Electrically tunable filter based on dielectric filled waveguide

Abstract

The invention discloses an electrically tunable filter based on a dielectric-loaded waveguide, and belongs to the technical field of dielectric-loaded waveguide filters. The dielectric-filled waveguide filter comprises a metal outer cavity in which paired cavity bodies are formed, the paired cavity bodies are communicated through a coupling window, and filling media are arranged in the cavity bodies; the metal columns I and the metal columns II are embedded into the filling medium, are arranged in pairs and are respectively arranged in the paired cavities; the control circuit is provided with an input feed network, an output feed network and a variable capacitance diode regulation and control circuit, and a variable capacitance diode can be reversely biased under the action of a direct current bias signal and is equivalent to a time-varying capacitor; wherein the filling medium, the metal outer cavity, the metal column I, the metal column II and the control circuit form a medium-filled waveguide resonant cavity. According to the filter, the working frequency of the filter is continuously adjustable, and the filter has the advantages of being high in isolation, small in size, convenient to tune, easy to integrate with a circuit and the like.

Description

Technical Field

[0001] The present invention relates to the field of dielectric-filled waveguide filters, and in particular to an electrically tunable filter based on a dielectric-filled waveguide. Background Art

[0002] The rapid development of 5G communication base stations and the Internet of Things (IoT) is placing higher demands on filter performance. Traditional metal waveguide filters are limited in size, power handling, quality factor, and insertion loss. While traditional mechanically adjusted high-Q resonators offer certain advantages, they are slow, lack practicality, and have a complex structure. Dielectric-filled electrically tunable filters can dynamically adjust parameters to achieve diverse functions. They offer significant advantages such as small size, high power handling, high quality factor, low insertion loss, rapid adjustment, and a simple structure. Therefore, dielectric-filled electrically tunable filters have important practical significance and application value in meeting the development needs of the communications and IoT sectors and improving the efficiency of spectrum resource utilization.

[0003] Dielectric-filled filters improve filtering performance by introducing high-dielectric-constant dielectric materials, which is of great significance for the miniaturization, integration, and low-loss of RF front-end circuits. Traditional filters often use cavity or microstrip line structures to achieve frequency selection, but they have disadvantages such as large size, limited quality factor (Q value), and difficulty in integration with planar circuits. In addition, dielectric-filled waveguide resonant cavity technology can significantly improve the selectivity and out-of-band suppression capability of the filter by optimizing the electromagnetic field distribution. At present, the design of dielectric-filled filters is mainly based on high-performance media such as ceramics and silicon-based composites, thus showing lower passband loss and stronger environmental adaptability in high-frequency and high-power scenarios such as millimeter-wave communications and satellite payloads. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention proposes an electrically tunable filter based on a dielectric-filled waveguide.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A first aspect of the present invention relates to an electrically tunable filter based on a dielectric-filled waveguide, comprising:

[0007] The metal outer cavity forms a pair of cavities inside, which are connected through coupling windows, and the cavity is filled with a filling medium;

[0008] The first metal pillar and the second metal pillar, which are embedded in the filling medium and arranged in pairs, are respectively arranged in the paired cavities;

[0009] and a control circuit having an input feeding network, an output feeding network, and a varactor diode control circuit. Under the action of a DC bias signal, the varactor diode can be reverse biased and equivalent to a time-varying capacitor;

[0010] The filling medium, the metal outer cavity, the first metal column, the second metal column and the control circuit constitute a dielectric-filled waveguide resonant cavity.

[0011] Optionally, the varactor diode control circuit includes a capacitor C, an inductor, a varactor diode, and a DC voltage source; the positive pole of the varactor diode is grounded, and the negative pole of the varactor diode is connected to one end of the capacitor C and one end of the inductor; the other end of the inductor is connected to the DC voltage source in turn, and the other end of the DC voltage source is grounded.

[0012] Optionally, the dielectric constant of the filling medium is 38.5, the loss tangent is 0.000134, and the material of the metal pillar 1 and the metal pillar 2 is metal copper.

[0013] Optionally, the impedance of the input feeding network and the output feeding network are both 50Ω.

[0014] Optionally, the coupling window is rectangular in shape.

[0015] Optionally, when a reverse bias voltage of the varactor diode is loaded on the varactor diode control circuit, the reverse bias voltage can change the capacitance value of the varactor diode.

[0016] Optionally, the input feed network and the output feed network are both arranged on an upper PCB board and connected to the filling medium, and the upper PCB board covers the upper end of the filling medium.

[0017] A second aspect of the present invention relates to the application of the above-mentioned electrically tunable filter based on dielectric-filled waveguide in radar, mobile communications and satellite communications.

