CN106972237B - Ultra-wideband high-performance NFC antenna system based on metal backshell - Google Patents

The application provides an ultra-wideband high-performance NFC antenna system based on a metal backshell, which enables an NFC antenna to resonate at a first resonant frequency by adjusting a matching circuit between a chip and the NFC antenna, and simultaneously the NFC antenna excites induced current on the metal backshell, on one hand, the metal backshell and the NFC antenna transmit signals to receiving equipment in a near field mode and interact with the receiving equipment; on the other hand, the current on the metal rear shell returns to the metal rear shell after passing through the resonant piece and the first adjusting capacitor to form a current loop, and the current loop can resonate at a second resonant frequency through the first adjusting capacitor, so that the superposition of the second resonant frequency and the first resonant frequency is realized. Compared with the prior art, the application has the advantages of simple structure and easy realization; and the frequency band is covered, the magnetic field intensity and the working distance of the working frequency band are improved, so that the NFC performance of the electronic equipment based on the metal backshell material is greatly improved, and better experience is brought to users.

Ultra-wideband high-performance NFC antenna system based on metal backshell

Technical Field

The application belongs to the technical field of near field communication, in particular relates to an antenna, and further relates to a multi-resonance ultra-wideband high-performance NFC antenna system, which mainly aims at mobile terminal equipment with a metal rear shell.

Background

The NFC near field communication technology is integrated and evolved by a non-contact Radio Frequency Identification (RFID) and interconnection technology, the working frequency is 13.56MHz, and three working modes of read-write, card simulation and P2P point-to-point can be supported. Because NFC technology can carry out recognition and data exchange with compatible equipment in a short distance, the electronic equipment with the full functions of NFC can replace traffic cards, bank cards, wallets, airport boarding cards, building access control keys and the like, and great convenience is provided for the life of consumers.

On the other hand, metallic materials such as aluminum, magnesium, stainless steel or alloy and the like have better gripping feel and anti-falling and scratch resistance than nonmetallic materials such as plastics, and are increasingly favored by consumers. To cater to consumers, many handset manufacturers such as the annual flagship handsets of hua, apple, samsung, OPPO, VIVO, nokia, etc. require support for NFC functionality and the handset housing is typically made of metal.

As is well known, the NFC antenna is usually adhered to the back shell of the mobile phone, and when the material of the back shell of the mobile phone is metal, the NFC antenna signal will be greatly weakened or even shielded, so how to design a high-performance NFC antenna becomes the subject of many personnel researches under the condition that the back shell of the mobile phone is made of metal.

In order to solve the problems, the scheme provides a multi-resonance ultra-wideband high-performance NFC antenna solution based on a metal backshell, which generates at least two resonances, covers a wider frequency band, and improves the magnetic field intensity of a working frequency band, so that the antenna has a higher working distance, greatly improves the NFC performance of electronic equipment based on the metal backshell material, and brings better experience to users.

Disclosure of Invention

To this end, the present application aims to provide an ultra wideband high performance NFC antenna system based on a metal back shell.

The aim of the application is achieved by the following technical scheme.

The ultra-wideband high-performance NFC antenna system based on the metal backshell comprises a backshell formed by connecting the metal backshell and a nonmetal backshell, wherein an NFC chip and an NFC antenna are arranged on the inner side wall of the metal backshell, the NFC antenna is composed of a magnet and a coil wound on the magnet, and the coil is connected with the NFC chip through a matching circuit; the non-metal rear shell is provided with a resonance piece, one end of the resonance piece is connected with the metal rear shell, and the other end of the resonance piece is connected with the metal rear shell through a first adjusting capacitor; the NFC chip, the matching circuit and the NFC antenna form a first resonant current loop, and the NFC antenna generates first resonance by adjusting the matching circuit; the metal rear shell, the resonant piece and the first adjusting capacitor form a second resonant current loop, the resonant piece generates second resonance by adjusting the first adjusting capacitor, and the second resonance is overlapped with the first resonance.

