U.S. patent application number 14/172236 was filed with the patent office on 2014-06-05 for radio frequency filter employing notch structure.
This patent application is currently assigned to KMW INC.. The applicant listed for this patent is KMW INC.. Invention is credited to Nam-Shin Park.
Application Number | 20140152403 14/172236 |
Document ID | / |
Family ID | 47669061 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140152403 |
Kind Code |
A1 |
Park; Nam-Shin |
June 5, 2014 |
RADIO FREQUENCY FILTER EMPLOYING NOTCH STRUCTURE
Abstract
The present invention relates to a radio frequency filter
employing a notch structure, wherein the notch structure is a dual
notch structure which comprises: a C notch structure formed in a
predetermined region at a partition between two cavities to be
cross-coupled; and an L notch structure formed together with the C
notch structure in a predetermined region at a partition between
two cavities.
Inventors: |
Park; Nam-Shin; (Hwaseong
Gyeonggi-Do, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KMW INC. |
Hwaseong |
|
KR |
|
|
Assignee: |
KMW INC.
Hwaseong
KR
|
Family ID: |
47669061 |
Appl. No.: |
14/172236 |
Filed: |
February 4, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/KR2012/006247 |
Aug 6, 2012 |
|
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14172236 |
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Current U.S.
Class: |
333/202 ;
333/203 |
Current CPC
Class: |
H03H 7/0115 20130101;
H01P 1/2084 20130101; H01P 1/2053 20130101 |
Class at
Publication: |
333/202 ;
333/203 |
International
Class: |
H01P 1/20 20060101
H01P001/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2011 |
KR |
10-2011-0078275 |
Claims
1. A radio frequency filter employing a dual notch structure,
comprising: a C type notch structure formed in a predetermined
region on a partition interposed between two cavities to be
cross-coupled; and an L type notch structure formed along with the
C type notch structure in the predetermined region of the partition
between the two cavities.
2. The radio frequency filter as claimed in claim 1, wherein the L
type notch structure extends to a lower end of the C type notch
structure and is formed on the partition.
3. The radio frequency filter as claimed in claim 1, wherein the L
type notch structure is formed in another region on the partition,
separately from the C type notch structure.
4. The radio frequency filter as claimed in claim 3, wherein the C
type notch structure is formed in a center region of the partition
by reference of a planar surface, and the L type notch structure is
formed around the C type notch structure in a certain region on the
partition.
5. The radio frequency filter as claimed in claim 1, wherein the
radio frequency filter is a three stage filter having a structure
in that first, second and third cavities are arranged in a
triangular shape, and are sequentially coupled, in which the dual
notch structure including the C type notch structure and the L type
notch structure together is formed on the partition interposed
between the first cavity and the third cavity, two notches are
created at a lower end of a processing band of the filter, and one
notch is created at an upper end of the processing band, so as to
implement notches at both ends of the processing band.
6. The radio frequency filter as claimed in claim 1, wherein the
radio frequency filter is a four stage filter having a structure in
that first, second, third and fourth cavities are arranged in pairs
in two columns, and sequentially cross-coupled, in which the dual
notch structure including the C type notch structure and the L type
notch structure is formed on a partition interposed between the
first cavity and the fourth cavity, and two notches are created at
each of the lower end and the upper end of the processing band of
the filter, so as to implement the dual notch which is a bilateral
symmetry.
7. The radio frequency filter as claimed in claim 1, wherein the
radio frequency filter is a six stage filter having a structure in
that first, second, third, fourth, fifth and sixth cavities are
arranged in three pairs in two columns, and sequentially
cross-coupled, in which the dual notch structure including the C
type notch structure and the L type notch structure is formed on a
partition interposed between the second cavity and the fifth
cavity, or a partition interposed between the first cavity and the
sixth cavity.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of International Application No.
PCT/KR2012/006247 filed on Aug. 6, 2012, which claims priority to
Korean Application No. 10-2011-0078275 filed on Aug. 5, 2011, which
applications are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a radio frequency filter
for use in a wireless communication system, and more particularly,
to a radio frequency filter employing a notch structure.
