CN110364792A - Dual-mode dielectric strip resonator and differential dual-passband filter comprising said resonator - Google Patents

Abstract

The present invention relates to a kind of bimodulus medium tape resonator and include the difference double-passband filter of the resonator.The present invention constitutes a bimodulus medium tape resonator, there are two similar TM for dual-mode resonator tool by loading a pair of of grounding rod under traditional medium tape₁₁Mould, and the two TM₁₁Mould can be independently controlled.The Q-unloaded of the two modesQ _u600 are both greater than in X-band, there is very high application value in many low-loss devices.And the two modes can be motivated by difference and be used to design difference double-passband filter.The external sort factor of the two passbands can be independently controlled with the coefficient of coup, while the common mode inhibition of passband is also in 25dB or more.In order to verify the idea put forward, a job is designed and assembles in the filter prototype of 8.13GHz and 11.13GHz, and simulation result and test result are surely closed well.

Description

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

technical field

The invention relates to a double-mode dielectric strip resonator and a differential double-passband filter including the resonator, belonging to the technical field of communication transmission.

Background technique

In recent years, circuits with differential structures 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 are designed, such as power dividers, phase shifters, antennas and bandpass filters, etc. Band-pass filters, as an essential device in the RF front-end, play a key role in frequency selection. In order to meet the needs of multi-band usage in RF systems, differential dual-passband filters have been proposed in the past few years.

There are many ways to design a differential dual-passband filter, such as paralleling two single-passband filters operating in different frequency bands, or using a dual-mode resonator. It is well known that a dual-mode resonator can be equivalent to two single-mode resonators, so the designed filter is small in size, and at the same time, two close passbands can be easily obtained, which meets the needs of most applications. Therefore, various techniques based on the principle of dual-mode resonators are used, such as microstrip and SIW have been widely developed, and they can be differentially excited to design dual-passband filters. Unfortunately, they have a relatively low unloaded figure of merit, 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, and the resonator uses a half-cut method to reduce the profile of the designed filter. However, its 3D structure is still a hurdle in RFIC design.

Contents of the invention

In view of the above defects, the present invention aims to provide 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.

For this reason, the technical solution adopted by the present invention is: a dual-mode dielectric strip resonator, including a metal cavity (1), a substrate (2) is arranged on one side of the metal cavity (1), and a substrate (2) is arranged on the substrate (2). There is a dielectric strip (3), and a ground rod (4) between the dielectric strip (3) and the base plate (2) is arranged on the lower surface of the dielectric strip (3).

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

Further, there are two ground rods (4), which are arranged symmetrically on the lower surface of the dielectric tape (3), and the ground rods (4) are arranged on the dielectric tape (3) in the width direction of the dielectric tape (3). of the middle.

Further, the metal cavity (1), the substrate (2) and the dielectric strip (3) are in the shape of a cuboid, and the ground rod (4) is in the shape of a cylinder.

The application of the above-mentioned dual-mode dielectric strip resonator involves using the dual-mode dielectric strip resonator in a differential dual-passband filter with two independently controllable bandwidths.

A differential double-passband filter including the resonator, including two coupled resonators, two pairs of differential microstrip lines (5) and a shielded metal cavity (1), the differential microstrip line (5 ) feeder and ground rod (4) are directly connected.

Further, a tuning screw (6) is also provided, and the tuning screw (6) is set on the upper part of the dielectric belt (3).

Further, let the length of the dielectric belt (3) be l1 _, the distance between the two ground rods (4) be l2 _, and the distance between the side of the dielectric belt (3) and the inner wall of the corresponding side of the metal cavity (1) be l _3. The width of the dielectric strip (3) is w, the thickness of the dielectric strip (3) is t, the extension length of the differential microstrip line (5) feeder is l _d, and the distance between the two dielectric strips (3) is s, 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 , and the diameter of the ground rod (4) is d _{1 ,} the diameter of the resonance screw (6) is d ₂ ;

The above dimensions are as follows: l ₁ = 17.8 mm, l ₂ = 9.7 mm, l ₃ = 2.1 mm, w = 2 mm, t = 1mm, l _d = 0.3 mm, s = 5.3 mm, h _s = 0.5 mm, h = 10 mm, a = 28 mm, b = 22 mm, d ₁ = 0.6 mm and d ₂ = 3 mm.

