A functionally reconfigurable filter based on a multi-mode resonant cavity

Abstract

The present invention discloses a functional reconfigurable filter based on a multi-mode resonant cavity, comprising: an input resonant cavity, a first output resonant cavity, a second output resonant cavity, an input feed network, a filter matching network, and an output feed network; the input resonant cavity is located at the center of the filter; the first output resonant cavity is located at the adjacent left side of the input resonant cavity; the second output resonant cavity is located at the adjacent right side of the input resonant cavity; the input feed network is located at the bottom of the input resonant cavity; the filter matching network is located at the top of the input resonant cavity; the output feed network is connected to the first output resonant cavity and the second output resonant cavity. The present invention can switch between the functions of a two-way single-pole double-throw filter switch and a duplexer function by changing the conduction and cutoff of each diode control circuit, and can achieve a low loss of about 0.45dB in different functional states, and has a high isolation characteristic of more than 30dB in the passband.

Description

Technical Field

[0001] The invention relates to the technical field of radio frequency filtering circuits, and in particular to a functionally reconfigurable filter based on a multi-mode resonant cavity. Background Art

[0002] With the development of the new generation of wireless communications, various industries and fields have put forward new requirements for wireless communications in terms of miniaturization, high performance and low cost. As an important RF passive component, filters have the function of filtering out clutter and reducing out-of-band noise. In order to meet the needs of high performance and integration, multifunctional collaborative fusion filter circuits have become a research hotspot, such as filter switches and filter power dividers.

[0003] Existing multifunctional filter circuits are mainly oriented towards planar resonators, including microstrip resonators, dielectric integrated waveguide (SIW) resonators, etc. For example, the design of the filter switch can integrate a diode circuit at the end of the microstrip resonator to quickly control the conduction and cutoff of the circuit, but the quality factor (Q value) of the planar circuit is low, resulting in large circuit losses. The filter switch design based on high-Q resonators is difficult to integrate the diode control circuit, and an external planar circuit is required for switch control, which has a complex structure. In addition, although the functions of components such as duplexers and power dividers can be realized in cavity resonators, the multifunctional fusion design needs to meet the characteristics and indicators of different circuits, and there is mutual interference between circuits, so high-performance multifunctional circuits are challenging.

[0004] In summary, the design of existing functional reconfigurable filters is subject to various technical limitations in practice. Summary of the invention

[0005] The present invention aims at the deficiencies in the existing functional reconfigurable filter technology and provides a functional reconfigurable filter based on a multi-mode resonant cavity. The functional reconfigurable filter of the present invention is based on the multi-mode resonance technology, analyzes the electromagnetic field distribution of multiple resonant modes in the feeding network and the cavity resonator, changes the coupling coefficient between the metal microstrip and the resonant mode by regulating the diode control circuit, realizes the functional reconfiguration requirement, and specifically completes the functions of a two-way single-pole double-throw filter switch and the function of a duplexer.

[0006] To achieve the above-mentioned object, the present invention provides a functionally reconfigurable filter based on a multi-mode resonant cavity, comprising: an input resonant cavity, a first output resonant cavity, a second output resonant cavity, an input feeding network, a filter matching network, and an output feeding network;

[0007] The input resonant cavity is located at the center of the filter;

[0008] The first output resonant cavity is located adjacent to the left side of the input resonant cavity;

[0009] The second output resonant cavity is located adjacent to the right side of the input resonant cavity;

[0010] The input feed network is located at the bottom of the input resonant cavity;

[0011] The filter matching network is located at the top of the input resonant cavity;

[0012] The output feeding network is connected to the first output resonant cavity and the second output resonant cavity.

[0013] Preferably, the input resonant cavity transmits energy with the first output resonant cavity and the second output resonant cavity respectively through a vertical coupling slot line; wherein the vertical coupling slot line is vertically distributed between the input resonant cavity and the output resonant cavity along the center line, and is used to realize the TE 101 mode is coupled from the input resonant cavity to the first output resonant cavity; or the TE 011 A mode is coupled from the input resonant cavity to the second output resonant cavity.

