JP3224564B2 - Magnetically coupled two-resonant circuit frequency division tag - Google Patents

Abstract

A batteryless, portable, frequency divider includes a first resonant LC circuit (70) that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant LC circuit (74) that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency. The first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit in response to receipt by the first circuit of electromagnetic radiation at the first frequency. At least one of the resonant circuits includes a variable reactance element, such as a variable capacitance diode (D1<.>, D1<..>) or a varactor. In a variable reactance element (D1<.>) of the first circuit (70), the reactance varies with variations in energy received by the first circuit for causing the second circuit to vary in reactance due to mutual reactive coupling to cause the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency. In a variable reactance element (D2<.>) of the second circuit (74), the reactance varies with variations in energy transferred from the first circuit for causing the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency. Both resonant circuits include inductance coils (L1<.>, L2<.>) that are disposed on a ferrite rod (72), for enhancing the magnetic coupling. The frequency divider is included in a tag utilized in a presence detection system. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to frequency dividers and, more particularly, to a portable, battery-less frequency divider included in a tag used in an object detection system.

[0002]

2. Description of the Related Art A portable and battery-less frequency divider is disclosed in Lincoln H .; Charlot, Jr.
U.S. Pat. No. 4,481,428 to Fred.
Wade Herman and Lincoln H.S. Ch
arlot, Jr. U.S. Pat. No. 4,670,740.

The frequency divider described in US Pat. No. 4,481,428 includes a first resonant circuit resonating at a first frequency for receiving a first frequency of electromagnetic radiation, and a second frequency of electromagnetic radiation. A second resonant circuit that resonates at a second frequency that is half of the first frequency for transmitting
The two resonant circuits have a second frequency at the second frequency only in response to the unrectified energy at the first frequency provided to the first resonant circuit by reception of the electromagnetic radiation at the first frequency.
Are electrically coupled to each other by a semiconductor switching device that obtains coupling of the first and second resonant resonance circuits to cause the first resonance circuit to transmit electromagnetic radiation. Each resonant circuit includes a fixed capacitance connected in parallel with the inductance coil. The coils are arranged perpendicular to each other so that the magnetic fields of the two coils are orthogonal to each other, in order to minimize the difficulty due to magnetic coupling between the coils when tuning the resonance circuit to the respective resonance frequencies. In one embodiment of this frequency divider that uses an air core coil for the first resonance circuit and a ferrite core coil for the second resonance circuit, the inner diameter of the air core coil further increases the magnetic coupling between the coils. To minimize it is made much larger than the diameter of the ferrite core coil.

The frequency divider described in US Pat. No. 4,670,740 is an inductor connected in parallel with a diode or varactor defining a resonant circuit for detecting electromagnetic radiation at a first predetermined frequency. And Dio
A second resonant circuit, which is a half of the first frequency at which the circuit resonates when the voltage across the diode or varactor is zero.
Respond to detection by transmitting electromagnetic radiation at a frequency of.

[0005]

SUMMARY OF THE INVENTION US Patent No. 4,670,740
The frequency divider described in U.S. Pat.
Less complex than the frequency divider described in US Pat. No. 428, whereby the former is inexpensive to manufacture, compactly packaged with a tag for attachment to an object to be detected by an object detection system, and further comprises a frequency divider. Starting the frequency division from the energy of the detected electromagnetic radiation because the circuit resonates at only the second frequency is ineffective.

The present invention is inexpensive and not complicated to manufacture,
U.S. Pat.
A frequency divider is provided which is more compactly packaged than the frequency divider described in U.S. Pat. No. 481,428.

[0007]

SUMMARY OF THE INVENTION In accordance with one aspect of the present invention, a battery-free, portable frequency divider is provided that resonates at a first frequency to receive electromagnetic radiation at a first frequency. One resonant circuit and a second resonant circuit resonating at a second frequency that is half the first frequency to transmit electromagnetic radiation at a second frequency, wherein the first resonant circuit is a first resonant circuit. Is coupled only magnetically to the second resonant circuit to transfer energy at the first frequency to the second resonant circuit in response to reception of the electromagnetic radiation at the first frequency by the first resonant circuit; The circuit is variable in response to a change in energy transferred from the first resonant circuit to transmit electromagnetic radiation at a second frequency in response to energy transferred from the first resonant circuit at a first frequency. Including a reactance element.

