RF SWITCH

• US 20100019861A1
• Filed: 02/04/2008
• Published: 01/28/2010
• Est. Priority Date: 02/05/2007
• Status: Active Grant

• Current Assignee: Kespion Company Limited
• Original Assignee: Emw Co., Ltd.
• Inventors: Shin, Dong Ryul, Sung, Won Mo, Ryou, Byung Hoon, Park, Chang Hyun, Kim, Jeong Pyo
• Granted Patent: US 8,102,221 B2
• Time in Patent Office: Days
• US Class Current: 333/103
• CPC Class Codes: H01P 1/15 by semiconductor devices

Abstract

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.

Claims

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 form 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.

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 are composed of N cells having the same electromagnetic characteristic with a CRLH transmission line characteristic.

4. The RF switch of claim 3, wherein each of the cells has an electrical length p, which is smaller than ¼

of a wavelength of a designed center frequency.

5. The RF switch of claim 3, wherein the first CRLH transmission line and the second CRLH transmission line composed of the N cells satisfy the following Equations:

$\begin{array}{c}{\mathrm{\Phi <br><br>}}_{\mathrm{CRLH}<br><br><br><br>1}=N·<br><br>\left(\mathrm{\omega <br><br>}<br><br>\sqrt{L_{\mathrm{RH}<br><br><br><br>1}<br><br>C_{\mathrm{RH}<br><br><br><br>1}}·<br><br>d+\frac{-1}{\mathrm{\omega <br><br>}<br><br>\sqrt{L_{\mathrm{LH}<br><br><br><br>1}<br><br>C_{\mathrm{LH}<br><br><br><br>1}}}\right)\\ =N·<br><br>\left({\mathrm{\Phi <br><br>}}_{\mathrm{RH}<br><br><br><br>1}<br><br>\left(\mathrm{\omega <br><br>}\right)+{\mathrm{\Phi <br><br>}}_{\mathrm{LH}<br><br><br><br>1}<br><br>\left(\mathrm{\omega <br><br>}\right)\right),\end{array}$ $\mathrm{and}$ $Z_O=\sqrt{\frac{L_{\mathrm{RH}<br><br><br><br>1}}{C_{\mathrm{RH}<br><br><br><br>1}}}=\sqrt{\frac{L_{\mathrm{LH}<br><br><br><br>1}}{C_{\mathrm{LH}<br><br><br><br>1}}}$

6. 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.

7. 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:

${\mathrm{\Phi <br><br>}}_{\mathrm{CRLH}<br><br><br><br>1}={\mathrm{\Phi <br><br>}}_{\mathrm{CRLH}<br><br><br><br>2}+\mathrm{\pi <br><br>}$ $\frac{\mathrm{\Delta <br><br>}<br><br><br><br>{\mathrm{\Phi <br><br>}}_{\mathrm{CRLH}<br><br><br><br>1}}{\mathrm{\Delta <br><br>}<br><br><br><br>\mathrm{\omega <br><br>}}=\frac{\mathrm{\Delta <br><br>}<br><br><br><br>{\mathrm{\Phi <br><br>}}_{\mathrm{CRLH}<br><br><br><br>2}}{\mathrm{\Delta <br><br>}<br><br><br><br>\mathrm{\omega <br><br>}},<br><br>\mathrm{and}<br><br><br><br>Z_O=\sqrt{\frac{L_{\mathrm{RH}}}{C_{\mathrm{RH}}}}=\sqrt{\frac{L_{\mathrm{LH}}}{C_{\mathrm{LH}}}}$

8. 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 form 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.