Reconfigurable non-reflection filter circuit structure

Abstract

The invention discloses a reconfigurable non-reflection filter circuit structure, the whole circuit structure of a main circuit module is vertically symmetrical about a horizontal center line, a capacitor is connected in parallel between the vertically symmetrical circuits, and the input end and the output end of the main circuit module are respectively connected with a port 1 and a port 2; a tunable band-pass filtering response is formed through a series inductor pair structure and a parallel capacitor pair structure of the main circuit module, and is used for carrying out preliminary attenuation and selective filtering on high-frequency components in input signals. Two mutual inductance inductor pairs are arranged between upper and lower symmetrical circuits of the main circuit and are used for forming one or more transmission zero points outside the band. And the parallel capacitor and the two pairs of mutual inductors form a transmission zero point, so that the stop band suppression and the frequency selectivity of the filter are improved. And the auxiliary circuit module is connected in parallel to the port 1 and is used for forming complementary band-stop response with the main circuit module. According to the invention, the tunable characteristic and the non-reflection characteristic are combined, and efficient impedance matching can be realized in a large frequency range.

Description

Technical Field

[0001] The invention relates to a radio frequency communication device, in particular to a reconfigurable reflectionless filter. Background Art

[0002] As wireless communication systems develop towards high frequency and broadband, the requirements for filter performance continue to increase. Reconfigurable filters have become key components to meet the needs of diversified frequency bands in complex electromagnetic environments due to their flexibility in frequency and bandwidth adjustment. Traditional reconfigurable filters dynamically adjust frequency and bandwidth by introducing adjustable elements (such as varactor diodes) into the circuit to adapt to different operating frequency bands. However, existing reconfigurable filters often fail to maintain good port impedance matching during the tuning process, resulting in increased port reflections and transmission losses, which adversely affect the overall performance of the system. Therefore, how to achieve impedance matching while reconstructing the frequency to reduce reflection losses and improve signal integrity has become an important technical challenge in current filter design.

[0003] As an emerging filter design, the reflectionless filter introduces absorption branches or load elements into the circuit so that the stopband signal is no longer reflected back to the input end, but is dissipated inside the device. This type of filter maintains constant port impedance over a wide frequency range, has excellent reflectionless characteristics, can effectively reduce reflection losses within the stopband, and reduces interference to the source end, thus showing significant advantages in high-frequency signal transmission and sensitive electromagnetic compatibility environments. The design of the reflectionless filter usually relies on complementary channels or symmetrical structures to achieve broadband reflectionless effects, but this structure increases the complexity and volume of the circuit, limiting its application in miniaturized and portable devices. Summary of the invention

[0004] Purpose of the invention: In view of the above-mentioned prior art, a reconfigurable reflectionless filter based on lumped elements is proposed to solve the problems of poor impedance matching, complex design, large circuit size and low integration of existing reflectionless and reconfigurable filters in high-frequency system applications.

[0005] Technical solution: A reconfigurable reflectionless filter circuit structure, including port 1, port 2, a main circuit module and an auxiliary circuit module; The circuit structure of the main circuit module is symmetrical about the horizontal midline, and a capacitor is connected in parallel between the upper and lower symmetrical circuits. The input end and the output end of the main circuit module are connected to port 1 and port 2 respectively. A tunable bandpass filter response is formed through the series inductor pair and the parallel capacitor pair structure of the main circuit module, which is used to perform preliminary attenuation and selective filtering on the high-frequency components in the input signal; two pairs of inductors with mutual inductance are arranged between the upper and lower symmetrical circuits of the main circuit, which are used to form one or more transmission zeros outside the band; the parallel capacitor and the two pairs of inductors with mutual inductance form a transmission zero together, which is used to improve the stopband suppression and the frequency selectivity of the filter; The auxiliary circuit module is connected in parallel at the port 1 to form a complementary band-stop response with the main circuit module.

[0006] Further, in the main circuit module, the upper and lower symmetrical single-side structure includes a series inductor structure and a parallel capacitor pair structure; the series inductor structure includes an inductor L1, an inductor L2, an inductor L3, an inductor L4 and a grounded inductor L5 connected in series in sequence, a grounded capacitor is connected in parallel between two adjacent inductors to form the parallel capacitor pair structure, and an adjustable capacitor C is connected in parallel between the inductor L3 and the inductor L4. t1 A capacitor C4 is connected in parallel between the upper and lower symmetrical circuits, and one end of the capacitor C4 is connected between the inductor L4 and the grounding inductor L5; between the upper and lower symmetrical structures, the inductor L4' and the inductor L4 form a pair of mutual inductance inductance pairs, and the relative grounding inductor L5 and the grounding inductor L5' form a pair of mutual inductance inductance pairs.

