Double-frequency cavity band elimination filter based on defect ridge waveguide

Abstract

The invention provides a double-frequency cavity band-stop filter based on a defect ridge waveguide, relates to the technical field of wireless communication, and solves the problems that a waveguide band-stop filter in the prior art is usually formed by loading stub resonators on a main waveguide transmission line at an interval of odd number times of 1 / 4 waveguide wavelength, and although the performance is good, the band-stop filter cannot be used normally. However, the additional resonant cavity causes the technical problems of large structure size and complex processing. According to the technical scheme, through grooves with step widths are etched in a metal ridge in the transmission direction to construct defect ridge waveguide band elimination units, and the double-frequency band elimination filter based on the defect ridge waveguide structure is provided. According to the invention, an extra resonant cavity is avoided, the size of the device is reduced, the passband insertion loss is relatively low, the stopband suppression level is good, and excellent performance is shown.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, specifically to a dual-frequency cavity bandstop filter based on a defective ridge waveguide. Background Technology

[0002] Filters are indispensable devices for eliminating spurious signals in radio frequency and microwave systems. Band-stop filters are more efficient in scenarios requiring high suppression levels within a narrow stopband while maintaining low insertion loss in adjacent passbands. With increasingly congested communication spectrum in the future, dual-stopband filters are gaining attention due to their ability to suppress spurious signals in two frequency bands simultaneously, thereby improving integration and reducing costs.

[0003] In microstrip circuit design, stepped impedance resonators and defective stepped impedance resonators, which offer greater design flexibility, are often used to construct dual-band stop filters. However, they generally suffer from high passband insertion loss and limited power capacity, which cannot be ignored in many applications. Rectangular waveguides, on the other hand, offer advantages such as low loss and high power capacity, making them suitable for designing high-performance band-stop filters. Traditional waveguide band-stop filters are typically constructed by loading stub resonators at odd multiples of 1 / 4 of the waveguide wavelength along the main waveguide transmission line. While these methods offer good performance, the added resonant cavities result in larger structural dimensions and more complex fabrication. Summary of the Invention

[0004] Therefore, this invention provides a dual-frequency cavity bandstop filter based on a defective ridge waveguide to solve the aforementioned problems. To address the issue of large size while maintaining good performance, this invention constructs defective ridge waveguide bandstop units by etching through-grooves of stepped width along the transmission direction on the metal ridge, thus proposing for the first time a dual-frequency bandstop filter based on a defective ridge waveguide structure. This invention avoids the use of an additional resonant cavity, thereby reducing the device size while exhibiting low passband insertion loss and good stopband rejection, demonstrating superior performance.

[0005] The present invention provides a dual-frequency cavity bandstop filter based on a defective ridge waveguide, comprising: a metal cavity, wherein a metal ridge is disposed within the metal cavity; and a stepped-width slot is formed within the metal ridge. The stepped-width slot extends laterally through the metal ridge.

[0006] Furthermore, the stepped width groove comprises three interconnected grooves extending along the z-axis of the metal ridge. The two side grooves are narrow, and the middle groove is wide. The outer ends of both side grooves extend downwards. The two side grooves have the same dimensions and structure, and the stepped width groove as a whole is symmetrical about the centerline along the y-axis of the middle groove. Three stepped width grooves are provided along the length of the metal ridge, namely a first stepped width groove, a second stepped width groove, and a third stepped width groove. The first, second, and third stepped width grooves are all identical in shape and size.

[0007] Furthermore, coaxial connections are provided at both ends of the metal cavity, and these coaxial connections are connected to the metal ridge. The distance between the first and second stepped width slots is equal to the distance between the second and third stepped width slots. The distance of the stepped width slots in the y-axis direction is the width, and the distance in the z-axis direction is the length.

[0008] The dual-band stop filter consists of three cascaded defective ridge waveguide bandstop units. These units are constructed by etching transversely penetrating stepped-width slots along the propagation direction (z-direction) of a metal ridge, exhibiting a dual-stopband response. In the analysis, it can be equivalently represented as a slot-line stepped impedance resonator (SIR) with both ends short-circuited. The characteristic impedance of each segment is determined by… Calculations show that L and C represent the distributed inductance and capacitance per unit length, respectively. When the slot width is narrow, the capacitance increases while Z decreases. Therefore, this slot-wire resonator has a high impedance in the middle and a low impedance at both ends.