[0014] Preferably, the input feeding network directly uses the metal wall at the bottom of the input resonant cavity as the metal ground; the input feeding network includes: a coaxial probe and an asymmetric cross metal microstrip line, wherein the end of the asymmetric cross metal microstrip line is open-circuited, and the coaxial probe is perpendicular to the center of the asymmetric cross metal microstrip line.

[0015] Preferably, the filter matching network directly uses the metal wall at the top of the input resonant cavity as the metal ground; the filter matching network is composed of symmetrical cross metal microstrip lines, and the ends of the symmetrical cross metal microstrip lines are open circuits.

[0016] Preferably, the output feeding network is composed of four output feeding sub-networks with completely identical structures, namely: a first output feeding sub-network, a second output feeding sub-network, a third output feeding sub-network and a fourth output feeding sub-network; these four output feeding sub-networks all include: a coaxial probe, a straight metal microstrip line and a diode control circuit, wherein the end of the straight metal microstrip line is open-circuited, and the diode control circuit is integrated at a position deviating from the middle of the straight metal microstrip line, and the straight metal microstrip line is divided into two parts of different lengths.

[0017] Preferably, the first output feeder network and the second output feeder network are respectively located at the top and bottom of the first output resonant cavity; and the metal walls at the top and bottom of the first output resonant cavity are directly used as the metal grounds of the first output feeder network and the second output feeder network;

[0018] The third output feeder network and the fourth output feeder network are respectively located at the top and bottom of the second output resonant cavity; and the metal walls at the top and bottom of the second output resonant cavity are directly used as the metal ground of the third output feeder network and the fourth output feeder network.

[0019] Preferably, the first output feed sub-network, the second output feed sub-network, the third output feed sub-network and the fourth output feed sub-network correspond to four output ports respectively: a first output port, a second output port, a third output port and a fourth output port; and the switching of the "on" and "off" states of the corresponding output ports is achieved by regulating the diode control circuits in the four output feed sub-networks.

[0020] Preferably, the diode control circuit comprises: a capacitor, a diode and two inductors;

[0021] One end of the capacitor is connected to the longer part of the straight metal microstrip line, and the other end is connected to the positive electrode of the diode. The negative electrode of the diode is connected to the shorter part of the straight metal microstrip line. Two inductors are also connected in parallel at both ends of the diode, and the other ends of the two inductors are connected to a DC power supply.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention utilizes a PCB feeding structure in a feeding network, solves the problems of large volume of traditional waveguide feeding and unstable probe feeding, and combines the advantages of small volume, low cost, flexible design of microstrip lines and multi-resonance modes and high quality factor of cavity resonators.

[0024] The present invention utilizes two fundamental modes TE of orthogonal and different frequencies in the cavity resonator. 101 and TE 011 Based on the electromagnetic field distribution relationship between the metal microstrip and the resonant mode, the output port is switched between the "on" and "off" states by regulating the forward and reverse bias of the PIN diode in the control circuit. When only one of the four output ports is in the "on" state, the two-way single-pole double-throw filter switch function can be realized; when only one output port in the first and second output resonant cavities is in the "on" state, the duplexer function can be realized.

[0025] The present invention integrates different functions into one device, which can reduce system complexity and system footprint, while avoiding losses and signal transmission delays caused by device cascading, effectively improving work efficiency and system performance.

[0026] When the output port of the present invention is in the "on" state, the diode is reverse biased, thereby reducing the influence of the diode loss on the filtering performance. In addition, the diode has the advantage of fast switching speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of the position of the top metal microstrip line according to an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of the position of the bottom metal microstrip line according to an embodiment of the present invention;

[0031] Figure 4 A front view of a functionally reconfigurable filter according to an embodiment of the present invention;

[0032] Figure 5 A schematic diagram of the filter switch result when a single output port of the first output resonant cavity is opened;

[0033] Figure 6 Schematic diagram of the filter switch result opened for a single output port of the second output resonant cavity;

[0034] Figure 7 Schematic diagram of the result of realizing the duplexer function.