BACKGROUND ART
[0003] The term "radio frequency filter (hereinafter, referred to
as `filter`) refers to an apparatus for performing a function of
passing or filtering signals in any predetermined frequency band,
which is classified into a low pass filter, a band pass filter, a
high pass filter, a band stop filter and the like according to a
frequency band to be filtered.
[0004] The filter has an important characteristic such as an
insertion loss and a skirt feature. The insertion loss means
electric power to be lost when the signals pass through the filter,
and the skirt feature means a steep extent of a passing band and a
filtering band of the filter.
[0005] The insertion loss and the skirt feature have a trade-off
relationship with each other according to the number of stages
(degrees) of the filter. As the stages of the filter increase, the
skirt feature becomes better but the insertion loss becomes
worse.
[0006] In order to improve the skirt feature of the filter without
the stages of the filter being increased, a method of forming a
notch (reduction pole) is generally used. This is a method capable
of enhancing the skirt feature of the filter, in which the notch is
formed in a specific frequency band without the stages of the
filter being increased, so as to enhance the skirt feature of the
filter.
[0007] There is a cross coupling method as a most general method
forming the notch. A technology relating to formation of the notch
using the cross coupling method is disclosed in U.S. Pat. No.
6,342,825, entitled "Band-pass filter having tri-section", issued
to Hershtig, Rafi and assigned to `K&L Microwave Co.` on Jan.
29, 2002.
SUMMARY
[0008] The invention has been made to solve the above-mentioned
problem in the prior art, and an aspect of the present invention is
to provide a radio frequency filter employing a notch structure
capable of providing a notch feature to the radio frequency
filter.
[0009] Another aspect of the present invention is to provide a
radio frequency filter employing a notch structure capable of
generating notch features at both ends of a three stage filter and
a four stage filter.
[0010] In accordance with an aspect of the present invention, a
radio frequency filter employing a notch structure is provided. The
radio frequency filter having a dual notch structure includes: a C
type notch structure formed on a predetermined portion of a
partition between two cavities to be cross coupled; and an L type
notch structure formed along the C type notch structure.
Advantageous Effect
[0011] As described above, the radio frequency filter employing the
notch structure according to the present invention has a more
efficient structure capable of providing multiple notch features to
the radio frequency filter, particularly, allowing a generation of
the notch feature in both the three stage filter and the four stage
filter.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a schematic view illustrating a structure of a
general three stage filter;
[0013] FIG. 2 is a graph illustrating a frequency filtering
characteristic of the three stage filter shown in FIG. 1;
[0014] FIG. 3 is a schematic view illustrating a structure of the
three stage filter employing a general notch structure;
[0015] FIG. 4 is a circuit diagram illustrating an equivalent
circuit of the three stage filter shown in FIG. 3;
[0016] FIG. 5 is a graph illustrating a frequency filtering
characteristic of the three stage filter shown in FIG. 3;
[0017] FIG. 6 is a schematic view illustrating a structure of the
three stage filter employing a notch structure according to a first
embodiment of the present invention;
[0018] FIG. 7 is a circuit diagram illustrating an equivalent
circuit of the three stage filter shown in FIG. 6;
[0019] FIG. 8 is a graph illustrating a frequency filtering
characteristic of the three stage filter shown in FIG. 3;
[0020] FIG. 9 is a schematic view illustrating a structure of four
stage filter employing a notch structure according to a second
embodiment of the present invention;
[0021] FIG. 10 is a circuit diagram illustrating an equivalent
circuit of the four stage filter shown in FIG. 9;
[0022] FIG. 11 is a graph illustrating a frequency filtering
characteristic of the four stage filter shown in FIG. 9;
[0023] FIG. 12 is a schematic view illustrating a structure of the
four stage filter employing a notch structure according to a third
embodiment of the present invention;
[0024] FIG. 13 is a graph illustrating a frequency filtering
characteristic of the four stage filter shown in FIG. 12;
[0025] FIG. 14 is a schematic view illustrating a structure of a
generally considered four stage filter;
[0026] FIG. 15 is a circuit diagram illustrating an equivalent
circuit of the four stage filter shown in FIG. 14;
[0027] FIG. 16 is a graph illustrating a frequency filtering
characteristic of the four stage filter shown in FIG. 14;
[0028] FIG. 17 is a schematic view illustrating a structure of six
stage filter employing a notch structure according to a fourth
embodiment of the present invention;
[0029] FIG. 18 is a circuit diagram illustrating an equivalent
circuit of the six stage filter shown in FIG. 17;
[0030] FIG. 19 is a graph illustrating a frequency filtering
characteristic of the six stage filter in FIG. 17;
[0031] FIG. 20 is a schematic view illustrating a structure of the
six stage filter employing a notch structure according to a fifth
embodiment of the present invention;
[0032] FIG. 21 is a graph illustrating a frequency filtering
characteristic of the six stage filter shown in FIG. 20;
[0033] FIG. 22 is a schematic view illustrating a structure of the
six stage filter employing a notch structure according to a sixth
embodiment of the present invention; and
[0034] FIG. 23 is a graph illustrating a frequency filtering
characteristic of the six stage filter shown in FIG. 22.
