CN104409808B - Comb filter based on multimode resonator - Google Patents

Abstract

The invention discloses a kind of comb filter based on multimode resonator, mainly solve the problems, such as that comb filter size is big, performance is not good.Which includes micro-strip medium substrate (1), metal ground plate (2), resonator (3), input and output feeder line (4).The resonator (3) is made up of two identicals, the five mould resonator being staggeredly placed, each five mould resonator by short-circuit minor matters (31), open circuit minor matters (32), U-shaped microstrip line (33), convex ring (34) and L-shaped open circuit minor matters (35,36) composition.The symmetrical centre of convex ring (34) is overlapped with the symmetrical centre of U-shaped microstrip line, and its top is connected with the bottom of U-shaped microstrip line；L-shaped open circuit minor matters are also connected on the bottom of U-shaped microstrip line.Input and output feeder line (4) is made up of an alignment interdigitation coupling feed.The present invention can reduce the size of comb filter, reduce design complexities, improve passband selectivity, can be used for wireless communication system.

Description

Multi-pass band filter based on multi-mode resonator

technical field

The invention belongs to the technical field of electronic devices, and in particular relates to the design of a microstrip multi-passband filter, which can be used for a radio frequency front end of a wireless communication system.

Background technique

Microwave filters are an indispensable and important part of communication systems, radar systems, and measurement systems. Therefore, microwave filters have always been the focus and hotspot of wireless communication system research. Modern wireless communication systems require radio frequency devices to work in multiple separate frequency bands to meet the needs of a multi-mode terminal to achieve different services, and transmit frequency signals of multiple discontinuous channels through one beam. This requires the use of multi-passband filters to suppress spurious noise signals. In the past, in order to realize multi-band communication, each frequency band required an independent filter, which made the overall system larger in size and power consumption, and higher in cost. If the filter of the RF front-end is designed in a multi-band form, the volume, cost and power consumption of the system can be greatly reduced, its reliability can be enhanced, and the communication system can be miniaturized and highly integrated.

In order to meet this demand, a lot of research work has been devoted to the design of multi-passband filters. In May 2010, Cheng, C.-M. et al. published a four-dimensional structure implemented with a defect ground structure in the journal IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS. Passband filter, however, the defective ground structure will affect the integrity of the ground plane signal when the filter is packaged; Hung-Wei, W. and Y. Ru-Yuan in IEEE MICROWAVE AND WIRELESSCOMPONENTS LETTERS in April 2011 Published a four-pass band filter realized by an asymmetrical ladder impedance resonator, but the size of the circuit becomes larger due to the use of more resonators in its design; in July 2012, Chi-Feng Chen presented at IEEE MICROWAVE AND A five-frequency filter based on a three-mode stub load ladder impedance resonator was published in the journal WIRELESS COMPONENTS LETTERS, but the insertion loss of the filter is too large, which affects its application; in September 2013, J.Xu et al. published in IEEE TRANSACTIONS ON MICROWAVE THEORY A number of multi-passband filters designed with open-circuit stub-loaded ladder impedance resonators were published in AND TECHNIQUES journals, but the selectivity of the filter passbands was not satisfactory.

Contents of the invention

The object of the present invention is to propose a multi-passband filter based on a multi-mode resonator to reduce the volume of the filter and improve the performance of the filter in view of the above-mentioned deficiencies in the prior art.

To achieve the above object, the present invention provides the following two technical solutions:

Technical solution one:

A multi-passband filter based on a multimode resonator, comprising a microstrip dielectric substrate 1, a metal ground plate 2, a resonator 3, an input and output feeder 4, and a ground hole 5 on the metal ground plate, characterized in that:

The input and output feeder 4 is composed of a pair of aligned interdigital coupling feeders, each feeder includes two interdigital branches 41, 42 and a section of 50 ohm microstrip line 43; the interdigital branches 41, 42 are connected in parallel at 50 The same end of the ohmic microstrip line 43;

Described resonator 3, it is made up of two identical four-mode resonators that are placed alternately, and each four-mode resonator is made of short-circuit stub 31, open-circuit stub 32, U-shaped microstrip line 33 and a convex ring 34; The short-circuit branch 31 is located at the symmetrical center of the U-shaped microstrip line inside the convex ring 34, and the open-circuit branch 32 is located at the symmetrical center of the U-shaped microstrip line outside the convex ring 34; the upper end A of the U-shaped microstrip line 33 is placed parallel to the interdigitated Between the branches 41 and 42, the lower end B is placed parallel to the inner side of the feeder 4; the symmetrical center of the convex ring 34 coincides with the symmetrical center of the U-shaped microstrip line 33, and the top of the convex ring 34 coincides with the bottom end of the U-shaped microstrip line C connected.

