Abstract:
A remotely-locatable tracking device and system is presented for use with a projectile that contacts a mobile target. The device is particularly useful with hunting arrows that contact a target animal. The device detaches from the arrow and attaches to the animal upon impact. The device is preferably comprised of a passive transponder and the system preferably uses a handheld transceiver to locate the transponder attached to the target animal.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to a system for locating a target that has been struck by a projectile, and more particularly, to a device that is carried by an arrow, is detachable from the arrow upon contacting a target, and is attachable to the target. The system can include a combination of integral and detachable transponders. A standard hunting arrow fitted with a transponder that attaches to a game animal upon impact is provided. A system and method for detecting the transponder and thereby locating the game animal is also presented. 
   2. Background Information 
   Hunting game animals with a bow and arrow has a long tradition in many parts of the world. When an arrow is shot from a bow, it can often be difficult to determine whether it hits its target or not. If the arrow misses the target, it often disappears in the brush. The loss of arrows is a matter of one expense that the hunter would ideally like to avoid. Further, if the shot is successful and the arrow hits and fatally wounds a target animal, the animal sometimes travels a significant distance before it succumbs. Depending on the terrain and the weather conditions, it can often be difficult to quickly locate an animal that has been dispatched with an arrow. Under all circumstances, it would be desirable to locate a targeted game animal that has been struck by an arrow and to do so in an expeditious and efficient manner. 
   While the arrow sometimes remains embedded in the game animal, in many other instances (especially with relatively small game such as white-tail deer) the arrow passes completely through the animal. Therefore, a tracking system that solely relies upon a device that is integral to the arrow and that remains with the arrow would be of little use in this instance. 
   Various approaches to aid in locating wayward arrows or game animals that retain the arrows after impact, are represented in the prior art. For example, U.S. Pat. No. 5,468,000 provides an arrow with an integral attachment that can be activated to emit an audible signal to facilitate location of the arrow and/or animal. 
   Many of the “integral arrow” devices presented in the prior art are directed to altering the structure, and consequently the aerodynamic properties, of the arrow wherein, for example, the shaft of the arrow contains a radio transmitter that allows later location of the arrow. 
   When a radio transmitter is incorporated as part of the structure of the arrow itself, it is not only important that the arrow contact the animal, it is also essential that the arrow remain with the animal until the animal succumbs. Often, after being struck by an arrow, an animal can break off a part of the arrow (e.g., disabling the device) or dislodge the arrow entirely, thus limiting the utility of a locator device that is incorporated into the arrow itself. In addition, if the arrow passes entirely through the animal, an integral arrow tracking device will only allow location of the arrow and not the animal. An additional disadvantage of a transmitter that is built into a shaft of an arrow is the expense of designing and building customized arrows. It would therefore be desirable if a tracking device were provided that is adaptable for use with standard arrows and therefore does not entail the expense of designing and building customized arrows. 
   Some other approaches are directed to the attachment of radio transmitter to a “standard arrow” of a type that a majority of archery hunters would commonly own. For example, U.S. Pat. No. 5,450,614 provides a jacket-like radio receiver that slips over the shaft of a standard arrow. Another approach has been to insert a radio transmitter between the arrowhead (e.g., broadhead) and the shaft of the arrow, such as is shown in U.S. Pat. No. 4,885,800. Alternatively, a transmitter may be secured along the length of the shaft as is shown in U.S. Pat. No 5,167,417. All of these prior art solutions suffer from the same limitations described above, namely that the arrow may pass completely through the game animal taking the transmitter with it, or an arrow that remains embedded in the animal may become broken off and disable the device, thus failing to aid in the location of the animal. These devices may also cause an undesirable change in the aerodynamic properties of the arrow. 
   Still another approach allows for a detachable radio transmitter to be attached to the shaft of the arrow. Upon the arrow penetrating the animal, the electronic signaling device is detached from the arrow and is embedded into the hide of the wounded game animal. However, location of the transmitter along the shaft could affect the trajectory of the arrow. Affixing a detachable tracking device at the front of a conventional arrow, for example, as part of the broadhead itself, or as a releasable insert between the broadhead and shaft, could eliminate most if not all of the above described limitations and difficulties. 
