Dual-mode dielectric strip resonator and differential dual-passband filter comprising the same

Abstract

The present invention relates to a dual-mode dielectric strip resonator and a differential dual-passband filter comprising the resonator. The present invention forms a dual-mode dielectric strip resonator by loading a pair of grounding rods under a conventional dielectric strip. The dual-mode resonator has two adjacent TM 11 module, and these two TM 11 The unloaded quality factor of these two modes is Q u In the X-band, both modes are greater than 600, which has high application value in many low-loss devices. And these two modes can be differentially excited and used to design differential dual-passband filters. The external quality factor and coupling coefficient of the two passbands can be independently controlled, and the common-mode rejection of the passband is also above 25dB. In order to verify the proposed idea, a filter prototype working at 8.13GHz and 11.13GHz was designed and assembled, and the simulation results were well consistent with the test results.

Description

Technical Field

[0001] The invention relates to a dual-mode dielectric strip resonator and a differential dual-passband filter comprising the resonator, belonging to the technical field of communication transmission. Background Art

[0002] In recent years, differential circuits have attracted a lot of attention due to their better performance against environmental noise and electromagnetic crosstalk than single-ended circuits. Following this trend, many differential devices have been designed, such as power dividers, phase shifters, antennas, and bandpass filters. Bandpass filters, as an essential component of the RF front end, play a key role in frequency selection. In order to meet the needs of multi-band use in RF systems, differential dual-passband filters have been proposed in the past few years.

[0003] There are many methods for designing differential dual-passband filters, such as connecting two single-passband filters working in different frequency bands in parallel, or using dual-mode resonators. It is well known that dual-mode resonators can be equivalent to two single-mode resonators, so the designed filter size is small, and two close passbands can be easily obtained, which meets the requirements of most applications. Therefore, various technologies based on the principle of dual-mode resonators are used, such as microstrip lines and SIW have been widely developed, and they can be differentially excited to design dual-passband filters. Unfortunately, they have a relatively low unloaded quality factor, resulting in relatively high losses, especially in high-frequency applications. In contrast, dielectric resonators made of high dielectric materials are a typical low-loss RF resonator and have been widely used in filters and antennas in the past few years. In view of this, a dual-mode dielectric resonator directly placed in the cavity is used to design a dual-passband filter. The resonator uses a half-cut method to reduce the profile of the designed filter. However, its 3D structure is still an obstacle in RF integrated circuit design. Summary of the invention

[0004] The present invention aims to solve the above-mentioned defects and provides a dual-mode dielectric strip resonator with reasonable structure, high external quality factor and good filtering performance, and a differential dual-passband filter including the resonator.

[0005] To this end, the technical solution adopted by the present invention is: a dual-mode dielectric strip resonator, comprising a metal cavity (1), a substrate (2) is arranged in one side of the metal cavity (1), a dielectric strip (3) is arranged on the upper surface of the substrate (2), a grounding surface is arranged on the lower surface of the substrate (2), and a grounding rod (4) is arranged between the lower surface of the dielectric strip (3) and the grounding surface.

[0006] Furthermore, the distance between the side edge of the dielectric strip (3) and the corresponding side inner wall of the metal cavity (1) is much greater than the thickness of the substrate (2).

[0007] Furthermore, there are two grounding rods (4), which are symmetrically arranged on the lower surface of the dielectric strip (3); in the width direction of the dielectric strip (3), the grounding rods (4) are arranged in the middle of the dielectric strip (3).

[0008] Furthermore, the metal cavity (1), the substrate (2) and the dielectric strip (3) are in the shape of a rectangular parallelepiped, and the grounding rod (4) is in the form of a cylinder.

[0009] The application of the dual-mode dielectric strip resonator is to use the dual-mode dielectric strip resonator for a differential dual-passband filter with two independently controllable bandwidths.

[0010] A differential dual-passband filter including the resonator comprises two coupled resonators, two pairs of differential microstrip lines (5) and a shielded metal cavity (1), wherein the feed lines of the differential microstrip lines (5) are directly connected to a grounding rod (4).

[0011] Furthermore, a tuning screw (6) is provided, and the tuning screw (6) is arranged on the upper part of the dielectric strip (3).

