CN110034361B - Miniaturized ultra-wideband filtering power division feed network for 5G communication and design method thereof - Google Patents
Miniaturized ultra-wideband filtering power division feed network for 5G communication and design method thereof Download PDFInfo
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Abstract
The invention relates to a miniaturized ultra-wideband filtering power division feed network facing 5G communication and a design method thereof, and compared with the prior art, the miniaturized ultra-wideband filtering power division feed network overcomes the defect that the miniaturization, high bandwidth and high filtering characteristic are difficult to realize at the same time. The microstrip circuit assembly comprises a 50-ohm input transmission line, a microstrip three-wire coupling structure and two 50-ohm output transmission lines, wherein the microstrip three-wire coupling structure comprises three first coupling conductors, a second coupling conductor and a third coupling conductor which are sequentially arranged in parallel, the tail end of the 50-ohm input transmission line is connected with the second coupling conductor, and the tail ends of the first coupling conductor and the third coupling conductor are respectively connected with the two 50-ohm output transmission lines. The invention realizes the functions of high bandwidth and high filtering on the miniaturized microwave medium substrate and meets the practical application requirement of 5G communication.
Description
Technical Field
The invention relates to the technical field of 5G communication, in particular to a miniaturized ultra-wideband filtering power division feed network for 5G communication and a design method thereof.
Background
With the rapid development of modern wireless communication technology, the commercialization of 5G communication has also been imminent. The industry and communications department has already published the frequency use plan in the 5G middle frequency band in China, and has defined the 3300-. With the research of 5G communication technology, the requirements for microwave radio frequency circuits are gradually increasing, and the performance characteristics of ultra wide band, high integration, miniaturization and low insertion loss are pursued.
In 5G communication systems, the filter is an indispensable part of the radio frequency front end, and the main function of the filter is filtering and frequency selection. By filtering out unwanted frequency signals, selecting useful signals and separating various different signals to suppress noise signals, interference to different circuits is reduced, and the performance of the filter affects the performance of the overall communication system. The power divider is also used as one of important circuits in a microwave radio frequency system, and is the main component hardware of a phased array radar, an active amplification circuit, an antenna array and the like. The power divider is used for dividing one path of input signals into two paths or multiple paths to output equal or unequal energy, and can also be used for combining multiple paths of signal energy into one path to output.
The two passive devices, i.e. the filter and the power divider, occupy a large space in the radio frequency front-end system, and limit the miniaturization design of the system to a certain extent. The declaration of the 5G communication frequency band means that the future frequency band will be increased, the increase of the frequency band has the greatest influence on the number of radio frequency front-end devices, and the number of the devices is increased sharply along with the increase of the number of the frequency bands supported by the terminal, so that the device is contradictory to a small-size circuit of a radio frequency system required under the future 5G communication. The conventional solution is to miniaturize the two devices separately, so that the size of the whole system can be reduced, but the size reduction of the whole system is very limited. And in the miniaturized design of the filter and the power divider, the insertion loss is partially sacrificed. Therefore, researchers have proposed the integrated design of the filter and the power divider, and two microwave devices with independent functions are integrated into a single device, so that the device can simultaneously realize the functions of signal filtering and power distribution. The integrated design method can directly reduce the size of the system structurally, improve the overall performance of the system and better complete the miniaturization and integration design of the modern communication system.
In recent years, the integrated design of the filter power division feed network can be generalized into three modes:
the first is to omit a 50-ohm microstrip connection line between the filter and the power divider in a cascading manner to realize the functions of power distribution and filtering at the same time, although the size and the loss of the circuit can be reduced to a certain extent, the effect is not obvious;
the second method is to use a filter to replace the quarter-wave line in the traditional power divider to achieve the purpose of integration, and the filter structure used for replacement in the design needs to satisfy that in the working frequency band, the phase difference between the input and the output is 90 degrees or odd times of 90 degrees, and the input and the output impedance is equal to the characteristic impedance of the quarter-wave line;
the third method is to adopt a special structure to carry out integrated comprehensive design on the two devices, the design method of the power divider is to replace a quarter-wave line of Wilkinson with a multimode resonator with band-pass characteristic and reconstruct the structure of the power divider by utilizing a coupling matrix by combining the idea of an equivalent quarter-impedance converter, and the volume of the devices can be obviously reduced by the filtering power dividing feed network designed by the method.
