High-selectivity broadband cavity band-pass filter for low-orbit satellite communication and manufacturing method of high-selectivity broadband cavity band-pass filter

Abstract

The invention discloses a high-selectivity broadband cavity band-pass filter for low-orbit satellite communication and a manufacturing method, particularly relates to the technical field of communication, and solves the problems that in the prior art, due to the fact that periodic metal strips are loaded on a micro-strip transmission line and a substrate integrated waveguide, the structural loss is large; a periodic unit is loaded in a metal waveguide to form the characteristics that the lower stop band of the artificial surface plasmon is poor in selectivity and the metal waveguide is not flexible enough; and existing metal waveguide artificial surface plasmon polaritons cannot effectively achieve the purpose that the upper stop band is wide enough. According to the technical scheme, on the basis of an artificial surface plasmon polariton band-pass filter with an inverted-T-shaped groove etched in a center ridge, a pair of symmetrical folding groove structures is etched to form a 1 / 4 wavelength resonator, the 1 / 4 wavelength resonator is used for generating a zero point in a lower stop band, the selectivity of the band-pass filter is improved, and meanwhile the wide stop band characteristic is achieved by controlling the length of a grating; according to the invention, the loss is lower, and a wider stop band is realized.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a high-selectivity broadband cavity bandpass filter for low-orbit satellite communication and a manufacturing method thereof. Background Art

[0002] In recent years, the rapid development of industries such as computers, micro-electromechanical systems, and advanced manufacturing has promoted the upgrading of communication technology and micro-satellite technology, which in turn has reduced the cost of satellite communications, and low-orbit satellite communications have shown a wide range of application prospects. Around 2015, several large-scale low-orbit satellite communication systems were proposed at home and abroad. With the rapid development of low-orbit satellite communications, the demand for high-performance and wide-stopband bandpass filters is gradually increasing. Due to the inherent low-pass characteristics and flexible upper cutoff frequency, artificial surface plasmon polaritons (artificial surface plasmons) have been widely studied and developed for the design of various broadband bandpass filters (bandpass filters). Due to the low loss and high power handling capabilities of waveguides, they are often combined with artificial surface plasmons to design high-performance artificial surface plasmon bandpass filters. Especially in metal waveguides, such as rectangular waveguides, gap waveguides, and ridge waveguides. Among them, ridge waveguides have a lower cutoff frequency than waveguides of the same size, which is conducive to the miniaturization of circuits and a wider single-mode operating bandwidth.

[0003] In the existing technology, the structure of loading periodic metal strips on microstrip transmission lines and substrate integrated waveguides is flexible, but has high loss and is difficult to meet the application requirements of low loss. The lower stopband selectivity of artificial surface plasmons loaded with periodic units in metal waveguides is poor and the metal waveguides are not flexible enough; and the existing bandpass filters composed of metal waveguides and artificial surface plasmons cannot effectively achieve the technical problem of wide enough upper stopband. Summary of the invention

[0004] Therefore, the present invention solves the problem that the structure of loading periodic metal strips on microstrip transmission lines and substrate integrated waveguides in the prior art is flexible but has high loss and is difficult to meet the application requirements of low loss; the lower cutoff characteristics of artificial surface plasmons formed by loading periodic units in metal waveguides only rely on the cutoff characteristics of the waveguide and are not flexible enough in design, and cannot meet the requirements of small size and good lower stopband roll-off performance; and the existing metal waveguide artificial surface plasmon bandpass filters cannot effectively achieve the technical problem of wide stopband suppression; the high-selectivity broadband cavity bandpass filter and preparation method for low-orbit satellite communication provided by the present invention designs a basic broadband bandpass filter by etching an inverted T-shaped groove on the central ridge, and explores the characteristics of artificial surface plasmons. Secondly, a 1 / 4 wavelength resonator is formed by etching a pair of symmetrical folded grooves at both ends of the central ridge of the ridge waveguide, successfully introducing a new zero point below the passband to increase the roll-off degree of the lower edge of the passband. At the same time, by controlling the length of the grating, the effect of wide stopband is achieved. The present invention realizes a broadband bandpass structure of 3.3GHz-5.8GHz. A return loss of less than -15dB and an insertion loss of 0.25dB are achieved within the band. Low loss and small size are achieved within a wide bandwidth of 55%, and a zero point that can change with the length of the folded slot is introduced into the ridge waveguide artificial surface plasmon bandpass filter. At the same time, the -30dB suppression level of the upper stopband is also extended from 5.95GHz to 20GHz, achieving a good stopband suppression effect. In addition, the central ridge has a lower impedance and can be directly connected to a coaxial connector, making the overall size more compact.

