Patent Application
20230335910
Embodiments generally relate to antennas. More particularly, embodiments relate to broadband multi-tap slot antennas.
Modern aircraft use antennas to transmit and receive information in the form of radio frequency (RF) energy. Due to space constraints, efforts have been made to reduce the size of aircraft antennas. Small antennas, however, tend to be either narrow band (e.g., limited operating frequency) or inefficient (e.g., relatively low gain).
In accordance with one or more embodiments, an antenna system comprises a cavity and a broadband antenna coupled to the cavity, the broadband antenna including surfaces defining a slot, wherein a cross-section of the cavity defines a resonant frequency range of the slot. The broadband antenna also includes a plurality of transmission lines, wherein the plurality of transmission lines bridge the slot and are spaced apart at a sub-wavelength distance with respect to a target frequency range of the antenna system, and a plurality of inductive tuning elements, each tuning element being disposed adjacent to one of the plurality of transmission lines, wherein the target frequency range is a function of the resonant frequency range and an impedance associated with the plurality of inductive tuning elements.
In accordance with one or more embodiments, an aircraft comprises an airframe and an antenna system coupled to the airframe. The antenna system includes a cavity and a broadband antenna, the broadband antenna including surfaces defining a slot, wherein a cross-section of the cavity defines a resonant frequency range of the slot. The broadband antenna also includes a plurality of transmission lines, wherein the plurality of transmission lines bridge the slot and are spaced at a sub-wavelength distance with respect to a target frequency range of the antenna system, and a plurality of inductive tuning elements, each inductive tuning element being disposed adjacent to one of the plurality of transmission lines, wherein the target frequency range is a function of the resonant frequency range and an impedance associated with the plurality of tuning elements.
In accordance with one or more embodiments, a method of fabricating an antenna system comprises providing a cavity and coupling a broadband antenna to the cavity, the broadband antenna including surfaces defining a slot, wherein a cross-section of the cavity defines a resonant frequency range of the slot. The broadband antenna also including a plurality of transmission lines, wherein the plurality of transmission lines bridge the slot and are spaced apart at a sub-wavelength distance with respect to a target frequency range of the antenna system, and a plurality of inductive tuning elements, each inductive tuning element being disposed adjacent to one of the plurality of transmission lines, wherein the target frequency range is a function of the resonant frequency range and an impedance associated with the plurality of inductive tuning elements.
The various advantages of the embodiments will become apparent to one skilled in the art by reading the following specification and appended claims, and by referencing the following drawings, in which:
Turning now to
Each of the processes of the method 100 may be performed or carried out by a system integrator, a third party, and/or an operator. In these examples, the operator may be a customer. For the purposes of this description, a system integrator may include, without limitation, any number of aircraft manufacturers and major-system subcontractors; a third party may include, without limitation, any number of venders, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on.
The aircraft 200 may include an airframe 202 with a plurality of systems 204 and an interior 206. Examples of the systems 204 include one or more of a propulsion system 208, an electrical system 210, a hydraulic system 212, an environmental system 214, and an antenna system 216. Any number of other systems may be included. Although an aerospace example is shown, different advantageous embodiments may be applied to other industries, such as the automotive industry and the ship building industry.
Technology embodied herein may be employed during any one or more of the aspects of the method 100. For example, components or subassemblies produced in the component and subassembly manufacturing stage 106 may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft 200 is in service 112.
Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during production processes, such as the component and subassembly manufacturing stage 106 and the system integration stage 108, for example, without limitation, by substantially expediting the assembly of or reducing the cost of the aircraft 200. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft 200 is in service 112 or during the maintenance and service stage 114.
For example, the antenna system 216 may include one or more broadband multi-tap slot antennas constructed according to an advantageous technology described herein may be designed for the aircraft 200 during the specification and design stage 102. Further, an advantageous embodiment may be used to implement a broadband multi-tap slot antenna during the component and subassembly manufacturing stage 106 and the system integration stage 108. As yet another example, a broadband multi-tap slot antenna according to an advantageous embodiment may be used during in service 112.
The different advantageous embodiments recognize that existing antennas have low gain or require a large size to obtain targeted bandwidths. As a result, a balance in reducing antenna size may be made between choosing lower gain for a larger bandwidth. Another choice may be to increase the size of the antenna to obtain a targeted gain.