However, with the continuous progress of the current communication technology and the gradual application of 5G, the communication requirements of more frequency bands will exist all the time, so the design requirements for ultra-wideband and miniaturized devices in the communication system are more remarkable, but the traditional filtering power division feed network cannot realize the ultra-wideband characteristics covering all the communication frequency bands of 3G, 4G and 5G, and has a limitation of larger size in part.
Therefore, the filtering power division feed network for 5G communication can meet the application requirement of 5G communication only by simultaneously having three requirements of miniaturization, high selectivity, ultra-wideband filtering characteristic and power distribution, and simultaneously has the requirement of synchronous operation of 3G and 4G communication systems.
Disclosure of Invention
The invention aims to solve the defects that a filter power division feed network in the prior art is difficult to realize miniaturization, high bandwidth and high filter characteristic at the same time, and provides a miniaturized ultra-wideband filter power division feed network for 5G communication and a design method thereof to solve the problems.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a miniaturized ultra-wideband filter power division feed network facing 5G communication comprises a microwave medium substrate, a micro-strip circuit assembly printed on the front surface of the microwave medium substrate, a metal ground plate printed on the back surface of the microwave medium substrate,
the microstrip circuit assembly comprises a 50-ohm input transmission line, a microstrip three-wire coupling structure and two 50-ohm output transmission lines, wherein the microstrip three-wire coupling structure comprises three first coupling conductors, a second coupling conductor and a third coupling conductor which are sequentially arranged in parallel, the tail end of the 50-ohm input transmission line is connected with the second coupling conductor, and the tail ends of the first coupling conductor and the third coupling conductor are respectively connected with the two 50-ohm output transmission lines;
the end of the 50 ohm input transmission line is connected with two short-circuit branch lines, the two short-circuit branch lines are respectively located on two sides of the microstrip three-line coupling structure, the two short-circuit branch lines correspond to each other in a mirror image mode, the tail ends of the two short-circuit branch lines are connected to the metal ground plate through metalized through holes, one end of the isolation resistor is connected to the head end of the first coupling conductor, the other end of the isolation resistor is connected to the head end of the third coupling conductor, the tail ends of the first coupling conductor and the third coupling conductor are respectively connected with the improved stepped impedance resonator, the two improved stepped impedance resonators are respectively located on two sides of the microstrip three-line coupling structure, and the two improved stepped impedance resonators correspond to each other in.
The high-impedance transmission line of the improved stepped impedance resonator is connected to the tail end of the first coupling conductor or the tail end of the third coupling conductor, the high-impedance transmission line of the improved stepped impedance resonator is arranged around the low-impedance transmission line by taking the low-impedance transmission line as a center, and the two improved stepped impedance resonators respectively generate two transmission zeros at two sides of the microstrip three-wire coupling structure.
The short-circuit branch lines are in a shape like a Chinese character 'ji', and two short-circuit branch lines respectively generate two transmission poles at the edge of the microstrip three-line coupling structure.
The transmission line widths of the first coupling conductor and the third coupling conductor are the same, the transmission line lengths of the first coupling conductor, the second coupling conductor and the third coupling conductor are the same, and the transmission line length of the first coupling conductor is one fourth of the wavelength of the central frequency.
The improved stepped impedance resonator is square, and the total length of the improved stepped impedance resonator is one half of the wavelength of the central frequency.
