Band stop filter of composite right/left handed structure and the manufacturing method thereof
Provided are a band stop filter of a CRLH structure and a manufacturing method thereof. A band stop filter of a CRLH structure according to an exemplary embodiment of the present invention includes a microstrip transmission line formed on a substrate; a right handed material (RHM) region including a first stub and a first capacitor connected to the microstrip transmission line in parallel and stopping a signal of a first frequency band passing through the microstrip transmission line; and a left handed material (LHM) region further provided between the first stub and the first capacitor to block a signal of a second frequency band passing through the microstrip transmission line.
1. A band stop filter of a composite right/left handed (CRLH) structure, comprising:
a microstrip transmission line formed on a substrate;
a right handed material (RHM) region including a first stub and a first capacitor connected to the microstrip transmission line in parallel and stopping a signal of a first frequency band passing through the microstrip transmission line; and
a left handed material (LHM) region further provided between the first stub and the first capacitor to block a signal of a second frequency band passing through the microstrip transmission line.
2. The band stop filter of claim 1 , wherein the LHM region includes a second capacitor and a second stub.
3. The band stop filter of claim 2 , wherein a capacitance C L of the second capacitor and an inductance L L of the second stub are determined by the following equations:
L
L
≈
2
N
Z
τ
[
1
-
(
ω
1
/
ω
2
)
2
]
π
ω
1
[
1
+
(
ω
1
/
ω
2
)
2
]
C
L
≈
2
N
[
0.76
-
(
ω
1
/
ω
2
)
2
]
π
ω
1
Z
τ
[
1
+
(
ω
1
/
ω
2
)
2
]
where ω 1 is 2πf 1 (in this case, f 1 is a central frequency of the first frequency band), ω 2 is 2πf 2 (in this case, f 2 is a central frequency of the second frequency band), Zτ is 50Ω, and N is 1.
4. The band stop filter of claim 2 , wherein characteristic values of the first stub and the first capacitor of the RHM region and characteristic values of the second stub and the second capacitor of the LHM region are adjustable, to thereby change the first frequency band and the second frequency band.
5. The band stop filter of claim 1 , wherein an inductance L R of the first stub and a capacitance of C R of the first capacitor are determined by the following equations:
L
R
≈
Z
τ
[
(
ω
1
/
ω
2
)
+
1.76
]
2
N
ω
2
[
1
-
(
ω
1
/
ω
2
)
2
]
C
R
≈
π
[
(
ω
1
/
ω
2
)
+
1
]
2
N
ω
2
Z
τ
[
1
-
(
ω
1
/
ω
2
)
2
]
where ω 1 is 2πf 1 (in this case, f 1 is a central frequency of the first frequency band), ω 2 is 2πf 2 (in this case, f 2 is a central frequency of the second frequency band), Zτ is 50Ω, and N is 1.
6. The band stop filter of claim 2 , wherein the first stub and the second stub are each configured as a microstrip or an inductor.
7. The band stop filter of claim 1 , wherein the band stop filter has a left handed characteristic where a β value of the band stop filter is 0 or a negative number.
8. The band stop filter of claim 1 , wherein the band stop filter is formed on one surface of the substrate.
9. The band stop filter of claim 1 , wherein each end of the microstrip transmission line is connected in series with a terminal.
10. The band stop filter of claim 2 , wherein at least one of the microstrip transmission line, the first stub, the second stub, the first capacitor, and the second capacitor is connected to a filter blocking a third frequency band.
11. A method for manufacturing a band stop filter of a composite right/left handed (CRLH) structure, comprising:
forming a microstrip transmission line on a substrate;
connecting in parallel a right handed material (RHM) region including a first stub and a first capacitor to the microstrip transmission line, and blocking a signal of a first frequency band passing through the microstrip transmission line; and
adding a left handed material (LHM) region blocking a signal of a second frequency band passing through the microstrip transmission line between the first stub and the first capacitor.