[0018] A third aspect of the present invention relates to a communication device, comprising the above-mentioned electrically tunable filter based on dielectric-filled waveguide.

[0019] Beneficial effects of the present invention:

[0020] (1) The present invention adopts a filling medium to design a tunable filter, so that the filter has a very high quality factor, and the optimal passband loss is only 0.7dB, achieving a high Q value and low loss design.

[0021] (2) The present invention introduces source-load coupling between the input feed and the output feed and a movable transmission zero on the right side of the passband, thereby achieving higher passband selectivity and out-of-band suppression level.

[0022] (3) The present invention achieves reconfigurable center frequency by regulating the varactor diode. Most of the tunable filters currently studied use two or more tuning elements, and most of them are mechanically adjusted. The tunable filters using varactor diodes are mostly microstrip filters, and there are few designs that directly adjust the three-dimensional electromagnetic field. The present invention innovatively proposes a tuning structure that uses a single varactor diode to achieve three-dimensional electromagnetic field regulation. When the reverse bias voltage of the varactor diode changes, the center frequency of the filter also changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below with reference to the accompanying drawings.

[0024] Figure 1 It is a structural schematic diagram of the dielectric-filled electrically tunable filter proposed in the present invention.

[0025] Figure 2 This is a top view of the dielectric-filled electrically tunable filter proposed in the present invention.

[0026] Figure 3 This is a left view of the dielectric-filled electrically tunable filter proposed in the present invention.

[0027] Figure 4 This is a front view of the dielectric-filled electrically tunable filter proposed by the present invention.

[0028] Figure 5 The present invention provides a circuit diagram of a varactor diode control circuit of a dielectric-filled electrically tunable filter.

[0029] Figure 6 It is the forward transmission characteristic curve and return loss curve of the filter after loading the reverse biased DC signal of the present invention.

[0030] In the figure: 1. Input feed network; 2. Output feed network; 3. Metal cavity surrounding the dielectric; 4. Metal pillar 1; 5. Metal pillar 2; 6. PCB circuit board; 7. Varactor diode control circuit; 8. Upper PCB board. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0032] In some embodiments of the present invention, Figure 1 and Figure 5As shown, the present invention proposes a dielectric-filled electrically tunable filter, including an input feed network 1, an output feed network 2, a metal external cavity 3, a metal column 1 4, a metal column 2 5, a PCB circuit board 6, a PCB varactor diode control circuit 7 and an upper PCB board 8; the dielectric-filled waveguide resonant cavity body is a filling dielectric, a dielectric with an electrical constant of 38.5 and a loss tangent of 0.000134, surrounded by the metal external cavity 3, the top of the dielectric is directly connected to the upper PCB board 8 used as the input feed network 1 and the output feed network 2, and the bottom of the dielectric is directly fixed to the PCB circuit board 6; the metal column 1 4 and the metal column 2 5 are embedded in the filling dielectric, and the other The end is connected to the PCB varactor diode control circuit; the input feeding network 1 is directly connected to the first cavity of the dielectric-filled waveguide resonant cavity by a coaxial device through the upper PCB board 8; the output feeding network 2 is directly connected to the second cavity of the dielectric-filled waveguide resonant cavity by a coaxial device through the upper PCB board; the inter-cavity coupling portion is processed with a rectangular window, and the rectangular coupling window directly connects the two cavities of the dielectric-filled waveguide resonant cavity to achieve electromagnetic energy coupling between the dielectric-filled waveguide resonant cavities; the PCB circuit board is fixed to the peripheral metal cavity by screws; the PCB varactor diode control circuit has two groups in total to achieve independent control of different varactor diodes.

[0033] As a further preferred embodiment, the metal pillar 1 4 and the metal pillar 2 5 are made of copper, the dielectric constant of the filling medium is 38.5, the loss tangent is 0.000134, the surface is silver-plated, and the material of the outer metal cavity is aluminum.

[0034] As a further preferred solution, the dielectric substrate of the PCB board adopts Rogers 4003 plate, which has a dielectric constant of 3.55, a thickness of 0.81 mm, and a dielectric loss tangent of 0.0027.

[0035] In some embodiments of the present invention, rectangular coupling windows are provided between adjacent cavities to achieve electromagnetic energy coupling between the cavities.

[0036] The PCB control circuit includes a varactor control circuit 7, which specifically includes a capacitor, an inductor, a varactor diode, and a DC voltage; the positive electrode of the varactor diode is grounded, and its negative electrode is connected to one end of the capacitor and one end of the inductor. Under the action of a low signal with a DC bias, the varactor diode is reverse biased and is equivalent to a time-varying capacitor.

[0037] The impedance of the input feeding network 1 and the output feeding network 2 are both 50.

