TWI640129B - Nfc antenna system and method of alteration of modulation depth - Google Patents

Abstract

The present invention discloses an NFC antenna system having at least one pair of solenoid windings (1) placed in a single plane and having a common axis (3). The solenoid windings (1) are connected to the excitation and are oriented in such a way that the magnetic fields of the solenoid windings (1) are opposite one another. The distance between the middle portions of the solenoid windings (1) is at least twice the length of the solenoid windings (1); when the length of the solenoid windings (1) is between 5 mm and 20 mm This distance is usually 35 mm to 45 mm in the range. In a preferred configuration, each of the solenoid windings (1) has its own independently controlled excitation element (4) whereby the excitation element has one of the modulated inputs connected and which has an identical excitation frequency. The end position of the excitation element (4) is independently controlled by the control input to open and close the end level, which allows for a simple change in modulation depth. In a pair of solenoid windings (1), the change can be set to range from 25% to 100% in a 25% step. A significant advantage of the present invention is the reduction of the surface required to place the NFC antenna on the carrier, primarily on the PCB of a mobile phone.

Description

Near field communication antenna system and method for changing modulation depth

The present technology relates to an antenna system having at least one pair of solenoid windings that replaces a flat helical antenna of one of the NFC platforms. The antenna system occupies a smaller surface of the carrier (mainly on the PCB) than the flat helical antenna and it allows for a simple change in modulation depth.

Flat spiral antennas are primarily used for communication via the NFC platform primarily in accordance with ISO/IEC 14443. The antennas of the transmitter and the antennas of the receiver are placed adjacent to one another, typically in a position above one another, and the antennas are in magnetically coupled communication. The proximity of the antenna creates one of the cores of the air transformer, as depicted on Figure 1. The NFC platform operates on a globally available and unlicensed radio ISM frequency of 13.56 MHz bandwidth. The transfer of data between the transmitter and the receiver is achieved by varying the strength of the magnetic field. The change can be 100% (OOK modulation) or 10% (AM). The transmission of data by one of the intensities of the magnetic field is disclosed in the standards ISO 14443 and ISO 18092. The receiving antenna typically has a circular shape with a diameter of about 40 mm, or it has a rectangular shape with a width of about 42 mm and a length of about 72 mm. The transmit antenna has a shape and size similar to that of the receive antenna; these shapes and sizes do not need to be identical; however, significant differences result in less effective magnetic field flow. The flat antenna is placed only in a free and usually large substrate (such as a plastic carrier for a payment card). In the case where a flat antenna is placed on the PCB of an electronic device (eg, placed on a PCB of a mobile phone), the loop of the flat antenna significantly limits the design of the PCB; therefore, it limits the placement and connection of other components on the PCB. According to the publications WO/2014/076669, WO/2013/098784, there are solutions which allow transmission of a strong electromagnetic field capable of affecting a transmitter antenna having a typical surface of a helical antenna (from a small antenna). These publications disclose one solution with a high level of miniaturization; this problem is not significant in the case of placing an NFC antenna on a PCB, since the PCB typically has a sufficiently large overall size. This technical solution for NFC antennas is desirable and not shown in the figures, where the NFC antenna will produce a magnetic field having a shape and size similar to that of a flat helical antenna, but it will not require a similar large surface for its configuration. It will provide more freedom for the design of the surrounding connections.