[0009] The dual stopband response of the defective ridge waveguide bandstop element corresponds to the fundamental mode frequency (f0) and the second harmonic frequency (f2), respectively. s With the total length of the groove fixed, f0 and f s This also depends on the width ratio (i.e., the impedance ratio R) and the electrical length ratio μ of the slots. When R > 1, increasing the width ratio or the length ratio (i.e., increasing R or μ) can reduce f. s / f0 brings the frequencies of the two modes closer together, which is beneficial for the design of dual-stopband devices. To reduce the longitudinal dimension, this invention folds three cascaded stepped-width slots, adjusting the width and length of the slots to achieve the desired frequency ratio, and precisely adjusting the geometric parameters of the slots and the distance between them to meet the design requirements of the proposed dual-band stop filter.

[0010] The present invention has the following advantages over the prior art:

[0011] 1. The present invention provides a dual-frequency cavity bandstop filter based on a defective ridge waveguide. A defective ridge waveguide bandstop unit is constructed by etching through-grooves of stepped width along the transmission direction on a metal ridge. This is the first time a dual-frequency bandstop filter based on a defective ridge waveguide structure has been proposed. It avoids the use of an additional resonant cavity, thus reducing the device size while exhibiting lower passband insertion loss and better stopband suppression, demonstrating superior performance.

[0012] 2. The dual-frequency cavity bandstop filter based on defective ridge waveguide provided by this invention constructs bandstop units by etching horizontally penetrating stepped-width slots on a metal ridge, introducing a dual-stopband response; it is the first time that a dual-frequency bandstop filter design has been proposed using a defective ridge waveguide structure, and good performance has been obtained.

[0013] 3. The dual-frequency cavity bandstop filter based on defective ridge waveguide provided by this invention has good power processing capability, lower insertion loss, simulated passband insertion loss of less than 0.2dB and return loss of more than 14.5dB; stopband rejection reaches 55dB and 35dB respectively, avoiding the use of additional resonant cavities and reducing device size. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0016] Figure 2 This is a structural dimensioning diagram of the present invention.

[0017] Figure 3 This is a simulation result diagram of the defective ridge waveguide bandstop unit of the present invention.

[0018] Figure 4 The frequency ratio f of the defective ridge waveguide bandstop unit in this invention is... s / f0 is a graph showing the results of the change in width ratio w2 / w3 or length ratio d2 / d3.

[0019] Figure 5 This is a simulation result diagram of a dual-frequency cavity bandstop filter based on a defective ridge waveguide according to the present invention.

[0020] Explanation of reference numerals in the attached figures:

[0021] 1. Metal cavity; 2. Metal ridge; 3. First step width groove; 4. Second step width groove; 5. Third step width groove. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] Figure 1This is a schematic diagram of the overall structure of the dual-frequency cavity bandstop filter based on a defective ridge waveguide provided in this embodiment. It includes: a metal cavity 1, with a metal ridge 2 disposed within the metal cavity 1; a stepped-width slot is formed within the metal ridge 2. The stepped-width slot extends laterally through the metal ridge 2. The stepped-width slot comprises three interconnected slot sections along the z-axis of the metal ridge, with the two side slots being narrow and the middle slot being wide. The outer ends of the two side slots extend downwards; the two side slots have the same dimensions and structure, and the stepped-width slot as a whole is symmetrical about the centerline along the y-axis of the middle slot. Three stepped-width slots are formed along the length of the metal ridge, namely a first stepped-width slot 3, a second stepped-width slot 4, and a third stepped-width slot 5. The first stepped-width slot 3, the second stepped-width slot 4, and the third stepped-width slot 5 all have the same shape and dimensions. Coaxial sections are provided at both ends of the housing 1, and these coaxial sections are connected to the metal ridge 2. Figure 1 The coaxial ends are port 1 and port 2, respectively. The distance between the first stepped width slot 3 and the second stepped width slot 4 is equal to the distance between the second stepped width slot 4 and the third stepped width slot 5. The distance of the stepped width slot in the y-axis direction is the width, and the distance in the z-axis direction is the length.

[0025] This application constructs a stepped-width groove that runs transversely through the metal ridge 2 along the propagation direction (z-direction). The groove is wider in the middle and narrower at both ends, exhibiting a dual stopband response. Figure 3 As shown. To reduce the length of the device, the dual-band stop filter is formed by etching three cascaded folded stepped-width slots on the metal ridge 2, with equal spacing between the slots. At the input and output ends, striplines are used to achieve the transition from the SMA to the ridge waveguide.

