Filtering attenuator with stable bandwidth

Abstract

The invention discloses a filtering attenuator with stable bandwidth, which relates to the technical field of microwave communication and comprises a radio frequency input port, a third-order transverse resonator array and a radio frequency output port. Three parallel paths are arranged between the input port and the output port. The first path is connected with a half-wavelength resonator in series. The second and third paths are respectively connected in parallel with the first and second open-circuit half-wavelength resonators; the half-wavelength resonator resonates at a center frequency, and the resonant frequencies of the two open-circuit resonators are respectively higher and lower than the center frequency; the key position of each resonator is integrated with a PIN diode and is provided with an independent biasing circuit. Compared with the prior art, the on-off state of each diode is controlled through voltage, and the circuit attenuation amount can be adjusted, so that stable bandwidth attenuation performance is realized; the design is simple in structure, is suitable for low-order topology, and has relatively high universality and expandability; the voltage control realizes continuous attenuation adjustment, and is suitable for a dynamic reconfigurable system.

Description

Technical Field

[0001] This application relates to the field of microwave communication technology, and in particular to a filter attenuator with stable bandwidth. Background Technology

[0002] As the core hub of wireless technologies such as satellite communication, 5G base stations, and radar detection, the performance of the radio frequency front-end system directly determines the signal processing quality and system reliability of the entire communication link. In complex and variable electromagnetic environments, filters and attenuators, as key passive components, play irreplaceable functional roles: filters effectively suppress out-of-band interference, adjacent channel leakage, and harmonic noise through precise frequency selection characteristics (such as L / S bandpass filters in satellite communication systems), ensuring the signal-to-noise ratio of the receiving channel; while attenuators, through dynamic power adjustment functions (such as high-precision digitally controlled attenuators that can achieve 0.5dB step adjustment), prevent low-noise amplifier saturation or analog-to-digital converter overload when the input signal strength fluctuates, thereby expanding the system's dynamic range and improving linearity.

[0003] However, in traditional RF architectures, filters and attenuators are usually cascaded and discrete. While this approach is simple to implement, it has several significant drawbacks: First, multiple independent components occupy a large amount of physical space, making it difficult to meet the high integration and miniaturization requirements of modern devices; second, the cascaded structure introduces additional insertion loss, which not only reduces system efficiency but also exacerbates thermal management pressures; third, impedance mismatch between filters and attenuators may cause frequency response distortion, affecting overall amplitude and phase consistency; and finally, the discrete solution also increases debugging complexity and manufacturing costs.

[0004] To overcome the aforementioned limitations, integrated filter-attenuator (Filtenuator) has emerged and is gradually becoming a reliable choice for high-frequency, high-density RF front-end designs. This integrated design combines filtering and attenuation functions within the same topology, effectively reducing link tiers, lowering insertion loss, improving impedance matching, and significantly enhancing system compactness and reliability. It is particularly suitable for applications with stringent requirements regarding size, power consumption, and performance.

[0005] Current integrated filter attenuators rely on manually changing resistor values ​​for adjustment, a method that has significant shortcomings in modern RF front-end systems. Specifically, manual adjustment is not only cumbersome and slow in response, but also struggles to achieve precise and rapid attenuation control, failing to meet the dynamic reconfigurability and real-time control requirements of modern communication systems. Furthermore, the introduction of manual adjustment limits the applicability of this design in highly integrated and automated systems, particularly in large-scale multi-channel systems or scenarios requiring frequent adjustments, severely restricting its practical application. In addition, existing technologies suffer from nonlinear bandwidth contraction, severely limiting the device's practicality in applications requiring dynamic power regulation while maintaining constant bandwidth. Summary of the Invention

