Coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling

Abstract

The utility model discloses a coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling, which comprises an external rectangular conductor cavity, and three or more coaxial resonators are arranged in the cavity; the top of the cavity is sealed by a conductor cover plate, a rectangular cavity conductor shell is provided with a through hole, the bottoms of the three or more coaxial conductor resonators are fixed in the rectangular cavity conductor shell and are in contact with the bottoms to form a short circuit, and the coaxial conductor resonators are mainly formed by bending a traditional coaxial line by 90 degrees to obtain a more compact structure; through flexible matching and combination, electric coupling, magnetic coupling and electromagnetic hybrid coupling can be achieved, meanwhile, no extra circuit control structure is needed for achieving corresponding coupling, and corresponding coupling can be achieved only by moving the distance between the resonators and designing the rotating angle of the bent resonance branch knots. According to the coaxial quasi-elliptical filter, different zero points can be generated by main coupling and cross coupling, the frequency selectivity can be improved, and the coaxial quasi-elliptical filter can be effectively designed.

Description

Technical Field

[0001] The utility model relates to the technical field of radio frequency devices, and in particular to a filter and a duplexer for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling between resonators, and more precisely, to a coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling. Background Art

[0002] Wireless communication systems are developing rapidly, and filters at the RF front end play an important role in wireless communication systems. Among them, cavities, dielectrics, coaxial resonators have high Q values ​​and are widely used in the design of various filters. At present, in order to improve the integration, selectivity and low cost of the system, higher requirements are put forward for the miniaturization design of bandpass filters for wireless communication systems. One of the miniaturization design methods of bandpass filters is to use dual-mode and multi-mode cavities or folded waveguides, and excite different TM modes and TE degenerate modes through different feeding to reduce the number of cavities, while ensuring a certain number of resonances, and introduce transmission zeros to improve the selectivity of the filter. The use of high-dielectric material resonators can also reduce the size of the bandpass filter, and can have a very high Q value, while maintaining good performance in terms of loss and thermal stability. Another method of miniaturizing metal cavities is to use metal pillars, which are common in combline filters. While reducing the size of the resonator, it excites the TEM mode, which also leads to a decrease in the Q value. Mushroom-shaped and conical metal pillars increase the capacitive load while reducing the size and improving the spurious-free frequency band. Coaxial cavity bandpass has the characteristics of high Q value, low insertion loss, high out-of-band suppression and easy implementation, and is often used in communication base station systems. Usually the coupling between resonators is achieved using coupling windows or screws, and the position and size of the aperture are adjusted to obtain the desired coupling effect, or it is achieved by a rectangular diaphragm, and the corresponding coupling is achieved by changing the position and size of the iris. In addition, if it is necessary to strengthen specific coupling, such as electrical coupling, a coupling probe can be used, which also increases the complexity of the structure (A.S. Rong, H. Yang, X.H. Chen and A. Cangellaris, "Efficient FDTD Modeling of Iris / Slots in Microwave Structures and Their Application in Combline Filter Design", IEEE Trans. Microwave. Theoretical Techniques, Vol. 49, No. 12, pp. 2266-2275□, December 2001.). If it is necessary to enhance the selectivity of the bandpass filter, the resonator can also be folded to achieve cross-coupling of non-adjacent resonators and generate transmission zeros. Transmission zeros can also be achieved by changing the direction of the resonator in the cavity straight structure to obtain non-adjacent coupling, and the coupling is controlled by a small metal plate. At the same time, hybrid coupling can also generate transmission zeros between adjacent resonators. Controlling the hybrid coupling to generate zeros by adding additional coupling metal rods and conductor strips also requires additional circuit structure control (H. Wang and Q.-X. Chu, "Inline coaxial quasi-elliptical filter with controllable hybrid electromagnetic coupling", IEEE Trans. Microwave. Theoretical Techniques, Vol. 57, No. 3, pp. 667-673□, March 2009), the design is relatively complex, and it is also easy to reduce the Q value of the designed filter.

[0003] In existing cavity filters, the coupling between adjacent or non-adjacent resonators is almost always controlled by additional circuit structures, including electric coupling, magnetic coupling, and electromagnetic hybrid coupling. Therefore, it is of great significance to study and design a coaxial resonator that can flexibly realize electric coupling, magnetic coupling, and electromagnetic hybrid coupling without the need for external circuit structures to control. Utility Model Content

[0004] The utility model aims to provide a coaxial resonator, which realizes electric coupling, magnetic coupling and electromagnetic hybrid coupling between adjacent resonators through flexible combination, thereby effectively improving the frequency selection characteristics of filters and duplexers.

