Patent Application
20210226342
Manufacturing monolithic printed circuit board advanced printed aperture technology is generally useful in X Band to Ku Band in terms of high yield printed circuit boards, radio-frequency integrated circuit (RFIC) assembly, and environmentally robust multi-layer printed circuit board active electronically scanned array (AESA) architectures. Extensions to C band and Ka band is possible. Other high-performance printed radiating element arrays, such as complex microstrip patches and top-hat loaded stacked patches are difficult to manufacture for frequencies in the C band or below.
At high frequencies above Ka band, space for required components and circuitry is not available within the ½λ by ½λ radiating element grid for planar aperture technology without the use of advanced packaging techniques such as die stacking, through silicon vias, and through mold vias. Embedded radiating elements on high dielectric constant materials (Si, SOI, GaAs or GaN, InP, etc.) exhibit high Q and narrow instantaneous bandwidth. A high dielectric constant exacerbates parasitic surface wave generation which causes poor AESA scan performance, including devastating scan blindness. Printed radiating elements benefit from as low a dielectric constant and lattice density as requirements allow (λ/2 element spacing at fhigh).
Other broadband printed radiating elements, such as complex microstrip patches and top-hat loaded stacked patches, are difficult to manufacture for higher millimeter wave frequencies due to their high sensitivity to mechanical and material property tolerances.
AESA beam width, and hence directivity, is a function of aperture size in terms of wavelength: one wavelength (λ) equals twelve inches at one GHz. Printed radiating element thickness is strongly correlated to operating frequency; the lower the frequency, the larger and thicker the printed circuit board material required. The maximum RF printed circuit board thickness available in the industry today is approximately 300 mils, placing a lower frequency limit of approximately six GHz for a standard patch antenna element. The required thickness for a printed aperture radiator at two GHz is approximately 800 mils.
With contemporary manufacturing processes, printed circuit board panel size is eighteen inches by twenty-four inches which is only 1.5 λ by 2.0 λ at one GHz; equating to a 14.0 dBi directivity and 25° 3-dB beam width, which is a very modest directionality. Adequate directionality requires subarray tilling utilizing multiple printed circuit boards which increases the assembly complexity to meet requirements for an uninterrupted periodic array lattice across multiple subarray panels for low side lobe level operation.
Parasitic surface waves cause scan anomalies and scan blindness in AESA apertures. A grounded dielectric slab parasitic surface wave can be excited in a printed AESA aperture as a function of dielectric constant and printed circuit board thickness; such parasitic surface wave is a function of wavelength. High directivity/narrow beam width arrays are volumetrically large, resulting in high weight due to printed circuit board material density. Furthermore, there are manufacturing constraints for low-risk printed antenna radiating elements/AESA radiating aperture subarrays and arrays. These constraints include available material parameters and tolerances, dielectric material homogeneity, dielectric constant, loss tangent, trace conductivity, printed circuit board thickness, available element count, copper etching tolerances, pressed thickness tolerance, minimum copper trace/space feature sizes, and available space for support circuitry. Manufacturing and reliability issues related to board thickness, via diameter, and hence via aspect ratio also limit printed antenna radiating elements/AESA radiating aperture subarrays and arrays. Larger printings have issues with lamination, warping, layer-to-layer registration, etc.
In one aspect, embodiments of the inventive concepts disclosed herein are directed to an antenna and manufacturing process for antennas that produce radiating elements of desired size for certain frequency bands by bump mounting radiating elements to the printed circuit board substrate. Driving circuitry can be stacked to save space and enable Dual Orthogonal Linear Polarization (DOLP). Also, the radiating elements may be made using a different dielectric constant material as compared to the connecting substrate.
In a further aspect, tiling radiating elements or sub-arrays or radiating elements with bump mounting allows for spatial separation that eliminates surface waves. In another aspect, bump mounted elements with less directivity allow broader elevation beam scanning down to horizon.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and should not restrict the scope of the claims. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the inventive concepts disclosed herein and together with the general description, serve to explain the principles.
