Patent Publication Number: US-7221323-B2

Title: Tag-along microsensor device and method

Description:
This application is a continuation-in-part of applicant&#39;s “Nano-antenna apparatus and method,” filed Dec. 11, 2004 as application Ser. No. 11/010,083 (published Jun. 16, 2005 as US 2005/0128146 A1), U.S. Pat. No. 7,068,225, which claims benefit of prior filed provisional patent application Ser. No. 60/529064 filed Dec. 12, 2003. All of the above cited applications are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION  
   1. Field of the Invention 
   The present invention relates to micro-sensors, particularly micro-sensors capable of adhering to a person, animal or vehicle and wireless relaying relevant position or other sensor information. The present invention further relates to a microsensor method of operation. Secondarily, the present invention also relates to antennas and to a system and method to utilize a conducting enclosure as a highly efficient electrically small antenna. 
   2. Description of the Prior Art 
   Ultra-wideband (UWB) systems are in great demand for precision tracking, radar, and communications. A commercially successful UWB system must be both small and very low power. Similarly, there is great interest at present in “smart dust,” miniature sensors, and other nano-devices that can wirelessly transmit data, positioning signals, or radar signals using very low power signals and utilizing wavelengths that may be much larger than the device itself. Highly efficient, electrically small antennas are a necessity for UWB systems, smart dust, nano-devices, and numerous other commercial and government applications. 
   Prior art efficient antennas commonly are on the order of a half-wavelength long for a dipole or a quarter-wavelength long for a monopole. For ultra-wideband (UWB) operation in the 3.1–10.6 GHz, a 5.3 cm dipole or a 2.6 cm monopole are called for (5.7 GHz center frequency). These antennas may be small enough for some applications. For other applications, even smaller antennas may be required. Efficient quarter to half wave antennas that operate in the upper VHF band or UHF band (for instance from 100 MHz on up) must be significantly larger than analogous microwave antennas. This is too large for many potential applications. In general however, no matter the application, there is always a need to make antennas smaller and less obtrusive while remaining efficient. Existing small VHF/UHF UWB antennas tend to be very inefficient including large current radiators, and resistively loaded antennas. Antennas smaller than a quarter-wavelength are usually referred to as electrically small antennas. In prior art, electrically small antennas are prone to be inefficient, particularly when significantly smaller than a quarter-wavelength. 
   In view of the foregoing, there is a great need for an efficient, electrically small UWB antenna for positioning, smart dust, nano-devices, and other applications. There is a further need for a method to effect efficient UWB transmissions from electrically small enclosures. Additionally, there is a need for an antenna apparatus that transcends traditionally accepted bounds of antenna size versus performance. There is a further need for a microsensor capable of adhering to a person, animal, or vehicle, and wirelessly relaying telemetry, sensor, position, and other data. These needs and more are met by the present invention. 
   SUMMARY OF THE INVENTION 
   Accordingly it is an object of the present invention to provide a microsensor capable of adhering to a person, animal, or vehicle, and wirelessly relaying telemetry, sensor, position, and other data. This need and others are met by a tag-along microsensor device and method. 
   A tag-along microsensor device comprises a means for transmitting a signal, adhesion means, and sensing means. In a preferred embodiment, a means for transmitting a signal includes a nano-antenna apparatus. Adhesion means may include mechanical, magnetic, or static electric adhesion means. Mechanical adhesion means may include a hook or barb, or a chemical adhesion means such as glue or other sticky chemical adhesive. Sensing means may include sensing of audio signals, accelerometers, gyroscopes, compass, gyrocompasses, or other sensors. 
   Alternatively, a tag-along microsensor method includes the steps of deploying a tag-along microsensor, transmitting a signal from a tag-along microsensor, receiving a signal, and acting on a signal. In a preferred embodiment, transmitting a signal includes the steps of charging a first conducting surface with respect to a second conducting surface, and discharging a first conducting surface with respect to a second conducting surface, so that the discharging forms a substantially continuous closed conducting shell from a first conducting surface and a second conducting surface. In other embodiments, deploying a tag-along microsensor results in a tag-along microsensor adhering to an entity such as a person, vehicle, or animal. In still further embodiments, receiving a signal may involve receiving a signal is in the vicinity of a location where a tag-along microsensor was deployed or at a location a substantial distance from where said tag-along microsensor was deployed. Acting on a signal may include recording data from a signal or intercepting an entity to which a tag-along microsensor is attached. 
   With these and other objects, advantages, and features of the invention that may become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the detailed description of the invention, the appended claims and to the several drawings herein. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-section of a preferred embodiment nano-antenna apparatus. 
       FIG. 2  is an effective electrical circuit diagram for a nano-antenna apparatus. 
       FIG. 3  is a flow chart describing a nano-antenna method of operation. 
       FIG. 4  is an exploded view of a preferred embodiment nano-antenna apparatus. 