Preferably, the resonance piece is a ring-shaped metal piece, a sheet-shaped metal piece or a strip-shaped metal piece, one end of the resonance piece is directly connected with the metal rear shell, and the other end of the resonance piece is connected with the metal rear shell through a first adjusting capacitor; and the metal rear shell, the resonant piece and the first adjusting capacitor form a second resonant current loop, and the resonant piece generates second resonance by adjusting the first adjusting capacitor.

Preferably, the resonance piece is a ring-shaped metal piece, a sheet-shaped metal piece or a strip-shaped metal piece, one end of the resonance piece is connected with the metal rear shell through a metal strip, and the other end of the resonance piece is connected with the metal rear shell through a first adjusting capacitor; and the metal rear shell, the metal strip, the resonant piece and the first adjusting capacitor form a second resonant current loop, and the resonant piece generates second resonance by adjusting the first adjusting capacitor.

Preferably, the resonance piece includes being located both sides and respectively with the ring-shaped metal piece that metal backshell both ends are connected and be located the strip metal piece between two ring-shaped metal pieces, all be formed with a gap between the ring-shaped metal of strip metal piece and both sides, strip metal piece one end is connected with the metal backshell through first metal strip, the other end loops through second metal strip, first regulation electric capacity with the metal backshell is connected, and metal backshell, first metal strip, strip metal piece, second metal strip, first regulation electric capacity form the second resonance current return circuit, make strip metal piece produce the second resonance through adjusting first regulation electric capacity.

Preferably, the coil is a zigzag coil, the magnet is located in the zigzag coil, one end of the zigzag coil, which is close to the connecting edge of the metal backshell and the nonmetal backshell, is located above the non-contact surface of the magnet and the metal backshell, one end, which is far away from the connecting edge of the metal backshell and the nonmetal backshell, is located below the contact surface of the magnet and the metal backshell, and the two sides of the zigzag coil extend downwards from one end, which is close to the connecting edge of the metal backshell and the nonmetal backshell, to one end, which is far away from the connecting edge of the metal backshell and the nonmetal backshell.

Preferably, the coil is an 8-shaped coil, the magnet is positioned in the 8-shaped coil, one ends of the 8-shaped coil, which are close to and far away from the connecting edge of the metal backshell and the nonmetal backshell, are positioned above the non-contact surface of the magnet and the metal backshell, two cross lines are formed in the middle of the 8-shaped coil, and the two cross lines are positioned below the contact surface of the magnet and the metal backshell.

Preferably, the coil is a spiral coil, and is spirally wound on the magnet.

Preferably, the metal backshell and the nonmetal backshell are connected through nano injection molding or bonding.

In addition, the application also provides an ultra-wideband high-performance multi-resonance NFC antenna system based on the metal backshell, which comprises a backshell formed by connecting the metal backshell and the nonmetal backshell, and is characterized in that an NFC chip and an NFC antenna are arranged on the inner side wall of the metal backshell, the NFC antenna is composed of a magnet and a coil wound on the magnet, and the coil is connected with the NFC chip through a matching circuit; the non-metal rear shell is provided with a resonance piece, one end of the resonance piece is connected with the metal rear shell, and the other end of the resonance piece is connected with the metal rear shell through a first adjusting capacitor; a plurality of second adjusting capacitors are arranged between the resonance piece and the metal rear shell on the non-metal rear shell, one end of each second adjusting capacitor is connected to the resonance piece through a first microstrip transmission line, and the other end of each second adjusting capacitor is connected to the metal rear shell through a second microstrip transmission line; the NFC chip enables the NFC antenna to resonate at a first resonant frequency through the matching circuit, the NFC antenna excites induction current on the metal backshell, the metal backshell and the NFC antenna transmit signals to the receiving device in a near field mode and interact with the receiving device, meanwhile, the current on the metal backshell returns to the metal backshell after passing through the first adjusting capacitor and each second adjusting capacitor through the resonant piece, the resonant piece resonates at a second resonant frequency through the first adjusting capacitor, and each first microstrip transmission line and each second microstrip transmission line correspondingly resonates at a corresponding resonant frequency through each second adjusting capacitor.

