U.S. patent application number 10/661998 was filed with the patent office on 2004-03-25 for rf detectable golf ball.
Invention is credited to Imblum, Raymond, Pierce, Thomas R., Pirritano, Anthony J..
Application Number | 20040058749 10/661998 |
Document ID | / |
Family ID | 27804904 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040058749 |
Kind Code |
A1 |
Pirritano, Anthony J. ; et
al. |
March 25, 2004 |
RF detectable golf ball
Abstract
The present invention provides a system for locating lost golf
balls which includes a golf ball that incorporates an array of
passive transponders and a radio frequency ("RF")
transmitter/receiver capable of energizing the passive transponder
array and of detecting a signal emitted by the array. Each passive
transponder functions as a tuned LC circuit that is charged by the
RF transponder/receiver and emits an RF signal, detectable by the
RF transmitter/receiver, for a finite period of time after the RF
transmitter/receiver is turned off.
Inventors: |
Pirritano, Anthony J.;
(Murrietta, CA) ; Imblum, Raymond; (Corona,
CA) ; Pierce, Thomas R.; (Huntington Beach,
CA) |
Correspondence
Address: |
FULWIDER PATTON LEE & UTECHT, LLP
200 OCEANGATE, SUITE 1550
LONG BEACH
CA
90802
US
|
Family ID: |
27804904 |
Appl. No.: |
10/661998 |
Filed: |
September 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10661998 |
Sep 12, 2003 |
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09293522 |
Apr 15, 1999 |
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6620057 |
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Current U.S.
Class: |
473/353 |
Current CPC
Class: |
A63B 43/00 20130101;
G01S 5/20 20130101; A63B 2225/54 20130101; A63B 29/021 20130101;
A63B 2024/0053 20130101; A63B 24/0021 20130101; G01S 3/38 20130101;
G01S 13/75 20130101 |
Class at
Publication: |
473/353 |
International
Class: |
A63B 043/00 |
Claims
What is claimed is:
1. A golf ball comprising: an array of flat-loop passive
transponders constructed of electrically conductive material having
respective planar inner and outer faces, wherein one passive
transponder is arranged along each of three mutually perpendicular
axes having a common point of intersection such that each passive
transponder is equidistant from the point of intersection and each
passive transponder is perpendicular to each of the other passive
transponders to provide a substantially omni-directional radiation
pattern; said transponders being configured with a discontinuous
loop having confronting edges spaced apart to form a slot of
predetermined gap; a layer of electrically insulating material
disposed on one face of said loop; dielectric material disposed in
said slot to cooperate in forming a capacitor, whereby the
effective capacitive reactance may be controlled by the width of
said gap and the choice of said dielectric material; a ball core
disposed inside said transponder loops; and a cover covering said
transponders.
2. The golf ball of claim 1 wherein: said array of passive
transponders is disposed on the surface of said core.
3. The golf ball of claim 1 wherein: said array of passive
transponders is encapsulated within said core.
4. The golf ball of claim 1 wherein: said array of passive
transponders is disposed on one surface of said cover.
5. The golf ball of claim 1 wherein: said flat loop is constructed
of copper foil.
6. The golf ball of claim 1 wherein: said dielectric material is in
the form of solder mask compound.
7. A golf ball comprising: at least one flat-loop inductor
constructed from electrically conductive material having planar
faces; said loop being configured with confronting edges spaced
apart to form a slot of predetermined gap at one point about the
circumference of said loop; a layer of electrically insulating
material disposed on one face of said loop; dielectric material
disposed in said slot to cooperate in forming a capacitor, whereby
the effective capacitive reactance may be controlled by the width
of said gap and the choice of said dielectric material; a ball core
disposed inside said transponder loops; and a cover covering said
transponders.
8. A system for finding lost golf balls comprising: a golf ball
incorporating at least one passive transponder configured to
resonate at a selected radio frequency and to emit a radio
frequency return signal upon being illuminated by a source RF
signal at said selected frequency; an RF transmitter/receiver
including a circuit operable to illuminate said passive transponder
with said source signal to charge said passive transponder and
including a circuit operable to detect said return signal, and
further including a helical antenna for transmission of said source
signal and detection of said return signal; and at least one
indicator included within said RF transmitter/receiver, responsive
to said return signal, wherein said indicator communicates
audio/visual signal strength information to a user.
9. The system for finding lost golf balls of claim 5 wherein: said
RF transmitter/receiver is hand-held.
10. The system for finding lost golf balls of claim 5 wherein: said
RF transmitter/receiver is battery operated.
11. A passive transponder comprising: a flat loop formed from
electrically conductive material, wherein said loop is of generally
circular configuration having planar faces; said loop being
configured with confronting edges spaced apart to form a slot of
predetermined gap at one point about the circumference of said
loop; a layer of electrically insulating material disposed on one
face of said loop; and dielectric material disposed in said slot to
cooperate in forming a capacitor, whereby the effective capacitive
reactance may be controlled by the width of said gap and the choice
of said dielectric material.
12. The passive transponder of claim 11 wherein: said loop has a
diameter of 0.600 inches, a width of 0.050 inches, and a material
thickness of 0.0028 inches.
13. The passive transponder of claim 11 wherein: said electrically
conductive material is copper foil.
14. The passive transponder of claim 11 wherein: said electrically
insulative material is kapton film.
15. The passive transponder of claim 11 wherein: said dielectric
material is solder mask compound.
16. A flat-loop inductor array comprising: an array of flat-loop
inductors, wherein one flat-loop inductor is arranged along each of
three mutually perpendicular axes having a common point of
intersection such that each flat-loop inductor is equidistant from
the point of intersection and each flat-loop inductor is
perpendicular to each of the other passive transponders to provide
a substantially omni-directional radiation pattern; said flat-loop
inductors are formed as a flat loop from electrically conductive
material, wherein said loop is of generally circular configuration
having planar faces; said loop being configured with confronting
edges spaced apart to form a slot of predetermined gap at one point
about the circumference of said loop; a layer of electrically
insulating material disposed on one face of said loop; and
dielectric material disposed in said slot to cooperate in forming a
capacitor, whereby the effective capacitive reactance may be
controlled by the width of said gap and the choice of said
dielectric material.
17. A system for tracking a golf ball in flight comprising: a golf
ball incorporating at least one passive transponder configured to
resonate at a selected radio frequency and to emit a radio
frequency return signal upon being illuminated by a source RF
signal at said selected frequency; at least two movable RF
transmitter/receivers operable to illuminate said passive
transponder with said source signal at said selected frequency and
operable to detect said return signal from said passive
transponder, and including a helical antenna for transmitting and
receiving said selected signals; a means for rotating said RF
transmitter/receivers to sweep the field of play at predetermined
periodic intervals with said selected RF signal; and a means for
visually displaying the flight path information generated by said
RF transponder.
18. The system for tracking a golf ball in flight of claim 17
wherein: said means for causing said RF transmitter/receivers to
sweep the field of play at predetermined periodic intervals
comprises an electromechanical drive mechanism.
