System and method for automatic direction finding

Abstract

The invention discloses a system and a method for automatic direction finding. 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 at a sampling rate up to a sampling rate sufficient to capture an entire frequency range associated with the 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 into a frequency domain representation. The method further includes generating a first orientation estimate for one of the plurality of radio sources based on the frequency domain representation by comparing relative amplitudes and phases of the first digital signal and the second digital signal represented in the frequency domain.

Description

Technical Field

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

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

[0003] In some operating environments, the use of ADF has decreased due to the benefits of other navigation systems such as the Global Positioning System (GPS). Among other reasons, the superior performance and global coverage provided by GPS, the ability of GPS to be more easily integrated with other avionics systems, and the smaller form factors available for GPS systems compared to traditional ADF have all stimulated the shift to GPS. However, ADF still exists on many aircraft, especially in areas where other navigation systems are unavailable or less effective as a backup to GPS. ADF also remains in use on smaller aircraft, older aircraft, etc., where switching to more complex navigation methods is not cost-effective. Summary of the Invention

[0004] In a specific embodiment, 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. 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 signal and the second signal over a frequency range up to a frequency range sufficient to capture the entire frequency range associated with a plurality of radio sources to generate a first digital signal and a second digital signal. The one or more processors are configured to convert the first digital signal and the second digital signal into a frequency domain representation. The one or more processors are further configured to generate a first bearing estimate of a radio source from the plurality of radio 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.

[0005] In another specific 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. The instructions, when executed by the one or more processors, cause the one or more processors to sample the first and second signals over a frequency range sufficient to capture the entire frequency range associated with multiple radio sources to generate first and second digital signals. The instructions, when executed by the one or more processors, cause the one or more processors to convert the first and second digital signals into frequency domain representations. The instructions, when executed by the one or more processors, cause the one or more processors to generate a first position estimate for a radio source from a plurality of radio 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 specific 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 sufficient to capture the 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 into a frequency domain representation. The method includes generating a first bearing estimate of a radio source from the plurality of radio 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.

[0007] In another specific embodiment, an apparatus includes means for receiving a first signal from a first loop antenna and a second signal from a second loop antenna. The apparatus includes means for sampling the first and second signals over a frequency range up to a frequency range sufficient to capture the entire frequency range associated with a plurality of radio sources to generate first and second digital signals. The apparatus includes means for converting the first and second digital signals into frequency domain representations. The apparatus includes means for generating a first bearing estimate for a radio source from the plurality of radio 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.

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

[0009] In another specific 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 an automatic direction finder, a first bearing estimate associated with a first orientation relative to a first radio 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 instructions, when executed by the one or more processors, 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 radio source. The second bearing estimate is based on a 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 the second signal from the second loop antenna. The instructions, when executed by the one or more processors, further cause the one or more processors to determine a position based on at least the first bearing estimate and the second bearing estimate.

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

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

[0012] In another specific embodiment, an antenna includes a core. The antenna includes a first loop antenna comprising a first plurality of conductive loops formed around the core. The antenna includes a second loop antenna comprising 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 comprising 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 specific 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, 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.

[0014] In another specific embodiment, a device includes a housing, an antenna housed within the housing, an electronics unit housed within the housing and coupled to the antenna, and an interface housed within the housing and coupled to the electronics unit, the interface configured to enable data to be transmitted from the electronics unit to a second device external to the housing. The antenna includes a core, a first loop antenna comprising a first conductive loop formed around the core, a second loop antenna comprising a second conductive loop formed around the core at a first angle relative to the first conductive loop, and a third loop antenna comprising 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, second, and third signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 An example system for automatic direction finding according to some examples of the subject disclosure is depicted.

[0016] Figure 2 Another example system for automatic direction finding according to some examples of the subject disclosure is depicted.

[0017] Figure 3 Another example system for automatic direction finding according to some examples of the subject disclosure is depicted.

[0018] Figure 4 Another example system for automatic direction finding according to some examples of the subject disclosure is depicted.

[0019] Figure 5Example antennas according to some examples of the subject disclosure are shown.

[0020] Figure 6 An example device for automatic direction finding according to some examples of the subject disclosure is shown.

[0021] Figure 7 An example determination of the position of an ADF according to some examples of the subject disclosure is shown.

[0022] Figure 8 is a flow chart of an example method for automatic direction finding according to some examples of the subject disclosure.

[0023] Figure 9 is a flow chart of another example method for automatic direction finding according to some examples of the subject disclosure.

[0024] Figure 10 is a flow chart of an example method for position estimation according to some examples of the subject disclosure.

[0025] Figure 11 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 examples of the subject disclosure. DETAILED DESCRIPTION

[0026] For efficient and safe aircraft operation, aircraft are often equipped with an automatic direction finder (ADF). In recent years, many aircraft have switched to using the Global Positioning System (GPS) for navigation instead of, or in addition to, the ADF. However, the ADF remains a valuable tool for aircraft navigation, particularly in situations where GPS equipment fails, GPS signals are unavailable (e.g., in geographical areas where GPS signals are blocked), or GPS signals are spoofed. The ADF described herein can be used as a standalone and / or alternative navigational aid.

[0027] An advantage of the subject disclosure is that it provides navigation redundancy independent of GPS. The systems and methods disclosed herein provide a redundant navigation tool that can be used in the event of a failure of other navigation systems like GPS or inertial navigation systems.

[0028] Another technical advantage of the subject disclosure is providing broader navigation coverage.The systems and methods disclosed herein can operate in areas where other navigation systems may be less effective or non-existent, such as remote or underdeveloped areas of the world.

[0029] Another technical advantage of the subject disclosure is providing navigation tool upgrades to older aircraft that have not been retrofitted with the latest navigation technology due to the costs associated with the latest navigation technology.

[0030] Another technical advantage of the subject disclosure is that it helps aircraft operators meet regulatory requirements while improving the efficiency and capabilities of ADFs. For example, a particular regulatory body may have specific requirements for the type of navigation equipment that must be installed on an aircraft. Certain regulatory frameworks have traditionally required ADFs and may continue to require them in the future.

[0031] Another technical advantage of the subject disclosure is that it improves the capabilities of the ADF carried on aircraft by most major aircraft operators. For example, as described in more detail below, the systems and methods disclosed herein can provide multiple position estimates that can be used to improve the accuracy of the aircraft's position using fault detection and troubleshooting operations, and can be used to provide an estimate of the aircraft's position.

[0032] Another technical advantage of the subject disclosure is that it reduces the overall size required for an ADF, thereby increasing the space available for other equipment on the aircraft. The systems and methods disclosed herein can also reduce the complexity required to accommodate certain conventional ADFs, such as by reducing the number and / or length of cables and other electronic equipment used to connect the ADF to other avionics of the aircraft.

[0033] The subject disclosure describes systems and methods for automatic direction finding.For example, an ADF is disclosed that has reduced size and weight, as well as additional capabilities, compared to certain widely used conventional ADFs.

[0034] As a specific example, the ADF can be a drop-in replacement for an ARINC 712 form factor ADF with large portions of the system removed. (The Airline Electronics Engineering Council (AEEC), the Aviation Maintenance Conference (AMC), and the Flight Simulator Engineering and Maintenance Conference (FSEMC) are aviation industry events organized by ARINC Industry Activities, an industry program of the SAE Industry Technologies Consortia (ITC). "ARINC" is a registered trademark of Arinc, Inc. of Annapolis, Maryland, United States. In this specific example, the ADF can include the functionality of a conventional ADF and the same interfaces and controls, allowing it to be easily integrated into an ARINC 712 form factor ADF.) The system and method disclosed herein can be used in an aircraft equipped with a Model 712 ADF without requiring changes to other systems on the aircraft (other than wiring and possibly removing the physical equipment rack) while performing the same functionality as a conventional ADF and functionality beyond that of a conventional ADF. Specifically, the systems and methods disclosed herein are capable of simultaneously performing bearing measurements for multiple non-directional beacons (NDB) or amplitude modulated (AM) radio stations operating in the frequency band of 190kHz to 1.75MHz, with high frequency transmissions in the 2MHz to 20MHz band also being used as a source of bearing measurements. Conventional ADFs can only track and measure the bearing of a single transmitter at a time. Therefore, two independent ADF receivers are required to obtain the two bearing measurements required for positioning. Using the ADF disclosed in the present subject matter, multiple software-based receiver chains can operate in parallel to track multiple signals and obtain bearings from multiple sources. The number of bearing measurements will be limited only by the available signal sources and the processing power of the system.

[0035] In certain embodiments, the systems and methods disclosed herein may include an arrangement of four intersecting loops, rather than the two intersecting loops used by some conventional ADFs. Using four loops provides more accurate azimuth measurements and enables fault detection and isolation of potential faults in one of the loop antennas. Generally speaking, any number of loops greater than or equal to two may be used. Using three loops may enable some fault detection. Using 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, and the accuracy of the resulting measurement.

[0036] The accompanying drawings and the following description illustrate specific exemplary embodiments. It should be understood that those skilled in the art will be able to design various arrangements that, although not explicitly described or shown herein, embody the principles described herein and are within the scope of the claims appended hereto. In addition, any examples described herein are intended to aid understanding of the principles of the present disclosure and should be construed as non-limiting. Therefore, the present disclosure is not limited to the specific embodiments or examples described below, but is defined by the claims and their equivalents.