In addition, the application also provides an ultra-wideband high-performance three-resonance NFC antenna system based on the metal backshell, which comprises a backshell formed by connecting the metal backshell and the nonmetal backshell, wherein an NFC chip and an NFC antenna are arranged on the inner side wall of the metal backshell, the NFC antenna is composed of a magnet and a coil wound on the magnet, and the coil is connected with the NFC chip through a matching circuit; the non-metal rear shell is provided with a resonance piece, one end of the resonance piece is connected with the metal rear shell, the other end of the resonance piece is connected with the metal rear shell through a first adjusting capacitor, and the middle of the resonance piece is connected with the metal rear shell through a first microstrip transmission line, a second adjusting capacitor and a second microstrip transmission line in sequence; the NFC chip enables the NFC antenna to resonate at a first resonant frequency through the matching circuit, the NFC antenna excites induction current on the metal backshell, the metal backshell and the NFC antenna transmit signals to the receiving device in a near field mode and interact with the receiving device, meanwhile, the current on the metal backshell returns to the metal backshell after passing through the second adjusting capacitor and the first adjusting capacitor through the resonant piece, the resonant piece resonates at a second resonant frequency through the first adjusting capacitor, the first microstrip transmission line resonates with the second microstrip transmission line resonates at a third resonance through the second adjusting capacitor, and at the moment, the third resonance, the second resonance and the first resonance are overlapped.

According to the NFC chip, the NFC antenna resonates at the first resonant frequency through the matching circuit, and meanwhile, the NFC antenna excites induction current on the metal backshell, so that on one hand, the metal backshell and the NFC antenna transmit signals to the receiving equipment in a near field mode and interact with the receiving equipment; on the other hand, the current on the metal rear shell returns to the metal rear shell after passing through the resonant piece and the first adjusting capacitor to form a current loop, and the current loop can resonate at a second resonant frequency through the first adjusting capacitor, so that the superposition of the second resonant frequency and the first resonant frequency is realized. Compared with the prior art, the application has the advantages of simple structure and easy realization; and the frequency band is covered, the magnetic field intensity and the working distance of the working frequency band are improved, so that the NFC performance of the electronic equipment based on the metal backshell material is greatly improved, and better experience is brought to users.

Drawings

Fig. 1 is a schematic structural diagram of an NFC antenna system according to a first embodiment of the present application;

FIG. 2 is a schematic diagram of a current distribution at a first resonant frequency according to the present application;

FIG. 3 is a graph showing the distribution of magnetic field strength at a first resonant frequency according to the present application;

FIG. 4 is a diagram showing the current distribution at the second resonant frequency according to the present application;

FIG. 5 is a graph showing the distribution of magnetic field strength at a second resonant frequency according to the present application;

FIG. 6 is a graph comparing the real impedance and the frequency of the single-resonance and double-resonance NFC antennas according to the present application;

fig. 7 is a schematic diagram of a zigzag NFC antenna structure according to the present application;

fig. 8 is a schematic diagram of a placement direction of a zigzag NFC antenna and a metal back shell according to the present application;

fig. 9 is a second schematic diagram of a placement direction of the zigzag NFC antenna and the metal back shell according to the present application;

fig. 10 is a schematic diagram of an NFC antenna structure in the shape of an "8" according to the present application;

fig. 11 is a schematic view of the placement direction of the 8-shaped NFC antenna and the metal back shell according to the present application;

fig. 12 is a schematic diagram of a spiral NFC antenna structure according to the present application;

fig. 13 is a schematic view of a placement direction of a spiral NFC antenna and a metal back shell according to the present application;

fig. 14 is a schematic structural diagram of an NFC antenna system according to a second embodiment of the present application;

fig. 15 is a schematic structural diagram of an NFC antenna system according to a third embodiment of the present application;

fig. 16 is a schematic structural diagram of an NFC antenna system according to a fourth embodiment of the present application;

FIG. 17 is a graph of the results of Smith assay of the present application;

FIG. 18 is a diagram showing a three-resonance generating mode according to the present application;

fig. 19 is a graph comparing the real part of impedance and the frequency relation of the single-resonance and the triple-resonance NFC antenna according to the present application.

Detailed Description

The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.

The ultra-wideband high-performance NFC antenna system based on the metal backshell, which is provided by the application, has the advantages of being simple in structure, easy to realize, capable of greatly improving NFC performance of electronic equipment made of the metal backshell, and the like, and has the advantages of being wide in coverage frequency band, strong in magnetic field intensity of a working frequency band and high in working distance.

