WO2001080258A2

WO2001080258A2 - A micro relay

Info

Publication number: WO2001080258A2
Application number: PCT/US2001/012508
Authority: WO
Inventors: William Trimmer
Original assignee: Standard Mems, Inc.
Priority date: 2000-04-18
Filing date: 2001-04-18
Publication date: 2001-10-25
Also published as: CA2344729C; WO2001080258A3; CA2344729A1; AU2001253609A1

Abstract

This invention relates to the area of microelectromechanical systems and micro relays and micro switches. The relays disclosed allow high currents, inductive loads, and high frequencies to be controlled using a relay that increases its resistance during opening and decreases its resistance during closing.

Description

A MICRO RELAY

Field of the Invention

This invention relates to the area of microelectromechanical systems and

micro relays and micro switches. The invention is particularly concerned with

mechanical relays and switches that can reliably control higher currents, inductive

loads, and high frequencies.

Background of the Invention Many problems can occur when miniaturizing, or micro sizing, relays. These

problems can make micro relays unreliable. One problem with micro relays is that

they tend to rapidly wear out. As the size of a relay is scaled down, the amount of

material contained in the relay's electrical contacts decreases rapidly. For an example,

if the size of a relay is scaled down by a factor of a thousand, the amount of material

in an electrical contact decreases by a factor of one billion, the surface area of the

contact decreases by a factor of one million, and the distance the switch moves to

closure decreases by a factor of a thousand. On conventionally sized, or macro sized,

relays the contacts can wear due to friction with other components and because of arcing and the formation of insulating oxides on contact surfaces that can be removed

by a slight abrading action. While a macro relay has sufficient material for the

removal and corruption of contact material, the small amount of material in a micro

relay contact can be quickly destroyed.

In addition, the small size of the micro relays makes the relays more

susceptible to dust and dirt. In a micro relay, small amounts of dust can cover the contact. Conventionally sized relays would still have sufficient contact area around a

small dust particle to make a suitable contact.

Another problem is that micro relays are more prone to arcing and burning

than conventional size relays. Micro relays have smaller gaps between the contact

points. Arcing is more prone to occur across these smaller gaps than to occur across

the larger gaps in a conventional sized relay. The arcing of micro relays in addition to

causing damage to the relay can also generate RF noise and signals, which can

interfere with other electronic components.

Micro relays can only carry a limited amount of electricity because of their

small size. Unfortunately, if several relays are put in parallel to increase the total

current carrying capability of the several relays, the relays tend to burn out, first one

then another. Specifically, the relays open at slightly different times, and the last one

to open carries the full current of the several relays. This high current increases the

likelihood that the contacts will burn, melt, or arc the contact. The likelihood that the

contacts will be damaged or destroyed by high current is especially probable if the

several switches are trying to switch an inductive or radio frequency, RF, load. An inductive load, for example, tries to maintain the current flow as the switch opens, and

can generate high voltages to sustain the current flow. (This is how the high voltage

for the spark plugs in a car is generated.) RF sources are also known for their ability

to arc across small gaps such as the opening contacts micro relays.

Figure 1 and figure 2 show a conventional micro switch, figure 1 the micro

switch sits upon a substrate, with inputs A and B on either side of the substrate. In the

center is a bar that shorts between the inputs to close the switch.

Figure 2 shows the switch in its open position, where the bar has moved away

from the input connector A. There is now an air gap separating inputs A and B. In the process of opening between figure 1 and figure 2, there is an abrupt breaking of the

contact when the connecting member separates from the input connector A.

Summary of the Invention In order to control the flow of high currents, inductive loads, and high

frequencies, this invention provides using relays that increase their resistance during

opening and decrease their resistance during closing.

hi one embodiment, the invention provides a relay comprising a substrate, a

variable resistance contact attached to the substrate, and a connecting member. The

resistance of the variable resistance contact varies along its length. The connecting

member is configured to contact the variable resistance contact at positions of

increasing resistance during opening and decreasing resistance during closing of the

relay.

Preferably, the relay is less than 2 millimeter in length. Preferably, the

variable resistance contact is a serpentine conductor. Preferably, the connecting

member is flexible. Preferably, the flexible member is curved away from the substrate

when the relay is open. Preferably, the connecting member is configured to

respond to an electrostatic force. Preferably, the electrostatic force is produced by

inter-digitated electrodes attached to at least one surface of the substrate or connecting

member. The connecting member can also preferably be configured to respond to a

magnetic force, a piezoelectric force, a thermally generated force, a force produced by

bimorph, or a force produced by a boiling bubble.

