A multi-antenna system and mobile terminal

Abstract

The application discloses a multi-antenna system and a mobile terminal. The multi-antenna system comprises a first antenna, a second antenna, a neutral line and a filter unit; the neutral line and the filter unit are connected between the first antenna and the second antenna; a current flowing through the neutral line and the filter unit and a phase difference of a space coupling electromagnetic wave between the first antenna and the second antenna satisfy 120 DEG <= <= 240 DEG; a passband range of a filter composed of the first antenna, the second antenna, the neutral line and the filter unit is 0.4GHz-8GHz. The application can realize decoupling in a 0.4-8GHz wide frequency band, and solves the problems of narrow bandwidth and poor adaptability existing in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of multi-antenna, in particular to a multi-antenna system and a mobile terminal. BACKGROUND

[0002] In a multi-antenna system, when the antenna spacing is limited, the mutual coupling effect will cause the isolation to deteriorate, and the channel capacity and communication efficiency to decrease.

[0003] In the prior art, the mutual coupling is mainly suppressed by the following ways, but all have significant limitations: 1. iMAT (Invert-Phase Mutual Antenna Technology), the principle of which is to connect antenna one and antenna two through a metal conductor, and to use the 180° phase difference between the conductor current and the spatial coupling electromagnetic wave to realize cancellation. The disadvantage of this technology is that the effective frequency band is narrow (usually <10% relative bandwidth), and it is only suitable for narrowband scenarios (such as traditional LTE frequency bands), and the performance sharply decreases in the 0.4-8GHz wide frequency band. 2. EBG (Electromagnetic Band Gap) structure, the principle of which is to suppress surface wave propagation through a periodic electromagnetic structure to reduce the coupling between antennas. The disadvantage of this technology is that the design is complex, the volume is large, the frequency band is limited (usually covering a single frequency band), and it is difficult to adapt to the 0.4-8GHz wide frequency band. 3. Decoupling network, the principle of which is to introduce a passive network (such as a capacitor or an inductor) to adjust the antenna port impedance and realize decoupling. The disadvantage of this technology is that it increases the complexity of the system, the bandwidth is limited (usually less than 30% of the relative bandwidth), and it needs to be redesigned for specific frequency bands. 4. Parasitic element decoupling, the principle of which is to place a parasitic element in the near-field region to cancel interference through coupling. The disadvantage of this technology is that it relies on specific frequency response, the bandwidth is narrow (less than 20% of the relative bandwidth), and it is sensitive to antenna layout, with poor universality. 5. Pattern diversity, the principle of which is to reduce coupling through the orthogonality of the antenna pattern. The disadvantage of this technology is that it requires a complex feed network, and it has poor adaptability to multi-band scenarios.

[0004] In summary, the prior art generally has the problems of narrow bandwidth and poor adaptability. SUMMARY

[0005] The present application provides a multi-antenna system and a mobile terminal to solve the problem of narrow bandwidth and poor adaptability in the prior art.

[0006] In a first aspect, an embodiment of the present application provides a multi-antenna system, comprising a first antenna, a second antenna, a neutralizing line and a filter unit; the neutralizing line and the filter unit are connected between the first antenna and the second antenna.

[0007] A phase difference between a current flowing through the neutral line and the filter unit and a spatially coupled electromagnetic wave between the first antenna and the second antenna satisfies: 120° ≤ ≤ 240°.

[0008] A passband range of a filter composed of the first antenna, the second antenna, the neutral line and the filter unit is 0.4GHz-8GHz.

[0009] Optionally, a phase difference between a current flowing through the neutral line and the filter unit and a spatially coupled electromagnetic wave between the first antenna and the second antenna satisfies: = 180°.

[0010] Optionally, the filter unit comprises an acoustic filter unit.

[0011] Optionally, the acoustic filter unit comprises an input terminal, an output terminal, a series resonator and a parallel resonator.

[0012] The input terminal is electrically connected with the first antenna, and the output terminal is electrically connected with the second antenna.