[0035] Explanation of the accompanying drawings: 1. rectangular resonant cavity; 2. coupling slot line; 3. input feeding network; 4. filter matching network; 5. first output feeding sub-network; 6. second output feeding sub-network; 7. third output feeding sub-network; 8. fourth output feeding sub-network; 11. input resonant cavity; 12. first output resonant cavity; 13. second output resonant cavity. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Before describing, let us first introduce the terms used in the present invention:

[0039] TE 101 Mode: This is a mode in the resonant cavity, where "TE" stands for transverse electric mode and "101" is the mode identifier, which indicates the distribution of the electric and magnetic fields in the two orthogonal directions of the resonant cavity. Specifically, "1" means that there is an electric field node (a node of the wave, where the electric field is zero) in one dimension of the resonant cavity, while "0" means that there is no node in the other dimension. "1" also means that there is an antinode (anti-node of the wave, where the magnetic field is strongest) in the direction of the magnetic field.

[0040] TE 011 Mode: Again, this is a mode in a resonant cavity, where "011" indicates the distribution of the electric field in two orthogonal directions. 011 In the pattern, a "0" indicates that there is no node of the electric field in either dimension, while a "1" indicates that there is an antinode in the direction of the magnetic field.

[0041] Embodiment 1

[0042] like Figure 1 As shown, it is a schematic diagram of the structure of this embodiment, including: a rectangular resonant cavity 1 composed of an input resonant cavity 11, a first output resonant cavity 12 and a second output resonant cavity 13, an input feeding network 3, a filter matching network 4 and an output feeding network.

[0043] The input resonant cavity 11 is located at the center of the entire circuit, the first output resonant cavity 12 is located on the adjacent left side of the input resonant cavity 11, and the second output resonant cavity 13 is located on the adjacent right side of the input resonant cavity 11. The input resonant cavity 11 transmits energy to the first output resonant cavity 12 and the second output resonant cavity 13 through the vertical coupling slot line 2; the vertical coupling slot line 2 is vertically distributed between the input resonant cavity 11 and the two output resonant cavities along the center line, and is used to realize the TE 101 mode is coupled from the input resonant cavity 11 to the first output resonant cavity 12; or the TE 011 The mode is coupled from the input resonant cavity 11 to the second output resonant cavity 13 .

[0044] The input feeding network 3 is located at the bottom of the input resonant cavity 11. The input feeding network 3 directly uses the metal wall at the bottom of the input resonant cavity 11 as the metal ground. The input feeding network 3 includes: a coaxial probe and an asymmetric cross metal microstrip line, wherein the end of the asymmetric cross metal microstrip line is open-circuited, and the coaxial probe is perpendicular to the center of the asymmetric cross metal microstrip line. The input feeding network 3 can simultaneously excite two TEs that are orthogonal to each other but have different frequencies in the rectangular resonant cavity 1. 101 and TE 011 model.

[0045] The filter matching network 4 directly uses the metal wall at the top of the input resonant cavity 11 as the metal ground; the filter matching network 4 is composed of symmetrical cross metal microstrip lines, and the ends of the symmetrical cross metal microstrip lines are open circuits. The introduction of the filter matching network 4 makes the entire structure more symmetrical, so that the two modes have field symmetry. In addition, the magnetic coupling between the symmetrically distributed filter matching network 4 and the two modes is always zero, which can achieve better impedance matching without affecting the resonance of the two modes.

[0046] The output feeding network is composed of four output feeding sub-networks with exactly the same structure, namely: a first output feeding sub-network 5, a second output feeding sub-network 6, a third output feeding sub-network 7 and a fourth output feeding sub-network 8; these four output feeding sub-networks all include: a coaxial probe, a straight metal microstrip line and a diode control circuit, wherein the end of the straight metal microstrip line is open-circuited, and a diode control circuit is integrated at a position deviating from the middle of the straight metal microstrip line, and the straight metal microstrip line is divided into two parts of different lengths.

[0047] The first output feeder network 5 and the second output feeder network 6 are respectively located at the top and bottom of the first output resonant cavity 12; and the metal walls at the top and bottom of the first output resonant cavity 12 are directly used as the metal ground of the first output feeder network 5 and the second output feeder network 6; the third output feeder network 7 and the fourth output feeder network 8 are respectively located at the top and bottom of the second output resonant cavity 13; and the metal walls at the top and bottom of the second output resonant cavity 13 are directly used as the metal ground of the third output feeder network 7 and the fourth output feeder network 8.