       FIG. 5  is a schematic diagram of a first alternate embodiment nano-antenna apparatus. 
       FIG. 6  is a schematic diagram of a second alternate embodiment nano-antenna apparatus. 
       FIG. 7  is a schematic diagram of a third alternate embodiment nano-antenna apparatus. 
       FIG. 8  is a cross-section diagram of a preferred embodiment tag-along microsensor. 
       FIG. 9  is a cross-section diagram of an alternate embodiment tag-along microsensor. 
       FIG. 10  is a flow chart describing a tag-along microsensor mode of operation. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Overview of the Invention 
   The present invention is directed to a tag-along microsensor device and method. A tag-along microsensor is a device capable of adhering to a person, animal, or vehicle and wirelessly relaying telemetry, sensor, position or other data. In a preferred embodiment, a tag-along microsensor employs a nano-antenna apparatus to effect wireless transmission. 
   The present invention is further directed to a nano-antenna apparatus and method. Instead of an antenna apparatus distinct from an associated RF device as taught in the prior art, the present invention teaches that an enclosure surrounding an RF device be used as an antenna. This conducting enclosure antenna makes best possible use of the available form factor for an RF device. Thus, a conducting enclosure antenna provides performance superior to a smaller antenna that is a mere adjunct to the device. A conducting enclosure antenna is also a “nano-antenna,” an antenna that potentially transcends traditionally accepted limits to antenna size and performance by offering the performance and efficiency of a typical quarter-wave antenna in a package that may 1% of a wavelength in dimension or even smaller. A nano-antenna apparatus is well-suited for use in conjunction with a tag-along microsensor. 
   The present invention will now be described more fully in detail with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown. This invention should not, however, be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
   Nano-Antenna Apparatus 
     FIG. 1  is a cross-section  100  of a preferred embodiment nano-antenna device  101 . Preferred embodiment nano-antenna device  101  comprises conducting enclosure antenna  103 , and dielectric layer  105 . For ease of theoretical calculation, conducting enclosure antenna  103 , is assumed to be spherical with radius R s , and dielectric layer  105  is assumed to have a thickness R d −R s . Thus, nano-antenna device  101  has a total radius R d . In practice, nano-antenna device  101  may assume a wide variety of form factors suitable for particular applications. Some of these form factors will be discussed later as particular alternate embodiments. Dielectric layer  105  also acts so as to electrically insulate conducting enclosure antenna  103  from electrical contact with surrounding space  106 . Surrounding space  106  may include not only free space, but also ground, human bodies, and any other objects in the immediate vicinity of nano-antenna device  101 . In practice, since most of the electrostatic energy is concentrated around the gap, it may be preferred for dielectric layer  105  to be thicker in the vicinity of the gap or have another non-uniform thickness profile. Similarly, dielectric layer  105  need not be characterized by a fixed dielectric constant, but rather may have a dielectric constant that varies according to a desired impedance taper. 
   Conducting enclosure antenna  103  further comprises a first conducting surface  107 , a second conducting surface  109 , and discharge switching means  113 . First conducting surface  107 , and second conducting surface  109  are separated by a gap region  111  with gap width g. Discharge switching means  113  further comprises first boundary discharge switch  115  and second boundary discharge switch  117 . First boundary discharge switch  115  and second boundary discharge switch  117  are preferentially high efficiency switches capable of switching speeds substantially faster than a characteristic time associated with a radiated signal from nano-antenna device  101 . First boundary discharge switch  115  and second boundary discharge switch  117  may be step recovery or other diodes, FET or other high speed transistors, MEMS devices, or other high speed, high efficiency switching devices. In alternate embodiments, discharge switching means  113  may further comprise filtering means to enable nano-antenna device  101  to radiate signals within a desired spectral mask. In a preferred embodiment, first boundary discharge switch  115  and second boundary discharge switch  117  act so as to electrically isolate gap region  111  from dielectric layer  105  and surrounding space  106 . In optional embodiments, discharge switching means  113  may further comprise internal discharge switch  118 . 
   In a preferred mode of operation, conducting enclosure antenna  103  begins in a charged state with first conducting surface  107  charged to a particular voltage with respect to second conducting surface  109 . Conversely (and equivalently), one may think of second conducting surface  109  charged to a particular voltage with respect to first conducting surface  107 . Charging switch  116  is useful in this charging process as will be explained further in reference to effective electrical circuit diagram  200 . Gap region  111 , dielectric layer  105 , and surrounding space  106  store electrostatic energy U tot =U in +U out  associated with the original charged state of first conducting surface  107  with respect to second conducting surface  109 . Discharge switching means  113  then acts so as to discharge first conducting surface  107  and second conducting surface  109 . Simultaneously, discharge switching means  113  acts so as to electrically isolate gap region  111  from dielectric layer  105  and surrounding space  106 . Thus in a preferred mode of operation, discharge switching means  113  partitions outside electrostatic energy U out  from inside electrostatic energy U in . Discharge switching means  113  thus causes outside electrostatic energy U out  stored in dielectric layer  105  and surrounding space  106  to be isolated, to decouple, and to radiate away as a UWB impulse. Discharge switching means  113  causes inside electrostatic energy U in  stored in gap region  111  to be absorbed or dissipated. 