Example 1

Referring to fig. 1, fig. 1 is a schematic structural diagram of an NFC antenna system according to a first embodiment of the application. In the NFC antenna system according to the embodiment, the coordinate axis +x represents pointing to the handset side along the long side of the handset, -X represents pointing to the handset key side along the long side of the handset, +z represents pointing to the screen direction along the handset, -Z represents pointing to the back case direction of the handset along the handset.

The antenna system comprises a rear shell, wherein the rear shell comprises a metal rear shell 200 and a nonmetal rear shell 202, the nonmetal rear shell 202 is made of plastic, glass, resin, foam or the like or a composite material formed by the plastic, the glass, the resin, the foam or the like, and the metal rear shell 200 and the nonmetal rear shell 202 are connected by adopting a nano injection molding process (or direct bonding by using glue).

An NFC chip 1 and an NFC antenna 3 are disposed on the inner side of the metal back case 200, and the NFC chip 1 is connected to the NFC antenna 3.

The NFC chip 1 may be a chip provided by semiconductor manufacturers such as enzhi pu, samsung, botong, fei, yi semiconductor, compound denier microelectronic, kunzhi, etc., and in this embodiment, enzhi pu PN548 is taken as an example.

The NFC antenna 3 is composed of a magnet and a coil wound on the magnet, and the coil is connected with the NFC chip 1 through a matching circuit. Wherein the magnet is made of magnetic materials including, but not limited to, ferrite, nanocrystalline, amorphous, silicon steel, etc.

The NFC chip 1, the matching circuit and the coil of the NFC antenna 3 form a first resonant current loop, and the NFC chip 1 can make the coil of the NFC antenna 3 generate a first resonance (in this embodiment, the first resonant frequency is about 13.5 MHz) through the matching circuit.

A resonance member is disposed on the non-metal rear housing 202, in this embodiment, the resonance member is an annular metal 201, and the annular metal 201 is made of the same material as the metal rear housing 200, one end of the resonance member is directly connected to the metal rear housing 200, and the other end is connected to the metal rear housing 200 through a first adjusting capacitor 2. The metal back shell 200, the annular metal 201 and the first adjusting capacitor 2 correspondingly form a second resonant current loop, and the annular metal 201 can generate second resonance (the second resonance frequency is about 15MHz in the embodiment) by adjusting the first adjusting capacitor 2, and the second resonance is overlapped with the first resonance.

The working principle of the antenna system in this embodiment is as follows: the electric signal is sent from the transmitting end of the NFC chip 1 of the mobile phone, the NFC antenna 3 can resonate at about 13.5MHz in the first resonance by adjusting the peripheral matching circuit of the NFC chip 1 of the mobile phone, and the NFC antenna 3 excites induction current on the metal backshell 200, at the moment, the metal backshell 200 and the NFC antenna 3 transmit signals to and interact with receiving equipment together in a near field mode, on the one hand, the current on the metal backshell part 200 flows onto the annular metal 201 and returns to the metal backshell 200 after passing through the first adjusting capacitor 2, the annular metal 201 resonates at about 15MHz in the second resonance by the first adjusting capacitor 2, and at the moment, the second resonance overlaps with the first resonance, so that a wider frequency band is covered, the magnetic field intensity of a working frequency band is enhanced, and the working distance of NFC is improved.

In this embodiment, the first resonant frequency f1 (13.5 MHz) is smaller than the second resonant frequency f2 (15 MHz). However, in other embodiments, the first resonant frequency f1 may be greater than the second resonant frequency f2, and the specific values of the first resonant frequency f1 and the second resonant frequency f2 may be determined according to practical use situations.

As shown in fig. 2 to 5, fig. 2 is a schematic diagram of current distribution at a first resonant frequency according to the present application; FIG. 3 is a graph showing the distribution of magnetic field strength at a first resonant frequency according to the present application; FIG. 4 is a diagram showing the current distribution at the second resonant frequency according to the present application; fig. 5 is a schematic diagram showing the distribution of magnetic field intensity at the second resonance frequency according to the present application.

