Filter circuit and high frequency communication circuit using the same

• US 20030102941A1
• Filed: 12/31/2002
• Published: 06/05/2003
• Est. Priority Date: 07/07/2000
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Yamada, Atsushi, Amano, Yoshihisa
• Granted Patent: US 6,876,276 B2
• Time in Patent Office: Days
• US Class Current: 333/202
• CPC Class Codes: H01P 1/2013 Coplanar line filters
• CPC Class Codes: H01P 1/20381 Special shape resonators
• CPC Class Codes: H01P 1/2053 the coaxial cavity resonators being disposed parall to each other

Abstract

In a distributed constant filter, two λ/2 open line resonator (8,9) are capacitive-coupled by an electromagnetic field coupling portion (13), and an input terminal (2) and an output terminal (3) are brought into mutual inductive coupling by an electromagnetic field coupling portion (10). The frequency of an attenuation pole can be close to a center frequency and the steepness of the filter characteristics can be increased.

Claims

1. (Twice Amended) A filter circuit selectively passing a predetermined frequency component of a signal input to an input terminal (2) to an output terminal (3), comprising:

an electromagnetic field coupling circuit (10) for connecting said input terminal (2) and a first terminal (6), and connecting said output terminal (3) and a second terminal (7), and bringing said input terminal (2) and said output terminal (3) into magnetic field coupling by mutual induction to each other;

at least three capacitors (11, 13, 12) connected in series between said first and second terminals (6, 7);

at least two resonators (8, 9) respectively connected to at least two nodes between said at least three capacitors (11, 13, 12).

3. (Twice Amended) The filter circuit according to claim 1, wherein

said filter circuit is formed of a line pattern made of a conductor formed on an insulator substrate (1),

said first and second terminals (6, 7) respectively include first and second lines (6, 7),

said electromagnetic field coupling circuit (10) includes

a third line (4) connected between said input terminal (2) and one end portion of said first line (6) and

a fourth line (5) connected between said output terminal (3) and one end portion of said second line (7),

said third and fourth lines (4, 5) are arranged parallel to each other in proximity,

said at least two resonance circuits (8, 9) respectively include at least two fifth lines (8, 9) having a predetermined line length,

the other end portion of said first line (6) and one fifth line (8), the other end portion of said second line (7) and another fifth line (9), and two fifth lines (8, 9) are capacitive-coupled to each other to form said at least three capacitors (11-13) respectively.

4. (Twice Amended) The filter circuit according to claim 3, wherein

said third and fourth lines (4, 5) are proximate to each other at a position of a quarter wave of a signal having a center frequency of said filter circuit from open ends of said first and second lines (6, 7).

5. (Amended) The filter circuit according to claim 1, wherein

each of said at least two resonators (8, 9) is a quarter wave short-circuited line resonator or a half wave open line resonator.

6. The filter circuit according to claim 1, wherein

said filter circuit is used as a part of a multiplexer type filter circuit.

7. A high frequency communication circuit device characterized in that a filter circuit according to claim 1 is used as a high frequency filter (68a, 78a) for removing a local signal or an image signal.

2. (Deleted)

8. Twice Amended) A filter circuit selectively passing a predetermined frequency component of a signal input to an input terminal (14) to an output terminal (15), comprising:

a first capacitor (16) connected between said input terminal (14) and said output terminal (15);

an electromagnetic field coupling circuit (10) for connecting said input terminal (14) and a first terminal (6), and connecting said output terminal (15) and a second terminal (7), and bringing said input terminal (14) and said output terminal (15) into magnetic field coupling by mutual conduction to each other;

at least three second capacitors (11, 13, 12) connected in series between said first and second terminals (6, 7); and

at least two resonators (8, 9) respectively connected to at least two nodes between said at least three second capacitors (11, 13, 12).

10. (Amended) The filter circuit according to claim 8, wherein

each of said at least two resonators (8, 9) is a quarter wave short-circuited line resonator or a half wave open line resonator.

11. The filter circuit according to claim 8, wherein

said filter circuit is used as a part of a multiplexer type filter circuit.

12. A high frequency communication circuit device characterized in that a filter circuit according to claim 8 is used as a high frequency filter (68a, 78a) for removing a local signal or an image signal.

13. (Added/Amended) The filter circuit according to claim 8, wherein

said filter circuit is formed of a line pattern made of a conductor formed on an insulator substrate (1),

said input terminal (14) and said output terminal (15) respectively include first and second lines (14, 15)

said first and second terminals (6, 7) respectively include third and fourth lines (6, 7),

said electromagnetic field coupling circuit (10) includes

a fifth line (4) connected between said first line (14) and one end portion of said third line (6) and

a sixth line (5) connected between said second line (15) and one end portion of said fourth line (7),

said fifth and sixth lines (4, 5) are arranged parallel to each other in proximity,

said at least two resonance circuits (8, 9) includes at least two seventh lines (8, 9) each having a predetermined line length,

said first and second lines (14, 15) are capacitive-coupled to each other to form said first capacitor (16), and

the other end portion of said third line (6) and one seventh line (8), the other end portion of said fourth line (7) and another seventh line (9), and two seventh lines (8, 9) are capacitive-coupled respectively to each other to form said at least three second capacitors (11-13).

14. (Added/Amended) The filter circuit according to claim 13, wherein

said fifth and sixth lines (4, 5) are proximate to each other at a position of a quarter wave of a signal having a center frequency of said filter circuit from open ends of said third and fourth lines (6, 7).

9. (Deleted)