   In a preferred mode of operation, nano-antenna device  101  becomes a radiator of electromagnetic ultra-wideband impulses associated with the decoupling of outside electrostatic energy U out  originally stored in dielectric layer  105  and surrounding space  106 . The efficiency of nano-antenna device  101  is a function of the fraction of energy originally stored in dielectric layer  105  and surrounding space  106  to the total electrostatic energy. 
   One may improve efficiency of nano-antenna device  101  by minimizing electrostatic energy U in  stored in gap region  111 . Electrostatic energy U in  stored in gap region  111  may be minimized by filling gap region  111  with a relatively low dielectric constant medium such as free space or air. Electrostatic energy U in  stored in gap region  111  may further be minimized by controlling the geometry of gap region  111 . For instance one might maximize gap with g subject to other design constraints. 
   Alternatively, one may improve efficiency of nano-antenna device  101  by maximizing electrostatic energy U out  stored in dielectric layer  105  and surrounding space  106 . Electrostatic energy U out  stored in dielectric layer  105  and surrounding space  106  may be maximized employing a relatively high dielectric constant medium in dielectric layer  105 . Electrostatic energy U out  stored in dielectric layer  105  and surrounding space  106  may further be maximized by controlling the geometry of first conducting surface  107  and second conducting surface  109 . 
   In summary, by minimizing electrostatic energy stored in gap region  111  U in  and/or by maximizing electrostatic energy U out  stored in dielectric layer  105  and surrounding space  106  efficiency of nano-antenna device  101  can be made very high, even though nano-antenna device  101  may be electrically quite small. These and other details of the present invention will become clear upon understanding an effective electrical circuit and a process flow diagram. 
   Effective Electrical Circuit 
     FIG. 2  is an effective electrical circuit diagram  200  for nano-antenna apparatus  101 . First conducting surface  107 , second conducting surface  109 , dielectric layer  105 , and surrounding space  106  cooperate to form outer capacitance C out    219 . First conducting surface  107 , second conducting surface  109 , and gap region  111  cooperate to form inner capacitance C in    221 . Discharge switching means  213  comprises discharge switch S 1    216 . 
   Discharge switch S 1    216  comprises boundary discharge switch  215 . Boundary discharge switch  215  in effective electrical circuit diagram  200  represents a plurality of actual switches such as first boundary discharge switch  115  and second boundary discharge switch  117 . In optional embodiments, discharge switch S 1    216  may be a double pole single throw switch further comprising internal discharge switch  218 . Internal discharge switch  218  acts so as to short out inner capacitance C in    221 . Here again, internal discharge switch  218  in effective electrical circuit diagram  200  represents a plurality of actual switches such as internal discharge switch  118 . To reiterate, although boundary discharge switch  215  is shown as a single individual boundary discharge switch  215  in effective electrical circuit diagram  200 , boundary discharge switch  215  represents the functionality of potentially many actual switches distributed around the periphery of gap region  111 . 
   Discharge switching means  213  may also include filtering means  223 . Filtering means  223  may be designed so as to ensure that nano-antenna device  101  radiates signals with spectral content within a desired spectral mask. If radiation from nano-antenna device  101  is not subject to a spectral mask, then filtering means  223  may not be required. Filtering means  223  is preferentially a diplexing filter in which out of band components are dissipated instead of reflected. 
   In alternate embodiments, discharge switching means  213  may be intended to discharge the parallel combination of outer capacitance C out    219  and inner capacitance C in    221  so slowly as to radiate no appreciable energy (i.e. adiabatically). Also under these circumstances, discharge switching means  213  may not require filtering means  223 . 
   In a preferred embodiment, discharge switching means  213  acts so as to electrically isolate outer capacitance C out    219  from inner capacitance C in    221 . Energy stored in inner capacitance C in    221  will be dissipated, for instance in internal discharge switch  218 . Discharge switching means  213  accomplishes this goal by transforming first conducting surface  107  and second conducting surface  109  into a continuous closed conducting surface that electrically isolates outer capacitance C out    219  from inner capacitance C in    221 . Similarly discharge switching means  213  acts to isolate boundary discharge switch  215  from internal discharge switch  218  so that internal discharge switch  218  discharges only inner capacitance C in    221 . 
   Nano-antenna apparatus  101  also includes additional functionality not shown in  FIG. 1 . Nano-antenna apparatus  101  further comprises charging means  225 . Charging means  225  includes charging switch S 2    227  and power source  229 . Charging switch S 2    227  may be implemented with step recovery or other diodes, FET or other high speed transistors, MEMS devices, or other switching devices. Power source  229  may further comprise a voltage source, battery, current source, charge pump, or other source of electric energy. Power source  229  also preferentially includes means for operation with alternate polarity so that nano-antenna device  101  can radiate flipped or BPSK signals. 