A battery-free portable frequency divider according to another aspect of the present invention includes a first resonant circuit resonating at a first frequency to receive electromagnetic radiation at a first frequency. A second resonant circuit that resonates at a second frequency that is half of the first frequency to transmit electromagnetic radiation at a second frequency, the first resonant circuit comprising a first frequency of electromagnetic radiation. Is only magnetically coupled to a second resonant circuit that transfers energy to a second resonant circuit in response to reception by the first resonant circuit, the first resonant circuit being coupled at a first frequency to the first resonant circuit. A first resonant circuit for causing a reactive change in the second resonant circuit by mutual reactive coupling to cause the second resonant circuit to transmit electromagnetic radiation at a second frequency in response to energy transferred from the second resonant circuit. React with changes in received energy Comprising a variable reactance element Nsu changes. In a preferred embodiment of this aspect of the invention, the second resonant circuit has a second reactance at a first frequency in response to energy transferred from the first resonant circuit.
A variable reactance element whose reactance changes with a change in energy transferred from the first resonance circuit to transmit electromagnetic radiation at a frequency of Each resonant circuit preferably includes an inductance coil disposed on the magnetic circuit means to enhance capacitance and magnetic coupling.

By using only magnetic coupling between the resonant circuits, expensive and energy consuming electrical connections for the resonant circuits as used in frequency division in conventional frequency dividers. The element need not be used. The present invention also provides a tag including such a frequency divider and an object detection system including such a tag. Additional features of the present invention are described in connection with the description of the following examples.

[0010]

Referring to FIG. 1, a preferred embodiment of a frequency divider according to the present invention comprises a first capacitor C1 connected in parallel with an inductance coil L1 wound on a linear ferrite rod 12. Resonance circuit 1
And a second resonance circuit 14 comprising a variable capacitance diode or a varactor D2 connected in parallel with a second inductance coil L2 wound around the ferrite rod 12.

A first resonance circuit 10 resonates at a first frequency f ₁ to receive electromagnetic radiation at a first frequency f ₁ , and a second resonance circuit 14 resonates at a second frequency f _2. The second frequency f which is half of the first frequency f ₁ to transmit
Resonates at ₂ . The first circuit 10, second circuit to transfer the first energy to a second circuit 14 at the frequency f ₁ in response to reception by the first circuit 10 of the first electromagnetic radiation of a frequency f ₁ To 14, it is only magnetically coupled by the ferrite rod 12 and air. The variable capacitance diode or varactor D2 of the second circuit 14 has a first frequency f
_{In step 1} the second is performed in accordance with the energy transferred from the first circuit 10.
Is a variable reactance element whose reactance changes due to a change in energy transferred from the first circuit 10 in order to transmit electromagnetic radiation at the frequency f ₂ of the second circuit 14.

The coil L1 of the first resonance circuit 10 has a first frequency f ₁ induced by the coil L2 of the second resonance circuit 14.
It is believed that this increases the electromagnetic radiation, thereby reducing the required magnetic field strength of the electromagnetic radiation of the first frequency f ₁ required to achieve frequency division.

Since the inductance value of each resonant circuit 10,14 is affected by the respective positions of the coils L1 and L2 on the ferrite rod 12 with respect to each other and to the end of the rod 12, the resonant circuits 10,14
Adjustment of the position of coils L1 and L2 on 12 tunes to resonance frequencies f1 and f2, respectively.

The coils L1 and L2 are ferrite rods
12, but because of the coupling between the coils L1 and L2, adjusting the position of the coil in one of the resonance circuits has a significant effect on the resonance frequency of the other resonance circuit, and Since it becomes difficult to tune the resonance circuit, it is necessary to prevent too strong coupling between the two coils L1 and L2. Therefore, the inner diameter d 'of each of the coils L1 and L2 is slightly larger than the cross-sectional diameter d''of the ferrite rod 12. Coil L1, L
2 is wound on a non-magnetic spacer member 16 which is adjustably mounted on the ferrite rod 12. In the preferred embodiment, the rod 12 has a diameter d '' of about 0.125 inches (0.
31 cm), and the inside diameter of each of the coils L1, L2 is about 0.15 inch (0.38 cm).

In order to achieve frequency division, the coupling coefficient "k" between the inductance coil L1 of the first resonance circuit 10 and the inductance coil L2 of the second resonance circuit 14 is in the range of zero to 0.6, The conversion of the energy of the electromagnetic radiation of the _first resonance frequency f ₁ received by the first resonance circuit 10 into the electromagnetic radiation emitted by the second resonance circuit 14 at the second frequency f ₂ is such that the coupling coefficient k is It is most effective at about 0.3.

In one preferred embodiment of FIG. 1, coils L1 and L2 are wound on opposite ends of a linear ferrite rod 12 having a diameter of about 0.125 inches (0.3 cm) and a length of 1.25 inches (3.2 cm). Each coil L1, L2 is
The ends of the coils L1, L2, which are approximately 0.375 inches (0.95 cm) long and are adjacent to each end of the rod 12, are located ± 0.125 inches from the end of the rod 12. The coil is
They should be separated by at least 0.375 inches to prevent any reciprocal coupling that would make tuning of the two resonant circuits 10,14 difficult. Each coil L1, L2 is approximately 3
Should not exceed 5%.