   Radio transmitters have been the device of choice in this field. A radio transmitter actively generates a signal that can typically be received by a hand-held location device (i.e., a receiver) carried by the hunter. However, the use of a radio transmitter presents several problems. 
   A radio transmitter requires a energy source, such as a battery, to generate the radio signals. Batteries add both weight and expense to the device. Also, because battery life is limited, some type of switch is typically employed to activate the radio transmitter so that the battery does not run down prior to being utilized. 
   One approach to conserve battery life has been to use an inertia switch to activate the radio transmitter upon shooting the arrow. One distinct disadvantage of using such a switched transmitter is the added weight of the battery and switch. To maintain accuracy over conventional distances, the hunter must somehow compensate for the heavier projectile. 
   Another problem with using a battery powered transmitter relates to the finite life of the battery. If the transmitter is turned on too soon (e.g. prior to contacting the animal) or if the animal is not located soon enough after contact (e.g. before the battery expires) there is no way to locate the transmitter once the battery power has drained and a signal is no longer being generated. 
   Thus, while the above-presented body of art describes arrows with detachable radio transmitters, these references do not teach or suggest a conventional arrow having a detachable radio transponder located at the front of the arrow wherein upon impact the transponder is attachable to the target. Such an invention would improve the state of the art significantly. 
   SUMMARY OF THE INVENTION 
   The present invention provides a tracking device that is releasably affixed to a standard arrow. The device incorporates a transponder and releases from the arrow at impact and attaches itself to the target upon contact. The transponder may be either active or passive, but is preferably passive such that it does not require its own source of power. A system and method for locating the transponder using various detection means such as a hand held transceiver, either with or without GPS technology is contemplated. 
   A transponder is a piece of electronic equipment that is designed to receive a specific signal and automatically transmit a specific reply. A transponder is able to take a high energy signal from an external source and utilize a portion of the energy of that signal to generate a responsive signal, albeit often a weaker signal than the signal received. In this sense, a transponder does not require a dedicated energy source. All that is required is a receiver that is capable of detecting the signal generated by the transponder in response to the energy received by the transponder from the external source. Therefore, a lightweight device that generates radio signals in response to a signal received is presented. Neither a battery nor a power switch is required in the most-preferred embodiments of the present invention which employ a transponder. 
   A passive transponder is basically a wire coil and capacitor surrounded in a protective envelope or covering. This unit (i.e. transponder and covering) can then be associated with a projectile. It is contemplated that upon impacting a target, the unit can detach from the projectile and attach to the target. The transponder may be self-contained, (i.e. with no external accessible connections) or it may be designed to connect with an external element, such as an antenna. 
   Passive transponders are activated by an external source that radiates a signal (i.e. transmits) in the area where the transponder is expected to be found. This may be done, for example, by use of a transceiver. The signal may be emitted via an inductive coil (e.g. the transmitter portion of a transceiver) that is held in the general vicinity of the transponder. When the transmitter&#39;s coil is near the passive transponder (which itself may be an inductive coil), the transponder accepts energy within its bandpass and stores it, reaching a sustained amplitude during the transmission cycle. When the transmission cycle ends, the transponder re-emits the energy at the transponder&#39;s resonant frequency with an exponentially decaying amplitude. A second coil within the transceiver unit (i.e. the receiver portion of the transceiver) acts as a receiving antenna which detects the re-radiated energy, alerting the operator, for example, with an audible tone or other indication of the transponder&#39;s presence and/or location. 
   Certain types of “active” transponders that could work with the present invention may include a power source such as a battery, which is incorporated into the circuitry. In this instance, the battery is used to power the signal processing circuit during operation of the transponder. An example of a battery powered radio transponder appears in U.S. Pat. No. 5,942,977, incorporated herein by reference. 
   Other types of transponders, such as “Half Duplex” (“HDX”) transponders, may include an element for receiving energy from the transmitter, such as a coil, and an element for storing energy, for example a capacitor. In an HDX system, when the signal from the transmitter is turned off the capacitor discharges into the circuitry of the transponder to power the transponder so it can emit or generate a signal. The circuit designs for both active and HDX transponders are known in the art and therefore they are not described in detail herein. (See U.S. Pat. No. 5,942,977). 
