Dielectric filter having resonators aligned to effect zeros of the frequency response

• US 5,675,301 A
• Filed: 05/23/1995
• Issued: 10/07/1997
• Est. Priority Date: 05/26/1994
• Status: Expired due to Fees

• Current Assignee: Pulse Finland Oy (Yageo Corporation)
• Original Assignee: Pulse Finland Oy (Yageo Corporation)
• Inventors: Nappa, Pauli, Ala-Kojola, Jouni
• Primary Examiner(s): LEE, BENNY T
• Application Number:
  US08/447,647
• Time in Patent Office: 868 Days
• Field of Search: 333/202, 333/203, 333/206, 333/222, 333/202 DB
• US Class Current: 333/202
• CPC Class Codes: H01P 1/2056 Comb filters or interdigital filters with metallised resonator holes in a dielectric block

Abstract

A dielectric filter advantageously comprises a body of a dielectric material rectangular in cross-section and confining at least two parallel holes (31'"'"', 32'"'"', 33'"'"') that extend through the body parallel to each other and parallel to the side surface (34) plane. Major portions of the body are coated with a conductive material which also covers the inner surfaces of the holes (31'"'"', 32'"'"', 33'"'"'), hence forming a transmission line resonator for each hole. The resonators may be quarter-wave or half-wave resonators. According to the invention, the holes are located on at least two lines in the long direction of the body in which case the center axis of at least one hole (32'"'"') is not located on the same plane parallel to the side surface (34) as the center axes of the rest of the holes. Advantageously, the distance (D) of the center axis of a hole from the center axis of an adjacent hole is identical for all holes. In this manner it is possible to manufacture a filter that has a smaller volume than a filter with identical electrical characteristics having all the holes on one line.

Claims

1. A radio frequency filter comprising:

a dielectric block having a first end and a second end, the dielectric block having an outer surface extending between the first end and the second end, and the outer surface having a coating of an electrically conductive material disposed thereon;

at least two holes disposed in the first end of said dielectric block, each said hole defining a respective line extending through the open end of each of the at least two holes as a first axis, the at least two holes respectively having an inner surface portion extending from the first end toward the second end and having a coating of the electrically conductive material disposed thereon to define respective transmission line resonators; and

at least one hole disposed in the first end between the at least two holes, each said at least one hole defining a respective line extending through the open end of the at least one hole as a second axis substantially parallel to the first axis, the at least one hole having an inner surface portion extending from the first end toward the second end and having a coating of the electrically conductive material to define another transmission line resonator, the first and second axis being spaced a predetermined distance from each other so that adjacent resonators are spaced an equal distance from one another and the spacing between non-adjacent resonators is determinative of the frequency response of the zeros in the frequency response of the filter.

2. A radio frequency filter as recited in claim 1, wherein the at least one hole formed in the first end on the second axis is equally spaced from the at least two holes disposed on the first axis.