Abstract:
A tuning head for use with a variable capacitor includes a coupler having a gap, a first optical fiber operatively coupled to the coupler, and a second optical fiber operatively coupled to the coupler. The first and second optical fibers are optically coupled across the gap when the gap is not obstructed. The tuning head further includes an obstruction member that is movable with respect to the coupler and is adapted to fit within the gap to selectively obstruct said optical coupling of said first and second optical fibers. A movement mechanism is also provided to create relative motion between said obstruction member and said coupler.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to a variable capacitor tuning apparatus, and more particularly to a variable capacitor tuning apparatus having an improved tuning head. 
     A known variable capacitor tuning arrangement  20  previously marketed by Jennings Technology, the owner of this patent, under, for example, model numbers CSVF/I-500-0315 or CVCJ/I-1000-0403 is shown in an exploded view in FIG.  1 . The variable capacitor tuning arrangement  20  typically included a variable capacitor  22  and a tuning head  24 . The tuning head  24  included a support thrust bearing  26 , a sensor mount  28 , an adjust plug  30 , fiber optic connectors  34 ,  36  and a lead screw  40 . 
     In implementing the known variable capacitor tuning arrangement  20 , a customer would provide an actuator  44 , a controller  46 , an emitter  48  and a detector  50 . In operation, the controller  46 , would send commands to the actuator  44 , which is a stepper motor. In response to the commands from the controller  46 , the actuator  44 , which is mechanically coupled to the tuning head  24  via the lead screw  40 , would cause the tuning head  24  to change the capacitance of the variable capacitor  22 . The tuning head  24  would change the capacitance of the variable capacitor  22  by meshing opposing conductive plates or cylinders to varying depths with respect to one another. The tuning head  24  would provide feedback to the controller  46  to indicate the position of the conductive plates or cylinders with respect to one another. 
     Referring now to the tuning head  24 , the sensor mount  28  was fixed to the support thrust bearing  26 . Both the sensor mount  28  and the adjust plug  30  had bores therein to accommodate the fiber optic cables (not shown) connected to the fiber optic connectors  34  and  36 . The lead screw  40  extended into the support thrust bearing  26  and engaged the adjust plug  30  so that when the lead screw  40  was turned by the actuator  44 , the adjust plug  30  moved closer to, or farther from, the top of the support thrust bearing  26  along the axis of the lead screw  40 . The adjust plug  30  was, in turn, coupled to the variable capacitor  22  so that when the adjust plug  30  moved, due to lead screw  40  rotation, the capacitance of the variable capacitor  22  changed. 
     The emitter  48  provided optical energy to the fiber optic connector  34 , which was fixed into the sensor mount  28 . Optical energy that was coupled into the fiber optic connector  34  was transmitted to the detector  50 , via the fiber optic connector  36  when the fiber optic cables associated with the fiber optic connectors  34  and  36  were aligned. In response to the optical energy, the detector  50  provided an electrical output signal to the controller  46 . The vertical position of the adjust plug  30  along the lead screw  40  axis was adjusted so that the fiber optic cable associated with the fiber optic connector  36  was aligned with the fiber optic cable associated with the fiber optic connector  34  when the variable capacitor  22  was tuned to a capacitance value of interest. 
     The controller  46  was programmed to recognize the signal provided to it by the detector  50  when the fiber optic cables were aligned and optical energy was coupled to the detector  50 . As the variable capacitor  22  was tuned away from the capacitance value of interest, the adjust plug  30  moved, the fiber optic cables associated with the fiber optic connectors  34  and  36  were no longer aligned, the detector  50  no longer received optical energy and changed the state of the signal that it provides to the controller  46 . Accordingly, the controller  46  could determine whether or not the variable capacitor  22  was tuned to the capacitance value of interest based on the signals provided to it by the detector  50 . 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a variable capacitor tuning apparatus, and more particularly to a variable capacitor tuning apparatus having an improved tuning head. 
     According to a first aspect, the present invention may be embodied in a tuning head for use with a variable capacitor including a coupler. The coupler including a first coupler portion, a second coupler portion disposed at a first position relative to the first coupler portion, a gap between the first coupler portion and the second coupler portion, a first fiber locating structure associated with the first coupler portion, a second fiber locating structure associated with the second coupler portion and the first coupler portion fixed relative to the second coupler portion to maintain alignment of the first fiber locating structure and the second fiber locating structure. The tuning head also includes a first optical fiber supported by the first fiber locating structure, a second optical fiber supported by the second fiber locating structure, wherein the first and second optical fibers are optically coupled across the gap when the gap is not obstructed by an obstruction member movable with respect to the coupler and adapted to fit within the gap to selectively obstruct the optical coupling of the first and second optical fibers and a movement mechanism adapted to create relative motion between the obstruction member and the coupler to control selective obstruction of the gap by the obstruction member. 
