Contactless smart card in the form of a metal ring

Abstract

The invention relates to contactless smart cards made in the form of rings. The inner side of a ring has an annular groove for housing an antenna and a chip module which has its own electrical capacitance and is connected to the antenna. The metal ring has a transverse slot, and the annular groove containing the antenna and the chip module is hermetically sealed across the full depth thereof. The transverse slot is hermetically sealed across the full width thereof, which is not less than 1 mm. The antenna is a multi-turn loop antenna made of copper wire. The self-resonant frequency of the antenna lies in the high-frequency band. The electrical capacitance of the chip module corresponds to a level that allows the antenna to operate at the self-resonant frequency. The technical result is that of improving signal quality while at the same time providing a high read rate even under the shielding effect of the metal body of the ring.

Description

[0001] Description

[0002] Contactless smart card in the form of a metal ring

[0003] Field of technology

[0004] The present invention relates to contactless smart cards made in the form of rings. This type of smart cards can be used to make contactless payments, for example, when using public transport, as a means of access to the transport network as a means of payment. In addition to contactless payment, payment rings can include a whole range of additional non-financial services, including identification applications of various types, etc.

[0005] State of the art

[0006] A solution is known from the prior art that discloses a contactless smart card in the form of a ring containing a connected frame antenna and a microchip on a conductive pad that supports NFC technology, and a one-piece housing, which has a recess on the side intended for adjoining the finger that accommodates the microchip with the antenna and is sealed along the entire height (see Russian patent for utility model No. 207076, published on 11.10.2021). The microchip is made with an electrical capacitance of at least 78 pF, and the recess is rectangular. A coating of ceramics, plastic, two-component epoxy pigmented compositions (epoxy resins) or composites based on a ceramic matrix is ​​used as a sealant. The housing is made of ceramics, plastic, epoxy resins or a composite material.

[0007] This technical solution allows for physical protection of the resonant circuit elements while maintaining the functionality of the smart card. However, this solution cannot be used when using a metal case due to the presence of a radio signal shielding effect.

[0008] Disclosure of invention

[0009] The technical result, which the proposed technical solution is aimed at achieving, consists in ensuring the possibility of increasing the quality of the signal with a simultaneously high reading speed under the influence of the shielding effect of the metal body of the ring on the specified speed.

[0010] The claimed technical result is achieved in that the contactless smart card in the form of a metal ring, on the inner side of which an annular recess is provided for placing an antenna and a chip module with its own electrical capacity, electrically connected to the antenna, wherein the metal ring has a cross-section, and the annular recess with the antenna and the chip module are sealed along the entire depth, wherein the cross-section is sealed along the entire width, which is at least 1 mm, and the antenna is a multi-turn frame antenna made of copper wire, wherein the natural resonant frequency of the antenna is in the high-frequency range, and the electrical capacity of the chip module corresponds to the level that ensures the operation of the antenna at its own resonant frequency.

[0011] In a more specific case, the high resonant frequency of the antenna is in the range of 13.56-15.5 MHz.

[0012] In a more specific case, the high resonant frequency of the antenna corresponds to 13.56 MHz.

[0013] Also, in a particular embodiment, the microchip is made with an electrical capacitance of at least 42 pF.

[0014] Also, in a particular embodiment, the number of antenna turns is 8. Also, in a particular embodiment, the signal reading radius is from 25 to 30 mm.

[0015] Also, in a particular embodiment, the copper wire from which the antenna is made has a thickness of 0.2 mm and is insulated with polyester varnish.

[0016] Also, in a particular embodiment, with a depth of the annular recess equal to 1.3 mm, the ratio of the length of the antenna wire to the length of the circumference of the annular recess is 7.8.

[0017] Brief description of the drawings

[0018] Fig. 1. General view of a metal ring without a resonant circuit.

[0019] Fig. 2. Geometric parameters of a contactless smart card in the form of a metal ring.

[0020] Fig. 3. Antenna with chip module.

