Abstract:
Structures and a method of manufacturing an oscillator are disclosed. The structure contains a substrate with a first and a second major surfaces, a first plurality of conductors arranged in a first pattern on the first major surface, and a second plurality of conductors arranged in a second pattern on the second major surface at a first angle to said first plurality of conductors to reflect and transmit incoming RF energy in cross polarization to a polarization of said incoming RF energy. The method disclosed teaches how to manufacture an oscillator using the structure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is related to co-pending application U.S. application Ser. No., 11/247,709, filed on the same date as the present application, for “An Electromagnetic Array Structure Capable of Operating as An Amplifier or an Oscilator” by Jonathan Lynch, the disclosure of which is incorporated herein by reference. This application is related to co-pending application U.S. application Ser. No. 10/664,112, filed on Sep. 17, 2003, for “Bias Line decoupling method for monolithic amplifier arrays” by Jonathan Lynch, the disclosure of which is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   This technology relates to structures for coupling power into and out of a quasi-optical structure. 
   BACKGROUND AND PRIOR ART 
   Power is difficult to produce at millimeter wave frequencies due to the low power output of transistors and the losses incurred by traditional power combiners at these frequencies. Free space combining, also called “quasi-optical” combining, eliminates the latter problem by allowing electromagnetic energy to combine in free space. 
   Quasi-optical arrays can provide high power by combining the outputs of many (e.g. thousands) of elements. Reflection amplifier arrays are a convenient way to produce power quasi-optically. The reflection amplifier arrays typically have orthogonally polarized input and output antennas in order to reduce mutual coupling between amplifier inputs and outputs. It is desirable to couple inputs and outputs together solely through a partial reflector in order to control the amplitude and phase delay of the coupled energy. Too much “parasitic” coupling between input and output alters the phases of the oscillators, causing decreased combining efficiency and potentially loss of synchronization. 
   Quasi-optical sources (oscillators) have been developed for millimeter wave power, and consist of a number of individual oscillators that are coupled together so that they mutually synchronize in phase and the radiation from all the elements combines coherently, typically in a (more or less) gaussian mode in front of the oscillator array. A number of different methods exist to realize the coupling network, from printed circuit transmission lines to partial reflectors. The key is to provide strong coupling between elements to ensure in-phase oscillation. 
   Many embodiments of oscillator arrays utilize “grid” amplifiers in a resonant cavity formed by a ground plane and a partial reflector. In this type of array the grid amplifiers have equal input and output polarizations so that polarization conversion at the partial reflector is not necessary. The drawback with this type of array is that it is difficult to optimize the efficiency since the grid amplifiers themselves are generally not impedance matched and driven under optimal conditions. 
   Most embodiments in the literature describe arrays that are “transmissive” and not reflective. See for example, J. W. Mink, “Quasi-optical power combining of solid state millimeter wave sources,” IEEE Trans. Microwave Theory Tech., vol. MTT-34, pp. 273-279, Feb. 1986 and Z. B. Popovic, M. Kim, and D. B. Rutledge, “Grid oscillators,” Int. J. Infrared Millimeter Waves, vol. 9, no. 7, pp. 647-654, 1988. This is primarily due to ease of measurements for the transmissive arrays—reflect array performance is difficult to measure since both the source and the load are collocated. However, reflect arrays have the very important advantage of being able to be directly bonded to a heat sink. This is very important for large arrays at millimeter wave frequencies, where efficiency drops considerably and the number of devices per unit area is high. 
   According to the present disclosure, embodiments of structures are described that collimate both the reflected and transmitted energy, and couples all of the reflected power into the orthogonal polarization, as required by the reflection amplifier array. 
   SUMMARY 
   According to the present disclosure, structures for coupling power into and out of a quasi-optical structure are disclosed. 
   According to a first embodiment, a structure is disclosed, comprising: a substrate, a first plurality of periodic pattern of conductors being supported by a first major surface of said substrate, a second plurality of periodic pattern of conductors being supported by a second major surface of said substrate, wherein said first plurality of periodic pattern of conductors are at a first angle to said second plurality of periodic pattern of conductors and said first and second plurality of periodic pattern of conductors reflect and transmit an incoming RF energy in cross polarization compared to a polarization of said incoming RF energy. 
   According to a second embodiment, an electromagnetic array structure is disclosed, comprising: a plurality of active amplification devices arranged in an array, wherein an input of each active amplification device is cross polarized with respect to an output of each active amplification device, a structure disposed in a spaced relation with the plurality of active amplification devices, wherein said structure contains a substrate and a first and second plurality of periodic pattern of conductors and said structure couples cross polarized input and output of each active amplification device so as to only reflect power in the same polarization as polarization of said input of each active amplification device. 
   According to a third embodiment, a structure is disclosed, comprising: a plurality of metal ribs connected by a frame adapted to reflect and transmit an incoming RF energy in cross polarization. 
   According to a fourth embodiment, an electromagnetic array structure is disclosed, comprising: a plurality of active amplification devices arranged in an array, wherein an input of each active amplification device is cross polarized with respect to an output of each active amplification device, a structure disposed in a spaced relation with the plurality of active amplification devices, wherein said structure contains a plurality of metal ribs and said structure couples cross polarized input and output of each active amplification device so as to only reflect power in the same polarization as polarization of said input of each active amplification device. 
   According to a fifth embodiment, a method for manufacturing an oscillator is disclosed, comprising: disposing a plurality of active amplification devices in an array, wherein an input of each active amplification device is cross polarized with respect to an output of each active amplification device, disposing a structure in a spaced relation with the plurality of active amplification devices so as to couple cross polarized input and output of each active amplification device, wherein said structure comprises a substrate, a first plurality of periodic pattern of conductors disposed on said first major surface of said substrate, a second plurality of periodic pattern of conductors disposed on said second major surface of said substrate, wherein said first plurality of periodic pattern of conductors are at a first angle to said second plurality of periodic pattern of conductors. 
   According to a sixth embodiment, a method for manufacturing an oscillator is disclosed, comprising: arranging a plurality of active amplification devices in to an array, wherein an input of each active amplification device is cross polarized with respect to an output of each active amplification device, providing a structure in a spaced relation with the plurality of active amplification devices so as to couple cross polarized input and output of each active amplification device, wherein said structure comprises a plurality of metal ribs. 
   According to a seventh embodiment, a structure is disclosed, comprising: a frequency selective surface which retransmits an incoming RF energy in a predetermined frequency range and also partially reflects said incoming RF energy in said predetermined frequency range, the reflected and retransmitted RF energies having an orthogonal polarization compared to polarization of said incoming RF energy. 

