阅读说明：本技术 一种5g频段腔体滤波器及其设计方法 (5G frequency band cavity filter and design method thereof ) 是由 罗兵 于 2020-12-15 设计创作，主要内容包括：本发明公开了一种5G频段腔体滤波器及其设计方法,所述5G频段腔体滤波器包括输入端口、输出端口、输入耦合装置、输出耦合装置、多个谐振器、多个调谐装置和腔体；所述输入端口与所述输入耦合装置连接,所述输出端口与所述输出耦合装置连接,多个所述谐振器和多个所述调谐装置设置在所述腔体内,所述调谐装置包括第一调谐装置和第二调谐装置；本发明为5G系统射频部分提供了良好的信号选择,可以解决5G通信系统易受外界干扰、通信速率不稳定的问题,可以提高5G系统的通信距离和通信容量,改善通信质量,提高5G系统用户对无线网络的体验感,推动5G系统网络的推广建设,促进通信事业的发展；本发明可广泛应用于滤波器设备技术领域。(The invention discloses a 5G frequency band cavity filter and a design method thereof, wherein the 5G frequency band cavity filter comprises an input port, an output port, an input coupling device, an output coupling device, a plurality of resonators, a plurality of tuning devices and a cavity; the input port is connected with the input coupling device, the output port is connected with the output coupling device, a plurality of resonators and a plurality of tuning devices are arranged in the cavity, and the tuning devices comprise a first tuning device and a second tuning device; the invention provides good signal selection for the radio frequency part of the 5G system, can solve the problems that the 5G communication system is easily interfered by the outside and the communication speed is unstable, can improve the communication distance and the communication capacity of the 5G system, improve the communication quality, improve the experience of a 5G system user on a wireless network, promote the popularization and construction of the 5G system network and promote the development of the communication business; the invention can be widely applied to the technical field of filter equipment.)

1. A5G frequency band cavity filter is characterized by comprising an input port, an output port, an input coupling device, an output coupling device, a plurality of resonators, a plurality of tuning devices and a cavity; the input port is connected with the input coupling device, the output port is connected with the output coupling device, a plurality of resonators and a plurality of tuning devices are arranged in the cavity, and the tuning devices comprise a first tuning device and a second tuning device;

the input port is used for receiving an original signal;

the output port is used for outputting signals processed by a plurality of resonators;

the input coupling device is used for controlling the coupling between the input port and a first resonator, and the first resonator is a resonator adjacent to the input port;

the output coupling device is used for controlling the coupling between the output port and a second resonator, and the second resonator is a resonator adjacent to the output port;

the resonators are used for controlling signals in a 5G frequency band in the original signals to pass;

the first tuning device is used for adjusting the resonant frequency generated by the resonator to be within a 5G frequency band;

the second tuning means is used to adjust the coupling coefficient between the resonators.

2. The 5G-band cavity filter according to claim 1, wherein the resonators are metal resonators or dielectric resonators, and the resonators are cylindrical or square.

3. The 5G-band cavity filter according to claim 2, wherein the resonators are spatially coupled to each other.

4. The 5G-band cavity filter according to claim 2, wherein the cavity is a metal rectangular cavity, when the resonator is cylindrical, the diameter of the cylinder does not exceed the wide side of the metal rectangular cavity, and when the resonator is square, the side length of the square does not exceed the wide side of the metal rectangular cavity.

5. The 5G frequency band cavity filter according to claim 1, wherein the first tuning device and the second tuning device are metal screws or dielectric screws; the length of the metal screw or the medium screw is determined by the coupling coefficient; when the first tuning device and the second tuning device are dielectric screws, copper or silver is electroplated on the outer layers of the dielectric screws.

6. A design method of a 5G frequency band cavity filter according to any one of claims 1 to 5, comprising:

determining a first design index of the 5G frequency band cavity filter, wherein the design index comprises the bandwidth, in-band insertion loss, in-band return loss, standing-wave ratio, order, transmission function and overall structure of the 5G frequency band cavity filter;

according to the first design index, obtaining a first numerical value by solving a Chebyshev function, wherein the first numerical value is a normalized element value of each circuit element of a Chebyshev function type low-pass prototype;

obtaining a coupling coefficient between adjacent resonators and an external quality factor of the 5G frequency band cavity filter according to the first numerical value and the relative bandwidth of the 5G frequency band cavity filter;

determining a second design index of the resonator, wherein the second design index comprises the material, the shape and the size and the resonant frequency of the resonator;

determining the distance between the resonators according to the coupling coefficient between the adjacent resonators;

simulating by advanced radio frequency simulation software according to the first design index, the second design index and the number of the resonators to obtain a primary simulation result;

and carrying out fine adjustment and optimization on the preliminary simulation result to obtain the 5G frequency band cavity filter.