[0038] In the filter of this embodiment, a reverse DC bias signal is loaded during operation to change the capacitance of the varactor diode, which is equivalent to changing the equivalent electrical length of the metal column loaded in the filling medium, thereby achieving continuous adjustment of the operating frequency.

[0039] In this embodiment, after selecting appropriate capacitance and inductance values ​​of the varactor diode, the change in capacitance of the varactor diode in this embodiment can regulate the electromagnetic field distribution between cavities, thereby achieving a change in the operating frequency.

[0040] In some other embodiments of the present invention, a filter is combined to perform further simulation tests.

[0041] like Figure 2 、 Figure 3 and Figure 4 As shown, a simulation test is performed on the dielectric-filled electrically tunable filter in this embodiment, and the parameters of the tested filter are as follows:

[0042] The outer metal cavity has a length of L1 = 24.75 mm, a width of W1 = 14 mm, and a height of H1 = 5.87 mm. The rectangular coupling window has lengths l3 = 3 mm and l4 = 3 mm, with a width w3 = 0.75 mm. The metal pillar has a height h3 = 4.4 mm and a diameter d1 = 1.5 mm. The dielectric filler has a length l2 = 20.75 mm, a width w2 = 10 mm, and a height h2 = 5 mm. The trench in the dielectric has a length l5 = 6 mm, a width w4 = 3 mm, and a height h4 = 1.5 mm. The coaxial probe has a diameter d2 = 0.63 mm and a length l6 = 3.5 mm. The dielectric substrate uses Rogers 4003 sheet material, which has a dielectric constant of 3.55, a thickness of 0.81 mm, and a dielectric loss tangent of 0.0027. The DC bias voltages Vdc are 5.51 V and 5.52 V, respectively. The DC blocking capacitor C2 is 5.6 pF, and the inductor L1 is 100 nH.

[0043] The test results are as follows Figure 6 As shown, the filter has an insertion loss of 1.8dB to 0.7dB within its operating frequency band. A movable transmission zero on the right side of the passband ensures excellent passband selectivity and out-of-band rejection. Return loss is better than 20dB. The operating frequency is continuously adjustable from 2.14GHz to 2.24GHz.

[0044] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0045] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0046] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. An electrically tunable filter based on a dielectric-filled waveguide, characterized in that: include: The metal outer cavity forms a pair of cavities inside, which are connected through coupling windows, and the cavity is filled with a filling medium; The first metal pillar and the second metal pillar, which are embedded in the filling medium and arranged in pairs, are respectively arranged in the paired cavities; and a control circuit having an input feeding network, an output feeding network, and a varactor diode control circuit. Under the action of a DC bias signal, the varactor diode can be reverse biased and equivalent to a time-varying capacitor; The filling medium, the metal outer cavity, the first metal column, the second metal column and the control circuit constitute a dielectric-filled waveguide resonant cavity.

2. The electrically tunable filter based on dielectric-filled waveguide according to claim 1, characterized in that: The varactor diode control circuit includes a capacitor C, an inductor, a varactor diode, and a DC voltage source; the positive electrode of the varactor diode is grounded, and the negative electrode of the varactor diode is connected to one end of the capacitor C and one end of the inductor; the other end of the inductor is connected to the DC voltage source in sequence, and the other end of the DC voltage source is grounded.

3. The electrically tunable filter based on dielectric-filled waveguide according to claim 1, characterized in that: The dielectric constant of the filling medium is 38.5, and the loss tangent is 0.000134.

4. The electrically tunable filter based on dielectric-filled waveguide according to claim 1, characterized in that: The impedance of the input feeding network and the output feeding network are both 50Ω.

5. The electrically tunable filter based on dielectric-filled waveguide according to claim 1, characterized in that: The coupling window is in a rectangular shape.

6. The electrically tunable filter based on dielectric-filled waveguide according to claim 1, characterized in that: When the varactor diode control circuit is loaded with a reverse bias voltage of the varactor diode, the reverse bias voltage can change the capacitance value of the varactor diode.

7. The electrically tunable filter based on dielectric-filled waveguide according to claim 1, characterized in that: The material of the metal pillar 1 and the metal pillar 2 is copper.

8. The electrically tunable filter based on dielectric-filled waveguide according to claim 1, characterized in that: The input feed network and the output feed network are both arranged on an upper PCB board and connected to the filling medium. The upper PCB board covers the upper end of the filling medium.

9. Application of the electrically tunable filter based on dielectric-filled waveguide according to any one of claims 1 to 8 in radar, mobile communications and satellite communications.

10. A communication device, characterized in that: The invention comprises the electrically tunable filter based on dielectric-filled waveguide according to any one of claims 1 to 7.

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