A design method for a miniaturized ultra-wideband filtering power division feed network for 5G communication comprises the following steps:
the design of the microstrip three-wire coupling structure sets the length of the microstrip three-wire coupling structure to be one fourth of the wavelength of the central frequency according to the central frequency,
the length of the microstrip three-wire coupling structure is d, the electrical length is theta, and the calculation formula is as follows:
β·d＝π
wherein: beta is the guided wave number of the dielectric material, lambdagFor guided wave length, c is the speed of light in free space, f0Is the center frequency, epsiloneffIs the effective dielectric constant of the dielectric material;
the design of the improved stepped impedance resonator determines an impedance ratio according to the position of a transmission zero point and the frequency of resonance generated by the improved stepped impedance resonator, and the conditional expression of the resonance generated is as follows:
Z1tanθ1-Z2cotθ2＝0；
the resistance of the isolation resistor is designed according to the Wilkinson's design theory and the relation determined under the odd-model analysis at Zino＝Z0And then obtaining better isolation, and calculating the resistance value of the isolation resistor, wherein the calculation formula is as follows:
wherein Z isaooAnd ZaeeIs the odd-odd and even-even mode impedance, ε, under excitation of the odd moderIs the relative dielectric constant of the dielectric material.
Advantageous effects
Compared with the prior art, the miniaturized ultra-wideband filtering power division feed network for 5G communication and the design method thereof realize high bandwidth and high filtering function on the miniaturized microwave dielectric substrate and meet the actual application requirement of 5G communication.
Compared with a Wilkinson type traditional filtering power division feed network, the power division feed network has wider passband bandwidth, and the bandwidth is further increased by loading a pair of short-circuit branch transmission lines at the tail ends of input transmission lines, so that the passband bandwidth covers all communication frequency bands of 3G, 4G and 5G, and the passband skirt band is steeper. Meanwhile, the loaded improved stepped impedance resonator can form two transmission zeros at two sides of a passband, so that the frequency selectivity is improved; the size of the whole circuit can be reduced by performing special folding treatment on the improved stepped impedance resonator, and the filtering power division feed network is ensured to have low insertion loss and better isolation characteristic.
Based on the filter power division feed network designed by the invention, the center frequency of the design simulation is 3.5GHz, and the obtained relative bandwidth reaches 101% from 1.73GHz to 5.26 GHz; the circuit size is 0.28 lambdag×0.21λg(ii) a The minimum insertion loss positions of the two output ports of the power amplifier respectively reach 3.16dB and 3.41dB, and the isolation in a passband is less than 10.3 dB; compared with the traditional Wilkinson type filter power divider, the power divider has the advantages of being provided with the rulerThe small size, the large relative bandwidth and the small insertion loss are suitable for the miniaturized and high-performance microwave circuit system, can adapt to a 5G communication base station, and are compatible with the application environment requirements of the 3G and 4G communication system.
Drawings
FIG. 1 is a schematic structural diagram of the present invention;
FIG. 2 is a schematic diagram of an equivalent circuit model according to the present invention;
FIG. 3a is an equivalent circuit diagram of the even mode excitation of the present invention;
FIG. 3b is an equivalent circuit diagram of the odd mode excitation of the present invention;
FIG. 4a is a graph comparing S parameters of different characteristic impedance levels of the low impedance transmission line of the improved ladder impedance resonator of the present invention;
FIG. 4b is a comparison of S parameters for different electrical lengths of the low impedance transmission line of the improved ladder impedance resonator of the present invention;
FIG. 5 is a comparison graph of S parameters of loaded and unloaded short-circuit stubs of the microstrip three-wire coupling structure of the present invention;
FIG. 6 is a comparison graph of S parameters of the present invention when the isolation resistors have different values;
FIGS. 7a and 7b are graphs comparing simulation and test results for the present invention;
the microwave antenna comprises a 101-50 ohm input transmission line, a 102-microstrip three-wire coupling structure, a 103-improved stepped impedance resonator, a 104-short-circuit branch line, a 105-isolation resistor, a 106-microwave dielectric substrate, a 107-50 ohm output transmission line, a 108-first coupling conductor, a 109-second coupling conductor and a 110-third coupling conductor.