7. The method according to claim 6, wherein the determining the first design index of the 5G band cavity filter specifically comprises:

setting the bandwidth of the 5G frequency band cavity filter as a 5G frequency band, wherein the in-band insertion loss is not more than 0.8dB, the in-band return loss is more than 25dB, and the standing-wave ratio is not more than 1.25;

determining a transmission function and an order of the 5G frequency band cavity filter;

determining that the integral structure of the 5G frequency band cavity filter comprises an input port, an output port, an input coupling device, an output coupling device, a plurality of resonators, a plurality of tuning devices and a cavity; the input port is connected with the input coupling device, the output port is connected with the output coupling device, a plurality of resonators and a plurality of tuning devices are arranged in the cavity, and the tuning devices comprise a first tuning device and a second tuning device; the input port is used for receiving an original signal; the output port is used for outputting signals processed by a plurality of resonators; the input coupling device is used for controlling the coupling between the input port and a first resonator, and the first resonator is a resonator adjacent to the input port; the output coupling device is used for controlling the coupling between the output port and a second resonator, and the second resonator is a resonator adjacent to the output port; the resonators are used for controlling signals in a 5G frequency band in the original signals to pass; the first tuning device is used for adjusting the resonant frequency generated by the resonator to be within a 5G frequency band; the second tuning means is used to adjust the coupling coefficient between the resonators.

8. The design method of the 5G frequency band cavity filter according to claim 7, wherein the expression of the transfer function is as follows:

wherein, | S₂₁(Ω) | represents the power transmission coefficient of the signal input from the input port of the 5G frequency band cavity filter and output from the output port, IL (Ω) represents the transmission function, and Ω represents the normalized angular frequency.

9. The design method of 5G band cavity filter according to claim 8, wherein the transmission coefficient | S of signal power input from the input port and output from the output port of the 5G band cavity filter₂₁(Ω) | is obtained by a first formula:where ε is the ripple coefficient in the passband of the 5G band cavity filter, T_n(Ω) is the Chebyshev function; wherein:

in the formula, L_ArThe maximum in-band insertion loss of the cavity filter is 5G;

wherein n represents a 5G bandThe order of the cavity filter.

10. The design method of 5G frequency band cavity filter according to claim 8,

the coupling coefficient between the adjacent resonators is calculated by the following formula:

in the formula, FBW represents the relative bandwidth of the 5G frequency band cavity filter, K_i，i+1Denotes the coupling coefficient between adjacent resonators, g_iAnd g_i+1Respectively representing normalized element values of circuit elements of the Chebyshev function type low-pass prototype;

the external quality factor of the 5G frequency band cavity filter is calculated by the following formula:

in the formula, Q_eRepresents the external quality factor, G, of the 5G frequency band cavity filter₀Is 1, g₁A normalized element value representing the 1 st element of the chebyshev function type low-pass prototype circuit;

wherein the content of the first and second substances,in the formula (f)₂Represents the lower cut-off frequency, f₁Denotes the upper cut-off frequency, f₀Representing the center frequency.

Technical Field

The invention relates to the technical field of filter equipment, in particular to a 5G frequency band cavity filter and a design method thereof.

Background

The filter is one of microwave devices which must be used by the 5G system, plays a key role in the system, can play a role in selecting frequency bands and channels, enables in-band signals to pass through almost without obstruction, can filter out harmonic waves and inhibit stray and other interference signals, and can be said that the normal operation of the 5G system cannot be separated from the filter with excellent performance; at present, various filters exist, such as lumped LC band-pass filters, microstrip filters, cavity filters and the like, but the lumped LC band-pass filters have large size and large insertion loss and are not suitable for filters in high frequency bands; the microstrip filter has low power, and the common single-mode cavity filter has larger size. For the 5G system which is built at present, the frequency band is high, and the frequency resources are in shortage; none of the filters currently used is suitable for 5G systems.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a 5G frequency band cavity filter and a design method thereof.