[0021] Implementation of the invention

[0022] The proposed technical solution (see Fig. 1-3) primarily provides the possibility of using a ferromagnetic material as a housing part in the form of a ring for a contactless smart card. The shape of the ring (1) and the individually selected size of the ring allow wearing the contactless smart card on a finger and can have the appearance of a piece of jewelry (see Fig. 1). In the general case, such a material as silver, gold, platinum, titanium, tungsten carbide, steel and other materials can be used as a ferromagnetic material. At the same time, the use of a ferromagnetic material, as previously noted, worsens the operation of the antenna-chip-module transceiver circuit due to the physical nature of the material used for the housing part. In order to ensure the operability of the smart card while simultaneously receiving high signal quality and high signal reception / transmission speed, it is first of all necessary to exclude complete shielding of the antenna module by the ferromagnetic housing.For this purpose, a cross-section (G) must be made in the ring. It has been experimentally established that with a cross-section less than 1 mm, the quality and speed of the signal are insufficient for the operation of a smart card in the form of a ring when using a resonant circuit with the characteristics listed below. In turn, the presence of a cross-section of 1 mm or more (for example, from 1 to 5 mm) ensures a sufficient signal level and high speed of its transmission for the operation of the proposed device. However, further increasing the width of the cross-section by more than 1 mm does not significantly increase the signal value. In this regard, the optimal cross-section width is 1 mm, but it can be set to more.

[0023] Fig. 2 shows a metal ring with the corresponding geometric parameters. In particular, the ring has a certain thickness - T, ring height - W, height of the inner ring recess - H, depth of the inner ring recess - D, cross-section - G. As an example, these dimensions can be as follows: W - 5 mm, H - 3.5 mm, T - 2.1 mm, D is 1.3 mm, G - 1.0 mm. The choice of parameter D is selected based on the internal diameter D of the metal ring, which in the standard version can correspond to 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, and taking into account the possibility of placing a resonant circuit (antenna - chip module) in the recess. Based on the values ​​of parameter D, the diameter of the annular recess is determined, into which the antenna with the chip module is subsequently installed, and, accordingly, the number of turns of the antenna is selected taking into account the diameter of the annular recess and the resonant frequency of the antenna.

[0024] For example, for a ring with an internal diameter D equal to 16 mm, the diameter of the annular recess (taking into account the parameter D = l.3 mm) will be 18.6 mm. Accordingly, to place the resonant circuit in the annular recess, the antenna turn diameter should be selected from values ​​lying within the range from 18 to 18.6 mm. In this case, the length of the antenna wire can be calculated taking into account the installation depth of the resonant circuit in the annular recess. The immersion depth of the resonant circuit is selected based on the need to form a protective sealing layer. Since two-component epoxy composites are usually used as a sealing compound, the thickness of the layer providing a protective and sealing function is usually from 1 mm or more (±0.1 mm for error). Moreover, some compounds are prone to shrinkage within 2 to 5%.Thus, when selecting the upper limit of material shrinkage as a percentage, the layer thickness can be selected at 1.05 mm (taking into account shrinkage of 5%). Taking this value into account, it is possible to calculate the radius of the circle within which the antenna turns are located. Thus, with a ring having an internal diameter of 16 mm, the radius will be 8 mm and, accordingly, the radius of the circle on which the antenna turns are located will be 9.05 mm (i.e. 8 + 1.05) or, when converted to diameter, this value will be 18.1 mm. This value determines the diameter of the antenna turn Dvitka, based on which it is possible to determine the total length of the wire to form the corresponding antenna based on the ring parameters. Thus, to calculate the length of the required wire, we determine the length of the turn circumference using the formula: T = LD. ВИ tka = 3.14 * 18.1 = 56.83 mm. Since the antenna is a multi-turn loop antenna, where the number of turns can be equal to 8, the total length of the wire will be 455 mm.

[0025] This ensures that the resonant circuit “antenna with chip module” is placed directly in the annular recess.

[0026] It is also worth noting that the combination of such design features as the length of the antenna wire, the antenna material, and the number of antenna turns affect the resonant frequency of the antenna. The resonant frequency of the antenna is its important parameter for receiving a signal at the appropriate frequency without interference and noise, which ensures the required signal quality with a high reading speed under the influence of the shielding effect of the metal ring body on the specified speed. At the same time, the selection of the parameters for the length and number of antenna turns is limited by the area where the resonant circuit is located. Thus, the minimum and maximum value of the antenna circuit turn depends on the diameter of the ring recess where the antenna turns are located. As indicated in the example above, with an optimal antenna turn diameter of 18.1 mm, the wire length will be 455 mm.It has been experimentally established that there is an optimal ratio of the parameters of the length of the wire L to the length of the circumference of the recess T. В notches- So, for the example given above (where the length of the wire is Ьwire = 455 MM), we determine the NOTCH CIRCUMFERENCE LENGTH T В recesses.