   In a preferred mode of operation, charging means  225  is intended to charge the parallel combination of outer capacitance C out    219  and inner capacitance C in    221  so slowly (adiabatically) as to radiate no appreciable energy. If charging means  225  is intended to charge the parallel combination of outer capacitance C out    219  and inner capacitance C in    221  so quickly as to radiate appreciable energy, then charging means  225  may further include filtering means  224  so as to ensure that nano-antenna device  101  radiates signals within a desired spectral mask. 
   Nano-Antenna Method of Operation 
     FIG. 3  is a flow chart  300  describing a method of operation  330  for transmitting UWB impulses. Method of operation  330  is a recursive operation that may repeat for as many cycles as are required to complete a desired transmission. nano-antenna method of operation  330  begins with process block  331  in which charging switch S 2    227  closes to enable charging means  225  to charge the parallel combination of outer capacitance C out    219  and inner capacitance C in    221 . In a preferred embodiment, process block  331  comprises a charging process in which charging takes place so slowly that substantially no radiation occurs (i.e. adiabatically). In alternate embodiments, process block  331  may comprise a charging process in which charging takes place so quickly that an impulse of radiation does occur. In further alternate embodiments, process block  331  may comprise a charging process with switchable polarity, thus enabling nano-antenna apparatus  101  to radiate signals with “flip” or BPSK modulation. 
   Method of operation  330  continues with decision block  333 . Decision block  333  assesses whether the parallel combination of outer capacitance C out    219  and inner capacitance C in    221  is adequately charged. If “No,” then method of operation  330  continues back at process block  331 . If “Yes,” then method of operation  330  continues at process block  335  in which charging switch S 2    227  opens to isolate the parallel combination of outer capacitance C out    219  and inner capacitance C in    221 . 
   Method of operation  330  continues with decision block  337 . Decision block  337  assesses whether the time has arrived to discharge the parallel combination of outer capacitance C out    219  and inner capacitance C in    221 . Decision block  337  (and potentially optional delay block  339 ) may act in accordance with a desired pulse position modulation scheme so as to cause a discharge and associated radiated energy to occur at a desired time. If “No,” then method of operation  330  continues with optional delay block  339  before continuing back at decision block  337 . If “Yes,” then method of operation  330  continues at process block  341  in which discharge switch S 1    216  closes to discharge the parallel combination of outer capacitance C out    219  and inner capacitance C in    221 . In a preferred embodiment, process block  341  comprises a discharging process in which discharging takes place so quickly that an impulse of radiation does occur. In alternate embodiments, process block  341  comprises a discharging process in which discharging takes place so slowly that substantially no radiation occurs (i.e. adiabatically). For proper function as a radiating device, at least one of process block  331  and process block  341  must not be adiabatic in order for radiation to occur. In yet other alternate embodiments, process block  331  and process block  341  may vary between rapid and adiabatic charging and/or discharging, respectively, in accordance with a particular modulation scheme. 
   Method of operation  330  continues with decision block  343 . Decision block  343  assesses whether the discharge of the parallel combination of outer capacitance C out    219  and inner capacitance C in    221  is complete. If “No,” then method of operation  330  continues back at process block  341 . If “Yes,” then method of operation  330  continues at process block  345  in which discharge switch S 1    216  opens to isolate the parallel combination of outer capacitance C out    219  and inner capacitance C in    221 . 
   Method of operation  330  continues with decision block  347 . Decision block  347  assesses whether the time has arrived to charge the parallel combination of outer capacitance C out    219  and inner capacitance C in    221 . If “No,” then method of operation  330  continues with optional delay block  349  before continuing back at decision block  347 . If “Yes,” then method of operation  330  continues back at process block  331 . 
   Theory of Nano-Antenna Operation and Design Examples 
   In a preferred embodiment, nano-antenna apparatus  101  acts so as to isolate or partitions outside electrostatic energy (U out =½C out  V 2 ) from inside electrostatic energy (U in =½C in  V 2 ). Conducting enclosure antenna  103  forms a substantially continuous closed conducting surface that substantially partitions total energy into outside electrostatic energy U out  and inside electrostatic energy U in . Outside electrostatic energy U out  then decouples and radiates away as a UWB impulse with a time dependence and frequency content dependent upon dimensional factors (like R s  and R d ) as well as properties of dielectric layer  105 . Since the same voltage difference V applies to both capacitances, outside electrostatic energy U out  and inside electrostatic energy U in . are directly proportional to outer capacitance C out    219  and inner capacitance C in    221 , respectively. Thus, the efficiency η of nano-antenna apparatus  101  is: 
   