The technical scheme adopted by the invention is as follows:

on one hand, the embodiment of the invention comprises a 5G frequency band cavity filter, which comprises an input port, an output port, an input coupling device, an output coupling device, a plurality of resonators, a plurality of tuning devices and a cavity; the input port is connected with the input coupling device, the output port is connected with the output coupling device, a plurality of resonators and a plurality of tuning devices are arranged in the cavity, and the tuning devices comprise a first tuning device and a second tuning device;

the input port is used for receiving an original signal;

the output port is used for outputting signals processed by a plurality of resonators;

the input coupling device is used for controlling the coupling between the input port and a first resonator, and the first resonator is a resonator adjacent to the input port;

the output coupling device is used for controlling the coupling between the output port and a second resonator, and the second resonator is a resonator adjacent to the output port;

the resonators are used for controlling signals in a 5G frequency band in the original signals to pass;

the first tuning device is used for adjusting the resonant frequency generated by the resonator to be within a 5G frequency band;

the second tuning means is used to adjust the coupling coefficient between the resonators.

Further, the resonator is a metal resonator or a dielectric resonator, and the resonator is cylindrical or cubic.

Furthermore, a plurality of resonators are coupled in a space coupling mode.

Further, the cavity is a metal rectangular cavity, when the resonator is cylindrical, the diameter of the cylinder is not more than the wide side of the metal rectangular cavity, and when the resonator is a cube, the side length of the cube is not more than the wide side of the metal rectangular cavity.

Further, the first tuning device and the second tuning device are metal screws or medium screws; the length of the metal screw or the medium screw is determined by the coupling coefficient; when the first tuning device and the second tuning device are dielectric screws, copper or silver is electroplated on the outer layers of the dielectric screws.

On the other hand, the embodiment of the invention includes a design method of a 5G frequency band cavity filter, which comprises the following steps:

determining a first design index of the 5G frequency band cavity filter, wherein the design index comprises the bandwidth, in-band insertion loss, in-band return loss, standing-wave ratio, order, transmission function and overall structure of the 5G frequency band cavity filter;

according to the first design index, obtaining a first numerical value by solving a Chebyshev function, wherein the first numerical value is a normalized element value of each circuit element of a Chebyshev function type low-pass prototype;

obtaining a coupling coefficient between adjacent resonators and an external quality factor of the 5G frequency band cavity filter according to the first numerical value and the relative bandwidth of the 5G frequency band cavity filter;

determining a second design index of the resonator, wherein the second design index comprises the material, the shape and the size and the resonant frequency of the resonator;

determining the distance between the resonators according to the coupling coefficient between the adjacent resonators;

simulating by advanced radio frequency simulation software according to the first design index, the second design index and the number of the resonators to obtain a primary simulation result;

and carrying out fine adjustment and optimization on the preliminary simulation result to obtain the 5G frequency band cavity filter.

Further, the determining a first design index of the 5G frequency band cavity filter specifically includes:

setting the bandwidth of the 5G frequency band cavity filter as a 5G frequency band, wherein the in-band insertion loss is not more than 0.8dB, the in-band return loss is more than 25dB, and the standing-wave ratio is not more than 1.25;

determining the order and the transmission function of the 5G frequency band cavity filter;

determining that the integral structure of the 5G frequency band cavity filter comprises an input port, an output port, an input coupling device, an output coupling device, a plurality of resonators, a plurality of tuning devices and a cavity; the input port is connected with the input coupling device, the output port is connected with the output coupling device, a plurality of resonators and a plurality of tuning devices are arranged in the cavity, and the tuning devices comprise a first tuning device and a second tuning device; the input port is used for receiving an original signal; the output port is used for outputting signals processed by a plurality of resonators; the input coupling device is used for controlling the coupling between the input port and a first resonator, and the first resonator is a resonator adjacent to the input port; the output coupling device is used for controlling the coupling between the output port and a second resonator, and the second resonator is a resonator adjacent to the output port; the resonators are used for controlling signals in a 5G frequency band in the original signals to pass; the first tuning device is used for adjusting the resonant frequency generated by the resonator to be within a 5G frequency band; the second tuning means is used to adjust the coupling coefficient between the resonators.