[0007] Further, the auxiliary circuit module includes a T-type circuit, a branch A, a branch B and a capacitor C5; the port 1 is connected in series with the T-type circuit and the branch A in sequence; the capacitor C5 is connected in parallel at the connection point between the T-type circuit and the branch A in series, and the other end of the capacitor C5 is connected to the branch B; wherein the T-type circuit is composed of an inductor L6 and an inductor L7 connected in series, and a grounding capacitor C6 is connected in parallel at the connection point; the branch A includes an inductor L8, an inductor L9, an inductor L1 connected in series in sequence; 10 And grounding resistor R, grounding capacitor C7 is connected in parallel at the input end of inductor L8, and grounding capacitor C7 is connected in parallel at inductor L9 and inductor L 10 The branch B includes an inductor L connected in series. 11 、Inductance L 12 、Inductance L 13 and grounded variable capacitor C t2 , in the inductor L 11 The input end is connected in parallel to the ground capacitor C9, and the inductor L 12 and inductor L 13 The capacitor C is connected to the ground in parallel 10 ; Inductor L8 and inductor L 11 Form a set of mutual inductance pairs.

[0008] Furthermore, by tuning the adjustable capacitor C t1 And the relative adjustable capacitor C t1 'The capacitance value achieves tuning of the center resonant frequency.

[0009] Furthermore, by tuning the variable capacitor C t2 Achieve a tunable reflection-free filter response.

[0010] Beneficial effects: The present invention proposes a reconfigurable reflectionless filter based on lumped elements, in which the center frequencies of the filter channel and the reflectionless channel are synchronously tuned, and the bandwidths of the passband and the stopband are matched, and finally the reflectionless tunable effect is achieved by using lumped elements. The present invention combines the tunable characteristics with the reflectionless characteristics, and can achieve efficient impedance matching within a large frequency range. This design can not only flexibly adjust the center frequency to meet the diverse frequency band requirements, but also maintain a low reflection state within the entire tuning range, significantly improving the system transmission efficiency and signal quality, and the overall structure is compact and easy to integrate, and can be widely used in miniaturized and integrated electronic communication systems.

[0011] Specifically, a tunable bandpass filter response is formed through the series inductor pair and parallel capacitor pair structure of the main circuit, which performs preliminary attenuation and selective filtering on the high-frequency components in the input signal. The mutual inductances M1 and M2 between the upper and lower symmetrical circuits of the main circuit increase the coupling between the signal paths, causing the signal to cancel out phase at a specific frequency, thereby forming one or more transmission zeros outside the band. Connecting capacitor C4 in parallel between the upper and lower circuits can further enhance the coupling, and together with the two pairs of mutual inductors, form a transmission zero, thereby improving the stopband suppression and the frequency selectivity of the filter.

[0012] The variable complementary auxiliary circuit structure loaded in parallel with the main circuit can realize the dynamic complementary response of the auxiliary circuit while realizing the tunable bandpass filter response of the main circuit. The reflected signal in the auxiliary circuit is dissipated through the grounding circuit in branch A, and a reflection-free filter response is realized. The variable capacitor C in branch B can be tuned. t2 , and through the configuration of the coupling capacitor C5 between branch A and branch B and the mutual inductance M3 between branch A and branch B, a dynamic balance with the complementary response of the main circuit is formed to achieve a reflection-free reconfigurable response. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of a reconfigurable reflectionless filter structure; Figure 2 It is a schematic diagram of the main circuit structure of a reconfigurable reflectionless filter; Figure 3 It is a schematic diagram of the auxiliary circuit structure of a reconfigurable reflectionless filter; Figure 4 In this embodiment, container C t and C t1 When changing | S 11 |parameters; Figure 5 In this embodiment, container C t and C t1 When changing | S 21 |Parameters. DETAILED DESCRIPTION

[0014] The present invention will be further explained below in conjunction with the accompanying drawings.

[0015] like Figure 1 As shown, a reconfigurable non-reflective filter circuit structure is composed of port 1, port 2, a main circuit module and an auxiliary circuit module. The input port of the main circuit module is connected to port 1, the output port is connected to port 2, and the auxiliary circuit module is connected in parallel at port 1.

[0016] like Figure 2 As shown, the circuit structure of the main circuit module is symmetrical about the horizontal midline, and is composed of a pair of series inductance pairs, a pair of parallel capacitor pairs and capacitor C4. Among them, a series inductance pair is composed of inductance L1, inductance L2, inductance L3, inductance L4 and grounding inductance L5 connected in series in sequence. The grounding capacitors connected in parallel between the inductance L1, inductance L2, inductance L3, inductance L4 and grounding inductance L5 constitute a parallel capacitor pair structure. Specifically, the grounding capacitor C1 is connected in parallel between the inductance L1 and the inductance L2, the grounding capacitor C2 is connected in parallel between the inductance L2 and the inductance L3, and the variable grounding capacitor C is connected in parallel between the inductance L3 and the inductance L4. t1 , inductor L4 and grounding inductor L5 are connected in parallel with grounding capacitor C3. The other end of inductor L1 is connected to port 1, and port 1, the above-mentioned series inductor pair and parallel capacitor pair circuit are mirror-copied upward along the horizontal midline to form a complete symmetrically distributed circuit module structure, and the upper and lower circuits are connected through capacitor C4, and port 1 is mirrored to form port 2. The relative inductor L4' and inductor L4 form a pair of mutual inductance inductance pairs, and the mutual inductance coefficient is M2; the relative grounding inductor L5 and grounding inductor L5' form a pair of mutual inductance inductance pairs, and the mutual inductance coefficient is M1.