Preferably, the relay has a second contact with a non-conducting layer existing

between the variable resistance contact and the second contact when the relay is open.

Preferably, the non-conducting layer is a sacrificial layer. Preferably, the relay is fabricated using a layer of silicon dioxide between the

contact points that is later dissolved in a solution containing hydrofluoric acid.

Preferably, the variable resistance contact is a conductor made of gold, platinum,

chrome, titanium, or mercury. Preferably, the substrate comprises a silicon surface or

a glass surface.

«

Preferably, a plurality of relays are placed in parallel and series to produce an

array. Preferably, resistors are placed between the relays of the array so that the

resistance of the array can be controlled by opening and closing relays in the array.

In another embodiment, the invention provides a method of preventing arcing

between a contact and a connecting member in a relay. The method comprises

providing a relay comprising at least one variable resistance contact and at least one

connecting member. The resistance of the variable resistance contact varies along its

length. The variable resistance contact is contacted at positions of increasing

resistance during opening of the relay and contacted at positions of decreasing

resistance during closing.

In another embodiment, the invention provides a dynamic antenna comprising a plurality of antenna elements. Relays interconnect the antenna elements. The relays

comprise a substrate, a variable resistance contact attached to the substrate, and a

connecting member configured to make electrical contact at several positions along

the variable resistance contact. The resistance of the vaiiable resistance contact varies

along its length.

Preferably, the configuration of the dynamic antenna can be changed by

connecting together antenna elements by closing individual relays. Preferably, the

impedance of the antenna is changed when the configuration of the antenna is changed. Preferably, the antenna elements and the relays are fabricated on the same

substrate. Preferably, antenna elements comprise a conducting metal.

Preferably, the relays in the dynamic antenna further comprise three electrodes

beneath the connecting member. Preferably, the three electrodes are connected to

three different control lines. Preferably, the three control lines are used to control the

opening and closing of the multiple relays of the dynamic antenna in a multiplexed

manner.

In another embodiment, the invention provides a method of making a dynamic

antenna. The method comprises providing a plurality of antenna elements on a

substrate, and connecting each antenna element to each adjacent element using a relay.

The relays in the dynamic antenna comprise a substrate, a variable resistance contact

attached to the substrate, and a connecting member configured to make electrical

contact at several positions along the variable resistance contact. The resistance of the

variable resistance contact varies along its length.

In yet another embodiment, the invention provides a relay anay comprising a

plurality of relays. The relays of the relay anay comprise a substrate, a variable

resistance contact attached to the substrate, a connecting member configured to make

electrical contact at several positions along the variable resistance contact, and three

electrodes placed beneath the connecting member. The resistance of the variable

resistance contact varies along its length. The connecting member makes electrical

contact to the variable resistance contact at positions of increasing resistance during

opening and decreasing resistance during closing. The three electrodes are connected

to three different control lines.

Preferably, the relay array is closed by activating all three electrodes beneath

the relay's connecting member. Preferably, a closed relay in the relay anay can be maintained in the closed position by a single active electrode. Preferably, the three

different control lines are connected to a plurality of relay electrodes in the anay.

Preferably, the three control lines are used to control the opening and closing of

multiple relays of the relay array in a multiplexed manner.

Brief Description of the Drawings

Figure 1 is a perspective view of a prior art relay;

Figure 2 is a front view of the prior art relay of figure 1;

Figure 3 is top view of a set inter-digitated electrodes;

Figure 4 is a perspective view of one embodiment of a relay;

Figure 5 is a front view of the relay of claim 4;

Figure 6 is a perspective view of the relay of claim 4 with the connecting member

removed;

Figure 7 is a top view of a dynamic antenna;

Figure 8 is a top view of one embodiment of a programmed dynamic antenna;

Figure 9 is a top view of a second embodiment of a programmed dynamic antenna;

Figure 10 is a top view of a third embodiment of a programmed dynamic antenna;

Figure 11 is a top view of a fourth embodiment of a programmed dynamic antenna;

Figure 12 is a top view of a fifth embodiment of a programmed dynamic antenna;

Figure 13 is a top view of a sixth embodiment of a programmed dynamic antenna;

Figure 14 is a front view of a relay for a dynamic antenna;

Figure 15 is close up view of antels and relays of a dynamic antenna. Detailed Description of the Invention

This invention relates to both relays that have an actuator to close the electrical

contact, and switches that are closed by external influences such as a manually

operated lever. Both the relays and switches will be hereafter refened to as relays.