With currently used antennas, the conductor may be made out of a material that provides surface resistivity in ohms per square. With this type of resistivity, increased bandwidth may be obtained, but with losses in gain.
As will be discussed in greater detail, the cross-section of the cavity 302 defines a resonant frequency range of the slot 306. The center copper layer 318 of the broadband antenna 304 includes a plurality of transmission lines 308 (
In an embodiment, the sub-wavelength distance is a fraction of the highest frequency in the target frequency range. Thus, if the target frequency range is 1.0 Gigahertz (GHz) to 4.0 GHz, the sub-wavelength distance might be on the order of 7.5 millimeters (mm, e.g., with A = C/ƒ, where λ is the wavelength in meters (m), C is the speed of light in m/second (m/s) and f is the frequency). Indeed, selecting the fraction to be less than 50% may enhance the directivity of the antenna system 300. More particularly, at half the wavelength the taps can provide a wide variety of functions or be combined for higher gain at the expense of beamwidth. Thus, the wavelength at 4 GHz is 75 mm, which would yield 37.5 mm for a sub-wavelength distance. Another example might have a period of 25.4 mm for a 1-4 GHz range, where 7.5 mm is also a sub-wavelength distance.
The center copper layer 318 of the broadband antenna 304 also includes a plurality of inductive tuning elements 310 (
More particularly, the input impedance per tap of an infinitely long, uniformly loaded slot antenna with no cavity 302 (e.g., open on both sides) has been calculated in closed form using a single unknown Galerkin method of the dual problem (e.g., strip in free space) as:
Where η0 is the wave impedance in free space, k0 is the wave number in free space, p is the period, γ is Euler’s constant, and w is the width of the slot 306. This impedance is a per tap impedance that is capacitive in nature with a relatively high real part. Since the only losses are radiative, the antenna is 100% efficient when conjugate matched.
Typical RF electronics use a 50 ohm impedance, so a goal is to have the slot 306 appear to be a 50 ohm load. This objective is achieved via two technological features as follows.
An inductance is placed in an electrically parallel relationship with the slot 306 to make the real part of the impedance 50 ohms/tap at the target (e.g., desired tuned) frequency. The illustrated cavity 302 behind the slot 306 provides this inductance and is accurately represented by a single turn solenoid (µ * Alp) where µ is the permeability of the cavity 302, p is the tap period and A is the area of the cavity 302. Controlling the inductance of the cavity 302, which may be over-sized, so an additional inductance in the form of the inductive tuning elements 310 is added in parallel to achieve the 50 ohm condition. The additional inductance can be electronically adjusted or fixed in the printed circuit board of the broadband antenna 304. The resulting impedance of the slot 306 with this parallel inductance is now 50 ohms in series with some inductive reactance, which was capacitive before the addition of the parallel inductance.
A series capacitance is added to cancel the inductive reactance at the tuned frequency. This capacitance can be either fixed by the capacitive patches 312 in the printed circuit board of the broadband antenna 304 or an electronic element that may be electronically controlled. The resulting input impedance at the tuned frequency is now 50 ohms and is theoretically 100% efficient when connected to the 50 ohm transmission lines 308 and a 50 ohm load.
A series capacitance 406 is added to cancel the inductive reactance at the tuned frequency. This capacitance 406 can be either fixed by the capacitive patches 312 (
Illustrated processing block 702 provides a cavity and block 704 couples a broadband antenna to the cavity. In the illustrated example, the broadband antenna includes surfaces defining a slot, wherein a cross-section of the cavity defines a resonant frequency range of the slot. The broadband antenna also includes a plurality of transmission lines, wherein the plurality of transmission lines bridge the slot and are spaced apart at a sub-wavelength distance with respect to a target frequency range of the antenna system. Moreover, the broadband antenna includes a plurality of inductive tuning elements, wherein each inductive tuning element is disposed adjacent to one of the plurality of transmission lines. Additionally, the target frequency range is a function of the resonant frequency range and an impedance associated with the plurality of inductive tuning elements.
In one example, the sub-wavelength distance is a fraction of a highest frequency in the target frequency range. For example, the fraction may be less than fifty percent to improve the directivity of the broadband antenna. Additionally, the impedance may include an inductance that is a function of a length of the plurality of inductive tuning elements. Block 704 may also include coupling a circuit to the plurality of inductive tuning elements, wherein the circuit is to adjust the inductance value. In an embodiment, the plurality of transmission lines include a multi-tap arrangement that enables dissipative losses to be recovered (e.g., by combining power received from the plurality of taps). The method 700 enhances performance at least to the extent that incorporating the inductive tuning elements into the broadband antenna reduces the size of the antenna system while maintaining relatively high efficiency and a broadband frequency response.