[0005] The present invention provides a high-selectivity broadband cavity bandpass filter for low-orbit satellite communication, comprising a shell, a cavity is provided in the shell; a central ridge is provided in the cavity; horizontal transition shafts are provided at both ends of the shell; the horizontal transition shaft is connected to both ends of the central ridge. A plurality of inverted T-shaped grooves are provided on the upper surface of the central ridge. The plurality of inverted T-shaped grooves form artificial surface plasmons; grooves with a depth lower than that of the inverted T-shaped grooves are provided on the left and right sides of the inverted T-shaped grooves to form transitional artificial surface plasmon grooves.

[0006] Furthermore, both sides of the bottom of the central ridge are provided with folding grooves which are opened from one end of the central ridge, penetrate the ridge and fold upward. A plurality of columns are arranged on the side walls of the cavity on both sides of the central ridge. The plurality of columns form a double grating structure; in the horizontal direction, the extension length of the columns at both ends of the central ridge gradually decreases.

[0007] Furthermore, the artificial surface plasmon and the double grating structure form a passband. The two folded grooves are bilaterally symmetrical.

[0008] Furthermore, the filter is entirely made of aluminum.

[0009] In the above technical solution, the technical effects and advantages provided by the present invention are:

[0010] 1. The present invention provides a highly selective broadband cavity bandpass filter for low-orbit satellite communications, which uses artificial surface plasmons and folded grooves etched on the central ridge to achieve the design of a highly selective broadband ridge waveguide bandpass filter. Compared with the artificial surface plasmon bandpass filter made on a dielectric plate, the metal waveguide used in this design has lower losses. Since the metal waveguide is not very flexible in designing filters, it is not possible to add structures to increase zero points as on dielectric plates. Therefore, it is designed to etch a pair of folded grooves on the central ridge to form a 1 / 4 wavelength resonator to add a zero point that can be moved arbitrarily in the lower stop band of the filter and is easy to manufacture.

[0011] 2. The present invention provides a high-selectivity broadband cavity bandpass filter for low-orbit satellite communications, which has an insertion loss of less than 0.25dB in the working frequency band, a bandwidth of up to 55%, a return loss of less than -15dB, and a suppression of less than -30dB in the upper stopband reaching 20GHz, achieving a wider stopband. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0013] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0014] Figure 2 The side view of the present invention Figure 1 ;

[0015] Figure 3 For the top view of the present invention Figure 1 ;

[0016] Figure 4 The side view of the present invention Figure 2 ;

[0017] Figure 5 For the top view of the present invention Figure 2 ;

[0018] Figure 6 It is the S parameter diagram of the bandpass filter of the present invention;

[0019] Figure 7 This is the insertion loss diagram of the present invention;

[0020] Figure 8This is a diagram showing the effect of the change in the length of the folding groove on the change in the zero point position of the present invention;

[0021] Fig. 9 This is a diagram showing the effect of the change in the depth of the artificial surface plasmon on the passband bandwidth of the present invention;

[0022] Fig.10 This is a diagram showing the effect of the change in grating structure length on the passband bandwidth of the present invention.