[0005] The purpose of the utility model can be achieved by adopting the following technical solutions:

[0006] A coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling, comprising a cavity and two coaxial feeding structures, wherein the cavity contains at least two bent coaxial resonators, and the top of the cavity is sealed by a conductor cover plate;

[0007] The bent coaxial resonator comprises a first conductor resonator and a second conductor resonator, wherein one end of the first conductor resonator is short-circuited and located at the bottom of the cavity, and the other end is connected to the second conductor resonator; coupling is controlled by adjusting the distance between the bent coaxial resonators and the angle between the second conductor resonator and the first conductor resonator;

[0008] The two coaxial feeding structures are arranged in the cavity.

[0009] Preferably, one end of the second conductor resonator is connected to the first conductor resonator, and the other end is connected to the branch conductor resonator, and one end of the branch conductor resonator is open.

[0010] Preferably, the length of the resonator is less than a quarter wavelength of the operating frequency.

[0011] Preferably, the cavity and the conductor resonator are subjected to a conductive treatment of electroplating on the outer surface after 3D resin printing.

[0012] Preferably, the multiple bent coaxial resonators in the cavity are arranged and combined according to requirements to achieve corresponding zero point positions.

[0013] Preferably, the cavity and the conductor resonator are integrally formed by 3D resin printing.

[0014] Preferably, the coaxial feeding structure is a coaxial probe.

[0015] Preferably, the coaxial feeding structure is parallel to the first conductor resonator.

[0016] Preferably, the two coaxial feeding structures are symmetrically placed with the central axis of the overall structure as the symmetry line, and are parallel to the second conductor resonator.

[0017] Preferably, the angle between the second conductor resonator and the branch conductor resonator is 90° to form a Γ shape.

[0018] The utility model proposes a novel coaxial resonator, and can realize electric coupling, magnetic coupling and electromagnetic hybrid coupling between adjacent resonators through flexible combination, has a simple structure, and can well improve the selectivity and out-of-band suppression performance of the filter.

[0019] Compared with the prior art, the utility model has the following advantages:

[0020] 1. Compared with the traditional coaxial structure, the coaxial resonator structure designed by the utility model is more compact, and can be flexibly combined to realize electric coupling, magnetic coupling and electromagnetic hybrid coupling. Compared with the ordinary Chebyshev response of the traditional coaxial filter, the utility model can achieve better quasi-elliptical filtering response, and the structure is more compact. Compared with the traditional coaxial structure, it can reduce a lot of volume and save costs better.

[0021] 2. The coaxial resonator proposed by the utility model does not need to add a coupling window or other circuit structure for the realization of coupling. The control of coupling only needs to be regulated by distance. The hybrid coupling can also be controlled by the branch angle regulation, and the corresponding zero point is generated at the same time. The third-order structure can generate a zero point through cross coupling, while the hybrid coupling can generate two zero points. At the same time, the zero point position can be better controlled, the frequency selectivity can be better improved, and the structure is simpler.

[0022] 3. The utility model has the advantages of simple and compact structure, easy production, strong practicality, high selectivity and good out-of-band suppression performance, and can well meet the requirements of modern communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic front view of the coaxial resonator structure of an embodiment of the utility model;

[0024] Figure 2 is a schematic diagram of the structure and dimensions of a bent coaxial resonator in an embodiment;

[0025] Figure 3 is an electric field distribution diagram of a bent coaxial resonator of an embodiment;

[0026] Figure 4 is a magnetic field distribution diagram of a bent coaxial resonator of an embodiment;

[0027] Figure 5 is a graph showing the relationship between the resonant frequency of the bent coaxial resonator and the branch conductor resonator and its different radii in the embodiment;

[0028] Figure 6 is a graph showing the relationship between the no-load quality factor of the resonator of the embodiment and the displacement of the resonator from the cavity;

[0029] Figure 7 is a diagram showing the relationship between the simulated external quality factor and the feeding probe and the bent coaxial resonator according to an embodiment;

[0030] Figure 8 are examples of electrical and magnetic coupling coefficients with L 12 Function diagram of ;

[0031] Figure 9a is a diagram of an electrical cross-coupling structure of a bent coaxial resonator according to an embodiment;

