CN105896007B - A kind of microwave band-pass filter - Google Patents

Abstract

The invention discloses a kind of compound groove microwave band-pass filters.Including dielectric-slab (1), dielectric-slab (1) is equipped with metal micro-strip (2), and the both sides of metal micro-strip (2) are equipped with metal (3)；Compound groove is distributed in the metal micro-strip (2)；The compound groove includes rectangle main groove (7), and sub- groove (8) is distributed on the side of rectangle main groove (7).The present invention has the characteristics that low transmission loss, avoids electromagnetic field strong reflection and anti-electromagnetic interference capability strong.

Description

A microwave bandpass filter

technical field

The invention relates to a filter used in the communication field, in particular to a microwave bandpass filter with a compound groove structure.

Background technique

In the era of big data, with the explosive growth of the demand for information, 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 technical problems have emerged. For example, 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. Therefore, the existing microwave devices cannot 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 bandpass filter. The invention has the characteristics of low transmission loss, avoiding strong reflection of electromagnetic field and strong ability of resisting electromagnetic interference.

The technical solution of the present invention: a microwave bandpass filter, comprising a dielectric board, a metal microstrip is arranged on the dielectric board, and metal grounds are provided on both sides of the metal microstrip; composite concave grooves are distributed on the metal microstrip groove; the compound groove includes a rectangular main groove, and sub-grooves are distributed on the sides of the rectangular main groove.

In the aforementioned microwave bandpass filter, the metal microstrip includes a coplanar waveguide section, and the coplanar waveguide section is connected to the artificial surface plasmon section through a transition section; the artificial surface plasmon section is distributed Has compound grooves.

In the aforementioned microwave bandpass filter, the transition section is provided with compound grooves with gradually changing depths.

In the aforementioned microwave bandpass filter, the coplanar waveguide section is provided with an interdigitated structure.

In the aforementioned microwave bandpass filter, the value of the depth D1 of the rectangular main groove is 3 to 6 mm, the value of the width D2 of the rectangular main groove is 1.0 to 4.0 mm, and the period p of the rectangular main groove is The value of the width D3 of the sub-groove is 0.1-0.5mm, the value of the depth D4 of the sub-groove is 0.1-1.0mm, and the value of the period p1 of the sub-groove is 0.1-0.5 mm.

In the aforementioned microwave bandpass filter, the value of the center starting position z of the interdigital structure is 4-8mm, the value of the gap width w1 of the interdigital structure is 0.1-0.5mm, and the single interdigital structure The value of the interdigital length L ₄ is 2.0-5.0 mm, the value of the single interdigital width w2 of the interdigital structure is 0.5-1.5 mm, and the value of the total length L ₅ of the interdigital structure is 25-40 mm.

In the aforementioned microwave band-pass filter, the edge of the metal ground at the transition section satisfies Y=h+g+w*(exp(a*(XL ₁ )/L ₂ )-1)/(expa-1 ) equation; where a is the curve shape coefficient, and its value is 5 to 20; h is the width of the metal microstrip, and its value is 8 to 15mm; g is the distance between the metal microstrip and the metal ground, and its value is 0.3 ~1mm, w is the width of the metal ground, its value is 20-35mm, L1 is the length _of the coplanar waveguide section, its value is 5-15mm, L2 is the length of the transition section, its value is 60-90mm.

Compared with the prior art, the present invention sets a series of composite grooves on the metal microstrip, the composite grooves include a rectangular main groove, and periodically arranged sub-grooves are distributed on the sides of the rectangular main groove. Groove, the sub-groove can effectively enhance the distributed capacitance and distributed inductance of the rectangular main groove, so that the electromagnetic wave is highly bound inside the composite groove during transmission, thus greatly reducing the transmission of multiple transmission lines due to too small spacing The electromagnetic interference that appears makes the anti-electromagnetic interference ability greatly enhanced, and also enhances the stability of the high-density microwave integrated circuit at the same time. Not only that, because the anti-electromagnetic interference ability is greatly enhanced, the present invention can also reduce the metal of the microwave integrated circuit. The spacing between microstrips can achieve high integration and miniaturization of devices, so it can better adapt to the development of today's large-scale microwave integrated circuits. Not only that, the present invention can regulate the cut-off frequency and electromagnetic field distribution of the microwave transmission line by adjusting the geometric dimensions of the composite groove, and at the same time adjust the confinement effect of electromagnetic waves. After conducting a large number of tests, the applicant found that when D1 is between 3 and 6mm, When D2 is between 1.0-4.0mm, p is between 3-8mm, p1 is between 0.1-0.5mm, D3 is between 0.1-0.5mm, and D4 is between 0.1-1.0mm, the composite groove has a good restraint on the electromagnetic field. Effect.