[0013] The series resonator is arranged in a loop between the input terminal and the output terminal in series; one end of the parallel resonator is connected in the loop between the input terminal and the output terminal, and the other end of the parallel resonator is grounded.

[0014] Optionally, the acoustic filter unit comprises a surface acoustic wave filter unit or a bulk acoustic wave filter unit.

[0015] Optionally, the filter unit comprises a low-temperature co-fired ceramic filter unit.

[0016] Optionally, the filter unit comprises an inductance-capacitance resonant circuit.

[0017] Optionally, the filter unit comprises a multi-section stepped-impedance microstrip line structure.

[0018] Optionally, the multi-section stepped-impedance microstrip line structure comprises a first microstrip line, a second microstrip line, a third microstrip line and a fourth microstrip line arranged along a first direction and isolated from each other; the first direction is an extension direction of the neutral line.

[0019] In a second aspect, an embodiment of the present application provides a mobile terminal, characterized in comprising the multi-antenna system of the first aspect.

[0020] The technical scheme of the embodiment of the present application sets the neutral line and the filter unit between the first antenna and the second antenna, sets the passband range of the filter composed of the first antenna, the second antenna, the neutral line and the filter unit as 0.4GHz-8GHz, and sets the phase difference between the current flowing through the neutral line and the filter unit and the spatial coupling electromagnetic wave between the first antenna and the second antenna satisfies: 120°<= <=240°, can realize decoupling in the 0.4-8GHz wide frequency band, and solves the problems of narrow bandwidth and poor adaptability existing in the prior art decoupling technology.

[0021] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0023] Figure 1 A structural schematic diagram of a multi-antenna system provided by the embodiment of the present application is provided.

[0024] Figure 2 A schematic diagram of the antenna return loss and the antenna isolation degree of the multi-antenna system provided by the embodiment of the present application and the existing multi-antenna system is provided.

[0025] Figure 3 Another structural schematic diagram of a multi-antenna system provided by the embodiment of the present application is provided.

[0026] Figure 4 A structural schematic diagram of a low-temperature co-fired ceramic filter unit provided by the embodiment of the present application is provided.

[0027] Figure 5 Another structural schematic diagram of a multi-antenna system provided by the embodiment of the present application is provided.

[0028] Figure 6 A structural schematic diagram of another multi-section stepped impedance microstrip line structure provided by the embodiment of the present application is provided.

[0029] Figure 7 A structural schematic diagram of a mobile terminal provided by the embodiment of the present application is provided. DETAILED DESCRIPTION

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices. The terms "upper," "lower," "left," "right," etc., indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings and are only used to describe the relative positional relationships between components or constituent parts, and do not specifically limit the specific installation orientation of each component or constituent part.

[0032] Figure 1 This is a schematic diagram of a multi-antenna system provided in an embodiment of the present invention, with reference to... Figure 1 This invention provides a multi-antenna system 100, including a first antenna 10, a second antenna 20, a neutralization line 30, and a filter unit 40. The neutralization line 30 and the filter unit 40 are connected between the first antenna 10 and the second antenna 20. The phase difference between the current flowing through the neutralization line 30 and the filter unit 40 and the spatially coupled electromagnetic wave between the first antenna 10 and the second antenna 20 is... Satisfy: 120°≤ ≤240°. The passband of the filter consisting of the first antenna 10, the second antenna 20, the neutralization line 30, and the filter unit 40 is 0.4GHz~8GHz.

[0033] It should be noted that the multi-antenna system 100 generally includes multiple antennas, and the first antenna 10 and the second antenna 20 in the embodiment of the present application refer to any two antennas that have mutual coupling effects and cause isolation deterioration, and are generally two antennas that are adjacent and close to each other. The first antenna 10 in the embodiment of the present application can be used as an input stage to transmit signals to the filter unit 40, and the second antenna 20 can be used as an output stage to receive processed signals, which is suitable for a multi-band coexistence scenario. It should be noted that in other feasible embodiments, the second antenna 20 can also be used as an input stage to transmit signals to the filter unit 40, and the first antenna 10 can also be used as an output stage to receive processed signals, which is not limited in the embodiment of the present application.