[0032] Figure 9b is a diagram of a magnetic cross-coupling structure of a bent coaxial resonator according to an embodiment;

[0033] Fig.10 is the electric and magnetic cross coupling coefficient of different L3 as L 13 The relationship diagram of the function change;

[0034] Fig.11 It is the coupled topology diagram of a TZ passband above a three-pole fifth-order bandpass filter;

[0035] Fig.12 It is a diagram of a TZ passband structure above a three-pole fifth-order bandpass filter;

[0036] Fig.13 It is a graph of the changing relationship between the simulated coupling matrix and the simulated EM;

[0037] Fig.14 It is the coupled topology diagram of a TZ passband below the three-pole fifth-order bandpass filter;

[0038] Fig.15 It is a structural diagram of a TZ passband below a three-pole fifth-order bandpass filter;

[0039] Fig.16 It is a comprehensive analysis diagram of simulated S parameter response and coupling matrix;

[0040] Fig.17 It is the model diagram of CCR filter;

[0041] Fig.18 It is the simulated S-parameter analysis diagram of CCR filter and bent coaxial resonator filter;

[0042] Fig.19 It is the structural diagram of the fifth-order filter;

[0043] Fig. 20 It is the coupling topology diagram of the fifth-order filter;

[0044] Fig.21 This is the final simulation result diagram of the fifth-order filter;

[0045] Fig. 22 It is a structural diagram of a duplexer;

[0046] Fig.23 is the coupling topology diagram of the duplexer;

[0047] Fig.24 This is the result of the optimization simulation of the duplexer using the coupling matrix;

[0048] Fig.25 It is a schematic diagram of a third-order cross-coupling filter realized by the electric coupling structure of the utility model;

[0049] Fig.26 This is a schematic diagram of a third-order cross-coupling filter realized by the magnetic coupling structure of the utility model;

[0050] Fig. 27 It corresponds to Fig.25 The simulated S-parameter diagram shows that the low-stop band has one more transmission zero than the traditional filter.

[0051] Fig.28 It corresponds to Fig.26 The simulated S-parameter diagram shows that the high-stop band has one more transmission zero than the traditional filter.

[0052] In the figure: 1. electroplating layer; 2. rectangular cavity; 3. coaxial feeding structure; 4. first conductor resonator; 5. second conductor resonator; 6. branch conductor resonator; 7. conductor cover plate. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the utility model clearer and more specific, the utility model is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0054] like Figure 1 As shown, the embodiment of the utility model provides a coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling, including a cavity 2 and a coaxial feeding structure, wherein the cavity 2 contains at least two or more bent coaxial resonators; the top of the cavity 2 is sealed by a conductor cover plate 7, which is fixedly connected by screws;

[0055] The bent coaxial resonator includes a first conductor resonator 4 and a second conductor resonator 5. One end of the first conductor resonator 4 is short-circuited and located at the bottom of the cavity 2, connected to the outside of the cavity 2 and placed on the ground to provide structural support, and the other end is connected to the second conductor resonator 5. The coupling is controlled by adjusting the distance between the bent coaxial resonators and the angle between the second conductor resonator 5 and the first conductor resonator 4. In order to verify the working mode of the resonator, as shown in FIG. Figure 3 The front and side views shown, Figure 4 As shown in the front view and top view, the electric field is strongest at the bent open end, while the magnetic field is strongest at the short end, and gradually weakens from the short end to the open end. The electromagnetic field distribution of the bent coaxial resonator is crucial to guiding the flexible combination of subsequent resonators to achieve controlled electric and magnetic coupling.

[0056] The control of electromagnetic hybrid coupling can also be controlled in the following manner: one end of the branch conductor resonator 6 is connected to the other end of the second conductor resonator 5, and the other end of the branch conductor resonator 6 is open, and the adjustment of the resonant frequency of the bent coaxial resonator is controlled by the angle between the branch conductor resonator 6 and the second conductor resonator 5. The branch conductor resonator 6 can be flexibly positioned at any part of the second conductor resonator 5, thereby providing versatility in achieving coupling between the two resonators. The resonant frequency can also be adjusted by adjusting the length of the branch conductor resonator 6.

[0057] Since the resonator arrangement is simpler in the hybrid coupling and the branch conductor resonator 6 is removed, the control of the electromagnetic hybrid coupling is controlled by the distance between the resonators and the bending angle of the second conductor resonator 5 to adjust the coupling.

