Dual-passband reconfigurable filtering attenuator

Abstract

The invention discloses a dual-passband reconfigurable filtering attenuator, which has independent and continuous tuning center frequency and attenuation capability, and belongs to the technical field of microwaves. The device comprises two U-shaped closed annular micro-strip resonators with different sizes and a shared H-shaped micro-strip line attenuation unit. The two resonators are oppositely arranged with the concave short edges thereof, and are respectively connected with the input / output port through slot coupling so as to generate a high-frequency passband and a low-frequency passband. By independently adjusting the variable capacitance diode bias voltage loaded on each resonator and the attenuation unit, the center frequencies of the two passbands can be respectively and independently tuned. The attenuation units are selectively coupled with odd modes of the corresponding resonators through two pairs of variable capacitance diodes on the attenuation units, and energy is discharged to a grounding resistor, so that amplitude attenuation of any one or two passbands is independently and continuously regulated and controlled. According to the invention, integration of filtering and attenuation functions is realized, and the device has the advantages of compact structure, flexible control and high integration level.

Description

Technical Field

[0001] This invention relates to microwave technology, and in particular to a reconfigurable dual-passband filter attenuator tuned and controlled by a varactor diode. Background Technology

[0002] With the development of wireless communication systems and the increasing scarcity of spectrum resources, the demand for reconfigurable microwave devices that can flexibly adapt to different communication scenarios and dynamically adjust performance is becoming increasingly urgent. Among many devices, filters and attenuators are two key components: filters are used to select useful signals and suppress out-of-band interference; attenuators are used to regulate signal power levels and prevent overload. In traditional solutions, these two are often designed separately and cascaded to achieve composite functions, but this often results in a large system size, low integration, and complex matching design of the cascade interface.

[0003] To overcome these shortcomings and achieve highly integrated, reconfigurable, multifunctional devices, researchers have begun exploring the integration of filtering and attenuation functions into a single design. In such designs, varactor diodes, due to their continuously tuned capacitance with bias voltage, become key components for dynamically reconfiguring circuit parameters such as center frequency and quality factor. By cleverly incorporating varactor diodes into the circuit topology, it is hoped that independent control of frequency tuning and amplitude attenuation in the filter passband can be achieved simultaneously on a single device, thus meeting the complex and ever-changing demands of modern communication. In traditional multi-band architectures, reconfigurable filters and attenuators are typically cascaded, which not only suppresses unwanted signals but also enables beam reconfiguration for each antenna array. However, this approach suffers from large size and high complexity in matching the cascaded discrete components. Therefore, integrating different functions into a mature reconfigurable filter to form a multifunctional fusion device is highly favored for its flexible reconfiguration, high integration density, and high space utilization.

[0004] However, while existing research has achieved good filtering and attenuation characteristics, its functionality is generally limited to single-band applications, and it has not yet been able to realize independent reconfigurable filtering and attenuation in multi-band scenarios such as dual-passband. (Summary of the Invention)

[0005] The technical problem to be solved by this invention is how to achieve independent, continuous and flexible electronic control tuning of the center frequency and amplitude attenuation of the high-frequency and low-frequency communication passbands in a single highly integrated device, so as to replace the traditional cascaded scheme and meet the requirements of modern wireless communication systems for miniaturization, reconfigurability and multi-functional integration.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is a dual-passband reconfigurable filter attenuator with independent and continuous tuning of the center frequency and attenuation capability, including an input port, an output port, an attenuation unit, a first resonator and a second resonator;

[0007] Both the first and second resonators are grounded U-shaped closed loop microstrip line structures. They are arranged with their short concave sides facing each other and are electromagnetically coupled to the input and output ports through coupling structures containing gaps, respectively, to generate high-frequency and low-frequency passbands.

[0008] The attenuation unit is an H-shaped microstrip line structure, and its two vertical arms are coupled to the top concave short side region of the first resonator and the second resonator through coupling elements.

[0009] The first and second resonators are equipped with varactor diodes for frequency tuning, and the attenuation unit is equipped with a pair of varactor diodes for attenuation tuning. By independently adjusting the bias voltage of each varactor diode, the center frequency and amplitude attenuation of the high-frequency passband and the low-frequency passband can be tuned independently and continuously.

[0010] Specifically, the first resonator and the second resonator have different physical dimensions. The second resonator is larger than the first resonator so that it can operate at a lower frequency band.

[0011] Specifically, the varactor diodes used for frequency tuning include a pair of even-mode-assisted tuning varactor diodes and a pair of frequency-integrated tuning varactor diodes:

[0012] The even-mode auxiliary tuning varactor diode is soldered to the center of the convex long side at the bottom of the corresponding resonator and grounded through a metallized via.