The frequency divider of this embodiment operates at a signal level several orders of magnitude lower than a conventional frequency divider of similar size. The efficiency of the frequency division of this frequency divider, determined by the function of the more important energy conversion, is very high, whereby the same order of magnitude of the frequency division as provided by a conventional frequency divider which is many times larger. The transmission of electromagnetic radiation at a resonance frequency f2 of ₂ is possible.

In this embodiment, the capacitance C1 is
A 680 picofarad capacitor and the diode or varactor D2 has a varactor junction capacitance of about 600 picofarads.

A variable capacitance diode or varactor D2 having one or more parallel varactor junctions having a non-linear variation in capacitance with a small level of supplied AC voltage, such as a Zener diode, is low. Because of the price, it is used as a voltage-responsive variable reactance element in the second resonance circuit 14. In other embodiments, many other devices that have the large non-linear capacitance changes required at the applied AC voltage, have relatively low losses, and have high Q-factors include variable capacitance diodes or varactors. Used instead. A ferromagnetic material having a lower magnetic loss than ferrite can be used as the rod 12 of the magnetic circuit means.

In another embodiment (not shown),
The only magnetic circuit means used to couple the coils of the different resonant circuits is air. This embodiment is not complicated,
Proper magnetic coupling can provide an object detection tag that is practical for certain applications due to the placement of the coils in close proximity to each other. However, in this embodiment, it is more difficult to tune each resonance circuit because there is no ferrite core that can fine-tune the resonance frequency by adjusting the position of the coil on the core as described above.

In various other preferred embodiments, the magnetic circuit means for coupling the coils of the different resonant circuits is a ferrite element having a shape other than a linear rod. Orientation pickled reaction tags including the frequency divider according to the change in shape of the magnetic circuit means is adjusted by the particular application and configuration for exciting an electromagnetic field in the first resonance frequency f _1.

In one such embodiment, as shown in FIG. 2A, the magnetic circuit means includes an L-type ferrite element 20. In this embodiment, the frequency divider is a first resonance circuit 22 composed of an inductance coil L1 wound around one end of an L-type ferrite element 20 and a capacitor C1 connected in parallel, and an L-type ferrite element. 20 includes a second resonant circuit 24 comprised of a variable capacitance diode or varactor D2 connected in parallel with a second inductance coil L2 wound around another end of the circuit. In other respects, the structure of the frequency divider of FIG. 2A is different from that of FIG.
Is the same as that described above with respect to the structure of the frequency divider of FIG.

In another embodiment, shown in FIG. 2B, two or more magnetic poles are oriented to provide a first resonance frequency f _1.
And the amount of coupling of the second resonance frequency f _{2 to} the surrounding space is provided in the magnetic circuit element 30. In this embodiment, the frequency divider is one of the ferrite elements 30.
A first resonance circuit 32 composed of a capacitor C1 connected in parallel with an inductance coil L1 wound around one end, and a second inductance coil L2 wound around another end of the ferrite element 30 in parallel. It includes a second resonant circuit 34 comprising a connected variable capacitance diode or varactor D2. In other respects, the structure of the frequency divider of FIG. 2B is the same as that of the frequency divider of FIG. 1 since the operation of the frequency divider of FIG. It is the same as described above with respect to the structure of the vessel.

The magnetic circuit means may include two or more separate ferrite rods that are magnetically coupled close to each other to optimize performance and / or may have a maximum manufacturable length of a single ferrite rod. Instead of using a ferrite rod, a large hole is provided in the magnetic circuit. At present, ferrite rods having a length / diameter ratio of 10 or 12 or more cannot be manufactured at low cost. By arranging a plurality of linear ferrite rods whose ends are in contact, the hole of the magnetic circuit can be enlarged.

Further, by providing an air gap in the magnetic circuit between the separated ferrite rods in which the coils of the separated resonance circuit are arranged, the mutual coupling between the coils can be reduced by reducing the magnetic resistance between the coils. Reduced,
This facilitates tuning of the isolated resonant circuit by adjusting the position of the coil on the rod.

In one embodiment using a plurality of ferromagnetic rods in a magnetic circuit as shown in FIG. 2 (c), the magnetic circuit means has end-to-end with air gaps 44 between them. Two linear ferromagnetic rods arranged opposite to each other
Includes 40,42. In this embodiment, the frequency divider is wrapped around a first resonance circuit 46 composed of an inductance coil L1 wrapped around one of the ferrite rods 40 and a capacitor C1 connected in parallel thereto, and another ferrite rod 42. A second resonance circuit 48 comprising a second inductance coil L2 connected in parallel and a variable capacitance diode or varactor D2 connected in parallel to the second inductance coil L2.
including. Otherwise, the structure of the frequency divider is similar to that described above with respect to the structure of the frequency divider of FIG. 1 since the operation of the frequency divider is similar to the operation of the frequency divider of FIG.

