U.S. patent application number 17/197027 was filed with the patent office on 2022-09-15 for common mode filter.
This patent application is currently assigned to HTC Corporation. The applicant listed for this patent is HTC Corporation. Invention is credited to Che-Jung Chang, Wei-Hong Gao, Chia-Chu Ho.
Application Number | 20220294406 17/197027 |
Document ID | / |
Family ID | 1000005564215 |
Filed Date | 2022-09-15 |
United States Patent
Application |
20220294406 |
Kind Code |
A1 |
Chang; Che-Jung ; et
al. |
September 15, 2022 |
COMMON MODE FILTER
Abstract
A common mode filter is disposed on a circuit board. A signal
layer of the circuit board has a differential signal wire pair. The
common mode filter has a slot structure and a filtering frequency
adjusting device. The slot structure is formed on a reference
voltage layer of the circuit board, wherein the slot structure
surrounds the differential signal wire pair. The filtering
frequency adjusting device is disposed on a corner part of the slot
structure, wherein the filtering frequency adjusting device
includes at least one of at least one capacitor and at least one
inductor, and is disposed on the circuit board across the
differential signal wire pair.
Inventors: |
Chang; Che-Jung; (Taoyuan
City, TW) ; Gao; Wei-Hong; (Taoyuan City, TW)
; Ho; Chia-Chu; (Taoyuan City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HTC Corporation |
Taoyuan City |
|
TW |
|
|
Assignee: |
HTC Corporation
Taoyuan City
TW
|
Family ID: |
1000005564215 |
Appl. No.: |
17/197027 |
Filed: |
March 10, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03H 7/0115 20130101;
H05K 2201/09036 20130101; H05K 1/0245 20130101; H03H 7/427
20130101; H05K 1/0216 20130101 |
International
Class: |
H03H 7/01 20060101
H03H007/01; H05K 1/02 20060101 H05K001/02 |
Claims
1. A common mode filter, disposed on a circuit board, and a signal
layer of the circuit board having a differential signal wire pair,
comprising: a slot structure, formed on a reference voltage layer
of the circuit board, wherein the slot structure surrounds the
differential signal wire pair; and a filtering frequency adjusting
device, configured above a bent part of the slot structure, wherein
the filtering frequency adjusting device comprises at least one of
at least one inductor and at least one capacitor, and is disposed
on the circuit board across the differential signal wire pair;
wherein the filtering frequency adjusting device comprises: a
plurality of passive components, having commonly coupled first
terminals, and the first terminals of the passive components are
coupled to a first reference voltage terminal; and a switch,
coupled to a plurality of second terminals of the passive
components, and selecting one of the second terminals of the
passive components to be coupled to a second reference voltage
terminal according to a control signal.
2. The common mode filter as claimed in claim 1, wherein two ends
of the filtering frequency adjusting device are respectively
coupled to a first reference voltage terminal and a second
reference voltage terminal on the circuit board.
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. The common mode filter as claimed in claim 1, wherein each of
the passive components is a capacitor or an inductor.
8. The common mode filter as claimed in claim 1, further
comprising: a controller, coupled to the switch, and adapted to
provide the control signal.
9. The common mode filter as claimed in claim 1, wherein the
filtering frequency adjusting device comprises at least one of a
variable capacitor and a variable inductor, a capacitance value of
the variable capacitor and an inductance value of the variable
inductor are respectively changed according to a first control
voltage and a second control voltage.
10. The common mode filter as claimed in claim 1, wherein the
filtering frequency adjusting device is detachably disposed on the
circuit board.
11. A common mode filter, disposed on a circuit board, and a signal
layer of the circuit board having a differential signal wire pair,
comprising: a slot structure, formed on a reference voltage layer
of the circuit board, wherein the slot structure surrounds the
differential signal wire pair; and a filtering frequency adjusting
device, configured above a bent part of the slot structure, wherein
the filtering frequency adjusting device comprises at least one of
at least one inductor and at least one capacitor, and is disposed
on the circuit board across the differential signal wire pair;
wherein the filtering frequency adjusting device comprises a first
capacitor and a second capacitor, and the first capacitor and the
second capacitor are coupled to each other.