[0034] For example, the neutral line 30 in the embodiment of the present application can adopt a metal conductor capable of transmitting current. Specifically, the metal conductor adopted by the neutral line 30 can be at least one of copper, aluminum gold, silver and the like. For example, Figure 1 The neutral line 30 in the embodiment of the present application includes a first neutral line 31 and a second neutral line 32. One end of the filter unit 40 is electrically connected to the first antenna 10 through the first neutral line 31, and the other end of the filter unit 40 is electrically connected to the second antenna 20 through the second neutral line 32.

[0035] For example, the filter unit 40 in the embodiment of the present application can adopt a tunable filter unit, which can cover an ultra-wide frequency band, and can form a cascaded bandpass filter network with the first antenna 10, the second antenna 20 and the neutral line 30, so as to realize efficient phase cancellation of the spatial coupling electromagnetic waves between the current flowing through the neutral line 30 and the filter unit 40 and the first antenna 10 and the second antenna 20. Compared with the prior art (iMAT, EBG, decoupling network), the embodiment of the present application has the advantages of wide bandwidth (relative bandwidth > 160%), strong adaptability (supporting Sub-1GHz to millimeter wave), easy integration, etc., and is suitable for 5G / 6G multi-band communication system. It should be noted that the passband range of the filter composed of the first antenna 10, the second antenna 20, the neutral line 30 and the filter unit 40 is 0.4GHz~8GHz, which does not mean that the working frequency range of the filter composed of the first antenna 10, the second antenna 20, the neutral line 30 and the filter unit 40 must be 0.4GHz~8GHz, but only means that the working frequency range of the filter composed of the first antenna 10, the second antenna 20, the neutral line 30 and the filter unit 40 is within 0.4GHz~8GHz.

[0036] Specifically, the working frequency range, insertion phase and group delay of the filter unit 40 and the physical length of the neutral line 30 can be designed according to the impedance characteristics of the first antenna 10 and the second antenna 20, so that the phase difference between the current flowing through the neutral line 30 and the filter unit 40 and the spatial coupling electromagnetic waves between the first antenna 10 and the second antenna 20 is satisfies: 120°≤ thereby making the current flowing through the neutralizing line 30 and the filter unit 40 and the spatially coupled electromagnetic wave energy between the first antenna 10 and the second antenna 20 partially or completely offset.

[0037] Figure 2 A schematic diagram of the antenna return loss and the antenna isolation of an existing multi-antenna system and the multi-antenna system in the embodiment of the present application is provided, and it should be noted that, Figure 2 the curve S1 in the figure represents the return loss curve of the existing first antenna 10 provided with only a neutralizing line, the curve S2 represents the return loss curve of the existing second antenna 20 provided with only a neutralizing line, the curve S3 represents the isolation curve of the existing first antenna 10 and the second antenna 20 provided with only a neutralizing line, the curve S4 represents the return loss curve of the first antenna 10 provided with the neutralizing line 30 and the filter unit 40 (for example, a surface wave filter unit) in the embodiment of the present application, the curve S5 represents the return loss curve of the second antenna 20 provided with the neutralizing line 30 and the filter unit 40 (for example, a surface wave filter unit) in the embodiment of the present application, and the curve S6 represents the isolation curve of the first antenna 10 and the second antenna 20 provided with the neutralizing line 30 and the filter unit 40 (for example, a surface wave filter unit), and by comparison, it can be known that the return loss curves of the two antennas of the existing multi-antenna system and the multi-antenna system in the embodiment of the present application are basically unchanged, that is, the added filter unit 40 (for example, a surface wave filter unit) will not affect the impedance matching performance of the first antenna 10 and the second antenna 20.