The present invention is a relay in which the resistance of the relay increases

gradually during opening, and decreases gradually during closing, rather than the

abrupt opening and closing of the contacts in a conventional relay. This gradual

increase can help absorb and dissipate the energy in the circuit, including the energy

associated with inductive and RF loads, greatly reducing damage to the relay.

A circuit carrying an inductive load can illustrate the benefits of the present

invention. When a conventional switch opens, the resistance increases dramatically,

typically from less than an ohm to over several million ohms. The inductive load will

generate a voltage spike as it attempts to keep the current flowing. This voltage spike

is what arcs across a conventional switch, causing the relay contacts to burn and

oxidize and pit. In the present invention, when the switch starts to open, the resistance

increases gradually, and the inductive load dissipates across the increasing resistance.

By the time the relay finally opens, the resistance across the relay is quite large, and the current still flowing is quite small.

The same phenomenon happens with a RF load across the switch. As the

switch opens, the resistance (and in this case also the inductance) increases, causing

the current flow through the switch to decrease until the switch can open safely with

out arcing when it finally does open completely.

The gradual opening of the relay also greatly improves the performance of

relays operating in parallel. The gradual opening allows for a more even distribution of cunent across several opening relays when operated in parallel. The micro relays

of the present invention open over a longer period of time than a typical relay and

resistively dissipate energy as they open. So even though relays operated in parallel

may begin opening at slightly different times, other parallel relays can begin opening

before the first relay is completely open. This allows the voltage to be dissipated

across all of the relays that are concunently, gradually, opening. Although slower

than typical relays, the gradual opening is still rapid compared to many phenomena

and the dissipation of electricity across the relay is rapid compared to the rate of

opening the mechanical relay. The actual rate of opening of the relay will depend on

many things including the scale of the micro relay and the force used to open the

relay.

A relay embodying the present invention can be of any scale, including full

scale, although it has been found that the benefits of the present invention are

particularly useful in small relays. The term micro relay herein refers to relays smaller

than 2 millimeters in length. Preferably the length of the micro relay is less than 2

millimeters, more preferably less than 1 millimeter, and even more preferably less than 100 microns.

One embodiment of the present invention is a relay that has two contacts. The two contacts have a non-conducting gap between them. A conducting connecting

member spans the gap between the two contacts. The connecting member can be

permanently connected to one of the two contacts. When the connecting member is in

the closed position, the connecting member can make detachable contact with the

other contact allowing cunent to flow from one contact to the other. When the

connecting member is in the open position, the connecting member is detached from one of the contacts. In the present invention, the contact that the connecting member makes

detachable contact with has varying resistance. As the contact closes, the connecting

member is designed to touch the varying resistance contact at a point of high

resistance and slowly contact the varying resistance contact at points of lower and

lower resistance. In this manner the cunent in the relay is slowly increased as the

relay closes. When the relay opens, the process is reversed. The connecting member

slowly detaches itself from the varying resistance contact. Detachment is made first at

points of lowest resistance and then at points of higher and higher resistance. In this

manner the cunent is slowly cut-off from the circuit as the circuit opens.

The varying resistance contact can be made in any manner that allows the

contact to have varying resistance at different points on the contact. A preferable

varying resistance contact is a serpentine contact made of a conducting material. A

serpentine contact is a contact that zig-zags back and forth perpendicular to the

direction that the connecting member closes. The serpentine contact becomes finer in

the direction of its end point. Both the length of the contact and the fact that the

contact becomes finer in the direction of its end point gives the contact varying

resistance along its length. The zig-zag configuration of the contact allows the contact to make greater contact with the connecting member at points along the contact.

Another preferable method of increasing the resistance of the contact along its length

is to use less conductive materials along the length of the contact.

The variable resistance contact, and specifically the serpentine contact, in

addition to dissipating cunent during relay opening and closing also provides an

extended contact region with several contact points. The extended contact region

allows for some of the contact points of the relay to be damaged by slight arcing while

still allowing the relay to operate. This is because this damage will most likely be at the end of the relay where little current flows through the relay. In addition, if one of

the contact points on the variable resistance contact is damaged, the relay can have

other contact points that still operate allowing the switch to still carry a cunent. The

extended contact and multiple contact points also make the relay less susceptible to

wear and dirt. Some of the contact points can wear out or become covered by dirt

while other contact points are still operable.