12. A common mode filter, disposed on a circuit board, and a signal
layer of the circuit board having a differential signal wire pair,
comprising: a slot structure, formed on a reference voltage layer
of the circuit board, wherein the slot structure surrounds the
differential signal wire pair; and a filtering frequency adjusting
device, configured above a bent part of the slot structure, wherein
the filtering frequency adjusting device comprises at least one of
at least one inductor and at least one capacitor, and is disposed
on the circuit board across the differential signal wire pair;
wherein the filtering frequency adjusting device comprises a first
capacitor and a first inductor, and the first capacitor and the
first inductor are coupled to each other.
13. A common mode filter, disposed on a circuit board, and a signal
layer of the circuit board having a differential signal wire pair,
comprising: a slot structure, formed on a reference voltage layer
of the circuit board, wherein the slot structure surrounds the
differential signal wire pair; and a filtering frequency adjusting
device, configured above a bent part of the slot structure, wherein
the filtering frequency adjusting device comprises at least one of
at least one inductor and at least one capacitor, and is disposed
on the circuit board across the differential signal wire pair;
wherein the filtering frequency adjusting device comprises a first
inductor and a second inductor, and the first inductor and the
second inductor are coupled to each other.
Description
BACKGROUND
Technical Field
[0001] The invention relates to a common mode filter, and
particularly relates to a common mode filter disposed on a printed
circuit board and capable of performing filtering frequency
adjustment.
Description of Related Art
[0002] In the conventional technical field, in a common mode filter
generated through a circuit layout, a center frequency of a
passband thereof is often controlled by a length of a slot
structure on a circuit board and a length of a transmission wire.
In this way, when a peripheral circuit applied to the circuit board
changes, a designer needs to redesign the layout of the slot
structure and the transmission wire, which increases the time
course of design. In addition, the formation of the slot structure
needs to match the topography of the layout of the circuit board.
In a limited space, it is probably unable to produce a suitable
slot structure effectively, and may cause poor performance in
impedance matching.
SUMMARY
[0003] The invention is directed to a common mode filter, which is
adapted to dynamically adjust a signal passband.
[0004] The invention provides a common mode filter disposed on a
circuit board. An active layer of the circuit board has a
differential signal wire pair. The common mode filter includes a
slot structure and a filtering frequency adjusting device. The slot
structure is formed on a reference voltage layer of the circuit
board, wherein the slot structure surrounds the differential signal
wire pair. The filtering frequency adjusting device is configured
above a bent part of the slot structure, wherein the filtering
frequency adjusting device includes at least one of at least one
inductor and at least one capacitor, and is configured on the
circuit board across the differential signal wire pair.
[0005] Based on the above description, in the common mode filter of
the invention, by arranging the filtering frequency adjusting
device on the slot structure of the circuit board, and dynamically
adjusting a passband of the common mode filter through a capacitor
and/or an inductor on the filtering frequency adjusting device,
efficiency of the common mode filter is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic diagram of a common mode filter
according to an embodiment of the invention.
[0007] FIG. 2 is a partial enlarged schematic diagram of a common
mode filter 100 according to the embodiment of FIG. 1 of the
invention.
[0008] FIG. 3A is a schematic diagram of an implementation of a
filtering frequency adjusting device of a common mode filter
according to an embodiment of the invention.
[0009] FIG. 3B illustrates a Smith chart of the implementation of
FIG. 3A.
[0010] FIG. 4A is a schematic diagram of another implementation of
a filtering frequency adjusting device of a common mode filter
according to an embodiment of the invention.
[0011] FIG. 4B illustrates a Smith chart of the embodiment of FIG.
4A.
[0012] FIG. 5 is a schematic diagram of a common mode filter
according to another embodiment of the invention.
[0013] FIG. 6 is a schematic diagram of another implementation of a
filtering frequency adjusting device of a common mode filter
according to an embodiment of the invention.