[0038] It should be noted that, under the premise that the first antenna 10, the second antenna 20, the neutral line 30 and the filter unit 40 together constitute a filter, the filter unit 40 in the embodiment of the present application can be set according to the known working frequency range of the first antenna 10 and the second antenna 20. Specifically, the frequency range of the spatially coupled electromagnetic wave between the first antenna 10 and the second antenna 20 can be determined first according to the working frequency range of the first antenna 10 and the second antenna 20, and then the filter unit 40 can be designed according to the frequency range of the spatially coupled electromagnetic wave, the working frequency range of the first antenna 10 and the working range of the second antenna 20 under the premise that the first antenna 10, the second antenna 20, the neutral line 30 and the filter unit 40 together constitute a filter, and the first antenna 10 and the second antenna 20 are respectively the first and last resonators of the filter. Compared with the way of constantly trying and error to design the filter unit 40, the above design method is more scientific, accurate and fast, and the obtained filter unit 40 can pass through a larger frequency range of current, and the coincidence degree of the frequency range of the spatially coupled electromagnetic wave between the first antenna 10 and the second antenna 20 is higher, thereby the isolation of the first antenna 10 and the second antenna 20 can be improved in a larger frequency range. For example, as shown by curves S1 and S4 in FIG. 1, the working frequency of the first antenna 10 is about 5GHz-7.3GHz, as shown by curves S2 and S5 in FIG. 1, the working frequency of the second antenna 20 is about 4.6GHz-6.0GHz, it can be understood that the frequency range of the spatially coupled electromagnetic wave between the first antenna 10 and the second antenna 20 is about 4.6GHz-7.3GHz, as shown by curve S6 in FIG. 1, in the frequency range of 4.6GHz-7.3GHz, the isolation of the first antenna 10 and the second antenna 20 which are provided with the neutral line 30 and the filter unit 40 (for example, the surface wave filter unit) is better than that of the first antenna 10 and the second antenna 20 which are provided with only the neutral line 30, the decoupling effect is better, and the frequency range in which good isolation (-30dB~-50dB) can be achieved is larger, solving the problem that the existing decoupling technology can only partially or completely cancel the spatially coupled electromagnetic wave between two antennas in a relatively narrow bandwidth (i.e. near the target frequency point), thereby reducing the coupling degree of the two antennas. Figure 2 Figure 2 Figure 2

[0039] ​​​Optionally, in the design of the multi-antenna system 100 in the embodiment of the application, a broadband antenna-neutralizing line-filter unit model can be established by using electromagnetic simulation software such as HFSS / CST, and the bandwidth and depth of the cancellation effect are optimized according to the simulation results, so that a multi-antenna system meeting the requirements is designed. The simulation and actual measurement results of the multi-antenna system 100 in the embodiment of the application show that: within the frequency band of 0.4GHz-8GHz, the isolation between the first antenna 10 and the second antenna 20 is improved by ≥12dB, and the effective bandwidth covers more than 90% of the target frequency band. Compared with the traditional iMAT technology (only 8dB is improved at 1.8-2.2GHz), the present application can improve 10dB and 15dB at low frequency band (0.4-1GHz) and high frequency band (5-8GHz) respectively. The passband adjustment error of the filter composed of the first antenna 10, the second antenna 20, the neutralizing line 30 and the filter unit 40 is <±1.5%, which meets the demand of multi-band cooperative work.

[0040] It should be noted that, in order to ensure the safety and reliability of the entire multi-antenna system 100, the first antenna 10, the second antenna 20 and other antennas of the multi-antenna system in the embodiment of the application are provided with grounding protection. Specifically, the first antenna 10, the second antenna 20 and other antennas of the multi-antenna system are directly grounded to ensure that the antennas themselves can be lightning and static electricity proof. Among them, the direct grounding of the antenna refers to the direct connection of the metal part (such as the support, the oscillator, the reflector, etc.) of the antenna itself with the ground; the feed lines of the first antenna 10, the second antenna 20 and other antennas of the multi-antenna system are also grounded to ensure that the equipment can be lightning and interference proof, and among them, the grounding of the feed line refers to the connection of the outer conductor (shield layer) of the coaxial cable (feed line) with the ground, which is mainly used for lightning protection, interference reduction and equipment safety protection.