[0006] Therefore, it is necessary to provide a voltage-adjustable filter attenuator with stable bandwidth to address the technical problems of slow response, low accuracy, difficulty in integrated control, and nonlinear bandwidth contraction in the traditional manual adjustment method.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: Firstly, a filter attenuator with a stable bandwidth includes: RF input port, third-order transverse resonator array, and RF output port; Three parallel signal transmission paths are provided between the radio frequency input port and the radio frequency output port, which are respectively referred to as the first path, the second path and the third path; The third-order transverse resonator array includes: a half-wavelength resonator connected in series with the first path, a first open-circuit half-wavelength resonator connected in parallel with the second path, and a second open-circuit half-wavelength resonator connected in parallel with the third path. The resonant frequency of the half-wavelength resonator is equal to the center frequency of the filter attenuator; the resonant frequency of the first open-circuit half-wavelength resonator is higher than the center frequency of the filter attenuator; the resonant frequency of the second open-circuit half-wavelength resonator is lower than the center frequency of the filter attenuator. The first PIN diode D1, the second PIN diode D2, and the third PIN diode D3 are respectively provided at the internal position of the half-wavelength resonator, the open end of the first open-circuit half-wavelength resonator, and the open end of the second open-circuit half-wavelength resonator. The first PIN diode D1, the second PIN diode D2, and the third PIN diode D3 are respectively provided with a first bias circuit, a second bias circuit, and a third bias circuit at their two ends.

[0008] Compared with the prior art, the beneficial effects of the technical solution of the present invention are: This invention employs a PIN diode instead of a traditional adjustable resistor. By changing the forward bias voltage applied to the PIN diode, its equivalent resistance value is dynamically modulated, thereby achieving continuous and precise electronic control adjustment of the passband attenuation. Through orderly distribution of losses and optimized bias design in the lateral resonator array, a constant 1-dB bandwidth is maintained at different attenuation levels, effectively overcoming the inherent defects of traditional adjustable filter attenuators, such as bandwidth narrowing and passband distortion at high attenuation. This invention represents a leap from manual to voltage control, significantly improving adjustment efficiency and system compatibility. This structure combines the advantages of voltage drive, fast response, and stable bandwidth, making it suitable for applications in modern RF front-end systems with high requirements for dynamic range, frequency stability, and integrated automation. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of a filter attenuator with stable bandwidth in some embodiments of this application; Figure 2 The transmission coefficient of a filter attenuator with stable bandwidth in some embodiments of this application is S. 21 The test performance data graph at that time; Figure 3 The transmission coefficient of a filter attenuator with stable bandwidth in some embodiments of this application is S. 11 The test performance data graph at that time; Figure 4 This is a test performance data graph of the group delay of a filter attenuator with stable bandwidth in some embodiments of this application.

[0010] The reference numerals in the attached figures are as follows: 101, RF input port; 102, RF output port; 103, half-wavelength resonator; 104, first open-circuit half-wavelength resonator; 105, second open-circuit half-wavelength resonator. Detailed Implementation

[0011] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the description of embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of units is not necessarily limited to those units, but may include other units not explicitly listed or inherent to those processes, methods, products, or apparatuses. The term "determine" broadly covers a wide variety of actions, including acquiring, calculating, processing, deriving, investigating, searching (e.g., searching in a table, database, or other data structure), probing, and similar actions; it may also include receiving (e.g., receiving information), accessing (e.g., accessing data in memory), and similar actions; it may also include generating, creating, establishing, and similar actions; and parsing, selecting, choosing, and similar actions, etc. Definitions of other terms will be given in the following description.

[0012] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. Furthermore, in the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if there is transmission of electrical signals or data between the connected objects.

[0013] It should be emphasized that the acquisition, transmission, storage, use, and processing of data in the technical solutions of this application all comply with the relevant provisions of national laws and regulations.

[0014] In the embodiments of this application, certain software, components, models and other existing solutions in the industry may be mentioned. These should be regarded as exemplary and are only intended to illustrate the feasibility of implementing the technical solution of this application. However, they do not mean that the applicant has used or necessarily used the solution.