Technical solution two:

A multi-passband filter based on a multimode resonator, comprising a microstrip dielectric substrate 1, a metal ground plate 2, a resonator 3, an input and output feeder 4, and a ground hole 5 on the metal ground plate, characterized in that:

The input and output feeder 4 is composed of a pair of aligned interdigital coupling feeders, each feeder includes two interdigital branches 41, 42 and a section of 50 ohm microstrip line 43; the interdigital branches 41, 42 are connected in parallel at 50 The same end of the ohmic microstrip line 43;

Described resonator 3, it is made up of two identical five-mode resonators that are placed alternately, each five-mode resonator is made up of short-circuit stub 31, open-circuit stub 32, U-shaped microstrip line 33, a convex ring 34 and two A L-shaped open-circuit branch 35,36 is formed; the short-circuit branch 31 is located at the symmetrical center of the U-shaped microstrip line inside the convex ring 34, and the open-circuit branch 32 is located at the symmetrical center of the U-shaped microstrip line outside the convex ring 34; the U-shaped microstrip The upper end A of the line 33 is placed between the interdigital branches 41 and 42 in parallel, and the lower end B is placed parallelly inside the feeder line 4; the center of symmetry of the convex ring 34 coincides with the center of symmetry of the U-shaped microstrip line 33, and the center of symmetry of the convex ring 34 The top end is connected to the bottom end C of the U-shaped microstrip line; two L-shaped open circuit branches 35 and 36 are symmetrically connected to the bottom end C of the U-shaped microstrip line 33 .

The present invention has the following advantages:

1. The present invention is designed by adopting multi-mode resonators, so that each filter can realize multi-passband response with only two identical resonators, which reduces the overall size of the filter and simplifies the complexity of the design Spend.

2. Since the present invention adopts the multi-mode resonator in the form of stub loading, the frequency of each resonance mode can be independently controlled, which increases the flexibility and freedom of design, and easily realizes the transformation from four-mode to five-mode.

3. Since the present invention uses quasi-interdigitated feeders for energy input and output, transmission zero points can be formed on both sides of each passband, and the out-of-band characteristics are improved without adding additional costs, so that each passband Belts have better selectivity.

4. Since the present invention adopts a complete metal ground plane, the signal integrity of the ground plane will not be affected when the filter is packaged.

Description of drawings

Fig. 1 is a structural diagram of the first embodiment of the present invention;

Fig. 2 is the side view of Fig. 1;

Fig. 3 is the structural diagram of the second embodiment of the present invention;

Fig. 4 is the side view of Fig. 3;

Fig. 5 is the transmission characteristic |S21| and the return loss |S11| simulation and test curve diagram of the first embodiment of the present invention;

FIG. 6 is a simulation and test curve diagram of transmission characteristic |S21| and return loss |S11| of the second embodiment of the present invention.

detailed description

Embodiments of the present invention are described in detail below in conjunction with accompanying drawings:

The first embodiment: design a four-pass band filter with a size of 27.5mm×23mm.

1 and 2, the four-pass bandpass filter of the present invention is mainly composed of a microstrip dielectric substrate 1, a metal ground plate 2, a resonator 3, an input and output feeder 4, and a ground hole 5. in:

The microstrip dielectric substrate 1 adopts a double-sided copper-clad laminate with a dielectric constant of 2.2 and a thickness of 1.0 mm. The metal ground plate 2 is placed under the double-sided copper-clad laminate, and the four-mode resonator 3 is placed above the double-sided copper-clad laminate. Input and output feeders 4 and ground hole 5. in:

The input-output feeder 4 is made up of a pair of aligned interdigital coupling feeders, and each feeder includes two interdigital stubs 41, 42 and a section of 50 ohm microstrip line 43; the interdigital stubs 41, 42 are connected in parallel on the 50 ohm The same end of the strip line 43; the length of the pair of interdigital branches 41, 42 is 13 mm, the width is 0.76 mm, and the distance between the two interdigital branches 41, 42 is 1.48 mm; the length of the 50 ohm microstrip line 43 6mm and 3mm wide.