     In some embodiments the first coupler portion is integral with the second coupler portion. 
     In some embodiments the obstruction member includes a transparent portion that does not obstruct the optical coupling of the first and second optical fibers when the transparent portion is within the gap, the transparent portion representing a capacitive set point of the variable capacitor. Additionally, the obstruction member may include an opaque portion that obstructs the optical coupling of the first and second optical fibers when the opaque portion is within the gap, the opaque portion representing a capacitive set point of the variable capacitor. 
     In other embodiments the obstruction member may include a plurality of transparent portions representing a plurality of capacitive set points of the variable capacitor. Additionally, the obstruction member may include a plurality opaque portions representing a plurality of capacitive set points of the variable capacitor. 
     According to a second aspect, the present invention may be embodied in a variable capacitor tuning system that includes a variable capacitor, an adjustment mechanism operatively coupled to the variable capacitor, the adjustment mechanism adapted to tune the variable capacitor, an actuator operatively coupled to the adjustment mechanism and adapted to interact with the adjustment mechanism to tune the variable capacitor and a coupler. The coupler having a first coupler portion, a second coupler portion disposed at a first position relative to the first coupler portion, a gap between the first coupler portion and the second coupler portion, a first fiber locating structure associated with the first coupler portion, a second fiber locating structure associated with the second coupler portion and the first coupler portion fixed relative to the second coupler portion to maintain alignment of the first fiber locating structure and the second fiber locating structure. The system may also include a first optical fiber supported by the first fiber locating structure, a second optical fiber supported by the second fiber locating structure, wherein the first and second optical fibers are optically coupled across the gap when the gap is not obstructed, an obstruction member movable with respect to the coupler and adapted to fit within the gap to selectively obstruct the optical coupling of the first and second optical fibers, a movement mechanism adapted to create relative motion between the obstruction member and the coupler to control selective obstruction of the gap by the obstruction member, an emitter optically coupled to the first optical fiber and a detector optically coupled to the second optical fiber. 
     According to a third aspect, the present invention may be embodied in a tuning head for use with a variable capacitor, wherein the tuning head includes a coupler having a gap and a plurality of fiber optic retaining members, a first optical fiber supported by the coupler, a second optical fiber supported by the coupler, wherein the first and second optical fibers are optically coupled across the gap when the gap is not obstructed, a first optical connector retained by a first one of the fiber optic retaining members and optically coupled to the first optical fiber, the first optical connector adapted to receive a first optical component, a second optical connector retained by a second one of the fiber optic retaining members and optically coupled to the second optical fiber, the second optical connector adapted to receive a second optical component, an obstruction member movable with respect to the coupler and adapted to fit within the gap to selectively obstruct the optical coupling of the first and second optical fibers and a movement mechanism adapted to create relative motion between the obstruction member and the coupler to control selective obstruction of the gap by the obstruction member. 
     According to a fourth aspect, the present invention may be embodied in a variable capacitor tuning system including a variable capacitor, an adjustment mechanism operatively coupled to the variable capacitor, the adjustment mechanism adapted to tune the variable capacitor, an actuator operatively coupled to the adjustment mechanism and adapted to interact with the adjustment mechanism to tune the variable capacitor, a coupler having gap and a plurality of fiber optic retaining members, a first optical fiber supported by the coupler, a second optical fiber supported by the coupler, wherein the first and second optical fibers are optically coupled across the gap when the gap is not obstructed, a first optical connector retained by a first of one of the fiber optic retaining members and optically coupled to the first optical fiber, a second optical connector retained by a second one of the fiber optic retaining members and optically coupled to the second optical fiber, an obstruction member movable with respect to the coupler and adapted to fit within the gap to selectively obstruct the optical coupling of the first and second optical fibers, a movement mechanism adapted to create relative motion between the obstruction member and the coupler to control selective obstruction of the gap by the obstruction member, an emitter optically coupled to the first optical connector and a detector optically coupled to the second optical connector. 