19. The system for tracking a golf ball in flight of claim 17
wherein: said means for causing said RF transmitter/receivers to
sweep the field of play at predetermined periodic intervals
comprises a switched antenna array for said RF
transmitter/receivers, and wherein said RF transmitter/receiver
array is sequentially pulsed at periodic intervals by an electronic
controller.
20. The system for tracking a golf ball in flight of claim 17
wherein: said means for causing said RF transmitter/receivers to
sweep the field of play at predetermined periodic intervals
comprises a combination of electromechanical drive mechanisms and
switched antenna arrays for said RF transponders, wherein said RF
transmitter/receiver arrays are sequentially pulsed at periodic
intervals by an electronic controller.
21. A locator apparatus comprising: a retrievable object including
a passive transponder device; said transponder device being
configured to resonate at a selected radio frequency and to emit a
radio frequency return signal upon being illuminated by a source RF
signal at said selected frequency; an active RF
transmitter/receiver including a circuit for illuminating said
passive transponder with an RF signal at said selected frequency to
excite said passive transponder and including a circuit for
detecting said emitted return signal and further including a
helical antenna for transmission of said selected source signal and
detection of said return signal; and at least one indicator
included within said RF transmitter/receiver, responsive to said
return signal, wherein said indicator communicates audio/visual
signal strength information to a user.
22. The locator apparatus as set forth in claim 21 wherein: said
passive transponder is in the form of a discontinuous loop which
includes a capacitance gap and is constructed of a lamination of an
insulative material and a metal foil conductor.
23. The locator apparatus as set forth in claim 21 wherein: said
insulative material and said metal foil conductor are kapton and
copper respectively.
24. The locator apparatus as set forth in claim 21 wherein: a
portable housing is constructed to house said transmitter,
receiver, antenna and indicator.
25. The locator apparatus as set forth in claim 21 wherein: said
passive transponder device includes a plurality of loop
transponders oriented at an angle of 90 degrees to each other.
26. The locator apparatus as set forth in claim 21 wherein: said
passive transponder loop capacitance gap is laser trimmed to
achieve a preselected resonance frequency.
27. The locator apparatus as set forth in claim 21 wherein: said
passive transponder is configured to resonate at substantially 2.45
ghz for substantially 800 nanoseconds after said illuminating
source RF signal is turned off.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to the field of movable object
location systems generally and more particularly to a system
utilizing an advanced radio frequency detection method for
detecting the location of golf balls.
[0003] 2. Description of the Prior Art
[0004] Golf is an increasingly popular game typically played in
teams of two or four. The course of play typically consists of nine
or eighteen holes with each hole consisting of a length of course a
few hundred yards long beginning with a "tee" and ending in a
"green" which contains the "hole". Golf is controlled by a number
of intricate rules one of which requires a player who loses a ball
to take a penalty stroke which harms that player's score. Thus,
players are understandably reluctant to take a penalty stroke
without making a time consuming effort to find the lost ball.
However, since only one team can play a "hole" at any given time,
the number of teams on the course and the speed of play is limited
to that of the slowest moving team. If one team stops play because
a particular player is searching for a lost ball, all of the teams
behind them are forced to stop play as well. This directly
conflicts with the desire of teams waiting to continue play and
with the financial incentives of golf course mangers who prefer to
have teams moving at swift pace through the course. Because of
these conflicting goals many courses have adopted a five minute
search rule. If a ball cannot be located after five minutes a
player is forced to take a penalty stroke. Most commonly golf balls
are lost during the course of play because the ball lands in a
particularly overgrown area of the course. The loss can occur even
though the ball was visible during its entire flight and the
approximate region in which the ball landed is known. Thus, there
have been many attempts at developing a device or method for
finding a lost golf ball.
[0005] Early attempts at developing a golf ball location device
have included U.S. Pat. No. 1,583,721, issued to Kane, May 4, 1926.
Kane disclosed a smoke signaling device wherein a golf ball emitted
a smoke signal prior to being hit. The golfer, after lighting a
fuse, could track his ball by watching the smoke trail left in the
air. Another early attempt was U.S. Pat. No. 1,620,290, issued to
Rubin, Mar. 8, 1927. This device comprised a golf ball which
contained a spring powered bell. Prior to hitting the ball, the
golfer would wind the spring which would start the bell ringing. A
more recent suggestion is British Patent No. 1,121,630, issued to
Pedrick. Jul. 31, 1968. Pedrick suggested manufacturing a golf ball
with a radioactive core. The golf ball when lost could then be
located by means of a Geiger counter. These early attempts are
provided as an illustration of the long felt and as yet unmet need
for an effective method of locating a lost golf ball.
[0006] The modern prior art concepts can be divided into two
categories, electronic golf balls and remote sensing systems. In
the electronic golf ball category there are generally two
approaches, golf balls incorporating battery powered radio
transmitters and golf balls incorporating battery powered audio
beepers. An example of the radio transmitter approach is U.S. Pat.
No. 3,782,730 entitled "Golf Ball", issued to Horchler. Jan. 1,
1974. This patent discloses a miniature, battery powered, radio
transmitter enclosed within a golf ball. Horchler uses a small
mercury cell, similar to a watch or camera battery, which powers a
squegging oscillator type transmitter circuit. The battery and
circuit are encapsulated within the golf ball. There are several
inherent problems with the Horchler device. One problem is that the
battery being encapsulated within the golf ball cannot be replaced.
Therefore, when the battery fails a relatively expensive golf ball
must be thrown away. It is also questionable whether a small
mercury cell could supply sufficient power to generate a
transmitter signal providing sufficient range to be practical
during actual play. Further, there is reason to doubt whether the
active components of the Horchler device could survive the
repetitive shock loads transmitted to a golf ball during a typical
game.
[0007] An example of the audio beeper approach to locating a lost
golf ball is U.S. Pat. No. 5,112,055 entitled "Golf Ball Including
Sound Emitting Means", issued to Barnhill. May 12, 1992. The
Barnhill golf ball contains a battery operated audio beeper circuit
which includes a latch type switch. Upon being struck, the force of
the blow imparted to the ball closes the switch causing the ball to
emit an audible beep. By means of the continuous beeping the golfer
may locate his ball. The beeper is turned off by pressing a golf
tee through a hole inside the golf ball and thereby resetting the
latch switch to the off position. While an interesting idea.
Barnhill has numerous potential drawbacks. If the beeper signal is
loud enough to allow a golfer to locate a lost ball from a distance
of one hundred or more yards it is likely to prove annoying to
other golfers. On the other hand if the beeper is quiet enough not
annoy other golfers it is not likely to be loud enough to allow the
golfer to find the lost ball. Further, as with Horchler, the life
of the Barnhill golf ball is limited to the life of the battery and
once again it is questionable whether the active components can
withstand the repetitive shock loads imparted to a golf ball during
the course of play.