In another embodiment of the present invention shown in FIG. 2D, the variable reactance element of the second resonance circuit is not a variable capacitance element as in the above-described embodiment but a variable inductance element L2 '. is there. In this embodiment, the frequency divider is an inductance coil L1.
A first capacitor C1 connected in parallel with
And a second resonance circuit 52 composed of a second capacitance C2 connected in parallel with the variable inductance element L2 '. The first resonance circuit 50 and the second resonance circuit 52 are only magnetically coupled by magnetic circuit means as described above with reference to the description of the alternative embodiment. Variable inductance element L2 'includes an inductance coil 56 and a low-loss ferromagnetic material 58 that exhibit a large change in permeability within a desired voltage range of the incident electromagnetic radiation at a _first predetermined frequency f1. . A low loss ferromagnetic material 58 is located in the magnetic circuit of the inductance coil 56. In this embodiment, not only the volumetric magnetic properties of the ferromagnetic material 58 but also the physical shape of the ferromagnetic material 58 have a great influence on the second resonance circuit 52 in the frequency divider characteristics. Ferrite material is preferred as ferromagnetic material 58. The composition of the material is selected to provide the desired properties at the selected operating frequency. In suitable designs of the resonant circuits 50,52, operation is possible from the low kilohertz range to the microwave range. Otherwise, the structure of the frequency divider is similar to that described above with respect to the structure of the frequency divider of FIG. 1, since the operation of the frequency divider is similar to the operation of the frequency divider of FIG. is there.

In the frequency divider embodiment of the present invention described above, the resonant circuit is described as including an inductance and a capacitance, since the described embodiment is designed for use at relatively low frequencies, respectively. ing. In embodiments of the frequency divider designed for use at higher frequencies, such as in the microwave region, the resonant circuit includes embodiments of microslip, stripline, and / or cavity technology.

Further, in the embodiment of the frequency divider of the present invention, the second resonance circuit may be a device that resonates mechanically at the second frequency. The mechanical resonator is a parallel LC
It is equivalent to a resonance circuit.

In one such embodiment, as shown in FIG. 2 (e), the frequency divider comprises a first resonant circuit comprising a capacitor C1 "connected in parallel with an inductance coil L1". 60, comprises a first second resonant circuit 62 comprised of a strip 64 of saturable magnetostrictive material for magnetic mechanical resonance at a frequency f ₂ which is half of the resonance frequency f ₁ of the resonant circuit 60. Coil L of first resonance circuit 60
1 ″ is magnetically coupled to the magneto-mechanical resonant strip 64 by being wrapped around the strip 64. The inner dimensions of the coil L1 '' are spaced from the strip 64 to avoid making tuning of the first resonant circuit 60 difficult.

[0031] The strip 64 has a length that is
Resonance in the first resonance circuit 60 and the resonance frequency f of the first resonance circuit 60.
_It functions as a variable reactance core of a magnetically permeable material that is variable according to the magnetic field level to convert the electromagnetic radiation received by the first resonant circuit 60 at frequency f _{1 to} electromagnetic radiation at frequency f ₂ , which is half of one.

In a preferred embodiment, the strip 64 is Lucian G. Ferguson and Lincol
nH. Charlot, Jr. US Patent No.
A saturable magnetostrictive amorphous ferromagnetic material as described in US Pat. No. 4,727,360.

In other respects, the structure of the frequency divider is similar to that described above with respect to the structure of the frequency divider of FIG. 1, since the operation of the frequency divider is similar to the operation of the frequency divider of FIG. Is the same.

Referring to FIG. 3, a preferred embodiment of the frequency divider according to the present invention comprises a variable capacitance diode or varactor D1 connected in parallel with an inductance coil L1 wound on a linear ferrite rod 72. And a second frequency circuit 74 composed of D2 connected in parallel with a second inductance coil L2 further wound around a ferrite rod 72.

The first resonance circuit 70 resonates at the first frequency f ₁ to receive the electromagnetic radiation at the first frequency f ₁ ,
The second resonant circuit 74 is half the first frequency f ₁ 2
Resonates at a second frequency f ₂ to at the frequency f ₂ transmit electromagnetic radiation. The first circuit 70 includes a second circuit responsive to reception of the electromagnetic radiation at the first frequency f ₁ by the first circuit 70.
It is only magnetically coupled by ferrite rod 72 and air gap to second circuit 74 to transfer energy to 74. The variable capacitance diode or varactor D1 of the first circuit 70 is connected to the second circuit 70 by mutual reactive coupling.
The reactance is changed at 74, thereby
By the first change of the received energy by the first circuit 70 in order to transmit the electromagnetic radiation to the second circuit at a second frequency f ₂ in response to the transferred energy from the circuit 70 of the frequency f ₁ It is a variable reactance element whose reactance changes. Variable capacitance diodes of the second circuit 74 - de or varactor D2 is reactance is transferred from the first circuit in response to energy being subsidized by the interaction coupling of the first circuit at the first frequency f ₁ a variable reactance element reactance by a change of the energy transferred from the first circuit 70 is changed in order to transmit the electromagnetic radiation to the second circuit 74 at the second frequency f _2.