[0058] Specifically, Figure 2 As shown, the bent coaxial resonator is located in a rectangular cavity, the first conductor resonator 4 has a width of r1 and a length of h1; the second conductor resonator 5 has a width of r2 and a length of h2; the branch conductor resonator 6 has a width of r2 and a width of h3. The length, width and height of the rectangular cavity shell are a×b×c, and d represents the front-to-back distance movement of the first conductor resonator in the cavity. The length of the conductor resonator is generally less than a quarter wavelength of the operating frequency.

[0059] The resonance characteristics of the bent coaxial resonator (ΓSCR) are fully analyzed using the electromagnetic simulator CST Eigenmode Solver. Figure 5Plotting the variation of the resonant frequency of the ГSCR, it is observed that the resonant frequency varies with the height of the curved portion. Therefore, the selection of the optimal distance and length of the second conductor resonator 5 and the branch conductor resonator 6 in the ГSCR is crucial and directly affects the subsequent coupling between the resonators and the control of the resonant frequency. The curved structure of the ГSCR allows for more efficient coupling control without the intervention of external circuits. One of the main key factors of the filter is the no-load quality factor (Qu) of the resonator.

[0060] Therefore, it is necessary to analyze the relationship between Qu and various parameters, such as Figure 6 As shown in the figure, it can be seen that the displacement has a significant effect on Qu. The closer the resonator is to the cavity, the greater the loss, which affects Qu.

[0061] The resonator and the external cavity are mainly formed in one piece by 3D resin printing. After the cavity 2 and the resonator are 3D printed, the outer surface can be plated with copper / silver for conductive treatment to ensure that they have good conductivity, and finally the surface is electroplated with a plating layer 1. As a preferred embodiment, the resonator is cylindrical, or other shapes, for example, the cylindrical shape can be replaced with a rectangular shape, and a bent structure can also be made.

[0062] The entire structure of the utility model does not require additional tuning screws to increase the complex external circuit structure. The realization of electrical and magnetic coupling is mainly achieved through the flexible combination of resonators, and the control of the coupling is mainly controlled by distance. The closer the distance between the resonators, the greater the corresponding coupling strength, and the farther the relative distance, the weaker the coupling, or cross coupling is introduced between the resonators.

[0063] In addition, in cavity 2, multiple bent coaxial resonators can be arranged and combined as needed to achieve corresponding zero point positions. The utility model proposes a coaxial resonator, and can achieve electric coupling, magnetic coupling and electromagnetic hybrid coupling between adjacent resonators through flexible combination. It has a simple structure and can greatly improve the selectivity and out-of-band suppression performance of the filter. The coupling between adjacent resonators mainly involves electric coupling and magnetic coupling, both of which play a vital role in designing the passband response of the filter. The design adopts a bent coaxial resonator, which is convenient for flexible combination and can achieve electromagnetic coupling without additional circuits. This makes it different from traditional coaxial cavity coupling, which requires additional windows or the use of coupling probes. Figure 8 As shown, the strength of the electrical coupling is mainly concentrated at the open end of the bent coaxial resonator, which is opposite to the port, emphasizing that electrical coupling is the main mechanism. 12Precise control of electrical coupling can be achieved. At the same time, the magnetic coupling strength is mainly concentrated between the first conductor resonator 4 of the bent coaxial resonator. By the opposite arrangement, magnetic coupling is prioritized. Manipulating the spacing between the resonators can effectively control the magnetic coupling. In order to effectively demonstrate the effect of the moving distance on the coupling between the bent coaxial resonators. The coupling coefficient k can be obtained by the following equation:

[0064]

[0065] Among them, f 01 and f 02 They represent the self-resonant frequencies of two adjacent resonators under weak coupling conditions. p1 and f p2 Represents the two shunt resonator frequencies when the two resonators are coupled to each other.

[0066] Figure 8 The coupling coefficients of electric coupling and magnetic coupling are shown as a function of the distance L between the two resonators. 12 It further studies the effect of different displacement distances on different coupling coefficients. The results show that as the distance between adjacent resonators decreases, the coupling coefficient increases and varies with the displacement distance. The overall design remains streamlined and easy to manage, without the need for additional circuitry to adjust for different coupling changes. This provides insightful guidance for subsequent design work.

