US4027384A
Expired / Lapsed
US
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Microwave absorbers
Assignee: United States Department of the Army
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Filing: 1976-11-19
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Granted: 1977-06-07
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Expires: 1996-11-19
Abstract
Abstract Microwave absorbers reduce radar cross-sections of airborne objects by attenuating reflectivity values. In Jaumann absorbers laminated layers are placed on the reflecting surfaces, the laminated layers being lossy layers separated by dielectric spacing layers. From the point of view of accuracy and reproducibility Jaumann absorbers have been difficult to construct. A mode of fabrication overcoming these difficulties is provided herein.
Inventors
- 👤 Thomas M. Connolly
- 👤 Eino J. Luoma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:48
CPC Classifications
H; H01; H01Q; H01Q17/00; H01Q17/004; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49016; Y10T29/49227
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
176 words
A process for fabricating a Jaumann microwave absorber of the type including a plurality of partially conductive lossy layers, separated by intermediate dielectric spacing layers all bonded together to form the absorber, which comprises, to form the lossy layers, applying to a base a film forming emulsion of pulverulent carbon, orienting and placing the pulverulent carbon on application to form a film having a homogeneity and isotropy such that average admittance values determined at a plurality of points in one degree of orientation do not differ from average values determined in another degree of orientation by more than ±0.02, bonding the lossy layer to an adjacent spacing layer having a dielectric constant of 1.03 and a loss tangent of 0.0001 by bonding means not disruptive to the pulverulent carbon conductance, orientation and film homogeneity, and maintaining a spacing layer thickness not greater than one-fourth of the wavelength at the highest frequency, such that the total thickness of the absorber is at least one-half of the wavelength at the lowest frequency of the range to be absorbed.
Claim 2
Dependent Claim
176 words
A process for fabricating a Jaumann microwave absorber of the type including a plurality of partially conductive lossy layers, separated by intermediate dielectric spacing layers all bonded together to form the absorber, which comprises, to form the lossy layers, applying to a base a film forming emulsion of pulverulent carbon, orienting and placing the pulverulent carbon on application to form a film having a homogeneity and isotropy such that average admittance values determined at a plurality of points in one degree of orientation do not differ from average values determined in another degree of orientation by more than ±0.02, bonding the lossy layer to an adjacent spacing layer having a dielectric constant of 1.03 and a loss tangent of 0.0001 by bonding means not disruptive to the pulverulent carbon conductance, orientation and film homogeneity, and maintaining a spacing layer thickness not greater than one-fourth of the wavelength at the highest frequency, such that the total thickness of the absorber is at least one-half of the wavelength at the lowest frequency of the range to be absorbed.
Claim 3
Dependent Claim
21 words
The process of claim 1 wherein a lossy layer is applied to the top of a spacing layer as the base.
Claim 4
Dependent Claim
21 words
The process of claim 2 wherein the orientation and placing to form the isotropic, homogeneous film is effected by silk screening.
Claim 5
Dependent Claim
13 words
The process of claim 2 wherein the bonding means entails a dry adhesive.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-06-06 | 1980-12-06 | 1981-06-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-06-06 | 1984-12-06 | 1985-06-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-06-06 | 1988-12-06 | 1989-06-07 | $7700.00 | Window Closed / Lapsed |