As shown in FIG. 3A, the winding directions of the coils L1 and L2 of the first and second resonance circuits 70 and 74 are as follows.
The beginning of the coil L1 of the first resonance circuit 70 is connected to the anode of the variable capacitance diode D1, and the beginning of the coil L2 of the second resonance circuit 74 is the cathode of the variable capacitance diode D2. To be connected to
This connection method uses a variable capacitance diode D1,
D2 is more conductive in the forward region of the conductive diode, thereby achieving a power limiting effect by reducing the overload effect at high input field levels shunting the current in each of coils L1 and L2. .

The coil L1 of the first resonance circuit 70 increases the electromagnetic radiation of the first frequency f ₁ induced by the coil L2 of the second resonance circuit 74, thereby achieving frequency division. It is considered that the strength of the magnetic field of the electromagnetic radiation required at the frequency f ₁ of ₁ is reduced, and the change of the reactance of the second resonance circuit is promoted by the mutual coupling by the variable reactance of the first resonance circuit.

The resonance circuits 70, 74 are affected by the respective inductance values of the coils L1 and L2 on the ferrite rod 72 with respect to each other and with respect to the end of the rod 72, so that the resonance circuits 70, 74 , it is adjusted to the resonance frequency f ₁ and f ₂ by adjusting the position of the coil L1 and L2 on the rod 72, respectively.

The coils L1 and L2 are ferrite rods
However, since there is a coupling between the coils L1 and L2, adjustment of the position of the coil of one of the resonance circuits has a large effect on the resonance frequency of the other resonance circuit, and both coils are wound. Since it becomes difficult to tune the resonance circuit, it is necessary to prevent too strong coupling between the two coils L1 and L2. Therefore, the inner diameter d 'of each of the coils L1 and L2 is slightly larger than the cross-sectional diameter d''of the ferrite rod 12. Coil L1, L
2 is wound on a non-magnetic spacer member 76 that is adjustably mounted on the ferrite rod 12.

In order to achieve frequency division, the coupling coefficient k between the inductance coil L1 of the first resonance circuit 70 and the inductance coil L2 of the second resonance circuit 74 should be in the range of zero to 0.6. And the conversion of the energy of the electromagnetic radiation at the _first resonance frequency f ₁ received by the first resonance circuit 70 into electromagnetic radiation radiated by the second resonance circuit 74 at the second frequency f ₂ is coupled. Coefficient k is about
0.3 is the most efficient.

In the preferred embodiment of FIG.
1 and L2 are 0.125 inches (0.3 cm) in diameter and 1.
Wound around the opposite end of a 25 inch (3.2 cm) linear ferrite rod 72. Each coil L1, L2 is approximately 0.375 inches (0.95 cm) in length and the ends of coils L1, L2 adjacent each end of rod 72 are located ± 0.125 inches from the end of rod 72. . The coils should be separated by at least 0.375 inches to prevent any reciprocal coupling that would make tuning of both resonant circuits 70,74 difficult. Each coil L1, L2 is about 35% of the length of the rod 72
Should be less than.

The frequency divider of this embodiment operates at a signal level several orders of magnitude lower than a conventional frequency divider of similar size. The efficiency of the frequency divider of this frequency divider as determined by the more important energy transmission function is very high, thereby providing the same order of magnitude frequency division as provided by a conventional frequency divider that is many times larger. Second
Allowing the transmission of electromagnetic radiation at a resonant frequency f ₂ of the.

In this embodiment, the variable capacitance diode or varactor D1 has a varactor junction capacitance of about 600 picofarads, and the variable capacitance diode or varactor D2 has a varactor junction capacitance of about 800 picofarads.

In an embodiment of the integrated circuit, a variable diode
Both the varactors or varactors D1, D2 are formed as a common cathode. In this embodiment, the frequency divider is a variable capacitance diode or varactor D1, D2.
Occurs over a large area due to the limited function of

A variable capacitance diode or varactor D1, D2 having one or more parallel varactor junctions having a non-linear variation in capacitance with a small level of supplied AC voltage, such as a Zener diode, First and second produced at low cost
Are used as voltage-responsive variable reactance elements in the resonance circuits 70 and 74. In other embodiments, many other devices that have the large non-linear capacitance change required at the supplied AC voltage, have sufficiently low losses, and have a high Q-factor include a variable capacitance diode or Can be replaced with varactor. A ferromagnetic material having lower magnetic loss than ferrite can be used as the rod 72 of the magnetic circuit means.