[0067] In filter design, introducing cross-coupling between non-adjacent resonators is a common method to flexibly generate transmission zeros TZ to improve selectivity. In this design, cross-coupling between non-adjacent bent coaxial resonators is easier to achieve than cross-coupling of traditional coaxial resonators. Cross-coupling can be divided into electrical cross-coupling and magnetic cross-coupling. The flexible combination of bent coaxial resonators allows for flexible design of TZ. Figure 9a As shown in the figure, the electrical cross coupling can control the coupling strength by adjusting the distance. 13 The L represents the distance between non-adjacent resonators, and L3 represents the distance between the middle resonator and the front and back resonators. Compared with the traditional method that requires an open-circuit probe, the simplicity of this design avoids the introduction of additional circuits. Figure 9b The proposed method is magnetic cross-coupling, which allows flexible control of coupling strength through distance adjustment. This method provides a more convenient implementation compared to traditional magnetic cross-coupling, which involves complex operations such as adding coupling windows, tuning screws, or short-circuiting metal wires.

[0068] By adjusting the polarity and strength of the cross-coupling, the position of the TZ can be precisely controlled. The cross-coupling coefficient can be obtained using the Y parameter extraction method and can be expressed as:

[0069]

[0070]

[0071]

[0072] Where M ii (f) is the normalized self-coupling parameter of the i-th resonator, M ij (f) is the normalized mutual coupling parameter of the i and j resonators, B i (f) is the input admittance Y extracted from port i ii The imaginary part, B ij (f) is the mutual admittance Y extracted from port i and j i,j The imaginary part, b i (f) is calculated by formula (3), where f is the frequency point of the sweep, f0 is the center frequency, Δf is the bandwidth, and C i is the equivalent capacitance.

[0073] Fig.10 The variation of the electric and magnetic cross-coupling coefficients as a function of L13 as the distance of the middle resonator moving back and forth can provide further understanding of how distance affects the coupling coefficient. It is worth noting that as the distance increases, both the electric and magnetic coupling coefficients gradually decrease, indicating a weakening of the coupling.

[0074] In filter design, TZ is mainly used to guide the design of filter coupling topology. Usually, the introduction of cross-coupling is a necessary step to generate TZ, which depends on incorporating additional coupling channels into the main coupling channel. To create TZ, at least two different signal transmission channels are generally required. When the two signal channels on these two channels have a phase difference of 180 degrees, that is, when the two signals are combined, TZ can be generated in the following cases: the amplitudes of the signals are equal at a specific frequency point of view. When the electrical cross-coupling is dominant, TZ will appear below the passband; when the magnetic cross-coupling is dominant, the transmission zero point appears above the passband, leveraging the coupling characteristics of the proposed bent coaxial resonator.

[0075] The advantages of the bent coaxial resonator of the present invention are illustrated below by designing and manufacturing a classic CT topology fifth-order filter and a third-order duplexer.

[0076] 1. One TZ above the passband.

[0077] Initially, a three-pole fifth-order bandpass filter (BPF) was designed with a center frequency of 1.03 GHz, a bandwidth span of 46.2 MHz, a fractional bandwidth of 4.66%, a return loss of 20 dB, and a TZ frequency of 1.08 GHz. The structure of the filter adopts a CT topology, such as Fig.11The coupled topology shown in the figure, where S / L represents the input and output ports, each node represents a resonator, and m 12 、m 23 、m 13 Respectively represent the coupling coefficient between resonators 1 and 2, the coupling coefficient between 2 and 3, and the coupling coefficient between 1 and 3, and MC(+) represents magnetic cross coupling. The solid line represents direct coupling, and the dashed line represents cross positive coupling, which is mainly magnetic in nature. This arrangement is conducive to generating one side of the TZ passband on the slope. The normalized coupling matrix filter is given as shown in the following equation (1):

[0078]

[0079] Where M1 represents the coupling matrix of the third-order bandpass filter with a high-frequency zero. Based on the coupling characteristics between the bent coaxial resonators, the structure of the three-pole BPF is as follows Fig.12 As shown in (a) and (b), m S1 represents the coupling between port 1 and resonator 1, m L3 Indicates the coupling between port 2 and resonator 3. The dimensions (mm) in the figure are: h1 = 33.9, h 12 =19.5,h 13 =14.5,h 22 =27.5,h 23 =22.3,h p =1.1,h w =31.3, h0=32.4, r1=3, r2=2.5, t=22.4, a=108, b=53.6, c=42, l1=16.1, l2=6.2, l3=3.6, l 12 =22.8,l 23 =22.8.