DETAILED DESCRIPTION
[0035] Hereinafter, an exemplary embodiment of the present
invention will be described in detail with reference to the
accompanying drawings.
[0036] Firstly, referring to FIGS. 1 to 5, formation of a notch
using a cross-coupling will be described. FIG. 1 is a schematic
perspective view illustrating a structure of a general three stage
filter, and FIG. 2 is a graph illustrating a frequency filtering
characteristic of the three stage filter shown in FIG. 1. FIG. 3 is
a schematic perspective view illustrating a structure of the three
stage filter employing a notch structure, FIG. 4 is a circuit
diagram illustrating an equivalent circuit of the three stage
filter shown in FIG. 3, and FIG. 5 is a graph illustrating a
frequency filtering characteristic of the three stage filter shown
in FIG. 3.
[0037] Typically, the filter has a structure in that a multiple
dielectric substances or metallic resonators are connected by
multiple stages in a plurality of cavities defined by a metal
housing and a cover, and in FIGS. 1 and 3, the illustration of the
structure of the metal housing will be omitted for convenience of
the description.
[0038] Referring to FIGS. 1 and 3, a three stage filter has a
structure in which a first cavity 11, a second cavity 12, and a
third cavity 13 are cross-coupled with one another, and have a
first resonator 21, a second resonator 22, and a third resonator
23, respectively. The first resonator 21 of the first cavity 11 is
connected with an input connector 31 to receive an input signal,
and the third resonator 13 of the third cavity 13 is connected with
an output connector 32 to provide an output signal.
[0039] Accordingly, a signal input into the input connector 31 is
output to the output connector 32 after sequentially passing the
first resonator 21, the second resonator 22, and the third
resonator 23, as indicated by an arrow in FIG. 1.
[0040] In the filter having no the notch structure as shown in FIG.
1, only a sequential coupling between adjacent resonators is
basically established, while in the filter employing a capacity (C)
type notch structure 41 as shown in FIG. 3, a cross coupling
between the resonators, which are not adjacent, is achieved.
[0041] The C type notch structure 41 has a metal stick forming a
capacitance coupling between the first resonator 21 and the third
resonator 23 as an important structure. The metal stick penetrates
an inner wall partitioning the first and third cavities 11 and 13.
At this time, the metal stick is covered with a supporting
substance of a dielectric material (not shown) such as Teflon in
order to electrically isolate the metal stick from the inner wall,
and joined to the inner wall. At this time, the inner wall may have
a through-hole structure formed therein in which the metal stick is
installed, or may have a lower portion at which the metal stick is
installed. However, since it is difficult to form the through-hole
in the inner wall in an operating process, an upper end of the
inner wall is partially cut off, and the metal stick covered with
the supporting substance is generally installed on the
corresponding cut off portion. Such a supporting substance
functions as an insulation of the metal stick, and also is fixed to
the corresponding portion at which the metal stick is installed
because of an engagement with the cut off portion of the inner
wall, resulting in a fixing of the metal stick.