The size parameters mentioned above can be scaled up or down proportionally.

The advantage of the present invention is: the present invention is proposed in a quasi-planar double-mode dielectric strip resonator to design a differential double-passband filter. By loading a pair of grounding rods under the traditional 1/2 wavelength dielectric strip resonator, a dual-mode dielectric strip resonator is obtained, and it has a high external quality factor. In addition, the proposed dielectric strip is placed on a low-permittivity substrate and excited by two differential microstrip lines to design the filter. In order to verify the correctness of the proposed idea, a differential double-pass band-pass filter is designed and fabricated, and its simulation results and test results are in good agreement.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the dual-mode dielectric strip resonator of the present invention.

Fig. 2 is a trend diagram of the resonance frequency and Q _u changing with l ₂ when l ₁ =17.8mm is fixed in the present invention.

Fig. 3 is when l ₂ =9.7mm is fixed, the variation trend graph of resonance frequency and Q _u as l ₁ changes.

Fig. 4 is a three-dimensional schematic diagram of a differential dual passband filter.

FIG. 5 is a top view of a differential dual passband filter.

Figure 6 is a side view of a differential dual passband filter.

Figure 7 is a trend diagram of the variation of the coupling coefficient of the low-pass band and the high-pass band as h _d changes under different s conditions.

Fig. 8 is a trend diagram of the change of the external quality factor of the low-pass band and the high-pass band with the change of l _d in the case of different d ₁ .

Fig. 9 is a graph showing the variation trend of the simulated frequency response as l ₁ changes when l ₂ =9.7mm is fixed.

Fig. 10 is a diagram of the simulation and test results of the designed differential dual-passband filter.

Detailed ways

The dual-mode dielectric strip resonator includes a metal cavity (1), a substrate (2) is arranged on one side of the metal cavity (1), a dielectric strip (3) is arranged on the substrate (2), and the The lower surface of the dielectric strip (3) is provided with a ground rod (4) between the dielectric strip (3) and the base plate (2).

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

Further, there are two ground rods (4), which are arranged symmetrically on the lower surface of the dielectric tape (3), and the ground rods (4) are arranged on the dielectric tape (3) in the width direction of the dielectric tape (3). of the middle.

Further, the metal cavity (1), the substrate (2) and the dielectric strip (3) are in the shape of a cuboid, and the ground rod (4) is in the shape of a cylinder.

The application of the above-mentioned dual-mode dielectric strip resonator involves using the dual-mode dielectric strip resonator in a differential dual-passband filter with two independently controllable bandwidths.

A differential double-passband filter including the resonator, including two coupled resonators, two pairs of differential microstrip lines (5) and a shielded metal cavity (1), the differential microstrip line (5 ) feeder and ground rod (4) are directly connected.

Further, a tuning screw (6) is also provided, and the tuning screw (6) is set on the upper part of the dielectric belt (3).

Further, let the length of the dielectric belt (3) be l1 _, the distance between the two ground rods (4) be l2 _, and the distance between the side of the dielectric belt (3) and the inner wall of the corresponding side of the metal cavity (1) be l _3. The width of the dielectric strip (3) is w, the thickness of the dielectric strip (3) is t, the extension length of the differential microstrip line (5) feeder is l _d, and the distance between the two dielectric strips (3) is s, 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 , and the diameter of the ground rod (4) is d _{1 ,} the diameter of the resonance screw (6) is d ₂ ;

The above dimensions are as follows: l ₁ = 17.8 mm, l ₂ = 9.7 mm, l ₃ = 2.1 mm, w = 2 mm, t = 1mm, l _d = 0.3 mm, s = 5.3 mm, h _s = 0.5 mm, h = 10 mm, a = 28 mm, b = 22 mm, d ₁ = 0.6 mm and d ₂ = 3 mm.