[0048] The first output feed sub-network 5, the second output feed sub-network 6, the third output feed sub-network 7 and the fourth output feed sub-network 8 correspond to four output ports: the first output port, the second output port, the third output port and the fourth output port, respectively. By regulating the diode control circuits in the four output feed networks, the switching of the "on" and "off" states of the corresponding output ports is achieved.

[0049] The output feed network integrates a diode control circuit including: capacitor (C), diode (PIN) and two inductors (L); one end of the capacitor is connected to the longer part of the metal microstrip line, and the other end is connected to the positive electrode of the diode. The negative electrode of the diode is connected to the shorter part of the metal microstrip line. Two inductors are also connected in parallel at both ends of the diode, and the other ends of the two inductors are connected to the DC power supply. When the diode is reverse biased, it can be equivalent to a 0.13pF capacitor, the corresponding output port is in the "on" state, and the mode can be received; when the diode is forward biased, it can be equivalent to a small resistor of 0.9Ω, the corresponding output port is in the "off" state, and the mode is suppressed.

[0050] When only one of the four output ports is in the "on" state, the two-way single-pole double-throw filter switch function can be realized; when only one output port in the first output resonant cavity 12 and the second output resonant cavity 13 is in the "on" state, the duplexer function can be realized; that is, when only one of the first and second output ports is in the "on" state, and at the same time only one of the third and fourth output ports is in the "on" state, the duplexer function is realized.

[0051] Embodiment 2

[0052] The specific internal structure, selected materials and achieved functional effects of the present invention will be described in detail below in conjunction with this embodiment.

[0053] In this embodiment, Figure 2 to Figure 4 As shown, L1 of the rectangular resonant cavity 1 is 56 mm, L2 is 49 mm, and L3 is 75 mm; the length H of the coupling slot line opened between the input resonant cavity 11 and the first output resonant cavity 12 and the second output resonant cavity 13 is 29 mm, and the width S is 2.2 mm; the (straight) metal microstrip line at both ends of the first output resonant cavity 12, where M1 = 43 mm, the (straight) metal microstrip line at both ends of the second output resonant cavity 13, where M2 = 41 mm, the (symmetrical) metal microstrip line at the top of the input resonant cavity 11 ) metal microstrip line, where M3=43mm, M4=42mm, and the (asymmetric) metal microstrip line at the bottom of the input resonant cavity 11, where M5=28mm, M6=28mm; the width W of the metal microstrip line is 7mm; the inductance value used by the diode control circuit in the first output resonant cavity 12 is 12.5nH, and the capacitance value is 4.5pF; the inductance value used by the diode control circuit in the second output resonant cavity 13 is 11.5nH, and the capacitance value is 3.5pF.

[0054] In this embodiment, the inner material of the rectangular resonant cavity 1 is silver-plated aluminum alloy; the dielectric substrates of the input feed network 3, the filter matching network 4 and the four output feed sub-networks are RO4370JXR plates with a thickness of 1.542 mm and a dielectric constant of 3. The diode in the control circuit is the SC-79 model of the Skyworks SMP1345 series.

[0055] Figure 5 and Figure 6 This is the result of a functional reconfigurable filter based on a multi-mode resonant cavity realizing a two-way single-pole double-throw filter switch function. The figure contains five curves, which are the S parameters from the input port to each output port. Figure 5 is the state where a single output port in the first output resonant cavity 12 is open, Figure 6is the state where a single output port in the second output resonant cavity 13 is open. From the results, it can be seen that the two passbands operate at 3.332 GHz and 3.658 GHz, the first passband has a 3dB absolute bandwidth of about 440 MHz, the minimum insertion loss is 0.446 dB, and the return loss in the passband is greater than 20 dB, the second passband has a 3dB absolute bandwidth of about 420 MHz, the minimum insertion loss is 0.412 dB, and the return loss in the passband is greater than 20 dB. In each switching state, the isolation in the passband is higher than 30 dB.