[0015] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent. To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0016] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Example 1 This embodiment provides a filter attenuator with stable bandwidth. (See attached document.) Figure 1 ,include: RF input port 101, third-order transverse resonator array and RF output port 102; Three parallel signal transmission paths are provided between the radio frequency input port 101 and the radio frequency output port 102, which are respectively referred to as the first path, the second path and the third path; The third-order transverse resonator array includes: a half-wavelength resonator 103 connected in series with the first path, a first open-circuit half-wavelength resonator 104 connected in parallel with the second path, and a second open-circuit half-wavelength resonator 105 connected in parallel with the third path. The resonant frequency of the half-wavelength resonator 103 is equal to the center frequency of the filter attenuator; the resonant frequency of the first open-circuit half-wavelength resonator 104 is higher than the center frequency of the filter attenuator; and the resonant frequency of the second open-circuit half-wavelength resonator 105 is lower than the center frequency of the filter attenuator. The first PIN diode D1, the second PIN diode D2, and the third PIN diode D3 are respectively provided at the internal position of the half-wavelength resonator 103, the open end of the first open-circuit half-wavelength resonator 104, and the open end of the second open-circuit half-wavelength resonator 105. The first PIN diode D1, the second PIN diode D2, and the third PIN diode D3 are respectively provided with a first bias circuit, a second bias circuit, and a third bias circuit at their two ends.

[0018] Compared to existing technologies, this invention uses a PIN diode instead of a traditional adjustable resistor. By changing the forward bias voltage applied to the PIN diode, its equivalent resistance value is dynamically modulated, thereby achieving continuous and precise electronic control adjustment of the passband attenuation. Through orderly distribution of losses and optimized bias design in the lateral resonator array, a constant 1-dB bandwidth is maintained at different attenuation levels, effectively overcoming the inherent defects of traditional adjustable filter attenuators, such as bandwidth narrowing and passband distortion at high attenuation. This invention represents a leap from manual to voltage control, significantly improving adjustment efficiency and system compatibility. This structure combines the advantages of voltage drive, fast response, and stable bandwidth, making it highly suitable for applications in modern RF front-end systems with high requirements for dynamic range, frequency stability, and integrated automation.

[0019] Example 2 This embodiment further provides a filter attenuator with stable bandwidth based on embodiment 1. (See attached document.) Figure 1 ,include: RF input port 101, third-order transverse resonator array and RF output port 102; Three parallel signal transmission paths are provided between the radio frequency input port 101 and the radio frequency output port 102, which are respectively referred to as the first path, the second path and the third path, and each path corresponds to three different resonant frequencies; The third-order transverse resonator array includes: a half-wavelength resonator 103 connected in series with the first path, a first open-circuit half-wavelength resonator 104 connected in parallel with the second path, and a second open-circuit half-wavelength resonator 105 connected in parallel with the third path. The resonant frequency of the half-wavelength resonator 103 is equal to the center frequency of the filter attenuator; the resonant frequency of the first open-circuit half-wavelength resonator 104 is higher than the center frequency of the filter attenuator; and the resonant frequency of the second open-circuit half-wavelength resonator 105 is lower than the center frequency of the filter attenuator. The first PIN diode D1, the second PIN diode D2, and the third PIN diode D3 are respectively provided at the internal position of the half-wavelength resonator 103, the open terminal of the first open-circuit half-wavelength resonator 104, and the open terminal of the second open-circuit half-wavelength resonator 105. The plurality of PIN diodes are located at key positions of the resonator. Adjustable resistors are introduced through the plurality of PIN diodes to achieve low impedance at high bias voltage and high impedance at low bias voltage, thereby achieving continuous adjustment of passband attenuation. By optimizing the loss distribution and port loss of each resonator, a constant 1-dB bandwidth is maintained within different attenuation ranges. The first PIN diode D1, the second PIN diode D2, and the third PIN diode D3 are respectively provided with a first bias circuit, a second bias circuit, and a third bias circuit at their respective ends. The plurality of bias circuits are used to independently control the bias voltage of each of the corresponding PIN diodes.