Detailed Description
So that the manner in which the above recited features of the present invention can be understood and readily understood, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings, wherein:
as shown in fig. 1, the miniaturized ultra-wideband filtering power division feed network for 5G communication according to the present invention includes a microwave dielectric substrate 106. The microwave dielectric substrate 106 can be Roger RO4003C, and has a dielectric constant of 3.55, a loss tangent of 0.027, and a thickness of 0.508 mm. The back of the microwave medium substrate 106 is printed with a metal grounding plate, the front of the microwave medium substrate 106 is printed with a microstrip circuit component, namely, a 50 ohm input transmission line 101 is connected with a microstrip three-wire coupling structure 102, two improved stepped impedance resonators 103 are symmetrically distributed at an output port, two short-circuit branch lines 104 are loaded at an input end, and an isolation resistor 105 is bridged at the starting ends of two non-adjacent transmission lines of the microstrip three-wire coupling structure. The 50 ohm input transmission line 101 and the two 50 ohm output transmission lines 107 are all in the form of microstrip lines and are matched with the SMA coaxial connectors.
The microstrip circuit assembly comprises a 50 ohm input transmission line 101, a microstrip three-wire coupling structure 102 and two 50 ohm output transmission lines 107. The microstrip three-wire coupling structure 102 can realize strong coupling between transmission lines, so as to realize bandwidth, the microstrip three-wire coupling structure 102 includes three first coupling conductors 108, second coupling conductors 109 and third coupling conductors 110 which are sequentially arranged in parallel, transmission line widths of the first coupling conductors 108 and the third coupling conductors 110 are the same, transmission line lengths of the first coupling conductors 108, the second coupling conductors 109 and the third coupling conductors 110 are the same, and a transmission line length of the first coupling conductors 108 is a quarter of a center frequency wavelength. The distance between two adjacent transmission lines (the first coupling conductor 108 and the second coupling conductor 109 or the second coupling conductor 109 and the third coupling conductor 110) is set according to the minimum machinable size, and by reducing the distance between the adjacent coupling lines, strong coupling can be obtained to increase the bandwidth.
The end of the 50 ohm input transmission line 101 is connected to a second coupling conductor 109 (the middle conductor of the microstrip three-wire coupling structure 102) (the head end) for introducing a port via an input signal. The ends of the first coupling conductor 108 and the third coupling conductor 110 are respectively connected to the two 50-ohm output transmission lines 107, and the two transmission line terminals of the microstrip three-wire coupling structure 102, which are not adjacent, are used as two output ports.
The tail end of the 50 ohm input transmission line 101 is connected with two short-circuit branch lines 104, the two short-circuit branch lines 104 are respectively positioned at two sides of the microstrip three-line coupling structure 102, and the two short-circuit branch lines 104 are in mirror image correspondence. Two transmission poles can be generated in the pass band by adding symmetrical short-circuit branches at the output port, and the poles are located at the boundary of the original pass band by controlling and changing the characteristic impedance of the branches to influence the positions of the poles so as to increase the bandwidth and increase the frequency width of the pass band.
The ends of the two short-circuit branch lines 104 are connected to the metal ground plate through metalized via holes, so that the microstrip line is connected with the ground plane of the dielectric substrate to form short-circuit connection, two transmission poles are additionally generated at the edge of the passband by the loading of the short-circuit branch lines 104, the bandwidth of the passband is further increased, and the length of the transmission line is one fourth of the corresponding center frequency. The position of the pole can be changed by adjusting the characteristic impedance of the transmission line. In the invention, the positions of transmission poles are located at the lowest and highest frequencies in the original passband, so that the passband bandwidth of the filtering power division feed network is increased and the passband skirt band becomes steeper. It should be noted that, conventionally, increasing the frequency width of the pass band is mostly achieved by increasing the coupling strength, such as further reducing the coupling line spacing, but it is limited by the precision of the processing technology. Therefore, the technology innovatively adopts the short-circuit branch line which is cascaded on the main transmission line, and the bandwidth is increased by introducing a transmission pole in the passband range; furthermore, the frequency position of the transmission pole is adjusted by calculating the length of the short-circuit branch, so that the transmission pole is positioned at two sides of the passband, the edge steepness of the passband is improved, and the frequency selection characteristic is improved.