[0013] A pair of frequency-integrated tuning varactor diodes are soldered back-to-back to the center of the concave short side of the top of the corresponding resonator, and a metallized through-hole for common grounding is provided between the two diodes.

[0014] Specifically, the varactor diodes loaded on the attenuation unit for attenuation tuning include a high-frequency passband attenuation control pair and a low-frequency passband attenuation control pair.

[0015] In the H-shaped structure, each vertical arm integrates a varactor diode belonging to the high-frequency passband attenuation control pair and a varactor diode belonging to the low-frequency passband attenuation control pair. The two diodes are mounted back to back with opposite cathodes.

[0016] The two varactor diodes of the high-frequency passband attenuation control pair are located above the upper left and upper right vertical arms of the H-shaped structure, respectively, while the two varactor diodes of the low-frequency passband attenuation control pair are located below the lower left and lower right vertical arms of the H-shaped structure, respectively.

[0017] Specifically, the attenuation unit also includes two grounding resistors, which are symmetrically welded to the middle crossbeam of the H-shaped structure and grounded through a metallized through-hole at the center.

[0018] This invention discloses a dual-passband reconfigurable filter attenuator with three different operating modes based on varactor diodes, achieving independent reconfigurability of the center frequencies of the two passbands and independent adjustable attenuation capabilities. By adjusting the bias state of each varactor diode, multiple operating modes can be achieved, including: low-frequency passband attenuation + high-frequency passband filtering; low-frequency passband filtering + high-frequency passband attenuation; and low-frequency passband attenuation + high-frequency passband attenuation.

[0019] The beneficial effects of this invention are that by utilizing a shared attenuation unit, the low-frequency passband and the high-frequency passband can dissipate energy through the same signal path, which greatly reduces the circuit area, simplifies the design complexity, and facilitates circuit implementation and control.

[0020] By adjusting the varactor diode, the center frequency and attenuation capability of the dual passband can be independently and continuously varied. This method has significant advantages such as low control complexity and simple design, and has great application prospects. Attached Figure Description

[0021] Figure 1 This is the overall circuit topology of the present invention.

[0022] Figure 2 This is a circuit diagram of the present invention.

[0023] Figure 3 The results are the S-parameter test results of this invention; wherein, Figure 3 (a) shows the results of adjusting the low-frequency passband attenuation capability while maintaining a fixed high-frequency passband; |S 11 |and|S 21 | represents the absolute values ​​of the amplitudes of the transmission coefficient S21 and the reflection coefficient S11, respectively; Figure 3 (b) shows the result of fixing the high-frequency passband, shifting the low-frequency passband, and then adjusting its attenuation capability. Figure 3 (c) shows the results of adjusting the attenuation capability of the high-frequency passband while keeping the low-frequency passband fixed. Figure 3 In Figure 3(d), the result is shown by fixing the low-frequency passband, shifting the frequency of the high-frequency passband, and then adjusting its attenuation capability. Figure 3(e) shows the result of simultaneously adjusting the attenuation capability of the low-frequency passband and the high-frequency passband.

[0024] Figure 4 This is a physical image of the device of the present invention. Detailed Implementation

[0025] Figure 1This demonstrates the basic topology of a dual-passband reconfigurable filter attenuator that integrates three functions. The circuit comprises two independent two-mode resonators R1 and R2 and a shared varactor diode-based attenuation unit A, all implemented via microstrip lines. In the topology, resonator R1 is coupled via path M... S1 and M L1 It is coupled to the input port (port 1) and the output port (port 2) respectively; the resonator R2 is coupled through the coupling path M. S2 and M L2 The two resonators are coupled to the input port (port 1) and the output port (port 2) respectively, and these coupling paths are marked with solid black lines in the diagram. Each resonator forms a passband through its own signal path: one path generates a low-frequency passband, and the other generates a high-frequency passband.

[0026] As shown by the dotted line in the figure, the attenuation unit is connected to both resonators in a controllable manner, which can independently adjust the attenuation of the high-frequency passband or the low-frequency passband, thus realizing independent control of the dual-passband attenuation.

[0027] From a working principle perspective, the signal in each dual-mode resonator can be decomposed into odd-mode and even-mode components. By precisely controlling the varactor diodes in the attenuation unit that act on the odd-mode components of resonators R1 and R2 respectively, the energy distribution and loss of the corresponding resonant modes can be changed in a targeted manner. Thus, without affecting the other passband, the amplitude attenuation level of the high-frequency or low-frequency passband can be adjusted independently and continuously.