   A “Full Duplex” (“FDX”) transponder generally does not include either a battery or an element for storing energy. Instead, energy is induced into the antenna or coil and used to power the signal processing circuitry of the transponder and generate the response concurrently with the emission of the emitted signal from the transmitter. FDX transponder circuits are also known in the art, an early example being disclosed in U.S. Pat. No. 4,333,072. 
   For each of the types of transponders presently in use, there are circumstances whereby the entire transponder must be encased in a sealed member so as to allow protection from, inter alia, environment elements. For example, in the present invention, prior to impact with a target the transponder may be exposed to a wide variety of temperatures and/or precipitation. After impact with a target, the transponder may need to be protected from various biological elements associated with the game animal. Accordingly, various references, including U.S. Pat. Nos. 4,262,632; 5,025,550; 5,211,129; 5,223,851 and 5,281,855, disclose methods of completely encapsulating the circuitry of various transponders within a ceramic, glass or plastic cylinders. Further, there are numerous commercial applications that teach enclosing transponders in protective coatings (such as plastic polymers or fiberglass) and therefore they are not described in detail herein. 
   The present invention is directed to the manufacture, method, and use of a remotely-locatable tracking device comprising a transponder housed within a device that is releasably affixed to an arrow. The transponder may be encased in a protective material to protect it from environmental and target specific elements. In a preferred embodiment of the present invention the transponder generally attaches to a target upon impact of a projectile with the target. 
   The structural mechanism that releasably affixes the transponder device adjacent to an arrow shaft preferably includes either, an adjustable friction device, a break-away connector, a cone-shaped cylinder, or a fragmentation broadhead. The adjustable friction devices contemplated include, for example, a detent ball and spring, or peg-and-hole configuration. The break-away connector employed may include a washer-type insert with a snap-joint, an insert with a spring clip, an insert with stretch tubing, a breakable membrane or an adhesive bond between the transponder and the arrow. The structure that connects the transponder device to a target upon impact of the arrow with the target may include, for example, implantation by a sharpened barb, insertion of a portion of the broadhead, or a similar attaching structure. Adherence of the transponder to the target may also be accomplished through the use of an adhesive, or for example, by a chemical reaction that is catalyzed upon contact with the target (e.g. two-part epoxy). 
   After shooting the arrow, the transponder may generally be located by the use of a hand-held transceiver. The transceiver is preferably tuned to transmit a signal of a particular frequency and intensity such that the transponder is capable of generating a detectable signal. The transceiver is capable of detecting the return signal from the transponder such that the location of the transponder may be determined. The transponder that generates the detectable return signal may be active but is preferable passive. The transceiver may integrate GPS technology as part of the overall detection system or methodology to help determine the location of the transponder. Alternatively, a separate GPS device can be used in conjunction with the hand-held transceiver. The system and methodology of transceiver and transponder preferably operate to assist a user (e.g. a hunter) in locating the transponder within a distance of less than 300 yards, more preferably within a distance of less than 600 yards, even more preferably, within a distance of up to 1000 yards, and most preferably, at distances in excess of 1000 yards. 
   Before explaining various exemplary embodiments of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways that would be clear to one skilled in the projectile art as well as those skilled in the electrical art. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
       FIG. 1  is an exploded view of a standard hunting arrow depicting the general location of certain inserts that can be used to releasably affix various tracking devices adjacent to an arrow shaft; 
       FIGS. 2A and 2B  show examples of break-away connections that are perpendicular to the shaft of the arrow; 
       FIG. 2C  shows the top view of the insert in  FIG. 2B  in accordance with a preferred embodiment. 
       FIGS. 3A and 3B  show examples of break-away connections that are parallel to the shaft of the arrow; 
       FIGS. 4A and 4B  depict examples of adjustable friction connections; 
       FIG. 4C  shows the tope view of the insert in  FIG. 4B  in accordance with a preferred embodiment. 
       FIGS. 5A and 5C  depict examples of adjustable friction connections; 
       FIGS. 5B and 5D  show the top views of the inserts of 
       FIGS. 5A and 5C , respectively, in accordance with a preferred embodiment. 