The present invention sets a transition section (replaced by its length symbol L2 below) between the coplanar waveguide section (replaced by its length symbol L ₁ below) and the artificial surface plasmon segment (replaced by its length symbol L ₃ below ₎ , At the same time, there is also a compound groove with gradually changing depth on L ₂ ; through this structure, the smooth transition of electromagnetic field propagation in L ₁ and L ₃ is realized, and the time-dependent mode of electromagnetic field conversion from quasi-TEM mode to SSPPs mode is avoided. The strong microwave electric field reflection that does not match the impedance; the applicant has found through a large number of experiments that when the edge of the metal ground at the L ₂ position satisfies Y=h+g+w*(exp(a*(XL ₁ )/L ₂ )-1)/(expa-1) equation, where the curve shape coefficient a is 5-20, the width h of the metal microstrip is 8-15mm, the distance g between the metal microstrip and the metal ground is 0.3-1mm, and the width of the metal ground is w When the length of the coplanar waveguide section is _5-15mm , and the length of the transition section L2 is _60-90mm , the transition of the electromagnetic field propagation is the most stable.

The present invention also has an interdigitated structure on the coplanar waveguide section; through the interdigitated structure, an attenuation pole can be generated in the lower stop band of the filter, the square coefficient of the filter can be improved, and it can be used to control the lower stop band of the filter. out-of-band features.

In order to better prove the beneficial effects of the present invention, the applicant conducted the following experiments: the applicant designed a microwave bandpass filter sample, and the parameters of the sample are shown in Table 1.

Table 1 Parameters of each part of the microwave filter sample (unit: mm)

The dielectric plate of this sample adopts a substrate with a dielectric constant of 2.65. The filter characteristic curve of this sample is calculated by time-domain finite difference as shown in Figure 4. In Figure 4, S11 is the filter reflection coefficient, and S21 is the filter transmission coefficient. , the sample is a band-pass filter, its center frequency is 4.7451GHz, and its -3dB passband is from 3.1504GHz to 6.3398GHz. The ripple jitter of the sample is better than 0.8dB in the whole passband, and the reflection in the passband is less than -10dB.

In order to illustrate the beneficial effects of the transition section in the present invention, the applicant has designed a comparative filter: the filter that does not contain the composite groove of transition section L ₂ and depth gradual change, and the dielectric plate of its filter adopts the same dielectric constant of 2.65 , and other structural parameters are the same as in Table 1. The filter characteristic curve is calculated by time domain finite difference as shown in Fig. 5. It is known from Figure 5 that the filter has no filtering effect, and its reflection coefficient greatly exceeds -10dB in the entire frequency band. It can be seen that the filter with compound grooves with gradually changing depths in the transition section has a good mode and impedance matching effect, so that the reflection characteristics of the filter are effectively improved.

In addition, the interdigitated structure can generate an attenuation pole in the lower stop band of the filter. The position of the pole is flexible and controllable, and the out-of-band characteristics of the low frequency band of the filter can be adjusted conveniently. Fig. 6 shows that when there is no such interfinger structure, the attenuation pole of the lower stop band (0-3 GHz) disappears. In the present invention, the finger insertion structure is set on the microstrip transmission line of the coplanar waveguide section, which does not increase the overall size of the filter and facilitates the miniaturization of the filter.

Figure 7 is the electric field distribution diagram around the composite groove when the sample works in the 4GHz frequency band. It can be seen from Figure 7 that the electric field is highly bound inside the composite groove and the diffusion is small.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a structural schematic diagram of A place in Fig. 1;

Fig. 3 is a schematic structural view at B of Fig. 1;

Fig. 4 is the S-parameter curve diagram of the sample.

Fig. 5 is the S parameter curve diagram of the filter that does not adopt transition section;

Fig. 6 is the S parameter graph of the filter that does not adopt interpolation structure;

Fig. 7 is a diagram of the electric field distribution in the normal direction of the composite groove when the filter sample works in the 4GHz frequency band.

The marks in the drawings are: 1-dielectric plate, 2-metal microstrip, 3-metal ground, 4-coplanar waveguide section, 5-transition section, 6-artificial surface plasmon section, 7-rectangular main concave Groove, 8-sub-groove, 9-interdigitated structure.

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 composite groove microwave bandpass filter, constituted as shown in Figures 1 and 2, comprising a dielectric plate 1, a metal microstrip 2 is arranged on the dielectric plate 1, and a metal ground 3 is provided on both sides of the metal microstrip 2; Composite grooves are distributed on the metal microstrip 2; the composite grooves include rectangular main grooves 7, and sub-grooves 8 are distributed on the sides of the rectangular main grooves 7.

The aforementioned metal microstrip 2 includes a coplanar waveguide section 4, and the coplanar waveguide section 4 is connected to the artificial surface plasmon section 6 through a transition section 5; the artificial surface plasmon section 6 is distributed with composite grooves .

The aforementioned transition section 5 is provided with compound grooves with gradually changing depths.

The aforementioned coplanar waveguide section 4 is provided with an interdigitated structure 9 .

The value of the depth D1 of the aforementioned rectangular main groove 7 is 3 to 6 mm, the value of the width D2 of the rectangular main groove 7 is 1.0 to 4.0 mm, and the period p of the rectangular main groove 7 is 3 to 8 mm; The width D3 of the sub-groove 8 is 0.1-0.5 mm, the depth D4 of the sub-groove 8 is 0.1-1.0 mm, and the period p1 of the sub-groove 8 is 0.1-0.5 mm.