     According to a fifth aspect, the present invention may be embodied in a tuning head for use with a variable capacitor, wherein the tuning head includes a coupler having a gap, a first optical fiber supported by the coupler, a second optical fiber supported by the coupler, wherein the first and second optical fibers are optically coupled across the gap when the gap is not obstructed, an obstruction member movable with respect to the coupler and adapted to fit within the gap to selectively obstruct the optical coupling of the first and second optical fibers, wherein the obstruction member comprises a plurality of transparent portions and a plurality of opaque portions each representing a plurality of capacitive set points of the variable capacitor and a movement mechanism adapted to create relative motion between the obstruction member and the coupler. 
     According to a sixth aspect, the present invention may be embodied in a variable capacitor tuning system including a variable capacitor, an adjustment mechanism operatively coupled to the variable capacitor, the adjustment mechanism adapted to tune the variable capacitor, an actuator operatively coupled to the adjustment mechanism and adapted to interact with the adjustment mechanism to tune the variable capacitor, a coupler having a gap, a first optical fiber supported by the coupler, a second optical fiber supported by the coupler, wherein the first and second optical fibers are optically coupled across the gap when the gap is not obstructed, an obstruction member movable with respect to the coupler and adapted to fit within the gap to selectively obstruct the optical coupling of the first and second optical fibers, wherein the obstruction member comprises a plurality of transparent portions and a plurality of opaque portions each representing a plurality of capacitive set points of the variable capacitor and a movement mechanism adapted to create relative motion between the obstruction member and the coupler to control selective obstruction of the gap by the obstruction member, an emitter operatively coupled to the first optical fiber and a detector operatively coupled to the second optical fiber. 
     The features and advantages of the invention will be apparent to those of ordinary skill in the art in view of the detailed description of the preferred embodiment, which is made with reference to the drawings, a brief description of which is provided below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a known tuning head and variable capacitor tuning arrangement; 
     FIG. 2 is a side elevational view, partially in section, of a variable capacitor assembly having a tuning head designed in accordance with the teachings of the present invention; 
     FIG. 3 is a exploded view of the tuning head shown in FIG. 2; 
     FIGS. 4 a - 4   c  are drawings of various flags or obstruction members that may be employed as shown in FIG. 3; and 
     FIG. 5 is a plan view of the coupler shown in FIGS.  2  and  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 illustrates an embodiment of a variable capacitor tuning arrangement  60 , designed in accordance with the teachings of the present invention, generally having a tuning head  62  and a variable capacitor  64 . Also shown in FIG. 2 are an actuator  66 , a controller  68 , an emitter  70  and a detector  72 . The tuning head  62  includes a support thrust bearing  76 , a bearing assembly  78 , an adjustment mechanism such as a lead screw  80 , a coupler  82 , fiber optic cables  84 ,  86 , fiber optic connectors  88 ,  90 , a flag  92 , and an adjust plug (not shown). The support thrust bearing  76  is coupled to the variable capacitor  64  through a flange  96  and does not move with respect to the variable capacitor  64 . The flag  92  serves as an obstruction mechanism that is inserted into the coupler  82 . The coupler  82  is coupled to an adjust plug (designated as  122  in FIG. 3) and moves along the lead screw  80  with respect to the variable capacitor  64  when the lead screw  80  is turned to tune the variable capacitor  64 . Together, the lead screw  80  and the adjust plug  122  form a movement mechanism that moves the coupler  82  with respect to the variable capacitor  64  when the lead screw  80  is turned. 
     As shown in detail in FIG. 3, the coupler  82  includes a gap or slot  100  that divides the coupler  82  into first and second portions  102 ,  104 . Although a slot  100  is shown, the gap could be a through hole or any other suitable structure. The first and second portions  102 ,  104  of the coupler  82  are machined to form first and second fiber locating structures. These structures are each adapted to receive fiber optic cable portions  106 ,  108  and include fiber optic retaining members or clips  110 ,  112  that engage flanges  114 ,  116  of the fiber optic connectors  88 ,  90 . In one embodiment, the fiber optic connectors  88 ,  90  and their associated fiber optic cable portions  106 ,  108  may be fabricated from a standard fiber optic cable and connector assembly available from Hewlett Packard under model number HFBR-RNS5DM. When the fiber optic cable portions  106 ,  108  are fully inserted into the coupler  82 , the flanges  114  and  116  will be retained by clips  110  and  112 , respectively. This configuration is advantageous because it allows for quick and easy replacement of the fiber optic cable portions  106 ,  108  and their associated fiber optic connectors  88 ,  90  without the use of set screws or the like. When fully inserted into the coupler  82 , the fiber optic cable portions  106 ,  108  abut the gap  100  and are adapted to couple optical energy across the gap  100  when the gap  100  is not obstructed. Further detail with regard to the coupler  82  may be found hereinafter with respect to FIG.  5 . 