In order to further make the structure compact and reduce the size, the short-circuit branch line 104 is bent into a shape like a Chinese character 'ji'.
According to the design theory requirement, the isolation degree is better by additionally arranging the isolation resistor 105, one end of the isolation resistor 105 is connected with the head end of the first coupling conductor 108, the other end of the isolation resistor 105 is connected with the head end of the third coupling conductor 110, namely, the isolation resistor 105 is connected across the head end of the first coupling conductor 108 and the head end of the third coupling conductor 110. The introduction of the isolation resistor can strengthen the isolation between the two output ports, the resistance values of different resistors are one of the main factors influencing the isolation characteristic, and the 0402 type packaging chip resistor can be adopted, so that the isolation performance between the two output ports can be enhanced, and the resistance value is 200 ohms.
The ends of the first coupling conductor 108 and the third coupling conductor 110 are connected to the improved ladder impedance resonator 103, and the improved ladder impedance resonator 103 is composed of a high characteristic impedance transmission line and a low characteristic impedance transmission line in the conventional manner. The two improved stepped impedance resonators 103 are respectively located on two sides of the microstrip three-wire coupling structure 102, and the two improved stepped impedance resonators 103 correspond in a mirror image manner. The improved stepped impedance resonator 103 is formed by changing a traditional stepped impedance resonator, and the stepped impedance resonator is connected with an output end, so that two transmission zeros can be generated on two sides of a passband, the steepness of the passband is improved, and the frequency selection characteristic is improved. It is to be noted that, in order to improve the frequency suppression characteristic, the conventional method is to increase the transmission zero by adding an open stub. However, the length of the branch line of this method varies with the quarter wavelength of the transmission zero point, which is disadvantageous for miniaturization of the circuit. Therefore, the technical innovation adopts the stepped impedance resonator to generate the zero point, the miniaturization of the structure is realized by adjusting the stepped impedance ratio, and the stepped impedance resonator is further bent in a shape of Chinese character 'ji' in combination with the circuit layout to make the circuit structure compact.
The high-impedance transmission line of the improved stepped-impedance resonator 103 is connected to the end of the first coupling conductor 108 or the third coupling conductor 110, and the high-impedance transmission line of the improved stepped-impedance resonator 103 is arranged around the low-impedance transmission line with the low-impedance transmission line as a center.
Preferably, the improved stepped impedance resonator 103 has a square shape, and the total length of the improved stepped impedance resonator 103 is one half of the wavelength of the center frequency, that is, the improved stepped impedance resonator sets the width and the size length of the low impedance transmission line to be approximately equal to each other in a rectangular shape, and the high impedance transmission line is folded and connected along the rectangular side of the low impedance transmission line. Thus, in practical use, the size of the circuit can be reduced. The introduction of the stepped impedance resonator can form a transmission zero point on two sides of a passband respectively, and the selectivity of the frequency can be improved.
Here, a design method of a miniaturized ultra-wideband filtering power division feed network for 5G communication is also provided, which includes the following steps:
in the first step, the microstrip three-line coupling structure 102 is designed, and the length of the microstrip three-line coupling structure 102 is set to be one quarter of the wavelength of the center frequency according to the center frequency. As shown in fig. 2, the characteristic impedance and the electrical length of the two transmission lines of the improved ladder impedance resonator are respectively denoted as Z1,Z2,θ1And theta2And the two characteristic impedances are divided and recorded as impedance ratio: rZ＝Z2/Z1The total electrical length of the two transmission lines is pi, and the characteristic impedance and the electrical length of the short-circuited stub line are denoted as Z3And theta3。
The length of the microstrip three-line coupling structure (102) is d, the electrical length is theta, and the calculation formula is as follows:
β·d＝π
wherein: beta is the guided wave number of the dielectric material, lambdagFor guided wave length, c is the speed of light in free space, f0Is the center frequency, epsiloneffIs the effective dielectric constant of the dielectric material;
secondly, the improved stepped impedance resonator 103 is designed, and an impedance ratio is determined according to the position of the transmission zero point and the frequency of resonance generated by the improved stepped impedance resonator 103, wherein the conditional expression of resonance generation is as follows:
Z1tanθ1-Z2cotθ2＝0。
the line width and the electrical length of the stepped impedance resonator are calculated assuming that the position of the zero point is known, and the line width of the microstrip three-wire coupling structure is calculated assuming that the return loss is known.