     
       
         
           
             
               
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                         C 
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                           C 
                           out 
                         
                       
                     
                   
                 
               
             
             
               
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   The severe dielectric interface may be prone to reflect signals and disperse the signals. Assuming dielectric losses and ohmic losses in conducting enclosure antenna  103 , in dielectric layer  105 , and discharge switching means  113  are negligible, the only other loss mechanism is radiation. A further consideration is that the boundary between dielectric layer  105  and surrounding space  106  lies within the near field zone, and thus energy is likely to “tunnel” through the boundary. In any event, a nano-antenna device  101  will radiate quite efficiently. 
   UHF Design Example 
   Consider spherical nano-antenna device  101  with a radius R s =10 cm and no dielectric. Spherical nano-antenna device  101  will then exhibit dipole like behavior with half power points around 200 MHz and 1000 MHz. A 20 cm diameter spherical nano-antenna device  101  may be too large for many applications. Consider instead a spherical nano-antenna device  101  with a radius R s =1 cm. By simple scaling relations, this dimensionally ten times smaller spherical nano-antenna device  101  will have a frequency response ten times higher: 2000 MHz to 10,000 MHz. Suppose this spherical nano-antenna device  101  with a radius R s =1 cm is embedded in dielectric layer  105  composed of a high dielectric constant material (such as TiO 2  with relative dielectric constant ε r =100). Dielectric layer  105  may be thus characterized by a relative dielectric constant ε r . Since electrical size scales as √{square root over (ε r )}, this spherical nano-antenna device  101  with a radius R s =1 cm will now have the same frequency response as a spherical nano-antenna device  101  with a radius R s =10 cm (i.e. 200 MHz to 1000 MHz). A dielectric layer  105  with thickness R s −R d  equal to radius R s  is sufficient to encompass a region in which about 90% of outside electrostatic energy U out  would be stored assuming there were no dielectric (other than free space). The exterior capacitance  219  will be about C out =15 pF and the interior capacitance  221  will be about C in =2 pF assuming a 60 mil gap. Thus a spherical nano-antenna device  101  with a conducting enclosure radius R s =1 cm and a dielectric radius R d =2 cm operating between 200–1000 MHz may be about the size of a golf ball with a diameter of 4 cm (a bit over 1.5 in). This nano-antenna device  101  will have an efficiency of: 
                 η   =         C   out         C   in     +     C   out         =         15   ⁢           ⁢   pF         2   ⁢           ⁢   pF     +     15   ⁢   pF         =     88   ⁢           ⁢   %                 (   2   )               
This efficiency is extraordinarily good for an antenna of electric radius 0.0133 λ(i.e. 2 cm radius antenna operational at 200 MHz or λ=1.5 m).
 
Microwave Design Example
 
   For a microwave frequency range design example, the frequency response of the previous section may be scaled up by a factor of ten so that the operational frequency lies between 2–10 GHz. As noted in the previous section, a nano-antenna device  101  with R s =1 cm has the correct frequency response, however the outside capacitance  219  will be about C out =0.15 pF and the interior capacitance  221  will be about C in =2 pF assuming a 60 mil gap. The efficiency will be: 
                 η   =         C   out         C   in     +     C   out         =         0.15   ⁢           ⁢   pF         2   ⁢           ⁢   pF     +     0.15   ⁢   pF         =     6.98   ⁢           ⁢   %                 (   3   )               
Ironically, an even smaller dielectrically loaded nano-antenna apparatus  101  will be more efficient.
 
   Consider a nano-antenna device  101  with R s =1 mm embedded in dielectric layer  105  composed of a high dielectric constant material (such as TiO 2  with relative dielectric constant ε r =100) out to a radius R d =2 mm. Then the frequency response is as desired (2–10 GHz), the exterior capacitance  219  will be about C out =1.5 pF and the interior capacitance  221  will be about C in =0.2 pF assuming a 5 mil gap. As before: 
                 η   =         C   out         C   in     +     C   out         =         1.5   ⁢           ⁢   pF         0.2   ⁢           ⁢   pF     +     1.5   ⁢   pF         =     88   ⁢           ⁢   %                 (   4   )               
With such dimensions, one could encapsulate a chip and make an ultra miniature UWB transmitter limited only by the constraints of the battery or power scavenging means.
 