     The flag  92 , which is mounted into the support thrust bearing  76  and may generally be termed an obstruction member, includes a removed or transparent portion  120 . When the tuning head  62  is assembled, the coupler  82  is fastened onto the adjust plug  122  using a set screw or other appropriate fastening means, and the flag  92  is fastened onto the support thrust bearing  76 . The support thrust bearing  76  is fastened onto the variable capacitor  64  (FIG. 2) over the coupler  82  and the adjust plug  122 , such that the coupler  82  and the adjust plug  122  are free to move axially with respect to the variable capacitor  64  within the support thrust bearing  76 . When the tuning head  62  is assembled, the flag  92  rides in the slot  100  and selectively obstructs optical energy produced by the emitter  70  as the coupler  82  moves with respect to the flag  92 , thereby preventing the optical energy from reaching the detector  72 . 
     A description of the operation of the tuning head  62  and the variable capacitor  64 , along with the actuator  66 , the controller  68 , the emitter  70  and the detector  72  will now be given with reference to FIGS. 2 and 3. The emitter  70 , which may be embodied in, for example, a Hewlett Packard model number T1512 infrared emitter, couples optical energy, via the fiber optic cable  84 , to the fiber optic coupler  88  and the fiber optic cable portion  106  that is mounted in the first portion  102  of the coupler  82 . The fiber optic cable portion  106  couples the optical energy up to the edge of the slot  100  in the first portion  102  of the coupler  82 . On the opposite side of the slot  100 , the fiber optic cable portion  108  is mounted in the second portion  104  of the coupler  82  and abuts the slot  100 . The fiber optic cable portions  106 ,  108  are coaxially aligned with one another. The flag  92  fits into the slot  100  and the slot  100  moves axially with respect to the flag  92  as the variable capacitor  64  is tuned. 
     When the removed portion  120  of the flag  92  is in the slot  100  and is aligned with the fiber optic cable portions  106 ,  108 , optical energy from the fiber optic cable portion  106  couples across the slot  100 , into the fiber optic cable portion  108  and on further to the detector  72 , which may be embodied in, for example, a Hewlett Packard model number R2521 infrared detector. However, when the coupler  82  is positioned such that the removed portion  120  is not aligned with the fiber optic cable portions  106 ,  108 , optical energy will not couple across the slot  100  because the flag  92  obstructs the path of the optical energy. Although, the emitter  70  and the detector  72  are described as being of the infrared-type, one of ordinary skill in the art will readily recognize that other types of emitters or detectors (e.g., laser-type) may be used in accordance with the teachings of the present invention. 
     The optical detector  72 , which is coupled to the fiber optic connector  90  via the fiber optic cable  86 , detects the presence or absence of optical energy and develops an appropriate output signal. For example, when the removed portion  120  of the flag  92  is aligned with the fiber optic cable portions  106 ,  108 , the optical detector  72 , upon receiving optical energy may generate a “logic one.” Conversely, when the removed portion  120  of the flag  92  is not aligned with the fiber optic cable portions  106 ,  108 , the optical detector  72  may generate a “logic zero.” In this case, the logic one signal indicates that the variable capacitor  64  is tuned to a particular capacitance value of interest because the centers of the fiber optic cable portions  106 ,  108  (and thus the upper capacitive plate of the capacitor  64 , which is fixed relative to the fiber optic cable portions  106 ,  108 ) are in a particular axial position with respect to the removed portion  120  of the flag  92 . Conversely, a logic zero indicates that the variable capacitor  64  is not tuned to a particular capacitance value of interest because there are many axial positions in which the fiber optic cable portions  106 ,  108  are not aligned with the removed portion  120  of the flag  92 . The logic signals from the detector  72  are coupled to the controller  68  that appropriately interprets the signals. 
