CN109244609B - A kind of square groove structure microwave filter with dual band operation characteristic - Google Patents

Abstract

The invention discloses a square groove structure microwave filter with dual frequency band working characteristics. Including a dielectric board, one surface of the dielectric board is provided with a metal microstrip, and the other surface is provided with a metal ground; the structure of the metal microstrip is: the middle part of the metal microstrip is provided with an artificial surface plasmon section, an artificial surface, etc. The two ends of the plasmon section are respectively connected to the microstrip waveguide section through the transition section; the artificial surface plasmon section and the transition section are distributed with hollow square grooves along the length direction of the metal microstrip. The grooves are connected by a hollowed-out square belt; the upper and lower edges of the square groove in the transition section are curves that gradually change and converge along the transition section to the direction of the microstrip waveguide section. The invention has low transmission loss, small reflection characteristics, excellent out-of-band suppression performance, strong anti-electromagnetic interference ability, and is suitable for the characteristics of high-frequency integrated circuits.

Description

A Square Slot Structure Microwave Filter with Dual-band Operating Characteristics

technical field

The invention relates to the technical field of filters, in particular to a square-slot microwave filter with dual-band operating characteristics.

Background technique

In today's big data era, with the explosive growth of information demand, the field of mobile communication requires the manufacture of microwave devices with higher integration. However, as the size of high-frequency integrated circuits continues to shrink, a series of technological Problems, such as when the size of the microwave device is small to a certain extent, the electromagnetic interference noise and RC delay of the device reach the limit, resulting in unstable operation of the device, so the existing microwave devices can no longer adapt to the development of today's large-scale microwave integrated circuits.

Contents of the invention

The object of the present invention is to provide a microwave filter with a square slot structure with dual-band operating characteristics. The invention has low transmission loss, small reflection characteristics, superior out-of-band suppression performance, strong anti-electromagnetic interference ability, and is suitable for the characteristics of high-frequency integrated circuits. The present invention can also utilize two different eigenmodes formed by periodic square grooves, so that the filter works in two different frequency bands, and realizes one function and multiple functions of the filter.

The technical solution of the present invention: a microwave filter with a square groove structure with dual-band operating characteristics, including a dielectric plate, one surface of the dielectric plate is provided with a metal microstrip, and the other surface is provided with a metal ground; the metal microstrip The structure is: the middle part of the metal microstrip is provided with an artificial surface plasmon section, and the two ends of the artificial surface plasmon section are respectively connected to the microstrip waveguide section through a transition section; the artificial surface plasmon section and On the transition section, there are hollow square grooves distributed along the length direction of the metal microstrip, and the adjacent two square grooves are connected by hollow square strips; the upper and lower edges of the square grooves in the transition section are along the transition section to the microstrip waveguide. A curve where the segment direction gradient converges.

In the aforementioned square slot structure microwave filter with dual-band operating characteristics, the curve is to satisfy the equation X=L ₁ +L ₂ *t ³ , Y=h*(exp(b*t-1)/(expb -1)) curve; where t is the independent variable parameter, b is the shape coefficient of the curve, h is the width of the metal microstrip; L ₁ is the length of the microstrip waveguide section, and L ₂ is the length of the transition section.

In the aforementioned square groove structure microwave filter with dual-band operating characteristics, h=2-8mm, L ₁ =5-15mm, L ₂ =10-60mm, t=0-1, b=6.5-80 .

In the aforesaid square groove structure microwave filter with dual-band operating characteristics, the thickness g of the dielectric plate=0.3～1.2mm, the side length a=0.5～5.0mm of the square groove, and the width β=0.5～5.0mm of the square band 3mm, the period of the square groove p=1～8mm.