The metalization of the contacts is important. Prefened materials are hard

enough to withstand repeated closures, have high conductivity, can deform slightly to

make a larger area contact, and do not oxidize readily. Gold, platinum, chrome,

titanium, and a host of other materials can be used as the contact material.. Often,

using two different materials on the two contacting surfaces improves the lifetime of

the contacts. Where it is allowed environmentally, mercury also makes an excellent

contact with a long lifetime.

The contacts are preferably mounted on a non conducting substrate. Preferable

substrates include silicon dioxide, and glass substrates. The contacts should be

mounted sufficiently far apart to prevent arcing when the relay is open. In a prefened

embodiment the non conducting part of the substrate is a sacrificial layer. Such a layer could be made of silicon dioxide, which could later be dissolved using

hydrofluoric acid to produce other components of a circuit.

Preferably the connecting member is a curved membrane that progressively

touches the varying resistance contact as it closes. Preferably the connecting member

is curved away from the varying resistance contact. When the relay is closed, the

connecting member is made to bend towards the varying resistance contact

progressively touching the contact at lower and lower resistive points until the relay is

completely closed. If a serpentine contact is used, this action allows the high resistance contacts on the serpentine conductor to be made first, and as the bar

progressively closes to the surface, lower and lower resistance contacts are made until

the bar finally shorts between the two contacts making a low resistance path.

Another preferable arrangement is a straight connecting member and a curved

substrate, this anangement, the connecting member is made to curve around the

substrate to contact the varying resistance contact at different points. Yet another

prefened anangement is a relatively flat connecting member and a flat substrate. The

connecting member could then be made to touch the varying resistance contact by

flexing the connecting member, the substrate, or both. Another prefened anangement

is to have the contact surfaces on the varying resistance contact mounted on springs of

appropriate length to enable the conect sequence of increased resistance during

contact closure.

Part or all of the connecting member can be conducting. In a prefened

embodiment, a conducting metal is deposited upon a flexible substrate. The flexible

substrate allows the connecting member to flex during relay opening and closing.

A flexible connecting member can be manufactured by a number of effective

techniques. A prefened connecting member, for micro relay designs, can be

manufactured using electronic silicon fabrication techniques. The connecting member

can be manufactured using a thin silicon layer as a substrate. Such a layer can be

comprised of, for example, poly silicon or silicon nitride, deposited using electronic

silicon fabrication techniques.

The connecting member can be formed from the relay's substrate by removing

a layer of material from beneath the portion of the substrate that will become the

connecting member. By removing a layer of substrate material a flap can be formed

on the substrate. Material beneath the connecting member can be removed using silicon surface micro machining technology such as dissolving silicon dioxide in a

hydrogen fluoride solution. Curving the flap to form the connecting member can be

accomplished by depositing a metal, such as aluminum, on the top surface of the

connecting member. Deposited aluminum is usually under tension and will cause the

connecting member to curve as desired. Metal or a conductive layer may be deposited

on both sides of the connecting member to improve conduction across the connecting

member and reduce the closed resistance of the relay. One or more of these

conducting layers may also improve the contact closure of the relay.

The operating parameters for a relay according to the present invention can

varying according to the scale of the relay, the materials used in the relay, and the

specific relay design used. For example, the connecting member may be 40 microns

long, 10 microns wide, and 1 micron thick. Typical parameters for a switch of this

general description are: open capacitance about 0.1 femto farad, closed resistance

about 1 ohm, switch time about 100 micro seconds, cunent about 100 milliamperes,

and breakdown voltage about 500 volts. These parameters can be varied over a wide

range of specifications depending upon the particular design of the micro relay.

The relay can be actuated using many different physical principals. In a

prefened embodiment, the substrate and connecting member each contain conducting

plates. When a voltage is placed between these plates, an electrostatic force causes

the connecting member to be attracted towards the substrate and the varying resistance

contact attached to the substrate. A curved shaped connecting member requires less

voltage to operate than a connecting member and substrate that are configured as two

parallel plates separated by some distance. This lowering of the operating voltage is

described in the paper "Microactuators for Aligning Optical Fibers" by R. Jebens, W.

Trimmer, and J. Walker, published in "Sensors & Actuators," 1989, pp. 65 to 73, and reprinted in the book "Micromechanics and MEMS, Classic and Seminal Papers to

1990," Edited by William Trimmer, page 237.

