CN111463525B

CN111463525B - Miniaturized third-order SD-HMSIW band-pass filter based on coplanar waveguide

Info

Publication number: CN111463525B
Application number: CN202010310347.1A
Authority: CN
Inventors: 许锋; 俞婷婷
Original assignee: Nanjing University of Posts and Telecommunications
Current assignee: Nanjing University of Posts and Telecommunications
Priority date: 2020-04-20
Filing date: 2020-04-20
Publication date: 2021-04-27
Anticipated expiration: 2040-04-20
Also published as: CN111463525A

Abstract

The invention discloses a miniaturized three-order SD-HMSIW band-pass filter based on a coplanar waveguide, which comprises a lower metal plate, a middle microwave dielectric plate and an upper metal plate, wherein the upper metal plate is a metal plate; the upper metal plate is provided with two rows of metal through holes positioned on the right-angle side of the triangle, one row of metal through holes positioned outside the hypotenuse of the isosceles right triangle, an input/output feeder line, a first metal through hole, a second metal through hole, a pair of coplanar waveguide resonators, a third metal through hole shared by the coplanar waveguide resonators, and a loaded trapezoid groove. The TE101 mode is close to the TE201 mode by introducing the first metal through hole, and meanwhile, the TE202 mode can be shifted to a higher frequency by introducing the second metal through hole, so that a wider stop band can be generated. Two quarter-wave coplanar waveguides (CPWs) are introduced to the open circuit side of the HMSIW, so that the resonance frequency of the TE201 mode can be reduced, the purpose of miniaturization of the filter is achieved, a transmission pole and a transmission zero can be generated, and the frequency selectivity of the filter is further improved.

Description

Miniaturized third-order SD-HMSIW band-pass filter based on coplanar waveguide

Technical Field

The invention relates to the technical field of microwaves, in particular to a miniaturized third-order SD-HMSIW (closed half-mode SIW) band-pass filter based on coplanar waveguides.

Background

With the rapid development of electronic information, increasingly tense spectrum resources are more deficient, and higher requirements are provided for the selectivity, integration and the like of a filter for improving communication capacity and reducing signal interference between adjacent channels. A filter is one of the key components in radar, communication and measurement systems, and its function is to allow a certain part of frequency signals to pass through smoothly. Substrate Integrated Waveguide (SIW) filters have the advantages of low cost, high quality factor, easy processing, easy integration, etc., and thus, SIW filters are widely used in wireless communication systems in the microwave and millimeter wave field today. But since the SIW filter is larger in size at low frequencies, this is less advantageous than other types of filters, such as microstrip filters. In order to reduce the size of the SIW device, we said a half-mode SIW (HMSIW) filter is applied to design a bandpass filter, and this structure does not reduce the quality factor much compared with the SIW, and the size is reduced almost by half. Therefore, a closed HMSIW (shielded half-mode SIW, SD-HMSIW) is complied with, and this structure has not only the advantage of high quality factor but also the advantage of electromagnetic shielding.

In order to meet the modern communication requirement of miniaturization, the single-cavity multi-mode technology is applied in the filter, and compared with the traditional cascade type filter of a single-cavity single mode, the single-cavity multi-mode filter has the advantages of small size and low cost. However, since it is difficult to implement a highly selective filter using a plurality of modes in a single cavity, an additional resonator is introduced into the single cavity to implement cross-coupling of the modes in the cavity and the additional resonator, thereby generating a transmission zero and improving frequency selectivity. Generally, a slot line resonator is often applied to a cavity to achieve additional resonance, but the slot line resonance has a problem of radiation, which may degrade the quality factor of the device while interfering with other devices.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to overcome the defects of large size, poor frequency selectivity and the like of the traditional SIW filter, and provides a miniaturized third-order SD-HMSIW band-pass filter based on a coplanar waveguide.

The technical scheme is as follows: in order to achieve the above purpose, the miniaturized third-order SD-HMSIW band-pass filter based on coplanar waveguide comprises a lower metal plate, a middle microwave dielectric plate, and an upper metal plate; the upper layer metal plate is provided with two rows of metal through holes positioned on right-angle sides of the triangle, one row of metal through holes positioned outside the bevel edge of the isosceles right triangle, an input/output feeder line, a first metal through hole, a second metal through hole, a pair of coplanar waveguide resonators, a third metal through hole shared by the coplanar waveguide resonators and a loaded trapezoid groove;

the two rows of metal through holes are respectively parallel to the right-angle sides of the triangle and are mutually vertical; the trapezoid-shaped groove is parallel to the hypotenuse of the isosceles right triangle, and the upper bottom of the trapezoid is surrounded by the row of metal through holes; the input/output feeder line consists of a transmission line and L-shaped grooves loaded on two sides of the transmission line; the coplanar waveguide resonator is positioned at the center of the hypotenuse of the isosceles right triangle and is parallel to the hypotenuse; the third metal through hole is positioned at the center of the pair of coplanar waveguide resonators; the second metal through hole is positioned right above the third metal through hole; the first metal through hole is positioned right above the second metal through hole.

