Dichroic plate

• US 3,924,239 A
• Filed: 06/27/1974
• Issued: 12/02/1975
• Est. Priority Date: 06/27/1974
• Status: Expired due to Term

• Current Assignee: Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, Philip D. Potter
• Original Assignee: Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, Philip D. Potter
• Inventors: Potter, Philip D., Fletcher, James C. Administrator of the National Aeronautics and Space (N/A)
• Primary Examiner(s): Lieberman, Eli
• Application Number:
  US05/483,851
• Time in Patent Office: 523 Days
• Field of Search: 343/753,754,755,909,911R
• US Class Current: 343/909
• CPC Class Codes: H01Q 15/0013 said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective

Abstract

A dichroic plate is disclosed for passing radiation within a particular frequency band and reflecting radiation outside of that frequency band. The value of the thickness of the plate is selected so that the plate acts as a resonant narrow band pass filter for the desired pass frequency, and the shapes of the apertures in the dichroic plate are selected to compensate for the phase shift caused by the air-plate interface presented to the signals passing therethrough.

Claims

1. A dichroic reflector plate of the type which reflects signals having a first frequency and passes signals therethrough having a second frequency, said reflector plate comprising a conductive plate having a pattern of holes therethrough, said conductive plate having a thickness which provides a resonant band pass response to signals including signals having said second frequency, said conductive plate having a thickness which is substantially equal to one-half the wave length which said second signal would have within a wave guide which has the same shaped aperture therethrough as the shape of an aperture through said dichroic reflector plate.

2. A dichoric reflector plate as recited in claim 1 wherein the apertures therethrough are circular.

3. A dichroic reflector plate as recited in claim 1 wherein the apertures therethrough are circularly shaped except for two opposite parallel flat regions.

4. In a dichroic plate reflector, having apertures therethrough, the method of compensating for undesIrable phase shift caused to signals passing through said apertures by the free space to aperture transition discontinuities, comprising shaping the cross section of each aperture which extends through said plate into a circle except for two opposite sides thereof which are flattened.

5. In a dichroic plate reflector, having apertures therethrough, the method of improving the efficiency of transmission therethrough of desired signals comprising establishing the thickness of said dichroic plate at a value equal to one half of the wavelength of said signals in a wave guide having the same cross section as the apertures in said dichroic plate.

6. In a dichroic plate reflector having apertures therethrough, the method of improving the efficiency of signal transmission and reducing the polarization degradation caused to signals passing therethrough comprising making said dichroic plate thickness equal to one half of the wavelength of said signals in a wave guide having the same cross section as an aperture in said dichroic plate, and shaping the cross section of each aperture in said dichroic plate into a circle except for flat sections at opposite ends of one radius.