   
     BRIEF DESCRIPTION OF THE FIGURES AND THE DRAWINGS 
       FIG. 1  depicts a side view of a frequency selective surface (FSS) in accordance with the present disclosure; 
       FIG. 2  depicts a top view of side A of the FSS depicted in  FIG. 1  in accordance with the present disclosure; 
       FIG. 3  depicts a top view of side B of the FSS depicted in  FIG. 1  in accordance with the present disclosure; 
       FIGS. 4 and 5  depict the FSS depicted in  FIG. 1  disposed between two lenses in accordance with the present disclosure; 
       FIGS. 6 and 7  depict top view of the lenses depicted in  FIGS. 4 and 5  in accordance with the present disclosure; 
       FIG. 8   a  depicts transmission and reflection of incoming RF energy through the FSS structure in  FIGS. 2 and 3  in accordance with the present disclosure; 
       FIG. 8   b  depicts a unit cell of a periodic conductive pattern disposed on the FSS of  FIG. 2  in accordance with the present disclosure; 
       FIG. 8   c  depicts an equivalent circuit for two unit cells depicted in  FIG. 8   a  in accordance with the present disclosure; 
       FIGS. 9   a  and  9   b  depict examples of an oscillator apparatus in accordance with the present disclosure; 
       FIG. 10  depicts an array of amplification devices in accordance with the present disclosure; 
       FIG. 11  depicts an amplification device in accordance with the present disclosure; 
       FIG. 12  depicts a top view of the oscillator apparatus shown in  FIG. 9   a  in accordance with the present disclosure; 
       FIG. 13   a  depicts a structure comprising a frequency selective surface (FSS) operating as a polarization filter in accordance with the present disclosure; 
       FIG. 13   b  depicts the FSS shown in  FIG. 13   a  disposed between two lenses in accordance with the present disclosure; 
       FIG. 14  depicts a top view of a structure comprising metal ribs in accordance with the present disclosure; 
       FIGS. 15   a ,  15   b  and  15   c  depict exemplary cross section of the structure shown in  FIG. 14  in accordance with the present disclosure; 
       FIG. 15   d  depicts a unit cell of the metal rib periodic pattern shown in  FIGS. 15   a ,  15   b  and  15   c  in accordance with the present disclosure; 
       FIGS. 15   e  and  15   f  depict equivalent circuits for unit equivalent circuit depicted in  FIG. 15   d  in accordance with the present disclosure; 
       FIGS. 16   a ,  16   b  and  16   c  depict examples of an oscillator apparatus in accordance with the present disclosure; 
       FIG. 17  depicts an array of amplification devices in accordance with the present disclosure; 
       FIG. 18  depicts an amplification device in accordance with the present disclosure; 
       FIG. 19  depicts a top view of the oscillator apparatus shown in  FIG. 16   a  in accordance with the present disclosure. 
   