[0042] Referring to FIGS. 2 and 4, it is understood that the three
stage filter having the C type notch structure 41 shown in FIG. 3
creates a notch at a lower portion of a processing band (a low
frequency band of the processing band), in comparison with the
general three stage filter.
[0043] A four or more stage filter may employ an inductor (L) type
notch structure as well as the C type notch structure 41, in which
the L type notch structure is constituted in the form of a window
formed in the partition between the receiving spaces of two
resonators to be cross-coupled, and creates an inductance coupling
between both resonators.
[0044] The three stage filter shown in FIG. 1 has no separate notch
structure, but since a weak coupling is created between the first
resonator 21 of the first stage filter and the third resonator 23
of the third stage filter through the third resonator 23 of the
third stage filter, a weak L type notch may be formed without
hardly having effect on the filtering characteristic.
[0045] In the above-described structure, particularly, the three
stage filter, the notch structure must have been employed only
between the first stage and the third stage. It has been recognized
that it has been difficult to implement multiple notches or to
create notches at both ends of the processing bands, that is, a
lower end and an upper end of the processing band, without a
special structure being added inside or outside of the filter.
[0046] FIG. 6 is a schematic perspective view illustrating a
structure of the three stage filter employing a notch structure
according to a first embodiment of the present invention, FIG. 7 is
a circuit diagram illustrating an equivalent circuit of the three
stage filter shown in FIG. 6, and FIG. 8 is a graph illustrating
the frequency filtering characteristic of the three stage filter
shown in FIG. 3. In FIG. 6, similarly to FIGS. 1 and 3, it is
omitted to show the structure of the metal housing for the
convenience of the description.
[0047] Referring to FIG. 6, the three stage filter employing the
notch structure according to the first embodiment of the present
invention includes a first cavity 11, a second cavity 12 and a
third cavity 13, which are arranged in the triangular form and
sequentially coupled, and which include a first resonator 21, a
second resonator 22, and a third resonator 23, respectively. The
first resonator 21 of the first cavity 11 is connected with an
input connector 31 to receive an input signal, and the third
resonator 13 of the third cavity 13 is connected with an output
connector 32 to provide an output signal.
[0048] At this time, according to the characteristic of the present
invention, the C type notch structure 41 is installed to the
partition between the first cavity 11 and the third cavity 13 to be
cross-coupled, and in addition the L type notch structure 51 of the
window structure extends to a lower end of the C type notch
structure 41 and is formed on the partition. In FIG. 6, although it
is shown that the L type notch structure 51 has an identical width
to the cut-off portion of the partition in order to install the C
type notch structure 41, the L type notch structure 51 is slightly
narrower than the width of the cut-off portion on which the C type
notch structure 41, i.e., a step portion, is installed, so that the
supporting substance is rigidly fixed to the partition on which the
C type notch structure 41 is installed.
[0049] As shown in FIG. 6, the notch structure according to the
first embodiment of the present invention may be regarded as a dual
notch structure in which the C type notch structure 41 and the L
type notch structure 51 are complex.
[0050] As described above, if the three stage filter employs the
dual notch structure of the present invention, it is understood
that the notches are created at both ends of the processing band of
the filter as indicated by an arrow in FIG. 8. That is, two notches
are created at the lower end of the processed band, while one notch
is created at an upper end of the processed band.
[0051] FIG. 9 is a schematic perspective view illustrating the
structure of the four stage filter employing the notch structure
according to the second embodiment of the present invention, FIG.
10 is a circuit diagram illustrating an equivalent circuit of the
four stage filter, and FIG. 11 is a graph illustrating a frequency
filtering characteristic of the four stage filter in FIG. 9.
[0052] Referring to FIG. 9, the four stage filter employing the
notch structure according to the second embodiment of the present
invention has a structure in that a first cavity 11, a second
cavity 12, a third cavity 13 and a fourth cavity 14 are arranged in
two columns and sequentially coupled with each other in two pairs.