Compared with prior art, the present invention has following advantage:

1. In the present invention, a metal microstrip is arranged on one surface of the dielectric plate, and a metal ground is arranged on the other surface. The metal microstrip is divided into _three sections, which are respectively the artificial surface plasmon section (substituted by its length symbol L3 below), The transition section (replaced by its length symbol L ₂ below) and the microstrip waveguide section (replaced by its length symbol L ₁ below); where the two ends of L ₃ are connected to L ₁ via L ₂ respectively; on L ₃ and L ₂ , There are hollow square grooves distributed along the length direction of the metal microstrip, and the upper and lower edges of the square grooves _on L2 are curves that converge gradually along the direction _of L2 to L1 _; in the above structure, because they are _on L2 The upper and lower edges of the square groove are curves that converge gradually along the direction of L ₂ to L ₁ , which realizes the smooth transition of electromagnetic field propagation in L ₁ and L ₃ , and avoids the transmission of electromagnetic field from quasi-TEM mode to SSPPs mode. Strong microwave electric field reflections due to mode and impedance mismatch.

For the curves of the upper and lower edges of the square groove _L2 of the present invention, the applicant has obtained through a large number of experiments that in the filter structure of the present invention, when the curves of the upper and lower edges of the square groove of L2 _satisfy the equation X=L ₁ +L ₂ *t ³ , Y=h*(exp(b*t-1)/(expb-1)), the transition of electromagnetic field propagation is the most stable; further, the applicant is constantly correcting the experimental parameters It was found that the best parameters for the present invention to realize the smooth transition of electromagnetic field propagation are as follows: t=0~1, b=6.5~80, h=2~8mm, L ₁ =5~15mm, L ₂ =10~60mm.

2. The present invention sets hollowed out square grooves on L ₃ , and the square grooves are connected by hollowed out square belts. Applying this structure to the microwave of the present invention, since the periodically arranged square slots have multiple eigenoperating modes, two different even-mode operating modes can be excited by using the waveguide port, so the filter of the present invention It can work in two different microwave frequency bands, realizing the ability of one filter to work in multiple formats. In addition, this structure allows the electromagnetic field to be bound around the square groove when the interface is transmitted, thereby greatly reducing the electromagnetic interference that occurs due to the small spacing when multiple transmission lines are transmitted, which greatly enhances the anti-interference ability of the present invention, and also enhances the The invention is used for the stability when working in high-density microwave integrated circuits. Not only that, because the anti-electromagnetic interference ability is greatly enhanced, the invention can also reduce the distance between the metal microstrips of the microwave integrated circuit to realize the miniaturization of the device, so it can better adapt to the development of today's large-scale microwave integrated circuits. The invention can also adjust the cut-off frequency and electromagnetic field distribution of the microwave transmission line by adjusting the geometric dimension of the square groove, and at the same time adjust the confinement effect of electromagnetic waves. After carrying out a large number of parameter correction experiments, the applicant found that, in the microwave structure of the present invention, when the side length a of the square groove is a=0.5～5.0mm, the width β=0.5～3mm of the square belt, and the period p of the square groove is 1～5mm. When the thickness is 8mm, the square groove has the best binding effect on the electromagnetic field.

To sum up, the invention has low transmission loss, small reflection characteristics, superior out-of-band suppression performance, strong anti-electromagnetic interference ability, and is suitable for the characteristics of high-frequency integrated circuits. The present invention can also utilize two different eigenmodes formed by periodic square grooves, so that the filter works in two different frequency bands, and realizes one function and multiple functions of the filter.

In order to better prove the beneficial effect of the present invention, the applicant has carried out the following experiments: the applicant designed a microwave filter sample with a square groove structure with dual-band operating characteristics, the front structure is shown in Figure 1, and the parameters of the sample are shown in Table 1.

Table 1 Parameters of each part of the microwave filter sample with a square slot structure with dual-band operating characteristics (unit: mm)