     While the above description indicates that the optical detector  72  generates a logic one signal when it receives optical energy, one skilled in the art will readily recognize that the sense of the output signal from the optical detector  72  may be inverted using, for example, standard Schmitt trigger inverter such as an 74HC14 device. In some embodiments, two such inverters may be used to buffer the output signal from the optical detector  72 . Additionally, one skilled in the art will recognize that although the emitter  70  and the detector  72  are described as connected to optical fibers  84  and  86 , respectively, it is possible to connect the emitter  70  to optical fiber  86  and the detector  72  to optical fiber  84 , without departing from the teachings of the present invention. 
     Although the flag  92  shown in FIG. 3 has only one removed portion  120 , as shown in FIGS. 4 a-   4   c , numerous types of flags  92  may be used in accordance with the teachings of the present invention. Flags  92  may have a single removed portion  120  or, optionally, may have an additional removed portion  124  or portions. Even though the flags shown in FIGS. 4 a  and  4   b , show only one and two removed portions  120 ,  124 , respectively, one of ordinary skill in the art will readily recognize that any number of removed portions may be used, wherein each removed portion corresponds to an axial position of the slot  100  with respect to the flag  92  and, therefore, corresponds to a particular capacitance value of interest to which the variable capacitor  64  is tuned. 
     The flags  92  shown in FIGS. 4 a  and  4   b  are premised on the concept that optical energy is normally blocked from the detector and, therefore, when optical energy is coupled to the detector, one of the removed portions  120 ,  124  must be aligned with the slot  100 . However, a flag  92  may use upstanding or opaque portions to indicate particular capacitance values. A flag  92  as shown in FIG. 4 c  that has upstanding portions  126 ,  128  may be used to indicate a particular capacitance value to which the variable capacitor  64  is tuned. During operation, a system using a flag  92  having upstanding portions  126 ,  128  considers the presence of optical energy at the detector  72  to be not indicative of a particular capacitance value of interest because there are many axial positions in which optical energy will be present at the detector  72 . Rather, an upstanding portion  126 ,  128  obstructing optical energy is indicative of a particular capacitance value of interest. 
     The use of multiple removed portions or multiple upstanding portions that correspond to particular capacitance values of interest is advantageous because it allows the controller  68  to automate the tuning of the variable capacitor  64  between various capacitance values using the actuator  66  as long as the controller  68  recalls the capacitance to which it is tuned. For example, if a detector  72  generates a logic one when it receives optical energy and if a flag  92  has four removed portions corresponding to, for example, 1.0 picofarad (pF), 10 pF, 100 pF, and 1000 pF, respectively, and the controller  28  recalls that the variable capacitor  64  is tuned currently to 10 pF, the controller  68  knows that by enabling the actuator  66  to tune the variable capacitor  64  down until the controller receives a logic zero and then a logic one, the variable capacitor  64  will be tuned to 1.0 pF. Similarly, if a flag  92  having four upstanding portions is used and the variable capacitor  64  is turned to 10 pF, the controller  68  knows that by tuning down the variable capacitor  64  that the variable capacitor  64  is turned to 1.0 pF when it receives a logic one and then a logic zero. 
     Although the flag  92  has been described as having either removed portions  120 ,  124  or upstanding portions  126 ,  128 , these portions may be considered transparent and opaque, respectively. Transparent portions allow optical energy from the emitter  70  to reach the detector  72 . Conversely, the opaque portions block optical energy and prevent it from reaching the detector  72 . In certain embodiments, these portions may be upstanding or removed, while in other embodiments, these portions may be formed from glass, plastic or other like materials. 
     Referring to FIG. 5, the coupler  82  includes the first and second portions  102  and  104 , a center portion  130  adapted to receive the adjust plug  122 , a set screw bore  132  adapted to receive a set screw that, when tightened, retains the adjust plug  122  within the center portion  130 . The first and second portions  102  and  104  of the coupler  82  also include through holes  134  and  136 , that accommodate the fiber optic connectors  88  and  90  and clips  110 ,  112  that engage the flanges  114 ,  116  of the fiber optic connectors  88 ,  90 . As shown in FIG. 5, the through holes  134  and  136  extend up to the slot  100 , thereby allowing the fiber optic cable portions  106 ,  108  of the fiber optic connectors  88  and  90  to abut the slot  100 . Although, the fiber locating structures are shown as through holes  134 ,  136  and clips  110 ,  112 , those of ordinary skill in the art will recognize that such locating structures may be embodied in other configuration such as slots and the like. 
     Numerous additional modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. This description is to be construed as illustrative only, and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and method may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which come within the scope of the appended claims is reserved.