Further, the expression of the transfer function is:

wherein, | S₂₁(Ω)|The transmission coefficient of the signal power input from the input port and output from the output port of the 5G frequency band cavity filter is shown, IL (omega) represents a transmission function, and omega represents normalized angular frequency.

Further, the power transmission coefficient | S of the signal input from the input port and output from the output port of the 5G frequency band cavity filter₂₁(Ω) | is obtained by a first formula:where ε is the ripple coefficient in the passband of the 5G band cavity filter, T_n(Ω) is the Chebyshev function; wherein:

in the formula, L_ArThe maximum in-band insertion loss of the cavity filter is 5G;

in the formula, n represents the order of the cavity filter of the 5G frequency band.

Further, the coupling coefficient between the adjacent resonators is calculated by the following formula:

in the formula, FBW represents the relative bandwidth of the 5G frequency band cavity filter, K_i，i+1Denotes the coupling coefficient between adjacent resonators, g_iAnd g_i+1Respectively representing normalized element values of circuit elements of the Chebyshev function type low-pass prototype;

the external quality factor of the 5G frequency band cavity filter is calculated by the following formula:

in the formula, Q_eRepresents the external quality factor, G, of the 5G frequency band cavity filter₀Is 1, g₁A normalized element value representing the 1 st element of the chebyshev function type low-pass prototype circuit;

wherein the content of the first and second substances,in the formula (I), wherein,in the formula (f)₂Represents the lower cut-off frequency, f₁Denotes the upper cut-off frequency, f₀Representing the center frequency.

The invention has the beneficial effects that:

the 5G frequency band cavity filter provided by the invention provides good signal selection for a radio frequency part of a 5G system, can solve the problems that the 5G communication system is easily interfered by the outside and the communication speed is unstable, can improve the communication distance and the communication capacity of the 5G system, improves the communication quality, improves the experience of a 5G system user on a wireless network, promotes the popularization and construction of the 5G system network, and promotes the development of the communication industry.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic structural diagram of a 5G frequency band cavity filter implemented in the present invention;

FIG. 2 is a schematic diagram of a single-cavity model of a resonator and a corresponding S-matrix network according to an embodiment of the invention;

FIG. 3 is a schematic diagram of one of the structures of the resonator according to the embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating the effect of the height of a metal resonator on the resonant frequency according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating the effect of the height of a metal resonator on the Q value according to an embodiment of the present invention;

fig. 6 is a flowchart illustrating steps of a method for designing a cavity filter of a 5G frequency band according to an embodiment of the present invention;

fig. 7 is a schematic diagram of a low-pass prototype of chebyshev function type according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.

The embodiments of the present application will be further explained with reference to the drawings.

Referring to fig. 1, an embodiment of the present invention provides a 5G frequency band cavity filter 100, including an input port 101, an output port 102, an input coupling device 103, an output coupling device 104, a plurality of resonators 105, a plurality of tuning devices 106, and a cavity 107; the input port 101 is connected to the input coupling device 103, the output port 102 is connected to the output coupling device 104, a plurality of resonators 105 and a plurality of tuning devices 106 are disposed in the cavity 107, and the tuning devices 106 include a first tuning device 106-1 and a second tuning device 106-2;

the input port 101 is used for receiving an original signal;

the output port 102 is configured to output signals processed by a plurality of resonators 105;

the input coupling device 103 is configured to control coupling between the input port 101 and a first resonator, where the first resonator is a resonator adjacent to the input port 101;

the output coupling device 104 is used for controlling the coupling between the output port 102 and a second resonator, which is a resonator adjacent to the output port;

a plurality of the resonators 105 are used to generate different resonance frequencies;

the first tuning device 106-1 is used for adjusting the resonance frequency generated by the resonator 105 to be within the 5G frequency band;

the second tuning means 106-2 is used to adjust the coupling coefficient between the resonators.