If electrodes on the connecting member and the substrate are used to actuate

the micro relay, the electrodes on the substrate can be placed along side the varying

resistance conductor in such a way that the connecting member overlaps the substrate

electrodes. Alternatively, the electrode on the substrate can be placed below the

varying resistance conductor, and preferably insulated from the conductor by an

insulating layer.

The electrodes on the substrate or on the connecting member can be inter-

digitated fingers of conducting electrodes, as shown in figure 3. When voltage is

applied between input 304 and input 306, an electric field is set up between the inter-

digitated fingers of conductor 300 and conductor 302. Either^' an alternating, a.c, or a

steady state, or d.c, voltage can be applied between input 304 and input 306 on the

inter-digitated conductors 300 and 302 to generate electric fields between the

interdigitated fingers. The inter-digitated conductors 300 and 302 can be on one

surface, and a conductor on the other surface. Alternatively the inter-digitated

conducting electrodes 300 and 302 could be on both surfaces. Either arrangement can be used to cause an attractive electrostatic force between the substrate and the

connecting member. The inter-digitated conducting electrodes 300 and 302 as shown

in figure 6 are less susceptible to many phenomena that reduce the electrostatic force

generated, for example trapped surface charges and depleted regions. A slightly

conducting insulator can be used to cover the inter-digitated electrodes or between the

substrate and the connecting member to reduce problems with surface charge. Electrodes can be placed on the substrate and connecting member in a number

of other ways, for example multiple layers of electrodes or regions of trapped charge

could be used in some designs to facilitate the electrostatic force.

In another prefened embodiment, the relay is actuated using a thermal

bimorph. A bimorph is formed by bonding together two materials of differing thermal

expansion, as the temperature changes the bimorph will bend. The connecting

member can be fabricated from two or more such materials possessing different

thermal expansion properties to provide the appropriate bending. To actuate this

actuator, a resistive heater can be placed on the bimorph.

h yet another prefened embodiment the relay is actuated magnetically.

Electromagnetic coils or a permanent magnet can be placed on the connecting

member. The connecting member can then be moved by changing the magnetic field

around the connecting member. In another embodiment, a solenoid external to the

connecting member is used to controUably attract the connecting member towards the varying resistance contact.

h another prefened embodiment the relay is actuated piezoelectrically. A

piezoelectric material produces a mechanical force when a voltage is applied. For

example, a connecting member can be formed from one or more piezoelectric materials forming a piezoelectric bimorph. A voltage can then be applied to the

connecting member to make the piezoelectric bimorph bend in a suitable manner.

Instead of a piezoelectric bimorph a single or stack of piezoelectric material can also

be used to actuate the micro relay. A promising piezoelectric material is called sol-

gel, and can be spun on a silicon wafer and integrated with other electronic silicon

fabrication technology process steps. Many other methods can be used to actuate the relay. Other actuating methods

include the use of fluidics and pressure related forces, manual activation (i.e. a person

touching a surface), accelerations, surface tension, and many other actuation methods

know in the art.

The extended opening time of the relay also allows many relays to be operated

in parallel without excessive relay burnout, h a set of conventional relays operated in

parallel, the last relay to open takes the full inductive load or sees the full RF field. In

time, this relay will burn out, leaving one fewer relays. Now the next slowest relay

burns out, and this continues until all the relays have failed, or the remaining relays

can no longer sustain the cunent through the switch. In the present invention, all of

the relays can open simultaneously over an extended period. Each relay handles part

of the inductive or RF load, and dissipates the energy associated with that load as the

resistance of the relay increases. By the time the parallel relays start to completely

open, the cunent has been dramatically reduced by the present high resistance of the

relays, and there is little cunent or energy left.

The relays of the present invention can also be operated in an anay, say of 10

rows and 10 columns. Operating relays in an anay increases both the cunent carrying

capability of the relay array and also the reliability. If one relay fails in the open

position, the relays in parallel with this relay are sufficient to carry the load. If one

relay fails in the closed position, the relays in series with this shorted relay are still

open, and block the flow of cunent. The larger the anay, the more relays that can fail

and still have the anay of relays function properly. This anay of relays is difficult to

implement with conventional relays because, as described above, the last opening

relay tends to burn, setting of a chain reaction of relay failure. Also, using an anay of

10 by 10 relays would be expensive using conventional macro switches because of the need to purchase 100 relays. However using microfabrication techniques, a large

number of micro relays can be fabricated simultaneously, for often not much more

expense than one macro relay.