[0041] In the embodiment of the application, the neutralizing line 30 and the filter unit 40 are arranged between the first antenna 10 and the second antenna 20, the passband range of the filter composed of the first antenna 10, the second antenna 20, the neutralizing line 30 and the filter unit 40 is 0.4GHz-8GHz, and the phase difference between the current flowing through the neutralizing line 30 and the filter unit 40 and the spatial coupling electromagnetic wave between the first antenna 10 and the second antenna 20 is satisfies: 140°≤ ≤240°, which can realize decoupling within the wide frequency band of 0.4GHz-8GHz, solving the problem of narrow bandwidth and poor adaptability existing in the existing decoupling technology. Moreover, the present application can be widely applied to smart phones, Internet of Things devices (Sub-1GHz), 5G base stations (Sub-8GHz) and millimeter wave communication systems, significantly improving the communication speed and reliability in the multi-band coexistence scene. Through modular design, the frequency band requirements of different global communication standards (such as NR, LTE-M, NB-IoT) can be quickly adapted.

[0042] On the basis of the above-mentioned embodiments, the phase difference between the current flowing through the neutral line 30 and the filter unit 40 and the spatially coupled electromagnetic wave between the first antenna 10 and the second antenna 20 is satisfies: = 180°.

[0043] Exemplarily, when the phase difference between the current flowing through the neutral line 30 and the filter unit 40 and the spatially coupled electromagnetic wave between the first antenna 10 and the second antenna 20 is 180°, the cancellation effect of the current flowing through the neutral line 30 and the filter unit 40 and the spatially coupled electromagnetic wave between the first antenna 10 and the second antenna 20 is optimal, and complete decoupling can be achieved.

[0044] In a feasible embodiment, the filter unit 40 comprises an acoustic filter unit.

[0045] Exemplarily, the acoustic filter unit has the advantages of high Q value, low insertion loss, ultra-miniaturization, wafer-level integration, excellent frequency stability, wide frequency band, etc., and the filter unit 40 adopts the acoustic filter unit, which not only enables the passband range of the filter composed of the first antenna 10, the second antenna 20, the neutral line 30 and the acoustic filter unit to reach 0.4GHz-8GHz, thereby being conducive to improving the isolation performance between antennas, but also ensures the miniaturization of the multi-antenna system 100, and the acoustic filter unit can be directly integrated into the existing multi-antenna system without complex structural modification or additional parasitic elements, and has strong compatibility.

[0046] Figure 3 Another structural schematic diagram of a multi-antenna system provided by the embodiment of the present application is shown in FIG. 2. Figure 3 The acoustic filter unit in the embodiment of the present application comprises an input terminal 41, an output terminal 42, a series resonator 43 and a parallel resonator 44. The input terminal 41 is electrically connected with the first antenna 10, and the output terminal 42 is electrically connected with the second antenna 20. The series resonator 43 is arranged in series in the loop between the input terminal 41 and the output terminal 42. One end of the parallel resonator 44 is connected in the loop between the input terminal 41 and the output terminal 42, and the other end of the parallel resonator 44 is grounded.

[0047] It should be noted that, Figure 3 The first antenna 10, the second antenna 20, the neutral line 30 and the acoustic filter unit in the embodiment of the present application can be regarded as a whole filter, and the first antenna 10 and the second antenna 20 can be regarded as the first-order resonator and the last-order resonator of the whole filter, respectively.

[0048] Exemplarily, referring to FIG. 1 and FIG. 2, Figure 1 and Figure 3The input terminal 41 of the acoustic filter unit (i.e., the filter unit 40) is electrically connected to the first antenna 10 through the first neutral line 31, the output terminal 42 of the acoustic filter unit (i.e., the filter unit 40) is electrically connected to the second antenna 20 through the second neutral line 32, three series resonators 43 are connected in series between the input terminal 41 and the output terminal 42, and one end of four parallel resonators 44 is arranged at both ends of the series resonators 43, and the other end of the four parallel resonators 44 is grounded. The resonant frequency and the anti-resonant frequency of the series resonators 43 and the parallel resonators 44 can be reasonably set to control the passband range of the filter composed of the first antenna 10, the second antenna 20, the neutral line 30, and the acoustic filter unit to be 0.4GHz-8GHz.

