Broadband filter with power division coupling function based on lumped element

Abstract

The utility model belongs to the technical field of filters, and particularly relates to a lumped element-based broadband filter with a power division coupling function, which comprises a first port, a second port, a third port, a fourth port, a 180-degree phase inverter, eight inductors and eight capacitors. One capacitor is connected in series between the two inductors to form a pi-type high-pass structure, and the two pi-type high-pass structures, the two capacitors and the 180-degree inverter are sequentially cascaded to form an annular structure. Compared with an existing microstrip line type and substrate integrated waveguide type coupling filter, the coupling filter provided by the utility model has the advantages of being more compact and higher in integration, and has the performances of high isolation, ultra wide band and the like; the method has important application value for reducing the size and design difficulty of a communication system and improving the integration performance of a radio frequency front end.

Description

Technical Field

[0001] The utility model belongs to the technical field of filters, in particular to a broadband filter with a power division coupling function based on lumped elements. Background Art

[0002] A coupling filter is an electronic component that performs directionally coupled sampling of the power of electromagnetic wave signals within a specified frequency band. It is widely used in power synthesis networks, antenna transceiver systems, and microwave measurement systems. The key performance evaluation indicators of coupling filters mainly include parameters such as insertion loss, coupling, isolation, reflection coefficient, and relative working bandwidth. As an important passive circuit, the coupler filter is generally used for power distribution and combination in the RF front-end circuit. The coupler filter is a four-port network device. The electromagnetic wave signal enters from the input port, and the power output passes through the through port and the coupling port respectively. The output signal is different not only in amplitude, but also in phase. The fourth port is an isolation port.

[0003] Traditional coupled filters, especially four-port coupled filters, are generally realized by optimizing the transmission line structure. Although the coupled filters realized by this distributed design method have good performance, they are often complex in structure and occupy a large area.

[0004] In summary, the existing traditional coupling filter circuit is complex and has a large structure size, which is not conducive to the development of communication systems towards ultra-miniaturization and integration. Utility Model Content

[0005] In view of the above-mentioned prior art, the utility model proposes a broadband filter with power division coupling function based on lumped elements, which solves the problems of the existing circuit structure being complex, large in size, poor in isolation performance, and insufficient bandwidth.

[0006] The specific technical solutions adopted by the utility model are as follows:

[0007] A broadband filter with power division coupling function based on lumped elements comprises a first port, a second port, a third port, a fourth port, a 180° inverter, 8 inductors and 8 capacitors. A capacitor is connected in series between two inductors to form a π-type high-pass structure, and two π-type high-pass structures, two capacitors and a 180° inverter are cascaded in sequence to form a ring structure. Four symmetrical nodes on the ring structure are cascaded to form an LC resonant branch composed of a series resonant loop.

[0008] A further improvement of the utility model is that in the above-mentioned ring structure, the inductance distribution parameters are symmetrical about left and right; the capacitance distribution parameters are symmetrical about top and bottom, and left and right.

[0009] A further improvement of the utility model is that in the above four LC resonant branches, the inductance values ​​are all equal and the capacitance values ​​are all equal.

[0010] According to a further improvement of the present invention, the four LC resonant branches are respectively connected to the first port, the second port, the third port and the fourth port of the coupling filter.

[0011] A further improvement of the utility model is that in the coupling filter, when the first port is used as an input port, the second port and the fourth port output signals of the same phase, and the third port is an isolation port; when the second port is used as an input port, the first port and the third port output signals of the same phase; in the coupling filter, when the third port is used as an input port, the second port and the fourth port output signals of anti-phase, and the first port is an isolation port; when the fourth port is used as an input port, the first port and the third port output signals of anti-phase.

[0012] The beneficial effects of the utility model are as follows: compared with the existing microstrip line type and substrate integrated waveguide type coupling filters, the utility model has the advantages of being more compact and more integrated, and takes into account the performance of high isolation and ultra-wideband, etc., and has important application value for reducing the volume and design difficulty of the communication system and improving the integration performance of the RF front end. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a circuit structure diagram of a coupling filter of the present utility model.

[0014] Figure 2 This is a schematic diagram of lumped parameters of the coupling filter circuit structure of the utility model.

[0015] Figure 3 The utility model is a schematic diagram of a lumped parameter circuit when the signals outputted by the through port and the coupled port of the coupled filter circuit are equal amplitude signals.

[0016] Figure 4 The reflection coefficient curve S11, insertion loss coefficient curve S21, and coupling coefficient curve S41 of Example 1 obtained by simulation.

[0017] Figure 5 FIG. 3 is the isolation curve S31 of Example 1 obtained by simulation.

