WO1994008417A1 - Radio frequency interference filter - Google Patents
Radio frequency interference filter Download PDFInfo
- Publication number
- WO1994008417A1 WO1994008417A1 PCT/US1993/009047 US9309047W WO9408417A1 WO 1994008417 A1 WO1994008417 A1 WO 1994008417A1 US 9309047 W US9309047 W US 9309047W WO 9408417 A1 WO9408417 A1 WO 9408417A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- inductor
- series
- ferrite
- core
- transformer
- Prior art date
Links
- 238000004804 winding Methods 0.000 claims abstract description 13
- 230000007613 environmental effect Effects 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims 2
- 230000001629 suppression Effects 0.000 abstract description 10
- 230000002411 adverse Effects 0.000 abstract 1
- 238000001914 filtration Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 230000005684 electric field Effects 0.000 description 2
- 238000009428 plumbing Methods 0.000 description 2
- 206010010144 Completed suicide Diseases 0.000 description 1
- RFIJBZKUGCJPOE-UHFFFAOYSA-N [Fe].[Ni].[Zn] Chemical compound [Fe].[Ni].[Zn] RFIJBZKUGCJPOE-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000006735 deficit Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000012811 non-conductive material Substances 0.000 description 1
- 230000001012 protector Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/28—Reducing interference caused by currents induced in cable sheathing or armouring
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/42—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns
- H03H7/425—Balance-balance networks
- H03H7/427—Common-mode filters
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/26—Improving frequency characteristic by the use of loading coils
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/738—Interface circuits for coupling substations to external telephone lines
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/738—Interface circuits for coupling substations to external telephone lines
- H04M1/74—Interface circuits for coupling substations to external telephone lines with means for reducing interference; with means for reducing effects due to line faults
Definitions
- the present invention relates to a Radio Frequency
- RFI filter for a telecommunications device, and more particularly to an RFI filter for telephone equipment that suppresses frequencies in the range from about 450 kHz to about
- Radio Frequency Interference can occur in a telecommunications network whose wiring is subject to strong radio frequency electrical fields.
- RFI is a problem in telecommunications because it impairs reception of the signal transmitted through the telecommunications network. Impairment of a transmitted signal is particularly undesirable in the transmission of voice frequency signals because of the need for a telephone subscriber to receive clear, accurate voice communications.
- each of a pair of inductors has a lead connectable respectively to tip and ring leads of the telephone circuitry.
- the second lead of each inductor is connected to a respective coil of a transformer.
- the free lead of each coil of the transformer is connectable to respective tip and ring leads.
- the pair of inductors form a first stage of filtering while the transformer provides a second stage of filtering.
- each of a pair of inductors has a lead connectable respectively to tip and ring leads of the telephone circuitry.
- each inductor is connected to a ferrite-core inductor.
- the free lead of each ferrite-core inductor is connectable to respective tip and ring leads.
- the pair of inductors form a first stage of filtering while the ferrite-core inductors provide the second stage of filtering.
- Each device provides suppression of RFI from 450 kHz to 150 MHz.
- a fuse may precede each inductor to protect the device from power surges and the like.
- Fig. 1 is a schematic diagram of an RFI filter in accordance with a preferred embodiment the invention.
- Fig. 2 is a schematic diagram of an RFI filter in accordance with a second preferred embodiment of the invention.
- FIG. 1 there is shown a schematic diagram of an RFI filter 10 in accordance with a preferred embodiment of the invention.
- the filter 10 has a first stage 20 for suppressing lower frequencies of RFI and a second stage 22 for suppressing higher frequencies of RFI.
- the filter 10 is insertable in series in the tip T and ring R conductors of telephone circuitry.
- a first inductor Ll and a second inductor L2 form the first suppression stage 20.
- the first inductor Ll is connectable in the tip T branch of circuitry while the second inductor L2 is connectable in the ring R branch of circuitry.
- a transformer is connected in series in the tip T and ring R circuitry.
- a first winding Wl of the transformer Tl is connected in series in the tip T branch of circuitry, following the first inductor Ll.