The first, second, third and fourth cavities 11, 12, 13 and 14 have
a first, second, third and fourth resonators 21, 22, 23 and 24
respectively. The first resonator 21 of the first cavity 11 is
connected with an input connector 31 to receive an input signal,
and the fourth resonator 14 of the fourth cavity 14 is connected
with an output connector 32 to provide an output signal.
[0053] At this time, according to the characteristic of the present
invention, the C type notch structure 41 is installed to the
partition between the first cavity 11 and the fourth cavity 14, and
in addition the L type notch structure 51 of the window structure
extends to a lower end of the C type notch structure 41 and is
formed on the partition. That is, the notch structure according to
the characteristic of the present invention shown in FIG. 9 may
have a similar structure to the dual notch structure shown in FIG.
6.
[0054] As described above, if the four stage filter employs the
dual notch structure of the present invention, it is understood
that the notches are created at both ends of the processing band of
the filter as shown in FIG. 11. That is, two notches are created at
the lower and upper ends of the processing band, so as to implement
the dual notches which are symmetrical to left and right.
[0055] FIG. 12 is a schematic perspective view illustrating a
structure of the four stage filter employing a notch structure
according to the third embodiment of the present invention, and
FIG. 13 is a graph illustrating the frequency filtering
characteristic of the four stage filter of FIG. 12. The equivalent
circuit of the notch structure according to the third embodiment
shown in FIG. 12 is identical to the equivalent circuit of the
second embodiment shown in FIG. 10.
[0056] Referring to FIG. 12, the four stage filter employing the
notch structure according to the third embodiment of the present
invention has a structure in that a first cavity 11, a second
cavity 12, a third cavity 13 and a fourth cavity 14 are
sequentially coupled with one another, similarly to the third
embodiment shown in FIG. 9. Each of the first resonator 12, the
second resonator 22, the third resonator 23 and the fourth
resonator 24 is prepared for each cavity. The first resonator 21 of
the first cavity 11 is connected with an input connector 31 to
receive an input signal, and the fourth resonator 14 of the fourth
cavity 14 is connected with an output connector 32 to provide an
output signal.
[0057] At this time, according to the characteristic of the present
invention, the C type notch structure 41 is installed to the
partition between the first cavity 11 and the fourth cavity 14, and
in addition the L type notch structure 51 of the window structure
is formed at another region on the partition, differently from the
C type notch structure 41. The C type notch structure 41 is formed
at a center portion of the partition by reference of a plane
surface, and the L type notch structure 51 is formed on any side of
the partition to correspond to the type notch structure 41.
[0058] If the L type notch structure 51 and the C type notch
structure 41 are separately installed on the partition, it is easy
to separately tune the L type notch and the C type notch.
[0059] In the case of employing the dual notch structure according
to the third embodiment of the present invention as described
above, as shown in FIG. 13, it is noted that the filter has the
filter characteristic almost similar to the filter characteristic
according to the second embodiment as shown in FIG. 11.
[0060] On the other hand, in FIG. 12, it is shown that the L type
notch structure 51 is formed at a position near the input connector
31 and the output connector 32. However, as indicated by an arrow
in FIG. 12, the L type notch structure 51 may be formed. In this
case, the filter also may have a similar characteristic. In this
case, however, the notch characteristic may be weak.
[0061] FIG. 14 is a schematic perspective view illustrating a
structure of a generally considered four stage filter, FIG. 15 is a
circuit diagram illustrating an equivalent circuit of the four
stage filter of FIG. 14, and FIG. 16 is a graph illustrating a
frequency filtering characteristic of the four stage filter of FIG.
14.
[0062] Referring to FIGS. 14 to 16, the four stage filter employing
the generally considered notch structure will be described. In
comparison with the four stage filter according to the
characteristic of the present invention, the four stage filter
shown in FIG. 14 has a C type notch structure 41 installed on a
partition interposed between the first cavity 11 and the third
cavity 13, and the general L type notch structure 42 may be
interposed between the first cavity 11 and the fourth cavity
14.
[0063] As described above, it is understood that only two notches
are created in the four stage filter employing the notch structure
as shown in FIG. 14.