The dielectric plate of this sample uses a substrate with a dielectric constant of 6.15, and the calculation results of the eigenmodes of the sample unit structure are shown in Figure 4. The first two even-mode eigenmodes are listed, in which the frequency band of mode 1 is 0-10.56 GHz, and the frequency band of mode 2 is 14.36-17.05 GHz, and they are negative group velocity eigenmodes. The characteristic curve of the filter (as shown in Figure 1) composed of unit structure is calculated by time-domain finite integration as shown in Figure 3. In Figure 3, S ₁₁ is the filter reflection coefficient, S ₂₁ is the filter transmission coefficient, and the sample is Dual passband filter, the first frequency band is low passband, the -3dB bandwidth is 0~10.31GHz, the insertion loss of the sample in this passband is very small, greater than -0.9dB, the ripple jitter is better than 0.45dB, the passband The internal reflection is less than -12.2dB, and the out-of-band suppression characteristic is excellent, and its square coefficient (ratio of 3dB bandwidth to 40dB bandwidth) can reach 0.96. The second frequency band is a band-pass band, the -3dB bandwidth is 14.73-18.69GHz, the lowest insertion loss of the sample in this pass-band is less than -0.91dB, the ripple jitter is better than 2.5dB, and the internal reflection of the pass-band is less than -10.8dB. It can be seen from Figure 3 and Figure 4 that the dual operating frequency bands of the filter correspond to eigenmode 1 and eigenmode 2, respectively, where eigenmode 2 has a negative group velocity. From the above, it can be seen that the filter sample has the ability to work in multiple communication systems with one device (that is, one function with multiple functions), which can effectively reduce the number of devices in the communication system and reduce the size of the equipment. At the same time, it can be seen from Figure 3 that the out-of-band suppression performance of the filter sample is superior.

Calculate the surface electric field distribution of the filter sample in Figure 1 when it works at 5 GHz, and the results are shown in Figure 5. Calculate the surface electric field distribution when the filter sample in Figure 1 works at 18 GHz, and the results are shown in Figure 6. 5,6 It is known that when the sample works in the passband, the electric field is an even mode, which corresponds to its eigenmode, and the electric field energy is localized around the square slot of the filter, and the diffusion to the surrounding is very small, which makes the filter resistant The ability of electromagnetic interference is greatly enhanced.

Calculate the surface electric field distribution of the filter sample in Figure 1 when it works at 12GHz, and the results are shown in Figure 7. Calculate the surface electric field distribution of the filter sample in Figure 1 when it works at 21GHz, and the results are shown in Figure 8. It can be seen from Figures 7 and 8 that when the filter operates at 12GH and 21GHz, it is out of the filter band, and the electric field energy is rapidly attenuated after being input from the input port of the filter, and cannot be transmitted to the output end. If it cannot be transmitted to the output terminal, it means that the electromagnetic signal exceeding this frequency will be effectively isolated, so as to realize the filtering function, that is, to filter out unnecessary interference signals.

Description of drawings

Fig. 1 is the front structure schematic diagram of the present invention;

Fig. 2 is the reverse structure schematic diagram of the present invention;

Fig. 3 is the S parameter curve diagram of sample;

Fig. 4 is the eigenmode dispersion relation curve diagram of the filter unit structure (the illustrations are the electric field distribution diagrams of mode 1 and mode 2 respectively from left to right);

Fig. 5 is the vertical surface electric field distribution diagram when the filter sample works in the first passband 5GHz;

Fig. 6 is the vertical surface electric field distribution diagram when the filter sample works at the second passband 18GHz;

Figure 7 The vertical surface electric field distribution of the filter sample when it works at 12GHz;

Figure 8 The vertical surface electric field distribution of the filter sample when it works at 21GHz.

The marks in the drawings are: 1-dielectric plate, 2-metal microstrip, 21-artificial surface plasmon section, 22-transition section, 23-microstrip waveguide section, 24-square groove, 25-square strip, 26-curve, 3-metal land.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but not as a basis for limiting the present invention.

Example. A microwave filter with a square groove structure with dual-band operating characteristics, as shown in Figures 1 and 2, including a dielectric plate 1, a metal microstrip 2 is provided on one surface of the dielectric plate 1, and a metal ground 3 is provided on the other surface The structure of the metal microstrip 2 is: the middle part of the metal microstrip 2 is provided with an artificial surface plasmon section 21, and the two ends of the artificial surface plasmon section 21 respectively pass through a transition section 22 and a microstrip waveguide section 23 Connection; the artificial surface plasmon section 21 and the transition section 22 are distributed with hollow square grooves 24 along the length direction of the metal microstrip 2, and the adjacent two square grooves 24 are connected by hollow square strips 25; The upper and lower edges of the square groove 24 of the transition section 22 are curves 26 that converge gradually along the transition section 22 to the direction of the microstrip waveguide section 23 .