According to the invention (the element lies in the fact that the distance between the middle portions of the solenoid winding is at least twice its length, and the windings are oriented and connected in such a way that the magnetic field of the windings or one another is opposite to each other) The NFC antenna system of a certain solenoid winding is substantially corrected, the at least one pair of solenoid windings being placed in a single plane and the longitudinal axes of the solenoid windings being substantially identical. The connection for achieving the reverse magnetic field will preferably be achieved in such a way that each of the solenoid windings has its own independently controlled excitation element, whereby the excitation element has its interconnected modulation input and the frequency of the excitation element the same. The term "solenil winding" primarily refers to a cylindrical coil having a plurality of threads of a conductor, wherein the length of the coil is greater than its diameter, and typically the length of the coil is at least twice its diameter. The solenoid winding in the solution according to the invention may have, but need not have, a core; it may also have a hollow. The term "substantially the same longitudinal axis"("the longitudinal axis is substantially the same") means that the full coaxial orientation is the best, but it also achieves sufficient results with a slight deviation from the mutual position. The distance of the solenoid winding corresponds to the size of the antenna of the receiver, preferably within the margin of the error (or limit) set by the length of the solenoid winding. The solenoid winding should be such that at least some of the magnetic field lines run around the windings of the antenna of the receiver when the solenoid windings traverse the plane of the antenna of the receiver. The important system solenoid winding has its magnetic field in the opposite phase, and the solenoid windings are oriented in opposite directions in opposite directions. This, together with a sufficient axial distance, produces a situation in which the magnetic field on the outer edge of the antenna system has a shape very similar to that of a flat helical antenna (Fig. 4) and one of the latitudes and latitudes. In the middle region (just at the level of the axes of the two solenoid windings), the latitude of the magnetic field lines is different from the latitude of the field lines of the flat helical antenna; the field lines are deformed to the axis of the solenoid winding Direction, but the synergistic antenna of the receiver never reaches the level of this axis during the approach. The latitude of the magnetic field lines in the incremental distance from the axis of the solenoid winding is more conventionally shaped as a flat helical antenna, wherein the magnetic field lines straddle the plane diagonally or vertically with the flat helical antenna of the receiver. The proximity (approximation) of the antenna of the receiver to the axis of the solenoid winding is in fact limited by the thickness of the body of the individual device (e.g., by the thickness of the mobile phone, etc.). A significant portion of the surface necessary for the placement of the magnetic field (which is sufficiently similar to that produced by a typical flat helical antenna) by one of the magnetic fields with opposite orientations, but at the same time saving (or spare) the placement of the antenna . The solenoid winding is preferably configured in a manner such that the receiver spans the plane of the flat helical antenna of the length of the solenoid winding, as depicted on FIG. During the new antenna system in which the invention and the NFC antenna of the receiver cooperate, if the length of the solenoid winding is in the range of 5 mm to 20 mm, it has been shown to be preferred; that is, the small winding is sufficient. . The cross section of the solenoid winding can have any shape (circular, rectangular, square, elliptical, etc.), but the surface of the cross section must be such that the resulting value is in the range of 750 nH to 2 μH and the quality Q =15 to 25 one way to choose. The distance between the middle portions of the solenoid windings is at least twice the length of the solenoid windings; preferably the distance between the central portions is 35 mm to 45 mm. These dimensions are not only the result of one of the routine, non-inventive actions of the familiar artisan during the dimensioning of the antenna system. Specifically, the size of the solenoid winding should be based on the relationship of the magnetic field flowing from the solenoid winding around the conductor of the flat spiral antenna of the receiver and the distance between the conductors running around the conductor, whereby the flat spiral antenna moves (close) to the plane of the solenoid winding. Therefore, the size of the important system solenoid windings corresponds to the size of the receiver's antenna and is typically standardized. As mentioned in the prior state of the art, a circular shaped receiving antenna typically has a diameter of about 40 mm, and in the case of a rectangular shape the receiving antenna has a width of about 42 mm and a length of about 72 mm. The distance between the middle of the solenoid winding is in the range of 35 mm to 45 mm, thus appearing to engage the size of the antenna of the receiver, which would otherwise be independent and part of a separate device. An NFC antenna according to the publication US 2008/0238799 A1 is proposed in accordance with the mutual coaxial arrangement of two solenoid windings according to the invention. However, the present disclosure describes and seeks different objectives; it attempts to create one of the possibilities of orienting the magnetic field in such a way that the magnetic field is reduced by half the space to the plane of the coil and one half of the space is strengthened in the opposite direction. Therefore, the magnetic field from one side of the half space can theoretically directly apply energy to the other side of the plane. If this theoretical preset is actually implemented, it will cause an enhancement of the magnetic field on the side of the antenna of the receiver. In one case, the pair of solenoid windings should be approached from which side the antenna of the receiver is not defined in