The size parameters mentioned above can be scaled up or down proportionally.

The present invention is further described below to better understand 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 grounded low dielectric constant substrate loaded with a dielectric strip with a high dielectric constant of 1/2 wavelength; the present invention loads a pair of ground rods under the traditional dielectric strip, Then a dual-mode dielectric strip resonator is formed, the dual-mode resonator has two adjacent TM ₁₁ modes, and the two TM ₁₁ modes can be independently controlled. The unloaded figure of merit Qu of these two modes is greater than 600 in the X _- band, which has high application value in many low-loss devices. And both 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 passbands 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 in good agreement with the test results.

Figure 1 is the proposed dual-mode dielectric strip resonator structure, in which the metal cavity is used to shield the signal. When the distance l ₃ from the side of the dielectric strip to the cavity is much greater than the thickness h _s of the dielectric substrate, the influence of the metal cavity on the dielectric strip can be ignored.

The ground rod of the present invention plays an important role in converting the traditional 1/2 wavelength dielectric strip resonator into a dual-mode dielectric strip resonator. The fundamental mode TM ₁₁ of the traditional 1/2 wavelength dielectric strip resonator is split into two close low frequency f _0L modes and high frequency f _0U modes. By changing the distance l ₂ of the two ground rods while keeping the length l ₁ of the entire dielectric strip constant, the two resonant frequencies and the unloaded quality factor of the dual-mode dielectric strip can be independently controlled. It can be seen from Figure 2 that both f _0L and f _0U become larger with the increase of l ₂ , while the low frequency Qu increases and the high frequency _Qu decreases _. Similarly, when l ₂ is fixed and l ₁ decreases, f _0U moves down while f _0L remains unchanged, as shown in Figure 3. It can be seen from Figure 2 and Figure 3 that due to the introduction of metal ground rods, the external quality factors of the two modes are slightly lower than the traditional dielectric strip, but the frequency in the X-band is also higher than 600, which is a microstrip line 5-10 times of that, it has high practical value in many low loss applications.

Figure 4-Figure 6 shows the structure of the designed differential dual passband filter. It consists of two coupled dielectric strip resonators with ground rods, two pairs of differential microstrip lines and a shielded metal cavity. The microstrip feeder is directly connected to the ground rod, and the feeder extension length l ₃ can be used to independently control the external quality factor Q _e of the two passbands with little effect on the dielectric strip.

Both differential mode passbands of the present invention are based on the 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 properties, the lumped parameters of its low-pass prototype are: = =1, = =1.4142, = = 1.4142, and = = 1. Then, the required coupling coefficients k ₁₂ and Q _e can be calculated. The coupling coefficient k ₁₂ =0.028 in the low frequency passband, the external quality factor Q _e =36, and the coupling coefficient k ₁₂ =0.025 in the high frequency passband, the external quality factor Q _e =39.

The coupling coefficient k of the two passbands is mainly determined by the distance s between the two dielectric strip resonators, as shown in Figure 7. Meanwhile, the coupling coefficient of the low-frequency passband and the high-frequency passband can be independently controlled by adjusting the lengths of 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 that of the high-frequency passband remains unchanged. For the Q _e of the two passbands, they both increase with the increase of the diameter of the metal via, as shown in Fig. 8 . At the same time _, the change of the extended length ld of the feeder will cause the change of the high-frequency passband _Qe but has no effect on the low-frequency passband Qe _. As shown in Figures 7 and 8, the two key parameters (coupling coefficient and external quality factor) for constructing filters can be independently controlled. This feature will make the construction of dual-passband filters easier to implement and therefore very applicable. value.

Fig. 9 shows the simulated frequency response of the proposed differential dual-passband filter. As previously thought, the two passbands can be tuned by l ₁ (the total length of the dielectric strip resonator). As l increases, the frequency _of the upper passband moves down while the frequency of the lower passband remains unchanged, consistent with the characteristics of the dual-mode dielectric resonator in Figure 3.

