Laminated high-frequency low-pass filter

• US 5,357,227 A
• Filed: 04/16/1993
• Issued: 10/18/1994
• Est. Priority Date: 04/16/1992
• Status: Expired due to Term

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Tonegawa, Ken, Okamura, Hisatake
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US08/048,381
• Time in Patent Office: 550 Days
• Field of Search: 333/202-205, 333/185, 333/175
• US Class Current: 333/185
• CPC Class Codes: H01P 1/2039 Galvanic coupling between Input/Output

Abstract

A laminated high-frequency low-pass filter includes a first dielectric layer. A second dielectric layer, a third dielectric layer, a fourth dielectric layer, and a fifth dielectric layer are laminated on the first dielectric layer. An earth electrode is formed on the first dielectric layer. A first capacitive open-circuited stub electrode, a second capacitive open-circuited stub electrode and a third capacitive open-circuited stub electrode are formed on the second dielectric layer. A first strip line electrode and a second strip line electrode are formed on the third dielectric layer. The first and second strip line electrodes are formed as meander lines. A shield electrode is formed on the fourth dielectric layer.

Claims

1. A laminated high-frequency low-pass filter comprising:

a first dielectric layer;

an earth electrode formed on said first dielectric layer;

a second dielectric layer connected to said first dielectric layer such that said earth electrode is disposed between said first and second dielectric layers;

a first and a second capacitive open-circuit stub electrode formed on said second dielectric layer;

a third dielectric layer connected to said first and second dielectric layers;

a strip line electrode comprising an inductor and being formed on said third dielectric layer, said strip line electrode having first and second ends;

a first connector connecting said first capacitive open-circuit stub electrode and said first end of said strip line electrode;

a second connector connecting said second capacitive open circuit stub electrode and said second end of said strip line electrode;

a capacitor formed by said strip line electrode, said first and second capacitive open-circuit stub electrodes and said first and second connectors, said first and second connectors connecting said capacitor and said inductor in parallel;

wherein a parallel resonance frequency between said inductor and said capacitor is approximately equal to the frequency at the wavelength ##EQU12## wherein L is a line length of said strip line electrode, and ε

_r is a relative dielectric constant around said strip line electrode.

2. A high-frequency low-pass filter according to claim 1, wherein said strip line electrode is a first strip line electrode, said capacitor is a first capacitor and said inductor is a first inductor, said filter further comprising:

a second strip line electrode comprising a second inductor and formed on said third dielectric layer, said second strip line electrode having first and second ends;

a third capacitive open-circuit stub electrode formed on said second dielectric layer;

a third connector connecting said first end of said second strip line electrode with said first capacitive open-circuit stub electrode;

a fourth connector connecting said second end of said second strip line electrode with said third capacitive open-circuit stub electrode;

a second capacitor formed by said second strip line electrode, said first and third capacitive open-circuit stub electrodes and said third and fourth connectors, said third and fourth connectors connecting said second capacitor and said second inductor in parallel;

wherein

a parallel resonance frequency between said second inductor and said second capacitor is approximately equal to the frequency at the wavelength ##EQU13## wherein L is a line length of said second strip line electrode, and ε

_r is a relative dielectric constant around said second strip line electrode.

3. A high-frequency low-pass filter according to claim 2, which further comprises a fourth dielectric layer formed on and operatively connected to said third dielectric layer such that said first and second strip line electrodes are disposed between said third dielectric layer and said fourth dielectric layer;

and

a shield electrode formed on and operatively connected to said fourth dielectric layer.

4. A high-frequency low-pass filter according to claim 3, which further comprises a fifth dielectric layer formed on and operatively connected to said fourth dielectric layer such that said shield electrode is disposed between said fourth dielectric layer and said fifth dielectric layer.

5. A laminated high-frequency low-pass filter comprising:

a first dielectric layer;

an earth electrode formed on said first dielectric layer;

a second dielectric layer formed on and operatively connected to said first dielectric layer such that said earth electrode is located between said first dielectric layer and said second dielectric layer;

a plurality of capacitive open-circuited stub electrodes formed on said second dielectric layer and located opposite to said earth electrode;

a third dielectric layer formed on and operatively connected to said second dielectric layer such that said plurality of capacitive open-circuited stub electrodes are located between said second dielectric layer and said third dielectric layer; and

two strip line electrodes each comprising an inductor, formed on said third dielectric layer and connected to said plurality of capacitive open-circuited stub electrodes to form a plurality of capacitors connected in parallel with said inductors, wherein

surface areas of said two strip line electrodes are different from each other.

6. A high-frequency low-pass filter according to claim 5, wherein the lengths of said two strip line electrodes are different from each other.

7. A high-frequency low-pass filter according to claim 5, which further comprises a fourth dielectric layer formed on said third dielectric layer and sandwiching said two strip line electrodes between said third dielectric layer and said fourth dielectric layer;

and

a shield electrode formed on said fourth dielectric layer.

8. A high-frequency low-pass filter according to claim 7, which further comprises a fifth dielectric layer formed on said fourth dielectric layer and sandwiching said shield electrode between said fourth dielectric layer and said fifth dielectric layer.

9. A high-frequency low-pass filter according to claim 6, which further comprises a fourth dielectric layer formed on said third dielectric layer and sandwiching said two strip line electrodes between said third dielectric layer and said fourth dielectric layer;

and

a shield electrode formed on said fourth dielectric layer.

10. A high-frequency low-pass filter according to claim 9, which further comprises a fifth dielectric layer formed on said fourth dielectric layer and sandwiching said shield electrode between said fourth dielectric layer and said fifth dielectric layer.