As can be seen from a comparison of fig. 2 and fig. 4, the current on the ring metal 201 in fig. 4 is greater than the current on the ring metal 201 in fig. 2. As described above, since the second resonance 15MHz is generated by the loop metal 201 and the first capacitor 2, the current on the loop metal 201 at the second resonance frequency is stronger than the current on the loop metal 201 at the first resonance frequency.

In comparison with fig. 3 and fig. 5, the magnetic field strength near the ring metal 201 in fig. 3 is greater than the magnetic field strength near the ring metal 201 in fig. 5, because the second resonance 15MHz is generated by the ring metal 201 and the first capacitor 2, the magnetic field strength near the ring metal 201 at the second resonance frequency is stronger than the magnetic field strength near the ring metal 201 at the first resonance frequency.

Fig. 6 is a graph comparing the real part of impedance and the frequency relation of the single-resonance and the double-resonance NFC antenna according to the present application. Wherein the solid line is the real part of impedance and the frequency curve graph of the single-resonance NFC antenna (single resonance is only the first resonance of double resonance), the dotted line is the real part of impedance and the frequency curve graph of the double-resonance NFC antenna, and compared with the solid line, the dotted line has more frequency points which are close to 30Ω, namely the bandwidth of the frequency band is widened in the double-resonance state. (the NFC chip of the Enzhi PN548 mobile phone requires that the antenna impedance is adjusted to 30+j0Ω at the working frequency point, and the antenna is matched with the NFC chip 1, so that the reflection is reduced, and the maximum energy transmission is realized).

It should be noted that, in this embodiment, the NFC antenna 3 is formed by a magnet and a coil wound on the magnet, and there are various options for the coil, and in this embodiment, different coils are further described below with reference to fig. 7 to 13.

As shown in fig. 7 to 9, fig. 7 is a schematic diagram of a zigzag NFC antenna structure according to the present application; fig. 8 is a schematic diagram of a placement direction of a zigzag NFC antenna and a metal back shell according to the present application; fig. 9 is a second schematic diagram of a placement direction of the zigzag NFC antenna and the metal back shell according to the present application.

The NFC antenna in this embodiment is composed of a magnet 62 and a "Z" shaped coil 61 wound around the magnet 62, wherein the "Z" shaped coil 61 and the magnet 62 located in the "Z" shaped coil 61 are all located in the outer rim of the metal back case 200.

Wherein, one end of the zigzag coil 61 near the connecting edge of the metal back shell 200 and the nonmetal back shell 202 is located above the magnet 62 (above the non-contact surface of the magnet and the metal back shell, that is, the surface of the magnet facing the mobile phone display screen), one end far away from the connecting edge of the metal back shell 200 and the nonmetal back shell 202 is located below the magnet 62 (below the contact surface of the magnet and the metal back shell, that is, the surface of the magnet facing the mobile phone back shell), and two sides of the zigzag coil extend downwards in a zigzag shape from one end near the connecting edge of the metal back shell 200 and the nonmetal back shell 202 to one end far away from the connecting edge of the metal back shell 200 and the nonmetal back shell 202 (see fig. 8).

In addition, in the case where the zigzag coil 61 in fig. 8 is rotated 180 ° around the X axis, as shown in fig. 9, the end near the connecting edge of the metal back case 200 and the non-metal back case 202 may be located below the magnet 62, while the end far from the connecting edge of the metal back case 200 and the non-metal back case 202 is located above the magnet 62, and both sides extend upward in a zigzag shape from the end near the connecting edge of the metal back case 200 and the non-metal back case 202 to the end far from the connecting edge of the metal back case 200 and the non-metal back case 202.

Although the dual resonance superposition effect can be achieved in fig. 8 and fig. 9, the performance of the antenna is different from the actual placement direction of the two coils, and the performance can be optimized only when the placement mode shown in fig. 8, that is, the "Z" coil 61 is placed above the magnet 62 (along the +z direction), and the NFC antenna coil 61 far from the edge of the metal back case 200 is placed below the magnet 62.

As shown in fig. 10, fig. 10 is a schematic structural diagram of an "8" NFC antenna according to the present application, as mentioned in chinese patent application publication No. CN 105024169a, the "8" NFC antenna design has better performance than others, so that it can be better applied to various mobile electronic devices.

