NARROW BANDPASS DIELECTRIC RESONATOR FILTER

摘要

An extremely narrow-band bandpass electromagnetic filter comprises a waveguide (1) dimensioned below cutoff and having two or more active sections (30) each containing a dieletric resonator (6). The number of resonators (6) corresponds to the number of poles of filtering. The physical dimensions of the waveguide (1) can advantageously be further reduced by means of passive coupling means (40), where the waveguide (1) cross-section is smaller than in the active sections (30). Each passive coupling means (40) inductively couples adjacent active sections (30). Mode suppression rods (10) electrically connect opposing waveguide walls (2, 3) midway between each pair of adjacent dielectric resonators (6). Preferred embodiments are illustrated, in which the resonators (6) are transversely oriented within the waveguide (1). Electromagnetic energy travels within the waveguide (1) in a single TE10 evanescent mode (TE01 delta within the resonators (6)). Dielectric tuning means (9) are generally aligned along the principal axis of each resonator (6). A number of such filters, exhibiting extremely narrow bandwidth, low insertion loss, and high Q, have been successfully built.