[0049] Optionally, in other possible embodiments, the acoustic filter unit in the embodiment of the present application can also include a longitudinal coupling resonator type filter unit (DMS), which can be arranged in series in a loop between the input terminal 41 and the output terminal 42 as shown in the figure. Figure 3

[0050] It should be noted that the acoustic filter unit in the embodiment of the present application can adopt a surface wave filter unit or a bulk acoustic wave filter unit, which is not limited in the embodiment of the present application, and can be selected by the person skilled in the art.

[0051] In another possible embodiment, the filter unit 40 in the embodiment of the present application includes a low-temperature co-fired ceramic filter unit.

[0052] For example, the low-temperature co-fired ceramic filter unit has the advantages of three-dimensional integration, high-density design, excellent radio frequency performance, high thermal stability, high reliability, and low cost. The filter unit 40 adopts the low-temperature co-fired ceramic filter unit, which not only enables the passband range of the filter composed of the first antenna 10, the second antenna 20, the neutral line 30, and the low-temperature co-fired ceramic filter unit to reach 0.4GHz-8GHz, thereby being conducive to improving the isolation performance between antennas, but also ensures the miniaturization and low cost of the multi-antenna system 100. Moreover, the low-temperature co-fired ceramic filter unit can be directly integrated into the existing multi-antenna system without complex structural modification or additional parasitic elements, and has strong compatibility.

[0053] Specifically, Figure 4 A structure diagram of a low-temperature co-fired ceramic filter unit provided by the embodiment of the present application is shown in the figure. Figure 4 The low-temperature co-fired ceramic filter unit in the embodiment of the present application includes a first protective layer 401, a first shielding layer 402, a first circuit layer 403, a second circuit layer 404, a second shielding layer 405, and a second protective layer 406 arranged in layers.

[0054] ​The first protective layer 401 can be a ceramic substrate made of high melting point ceramic (such as Al2O3, AlN) or low temperature sintering medium (such as glass-ceramic composite material) and the like, and the bottom (i.e. the side surface of the first protective layer 401 away from the first shielding layer 402) is usually large-area metallized to form a metallized layer. The first protective layer 401 can be used as a heat dissipation substrate, as a contact layer between the device and the PCB / packaging substrate, and the heat can be quickly dissipated through the metallized layer (especially suitable for power filter units). The first protective layer 401 can also be used as a main ground layer to provide a global ground reference and interconnect with the internal ground layer through a via to form a low-impedance return path. The first protective layer 401 can also be used as a mechanical support layer to enhance the overall structural strength of the device and facilitate mounting.

[0055] The first shielding layer 402 and the second shielding layer 405 are large-area metal layers that can include periodic ground vias or isolation grooves. The first shielding layer 402 and the second shielding layer 405 can isolate adjacent signal layers to suppress electromagnetic coupling (such as crosstalk) and improve filter unit Q value and out-of-band rejection, thereby serving as a shield and isolation. The first shielding layer 402 and the second shielding layer 405 can also serve as a return path to provide a low-impedance ground channel for high-frequency signals, reducing parasitic radiation and loss. The flat metal surface in the first shielding layer 402 and the second shielding layer 405 enhances the structural rigidity of the ceramic substrate, improving the mechanical stability of the low-temperature co-fired ceramic filter unit.

[0056] The metal layer (i.e. the first circuit layer 403 and the second circuit layer 404) includes transmission line and resonator layers, cross-coupling layers, and structures such as microstrip lines, striplines, coplanar waveguides (CPW) or coupling lines. Two non-adjacent signal layers can be electromagnetically coupled through metallized vias or cross-layer coupling structures (such as "U" type cross lines). The first circuit layer 403 and the second circuit layer 404 can be used as half-wavelength resonators to control the resonant frequency and generate transmission zeros through size and layout.