[0008] Of the remote sensing methods for locating golf balls
disclosed in the prior art there are three main types, proximity
sensors, optical systems based on charge coupled device (CCD)
sensors, and radar type systems. An example of the proximity sensor
approach is U.S. Pat. No. 4,660,039, entitled "System For Locating
A Sport Object", issued to Barricks et al. Apr. 21, 1987. Barricks
discloses a low frequency radio transmitter and a golf ball wherein
strips of conductive material are placed around the perimeter of
the ball. Barricks operates on the well known principle that when
an electromagnetic (EM) field comes into contact with a conductor
an electrical current commonly referred to as an "eddy current" is
induced in the conductor. When the EM field first contacts the
conductor, the induced current causes the transmitter to see an
increased load or power drain. A proximity sensor included with the
transmitter senses the increased power drain and thereby the
presence of the ball can be inferred. The primary disadvantage of
this approach is that proximity to a conductor produces only a
slight power drain on a transmitter. Therefore, even very sensitive
proximity sensors require that the transmitter and conductor be in
close spacial relation in order to generate a detectable
differential in power drain. In industrial applications proximity
sensors have an effective range of a few inches to about two feet,
in actual practice, a golf ball locator based on a proximity sensor
approach would likely be limited to a similarly short effective
range.
[0009] An example of the CCD approach is U.S. Pat. No. 5,662,533,
entitled "Golf Ball Locator Apparatus", issued to Chadwell, Sep. 2,
1997. Chadwell teaches a system comprising a hand held infrared
light source which includes an array of charge coupled devices
designed to be particularly sensitive to infrared light, a golf
ball coated with a clear coating that is formulated to be highly
reflective of infrared light, and circuitry capable of detecting
reflected infrared light. One disadvantage of the Chadwell method
is that infrared radiation will not penetrate foliage. Thus if the
lost golf ball is obscured by grass, leaves, brush or other type of
foliage the detection system taught by Chadwell will not be
effective.
[0010] An example of the radar approach to golf ball detection is
U.S. Pat. No. 5,662,534, entitled "Golf Ball Finding System",
issued to Kroll et al., Sep. 2, 1997. The system taught by Kroll
uses radar principles well known to those skilled in the art. Kroll
discloses a hand held radar transponder and a four quadrant corner
reflector encapsulated within a golf ball. Kroll teaches that radar
waves impinging on the reflector at an oblique angle will, after
multiple reflections within a quadrant, be reflected directly back
to the radar source. Kroll estimates, by calculation, that to
locate a golf ball by radar means using the disclosed four quadrant
reflector a minimum transmitter frequency of 15 Ghz would be
required. Kroll further calculates that an effective range of 500
feet could be obtained at this frequency and that the transponder
could be powered by ordinary dry cell batteries "as is done with a
flashlight." While detection of a golf ball by radar means is quite
feasible, it is highly questionable whether a transmitter operating
at 15 Ghz could be powered by a sufficiently small number of
ordinary dry cell batteries such that the device could be hand
held. Further, it is questionable whether an impinging radar wave
striking the reflector at an oblique angle will be reflected
directly back to the transmitter as is required for the Kroll
device to operate. In addition, a four quadrant corner reflector
would cut through the core of the golf ball severing it into
fourths, thereby ruining its flight characteristics.
[0011] Although the prior art discloses a multitude of systems for
locating a lost golf ball, all of the methods taught possess
certain drawbacks. Thus, it is clear that there remains room for
improvement. What is needed therefore is a remote sensing golf ball
location system of sufficiently low power consumption to be light
weight and portable, and preferably hand held. In addition, such a
system should not compromise the integrity of the golf ball bounce
and flight characteristics. Further, such a system should possess
sufficient range to be of practical utility and such a system
should be able to locate a golf ball regardless of the ball's
physical orientation on the course or whether the ball is obscured
by foliage.
SUMMARY OF THE INVENTION
[0012] The present invention provides a system which may be
employed for locating lost golf balls which includes a golf ball
that incorporates an array of passive transponders and a radio
frequency ("RF") transmitter/receiver capable of energizing the
passive array and of detecting a signal emitted by the array. Each
passive transponder is a capacitively loaded flat-loop inductor of
predetermined configuration. The array comprises three flat-loop
inductors arranged in a predetermined spatial relationship within
the interior of a golf ball. Each flat-loop inductor functions as a
tuned LC circuit that is charged by the RF transmitter/receiver and
emits a radio frequency signal, detectable by the
transmitter/receiver, for a finite period of time after the RF
transmitter/receiver is turned off.
[0013] It should be noted that the present invention does not
utilize radar principles. The amount of RF energy emitted by the
passive transponders is orders of magnitude greater than that which
would be reflected back from the conductive surfaces contained
within the golf ball by an impinging electromagnetic wave. With our
device, RF energy is emitted from the surface of the golf ball for
hundreds of nanoseconds after the RF energy from the transmitter is
no longer striking the surface of the ball. Therefore, the
emissions are not radar, since radar emissions from a target stop
as soon as the energy from the radar transmitter is shut off.
[0014] The present invention possesses several advantages over the
prior art. The passive array incorporated in the golf ball of the
present invention contains no conventional electronic, components
and is therefore impervious to the impact loading produced by
hitting a golf ball during the normal course of play. Further, the
signal emitted by the passive array is omni-directional and
therefore detectable by the transmitter/receiver regardless of the
orientation of the golf ball on the course. Also, the present
invention can detect a golf ball incorporating the passive array
regardless of whether the ball is obscured by foliage. In addition,
the RF transmitter/receiver of the present invention possesses
sufficient transmitter power to provide an effective range of at
least 100 feet, yet power consumption is sufficiently low such that
the transponder/receiver can be operated with ordinary dry cell
batteries. Other features and advantages of the invention will
become apparent from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] For a better understanding of the invention and the features
thereof, reference is made to the following description which is to
be read in conjunction with the accompanying drawings wherein:
[0016] FIG. 1 is a perspective view of a location system embodying
the present invention;
[0017] FIG. 2 is a diagrammatic view of the golf ball shown in FIG.
1., enlarged in scale, an emitter array composed of flat-loop
inductors is shown in solid line, while the golf ball cover is
shown in phantom line;
[0018] FIG. 3 is a perspective view, enlarged in scale, of one of
the flat-loop inductors which form the emitter array shown in FIG.
2;
[0019] FIG. 4 is a partial front view, enlarged in scale, of the
slot portion of the flat-loop inductor shown in FIG. 3;
[0020] FIG. 5 is a sectional view, enlarged in scale, of a cross
section of the flat-loop inductor as taken along the line 5-5 in
FIG. 3;
[0021] FIG. 6 is a schematic circuit showing the idealized
capacitive and inductive elements of the flat-loop inductor shown
in FIG. 3;
[0022] FIG. 7 is a graph depicting the rate of oscillation decay of
the flat-loop inductor of FIG. 3;
[0023] FIG. 8 is a generalized perspective view, enlarged in scale,
of an antenna included in the RF transponder shown in FIG. 1;
[0024] FIG. 9 is a graph showing the electromagnetic field
intensity in volts/meter of a signal returned from a flat-loop
inductor at the antenna of FIG. 8;
[0025] FIG. 10 is a graph showing the electromagnetic field power
in dbm of a signal returned from a flat-loop inductor at the
antenna of FIG. 8;
[0026] FIG. 11 is block diagram of transmitter and receiver
circuits suitable for use in the RF transponder, shown in FIG. 1,
of the present invention; and
[0027] FIG. 12 is a generalized perspective view of a system for
tracking the flight path of a golf ball embodying features of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] Referring to FIG. 1, the movable object location system of
the present invention has particular application as a golf ball
location system including a portable hand held, radio frequency
transmitter/receiver 10, and a golf ball of unique design 30. The
transmitter/receiver includes generally, a single housing which
houses, a battery pack 16, a high gain helical antenna 20, and as
shown in FIG. 11, a transmitter circuit 100, and a receiver circuit
200.