Fig. 11 is a schematic diagram of the placement direction of the 8-shaped NFC antenna and the metal back shell according to the present application. The NFC antenna in this embodiment is composed of a magnet 72 and an "8" shaped coil 71 wound around the magnet 72, wherein the "8" shaped coil 71 and the magnet 72 located in the "8" shaped coil 71 are all located in the outer side frame of the metal back case 200.

The magnet 72 is located in the "8" shaped coil 71, and one end of the "8" shaped coil 71 near to and far from the connecting edge of the metal back shell and the non-metal back shell is located above the magnet 72 (above the non-contact surface of the magnet and the metal back shell, that is, the surface of the magnet facing the display screen of the mobile phone), and two intersecting lines correspondingly formed in the middle are located in the middle part below the magnet 72 (below the contact surface of the magnet and the metal back shell, that is, the surface of the magnet facing the back shell of the mobile phone, see fig. 10 and 11).

Of course, alternatively, the antenna in fig. 11 may be correspondingly rotated 180 ° around the X-axis, and a dual resonance superposition effect may be generated, where the magnet 72 is also located in the "8" shaped coil 71, and one end of the "8" shaped coil, which is close to and far from the connecting edge of the metal back shell and the non-metal back shell, is located below the magnet 72, and two intersecting lines formed in the middle of the "8" shaped coil are correspondingly located in the middle portion above the magnet 72. However, this arrangement is not ideal, and only when the end of the 8-shaped coil near the connecting edge of the metal back shell and the non-metal back shell is located above the magnet 72, the antenna performance is optimal, and the antenna is correspondingly arranged after rotating 180 ° around the X-axis, which is not as good as the arrangement of fig. 10 and 11.

As shown in fig. 12 to 13, fig. 12 is a schematic structural diagram of a spiral NFC antenna according to the present application; fig. 13 is a schematic view illustrating a placement direction of a spiral NFC antenna and a metal back shell according to the present application. The NFC antenna in this embodiment is composed of a magnet 82 and a spiral coil 81 wound on the magnet 82, wherein the spiral coil 81 and the magnet 82 located in the spiral coil 81 are all located in the outer side frame of the metal back case 200.

The coil is a spiral coil 81, which is spirally wound around a magnet 82, and the corresponding side view is shown in fig. 13. In particular, as described in chinese patent application publication No. CN 106374209a, when the NFC antenna formed by winding the spiral coil 81 around the magnet 82 is small in size (about 6mm×3mm×1 mm), it can also be used as an NFC antenna in the present application and achieve the present effect.

The above-mentioned "zigzag" coil, the "8" coil and the spiral coil can all achieve the best effect that the present embodiment can produce double resonance superposition, but in practice any other coil (the coil can excite the current beneficial to the antenna in the metal back shell area) can be used, including but not limited to spiral, zigzag, "8" coil, O-shaped, rectangular and irregular winding mode coils, etc.; the magnets used in this embodiment also include, but are not limited to, ferrite, nanocrystalline, amorphous, silicon steel, etc., and the NFC antenna formed by the appropriate stacking and arrangement of the coils and magnets can achieve similar effects in this embodiment.

Example two

Fig. 14 is a schematic structural diagram of an NFC antenna system according to a second embodiment of the present application.

Compared with the first embodiment, the difference is that the resonance element disposed on the non-metal back shell 202 is a sheet metal element 203, one end of the sheet metal element 203 is connected with the metal back shell 200 through a metal strip 204, and the other end is connected with the metal back shell 200 through a first adjusting capacitor 2; and the metal back shell 200, the metal strip 204, the sheet metal piece 203 and the first adjusting capacitor 2 form a second resonance current loop, and the sheet metal piece 203 can generate a second resonance by adjusting the first adjusting capacitor 2.