[0012] Furthermore, assuming that the length of the dielectric strip (3) is l1, the distance between the two grounding rods (4) is l2, the distance between the side edge of the dielectric strip (3) and the corresponding side inner wall of the metal cavity (1) is l3, the width of the dielectric strip (3) is w, the thickness of the dielectric strip (3) is t, and the extension length of the differential microstrip line (5) feeder is l d , the distance between the two dielectric strips (3) is s, and the thickness of the substrate (2) is h s , the height of the metal cavity (1) is h, the length of the metal cavity (1) is a, the width of the metal cavity (1) is b, the diameter of the grounding rod (4) is d1, and the diameter of the tuning screw (6) is d2;

[0013] The above-mentioned dimensional parameters are as follows: l1=17.8mm, l2=9.7mm, l3=2.1mm, w=2 mm, t=1mm, l d =0.3mm,s=5.3mm,h s =0.5mm,h=10mm,a=28mm,b=22mm, d1=0.6mm and d2=3mm.

[0014] The above-mentioned dimensional parameters can be enlarged or reduced proportionally.

[0015] The advantages of the present invention are as follows: the present invention proposes a quasi-planar dual-mode dielectric strip resonator for designing a differential dual-passband filter. By loading a pair of grounding rods under a conventional half-wavelength dielectric strip resonator, a dual-mode dielectric strip resonator is obtained, and it has a higher external quality factor. In addition, the proposed dielectric strip is placed on a low dielectric constant substrate and excited by two differential microstrip lines to design a filter. In order to verify the correctness of the proposed idea, a differential dual-passband bandpass filter is designed and processed, and its simulation results and test results are well matched. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the dual-mode dielectric strip resonator of the present invention.

[0017] Figure 2 For the present invention, when l1=17.8mm is fixed, the resonant frequency and Q U The trend graph as l2 changes.

[0018] Figure 3 When l2=9.7mm is fixed, the resonant frequency and Q U The trend graph as l1 changes.

[0019] Figure 4 A three-dimensional schematic diagram of a differential dual-passband filter.

[0020] Figure 5 A top view of the differential dual-passband filter.

[0021] Figure 6 Side view of a differential dual-passband filter.

[0022] Figure 7 The coupling coefficient between the low passband and the high passband changes with h under different conditions. d A graph showing the changing trends of changes.

[0023] Figure 8 The external quality factor of the low passband and high passband varies with l under different d1 conditions. d A graph showing the changing trends of changes.

[0024] Fig. 9 This is the trend diagram of the simulated frequency response as l1 changes when l2=9.7mm is fixed.

[0025] Fig.10 Figure 2 shows the simulation and test results of the designed differential dual-passband filter. DETAILED DESCRIPTION

[0026] A dual-mode dielectric strip resonator comprises a metal cavity 1, wherein a substrate 2 is arranged in one side of the metal cavity 1, a dielectric strip 3 is arranged on the upper surface of the substrate 2, a grounding surface is arranged on the lower surface of the substrate 2, and a grounding rod 4 is arranged between the lower surface of the dielectric strip 3 and the grounding surface.

[0027] Furthermore, the distance between the side edge of the dielectric strip 3 and the inner wall of the corresponding side of the metal cavity 1 is much greater than the thickness of the substrate 2 .

[0028] Furthermore, there are two grounding rods 4 symmetrically arranged on the lower surface of the dielectric strip 3 , and the grounding rods 4 are arranged in the middle of the dielectric strip 3 in the width direction of the dielectric strip 3 .

[0029] Furthermore, the metal cavity 1, the substrate 2 and the dielectric strip 3 are in a rectangular parallelepiped shape, and the grounding rod 4 is in a cylindrical form.

[0030] The application of the dual-mode dielectric strip resonator is to use the dual-mode dielectric strip resonator for a differential dual-passband filter with two independently controllable bandwidths.

[0031] A differential dual-passband filter including the resonator includes two coupled resonators, two pairs of differential microstrip lines 5 and a shielded metal cavity 1, wherein the feeder of the differential microstrip line 5 is directly connected to a ground rod 4.

[0032] Furthermore, a tuning screw 6 is provided, and the tuning screw 6 is arranged on the upper part of the dielectric strip 3 .

[0033] Furthermore, let the length of the dielectric strip 3 be l1, the distance between the two grounding rods 4 be l2, the distance between the side edge of the dielectric strip 3 and the inner wall of the corresponding side of the metal cavity 1 be l3, the width of the dielectric strip 3 be w, the thickness of the dielectric strip 3 be t, and the extension length of the differential microstrip line 5 be l d , the distance between the two dielectric strips 3 is s, and the thickness of the substrate 2 is h S , the height of the metal cavity 1 is h, the length of the metal cavity 1 is a, the width of the metal cavity 1 is b, the diameter of the grounding rod 4 is d1, and the diameter of the tuning screw 6 is d2;

[0034] The above-mentioned dimensional parameters are as follows: l1=17.8mm, l2=9.7mm, l3=2.1mm, w=2 mm, t=1mm, l d =0.3mm,s=5.3mm,h s =0.5mm,h=10mm,a=28mm,b=22mm, d1=0.6mm and d2=3mm.