The numerous advantages of the embodiments of the inventive concepts disclosed herein may be better understood by those skilled in the art by reference to the accompanying figures in which:
Before explaining at least one embodiment of the inventive concepts disclosed herein in detail, it is to be understood that the inventive concepts are not limited in their application to the details of construction and the arrangement of the components or steps or methodologies set forth in the following description or illustrated in the drawings. In the following detailed description of embodiments of the instant inventive concepts, numerous specific details are set forth in order to provide a more thorough understanding of the inventive concepts. However, it will be apparent to one of ordinary skill in the art having the benefit of the instant disclosure that the inventive concepts disclosed herein may be practiced without these specific details. In other instances, well-known features may not be described in detail to avoid unnecessarily complicating the instant disclosure. The inventive concepts disclosed herein are capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.
As used herein a letter following a reference numeral is intended to reference an embodiment of the feature or element that may be similar, but not necessarily identical, to a previously described element or feature bearing the same reference numeral (e.g., 1, 1a, 1b). Such shorthand notations are used for purposes of convenience only, and should not be construed to limit the inventive concepts disclosed herein in any way unless expressly stated to the contrary.
Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by anyone of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).
In addition, use of the “a” or “an” are employed to describe elements and components of embodiments of the instant inventive concepts. This is done merely for convenience and to give a general sense of the inventive concepts, and “a” and “an” are intended to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.
Finally, as used herein any reference to “one embodiment,” or “some embodiments” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the inventive concepts disclosed herein. The appearances of the phrase “in some embodiments” in various places in the specification are not necessarily all referring to the same embodiment, and embodiments of the inventive concepts disclosed may include one or more of the features expressly described or inherently present herein, or any combination of sub-combination of two or more such features, along with any other features which may not necessarily be expressly described or inherently present in the instant disclosure.
Broadly, embodiments of the inventive concepts disclosed herein are directed to an antenna and manufacturing process for antennas that produce radiating elements of desired size for certain frequency bands by bump mounting radiating elements to the printed circuit board substrate. Driving circuitry can be stacked to save space. Also, the radiating elements may be made using a different dielectric constant material as compared to the substrate. Tiling radiating elements or sub-arrays or radiating elements with bump mounting allows for spatial separation that eliminates surface waves.
Referring to
Transmission line beam former design benefits from high dielectric constant materials because high dielectric constants allow for physically smaller components. However, antenna radiating elements benefit from low dielectric constant materials to extinguish surface waves.
The radiating element 100 is then attached to an interconnecting printed circuit board with a continuous ground plane 102 via a plurality of solder balls 104 (bump mounted). In at least one embodiment, surface tension locates the solder balls 104 at the appropriate locations on the radiating element 100 and interconnecting printed circuit board with a continuous ground plane 102 where the fabrication process for each of the radiating element 100 and interconnecting printed circuit board with a continuous ground plane define electrically conductive attach points. Such attachment points may be part of the lithographic fabrication process of the interconnecting printed circuit board with a continuous ground plane 102. Because the attachment points are defined by the lithographic fabrication process, surface tension positioning increases placement accuracy.
The interconnecting printed circuit board with a continuous ground plane 102 may be fabricated with a low degree of warp and twist relative to an interconnecting printed wiring board with integral radiating elements.
In some embodiments, when the radiating elements 100 are smaller than ½λ spacing on the interconnecting printed circuit board with a continuous ground plane 102, the antenna may have low gain, enabling broad beam scanning to the horizon.
In at least one embodiment, radiating elements 100 are organized into an array 106 on the interconnecting printed circuit board with a continuous ground plane 102 with each of the radiating elements 100 separated from neighboring radiating elements 100 by an isolation gap 108. Array lattices may be rectangular or triangular, though rectangular may be preferred for tiling. Furthermore, in at least one embodiment, radiating element arrays 106 may be fabricated as a single piece of multiple radiating elements 100; the array 106 then being bump mounted. Arrays 106 of less than ½λ spacing may be used to produce different printed apertures. Arrays 106 could be multi-chip modules, with multiple chips.
