Ceramic filter with integrated harmonic response suppression using orthogonally oriented low-pass filter

• US 5,929,721 A
• Filed: 08/06/1996
• Issued: 07/27/1999
• Est. Priority Date: 08/06/1996
• Status: Expired due to Fees

• Current Assignee: CTS Corporation
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Munn, Robert J., Heine, David R., Ballance, Mark H.
• Primary Examiner(s): LEE, BENNY T
• Application Number:
  US08/692,547
• Time in Patent Office: 1,085 Days
• Field of Search: 333/134, 333/203, 333/206, 333/222, 333/202, 333/FOR 202 DB
• US Class Current: 333/134
• CPC Class Codes: H01P 1/2136 using comb or interdigital filters; using cascaded coaxial cavities H01P1/2131, H01P1/2135 take precedence

Abstract

A ceramic filter (100) with integrated harmonic response suppression has a ceramic monolithic block filter having a predetermined passband defined by tuned resonators located between an input and an output (116); and at least one of a harmonic trap filter, a lowpass filter and a lowpass microstrip filter, each having an inductive and a capacitive component. This is achievable with a design which incorporates an integrated harmonic response suppression filter directly in or on the dielectric ceramic monolithic block. This can result in a substantial savings in space, cost, and part count in an electronic telecommunications device.

Claims

1. A ceramic filter with integrated harmonic response suppression, comprising:

a ceramic monolithic block filter having a predetermined passband defined by tuned resonators located within the monolithic block between an input pad and an output pad; and

a lowpass filter having a resonator cavity, substantially perpendicular to all of the tuned resonators, coupled to one of the input pad and the output pad, and comprising a circuit having an inductive element, a first capacitive element and a second capacitive element, the circuit providing higher order harmonic suppression;

the inductive element provided by the resonator cavity;

the first capacitive element is defined by a first substantially rectangular unmetallized region having a first predetermined metallized region therein and an adjacent shield metallization which substantially surrounds side surfaces of the monolithic block filter, the first predetermined metallized region connected to the resonator cavity on a first one of said side surfaces of the ceramic monolithic block filter, and connected to said one of the input pad and the output pad;

the second capacitive element is defined by a second substantially rectangular unmetallized region having a second predetermined metallized region therein and said adjacent shield metallization which substantially surrounds the side surfaces of the monolithic block filter, the second predetermined metallized region connected to the resonator cavity on a second one of said side surfaces of the ceramic monolithic block filter, and is capacitively coupled to the tuned resonators; and

the ceramic monolithic block filter defining a first filter and the lowpass filter defining a second filter.

2. The ceramic filter of claim 1, wherein the lowpass filter is coupled between the ceramic monolithic block filter and an antenna pad defined by said one of the input pad and output pad.

3. The ceramic filter of claim 1, wherein a metallization pattern connects said one of the input pad and the output pad of the ceramic monolithic block filter with the lowpass filter, the metallization pattern also creating a capacitive coupling between adjacent ones of the tuned resonators.

4. The ceramic filter of claim 1, wherein a frequency of the lowpass filter is related to an external dimension of the ceramic monolithic block filter that is perpendicular to the plane wherein all the tuned resonators are located.

5. The ceramic filter of claim 1, wherein the first filter is a duplexer, comprising:

a receive filter portion and a transmit filter portion, each filter portion having a respective predetermined passband and stopband; and

the lowpass filter is coupled to an antenna pad of the duplexer filter.