In another embodiment (not shown),
The only magnetic circuit means used to couple the coils of the different resonant circuits is air. This embodiment is not complicated and proper magnetic coupling can provide an object detection tag that is practical for certain applications due to the placement of the coils in close proximity to each other. However, in this embodiment, it is more difficult to tune each resonance circuit because there is no ferrite core that can fine-tune the resonance frequency by adjusting the position of the coil on the core as described above.

In various preferred alternative embodiments (not shown), the magnetic circuit means for coupling the coils of the different resonant circuits is a ferrite element having a shape other than a linear rod. Orientation pickled reaction tags including the frequency divider according to the change in shape of the magnetic circuit means is adjusted by the particular application and configuration for exciting an electromagnetic field in the first resonance frequency f _1. In one such embodiment, the magnetic circuit means comprises an inductance coil of a resonant circuit wound around one end of the L-shaped ferrite element and an inductance coil of another resonant circuit wound around another end of the L-shaped ferrite element. Includes an L-type ferrite element having a coil.
Otherwise, the structure of such a frequency divider is
Since the operation of such a frequency divider is similar to that of the frequency divider of FIG. 3, it is the same as that described above for the structure of the frequency divider of FIG.

In such another embodiment, the two or more magnetic poles are oriented, and the first resonant frequency f ₁ and the second
It is provided in the magnetic circuit elements to control the amount of binding to the surrounding space of the resonance frequency f _2. In other respects, the structure of the frequency divider of such an embodiment is similar to that of the frequency divider of FIG. 3 since the operation of the frequency divider of such an embodiment is similar to that of the frequency divider of FIG. Same as described above for the structure.

The magnetic circuit means may include two or more separate ferrite rods that are magnetically coupled close to each other to optimize performance and / or may have a maximum manufacturable length of a single ferrite rod. Instead of using ferrite rods, large holes are provided in the magnetic circuit. Currently, ferrite rods have a length to diameter ratio of 10 or 12
These cannot be manufactured cheaply. By arranging a plurality of linear ferrite rods whose ends are in contact, the hole of the magnetic circuit is enlarged.

By providing an air gap in the magnetic circuit between the separated ferrite rods on which the coils of the separated resonance circuit are respectively installed, the magnetic coupling between the coils reduces the magnetic resistance between the coils. Tuned, thereby facilitating tuning of the isolated resonant circuit by adjusting the position of the coil on the rod.

In one embodiment in which a plurality of ferromagnetic rods are used in a magnetic circuit, the magnetic circuit means has two linear stiffeners arranged end-to-end with an air gap between them. Includes magnetic rod. In this embodiment, the inductance coil of the first resonance circuit is wound around one of the ferrite rods, and the inductance coil of the second resonance circuit is wound around another ferrite rod. Otherwise, the structure of the frequency divider of such an embodiment is the same as that described above for the structure of the frequency divider of FIG. 3, since such an embodiment is similar to the operation of the frequency divider of FIG. Is the same as

In another embodiment of the invention shown in FIG. 4, the frequency divider according to the invention comprises a variable capacitance diode or a parallel connection of an inductance coil L1 wound on a linear ferrite rod 82. It includes a first resonance circuit 80 composed of a varactor D1, and a second resonance circuit 84 composed of a capacitance C2 connected in parallel with a second inductance coil L2 wound around a ferrite rod 82.

The first resonance circuit 80 resonates at the first frequency f ₁ to receive electromagnetic radiation at the first frequency f ₁ , and the second resonance circuit 84 operates at half the first frequency f ₁ . In order to transmit electromagnetic radiation at some second frequency f ₂ , the second frequency f ₂
Resonates at ₂ . The first circuit 80 has a first frequency f ₁
Is coupled only magnetically to the second circuit 84 by the ferrite rod 82 and the air gap to transfer energy to the second circuit 84 in response to reception by the first circuit 80 of the electromagnetic radiation. Variable capacitance diode of the first circuit 80 - de or varactor D1 is reactance first frequency f ₁
In response to the energy transferred from the first circuit 80 to transmit electromagnetic radiation at a _second frequency f ₂ by the first circuit 80 such that a change in reactance results in a second circuit 84 due to mutual coupling. This is a variable reactance element whose reactance changes according to a change in received energy.

The embodiment of FIG. 4 is much less efficient than the embodiment described above, but the variable reactance is reflected back to the second resonance circuit 84 by the magnetic coupling of the two resonance circuits 80,84. Therefore, it functions as a frequency divider.

In other respects, the structure of the frequency divider of FIG. 4 is the same as that of the frequency divider of FIG. 3 since the operation of the frequency divider of FIG. 4 is similar to that of the frequency divider of FIG. Same as what was done.