   DETAILED DESCRIPTION 
   The present disclosure provides a method for coupling power into and out of a reflection amplifier array for quasi-optical power combining. The reflection amplifier array offers a simple and versatile method of producing large amounts of power at millimeter wave frequencies. This approach, however, requires that some of the power that is radiated from the array be reflected back to the array in the orthogonal polarization, with the remaining power being radiated away into free space to form the output beam. In addition, it is desired that both the reflected wave and transmitted wave be collimated so that the phases fronts are as flat as possible. The present disclosure describes structures that accomplish this. 
   In one exemplary embodiment, a structure  10  is shown in  FIGS. 1-3 . The structure  10 , as shown in  FIGS. 1-3  consists of a frequency selective surface (FSS)  20  having a periodic pattern of conductors  50  and  60  disposed on the surfaces A and B, respectively, of FSS  20 .  FIG. 1  shows a side view of the structure  10 .  FIGS. 2 and 3  show a periodic pattern of conductors  50  and  60  disposed on the surfaces A and B, respectively, of FSS  20 . Although the periodic pattern of conductors  50  and  60  in this embodiment are aligned so as to be substantially parallel to each other, this is not necessarily a requirement and it shall be understood that other alignments of the periodic pattern of conductors  50  and  60  are possible. 
   The structure  10  may optionally have the frequency selective surface (FSS)  20  sandwiched between two planar-convex lenses  30  and  40  as shown in  FIGS. 4 and 5 .  FIG. 4  shows a side view of the structure  10  with the lenses  30  and  40  and  FIG. 5  shows an exploded side view of the structure  10  with lenses  30  and  40  separated from FSS  20  for clarity reasons.  FIGS. 6 and 7  show top view of lenses  30  and  40  respectively. 
   Referring to  FIG. 8   a , the FSS  20  as depicted in  FIGS. 2 and 3  has the following properties at the operating frequency: power in Einput polarization is actually a combination of Einput-z polarization and Einput-x polarization, as shown in  FIG. 8   a . The power Einput-z polarization relative to the periodic pattern of conductors  50  and  60  is partially reflected back with the same polarization and the remainder is transmitted in the same polarization. Similarly, the power Einput-x polarization relative to the periodic pattern of conductors  50  and  60  is partially reflected back with the same polarization, but with a 180 deg phase reversal, and the remainder is transmitted in the same polarization, also with phase reversal. The Einput-z polarization and Einput-x (180 deg. phase shift) polarization combine to form power in Eoutput polarization, as shown in  FIG. 8   a . Hence, only power with Eoutput polarization is reflected and transmitted by the structure  10 . This being the case, the energy wave (assumed to be 0 deg polarization) incident on the structure  10  reflects no power back with the same polarization, but reflects only in the orthogonal polarization. In addition, power that is transmitted through the structure  10  is also in the orthogonal polarization. 
   If the structure  10  contains the two optional planar-convex lenses  30  and  40 , the coupling of reflected power is given by 
             1     1   +       [       n   2       n   1       ]     2         ,         
where n 2  is the index of refraction of substrate  25 , and n 1  is the index of refraction of the lens  30  or  40 . For n 1 =n 2 , structure  10  produces 3 dB coupling.
 