- the second winding W2 of the transformer Tl is connected in series in the ring R branch of circuitry, following the second inductor L2.
- an RFI filter 12 also has a first stage 20 for suppressing lower frequencies of RFI and a second stage 22 for suppressing higher frequencies of RFI.
- the filters 10, 12 differ in only one aspect.
- the filter 12 of the alternative preferred embodiment has a pair of ferrite-core inductors L3, L4 rather than a transformer Tl serving as the second suppression stage 22.
- a first inductor Ll and a second inductor L2 form the first suppression stage 20.
- Each ferrite-core inductor L3, L4 is connected in series with a respective first-stage 20 inductor Ll, L2.
- a suitable type of ferrite-core inductor is part number 28C0236-OBW sold by the Steward company of Chattanooga, Tennessee, United States of America.
- the Steward inductor's core is generally believed to be of a nickel-zinc-iron suicide material.
- Steward part number 28C0236-OBW is a 6-hole cylinder type of core having two and one-half (2 1/2) turns.
- the first stage 20 suppresses RFI in the range of 450 kHz to 10 MHz.
- the second stage 22 suppresses RFI in the range of 10 MHz to 150 MHz.
- the filter 10, 12 is balanced.
- the tip T and ring R outputs of circuitry containing the filter 10, 10 are balanced.
- the filter 10, 12 attenuates both the tip T and ring R branches of circuitry simultaneously.
- the filter 10, 12 works well to suppress RFI in voice-frequency loops. A separate ground connection is not required to install the device.
- neither filter 10, 12 requires a ground connection to perform RFI filtering. It is important that the devices 10, 12 do not require grounding because a ground connection may not be readily available at a point of desired installation. This is particularly true when it is desirable to install the device 10, 12 near the user interface of a telephone system because traditionally plumbing in a telephone subscriber's business or residence has been used as the point of ground connection. In modern-day construction, many plumbing lines and some fixtures are made of non-conductive materials such as PVC rather than the metals that were previously used.
- the filter 10, 12 may be inserted at any point in the telephone circuitry but works well when inserted close to or at the subscriber interface of the telephone system circuitry.
- the filter 10, 12 When the filter 10, 12 is installed closest to the customer interface, for example, at the protector to the demodulation circuitry, suppression of RFI preceding the subscriber equipment is possible.
- the filter 10, 12 reduces the level of longitudinally conducted RFI present at a telephone subscriber network interface when the network wiring is subject to strong radio frequency electrical fields.
- a fuse Fl, F2 may respectively precede each inductor Ll, L2 to provide protection from power surges or overloads.
- the device may be encapsulated or otherwise enclosed so that it is useful under various environmental conditions.
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Filters And Equalizers (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP93922349A EP0614588A4 (en) | 1992-09-25 | 1993-09-27 | Radio frequency interference filter. |
US08/244,286 US6078662A (en) | 1992-09-25 | 1993-09-27 | Radio frequency interference filter |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US95139692A | 1992-09-25 | 1992-09-25 | |
US07/951,396 | 1992-09-25 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1994008417A1 true WO1994008417A1 (en) | 1994-04-14 |
Family
ID=25491648
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1993/009047 WO1994008417A1 (en) | 1992-09-25 | 1993-09-27 | Radio frequency interference filter |
Country Status (4)
Country | Link |
---|---|
US (1) | US6078662A (en) |
EP (1) | EP0614588A4 (en) |
CA (1) | CA2124203A1 (en) |
WO (1) | WO1994008417A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2741491A1 (en) * | 1995-11-17 | 1997-05-23 | France Telecom | Low pass filter for use on bifilar telephone line |
