US 10,374,572 B2Granted

Radiofrequency filter with improved attenuation of common mode signals

OwnerJohn Gordon Ramseyinventor

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Abstract

A radiofrequency filter utilizing a common mode choke both as a traditional common mode choke as well as the inductance in a low pass filter. Filter topology as well as component selection is optimized for wide band operation. Common mode chokes allow differential currents to pass with little attenuation while common mode currents are effectively presented with an inductance in the common current path. This inductance is used in a low pass filter configuration to present an even higher attenuation to common mode currents. The use of multiple chokes and/or differing core materials contributes to wider band operation without pronounced resonances. The capacitance used in the low pass filter is connected in a way as to reduce its effect on the data signals while still being effective in filtering.

Claims18

Dependent claims

A radiofrequency filter circuit comprising:

a first input terminal and a second input terminal;
a first output terminal and a second output terminal;
a first signal path between the first input terminal and the first output terminal;
a second signal path between the second input terminal and the second output terminal;
a first common mode choke having a first set of bifilar windings and a second set of bifilar windings and a second common mode choke having a first set of bifilar windings and a second set of bifilar windings where the first set of bifilar windings on the first common mode choke is in series with the first set of bifilar windings on the second common mode choke such that the first set of bifilar windings on the first common mode choke in series with the first set of bifilar windings on the second common mode choke are in the first signal path between the first input terminal and the first output terminal and where the second set of bifilar windings on the first common mode choke is in series with the second set of bifilar windings on the second common mode choke such that the second set of bifilar windings on the first common mode choke in series with the second set of bifilar windings on the second common mode choke are in the second signal path between the second input terminal and the second output terminal;
a first capacitive structure in the first signal path between the first input terminal and the first output terminal and electrically connected at a point between the first set of bifilar windings on the first common mode choke and the first set of bifilar windings on the second common mode choke and ground;
a second capacitive structure in the second signal path between the second input terminal and the second output terminal and electrically connected at a point between the second set of bifilar windings on the first common mode choke and the second set of bifilar windings on the second common mode choke and ground;
and
a third common mode choke having a first set of bifilar windings and a second set of bifilar windings where the first set of bifilar windings of the third common mode choke is connected in series with the first capacitive structure and the second set of bifilar windings of the third common mode choke is connected in series with the second capacitive structure.

6 more elements

A universal serial bus (USB) filter circuit comprising:

a first radiofrequency filter circuit, a second radiofrequency filter circuit and a third radiofrequency filter circuit;
wherein each radiofrequency filter circuit comprises:
a first input terminal and a second input terminal;
a first output terminal and a second output terminal;
a first signal path between the first input terminal and the first output terminal;
a second signal path between the second input terminal and the second output terminal;
a first common mode choke having a first set of bifilar windings and a second set of bifilar windings and a second common mode choke having a first set of bifilar windings and a second set of bifilar windings where the first set of bifilar windings on the first common mode choke is in series with the first set of bifilar windings on the second common mode choke such that the first set of bifilar windings on the first common mode choke in series with the first set of bifilar windings on the second common mode choke are in the first signal path between the first input terminal and the first output terminal and where the second set of bifilar windings on the first common mode choke is in series with the second set of bifilar windings on the second common mode choke such that the second set of bifilar windings on the first common mode choke in series with the second set of bifilar windings on the second common mode choke are in the second signal path between the second input terminal and the second output terminal;
a first capacitive structure in the first signal path between the first input terminal and the first output terminal and electrically connected at a point between the first set of bifilar windings on the first common mode choke and the first set of bifilar windings on the second common mode choke and ground;
a second capacitive structure in the second signal path between the second input terminal and the second output terminal and electrically connected at a point between the second set of bifilar windings on the first common mode choke and the second set of bifilar windings on the second common mode choke and ground;
and
a third common mode choke having a first set of bifilar windings and a second set of bifilar windings where the first set of bifilar windings of the third common mode choke is connected in series with the first capacitive structure and the second set of bifilar windings of the third common mode choke is connected in series with the second capacitive structure.

8 more elements

A radiofrequency filter circuit comprising:

a first input terminal and a second input terminal;
a first output terminal and a second output terminal;
a first signal path between the first input terminal and the first output terminal;
a second signal path between the second input terminal and the second output terminal;
a first common mode choke having a first set of bifilar windings and a second set of bifilar windings and a second common mode choke having a first set of bifilar windings and a second set of bifilar windings where the first set of bifilar windings on the first common mode choke is in series with the first set of bifilar windings on the second common mode choke such that the first set of bifilar windings on the first common mode choke in series with the first set of bifilar windings on the second common mode choke are in the first signal path between the first input terminal and the first output terminal and where the second set of bifilar windings on the first common mode choke is in series with the second set of bifilar windings on the second common mode choke such that the second set of bifilar windings on the first common mode choke in series with the second set of bifilar windings on the second common mode choke are in the second signal path between the second input terminal and the second output terminal;
a first capacitive structure in the first signal path between the first input terminal and the first output terminal and electrically connected at a point between the first set of bifilar windings on the first common mode choke and the first set of bifilar windings on the second common mode choke and ground;
a second capacitive structure in the second signal path between the second input terminal and the second output terminal and electrically connected at a point between the second set of bifilar windings on the first common mode choke and the second set of bifilar windings on the second common mode choke and ground;
a third common mode choke having a first set of bifilar windings and a second set of bifilar windings where the first set of bifilar windings of the third common mode choke is connected in series with the first capacitive structure and the second set of bifilar windings of the third common mode choke is connected in series with the second capacitive structure;
a radiofrequency shielded housing to contain the radiofrequency filter circuit;
a cover plate to enclose the radiofrequency filter circuit in the radiofrequency shielded housing;
an input connector electrically connected to the first input terminal and the second input terminal;
and
an output connector electrically connected to the first output terminal and the second output terminal.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/727,582Filed 7 Oct 2017 · us provisional application
Priority: 14 Oct 2016
Published: US 2018/0109041 A119 Apr 2018
Granted: 6 Aug 2019
Term ends: Not estimatedThe source records don’t support an estimate.

Classification15 codes

H03H 7/427
Balance-balance networks: common-mode filters
H01P 1/225
Attenuating devices: coaxial attenuators
H01R 13/659
Shield structure: with plural ports for distinct connectors
H03H 7/00
Multiple-port networks comprising only passive electrical elements as network components

Family

Application62/408,467Us provisional application · filed 14 Oct 2016
US 2018/0109041 A1Pre-grant publication · published 19 Apr 2018
US 10,374,572 B2This patent

From the US filing history. Foreign family members aren’t listed.

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