US 4,423,396 A · Bandpass filter for UHF band

Abstract

In a bandpass filter having five or more resonator stages, a sub transmission line is coupled to the main transmission line at the first and fourth resonators. The first to fourth resonators provide peak attenuation points at both sides of the center frequency in the attenuation curve, while the remaining resonators following the fourth resonator further sharpen the attenuation characteristics of the bandpass filter. The main and sub transmission lines may be formed by striplines on a printed circuit board, while the sub transmission line can be capacity coupled to the main transmission line. Coupling capacitances are freely set by setting the length of each gap between adjacent striplines to a desired value. Thus, the peak attenuation points can be accurately controlled to provide a bandpass filter having superior characteristics.

Claims9

Dependent claims

A bandpass filter for UHF band, comprising:

(a) a dielectric substrate;
(b) a main transmission line having input and output electrodes, said main transmission line being formed of a plurality of striplines formed in line on said dielectric substrate;
(c) five or more resonators respectively coupled to said striplines between said input and output electrodes;
(d) first and second coupling striplines formed on said dielectric substrate, said first coupling stripline being located adjacent to the first stripline which is immdediately next to said input electrode, said second coupling stripline being located adjacent to the fourth stripline;
and
(e) a sub transmission line stripline formed on said dielectric substrate and interposed between said first and second coupling striplines.

3 more elements

Dependencies are inferred from the claim text.

Bandpass filter for UHF band

Life of this patent

Bandpass filter for UHF band

Life of this patent

Abstract

Claims9