   These two examples illustrate how proper choice of a dimension of a nano-antenna device volume (such as R s  and R d ) and proper choice of a dielectric constant characterizing a dielectric layer result in a desired frequency response. 
   Detailed Description of Nano-Antenna Apparatus 
     FIG. 4  is an exploded view  400  of a preferred embodiment nano-antenna apparatus  101 . Nano-antenna apparatus  101  comprises dielectric layer  105  and conducting enclosure antenna  103 . Conducting enclosure antenna  103  further comprises first conducting surface  107 , second conducting surface  109 , and gap region  111 . Nano-antenna apparatus  101  occupies a substantially spheroidal volume. 
   First conducting hemisphere  451  and first ground plane  455  of first printed circuit board  453  cooperate to form first conducting surface  107 . First conducting surface  107  forms a substantially closed conducting shell except for a limited number of optional pass-throughs, orifices, or vias to allow first printed circuit board  453  or other devices within first conducting surface  107  to connect to devices within second conducting surface  109 , user interfaces, sensors, or other external devices. First printed circuit board  453  further provides a location for associated circuitry such as charging means  225  and discharge switching means  113 . Additionally, first printed circuit board  453  may support control or processor functionality, sensor or transducer functionality, modulation functionality, input/output functionality, data storage functionality, or any other functionality useful for a particular application of nano-antenna device  101 . In particular first printed circuit board  453  can support functionality to enable nano-antenna device  101  to be an electrically small transmitter capable of communication, positioning, radar, or other useful application. In alternate embodiments, first printed circuit board  453  can support functionality to enable nano-antenna device  101  to be a receiver as well as a transmitter. Any or all of these functionalities may be implemented in electronic devices within first conducting surface  107 . “Electronic devices” include but are not necessarily limited to circuit board  453 , other circuit boards, components, or other devices. Thus in a preferred embodiment, first conducting surface  107  is not only an antenna but also encloses electronic devices. 
   Second conducting hemisphere  457  and second ground plane  459  of second printed circuit board  461  cooperate to form second conducting surface  109 . Second conducting surface  109  forms a substantially closed conducting shell except for a limited number of optional pass-throughs, orifices, or vias to allow second printed circuit board  461  or other devices within second conducting surface  109  to connect to devices within first conducting surface  107 , user interfaces, sensors, transducers, or other external devices. For instance, second conducting surface  109  may enclose a battery  463  or other power supply means. Battery  463  may further function as a weight to tend to orient conducting enclosure antenna  103  in a desired orientation. 
   In alternate embodiments, printed circuit board  461  may be replaced by second ground plane  459  with adequate thickness to provide sufficient mechanical strength. In still further embodiments, second conducting hemisphere  457  and second ground plane  459  may cooperate to form an empty closed conducting shell. Thus, second conducting surface  109  behaves as an antenna element, but may or may not also be an enclosure. 
   First ground plane  455 , second ground plane  459 , and insulating spacer  465  cooperate to form gap region  111 . Insulating spacer  465  may further comprise ribs  467  to provide additional mechanical support and to maintain a uniform spacing between first ground plane  455  and second ground plane  459 . Insulating spacer  465  further comprises vias or passthroughs like first via  469  second via  471 , and third via  473 . 
   Discharge switching means  113  comprise a variety of discharge switches like first boundary discharge switch  115  and second boundary discharge switch  117 . First boundary discharge switch  115  provides an electrical connection between first conducting surface  107  and second conducting surface  109 , intermediate gap region  111  through first via  469 . Similarly, second boundary discharge switch  117  provides an electrical connection between first conducting surface  107  and second conducting surface  109 , intermediate gap region  111  through second via  471 . In alternate embodiments, discharge switching means  113  may further comprise transmit/receive switching means to enable a nano-antenna device to receive signals as well as transmit. 
   Charging means  225  comprise a plurality of charging switches like charging switch  116 . charging switch  116  provides an electrical connection between first conducting surface  107  and second conducting surface  109 , intermediate gap region  111  through third via  473 . 
   In a preferred mode of operation, discharge switching means  113  acts so as to unify first conducting hemisphere  451  and second conducting hemisphere  457  into a single closed conducting shell. In this embodiment, first conducting hemisphere  451  and second conducting hemisphere  457  enclose a substantially spheroidal volume. Thus, first conducting hemisphere  451  and second conducting hemisphere  457  form a Faraday cage that isolates interior energy in gap region  111  from exterior energy in dielectric layer  105  and surrounding space  106 . Although discharge switch  215  is shown as a single ring of boundary discharge switches including first boundary discharge switch  115  and second boundary discharge switch  117 , in practice discharge switch  215  may employ as many switches in as high a density and as thick a layer as are required to unify first conducting hemisphere  451  and second conducting hemisphere  457  into a single closed conducting shell well enough for a desired efficiency. As usual, a designer must weigh performance versus cost and complexity considerations. 