[0037] Specific embodiments are described herein with reference to the accompanying drawings. In the specification, common features are indicated by common reference numerals throughout all drawings. In some figures, multiple instances of a particular type of feature are used. Although the features are physically and / or logically different, each feature uses the same reference numeral, and the different instances are distinguished by adding a letter to the reference numeral. When a feature is referred to herein as a group or type (for example, when a specific one is not mentioned), the reference numeral is used without a distinguishing letter. However, when a specific feature of multiple features of the same type is referred to herein, the reference numeral is used with a distinguishing letter. For example, with reference to Figure 3 , multiple loop antennas are shown and are associated with reference numerals 302A, 302B, 302C, and 302D. When referring to a specific one of these loop antennas, such as loop antenna 302A, a distinguishing letter "A" is used. However, when referring to any one of these loop antennas, reference numeral 302 is used without a distinguishing letter.

[0038] As used herein, various terms are used only to describe particular embodiments and are not intended to be limiting. For example, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, some features described herein are in some embodiments singular and in other embodiments plural. For illustration, Figure 1 Depicts a system comprising one or more processors ( Figure 1 106), indicating that in some embodiments, the system 100 includes a single processor 106, while in other embodiments, the system 100 includes multiple processors 106. For ease of reference herein, features are generally introduced as "one or more" features and are subsequently referenced in the singular or optionally in the plural (as indicated by "a plurality") unless aspects relating to multiple features are being described.

[0039] The terms "comprise," "comprises," and "comprising" may be used interchangeably with "include," "includes," or "including." Additionally, the term "wherein" may be used interchangeably with the term "wherein." As used herein, "exemplary" indicates an example, implementation, and / or aspect and should not be construed as limiting or indicating a preference or preferred implementation. As used herein, ordinal terms (e.g., "first," "second," "third," etc.) used to modify elements such as structures, components, operations, etc. do not, by themselves, indicate any priority or order of the element relative to another element, but merely distinguish the element from another element with the same name (however, the ordinal term is used). 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.

[0040] As used herein, "generate," "calculate," "use," "select," "access," and "determine" are interchangeable unless the context indicates otherwise. For example, "generating," "calculating," or "determining" a parameter (or signal) may refer to actively generating, calculating, or determining a parameter (or signal), or may refer to using, selecting, or accessing an already generated parameter (or signal), such as a parameter (or signal) generated by another component or device. As used herein, "coupling" may include "communicatively coupling," "electrically coupling," or "physically coupling," and may also (or alternatively) include any combination thereof. Two devices (or components) may be coupled (e.g., communicatively coupling, electrically coupling, or physically coupling) directly or indirectly via one or more other devices, components, wires, buses, networks (e.g., a wired network, a wireless network, or a combination thereof). As an illustrative, non-limiting example, two electrically coupled devices (or components) may be included in the same device or different devices and may be connected via an electronic device, one or more connectors, or inductive coupling. In some embodiments, two devices (or components) that are communicatively coupled, such as in electrical communication, can send and receive electrical signals (digital or analog) directly or indirectly, such as 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 intervening components.

[0041] Figure 1An example system 100 for automatic direction finding according to some examples of the subject disclosure is depicted. In some embodiments, 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 each other. The loop antennas 126-131 may be wound on a common core. For example, the loop antennas 126-130 may be wound across opposing planes of a hexagonal core, as described below with reference to FIG. Figure 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 radio sources 138, 140. For example, the radio sources 138, 140 may include NDBs, AM radio towers, and the like.

[0042] In some embodiments, 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 embodiments, 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 transmit first signal 132, second signal 134, third signal 136, fourth signal 137, or some combination thereof to computing device 102 via a communication link, such as a coaxial cable.

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

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

[0045] In some embodiments, the signal converter 142 can 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 142 can be configured to perform a fast Fourier transform on the digital signals 114-119. In one particular aspect, the signal sampler 104 is configured to sample the signals 132-137 using a sampling rate that is high enough to capture the entire bandwidth of interest, which can be referred to as the Nyquist frequency. The signal converter 142 can then immediately convert the digital signals 114-119 to generate the frequency domain representation 144. In one particular example, the bandwidth of interest can be associated with the operating frequency range of the radio sources 138, 140 (e.g., 0.19-1.75 MHz). The source transmitter frequency data 124 can be included in a database stored in the memory 108, which can also include the known locations of the radio sources 138, 140.

[0046] In some embodiments, the position estimate generator 112 may be configured to generate a position estimate for each radio source 138, 140 based on the frequency domain representation 144. Figure 3 and Figure 4 In more detail, position estimate generator 112 may include one or more components for generating a first position estimate 120 associated with first radio source 138 and a second position estimate 122 associated with second radio source 140 based on frequency domain representation 144. In one particular aspect, processor 106 may be configured to generate multiple position estimates 122 for each radio source 138, 140 in parallel processing operations.

[0047] In some embodiments, the system 100 may further include a sensing antenna coupled to the processor 106. The sensing antenna may be a non-directional antenna having sufficient sensitivity to distinguish the relative phases of the loop antennas 126-130. The processor 106 may be configured to receive signals from the sensing antenna and determine the relative phases of the first signal 132, the second signal 134, the third signal 136, and the fourth signal 137 received by the sensing antenna, as well as the phases of the first signal 132, the second signal 134, the third signal 136, and the fourth signal 137 received by the loop antenna.

[0048] In some embodiments, processor 106 is further configured to generate an overall bearing estimate for one or more of radio sources 138, 140. In some aspects, the overall bearing estimate can be derived by averaging the first bearing estimate 120 and the second bearing estimate 122 for one or more of radio sources 138, 140. In the same or alternative aspects, processor 106 can be configured to use other means of generating the overall bearing estimate. For example, first bearing estimate 120 and second bearing estimate 122 can be used to best fit a sine wave that corresponds to an expected distribution of amplitude and phase for waves arriving from a given angle. The phase of the best-fit sine wave can indicate the angle of arrival. If a particular loop antenna fails, system 100 can detect and isolate the faulty measurement while still continuing to generate bearing measurements.

[0049] In some aspects, the processor 106 can also be configured to apply a fault detection operation, a fault removal operation, or some combination thereof to the plurality of position estimates 120, 122 of the radio sources 138, 140. For example, the fault detection operation can be based on comparing two different measurements made using two different pairs of loop antennas. The resulting comparison result can be compared to a fault detection threshold to detect a fault. If the comparison result exceeds the fault detection threshold, there is a possible fault in one of the loop antennas (e.g., one or more of the first loop antenna 126, the second loop antenna 128, and the third loop antenna 130), which results in inconsistent measurements.

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

[0051] although Figure 1 Certain components of the system 100 are shown, but more, fewer, and / or different components may be present without departing from the scope of the subject disclosure. For example, although four loop antennas 126-131 are shown, two, three, or more than four loop antennas may be present. Figure 3-Figure 5 、 Figure 7 and Figure 8 A specific example of implementing four loop antennas is described in more detail. As another example, as described above, computing device 102 and loop antennas 126-131 can be an integrated unit. As another example, memory 108 can include a database that includes known locations of radio sources 138, 140.

[0052] In operation, the processor 106 may receive a first signal 132, a second signal 134, a third signal 136, and a fourth signal 137 from radio sources 138, 140. The amplitude of a particular received signal from the first source depends on the angle of arrival of the particular received signal. For example, for a simple sinusoidal source signal, the amplitude S(t) may be calculated using the following formula: where θ is the angle of arrival measured from the plane of the antenna loop, ω is the frequency of the carrier, and is an arbitrary phase of the carrier.

[0053]

[0054] In this type of configuration, two 90-degree intersecting loops can be used to determine the angle of arrival θ. The amplitudes S1(t) and S2(t) of the two intersecting loops can be calculated using the following formula.

[0055]

[0056]

[0057] The processor 106 may be configured to measure the amplitude of each signal and calculate the ratio of one signal to the other as shown below.

[0058]

[0059] The processor 106 may then be configured to calculate the angle B associated with the angle of arrival θ using the following formula.

[0060]

[0061] Because of the absolute value in the division portion of the formula, angle B always has a value within the range of 0 to 180 degrees. The angle of arrival θ is either angle B or B+180 degrees. 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.

[0062] Although the bearing estimate from the loop antenna can be used to generate the overall bearing estimate, adding additional bearing estimates from additional antennas enables additional functionality of the ADF. For example, Figure 1 The four-antenna implementation shown and Figure 3-Figure 5 The four-antenna embodiment shown allows for overdetermination of the overall position estimate, which in turn can enable fault detection, troubleshooting, additional functionality, or some combination thereof. Additional functionality can also be achieved by sampling the input radio signal across the entire frequency band of the radio sources 138, 140.

[0063] In a specific example using four loop antennas A, B, C, and D arranged at increasing 45 degree angles relative to each other (e.g., as Figure 5 As shown), the following formula can be used to describe the signals from the first source received by the four loop antennas (i.e., S A (t), S B (t), S C (t) and S D (t)) of the signal amplitude.

[0064]

[0065]

[0066]

[0067]

[0068] Since the A-loop and C-loop form a first pair of perpendicular cross-loops, and the B-loop and D-loop form a second pair of perpendicular cross-loops, measurements from four antennas can be made, and the processor 106 can be configured to average the overall bearing estimate provided by the two sets of perpendicular cross-loops as shown in the following formula, where B AC is the θ of the AC loop AC The associated angle, B BD is the arrival angle θ with the BD loop pair BD The associated angle, and is angle B AC and B BD The average value of .

[0069]

[0070]

[0071]

[0072] Because of the absolute value in the division portion of the formula, the values ​​of the various angles B in the above three formulas are always within the range of 0 degrees to 180 degrees. The corresponding angle θ for one of the various angles B is the value of angle B or B+180 degrees. 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.