[0064] FIG. 17 is a schematic perspective view illustrating the
structure of the six stage filter employing the notch structure
according to the fourth embodiment of the present invention, FIG.
18 is a circuit diagram illustrating an equivalent circuit of the
six stage filter, and FIG. 19 is a graph illustrating a frequency
filtering characteristic of the six stage filter in FIG. 17.
[0065] Referring to FIG. 17, the six stage filter employing the
notch structure according to the fourth embodiment of the present
invention has a structure in that a first cavity 11, a second
cavity 12, a third cavity 13, a fourth cavity 14, a fifth cavity
15, and a sixth cavity 16 are arranged in two columns, each of
which has three cavities, and are sequentially coupled with each
other.
[0066] At this time, according to the characteristic of the present
invention, the C type notch structure 41 is installed to the
partition between the second cavity 12 and the fourth cavity 15,
and in addition the L type notch structure 51 of the window
structure extends to a lower end of the C type notch structure 41
and is formed on the partition. That is, the notch structure
according to the characteristic of the present invention shown in
FIG. 17 may have a similar structure to the dual notch structure
shown in FIG. 9.
[0067] In the case that the six stage filter employs the dual notch
structure of the present invention as described above, it is
understood that an additional notch is created at a lower end of
the processing band of the filter as indicated by an arrow in FIG.
19.
[0068] FIG. 20 is a schematic perspective view illustrating a
structure of a six stage filter employing a notch structure
according to the fifth embodiment of the present invention, and
FIG. 21 is a graph illustrating the frequency filtering
characteristic of the six stage filter of FIG. 20. The equivalent
circuit of the notch structure according to the fifth embodiment
shown in FIG. 20 may be identical to the equivalent circuit of the
fourth embodiment shown in FIG. 18.
[0069] Referring to FIG. 20, in the six stage filter employing the
notch structure according to the fifth embodiment of the present
invention, the C type notch structure 41 is installed on a
partition between the second cavity 12 and the fourth cavity 15,
similarly to the filter in FIG. 17. The L type notch structure 51
of a window structure may be formed at another region on the
partition, separately from the C type notch structure 41. That is,
the notch structure according to the characteristic of the present
invention shown in FIG. 20 may have a similar structure to the dual
notch structure shown in FIG. 12.
[0070] In the case of employing the dual notch structure according
to the fifth embodiment of the present invention as described
above, as shown in FIG. 21, it is noted that the filter has the
filter characteristic almost similar to the filter characteristic
according to the fourth embodiment as shown in FIG. 19.
[0071] FIG. 22 is a schematic perspective view illustrating a
structure of the six stage filter employing a notch structure
according to the sixth embodiment of the present invention, and
FIG. 23 is a graph illustrating the frequency filtering
characteristic of the six stage filter of FIG. 22.
[0072] Referring to FIG. 22, the six stage filter employing the
notch structure according to the sixth embodiment of the present
invention has a similar structure to the structures of the
embodiments shown in FIGS. 17 and 20, but has the difference in
that the C type notch structure 41 and the L notch type structure
51 extending to a lower end of the C type notch structure 41 are
formed at a first stage, i.e., a partition between a first cavity
11 and a sixth cavity 16.
[0073] In view of the filtering characteristic of the filter having
the structure, as shown in FIG. 23, two notches are created at each
of a lower end and an upper end of the processing band of the
filter.
[0074] As described above, the radio frequency filter employing the
notch structure according to the embodiments of the present
invention may be implemented, and also the notch structure
according to the characteristic of the present invention may be
applied to multiple stage filters having more than the six stages,
beyond the above-described embodiments. Further, two or more dual
notch structures having a combination of the L type notch and the C
type notch according to the characteristic of the present invention
may be employed to the multiple stage filters having more stage
than the six stage filter. Furthermore, the general L type notch
structure or the general C type notch structure is adjustably
incorporated with the dual notch structure according to the
characteristic of the present invention, and a combination of the L
type notch or the C type notch with the dual notch structure may be
employed to the filter.
* * * * *