Four-port narrow-band coupling filter based on lumped element

Abstract

The utility model belongs to the technical field of filters, and particularly relates to a four-port narrow-band coupling filter based on lumped elements, which comprises four ports, namely a first port, a second port, a third port and a fourth port, a 180-degree inverter, four inductors and four capacitors, the four capacitors and the 180-degree phase inverter are sequentially connected in series to form an annular structure, the four inductors are connected to the connecting positions of every two capacitors and the connecting positions of the capacitors and the phase inverter respectively, and the other ends of the four inductors are grounded. Compared with an existing microstrip line type and substrate integrated waveguide type narrow-band coupling filter, the narrow-band coupling filter provided by the utility model has the advantages of being more compact and higher in integration, and also has the performance of high isolation 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 four-port narrow-band coupling filter based on lumped elements. Background Art

[0002] A coupling filter is an electronic component that performs directional coupling sampling on the power of electromagnetic wave signals. 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 degree, operating frequency, isolation, reflection coefficient, and relative operating bandwidth.

[0003] As an important passive circuit, the coupling filter is generally used for power distribution and combination in the RF front-end circuit. The coupling filter is a four-port network device. The electromagnetic wave signal within the working bandwidth enters from the input port, and the power is output 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 the isolation port.

[0004] Traditional coupled filters are generally realized by optimizing the passive transmission line structure. Although the filter implemented by this distributed design method has good performance, it is often implemented with a complex structure and is therefore subject to factors such as area, cost, and process.

[0005] In summary, the existing traditional coupling filter circuit is complex, has a large structure size, and has poor isolation performance, which is not conducive to the development of communication systems towards ultra-miniaturization and integration. Utility Model Content

[0006] In view of the above-mentioned prior art, the utility model proposes a four-port narrowband coupling filter based on lumped elements to solve the problems of the existing circuit structure being complex, large in size, poor in isolation performance, and insufficient bandwidth.

[0007] The specific technical solutions adopted by the utility model are as follows:

[0008] A four-port narrowband coupling filter based on lumped elements comprises four ports set as a first port, a second port, a third port and a fourth port, a 180° inverter, four inductors and four capacitors. The four capacitors and the 180° inverter are sequentially connected in series to form a ring structure. The four inductors are respectively connected at the connection between two capacitors and at the connection between the capacitor and the inverter. The other ends of the four inductors are grounded. The first port, the second port, the third port and the fourth port are sequentially arranged at the connection between the inductor and the capacitor.

[0009] In the above technical solution, the inductance parameters are the same; and the capacitance distribution parameters are symmetrical about the top and bottom and the left and right.

[0010] In the above technical solution, 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. When the third port is used as an input port, the second port and the fourth port output signals of opposite phases, 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 opposite phases.

[0011] In the above technical solution, when any port is used as an input port, the signal amplitudes output from the through port and the coupled port can be adjusted in a specific proportion by appropriately adjusting the lumped parameters of the circuit.

[0012] The beneficial effects of the utility model: compared with the existing microstrip line type and substrate integrated waveguide type narrowband coupling filters, the utility model has the advantages of being more compact and more integrated, and takes into account the performance of high isolation, etc., and has important application value in 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 narrow-band coupling filter of the utility model.

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

[0015] Figure 3 The reflection coefficient curve S11, insertion loss coefficient curve S21, and coupling coefficient curve S41 of Example 1 obtained by simulation.

[0016] Figure 4 FIG. 3 is the isolation curve S31 of Example 1 obtained by simulation.

[0017] Figure 5 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

[0018] 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.

[0019] like Figure 1As shown, a four-port narrowband coupling filter based on lumped elements includes a first port 1, a second output port 2, a third port 3, a fourth output port 4, four inductors 2a-2d, four capacitors 1a-1d and a 180° inverter 3. Capacitor 1a, capacitor 1b, capacitor 1c, capacitor 1d and inverter 3 are connected in series to form a ring structure, the connection between capacitor 1d and capacitor 1a is connected to one end of inductor 2a, and the other end of inductor 2a is grounded; the connection between capacitor 1a and capacitor 1b is connected to one end of inductor 2b, and the other end of inductor 2b is grounded; the connection between capacitor 1c and capacitor 1d is connected to one end of inductor 2d, and the other end of inductor 2d is grounded; the connection between capacitor 2c and inverter 3 is connected to one end of inductor 2c, and the other end of inductor 2c is grounded. A first port 1 is provided at the connection between the inductor 2a and the capacitor 1a; a second port 2 is provided at the connection between the inductor 2b and the capacitor 1a; a third port 3 is provided at the connection between the inductor 2c and the inverter; and a fourth port 4 is provided at the connection between the inductor 2d and the capacitor 1c.

[0020] In order to better illustrate the technical effect of the present invention, Figure 2 A schematic diagram of the parameter relationship of the lumped elements of the implementation case is given.

[0021] The above circuit schematic diagram is simulated using ADS simulation software. The S parameter curve obtained by simulation is as follows Figure 3 and Figure 4 shown. Figure 3 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 4 Isolation coefficient S31

[0022] 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 5 shown. Figure 5 The 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.

[0023] 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 four-port narrowband coupled filter 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, four inductors and four capacitors. The four capacitors and the 180° inverter are connected in series in sequence to form a ring structure. The four inductors are connected at the connection between two capacitors and at the connection between the capacitor and the inverter respectively. The other ends of the four inductors are grounded. The first port, the second port, the third port and the fourth port are arranged in sequence at the connection between the inductor and the capacitor.

2. The four-port narrowband coupled filter based on lumped elements according to claim 1, characterized in that: The inductance parameters are the same.

3. The four-port narrowband coupled filter based on lumped elements according to claim 1, characterized in that: The capacitance distribution parameters are symmetrical about top and bottom and left and right.

4. The four-port narrowband coupled filter based on lumped elements according to claim 1, characterized in that: In the narrowband 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.

5. The four-port narrowband coupled filter based on lumped elements according to claim 1, characterized in that: In the narrowband coupling filter, when the third port is used as an input port, the second port and the fourth port output inverted signals, 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 inverted signals.

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