[0073] By using multiple sets of orientation estimates from multiple interleaved loop antenna pairs, processor 106 can generate a detection statistic d based on a comparison of the multiple measurements as shown below. If d exceeds a fault detection threshold, processor 106 can be configured to generate an alert, e.g., indicating that a fault may exist in one of the loops, causing inconsistent measurements. As described above, other fault detection methods may also be used without departing from the scope of the present subject disclosure.

[0074] d=|θ AC -θ BD |

[0075] In some aspects, system 100 can include multiple software-based receiver chains. In these aspects, computing device 102 can include a greater number of receivers in a smaller physical package. In some configurations, the number of position measurements can be limited only by the processing and other computing resources of computing device 102.

[0076] In some embodiments, the 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. The system 100 may also include Figure 1 Components not shown in FIG. For example, computing device 102 may further 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, for example, via a data bus (such as an ARINC 429 bus). As further examples, system 100 may further include one or more input / output interfaces, one or more network interfaces, and the like. Furthermore, although Figure 1 The memory 108 of the system 100 is illustrated as storing certain data, but more, less, and / or different data may be present in the memory 108 without departing from the scope of the subject disclosure.

[0077] In addition, despite Figure 1 Certain operations are illustrated as occurring within computing device 102, but these operations may be performed by other components of system 100 without departing from the scope of the present subject matter. For example, one or more components external to computing device 102 may be configured to host or otherwise incorporate some or all of signal sampler 104, signal converter 142, position estimate generator 112, or some combination thereof. Such components may be located remotely from computing device 102 and may be accessed via a modem of computing device 102.

[0078] In addition, despite Figure 1 The processor 106 and memory 108 are illustrated as being integrated into a single computing device 102, but other configurations are possible without departing from the scope of the present subject disclosure. For example, the memory 108 may be stored as a separate data storage device and integrated into the navigation computer, while the processor 106 may be integrated into an ADF remote from the navigation computer. As an additional example, one or more components of the computing device 102 may be distributed across multiple computing devices (e.g., a set of processor cores).

[0079] 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-azimuth positioning solution that enables an aircraft to identify its geographic location based on multiple radio signals received from each of multiple radio sources 138, 140, as described in more detail below.

[0080] Figure 2Another example system 200 for automatic direction finding according to some examples of the subject disclosure is depicted. In some implementations, 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 radio signal received from a radio source 138, 140.

[0081] In some embodiments, 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 a plurality of loop antennas, including a first loop antenna 126 and a second loop antenna 128, wherein each loop antenna is configured to receive radio signals from a plurality of radio sources 138, 140. Figure 1 As described above, in some embodiments, the automatic direction finder 204 may include more than two loop antennas. In one particular aspect, the automatic direction finder 204 generally corresponds to Figure 1 computing device 102.

[0082] The processor 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 210 may also be configured to generate a first plurality of orientation measurements 228 for the first signal 236 and to generate a second plurality of orientation measurements 230 for the second signal 238. In one particular aspect, the first plurality of orientation measurements 228 and the second plurality of orientation measurements 230 may be stored in the memory 212.

[0083] In some aspects, processor 210 can be configured to generate a first portion 232 of a first plurality of orientation measurements 228 associated with radio signals received by first loop antenna 126 from first radio source 138, a second portion 234 of the first plurality of orientation measurements 228 associated with radio signals received by first loop antenna 126 from second radio source 140, a first portion 233 of a second plurality of orientation measurements 230 associated with radio signals received by second loop antenna 128 from first radio source 138, and a second portion 235 of the second plurality of orientation measurements 230 associated with radio signals received by second loop antenna 128 from second radio source 140.

[0084] In some implementations, the processor 210 can be configured to generate a first position estimate 242 associated with a first orientation of the automatic direction finder 204 relative to the first radio source 138 and transmit the first position estimate 242 to the computing device 202. The processor 210 can also be configured to generate a second position estimate 244 associated with a second orientation of the automatic direction finder 204 relative to the second radio source 140 and transmit the second position estimate 244 to the computing device 202.

[0085] In some implementations, computing device 202 includes one or more processors 206 coupled to memory 208. Processor 206 can be configured to receive a first position estimate 242 and a second position estimate 244 from automatic direction finder 204.

[0086] In some implementations, computing device 202 may include a location determination system 214 configured to determine location 216 based on at least first position estimate 242 and second position estimate 244, as described below with reference to Figure 8 and Figure 9 Described in more detail.

[0087] In some aspects, the system 200 may also include an aircraft control system 220 configured to transmit one or more aircraft control signals 224 to the computing device 202. For example, the aircraft control system 220 may include, be integrated into, or otherwise be part of a control system of the aircraft that is configured to generate the aircraft control signals 224 associated with the flight state of the aircraft, the control configuration of the aircraft, etc. As a specific example, the aircraft control signals 224 may include one or more signals indicating the pilot's intention to switch to the ADF 204 for navigation in place of or in addition to an alternative navigation tool such as GPS. In some embodiments, the processor 206 may be configured to determine the position 216 in response to the aircraft control system 220 of the aircraft.

[0088] In the same or alternative aspects, system 200 can also include a positioning system 222 communicatively coupled to computing device 202. Positioning system 222 can include, for example, a GPS unit, an inertial navigation device, or some combination thereof. In one particular aspect, positioning system 222 can be configured to transmit a positioning system failure indication signal 226 associated with a failure of positioning system 222. For example, positioning system failure indication signal 226 can include one or more signals indicating a loss of satellite signals, a power failure, a computing failure, etc. associated with positioning system 222. In some implementations, processor 206 can be configured to determine location 216 in response to positioning system failure indication signal 226 indicating a failure associated with positioning system 222.

[0089] In some embodiments, the radio sources 138, 140 may be NBD, AM radio sources, etc., as described above with reference to Figure 1 In some aspects, the processor 206 can be configured to determine the location 216 based on at least the known location of the first radio source 138 and the known location of the second radio source 140. In one particular aspect, the known locations of the radio sources 138, 140 can be stored as part of a known location dataset 218 stored in the memory 208. In one particular aspect, the known location of the first radio source 138 is a measurement of the location of the first radio source 138 relative to the center of the Earth, the known location of the second radio source 140 is a measurement of the location of the second radio source 140 relative to the center of the Earth, or some combination thereof, as described below with reference to Figure 9 Described in more detail.

[0090] In the same or alternative specific aspects, the processor 206 can be configured to determine the position of the aircraft based on an initial position of the first radio source 138 and the second radio source 140 and an iterative process of setting known positions. The initial position can include the last known position or starting position of the aircraft, an arbitrary position, or any combination thereof. Figure 9 In more detail, the iterative process may begin with an initial position and determine the position of the aircraft by analyzing first position estimate 242 and second position estimate 244 .

[0091] In some embodiments, the 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. The system 200 may also include Figure 2 Components not shown in FIG. For example, computing device 202 may also include a receiver configured to receive first position estimate 242, second position estimate 244, or some combination thereof. The receiver may be configured to receive data, for example, via a data bus (such as an ARINC 429 bus). As further examples, system 200 may also include one or more input / output interfaces, one or more network interfaces, and the like. Furthermore, although Figure 1 The memory 208 of the system 200 is illustrated as storing certain data, but more, less, and / or different data may be present in the memory 208 without departing from the scope of the subject disclosure.

[0092] In addition, despite Figure 2Certain operations are illustrated as occurring within computing device 202, but these operations may be performed by other components of system 200 without departing from the scope of the present subject disclosure. For example, one or more components external to computing device 202 may be configured to host or otherwise incorporate location determination system 214. Such components may be located remotely from computing device 202 and may be accessed via a modem of computing device 202.

[0093] In addition, despite Figure 2 The processor 206 and memory 208 are shown as being integrated into a single computing device 202, but other configurations are possible without departing from the scope of the present subject disclosure. For example, the memory 208 may be stored as a separate data storage device and integrated into the aircraft navigation computer, while the processor 206 may be integrated into an ADF remote from the navigation computer. As an additional example, one or more components of the computing device 202 may be distributed across multiple computing devices (e.g., a set of processor cores).

[0094] although Figure 2 Only two loop antennas 126, 128 are shown as being used in the system 200, but more loop antennas may be used without departing from the scope of the subject disclosure. For example, the automatic direction finder 204 may include and / or receive signals from, for example, Figure 1 and Figure 3-Figure 5 The radio signals of the four loop antennas shown, or any number of loop antennas, are shown. The functionality of automatic direction finder 204, computing device 202, and system 200, as further described below, is achieved by using multiple loop antennas and multiple bearing estimates from each loop antenna, where a portion of each of the multiple bearing estimates is associated with a specific radio source.

[0095] Figure 3 Another example system 300 for automatic direction finding according to some examples of the subject disclosure is shown. Example system 300 includes one or more processors 328 coupled to loop antennas 302A, 302B, 302C, and 302D. Loop antennas 302A-D may be wound across a plane of a common octagonal core. Processor 328 is configured to process incoming radio signals from loop antennas 302A-D. Processor 328 generally corresponds to Figure 1 processor 106, Figure 2 processor 210 or some combination thereof.

[0096] In some embodiments, each of the loop antennas 302A-D is coupled to a corresponding matching network 312A-D and a matching amplifier 322A-D. After amplification, the radio signal is transmitted to a corresponding analog-to-digital converter (ADC) 326A-D before being transmitted to a processor 328. In some aspects, the processor 328 can 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 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 328 via the matching network 320, the amplifier 334, and the ADC 336. When utilizing the above formula, the sensing antenna 310 allows for determining an orientation estimate within a 360-degree range relative to the orientation associated with the loop antennas 302A-D.