[0028] exist Figure 1 In the topology shown, the connection between the attenuation unit and resonators R1 and R2 is physically defined as a strong coupling path to the odd modes (O1, O2) of the two resonators. This design is achieved by precisely connecting the varactor diodes in the attenuation unit to specific locations on the resonator layout that are sensitive to odd-mode responses but sluggish to even-mode responses, thereby ensuring the selectivity and independence of attenuation control over the target passband.

[0029] To clearly explain the working principle, in Figure 1 In the illustrated topology, the electromagnetic field of each two-mode resonator, R1, can be decomposed into two orthogonal basic modes: even mode E1 and odd mode O1. Similarly, the electromagnetic field of R2 can be decomposed into two orthogonal basic modes: even mode E2 and odd mode O1. The even and odd modes correspond to different resonant frequencies and are coupled together to the port, forming a filter passband (such as a high-frequency passband or a low-frequency passband). The core of this invention lies in the shared attenuation unit, which, through a controllable coupling path, selectively and strongly couples with the odd-mode components (O1 or O2) of a specific resonator.

[0030] The specific circuit of the filter attenuator described in this invention is implemented using planar microstrip line technology, and its physical layout is as follows: Figure 2 As shown. The circuit is based on a two-layer printed circuit board (PCB) structure, where the top layer is a metal layer with a specific pattern, and the bottom layer is a complete ground metal plate. The top metal layer is connected through metallized vias distributed throughout the circuit. Figure 2 The gray grounding hole is connected to the underlying ground, thus forming a standard microstrip transmission line environment.

[0031] The core of the circuit consists of the following parts:

[0032] 1. Resonator Structure

[0033] Both resonators R1, which forms the high-frequency passband, and R2, which forms the low-frequency passband, are grounded, U-shaped closed-loop microstrip lines. The two resonators are arranged with their short, concave top sides facing each other. Resonators R1 and R2 have different physical dimensions. Specifically, the ring arm length (or total area) of resonator R2 is greater than that of resonator R1 to ensure it resonates at a lower frequency band, thus generating the low-frequency and high-frequency passbands respectively.

[0034] Each resonator is loaded with two sets of varactor diodes for independent tuning of its dual-mode characteristics:

[0035] (1) Varactor diode for even-mode auxiliary tuning (C e1 Or C e2 ): This is welded to the center of the convex long side (the longest side opposite the concave short side at the top) of the bottom of the U-shaped resonator, and grounded at this point through a metallized via. This position corresponds to the voltage antinode of the even mode of this microstrip line, and is mainly used for independent and fine-tuning of the even mode resonant frequency.

[0036] (2) Varactor diode pair used for frequency synthesis tuning (C o1 or C o2 (Correct): The diodes are soldered back-to-back to the middle of the concave short side (the horizontal line protruding inward in the concave shape) at the top of the U-shaped resonator. A common grounding hole is provided between the pairs of symmetrical tuning varactor diodes (at the center of the horizontal line protruding inward in the concave shape). This position is a sensitive node for the electromagnetic field distribution of the resonator and can be strongly coupled to both odd and even modes at the same time. Therefore, it can achieve comprehensive wide-range tuning of the odd and even mode resonant frequencies of the resonator and is the core actuator for controlling the passband center frequency.

[0037] Resonator R1 generates the high-frequency passband, and resonator R2 generates the low-frequency passband. This is achieved by independently adjusting the capacitance (C) of each resonator. o Regarding C e The bias voltage can be used to achieve independent continuous tuning of the center frequencies of the two passbands.

[0038] 2. Input / output coupling method

[0039] The resonator is coupled to the input port (port 1) and the output port (port 2) using a slot coupling mechanism. This method is a non-contact electromagnetic energy transfer method. By controlling the geometry (width and length) of the slot and its position relative to the resonator, the coupling strength can be flexibly adjusted, thereby affecting the passband bandwidth and matching characteristics.

[0040] 3. Attenuation Unit Structure and Working Principle

[0041] The main body of the attenuation unit is an H-shaped microstrip line structure. The two vertical arms of this structure are coupled to the concave short sides at the top of resonators R1 and R2 via DC blocking capacitors at their top and bottom ends, respectively, thus establishing a non-contact, controllable signal path. This design ensures that the DC bias voltage can be applied independently and separately to C. a1 and C a2 Yes, and at the same time prevents RF signals from leaking into the bias network.

[0042] Each vertical arm of the H-type structure integrates two varactor diodes, one C and one C. a1 And a C a2 These two diodes are mounted back-to-back with opposite cathodes, meaning their cathodes face the top and bottom (outer sides) of the vertical arm, respectively. High-frequency passband attenuation control pair (C a1 (Pair): Composed of the diodes located above the upper left vertical arm and the upper right vertical arm. Low-frequency passband attenuation control pair (C) a2 (Correct): It is composed of the diode below the lower left vertical arm and the diode below the lower right vertical arm.