   Although the periodic pattern of conductors  50  and  60  in  FIGS. 2 and 3  are represented as crenulated lines, it shall be understood that the periodic pattern of conductors  50  and  60  can have different shapes, including but not limited to structures disclosed in B. A. Munk “Frequency Selective Surface, Theory and Design” Wiley, 2000, for this technology to work. The spacing between the periodic pattern of conductors  50  and  60  may be any where from 
           1   50         
of a wavelength of an incoming RF energy to about
 
           1   2         
of the wavelength of an incoming RF energy and the width of the periodic pattern of conductors  50  and  60  may be about
 
           1   8         
of a wavelength of an incoming RF energy. It shall be understood that the width of the periodic pattern of conductors  50  and  60  can vary depending on the orientation and pattern of the periodic pattern of conductors  50  and  60 . The thickness of substrate  25  can be about
 
           1   4         
of a wavelength of an incoming RF energy.
 
     FIG. 8   b  depicts a unit cell  65  of the periodic pattern of conductors  50 . The unit cell  65  is about 
           1   2         
of the wavelength of an incoming RF energy in the X and Z dimensions.  FIG. 8   c  depicts an equivalent circuit  70  for two unit cells  65  disposed on top of each other on surfaces A and B of substrate  25 . The energy wave in vertical polarization gives rise to an inductive shunt susceptance Bver, and the energy wave in the horizontal polarization gives rise to a capacitive shunt susceptance Bhoriz. The optimal values for the shunt susceptances can be derived though:
 
   
     
       
         
           Bhoriz 
           = 
           
             
               - 
               Bvert 
             
             = 
             
               
                 1 
                 
                   377 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Ohms 
                 
               
               ⁢ 
               
                 
                   
                     
                       n 
                       1 
                       2 
                     
                     + 
                     
                       n 
                       2 
                       2 
                     
                   
                 
                 . 
               
             
           
         
       
     
   