[0080] The input (node ​​S) and output (node ​​L) of the BPF are realized by feeding with metal probes, and the external coupling is adjusted by modifying the distance between the metal probe and the resonator. The analysis described earlier indicates that the three mutual resonant coupling coefficients, m12, m13, and m23 can be individually controlled by adjusting the moving distance. Following the design analysis described above, all the dimensions of the BPF have been determined, Fig.13Comparison between the simulated coupling matrix and the simulated EM response of the three-pole BPF with TZ located on the upper side of the passband. S11 refers to the reflection coefficient parameter, which indicates the part of the signal input from port 1 that is reflected back. In the filter, S11 is used to measure the reflection loss or matching performance of the filter's input port. S21 refers to the transfer coefficient parameter, which indicates the part of the signal input from port 1 that is transmitted to port 2. In the filter, S21 is used to measure the transmission loss or transmission characteristics of the filter. Comprehensive analysis method based on the coupling matrix. It can be seen that the two methods fit well, and the center frequency, passband bandwidth, return loss and transmission zero meet the design indicators.

[0081] 2. One TZ below the passband

[0082] The filter is designed as a three-pole bandpass filter with a center frequency of 1.03GHz and a bandwidth of 54MHz. It achieves a maximum passband return loss of 20.0dB, a TZ frequency of 0.99GHz, and a coupled topology BPF with enhanced frequency selectivity such as Fig.14 As shown in the structure diagram Fig.15 As shown in (a) and (b), the dimensions (mm) in the figure are: h1 = 33.9, h 12 =25.8,h 13 =18.9,h 22 =20.5,h 23 =22.3,h p =1.63,h w =36.8, h0=32.9, r1=3, r2=2.5, t=33.4, a=100, b=52.1, c=42, l1=9.6, l2=10.4, l3=6.8, l 12 =47,l 13 =21.6. The cross coupling is negative, mainly electrical coupling in nature, resulting in a lower passband. The normalized coupling matrix is ​​shown in equation (2):

[0083]

[0084] Where M2 represents the coupling matrix of the third-order bandpass filter with a low-frequency zero. From the comparison of the coupling matrix formulas (1) and (2), it can be seen that the main difference between them is the change in the sign of the coupling coefficient m13 from positive to negative, which is due to the polarity of the cross-coupling. The flexible adjustment of the polarity change of the cross-coupling is achieved through the combination of resonators. The determination of the geometric parameters of the three-pole BPF is based on the coupling matrix formula, which is consistent with formula (7). Fig.16 The comparison of the simulated S-parameter response (solid line) and the coupled matrix synthesis analysis method (dashed line) is shown. It can be seen from the figure that the simulated response and the synthesis analysis response are very consistent.

[0085] The above demonstrates that multiple cascaded triplets (CTs) on a bent coaxial resonator can be flexibly designed to achieve high-order BPFs with both high and low-frequency TZ filter designs using a coupling scheme.

[0086] 3. TZ on both sides of the five-pole BPF

[0087] like Fig.17 As shown in (a) and (b), the dimensions (mm) in the figure are: h1 = 34, h 12 =20.9,h 13 =15.8,h 22 =26.8,h 21 =23.9,h p =1.63,h 31 =16.2,h 32 =26.6, t1=28.1, t2=32, h 41 =18.8,h 42 =22.7,h 51 =22.4,h 52 =22,h w =14.9, h0==33.1, a=197, b=62.6, c=42, l 10 =15.6,l 11 =14.1,l 20 =7.1,l 21 =26.9,l 23 =34.6, l 35 =24.9,l 40 =12.9,l 44 =48.1,l 50 =13, the bandwidth of the fifth-order filter with a center frequency of 1.03 GHz is 41.3 MHz. A pair of TZs are located at 1.00 GHz and 1.06 GHz respectively. Fig.18 For the corresponding topology, a common resonator is shared to form a pair of triplets, each of which generates a passband with a high and low frequency zero point below and above. Two CTs (Cascade Triplet) are designed using the above, and the fifth-order normalized target coupling matrix BPF is given as follows:

[0088]

[0089] Where M3 represents the coupling matrix of the fifth-order bandpass filter with high and low frequency zeros. The simulation result BPF of the final design of the fifth-order filter is as follows Fig.19 As shown, it shows excellent agreement with the calculated coupling matrix, and the two controllable transmission zeros at 1.00 GHz and 1.06 GHz indicate good filtering performance.