The working principle of the antenna system in this embodiment is as follows: the electric signal is sent from the transmitting end of the mobile phone NFC chip 1, the NFC antenna 3 can resonate at about 13.5MHz in the first resonance by adjusting the peripheral matching circuit of the mobile phone NFC chip 1, and the NFC antenna 3 excites induction current on the metal rear shell 200, at the moment, the metal rear shell 200 and the NFC antenna 3 transmit signals to and interact with receiving equipment together in a near field mode, on the other hand, current on the metal rear shell 200 flows onto the sheet metal piece 203 through the metal strip 204 and then returns to the metal rear shell 200 after passing through the first adjusting capacitor 2, the sheet metal piece 203 resonates at about 15MHz in the second resonance through the first adjusting capacitor 2, and the second resonance is overlapped with the first resonance at the moment, so that a wider frequency band is covered, the magnetic field strength of a working frequency band is enhanced, and the working distance of NFC is improved.

The four card response distances at single resonance (only the double resonance first resonance) and double resonance for implementing the first and second embodiments will be described in comparison with the following table.

As can be seen from the comparison table of the card reading distances, the corresponding dual resonance and single resonance of the structure of FIG. 1 in the embodiment are respectively improved by 47.7%, 25.2%, 59.2% and 131.7%.

Compared with the single resonance and the double resonance under the structure of FIG. 14 corresponding to the second embodiment, the response distances of the four cards are respectively increased by 112.9%, 56%, 86.7% and 247.1%

Therefore, the card reading distance of the NFC antenna can be greatly improved through double resonance generated by superposition of the first resonance and the second resonance, and NFC performance of the electronic equipment made of the metal rear shell material is greatly improved.

The composition and other structures of the NFC antenna in the first embodiment and the corresponding operation principle are basically the same as those of the present embodiment, and are not described herein.

Example III

Fig. 15 is a schematic structural diagram of an NFC antenna system according to a third embodiment of the present application, as shown in fig. 15.

The difference between this embodiment and the first embodiment is that the area of the non-metal rear case 202 is greatly reduced; the second is that the resonance element arranged on the non-metal back shell 202 is a ring-shaped metal 201, one end of the resonance element is connected with the metal back shell 200 through a metal strip 204, and the other end is connected with the metal back shell 200 through a first adjusting capacitor 2; and the metal back shell 200, the metal strip 204, the annular metal 201 and the first adjusting capacitor 2 form a second resonance current loop, and the annular metal 201 can generate second resonance by adjusting the first adjusting capacitor 2.

The working principle of the antenna system in this embodiment is as follows: the electric signal is sent from the transmitting end of the mobile phone NFC chip 1, the NFC antenna 3 can resonate at about 13.5MHz in the first resonance by adjusting the peripheral matching circuit of the mobile phone NFC chip 1, and the NFC antenna 3 excites induction current on the metal rear shell 200, at the moment, the metal rear shell 200 and the NFC antenna 3 transmit signals to and interact with receiving equipment in a near field mode, on the one hand, the current on the metal rear shell 200 flows onto the annular metal 201 through the metal strip 204 and then returns to the metal rear shell 200 after passing through the first adjusting capacitor 2, the annular metal 201 resonates at about 15MHz in the second resonance through the first adjusting capacitor 2, and the second resonance is overlapped with the first resonance at the moment, so that a wider frequency band is covered, the magnetic field strength of a working frequency band is enhanced, and the working distance of NFC is improved.

The composition and other structures of the NFC antenna in the first embodiment and the corresponding operation principle are basically the same as those of the present embodiment, and are not described herein.

Example IV

As shown in fig. 16 and 17, fig. 16 is a schematic structural diagram of an NFC antenna system according to a fourth embodiment of the present application; FIG. 17 is a graph showing the results of Smith assay of the present application.

In this embodiment, the resonant member is a ring metal, but the ring metal members 201 and 201' are disconnected from the strip metal member 205 and are filled with non-metal rear shell parts, so the strip metal member 205 is the resonant member in this embodiment. One end of the strip-shaped metal piece 205 is connected with the metal back shell 200 through the first metal strip 204, the other end of the strip-shaped metal piece is connected with the metal back shell 200 through the second metal strip 204 'and the first adjusting capacitor 2 in sequence, and the metal back shell 200, the first metal strip 204, the strip-shaped metal piece 205, the second metal strip 204' and the first adjusting capacitor 2 form a second resonance current loop, and the strip-shaped metal piece 205 can generate second resonance through adjusting the first adjusting capacitor 2.