In another embodiment of the frequency divider of the present invention, one of the inductance coils of the first and second resonance circuits may be a variable reactance element. Such a variable inductance element is the first element of the embodiment of FIG.
3 or in addition to the variable capacitance diodes or varactors of the first and second resonance circuits of the embodiment of FIG. The variable inductance element is formed by winding a coil around a low-loss ferromagnetic material 58 that produces a large change in permeability within the desired voltage range of the incident electromagnetic radiation at the resonant frequency of each resonant circuit. In these embodiments, not only the volumetric magnetic properties of the ferromagnetic material, but also the physical form of the ferromagnetic material, have a significant effect on the frequency divider characteristics of the resonant circuit. The ferrite material is preferably a ferromagnetic material. The composition of the material is selected to provide the desired properties at the selected operating frequency. In a suitable design, operation is possible from the low kilohertz range to the microwave range.

In the frequency divider embodiment of the present invention described above, the resonant circuit is described as including inductance and capacitance since the described embodiment is designed for use at relatively low frequencies. I have. In embodiments of the frequency divider designed for use at higher frequencies, such as in the microwave region, the resonant circuit includes embodiments of microslip, stripline, and / or cavity technology.

The frequency divider of the present invention is used in a preferred embodiment of the object detection system according to the present invention as shown in FIG. Such a system includes a transmitter 90, a tag 91 and a detection system 92. The transmitter is an audit zone.
An electromagnetic radiation signal 94 of a first predetermined frequency is transmitted to the computer 96.

The tag 91 is attached to an object (not shown) such as a commodity detected in the inspection zone 96. Tag 91
Includes a battery-free portable frequency divider according to the present invention, such as the frequency divider described above with respect to FIGS.

The detection system 92 detects electromagnetic radiation 98 in the monitoring zone 96 at a second predetermined frequency, which is half the first predetermined frequency, whereby the monitoring zone 96 is detected. Detect the presence of a tag inside.

The object detection system using the tag including the frequency divider according to the present invention can be applied to an application using a long-range tag,
It is used in a variety of applications that take advantage of the size and effectiveness of such frequency dividers, including applications using small tags where only short transmission areas are needed. In one embodiment, a small tag containing the frequency divider of the present invention is injected subcutaneously into an animal, and such an animal is counted by an object detection system.

In another embodiment, a small tag containing the frequency divider of the present invention is plugged into an explosive non-metallic canister, such a canister being detected by an object detection system.

In another embodiment, a tag comprising a frequency divider of the present invention having a relatively large dimension is inserted into a non-metallic stock that is detected by an object detection system, and the gun is detected by the object detection system. Is done.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a preferred embodiment of the frequency divider of the present invention.

FIG. 2 is a circuit diagram of another preferred embodiment of the frequency divider of the present invention.

FIG. 3 is a schematic perspective view and a circuit diagram of another preferred embodiment of the frequency divider of the present invention.

FIG. 4 is a circuit diagram of another preferred embodiment of the frequency divider of the present invention.

FIG. 5 is a block diagram of an object detection system including a tag according to the present invention.

[Explanation of symbols]

10, 14 ... resonance circuit, 12 ... ferrite rod, 90 ... transmitter, 91 ... tag, 92 ... detection system, 96 ... monitoring zone.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Ming Len Liang, USA 34346, Florida, Clearwater, Spoonville Lane 14001 (56) References JP-A-57-196604 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) G08B 13/24 G01V 3/12

Claims (10)