[0043] Two grounding resistors R t They are symmetrically welded to the middle crossbeam of the H-shaped structure, and each is connected to two grounding resistors R. t A metallized via at the center of the via is grounded to dissipate leaked radio frequency energy. R in the embodiment... t It is 5 ohms.

[0044] Attenuation control mechanism: by adjusting C a1 or C a2 By applying a bias voltage, its equivalent capacitance can be changed, thereby controlling the leakage intensity of the odd-mode energy of the corresponding resonator to the attenuation unit. The leaked RF signal energy is absorbed by two grounding resistors R connected in series. t The absorption and conversion of energy into heat leads to an increase in the insertion loss of the corresponding passband of the resonator, thus achieving amplitude attenuation.

[0045] Independent control function: Specifically, adjusting C a1The bias voltage can independently control the attenuation of the high-frequency passband (resonator R1), adjusting C a2 The bias voltage can independently control the attenuation of the low-frequency passband (resonator R2). This enables independent and continuous control of the dual-passband attenuation capability.

[0046] 4. Introduction of out-of-band zeros

[0047] At the filter input port (port 1), a short-circuited microstrip line is connected in parallel, which is equivalent to a series inductor. This inductor, together with a 13pF fixed capacitor connected in series on the input microstrip line, introduces a transmission zero in the frequency domain. This zero is designed within the stopband between the low and high frequency passbands, which can significantly improve the filter's out-of-band rejection performance.

[0048] 5. DC bias circuit

[0049] To achieve compatibility with all varactor diodes (including C) e1 C e2 C o1 Yes, C o2 Yes, C a1 Yes, C a2 To ensure the independent and precise control of the DC bias and the integrity of the radio frequency signal in the specific circuit implementation of this invention, all varactor diodes (including C) in the circuit are subject to independent and precise control. e1 C e2 C o1 Yes, C o2 Yes, C a1 Yes, C a2 All (yes) follow a uniform connection standard: the cathode of each varactor diode is connected in series with a DC blocking capacitor (100pF in this example) before being connected to the microstrip line, and the cathode faces the outer edge of the circuit layout (referred to as facing outwards). The DC blocking capacitor in this example is 100pF.

[0050] Each varactor diode's cathode is connected to an independent DC bias voltage source via a 100 kohm bias resistor between itself and the DC blocking capacitor. The bias resistor establishes a stable DC bias path and works in conjunction with the DC blocking capacitor to effectively isolate the RF signal from the DC power supply. The entire circuit has six voltage controls, allowing for flexible control of all bias voltages to successfully adjust the designed filter response and attenuation levels.

[0051] 6. Dimensional parameters

[0052] The optimized circuit size parameters obtained after simulation optimization design are as follows: the vertical arm height L0 of the concave-shaped resonator R1 is 10 mm, the bottom long side length L1 of the concave-shaped resonator R1 is 30 mm, the inner concave depth L2 of the concave-shaped resonator R1 is 6.1 mm, the top outer convex short side length L3 of the concave-shaped resonator R1 is 8 mm, the distance between the inner concave short sides of the two opposite concave shapes of the resonator R1 and the resonator R2 (the height of the attenuation unit H-shaped structure) L4 = 11.12, the distance between the two vertical arms of the attenuation unit H-shaped structure L5 = 8 mm, the vertical arm height L6 of the concave-shaped resonator R2 is 10 mm, the bottom long side length L7 of the concave-shaped resonator R2 = 40 mm, the inner concave depth of the concave-shaped resonator R2 is the same as L2, the top outer convex short side length of the concave-shaped resonator R2 is the same as L3, and the width W of the main transmission line connecting port 1 and port 2 m = 1.17 mm , the width W of the resonator microstrip line m1 = 1 mm, and the coupling gap width g between the main transmission line and the top outer convex short sides of the two concave-shaped resonators is 0.1 mm.

[0053] 7. Functions achieved

[0054] ① The low-frequency passband maintains the filtering characteristic, and the high-frequency passband realizes adjustable amplitude attenuation;

[0055] ② The low-frequency passband realizes adjustable amplitude attenuation, and the high-frequency passband maintains the filtering characteristic;

[0056] ③ Both the low-frequency passband and the high-frequency passband can realize adjustable amplitude attenuation.

[0057] In summary, through the "mode selection coupling" mechanism, the present invention uses a shared attenuation unit to achieve independent and precise control of the attenuation capabilities of the dual passbands.