[0014] FIG. 7 is a schematic diagram of another implementation of a
filtering frequency adjusting device of a common mode filter
according to an embodiment of the invention.
DESCRIPTION OF THE EMBODIMENTS
[0015] Referring to FIG. 1, FIG. 1 is a schematic diagram of a
common mode filter according to an embodiment of the invention. The
common mode filter 100 of the embodiment of the invention is
disposed on a circuit board 10. An active layer of the circuit
board 10 is provided with a differential signal wire pair composed
of differential signal wires WIR1 and WIR2. The common mode filter
100 includes a slot structure 110 and a filtering frequency
adjusting device 120. The slot structure 110 is disposed on a
reference voltage layer of the circuit board 10, where the
reference voltage layer and the active layer may be located in
different layers of the circuit board 10, and the reference voltage
layer and the active layer may be overlapped with each other. The
reference voltage layer may be electrically coupled to a ground
voltage or a power supply voltage, and may be used as a reference
plane for a differential signal pair transmitted by the
differential signal wires WIR1 and WIR2.
[0016] It should be noted that in the embodiment, the slot
structure 110 is configured by surrounding the differential signal
wires WIR1 and WIR2. In the embodiment, the slot structure 110 has
a bent part at a first side 51, and the slot structure 110 has an
opening portion at a second side S2. The filtering frequency
adjusting device 120 may cover the bent part located at the first
side 51 of the slot structure 110.
[0017] In an embodiment of the invention, the filtering frequency
adjusting device 120 may have one or a plurality of capacitors. In
another embodiment of the invention, the filtering frequency
adjusting device 120 may have one or a plurality of inductors. In
still another embodiment of the invention, the filtering frequency
adjusting device 120 may have one or a plurality of capacitors and
one or a plurality of inductors.
[0018] It should be noted that the filtering frequency adjusting
device 120 may be disposed on the circuit board 10 in a manner of
surface mount device (SMD). The filtering frequency adjusting
device 120 may be electrically connected to the reference voltage
layer through a conductive via on the circuit board 10, where the
reference voltage layer may be a reference ground layer in the
circuit board 10.
[0019] Referring to FIG. 2, FIG. 2 is a partial enlarged schematic
diagram of the common mode filter 100 according to the embodiment
of FIG. 1 of the invention. A situation that the filtering
frequency adjusting device 120 includes a capacitor C1 is taken as
an example for description. Two ends of the capacitor C1 are
respectively connected to the reference voltage layer of the
circuit board 10 through conductive vias VIA1 and VIA2 on the
circuit board 10. In addition, the filtering frequency adjusting
device 120 is disposed above a bent part 140 of the slot structure
110.
[0020] It should be noted that the filtering frequency adjusting
device 120 of the embodiment of the invention may be detachably
disposed on the circuit board 10. To be specific, according to
application conditions of the circuit board 10, in response to
different peripheral circuit settings and a frequency of the
transmitted differential signal pair, a designer may select a
suitable filtering frequency adjusting device 120 for soldering on
the circuit board 10. When the application conditions of the
circuit board 10 are changed, the designer does not need to change
an overall layout of the circuit board, and only needs to
disassemble and replace with the appropriate filtering frequency
adjusting device 120 to achieve impedance matching.
[0021] Referring to FIG. 3A and FIG. 3B below, where FIG. 3A is a
schematic diagram of an implementation of a filtering frequency
adjusting device of a common mode filter according to an embodiment
of the invention, and FIG. 3B illustrates a Smith chart of the
implementation of FIG. 3A. In FIG. 3A, a filtering frequency
adjusting device 300 includes a capacitor C1 and a capacitor C2.
The capacitor C1 is connected between a connection port PT1 and a
connection port PT2. The capacitor C2 is connected between the
connection port PT2 and a reference ground terminal GND. Referring
to the Smith chart in FIG. 3B, before the filtering frequency
adjusting device 300 is added, an equivalent impedance value of a
transmission wire may fall at a position 310 in the Smith chart.