EP0778683A3 (en) * | 1995-12-04 | 1999-08-18 | Fujitsu Limited | Terminal equipment for telecommunications and information processing |
NL1005277C2 (en) * | 1997-02-14 | 2001-09-28 | Adrianus Henzen | Construction of a brick wall, uses bricks and mortar that have had components added to provide water repellency and moisture impermeability |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6470059B2 (en) * | 2000-12-28 | 2002-10-22 | Sbc Technology Resources, Inc. | Automatic filter for asymmetric digital subscriber line system |
US7120211B2 (en) | 2002-03-21 | 2006-10-10 | Conexant, Inc. | Adaptive RFI canceller for DSL |
US7620154B2 (en) * | 2002-12-23 | 2009-11-17 | Cambron G Keith | Equivalent working length determinative system for digital subscriber line circuits |
TWI505665B (en) * | 2012-07-06 | 2015-10-21 | Cyntec Co Ltd | Network communication device |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2144950A (en) * | 1936-09-04 | 1939-01-24 | Lorenz C Ag | Filter for separating high frequencies from low frequencies |
US2297215A (en) * | 1938-05-11 | 1942-09-29 | Hagen Wolfgang | Electric filter device |
US2362549A (en) * | 1942-09-23 | 1944-11-14 | Bell Telephone Laborateries In | Wave transmission network |
US2621252A (en) * | 1949-02-11 | 1952-12-09 | Sylvania Electric Prod | Interference-suppression network |
US3987380A (en) * | 1974-09-12 | 1976-10-19 | Amp Incorporated | Plating encapsulation to inhibit dendritic growth |
US5077543A (en) * | 1991-02-07 | 1991-12-31 | Ungermann-Bass, Inc. | Balanced low-pass common mode filter |
US5200718A (en) * | 1990-10-23 | 1993-04-06 | Smk Co., Ltd. | Balun transformer with common mode coil |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60242710A (en) * | 1984-05-17 | 1985-12-02 | Aihoku Denpa Kenkyusho | Device for preventing radio wave interference produced by electromagnetic wave invaded to circuit of electronic appliance |
JPS6258608A (en) * | 1985-09-06 | 1987-03-14 | Murata Mfg Co Ltd | Inductor for removal of noise |
US4751607A (en) * | 1986-08-11 | 1988-06-14 | American Telephone And Telegraph Company | Communication line transient protection |
-
1993
- 1993-09-27 CA CA002124203A patent/CA2124203A1/en not_active Abandoned
- 1993-09-27 US US08/244,286 patent/US6078662A/en not_active Expired - Fee Related
- 1993-09-27 WO PCT/US1993/009047 patent/WO1994008417A1/en not_active Application Discontinuation
- 1993-09-27 EP EP93922349A patent/EP0614588A4/en not_active Withdrawn
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2144950A (en) * | 1936-09-04 | 1939-01-24 | Lorenz C Ag | Filter for separating high frequencies from low frequencies |
US2297215A (en) * | 1938-05-11 | 1942-09-29 | Hagen Wolfgang | Electric filter device |
US2362549A (en) * | 1942-09-23 | 1944-11-14 | Bell Telephone Laborateries In | Wave transmission network |
US2621252A (en) * | 1949-02-11 | 1952-12-09 | Sylvania Electric Prod | Interference-suppression network |
US3987380A (en) * | 1974-09-12 | 1976-10-19 | Amp Incorporated | Plating encapsulation to inhibit dendritic growth |
US5200718A (en) * | 1990-10-23 | 1993-04-06 | Smk Co., Ltd. | Balun transformer with common mode coil |
US5077543A (en) * | 1991-02-07 | 1991-12-31 | Ungermann-Bass, Inc. | Balanced low-pass common mode filter |
Non-Patent Citations (1)
Title |
---|
See also references of EP0614588A4 * |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2741491A1 (en) * | 1995-11-17 | 1997-05-23 | France Telecom | Low pass filter for use on bifilar telephone line |
EP0778683A3 (en) * | 1995-12-04 | 1999-08-18 | Fujitsu Limited | Terminal equipment for telecommunications and information processing |
NL1005277C2 (en) * | 1997-02-14 | 2001-09-28 | Adrianus Henzen | Construction of a brick wall, uses bricks and mortar that have had components added to provide water repellency and moisture impermeability |
Also Published As
Publication number | Publication date |
---|---|
EP0614588A4 (en) | 1995-10-04 |
EP0614588A1 (en) | 1994-09-14 |
CA2124203A1 (en) | 1994-04-14 |
US6078662A (en) | 2000-06-20 |
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