       FIG. 6  shows an exploded view of a fragmentation broadhead with break-away components; 
       FIG. 7  shows an exploded view of a detachable barb assembly with a treaded coupler oriented between a broadhead and arrow shaft; 
       FIG. 8  is an enlarged view of the transponder package/assembly including the transponder chip, components, and the housing/covering. 
       FIG. 9  is a schematic of a transponder circuit depicting an arrangement of components in accordance with a preferred embodiment; 
       FIG. 10  is a schematic of a reader/detector/transceiver depicting an arrangement of components in accordance with a preferred embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   While specific embodiments and methods for practicing this invention are described in detail, those skilled in the art will recognize various manifestations and details that could be developed in light of the overall teachings herein. Accordingly, the particular arrangements disclosed are meant to be illustrative only. 
   In general, the present invention is directed to a tracking device that is releasably attached to a hunting arrow. In a preferred embodiment, the tracking device is mounted to an arrow using an insert that is adaptable to affix the device to any type or variety of hunting arrow (e.g., standard or customized). In some embodiments, the tracking device is comprised of a passive transponder incorporated into a carrying mechanism such that the device releases from the insert upon impact and attaches to the target. In certain embodiments the carrying mechanism may also serve as an antenna for the transponder to receive and or transmit signals. In other embodiments, more than one transponder may be utilized such that one detaches from the arrow upon impact and one remains with the arrow. 
   With reference to  FIG. 1 , a standard hunting arrow  100  is shown with a broadhead  106 , a shaft  103 , fletching  102  and a nock  101 . The shaft generally extends from the broadhead  106  to the nock  101 . Typically, a threaded receptacle  104  is provided at one end of the shaft for accepting a threaded protrusion  107  of the broadhead  106 . In one embodiment of the present invention, an insert  105  is located between the shaft  103  and the broadhead  106  and may be secured to the arrow  100  when the threaded protrusion  107  is tightened within the threaded receptacle  104 . This insert may be used to releasably affix a tracking device to the arrow  100  in an unlimited variety of ways in accordance with the present invention, and as exemplified further herein. 
     FIG. 2  shows two embodiments of the present invention that employ a break-away connection between the tracking device and the insert. Both of the break-away connections depicted in  FIG. 2  are perpendicular to the shaft of the arrow. With respect to  FIG. 2A , a washer-type insert  215  is located between the broadhead  206  and shaft  203 . The insert  215  is structurally connected to a sickle-shaped tubular tracking device  218 . The connection  216  between the insert  215  and the tracking device  218  is breakable upon application of the force that is generated upon impact of the arrow with the target. The connection  216  may be manufactured of any variety of material or type of configuration that allow the device  218  to separate from the insert  215  upon impact with a target. 
   The tubular tracking device  218  shown in  FIG. 2A  can house a transponder (not shown) of a type and specification as described herein. The tracking device  218  and washer-type insert  215  may be constructed of a variety of suitable materials, including, for example, stainless steel, spring steel, aluminum, plastic polymers, fiberglass or some combination of components made of metal alloy and plastic. 
   With respect to  FIG. 2B , a washer-type insert  242  is located between the broadhead  230  and the arrow shaft  250 . The tracking device  238  is fixedly secured to the insert  242  at a part distal to the arrow shaft  250 . The hairpin-shaped tracking device  238  houses a transponder assembly  246  of a type and specification as described further herein. It is preferable that the transponder assembly weigh less than 200 grams, more preferably less than 100 grams, even more preferably, less than 50 grams and most preferably less than 25 grams. 
   In the embodiment shown in  FIG. 2B  it is possible to rotatably adjust the tracking device  238  within its attachment to the insert  242 .  FIG. 2C  displays a top view of the washer-type insert  242 . The insert  242  possesses a first hole  266  through which the threaded protrusion  240  of the broadhead  230  is inserted into the arrow shaft  250 . The insert  242  also possesses a second smaller hole  258  distal to the first hole for securing the tracking device  238 . This distal hole  258  can serve as a pivot point for rotatably adjusting the tracking device  238 . The insert  242  has a joint  262  located between the first hole  266  and the second hole  258  such that the portion of the insert  242  containing the tracking device  238  can “break-away” from the main arrow at this notched-joint  262 , upon impact with the target due to the force that is generated by contact with the target. The joint  262  may consist of a weakened, narrowed, notched or perforated portion of the insert  242 . 