[0097] In some embodiments, the processor 328 can be configured to provide an output to the connector 330 to further communicate with other aspects of the automatic direction finding system (e.g., Figure 1 The system 300 may also include power supply circuitry 332 configured to provide additional signal conditioning, power distribution, other appropriate power-related functions, or some combination thereof to the output.

[0098] In operation, the system 300 receives radio signals from four loop antennas 302A-D arranged at increasing 45 degree angles relative to each other, as described below with reference to Figure 4 As stated. Figure 3 In the illustrative example, the frequency range of the ADF receiver is from 190 kHz to 1.75 MHz, direct analog-to-digital conversion can be used with a moderate sampling rate (e.g., 4 megasamples per second) and still above the Nyquist sampling rate T, and the signal can be converted to baseband represented as in-phase and quadrature components during digital processing. The digitized RF signals of all five channels corresponding to the signals received by the four loop antennas 302A-D and the sensing antenna 310 are provided to the processor 328. The system 300 is configured to immediately digitize the incoming radio signals and process the digital signals.

[0099] although Figure 3 Certain components are shown in a particular configuration, but system 300 may include more, fewer, and / or different components without departing from the scope of the present disclosure. For example, processor 328 may include multiple processors for different tasks. For example, in one particular configuration, a field programmable gate array (FPGA) may be included to support digital signal processing, and a separate processor may be configured to handle input / output and other maintenance-type functions.

[0100] Figure 4 An example system 400 for automatic direction finding according to some examples of the subject disclosure is shown. The system 400 may include a system configured to receive data corresponding to a direction received by an antenna (e.g., Figure 3 One or more processors 420 of the plurality of voltage signals 402 corresponding to the radio signals received by the loop antennas 302A-D and the sensing antenna 310).

[0101] In some implementations, each of the plurality of voltage signals 402 may be converted into a digital signal via a corresponding ADC 414. Figure 4 As shown, the voltage signal 402 includes a voltage signal 402 that is connected to a radio source (e.g., Figure 1 and Figure 2 , 140) as shown at stage 404. As shown at stage 406, the system 400 can be configured to sample the signal at the ADC 414 over the entire frequency range of the radio signal associated with the radio source. The system 400 can also be configured to transform the digital signal output from the ADC 414 to the frequency domain. For example, the system 300 can include circuitry 416 configured to perform a fast Fourier transform (FFT) on each digital signal output from the ADC 414. As shown at stage 408, in some aspects, the transformed digital signal can be separated into one or more data streams for parallel processing. In some aspects, the FFT circuitry 416 can include a processor (e.g., Figure 1 processor 106, Figure 2 One or more components of the processor 206, processor 420, etc.) that execute instructions that cause one or more components of the processor to convert the digital signal output from the ADC 414 to the frequency domain.

[0102] The system 400 can also be configured to apply a corresponding bandpass filter (BPF) 418 in the frequency domain to the frequency domain digital signal from the FFT circuitry 416. As shown at stage 410, the BPF 418 can operate to select one or more channels of interest within a frequency range. For example, a particular BPF 418 can be selected to correspond to a radio source (e.g., Figure 1 and Figure 2 The transformed digital signal can be provided to multiple processing streams for parallel processing, as shown at stage 408. In such a configuration, multiple BPFs 418 can be used to select multiple portions of the radio frequency range of interest.

[0103] The processor 420 may be configured to receive a signal of interest in the frequency domain, as shown at stage 412. The processor 420 may be configured to determine the amplitude and phase of the radio signal received by the plurality of loop antennas of the ADF, as described above with reference to Figure 1 The processor 420 may be configured to estimate the direction of arrival associated with each radio signal and generate a plurality of bearing estimates, as described above with reference to Figure 1 and Figure 2 In some aspects, processor 420 may also be configured to perform additional functionality. For example, processor 420 may be configured to perform additional processing, such as Morse code demodulation, on a radio source that is an NBD transmitter. Similarly, processor 420 may be configured to perform demodulation of an AM radio signal to recover an audio signal.

[0104] In some aspects, processor 420 may be configured to implement multiple processing chains 422. Each of the multiple processing chains may be configured to generate a position estimate in a corresponding channel of interest. For example, processing chain 422A may be configured to generate a position estimate associated with a first channel associated with a first radio source, processing chain 422B may be configured to generate a position estimate associated with a second channel associated with a second radio source, and so on, until processing chain 422C may be configured to generate a position estimate associated with an nth channel associated with an nth radio source. For purposes of the subject disclosure, a channel may be associated with a particular radio source (e.g., Figure 1 For example, a first channel may be associated with a first radio source and a second channel may be associated with a second radio source. Figure 2 and references below Figure 7-Figure 9 As described in more detail, multiple position estimates may be used to generate an estimate of the aircraft's current position.

[0105] exist Figure 4 In the illustrative example of FIG, system 400 analyzes voltage signals 402 from four loop antennas and one sensing antenna (eg, as described below with reference to FIG). Figure 5 418). The voltage signal is sampled, converted, and filtered for signals in N channels. The number of channels (and the associated number of processing chains 422 and related components such as BPF 418) may depend on the specific implementation of system 400. For example, the number of channels may be selected based on the highest number of expected radio 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. Additionally, although Figure 4Five voltage signals 402 are shown, but without departing from the scope of the subject disclosure, there may be more, fewer, and / or different voltage signals 402. For example, system 400 may be configured to process voltage signals 402 associated with three or five or more loop antennas.

[0106] The above systems 300 and 400 have described exemplary operations using voltage signals output by four loop antennas arranged at increasing angles of 45 degrees to each other. Figure 5 An exemplary embodiment of this arrangement of four loop antennas is described in more detail.

[0107] Figure 5 An example antenna 500 according to some examples of the subject disclosure is shown. Antenna 500 includes: a core 502; a first loop antenna 504A including a first conductive loop 506 surrounding 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 surrounding 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.

[0108] exist Figure 5 In the example of , 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 can also be described relative to the y-axis 503 at the center of the core 502. For example, the first loop antenna 504A can be positioned at a zero degree angle relative to the y-axis 503, the third loop antenna 504B can be positioned at a 45 degree angle clockwise relative to the y-axis 503, the second loop antenna 504C can be positioned at a 90 degree angle clockwise relative to the y-axis 503, and the fourth loop antenna 504D can be positioned at a 135 degree angle clockwise relative to the y-axis 503. Although Figure 5 Four loop antennas 504A-504D are shown, but other configurations of three or more loop antennas are possible without departing from the scope of the subject disclosure. For example, antenna 500 may include three loop antennas 504A-504C arranged at a 60 degree angle relative to each other.

[0109] In some embodiments, the core 502 of the antenna 500 can be substantially octagonal to accommodate two pairs of crossed loop antennas (or a total of four loop antennas). The loop antennas 504A-D can be wrapped around a core comprising ferrite to increase the effective electrical size of the loop antennas 504A-D. For example, the core 502 can comprise ferrite to increase the effective electrical size of the antenna 500.

[0110] In some embodiments, the antenna 500 may also include a sensing antenna, as described above with reference to Figures 1-4 As described and referred to below Figure 6 In some aspects, the antenna 500 may further include a first matching network coupled to the first loop antenna 504A, a second matching network coupled to the second loop antenna 504C, a third matching network coupled to the third loop antenna 504B, a fourth matching network coupled to the fourth loop antenna 504D, or some combination thereof, as described above with reference to Figure 4 and Figure 5 Described in more detail.

[0111] As mentioned above Figure 1-Figure 5 In more detail, the system may be configured to estimate the angle of arrival 520 of a radio signal 522 entering the antenna 500 . Figure 5 The two crossed loop pairs of loop antennas shown (eg, crossed loop antenna pair 504A, 504C and crossed loop antenna pair 504B, 504D) may implement additional ADF functionality, such as fault detection and correction.

[0112] Although antenna 500 includes two crossed loop antenna pairs, any number of crossed loop antenna pairs greater than two may be included without departing from the scope of the subject disclosure. Any number of loops greater than two can generate redundant measurements that can be used for measurement noise reduction and fault detection.

[0113] Furthermore, although antenna 500 illustrates a substantially octagonal core 502, other shapes are possible without departing from the scope of the present disclosure. For example, if antenna 500 includes three loop antennas, core 502 may be substantially hexagonal. Generally speaking, core 502 is a regular polygon having 2*N sides, where N is the number of loop antennas.

[0114] In some embodiments, antenna 500 may be included in, incorporated into, or otherwise associated with an ADF device. Figure 6An example device 600 for automatic direction finding according to some examples of the subject disclosure is shown. 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.

[0115] The electronic unit 604 includes a receiver 608 configured to receive signals from Figure 5 The electronic unit 604 may also include one or more software defined radio components 610 configured to process the signals associated with the first loop and the second loop. The software defined radio component 610 may include the above referenced Figure 3 and Figure 4 In some aspects, device 600 may further include a sensing antenna 614 coupled to electronics unit 604 .

[0116] The interface 606 may be configured to enable data to be transferred from the electronic unit 604 to a second device external to the housing 602. For example, the interface 606 may be configured to enable data to be transferred from the electronic unit 604 to a second device external to the housing 602. Figure 2 Data of first position estimate 242 and second position estimate 244 is communicated to computing device 202 for further processing, display by a display device, or both. In one particular aspect, interface 606 comprises an ARINC 429 interface.

