CN112448113A - Butterfly-shaped microstrip filtering power divider - Google Patents

Butterfly-shaped microstrip filtering power divider Download PDF

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CN112448113A
CN112448113A CN202011299554.8A CN202011299554A CN112448113A CN 112448113 A CN112448113 A CN 112448113A CN 202011299554 A CN202011299554 A CN 202011299554A CN 112448113 A CN112448113 A CN 112448113A
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coupling line
parallel coupling
line structure
power divider
impedance
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叶玲婕
王逸然
徐晨霄
程勇
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Nanjing University of Posts and Telecommunications
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Nanjing University of Posts and Telecommunications
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P5/00—Coupling devices of the waveguide type
    • H01P5/12—Coupling devices having more than two ports
    • H01P5/16—Conjugate devices, i.e. devices having at least one port decoupled from one other port
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/203—Strip line filters

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Abstract

The invention discloses a butterfly-shaped microstrip filtering power divider, which belongs to the technical field of communication, has a filtering function on the basis of power division, and has the advantages of good in-band insertion loss and isolation, small size, simple design and the like. Compared with the traditional Wilkinson power divider, the parallel coupling line is mainly adopted to replace a quarter-wavelength transmission line in the power divider, and the open-circuit stub of step impedance is added, so that the defects of poor harmonic response and out-of-band rejection are overcome. The parallel coupling line structure is used for realizing a filtering function and obtaining better port matching; by adjusting the impedance ratio of the step impedance open stub, the first transmission zero points on two sides of the transmission passband of the filtering power divider can be moved, so that the high-frequency selection characteristic is realized; finally, a real object made of Rogers5880 serving as a substrate material has the measured central frequency of 3GHz, the relative bandwidth of 56%, the pass band insertion loss of less than 0.34dB, the return loss of better than 17dB, the port isolation of higher than 18.7dB and the overall size of 43mm multiplied by 44 mm.

