Millimeter-Wave Dichroic Plates for High Angles of Incidence

Dichroic plates for cutoff wavelengths down to about a millimeter and high angles of incidence can be fabricated by numerically controlled milling of rectangular arrays of waveguide slots in half-wavelength-thick metal plates. A plate of this type is used to separate higher- and lower-frequency components of incident electromagnetic radiation linearly polarized along a specified axis; the plate is designed to reflect most of the incident electromagnetic radiation at frequencies below its cutoff frequency while allowing most of the radiation at higher frequencies to pass through.