US3649934A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Quasi-optical low-pass absorption type filtering system
Assignee: United States Department of the Navy
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Filing: 1970-07-17
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Granted: 1972-03-14
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Expires: 1990-07-17
Abstract
Abstract Microwaves including millimeter waves and possibly infrared systems are filtered by reflectively focusing and refocusing input electromagnetic waves between sets of parallel metal plates the end portions of which are curved to form the respective mirror surfaces. The individual plates are spaced one from the other a distance equal to about one half wavelength or less in the low-pass band and the spacing between plates is filled with an absorbent material (in the regions away from the plate edges). Filtering is achieved by absorbing wavelengths of frequencies higher than the pass band in the absorbing material.
Inventors
- 👤 George L Matthael
- 👤 David A Leedom
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 02:24
CPC Classifications
H; H01; H01P; H01P1/00; H01P1/24; H01P1/26; H01Q; H01Q15/00; H01Q15/0006; H01Q15/0013
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
123 words
A low-pass quasi-optical filter system for filtering and transmitting input electromagnetic wave energy, the system comprising: a plurality of spaced parallel plates having metallic end portions spaced one from the other a distance of about a half wavelength at the cutoff frequency, said end portions being curved for reflectively focusing said input energy, absorptive material disposed in the spacing between the plates, means for polarizing the E field of the system parallel to said plates, launching means for said input energy, and means for receiving said reflectively focused input energy, whereby said input energy for frequencies in the pass band of the system is reflectively transmitted in a zigzag path with frequencies higher than the pass band being absorbed in said absorptive material.
Claim 2
Dependent Claim
123 words
A low-pass quasi-optical filter system for filtering and transmitting input electromagnetic wave energy, the system comprising: a plurality of spaced parallel plates having metallic end portions spaced one from the other a distance of about a half wavelength at the cutoff frequency, said end portions being curved for reflectively focusing said input energy, absorptive material disposed in the spacing between the plates, means for polarizing the E field of the system parallel to said plates, launching means for said input energy, and means for receiving said reflectively focused input energy, whereby said input energy for frequencies in the pass band of the system is reflectively transmitted in a zigzag path with frequencies higher than the pass band being absorbed in said absorptive material.
Claim 3
Dependent Claim
43 words
The system of claim 1 wherein a plurality of sets of three spaced parallel plates are provided, said nets being disposed for focusing and refocusing said input energy to reflectively channel said energy in a zigzag path defined by successive sets of plates.
Claim 4
Dependent Claim
20 words
The system of claim 2 wherein said launching means is formed to minimize trapped mode activity in the pass band.
Claim 5
Dependent Claim
31 words
The system of claim 3 further including means for receiving the focused output of said system, said output means also being formed to minimize trapped mode activity in the pass band.
Claim 6
Dependent Claim
45 words
The system of claim 4 wherein said launching and output means both include a horn antenna and a shaped body of a dielectric material carried by each of the horns, said shaping as well as the dielectric material being selected for minimizing said trapped modes.
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) | 1975-03-14 | 1975-09-13 | 1976-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-14 | 1979-09-13 | 1980-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-14 | 1983-09-13 | 1984-03-14 | $7700.00 | Window Closed / Lapsed |