[0029] Referring to FIG. 2, the golf ball includes a core 31, a
cover 32 and disposed between the cover and the core is a passive
inductor array, generally designated 36. The array includes three
passive transponders in the form of flat-loop inductors, generally
designated 33. The core and the cover are composed of conventional
materials well known to those skilled in the art of golf ball
manufacture. Referring now to FIGS. 3, 4 and 5, each flat loop
inductor 33 is formed as a discontinuous flat loop 40 of generally
circular configuration and of rectangular cross section. The flat
loop 40 has planar oppositely facing flat faces 34. In the
preferred embodiment, each loop possesses an outside diameter d of
0.600 inches and a width b of 0.050 inches. The discontinuous
portion of the loop forms a narrow diagonal slot 37, of
predetermined angle .alpha. and gap p. The slot 37 is formed with
substantially parallel confronting edges. In the preferred
embodiment, the slot angle .alpha. is 22.5 degrees and the slot gap
p is 0.004 inches. The preferred material for the loop is copper
foil, with a thickness c of 0.0028 inches, which is laminated to a
kapton substrate. It is to be understood that only the presently
preferred configuration for the passive transponder has been
described. The transponder is not limited in configuration to a
flat circular loop but may be of ellipsoidal or of non-circular
configuration. Further, the loop material is not limited to copper
but rather may be of gold, silver, aluminum, vapor deposited metal,
or of any other conductive material which is capable of being
formed into a thin foil or film. The substrate also is not limited
to kapton but may be of any suitable electrical insulating
material.
[0030] The helical transmitter antenna of the hand held unit emits
an electromagnetic field at 2.45 Ghz. The passive transponder in
the golf ball is a Loop of copper ideally shaped and dimensioned to
be a 0.39 wavelength antenna at 2.45 Ghz. The electrical aperture
of the Loop is larger than the physical copper surface of the Loop.
In fact, a 0.39 wavelength antenna is ideal because it propagates a
larger electrical aperture for its size. The electrical aperture
includes the entire center of the Loop as well as an area around
the Loop, since it is an antenna.
[0031] The current flow in the loop (antenna) is dependant upon (1)
the power density of the impinging field (from the transmitter);
and (2) the aperture presented by the loop antenna, and therefore
the dimensional geometry of the Loop.
[0032] Power Density of the Impinging Field
[0033] The formula set below (labeled Propagation) has been
employed to calculate that a one watt 2.45 Ghz transmitter with our
selected design helical transmitter antenna will propagate an
e-field strength (Eo) of 0.013387 volts per meter at a distance of
300 feet (91.44 meters).
[0034] Aperture of the Loop Antenna
[0035] The formula set below (labeled Loop Oscillation) shows that
for a Loop antenna of our dimensions (C) spaced in a 2.45 Ghz
e-field (at 300 feet from the transmitter), the 2.45 Ghz e-field
will induce a current flow (I) of 9.4 E-4 amperes. The value is
independent of the inherent inductance or capacitance of the
antenna structure. The ability for the antenna to "pick-up" this
much current from such a long distance with such a physically small
antenna is key to the range of our invention. The e-field is a 2.45
Ghz oscillation and continues to stimulate the antenna with
in-phase stimulus tuned to the antenna's frequency, energizing the
antenna to a higher energy state; much like a sound wave of a
particular musical note, continuing to re-enforce the vibrations of
tuning fork for that same musical note.
[0036] Energy Storage
[0037] Antennas have an inherent inductance whether thy be a rod
(dipole antenna) or loop. The inductance of the loop (L) is
calculated below to be 5.412 E-8 Henries. (Refer to formula labeled
"Loop Inductance and Capacitance).
[0038] The energy (UB) coupled into the inductance of the Loop
antenna is a function of the Loop current flowing through the
inductance of the Loop while the Loop antenna is energized by the
field. The energy in the Loop is calculated to be 2.391E-14 joules.
(See formula 3 under Loop Oscillations.)
[0039] The ends of the Loop antenna face each other and form a
narrow diagonal slot 37 that is filled with a compound that acts as
a dielectric and in conjunction with the faces of the slot
functions as a capacitor with a value of 0.078 picofarads. (Refer
to (C) formula labeled Loop Inductance and Capacitance.) The
capacitance value was picked to tune the combination of the
capacitive reactance and inductive reactance of the Loop antenna to
2.45 Ghz.
[0040] The current flowing through the Loop charges the capacitor
to a maximum level of 6.106E-14 Coulombs (q), thus storing
capacitive energy. (See formula 4 in formula set labeled Loop
Oscillation.)
[0041] Charging the Loop
[0042] As long as the loop antenna is impinged upon by the 2.45 Ghz
field, the Loop antenna continues to be energized by the field,
converting the field oscillations to current in the antenna Loop
alternately in one direction (positive cycle) charging the
capacitor and then inducting current in the Loop in the opposite
direction (negative cycle) where the capacitor discharges into the
Loop adding to the current induced by the negative phase of the
field and then the capacitor is recharged in the negative cycle as
the negative current peaks in the Loop antenna In this way, the
Loop and the capacitor exchange energy driven by the 2.45 Ghz
field.
[0043] Loop Radiation After Transmitter Turned Off
[0044] Once the hand held transmitter/receiver turns off, and the
impinging field stops, the Loop antenna continues to exchange
energy between the capacitor and the inductance of the Loop antenna
at its tuned 2.45 Ghz rate, but now the current flowing through the
Loop is no longer reconstructed by an outside energizing field.
Instead the current flowing through the Loop antenna dissipates an
e-field around the Loop antenna at a rate of 2.45 Ghz. When current
flows in a positive direction the field builds up around the Loop,
some energy is dissipated as RFI that the hand held receiver can
detect. However when the field collapses it induces current in the
opposite direction in the Loop antenna (at a rate of 2.45 Ghz)
charging the capacitor in the negative polarity direction but with
less energy. The Oscillation continues in the Loop antenna;
however, the oscillation energy decays with each cycle, primarily
due to the energy dissipated as an RF Field.
[0045] The formula below calculate:
[0046] 1. The Oscillation decay formula in the loop (qe(n)) in
coulombs over time along with a graph labeled FIG. 7.
[0047] 2. The resulting e-field strength formula at the hand held
receiver antenna (Es(n)) in volts/meter over time and its decay
with a graph labeled FIG. 9.
[0048] 3. The Field Power formula at the hand held receiver antenna
(Ss(n)) in dbm over time and its decay with a graph labeled FIG.