In the embodiment, the resonator is a cylindrical metal resonator, a symmetrical structure is used according to the frequency band of the 5G frequency band cavity filter to be designed, after the initial physical size is obtained through theoretical calculation, the result of electromagnetic simulation software is compared with the calculation result, the final Q value can reach more than 2500, the fundamental frequency resonance frequencies are 3.516GHz respectively, the adjacent high-order resonance frequencies are 13.779GHz, the fundamental frequency is basically consistent with the 5G frequency band (3300 MHz-3600 MHz), and the high-order resonance frequencies are far away from the fundamental frequency and have small influence on the fundamental frequency. By adding the plurality of cylindrical metal resonators into the 5G frequency band cavity filter and introducing coupling between the cylindrical metal resonators, the design of the multi-order filter is realized, the out-of-band rejection capability of the 5G frequency band cavity filter is improved, and the spatial coupling is adopted among the plurality of cylindrical metal resonators, so that the coupling capability among the resonators can be enhanced, and the size of the filter is saved. Meanwhile, parameters such as an input port and an output port are accurately designed, so that the 5G frequency band cavity filter has a good standing-wave ratio (SWR), extremely high out-of-band rejection capability and extremely low in-band Insertion Loss (IL), the problems that 5G system communication is easily interfered by the outside world and communication speed is unstable can be solved, the experience of a 5G user on a wireless network can be improved, and the popularization and construction of the 5G system network can be promoted. The cavity 107 is a metal cavity, and a common metal CNC machining mode is adopted, so that the machining cost of the metal cavity is reduced. The finally designed 5G frequency band cavity filter is small in size and only 9mm multiplied by 50mm multiplied by 10 mm.

In this embodiment, the input signal power is up to 100W, so the resonators are designed to have higher power-bearing capability and smaller volume, wherein the calculation of the resonance frequency generated by each resonator can be obtained by solving the nonlinear equation thereof using an equivalent circuit, specifically, the single-cavity model shown in fig. 2(a) can be equivalent to the S matrix network of fig. 2(b), and ideal conductive walls (PECs) are placed at the positions divided into d1 and d2 according to the reference plane (cavity) on both sides of the metal resonance cylinder, and the S matrix [ SP 1 and d2 ] of the metal round rod is formed by placing the S matrix [ SP matrix of the metal round rod ]]Cascaded with rectangular waveguides with length d1 and d2 at both ends to obtain an equivalent S matrix [ St]And solving a corresponding nonlinear equation by adopting PEC terminal conditions at two ends of the cavity to obtain the resonant frequency of the single cavity. The resonant frequency of the metal resonator can be adjusted by loading a capacitor, and the resonant frequency can be dynamically changed, so that the resonator designed based on the same design scheme can be adjusted in resonant frequency and used in different filtering frequency bands. The Q value of the resonator can be changed to a certain extent through the height of the upper semi-cylinder of the resonator, the Q value of the resonator can be influenced after the resonator is added into the external cavity, and the Q value can be adjusted through properly adjusting the structure and the size of the external cavity. Because the equation calculation is complex, the resonant frequency can be obtained by adopting a computer simulation mode. After the resonant frequency is calculated, the coupling coefficient between the resonators can be further calculated, wherein the calculation formula of the coupling coefficient is as follows:in the formula (f)₁Denotes the resonance frequency, f, of the resonator 1₂Denotes the resonance frequency of the resonator 2, and k denotes the coupling coefficient between the resonator 1 and the resonator 2. Of course, the resonator may be cylindrical, rectangular, or other shape; the resonant frequency of the resonator can be tuned by tuning a metal column or a dielectric column, a tuning device can be arranged on the upper semi-column or the lower semi-column, and the resonant frequency can be adjusted according to the requirements of an actual filter. Because the number of resonators is related to the out-of-band rejection and insertion loss of the 5G frequency band cavity filter, the number of metal cylindrical resonators arranged in the 5G frequency band cavity filter can be 5, 7 or any other number, but although the number of the metal cylindrical resonators is more, the out-of-band rejection of the 5G frequency band cavity filter is higher, the insertion loss of the 5G frequency band cavity filter is increased, the tuning difficulty is increased greatly, the speed is reduced, and the simulation also needs higher memory and CPU processing capacity. Therefore, the number of the cylindrical metal resonators is generally determined according to the design index of the cavity filter in the 5G frequency band, and the more the number of the cylindrical metal resonators, the better the number of the cylindrical metal resonators is.

Further, the resonator 105 is a metal resonator or a dielectric resonator, and the resonator 105 is cylindrical or cubic; the resonance frequency is determined by the diameter of the cylinder or the side length of the cube.