The resonator 3 is composed of two identical four-mode resonators placed alternately. Each four-mode resonator consists of a short-circuit branch 31, an open-circuit branch 32, a U-shaped microstrip line 33 and a convex ring 34; The length of the open circuit branch 32 is 4.1mm, and the width is 0.5mm; the U-shaped microstrip line symmetry center of the open circuit branch 32 is located at the outer side of the convex ring 34, and the length of the open circuit branch 32 is 7mm, and the width is 1.5mm; the upper end of the U-shaped microstrip line 33 A is placed in parallel between the interdigitated branches 41, 42; the symmetrical center of the convex ring 34 coincides with the symmetrical center of the U-shaped microstrip line 33, and the top of the convex ring 34 is connected to the bottom end C of the U-shaped microstrip line 33 .

Described U-shaped microstrip line 33, its upper end A is parallel to feeder line 4, and length is 13mm, width is 1.0mm, and its lower end B is parallel to feeder line 4, and length is 13mm, width is 1.0mm, and its bottom end C is vertical On the feeder 4, the length is 16.5mm, and the width is 1.0mm; the total length of the U-shaped microstrip line 33 is 42.5mm, and the distance between its upper end A and the interdigital branches 41, 42 is 0.24mm, and its upper end A and 50 The distance of the ohmic microstrip line (43) is 2.5 mm.

The convex ring 34 is composed of upper and lower three parallel lines and two pairs of upper and lower vertical lines connected to each other, wherein the length _of the upper parallel line L1 is 2.5mm and the width is 1mm _; the length of the lower parallel line L5 is 12.5mm, width 0.5mm; middle parallel line L ₃ length L ₅ -L ₁ , width 0.5mm; two upper vertical lines L ₂ length 3mm, width 0.5mm; two lower vertical lines The length of L ₄ is both 2.5 mm and the width is 0.5 mm; the two upper vertical lines L ₂ are connected to the U-shaped microstrip line 33 .

The ground hole 5 is a metallized via hole with a radius of 0.25 mm.

The second embodiment: design a five-pass band filter with a size of 29mm×22.9mm.

3 and 4, the five-band bandpass filter of the present invention is mainly composed of a microstrip dielectric substrate 1, a metal ground plate 2, a resonator 3, an input and output feeder 4, and a ground hole 5. in:

The microstrip dielectric substrate 1 adopts a double-sided copper-clad laminate with a dielectric constant of 2.2 and a thickness of 1.0 mm. The metal ground plate 2 is placed under the double-sided copper-clad laminate, and the five-mode resonator 3 is placed above the double-sided copper-clad laminate. Input and output feeders 4 and ground hole 5. in:

The input and output feeder 4 is composed of a pair of aligned interdigital coupling feeders, and each feeder includes two interdigital stubs 41, 42 and a section of 50 ohm microstrip line 43; the interdigital stubs 41, 42 are connected in parallel at 50 ohm The same end of the microstrip line 43; the length of the interdigital branches 41 and 42 is 13mm, the width is 0.76mm, and the distance between the two interdigital branches 41 and 42 is 1.48mm; the length of the 50-ohm microstrip line 43 is 7mm , a width of 3mm.

Described resonator 3, it is made up of two identical five-mode resonators that are placed alternately, each five-mode resonator is made up of short-circuit stub 31, open-circuit stub 32, U-shaped microstrip line 33, a convex ring 34 and two A L-shaped open-circuit branch 35,36 is formed; the short-circuit branch 31 is located at the symmetrical center of the U-shaped microstrip line inside the convex ring 34, and the length of the short-circuit branch 31 is 4.1 mm and the width is 0.5 mm; the open-circuit branch 32 is located at the convex ring 34 The symmetrical center of the outer U-shaped microstrip line, the length of the open branch 32 is 7mm, and the width is 1.5mm; the upper end A of the U-shaped microstrip line 33 is placed between the interdigital branches 41 and 42 in parallel, and the lower end B is placed in parallel with the feeder 4 inside; the center of symmetry of the convex ring 34 coincides with the center of symmetry of the U-shaped microstrip line 33, and the top of the convex ring 34 is connected to the bottom end C of the U-shaped microstrip line; two L-shaped open circuit branches 35, 36 are symmetrical It is connected to the bottom end C of the U-shaped microstrip line 33 .

Described U-shaped microstrip line 33, its upper end A is parallel to feeder line 4, and its length is 13mm, width is 1.0mm, and its lower end B is parallel to feeder line 4, and length is 13mm, width is 1.0mm, and its bottom end C It is perpendicular to the feeder 4 and has a length of 16.5 mm and a width of 1.0 mm; the total length of the U-shaped microstrip line 33 is 42.5 mm, and the distance between the upper end A of the U-shaped microstrip line 33 and the interdigital branches 41, 42 is 0.24 mm. mm.

