Micro-electro mechanical system having single anchor

Details Micro-electro mechanical system having single anchor Micro-electro mechanical system having single anchor

2002-05-10

2003-09-30

Pascal, Robert (Department: 2817)

Wave transmission lines and networks

Long line elements and components

Switch

C333S246000

Reexamination Certificate

active

06628183

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-frequency micro-electro mechanical system (hereinafter, “MEMS”), and more particularly, to an MEMS switch having a single anchor.
2. Description of the Related Art
An MEMS switch is a switch that is commonly adopted for signal routing or impedance matching networks in a wire communication system that uses microwave or millimeter wave.
In the existing monolithic microwave integrated circuits, a radio frequency (RF) switch is realized mainly with GaAs FET or a pin diode. However, the use of these elements causes a considerable insertion loss when the RF switch is switched on, and deteriorates signal separation characteristics when the RF switch is switched off.
To improve these problems, much research is made on developing various MEMS switches, and further, a tremendous increase in Mobile communication phone markets increases the importance of the MEMS switches. As a result, a variety of MEMS are suggested.
FIG. 1
is a plan view of a conventional MEMS switch. Referring to
FIG. 1
, a moving plate
10
is bilateral symmetry, being placed across input-output transmission lines
12
and
14
and a grounding line
16
, as shown in FIG.
2
. Referring to
FIG. 2
, the input-output transmission lines
12
and
14
are installed on a substrate S to be distant away from each other, and the moving plate
10
is placed over these input-output transmission lines
12
and
14
.
Here, reference numerals
18
and
20
denote first and second anchors for holding the moving plate
10
. The first and second anchors
18
and
20
are symmetrical with regard to the input-output transmission lines
12
and
14
, and connected to the both ends of the moving plate
10
via first and second springs
22
and
24
, respectively. Due to this structure, with the first and second anchors
18
and
20
as holding points, the moving plate
10
is in contact with the input-output transmission lines
12
and
14
by a driving electrode (not shown) when a driving force is given to the moving plate
10
, and returns back to the original position when the driving force is canceled from the moving plate
10
.
FIG. 3
is a cross-sectional view of the conventional MEMS switch of
FIG. 1
, taken along the line
3
-
3
′. Referring to
FIG. 3
, first and second driving electrodes
26
and
28
are installed between the first and second anchors
18
and
20
, and actuate the moving plate
10
to be in contact the first and second anchors
18
and
20
. The first and second driving electrodes
26
and
28
are separated from each other at a predetermined interval.
Although not shown in the drawings, the input-output transmission lines
12
and
14
and the grounding line
16
are positioned between the first and second driving electrodes
26
and
28
.
Referring to
FIGS. 1 and 2
, the conventional MEMS switch has the moving plate
10
across the input-output transmission lines
12
and
14
and the grounding line
16
. Thus, when the moving plate
10
is actuated, it comes in contact with the grounding line
16
, which causes the leakage of a transmitted signal. Also, the both ends of the moving plate
10
are fixed by the first and second anchors
18
and
20
. For this reason, the moving plate
10
may transform upward and downward in the event that it thermally expands. A change in the shape of the moving plate
10
may increase driving voltage or power consumption when the MEMS switch is turned on.
SUMMARY OF THE INVENTION
To solve the above-described problems, it is an object of the present invention to provide an MEMS switch capable of preventing an increase in driving voltage due to the leakage of a transmitted signal or the transformation of a moving plate, or power consumption when the MEMS switch is on.
Accordingly, to achieve the above object, there is provided an MEMS switch including: a substrate; grounding lines installed on the substrate to be distant away from each other; signal transmission lines positioned at predetermined intervals between the grounding lines; an anchor placed between the signal transmission lines; a driving electrode not being in contact with the anchor, the signal transmission lines and the grounding lines, the driving electrode for encircling the anchor; and a moving plate positioned on the driving electrode to be overlapped with portions of the signal transmission lines, the moving plate connected to the anchor elastically.
Here, the moving plate is connected to the anchor via springs, and the moving plate and the anchor are connected to each other via four planar springs.
Preferably, the width of the moving plate perpendicular to the grounding lines is the same as the widths of the signal transmission lines.
Preferably, the driving electrode is geometrically shaped the same as the moving plate.
One end of each of the four planar spring is connected to the four corners of the anchor, but the one end of each plate spring is connected to one of two surface consisting of each corner, and the other end of each planar spring is extended from the one end along the surface of the anchor, to which the one end is connected, to connect to the inner surface of the moving plate which is opposite to the other surface of the anchor adjacent to the surface to which the one end is connected.
In an MEMS switch according to the present invention, a moving plate is positioned between grounding lines such that it can be actuated not in contact with these grounding lines. Thus, the MEMS switch according to the present invention is capable of completely transmitting a signal even if the moving plate comes in contact with the grounding lines, or these grounding lines are broken or become narrow. Also, the moving plate is hold by a single anchor, and thus, it is possible to prevent deformation of the moving plate upward and downward even if a substrate expands due to heat from the outside. Therefore, power consumption can be prevented when driving voltage for actuating the moving plate increases or the MEMS switch is switched on.


REFERENCES:
patent: 5619061 (1997-04-01), Goldsmith et al.
patent: 6147856 (2000-11-01), Karidis
patent: 6396372 (2002-05-01), Sakata et al.
patent: 6486425 (2002-11-01), Seki
patent: 6549394 (2003-04-01), Williams
patent: 4305033 (1993-10-01), None
patent: 1024512 (2000-08-01), None

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