After the filtering frequency adjusting device 300 is added, the
capacitor C1 may make the equivalent impedance value of the
transmission wire to move to a position 320 through a path P1, and
the capacitor C2 may make the equivalent impedance value of the
transmission wire to move to a position 330 through a path P2, and
complete the design of impedance matching.
[0022] Referring to FIG. 4A and FIG. 4B below, where FIG. 4A is a
schematic diagram of another implementation of a filtering
frequency adjusting device of a common mode filter according to an
embodiment of the invention, and FIG. 4B illustrates a Smith chart
of the embodiment of FIG. 4A. In FIG. 4A, a filtering frequency
adjusting device 400 includes a capacitor C3 and an inductor L1.
The capacitor C3 is connected between the connection port PT1 and
the connection port PT2. The inductor L1 is connected between the
connection port PT2 and the reference ground terminal GND.
Referring to the Smith chart of FIG. 4A, before the filtering
frequency adjusting device 400 is added, the equivalent impedance
value of the transmission wire may fall at a position 410 in the
Smith chart. After the filtering frequency adjusting device 400 is
added, the capacitor C3 may make the equivalent impedance value of
the transmission wire to move to a position 420 through a path P3,
and the inductance L1 may make the equivalent impedance value of
the transmission wire to move to a position 430 through a path, and
complete the design of impedance matching.
[0023] According to the implementations of FIG. 3A and FIG. 4A, it
is known that in response to original impedance states of the
transmission wire of different states, an adjustment operation of
impedance matching of the common mode filter of the embodiment of
the invention may be effectively completed by replacing with the
suitable filtering frequency adjusting device 400, and a reflection
phenomenon that probably occurs in signal transmission is
effectively reduced, and signal transmission quality is
enhanced.
[0024] Referring to FIG. 5, FIG. 5 is a schematic diagram of a
common mode filter according to another embodiment of the
invention. A common mode filter 500 of the embodiment of the
invention is disposed on a circuit board 50. An active layer of the
circuit board 50 is provided with a differential signal wire pair
composed of differential signal wires WIR1 and WIR2. The common
mode filter 500 includes a slot structure 510 and a filtering
frequency adjusting device 520. The slot structure 510 is disposed
on a reference voltage layer of the circuit board 50, where the
reference voltage layer and the active layer may be located in
different layers of the circuit board 50, and the reference voltage
layer and the active layer may be overlapped with each other. The
reference voltage layer may be electrically coupled to the ground
voltage or the power supply voltage, and may be used as a reference
plane for the differential signal pair transmitted by the
differential signal wires WIR1 and WIR2.
[0025] It should be noted that in the embodiment, the slot
structure 510 is configured by surrounding the differential signal
wires WIR1 and WIR2. Compared to the embodiment of FIG. 1, the slot
structure 510 may have a shape different from that of the slot
structure 110. In the embodiment, the slot structure 510 has a
plurality of curved insulating structures. The differential signal
wires WIR1 and WIR2 may be configured on the curved insulating
structures and the slot structure 510.
[0026] It should be noted that in the embodiment of the invention,
the shape of the slot structure 510 is not fixedly restricted, and
the designer may adjust the shape of the slot structure 510
according to an actual layout state.
[0027] Referring to FIG. 6, FIG. 6 is a schematic diagram of
another implementation of a filtering frequency adjusting device of
a common mode filter according to an embodiment of the invention. A
filtering frequency adjusting device 610 includes a plurality of
passive components PC1-PC4 and a switch 611. The passive components
PC1-PC4 have commonly coupled first terminals, and are electrically
connected to a conductive via VIA2. A plurality of second terminals
of the passive components PC1-PC4 are respectively coupled to a
plurality of terminals of the switch 611. The switch 611 further
has another terminal coupled to a conductive via VIAL The switch
611 further receives a plurality of sub-signals CT1 and CT2 of a
control signal CTS, and selects one of the second terminals of the
passive components PC1-PC4 to be coupled to the conductive via VIA1
according to the sub-signals CT1 and CT2. In the embodiment, the
conductive via VIA1 may be electrically coupled to a first
reference voltage terminal, and the conductive via VIA2 may be
electrically coupled to a second reference voltage terminal. The
first reference voltage terminal and the second reference voltage
terminal may be two different terminals on the reference voltage
layer of the circuit board.