The L-shaped open branch 35,36 has a length of 5.75 mm and a width of 0.4 mm parallel to the bottom part of the U-shaped microstrip line 33; it is perpendicular to the bottom part of the U-shaped microstrip line 33 and the U-shaped microstrip The distance between the center of symmetry of the line (33) is 2.5 mm, its length is 2.25 mm, and its width is 0.4 mm.

The convex ring 34 is composed of three parallel lines up and down and two pairs of vertical lines up and down. _The length of the upper parallel line L1 is 4.2mm and the width is 1mm _; The length of the middle parallel line L ₃ is L ₅ -L ₁ and the width is 0.2mm; the length of the two upper vertical lines L ₂ is 3mm and the width is 0.2mm; the length of the two lower vertical lines L ₄ is The two upper vertical lines L ₂ are connected to the U-shaped microstrip line 33 , and the width is 0.2 mm.

The ground hole 5 is a metallized via hole with a radius of 0.25 mm.

Effect of the present invention can be further illustrated by following simulation and test experiment:

Simulation 1. The first embodiment of the present invention is simulated in the three-dimensional electromagnetic simulation software HFSS, and the response curve of the obtained four-pass band filter is shown in dotted line in FIG. 5 .

Simulation 2. The second embodiment of the present invention is simulated in the three-dimensional electromagnetic simulation software HFSS, and the obtained response curve of the five-pass band filter is shown in dotted line in FIG. 6 .

Test 1. Use a vector network analyzer to test the processed four-pass band filter, and the response curve of the obtained four-pass band filter is shown as the solid line in Fig. 5 .

Test 2. The processed five-pass band filter was tested by using a vector network analyzer, and the response curve of the five-pass band filter obtained is shown in the solid line in Fig. 6 .

As can be seen from the response curve diagram of the four-pass band filter of Fig. 5, the four-pass band filter of the first embodiment forms a passband respectively at 1.57GHz, 2.5GHz, 3.5GHz, and 5.2GHz, and each passband The internal insertion loss is 1.0dB, 0.33dB, 1.33dB, 1.9dB, and the in-band return loss can reach more than 20dB, and there is a transmission zero point on both sides of each passband, so that each passband has a good selectivity.

As can be seen from the response curve diagram of the five-passband filter of Fig. 6, the five-passband filter of the second embodiment forms a passband respectively at 1.57GHz, 2.5GHz, 3.5GHz, 5.2GHz, and 5.9GHz. The insertion loss in each passband is 1.0dB, 0.4dB, 1.1dB, 1.6dB, 1.9dB, and the return loss in the band can reach more than 16dB, and there is a transmission zero point on both sides of each passband, so that each Both passbands have good selectivity.

The above examples are preferred embodiments of the present invention and do not constitute any limitation to the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Claims (9)

