External noise intrusion prevention device, signal amplifier, protector and antenna plug

• US 20020100060A1
• Filed: 01/22/2002
• Published: 07/25/2002
• Est. Priority Date: 01/22/2001
• Status: Active Grant

• Current Assignee: Maspro Denkoh Corporation (Hashiyama Kabushiki Kaisha)
• Original Assignee: Maspro Denkoh Corporation (Hashiyama Kabushiki Kaisha)
• Inventors: Sugiura, Toshihiro
• Granted Patent: US 7,039,360 B2
• Time in Patent Office: Days
• US Class Current: 725/127
• CPC Class Codes: H03H 7/01 Frequency selective two-port networks
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

An external noise intrusion prevention device preventing intrusion of external noise into a central conductor of a trunk cable in an up signal frequency band is provided. A first filter circuit 3 letting a signal in frequencies of 54 MHz or higher pass is provided between an input terminal 1 and an output terminal 2. A front filter circuit 4a and a rear filter circuit 4b, which constitute a second filter circuit 4, are provided on both ends of the external noise intrusion prevention device, respectively. A noise elimination circuit 6 formed by cascading two connection transformers 6a and 6b is also provided. The two connection transformers 6a and 6b are connected to each other while being arranged in a line symmetrical manner.

Claims

1. An external noise intrusion prevention device having an input terminal and an output terminal connectable to a coaxial cable, comprising:

a first filter circuit letting a signal in a predetermined frequency band pass, the input terminal and the output terminal connected to each other through the first filter circuit;

a second filter circuit letting a signal in a predetermined frequency band different from said predetermined frequency band pass; and

a noise elimination circuit connected between the input terminal and the output terminal through the second filter, wherein

the noise elimination circuit is formed by cascading two connection transformers each having a primary winding and a secondary winding, the two connection transformers being a front connection transformer and a rear connection transformer, one end of the primary winding of the front connection transformer connected to a core on said input terminal side and the other end of the primary winding of the front connection transformer connected to an input-side ground section, one end of the secondary winding of the rear connection transformer connected to a core on said output terminal side and the other end of the secondary winding of the rear connection transformer connected to an output-side ground section.

3. An external noise intrusion prevention device according to claim 1 or 2, wherein

the input-side ground section is connected to the output-side ground section to prevent a direct current from passing.

4. A protector comprising:

an arrester; and

a choke coil, the protector preventing an abnormal voltage entering from an input terminal from flowing from an output terminal, the protector comprising an external noise intrusion prevention device according to any one of claims 1 to 3, the external noise intrusion prevention device provided on an output terminal section.

5. A signal amplifier provided midway along a bi-directional CATV trunk letting an up signal and a down signal pass, and amplifying at least the down signal from a center station, the signal amplifier comprising:

an external noise intrusion prevention device according to claim 1 or 2, the external noise intrusion prevention device provided in an output section outputting the down signal.

8. An antenna plug having two coaxial cable connection terminals on both ends, respectively, and comprising an external noise intrusion prevention circuit according to any one of claims 1 to 3, the external noise intrusion prevention device interposed between the two coaxial cable connection terminals.

2. An external noise intrusion prevention device having an input terminal and an output terminal connectable to a coaxial cable, comprising:

a first filter circuit letting a signal in a predetermined frequency band pass, the input terminal and the output terminal connected to each other through the first filter circuit;

a second filter circuit letting a signal in a predetermined frequency band different from said predetermined frequency band pass; and

a noise elimination circuit connected between the input terminal and the output terminal through the second filter, wherein

the noise elimination circuit consists of a transformer having a turns ratio of 1 to 1, one end of a primary winding of the transformer connected to a core on said input terminal side and the other end of the primary winding connected to an input-side ground section, one end of a secondary winding of the transformer connected to a core on said output terminal side and the other terminal of the secondary winding connected to an output-side ground section.

6. A signal amplifier provided midway along a bi-directional CATV trunk letting an up signal and a down signal pass, and amplifying at least the down signal from a center station, the signal amplifier comprising:

a noise elimination circuit provided in an output section outputting the down signal, and consisting of a pair of connection transformers, the pair of connection transformer being a front connection transformer and a rear connection transformer cascaded to each other, one end of a primary winding of the front connection transformer connected to said output section and the other end of the primary winding of the front connection transformer connected to a ground section of the output section, one end of a secondary winding of the rear connection transformer connected to a core of an output terminal of said signal amplifier and the other end of the secondary winding of the rear connection transformer connected to a ground section of the output terminal.

7. A signal amplifier provided midway along a bi-directional CATV trunk letting an up signal and a down signal pass, and amplifying at least the down signal from a center station, the signal amplifier comprising:

a noise elimination circuit provided in an output section outputting the down signal, and consisting of a transformer having a turns ratio of 1 to 1, one end of a primary winding of the transformer connected to said output section and the other end of the transformer connected to a ground section of the output section, one end of a secondary winding of the transformer connected to a core of an output terminal of said signal amplifier and the other end of the secondary winding of the transformer connected to a ground section of the output terminal.

9. An antenna plug having two coaxial cable connection terminals on both ends, respectively, and comprising an external noise intrusion prevention circuit interposed between the two coaxial cable connection terminals, wherein

the noise elimination circuit is formed by cascading two connection transformers each having a primary winding and a secondary winding, the two connection transformers being a front connection transformer and a rear connection transformer, one end of the primary winding of the front connection transformer connected to a core of one of the coaxial cable connection terminals or one of F-type connection terminals and the other end of the primary winding of the front connection transformer connected to a ground section of one of the coaxial cable connection terminals or one of the F-type connection terminals, one end of the secondary winding of the rear connection transformer connected to a core of the other one of the coaxial cable connection terminals or the other one of the F-type connection terminals and the other end of the secondary winding of the rear connection transformer connected to a ground section of the other one of the coaxial cable connection terminals or the other one of the F-type connection terminals.

10. An antenna plug having two coaxial cable connection terminals on both ends, respectively, and comprising an external noise intrusion prevention circuit interposed between the two coaxial cable connection terminals, wherein

the noise elimination circuit consists of a transformer having a turns ratio of 1 to 1, one end of a primary winding of the transformer connected to a core of one of the coaxial cable connection terminals or one of F-type connection terminals and the other end of the primary winding of the transformer connected to a ground section of one of the coaxial cable connection terminals or one of the F-type connection terminals, one end of the secondary winding of the transformer connected to a core of the other one of the coaxial cable connection terminals or the other one of the F-type connection terminals and the other end of the secondary winding of the transformer connected to a ground section of the other one of the coaxial cable connection terminals or the other one of the F-type connection terminals.