Patent Grant
8081118
The present disclosure relates to phased array antennas, and more particularly to a phased array antenna radiator assembly having improved thermal conductivity and electrostatic discharge protection.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
When manufacturing a scalable phased array antenna for space-based operation, the challenge is fabricating a phased array radiator assembly that is simple to manufacture in large quantities, has low mass, and a low profile, and will meet challenging performance requirements. These requirements include good thermal conductivity through the internal radiator structure, good end-of-life thermal radiative properties (solar absorptance and emittance) at the outer exposed surface of the antenna, and the electrostatic discharge (ESD) grounding requirement for the floating metal elements without compromising the required low RF loss performance. In addition, the materials selected must be capable of resisting degradation due to the natural radiation environment or through atomic oxygen (AO) erosion.
Existing solutions that have good RF properties, for example certain commercially available foams, typically have generally unacceptable thermal conductivity for an application where passive cooling of a phased array antenna is required. As such, pre-existing foams are generally considered to be unacceptable for dissipating heat from the printed wiring board (PWB) modules of a scalable phased array antenna through the radiator assembly of the antenna. Existing solutions using heat pipes and radiators at the edges of the arrays to dissipate heat are heavy and increase the complexity in integration and test for a phased array antenna. Such solutions often significantly increase the cost of manufacture as well.
Many current radiator designs have a gapped radome, which is also termed a “sunshield blanket”, disposed over the antenna aperture above the foam tile assembly. This arrangement is also generally viewed as unacceptable for dissipating heat. To ESD ground floating metal patches, an existing solution is to have a ground pin at the center of each patch. However, this is very difficult and complex to accomplish with foam since manufacturing plated via holes through the foam is not a standard PWB process with proven reliability, and may not be useful for stacked patch configurations.
In general, a primary disadvantage of existing radiator designs for a phased array antenna is that they are highly complex to manufacture. The current solutions are not practical for manufacturing in quantities sufficiently large to make a phased array antenna. Also, the thermal conductivity of presently available foam tile is too low for dissipating heat, while other heat dissipating solutions (e.g., heat pipes) and other grounding methods (e.g., metal pins) add weight. Moreover, flouropolymer based adhesives can be degraded by space radiation effects.
In one aspect a phased array antenna radiator assembly is disclosed. The radiator assembly may comprise a thermally conductive foam substrate, a plurality of metal radiating elements bonded to the foam substrate, and a radome supported adjacent said metal radiating elements.
In another aspect a phased array antenna radiator assembly is disclosed that may comprise a thermally conductive substrate, a plurality of metal radiating elements bonded to the thermally conductive substrate, a radome supported adjacent said metal radiating elements, and an electrostatically dissipative adhesive in contact with said radiating elements for bonding said radome to said thermally conductive substrate.
In another aspect a method is disclosed for forming a phased array antenna radiator assembly. The method may comprise forming a plurality of radiating elements on a thermally conductive foam substrate, laying a radome over the radiating elements, and bonding the radome to the foam substrate.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring to
With reference to
The radome 12 may be constructed of any suitable material that is essentially RF transparent. For example, the radome 12 may be constructed of KAPTON®. Alternatively, the radome may be constructed as a multilayer laminate.
Referring to
Although the thickness of the various layers shown in
A significant feature of the radiator assembly 10 is the use of the low RF loss, syntactic foam substrates 30 and 38. Foam substrates 30 and 38 each form an excellent thermal path through the thickness of their respective radiating layer 14 or 16. Thus, no “active” cooling of the radiator assembly 10 is required. By “active” cooling it is meant a cooling system employing water or some other cooling medium that is flowed through a suitable network or grid of tubes to absorb heat generated by the radiator assembly 10 and transport the heat to a thermal radiator to be dissipated into space. The use of active cooling significantly increases the cost and complexity, size and weight of a phased array antenna system. Thus, the passive cooling that is achieved through the use of the syntactic foam substrates 30 and 38 enables the radiator assembly 10 to be made to smaller dimensions and with less weight, less cost and less manufacturing complexity than previously manufactured phased array radiating assemblies.
The syntactic foam substrates 30 and 38 each may be formed as fully-crosslinked, low density, composite foam substrates that exhibit low loss characteristics in the microwave frequency range. The foam substrates 30 and 38 may each have a dielectric constant as shown in
An additional significant benefit of the construction of the radiator assembly 10 is the use of the electrostatically dissipative adhesive 26 to bond the radome 12 to the syntactic foam substrate 30, and the electrostatically dissipative adhesive 34 to bond the syntactic foam substrate 30 to the syntactic foam substrate 38. In this example the adhesives 26 and 34 are the same, however, slightly different adhesive formulations could be used provided they each possess an electrostatically dissipative quality. Adhesive 26 extends over and around each of the radiating elements 14a and physically contacts each of the radiating elements 14a. The adhesive 26 allows any electrostatic charge buildup on the radiating elements 14a to be conducted away from the radiating elements 14a. The same construction applies for electrostatically dissipative adhesive 34, which surrounds and extends over the radiating elements 16a, and is in contact with each radiating element. It will be appreciated that the electrostatically dissipative adhesives 26 and 34 will each be coupled to ground when the radiator assembly 10 is supported on the printed wiring board 24 shown in
Another important feature of the electrostatically dissipative layer 26 is that it helps to form a thermally conductive path to the syntactic foam substrate 30 and eliminates the gap that would typically exist between the radome 12 and the top level of radiating elements 14a. By eliminating the gap between the inner surface of the radome 12 and the radiating elements 14a, an excellent thermal path is formed from the radome 12 through the first radiating layer 14. The electrostatically dissipative adhesive 34 operates in similar fashion to help promote thermal conductivity of heat from the first syntactic substrate 30 to the second syntactic substrate 38, while also providing a conductive path to bleed off any electrostatic charge that develops on the radiating elements 16a.
Referring now to
At operation 108 each stackup is placed in a vacuum or laminate press at the cure temperature of the epoxy film adhesive for a predetermined cure time sufficient to cure the stackup. After the epoxy cures, a material “core” is formed that can undergo further printed wiring board processing (e.g., photolithography, etching, plating, etc.).
At operation 110 a photolithographic process is used to image a mask of the radiating elements onto the copper foil. At operation 112 an etching process is then used to selectively remove the copper which will not be needed to form the radiating elements 14a and 16a on the radiating layers 14 and 16, respectively.
At operation 114, after the foam core undergoes photolithography and etching processes, the electrostatically dissipative adhesive is applied to the top core and between all additional cores that now have radiating elements (i.e., elements 14a or 16a) formed on them. At operation 116 the radome is applied to the electrostatically dissipative adhesive on an upper surface of the top core. At operation 118 the final stackup (i.e., the stackup comprising both foam cores) then undergoes another cure process which hardens the electrostatically dissipative adhesive and makes all the layers permanently adhere to one another to form an assembly. At operation 120 final machining is performed to cut the oversized material stackup to the antenna radiator assembly's 10 final dimensions.
The radiator assembly 10 of the present disclosure does not require the expensive and complex active heating required of other phased array antennas, and can further be manufactured cost effectively using traditional manufacturing processes. The passive cooling feature of the radiator assembly 10 enables the radiator assembly to be made even more compact than many previously developed phased array radiator assemblies, and with less complexity, less weight and less cost. The passive cooling feature of the radiator assembly 10 is expected to enable the radiator assembly 10 to be implemented in applications where cost, complexity or weight might otherwise limit an actively cooled phased array antenna from being employed such as for space based radar and communications systems.
While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.
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| Number | Date | Country | |
|---|---|---|---|
| 20090284436 A1 | Nov 2009 | US |
