| 摘要 |
1490594 E-M wave filtering device THOMSON-CSF 8 Aug 1975 [9 Aug 1974] 33246/75 Heading H4A A low-pass filter which passes e-m waves of frequency below a cut-off value while reflecting higher frequency waves comprises a dielectric sheet substrate 1 supporting parallel alignments 2-6 of metal elements on one of its faces and alignments 7-13 on its other face. The element length is just less than half the wavelength at the desired cut-off frequency. The orthogonal arrangement of the alignments as shown provides a double polarization of the waves. If the central part of each element is made wider or narrower than the remainder, the slope of the filter attenuation-versus-frequency characteristic is reduced or the cut-off frequency is reduced, respectively. Substrate 1 may be flat or curved. The filter may be used as a curved reflector for the high-frequency band of a dual-band antenna, while passing the low-frequency band without significant attenuation. Substrate 1 is a printed circuit board, a sheet of foamed dielectric, or a three-layer structure (having a cellular core).
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