[0018] Figure 6 The S-parameter diagram obtained by simulation when the lumped parameters of each component are appropriately adjusted so that the signals output by the through port and the coupled port of the circuit are equal-amplitude signals. DETAILED DESCRIPTION

[0019] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.

[0020] like Figure 1 As shown, a broadband filter with power division coupling function based on lumped elements is composed of a first port 1, a second output port 2, a third port 3, a fourth output port 4, 8 inductors 5a-5d and 7a-7d, 8 capacitors 6a-6d and 8a-8d, and a 180° inverter 9. Among them, the inductor 7a and the inductor 7d are connected in series with the capacitor 8d, and the other ends of the inductor 7a and the inductor 7d are grounded; the inductor 7b and the inductor 7c are connected in series with the capacitor 8b, and the other ends of the inductor 7b and the inductor 7c are grounded. The connection point between the inductor 7a and the capacitor 8d is connected in parallel with one end of the capacitor 8a, and the connection point between the inductor 7b and the capacitor 8b is connected in parallel with the other end of the capacitor 8a; the connection point between the inductor 7d and the capacitor 8d is connected in parallel with one end of the capacitor 8c, and the other end of the capacitor 8a is connected in series with one end of the inverter 9, and the connection point between the inductor 7c and the capacitor 8b is connected in parallel with the other end of the inverter. A branch consisting of a capacitor 5a and an inductor 6a in series is connected in parallel at the connection between the inductor 7a and the capacitor 8a, and the other end of the branch is connected to the first port 1; a branch consisting of a capacitor 5b and an inductor 6b in series is connected in parallel at the connection between the inductor 7b and the capacitor 8b, and the other end of the branch is connected to the second port 2; a branch consisting of a capacitor 5c and an inductor 6c in series is connected in parallel at the connection between the inductor 7c and the 180° inverter 9, and the other end of the branch is connected to the third port 3; a branch consisting of a capacitor 5d and an inductor 6d in series is connected in parallel at the connection between the inductor 7d and the capacitor 8c, and the other end of the branch is connected to the fourth port 4.

[0021] In order to better illustrate the technical effect of the utility model, Figure 2 A schematic diagram of the parameter relationship of the lumped elements of the implementation case is given. Figure 3 A schematic diagram of lumped element parameters is given for an implementation example when the through port and coupled port output equal-amplitude signals.

[0022] The above circuit schematic diagram is simulated using ADS simulation software. The S parameter curve obtained by simulation is as follows Figure 4 and Figure 5 shown. Figure 4 In the figure, they are the insertion loss coefficient S21 and the coupling coefficient S41 respectively, and the solid line is S11, i.e. the reflection coefficient. Figure 5 Isolation coefficient S31

[0023] The parameters of the lumped element are appropriately adjusted so that the output signals of the through port and the coupled port are equal amplitude signals. The above circuit schematic is simulated using the ADS simulation software. The S parameter curve obtained by simulation is as follows: Figure 6 shown. Figure 6The dashed lines in the middle are S21 and S41, i.e., the insertion loss coefficient and the coupling coefficient, and the solid line is S11, i.e., the reflection coefficient.

[0024] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A broadband filter with power division coupling function based on lumped elements, characterized in that: The invention comprises four ports set as a first port, a second port, a third port and a fourth port, a 180° inverter, eight inductors and eight capacitors, two of the inductors are connected in series with one capacitor to form a π-type high-pass structure, two of the π-type high-pass structures, two of the capacitors and one of the 180° inverters are cascaded in sequence to form a ring structure, four symmetrical nodes on the ring structure are each cascaded with an LC resonant branch composed of a series resonant circuit, and the other ends of the four LC resonant branches are respectively provided with a first port, a second port, a third port and a fourth port.

2. The broadband filter with power division coupling function based on lumped elements according to claim 1, characterized in that: In the ring structure, the value of the inductor is symmetrical about the geometric structure, and the value of the capacitor is symmetrical about the top and bottom and the left and right.

3. The broadband filter with power division coupling function based on lumped elements according to claim 1, characterized in that: The capacitors of the LC resonance branch have the same capacitance value, and the inductors have the same inductance value.

4. The broadband filter with power division coupling function based on lumped elements according to claim 1, characterized in that: In the broadband filter with power division coupling function, when the first port is used as the input port, the second port and the fourth port output signals of the same phase, and the third port is an isolation port; when the second port is used as the input port, the first port and the third port output signals of the same phase.

5. The broadband filter with power division coupling function based on lumped elements according to claim 1, characterized in that: In the broadband filter with power division coupling function, when the third port is used as the input port, the second port and the fourth port output are anti-phase signals, and the first port is an isolation port; when the fourth port is used as the input port, the first port and the third port output are anti-phase signals.

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