[0035] The above-mentioned dimensional parameters can be enlarged or reduced proportionally.

[0036] The present invention is further described below for a better understanding of the present invention: The present invention proposes a novel design of a dual-passband dielectric strip filter with independent control. The traditional dielectric strip is composed of a dielectric strip with a high dielectric constant of half the wavelength loaded on a grounded low dielectric constant substrate; the present invention forms a dual-mode dielectric strip resonator by loading a pair of grounding rods under the traditional dielectric strip. The dual-mode resonator has two adjacent TM 11 module, and these two TM 11 The two modes can be controlled independently. The unloaded quality factor Q of these two modes is U In the X-band, both modes are greater than 600, which has high application value in many low-loss devices. And these two modes can be differentially excited and used to design differential dual-passband filters. The external quality factor and coupling coefficient of the two passbands can be independently controlled, and the common-mode rejection of the passband is also above 25dB. In order to verify the proposed idea, a filter prototype working at 8.13GHz and 11.13GHz was designed and assembled, and the simulation results were well consistent with the test results.

[0037] Figure 1 The proposed dual-mode dielectric strip resonator structure, in which the metal cavity is used to shield the signal. When the distance l3 from the side of the dielectric strip to the cavity is much greater than the thickness h of the dielectric substrate S When , the influence of the metal cavity on the dielectric strip can be ignored.

[0038] The ground rod of the present invention plays an important role in converting the conventional half-wavelength dielectric strip resonator into a dual-mode dielectric strip resonator. 11 The mode is split into two close low-frequency f 0L Mode and high frequency f 0U By changing the distance l2 between the two ground rods while keeping the length l1 of the entire dielectric strip unchanged, the two resonant frequencies and the unloaded quality factor of the dual-mode dielectric strip can be independently controlled. Figure 2 It can be seen that f 0L and f 0U As l2 increases, the low-frequency Q U Increased high frequency Q U Similarly, when l2 is fixed and l1 is reduced, f 0U Move down and f 0L unchanged, such as Figure 3 As shown. Figure 2 and Figure 3It can be seen that due to the introduction of the metal ground rod, the external quality factor of the two modes is slightly lower than that of the traditional dielectric strip, but the X-band frequency is also higher than 600, which is 5-10 times that of the microstrip line, and has high practical value in many low-loss applications.

[0039] Figure 4-Figure 6 The structure of the designed differential dual passband filter is presented. It consists of two coupled dielectric strip resonators with ground bars, two differential microstrip lines and a shielded metal cavity. The microstrip feed line is directly connected to the ground bar, and the feed line extension length l3 can be used to independently control the external quality factor Q of the two passbands. e , and has no effect on the dielectric strip.

[0040] The two differential mode passbands of the present invention are both based on Butterworth prototype design. The center frequency of the low-frequency passband is 8.13GHz, and the relative bandwidth is 3.9%, while the center frequency of the high-frequency passband is 11.13GHz, and its relative bandwidth is 3.6%. Based on these performances, the lumped parameters of its low-pass prototype are: = =1, = =1.4142, = =1.4142, and = = 1. Then, the required coupling coefficient k 12 and Q e The coupling coefficient k of the low-frequency passband can be calculated. 12 =0.028, external quality factor Q e =36, and the coupling coefficient k of the high-frequency passband 12 =0.025, external quality factor Q e =39.

[0041] The coupling coefficient k of the two passbands is mainly determined by the distance s between the two dielectric strip resonators, as Figure 7 As shown. At the same time, the coupling coefficient of the low-frequency passband and the coupling coefficient of the high-frequency passband can be independently controlled by adjusting the length of the two tuning screws on the dielectric strip resonator. As the length of the tuning screw increases, the coupling coefficient of the low-frequency passband increases while the coupling coefficient of the high-frequency passband remains unchanged. For the Q of the two passbands e , they all increase with the increase of metal via diameter, such as Figure 8 As shown. At the same time, the length of the feeder extension is l d The change in the high frequency passband Q e The change in low frequency passband Q e No impact. Figure 7 and 8As shown, the two key parameters of constructing the filter (coupling coefficient and external quality factor) can be controlled independently. This feature makes it easier to build a dual-passband filter and is therefore very valuable in application.