[0057] The material of the second protective layer 406 includes high melting point ceramic (such as Al2O3, AlN) or low temperature sintering medium (such as glass-ceramic composite material), and the surface (i.e. the side surface of the second protective layer 406 away from the second shielding layer 405) can be plated with metal (such as Ag, Au). The second protective layer 406 can encapsulate the internal circuit to prevent damage to the device from external mechanical stress, moisture, dust and the like, thereby serving as a mechanical protection. The second protective layer 406 can also isolate the external environment to improve the reliability of the device (especially in high temperature and high frequency scenarios), thereby serving as an environmental seal. The second protective layer 406 can also be partially designed as part of the ground plane or reserved for a bonding pad (for gold wire bonding to connect external circuits), thereby serving as an auxiliary ground.

[0058] In another possible implementation, the filter unit 40 in the embodiment of the present application comprises an inductor-capacitor resonant circuit.

[0059] By way of example, the inductor-capacitor resonant circuit has advantages of high-frequency performance, high Q value, flexible tuning and low cost, etc. The filter unit 40 adopts the inductor-capacitor resonant circuit, which not only enables the passband range of the filter composed of the first antenna 10, the second antenna 20, the neutral line 30 and the inductor-capacitor resonant circuit to reach 0.4GHz-8GHz, thereby being conducive to improving the isolation performance between antennas, but also ensures the miniaturization, flexibility and low cost of the multi-antenna system 100.

[0060] By way of example, the filter unit 40 adopts the inductor-capacitor resonant circuit, Figure 5 Another structural schematic diagram of a multi-antenna system provided by the embodiment of the present application is shown in FIG. 4, which is described below with reference to FIG. 4. Figure 5 The inductor-capacitor resonant circuit (i.e. the filter unit 40) comprises a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a second inductor L2, a third inductor L3 and a fourth inductor L4. One end of the third capacitor C3 is electrically connected to the first antenna 10. The other end of the third capacitor C3 is electrically connected to one end of the second inductor L2. The other end of the second inductor L2 is electrically connected to one end of the third inductor L3. The other end of the third inductor L3 is electrically connected to one end of the fourth capacitor C4. One end of the fourth capacitor C4 is electrically connected to the second antenna 20. One end of the fifth capacitor C5 is electrically connected to the other end of the second inductor L2, and the other end of the fifth capacitor C5 is grounded. One end of the fourth inductor L4 is electrically connected to one end of the third inductor L3, and the other end of the fourth inductor L4 is grounded.

[0061] By way of example, Figure 5 The inductor-capacitor resonant circuit shown in FIG. 4 is a three-order bandpass filter unit, and the filter composed of the first antenna 10, the second antenna 20, the neutral line 30 and the inductor-capacitor resonant circuit can cover the frequency band of 0.4GHz-8GHz. By connecting multiple groups of variable capacitors (e.g. BST varactor diodes) and adjustable inductors in parallel, dynamic segmented adjustment of the passband (e.g. the low frequency band of 0.4-2GHz and the high frequency band of 3-8GHz) can be realized.

[0062] It should be noted that, Figure 5 The first antenna 10, the second antenna 20, the neutral line 30 and the inductor-capacitor resonant circuit in FIG. 4 can be regarded as an entire filter, and the first antenna 10 and the second antenna 20 can be regarded as the first-order resonator and the last-order resonator of the entire filter, respectively.

[0063] The embodiment of the present application provides a circuit of an inductor-capacitor resonant circuit (i.e. the filter unit 40), which can help field technicians to quickly predict the performance of the filter unit 40, thereby being conducive to improving the design efficiency of the multi-antenna system in the embodiment of the present application.

[0064] In yet another possible implementation, the filter unit 40 comprises a multi-section stepped impedance microstrip line structure.

[0065] By way of example, the filter unit 40 employs a multi-section stepped impedance microstrip line structure to form a distributed bandpass filter unit. The multi-section stepped impedance microstrip line structure has the advantages of flexible frequency response control, wide frequency band, miniaturization, low loss, flexible design and easy fabrication. By employing the multi-section stepped impedance microstrip line structure, the filter unit 40 not only enables the passband range of the filter composed of the first antenna 10, the second antenna 20, the neutral line 30 and the multi-section stepped impedance microstrip line structure to reach 0.4GHz-8GHz, thereby facilitating improvement of the isolation performance between the antennas, but also ensures miniaturization, flexibility and low cost of the multi-antenna system 100.