     FIG. 3  displays two embodiments of the present invention that also employ break-away connections between the tracking device and the arrow. In these examples, the break-away connections are parallel to the shaft of the arrow. With reference to  FIG. 3A , a broadhead  300  is shown attached to an arrow shaft  316 . The tracking device  304  is attached to the arrow shaft  316  by the use of adhesive  308 . No insert between the arrow shaft and the broadhead is required in this embodiment. As previously described, the hairpin-shaped tracking device  304  houses a transponder assembly  312 . For example, the transponder  312  may be encased in a protective material that is integrally formed to the other structure(s) of the tracking device  304 . The force generated when the arrow strikes the target causes the tracking device  304  to break away from the arrow shaft  316  at the point of the adhesive  308 . 
   In  FIG. 3B , the tracking device  332  is attached to an insert  328  by the use of stretchable tubing  324 . An insert  328  is located between the broadhead  320  and the arrow shaft  336 . The insert  328  possesses a small protrusion  322  on one aspect for connecting a piece of stretchable tubing  324 . The other end of the stretchable tubing  324  can then be attached to the tracking device  332 . The tracking device  332  preferably contains a transponder assembly  340  as described further herein. In this embodiment, when the arrow strikes the target, the force generated upon impact causes implantation of the tracking device  332  into the target with the continued penetration of the arrow stretching the tubing  324  to a breaking point, thus causing the device  332  to detach from the insert  328  and remain with the target. 
     FIG. 4  displays two embodiments of the present invention that employ adjustable friction devices for releasably attaching the tracking device to the arrow. In  FIG. 4A , a conical tracking device  404  is releasably attached to the arrow shaft  408  behind the broadhead  400 . At both ends of the tracking device  404  is a generally circular opening. The first opening  402  towards the broadhead  400  is typically smaller than the second opening  406  furthest from the broadhead  400 . The transponder (not shown) may be incorporated within the wall  410  of the conical tracking device  404  or, alternatively, the transponder (not shown) may be adhered to a wall  410  of the conical tracking device  404 . A stretchable membrane  412  may be used to secure the tracking device  404  to the arrow shaft  408 . The membrane  412  could be composed of any appropriate elastic material, including, for example, plastic or latex film. The threaded portion of the broadhead  400  may be inserted through an opening in the membrane (for example, as shown in  FIG. 2C  element  266 ) and attached to the arrow shaft  408  in standard fashion. When the arrow strikes and enters a target, the barbs  414  on the tracking device  404  engage the target. As the arrow proceeds into the target the length of the arrow shaft  408  passes through the tracking device  404 . The large opening  406  (i.e. furthermost from the broadhead) of the conical tracking device  404  serves to “funnel” the device  404  over the fletching of the arrow upon impact with the target thereby rupturing the membrane  412 , and allowing the tracking device  404  to slide completely off of the arrow shaft  408  and remain with the target. 
   In the embodiment displayed in  FIG. 4B , a washer-type insert  420  is located adjacent to the broadhead  430  and the arrow shaft  440 . The tracking device  416  is releasably affixed within an opening (shown as  432  in  FIG. 4C ) in the insert  420 . The opening  432  is of slightly smaller diameter than the arm  418  of the tracking device  416 . Thus, the tracking device  416  is secured to the insert  420  by the friction created by virtue of the varying diameters of the arm  418  and the opening  432 . The hairpin-shaped device  416  preferably houses a passive transponder  424  that can be used to locate a target as described further herein. Preferably, when the arrow strikes the target the tracking device  416  disengages from the insert  420  by overcoming the friction of the arm  418  within the opening  432  and attaches to the target. 
   In  FIG. 5A  an insert  540  is shown located adjacent to the broadhead  532  and the arrow shaft  548 . The tracking device  536  is similar to those previously described in  FIGS. 2B ,  3 A,  3 B and  4 B. In this adjustable friction insert  540 , the tracking device  536  is releasably affixed to the insert  540  by the mechanism which is best viewed in the overhead view of the insert  540  shown in FIG.  5 B. 