[0027] In the calculation (as an example), the minimum value of D equal to 1.3 mm and the minimum value of the inner diameter of the ring D equal to 16 mm were used. Thus, the inner diameter of the annular recess will be equal to the sum of the inner diameter of the ring D and the doubled value of D. Next, the circumference of the annular recess is determined by the formula =л(Д+2О). For a ring measuring 16 mm, the diameter of the annular recess will be 18.6 mm. Accordingly, the circumference of the annular recess will be equal to 58.4 mm. Thus, the ratio of the length parameters Tpr 0В0Д and to the length of the circumference of the notch T Вof the recess will be 7.8 (i.e. 455 / 58.4 = 7.8) - this value can be taken as the coefficient K for calculating the length of the wire. Considering the rather small size of the annular recess, the coefficient K can be taken as the optimal parameter. At the same time, it was experimentally established that this parameter can also be used when calculating the length of the wire for other values ​​of the diameter of the annular recess.

[0028] For example, for a ring with a diameter of 17 mm, the value of the circumference of the annular recess will be T ВЫ capacious =61.54 mm. Accordingly, the value of the wire length will be 7.8 times greater, which will be 480 mm. Other values ​​of the wire length parameters are also allowed (7.8±0.1...0.15 - tolerance parameters), but within the limits that allow placing the resonant circuit in the cavity of the annular recess. The tolerance value from 0.1 to 0.15 mm is taken into account in the case of tuning the resonant frequency. Thus, the use of the calculated value of the coefficient K leads to obtaining the required diameter of the antenna turn, which is positioned at the optimal depth of the annular recess, which automatically leads to the formation of the required thickness of the protective sealing layer, which ensures the operability of the resonant circuit with high signal quality at a simultaneously high reading speed under the influence of the shielding effect of the metal body of the ring on the specified speed.

[0029] The design of the ring and the resonant circuit are shown more clearly in Figs. 2 and 3. The metal ring (1) has an annular recess on the inner side for placing the antenna and the chip module in it. The recess is a groove or depression made along the entire length of the circumference of the inner side of the ring. The antenna (2) and the chip module (3) connected to it are sealed in the annular recess so that the sealing compound fills the entire cavity along its entire depth D and height H. Two-component epoxy composites are used as a sealing compound. Fig. 4 shows a view of the ring with a sealing compound in the annular cavity. The recess has a U-shaped cross-section, which allows for even fixation of the antenna with the chip module in it. The sealing compound not only secures (fixes) the resonant circuit elements in the cavity of the annular recess, but also allows for the elimination of direct contact of the resonant circuit elements with the metal body.This is a necessary element of the design of the proposed device to ensure the operability of the antenna and achieve the appropriate signal quality with a simultaneously high reading speed under the influence of the shielding effect of the metal body of the ring on the specified speed.

[0030] The cross-section G is also filled with a sealing compound over the entire width, which can be from 1 mm to 5 mm. This additionally ensures the formation of a protective layer for the antenna on the side of the cross-section and, accordingly, ensures the operability of the resonant circuit with high signal quality at the same time with a high reading speed under the influence of the shielding effect of the metal body of the ring on the specified speed.

[0031] The antenna (2) is a multi-turn circuit made of copper wire, which is insulated with polyester varnish to prevent short-circuiting of the turns to the metal housing and to each other, which in turn ensures the operability of the resonant circuit and high-quality signal transmission at high speed. Copper wire has good conductivity, which allows the signal to be transmitted over the required distance and with minimal losses. Copper is also strong and durable, which makes it an ideal material for antennas. At the same time, copper is subject to oxidation and contact corrosion when interacting with another metal. Contact corrosion and oxidation significantly degrade the properties of copper and, accordingly, affect the operability and characteristics of the signal (speed, range, power, etc.). In this regard, when installing the resonant circuit in a recess in a metal ring, it is necessary to exclude direct contact of metal surfaces.Therefore, covering the antenna turns with polyester varnish is mandatory. Enameled heat-resistant high-strength wire with polyvinyl acetate insulation (PTEV-2) can be used as the antenna wire. The wire thickness is selected based on the requirements for the antenna characteristics and is 0.2 mm (the wire thickness is one of the parameters that affects the circuit inductance).

