RF switch
The present invention provides an RF switch, including a diode adapted to operate as a switch when a control current is applied thereto, a first CRLH transmission line of a Φ degree phase, which provides one signal transfer path from a terminal 1 to a terminal 2 when the diode is shorted due to application of a control current, and a second CRLH transmission line of a Φ-180 degree phase, which has a 180 degree phase difference from that of the first CRLH transmission line and provides the other signal transfer path from the terminal 1 to the terminal 2 . The present invention provides an RF switch having a broad-band characteristic by employing a CRLH transmission line. More specifically, the present invention provides a ring-shaped RF switch, which has a broad-band characteristic and can also be miniaturized at a low frequency band, by employing a CRLH transmission line having a 180 degree phase difference in a broad band.
1. An RF switch comprising:
a diode adapted to operate as a switch when a control current is applied thereto;
a first CRLH transmission line of a Φ degree phase, which provides one signal transfer path from a terminal 1 to a terminal 2 when the diode is shorted due to application of a control current; and
a second CRLH transmission line of a Φ-180 degree phase, which has a 180 degree phase difference from that of the first CRLH transmission line and provides the other signal transfer path from the terminal 1 to the terminal 2 , wherein the first CRLH transmission line and the second CRLH transmission line comprise N cells having the same electromagnetic characteristic with a CRLH transmission line characteristic, and wherein each of the cells has an electrical length p, which is smaller than ¼ of a wavelength of a designed center frequency.
2. The RF switch of claim 1 , wherein the Φ degree of the first CRLH transmission line is adjusted by controlling capacitance and inductance values included in a transmission line.
3. The RF switch of claim 1 , wherein the first CRLH transmission line and the second CRLH transmission line composed of the N cells satisfy the following Equations:
Φ
CRLH
1
=
N
·
(
ω
L
RH
1
C
RH
1
·
d
+
-
1
ω
L
LH
1
C
LH
1
)
=
N
·
(
Φ
RH
1
(
ω
)
+
Φ
LH
1
(
ω
)
)
,
and
Z
O
=
L
RH
1
C
RH
1
=
L
LH
1
C
LH
1
.
4. The RF switch of claim 1 , wherein the diode includes a PIN diode, which has an excellent linearity and very small distortion and can be switched at high speed.
5. The RF switch of claim 1 , wherein the first CRLH transmission line and the second CRLH transmission line satisfy the following Equations in order to satisfy a constant phase difference:
Φ
CRLH
1
=
Φ
CRLH
2
+
π
Δ
Φ
CRLH
1
Δ
ω
=
Δ
Φ
CRLH
2
Δ
ω
,
and
Z
O
=
L
RH
C
RH
=
L
LH
C
LH
.
6. A radio terminal comprising an RF switch comprising:
a diode adapted to operate as a switch when a control current is applied thereto;
a first CRLH transmission line of a Φ degree phase, which provides one signal transfer path from a terminal 1 to a terminal 2 when the diode is shorted due to application of a control current; and
a second CRLH transmission line of a Φ-180 degree phase, which has a 180 degree phase difference from that of the first CRLH transmission line and provides the other signal transfer path from the terminal 1 to the terminal 2 , wherein the first CRLH transmission line and the second CRLH transmission line comprise N cells having the same electromagnetic characteristic with a CRLH transmission line characteristic, and wherein each of the cells has an electrical length p, which is smaller than ¼ of a wavelength of a designed center frequency.