   With respect to  FIG. 5B , the insert  540  possesses a first opening  572  through which the broadhead  532  may be screwed into the arrow shaft  54  insert also has a second opening  568  into which the tracking device  536  is engaged. The insert  540  has a screw  560  engaged within a threaded channel perpendicular to the opening  568 . The screw  560  is adjacent to a spring  564  that is itself adjacent to a ball bearing  556 . The ball bearing partially occludes the second opening  568 . The screw  560  may be rotated to adjust the size of the opening  568 , thereby adjusting the tension with which the insert  540  engages the tracking device  536 . Preferably, the tension is set so that, as the arrow strikes the target, and the point  538  of the device penetrates the target, the tracking device  536  disengages from the insert  540  and remains in the target. 
     FIG. 5C  displays an embodiment of the present invention that employs an alternate friction-dependent releasable attachment between the tracking device and the arrow. The tracking device  504  is secured to the arrow by a spring clip  512 . An annular insert  508  is located adjacent to the broadhead  500  and the arrow shaft  520 . A spring clip  512  is releasably affixed around the circumference of the annular insert  508 . The tracking device  504  is secured to the spring clip  512 , for example, by engaging an opening  528  within the spring clip  512 . The hairpin-shaped tracking device  504  houses a transponder  516 . 
   The inset  FIG. 5D  displays a top view of the annular insert  508  and spring clip  512 . The spring clip  512  fits over the circumference of the annular insert  508  and thereby remains secure during flight of the arrow due to the tension created between the variation in diameter between the outside of the annular insert  508  and the inside diameter of the spring clip  512 . Preferably, upon impact of the arrow with the target, the force generated by the arrow upon penetrating the target causes the tracking device  504  to be released with the spring clip  512  from the annular insert  508  to thereby attach to and remain with the target. 
     FIG. 6  displays an embodiment of the present invention that employs a fragmenting broadhead  606  as the carrier for the tracking device  600 . In  FIG. 6 , the tracking device  600  is shown above the arrow shaft  608  and below a two-blade broadhead  606 . As shown, the broadhead  606  has a pair of parallel grooves  610  located on opposite sides of the broadhead&#39;s surface that engage the tracking device  600 . The tracking device  600  is composed of two blades  602  of similar size and shape to the broadhead that will slide into the grooves  610  of broadhead  606 . The circular ring  604  that is located between the blades  602  of the tracking device  600 , further secures the device  600  between the arrow shaft  608  and the broadhead  606 . A transponder  628  may either be attached to one (or both) of the blades  602  of the tracking device, or the blades  602  could integrally house (e.g. be formed around) the transponder assembly upon initial construction. As the arrow enters the target, the two components  602  of the tracking device  600  may fragment away from and separate from the ring  604  and the broadhead  606 . The connection between the two components  602  and the ring  604  is such that the impact of the arrow striking the target is sufficient to disrupt the connections between the components  602  and the ring  604  and the grooves  610 , and allow the tracking device  600  to remain with the target. The blades  602  may be composed of any suitable material including, for example, light weight metals, high impact plastic carbon fiber overlay or fiberglass. As mentioned previously, the blades  602  may also serve as the housing for a transponder unit. 
   A break-away barb assembly is shown in  FIG. 7  wherein the transponder  728  can be either molded into the barb  716  or adhered to its surface. Preferably, the barb  716  is preferably constructed of a durable material such as metal, high impact plastic or fiberglass, and of sufficient strength to withstand impact with a target. Preferably the energy of impact will be sufficient to release the barb  716  (containing transponder  728 ) from the coupler  704 , over the arrow shaft  724  to imbed the barb  716  into the target. 
   One embodiment of this concept as shown in  FIG. 7  incorporates three components that are carried between a standard broadhead  700  and arrow shaft  724 . The first component is a threaded coupler  704  that is machined to receive a threaded broadhead  700  at one end and threaded to connect with a standard arrow shaft  724  at the other end. The threaded coupler  704  may include a detachable release to engage a second component, such as a bushing  712  that is connected to the threaded coupler  704  preferably by ball detents  708 . The bushing serves to frictionally retain the third component, the barb  716 , in releasable engagement with the coupler  704 . 