10.
[0049] As will be appreciated by those skilled in the art, all of
the calculations for single Loop Antenna apply directly to the
three Loop quasi-isotropic array since the array has the same field
strength as a single Loop but functions from any orientation.
[0050] With reference to FIGS. 3, 4, and 5, the loop inductance,
capacitance, resonant frequency and oscillation decay time are
calculated as follows. The physical constants used in the
calculations and a calculation of the loop (conductor) total length
are summarized in Table 1.
[0051] Note for discussion of the impinging electro-magnetic field
intensity see the antenna design and signal propagation
calculations; infra pages 32 and 34.
1TABLE 1 Physical Constants .zeta..sub.i := .pi. .multidot. d.sub.i
conductor total length, in .zeta..sub.i = 1.885 .zeta. := .0254
.multidot. .zeta..sub.i conductor total length, meters .zeta. =
0.048 .mu..sub.o := 4 .multidot. .pi. .multidot. 10.sup.-7
permeability free space, H/m .mu..sub.o = 1.257 .multidot.
10.sup.-6 1 o := 1 36 10 9 permittivity free space, F/m
.epsilon..sub.o = 8.842 .multidot. 10.sup.-12 .sigma. := 5.8
.multidot. 10.sup.7 conductivity copper, S/m 2 a := d - c 2 mean
radius, meters a = 7.584 .multidot. 10.sup.-3 3 c o := 1 o o speed
light, m/s c.sub.o = 3 .multidot. 10.sup.8 4 o := c o f free space
wavelength (fs-.lambda.), meters .lambda..sub.o = 0.122
[0052] The geometric data for the preferred embodiment of the loop
inductor along with the design frequency and dielectric constant of
the capacitor's gap material are summarized in Table 2.
2TABLE 2 Geometric Data diameter of core (O.D.), in d.sub.i := .60
d := .0254 .multidot. d.sub.i conductor thickness, in c.sub.i :=
.0028 c := .0254 .multidot. c.sub.i conductor width, in b.sub.i :=
.050 b := .0254 .multidot. b.sub.i gap width, inches p.sub.i :=
.004 p := .0254 .multidot. p.sub.i gap error spread, inches
p.sub.i.delta. := .0002 p.sub..delta. := 0254 .multidot.
p.sub.i.delta. frequency, Hz f := 2.45 .multidot. 10.sup.9
dielectric constant .epsilon..sub.r := 3.8 diameter of core (O.D.),
meters d = 0.015 conductor thickness, meters c = 7.112 .multidot.
10.sup.-5 conductor width, meters b = 1.27 .multidot. 10.sup.-3 gap
width, meters p = 1.016 .multidot. 10.sup.-4 gap error spread,
meters p.sub..delta. = 5.08 .multidot. 10.sup.-6 frequency, Hz f :=
2.45 .multidot. 10.sup.9 dielectric constant .epsilon..sub.r :=
3.8
[0053] Loop Inductance
[0054] Where L.sub.ext is the inductance produced by flux coupling
around the perimeter of the loop and L.sub.int is the inductance
produced by an equivalent length of straight conductor.
3 5 L ext := o a ( a - c 2 ) 2 0 2 cos ( ) a 2 + ( a - c 2 ) 2 - 2
L.sub.ext = 5.172 .multidot. 10.sup.-8 6 L int := o ( a + c 2 ) 4
internal inductance, Henries L.sub.int = 2.394 .multidot. 10.sup.-9
L := L.sub.ext + L.sub.int total inductance, Henries L = 5.412
.multidot. 10.sup.-8
[0055] Loop Capacitance
4 7 C := ( 1 2 f ) 2 1 L capacitance, Farads C = 7.798 .multidot.
10.sup.-14 8 b c := p C o r c capacitor face length, m b.sub.c =
3.315 .multidot. 10.sup.-3 9 b c = 0.13053 1 m in 10 p := asin ( b
b c ) gap angle to edge, radians .alpha..sub.p = = 0.393
.alpha..sub.p = 22.523 .multidot. deg 11 C e := c b c o r p + p
capacitance with dimensional tolerance added C.sub.e = 7.426
.multidot. 10.sup.-14
[0056] Loop (Oscillation) Frequency
5 12 f e := 1 2 L C e 13 f o := 1 2 L C f.sub.e = 2.511 .multidot.
10.sup.9 f.sub.o = 2.45 .multidot. 10.sup.9 f.sub..delta. :=
(f.sub.e - f.sub.o) .multidot. 10.sup.-6 total frequency deviation
due to gap tolerance, MHz f.sub..delta. = 60.503 MHz
[0057] Loop Resistance
6 14 C := f c o circumferance in wavelengths C.sub..lambda. = 0.391
15 := 1 f o skin depth, meters .delta. = 1.335 .multidot. 10.sup.-6
16 R dc := 1 ( b c ) low-frequency conductor resistance, .OMEGA./m
R.sub.dc = 0.191 17 R hf := 1 ( ( b c ) - ( ( b c ) - ( b - ) ( c -
) ) high-frequency conductor resistance, .OMEGA./m R.sub.hf = 0.195
18 R r := 60 2 C 0 C Jn ( 2 , y ) y radiation resistance,
.OMEGA.(Jn = 2nd order Bessel function) R.sub.r = 0.572 R :=
R.sub.hf .multidot. .zeta. + R.sub.r conductor resistance, .OMEGA.
R = 0.582
[0058] Loop Oscillation Decay Calculation
[0059] Referring now to FIG. 7, each flat-loop-inductor is
constructed so that it continues to oscillate and emit an RF signal
for a finite period of time after the illuminating source RF signal
is turned off. The rate of oscillation decay is as determined as
follows. Note, represents the impinging electromagnetic field
intensity at the loop-inductor. This calculation is illustrated
with the RF transponder antenna design.
7 19 C := C = 0.391 loop wavelength circumference, .lambda. 20 I :=
E r 60 C J1 ( C sin ( ) ) induced current, amperes (J1 = Bessel
function) I = 9.4 .multidot. 10.sup.-4 21 U B := 1 2 L I 2 energy
coupled to inductor U.sub.B = 2.391 .multidot. 10.sup.-14 22 q := I
L C charge on capacitor, max q = 6.106 .multidot. 10.sup.-14 23 U E
:= 1 2 q 2 C energy stored by capacitor U.sub.E = 2.391 .multidot.
10.sup.-14
[0060] Rate of Oscillation Decay Calculation
[0061] n:=0, 0.001 . . . 2 t(n):=n.multidot.10.sup.-6
[0062] corrected angular frequency; note that loop resistance
changes oscillation frequency by an insignificant amount
8 24 ' := 1 L C - ( R 2 L ) 2 25 f ' := ' 2 f' = 2.449999851
.multidot. 10.sup.9f = 2.45 .multidot. 10 Hz (L-C-R) Hz (L-C) 26 q
e ( n ) := q e - R t ( n ) 2 L cos ( ' t ( n ) )
[0063] From FIG. 7, it can be seen that for the preferred
embodiment the flat-loop-inductor continues to emit an RF signal
for substantially 800 nanoseconds after discontinuation of the
illuminating source signal.