Referring to fig. 3, in the present embodiment, the resonator is made of a common aluminum material, the resonator is composed of an upper half portion and a lower half portion, a diameter (D1) of the upper half portion is smaller than a diameter (D2) of the lower half portion, a height (H1) of the upper half cylindrical shape and a height (H2) of the lower half cylindrical shape both have an influence on a resonance frequency and a Q value of the resonator, and specifically, referring to fig. 4, it can be seen from fig. 4 that the influence of the height (H1) of the upper half cylindrical shape on the resonance frequency of the main mode of the resonator is substantially linear; referring to fig. 5, it can be seen from fig. 5 that the influence of the height of the upper half cylinder (H1) on the Q value of the resonator main mode is substantially linear.

Specifically, in this embodiment, the basic parameters of the metal resonator are determined by the standing wave analysis, the basic dimensions of the metal resonator box cannot be designed to be 2.4mm in the upper half cylinder diameter (D), 10.6mm in the height (H), 3.5mm in the lower half cylinder diameter (D), and 2.5mm in the height (H), a parameter model of the metal resonator is put into HFSS simulation, so as to obtain the corresponding relationship between the resonant frequency and the Q value of a plurality of modes, a mode in which the resonant frequency is close to a 5G frequency band (3.5GHz) can be defined as a fundamental mode (a fundamental mode), a mode in which the resonant frequency is far greater than the fundamental mode is defined as a higher-order mode, the influence of the higher-order mode on the fundamental mode is small, and the Q value of the fundamental mode is 2804.

Further, a plurality of resonators 105 are coupled by spatial coupling.

In this embodiment, based on the coupling theory, the resonators and the resonators are coupled in a spatial direct coupling manner, so that the compactness of the resonators can be improved, the overall size of the filter can be reduced, but the debugging difficulty can be increased, in order to facilitate the debugging of the 5G frequency band cavity filter, the electromagnetic field distribution characteristics of the fundamental mode of the resonator can be analyzed, a model is established by using high-frequency electromagnetic field simulation software, and the electric field distribution of the fundamental mode is analyzed, for example, if the electric field distribution of the fundamental mode is analyzed from left to right, the electric field at the intersection of the upper and lower cylinders of the 1 st, 3 rd and 5 th resonators is strong, so that the 1 st, 3 th and 5 th resonators can be considered to be tuned in a.

Further, the cavity 107 is a metal rectangular cavity, and the length of the side of the cylinder or the cube does not exceed the width of the metal rectangular cavity.

In this embodiment, the cavity 107 is a metal cavity and is designed to be rectangular, and a common metal CNC machining method is used, so that the machining cost of the metal cavity can be reduced, and the finally designed cavity has a small volume of only 9mm × 52mm × 12 mm.

Further, the first tuning device and the second tuning device are metal screws or medium screws; the length of the metal screw or the medium screw is determined by the coupling coefficient; when the first tuning device and the second tuning device are dielectric screws, copper or silver is electroplated on the outer layers of the dielectric screws.

In this embodiment, the first tuning device of the 5G frequency band cavity filter is used to adjust the resonant frequency, and is a metal screw or a dielectric screw, and the length of the first tuning device is determined by the resonant frequency required by tuning, and may be a square structure or a cylindrical structure, and the diameter and the side length of the first tuning device may affect the resonant frequency, and the diameter and the side length of the first tuning device are determined by the size of the resonant frequency, but the diameter or the side length of the first tuning device cannot be greater than the wide side of the cavity of the 5G frequency band cavity filter; the second tuning device of the 5G frequency band cavity filter is used for adjusting a coupling coefficient between the resonators, is also a metal screw or a dielectric screw, and has a length determined by the coupling coefficient required for tuning, which can be a square structure or a cylindrical structure, and the diameter and the side length of the second tuning device influence the coupling strength, and the diameter and the side length of the second tuning device are determined by the size of the coupling coefficient, but cannot be larger than the wide side of the cavity of the 5G frequency band cavity filter. The number of the second tuning devices can be 1 or more, the second tuning devices can be applied to the outside of the cavity filter of the 5G frequency band and can also be applied to the inside of the cavity, and the tuning quantity can be set according to the requirement of the actual filter; the second tuning device may be disposed between adjacent resonators, between the input coupling device and the adjacent resonators, or between the output coupling device and the adjacent resonators, the adjustment of the coupling coefficient refers to the theoretically calculated coupling coefficient, and refers to the index parameter of the actual filter, the second tuning device may be a metal small cylinder, or a non-metal small cylinder, and the second tuning device may be mounted on the top surface of the 5G frequency band cavity filter, or on the bottom surface of the 5G frequency band cavity filter.