[0056] Figure 7 The figure is a result of realizing the duplexer function of a functionally reconfigurable filter based on a multi-mode resonant cavity. It is a state in which one output port in each of the first output resonant cavity 12 and the second output resonant cavity 13 is open. The figure contains five curves, which are the S parameters from the input port to each input and output port. From the results, it can be seen that the minimum insertion loss of the first passband is 0.475dB, the minimum insertion loss of the second passband is 0.443dB, the return loss in the passband is greater than 20dB, and in each switching state, the isolation in the passband is higher than 30dB.

[0057] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A functionally reconfigurable filter based on a multi-mode resonant cavity, characterized in that: include: An input resonant cavity, a first output resonant cavity, a second output resonant cavity, an input feeding network, a filter matching network, and an output feeding network; The input resonant cavity is located at the center of the filter; The first output resonant cavity is located on the adjacent left side of the input resonant cavity; the second output resonant cavity is located on the adjacent right side of the input resonant cavity; the input resonant cavity transmits energy with the first output resonant cavity and the second output resonant cavity respectively through a vertical coupling slot line; wherein the vertical coupling slot line is vertically distributed along the center line between the input resonant cavity and the first output resonant cavity and the second output resonant cavity, and is used to realize the TE 101 mode is coupled from the input resonant cavity to the first output resonant cavity; or the TE 011 A mode is coupled from the input resonant cavity to the second output resonant cavity; The input feed network is located at the bottom of the input resonant cavity; The filter matching network is located at the top of the input resonant cavity; The output feeding network is connected to the first output resonant cavity and the second output resonant cavity.

2. The functionally reconfigurable filter based on a multi-mode resonant cavity according to claim 1, characterized in that: The input feeding network directly uses the metal wall at the bottom of the input resonant cavity as a metal ground; The input feeding network comprises: a coaxial probe and an asymmetric cross metal microstrip line, wherein the end of the asymmetric cross metal microstrip line is an open circuit, and the coaxial probe is perpendicular to the center of the asymmetric cross metal microstrip line.

3. The functionally reconfigurable filter based on a multi-mode resonant cavity according to claim 1, characterized in that: The filter matching network directly uses the metal wall at the top of the input resonant cavity as a metal ground; the filter matching network is composed of symmetrical cross metal microstrip lines, and the ends of the symmetrical cross metal microstrip lines are open circuits.

4. The functionally reconfigurable filter based on a multi-mode resonant cavity according to claim 1, characterized in that: The output feeding network is composed of four output feeding sub-networks with completely identical structures, namely: a first output feeding sub-network, a second output feeding sub-network, a third output feeding sub-network and a fourth output feeding sub-network; the four output feeding sub-networks all include: a coaxial probe, a straight metal microstrip line and a diode control circuit, wherein the end of the straight metal microstrip line is open-circuited, and the diode control circuit is integrated at a position deviating from the middle of the straight metal microstrip line, and the straight metal microstrip line is divided into two parts of different lengths.

5. The functionally reconfigurable filter based on a multi-mode resonant cavity according to claim 4, characterized in that: The first output feeder network and the second output feeder network are respectively located at the top and bottom of the first output resonant cavity; and the metal walls at the top and bottom of the first output resonant cavity are directly used as the metal grounds of the first output feeder network and the second output feeder network; The third output feeder network and the fourth output feeder network are respectively located at the top and bottom of the second output resonant cavity; and the metal walls at the top and bottom of the second output resonant cavity are directly used as the metal ground of the third output feeder network and the fourth output feeder network.

6. The functionally reconfigurable filter based on a multi-mode resonant cavity according to claim 4, characterized in that: The first output feed sub-network, the second output feed sub-network, the third output feed sub-network and the fourth output feed sub-network correspond to four output ports respectively: a first output port, a second output port, a third output port and a fourth output port; by regulating the diode control circuits in the four output feed sub-networks, the switching of the "on" and "off" states of the corresponding output ports is achieved.

7. The functionally reconfigurable filter based on a multi-mode resonant cavity according to claim 4, characterized in that: The diode control circuit includes: a capacitor, a diode and two inductors; One end of the capacitor is connected to the longer part of the straight metal microstrip line, and the other end is connected to the positive electrode of the diode. The negative electrode of the diode is connected to the shorter part of the straight metal microstrip line. Two inductors are also connected in parallel at both ends of the diode, and the other ends of the two inductors are connected to a DC power supply.

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