Description

Butterfly-shaped microstrip filtering power divider
Technical Field
The invention belongs to the technical field of communication, and particularly relates to a butterfly-shaped microstrip filtering power divider.
Background
In communication and radar systems, a power divider is one of important devices. The power divider is a device which divides one path of input signal energy into two paths or multiple paths of energy with equal or unequal outputs, or conversely synthesizes multiple paths of signal energy into one path of output, and is also called a combiner. Certain isolation degree should be guaranteed between output ports of one power divider. Technical indexes of the power divider include frequency range, bearing power, main path to branch path distribution loss, insertion loss between input and output, isolation between branch path ports, voltage standing wave ratio of each port and the like.
Filters are also important in the field of communication radars and the like. The filter can effectively filter the frequency point of the specific frequency in the power line or the frequencies except the frequency point to obtain a power signal of the specific frequency or eliminate the power signal of the specific frequency. The technical indexes of the filter comprise passband bandwidth, insertion loss, passband ripple, return loss, stopband suppression degree, in-band phase linearity, group delay and the like.
In the traditional situation, a filter and a power divider are taken as two discrete devices, a signal is divided into two parts by using one power divider, and then the two output filters are used for respectively filtering the signal; or filtering the circuit first and then distributing the power to the signal will have a great impact on the size and other aspects. The filtering power divider can simultaneously realize the functions of filtering and power dividing, and has important significance in exploring the filtering power divider with small size and good filtering function.
Power splitters are widely used today in radio frequency and microwave circuits. A conventional wilkinson power divider may perform power division in any ratio. However, the pass-band of the wilkinson power divider appears periodically.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a butterfly-shaped microstrip filtering power divider which has the advantages of high control precision, good dynamic performance and the like.
The technical scheme is as follows: in order to achieve the purpose, the invention provides the following technical scheme:
a butterfly microstrip filter power divider comprises a first port, a second port and a third port, wherein the first port is connected to the left ends of a first parallel coupling line structure and a second parallel coupling line structure; the right ends of the first parallel coupling line structure and the second parallel coupling line structure are connected with an isolation resistor R in a bridging mode; the right end of the first parallel coupling line structure is connected to a first line node and a third line node simultaneously; the right end of the second parallel coupling line structure is connected to the second line section and the fourth line section simultaneously; said first node is connected to a second port, said second node is connected to a third port, and said third node is connected to a first stepped-impedance structure; and the fourth node is connected with the second step impedance structure.
Furthermore, the length L1 of the first parallel coupling line structure and the second parallel coupling line structure is 19mm, the width W2 is 0.4mm, and g is 0.2 mm.
Further, the length L2 of the first, second and third segments is 8mm, L3 is 12mm, L7 is 8mm, L8 is 15.5mm, the width W1 is 3.15mm, and W3 is 1.7 mm.
Further, the length L4 of the first impedance step structure and the second impedance step structure is 5mm, L5 is 6mm, and the width W4 is 0.5 mm; the isolation resistor R is 360 omega.
Furthermore, the impedance of the even mode characteristic of the first parallel coupling line structure and the second parallel coupling line structure is Z0eThe odd mode characteristic impedance is Z0oAnd the electrical length is theta, and the characteristic impedances of the two sections of transmission lines of the step impedance open stub are respectively as follows: z1、Z2Electrical length θ, by even mode analysis: according to the even-mode equivalent circuit diagram of the filter power divider, the impedance Z 'of the step impedance open stub loaded from the center point to the center'inComprises the following steps:
Figure BDA0002786384750000021
for the parallel coupling line structure, the current I in the lines of the first parallel coupling line structure and the second parallel coupling line structure is obtained by the voltage-current relation2、I4Respectively as follows:
I2＝I4＝0
the equivalent impedance matrix of the corresponding first parallel coupling line structure and the second parallel coupling line structure is as follows:
Figure BDA0002786384750000022
wherein:
Figure BDA0002786384750000023
when the right even-mode excitation is adopted, the input impedance Z seen from the right end of the upper side coupling line can be obtainedRin1Comprises the following steps:
Figure BDA0002786384750000024
