example 2, further including a third loop antenna, wherein the one or more processors are coupled to the third loop antenna, and the one or more processors are further configured to receive a third signal from the third loop antenna and sample the third signal over the frequency range associated with the wireless source to generate a third digital signal, and the one or more processors are configured to convert the first digital signal, the second digital signal, and the third digital signal to the frequency domain representation.

[0139]

[0149] Example 4 includes the automatic direction finder of example 3, wherein the one or more processors are further configured to generate an estimate of a second bearing of the wireless source based on the frequency domain representation.

[0140]

[0150] Example 5 includes the automatic direction finder of example 4, wherein the one or more processors are further configured to: apply fault exclusion operations to the first bearing estimate and the second bearing estimate of the wireless source.

[0141]

[0151] Example 6 includes the automatic direction finder of example 4 or example 5, wherein the one or more processors are further configured to: generate an estimate of an overall orientation of the wireless source, the estimate of the overall orientation including an average of the first orientation estimate and the second orientation estimate of the wireless source.

[0142]

[0152] Example 7 includes the automatic direction finder of any one of Examples 1 to 6, and further includes a detection antenna.

[0143]

[0153] Example 8 includes the automatic direction finder of any one of examples 1 to 7, wherein the automatic direction finder is an integrated unit.

[0144]

[0154] Example 9 includes the automatic direction finder of example 8, wherein the integrated unit is a system on a chip.

[0145]

[0155] Example 10 includes the automatic direction finder of any one of Examples 1 to 9, wherein the frequency range is approximately 0.19 to 1.75 MHz.

[0146]

[0156] According to Example 11, a method includes receiving a first signal from a first loop antenna and receiving a second signal from a second loop antenna; sampling the first signal and the second signal over a frequency range associated with a wireless source to generate a first digital signal and a second digital signal; converting the first digital signal and the second digital signal to a frequency domain representation; and generating an estimate of a first orientation of the wireless source based on the frequency domain representation.

[0147]

[0157] Example 12 includes the method of example 11, in which generating the first bearing estimate of the wireless source includes generating the first bearing estimate of the wireless source in a parallel processing operation.

[0148]

[0158] Example 13 includes the method of example 11 or example 12, further including receiving a third signal from a third loop antenna and sampling the third signal over the frequency range associated with the wireless source to generate a third digital signal, and converting the first digital signal and the second digital signal to the frequency domain representation includes converting the first digital signal, the second digital signal, and the third digital signal to the frequency domain representation.

[0149]

[0159] Example 14 includes the method of example 13, further including generating an estimate of a second bearing of the wireless source based on the frequency domain representation.

[0150]

[0160] Example 15 includes the method of example 14, further including generating an estimate of an overall orientation of the wireless source, the estimate of the overall orientation including an average of the first orientation estimate and the second orientation estimate of the wireless source.

[0151]

[0161] According to Example 16, a non-transitory computer-readable medium includes instructions that, when executed by one or more processors, cause the one or more processors to receive a first signal from a first loop antenna and a second signal from a second loop antenna; sample the first signal and the second signal at a sampling rate high enough to capture an entire frequency range associated with a plurality of wireless sources to generate a first digital signal and a second digital signal; convert the first digital signal and the second digital signal to a frequency domain representation; and generate a first bearing estimate for a wireless source of the plurality of wireless sources based on the frequency domain representation by comparing relative amplitudes and phases of the signals represented in the frequency domain.

[0152]

[0162] Example 17 includes the non-transitory computer-readable medium of Example 16, wherein the instructions, when executed by the one or more processors, cause the one or more processors to generate estimates of the first orientations of the wireless sources in parallel processing operations.

[0153]

[0163] Example 18 includes the non-transitory computer-readable medium of Example 16 or Example 17, wherein the instructions, when executed by one or more processors, further cause the one or more processors to receive a third signal from a third loop antenna and sample the third signal over the frequency range associated with the wireless source to generate a third digital signal; and the instructions, when executed by the one or more processors, cause the one or more processors to convert the first digital signal and the second digital signal to the frequency domain representation, including converting the first digital signal, the second digital signal, and the third digital signal to the frequency domain representation.

[0154]

[0164] Example 19 includes the non-transitory computer-readable medium of example 18, wherein the instructions, when executed by one or more processors, further cause the one or more processors to generate an estimate of a second bearing of the wireless source.