   Alternate Nano-Antenna Device Embodiments 
   Preferred embodiment nano-antenna device  101  is substantially spheroidal. A spherical form factor is compact and produces a non-dispersive impulse waveform. A spherical form factor also lends itself well to theoretical analysis. The teachings of the present invention are not limited to spherical form factors, however. Alternate form factors include but are not limited to prolate spheroids, oblate spheroids, and Cartesian rectangular solids. Any form factor is likely to require modification and adaptation to the demands of a particular application, so these particular examples should be considered as merely illustrative and not exhaustive. This section will survey a few possible alternate form factors so as to give some small indication of the wide variety of variations possible for implementation of the present invention. 
   First Alternate Embodiment 
     FIG. 5  is a schematic diagram  500  of a first alternate embodiment nano-antenna apparatus  501 . First alternate embodiment nano-antenna apparatus  501  comprises a dielectric layer  505 , a first conducting surface  507  and a second conducting surface  509 . First conducting surface  507  and second conducting surface  509  are separated by a gap region  511 . First alternate embodiment nano-antenna apparatus  501  occupies a volume that is substantially similar to a prolate spheroid. 
   Although in general an approximate symmetry in relative size is preferred, first conducting surface  507  is much smaller in extent than second conducting surface  509 . In this embodiment, first conducting surface  507  is a protuberance on second conducting surface  509 . Such an asymmetric form factor is preferred if the frequency content of a desired radiated signal is higher than would otherwise be radiated by a symmetric configuration. Shaping of first conducting surface  507  and second conducting surface  509  also enables a degree of control over the radiated spectrum. 
   Second Alternate Embodiment 
     FIG. 6  is a schematic diagram  600  of a second alternate embodiment nano-antenna apparatus  601 . Second alternate embodiment nano-antenna apparatus  601  comprises a dielectric layer  605 , a first conducting surface  607  and a second conducting surface  609 . First conducting surface  607  and second conducting surface  609  are separated by a gap region  611 . 
   Second alternate embodiment nano-antenna apparatus  601  has an oblate spheroidal form factor. Such a form factor is useful where a predictable device orientation is preferred. For instance, if nano-antenna apparatus  601  were deployed out of an aerial vehicle, nano-antenna apparatus  601  would likely come to rest with short axis  675  in a substantially vertical orientation. 
   Further, gap region  611  has a serrated or meandering form factor. The extra length of this serrated or meandering form factor helps concentrate additional electrostatic energy outside nano-antenna apparatus  601 , thus making nano-antenna apparatus  601  more efficient. 
   Third Alternate Embodiment 
     FIG. 7  is a schematic diagram  700  of a third alternate embodiment nano-antenna apparatus  701 . Third alternate embodiment nano-antenna apparatus  701  comprises a dielectric layer  705 , a first conducting surface  707  and a second conducting surface  709 . A first conducting surface  707  and a second conducting surface  709  are separated by a gap region  711 . 
   Third alternate embodiment nano-antenna apparatus  701  has an approximately Cartesian rectangular solid form factor, preferred for many consumer devices. Various ratios of height to width to depth may be appropriate for various applications. Third alternate embodiment nano-antenna apparatus  701  may also be more manufacturable. 
   Preferred Embodiment Tag-Along Microsensor 
     FIG. 8  is a cross-section diagram  800  of a preferred embodiment tag-along microsensor  801 . Tag-along microsensor  801  includes a means for transmitting signals: a nano-antenna device comprising a first conducting surface  107  and a second conducting surface  109  separated by a gap region  111 . Tag-along microsensor  801  further comprises dielectric layer  105  and adhesion means  851 . In a preferred embodiment tag-along microsensor  801 , adhesion means  851  comprise mechanical adhesion means such as a hook  852  or a barb  853 . Thus tag-along microsensor  801  is capable of sticking to or attaching itself to fabric, clothes, or hair. Tag-along microsensor  801  behaves in a way analogous to many seeds that attach themselves to animals or to the human clothing to ensure a broad area of seed dispersal. One plant employing this strategy is hoary tick-trefoil (desmodium canescens). The seeds of this legume are covered with Velcro like hairs that cause the seeds to adhere to animals or human clothing. Tag-along microsensor  801  includes adhesion means  851  to yield a similar effect. Adhesion means  851  enable tag-along microsensor  801  to be picked up and carried great distances from an original location. 
   Tag-along microsensor  801  further includes sensing means: a variety of sensor devices including potentially means of receiving and analyzing audio signals, inertial navigation means like an accelerometer, gyroscope, compass, or gyrocompass, chemical, biological or nuclear sensors, or other sensors recording information of value. 
   Alternate Embodiment Tag-Along Microsensor 
     FIG. 9  is a cross-section diagram  900  of an alternate embodiment tag-along microsensor  901 . A tag-along microsensor  901  is a nano-antenna device comprising a first conducting surface  107  and a second conducting surface  109  separated by a gap region  111 . Thus tag-along microsensor  901  includes a means for transmitting signals. Tag-along microsensor  901  further comprises dielectric layer  105  and adhesion means  951 . In an alternate embodiment tag-along microsensor  901 , adhesion means  951  are chemical adhesion means comprising a layer of glue or other adhesive. Adhesion means  951  may be deployed in response to a particular environmental stimulus detected by a sensor. 