   Although the structure  10  in  FIGS. 1-7  is represented as circle, it shall be understood that peripheral edge of the structure  10  can have different shapes, including, but not limited to, square and/or rectangular shapes. 
   The disclosed structure  10  may be used as part of an oscillator  100  shown in  FIG. 9   a  and an oscillator  101  shown in  FIG. 9   b . The oscillators  100  and  101  utilize amplification devices  110  with crossed input/output polarizations arranged in an array  115 , as depicted in  FIGS. 10 and 11 . The array  115  may be disposed on a substrate  118 , as depicted in  FIGS. 9   a  and  9   b , and the substrate  118  may be disposed in a heatsink  119 , again as shown in  FIGS. 9   a  and  9   b . The amplification device  110  depicted in  FIGS. 10 and 11  may include, a ground plane (not shown), two patch antennas, namely input antenna  125  and output antenna  126 , as well as an amplifier  130 , and a bias grid  135  supplying bias voltage to the amplifier  130 , as disclosed in more detail in U.S. patent application Ser. No. 10/664,112, filed on Sep. 17, 2003 which is incorporated herein by reference in its entirety. It is to be understood that patch antennas are only used as an example and that radiating elements, like horn, slot, cavity backed slot, cavity backed patch, dipole, can also be used for the disclosed apparatus. 
   The input antennas  125 , as depicted in  FIGS. 10 and 11 , are polarized in the X direction by outputting the incoming energy at feed point A of the input antennas  125 . Hence, only the energy polarized in the X direction will propagate from the input antennas  125  to the amplifiers  130 . The output antennas  126 , as depicted in  FIGS. 10 and 11 , are polarized in the Z direction by inputting amplified energy from the amplifiers  130  at feed point B of the output antennas  126 . Hence, the output antennas  126  will reradiate the energy polarized in the Z direction. 
   Although the input antennas  125 , depicted in  FIGS. 10 and 11 , are polarized in the X direction and the output antennas  126 , depicted in  FIGS. 10 and 11 , are polarized in the Z direction, it is to be understood that the input antennas  125  can be polarized in any direction. However, the cross polarization of the input antennas  125  and output antennas  126  reduces parasitic coupling and improves the coupling control as will become evident below. 
   The structure  10  utilized by the oscillators  100  and  101 , as depicted in  FIGS. 9   a  and  9   b , provides a mechanism to reflect a specific amount of power back towards the array  115  but in the orthogonal polarization so as to couple the input antennas  125  and output antennas  126 , as shown in  FIGS. 9   a  and  9   b . The power that is not reflected is radiated through the structure  10  to form an output beam that is also polarized in the Z direction, as shown in  FIGS. 9   a  and  9   b . To ensure that power from amplifiers is utilized with maximum efficiency the structure  10  mostly reflects and transmits power that is orthogonal to the power transmitted by the output antennas  126 . The structure  10  also is able to collimate the reflected energy to create a narrow transmitted beam of energy with minimal diffraction. The ability of the structure  10  to collimate is important because it couples the oscillating elements in a way that produces in-phase oscillation and improves power combining efficiency. 
   Although there may be extraneous non-orthogonal reflection off of the lenses  30  and  40  due to transition between the lenses and air, the non-orthogonal reflections are minimal and may be even further minimized by coating the lenses  30  and  40  with a coating (not shown) that is about 
           1   4         
of a wavelength of an incoming RF energy in thickness and has an index of refraction that may be about √{square root over (n)} where n is an index of refraction of the lens  30  or  40 .
 
   The oscillators  100  and  101  may operate without any external power supply as shown in  FIGS. 9   a  and  9   b . Any electrical noise in the oscillators  100  and  101  is amplified by the amplifier  130  and supplied to the output antennas  126 . The output antennas  126  output the energy which reflects off of the structure  10 , is absorbed by the input antennas  125  causing the oscillators  100  and  101  to operate as an oscillator. 
     FIG. 12  depicts top view of the oscillator  100 . In  FIG. 12  the structure  10  is depicted as being translucent in order to show the array  115  of amplification devices  110  below; however, it should be understood that the structure  10  may well be opaque and is only shown as being translucent to help depict its overall relation to the underlying structure. 
   The structure  10  and the array  115  shown in  FIG. 12  and the amplification device  110  shown in  FIG. 11  are not drawn to scale. The diameter of the structure  10  may be twice the width of the array  115  and the size of the amplification device  110  may be about 
           1   2         
of a wavelength of an incoming RF energy.
 