The aforementioned curve 26 is a curve satisfying the equation X=L ₁ +L ₂ *t ³ , Y=h*(exp(b*t-1)/(expb-1)); wherein t is an independent variable parameter, and b is Curve shape factor, h is the width of the metal microstrip 2; L ₁ is the length of the microstrip waveguide section 23, and L ₂ is the length of the transition section 22.

The aforementioned h=2-8mm, L ₁ =5-15mm, L ₂ =10-60mm, t=0-1, b=6.5-80.

The thickness g of the aforementioned dielectric plate 1 is 0.3-1.2 mm, the side length a of the square groove 24 is 0.5-5.0 mm, the width β of the square belt 25 is 0.5-3.0 mm, and the period p of the square groove 24 is 1-8 mm. The length L ₃ of the artificial surface plasmon segment 21 can be set according to the size of the filter, and this parameter only affects the size of the filter and does not affect the performance of the filter. The length of the artificial surface plasmon segment 21 may refer to L ₃ =20-80 mm.

Working principle: The electromagnetic field of the quasi-TEM mode is transmitted from the left microstrip waveguide section 23 to the transition section 22, and gradually becomes the electromagnetic field of the SSPPs mode in the transition section 22, and the electromagnetic fields of the quasi-TEM mode and the SSPPs mode coexist in the transition section 22 , when the artificial surface plasmon segment 21, it is completely transformed into the electromagnetic field of the SSPPs mode, and is transmitted at L ₃ , after the transmission, the electromagnetic field of the SSPPs mode is transformed into the electromagnetic field of the quasi-TEM mode through the transition section on the right, which is formed by the microstrip on the right Waveguide segment output. When the electromagnetic field propagates in the microstrip waveguide section 23, the mode of the electromagnetic field in this section is a quasi-TEM mode, and this mode electromagnetic field is bound in the medium between the microstrip waveguide section 23 and the metal ground 3; when the transition section 22 propagates, the section The internal quasi-TEM mode and the SSPPs mode coexist, and the electromagnetic field of the quasi-TEM mode is bound in the medium between the transition section 22 and the metal ground 3, and the electromagnetic field of the SSPPs mode is bound around the square groove; when propagating in L ₃ , in this section is SSPPs mode, where the electromagnetic field is bound around the square slot.

Claims (2)

1. A square groove structure microwave filter with dual-band operating characteristics is characterized in that: it comprises a dielectric plate (1), and the dielectric plate (1) is provided with a metal microstrip (2) on one surface, and the other surface is provided with a Metal ground (3); the structure of the metal microstrip (2) is: the middle part of the metal microstrip (2) is provided with an artificial surface plasmon section (21), and the artificial surface plasmon section (21) The two ends are respectively connected to the microstrip waveguide section (23) via the transition section (22); the artificial surface plasmon section (21) and the transition section (22) are distributed along the length direction of the metal microstrip (2) There are hollowed out square grooves (24), connected by hollowed out square belts (25) between adjacent two square grooves (24); the upper and lower edges of the square grooves (24) in the transition section (22) are all along the transition section (22) Curve (26) gradually changing and converging to the microstrip waveguide section (23) direction; described curve (26) is to satisfy equation X=L ₁ +L ₂ *t ³ , Y=h*(exp(b* t-1)/(expb-1)) curve; wherein t is an independent variable parameter, b is a curve shape coefficient, and h is a metal microstrip (2) width; L ₁ is a microstrip waveguide section (23) length, L ₂ is the length of the transition section (22); said h=2-8mm, L ₁ =5-15mm, L ₂ =10-60mm, t=0-1, b=6.5-80. 2. the square groove structure microwave filter with dual-band operating characteristics according to claim 1, is characterized in that: the thickness g=0.3～1.2mm of described dielectric plate (1), the side of square groove (24) The length a=0.5～5.0mm, the width β=0.5～3mm of the square belt (25), and the period p=1～8mm of the square groove (24).