[0028] In FIG. 6, the passive components PC1-PC4 may be a plurality
of capacitors, respectively. In other embodiments of the invention,
any one of the passive components PC1-PC4 may also be a resistor,
an inductor, or a combination of at least two of a capacitor, a
resistor, and an inductor, which is not limited by the
invention.
[0029] In addition, in the embodiment, the number of the passive
components PC1-PC4 may be more than four. Within an allowable
layout range of the circuit board, the filtering frequency
adjusting device 610 may include any number of the passive
components. In addition, the number of the sub-signals CT1 and CT2
of the control signal CTS may be designed according to the number
of the passive components PC1-PC4. If the number of the sub-signals
CT1 and CT2 of the control signal CTS is N, the number of the
passive components PC1-PC4 may be 2.sup.N at most, and N is a
positive integer.
[0030] In another aspect, the common mode filter of the embodiment
of the invention may further include a controller 620. The
controller 620 is coupled to the filtering frequency adjusting
device 610, and is used to generate the sub-signals CT1 and CT2 of
the control signal CTS. The controller 620 may generate the control
signal CTS according to specification information or command
information of the circuit board. The above-mentioned command
information is issued by an external electronic device or a
user.
[0031] According to the above description, through a switching
operation of the passive components PC1-PC4 of the filtering
frequency adjusting device 610, a passband of the common mode
filter of the embodiment of the invention may be dynamically
adjusted to improve the use efficiency of the common mode
filter.
[0032] In terms of a hardware framework, the switch 611 may be
constructed by using an antenna switch well known in the art. The
controller 620 may be a processor with computing capability.
Alternatively, the controller 620 may be a hardware circuit
designed through a hardware description language (HDL) or any other
digital circuit design method known to those with ordinary
knowledge in the art, and implemented through a field programmable
logic gate array (FPGA), a complex programmable logic device
(CPLD), or an application-specific integrated circuit (ASIC).
[0033] Referring to FIG. 7 below, FIG. 7 is a schematic diagram of
another implementation of a filtering frequency adjusting device of
a common mode filter according to an embodiment of the invention.
The filtering frequency adjusting device includes a variable
capacitor VC1 and/or a variable inductor VL1. The common mode
filter further includes a controller 720. The controller 720 is
used to send a control voltage CTRV to the variable capacitor VC1
and/or the variable inductor VL1, and is used to adjust a
capacitance value of the variable capacitor VC1 and/or adjust an
inductance value of the variable inductor VL1. When the filtering
frequency adjusting device has both of the variable capacitor VC1
and the variable inductor VL1 at the same time, the controller 720
may send different control voltages to respectively adjust the
capacitance value of the variable capacitor VC1 and the inductance
value of the variable inductor VL1. Different from the
implementation of FIG. 6, the controller 720 of the embodiment may
adjust the inductance and capacitance values provided by the
filtering frequency adjusting device in an analog manner, and
dynamically adjust the passband of the common mode filter to
improve the use efficiency of the common mode filter.
[0034] In summary, in the common mode filter of the embodiment of
the invention, the filtering frequency adjusting device is
configured on the slot structure, and the equivalent impedance
provided by the filtering frequency adjusting device is used to
adjust the passband of the common mode filter to achieve impedance
matching of the transmission wire. In this way, the reflection
phenomenon generated in signal transmission may be effectively
reduced to improve the signal quality. In addition, in the
embodiment of the invention, by dynamically adjusting the
equivalent impedance of the filtering frequency adjusting device,
the adjustment operation of impedance matching may be completed
without changing a layout design of the circuit board.
* * * * *