Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-10-21
2001-06-19
Gaffin, Jeffrey (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S753000, C361S762000, C361S764000, C361S780000, C361S794000, C361S795000, C333S246000, C333S247000, C333S248000, C343S7000MS
Reexamination Certificate
active
06249439
ABSTRACT:
TECHNICAL FIELD
The present invention relates to microwave and millimeter wave circuit assemblies, and more particularly, to millimeter wave circuits for satellite communication applications.
BACKGROUND ART
Microwave and millimeter wave multichip assemblies are expensive to design and develop and require substantial labor commitments to manufacture. Prototyping and production lead times are long and yield rates are low. Traditional monolithic microwave integrated circuit (MMIC) assemblies are produced with machined metal housings, generally of aluminum or Kovar material and use alumina, beryllia, aluminum nitride or similar co-fired ceramic substrates. These prior art assemblies are multiple material systems fabricated using many different process steps. These process steps are costly since the assemblies cannot be fabricated in a fully automated operation in large quantities by such processing techniques.
In a traditional MMIC assembly, a fired ceramic substrate is provided for structural integrity. Circuits are then built on the substrate in stacked layers. Each layer starts with “green” state materials and is then processed in the “green” state (screen-printing, via formation, etc.). Each layer is then cured at a slightly elevated temperature (<100° C.) so that the metalization is dried and will stick to the “green” ceramic layers for the duration of processing. Several different layers are produced in this manner as required for the final assembly. The built-up layers are then pressed together so that the materials of adjacent “green” layers contact each other. The assembly is then heated to temperatures ranging from 800° to 1800° C. to sinter the ceramic material.
Besides the complex processes required to produce traditional MMIC assemblies, ceramics have inferior mechanical properties. The disadvantages include susceptibility to cracking and lower reliability. Furthermore, ceramic substrates do not allow large numbers of user channels to be formed from a single antenna aperture. This leads to weight and cost penalties at the spacecraft level.
Thus there is a need for a microwave phased array assembly using conventional (PWB) processes, which includes integrated RF, digital, analog and antenna elements, as well as other possible functions, such as I/O.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to provide a less expensive microwave and millimeter wave assembly. Another object of the invention is to produce a microwave and millimeter wave assembly using conventional PWB processes.
In one aspect of the invention, a millimeter wave phased array assembly has a multilayer board consisting of several laminated printed wiring boards (PWBs) and a frame having a waveguide input and output. The PWBs are made of a high frequency laminate material and have a pattern of metalization to perform varying electronic tasks. These tasks include electrical interconnection, RF signal transmission, DC current routing and DC signal routing.
The multilayer board of the present invention is comprised of several components. These components include several adjacent interconnect layers, a lower ground layer, a RF layer, an upper ground layer and several MMIC chips. The interconnect layers provide electrical connection between components and the other layers. The lower ground layer is laminated on top of the interconnect layers and provides electromagnetic shielding. The RF layer is laminated on top of the lower ground layer and provides RF connection between components. The upper ground layer is laminated on top of the RF layer and provides electromagnetic shielding.
The multilayer board also has at least one MMIC chip cavity. The cavity is formed in the top three layers (upper ground, RF and lower ground) and at least one interconnect layer. The cavity is provided in the multilayer board for mounting and connecting a MMIC chip.
The present invention thus achieves a microwave and millimeter wave phased array assembly using conventional PWB processes. This results in lower manufacturing costs as compared to conventional ceramic MMIC processes. The phased array package has the added advantage of allowing a larger number of user channels than traditional assemblies.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.
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DeMore Walter R.
Holloway Richard A.
Holmes Bruce A.
Johnson Benjamin T.
Londre Dale A.
Gaffin Jeffrey
Gudmestad Terje
Hughes Electronics Corporation
Vigushin John B.
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