The first metal through hole, the second metal through hole and the third metal through hole are all located on the height of the hypotenuse of the triangle.

By adjusting the aperture of the first metal via, the resonant frequency of the TE101 mode of the filter can be controlled.

By adjusting the aperture of the second metal via, the resonant frequency of the TE202 mode of the filter can be controlled.

The coplanar waveguide resonator has an electrical length of one quarter of a wavelength corresponding to a center frequency.

The bandwidth of the filter can be changed by introducing the coplanar waveguide, generating a transmission zero point at the upper edge of the passband and adjusting the length of the coplanar waveguide.

Has the advantages that: compared with the prior art, the invention has the following remarkable technical effects:

compared with the traditional SIW band-pass filter, the band-pass filter realized by using the SD-HMSIW structure has the advantages of miniaturization and electromagnetic shielding.

The SD-HMSIW third-order band-pass filter disclosed by the invention can simultaneously realize three-mode resonance in the half-mode SIW, has a very small size compared with the three-mode resonance realized by the cascaded SIW, and is particularly suitable for future millimeter wave communication systems.

Thirdly, the invention introduces a pair of coplanar waveguides in the SD-HMSIW, which not only can further reduce the frequency of the fundamental mode TE201, namely reduce the size, but also introduces a transmission zero point, thereby improving the frequency selectivity of the filter.

The SD-HMSIW third-order band-pass filter can change the bandwidth of the filter by adjusting the aperture of the first metal through hole and the length of the coplanar waveguide, so that the design of the filter is more diversified.

Drawings

FIG. 1 is a schematic three-dimensional structure of an embodiment of the present invention;

FIG. 2 is a schematic diagram of a layered structure according to an embodiment of the present invention (omitting through holes on a lower metal plate);

FIG. 3 is a top plan view of the strip parameters of the upper metal sheet in an embodiment of the present invention;

FIG. 4 is a graph illustrating the relationship between the aperture of the first metal via and the passband bandwidth according to an embodiment of the present invention;

FIG. 5 is a graphical representation of the length of a coplanar waveguide versus passband bandwidth in an embodiment of the present invention;

FIG. 6 is a simulated response diagram of an embodiment of the present invention.

Detailed Description

In order to embody the novelty and inventive step of the present invention, the physical mechanism of the SD-HMSIW filter is further analyzed below. In the analysis, the embodiments of the present invention will be described with reference to the drawings and specific examples, but the embodiments are not limited thereto. Without loss of generality, the microstrip filter of the invention realizes a band-pass frequency response, the center frequency is 4.8GHz, the relative bandwidth is 10.4%, the in-band return loss is more than 15dB, the insertion loss is lower than 1.31dB, the impedance of the input and output feeder lines is set to be 50 Ohm, and the ideal frequency response is shown in figure 6.

As shown in fig. 1 and fig. 2, a miniaturized third-order SD-HMSIW band-pass filter based on coplanar waveguide according to an embodiment of the present invention includes a lower metal plate 1, an intermediate microwave dielectric plate 2, and an upper metal plate 3; the upper metal plate 3 is provided with two rows of metal through holes 4 positioned on the right-angle side of the triangle, one row of metal through holes 12 positioned outside the hypotenuse of the isosceles right triangle, an input/output feeder (composed of a transmission line 5 and L-shaped grooves 6 on both sides), a first metal through hole 7, a second metal through hole 8, a pair of coplanar waveguide resonators 10 (sharing a third metal through hole 9), and a loaded trapezoidal groove 11. Two rows of metal through holes 4 are parallel to the right-angle sides of the triangle respectively and are perpendicular to each other, the trapezoidal groove 11 is parallel to the hypotenuse of the isosceles right triangle, and the upper bottom of the trapezoid is surrounded by one row of metal through holes 12. The coplanar waveguide resonator 10 is located at the center of the hypotenuse of the isosceles right triangle and is parallel to the hypotenuse, the third metal through hole 9 is located at the center of the coplanar waveguide resonator 10, the second metal through hole 8 is located right above the third metal through hole 9, and the first metal through hole 7 is located right above the second metal through hole 8.

In order to realize the characteristics of three-mode band-pass response and miniaturization, an SD-HMSIW structure is used, and the structure has the advantages of shielding electromagnetic waves and interfering other devices. Firstly, designing the length of a right-angle side of the SD-HMSIW according to the center frequency of a band-pass filter, so that the resonance frequency of a TE201 mode is the center frequency of the center frequency; secondly, introducing a first metal through hole 7, and adjusting the radius of the through hole to enable the TE101 mode to be close to the TE201 mode, namely close to the center frequency; then, a second metal via 8 is added, which has no great influence on the frequencies of the first two modes, but the radius of the via is adjusted to shift the first higher order mode, i.e. TE202, to a high frequency, so that the advantage of a wide stop band can be formed; finally, a pair of coplanar waveguides is added to the hypotenuse of the triangle, and they share the third metal via 9, and the electrical length of each coplanar waveguide is one quarter of the wavelength corresponding to the center frequency, so that the bandpass response of the three modes is formed.