[0117] In some embodiments, the device 600 may be integrated into, incorporated into, or otherwise mounted on a portion 612 of an aircraft. For example, the device 600 may be attached to an exterior surface of an aircraft to facilitate communication with a radio source (e.g., Figure 1 In one particular configuration, the device 600 can be mounted so that the loop antenna 504A faces a forward direction associated with the normal forward direction of the aircraft.

[0118] Figure 7 An example determination 700 of the position of an ADF according to some examples of the subject disclosure is shown. Certain conventional methods for solving for multiple position fixes are performed in two-dimensional space (e.g., latitude / longitude space) with corrections and compensations to account for a non-flat Earth. The systems and methods disclosed herein implement an alternative three-dimensional, vector-based approach. Certain other methods (such as those based on spherical geometry) may be more complex than vector-based methods and may involve approximations that may limit performance in certain circumstances (e.g., very high latitudes, etc.).

[0119] Example determination 700 shows an unknown position 702 of an aircraft relative to a known position 706 of a first radio source, a known position 704 of a second radio source, and a known position 708 of the center of the Earth. Determination 700 includes unit vectors 710, 713 pointing from unknown position 702 to known positions 706, 704, respectively.

[0120] As mentioned above Figures 1-6 As described above, the system can obtain azimuth measurements from multiple loop antennas. One or more processors (e.g., Figure 1 processor 106, Figure 2 The processor 206 or some combination thereof) can be configured to model each orientation measurement as being taken from an unknown position 702 (P u = [xyz]) points to known locations 706, 704 (P i ). The vectors 722, 718 from the known location 708 at 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 a memory (e.g., Figure 1 in the memory 108).

[0121] As a simplified example, if the altitudes of the known locations 704, 706 are assumed to be the same as the altitude of the unknown location 702, then the unknown location 702 in the Earth Centered Earth Fixed (ECEF) coordinate system may be represented by the vector 720 Vector 720 is related to the known position of the i-th radio source by the following expression Related, among them is a vector from unknown position 702 to known positions 706, 704 (e.g., vectors 714, 716), and is a vector from known location 708 to known locations 706, 704 (e.g., vectors 722, 718), where:

[0122]

[0123] The processor may be configured to estimate the direction of the vector 720 by measuring the direction of arrival of radio signals from radio sources that are known locations 704, 706. is a unit vector pointing from unknown location 702 to known location 706 taking into account the direction of arrival of the radio signal from known location 706, and unit vector 713 is a unit vector pointing from unknown location 702 to known location 704 taking into account the direction of the radio signal from known location 704, then vector 720 can be represented by the following formula, where R i is the magnitude of vector 720 and is unknown:

[0124]

[0125] For any observation, Extending this relationship to the individual x, y, and z coordinate components yields the following three equations:

[0126]

[0127]

[0128]

[0129] The above equations include four unknowns: three unknown user position states and one unknown vector quantity. Each position measurement adds an additional unknown. For example, two position measurements give the following six equations:

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136] The unknowns can be collected and rearranged into a matrix form as follows:

[0137]

[0138] With six equations and five unknowns, the system can be solved using the generalized pseudoinverse: The above formula can be expanded to accommodate additional orientation measurements. Each new orientation measurement adds three rows and one column to the H matrix. The first three columns of the added rows are always an identity matrix. Except for the three rows containing elements of unit vectors, the added columns are all zero. All other rows and columns are set to zero. As long as there are at least as many or more equations as there are unknowns, this system can be solved. Those of ordinary skill in the art will recognize how to expand the matrix representation of the linear system of equations to accommodate additional orientation measurements. For example, if a third orientation measurement is available, the system of equations expressed in matrix form will be:

[0139]

[0140] In some embodiments, the angle of arrival measurements are actually generated in the aircraft body coordinate system, and the processor can convert these measurements to ECEF coordinates. Using the pitch, roll, and heading of the aircraft, a transformation from the aircraft reference system to the local hierarchy reference system can be completed. This vector can then be converted from the local hierarchy to ECEF. In order to perform the transformation, this transformation requires estimating the latitude, longitude, and altitude of the origin of the local hierarchy body coordinate system. The processor can be configured to perform calculations using the best available estimate of the aircraft's position to obtain a new estimate of the position. This process can be repeated until the difference between the new estimate and the previous estimate meets a position estimate accuracy threshold.

[0141] Figure 8 is a flow chart of an example method 800 for automatic direction finding according to some examples of the subject disclosure. The method 800 may be initiated, performed, or controlled by one or more processors executing instructions, such as a processor executing instructions from memory 108. Figure 1 Processor 106 that executes instructions from memory 208 Figure 2 The processor 206 of the processor 206, the processor 210 executing instructions from the memory 212, or a combination thereof is started, executed or controlled.

[0142] In some embodiments, 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, Figure 1 The processor 106 may receive a first signal 132 from the first loop antenna 126 and a second signal 134 from the second loop antenna 128 .

[0143] The 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 plurality of radio sources to generate a first digital signal and a second digital signal at block 804. For example, Figure 1The processor 106 may sample the first signal 132 and the second signal 134 to generate the first digital signal 114 and the second digital signal 116 .

[0144] The method 800 also includes converting the first digital signal and the second digital signal into a frequency domain representation at block 806. For example, Figure 1 The processor 106 may convert the first digital signal 114 and the second digital signal 116 into a frequency domain representation 144 .

[0145] The method 800 also includes generating a first position estimate of a radio source from the plurality of radio sources based on the frequency domain representation by comparing relative amplitudes and phases of the signals represented in the frequency domain at block 808. For example, Figure 1 The processor 106 may generate the first position estimate 120 of the radio source 138 based on comparing the relative amplitudes and phases of the frequency domain representations 144 .

[0146] In some embodiments, method 800 may include more, fewer, and / or different steps without departing from the scope of the subject disclosure. For example, method 800 may also include Figure 1 The method 800 may further include applying a fault detection operation, a fault removal operation, or both to the plurality of position estimates 120, 122. As another example, the method 800 may further include generating an overall position estimate for one of the one or more radio sources, wherein the overall position estimate comprises an average of the plurality of first and second position estimates 120, 122 for the radio sources 138, 140.

[0147] Figure 9 is a flow chart of an example method 900 for automatic direction finding according to some examples of the subject disclosure. The method 900 may be initiated, performed, or controlled by one or more processors executing instructions, such as a processor executing instructions from memory 108. Figure 1 Processor 106 that executes instructions from memory 208 Figure 2 The processor 206 of the processor 206, the processor 210 executing instructions from the memory 212, or a combination thereof is started, executed or controlled.

[0148] In some embodiments, method 900 includes receiving, at block 902, a first bearing estimate associated with a first orientation relative to a first radio source from an automatic direction finder, wherein the first bearing estimate is based on a first plurality of bearing estimates, and wherein a first portion of the first plurality of bearing estimates 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 estimates is generated by one or more processors based on a second signal from a second loop antenna. For example, Figure 2Processor 206 may receive, from automatic direction finder 204, a first bearing estimate 242 associated with a first bearing relative to first radio source 138, the first bearing estimate 242 being based on a first plurality of bearing measurements 228, wherein a first portion 232 of the first plurality of bearing measurements 228 is generated by processor 210 based on a first signal 236 from first loop antenna 126, and a second portion 234 of the first plurality of bearing measurements 228 is generated by processor 210 based on a second signal 238 from second loop antenna 128.

[0149] exist Figure 9 In an example of , method 900 further includes receiving, at block 904, a second bearing estimate associated with a second orientation relative to a second radio source from an automatic direction finder, wherein the second bearing estimate is based on a second plurality of bearing estimates, and wherein a first portion of the second plurality of bearing estimates is generated by one or more processors based on a first signal from the first loop antenna, and a second portion of the second plurality of bearing estimates is generated by one or more processors based on a second signal from the second loop antenna. For example, Figure 2 Processor 206 may receive, from automatic direction finder 204, a second bearing estimate 244 associated with a second bearing relative to second radio source 140, the second bearing estimate 244 being based on a second plurality of bearing estimates 230, wherein a first portion 233 of the second plurality of bearing estimates 230 is generated by processor 210 based on a first signal 236 from first loop antenna 126, and a second portion 235 of the second plurality of bearing estimates 230 is generated by processor 210 based on a second signal 238 from second loop antenna 128.

[0150] exist Figure 9 In the example of , method 900 also includes determining a position based on at least the first position estimate and the second position estimate at block 906. Figure 2 Processor 206 may determine location 216 based on at least first position estimate 242 and second position estimate 244 .

[0151] In some embodiments, method 900 may include more, fewer, and / or different steps without departing from the scope of the subject disclosure. For example, method 900 may further receive a third direction estimate associated with a third orientation relative to a third radio source from an automatic direction finder, and determine a position based on at least the first direction estimate, the second direction estimate, and the third direction estimate.

[0152] Figure 10is a flow chart of an example method 1000 for position estimation according to some examples of the subject disclosure. The method 1000 may be initiated, performed, or controlled by one or more processors executing instructions, such as a processor executing instructions from memory 108. Figure 1 Processor 106 that executes instructions from memory 208 Figure 2 In one particular aspect, method 1000 illustrates Figure 7 Example determination 700. In some implementations, method 1000 may be initiated, performed, or controlled starting from block 1001.

[0153] In some embodiments, method 1000 includes measuring a bearing to a transmitter location at block 1002. For example, as described above with reference to Figure 1 and 2 In more detail, the processor 106, 206 may generate Figure 1 The position measurements of the radio sources 138, 140 (e.g., Figure 2 In some aspects, the orientation measurements may be in the form of an angle θ from the nose of the aircraft on which the ADF is mounted to each emitter. i To obtain.