[0023] Description of reference numerals:

[0024] 1. Central ridge; 2. Artificial surface plasmon; 3. Folded groove; 4. Double grating structure; 5. Horizontal transition axis; 6. Shell; 7. Cavity. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0026] Embodiment 1:

[0027] Figure 1-3 The 3D structure diagram, side view and top view of the high-selectivity broadband cavity bandpass filter for low-orbit satellite communication provided by this embodiment are respectively shown, which includes an inverted T-shaped groove etched on the central ridge 1 to form an artificial surface plasmon 2 structure and an etched symmetrical folded groove 3 structure, wherein the progressive depths hs1 and hs2 are used as transition-shaped artificial surface plasmons, and a double grating structure 4 is loaded at both ends of the central ridge 1. The ridge waveguide is fed using a horizontal transition axis 5. The entire invention is made of metal aluminum.

[0028] like Figure 4 As shown in FIG. 1 , firstly, according to the value of the center frequency, the initial size of the overall ridge waveguide is determined, and then an inverted T-shaped groove is etched on the center ridge 1 to form an artificial surface plasmon 2. Then, a pair of symmetrical folded grooves 3 are etched at both ends of the center ridge 1. At the same time, the two sides of the center ridge 1 are loaded as follows. Figure 5 The two rows of columns in the middle form a double grating structure 4. The two ends of the central ridge 1 are connected to Figure 5 The horizontal transition axis 5 shown is connected. Finally, a high-selectivity broadband bandpass filter is made.

[0029] like Figure 5As shown, the design has two ports, which are the horizontal transition axes 5 at both ends. The signal is input from the left port, through the coaxial to the central ridge 1, and then through the transition-shaped artificial surface plasmon to reach the middle standard artificial surface plasmon 2 to achieve impedance matching, realize the bandpass characteristic, and finally the signal is output from the right port. The working frequency band of the present invention is 3.3GHz-5.8GHz. The etched folded groove makes the wave transmitted by the waveguide concentrate in the etched folded groove on the left end when the filter works at 2.9GHz, so that there is no wave transmission in the entire filter, which introduces a zero point below the passband to increase the lower edge of the passband. After we determine the size of the ridge waveguide according to the center frequency, we load the artificial surface plasmon with low-pass characteristics to form an upper stopband. In order to achieve the performance of widening the stopband, the design increases the length of the grating so that the electric field at the ridge closest to the grating is perpendicular to the electric field in the transmission direction, so that the high-order mode of the artificial surface plasmon cannot be effectively excited. Thereby, the design of a broadband bandpass filter with high selectivity can be realized.

[0030] This design proposes etching a pair of 1 / 4 wavelength folded grooves 3 at both ends of the central ridge 1 to add a zero point below the passband that can move with the change of the overall length of the groove, indicating that the etched folded groove 3 has the excellent characteristic of increasing the passband roll-off degree. Among them, the inverted T-groove artificial surface plasmon 2 is directly connected to the horizontal transition axis 5 through the transition artificial surface plasmons at both ends to achieve a good matching characteristic.

[0031] The simulation results of this case study on the design of a highly selective broadband bandpass filter by loading artificial surface plasmons on a ridge waveguide are shown in Figure 6-Figure 10 , the center frequency is f0 = 4.5 GHz, the frequency range is 3.3 GHz-5.8 GHz, where S 11 Less than -15dB, insertion loss less than 0.25dB. Figure 6 The overall S-parameter graph of the filter is shown. As shown in the figure, the overall selectivity of the filter is high, and the overall return loss is -15dB; Figure 7 The performance of the filter passband is shown, with a stable insertion loss S in the passband. 21 ; Figure 8 , showing that as the length of the folding slot 3 increases (characterized by the parameter l1), the position of the zero point moves toward lower frequencies; Fig. 9 The effect of the inverted T-slot depth parameter hs on the filter cutoff frequency is shown. As hs increases, the filter cutoff frequency decreases; Fig.10 The effect of the length lg of the double grating structure 4 on the lower cutoff frequency is shown. As the grating length increases, the lower cutoff frequency increases.