[0155]

[0165] Example 20 includes the non-transitory computer-readable medium of example 19, wherein the instructions, when executed by one or more processors, cause the one or more processors to generate an estimate of an overall orientation of the wireless source, the estimate of the overall orientation comprising an average of the first orientation estimate and the second orientation estimate of the wireless source.

[0156]

[0166] According to Example 21, a system includes one or more processors configured to perform the following: receiving from an automatic direction finder a first bearing estimate associated with a first orientation relative to a first wireless source, the first bearing estimate being based on a first plurality of orientation measurements, a first portion of the first plurality of orientation measurements being based on a first signal from a first loop antenna, and a second portion of the first plurality of orientation measurements being based on a second signal from a second loop antenna; receiving from the automatic direction finder a second bearing estimate associated with a second orientation relative to a second wireless source, the second bearing estimate being based on a second plurality of orientation measurements, a first portion of the second plurality of orientation measurements being based on the first signal from the first loop antenna, and a second portion of the second plurality of orientation measurements being based on the second signal from the second loop antenna; and determining a location based at least on the first bearing estimate and the second bearing estimate.

[0157]

[0167] Example 22 includes the system of Example 21, wherein the one or more processors are configured to determine the location in response to a signal indicating a fault associated with another positioning system.

[0158]

[0168] Example 23 includes the system of example 21 or example 22, wherein the one or more processors are configured to perform the determining of the position in response to one or more controls of the aircraft.

[0159]

[0169] Example 24 includes the system of any one of Examples 21 to 23, wherein the one or more processors are configured to: determine the location based at least on a known location of the first wireless source and a known location of the second wireless source.

[0160]

[0170] Example 25 includes the system of example 24, wherein the known position of the first radio source is a measurement of the position of the first radio source relative to the center of the Earth.

[0161]

[0171] Example 26 includes the system of any one of examples 21 to 25, wherein the one or more processors are configured to perform the determining of the location based on an iterative process.

[0162]

[0172] Example 27 includes the system of example 26, wherein the iterative process includes a process based at least on an initial position.

[0163]

[0173] Example 28 includes the system of example 27, in which the initial position includes a last known position, a start position, an arbitrary position, or a combination thereof.

[0164]

[0174] Example 29 includes the system of any one of examples 21 to 28, wherein at least one of the first wireless source or the second wireless source is an omnidirectional beacon.

[0165]

[0175] Example 30 includes the system of any one of examples 21 to 29, wherein at least one of the first wireless source or the second wireless source is an amplitude modulated radio station.

[0166]

[0176] According to Example 31, a non-transitory computer-readable medium includes instructions that, when executed by one or more processors, cause the one or more processors to receive from an automatic direction finder a first bearing estimate associated with a first orientation relative to a first wireless source, the first bearing estimate being based on a first plurality of bearing measurements, a first portion of the first plurality of bearing measurements being generated by the one or more processors based on a first signal from a first loop antenna, and a second portion of the first plurality of bearing measurements being generated by the one or more processors based on a second signal from a second loop antenna. receiving from the automatic direction finder a second bearing estimate associated with a second orientation relative to a second wireless source, the second bearing estimate being based on a second plurality of bearing measurements, a first portion of the second plurality of bearing measurements being generated by the one or more processors based on the first signal from the first loop antenna, and a second portion of the second plurality of bearing measurements being generated by the one or more processors based on the second signal from the second loop antenna; and determining a location based at least on the first bearing estimate and the second bearing estimate.

[0167]

[0177] Example 32 includes the non-transitory computer-readable medium of example 31, wherein the instructions, when executed by one or more processors, cause the one or more processors to determine the location in response to a signal indicative of a fault associated with another positioning system or one or more controls of the aircraft.

[0168]

[0178] Example 33 includes the non-transitory computer-readable medium of example 31 or example 32, wherein the instructions, when executed by one or more processors, cause the one or more processors to determine the location based at least on a known location of the first wireless source and a known location of the second wireless source.

[0169]

[0179] Example 34 includes the non-transitory computer-readable medium of example 33, wherein the known location of the first wireless source is a measurement of a location of the first wireless source relative to a center of the Earth.