[0042] Fig. 9 shows the simulated frequency response of the proposed differential dual passband filter. As expected, the two passbands can be tuned by l1 (the total length of the dielectric strip resonator). As l1 increases, the frequency of the upper passband moves down while the lower passband frequency remains unchanged, which is consistent with Figure 3 The characteristics of the dual-mode dielectric resonator in are consistent.

[0043] according to Figure 7 and Figure 8 The coupling coefficient k and external quality factor Q extracted from e The size parameters of the proposed filter are as follows: l1=17.8mm,l2=9.7mm,l3=2.1mm,w=2 mm,t=1mm,l d =0.3mm,s=5.3mm,h s =0.5mm,h=10mm,a=28mm,b=22mm, d1=0.6mm and d2=3mm.

[0044] To verify the validity of the idea, a differential dual-passband filter using dual-mode dielectric strip resonators was designed, assembled, and tested; Fig.10 The simulation and test results of the filter are shown, and the stability is good. The center frequencies of the low passband and high passband tested are 8.13GHz and 11.13GHz respectively, and their relative insertion losses are 0.88 and 1.28dB respectively. The return loss of these two passbands is better than 14dB, and their common mode rejection in the two passband ranges is better than 25dB.

[0045] A dual-mode dielectric strip resonator has been investigated and used to design a differential filter with two independently controllable bandwidths. The proposed dielectric strip resonator has two TM 11 mode, they are easily excited by the differential microstrip line, so a dual-passband differential mode response can be obtained. At the same time, the proposed dual-passband filter also has a planar structure. Its good filtering performance also shows that this dual-mode dielectric strip resonator will become an excellent choice for future applications.

Claims

1. A dual-mode dielectric strip resonator, characterized in that: It comprises a metal cavity (1), a substrate (2) is arranged in one side of the metal cavity (1), a dielectric strip (3) is arranged on the upper surface of the substrate (2), a grounding surface is arranged on the lower surface of the substrate (2), and a grounding rod (4) is arranged between the lower surface of the dielectric strip (3) and the grounding surface; The distance between the side edge of the dielectric strip (3) and the inner wall of the corresponding side of the metal cavity (1) is much greater than the thickness of the substrate (2); There are two grounding rods (4), which are symmetrically arranged on the lower surface of the dielectric strip (3); in the width direction of the dielectric strip (3), the grounding rods (4) are arranged in the middle of the dielectric strip (3); The fundamental mode TM of the dual-mode dielectric strip resonator 11 The mode splits into low frequency f OL Mode and high frequency f OU mode, keeping the length of the dielectric strip unchanged and adjusting the distance between the two ground rods, thus independently controlling the low frequency f OL Mode and high frequency f OU The resonant frequency and unloaded quality factor of the mode; The metal cavity (1), the substrate (2) and the dielectric strip (3) are in the shape of a rectangular parallelepiped, and the grounding rod (4) is in the form of a cylinder.

2. Application of the dual-mode dielectric strip resonator according to claim 1, characterized in that: The dual-mode dielectric strip resonator is used in a differential dual-passband filter with two independently controllable bandwidths.

3. A differential dual-passband filter comprising the resonator according to claim 1, characterized in that: It comprises two coupled resonators, two pairs of differential microstrip lines (5) and a metal cavity (1), wherein the differential microstrip line (5) feed line and a grounding rod (4) are directly connected.

4. The differential dual-passband filter according to claim 3, characterized in that: A tuning screw (6) is also provided, and the tuning screw (6) is arranged on the upper part of the dielectric strip (3).

5. The differential dual-passband filter according to claim 3, characterized in that: Assume that the length of the dielectric strip (3) is l1, the distance between the two grounding rods (4) is l2, the distance between the side edge of the dielectric strip (3) and the corresponding side inner wall of the metal cavity (1) is l3, the width of the dielectric strip (3) is w, the thickness of the dielectric strip (3) is t, and the extension length of the differential microstrip line (5) feeder is l d , the distance between the two dielectric strips (3) is s, and the thickness of the substrate (2) is h s , the height of the metal cavity (1) is h, the length of the metal cavity (1) is a, the width of the metal cavity (1) is b, the diameter of the grounding rod (4) is d1, and the diameter of the tuning screw (6) is d2; The above-mentioned dimensional parameters are as follows: l1=17.8mm, l2=9.7mm, l3=2.1mm, w=2 mm, t=1mm, l d =0.3mm,s=5.3mm,h s =0.5mm,h=10mm,a=28mm,b=22mm, d1=0.6mm and d2=3mm.

6. The differential dual-passband filter according to claim 5, characterized in that: The size parameters are enlarged or reduced proportionally.

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