[0020] In this embodiment, the resonant frequency corresponding to the first path is the center frequency of the designed filter, and this path provides a 0-degree phase delay; the resonant frequency corresponding to the second path is slightly higher than the center frequency, and this path provides a 180-degree phase delay; the resonant frequency corresponding to the third path is slightly lower than the center frequency, and this path also increases the phase delay by 180 degrees. This layout will generate a pair of transmission zeros at the upper and lower edges of the passband.

[0021] In some preferred embodiments, the RF input port 101, the RF output port 102, the transmission lines of the three parallel signal transmission paths, and each resonator in the third-order transverse resonator array are microstrip line structures. The three parallel signal transmission paths are all quarter-wavelength transmission lines, used as impedance transformers.

[0022] In this embodiment, the RF input port 101 is a 50Ω microstrip line used to receive input RF signals; the RF output port 102 is a 50Ω microstrip line used to output filtered and attenuated signals.

[0023] The transmission lines of the three parallel signal transmission paths provide impedance transformation between the RF input port 101 and the RF output port 102 for each resonator in the third-order transverse resonator array, and each of the three parallel signal transmission paths provides a 180-degree phase delay.

[0024] In some preferred embodiments, the RF input port 101 and the RF output port 102 are respectively provided with an input matching resistor and an output matching resistor; One end of the input matching resistor and the output matching resistor are respectively connected to the RF input port 101 and the RF output port 102, and the other end is grounded. The input matching resistor and the output matching resistor provide a fixed port loss to control the passband ripple. The RF input port 101 and the RF output port 102 are connected to the three parallel signal transmission paths via DC blocking capacitors to avoid crosstalk between DC currents in each path; at all DC bias voltage input ports, bypass capacitors are connected in parallel to ground to filter out power supply noise.

[0025] In this embodiment, both the input matching resistor and the output matching resistor are 350 Ohm, and the DC blocking capacitor is 22pF.

[0026] In some preferred embodiments, the first bias circuit includes a first branch and a second branch; The first branch includes a first inductor, one end of which is connected to the anode of the first PIN diode D1, and the other end is connected to a first DC bias voltage V1; the second branch includes a second inductor, one end of which is connected to the cathode of the first PIN diode D1, and the other end is grounded. The second bias circuit includes a third inductor, one end of which is connected to the anode of the second PIN diode D2, and the other end is externally connected to a second DC bias voltage V2. The third bias circuit includes a fourth inductor element, one end of which is connected to the anode of the third PIN diode D3, and the other end is externally connected to a third DC bias voltage V3. The cathodes of the second PIN diode D2 and the third PIN diode D3 are grounded respectively.

[0027] In this embodiment, for the first path, a first bias circuit is required to be led out from the left and right ends of the first PIN diode D1, which includes a first branch and a second branch to provide a path for the DC circuit; the DC voltage is applied to the anode side of the first PIN diode D1 at the first branch, and the DC current flows out from the cathode and flows to ground through the second branch on the right. At the same time, in order to prevent the radio frequency signal from leaking from the DC path, a high-frequency inductor needs to be connected in series in each branch.

[0028] For the second and third paths, since the second PIN diode D2 and the third PIN diode D3 are loaded at the open terminals of the first open-circuit half-wavelength resonator 104 and the second open-circuit half-wavelength resonator 105, it is only necessary to lead out the second bias circuit and the third bias circuit from the left side of the first open-circuit half-wavelength resonator 104 and the second open-circuit half-wavelength resonator 105, respectively, to bias the second bias circuit and the third bias circuit with DC voltage, and connect them to the anodes of the second PIN diode D2 and the third PIN diode D3, respectively, while the cathodes are grounded. The radio frequency signal and the DC current will flow to ground through the cathodes. At the same time, in order to prevent the radio frequency signal from leaking from the DC path, a high-frequency inductor needs to be connected in series with the second bias circuit and the third bias circuit, respectively.