[0017] like Figure 3As shown, the auxiliary circuit module consists of a T-type circuit, branch A, branch B and capacitor C5. Port 1 is connected in series with the T-type circuit and branch A in turn; capacitor C5 is connected in parallel at the connection point between the T-type circuit and branch A in series, and the other end of capacitor C5 is connected to branch B to form a complete auxiliary circuit module. Among them, the T-type circuit is composed of inductor L6 and inductor L7 connected in series, and a grounding capacitor C6 is connected in parallel at the connection point between inductor L6 and inductor L7. Branch A consists of inductor L8, inductor L9, inductor L 10 , grounding capacitor C7, grounding capacitor C8 and grounding resistor R, among which inductor L8, inductor L9, inductor L 10 and grounding resistor R in series, and grounding capacitor C7 is connected in parallel at the input end of inductor L8, and grounding capacitor C7 is connected in parallel at the input end of inductor L9 and inductor L 10 The grounding capacitor C8 is connected in parallel between them. Branch B consists of inductor L 11 、Inductance L 12 、Inductance L 13 , grounding capacitor C9, grounding capacitor C 10 And the grounded variable capacitor C t2 The inductor L 11 、Inductance L 12 、Inductance L 13 and grounded variable capacitor C t2 In series, in the inductor L 11 The input end is connected in parallel to the ground capacitor C9, and the inductor L 12 and inductor L 13 The capacitor C is connected to the ground in parallel 10 The capacitor C5 is connected in parallel with the input end of the inductor L8. 11 Between the input terminals; inductor L8 and inductor L 11 A set of mutual inductance pairs is formed, and the mutual inductance coefficient is M3.

[0018] The microwave radio frequency signal is input through port 1, and forms a basic bandpass filter response in the structure of the series inductor pair and parallel capacitor pair through the main circuit. The signal that generates the bandpass filter response passes through the mutual inductance M2 between the inductor L4' and the inductor L4 and the mutual inductance M1 between the inductor L5 and the inductor L5', so that the signal has phase cancellation at a specific frequency, thereby forming one or more transmission zeros outside the band. The formation of transmission zeros increases the attenuation of out-of-band signals and enhances the stopband suppression capability of the filter. Capacitor C4 is connected in parallel between the upper and lower circuits. Under the appropriate configuration of capacitor C4 and mutual inductance M1 and M2 parameters, the circuit forms a transmission zero on the right side of the passband, further suppressing out-of-band signals and enhancing frequency selectivity. Finally, the signal is output through port 2. Since the circuit is completely symmetrical from top to bottom, the phase consistency and impedance matching of the signal transmission path are ensured, and the low insertion loss and stable frequency response of the filter are maintained. And in the variable capacitor C t1 ' and variable capacitor C t1Under the action of and, the center resonant frequency can be tuned by tuning the capacitance value. Since the auxiliary circuit and the main circuit form a complementary band-stop response, the reflected signal in the band-stop range of the main circuit will be introduced into the auxiliary circuit through the parallel branch, and then flow to the grounding resistor R to be dissipated to achieve a non-reflection effect. t1 and variable capacitor C t1 'When tuning, the variable capacitor C in the auxiliary circuit t2 and inductor L8 and inductor L 11 The configuration of mutual inductance parameters forms a dynamic balance of complementary responses, which is achieved by tuning the variable capacitor C t2 A tunable reflection-free filter response can be achieved.

[0019] This embodiment provides a reconfigurable non-reflection filter with a center frequency of 2 GHz, and its specific parameters are: L6 = 2.6nH, L7 = 2.9nH, L8 = L 11 =0.3nH, L9=L 10 =6.0nH, L 12 =L 13 =1.4nH, L1'=L1=L3'=L3=0.7nH, L2'=L2=8.4nH, L4'=L4=L5'=L5=0.66nH, C6=1.4pF, C7=C9=0.135pF, C5=0.4pF, C 10 =0.67pF, C8=0.7pF, C1=C1'=0.9pF, C2=C2'=0.2pF, C3=C3'=0.3pF, M1=0.15nH, M2=0.06nH, M3=0.06nH; C t1 =C t1 ', the adjustable range is 1.1pF-13.6pF; C t2 The adjustable range is 3.0pF-6.3pF.