[0064] As described, during each resonate cycle each
flat-loop-inductor 33 emits a circularly polarized directional RF
signal in a direction substantially parallel to the plane of each
loop. Therefore, in order to generate a substantially
omnidirectional response to an incoming RF signal three passive
transponders are arranged in an array along three mutually
perpendicular axes such that each transponder is equidistant from
the point of intersection of the three axes and each transponder is
perpendicular to each of the other transponders. Such an
arrangement will produce a quasi-isotropic response from the array.
The array's response is quasi-isotropic because although the array
will respond when illuminated with a 2.45 ghz signal from any
angle, signal intensity is detectably stronger at points coplanar
with one of the flat-loop inductors.
[0065] Because of the variation in signal intensity it is possible
to gain additional information besides golf ball location. For
example, in flight rotation of a golf ball incorporating the above
described array will produce a degree of amplitude modulation in
the RF signal. Circuitry may be incorporated into the RF
transponder that will detect and decode the resulting amplitude
modulation. This decoded signal can be used to provide a golfer
with ball spin information that will allow the golfer to determine
the degree of hook or slice applied to the ball.
[0066] It should also be noted that the above described array can
be tuned to a frequency which is not exactly the same frequency as
the transmitter which illuminates and energizes the array. The
tuned frequency of the array would be close enough to the
transmitter frequency that the transmitter would still energize the
array, but the array would radiate at a frequency sufficiently
separate from the transmitter that a continuous wave receiver with
a very narrow bandpass could detect the array. In addition, those
skilled in the art will appreciate that frequency doubling
techniques can be used with the passive transponder of the present
invention.
[0067] In the preferred embodiment the array of flat-loop inductors
described above is formed on the surface of a golf ball core.
However, it would be equally effective to encapsulate the array
within a golf ball core or to form the array on the inner or even
the outer surface of the ball jacket. Other manufacturing
variations are also possible as will occur to those skilled in the
art.
[0068] Through prototype testing and sophisticated computer
modeling it has been determined that when illuminating a golf ball
embodying the present invention with a 2.45 Ghz signal from a
transmitter with a broadcast power of one watt an effective
detection range of 300 feet can be achieved with a sufficiently
sensitive receiver. At a power consumption of approximately one
watt, ordinary dry cell batteries, of a type readily available to
consumers, are able to supply sufficient power to operate the RF
transponder for a period of several hours. Since only intermittent
use is anticipated during the course of play, it will be
appreciated that the RF transponder will have a long battery life
thereby increasing its utility to golfers.
[0069] Referring to FIG. 11, the RF transponder incorporates
discrete transmitter 100 and receiver 200 circuits which utilize
the same antenna 20. Switching between the circuits is accomplished
by means of an RF switch 92. The transmitter is comprised of a
power supply 102 which provides power to an oscillator which
generates a sine wave output at a sub-harmonic of the broadcast
frequency. A frequency multiplier 106 boosts the oscillator output
to the desired broadcast frequency. The frequency multiplier drives
an amplifier 108 which produces a continuous non-modulated carrier
wave at the frequency of the multiplier 106 output. Those skilled
in the art will appreciate that the amplifier 108 may be driven
directly by an oscillator operating at the broadcast frequency,
thus skipping the frequency multiplier, at the concurrent expense
of increased power consumption. The output of the carrier wave
amplifier 108 is further boosted by power amplifier 110. The
maximum continuous transmitter broadcast power is one watt at a
frequency of 2.45 Ghz for the hand-held unit shown.
[0070] With continued reference to FIG. 11, to overcome the
difficulties involved in detecting and amplifying modulated high
frequency carrier wave signals, the receiver circuit 200 includes
two "step down", intermediate frequency (IF), amplifier stages. The
incoming antenna or carrier signal first passes through a band pass
filter 202. The band pass filter (BPF) selectively passes signals
at the transmitter frequency which corresponds to the frequency
emitted by the passive array 36. By selectively passing signals at
the transmitter frequency only, the BPF minimizes false echoes that
may be generated from extraneous RF sources located on or near the
golf course.
[0071] The filtered antenna signal passes to a first
amplifier/mixer stage, generally designated 204. The first
amplifier/mixer stage "steps down" the incoming signal to a first
intermediate (IF) frequency. The first IF frequency is itself
"stepped down" to a second IF frequency which can be detected and
used to drive an audio/visual display.
[0072] Again referring to FIG. 11, the first amplifier/mixer stage
204 functions as follows: The filtered antenna signal passes
through a low noise amplifier 206 thereby boosting the signal
strength to a point sufficient to overcome the noise produced by
the subsequent circuit stages. The boosted antenna signal, is
injected into a heterodyne mixer 208 where it is combined with a
signal originating from a local oscillator 210. The heterodyne
mixer subtracts, in a non-linear manner, the local oscillator
frequency from the carrier frequency to produce a first "stepped
down" IF frequency or difference frequency, also commonly referred
to as a "beat" frequency.
[0073] The local oscillator 210 generates a sine wave output which
is fed into a buffer amplifier 214. The buffer amplifier serves to
isolate the local oscillator from the mixer load and thereby
improve the local oscillator's frequency stability. The buffer
amplifier's output passes through a ceramic filter 216, which
filters out power supply and other extraneous circuit noise and
thereby provides a clean signal to the heterodyne mixer 208.
[0074] Coupling between the first amplifier/mixer stage 204 and the
second amplifier/mixer stage, generally designated 220, is
accomplished by means of a first IF band pass filter 218, tuned to
selectively pass frequencies at the first IF frequency. The filter
selects the mixer product transferred to the second IF
amplifier/mixer stage and prevents off channel signals caused by
intermodulation of the carrier and local oscillator from entering
the second stage. Off channel signals represent the sums and
differences of integer multiples of components of the original
intermixed or heterodyned waves.
[0075] The output from the first IF band pass filter passes into a
second amplifier stage, generally designated 220. The second stage
amplifier/mixer "steps down" the first IF frequency producing a
second IF signal which is of sufficiently low frequency to drive an
audio/visual display. The second amplifier/mixer stage 220
functions in a manner similar to the first amplifier/mixer stage
204, as follows: The incoming first IF signal is amplified by a low
noise amplifier 229 and is injected into a heterodyne mixer 222. A
local oscillator 226 produces a sine wave output which is isolated
from the mixer load by a buffer 228 and from which power supply
noise is filtered out by a local oscillator filter 230. The now
clean waveform which is of a frequency comparatively less than the
first IF frequency is fed into the second mixer 222. The resulting
mixer output is the second IF frequency. The second IF frequency is
fed into a band pass filter 236 where off channel frequencies are
blocked out. The now filtered second IF frequency enters a detector
240 which generates a signal strength indicator output suitable for
driving an LED readout, an audio beeper, or other type of signaling
device. The detector output passes to a comparator 232 which
compares the detected signal to a reference signal. If the strength
of the detected signal is sufficient to indicate the location of a
golf ball, the audio/visual display 234 is activated.