[0029] By changing the voltages of V1, V2, and V3, the equivalent resistances of D1, D2, and D3 can be adjusted independently, thereby precisely controlling the loss distribution of the three paths and achieving attenuation adjustment within the range of 3-13dB while maintaining a constant bandwidth of 1-dB.

[0030] In some preferred embodiments, the first PIN diode D1 is disposed at the center of the half-wavelength resonator 103.

[0031] In some preferred embodiments, the first, second, third, and fourth inductors are all radio frequency chokes to prevent radio frequency leakage.

[0032] In this embodiment, the radio frequency choke is 110nH.

[0033] In some preferred embodiments, the microstrip line structure length of each resonator in the third-order transverse resonator array is determined by the electrical length corresponding to its resonant frequency, and its physical width ranges from [1, 3.5] mm.

[0034] In some preferred embodiments, the length of the transmission line of the three parallel signal transmission paths is determined by the nominal length of the resonant frequency of the corresponding path, and its width needs to be determined in combination with the width of the resonator of the corresponding path and the required filter bandwidth, and its physical width ranges from [0.24, 2] mm.

[0035] In some preferred embodiments, the filter attenuator is disposed on the upper surface of a preset dielectric substrate, the lower surface of the dielectric substrate is provided with a ground plane, and the dielectric substrate has through holes for grounding.

[0036] In this embodiment, the dielectric substrate has a dielectric constant of 3.0 and a thickness of 0.762 mm.

[0037] In some preferred embodiments, the ground plane is specifically a metal ground plane with the same shape and size as the dielectric substrate.

[0038] In the actual implementation process, the parasitic capacitance (about 0.25 pF) and inductance (about 0.2 nH) introduced by the PIN diode will reduce the resonant frequency. Therefore, before processing, the theoretical length of all resonators needs to be shortened by 0.3~0.5 mm in advance to ensure that the final center frequency is stable near the target frequency.

[0039] Example 3 This embodiment further provides a simulation experiment of a filter attenuator with stable bandwidth based on embodiment 2. This embodiment uses a vector network analyzer (VNA) for testing and performs dual-port calibration on the VNA to eliminate the influence of the test cable.

[0040] Figure 2 and Figure 3 The transmission coefficient S with attenuation of 3~13dB measured in this example is shown respectively. 21 and reflection coefficient S 11 ,from Figure 2 As can be seen, the center frequency of this example is 2.1 GHz, generating a pair of transmission zeros above and below the passband, which significantly improves frequency selectivity. To verify bandwidth stability, we measured the amplitude non-flatness values ​​in the 1.9–2.3 GHz range under different attenuation levels, and the results were all within the range of 2.1 GHz. Within 0.5dB, this proves that it can maintain stable bandwidth within the 1.9~2.3GHz bandwidth range, and has high in-band flatness.

[0041] And from Figure 3 The different attenuation values ​​maintain a good match within the bandwidth range, and it is clear that there are two reflection poles.

[0042] Figure 4 The group delay measured in this example is shown. As can be seen from the figure, the group delay is stable at around 1.5ns under different attenuation levels within the 1.9~2.3GHz bandwidth range.

[0043] The key design parameters and measured performance of this embodiment are shown in Table 1: Table 1 Key Design Parameters and Measured Performance Data

[0044] It is understood that the options in Embodiment 2 above also apply to this embodiment, so they will not be described again here.

[0045] The same or similar labels correspond to the same or similar parts; The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this application. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0046] In different specific implementations, the methods or systems described in this application can be implemented in software, hardware, or a combination thereof. Furthermore, the order of the method steps can be changed, and various elements can be added, reordered, combined, omitted, or modified.

[0047] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application, nor are they intended to limit this application. For those skilled in the art, other variations or modifications can be made based on the above description. The separate structural / functional modules or units can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part. The structure and function of the separate components can be implemented as a combined structure or component. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of the claims of this application.