the input impedance is then:
Figure BDA0002786384750000031
the reflection coefficient of the second port under the excitation of the even mode is as follows:
Figure BDA0002786384750000032
further, odd mode analysis is performed on the first parallel coupling line structure and the second parallel coupling line structure:
according to the odd-mode equivalent circuit diagram of the filter power divider, for the parallel coupling line structure, the current I in the two first parallel coupling line structures and the current I in the second parallel coupling line structure are obtained according to the voltage-current relationship2、I4Respectively as follows:
Figure BDA0002786384750000033
wherein V1For the first port voltage, R is the bridge resistor, and the equivalent impedance matrix of the coupling line structure at this time is:
Figure BDA0002786384750000034
the impedance from the center point to the first port 1 is:
Figure BDA0002786384750000035
the input impedance is then:
Figure BDA0002786384750000036
the reflection coefficient of the second port under the excitation of the odd mode is as follows:
Figure BDA0002786384750000037
has the advantages that: compared with the prior art, the butterfly-shaped microstrip filtering power divider has the filtering function on the basis of power division, and has the advantages of good frequency response, small size, simple design and the like. The filtering power divider provided by the invention can simultaneously have a filtering function on the basis of power division, and has the advantages of good frequency response, small size, simple design and the like; compared with the traditional Wilkinson power divider, the power divider mainly adopts a coupled line filter to replace a quarter-wavelength transmission line in the power divider, and adds an open-circuit stub of step impedance.
Drawings
Fig. 1 is a schematic diagram of a microstrip line structure;
FIG. 2 is a schematic diagram of a butterfly microstrip filter power divider;
FIG. 3 is a schematic diagram of a parallel coupled two-wire configuration;
FIG. 4 is a schematic diagram of a butterfly microstrip filter power divider with dimension labels;
FIG. 5 is a graph of simulation results and test results for | S11| and | S21| of an embodiment;
FIG. 6 is a graph of simulation results and test results for | S22| and | S32| of an embodiment;
FIG. 7 is a first even-mode equivalent circuit diagram of the filter power divider;
FIG. 8 is a second even-mode equivalent circuit diagram of the filter power divider;
fig. 9 is an odd-mode equivalent circuit diagram of the filtering power divider.
Detailed Description
In order to more fully understand the structure of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and the specific embodiments, but the actual embodiments are not limited to this example.
The filtering power divider provided by the invention has a filtering function on the basis of power division, and has the advantages of good frequency response, small size, simple design and the like.
The structure of the filter power divider of the invention is shown in fig. 1. Compared with the traditional Wilkinson power divider, the power divider mainly adopts a coupled line filter to replace a quarter-wavelength transmission line in the power divider, and adds an open-circuit stub of step impedance.
The filtering power divider is a planar power divider with a wide pass band and a wide stop band, and divides input power into two parts.
The structure of the filtering power divider described in the present invention is shown in fig. 2, where a first port 1 is connected to the left ends of two sections of a first parallel coupling line structure 11 and a second parallel coupling line structure 12; the right ends of the first parallel coupling line structure 11 and the second parallel coupling line structure 12 are connected across an isolation resistor R; the right end of the first parallel coupling line structure 11 is connected to the first wire node 21 and the third wire node 23; at the right end of the second parallel coupled line structure 12, to both the second 22 and fourth 24 wire nodes; the first node 21 is connected to the second port 2, the second node 22 is connected to the third port 3, and the third node 23 is connected to the first stepped-impedance structure 31; the fourth node 24 is connected to a second stepped-impedance structure 32; the microstrip filtering power divider is formed.
The dielectric constant of the dielectric plate material is 1.016mm, and the thickness h of the dielectric plate is equal to 1.016 mm. The length L1 of the parallel coupling line is 19mm, the width W2 is 0.4mm, and g is 0.2 mm; the length of the wire joint is L2-8 mm, L3-12 mm, L7-8 mm, L8-15.5 mm, the width W1-3.15 mm, and the width W3-1.7 mm; the length L4 of the stepped impedance structure is 5mm, L5 is 6mm, and the width W4 is 0.5 mm; the isolation resistance R is 360 Ω.
The filter power divider is composed of parallel coupling lines and step impedance open-circuit stub lines. Because the broadband filtering power divider has symmetry, the broadband filtering power divider can be analyzed by using an odd-even mode analysis method, and the even-mode characteristic impedance of the parallel coupling line is Z0eThe odd mode characteristic impedance is Z0oAnd the electrical length is theta, and the characteristic impedances of the two sections of transmission lines of the step impedance open stub are respectively as follows: z1、Z2The electrical length is theta, the impedances of the three ports are all 50 ohms, and an isolation resistor is added between the two coupling lines, so that good isolation and matching performance are realized.