[0154] In some embodiments, method 1000 includes forming a unit vector in the aircraft reference frame for each orientation measurement at block 1004. For example, as described above with reference to Figure 7 As stated, Figure 1 and Figure 2 The processor 106 , 206 may be configured to form the unit vectors 710 , 713 in the aircraft reference frame.

[0155] In some embodiments, method 1000 includes transforming the unit vectors in the aircraft reference frame to the ECEF reference frame using the best estimate of the user's position at block 1006. For example, Figure 1 and Figure 2 The processor 106, 206 may be configured to use the best estimate of the aircraft's position to Figure 7 The unit vectors 710 and 713 of are transformed to the ECEF reference frame.

[0156] In some embodiments, method 1000 includes filling the H matrix with unit vector elements at block 1008. For example, as described above with reference to Figure 7 Described in more detail, Figure 1 and Figure 2The processor 106, 206 may fill the H matrix with unit vector elements. The method 1000 also includes calculating a new estimate of the position at 1010. For example, as described above with reference to Figure 7 Described in more detail, Figure 1 and Figure 2 The processor 106, 206 may calculate a new position estimate.

[0157] In some embodiments, method 1000 includes comparing the new position estimate to the last position estimate at block 1012. For example, Figure 1 and Figure 2 The processor 106, 206 can compare the new position estimate with the last position estimate. In some aspects, as described above with reference to Figure 7 As described, method 1000 can be an iterative process.

[0158] In some embodiments, method 1000 includes determining whether the new position estimate and the last position estimate match within a tolerance at block 1014. For example, as described in more detail above with reference to FIG. Figure 1 and Figure 2 The processor 106, 206 may determine whether the new position estimate and the last position estimate match within a position estimate accuracy threshold.

[0159] If the positions match within the tolerance, method 1000 includes outputting a new position estimate at block 1016. For example, Figure 1 and Figure 2 The processor 106, 206 may output the position estimate. The method 1000 may then include determining at block 1018 whether another measurement is needed. For example, Figure 1 and Figure 2 The processor 106, 206 may determine whether another measurement is needed. If another measurement is needed, the method 1000 may return to block 1002, where the method 1000 may continue to find an estimate of the new position. If another measurement is not needed, the method 1000 may proceed to block 1020, where, in some embodiments, the method 1000 may end. Referring again to block 1014, if the positions do not match within the tolerance, the method 1000 may return to block 1006, where the method 1000 may continue to iterate to identify an acceptable position estimate.

[0160] In some embodiments, 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 the steps of method 1000 (e.g., blocks 1008, 1010) without departing from the scope of the present disclosure.

[0161] The above reference can be implemented Figures 1-10 The methods described herein can achieve one or more of the technical advantages detailed above. For example, the methods 800, 900, and 1000 can enable an automatic direction finder (ADF) with improved capabilities (eg, fault detection) in a smaller physical size than some conventional ADFs.

[0162] Figure 11 is a block diagram of a computing environment 1100 including a computing device 1110 configured to support various aspects of computer-implemented methods and computer-executable program instructions (or codes) according to some examples of the subject disclosure. For example, the computing device 1110 or some portion thereof is configured to execute instructions to initiate, perform, or control the above-referenced Figures 1-9 In one particular aspect, the computing device 1110 may include, correspond to, or be included in Figure 1 computing device 102, Figure 2 computing device 202, Figure 2 Automatic direction finder 204, Figure 3 Components of the system 300, Figure 4 components of the system 400, one or more servers, one or more virtual devices, or a combination thereof.

[0163] The computing device 1110 includes one or more processors 1120. In one particular aspect, the processor 1120 corresponds to Figure 1 processor 106, Figure 2 processor 206, Figure 2 110, or some combination thereof. The processor 1120 is configured to communicate with a 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. The 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. The system memory 1130 stores an operating system 1132, which may include a basic input / output system for booting the computing device 1110 and a complete operating system that enables the computing device 1110 to interact with users, other programs, and other devices. The system memory 1130 stores system (program) data 1138, such as Figure 1 Source transmitter frequency data 124, Figure 2 A known location dataset 218, a plurality of position measurements 1105 (including, for example, Figure 2 The first plurality of orientation measurements 228 and the second plurality of orientation measurements 230 ) or a combination thereof.

[0164] System memory 1130 includes one or more applications 1134 (eg, instruction sets) that can be executed by processor 1120. As an example, one or more applications 1134 include programs that can be executed by processor 1120 to start, control, or perform a reference Figures 1-9 For illustration, one or more applications 1134 include instructions 1136 executable by the processor 1120 to initiate, control, or perform the operations described herein. Figure 2 The one or more operations described herein are for determining a position based on at least the first and second position estimates 242 and 244 received by the automatic direction finder 204 of the embodiment of the present invention. As another example, the one or more applications 1134 include instructions 1136 executable by the processor 1120 to initiate, control, or perform a reference reception process. Figure 1 The present invention also provides one or more operations described herein for detecting first, second, and third signals 132, 134, 136 of a plurality of radio sources, converting these signals into corresponding digital signals 114, 116, 118 of a frequency domain representation 120, and generating a first position estimate 122 for radio sources 138, 140 in the plurality of radio sources based on the frequency domain representation 120.

[0165] In particular embodiments, system memory 1130 includes a non-transitory computer-readable medium (e.g., a computer-readable storage device) storing instructions 1136 that, when executed by processor 1120, cause processor 1120 to initiate, perform, or control operations for automatic direction finding. These 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. These operations also include converting the first signal into a first digital signal, converting the second signal into a second digital signal, and converting the third signal into a third digital signal. These operations also include processing the first digital signal, the second digital signal, and the third digital signal over frequency bands associated with one or more radio sources to generate sampled signals. These operations also include generating a plurality of position estimates for each of the one or more radio sources based on the sampled signals.

[0166] In the same or alternative embodiments, system memory 1130 includes a non-transitory computer-readable medium (e.g., a computer-readable storage device) storing instructions 1136 that, when executed by processor 1120, cause processor 1120 to initiate, perform, or control operations for automatic direction finding. These operations include receiving a first bearing estimate associated with a first orientation relative to a first radio source from an automatic direction finder, wherein the first bearing estimate is based on a first plurality of bearing estimates, and wherein a first portion of the first plurality of bearing estimates 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 estimates is generated by one or more processors based on a second signal from a second loop antenna. These operations also include receiving a second bearing estimate associated with a second orientation relative to a second radio source from the automatic direction finder, wherein the second bearing estimate is based on a second plurality of bearing estimates, and wherein a first portion of the second plurality of bearing estimates is generated by one or more processors based on the first signal from the first loop antenna, and a second portion of the second plurality of bearing estimates is generated by one or more processors based on the second signal from the second loop antenna. The operations also include determining a position based on at least the first position estimate and the second position estimate.

[0167] One or more storage devices 1150 include non-volatile storage devices, such as magnetic disks, optical disks, or flash memory devices. In a specific example, storage devices 1150 include removable and non-removable storage devices. Storage devices 1150 are configured to store an operating system, an image of the operating system, applications (e.g., one or more of applications 1134), and program data (e.g., program data 1138). In a specific aspect, system memory 1130, storage devices 1150, or both include tangible computer-readable media. In a specific aspect, one or more of storage devices 1150 are external to computing device 1110.

[0168] One or more input / output interfaces 1140 enable the computing device 1110 to communicate with one or more input / output devices 1170 to facilitate user interaction. For example, one or more input / output interfaces 1140 may include a display interface, an input interface, or both. For example, the input / output interface 1140 is suitable for receiving input from a user, receiving input from another computing device, or a combination thereof. In some embodiments, the input / output interface 1140 complies with one or more standard interface protocols, including a serial interface (e.g., a universal serial bus (USB) interface or an Institute of Electrical and Electronics Engineers (IEEE) 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 of Piscataway, New Jersey, USA). In some embodiments, the input / output device 1170 includes one or more user interface devices and displays, including some combination of buttons, keyboards, pointing devices, displays, speakers, microphones, touch screens, and other devices.

[0169] The processor 1120 is 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, Figure 2 Automatic direction finder 204.

[0170] In some embodiments, a non-transitory computer-readable medium (e.g., a computer-readable storage device) stores instructions that, when executed by one or more processors, cause one or more processors to initiate, perform, or control operations to implement some or all of the above functions. For example, the instructions may be executed to implement Figures 1-10 In some embodiments, Figures 1-10 Part or all of one or more operations or methods may be implemented 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)) that execute instructions, dedicated hardware circuitry, or any combination thereof.

[0171] The illustrations of the examples described herein are intended to provide an overall understanding of the structures of the various embodiments. These illustrations are not intended to be a complete description of all elements and features of the apparatus and systems utilizing the structures or methods described herein. For those skilled in the art, many other embodiments will be apparent after reading this disclosure. Other embodiments may be utilized and derived from this disclosure so that structural and logical replacements and changes may be made without departing from the scope of this disclosure. For example, method operations may be performed in an order different from that shown in the figures, or one or more method operations may be omitted. Therefore, this disclosure and the accompanying drawings should be considered to be illustrative and not restrictive.

[0172] Furthermore, although specific examples have been illustrated and described herein, it should be understood that any subsequent arrangement designed to achieve the same or similar results may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent modifications or variations of the various embodiments. Combinations of the above embodiments, as well as other embodiments not specifically described herein, will be apparent to those skilled in the art upon reading the specification.