According to the coupling coefficient k and external quality factor Q _e extracted from Fig. 7 and Fig. 8, the size parameters of the proposed filter are as follows: l ₁ = 17.8 mm, l ₂ = 9.7 mm, l ₃ = 2.1 mm, w = 2 mm, t = 1 mm, l _d = 0.3 mm, s = 5.3 mm, h _s = 0.5 mm, h = 10 mm, a = 28 mm, b = 22 mm, d ₁ = 0.6 mm and d ₂ = 3 mm.

In order to verify the effectiveness of the idea, a differential dual-passband filter using a dual-mode dielectric strip resonator was designed, assembled and tested; Fig. 10 shows the simulation and test results of the filter, and the fit is good. The center frequencies of the tested low-pass band and high-pass band are 8.13GHz and 11.13GHz respectively, and their relative insertion losses are 0.88 and 1.28dB respectively. The return loss in both passbands is better than 14dB, and their common-mode rejection in both passbands is better than 25dB.

A dual-mode dielectric strip resonator of the present invention has been studied and used to design a differential filter with two independently controllable bandwidths. The proposed dielectric strip resonator has two TM ₁₁ modes close to the resonance frequency, which are easily excited by the differential microstrip line, so that the 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 indicates that this dual-mode dielectric strip resonator will be an excellent choice for future applications.

Claims (9)

1. The dual-mode dielectric strip resonator is characterized in that it includes a metal cavity (1), a substrate (2) is arranged on one side of the metal cavity (1), and a dielectric strip ( 3), a ground rod (4) between the dielectric strip (3) and the base plate (2) is arranged on the lower surface of the dielectric strip (3). 2. The dual-mode dielectric strip resonator according to claim 1, characterized in that, the distance between the side 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) . 3. The dual-mode dielectric strip resonator according to claim 1, characterized in that, there are two ground rods (4), which are symmetrically arranged on the lower surface of the dielectric strip (3), and on the dielectric strip (3) ) The ground rod (4) is arranged in the middle of the dielectric belt (3) in the width direction. 4. The dual-mode dielectric strip resonator according to claim 1, characterized in that, the metal cavity (1), the substrate (2) and the dielectric strip (3) are in the shape of a cuboid, and the ground rod (4) in cylindrical form. 5. The application of the dual-mode dielectric strip resonator according to any preceding claim, wherein the dual-mode dielectric strip resonator is used for a differential dual-passband filter with two independently controllable bandwidths . 6. A differential dual passband filter comprising the resonator of the preceding claim, characterized in that it comprises two coupled resonators, two pairs of differential microstrip lines (5) and a shielded metal cavity (1) , the differential microstrip line (5) feeder is directly connected to the ground rod (4). 7. The differential double-passband filter according to claim 6, characterized in that a tuning screw (6) is further provided, and the tuning screw (6) is arranged on the upper part of the dielectric strip (3). 8. The differential double-passband filter according to claim 6, characterized in that, the length of the dielectric strip (3) is l _1, the distance between the two ground rods (4) is l _{2, and the} dielectric strip (3) ) from the side of the metal cavity (1) to the inner wall of the corresponding side is l _3, 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, 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 metal cavity ( The width of 1) is b , the diameter of the ground rod (4) is d _{1 , and} the diameter of the resonance screw (6) is d ₂ ; The above dimensions are as follows: l ₁ = 17.8 mm, l ₂ = 9.7 mm, l ₃ = 2.1 mm, w = 2 mm, t = 1mm, l _d = 0.3 mm, s = 5.3 mm, h _s = 0.5 mm, h = 10 mm, a = 28 mm, b = 22 mm, d ₁ = 0.6 mm and d ₂ = 3 mm. 9. The differential dual passband filter according to claim 8, characterized in that, the above-mentioned size parameters can be enlarged or reduced proportionally.