Another advantage of the present invention is a large array of relays can be

multiplexed. For example, an anay of 100 relays which is organized as a square anay

often rows and ten columns, can be controlled with ten row control lines and ten

column control lines and 10 latching lines for a total of 30 signal lines. If these relays

were not multiplexed at least 100 control lines would be needed. This multiplexing

reduces the complexity, the number of interconnects, and the amount of electronics to

control these relays. As the number of relays increases, this multiplexing becomes

even more advantageous. In one application, each micro relay is in series with a

particular resistor. By opening and closing the appropriate relays, the total resistance

of the relay anay can be conveniently controlled. This might be especially useful in

applications such as feed back circuits in operational amplifiers.

Combinations of micro relays can also be used to forai an "intelligent

antenna." An array of micro relays can be used to dynamically reconfigure an

antenna. The use of these micro relays opens a whole new world of antenna design.

An antenna produced using the relays as previously described are more durable since

these relays can handle high loads, and particularly RF loads, with minimal burning

and arcing.

A prefened antenna is one that can dynamically change its size and shape as

the electronics changes frequency. The antenna can change their impedance to conect

for mismatches in the electronics. To focus the antenna in a different direction, the

antenna simply changes shape. Such an antenna can be an anay of antenna elements

made out of a conducting material. The antenna elements are interconnected using micro relays. The size and shape of the antenna can then be changed as needed by

connecting the desired set of antenna elements by opening and closing the appropriate

relays.

A dynamic antenna using micro relays could be as small as 4 inches in

diameter, a millimeter thick and contain 100,000 antenna elements. Alternatively the

dynamic antenna might be a surface several meters across tiled with smaller intelligent

antenna segments.

Figures 4, 5, and 6 show one embodiment the present invention, i figure 4, a

relay 400 comprises a first contact 402, a second contact 404, a connecting member

406, and a substrate 408. The first contact 402 is a serpentine conductor that zig-zags

back in forth perpendicular to the connecting member 406. The connecting member

406 is permanently attached to the second contact 404. i figure 4, the connecting

member 406 is in the fully closed position. In the fully closed position, the connecting

member 406 makes is flush with the first contact 402 maximizing the contact area and

minimizing the resistance of the relay. An input 410 is connected to serpentine

conductor 402 and an input 412 is connected to the second contact 404.

Figure 5 is a front view of the relay in the open position. The side view shows that the serpentine conductor that forms the first contact 402 has many contact points

along its length. The serpentine conductor 402 becomes narrower along its length,

which increases the resistance of the serpentine conductor. In the open position, the

connecting member 406 is bent away from the serpentine conductor 402 so that there

is no contact between the serpentine conductor and the connecting member 406. In

the open position cunent can not flow from the serpentine conductor 402 to the

second contact 404 or vice versa. Figure 6 is a perspective view of the relay with the connecting member 406

removed so that the configuration of the connecting member can more easily be

viewed. In figure 5 the zig-zag configuration of the serpentine conductor 402 can be

seen. Also the width of the serpentine conductor 402 becomes nanower as it moves

away from input 410, increasing the resistance. As the connecting member 406,

shown above in this figure, begins to move towards the substrate 408, it first contacts

the serpentine conductor at its extreme from input 410. The relay has now closed, but

there is a large resistance between inputs 410 and 412 because the cunent must travel

the entire length of the serpentine conductor. As the connecting member moves progressively down towards the substrate 408, it contacts the serpentine conductor

closer 402 and closer to the input 410, and the resistance across the switch decreases.

Finally the connecting member shorts out the entire serpentine conductor 402 and

makes contact at the base of the input 410 giving the minimum resistance for this

relay.

Figure 7 is a top view of a dynamic antenna 700 that uses micro relays to

change the antenna's size and shape. Figure 7 shows a silicon wafer 704 covered with

small gold squares 702. Each one of these gold squares 702 is an antenna element (an

antel). The antenna elements 702 can be electrically connected together to form an

antenna of the desired shape and size. Micro relay switches will be between the

antenna elements interconnecting the elements. By opening and closing the

appropriate relays, an antenna of the desired shape and size can be configured, hi a

typical design the gold squares 702 may be 200 microns on a side, and separated by 50

micron air gaps. On a 4 inch wafer there can be about 12,000 of these gold squares

702. The shape, size, and interconnectability of the gold squares 702 are design

parameters the antenna designer can conveniently specify. In figure 8, certain of these gold squares 702 have been electrically connected

together to form a loop antenna. (The elements connected together have are shown in

a darker shade of gray.) If one wants a different impedance, different elements are

interconnected to form a slightly different sized loop.