In particular, by adjusting the radius of the first metal via 7, the lower edge of the pass band can be adjusted individually, so that the bandwidth of the three-mode band-pass filter can be adjusted, the specific variation of which is shown in fig. 4. Further, the upper edge of the passband can be scaled by adjusting the length of the coplanar waveguide to narrow the bandwidth of the passband, which is characterized as shown in fig. 5. Therefore, the three-mode band-pass filter has variable transmission response, and is more suitable for future millimeter wave communication systems.

The filter is simulated by using three-dimensional simulation software HFSS, the relative dielectric constant of the dielectric substrate used by the filter is 2.2, the height of the dielectric substrate is 1mm, and as shown in figure 3, the main structural parameters of the filter are as follows: l₁＝44mm,l₂＝3.05mm, l₃＝12.1mm,d＝0.8mm,d₁＝1.4mm,d₂＝0.9mm,s₁＝0.5mm,s₂＝0.2mm,e₁＝9.3mm,e₂＝7mm, e₃21 mm. Wherein d is₂Is the diameter of the first metal via e₁Is the length of a quarter wave coplanar waveguide (CPW). The simulation result is shown in FIG. 6, and it can be seen that the operating center frequency of the filterThe ratio and relative bandwidth are 4.8GHz and 10.4% respectively, with a return loss of better than 15dB and an insertion loss of less than 1.31dB at the operating frequency of the filter from 4.55GHz to 5.05 GHz. Due to the loading of a pair of coplanar waveguides (CPWs), the filter can generate three poles, respectively f₁，f₂，f₃And less insertion loss, and a zero point f is generated due to the introduced CPWs_zTherefore, the position of the upper stop band is steeply dropped, and the out-of-band rejection performance of the filter is effectively improved. Wherein the transmission zero point f_zAt 5.2GHz and the suppression level is 27 dB. Furthermore, the frequency range where out-of-band rejection reaches 20dB is 5.15GHz to 6.95 GHz.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, and simplifications are intended to be included in the scope of the present invention.

Claims

1. A miniaturized three-order closed HMSIW (SD-HMSIW) band-pass filter based on coplanar waveguides is characterized by comprising a lower metal plate (1), a middle microwave dielectric plate (2) and an upper metal plate (3); the upper layer metal plate (3) is provided with two rows of metal through holes (4) positioned on right-angle sides of the triangle, one row of metal through holes (12) outside the bevel edge of the isosceles right triangle, an input/output feeder line, a first metal through hole (7), a second metal through hole (8), a pair of coplanar waveguide resonators (10) and a third metal through hole (9) shared by the coplanar waveguide resonators, and a loaded trapezoidal groove (11);

the two rows of metal through holes (4) are parallel to the right-angle sides of the triangle and are vertical to each other;

the trapezoid-shaped groove (11) is parallel to the hypotenuse of the isosceles right triangle, and the upper bottom of the trapezoid is parallel to the row of metal through holes (12);

the input/output feeder line consists of a transmission line (5) and L-shaped grooves (6) loaded on two sides of the transmission line (5);

-the coplanar waveguide resonator (10) is highly symmetrical with respect to an isosceles right triangle; the groove forming the coplanar waveguide resonator (10) is connected with the trapezoidal groove (11), and the coplanar waveguide resonator (10) is parallel to the hypotenuse of the isosceles right triangle;

the third metal via (9) is located at the center of a pair of coplanar waveguide resonators (10);

the second metal through hole (8) is positioned right above the third metal through hole (9);

the first metal through hole (7) is positioned right above the second metal through hole (8).

2. -the miniaturized third-order SD-HMSIW bandpass filter based on coplanar waveguides according to claim 1, characterized in that the first (7), second (8) and third (9) metal vias are all at the height of the hypotenuse of the triangle.

3. The coplanar waveguide based miniaturized third order SD-HMSIW band-pass filter according to claim 1, characterized in that the resonance frequency of the TE101 mode of the filter is controlled by adjusting the aperture of the first metal via (7).

4. The coplanar waveguide based miniaturized third order SD-HMSIW bandpass filter according to claim 1, wherein the resonance frequency of the TE202 mode of the filter is controlled by adjusting the aperture of the second metal via (8).

5. -the miniaturized third-order SD-HMSIW band-pass filter based on coplanar waveguides as claimed in claim 1, characterized in that the electrical length of the coplanar waveguide resonators (10) is a quarter of the wavelength corresponding to the central frequency.

6. The coplanar waveguide based miniaturized third order SD-HMSIW bandpass filter according to claim 1, wherein the bandwidth of the filter can be changed by introducing the coplanar waveguide, creating a transmission zero at the upper edge of the passband, adjusting the length of the coplanar waveguide.