In this structure, the first resonance is generated by adjusting the peripheral matching circuit of the mobile phone NFC chip 1 to make the NFC antenna 3 resonate, and the metal back case 200, the first metal strip 204, the strip metal piece 205, the second metal strip 204', the first capacitor 2, and the metal back case 200 form a second resonance current loop, so that the strip metal 205 generates the second resonance by adjusting the first capacitor 2.

It should be specifically mentioned that the NFC antenna 3 may be disposed on the metal back shell 200 or the non-metal back shell portion 202, or may be partially disposed on the metal back shell portion 200 or partially disposed on the non-metal back shell portion 202, but for the same metal structure, the NFC antenna performance in the manner of fig. 16 is better than that in the manner of fig. 1, 14 and 15.

The foregoing is a description of the dual-resonant ultra-wideband high performance NFC antenna system of the present application, and in fact, the schemes and structures described herein are applicable to both tri-resonant and multi-resonant NFC antenna systems, as will be described below with reference to fig. 18 and 19.

As shown in fig. 18 and 19, fig. 18 is a diagram showing a three-resonance generating mode structure of the present application; fig. 19 is a graph comparing the real part of impedance and the frequency relation of the single-resonance and the triple-resonance NFC antenna according to the present application.

Compared with the dual-resonance NFC antenna system (structure of FIG. 1), the three-resonance NFC antenna system of the present application has the same basic principle, and is characterized in that a resonance element 201 is disposed on a non-metal back case 202, one end of the resonance element 201 is connected with a metal back case 200, the other end is connected with the metal back case 200 through a first adjusting capacitor 2, and the middle is connected with the metal back case 200 through a first microstrip transmission line 103', a second adjusting capacitor 2', and a second microstrip transmission line 103 in sequence; the NFC chip 1 resonates the NFC antenna 3 at a first resonant frequency through a matching circuit, the NFC antenna 3 excites an induced current on a metal back shell, the metal back shell 200 and the NFC antenna 3 together transmit signals to and interact with a receiving device in a near field form, meanwhile, the current on the metal back shell 200 returns to the metal back shell after passing through a resonant element 201 and passing through a second adjusting capacitor 2' and a first adjusting capacitor 2 respectively, the resonant element 201 resonates at a second resonant frequency through the first adjusting capacitor 2, and the first microstrip transmission line 103' and the second microstrip transmission line 103 resonate at a third resonance through the second adjusting capacitor 2', and at this time, the third resonance, the second resonance and the first resonance are overlapped.

The composition and other structures of the NFC antenna in the first embodiment and the corresponding operation principle are basically the same as those of the present embodiment, and are not described herein.

Finally, it should be noted that the PCB board in the mobile phone is usually placed in the +z direction of the metal back shell 200 shown in fig. 1, and when the PCB board is added, similar effects can be achieved based on the principle of the present case or the improvement made.

In addition, it should be emphasized that the foregoing embodiments are merely illustrative of dual-resonant and triple-resonant NFC antenna systems, and it is clear from the foregoing embodiments that all multi-resonant ultra-wideband high performance NFC antennas based on metal backshells are within the scope of the present application based on the dual-resonant or triple-resonant superposition principles of the present application, which should not be construed as limiting the present application.

In summary, according to the NFC chip of the present application, the NFC antenna resonates at the first resonant frequency through the matching circuit, and at the same time, the NFC antenna excites the induced current on the metal back shell, so that on one hand, the metal back shell and the NFC antenna transmit signals to and interact with the receiving device in a near field form; on the other hand, the current on the metal back shell can return to the metal back shell after passing through the resonant piece, the first adjusting capacitor or other adjusting capacitors, so that a second resonant frequency or other resonant frequencies are correspondingly generated, and superposition of multiple resonant frequencies is realized. Compared with the prior art, the application has simple structure and easy realization; the electronic equipment not only can cover a wider frequency band, but also can improve the magnetic field intensity of a working frequency band and realize a longer working distance, so that the NFC performance of the electronic equipment based on the metal backshell material is greatly improved, and better experience is brought to a user.

The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the application.