In at least one embodiment, radiating elements 100 are bump attached via solder balls 104 to a corrugated ¼λ choke interconnecting printed circuit board with a continuous ground plane 102, for example as used in GPS surveyor applications, to extinguish ground currents and enhance side scan dual orthogonal linearly polarized or circularly polarized wide scan operations.
Bump mounting allows for non-traditional assemblies of electromagnetic components to solve problems that are potentially insurmountable with existing monolithic multi-layer circuit boards.
Low frequency challenges are related to absolute size. For example, as the frequency decreases from 1 GHz down to 700 MHz, the wavelength increases from 12 inches to 17.14 inches in which substrate height also increases as 0.7 times more beyond the PCB fabrication limit. Antennas operating in those frequency ranges may be prohibitively large with current technology.
In at least one embodiment, different regions of the array 106 may operate at different frequencies. For example, the center of the array 106 may operate at highest frequency with the tightest lattice density, with the lattice density decreasing outwardly as the array 106 expands to lower and lower frequency regions.
A common beam forming network may engage all of the radiating elements 100 and could be either analog or digital. The common ground plane 102 is what all of the circuitry drives against from an RF perspective.
Referring to
In at least one embodiment, the radiating elements 200 are separated from each other by an isolation gap 208 that breaks up the monolithic grounded dielectric slab and suppress surface waves.
Referring to
In at least one embodiment, neighboring radiating elements 302, 310 are separated by isolation gaps 304, 312 to prevent surface waves. Also, in at least one embodiment, an array may include larger radiating elements 302 in a center region to enhance gain, with smaller radiating elements 310 in the outer regions to enhance scan angle.
Referring to
A stack 400 according to such embodiment may solve the dual-orthogonal linear polarization array lattice compaction problem for millimeter wave arrays. First order dual-orthogonal linear polarization packaged circuitry requires up to twice the amount of surface area to implement relative to a single, linear polarization, which lowers the conflict free operational frequency by two times. For higher than twenty GHz operation, the required board array for dual-orthogonal linear polarization is in conflict with the array lattice size density required for grating lobe-free operation. Transmit/receiver die stacking on the radiating element 402 can enable dual-orthogonal linear polarization or any other arbitrary polarization operation to reside in the same surface area as compared to single, linear polarization.
Embodiments of the present disclosure enable arbitrary polarization by combining vertical polarization circuitry 408 and horizontal polarization circuitry 406 with the appropriate amplitude and phase.
Referring to
Embodiments of the present disclosure allow the window of efficient manufacturing to be expanded because the limitations of the printed circuit board are not imposed on the radiating element, and the limitations of the radiating element are not imposed on the beam forming circuitry.
Embodiments of the present disclosure enable complex printed radiator element arrays that operate below the C band, and/or high frequency phased arrays that operate in bands higher than the Ka-Band while also eliminating or suppressing parasitic surface waves. Especially for dual-orthogonally polarized radiating elements, embodiments of the present disclosure reduce manufacturing complexity. Non-traditional and traditional printed circuit board fabrication methods may be combined. Broad angle, low-to-the-horizon scan performance with different element sizes allows for beam width/gain balancing.
One existing method for suppressing parasitic surface waves includes surrounding radiating elements with vias. Such method is inefficient for antennas with hundreds or thousands of radiating elements. Embodiments of the present disclosure obviate the need for such vias.
It is believed that the inventive concepts disclosed herein and many of their attendant advantages will be understood by the foregoing description of embodiments of the inventive concepts disclosed, and it will be apparent that various changes may be made in the form, construction, and arrangement of the components thereof without departing from the broad scope of the inventive concepts disclosed herein or without sacrificing all of their material advantages; and individual features from various embodiments may be combined to arrive at other embodiments. The form herein before described being merely an explanatory embodiment thereof, it is the intention of the following claims to encompass and include such changes. Furthermore, any of the features disclosed in relation to any of the individual embodiments may be incorporated into any other embodiment.
