| 摘要 |
A sharp-cutoff VHF elliptic filter includes a folded signal path and internally coupled feedback in a conductive enclosure. Sized for the power requirements of commercial television broadcast transmission, the filter implements the elliptic filter equation through use of cavities, resonators, and couplers. The negative feedback required by the elliptic filter equation is implemented by folding the RF signal path and coupling the feedback energy through a gap in an internal septum to sum negatively with the signal in the main signal path. The elliptic filter can have an interdigital configuration , which puts successive resonators on opposite walls of the enclosure and couples the signal at half-wavelength spacing. The elliptic filter can alternatively have a comb line configuration, which places all resonators on one wall and employs full-wavelength spacing.
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