FIG. 3a shows a binary structure under even mode excitation, etcThe characteristic impedance of the coupled line is respectively marked as Z under the excitation of the even mode0e,Z0oThe input impedance of the stepped-impedance resonator is denoted as ZtThe input impedance of port 4 of the slave coupled line is denoted as Zin4The input impedance of the short-circuited stub is noted as ZinsThe input impedance inputted from the port 2 is denoted as Zine. The calculation formulas are respectively as follows:
Zins＝jZ3tanθ3
known return loss
Since the filter circuit can be regarded as a lossless circuit when the transmission coefficient is large
At is in | S12When | ═ 0, a transmission zero is obtained, and the generation conditions of the transmission zero are as follows:
Z1tanθ1-Z2cotθ2＝0
from the known return loss, Z can be calculatedineZ in the case of a defined zero point and knownineLower Zin4May be calculated. The coupled line structure can then be regarded as a two-port network, Zin4Can be expressed by self-impedance and transmission impedance.
Therefore, the characteristic impedance under the excitation of the even mode can be calculated, and the line width of the coupled line can be calculated.
So far, the characteristic impedance Z can be adjusted based on the length of the short-circuit branch line being a quarter wavelength according to the design method of the microstrip three-wire coupling structure 1023And electrical length theta3The bandwidth is increased by making the transmission pole fall at the proper position.
And thirdly, designing the resistance value of the isolation resistor 105.
According to the relationship determined under Wilkinson's design theory and singular analysis, in Zino＝Z0Better isolation is obtained, and the resistance value of the isolation resistor is calculated. As shown in fig. 3b, it is an equivalent diagram of the binary structure under the odd mode excitation, and the characteristic impedances of the coupled lines are respectively denoted as Z under the odd mode excitationaoeThe input impedance inputted from the port 2 is denoted as ZinoThe input impedance of port 4 of the slave coupled line is denoted as Zi'n4The input impedance of the stepped-impedance resonator is denoted as ZtThe calculation formula therebetween is as follows:
wherein Z isaooAnd ZaeeAre odd-odd mode and even-even mode under odd mode excitationMode impedance,. epsilonrIs the relative dielectric constant of the dielectric material. According to Wilkinson's design theory, when ZinoIs equal to Z0Better isolation characteristics will result. Thus in ZaooAnd ZaeeIn certain cases, the resistance value of the resistor can be calculated according to the above formula.
By the method, the limitation of the processing precision of the existing circuit board process is broken through, on the basis of the three-wire coupling transmission line, the passband width is increased, the passband edge selection characteristic is improved, and the out-of-band rejection degree is increased by adding short-circuit branch lines, step impedance resonators and the like on the main transmission line. Meanwhile, in order to further realize compact circuit structure, the structural size and the position of an innovative means are calculated by reasonably distributing the positions of the transmission poles of the pass band and the transmission zeros outside the band in combination with the layout of the circuit structure. Compared with the traditional method, the filtering power division circuit designed by the invention can simultaneously realize the advantages of miniaturization, large bandwidth, good frequency selection characteristic, deep out-of-band rejection and the like.
As shown in fig. 4a and 4b, which provide S at different linewidths and lengths of the low impedance transmission line of the improved resonator provided according to the present invention21Parameter diagram, S21The transmission coefficient from the input port to the upper output port is the transmission coefficient when all ports are connected with 50 ohm load. The solid line, the dot-dash line, and the dotted line in FIG. 4a represent S when the line width (W5) of the low impedance line is equal to 3.9, 2.9, and 1.9mm, respectively21The graph, the solid line, the dashed line and the chain line in FIG. 4b respectively represent S when the length of the low impedance line (l2) is equal to 2.8, 3.3 and 3.8mm21Graph is shown. As can be seen from fig. 4a and 4b, decreasing the length of the low impedance transmission line and or increasing the width of the transmission line increases the resonant frequency and the zero point moves to the right. Because the position where the zero point is generated is determined by the impedance ratio and the electrical length of the resonator in accordance with the condition of the zero point generation.