[0090] 4. Duplexer design

[0091] Duplexers are often used in wireless communication systems. They not only provide frequency selective filtering functions with the functions of single-channel filters, but also have frequency division functions. Therefore, the effectiveness of evaluating a duplexer mainly depends on the loss and isolation inserted into its two passbands. In combination with the above, a CT-type duplexer constructed using a bent coaxial resonator is provided. In the design of this duplexer, the key lies in the selection of a frequency distribution network, which is usually divided into a T-junction and a star-junction structure. In this embodiment, the duplexer is as follows: Fig. 20 The structure shown in (a) and (b) has the following dimensions (mm): h1 = 34, h 12 =23.3,h 13 =26.3,h 22 =22.4,h 21 =21.3,h p1 =1.63,h p2 =1.7,h 31 =21.8,h 32 =25, t1=33.1, t2=22, t3=23.3, t4=45, h 41 =24.8,h 42 =28.5,h 51 =23.8,h 52 =30.5,h 61 =19.2,h 62 =23.5,h w =41.3, h0=33.1, ht=33.1, h0=144.4, a=257, b=62.6, c=52, l 11 =15.1,l 10 =6.6, l 13 =35.7,l 20 =50.5,l 22 =9.1,l 34 =23.5,l 45 =30, l 50 =70, l 56 =30, l 60 =13.

[0092] The frequency division structure of the duplexer adopts a coaxial T-shaped branch structure. The return loss unit of the duplexer can be further improved by its length. The branch structure parameters can be achieved through careful optimization, including the length of the branch structure, the input coupling to the high-frequency and low-frequency filters, and the corresponding resonator frequency. The specific topology of the design is as follows Fig.21As shown. In this structure, as analyzed in the previous section, the coupling between resonators is controlled by distance. The coupling of each port is controlled by adjusting the length of the probe and the height of the horizontal resonator. For example, the design of this duplexer is as follows:

[0093] The lower frequency band is 0.90-0.96GHz, and the higher frequency band is 1.00-1.07GHz. The return loss of the two passbands is less than 20dB. The isolation between the two bands is greater than 43Db.

[0094] Based on the above, the normalized coupling matrix can be calculated as follows:

[0095]

[0096] Wherein M4 represents the coupling matrix of the duplexer.

[0097] Based on the coupling relationship described above, the initial value of the duplexer can be obtained through the previous analysis, and the coupling matrix is ​​further used to optimize the simulation results, such as Fig. 22 As shown, there is very good agreement between the two, and the results of the above equation are observed through coupling matrix simulation and ideal S-parameter response, which once again well verifies the proposed structure and design process of the duplexer.

[0098] The performance of a fifth-order bandpass filter (BPF) duplexer was verified using 3D printing technology based on stereolithography (SLA) and the application of metal plating on the surface of the printed object. The samples were plated with silver / copper treatment. Each sample consists of two parts: the bent coaxial resonator and the base plate are printed as a unit, and the other is the filter cover. The two parts are assembled and fixed together using screws. SMA connectors are installed on the BPF and coaxial duplexer as input and output connections. Although CNC machining can also be adopted, this requires dividing the design into separate parts, resulting in increased manufacturing time and cost. In contrast, the use of 3D printing technology has proven to be more cost-effective.

[0099] The coaxial feeding structure includes two coaxial probes 3, which can be used to connect an external input / output device; the two coaxial probes 3 are located on the inner walls of both sides of the cavity 2 for coupling feeding.

[0100] The coaxial probe 3 can be parallel to the second conductor resonator 5 and symmetrically placed with the central axis of the overall structure as the symmetry line.

[0101] In this embodiment, the feeding structure of the bent coaxial resonator is as follows: Figure 7 As shown in the figure, the probe feeding method is used to achieve external port coupling (Qe). The calculation formula of the external quality factor (Qe) is: where ω0 and τ max is the reflection coefficient parameter |S 11The resonant frequency and maximum group delay of | are in the resonant state respectively. The coupling mechanism is mainly adjusted by adjusting the length of the probe and the distance from the gap to the resonator. Figure 7 The simulation in the extracts the relevant h p The effective control of the Qe value can be observed at different probe lengths t. Therefore, the external coupling of the fundamental mode can be effectively controlled by a reasonable configuration, and the distance h between the probe length and the resonator is selected. p A wide range of Qe can be obtained by different combinations of and.

[0102] Some embodiments of third-order bandpass filters are provided below. 11 | It is generally required to be less than -15dB, which is a normal standard. That is to say, the filter in the utility model can work normally within the passband frequency band under the condition of meeting the requirements, and has high selectivity and good out-of-band suppression performance.