   A second embodiment represented is an arrangement using more than one transponder. For example, with reference to  FIG. 7 , a first transponder  728  may be incorporated into a break-away tracking device  716  and a second transponder  730  may be incorporated, into the broadhead  700  such that it remains with the arrow. Any number and combination of fixed and detachable transponders are contemplated with the various embodiments of the present invention previously described herein. Also, any of the previously described fixed tracking devices that are integral to an arrow shaft may be used in combination with the releasable devices of the present invention. 
   A graphical depiction of a transponder unit  800  (i.e., transponder assembly) that may be used with the present invention is shown in FIG.  8 . The transponder unit  800  consists of a transponder chip  802 , at least one capacitor  804 , and a coil  806 , all of which are integrated within a housing  808  to form a unit. As discussed previously, this unit  800  is assembled within its housing  808  to withstand various elements and external forces that are anticipated by the practice of this invention. 
   An example of a circuit layout of the transponder unit (absent the housing) is shown in FIG.  9 . The transponder unit preferably includes a coil  922  to receive a signal, and a 1-bit transponder chip  920  that operates in the microwave frequency range of about 2.45 GHz to process the received signal and emit a return signal. Regardless of the frequency chosen, the transponder can preferably be “tuned” or matched for receiving a signal from a transmitter. Further, the transponder may be uniquely identifiable, for example, as shown in U.S. Pat. Nos. 5,491,483, and 5,764,156, both incorporated herein by reference for this teaching. The transponder unit may include two capacitors  914  that are wired in parallel with each other and in series with a diode  926 . A circuit diagram displaying an example of the connections between electronic components that may be used to make a passive transponder unit in accordance with the present invention is shown in FIG.  9 . 
   The signal may be generated, transmitted, received and detected by a device that is constructed in accordance with the exemplary circuit diagram shown in FIG.  10 . The device of  FIG. 10  is a transceiver in that it both transmits a signal to and receives signals from a transponder. Alternatively, the system and method of the present invention could be practiced with a separate transmitter unit and a separate receiver unit, but it is preferable to integrate these functions into a single device. 
   The transceiver of  FIG. 10  contains a battery pack  1010 , a first capacitor  1012  having a value for example of 47 nano farads (nF) +/−20 nF, a second capacitor  1014  having a value for example of 22 nF +/−10 nF, a third capacitor  1016  and a fourth capacitor  1018  each having a value for example of 1.5 nF +/−0.25 nF, and a fifth capacitor  1020  having a value for example of 700 pF. 
   Also shown in  FIG. 10  are three resisters ( 1022 ,  1024 ,  1026 ) a diode  1028 , and a coil  1036  (having a value, for example, of 1.35 mH) for receiving a return signal from a transponder. Reader chip  1030  in conjunction with microchip  1032  read the incoming signal, interpret the signal and, with oscillator  1034 , generate and send out a signal (e.g. 2.45 GHz) to the transponder. 
   Preferably the transponder is tuned to receive the signal sent from the transceiver. The transceiver may also function to provide the operator with an indicator of direction, preferable by means of a visual cue such as a light array. Similarly, the transceiver unit will preferably function to output an indicator of distance, for example, by showing the relative strength of the return signal being received from the transponder. 
   In addition to bilateral signal generation, transmission, receipt, retransmission and detection as described, the use of triangulation methods are also contemplated. For example, Global Positioning System (GPS) technology could easily be incorporated into the methods of the present invention. One example of augmenting the present invention with GPS technology would be for the operator to carry a separate GPS unit to record his position prior to beginning signal transmission to locate a tracking device previously imbedded in a target. Upon sending and receiving an initial signal, the operator could use the GPS reading to establish a “search zone” where the target is most likely to be found. This zone could be established from a combination of signal direction (as indicated by the transceiver unit) and distance (as indicated by a known range of detection or an indicator of signal strength, for example). Upon conducting the search, the operator could record his movement using the output from the GPS unit to thereby conduct a systematic search for the target. 
   While specific embodiments and methods for practicing this invention have been described in detail, those skilled in the art will recognize various manifestations and details that could be developed in light of the overall teachings herein. Accordingly, the particular arrangements disclosed are meant to be illustrative only and the following claims are to be given their full breadth.