[0173] An abstract of the present disclosure has been submitted, but it should be understood that it is not used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing detailed description, various features may be grouped together or described in a single embodiment for the purpose of simplifying the present disclosure. The above examples illustrate but do not limit the present disclosure. It should also be understood that many modifications and variations are possible based on the principles of the subject disclosure. As reflected in the appended claims, the claimed subject matter may involve fewer than all the features of any disclosed example. Therefore, the scope of the present disclosure is defined by the appended claims and their equivalents.

[0174] Furthermore, the present disclosure includes embodiments described according to the following examples:

[0175] According to Example A1, 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: receive a first signal from the first loop antenna and a second signal from the second loop antenna; sample the first signal and the second signal at a sampling rate high enough to capture the entire frequency range associated with multiple radio sources to generate a first digital signal and a second digital signal; convert the first digital signal and the second digital signal into a frequency domain representation; and based on the frequency domain representation, generate a first bearing estimate of one of the multiple radio sources by comparing the relative amplitudes and phases of the first digital signal and the second digital signal represented in the frequency domain.

[0176] Example A2 includes the automatic direction finder of Example A1, wherein the one or more processors are configured to simultaneously generate multiple bearing estimates for the multiple radio sources in parallel processing operations based on a single time domain sample of each of the first loop antenna and the second loop antenna.

[0177] Example A3 includes the automatic direction finder of Example A1, and further includes a third loop antenna, wherein the one or more processors are coupled to the third loop antenna, and wherein the one or more processors are further configured to: receive a third signal from the third loop antenna; and sample the third signal at a sampling rate high enough to capture the entire frequency range to generate a third digital signal, 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.

[0178] Example A4 includes the automatic direction finder of Example A3, wherein the one or more processors are further configured to generate the first and second bearing estimates for one of the plurality of radio sources based on the frequency domain representation.

[0179] Example A5 includes the automatic direction finder of Example A4, wherein the one or more processors are further configured to apply a fault detection operation to the first bearing estimate and the second bearing estimate.

[0180] Example A6 includes the automatic direction finder of Example A4, wherein the one or more processors are further configured to generate an overall bearing estimate of the radio source, and wherein the overall bearing estimate comprises an average of the first bearing estimate and the second bearing estimate.

[0181] Example A7 includes the automatic direction finder of Example A1, and further includes a sensing antenna.

[0182] Example A8 includes the automatic direction finder of Example A1, wherein the automatic direction finder is an integrated unit.

[0183] Example A9 includes the automatic direction finder of Example A8, wherein the integrated unit is a system on a chip.

[0184] Example A10 includes the automatic direction finder of Example A1, wherein the frequency range is approximately 0.19-1.75 MHz.

[0185] According to example Al l, a method comprises: receiving a first signal from a first loop antenna and a second signal from a second loop antenna; sampling the first signal and the second signal at a sampling rate up to sufficient to capture an entire frequency range associated with a plurality of radio sources 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 based on the frequency domain representation, generating a first bearing estimate for one of the plurality of radio sources by comparing relative amplitudes and phases of the first digital signal and the second digital signal represented in the frequency domain.

[0186] Example A12 includes the method of example Al l, and further including generating a plurality of bearing estimates for different ones of the plurality of radio sources in a parallel processing operation.

[0187] Example A13 includes the method of example Al l, and further including: receiving a third signal from a third loop antenna; sampling the third signal at a sampling rate up to sufficient to capture the entire frequency range to generate a third digital signal; and converting the third digital signal to the frequency domain representation.

[0188] Example A14 includes the method of example A13, and further including generating a second bearing estimate for a particular one of the plurality of radio sources based on the frequency domain representation.

[0189] Example A15 includes the method of example A14, and further including generating an overall bearing estimate for the radio source, and wherein the overall bearing estimate comprises an average of the first bearing estimate and the second bearing estimate obtained from signals from different pairs of loop antennas.

[0190] According to example Al 6, a non-transitory computer-readable medium comprises 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 up to sufficient to capture an entire frequency range associated with a plurality of radio 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 based on the frequency domain representation, generate a first bearing estimate for one of the plurality of radio sources by comparing relative amplitudes and phases of the first digital signal and the second digital signal represented in the frequency domain.

[0191] Example A17 includes the non-transitory computer-readable medium of Example A16, wherein the instructions, when executed by one or more processors, cause the one or more processors to generate a plurality of position estimates for different ones of the plurality of radio sources in parallel processing operations.

[0192] Example A18 includes the non-transitory computer-readable medium of Example A16, 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; sample the third signal at a sampling rate high enough to capture the entire frequency range to generate a third digital signal; and convert the third digital signal to the frequency domain representation.

[0193] Example A19 includes the non-transitory computer-readable medium of Example A18, wherein the instructions, when executed by one or more processors, further cause the one or more processors to generate a second position estimate for a particular radio source in the plurality of radio sources based on the frequency domain representation.

[0194] Example A20 includes the non-transitory computer-readable medium of Example A19, wherein the instructions, when executed by one or more processors, further cause the one or more processors to generate an overall bearing estimate for the radio source, and wherein the overall bearing estimate comprises an average of the first bearing estimate and the second bearing estimate obtained from signals from different loop antenna pairs.

[0195] 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, the one or more processors being configured to: receive a first signal from the first loop antenna and a second signal from the second loop antenna; sample the first signal and the second signal at a sampling rate high enough to capture the entire frequency range associated with multiple radio sources to generate a first digital signal and a second digital signal; convert the first digital signal and the second digital signal into a frequency domain representation; and generate a first bearing estimate of one of the multiple radio sources based on the frequency domain representation by comparing the relative amplitudes and phases of the signals represented in the frequency domain.

[0196] Example 2 includes the automatic direction finder of any of Example 1, wherein the one or more processors are configured to generate the first position estimate of the radio source by generating the first position estimate of the radio source in parallel processing operations.

[0197] Example 3 includes the direction finder of Example 1 or Example 2, and further includes a third loop antenna, and wherein the one or more processors are coupled to the third loop antenna, the one or more processors are further configured to: receive a third signal from the third loop antenna; and sample the third signal at the frequency range associated with the radio source to generate a third digital signal, wherein 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.

[0198] Example 4 includes the direction finder of Example 3, wherein the one or more processors are further configured to generate a second bearing estimate of the radio source based on the frequency domain representation.

[0199] Example 5 includes the direction finder of Example 4, wherein the one or more processors are further configured to apply a troubleshooting operation to the first bearing estimate and the second bearing estimate of the radio source.

[0200] Example 6 includes the direction finder of Example 4 or Example 5, wherein the one or more processors are further configured to generate an overall bearing estimate of the radio source, and wherein the overall bearing estimate comprises an average of the first bearing estimate and the second bearing estimate of the radio source.

[0201] Example 7 includes the direction finder of any one of Examples 1 to 6, and further includes a sense antenna.

[0202] Example 8 includes the direction finder of any one of Examples 1 to 7, wherein the direction finder is an integrated unit.

[0203] Example 9 includes the direction finder of Example 8, wherein the integrated unit is a system on a chip.

[0204] Example 10 includes the direction finder of any one of Examples 1 to 9, wherein the frequency range is approximately 0.19-1.75 MHz.

[0205] According to Example 11, a method includes: receiving a first signal from a first loop antenna and a second signal from a second loop antenna; sampling the first signal and the second signal at a frequency range associated with a radio 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 a first bearing estimate of the radio source based on the frequency domain representation.

[0206] Example 12 includes the method of Example 11, wherein the generating the first bearing estimate value for the radio source comprises generating the first bearing estimate value for the radio source in a parallel processing operation.

[0207] Example 13 includes the method of Example 11 or Example 12, and further comprising: receiving a third signal from a third loop antenna; and sampling the third signal to generate a third digital signal at the frequency range associated with the radio source, wherein the converting the first digital signal and the second digital signal to the frequency domain representation comprises converting the first digital signal, the second digital signal, and the third digital signal to the frequency domain representation.

[0208] Example 14 includes the method of Example 13, and further comprising generating a second bearing estimate value for the radio source based on the frequency domain representation.

[0209] Example 15 includes the method of Example 14, and further comprising generating an overall bearing estimate value for the radio source, wherein the overall bearing estimate value comprises an average of the first bearing estimate value and the second bearing estimate value for the radio source.

[0210] 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 radio 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 based on the frequency domain representation, generate a first bearing estimate value for one of the plurality of radio sources by comparing relative amplitudes and phases of the signals represented in the frequency domain.

[0211] Example 17 includes the non-transitory computer-readable medium of Example 16, wherein the instructions, when executed by one or more processors, cause the one or more processors to generate the first bearing estimate value for the radio source in a parallel processing operation.

[0212] 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 at the frequency range associated with the radio source to generate a third digital signal, and wherein 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 includes converting the first digital signal, the second digital signal, and the third digital signal to the frequency domain representation.

[0213] 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 a second bearing estimate value for the radio source based on the frequency domain representation.

[0214] Example 20 includes the non-transitory computer-readable medium of Example 19, wherein the instructions, when executed by one or more processors, further cause the one or more processors to generate an overall bearing estimate value for the radio source, and wherein the overall bearing estimate value includes an average of the first bearing estimate value and the second bearing estimate value for the radio source.