Claims

1. A filter attenuator with stable bandwidth, characterized in that, include: RF input port (101), third-order transverse resonator array and RF output port (102). Three parallel signal transmission paths are provided between the radio frequency input port (101) and the radio frequency output port (102), which are respectively referred to as the first path, the second path and the third path; The third-order transverse resonator array includes: a half-wavelength resonator (103) connected in series with the first path, a first open-circuit half-wavelength resonator (104) connected in parallel with the second path, and a second open-circuit half-wavelength resonator (105) connected in parallel with the third path. The resonant frequency of the half-wavelength resonator (103) is equal to the center frequency of the filter attenuator; the resonant frequency of the first open-circuit half-wavelength resonator (104) is higher than the center frequency of the filter attenuator; and the resonant frequency of the second open-circuit half-wavelength resonator (105) is lower than the center frequency of the filter attenuator. The first PIN diode D1, the second PIN diode D2, and the third PIN diode D3 are respectively provided at the internal position of the half-wavelength resonator (103), the open end of the first open-circuit half-wavelength resonator (104), and the open end of the second open-circuit half-wavelength resonator (105). The first PIN diode D1, the second PIN diode D2, and the third PIN diode D3 are respectively provided with a first bias circuit, a second bias circuit, and a third bias circuit at their two ends.

2. The filter attenuator with stable bandwidth according to claim 1, characterized in that, The radio frequency input port (101), the radio frequency output port (102), the transmission lines of the three parallel signal transmission paths, and each resonator in the third-order transverse resonator array are microstrip line structures. The transmission lines of the three parallel signal transmission paths are all quarter-wavelength transmission lines.

3. The filter attenuator with stable bandwidth according to claim 1, characterized in that, The RF input port (101) and the RF output port (102) are respectively provided with an input matching resistor and an output matching resistor; One end of the input matching resistor and the output matching resistor are respectively connected to the RF input port (101) and the RF output port (102), and the other end is respectively grounded; The radio frequency input port (101) and the radio frequency output port (102) are respectively connected to the three parallel signal transmission paths via DC blocking capacitors.

4. A filter attenuator with stable bandwidth according to claim 1, characterized in that, The first bias circuit includes a first branch and a second branch; The first branch includes a first inductor, one end of which is connected to the anode of the first PIN diode D1, and the other end is connected to a first DC bias voltage V1; the second branch includes a second inductor, one end of which is connected to the cathode of the first PIN diode D1, and the other end is grounded. The second bias circuit includes a third inductor, one end of which is connected to the anode of the second PIN diode D2, and the other end is externally connected to a second DC bias voltage V2. The third bias circuit includes a fourth inductor element, one end of which is connected to the anode of the third PIN diode D3, and the other end is externally connected to a third DC bias voltage V3. The cathodes of the second PIN diode D2 and the third PIN diode D3 are grounded respectively.

5. A filter attenuator with stable bandwidth according to claim 4, characterized in that, The first PIN diode D1 is located at the center of the half-wavelength resonator (103).

6. A filter attenuator with stable bandwidth according to claim 4, characterized in that, The first, second, third, and fourth inductors are all radio frequency chokes.

7. A filter attenuator with stable bandwidth according to claim 2, characterized in that, The length of the microstrip line structure of each resonator in the third-order transverse resonator array is determined by the electrical length corresponding to its resonant frequency, and its physical width ranges from [1, 3.5] mm.

8. A filter attenuator with stable bandwidth according to claim 7, characterized in that, The length of the transmission line of the three parallel signal transmission paths is determined by the nominal length of the resonant frequency of the corresponding path, and its width needs to be determined in combination with the width of the resonator of the corresponding path and the required filter bandwidth. Its physical width range is [0.24, 2] mm.

9. A filter attenuator with stable bandwidth according to any one of claims 1-8, characterized in that, The filter attenuator is disposed on the upper surface of a preset dielectric substrate, and a ground plane is disposed on the lower surface of the dielectric substrate. The dielectric substrate has vias for grounding.

10. A filter attenuator with stable bandwidth according to claim 9, characterized in that, The ground plane is specifically a metal ground plane with the same shape and size as the dielectric substrate.

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