As shown in FIG. 5, it provides the distributed S when the short-circuited branch is loaded or not according to the present invention11Parameter comparison graph, S11Which refers to the reflection coefficient when the input port is connected to a 50 ohm load. The solid line and the chain line respectively represent the load timeRoad-branch-line and S without load11Graph is shown. As can be seen from fig. 5, when the short-circuited stub is loaded, two transmission poles are additionally formed in the passband, which further expands the passband bandwidth and steepens the passband skirt, thereby improving the frequency selectivity.
As shown in fig. 6, which provides S of different resistance values according to the present invention23And (5) comparing the parameters. S23The isolation between the two output ports is the input port connected with the load. The solid, dotted and dashed lines represent, in succession, S at resistances equal to 160 ohm, 200 ohm and 240 ohm23Graph is shown. As can be seen from fig. 6, when the resistance is equal to 200 ohms, the isolation between the two ports in the strip will be better than when the resistance is equal to 160 ohms and 240 ohms. Since it can be seen from the analysis in the design step that the factor that affects the isolation performance of the two ports after the mode impedance is determined will be the magnitude of the resistance of the resistor.
As shown in fig. 7, a simulation and test result comparison chart of the miniaturized ultra-wideband filtering power division feed network designed based on the microstrip three-wire coupling structure provided by the invention is shown. S in FIG. 7a11The reflection coefficient S is the reflection coefficient when the input port is connected with a 50 ohm load21The transmission coefficient from the input port to the upper output port, S, when all ports are connected with 50 ohm load31The transmission coefficient from the input port to the lower output port is the transmission coefficient when all ports are connected with 50 ohm load. S in FIG. 7b22The reflection coefficient S of the output port connected with a 50 ohm load23The isolation between the two output ports is the input port connected with the load. The simulation is basically consistent with the test result, and the test result shows that the center frequency is 3.34GHz, the minimum insertion loss of the output port in the passband is 3.14dB, the 3dB relative bandwidth is 95.2%, the frequency range is 1.75 to 4.93GHz, the positions of two transmission zero points are respectively 1.35GHz and 5.85GHz, and the isolation of the power division port is greater than 10.3 dB.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (5)
1. The utility model provides a towards miniaturized ultra wide band filter merit of 5G communication divides feed network, includes microwave medium base plate (106), and the front of microwave medium base plate (106) is printed and is had microstrip circuit subassembly, and the back printing of microwave medium base plate (106) has the metal ground plate, its characterized in that:
the microstrip circuit assembly comprises a 50-ohm input transmission line (101), a microstrip three-wire coupling structure (102) and two 50-ohm output transmission lines (107), wherein the microstrip three-wire coupling structure (102) comprises three first coupling conductors (108), a second coupling conductor (109) and a third coupling conductor (110) which are sequentially arranged in parallel, the tail end of the 50-ohm input transmission line (101) is connected with the second coupling conductor (109), and the tail ends of the first coupling conductor (108) and the third coupling conductor (110) are respectively connected with the two 50-ohm output transmission lines (107);
the tail end of the 50-ohm input transmission line (101) is connected with two short-circuit branch lines (104), the two short-circuit branch lines (104) are respectively located on two sides of the microstrip three-line coupling structure (102), the two short-circuit branch lines (104) correspond to each other in a mirror image mode, metalized via holes at the tail ends of the two short-circuit branch lines (104) are connected to the metal ground plate, one end of an isolation resistor (105) is connected to the head end of a first coupling conductor (108), the other end of the isolation resistor (105) is connected to the head end of a third coupling conductor (110), the tail ends of the first coupling conductor (108) and the third coupling conductor (110) are respectively connected with an improved stepped impedance resonator (103), the two improved stepped impedance resonators (103) are respectively located on two sides of the microstrip three-line coupling structure (102), and the two improved stepped impedance resonators (103) correspond to each other; the high-impedance transmission line of the improved stepped impedance resonator (103) is connected to the tail end of the first coupling conductor (108) or the tail end of the third coupling conductor (110), the high-impedance transmission line of the improved stepped impedance resonator (103) is arranged around the low-impedance transmission line by taking the low-impedance transmission line as a center, and the two improved stepped impedance resonators (103) respectively generate two transmission zeros at two sides of the microstrip three-wire coupling structure (102).