advance. The proposed invention (as opposed to the publication US 2008/0238799 A1) reveals the geometry of the distribution of the solenoid windings relative to the antenna of the receiver and the opposite orientation of the magnetic fields in a pair of solenoid windings, among which other independent excitations The component is used for this latter purpose. These are used to achieve the characteristics necessary for the stated goal of the small solenoid winding to mimic the radiation (emission) of one of the large surfaces of the helical antenna. The common axis of the two solenoid windings is in an internal configuration of at least 3 mm to 5 mm from the edge of the device in which the antenna system is placed. Preferably, the antenna system according to the present invention is placed in a mobile communication device (e.g., placed in a mobile phone). In the case where the mobile phone is at the center of the PCB, the solenoid winding can be placed at the edge of the PCB. To achieve the opposite orientation of the magnetic field on the solenoid windings, the windings have independent excitation; in this case the solenoid windings are not connected in series or in parallel to a common excitation element. This is advantageous if the change in the modulation depth of the transmitted signal is achieved, if each of the solenoid windings L1, L2 is controlled by an excitation element having an end level operating in the bridge. The solenoid winding L1 will be energized by A1, A3 and the solenoid winding L2 will be energized by A7, A8. The two excitation components will operate with the same frequency 13.56 MHz and they will have a common digital modulation signal on the MOD input. The end positions of the excitation elements can be turned off by respective control inputs D1, D2, D3, D4, which are synchronized with the digital modulation signals on the MOD input. A new method of changing (changing) the modulation depth during transmission by the NFC platform is due to the fact that the strength of the magnetic field changes by opening and closing the end level of the excitation element in one of the desired modulation rhythms. This is a very effective method compared to the methods used to date (where amplitude modulation is achieved by standard means of inserting additional losses (usually by their values in a rhythm of the modulation). However, the effectiveness of this solution is low and the loss of energy is not necessary when compared to solutions having switchable end positions according to the present invention. Using an antenna system with two solenoid windings L1, L2, it is possible to change the four levels of the 25% layered stack according to the following scheme of closing (0) and opening (1) the end position of the excitation element. Change depth: <TABLE border="1"borderColor="#000000"width="85%"><TBODY><tr><td><b>Enter</b></td><td><b> Modulation depth</b></td></tr><tr><td><b>D1</b></td><td><b>D2</b></td><td ><b>D3</b></td><td><b>D4</b></td></tr><tr><td> 1 </td><td> 0 </td ><td> 0 </td><td> 0 </td><td> 25% </td></tr><tr><td> 1 </td><td> 1 </td><Td> 0 </td><td> 0 </td><td> 50% </td></tr><tr><td> 1 </td><td> 1 </td><td> 1 </td><td> 0 </td><td> 75% </td></tr><tr><td> 1 </td><td> 1 </td><td> 1 </td><td> 1 </td><td> 100% </td></tr></TBODY></TABLE> The antenna system according to the present invention reduces the surface necessary for the accumulation region of the NFC antenna and also Allows for effective changes in modulation depth. If two or more pairs of solenoid windings are used, an improved shape of the magnetic field and an increase in the latitude and total radiation efficiency are achieved. In this configuration, it is still pervasive that the individual pairs of solenoid windings have a common axis and that they have a magnetic field that is oriented in the opposite direction. The optimized latitude of the magnetic field of the solenoid winding (as depicted in Figure 4) is achieved in a vertical plane through the axis of the solenoid winding. In other vertical planes that partially rotate around the axis of the antenna of the receiver, the latitude of the magnetic field is different. Use multiple pairs of solenoid windings to achieve the desired latitude in multiple planes. Increasing the number results in a better simulation of the magnetic field of a typical flat antenna; however, it will naturally be limited by the available surface on the PCB. The key system achieves the desired effect even when using a single pair of solenoid windings, which can be advantageous and without the need to be placed on a PCB (e.g., placed on its edges or corners). In the case of two pairs of configurations, the shaft of a pair of solenoid windings may be perpendicular to the axis of the second pair, whereby the middle of the solenoid winding is placed in a circle. This geometry produces a circular configuration. In the case of a quadrilateral configuration, the axes of the two pairs of solenoid windings are parallel. The circular or quadrilateral surface defined by the middle of the solenoid winding should be in the range from 1200 mm ² to 2000 mm ² . In the case of multiple pairs of configurations, the phase of the individual levels (antennas) is adjusted in such a way that the resulting latitude of the signal induced in the antenna of the receiver is sinusoidal. The setting of the excitation element eliminates the size and angular deviation from the main rules of the configuration according to the invention. If such geometric deviations are required by the design of the PCB, the deviation is acceptable. In general, PCB designs require a rectangular architecture in which the outer surfaces of individual components on the board are parallel or perpendicular. The antenna system according to the present invention can be suitably adjusted to such conditions. The advantages of the present invention are primarily a significant savings over the surface necessary for placement of an NFC antenna on a flat helical antenna for use in accordance with the specific recommendations of the respective standards. One of the received magnetic fields is detected on the antenna of the receiver as if it were transmitted by a typical flat helical antenna. Another aspect of effective orientation and control that does not require depth modulation of the capability loss in the excitation component.