(57) [Claims] 1. A first resonant circuit resonating at a first frequency to receive electromagnetic radiation at a first frequency, and a half of the first frequency to transmit electromagnetic radiation at a second frequency. A second resonant circuit that resonates at a second frequency, wherein the first resonant circuit responds to the first resonant circuit for receiving electromagnetic radiation at the first frequency. Is only magnetically coupled to the second resonant circuit for transferring energy to the second resonant circuit, the second resonant circuit being configured to respond to the energy transferred from the first resonant circuit at the first frequency.
A variable reactance element whose reactance changes by a change in energy transferred from the first resonance circuit to transmit electromagnetic radiation at a frequency of Divider. 2. A first resonant circuit resonating at a first frequency to receive electromagnetic radiation at a first frequency, and a half of the first frequency to transmit electromagnetic radiation at a second frequency. A second resonance circuit that resonates at a second frequency, wherein the first resonance circuit supplies energy to the second resonance circuit in response to reception of electromagnetic radiation of the first frequency by the first resonance circuit. Is coupled magnetically only to the second resonant circuit to transfer the second resonant circuit at a second frequency in response to energy transferred from the first resonant circuit at a first frequency.
The resonant circuit comprises a variable reactance element whose reactance changes by a change in energy received by the first resonant circuit to change reactance in the second resonant circuit by mutual reactive coupling to transmit electromagnetic radiation. A portable frequency divider which does not require a battery. 3. The method according to claim 1, wherein the second resonance circuit has a first frequency at a first frequency.
To cause the second resonant circuit to transmit electromagnetic radiation at a second frequency in response to energy transferred from the resonant circuit of
3. The frequency divider according to claim 2, further comprising a variable reactance element that changes according to a change in energy transferred from the resonance circuit. 4. The frequency divider according to claim 1, wherein each resonance circuit includes an inductance coil disposed on magnetic circuit means for increasing capacitance and magnetic coupling. 5. A separate pair of linear ferromagnetic rods, each resonant circuit including an inductance coil disposed on magnetic circuit means for enhancing capacitance and magnetic coupling, wherein the magnetic circuit means is aligned end to end. Composed of
A coil of one resonance circuit is arranged on one rod,
2. The frequency divider according to claim 1, wherein the coil of the other circuit is disposed on the other rod. 6. A frequency divider comprising: a frequency divider; and means for attaching the frequency divider to an object detected by the object detection system, wherein the frequency divider has a first frequency for receiving electromagnetic radiation of a first frequency. A first resonant circuit that resonates at a frequency and a second resonant circuit that resonates at a second frequency that is half of the first frequency for transmitting electromagnetic radiation at a second frequency; Resonantly transfers the energy at the first frequency to the second resonant circuit at a first frequency in response to reception of the first frequency electromagnetic radiation by the first resonant circuit. A first resonant circuit coupled to the second resonant circuit for transmitting electromagnetic radiation to the second resonant circuit at a second frequency in response to energy transferred from the first resonant circuit at the first frequency; Reactor by change of energy transferred from circuit A tag for use in an object detection system, comprising a variable reactance element whose resistance varies. 7. A frequency divider comprising: a frequency divider; and means for attaching the frequency divider to an object detected by the object detection system, wherein the frequency divider has a first frequency for receiving electromagnetic radiation of a first frequency. A first resonant circuit that resonates at a frequency and a second resonant circuit that resonates at a second frequency that is half of the first frequency for transmitting electromagnetic radiation at a second frequency; Is magnetically coupled only to the second resonant circuit for transferring energy to the second resonant circuit in response to reception of electromagnetic radiation at the first frequency by the first resonant circuit; Of the second resonant circuit is configured to transmit the electromagnetic radiation at the second frequency in response to the energy transferred from the first resonant circuit at the first frequency. First to cause reactance change in the circuit A tag used for an object detection system, comprising: a variable reactance element whose reactance changes according to a change in energy received by the resonance circuit. 8. The second resonance circuit has a first frequency at a first frequency.
And a variable reactance element whose reactance changes according to a change in energy transferred from the first resonance circuit to transmit electromagnetic radiation at the second frequency in accordance with energy transferred from the resonance circuit. The tag described. 9. A monitor comprising: means for transmitting an electromagnetic radiation signal at a first frequency into a monitoring zone; a frequency divider; and means for attaching the frequency divider to an object detected by the object detection system. A tag for attachment to an object detected in the zone; and means for detecting electromagnetic radiation of a second frequency in the monitoring zone, wherein the frequency divider in the tag comprises a first frequency divider. First to receive electromagnetic radiation of frequency
A first resonant circuit that resonates at a frequency of: and a second resonant circuit that resonates at a second frequency that is half of the first frequency to transmit electromagnetic radiation at a second frequency, 1
Resonantly transfers the energy at the first frequency to the second resonant circuit at a first frequency in response to reception of the first frequency electromagnetic radiation by the first resonant circuit. Coupled to the second resonant circuit, wherein the energy transferred from the first resonant circuit for transmitting electromagnetic radiation at the second frequency in response to the energy transferred from the first resonant circuit at the first frequency An object detection system, comprising: a variable reactance element whose reactance changes according to a change in the value. 10. A monitor comprising: means for transmitting an electromagnetic radiation signal at a first frequency into a monitoring zone; a frequency divider; and means for attaching the frequency divider to an object detected by the object detection system. A tag for attachment to an object detected in the zone; and means for detecting electromagnetic radiation of a second frequency in the monitoring zone, wherein the frequency divider in the tag comprises a first frequency divider. A first resonant circuit that resonates at a first frequency to receive electromagnetic radiation at a frequency, and resonates at a second frequency that is half the first frequency to transmit electromagnetic radiation at a second frequency; A second resonant circuit, wherein the first resonant circuit includes a second resonant circuit for transferring energy to the second resonant circuit in response to reception of the first frequency of electromagnetic radiation by the first resonant circuit. Coupled only magnetically to the resonant circuit,
A first resonant circuit is coupled to the second resonant circuit at a second frequency in response to energy transferred from the first resonant circuit at a first frequency to transmit electromagnetic radiation to the second resonant circuit at a second frequency. An object detection system, comprising: a variable reactance element whose reactance changes according to a change in energy received by the first resonance circuit to cause a change in reactance in the resonance circuit.