Different antenna arrays can be configured as easily as connecting different

antenna elements together. Figures 9, 10, 11, and 12 show a few of the many possible

antenna designs.

Figures 13, 14, and 15 show a prefened way of controlling the antels 702.

Figure 13 shows that there are three groups of control lines going into the intelligent

antenna anay 700. (h the present example, the intelligent antenna is shown as rows

and columns of antels 702 on a round silicon wafer 704.) These control lines are Data

1302, Column Address 1304, and Enable 1306. At each intersection of these three

control lines is a set of micro relays 1400, shown in figures 14 and 15 that control

whether this antel is connected to the next antel 702. By using control lines 1302,

1304, and 1306, each antel 702 can be electrically connected to the four nearest neighboring antels.

hi operation a single column of antels is controlled during each programming cycle. Initially the Column Addresses 1304 and Enable lines 1306 have low voltage,

or zero voltage. During the first programming cycle, data is entered on the Data

control lines 1302. This data controls which relay sets 1400 are to be closed or open.

The Column Address line 1304 for the column to be program is activated, or brought

to a high voltage state, and then the Enable line 1306 for this column is brought high.

This latches the data into this column, and the desired relay sets in this column are

kept on or off as desired during the rest of the program cycles. As long as the Enable

line 1306 on this column is kept high, the data will remain latched into this column and the conect relays 1400 will remain open or closed in this column. Next the data

for the next column to be programmed is placed on the Data lines 1302 and the

Column Address 1304 and Enable line 1306 for the next column being programmed

are brought high, latching this data in the second column to be programmed. This

cycle is continued until all the desired columns are programmed and the appropriate

relays 1400 connecting the antels 702 are open or closed.

To re-program a column, the Data line 1302, the Column Address line 1304

and the Enable line 1306 for that column are brought low. Then the programming

cycle repeats, data is entered on the Data lines, and that Column Address and Enable

line are brought high.

A relay that responds to voltage changes in the Data, Column and Enable lines

is shown in figure 14. Applying a voltage to the Data line applies a voltage to the

electrode on the substrate labeled 1402. This pulls the connecting member 1410

towards the substrate 1412 in the region of the electrode 1402. Next applying a

voltage to the Column line applies voltage to the electrode on the substrate labeled

1404. This pulls the connecting member 1410 down over the region over electrode

1404. Finally applying a voltage to the Enable line applies a voltage to the electrode

on the substrate labeled 1406. This pulls the connecting member 1410 all the way, so

that connecting member 1410 makes contact with variable resistance contact 1408

closing the switch. As long as electrode 1406 is activated, it will hold the connecting

member down 1410 to the substrate and keep the switch 1400 closed regardless of

what electrodes 1402 and 1404 do.

To re-program the column, electrodes 1402, 1404, and 1406 are brought low,

the relay 1400 opens, and the programming cycle starts again. During subsequent

programming cycles when other columns are being programmed, the Column line programmed above is kept low, and this inhibits other programming cycles from

closing the switches in this column.

Figure 15 shows several antels 702, and in the blow up, three connecting

members 1410 attached to three relays are shown with the Data line 1302, Column

Address line 1304, and Enable line 1306 beneath these connecting members 1410.

Again, as voltages are applied to control lines 1302, 1304, and 1306 in the conect

sequence, the relay is latched closed, connecting the antels 702. However if any of

these lines is not activated, the switch will not close during this programming cycle.

Having now fully described this invention, it will be appreciated by those

skilled in the art that the invention can be performed within a wide range of

parameters within what is claimed, without departing from the spirit and scope of the

invention.

Claims

What is claimed is:

1. A relay comprising:

a substrate;

a variable resistance contact attached to the substrate, wherein the

resistance of the variable resistance contact varies along its length; and

a connecting member configured to contact the variable resistance

contact at positions of increasing resistance during opening and decreasing

resistance during closing.

2. The relay of claim of 1 , wherein the relay is less than 2 millimeter in

length.

3. The relay of claim 1 , wherein the variable resistance contact comprises a serpentine conductor.

4. The relay of claim 1, wherein the connecting member is flexible.

5. The relay of claim 4, wherein the flexible member is curved away from

the substrate when the relay is open.

6. The relay of claim 1 , wherein the connecting member is configured to

respond to an electrostatic force.