[0103] Embodiment 1:

[0104] This embodiment designs a third-order bandpass filter, which can generate a low-frequency zero point through electrical cross-coupling, such as Fig.23 As shown, the filter comprises three bent coaxial resonators and a coaxial feeding structure coupled in parallel with two left and right horizontal resonators (second conductor resonators 5). The two coaxial feeding structures are symmetrically placed with the central axis of the overall structure as the symmetry line.

[0105] like Fig.25 As shown in the S parameter response of the above structure, it can be seen that the filter is a third-order filter with a passband center frequency of 1.03 GHz. 11 |Less than -20dB, the lower resistance band has a transmission zero.

[0106] Embodiment 2:

[0107] This embodiment designs a third-order bandpass filter, which can generate a high-frequency zero point through magnetic cross coupling, such as Fig.24 As shown, the filter includes three bent coaxial resonators and a coaxial feeding structure coupled in parallel with two left and right horizontal resonators (second conductor resonators 5). The two coaxial feeding structures are symmetrically placed with the central axis of the overall structure as the symmetry line.

[0108] like Fig.26 As shown in the S parameter response of the above structure, it can be seen that the filter is a third-order filter with a passband center frequency of 1.03 GHz. 11 |Less than -20dB, there is a transmission zero in the upper stop band.

[0109] Embodiment three:

[0110] This embodiment designs a third-order bandpass filter, which can generate a high-frequency zero point and a low-frequency zero point by generating hybrid coupling through adjacent resonators, such as Fig. 27 As shown, the filter includes three bent coaxial resonators and a coaxial feeding structure coupled in parallel with two left and right vertical resonators (first conductor resonators 4), and the overall structure may be asymmetric.

[0111] like Fig.28 As shown in the S parameter response of the above structure, it can be seen that the filter is a third-order filter with a passband center frequency of 1.03 GHz. 11 | is less than -20dB, and the upper and lower stop bands each have a transmission zero point, and compared with the first and second embodiments, this embodiment has higher selectivity and better out-of-band suppression performance.

[0112] The preferred embodiments of the utility model disclosed above are only used to help explain the utility model. The preferred embodiments do not describe all the details in detail, nor do they limit the utility model to only the specific implementation methods described.

Claims

1. A coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling, characterized in that: comprising a cavity (2), Two coaxial feeding structures, the cavity (2) contains at least two bent coaxial resonators, and the top of the cavity (2) is sealed by a conductor cover plate (7); The bent coaxial resonator comprises a first conductor resonator (4) and a second conductor resonator (5); one end of the first conductor resonator (4) is short-circuited and located at the bottom of the cavity (2), and the other end is connected to the second conductor resonator (5); the coupling is controlled by adjusting the distance between the bent coaxial resonators and the angle between the second conductor resonator (5) and the first conductor resonator (4); The two coaxial feeding structures are arranged in the cavity (2).

2. The coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling according to claim 1, characterized in that: One end of the second conductor resonator (5) is connected to the first conductor resonator (4), and the other end is connected to the branch conductor resonator (6); one end of the branch conductor resonator (6) is open-circuited.

3. The coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling according to claim 1, characterized in that: The length of the resonator is less than one quarter wavelength of the operating frequency.

4. The coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling according to claim 1, characterized in that: The cavity (2) and the conductor resonator are subjected to a conductive treatment of electroplating on the outer surface after 3D resin printing.

5. The coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling according to claim 1, characterized in that: The multiple bent coaxial resonators in the cavity (2) are arranged and combined according to requirements to achieve corresponding zero point positions.

6. The coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling according to claim 1, characterized in that: The cavity (2) and the conductor resonator are integrally formed by 3D resin printing.

7. The coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling according to claim 1, characterized in that: The coaxial feeding structure is a coaxial probe (3).

8. The coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling according to claim 1, characterized in that: The coaxial feeding structure is parallel to the first conductor resonator (4).

9. The coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling according to claim 1, characterized in that: The two coaxial feeding structures are symmetrically placed with the central axis of the overall structure as the symmetry line and are connected to the second conductor resonator. (5)Parallel.

10. The coaxial resonator for realizing electric coupling, magnetic coupling and electromagnetic hybrid coupling according to any one of claims 2 to 9, characterized in that: The angle between the second conductor resonator (5) and the branch conductor resonator (6) is 90°, so as to form a Γ shape.

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