[0215] According to Example 21, a system includes one or more processors configured to: receive, from an automatic direction finder, a first bearing estimate value associated with a first orientation relative to a first radio source, wherein the first bearing estimate value is based on a first plurality of bearing measurement values, and wherein a first portion of the first plurality of bearing measurement values is based on a first signal from a first loop antenna and a second portion of the first plurality of bearing measurement values is based on a second signal from a second loop antenna; receive, from the automatic direction finder, a second bearing estimate value associated with a second orientation relative to a second radio source, wherein the second bearing estimate value is based on a second plurality of bearing measurement values, and wherein a first portion of the second plurality of bearing measurement values is based on the first signal from the first loop antenna and a second portion of the second plurality of bearing measurement values is based on the second signal from the second loop antenna; and determine a position based at least on the first bearing estimate value and the second bearing estimate value.

[0216] Example 22 includes the system of Example 21, wherein the one or more processors are configured to determine the position in response to a signal indicative of a fault associated with another direction finding system.

[0217] Example 23 includes the system of example 21 or example 22, wherein the one or more processors are configured to determine the position in response to one or more controls of the aircraft.

[0218] Example 24 includes the system of any of examples 21 to 23, wherein the one or more processors are configured to determine the position based at least on a known position of the first radio source and a known position of the second radio source.

[0219] Example 25 includes the system of example 24, wherein the known position of the first radio source is a measure of a position of the first radio source relative to a center of the Earth.

[0220] Example 26 includes the system of any of examples 21 to 25, wherein the one or more processors are configured to determine the position based on an iterative process.

[0221] Example 27 includes the system of example 26, wherein the iterative process includes a process based at least on an initial position.

[0222] Example 28 includes the system of example 27, wherein the initial position includes a last known position, a starting position, an arbitrary position, or a combination thereof.

[0223] Example 29 includes the system of any of examples 21 to 28, wherein at least one of the first radio source or the second radio source is a non-directional beacon.

[0224] Example 30 includes the system of any of examples 21 to 29, wherein at least one of the first radio source or the second radio source is an amplitude modulated radio station.

[0225] According to Example 31, a non-transitory computer-readable medium comprises 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 radio source, wherein the first bearing estimate is based on a first plurality of bearing measurements, and wherein 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; receive, from the automatic direction finder, a second bearing estimate associated with a second orientation relative to a second radio source, wherein the second bearing estimate is based on a second plurality of bearing measurements, and wherein a 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 a 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; and determine a position based at least on the first bearing estimate and the second bearing estimate.

[0226] Example 32 comprises the non-transitory computer-readable medium of Example 31, wherein the instructions, when executed by the one or more processors, cause the one or more processors to determine the position in response to a signal indicative of a fault associated with another position system or one or more controls of an aircraft.

[0227] Example 33 comprises the non-transitory computer-readable medium of Example 31 or Example 32, wherein the instructions, when executed by the one or more processors, cause the one or more processors to determine the position based at least on a known position of the first radio source and a known position of the second radio source.

[0228] Example 34 comprises the non-transitory computer-readable medium of Example 33, wherein the known position of the first radio source is a measure of a position of the first radio source relative to a center of the Earth.

[0229] Example 35 comprises the non-transitory computer-readable medium of any of Examples 31 to 34, wherein the instructions, when executed by the one or more processors, cause the one or more processors to determine the position based on an iterative process, wherein the iterative process comprises a process based at least on an initial position.

[0230] Example 36 comprises the non-transitory computer-readable medium of Example 35, wherein the initial position comprises a last known position, a starting position, an arbitrary position, or a combination thereof.

[0231] Example 37 includes the non-transitory computer-readable medium of any of Examples 31-36, wherein at least one of the first radio source or the second radio source is a non-directional beacon or an amplitude modulated radio station.

[0232] 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 radio source, wherein the first bearing estimate is based on a first plurality of bearing measurements, and wherein 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 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 radio source, wherein the second bearing estimate is based on a second plurality of bearing measurements, and wherein a 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 a 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; and determining a position based at least on the first bearing estimate and the second bearing estimate.

[0233] Example 39 includes the method of Example 38, wherein the determining the position includes determining the position based at least on a known position of the first radio source and a known position of the second radio source, and wherein the known position of the first radio source is a measure of a position of the first radio source relative to a center of the Earth.

[0234] Example 40 includes the method of Example 38 or Example 39, wherein the determining the position includes determining the position based on an iterative process; 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 some combination thereof.

[0235] According to Example 41, an antenna includes a core; a first loop antenna including a first conductive loop formed around the core; a second loop antenna including a second conductive loop 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 conductive loop.

[0236] Example 42 includes the antenna of Example 41, wherein the core is substantially octagonal.

[0237] Example 43 includes the antenna of Example 41 or Example 42, wherein the core includes a ferrite.

[0238] Example 44 includes the antenna of any of Examples 41-43, and further including a sense antenna.

[0239] Example 45 includes the antenna of any of Examples 41-44, and further including a first matching network coupled to the first loop antenna.

[0240] Example 46 includes the antenna of Example 45, and further including a second matching network coupled to the second loop antenna.

[0241] Example 47 includes the antenna of Example 46, and further including a third matching network coupled to the third loop antenna.

[0242] According to Example 48, an apparatus includes an antenna. 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 conductive loop 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 conductive loop. The apparatus further includes an electronic unit coupled to the antenna, wherein the electronic 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 electronic unit further includes a software-defined radio component configured to process signals associated with the first signal, the second signal, and the third signal.

[0243] Example 49 includes the apparatus of Example 48, wherein the core is substantially octagonal.

[0244] Example 50 includes the apparatus of Example 48 or Example 49, wherein the core includes a ferrite.

[0245] Example 51 includes the apparatus of any of Examples 48-50, and further including a sense antenna.

[0246] Example 52 includes the apparatus of any of Examples 48-51, further including a first matching network coupled to the first loop antenna.

[0247] Example 53 includes the apparatus of Example 52, further including a second matching network coupled to the second loop antenna.

[0248] Example 54 includes the apparatus of Example 53, further including a third matching network coupled to the third loop antenna.

[0249] According to Example 55, an apparatus comprises: a housing; an antenna housed within the housing. The antenna comprises: a core; a first loop antenna comprising a first conductive loop formed around the core; a second loop antenna comprising a second conductive loop formed around the core at a first angle relative to the first conductive loop; and a third loop antenna comprising a third conductive loop formed around the core at a second angle relative to the first loop conductive loop. The apparatus further comprises an electronic unit housed within the housing and coupled to the antenna. The electronic unit comprises 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 electronic unit further comprises a software-defined radio component configured to process signals associated with the first signal, the second signal, and the third signal. The electronic unit further comprises an interface housed within the housing and coupled to the electronic unit, wherein the interface is configured to enable data to be communicated from the electronic unit to a second apparatus external to the housing.

[0250] Example 56 includes the apparatus of Example 55, wherein the interface comprises an ARINC 429 interface.

[0251] Example 57 includes the apparatus of Example 55 or Example 56, wherein the core is substantially octagonal.

[0252] Example 58 includes the apparatus of any of Examples 55 to 57, wherein the core comprises a ferrite.

[0253] Example 59 includes the apparatus of any of Examples 55 to 58, and further comprising a sense antenna.

[0254] Example 60 includes the apparatus of any of Examples 55 to 59, and further comprising a first matching network coupled to the first loop antenna.

[0255] Example 61 includes the antenna of any of Examples 41 to 47, wherein the first angle is substantially 90 degrees.

[0256] Example 62 includes the antenna of Example 61, wherein the second angle is substantially 45 degrees.

[0257] Example 63 includes the antenna of any of Examples 41 to 47, wherein the first angle is substantially 60 degrees.

[0258] Example 64 includes the antenna of Example 63, wherein the second angle is substantially 120 degrees.

[0259] Example 65 includes the apparatus of any of Examples 48 to 60, wherein the first angle is substantially 90 degrees.

[0260] Example 66 includes the device of Example 65, wherein the second angle is substantially 45 degrees.

[0261] Example 67 includes the device of any of Examples 48 to 60, wherein the first angle is substantially 60 degrees.

[0262] Example 68 includes the device of Example 67, wherein the second angle is substantially 120 degrees.

[0263] Example 69 includes the antenna of any of Examples 41 to 47, wherein the core is substantially hexagonal.

[0264] Example 70 includes the antenna of any 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.

[0265] Example 71 includes the device of any of Examples 48 to 60, wherein the core is substantially hexagonal.

[0266] Example 72 includes the device of any 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), comprising: a first loop antenna (126); a second loop antenna (128); as well as One or more processors (106) coupled to the first loop antenna and the second loop antenna, wherein the one or more processors are configured to: receiving a first signal (132) from the first loop antenna and a second signal (134) from the second loop antenna; sampling the first signal and the second signal at a sampling rate high enough to capture the entire frequency range associated with the plurality of radio 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 frequency domain representation; as well as Based on the frequency domain representation, a first position estimate (122) of a radio source from the plurality of radio sources is generated by comparing relative amplitudes and phases of the first digital signal and the second digital signal represented in the frequency domain.

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

3. The automatic direction finder of claim 1 , further comprising a third loop antenna, wherein the one or more processors are coupled to the third loop antenna, and wherein the one or more processors are further configured to: receiving a third signal from the third loop antenna; and The third signal is sampled at a sampling rate high enough to capture the entire frequency range to generate a third digital signal, 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 . The automatic direction finder of claim 3 , wherein the one or more processors are further configured to generate the first and second bearing estimates for one of the plurality of radio 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 a fault detection operation to the first and second position estimates.

6. The automatic direction finder of claim 4, wherein the one or more processors are further configured to generate an overall bearing estimate for the radio source, and wherein the overall bearing estimate comprises an average of the first bearing estimate and the second bearing estimate. The automatic direction finder according to 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. The automatic direction finder of claim 1, wherein the frequency range is approximately 0.19-1.75 MHz.

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