[0076] Switching between the transmitter and receiver is
accomplished by means of a high speed single pole double throw RF
switch 92. An impedance matching network 90 may be placed between
the antenna and the switch in order to match antenna and circuit
impedance. Switching frequency is controlled by a multivibrator 94.
The multivibrator cycles the switch between the transmitter and
receiver circuits. The vibrator time constant is substantially
equal to the sum of the time required for a transmitted signal to
travel 100 feet, for the passive array to energize and emit a
signal, and for an emitted signal to travel back to the antenna.
The multivibrator is turned on by means of a momentary contact
switch 112.
[0077] Those skilled in the art will appreciate that the circuits
disclosed in FIG. 11 represent one practical embodiment of
transmitter and receiver circuits suitable for use in the RF
transponder of the present invention and that variations of these
circuits are possible. It will also be appreciated that the
circuits may utilize individual components for each functional
element or may consist of monolithic integrated circuits
incorporating multiple functions.
[0078] Referring to FIG. 8, the antenna 20, incorporated in RF
transmitter/receiver 10, is of a helical, directional design, of
140 ohm impedance, tuned for maximum gain (16 dB) at a frequency of
2.45 Ghz. The antenna develops a radiation pattern of approximately
30 degrees and is circularly polarized. Circular polarization
allows the antenna to be energized by a passive transponder
emission regardless of the spacial orientation of the emitted
signal. The antenna is physically constructed as a single coil nine
turn helix 22 with a diameter of 1.642 inches and a pitch angle of
14 degrees utilizing 0.102 inch diameter wire. The antenna utilizes
a ground plane of substantially 2.41 inches. In the preferred
embodiment the coil is wound onto a form and encapsulated in a
durable plastic material by means of an injection molding
process.
[0079] The geometric data needed to perform the antenna design
calculations are summarized in Table 3. Reference should also be
made to Table 1 Physical Constants.
9TABLE 3 Geometric Data For Antenna Design Calculations transmit
antenna frequency, Hz f.sub.ant := 2450 .multidot. 10.sup.6
distance separating antenna and sensor, feet d.sub.f := 300
transmitter power to antenna, watts S.sub.tt = 1 helix diameter, in
D.sub.ain := 1.642 conductor diameter, inches d.sub.win := .102
Number of turns N := 9 Pitch angle, degrees .alpha..sub.d := 14
[0080] Antenna Design Calculations
10 D.sub.a := .0254 .multidot. D.sub.ain helix diameter, meters
D.sub.a = 0.042 27 d w := d win .0254 conductor diameter, meters
d.sub.w = 2.591 .multidot. 10.sup.-3 28 := d 180 pitch angle,
radians .alpha. = 0.244 29 ant := c o f ant free-space wavelength
(fs-.lambda.), meters .lambda..sub.ant = 0.12245
[0081] Helix circumference range of 0.7<C.sub..lambda.<1.4 is
valid for axial beam mode
11 30 C ant := D a ant helix circumference, fs-.lambda.
C.sub..lambda.ant = 1.07 C.sub.c := C.sub..lambda. .multidot.
.lambda..sub.ant C.sub.c = 0.048 m 31 L := C ant cos ( ) turn
length, fs-.lambda. L.sub..lambda. = 1.103 L.sub.c :=
L.sub..lambda. .multidot. .lambda..sub.ant L.sub.c = 0.135 m 32 D
:= C ant helix diameter, fs-.lambda. D.sub..lambda. = 0.341 D.sub.c
:= D.sub..lambda. .multidot. .lambda..sub.ant D.sub.c = 0.042 m
[0082] Antenna Design Calculations
[0083] Helix turn spacing range of 0.15<S.sub..lambda.<0.5 is
valid for axial beam mode
12 33 S := L 2 - C ant 2 helix turn spacing, fs-.lambda..
S.sub..lambda. = 0.267 S := S.sub..lambda. .multidot.
.lambda..sub.ant S = 0.033 m A.sub..lambda. := N .multidot.
S.sub..lambda. length of helix, fs-.lambda. A.sub..lambda. = 2.401
A := A.sub..lambda. .multidot. .lambda..sub.ant A = 0.294 m 34 B 3
dB := 52 C ant N S half power beam-width. degrees B.sub.3dB =
31.361 35 B nul := 115 C ant N S beam-width, first null, degrees
B.sub.nul = 69.357 G.sub.tt := 15 .multidot.
C.sub..lambda.ant.sup.2 .multidot. N .multidot. S.sub..lambda.
directivity G.sub.tt = 41.239 G.sub.dB := 10 .multidot.
log(G.sub.tt) gain, dB (disregarding ant. efficiency) G.sub.dB =
16.153 Z.sub.in := 140 .multidot. C.sub..lambda.ant terminal
resistance, .OMEGA. Z.sub.in = 149.806 D.sub.gp := .lambda..sub.ant
.multidot. 5 minimum ground plane diameter, m D.sub.gp = 0.061
D.sub.gp .multidot. 39.37 = 2.41 in.
[0084] Signal Propagation Calculations
13 36 := c o f ant .lambda. = 0.122 wavelength transmit, meters
d.sub.s := d.sub.f .multidot. 0.3048 d.sub.s = 91.4 distance
separation, meters 37 S t := 10 log ( S tt .001 ) S.sub.t = 30
transmitter circuit output power, dBm G.sub.t := 10 .multidot.
log(G.sub.tt) G.sub.t = 16.153 transmitter antenna gain, dB 38 P t
:= 20 log ( 4 d S ) P.sub.t = 79.448 path loss, dB (reciprocal
term) 39 S rr := S tt G tt ( 4 d S ) S.sub.rr = 4.683 .multidot.
10.sup.-7 signal power at loop, watts S.sub.r := (S.sub.t +
G.sub.t) - P.sub.t S.sub.r = -33.295 impinging signal power, dBm 40
S rr := 10 S r 0.1 - 3 S.sub.rr = 4.683 .multidot. 10.sup.-7
impinging signal power, watts 41 E := S rr ( o o ) 1 2 E.sub..phi.
= 0.013287 impinging e-field intensity, V/m 42 := 2 r := 1 e-field
to loop angle of Incidence, radians
[0085] Return Signal
[0086] The following equations are used to calculate the field
strength and power of the RF signal returned from the loop inductor
at the RF transmitter/receiver helical antenna. The results are
presented graphically in FIG. 9 which graphs field strength decay
in volts per meter as a function of time and in FIG. 10 which
graphs field power decay in dbm as a function of time.