[0058] Embodiment

[0059] As Figure 4 shown, a dual-passband filter attenuator is implemented using microstrip technology. The substrate material is Rogers 6010 with a thickness of 1.27 mm. The varactor diodes C O , C e, C a select the MA46H202 and MA46H204 model varactor diodes of MACOM Corporation. The resistor R t selects the chip resistor with the package model 0402, and the resistance values are all 5 ohms. The capacitor constituting the out-of-band zero point selects the chip capacitor with the package model 0402, and the capacitance value is 13 picofarads.

[0060] Figure 3The S-parameter test results of the embodiments are shown. It can be seen that the present invention successfully realizes three different working modes, and the center frequency can be reconfigured in both the low-frequency passband and the high-frequency passband. The above results verify the correctness and superiority of the present invention.

Claims

1. A dual-passband reconfigurable filter attenuator, characterized in that, include: Input port, output port, attenuation unit, first resonator and second resonator; Both the first and second resonators are grounded U-shaped closed loop microstrip line structures. They are arranged with their short concave sides facing each other and are electromagnetically coupled to the input and output ports through coupling structures containing gaps, respectively, to generate high-frequency and low-frequency passbands. The attenuation unit is an H-shaped microstrip line structure, and its two vertical arms are coupled to the top concave short side region of the first resonator and the second resonator through coupling elements. The first and second resonators are equipped with varactor diodes for frequency tuning, and the attenuation unit is equipped with a pair of varactor diodes for attenuation tuning. By independently adjusting the bias voltage of each varactor diode, the center frequency and amplitude attenuation of the high-frequency passband and the low-frequency passband can be tuned independently and continuously.

2. The dual passband reconfigurable filter attenuator as claimed in claim 1, wherein, The first resonator and the second resonator have different physical dimensions. The second resonator is larger than the first resonator so that it can operate at a lower frequency band.

3. The dual passband reconfigurable filter attenuator of claim 1, wherein, The varactor diodes used for frequency tuning include even-mode-assisted tuning varactor diodes and frequency-combined tuning varactor diode pairs: The even-mode auxiliary tuning varactor diode is soldered to the center of the convex long side at the bottom of the corresponding resonator and grounded through a metallized via. A pair of frequency-integrated tuning varactor diodes are soldered back-to-back to the center of the concave short side of the top of the corresponding resonator, and a metallized through-hole for common grounding is provided between the two diodes.

4. The dual passband reconfigurable filter attenuator of claim 1, wherein, The varactor diodes loaded on the attenuation unit for attenuation tuning include a high-frequency passband attenuation control pair and a low-frequency passband attenuation control pair. In the H-shaped structure, each vertical arm integrates a varactor diode belonging to the high-frequency passband attenuation control pair and a varactor diode belonging to the low-frequency passband attenuation control pair. The two diodes are mounted back to back with opposite cathodes. The two varactor diodes of the high-frequency passband attenuation control pair are located above the upper left and upper right vertical arms of the H-shaped structure, respectively, while the two varactor diodes of the low-frequency passband attenuation control pair are located below the lower left and lower right vertical arms of the H-shaped structure, respectively.

5. The dual-band reconfigurable filter attenuator of claim 4, wherein, The attenuation unit also includes two grounding resistors, which are symmetrically welded to the middle crossbeam of the H-shaped structure and grounded through a metallized through-hole at the center.

6. The dual passband reconfigurable filter attenuator of claim 1, wherein, At the input port, a short-circuited microstrip line is connected in parallel. This microstrip line and a fixed capacitor connected in series on the input microstrip line together form a transmission zero. The transmission zero is located in the stopband between the high-frequency passband and the low-frequency passband.

7. The dual passband reconfigurable filter attenuator of claim 1, wherein, The cathodes of all varactor diodes are connected in series with a DC blocking capacitor and then connected to the microstrip line, with their cathodes facing the outer edge of the circuit layout.

8. The dual-band reconfigurable filter attenuator of claim 7, wherein, The cathode nodes of the varactor diodes used for frequency tuning and attenuation tuning are each connected to their respective independent DC bias voltage sources via a bias resistor.

9. The dual passband reconfigurable filter attenuator of claim 1, wherein, The high-frequency passband and low-frequency passband can achieve the following operating modes by adjusting the bias voltage of the corresponding varactor diodes: low-frequency passband filtering and high-frequency passband attenuation, low-frequency passband attenuation and high-frequency passband filtering, and simultaneous attenuation of both low-frequency and high-frequency passbands.

10. An electronic device, comprising: A dual-band reconfigurable filter attenuator comprising the filter attenuator of any one of claims 1 to 9.

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