[0032] Embodiment 2:

[0033] This embodiment provides a method for manufacturing the high-selectivity broadband cavity bandpass filter for low-orbit satellite communication, comprising the following steps:

[0034] S1: First, determine the size of the ridge waveguide, and determine the size of the cavity 7 and the internal center ridge 1 according to the center frequency of the target operating frequency band, so that the ridge waveguide can work at TE within the target frequency band. 10 model;

[0035] S2: Etching an inverted T-shaped groove downward on the central ridge 1 and loading a grating structure on both sides of the center to achieve a bandpass characteristic, and controlling the upper cutoff frequency by adjusting the depth of the groove. By adjusting, a suitable groove depth is found (in this design, the groove depth hs is 5.2 mm, and the transition depths hs1 and hs2 on both sides of the artificial surface plasmon in the middle section are used for transition), and the order and size of the double grating structure 4 are determined. By adjusting the order and extension length of the double grating 4, the lower cutoff frequency is controlled (in this design, the length lg of the grating is 4.6 mm, and the gratings with transition lengths lg1 and lg2 are used for transition);

[0036] S3: a pair of folded grooves 3 are etched at two sections of the central ridge 1 to generate an arbitrarily movable zero point in the lower stop band (the length of each groove is 1 / 4 of the wavelength at the zero point);

[0037] S4: Optimize relevant parameters to achieve the best matching result, as shown in Table 1 below;

[0038] Table 1: Filter parameter table

[0039]

[0040]

[0041] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A highly selective broadband cavity bandpass filter for low-orbit satellite communications, characterized in that: The invention comprises a shell (6), wherein a cavity (7) is provided in the shell (6); a central ridge (1) is provided in the cavity (7); horizontal transition shafts (5) are provided at both ends of the shell (6); and the horizontal transition shafts (5) are connected to both ends of the central ridge (1).

2. The high-selectivity broadband cavity bandpass filter for low-orbit satellite communications according to claim 1, characterized in that: The upper surface of the central ridge (1) is provided with a plurality of inverted T-shaped grooves.

3. The high-selectivity broadband cavity bandpass filter for low-orbit satellite communication according to claim 2, characterized in that: A plurality of the inverted T-shaped grooves form artificial surface plasmons (2).

4. The high-selectivity broadband cavity bandpass filter for low-orbit satellite communications according to claim 3, characterized in that: Folding grooves (3) are provided on both sides of the bottom of the central ridge (1).

5. The high-selectivity broadband cavity bandpass filter for low-orbit satellite communication according to claim 4, characterized in that: A plurality of columns are arranged on the side walls of the cavity (7) at the front and rear sides of the central ridge (1).

6. The high-selectivity broadband cavity bandpass filter for low-orbit satellite communications according to claim 5, characterized in that: A plurality of the pillars form a double grating structure (4).

7. The high-selectivity broadband cavity bandpass filter for low-orbit satellite communications according to claim 6, characterized in that: The artificial surface plasmon (2) and the double grating structure (4) form a passband.

8. The high-selectivity broadband cavity bandpass filter for low-orbit satellite communications according to claim 4, characterized in that: The two folding grooves (3) are bilaterally symmetrical.

9. The high-selectivity broadband cavity bandpass filter for low-orbit satellite communication according to claim 8, characterized in that: The filter is made entirely of aluminum.

10. The method for manufacturing a high-selectivity broadband cavity bandpass filter for low-orbit satellite communication according to any one of claims 1 to 9, characterized in that: The steps include: S1: First, determine the size of the ridge waveguide, and determine the size of the cavity (7) and the internal center ridge (1) according to the center frequency of the target operating frequency band, so that the ridge waveguide works at TE within the target frequency band. 10 model; S2: etching an inverted T-shaped groove downward on the central ridge (1) and loading a grating structure on both sides of the center as the basis of a bandpass filter, and then etching a pair of folded grooves (3) at both ends of the central ridge (1) to form a 1 / 4 wavelength resonator for generating a zero point that can be moved arbitrarily in the lower stopband; S3: controlling the position of the zero point in the lower stop band by adjusting the length of the etched folded groove (3); controlling the upper cutoff frequency by adjusting the depth of the groove, determining the order and size of the double grating structure (4) by adjusting the depth of the groove, and controlling the lower cutoff frequency by adjusting the order and extension length of the double grating structure (4); S4: Optimize relevant parameters to achieve the best matching result.

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