[0066] Specifically, Figure 6 Another multi-section stepped impedance microstrip line structure provided by the embodiments of the present application is shown in the structure diagram of Figure 6 The multi-section stepped impedance microstrip line structure comprises a first microstrip line 411, a second microstrip line 412, a third microstrip line 413 and a fourth microstrip line 414 arranged along a first direction X and isolated from each other. The first direction X is the extension direction of the neutral line 30.

[0067] By way of example, by optimizing the length and width of each microstrip line (the first microstrip line 411, the second microstrip line 412, the third microstrip line 413 and the fourth microstrip line 414), the filter composed of the first antenna 10, the second antenna 20, the neutral line 30 and the multi-section stepped impedance microstrip line structure can achieve full-band coverage in the frequency range of 0.4GHz-8GHz, and the impedance characteristics of the first antenna 10 and the second antenna 20 are matched to 50Ω through electromagnetic simulation.

[0068] Based on the same inventive concept, the present application also provides a mobile terminal. Figure 7 A structure diagram of a mobile terminal provided by the embodiments of the present application is shown in Figure 7 The mobile terminal 200 in the embodiments of the present application comprises the multi-antenna system 100 provided by any of the above embodiments of the present application, and therefore has the technical features of the multi-antenna system 100 and the beneficial effects thereof. The same parts can be referred to the above description.

[0069] The above detailed description does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A multiple antenna system, characterized by, The filter includes a first antenna, a second antenna, a neutral line and a filter unit; the neutral line and the filter unit are connected between the first antenna and the second antenna; a phase difference of a spatially coupled electromagnetic wave between the first antenna and the second antenna satisfies: 120° ≤ ≤ 240°; The passband range of the filter composed of the first antenna, the second antenna, the neutral line and the filter unit is 0.4GHz-8GHz; The first antenna and the second antenna are used as the first and last resonators of the filter respectively; the frequency range of the spatially coupled electromagnetic wave between the first antenna and the second antenna is determined according to the working frequency range of the first antenna and the second antenna, and then the filter unit is designed according to the frequency range of the spatially coupled electromagnetic wave, the working frequency range of the first antenna and the working range of the second antenna.

2. The multiple antenna system of claim 1, wherein, a phase difference of the spatially coupled electromagnetic wave between the first antenna and the second antenna satisfies: = 180°.

3. The multiple antenna system of claim 1, wherein, The filter unit includes an acoustic filter unit.

4. The multiple antenna system of claim 3, wherein, The acoustic filter unit includes an input terminal, an output terminal, a series resonator and a parallel resonator; The input terminal is electrically connected with the first antenna, and the output terminal is electrically connected with the second antenna; The series resonator is arranged in series in the loop between the input terminal and the output terminal; one end of the parallel resonator is connected in the loop between the input terminal and the output terminal, and the other end of the parallel resonator is grounded.

5. The multiple antenna system of claim 3, wherein, The acoustic filter unit includes a surface acoustic wave filter unit or a bulk acoustic wave filter unit.

6. The multiple antenna system of claim 1, wherein, The filter unit includes a low-temperature co-fired ceramic filter unit.

7. The multiple antenna system of claim 1, wherein, The filter unit includes an inductance-capacitance resonant circuit.

8. The multiple antenna system of claim 1, wherein, The filter unit includes a multi-section stepped impedance microstrip line structure.

9. The multiple antenna system of claim 8, wherein, The multi-section stepped impedance microstrip line structure includes a first microstrip line, a second microstrip line, a third microstrip line and a fourth microstrip line arranged along a first direction and isolated from each other; the first direction is the extension direction of the neutral line.

10. A mobile terminal, characterized by The multi-antenna system includes any one of claims 1-9.

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