7. The relay of claim 6, wherein the electrostatic force is produced by

inter- digitated electrodes attached to at least one surface of the substrate or

connecting member.

8. The relay of claim 1 , wherein the connecting member is configured to

respond to a magnetic force.

9. The relay of claim 1 , wherein the connecting member is configured to

respond to a piezoelectric force.

10. The relay of claim 1, wherein the connecting member is configured to

respond to a thermally generated force.

11. The relay of claim 1 , wherein the connecting member is configured to

respond to a force produced by bimorph.

12. The relay of claim 1 , wherein the connecting member is configured to respond to a force produced by a boiling bubble.

13. The relay of claim 1 , further comprising a second contact, wherein a

non conducting layer exist between the variable resistance contact and the second

contact when the switch is open.

14. The relay of claim 13, wherein the non conducting layer is a sacrificial

layer.

15. The relay of claim 1 , fabricated using a layer of silicon dioxide

between the contact points that is later dissolved in a solution containing

hydrofluoric acid.

16. The relay of claim 1, wherein the variable resistance contact is a

conductor selected from the group consisting of gold, platinum, chrome, titanium,

and mercury.

17. The relay of claim 1, wherein the substrate comprises a silicon surface.

18. The relay of claim 1 , wherein the substrate comprises a glass surface.

19. The relay of claim 1 wherein a plurality of relays are placed in parallel

and series to produce an anay.

20. The anay of claim 19, wherein resistors are placed between the relays of the anay, wherein the resistance of the anay can be controlled by opening and

closing relays in the array. .

21. A method of preventing arcing between a contact and a connecting

member in a relay comprising:

providing a relay comprising at least one variable resistance contact

and at least one connecting member, wherein the resistance of the variable

resistance contact varies along its length; contacting the variable resistance contact at positions of increasing

resistance during opening of the relay; and

contacting the variable resistance contact at positions of decreasing

resistance during closing.

22. The method of claim 21, wherein the variable resistance contact

comprises a serpentine conductor.

23. The method of claim of claim 21 , wherein the relay is less than 2

millimeters in length.

24. A dynamic antenna comprising;

a plurality of antenna elements; and

relays interconnecting the antenna elements, wherein each of the relays comprise a substrate, a variable resistance contact attached to the substrate,

wherein the resistance of the variable resistance contact varies along its length,

and a connecting member designed to make electrical contact at several positions

along the variable resistance contact.

25. The dynamic antenna of claim 24, wherein the configuration of the

dynamic antenna can be changed by connecting together antenna elements by

closing individual relays.

26. The dynamic antenna of claim 24, wherem the impedance of the

dynamic antenna is changed when the configuration of the dynamic antenna is

changed.

27. The dynamic antenna of claim 24, wherein the antenna elements and

the relays are fabricated on the same substrate.

28. The dynamic antenna of claim 24, wherein the antenna elements comprise a conducting metal.

29. The dynamic antenna of claim 24, wherein the relay further comprises

three electrodes beneath the connecting member, and wherem the three electrodes

are connected to three different control lines.

30. The dynamic antenna of claim 29, wherein the three control lines are

used to control the opening and closing of the multiple relays of the dynamic antenna in a multiplexed manner.

31. A method of making a dynamic antenna comprising:

providing a plurality of antenna elements on a substrate;

connecting each antenna element to each adjacent element using a

relay, wherein the relay comprises a substrate, a contact attached to the substrate,

wherein the resistance of the variable resistance contact varies along its length, and

a connecting member configured to make electrical contact at several positions

along the variable resistance contact.

32. A relay anay comprising:

a plurality of relays, wherein each of the relays comprise:

a substrate;

a variable resistance contact attached to the substrate, wherein

the resistance of the variable resistance contact varies along its

length;

a connecting member configured to contact the variable

resistance contact at positions of increasing resistance during

opening and decreasing resistance during closing; and

three electrodes placed beneath the connecting member,

wherein the three electrodes are connected to three different control lines.

33. The relay anay of claim 32, wherein a relay is closed by activating all

three electrodes beneath the relay's connecting member.

34. The relay anay of claim 32, wherein a closed relay can be maintained in the closed position by a single active electrode.

35. The relay anay of claim 32, wherein the three different control lines are

connected to a plurality of relay electrodes in the relay anay.

"_

36. The relay anay of claim 32, wherein the three control lines are used to

control the opening and closing of multiple relays of the relay anay in a multiplexed manner.