Abstract:
An array of micro electromechanical switches (MEMs) ( 21 - 35 ) is actuated by a source of one or more light beams, such as a laser ( 60 ). A positioning unit ( 70 ) is arranged to direct the one or more light beams onto the MEMs, thereby actuating them without the need for control lines. The positioning unit may include a scanning unit ( 80 ) which positions a rotatable mirror ( 72 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to control of switches, and more specifically, relates to control of switches with light beams.  
           [0002]    Micro electromechanical switches (MEMs) are finding applications in a variety of fields. The MEMs typically are controlled by control lines etched onto semiconductor chips. For many applications, the control lines occupy a significant percentage of the available chip real estate. For example, in applications involving thousands of MEMs, the large number of requisite control lines quickly overwhelm the available area on the chip, thereby limiting performance. This invention addresses the problem and provides a solution.  
         BRIEF SUMMARY OF THE INVENTION  
         [0003]    The preferred embodiment is useful in an array of micro electromechanical switches. In such an environment, the preferred embodiment comprises generating one or more light beams. The one or more light beams are directed onto predetermined ones of the switches, preferably with a positioning unit which may comprise, for example, a laser and mirror or an array of light emitting diodes.  
           [0004]    By using the foregoing techniques, switches may be controlled with hardware which is smaller and lighter than the known hardware. In addition, thousands of switches may be activated and controlled quickly without any wiring system. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a schematic diagram illustrating a conventional prior art circuit board for a 15 element MEMs circuit accessed by control wires which are grown into the circuit board.  
         [0006]    [0006]FIG. 2 is a schematic diagram illustrating a preferred embodiment of the invention utilizing a laser beam and mirror.  
         [0007]    [0007]FIG. 3 is a schematic diagram illustrating an alternative embodiment of the invention utilizing a row of light emitting diodes mounted on a movable scan bar. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0008]    Referring to FIG. 1, a conventional MEMs circuit comprises a circuit board  10  on which 15 MEMs  21 - 35  (represented by dots) are mounted in a well known manner. MEMs  21 - 25  are arranged in a row along a line  40 , MEMs  26 - 30  are arranged in a row along a line  41 , and MEMs  31 - 35  are arranged in a row along a line  42 . The MEMs  21 - 35  are spaced 1 unit from each other and are accessed and controlled by independent conductors grown into circuit board  10 , such as control lines  51 ,  52  and  53 . Circuit board  10  may comprise a semiconductor chip, or a conventional circuit board on which copper control lines are etched. Additional details about MEMs and lines used to control them are described in U.S. application Ser. No. 09/676,007, entitled “Radio Receiver Automatic Frequency Control Techniques,” filed Sep. 29, 2000, in the name of Michael H. Myers, assigned to a common assignee and incorporated into this application by reference.  
         [0009]    One application for circuit board  10  is a micro-thruster for an orbiting satellite. When current is applied to one of control line  51 , a small resistor connected to the control line (not shown) is heated which causes the actuation of MEMs  25 , connected to the energized control line. The actuated MEMs creates a micro-thrust.  
         [0010]    Referring to FIG. 2, the preferred embodiment includes a circuit board  10 A which is like board  10 , except that there is no need for control lines  50 . A source of light, such as a laser  60 , is located at one end of board  10 A as shown. As used in this specification, the term light means not only visible light, but other radiation in the electromagnetic spectrum near the visible light band, including infrared radiation and ultraviolet radiation.  
         [0011]    Laser  60  generates a laser beam along a path  62  to a positioning unit  70  which includes a mirror  72  having a flat reflective surface  74 . Surface  74  reflects the laser beam onto MEMs  32  along a path  63 , thereby actuating MEMs  32 . Mirror  72  is rotatable around a vertical axis  76  in order to move path  63  to other MEMs aligned with MEMs  32 , such as MEMs  27  and  22 .  
         [0012]    Positioning unit  70  also includes a scanning unit  80  which comprises a bar  82  arranged parallel to the surface of board  10 A. Mirror  72  is rotatably mounted on bar  82  as shown. Bar  82  is carried by legs  84  and  86  which in turn are carried by wheels  88  and  90 . The wheels  88  and  90  are rotated to cause bar  82  to move in the opposite directions indicated by arrow  92 . Thus, bar  82  can be moved from end  12  to end  14  of board  10 A and from end  14  to end  12 .  
         [0013]    In use, laser  60  is pulsed to generate pulses of light along path  62 . Mirror  72  reflects the pulses of light onto desired MEMs. Scanning is performed one row at a time while bar  82  is moved in one of the directions indicated by arrow  92 , and rotating mirror  72  is moved to cover each MEMs on board  10 A. A pulse of light from laser  60  has enough energy to actuate one of the MEMs in a well known manner. For example, an optical window could be used to seal the MEMs, and laser light of sufficient intensity could be directed through the window to actuate the MEMs. Alternatively, a resistive element could be buried just below the surface of the MEMs, and the light beam could be directed against the resistor. The light striking the resistor would heat the resistor which, in turn, would heat the MEMs to cause actuation. If a MEMs is not intended to be actuated, laser  60  is momentarily deactivated so that no light is generated as path  63  is positioned toward the MEMs.  
         [0014]    As an alternatively to the embodiment shown in FIG. 2, mirror  72  could be angled to cover the MEMs on board  10 A in sectors. In this embodiment, bar  82  could remain stationary.  
         [0015]    Referring to FIG. 3, the underside of bar  82  is fitted with three light emitting diodes  101 - 103  aligned in a row corresponding to a column of MEMs, such as  23 ,  28  and  33 . That is, diodes  101 - 103  are spaced in the same manner as a column of MEMs, such as  23 ,  28  and  33 . In use, bar  82  is moved from end  12  to end  14  of board  10 A so that diodes  101 - 13  pass over successive columns of MEMs. As bar  82  passes over the MEMs, the diodes are selectively pulsed to generate one to three beams of light which strike selected ones of the MEMs. The beams of light from the diodes actuate the MEMs in the same manner described in connection with the laser beam shown in FIG. 2.  
         [0016]    While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is therefore contemplated by the appended claims to cover such modifications as incorporate those features which come within the spirit and scope of the invention. For example, thousand or tens of thousands of switches may be activated and controlled by this system. Or as another example, the light beams described in the specification need not be used to activate only micro thruster MEMs, but could be used to activate other types of MEMs, such as phase shifters for phased arrays. In the latter case, the MEMs would be configured for multiple activation and reset and not just for single firings. The intensity of the light in the beams could be used to shift the phase and/or amplitude of a phase shifter circuit.