And (3) even mode analysis: 7-8 even-mode equivalent circuit diagrams of filtered power dividers having center-to-center loaded stepped-impedance open stubs impedance Z'inComprises the following steps:
Figure BDA0002786384750000051
for the parallel coupling line structure, the current I in the two coupling lines can be obtained according to the voltage-current relation2、I4Respectively as follows:
I2＝I4＝0
the equivalent impedance matrix of the corresponding coupling line structure is:
Figure BDA0002786384750000052
wherein:
Figure BDA0002786384750000053
when the right even-mode excitation is adopted, the input impedance Z seen from the right end of the upper side coupling line can be obtainedRin1Comprises the following steps:
Figure BDA0002786384750000054
the input impedance is then:
Figure BDA0002786384750000055
the reflection coefficient of the second port 2 under the excitation of the even mode is as follows:
Figure BDA0002786384750000061
and (3) odd mode analysis: according to the odd-mode equivalent circuit diagram of the filtering power divider in fig. 9, for the parallel coupled line structure, the current I in the two coupled lines can be obtained from the voltage-current relationship2、I4Respectively as follows:
Figure BDA0002786384750000062
wherein V1For the voltage at the first port 1, R is the bridge resistor, and the equivalent impedance matrix of the coupling line structure at this time is:
Figure BDA0002786384750000063
the impedance from the center point to the first port 1 is:
Figure BDA0002786384750000064
the input impedance is then:
Figure BDA0002786384750000065
the reflection coefficient of the second port 2 under the excitation of the odd mode is as follows:
Figure BDA0002786384750000066
the filtering power divider of the invention is used for halving the input signal and has the filtering function. The structure of the filtering power divider is vertically symmetrical. The analysis may be performed using a parity-mode analysis method.
Examples
The filter power divider in the example is a plane power divider with wide pass band and wide stop band, can divide the input power into two parts, has the center frequency of 3GHz and the relative bandwidth of 56 percent, has the pass band insertion loss of less than 0.32dB, has the return loss of better than-18 dB, and generates two transmission zeros at 1.8GHz and 4.3 GHz.
In the first step, we design the equivalent lumped parameter circuit diagram of the filter. And determining the parameter value of each element according to the technical index.
And secondly, obtaining the electrical parameters of the distributed parameter circuit by the lumped parameter element value.
And thirdly, determining the microstrip substrate. Without loss of generality, Rogers5880 is selected as the dielectric plate material, and the dielectric constant epsilon of the dielectric plate materialr2.2, and the thickness h of the dielectric plate is 1.016 mm. And calculating according to the electrical parameters to obtain structural parameters of the filtering power divider, and optimizing and adjusting to make the structural parameters meet the technical indexes, so that the finally obtained structure is as shown in fig. 5. The structure is composed of parallel coupling lines and step impedance open-circuit stub lines, input signals are equally divided through the two symmetrical parallel coupling lines, and the isolation resistor R is arranged at the tail ends of the feeder lines inside the two parallel coupling line structures, so that isolation and output matching between the two output ports are realized. The respective structural parameters (unit: mm) of FIG. 4 are as follows: w1-3.15, W2-0.4, W3-1.7, W4-0.5, L1-19, L2-8, L3-12, L4-5, L5-6, L6-8, L7-8, L8-15.5, g-0.2, and R-360 Ω.
A comparison graph of the simulation result and the test result obtained by simulating and testing the filter power divider in the embodiment is shown in fig. 5 and 6. As can be seen from the figure, the simulation result is substantially in accordance with the test result, and the function of the filtering power divider is well realized. The comparison between the simulation result and the actually measured data shows that the test result is basically consistent with the simulation result, the passband range has slight frequency deviation, the deterioration is about 1dB, the isolation is about 1.3dB, and the errors are probably caused by the incomplete symmetry of the processing precision and the isolation resistance welding.
In summary, the above-mentioned embodiments fully illustrate the advantages of the filter power divider proposed by this patent, such as good frequency response, small size, and simple design. The scope of the present invention is not limited to the above embodiments, and those skilled in the art can make various modifications without departing from the spirit of the present invention, and these modifications are all included in the scope of the present invention.