The value of the center starting position z of the aforementioned interdigital structure 9 is 4-8 mm, the value of the gap width w1 of the interdigital structure 9 is 0.1-0.5 mm, and the value of the single interdigital length L4 of the interdigital structure ₉ is The value is 2.0-5.0 mm, the value of the single finger width w2 of the interdigital structure 9 is 0.5-1.5 mm, and the value of the total length L ₅ of the interdigital structure 9 is 25-40 mm.

In the aforementioned microwave bandpass filter, the edge of the metal ground 3 at the position of the transition section 5 satisfies Y=h+g+w*(exp(a*(XL ₁ )/L ₂ )-1)/(expa -1) the curve of the equation; wherein a is the curve shape coefficient, and its value is 5 to 20; h is the width of the metal microstrip, and its value is 8 to 15mm; g is the distance between the metal microstrip 2 and the metal ground 3, and The value is 0.3~1mm, w is the width of the metal ground, the value is 20~35mm, L1 is the length _of the coplanar waveguide section, the value is 5~15mm, L2 is the length of the transition section, the value is 60~ 90mmm.

Working principle of the present invention: the electromagnetic field of the quasi-TEM mode is transmitted to the transition section 5 by the filter of the coplanar waveguide section 4 on the left through the finger structure 9, and gradually becomes the electromagnetic field of the SSPPs mode in the transition section 5, and in the transition section The electromagnetic fields of the quasi-TEM mode and the SSPPs mode coexist in 5. When the electromagnetic field reaches the artificial surface plasmon section 6, it is completely transformed into the electromagnetic field of the SSPPs mode, and is transmitted in L _3. After transmission, the electromagnetic field of the SSPPs mode passes through the transition on the right The electromagnetic field transformed into the quasi-TEM mode by the segment is output by the interfinger structure and the coplanar waveguide segment on the right. When the electromagnetic field propagates in the coplanar waveguide section 4, the mode of the electromagnetic field in this section is a quasi-TEM mode, and this mode electromagnetic field is bound in the dielectric plate between the coplanar waveguide section 4 and the metal ground 3; when the transition section 5 propagates, the The quasi-TEM mode and SSPPs mode coexist in the segment, and the electromagnetic field of the quasi-TEM mode is bound in the dielectric plate between the transition section 5 and the metal ground 3, and the electromagnetic field of the SSPPs mode is bound in the composite groove; when propagating in L ₃ , the Inside the segment is the SSPPs mode, and the electromagnetic field of this mode is bound inside the composite groove.

Claims (5)

1. a kind of microwave band-pass filter, it is characterised in that：Including dielectric-slab（1）, dielectric-slab（1）Be equipped with metal micro-strip （2）, metal micro-strip（2）Both sides equipped with metal（3）；The metal micro-strip（2）On compound groove is distributed with；Described answers It includes rectangle main groove to close groove（7）, rectangle main groove（7）Side on sub- groove is distributed with（8）；The metal micro-strip （2）Including co-planar waveguide section（4）, co-planar waveguide section（4）Through changeover portion（5）With artificial surface phasmon section（6）Connection；It is described Artificial surface phasmon section（6）On compound groove is distributed with；The co-planar waveguide section（4）It is equipped with interdigital structure（9）.

2. microwave band-pass filter according to claim 1, it is characterised in that：The changeover portion（5）It is equipped with depth The compound groove of gradual change.

3. microwave band-pass filter according to claim 1 or 2, it is characterised in that：The rectangle main groove（7）Depth The value for spending D1 is 3~6mm, rectangle main groove（7）Width D 2 value be 1.0~4.0mm, rectangle main groove（7）Week Phase p is 3~8mm；The sub- groove（8）Width D 3 value be 0.1~0.5mm, sub- groove（8）Depth D4 value For 0.1~1.0mm, sub- groove（8）1 value of period p be 0.1~0.5mm.

4. microwave band-pass filter according to claim 1, it is characterised in that：The interdigital structure（9）Center rise The value of beginning position z is 4~8mm, interdigital structure（9）Gap width w1 value be 0.1~0.5mm, interdigital structure（9）'s Single tine refers to length L₄Value be 2.0~5.0mm, interdigital structure（9）Single tine finger widths w2 value be 0.5~1.5mm, fork Refer to structure（9）Overall length L₅Value be 25~40mm.

5. microwave band-pass filter according to claim 1, it is characterised in that：In changeover portion（5）The metal of position （3）Edge be to meet Y=h+g+w* (exp (a* (X-L₁)/L₂) -1) curve of/(expa-1) equation；Wherein a is curved shape Shape coefficient, value are 5~20；H is metal micro-strip width, and value is 8~15mm；G is metal micro-strip（2）With metal （3）Spacing, value are 0.3~1mm, and for metal width, value are 20~35mm, L to w₁For the length of co-planar waveguide section, Its value is 5~15mm, and L2 is transition section length, and value is 60~90mmm.