Illustrated processing block 802 incorporates a plurality of capacitive patches into the broadband antenna, wherein each capacitive patch is disposed adjacent to one of the tuning elements. Block 804 couples each capacitive patch to an end of one of the plurality of transmission lines, wherein the impedance further includes a capacitance value of the plurality of capacitive elements. The method 800 therefore further enhances performance at least to the extent that the capacitive patches cancel the inductive reactance at the tuned frequency.
In an embodiment, the sub-wavelength distance is a fraction (e.g., less than fifty percent) of a highest frequency in the target frequency range. Additionally, the impedance may include an inductance value that is a function of the length of the plurality of inductive tuning elements 910. In such a case, the antenna system 900 may further include a circuit 912 coupled to the plurality of inductive tuning elements, wherein the circuit 912 adjusts the inductance value (e.g., to change the target frequency range). In one example, the broadband antenna 904 further includes a plurality of capacitive patches 914, wherein each capacitive patch 914 is coupled to an end of one of the plurality of transmission lines 908. Each capacitive patch 914 may also be disposed adjacent to one of the inductive tuning elements 910. Thus, the impedance may further include the capacitance value of the plurality of capacitive patches 914. In an embodiment, the plurality of transmission lines 908 include a multi-tap arrangement that enables dissipative losses to be recovered.
Example one includes an antenna system comprising a cavity, and a broadband antenna coupled to the cavity, the broadband antenna including surfaces defining a slot, wherein a cross-section of the cavity defines a resonant frequency range of the slot, a plurality of transmission lines, wherein the plurality of transmission lines bridge the slot and are spaced apart at a sub-wavelength distance with respect to a target frequency range of the antenna system, and a plurality of inductive tuning elements, each inductive tuning element being disposed adjacent to one of the plurality of transmission lines, wherein the target frequency range is a function of the resonant frequency range and an impedance associated with the plurality of inductive tuning elements.
Example two includes the antenna system of example one, wherein the sub-wavelength distance is a fraction of a highest frequency in the target frequency range.
Example three includes the antenna system of example two, wherein the fraction is less than fifty percent.
Example four includes the antenna system of example one, wherein the impedance includes an inductance value that is a function of a length of the plurality of inductive tuning elements.
Example five includes the antenna system of example four, further including a circuit coupled to the plurality of inductive tuning elements, wherein the circuit is to adjust the inductance value.
Example six includes the antenna system of example one, wherein the broadband antenna further includes a plurality of capacitive patches, each capacitive patch being coupled to an end of one of the plurality of transmission lines and disposed adjacent to one of the inductive tuning elements, and wherein the impedance includes a capacitance value of the plurality of capacitive patches.
Example seven includes the antenna system of example one, wherein the plurality of transmission lines include a multi-tap arrangement that enables dissipative losses to be recovered.
Example eight includes an aircraft comprising an airframe, and an antenna system coupled to the airframe, wherein the antenna system includes a cavity, and a broadband antenna, the broadband antenna including surfaces defining a slot, wherein a cross-section of the cavity defines a resonant frequency range of the slot, a plurality of transmission lines, wherein the plurality of transmission lines bridge the slot and are spaced apart at a sub-wavelength distance with respect to a target frequency range of the antenna system, and a plurality of inductive tuning elements, each inductive tuning element being disposed adjacent to one of the plurality of transmission lines, wherein the target frequency range is a function of the resonant frequency range and an impedance associated with the plurality of inductive tuning elements.
Example nine includes the aircraft of example eight, wherein the sub-wavelength distance is a fraction of a highest frequency in the target frequency range.
Example ten includes the aircraft of example nine, wherein the fraction is less than fifty percent.
Example eleven includes the aircraft of example eight, wherein the impedance includes an inductance value that is a function of a length of the plurality of inductive tuning elements.
Example twelve includes the aircraft of example eleven, wherein the antenna system further includes a circuit coupled to the plurality of inductive tuning elements, wherein the circuit is to adjust the inductance value.