12. The method of claim 11 , further comprising determining an inductance of the first stub and a capacitance C R of the first capacitor by the following equations:
L
R
≈
Z
τ
[
(
ω
1
/
ω
2
)
+
1.76
]
2
N
ω
2
[
1
-
(
ω
1
/
ω
2
)
2
]
C
R
≈
π
[
(
ω
1
/
ω
2
)
+
1
]
2
N
ω
2
Z
τ
[
1
-
(
ω
1
/
ω
2
)
2
]
where ω 1 is 2πf 1 (in this case, f 1 is a central frequency of the first frequency band), ω 2 is 2πf 2 (in this case, f 2 is a central frequency of the second frequency band), Zτ is 50Ω, and N is 1.
13. The method of claim 11 , further comprising determining an inductance L L of a second stub and a capacitance C L of a second capacitor by the following equations, the LHM region including the second stub and the second capacitor:
L
L
≈
2
N
Z
τ
[
1
-
(
ω
1
/
ω
2
)
2
]
π
ω
1
[
1
+
(
ω
1
/
ω
2
)
2
]
C
L
≈
2
N
[
0.76
-
(
ω
1
/
ω
2
)
2
]
π
ω
1
Z
τ
[
1
+
(
ω
1
/
ω
2
)
2
]
where ω 1 is 2πf 1 (in this case, f 1 is a central frequency of the first frequency band), ω 1 is 2πf 2 (in this case, f 2 is a central frequency of the second frequency band), Z τ is 50Ω, and N is 1.
14. The method of claim 11 , further comprising:
mounting a respective terminal at each end of the microstrip transmission line; and
connecting a line in series to each of the terminals at each end of the transmission line.
15. The method of claim 13 , further comprising confirming whether a β value calculated by the following equation is a negative number:
β
=
β
PRH
+
β
PLH
=
ω
1
L
R
C
R
-
1
ω
2
L
L
C
L
where L R is an inductance of the first stub and C R is a capacitance of the first capacitor.
16. The method of claim 15 , further comprising if the β value is not a negative number, changing at least one of the capacitance of the first capacitor and the capacitance of the second capacitor.
17. The method of claim 13 , further comprising:
changing at least one of characteristic values of the first stub and the first capacitor of the RHM region and characteristic values of the second stub and the second capacitor of the LHM region to thereby change the first frequency band and the second frequency band.
18. A method for manufacturing a band stop filter of a composite right/left handed (CRLH) structure, comprising:
determining first and second frequency bands to be blocked;
designing a first stub, a second stub, a first capacitor, and a second capacitor according to the determination;
forming, on a substrate, a microstrip transmission line, the first stub connected to the microstrip transmission line in parallel, and the second stub formed to be spaced by a predetermined interval from the first stub;
further connecting the first capacitor between a second end of the first stub and a first end of the second stub;
connecting the first end of the second stub to a first end of the second capacitor; and
connecting a second end of the second stub and a second end of the second capacitor to a ground,
wherein an inductance L R of the first stub, an inductance L L of the second stub, a capacitance C R of the first capacitor, and a capacitance C L of the second capacitor are determined by the following equations:
L
R
≈
Z
τ
[
(
ω
1
/
ω
2
)
+
1.76
]
2
N
ω
2
[
1
-
(
ω
1
/
ω
2
)
2
]
C
R
≈
π
[
(
ω
1
/
ω
2
)
+
1
]
2
N
ω
2
Z
τ
[
1
-
(
ω
1
/
ω
2
)
2
]
L
L
≈
2
N
Z
τ
[
1
-
(
ω
1
/
ω
2
)
2
]
π
ω
1
[
1
+
(
ω
1
/
ω
2
)
2
]
C
L
≈
2
N
[
0.76
-
(
ω
1
/
ω
2
)
2
]
π
ω
1
Z
τ
[
1
+
(
ω
1
/
ω
2
)
2
]
where ω 1 is 2πf 1 , f 1 being a central frequency of the first frequency band, ω 2 is 2πf 2 , f 2 being a central frequency of the second frequency band, Zτ is 50Ω, and N is 1.