In this embodiment, the finally designed 5G frequency band cavity filter has a center frequency of 3.45GHz, a bandwidth of 100MHz, a return loss greater than 28.9dB (a general index of 12dB), an insertion loss less than 0.24dB (a general index of 1dB), a standing-wave ratio less than 1.07 (a general index of 1.6), an attenuation of 46dB of out-of-band 20MHz (3.20GHz), and a volume of 9mm × 52mm × 12 mm; the 5G frequency band cavity filter designed by the embodiment has strong out-of-band rejection capability, the overall performance is far superior to that of the similar filter, the anti-interference performance of the system can be improved, and the reliability of the system can be improved.

The 5G frequency band cavity filter provided by the embodiment of the invention has the following technical effects:

the 5G frequency band cavity filter provided by the embodiment of the invention provides good signal selection for a radio frequency part of a 5G system, can solve the problems that the 5G communication system is easily interfered by the outside and the communication speed is unstable, can improve the communication distance and the communication capacity of the 5G system, improves the communication quality, improves the experience of a 5G system user on a wireless network, promotes the popularization and construction of the 5G system network, and promotes the development of the communication industry.

Referring to fig. 6, an embodiment of the present invention provides a design method of a 5G frequency band cavity filter, including but not limited to the following steps:

s1, determining a first design index of the 5G frequency band cavity filter, wherein the design index comprises the bandwidth, in-band insertion loss, in-band return loss, standing-wave ratio, order, transmission function and overall structure of the 5G frequency band cavity filter;

s2, according to the first design index, obtaining a first numerical value by solving a Chebyshev function, wherein the first numerical value is a normalized element value of each circuit element of a Chebyshev function type low-pass prototype;

s3, obtaining a coupling coefficient between adjacent resonators and an external quality factor of the 5G frequency band cavity filter according to the first numerical value and the relative bandwidth of the 5G frequency band cavity filter;

s4, determining a second design index of the resonator, wherein the second design index comprises the material, the shape and the size and the resonant frequency of the resonator;

s5, determining the distance between the resonators according to the coupling coefficient between the adjacent resonators;

s6, according to the first design index, the second design index and the number of the resonators, simulating through advanced radio frequency simulation software to obtain a preliminary simulation result;

and S7, fine adjustment and optimization are carried out on the preliminary simulation result to obtain the 5G frequency band cavity filter.

Further, step S1 is to determine a first design index of the cavity filter in the 5G frequency band, specifically:

s101, setting the frequency width of the 5G frequency band cavity filter to be a 5G frequency band, wherein the in-band insertion loss is not more than 0.8dB, the in-band return loss is more than 25dB, and the standing-wave ratio is not more than 1.25;

s102, determining the order and the transmission function of the 5G frequency band cavity filter;

s103, determining that the integral structure of the 5G frequency band cavity filter comprises an input port, an output port, an input coupling device, an output coupling device, a plurality of resonators, a plurality of tuning devices and a cavity; the input port is connected with the input coupling device, the output port is connected with the output coupling device, and the plurality of resonators and the plurality of tuning devices are arranged in the cavity; the input port is used for receiving an original signal; the output port is used for outputting signals processed by a plurality of resonators; the input coupling device is used for controlling the coupling between the input port and a first resonator, and the first resonator is a resonator adjacent to the input port; the output coupling device is used for controlling the coupling between the output port and a second resonator, and the second resonator is a resonator adjacent to the output port; the resonators are used for controlling signals in a 5G frequency band in the original signals to pass; the first tuning device is used for adjusting the resonant frequency generated by the resonator to be within a 5G frequency band, and the first tuning device is one of the plurality of tuning devices; the second tuning device is used for adjusting the coupling coefficient between the resonators, and the second tuning device is one of the plurality of tuning devices.