[0170]

[0180] Example 35 includes the non-transitory computer-readable medium of any one of Examples 31 to 34, wherein the instructions, when executed by one or more processors, cause the one or more processors to determine the location based on an iterative process, the iterative process including a process based at least on an initial location.

[0171]

[0181] Example 36 includes the non-transitory computer-readable medium of example 35, in which the initial location includes a last known location, a starting location, an arbitrary location, or a combination thereof.

[0172]

[0182] Example 37 includes the non-transitory computer-readable medium of any one of Examples 31 to 36, wherein at least one of the first wireless source or the second wireless source is an omnidirectional beacon or an amplitude-modulated radio station.

[0173]

[0183] According to Example 38, a method includes receiving, from an automatic direction finder, a first bearing estimate associated with a first orientation relative to a first wireless source, the first bearing estimate being based on a first plurality of bearing measurements, a first portion of the first plurality of bearing measurements being generated by the one or more processors based on a first signal from a first loop antenna, and a second portion of the first plurality of bearing measurements being generated by the one or more processors based on a second signal from a second loop antenna; receiving, from the automatic direction finder, a first bearing estimate associated with a first orientation relative to a second wireless source, the first bearing estimate being based on a first plurality of bearing measurements, a first portion of the first plurality of bearing measurements being generated by the one or more processors based on a first signal from a first loop antenna, and a second portion of the first plurality of bearing measurements being generated by the one or more processors based on a second signal from a second loop antenna; receiving a second orientation estimate associated with a second orientation, the second orientation estimate being based on a second plurality of orientation measurements, a first portion of the second plurality of orientation measurements generated by the one or more processors based on the first signal from the first loop antenna, and a second portion of the second plurality of orientation measurements generated by the one or more processors based on the second signal from the second loop antenna; and determining a location based at least on the first orientation estimate and the second orientation estimate.

[0174]

[0184] Example 39 includes the method of example 38, wherein determining the location includes determining the location based at least on a known location of the first wireless source and a known location of the second wireless source, and the known location of the first wireless source is a measurement of the first wireless source relative to the center of the Earth.

[0175]

[0185] Example 40 includes the method of example 38 or example 39, wherein determining the location includes determining the location based on an iterative process, and the iterative process includes a process based at least on an initial position, and the initial position includes a last known position, a starting position, an arbitrary position, or a combination thereof.

[0176]

[0186] According to Example 41, an antenna includes a core, a first loop antenna including a first plurality of conductive loops formed around the core, a second loop antenna including a second plurality of conductive loops formed around the core at a first angle relative to the first plurality of conductive loops, and a third loop antenna including a third plurality of conductive loops formed around the core at a second angle relative to the first plurality of conductive loops.

[0177]

[0187] Example 42 includes the antenna of example 41, wherein the core is substantially octagonal.

[0178]

[0188] Example 43 includes the antenna of example 41 or example 42, wherein the core includes ferrite.

[0179]

[0189] Example 44 includes the antenna of any one of examples 41 to 43, further including a sensing antenna.

[0180]

[0190] Example 45 includes the antenna of any one of Examples 41 to 44, further including a first matching network coupled to the first loop antenna.

[0181]

[0191] Example 46 includes the antenna of example 45, further including a second matching network coupled to the second loop antenna.

[0182]

[0192] Example 47 includes the antenna of example 46, further including a third matching network coupled to the third loop antenna.

[0183]

[0193] According to Example 48, a device includes an antenna. The antenna includes a core, a first loop antenna including a first plurality of conductive loops formed around the core, a second loop antenna including a second plurality of conductive loops formed around the core at a first angle relative to the first plurality of conductive loops, and a third loop antenna including a third plurality of conductive loops formed around the core at a second angle relative to the first plurality of conductive loops. The device also includes an electronics unit coupled to the antenna. The electronics unit includes a receiver configured to receive a first signal from the first loop antenna, receive a second signal from the second loop antenna, and receive a third signal from the third loop antenna. The electronics unit also includes a software-defined radio component configured to process signals associated with the first signal, the second signal, and the third signal.

[0184]

[0194] Example 49 includes the device of example 48, wherein the core is substantially octagonal.

[0185]

[0195] Example 50 includes the device of example 48 or example 49, wherein the core comprises ferrite.

[0186]

[0196] Example 51 includes the device of any one of examples 48 to 50, further including a sensing antenna.