   Referring to  FIGS. 13   a  and  13   b , the structure  10  may further operate as a polarization filter for transmitting energy  80  that is cross-polarized to the input energy  75 . The part of the input energy  75  polarized in the X direction would be reflected back  85  in the Z polarization while the remaining energy  80  will propagate through the structure  10  also in the Z polarization. 
   In another exemplary embodiment, a structure  150  is shown in  FIG. 14 . The structure  150 , as shown in  FIGS. 14 and 15  consists of metal ribs  170  attached to, for example, a frame  180 .  FIG. 14  shows a bottom view of metal ribs  170  held together by a frame  180 . 
     FIGS. 15   a  and  15   b  depict possible exemplary cross sections of the structure  150  along the line  15 .  FIG. 15   a  depicts a cross section wherein the metal ribs  170  are disposed in a straight line and  FIG. 15   b  depicts a cross section wherein the metal ribs  170  are disposed having a parabolic curvature. The structure  150  shown in  FIG. 15   b  may optionally contain a lens  160  as shown in  FIG. 15   c.    
   The metal ribs  170  as depicted in  FIGS. 14 and 15   a - c  have the following properties at the operating frequency: power incident with about +45 degrees polarization with respect to the metal ribs  170  is partially reflected back from the metal ribs  170  with the same polarization and the remainder is transmitted through the slots between the metal ribs  170  in the same polarization. Similarly, power incident with about −45 degrees polarization with respect to the metal ribs  170  is partially reflected back from the metal ribs  170  with the same polarization, but with a 180 deg phase reversal, and the remainder is transmitted through the slots between the metal ribs  170  with the same polarization, also with phase reversal. This being the case, the energy wave (assumed to be 0 deg polarization) incident on the metal ribs  170  reflects no power back in the same polarization, but reflects only in the orthogonal polarization. In addition, power that is transmitted through the slots between the metal ribs  170  is also in the orthogonal polarization. The collimation of the transmitted wave is accomplished with the lens  160  shown in  FIG. 14 . Collimation of the reflected wave is accomplished by the parabolic curvature of the metallic side of the structure. 
     FIG. 15   d  depicts a unit cell  171  of the metal ribs  170 . The centers of the metal ribs  170  in the unit cell  171  may be about 
           1   2         
of the wavelength of an incoming RF energy away from each other. The widest gap between the metal ribs  170  in the unit cell  171  may be about
 
           1   4         
of the wavelength of an incoming RF energy. The smallest gap between the metal ribs  170  in the unit cell  171  may be about
 
           1   8         
of the wavelength of an incoming RF energy.  FIGS. 15   e  and  15   f  depict equivalent circuits  172 ,  173 , respectively, for the unit cell  171 . The energy wave in horizontal polarization gives rise to an inductive shunt susceptance as shown in  FIG. 15   e , and the energy wave in the vertical polarization gives rise to a capacitive shunt susceptance as shown in  FIG. 15   f.    
   Although the metal ribs  170  in  FIGS. 14-15   d  are T-shaped, it shall be understood other rib shapes that are straight, rounded or flared may also be implemented. 
   Although the structure  150  in  FIGS. 14-15   c  is represented as circle, it shall be understood that the peripheral edge of the structure  150  can have different shapes, including, but not limited to, square and/or rectangular shapes. 
   The disclosed structure  150  may be used as part of an oscillator  200 ,  201  and  202  shown in  FIGS. 16   a - c . The oscillators  200 ,  201 ,  202  utilize amplification devices  210  with crossed input/output polarizations arranged in an array  215 , as depicted in  FIGS. 17 and 18 . The array  215  may be disposed on a substrate  218 , as depicted in  FIGS. 16   a - c . The substrate  218  may be disposed in a heatsink  219 , as shown in  FIGS. 16   a - c . The amplification device  210  depicted in  FIGS. 17 and 18  may include a ground plane (not shown), two patch antennas, namely input antenna  225  and output antenna  226 , as well as an amplifier  230 , and a bias grid  235  supplying bias voltage to the amplifier  230 , as disclosed in more detail in U.S. patent application Ser. No. 10/664,112, filed on Sep. 17, 2003, which is incorporated herein by reference in its entirety. It is to be understood that patch antennas are only used as an example and that radiating elements, like horn, slot, cavity backed slot, cavity backed patch, dipole, can also be used for the disclosed apparatus. 
   The input antennas  225 , as depicted in  FIGS. 17 and 18 , are polarized in the X direction by outputting the incoming energy at feed point C of the input antennas  225 . Hence, only the energy polarized in the X direction will propagate from the input antennas  225  to the amplifiers  230 . The output antennas  226 , as depicted in  FIGS. 17 and 18 , are polarized in the Z direction by inputting amplified energy from the amplifiers  230  at feed point D of the output antennas  226 . Hence, the output antennas  226  will reradiate the energy polarized in the Z direction. 
   Although the input antennas  225 , depicted in  FIGS. 17 and 18 , are polarized in the X direction and the output antennas  226 , depicted in  FIGS. 17 and 18 , are polarized in the Z direction, it is to be understood that the input antennas  225  can be polarized in any direction. However, the cross polarization of the input antennas  225  and output antennas  226  reduces parasitic coupling and improves the coupling control as will become evident below. 
   The structure  150  utilized by oscillators  200 ,  201 ,  202 , as depicted in  FIGS. 16   a - c , provides a mechanism to reflect some power back towards the array  215  but in the orthogonal polarization so as to couple the input antennas  225  and output antennas  226 , as shown in  FIGS. 16   a - c . The power that is not reflected is radiated through the structure  150  to form an output beam that is also polarized in the Z direction, as shown in  FIGS. 16   a - c . To ensure that power from amplifiers is utilized with maximum efficiency the structure  150  mostly reflects and transmits power that is orthogonal to the power transmitted by the output antennas  226 . 
   Although there may be extraneous non-orthogonal reflection off of the lens  160  due to transition between the lens and air, the non-orthogonal reflections are minimal and may be even further minimized by coating the lens  160  with a coating (not shown) that is about 
           1   4         
of a wavelength in thickness and has an index of refraction that may be about √{square root over (n)} where n is an index of refraction of the lens  160 .
 