Claims (6)

1. A butterfly microstrip filtering power divider is characterized in that: the device comprises a first port (1), a second port (2) and a third port (3), wherein the first port (1) is connected to the left ends of a first parallel coupling line structure (11) and a second parallel coupling line structure (12); the right ends of the first parallel coupling line structure (11) and the second parallel coupling line structure (12) are connected across an isolation resistor R; the right end of the first parallel coupling line structure (11) is connected to a first line node (21) and a third line node (23) at the same time; at the right end of the second parallel coupling line structure (12), the second parallel coupling line structure is simultaneously connected to a second wire section (22) and a fourth wire section (24); said first junction (21) being connected to the second port (2), said second junction (22) being connected to the third port (3), said third junction (23) being connected to the first stepped-impedance structure (31); the fourth node (24) is connected with the second step impedance structure (32).
2. The butterfly microstrip filter power divider of claim 1, characterized in that: the length L1 of the first parallel coupling line structure (11) and the second parallel coupling line structure (12) is 19mm, the width W2 is 0.4mm, and the g is 0.2 mm.
3. The butterfly microstrip filter power divider of claim 1, characterized in that: the length L2 of the first line section (21), the second line section (22) and the third line section (23) is 8mm, the length L3 is 12mm, the length L7 is 8mm, the length L8 is 15.5mm, the width W1 is 3.15mm, and the width W3 is 1.7 mm.
4. The butterfly microstrip filter power divider of claim 1, characterized in that: the length L4 of the first impedance step structure (31) and the second impedance step structure (32) is 5mm, the length L5 is 6mm, and the width W4 is 0.5 mm; the isolation resistor R is 360 omega.
5. The butterfly microstrip filter power divider of claim 1, characterized in that: the even-mode characteristic impedance of the first parallel coupling line structure (11) and the second parallel coupling line structure (12) is Z0eThe odd mode characteristic impedance is Z0oAnd the electrical length is theta, and the characteristic impedances of the two sections of transmission lines of the step impedance open stub are respectively as follows: z1、Z2Electrical length θ, by even mode analysis: according to the even-mode equivalent circuit diagram of the filter power divider, the impedance Z of the step impedance open stub loaded from the center point to the centeri′nComprises the following steps:
Figure FDA0002786384740000011
for the parallel coupling line structure, the current I in the lines of the first parallel coupling line structure (11) and the second parallel coupling line structure (12) is obtained by the voltage-current relation2、I4Respectively as follows:
I2＝I4＝0
the equivalent impedance matrix of the corresponding first parallel coupling line structure (11) and the second parallel coupling line structure (12) is as follows:
Figure FDA0002786384740000021
wherein:
Figure FDA0002786384740000022
when the right even-mode excitation is adopted, the input impedance Z seen from the right end of the upper side coupling line can be obtainedRin1Comprises the following steps:
Figure FDA0002786384740000023
the input impedance is then:
Figure FDA0002786384740000024
the reflection coefficient of the second port (2) under the excitation of the even mode is as follows:
Figure FDA0002786384740000025
6. the butterfly microstrip filter power divider of claim 5, characterized in that: performing odd mode analysis on the first parallel coupling line structure (11) and the second parallel coupling line structure (12):
according to the odd-mode equivalent circuit diagram of the filter power divider, for the parallel coupling line structure, the current I in the two first parallel coupling line structures (11) and the second parallel coupling line structure (12) is obtained according to the voltage-current relationship2、I4Respectively as follows:
Figure FDA0002786384740000026
wherein V1Is as followsOne port (1) voltage, R is the cross-over resistance, and the equivalent impedance matrix of the coupling line structure at this time is:
Figure FDA0002786384740000027
the impedance from the center point to the first port (1) is:
Figure FDA0002786384740000031
the input impedance is then:
Figure FDA0002786384740000032
the reflection coefficient of the second port (2) under the excitation of an odd mode is as follows:
Figure FDA0002786384740000033
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CN114530677A (en) * 2022-01-27 2022-05-24 恒尔威科技(苏州)有限公司 Ultra-wideband miniaturized cavity combiner
CN114824715A (en) * 2022-03-29 2022-07-29 中国人民解放军国防科技大学 W-band filtering power divider based on rectangular micro-coaxial structure
CN115360487A (en) * 2022-09-05 2022-11-18 重庆邮电大学 Plane filtering power divider with broadband external suppression

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CN115360487A (en) * 2022-09-05 2022-11-18 重庆邮电大学 Plane filtering power divider with broadband external suppression
CN115360487B (en) * 2022-09-05 2023-08-11 重庆邮电大学 Plane filtering power divider with broadband external suppression

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