1. A multi-passband filter based on a multimode resonator, comprising a microstrip dielectric substrate (1), a metal ground plate (2), a resonator (3), an input and output feeder (4), and a metal ground plate There is a grounding hole (5), which is characterized in that: The input-output feeder (4) is made up of a pair of aligned interdigital coupling feeders, each feeder includes two interdigital branches (41, 42) and a section of 50 ohm microstrip line (43); the interdigital branches ( 41,42) are connected in parallel at the same end of the 50 ohm microstrip line (43); Described resonator (3), it is made up of two identical four-mode resonators that are placed alternately, and each four-mode resonator is made up of short-circuit stub (31), open-circuit stub (32), U-shaped microstrip line (33) Constituted with a convex ring (34); the short-circuit branch (31) is located at the U-shaped microstrip line symmetry center inside the convex ring (34), and the open circuit branch (32) is located at the U-shaped microstrip outside the convex ring (34) The center of line symmetry; the upper end (A) of the U-shaped microstrip line (33) is placed parallelly between the interdigital branches (41, 42), and the lower end (B) is placed parallelly inside the feeder line (4); the convex ring (34) The center of symmetry coincides with the center of symmetry of the U-shaped microstrip line (33), and the top of the convex ring (34) is connected to the bottom (C) of the U-shaped microstrip line. 2. the multi-pass band filter based on multimode resonator according to claim 1, is characterized in that, the length of interdigital branch (41,42) is 13mm, and wide is 0.76mm, two interdigital branch (41 , 42) is 1.48mm; the length of the 50 ohm microstrip line (43) is 6mm, and the width is 3mm. 3. the multi-pass band filter based on multimode resonator according to claim 1, is characterized in that, the length of short-circuit stub (31) is 4.1mm, and the width is 0.5mm; The length of open-circuit stub (32) is 7.0mm mm, the width is 1.5mm. 4. the multi-passband filter based on multimode resonator according to claim 1, is characterized in that, the upper end (A) of U-shaped microstrip line (33) is parallel to feeder line (4), and its length is 13mm, The width is 1.0mm; the lower end (B) of the U-shaped microstrip line (33) is parallel to the feeder line (4), and its length is 13mm, and its width is 1.0mm; the bottom end (C) of the U-shaped microstrip line (33) is vertical In feeder (4), its length is 16.5mm, and width is 1.0mm; The total length of U-shaped microstrip line (33) is 42.5mm; , 42) is 0.24mm away, and its distance to the 50 ohm microstrip line (43) is 2.5mm. 5. The multi-passband filter based on multimode resonators according to claim 1, wherein the convex ring (34) is composed of three parallel lines up and down and two pairs of vertical lines up and down, wherein the upper parallel line The length of L ₁ is 2.5 mm and the width is 1 mm; the length of the lower parallel line L ₅ is 12.5 mm and the width is 0.5 mm; the length of the middle parallel line L ₃ is L ₅ -L ₁ and the width is 0.5 mm; The length of the vertical line L ₂ is both 3 mm and the width is 0.5 mm; the length of the two lower vertical lines L ₄ is 2.5 mm and the width is 0.5 mm; the two upper vertical lines L ₂ and the U-shaped microstrip line (33) connected. 6. A multi-passband filter based on a multimode resonator, comprising a microstrip dielectric substrate (1), a metal ground plate (2), a resonator (3), an input and output feeder (4), and a metal ground plate There is a grounding hole (5), which is characterized in that: The input-output feeder (4) is made up of a pair of aligned interdigital coupling feeders, each feeder includes two interdigital branches (41, 42) and a section of 50 ohm microstrip line (43); the interdigital branches ( 41,42) are connected in parallel at the same end of the 50 ohm microstrip line (43); Described resonator (3), it is made up of two identical five-mode resonators that are placed alternately, and each five-mode resonator is made up of short-circuit stub (31), open-circuit stub (32), U-shaped microstrip line (33) , a convex ring (34) and two L-shaped open-circuit branches (35, 36); the short-circuit branch (31) is located at the U-shaped microstrip line symmetry center inside the convex ring (34), and the open-circuit branch (32) is located at The symmetrical center of the U-shaped microstrip line outside the convex ring (34); the upper end (A) of the U-shaped microstrip line (33) is placed in parallel between the interdigital branches (41, 42), and the lower end (B) is placed in parallel Inside the feeder (4); the center of symmetry of the convex ring (34) coincides with the center of symmetry of the U-shaped microstrip line (33), and the top of the convex ring (34) is connected to the bottom end (C) of the U-shaped microstrip line ; Two L-shaped open-circuit branches (35, 36) are symmetrically connected to the bottom end (C) of the U-shaped microstrip line (33). 7. the multi-passband filter based on multimode resonator according to claim 6, is characterized in that, the length of L-shaped open-circuit stub (35,36) parallel to U-shaped microstrip line (33) bottom part is 5.75mm, and the width is 0.4mm; the L-shaped open circuit branch (35,36) is perpendicular to the U-shaped microstrip line (33) bottom part and the U-shaped microstrip line (33) The distance from the center of symmetry is 2.5mm, and its length is 2.25mm and 0.4mm wide. 8. the multi-passband filter based on multimode resonator according to claim 6, is characterized in that, the length of short-circuit stub (31) is 4.1mm, and the width is 0.7mm; The length of open-circuit stub (32) is 4.5mm mm, the width is 1mm. 9. The multi-passband filter based on multimode resonators according to claim 6, wherein the convex ring (34) is composed of three parallel lines up and down and two pairs of vertical lines up and down, wherein the upper parallel line The length of L ₁ is 4.2 mm, and the width is 1 mm; the length of the lower parallel line L ₅ is 9.8 mm, and the width is 1 mm; the length of the middle parallel line L ₃ is L ₅ -L ₁ , and the width is 0.2 mm; The length of the line L ₂ is 3 mm, and the width is 0.2 mm; the length of the two lower vertical lines L ₄ is 3 mm, and the width is 0.2 mm; the two upper vertical lines L ₂ and the U-shaped microstrip line (33 ) connected.