[0020] Figure 4 , Figure 5 The center frequency obtained by simulation in this embodiment varies with C t2 and C t1 , C t1 'The frequency response curve of the change. The tuning range of the center frequency in this embodiment is between 1.74-2.34GHz, the corresponding relative center frequency tuning range is 29.4%, and the insertion loss in the band is less than 0.252dB. In the entire tuning range, the return loss in the band is less than 8.45dB, between 0.73GHz-3.79GHz, |S 11| are all less than -10dB, and the frequency selectivity is good. It can be seen from this that when the center frequency is tunable, the embodiment can still ensure the non-reflection response of the reflected signal and has a reconfigurable non-reflection bandpass filtering characteristic.

[0021] The tunable filter of the present invention is composed of lumped elements, and has the advantages of miniaturization and integration; it can realize flexible frequency tuning within a wide frequency band, and maintain stable non-reflection characteristics within the entire tuning range, and also has good impedance matching and frequency selection characteristics. In addition, since the filter channel and the non-reflection channel can be tuned synchronously, the absolute bandwidth is constant and the insertion loss within the band is not significantly deteriorated, the non-reflection bandwidth is wide, and the absorption effect is good.

[0022] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A reconfigurable reflectionless filter circuit structure, characterized in that: It includes port 1, port 2, a main circuit module and an auxiliary circuit module; The circuit structure of the main circuit module is symmetrical about the horizontal midline, and a capacitor is connected in parallel between the upper and lower symmetrical circuits. The input end and the output end of the main circuit module are connected to port 1 and port 2 respectively. A tunable bandpass filter response is formed through the series inductor pair and the parallel capacitor pair structure of the main circuit module, which is used to perform preliminary attenuation and selective filtering on the high-frequency components in the input signal; two pairs of inductors with mutual inductance are arranged between the upper and lower symmetrical circuits of the main circuit, which are used to form one or more transmission zeros outside the band; the parallel capacitor and the two pairs of inductors with mutual inductance form a transmission zero together, which is used to improve the stopband suppression and the frequency selectivity of the filter; The auxiliary circuit module is connected in parallel at the port 1 to form a complementary band-stop response with the main circuit module.

2. The reconfigurable reflectionless filter circuit structure according to claim 1, characterized in that: In the main circuit module, the upper and lower symmetrical single-side structure includes a series inductor structure and a parallel capacitor pair structure; the series inductor structure includes an inductor L1, an inductor L2, an inductor L3, an inductor L4 and a grounded inductor L5 connected in series in sequence, a grounded capacitor is connected in parallel between two adjacent inductors to form the parallel capacitor pair structure, and an adjustable capacitor C is connected in parallel between the inductor L3 and the inductor L4. t1 A capacitor C4 is connected in parallel between the upper and lower symmetrical circuits, and one end of the capacitor C4 is connected between the inductor L4 and the grounding inductor L5; between the upper and lower symmetrical structures, the inductor L4' and the inductor L4 form a pair of mutual inductance inductance pairs, and the relative grounding inductor L5 and the grounding inductor L5' form a pair of mutual inductance inductance pairs.

3. The reconfigurable reflectionless filter circuit structure according to claim 1 or 2, characterized in that: The auxiliary circuit module includes a T-type circuit, a branch A, a branch B and a capacitor C5; the port 1 is connected in series with the T-type circuit and the branch A in sequence; the capacitor C5 is connected in parallel at the connection point between the T-type circuit and the branch A, and the other end of the capacitor C5 is connected to the branch B; wherein the T-type circuit is composed of an inductor L6 and an inductor L7 connected in series, and a capacitor C6 connected in parallel at the connection point; the branch A includes an inductor L8, an inductor L9, an inductor L1 connected in series in sequence 10 And grounding resistor R, grounding capacitor C7 is connected in parallel at the input end of inductor L8, and grounding capacitor C7 is connected in parallel at inductor L9 and inductor L 10 The branch B includes an inductor L connected in series. 11 、Inductance L 12 、Inductance L 13 and grounded variable capacitor C t2 , in the inductor L 11 The input end is connected in parallel to the ground capacitor C9, and the inductor L 12 and inductor L 13 The capacitor C is connected to the ground in parallel 10 ; Inductor L8 and inductor L 11 Form a set of mutual inductance pairs.

4. The reconfigurable reflectionless filter circuit structure according to claim 3, characterized in that: By tuning the adjustable capacitor C t1 And the relative adjustable capacitor C t1 'The capacitance value achieves tuning of the center resonant frequency.

5. The reconfigurable reflectionless filter circuit structure according to claim 4, characterized in that: By tuning the variable capacitor C t2 Achieve a tunable reflection-free filter response.

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