14 43 I ( n ) := q e ( n ) L C loop current, amperes .omega. := 2
.multidot. .pi. .multidot. f radial frequency, rad/s 44 := 2 phase
constant
[0087] Field Strength (Volts/Meter) (See FIG. 9.) 45 E ( n ) := - j
O I ( n ) - j d S 4 d S a 2 j J1 ( a sin ( E ( 0 ) = 1.44 10 - 4 V
/ m
[0088] Field Power (Dbm) (See FIG. 10.) 46 S S ( n ) := 10 log ( E
( n ) ) 2 O O 1 10 - 3
[0089] As can be seen from FIG. 10, at the time the illuminating RF
transmitter/receiver shuts off, the return signal possesses a
strength of over -80 dbm at the RF transponder antenna which decays
to approximately -100 dbm within 600 nanoseconds. Design
simulations indicate that the receiver circuit disclosed has
sufficient sensitivity to detect signals down to approximately -96
dbm. With the given return signal strength and receiver sensitivity
our studies indicate that a golf ball embodying the passive
transponder array of the present invention can be readily detected
at a range in excess of 100 feet by a hand held, battery operated
RF transponder incorporating the disclosed receiver/transmitter
circuits and helical antenna.
[0090] In order to ensure that the golf ball location system of the
present invention operates as described particular care must be
taken in manufacturing the flat-loop inductors. In order for the
location system to be operative the flat-loop inductors must
resonate at substantially 2.45 Ghz. Each loop inductor is etched
onto insulative substratum using conventional photo-resistive
etching techniques on two ounce copper foil. The accuracy of the
etching process results in a +/-0.0005 inch tolerance on each
inductor edge. Thus, the total tolerance variation of the critical
loop gap is +/-0.001 inches. With this tolerance variation the
resonant frequency of each loop inductor would vary significantly
from one unit to next, thereby requiring that the receiver possess
a wide bandpass to sense all of the resulting frequency variations.
A wide bandpass degrades a receiver's signal to noise to ratio and
makes it less able to detect low level signals. Therefore, in
manufacturing the loop inductor a calibration process is included
where each loop gap is laser trimmed to achieve a precise
frequency. Also, the insulative substratum is cut away in the
center of the loop. This allows the loop to more easily conform to
the spherical radius of a golf ball and to lie tangent to the ball
core surface.
[0091] In use, the golf ball location system of the present
invention operates as follows: Assume a golfer has just hit a drive
using a ball incorporating the passive array 36. Now, further
assume that the unfortunate golfer looked upward and was
momentarily blinded by the sun and thus lost his or her ball. At
this point, the golfer will take the RF transmitter/receiver 10
(FIG. 1) and point the transponder in the general direction where
he or she thought the ball went while depressing the momentary
contact switch 112 (FIG. 11). Depressing switch 112 turns on the
multivibrator 94.
[0092] Referring to FIG. 11, in response the multivibrator 94 will
begin cyclic operation of the transmitter and receiver circuits.
The vibrator starts each cycle by simultaneously activating the
transmitter 100 and the RF switch 92, thereby coupling the
transmitter circuit to the antenna 20 thus causing a carrier wave
pulse to be emitted for a predetermined period of time.
Subsequently, the vibrator again activates the RF switch thereby
coupling the receiver circuit 204 to the antenna while
simultaneously shutting off the transmitter and turning on the
receiver. The multivibrator will allow the receiver to "listen" for
an incoming signal for a period of time substantially equal to the
time required for an outgoing transmitter signal to travel 100
feet, and energize the passive array causing the array to emit a
signal, and for the emitted signal to return. If a return signal is
detected the receiver will alert the golfer by means of the
audio/visual display 234. Subsequently, the cycle repeats for as
long as the momentary contact switch is depressed.
[0093] From the golfer's point of view, after depressing the
momentary contact or "on" switch 112, he or she may look to see if
the audio/visual display 234 has located the ball. The golfer may
sweep the transmitter/receiver 10 from side to side until he or she
detects a reading indicating the location of the ball. If the ball
is not visible on the field of play the golfer need only walk in
the direction the transmitter/receiver is pointing and sweep the
unit slightly from side to side. By observing the audio/visual
display which may include a signal strength meter and an audio
beeper responsive to the return signal generated by the ball and
advancing in the direction indicated by the display, the golfer
will be able to precisely locate the ball.
[0094] Referring to FIG. 12, in a second additional embodiment of
the present invention, a pair of RF transmitter/receivers 60 which
are similar in design to transmitter/receiver 10, but of greater
power handling capacity and correspondingly greater range, may be
utilized to track the flight path of a golf ball incorporating the
passive array 36. By coupling each RF transmitter/receiver with an
electromechanical drive mechanism 11 which sweeps the
transmitter/receivers across the field of play, the in-flight
location of a golf ball can be determined at discrete points in
time. The data points from a pair of transmitter/receivers may be
employed to reconstruct the 3-dimensional path of a golf ball by
means of triangulation. Computer graphing programs well known to
those skilled in the relevant art could be utilized to display the
results. Those skilled in the relevant art will also appreciate
that the electro-mechanical drive mechanism 11 can be replaced by a
phased or switched array of antennas which are sequentially pulsed
by an electronic controller.
[0095] A further variation of the in-flight tracking concept makes
use of the omni-directional nature of the signal emitted by the
array 36. Since an omni-directional signal has a 360 degree
radiation pattern it is not necessary that the same transmitter
both send the energizing pulse and detect the return signal.
Therefore, the golf ball could be pulsed by a broadcasting RF
transmitter/receiver 60 and the return signal detected by a
plurality of "listening" receivers 70 (FIG. 12). The golf ball's in
flight location could then be determined by triangulation among the
"listening" receivers. In the system just described the "listening"
receivers would have to be placed such that they don't directly
face the broadcasting transmitter/receiver, or the "listening"
receivers would have to be synchronized with the broadcasting
transmitter/receiver such that the "listening" receivers are turned
off when the broadcasting transmitter/receiver is transmitting.
Methods for synchronizing an array of transmitter/receivers are
well known to those skilled in the art.
[0096] It will be appreciated by those skilled in the art that the
golf ball locating system of the present invention provides a novel
golf ball containing a passive transponder array designed to work
in conjunction with an RF transmitter/receiver which includes a
circularly polarized helical antenna. It will be further
appreciated that the system can be readily adapted for either
locating stationary golf balls or for tracking golf balls in
flight. The tracking of golf balls in flight, and/or detection of
ball spin can be mated to golf course video simulation systems to
provide in-play review information including flight path data, and
distance, and spin overlaid on the golf course layout to
realistically reconstruct portions of or entire game play,
including courses using global positioning systems. In addition,
the system may be readily adapted to other uses such as tracking or
locating people or movable objects. For example, a "tag" composed
of an array of transponders could be produced for the purpose of
locating skiers buried in an avalanche. A ski resort could issue
transponder equipped tags with lift tickets. (or skiers could wear
clothing incorporating "tags") and thereby greatly increase the
odds of locating skiers lost due to injury, avalanche, or blizzard
(whiteout) conditions. Users of a location system embodying the
present invention could acquire array equipped tags which could be
attached to luggage, keyrings, or any other object the user wishes
to be able to locate more easily. Also, an isotropic "tag" could be
formed into the plastic grip of a gun allowing an officer to
determine if a car stopped for a traffic violation contained weapon
before approaching the car.
[0097] While only the present preferred embodiment and one
application of the location system of the present invention has
been described in detail, as will be apparent to those skilled in
the art, certain changes and modifications can be made without
departing from the scope of the invention as described in the
following claims.
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