Example 1 In this example according to Figures 2, 3, 4 and 5, the antenna system has two solenoid windings 1 labeled L1 and L2. In this example, the solenoid winding 1 is formed of a conductor wound on a flat core and has a length of 10 mm. The inductance of the solenoid winding 1 is μH; its quality is 20. The solenoid windings 1 are placed on the PCB of the mobile phone in such a way that they have a common longitudinal axis 3 . The final deviation in the coaxiality caused by the common production irregularities when the components are mounted on the PCB does not affect the achieved results. The end of the solenoid winding 1 is 30 mm, which corresponds to a distance of 40 mm from the middle. The shaft 3 of the solenoid winding is substantially parallel to the shorter edge of the mobile phone and its distance from the edge of the mobile phone is about 4 mm, which is depicted in FIG. When comparing the typical NFC flat-helical antennas of Figures 5 and 6, immediate significant savings in surface space affected by NFC construction are achieved. The solenoid winding 1 in the form of two small components is simply placed during the design of the PCB of the NFC device 2 than the flat helical antenna. The solenoid windings 1 are connected in opposite directions such that the magnetic field of the solenoid windings is in the opposite phase. Example 2 In this example the antenna system from the previous example has two independently controlled excitation elements 4 according to Figure 7. Each of the solenoid windings 1 L1, L2 is controlled by two end levels operating in the bridge. Turning the end positions A1, A3, A7, A8 on and off in the modulation device allows the depth modulation to be set to range from 25% to 100% with a 25% step. One of the energies that do not have heat resistance during the closing of the end level does not need to be converted. Example 3 uses two pairs of identical solenoid windings 1 in this example according to Fig. 8; this is arranged in the circle in such a way that the middle of the solenoid winding 1 is on a circle and the solenoid winding The axes 3 of 1 are perpendicular to each other and the intersection of the axes is in the middle of the circle. The diameter of the circle (within the margin of ±10 mm) corresponds to the size of the antenna of the receiver. Example 4 In this example according to Fig. 9, two pairs of solenoid windings 1 were used , which were arranged in a quadrilateral shape. The middle of the solenoid winding 1 is on the opposite side of the quadrilateral; the axis 3 of the solenoid winding 1 is parallel to each other. Industrial utilization industry utilization is obvious. According to the present invention, it is possible to industrially and repeatedly constitute and use an NFC antenna system having a small assembly space and it is also possible to effectively change the modulation depth.