[0032] The number of turns in the general case can correspond to 8 and be a constant parameter for any type of ring. It should be noted that as a particular example of implementation, the total length of the wire for forming the antenna can vary from 455-651 mm (the length of the wire can also be in the range of 455-660 mm with the appropriate tolerance, size of the annular recess, etc.) depending on the diameter of the recess of the metal ring and taking into account obtaining the required value of the resonant frequency lying in the high-frequency range. In this case, this linear size, the antenna material (2), the value of the chip module capacitance (3), the number of antenna turns (2) provide tuning of the antenna to its own resonant frequency, the operating range of which is in the high-frequency range. According to the generally accepted frequency classification, high frequencies include frequencies from 13 to 30 MHz (see GOST 14443).In a particular example of implementation, with a frequency range from 13.5 to 15.5 MHz, the reading range will be within 25-30 mm. Since it is clear to a specialist that the antenna turns allow minimizing the size of the antenna itself (which is due to the size of the annular recess) while maintaining high signal quality, then choosing a different number of turns in the antenna is also possible, provided that the high resonant frequency of the antenna is maintained. It will also be clear to a specialist that other ranges of high resonant frequency, which in the general case can be within 13-30 MHz, are also possible with an appropriate choice of the parameters of the resonant circuit of the antenna (for example, the parameters of capacitance and inductance).

[0033] Additional specific examples of the implementation of the proposed solution are given in Table 1. Specific examples of implementation show the industrial applicability of a contactless smart card in the form of a metal ring, and also show the possibility of achieving the declared technical result when using a resonant circuit with a chip module having its own capacitance and a multi-turn antenna with a high resonant frequency.

[0034] Table 1

[0035] Table 1 shows possible wire length values, however, these values ​​may differ slightly within the tolerance limits.

[0036] It should be noted that the short wavelength in the high frequency range allows the formation of a compact antenna with the required characteristics in terms of signal quality while maintaining a high reading speed.

[0037] Thus, the parameters of the length and thickness of the wire, as well as the material for the antenna, additionally affect the signal quality at a high reading speed under the influence of the shielding effect of the metal body of the ring. The chip module (3) is a microchip with a crystal (4). The chip module microcircuit (3) is designed with the ability to accumulate an electric charge necessary to ensure the operability of the resonant circuit of the smart card with a high signal quality at a high reading speed. In this case, the chip module (3) supports NFC technology and is designed with its own electric capacitance of at least 42 pF, sufficient to ensure the operability of the circuit at a high resonant frequency of the antenna and to ensure high signal quality at a high signal transmission speed. The specified capacitance value was obtained as a result of testing microchips with different capacitances. This electric capacitance, as already noted above, should be at least 42 pF.

[0038] The antenna (2) is electrically connected to the chip module (3), forming a resonant circuit, as shown in Fig. 3.

[0039] Thus, the combination of such features as the presence of a 1 mm cross-section, the level of the antenna resonant frequency (high frequency), the antenna material (copper wire), as well as the presence of its own capacitance (ensuring the operation of the resonant circuit in the range of high resonant frequencies of the antenna) and a sealing compound (preventing contact with the metal body of the ring), ensure high signal quality at a high transmission speed.

[0040] The particular features of the proposed technical solution, such as high resonant frequency of the antenna in the range from 13-15.5 MHz, chip module capacity of at least 42 pF, number of antenna turns equal to 8, reading radius from 25 to 30 mm, copper wire thickness of 0.2 mm and its coating with polyester varnish, ratio of the antenna wire length to the circumference of the annular recess, equal to 7.8, also provide an impact on the specified technical result, namely, ensuring the possibility of improving the signal quality with a simultaneously high reading speed under the influence of the shielding effect of the metal body of the ring on the specified speed.

Claims

Invention formula 1. A contactless smart card in the form of a metal ring, on the inner side of which an annular recess is provided for placing an antenna and a chip module with its own electrical capacity, electrically connected to the antenna, characterized in that the metal ring has a cross-section, and the annular recess with the antenna and the chip module are sealed along the entire depth, while the cross-section is sealed along the entire width, which is at least 1 mm, and the antenna is a multi-turn frame antenna made of copper wire, wherein the natural resonant frequency of the antenna is in the high-frequency range, and the electrical capacity of the chip module corresponds to a level that ensures the operation of the antenna at its own resonant frequency.

2. A contactless smart card according to item 1, characterized in that the high resonant frequency of the antenna is 13.56 MHz.

3. A contactless smart card according to item 1, characterized in that the high resonant frequency of the antenna is in the range of 13-15.5 MHz.

4. A contactless smart card according to item 1, characterized in that the chip module is made with its own electrical capacitance of at least 42 pF.

5. A contactless smart card according to item 1, characterized in that the number of antenna turns is 8.

6. A contactless smart card according to item 1, characterized in that the signal reading radius is from 25 to 30 mm.

7. A contactless smart card according to item 1, characterized in that the copper wire from which the antenna is made has a thickness of 0.2 mm and is insulated with polyester varnish.

8. A contactless smart card according to claim 1, characterized in that with a depth of the annular recess equal to 1.3 mm, the ratio of the length of the antenna wire to the length of the circumference of the annular recess is 7.8.

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