[0187]

[0197] Example 52 includes the device of any one of Examples 48 to 51, further including a first matching network coupled to the first loop antenna.

[0188]

[0198] Example 53 includes the device of example 52, further including a second matching network coupled to the second loop antenna.

[0189]

[0199] Example 54 includes the device of example 53, further including a third matching network coupled to the third loop antenna.

[0190]

[0200] According to Example 55, a device includes an antenna housed within a housing. The antenna includes a core, a first loop antenna including a first plurality of conductive loops formed around the core, a second loop antenna including a second plurality of conductive loops formed around the core at a first angle relative to the first plurality of conductive loops, and a third loop antenna including a third plurality of conductive loops formed around the core at a second angle relative to the first plurality of conductive loops. The device also includes an electronics unit housed within the housing and coupled to the antenna. The electronics unit includes a receiver configured to receive a first signal from the first loop antenna, a second signal from the second loop antenna, and a third signal from the third loop antenna. The electronics unit also includes a software-defined radio component configured to process signals associated with the first signal, the second signal, and the third signal. The electronics unit also includes an interface housed within the housing and coupled to the electronics unit. The interface is configured to allow data transfer from the electronics unit to a second device external to the housing.

[0191]

[0201] Example 56 includes the device of example 55, wherein the interface includes an Aeronautical Radio, Inc. 429 interface.

[0192]

[0202] Example 57 includes the device of example 55 or example 56, wherein the core is substantially octagonal.

[0193]

[0203] Example 58 includes the device of any one of examples 55 to 57, wherein the core includes ferrite.

[0194]

[0204] Example 59 includes the device of any one of examples 55 to 58, further including a sensing antenna.

[0195]

[0205] Example 60 includes the device of any one of examples 55 to 59, further including a first matching network coupled to the first loop antenna.

[0196]

[0206] Example 61 includes the antenna of any one of examples 41 to 47, wherein the first angle is substantially 90 degrees.

[0197]

[0207] Example 62 includes the antenna of example 61, wherein the second angle is substantially 45 degrees.

[0198]

[0208] Example 63 includes the antenna of any one of examples 41 to 47, wherein the first angle is substantially 60 degrees.

[0199]

[0209] Example 64 includes the antenna of example 63, wherein the second angle is substantially 120 degrees.

[0200]

[0210] Example 65 includes the device of any one of Examples 48 to 60, wherein the first angle is substantially 90 degrees.

[0201]

[0211] Example 66 includes the device of example 65, wherein the second angle is substantially 45 degrees.

[0202]

[0212] Example 67 includes the device of any one of Examples 48 to 60, wherein the first angle is substantially 60 degrees.

[0203]

[0213] Example 68 includes the device of example 67, wherein the second angle is substantially 120 degrees.

[0204]

[0214] Example 69 includes the antenna of any one of examples 41 to 47, wherein the core is substantially octagonal.

[0205]

[0215] Example 70 includes the antenna of any one of examples 41 to 47, wherein the core is a regular polygon having a number of sides equal to twice the number of loop antennas of the antenna.

[0206]

[0216] Example 71 includes the device of any one of Examples 48 to 60, wherein the core is substantially octagonal.

[0207]

[0217] Example 72 includes the device of any one of examples 48 to 60, wherein the core is a regular polygon having a number of sides equal to twice the number of loop antennas of the antenna.

Claims

1. An automatic direction finder (100), a first loop antenna (126); a second loop antenna (128); and one or more processors (106) coupled to the first loop antenna and the second loop antenna, the one or more processors: receiving a first signal (132) from the first loop antenna and a second signal (134) from the second loop antenna; sampling the first and second digital signals at a sampling rate high enough to capture an entire frequency range associated with a plurality of wireless sources to generate a first digital signal (114) and a second digital signal (116); converting the first digital signal and the second digital signal to a frequency domain representation; and generating a first bearing estimate (122) for a wireless source of the plurality of wireless sources based on the frequency domain representation by comparing the relative amplitudes and phases of the first and second digital signals represented in the frequency domain.

2. 2. The automatic direction finder of claim 1, wherein the one or more processors are configured to simultaneously generate multiple bearing estimates for the multiple wireless sources in parallel processing operations based on a single time-domain sampling of each of the first loop antenna and the second loop antenna.