[0026] A stepped-width slot can be equivalent to a slot-line stepped impedance resonator (SIR) with both ends short-circuited. The characteristic impedance of each segment is determined by... Calculations show that L and C represent the distributed inductance and capacitance per unit length, respectively. When the slot width is narrow, the capacitance increases while Z decreases; therefore, the slot-line resonator has a high impedance in the middle and a low impedance at both ends. Its dual stopband response corresponds to the fundamental mode frequency (f0) and the second harmonic frequency (f...). s With the total length of the groove fixed, f0 and f s This also depends on the width ratio (i.e., the impedance ratio R) and the electrical length ratio μ of the slots. When R > 1, increasing the width ratio or the length ratio (i.e., increasing R or μ) can reduce f. s / f0, such as Figure 4 As shown, this brings the frequencies of the two modes closer together, which is beneficial for the design of dual stopband devices.

[0027] Example 2

[0028] This embodiment provides the overall design flow of the dual-frequency cavity bandstop filter based on a defective ridge waveguide, including the following steps: First, the size of the ridge waveguide is reasonably selected to ensure a relatively wide single-mode operating bandwidth, while stripline matching is used to achieve the transition from SMA to the ridge waveguide. Second, the initial slot size of the defective ridge waveguide bandstop unit is determined through electromagnetic simulation to meet the requirements of the target frequency band. Next, the three folded slots are cascaded. Finally, based on the above analysis, the geometric parameters of the slots and the distance between them are precisely adjusted to meet the design requirements of the proposed dual-frequency bandstop filter. The filter designed using the above method is simulated, and the simulation results are as follows: Figure 5 As shown, the center frequencies of this dual-band bandpass filter are 9.1 and 12.78 GHz, with 3 dB bandwidths of approximately 118 and 160 MHz, respectively. The stopband rejection levels exceed 55 dB and 35 dB, respectively. The passband performance is good, with a return loss better than 14.5 dB and an insertion loss less than 0.2 dB.

[0029] like Figure 2 As shown, it displays the dimensions of the housing 1, the metal ridge 2, and the ends of the stepped width groove before they fold downwards and extend. The parameters involved in this embodiment are: a = 16, b = 10, a 1 = 6, b 1 = 8.6, l 2 = 1.2, d 3 = 8.1, d 2 = 2.9, w 2 = 4 and w 3 = 1.5; unit: mm).

[0030] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A dual-frequency cavity bandstop filter based on a defective ridge waveguide, characterized in that, include: A metal cavity (1) is provided inside the metal cavity (1); a stepped width groove is provided inside the metal ridge (2).

2. The dual-frequency cavity bandstop filter based on a defective ridge waveguide according to claim 1, characterized in that, The stepped width groove extends laterally through the metal ridge (2).

3. The dual-frequency cavity bandstop filter based on a defective ridge waveguide according to claim 2, characterized in that, The stepped width groove includes three interconnected grooves opened along the z-axis direction of the metal ridge (2). The two side grooves are narrow, the middle groove is wide, and the outer ends of the two side grooves extend downward.

4. The dual-frequency cavity bandstop filter based on a defective ridge waveguide according to claim 3, characterized in that, The stepped width groove is provided in three sections along the length of the metal ridge (2), namely the first stepped width groove (3), the second stepped width groove (4), and the third stepped width groove (5).

5. The dual-frequency cavity bandstop filter based on a defective ridge waveguide according to claim 4, characterized in that, The first step width groove (3), the second step width groove (4) and the third step width groove (5) have the same shape and size.

6. The dual-frequency cavity bandstop filter based on a defective ridge waveguide according to claim 5, characterized in that, The metal cavity (1) has coaxial ends, and the coaxial ends are connected to the metal ridge (2).

7. The dual-frequency cavity bandstop filter based on a defective ridge waveguide according to claim 6, characterized in that, The distance between the first step width slot (3) and the second step width slot (4) is equal to the distance between the second step width slot (4) and the third step width slot (5).

8. The dual-frequency cavity bandstop filter based on a defective ridge waveguide according to claim 7, characterized in that, The distance of the stepped width groove in the y-axis direction is the width, and the distance in the z-axis direction is the length.

Images