Example thirteen includes the aircraft of example eight, wherein the broadband antenna further includes a plurality of capacitive patches, each capacitive patch being coupled to an end of one of the plurality of transmission lines and disposed adjacent to one of the inductive tuning elements, and wherein the impedance includes a capacitance value of the plurality of capacitive patches.
Example fourteen includes the aircraft of example eight, wherein the plurality of transmission lines include a multi-tap arrangement that enables dissipative losses to be recovered.
Example fifteen includes a method of fabricating an antenna system, the method comprising providing a cavity, and coupling a broadband antenna to the cavity, the broadband antenna including surfaces defining a slot, wherein a cross-section of the cavity defines a resonant frequency range of the slot, a plurality of transmission lines, wherein the plurality of transmission lines bridge the slot and are spaced apart at a sub-wavelength distance with respect to a target frequency range of the antenna system, and a plurality of inductive tuning elements, each inductive tuning element being disposed adjacent to one of the plurality of transmission lines, wherein the target frequency range is a function of the resonant frequency range and an impedance associated with the plurality of inductive tuning elements.
Example sixteen includes the method of example fifteen, wherein the sub-wavelength distance is a fraction of a highest frequency in the target frequency range.
Example seventeen includes the method of example sixteen, wherein the fraction is less than fifty percent.
Example eighteen includes the method of example fifteen, wherein the impedance includes an inductance value that is a function of a length of the plurality of inductive tuning elements.
Example nineteen includes the method of example eighteen, further including coupling a circuit to the plurality of inductive tuning elements, wherein the circuit is to adjust the inductance value.
Example twenty includes the method of example fifteen, further including incorporating a plurality of capacitive patches into the broadband antenna, wherein each capacitive patch is disposed adjacent to one of the tuning elements, and coupling each capacitive patch to an end of one of the plurality of transmission lines, wherein the impedance includes a capacitance value of the plurality of capacitive patches.
Example twenty-one includes the method of example fifteen, wherein the plurality of transmission lines include a multi-tap arrangement that enables dissipative losses to be recovered.
Embodiments are applicable for use with all types of semiconductor integrated circuit (“IC”) chips. Examples of these IC chips include but are not limited to processors, controllers, chipset components, programmable logic arrays (PLAs), memory chips, network chips, systems on chip (SoCs), SSD (solid state drive)/NAND controller ASICs, and the like. In addition, in some of the drawings, signal conductor lines are represented with lines. Some may be different, to indicate more constituent signal paths, have a number label, to indicate a number of constituent signal paths, and/or have arrows at one or more ends, to indicate primary information flow direction. This, however, should not be construed in a limiting manner. Rather, such added detail may be used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit. Any represented signal lines, whether or not having additional information, may actually comprise one or more signals that may travel in multiple directions and may be implemented with any suitable type of signal scheme, e.g., digital or analog lines implemented with differential pairs, optical fiber lines, and/or single-ended lines.
Example sizes/models/values/ranges may have been given, although embodiments are not limited to the same. As manufacturing techniques (e.g., photolithography) mature over time, it is expected that devices of smaller size could be manufactured. In addition, well known power/ground connections to IC chips and other components may or may not be shown within the figures, for simplicity of illustration and discussion, and so as not to obscure certain aspects of the embodiments. Further, arrangements may be shown in block diagram form in order to avoid obscuring embodiments, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements are highly dependent upon the platform within which the embodiment is to be implemented, i.e., such specifics should be well within purview of one skilled in the art. Where specific details (e.g., circuits) are set forth in order to describe example embodiments, it should be apparent to one skilled in the art that embodiments can be practiced without, or with variation of, these specific details. The description is thus to be regarded as illustrative instead of limiting.
The term “coupled” may be used herein to refer to any type of relationship, direct or indirect, between the components in question, and may apply to electrical, mechanical, fluid, optical, electromagnetic, electromechanical or other connections. In addition, the terms “first”, “second”, etc. may be used herein only to facilitate discussion, and carry no particular temporal or chronological significance unless otherwise indicated.
As used in this application and in the claims, a list of items joined by the term “one or more of” may mean any combination of the listed terms. For example, the phrases “one or more of A, B or C” may mean A; B; C; A and B; A and C; B and C; or A, B and C.
Those skilled in the art will appreciate from the foregoing description that the broad techniques of the embodiments can be implemented in a variety of forms. Therefore, while the embodiments have been described in connection with particular examples thereof, the true scope of the embodiments should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and following claims.