3. a third loop antenna, wherein the one or more processors are coupled to the third loop antenna, and the one or more processors: receiving a third signal from the third loop antenna; and 2. The automatic direction finder of claim 1, further configured to: sampling the third signal at a sampling rate high enough to capture the entire frequency range to generate a third digital signal; and wherein the one or more processors are configured to convert the first digital signal, the second digital signal, and the third digital signal into the frequency domain representation.

4. 4. The automatic direction finder of claim 3, wherein the one or more processors are further configured to generate the first bearing estimate and a second bearing estimate for a wireless source of the plurality of wireless sources based on the frequency domain representation.

5. The automatic direction finder of claim 4 , wherein the one or more processors are further configured to apply fault detection operations to the first orientation estimate and the second orientation estimate.

6. 5. The automatic direction finder of claim 4, wherein the one or more processors are further configured to generate an estimate of a general orientation of the wireless source, the estimate of general orientation comprising an average of the first orientation estimate and the second orientation estimate.

7. The automatic direction finder of claim 1 further comprising a sensing antenna.

8. The automatic direction finder of claim 1 , wherein the automatic direction finder is an integrated unit.

9. The automatic direction finder according to claim 8 , wherein the integrated unit is a system on a chip.

10. 2. The automatic direction finder of claim 1, wherein the frequency range is approximately 0.19 to 1.75 MHz.

11. receiving a first signal (132) from a first loop antenna (126) and a second signal (134) from a second loop antenna (128); sampling the first and second signals at a sampling rate high enough to capture an entire frequency range associated with a plurality of wireless sources to generate a first digital signal and a second digital signal; converting the first digital signal and the second digital signal into a frequency domain representation (144); and generating, based on the frequency domain representation, a first bearing estimate (122) for a wireless source of the plurality of wireless sources by comparing relative amplitudes and phases of the first and second digital signals represented in the frequency domain.

12. The method of claim 11 , further comprising generating a plurality of bearing estimates for different ones of the plurality of wireless sources in parallel processing operations.

13. receiving a third signal from a third loop antenna; sampling the third signal at a sampling rate high enough to capture the entire frequency range to generate a third digital signal; and The method of claim 11 , further comprising converting the third digital signal to the frequency domain representation.

14. The method of claim 13 , further comprising generating a second bearing estimate for a particular wireless source of the plurality of wireless sources based on the frequency domain representation.

15. 15. The method of claim 14, further comprising generating an estimate of a general orientation of the wireless source, the general orientation estimate comprising an average of the first orientation estimate and the second orientation estimate obtained from signals from different pairs of loop antennas.

16. A non-transitory computer-readable medium containing instructions that, when executed by one or more processors (106, 206), cause the one or more processors to: receiving a first signal (132) from a first loop antenna (126) and a second signal (134) from a second loop antenna (128); sampling the first and second digital signals at a sampling rate high enough to capture an entire frequency range associated with a plurality of wireless sources to generate a first digital signal (114) and a second digital signal (116); converting the first digital signal and the second digital signal into a frequency domain representation (144); and generating a first bearing estimate (122) for a wireless source of the plurality of wireless sources based on the frequency domain representation by comparing the relative amplitude and phase of the first and second digital signals represented in the frequency domain.

17. 17. The non-transitory computer-readable medium of claim 16, wherein the instructions, when executed by the one or more processors, cause the one or more processors to generate multiple bearing estimates for different wireless sources of the plurality of wireless sources in parallel processing operations.

18. The instructions, when executed by the one or more processors, cause the one or more processors to: receiving a third signal from a third loop antenna; sampling the third signal at a sampling rate high enough to capture the entire frequency range to generate a third digital signal; and 17. The non-transitory computer-readable medium of claim 16, further comprising: converting the third digital signal to the frequency domain representation.

19. 20. The non-transitory computer-readable medium of claim 18, wherein the instructions, when executed by one or more processors, further cause the one or more processors to generate a second bearing estimate for a particular wireless source of the plurality of wireless sources based on the frequency domain representation.

20. 20. The non-transitory computer-readable medium of claim 19, wherein the instructions, when executed by one or more processors, further cause the one or more processors to generate an estimate of an overall bearing of the wireless source, the estimate of overall bearing comprising an average of the first bearing estimate and the second bearing estimate obtained from signals from different pairs of loop antennas.

Images