Band-pass filter

Claim 2

A bandpass type filter as claimed in claim 1, wherein said separator has a plurality of conductive bars (9) arranged at a predetermined interval, for short-circuiting the ground conductors of the first and second dielectric substrates (3a, 3b).

Claim 3

A bandpass type filter as claimed in claim 2, wherein said filter satisfies a following relationship : λ₀ / (2 √ ε ¯ ) > W > 5t, where W is the interval of the conductive bars (9), ε is a dielectric constant of the dielectric substrate, λ₀ is a wavelength at the working frequency in vaccum, and t is a width of a narrow width part (5₁) of an internal conductor (5).

Claim 4

A bandpass type filter as claimed in claim 1, wherein a conductive relay pattern (9b) for coupling said conductive bars with each other is formed in the circuit pattern face.

Claim 5

A bandpass type filter as claimed in claim 1, wherein said filter has a slit (30) formed in one of the first and second dielectric substrates (3a, 3b) and opened to the resonance element (5) on the circuit pattern face, for trimming the resonance element by means of a light beam (33).

Claim 6

A bandpass type filter as claimed in claim 5, wherein said slit is a slender slit (30) elongated along the longitudinal direction of the resonance element (5).

Claim 7

A bandpass type filter as claimed in claim 6, wherein said filter satisfies a following relationship : s < b/2, where s is a width of said slit, and b is a thickness of the dielectric structure.

Claim 8

A bandpass type filter as claimed in claim 7, wherein said slit (30) is formed so that a side of the slit is positioned within a longitudinal center line of the resonance element (5).

Claim 9

A bandpass type filter as claimed in claim 1, wherein said coupling means is a hole (7a) formed in said dielectric substrate.

Claim 10

A bandpass type filter as claimed in claim 1, wherein said coupling means is a hole formed in said dielectric substrate, and a conductive bar (7b) inserted in said hole and elongated to a position near the two resonance elements (5) coupled with each other.

Claim 11

A bandpass type filter as claimed in claim 10, wherein conductive disks (7c) which are parallel with a face of the resonance element are attached to both ends of said conductive bar (7b), respectively.

Claim 12

A bandpass type filter as claimed in claim 1, wherein said coupling means is a hole formed in said dielectric substrate, and a conductive loop (7d) directly coupled with one of the resonance elements (5) and elongated to a position near the other resonance element, via said hole.

Claim 13

A bandpass type filter as claimed in claim 1, wherein a conductor which constitutes said resonance element (5) is formed by mixing metal powder (54) having a melting point lower than that of silver with a paste of scale shaped metallic silver (52), painting the mixed paste on the dielectric substrate, and the sintering the painted dielectric substrate.

Claim 14

A bandpass type filter as claimed in claim 1, wherein said resonance element (5) with a length equal to or less than λ/4 has, along a longitudinal direction thereof, a first section (5₁) of a narrow line width and a second section (5₂) of a line width wider than the first section, an end (8) of the first section being short-circuited to the ground conductors, and an end of the second section being electrically opened.

Claim 15

A bandpass type filter as claimed in claim 14, wherein the narrow width section (5₁) of said resonance element (5) is divided in a comb shape and is coupled to the wide width section (5₂).

Claim 16

A bandpass type filter as claimed in claim 1, wherein only one ground conductor (6) is commonly disposed between the two adjacent unit lamination structures (3, 4).

Claim 17

A bandpass type filter as claimed in claim 1, wherein a heat radiator (10) is coupled to the ground conductor (6) of one (4) of the unit lamination structure.

Claim 18

A producing process of a bandpass type filter having a piled structure of a plurality of unit lamination structures (3 ; 4) each of which is constituted by a first dielectric substrate (3a ; 4a) provided with a bottom face on which a first ground conductor (6) is attached on, by a circuit pattern face attached on first dielectric substrate (3a ; 4a), and by a second dielectric substrate closely contacted to the first dielectric substrate via said circuit pattern face and provided with a top face on which a second ground conductor (6) is attached on ; said circuit pattern face having at least one resonance element (5) formed at a predetermined interval so that the resonance element is commonly grounded at one end of the resonance element to the ground conductors, said filter having : a coupling means (7a ; 7b ; 7c) for electromagnetically coupling two resonance elements (5a,5b ; 5b,5c ; 5c,5d) disposed in different unit lamination structures (3, 4), said coupling means being formed in the dielectric substrate (3b) between said two resonance elements ; a separator (9) for electromagnetically separating the resonance elements (5a,5c ; 5b,5d) on each of the unit lamination structures (3, 4) ; and first and second input/output terminals (1, 2) coupled with the resonance elements disposed in end portions, said terminals being capable of coupling with an external circuit ; wherein said process has the steps of : piling sheets which are obtained by cutting an unsintered ceramic sheet to a certain shape, and by painting conductive paste on the shaped sheet ; and sintering the piled assembly at a temperature in the range between 870 °C and 940 °C ; said conductive paste including metallic silver (52) in a scale shape and powder of alloy (54) of silver and a metal capable of being alloyed with silver.