1‧‧‧Solenoid winding

2‧‧‧Incoming Communication (NFC) device

3‧‧‧ vertical axis

4‧‧‧Exciting components

A‧‧‧ distance

A1‧‧‧ end level

A3‧‧‧ end level

A7‧‧‧ end level

A8‧‧‧ end level

D1‧‧‧Control input

D2‧‧‧Control input

D3‧‧‧Control input

D4‧‧‧Control input

L1‧‧‧ Solenoid winding

L2‧‧‧ Solenoid winding

The invention is further disclosed by Figures 1 to 9. The specific ratios depicted for the dimensions of the solenoid windings and the examples of the mutual position of the latitude of the magnetic field lines and the multiple pairs of configurations are merely illustrative and are not to be construed as limiting the scope of protection. 1 is a schematic depiction of one of the magnetic fields during inductive coupling between a transmitter and a receiver in accordance with the state of the art in which a typical flat spiral antenna is used on the side of the transmitter and receiver. 2 is an antenna system having a single pair of solenoid windings on a common longitudinal axis and having a central distance A. Figure 3 depicts the magnetic field near the solenoid winding; the number of threads is only shown. 4 depicts a magnetic field of a similarly latitudinal solenoid winding having the position of the antenna of the receiver as in the case of the typical flat helical antenna of FIG. Figure 5 is an example of the placement of a single pair of solenoid windings at the edge of an NFC communication device. Figure 6 presents a comparison with one of the previous figures; it depicts a similar NFC device with a typical flat helical antenna according to the state of the art. Figure 7 is an illustration of one of the excitation elements with independently controlled end levels A1, A3, A7, A8. Figure 8 is an example of the placement of four solenoid windings in a circle. Figure 9 is an example of the placement of four solenoid windings in a quadrilateral.

Claims (16)

An NFC antenna system having at least one pair of solenoid windings (1), the length of the solenoid windings (1) being greater than the diameter of the solenoid windings (1) and the solenoid windings (1) Placed in a single plane, and the solenoid windings (1) have a common longitudinal axis (3), and the solenoid windings (1) are connected to an excitation, characterized by the solenoids A distance between the middle portions of the windings (1) is at least twice the length of the solenoid windings (1), and the solenoid windings (1) are such that the solenoid windings (1) The magnetic fields are oriented opposite one another towards the excitation and are connected to the excitation. The NFC antenna system of claim 1, wherein the distance between the solenoid windings (1) corresponds to a size of an antenna of a receiver; preferably an error limit is the solenoid winding (1) One of the lengths. An NFC antenna system according to claim 1 or 2, wherein each of the solenoid windings (1) has its own independently controlled excitation element (4), whereby the excitation elements (4) have one of the connected modulation inputs And the excitation elements (4) have a same excitation frequency. The NFC antenna system of claim 1 or 2, wherein the length of the solenoid windings (1) is in a range from 5 mm to 20 mm and between the middle portions of the solenoid windings (1) This distance is in the range from 35 mm to 45 mm. The NFC antenna system of claim 1 or 2, wherein each of the pair of solenoid windings (1) is identical. The NFC antenna system of claim 1 or 2, wherein one of the solenoid windings (1) is in a range from 750 nH to 2 μH and the quality Q is in a range from 15 to 25. The NFC antenna system of claim 1 or 2, wherein each of the solenoid windings (1) L1, L2 is controlled by the excitation element (4) having two end levels, the two end levels operating in a bridge. The NFC antenna system of claim 7, wherein the end levels are independently controlled by the control input to turn the end levels off and on. The NFC antenna system of claim 1 or 2, wherein the solenoid windings (1) have a hollow or a core. The NFC antenna system of claim 1 or 2, wherein the NFC antenna system is placed in an NFC device (2), preferably placed in a mobile communication device, and more preferably placed in a mobile phone. The NFC antenna system of claim 10, wherein the distance between the shaft (3) and an edge of one of the NFC devices (2) is at least 3 mm, preferably at least 5 mm. The NFC antenna system of claim 1 or 2, wherein the NFC antenna system has two pairs of the solenoid windings (1); the axis (3) of the first pair of the solenoid windings (1) is vertical In the second pair of the shafts (3) of the solenoid windings (1), and the central portions of the solenoid windings (1) are located on a circle, the middle of the circle being at the same One of the axes (3) is in the intersection. The NFC antenna system of claim 1 or 2, wherein the NFC antenna system has two pairs of the solenoid windings (1); the first pair of the solenoid windings (1) of the shaft (3) Parallel to the axis (3) of the second pair of the solenoid windings (1), and the central portions of the solenoid windings (1) are on opposite sides of a quadrilateral. The NFC antenna system of claim 12, wherein the circular or quadrilateral surface defined by the middle portions of the solenoid windings (1) is between 1200 mm ² and 2000 mm ² . A method of changing one of modulation depths during transmission through one of the antenna systems of any one of claims 7 to 14, characterized in that one of the magnetic field strengths and the modulation depth is required by One of the modulation rhythms opens and closes the individual end level changes of the excitation element (4). The method of claim 15, wherein the change in the modulation depth during the transmission through the antenna system, wherein one of the single pair of solenoid windings (1) is set to have a step of 25% It ranges from 25% to 100%.