2. The miniaturized ultra-wideband filtering power division feed network oriented to 5G communication according to claim 1, characterized in that: the short-circuit branch lines (104) are in a shape of a Chinese character 'ji', and the two short-circuit branch lines (104) respectively generate two transmission poles at the edge of the passband of the microstrip three-line coupling structure (102).
3. The miniaturized ultra-wideband filtering power division feed network oriented to 5G communication according to claim 1, characterized in that: the transmission line widths of the first coupling conductor (108) and the third coupling conductor (110) are the same, the transmission line lengths of the first coupling conductor (108), the second coupling conductor (109) and the third coupling conductor (110) are the same, and the transmission line length of the first coupling conductor (108) is one fourth of the wavelength of the central frequency.
4. The miniaturized ultra-wideband filtering power division feed network oriented to 5G communication according to claim 1, characterized in that: the improved stepped impedance resonator (103) is square, and the total length of the improved stepped impedance resonator (103) is one half of the wavelength of the central frequency.
5. The design method of the miniaturized ultra-wideband filtering power division feed network facing 5G communication according to claim 1, characterized by comprising the following steps:
51) the design of the microstrip three-line coupling structure (102) sets the length of the microstrip three-line coupling structure (102) to be one quarter of the wavelength of the central frequency according to the central frequency,
the length of the microstrip three-line coupling structure (102) is d, the electrical length is theta, and the calculation formula is as follows:
β·d＝π
wherein: beta is the guided wave number of the dielectric material, lambdagFor guided wave length, c is the speed of light in free space, f0Is the center frequency, epsiloneffIs the effective dielectric constant of the dielectric material;
52) the design of the improved stepped impedance resonator (103) determines an impedance ratio according to the position of a transmission zero point and the frequency of resonance generated by the improved stepped impedance resonator (103), and the conditional expression of the resonance generated is as follows:
Z1 tanθ1-Z2cotθ2＝0；
the characteristic impedance and the electrical length of the two transmission lines of the improved stepped-impedance resonator are respectively denoted as Z1、Z2、θ1And theta2；
53) The value of the isolation resistor (105) is designed according to the relation determined under Wilkinson's design theory and singular mode analysis, in Zino＝Z0And then obtaining better isolation, and calculating the resistance value of the isolation resistor, wherein the calculation formula is as follows:
wherein Z isaooAnd ZaeeIs the odd-odd and even-even mode impedance, ε, under excitation of the odd moderIs the relative permittivity of the dielectric material;
the characteristic impedance of the coupled line is recorded as Z under the excitation of the odd modeaoeThe input impedance inputted from the port 2 is denoted as ZinoThe input impedance from port 4 of the coupled line is denoted as Z'in4The input impedance of the stepped-impedance resonator is denoted as Zt。
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| CN113823885B (en) * | 2021-09-13 | 2023-02-03 | 安徽大学 | Filter |
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| CN116054771B (en) * | 2023-04-03 | 2023-06-30 | 南通至晟微电子技术有限公司 | Reflection-free broadband filter |
| CN116151038B (en) * | 2023-04-18 | 2023-06-27 | 安徽大学 | Analysis method of circular polarization MIMO microstrip antenna array self-decoupling technology |
| CN116613491B (en) * | 2023-07-18 | 2023-10-13 | 成都华兴汇明科技有限公司 | Frequency-selecting network with three transmission zero points and microwave oscillator constructed by same |
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