Further, the expression of the transfer function described in step S102 is:

wherein, | S₂₁(Ω) | represents the power transmission coefficient of the signal input from the input port of the 5G frequency band cavity filter and output from the output port, IL (Ω) represents the transmission function, and Ω represents the normalized angular frequency.

Further, the power transmission coefficient | S of the signal input from the input port and output from the output port of the 5G frequency band cavity filter₂₁(Ω) | is obtained by a first formula:where ε is the ripple coefficient in the passband of the 5G band cavity filter, T_n(Ω) is the Chebyshev function; wherein:

in the formula, L_ArThe maximum in-band insertion loss of the cavity filter is 5G;

in the formula, n represents the order of the cavity filter of the 5G frequency band.

Further, the coupling coefficient between the adjacent resonators in step S3 is calculated by the following formula:

in the formula, FBW represents the relative bandwidth of the 5G frequency band cavity filter, K_i，i+1Denotes the coupling coefficient between adjacent resonators, g_iAnd g_i+1Respectively representing normalized element values of circuit elements of the Chebyshev function type low-pass prototype;

in step S3, the external quality factor of the 5G band cavity filter is calculated by the following formula:

in the formula, Q_eRepresents the external quality factor, G, of the 5G frequency band cavity filter₀Is 1, g₁A normalized element value representing the 1 st element of the chebyshev function type low-pass prototype circuit;

wherein the content of the first and second substances,in the formula (f)₂Represents the lower cut-off frequency, f₁Denotes the upper cut-off frequency, f₀Representing the center frequency.

Specifically, in this embodiment, after the design index of the filter is determined, the coupling topology of the filter is selected, and the calculation of the corresponding design parameter is a critical step. An example of the present design employs a CQ coupling topology. The calculation of the design parameters firstly needs to solve the filter transfer function

In the above formula, | S₂₁(omega) I represents the power transmission coefficient of the signal input from the 1 port and output from the 2 port of the filter, epsilon is the ripple coefficient in the filter passband, T_n(Ω) is the Chebyshev function, defined as:

(2) in the formula, L_ArN represents the order of the filter for the maximum insertion loss in the band, and Ω is the normalized angular frequency in the formulae (1) and (3). And in combination with the in-band maximum insertion loss, we can obtain:

according to the formulas (1) to (4), the filter passband cutoff frequency omega is given_cInsertion loss L at 1_ArWith outer omega_sStop band suppression loss L of_AsWith equal parameters, the low-pass prototype of the Chebyshev function type shown in FIG. 7 can be obtainedNormalized element value g of_iThe normalized element value is processed by impedance conversion, frequency conversion and the like and then corresponds to the designed filter parameter. That is to say, the 5G frequency band cavity filter preliminarily designs and determines indexes such as out-of-band rejection level, order and overall structure of the filter through theoretical calculation, and obtains the normalized element G of each circuit element parameter of the low-pass prototype by solving the Chebyshev function_iValue and using a formula

In the above formulas (5) and (6), FBW is the relative bandwidth of the filter, and the expression is

(5) In the formula (7), K_i，i+1Representing the coupling coefficient, Q, between adjacent resonators_eRepresenting the external quality factor of the filter. Calculating the corresponding coupling coefficient K_i，i+1And Q_eAfter the value (loaded Q value), the theoretical value is simulated through high-level radio frequency simulation software ADS to obtain a preliminary simulation result, and the preliminary simulation result is subjected to fine tuning and optimization to enable the simulation result to be far superior to an expected index. And then designing a metal resonator which is easy to process and has a high no-load Q value, carrying out comprehensive simulation by using HFSS (high frequency distortion) electromagnetic simulation software, carrying out a large amount of simulation optimization to obtain a final optimized simulation result, actually manufacturing, carrying out processing test, modifying the size, and continuing to test and verify to obtain the final 5G frequency band cavity filter.

The design method of the 5G frequency band cavity filter provided by the embodiment of the invention has the following technical effects:

the design method of the 5G frequency band cavity filter adopts a mode of combining calculation and simulation, does not use the traditional mode of scanning parameters or optimally determining the parameters, accurately determines the coupling between each resonator by utilizing the relation between the coupling coefficient and each tuning device, and finally utilizes the HFSS (high frequency synchronous system) comprehensive simulation of electromagnetic field simulation software to optimize the design target and greatly save the design time of the 5G frequency band cavity filter.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.