   The oscillators  200 ,  201 ,  202  may operate without any external power supply as shown in  FIGS. 16   a - c . Any electrical noise in the oscillators  200 ,  201 ,  202  is amplified by the amplifier  230  and supplied to the output antennas  226 . The output antennas  226  output the energy which reflects off of the structure  150 , is absorbed by the input antennas  225  causing the oscillator  200  to operates as an oscillator. 
     FIG. 19  depicts top view of the oscillator  200 . In  FIG. 19  the structure  150  is depicted as being translucent in order to show the array  215  of amplification devices  210  below; however, it should be understood that the structure  150  may well be opaque and is only shown as being translucent to help depict its overall relation to the underlying structure. 
   The structure  150  and the array  215  shown in  FIG. 19  and the amplification device  210  shown in  FIG. 18  are not drawn to scale. The diameter of the structure  150  may be twice the width of the array  215  and the size of the amplification device  210  may be about 
           1   2         
of a wavelength of an incoming RF energy.
 
   The foregoing Detailed Description of exemplary and preferred embodiments is presented for purposes of illustration and disclosure in accordance with the requirements of the law. It is not intended to be exhaustive nor to limit the invention to the precise form(s) described, but only to enable others skilled in the art to understand how the invention may be suited for a particular use or implementation. The possibility of modifications and variations will be apparent to practitioners skilled in the art. No limitation is intended by the description of exemplary embodiments which may have included tolerances, feature dimensions, specific operating conditions, engineering specifications, or the like, and which may vary between implementations or with changes to the state of the art, and no limitation should be implied therefrom. Applicant has made this disclosure with respect to the current state of the art, but also contemplates advancements and that adaptations in the future may take into consideration of those advancements, namely in accordance with the then current state of the art. It is intended that the scope of the invention be defined by the Claims as written and equivalents as applicable. Reference to a claim element in the singular is not intended to mean “one and only one” unless explicitly so stated. Moreover, no element, component, nor method or process step in this disclosure is intended to be dedicated to the public regardless of whether the element, component, or step is explicitly recited in the Claims. No claim element herein is to be construed under the provisions of 35 U.S.C. Sec. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for . . . ” and no method or process step herein is to be construed under those provisions unless the step, or steps, are expressly recited using the phrase “step(s) for . . . .”