   In alternate embodiments, a tag-along microsensor  901  may use a variety of alternate adhesion means including magnetic or static electric adhesion means. Magnetic adhesion means may include using a first conducting surface  107  or a second conducting surface  109  made of a ferromagnetic, rare earth magnetic, or other permanent magnetic material. Alternatively, one or more permanent magnetic may be embedded in tag-along microsensor  901  to effect such magnetic adhesion. Magnetic adhesion means are of particular value if it is desirable for a tag-along microsensor  901  to adhere to a vehicle or vessel. 
   Static electric adhesion means may be implemented by imparting an appropriate net electric charge to tag-along microsensor  901 . Dielectric layer  105  tend to preserve this electric charge, making tag-along microsensor  901  behave like an electret. 
   Tag-Along Microsensor Mode of Operation 
     FIG. 10  is a flow chart  1000  describing a tag-along microsensor mode or method of operation  1060 . Mode of operation  1060  begins at start block  1055 . Mode of operation  1060  continues with deploy process  1057 . 
   In deploy process  1057 , tag-along microsensors (like tag-along microsensor  801 ) are distributed across an area of interest. Deployment process  1057  may include broadcasting tag-along microsensors from airplanes, helicopters or other vehicles, or manually distributing, spraying, spreading, positioning, arranging, or installing tag-along microsensors in particular areas of interest. In alternate embodiments, deploy process  1057  may include a deployment in response to certain environmental stimuli such as an audio or other detection of approaching people or vehicles. In a preferred embodiment, deploy process  1057  results in a tag-along microsensor  801  adhering to an entity such as a person, an animal, or a vehicle. Deploy process  1057  can result in a large number of tag-along microsensors being deployed across an area of interest. 
   Tag-along microsensor mode of operation  1060  continues with battery decision block  1061 . If a tag-along microsensor  801  no longer has adequate energy, battery decision block  1061  leads to end block  1063  and tag-along microsensor mode of operation  1060  terminates. A tag-along microsensor  801  may use battery energy, capacitor stored energy, vibrational energy, or other energy scavenged from the environment of a tag-along microsensor  801 . If a tag-along microsensor  801  has adequate energy, then battery decision block  1061  leads to transmit decision block  1065 . 
   Transmit decision block  1065  may lead to a transmission under a variety of circumstances. A tag-along microsensor  801  may transmit at periodic intervals. A tag-along microsensor  801  may transmit in response to particular stimuli detected by a sensor. If a tag-along microsensor  801  does not transmit, then transmit decision block  1065  leads to wait block  1067 . 
   Wait block  1067  introduces a delay in tag-along microsensor mode of operation  1060 . Once the delay of wait block  1067  is complete, tag-along microsensor mode of operation  1060  continues with battery decision block  1061 . 
   If a tag-along microsensor  801  does transmit, then transmit decision block  1065  leads to transmit block  1067 . In a preferred embodiment, transmit block  1067  is a method of operation for transmitting UWB impulses, like method of operation  330 . Transmit block  1067  leads to receive decision block  1071 . 
   Tag-along microsensor mode of operation  1060  continues with receive decision block  1071 . If signals transmitted in transmit block  1067  are not received, then tag-along microsensor mode of operation  1060  continues with wait block  1067 . If signals transmitted in transmit block  1067  are received, then tag-along microsensor mode of operation  1060  continues with receive block  1073 . 
   Receive block  1073  describes reception of signals transmitted by tag-along microsensor  801  in transmit block  1067 . Receive block  1073  may represent reception of signals by receivers located substantially in the vicinity of where a tag-along microsensor  801  was deployed in deploy block  1057 , or receive block  1073  may represent reception of signals by receivers at distant locations such as checkpoints, chokepoints, or other location potentially traversed by an entity to which tag-along microsensor  801  may be attached. 
   Tag-along microsensor mode of operation  1060  continues with action decision block  1075 . Data or intelligence received in signals from a tag-along microsensor  801  in receive block  1073  are evaluated. If action is not warranted, then tag-along microsensor mode of operation  1060  continues with wait block  1067 . If action is warranted, then tag-along microsensor mode of operation  1060  continues with action block  1077 . 
   Action block  1077  represents acting on intelligence, data, telemetry, or other information received in receive block  1073 . Action block  1077  may include logging, recording, or otherwise storing data received from a tag-along microsensor  801  in receive block  1073 . Action block  1077  may also include action to intercept, engage or otherwise deal with an entity to which tag-along microsensor  801  is attached. Once action block  1077  is complete, tag-along microsensor mode of operation  1060  continues with wait block  1067 . 
   Specific alternate embodiments have been presented solely for purposes of illustration to aid the reader in understanding a few of the great many contexts in which the present invention will prove useful. It should also be understood that, while the detailed drawings and specific examples given describe preferred embodiments of the invention, they are for purposes of illustration only, that the apparatus and method of the present invention are not limited to the precise details and conditions disclosed and that various changes may be made therein without departing from the spirit of the invention which is defined by the following claims: