CN112952313A - Microwave frequency-selecting device based on waveguide - Google Patents
Microwave frequency-selecting device based on waveguide Download PDFInfo
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- CN112952313A CN112952313A CN202110107314.1A CN202110107314A CN112952313A CN 112952313 A CN112952313 A CN 112952313A CN 202110107314 A CN202110107314 A CN 202110107314A CN 112952313 A CN112952313 A CN 112952313A
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- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
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Abstract
The invention discloses a microwave frequency selecting device based on a band gap closed loop, which comprises a closed loop band gap structure, an input waveguide and an output waveguide, wherein the closed loop band gap structure is a closed loop columnar structure formed by enclosing an inner loop metal sheet, an outer loop metal sheet, an upper metal sheet and a lower metal sheet end to end, the ratio of the inner loop cross-sectional area to the outer loop cross-sectional area of the closed loop band gap structure is more than 90%, the side edge of the closed loop band gap structure is respectively provided with an input port and an output port, the input port is connected with the port of the input waveguide, and the output port is connected with the port of the output waveguide.
Description
Technical Field
The invention belongs to the field of microwaves, and particularly relates to a microwave frequency-selecting device based on a band-gap closed loop.
Background
The research and development of microwave frequency-selecting devices is an important direction in the field of microwave engineering. The microwave frequency-selecting device has wide application in various microwave radio frequency devices. The existing microwave frequency-selecting device is mainly realized by two technical approaches, namely, by multistage series connection of frequency-selecting circuits of LC elements or by frequency selection of microstrip filtering.
However, for the implementation mode of multistage series connection of frequency selection circuits of LC elements, the higher the requirement on filtering accuracy, the more LC frequency selection circuits need to be connected in series, which results in that the cost of such high-accuracy filter device is high, the structure is complex, the LC elements are easy to be damaged, the borne power is small, and the high-accuracy filter device is not suitable for high-power microwave radio frequency equipment, and the frequency of the used frequency is low, and is not suitable for high-frequency filtering. Furthermore, microstrip filtering frequency selection is adopted, so that the mode has the advantages of slow frequency response, large transmission loss, smoother filtering frequency selection curve, poor frequency selection sensitivity and smaller borne power. Meanwhile, the medium is filled in the waveguide metal box, the impedance matching of the whole structure with the transmission line is realized only at the cut-off frequency point of the waveguide box, the electromagnetic wave at the cut-off frequency point of the waveguide box smoothly passes through, and the electromagnetic wave at other frequency points is stopped, so that the frequency selection characteristic is realized.
Disclosure of Invention
Aiming at the defects or the improvement requirements of the prior art, the invention provides a microwave frequency selection device based on a band gap closed loop, aiming at solving the technical problem that the microwave frequency selection device can be flexibly adjusted while realizing high-frequency filtering.
In order to achieve the above object, according to one aspect of the present invention, there is provided a microwave frequency selecting device based on a band-gap closed loop, the microwave frequency selecting device includes a closed-loop band-gap structure, an input waveguide, and an output waveguide, the closed-loop band-gap structure is a closed-loop columnar structure surrounded by an inner-loop metal sheet, an outer-loop metal sheet, an upper metal sheet, and a lower metal sheet in an end-to-end manner, a ratio of an inner-loop cross-sectional area to an outer-loop cross-sectional area of the closed-loop band-gap structure is greater than 90%, side edges of the closed-loop band-gap structure are respectively provided with an input port and an output port, the input.
As a further improvement of the invention, the cut-off frequency of the microwave frequency-selecting device is adjusted by changing the height of the closed-loop band gap structure.
As a further improvement of the invention, the input impedance Z of the microwave frequency-selective device1The method specifically comprises the following steps:
Z1＝Z0ao/a1-jωμ0(1-S1/S)S/a1
wherein Z is0Characteristic impedance of the input waveguide (to achieve impedance matching, the characteristic impedance of the input waveguide is the same as the characteristic impedance of the output waveguide), aoIs the width of the input port, a1Is the width of the output port, S1Is the cross-sectional area of the inner ring of the closed-loop band gap structure, S is the cross-sectional area of the outer ring of the closed-loop band gap structure, omega is the frequency of the microwave passing through the microwave frequency-selecting device, mu0The closed loop with closed loop band gap structure has filled medium magnetic permeability.
As a further improvement of the invention, the equivalent permeability mu of the microwave frequency-selecting deviceeffThe method specifically comprises the following steps:
wherein S is1Is the cross-sectional area of the inner ring of the closed-loop bandgap structure, and S is the cross-sectional area of the outer ring of the closed-loop bandgap structure.
As a further improvement of the invention, the closed-loop internal filling medium of the closed-loop band gap structure is air.
As a further improvement of the invention, the cut-off frequency of the microwave frequency-selecting device is adjusted by changing the closed-loop internal filling medium of the closed-loop band gap structure.
The cross sections of the inner ring and the outer ring of the closed-loop band gap structure can be in any shape, and preferably, the cross sections of the inner ring and the outer ring of the closed-loop band gap structure are rectangular, triangular or circular.
As a further improvement of the invention, the cross sections of the inner ring and the outer ring of the closed ring-shaped band gap structure are both square, the side length of the cross section of the inner ring is 168mm, the side length of the cross section of the outer ring is 172.72mm, the height of the closed ring-shaped band gap structure is 63.13mm, and the closed ring internal filling medium of the closed ring-shaped band gap structure is polytetrafluoroethylene.
As a further improvement of the invention, the cut-off frequency of the microwave frequency-selecting device is 2.376 GHz.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
according to the microwave frequency-selecting device based on the band-gap closed loop, the closed-loop band-gap structure formed by nesting the double-layer metal frames is adopted, and the height of the closed-loop band-gap structure and the ratio of the cross-sectional area of the inner ring to the cross-sectional area of the outer ring of the closed-loop band-gap structure are set, so that the whole structure can only allow electromagnetic waves intercepted to a frequency point by the waveguide box to pass through, the passing ratio of the electromagnetic waves is guaranteed, and the electromagnetic waves with other frequencies are prevented, so that the function of filtering and frequency selecting is realized.
According to the microwave frequency selection device based on the band gap closed loop, the cut-off frequency of the microwave frequency selection device is adjusted by changing the height of the closed loop band gap structure, and the cut-off frequency of the microwave frequency selection device can also be adjusted by changing the filling medium in the closed loop of the closed loop band gap structure.
According to the microwave frequency selecting device based on the band gap closed loop, the inner ring cross section and the outer ring cross section of the closed-loop band gap structure are both set to be square, the side length of the inner ring cross section and the side length of the outer ring cross section are set, and the closed-loop inner filling medium of the closed-loop band gap structure is set, so that the cutoff frequency of the microwave frequency selecting device is 2.376GHz, and meanwhile the electromagnetic wave transmittance of the whole structure is guaranteed.
According to the microwave frequency selection device based on the band gap closed loop, the band gap of air is often filled with other non-conductive media (such as liquid and other types of gas, namely the dielectric constant of substances in the band gap is changed), so that the frequency selection point (namely cut-off frequency) of the structure can be effectively adjusted, and the flexible adjustment of the frequency selection point is realized.
Drawings
Fig. 1 is a schematic structural diagram of a microwave frequency selecting device based on a bandgap closed loop according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other. The present invention will be described in further detail with reference to specific embodiments.
A microwave frequency-selecting device based on a band-gap closed loop comprises a closed-loop band-gap structure, an input waveguide and an output waveguide, wherein the closed-loop band-gap structure is a closed-loop columnar structure formed by enclosing an inner-loop metal sheet, an outer-loop metal sheet, an upper metal sheet and a lower metal sheet in an end-to-end mode, the ratio of the inner-loop cross-sectional area to the outer-loop cross-sectional area of the closed-loop band-gap structure is larger than 90%, an input port and an output port are arranged on the side edge of the closed-loop band-gap structure respectively, the input port is connected with the port of the input waveguide. By the above method, ideal conductor (PEC) can be filled in the dielectric constant near-zero (ENZ) medium, and the volume ratio of the PEC in the ENZ medium is more than 90%, so that the structure of the ENZ medium containing the PEC can be equivalent to a double near-zero (EMNZ) medium with excellent magnetic permeability and dielectric constant, thereby ensuring smooth and lossless passing of electromagnetic wave.
As a preferred example, the cutoff frequency of the microwave frequency selective device is adjusted by changing the height of the closed-loop bandgap structure.
As a preferred example, assume an ENZ medium with arbitrary cross-section and cross-sectional area S and magnetic permeability of μr0(Here μr0Any real number) is vertically incident on the ENZ medium from left to right, the magnetic field H direction of the electromagnetic wave is along the y axis, and at the moment, due to wave impedance mismatch, the electromagnetic wave is greatly reflected on the incident surface of the ENZ medium and cannot effectively penetrate through the ENZ medium. Subsequently doping the ENZ medium with a cross-sectional area S1The PEC material of (a). Therefore, the input impedance Z of the microwave frequency-selecting device can be deduced1The method specifically comprises the following steps:
Z1＝Z0ao/a1-jωμ0(1-S1/S)S/a1
wherein Z is0Characteristic impedance of the input waveguide (to achieve impedance matching, the characteristic impedance of the input waveguide is the same as the characteristic impedance of the output waveguide), aoIs the width of the input port, a1Is the width of the output port, S1Is the cross-sectional area of the inner ring of the closed-loop band gap structure, S is the cross-sectional area of the outer ring of the closed-loop band gap structure, omega is the frequency of the microwave passing through the microwave frequency-selecting device, mu0The closed loop with closed loop band gap structure has filled medium magnetic permeability.
As a preferred example, the equivalent permeability μ of the microwave frequency-selective deviceeffThe method specifically comprises the following steps:
wherein S is1Is the cross-sectional area of the inner ring of the closed-loop bandgap structure, and S is the cross-sectional area of the outer ring of the closed-loop bandgap structure. Due to the equivalent permeability mu of the frequency-selecting deviceeffFrom S1The ratio of/S is determined, and S1The larger the ratio of/S, the larger the value of μeffThe closer to zero, the better the electromagnetic wave transmittance of the entire structure.
The factors for determining the electromagnetic transmission capability of the microwave frequency-selecting device can be obtained through the input impedance and the equivalent magnetic permeability of the frequency-selecting device, and the factors lie in the ratio of the cross-sectional areas of the inner ring and the outer ring, so that the ratio is irrelevant to the shape of the ring, the cross-sectional shape of the closed air band gap ring is changed, the height of the ring (used for determining the frequency-selecting point) and the ratio of the cross-sectional areas of the inner ring and the outer ring are still kept unchanged, the frequency-selecting point and the electromagnetic transmission capability of the ring are not changed, and preferably, the cross-sections of the inner ring and the outer ring of. Therefore, the closed air band gap ring structure is light and handy, and the sensitivity is high, and after the height is determined according to the frequency selection point, as long as the sectional area ratio inside and outside the closed ring is ensured to be more than 90%, the sectional shape can be arbitrary, and the closed air band gap ring structure has good use flexibility and practicability in a microwave circuit.
Preferably, the closed-loop internal filling medium of the closed-loop bandgap structure is air. The internal filling medium is air, for example, the air band gap may be filled with other non-conductive media (such as liquid and other types of gas, i.e., the dielectric constant of the substance in the band gap is changed), so that the frequency selection point (i.e., the cut-off frequency) of the structure may be effectively adjusted, and the flexible adjustment of the frequency selection point is realized.
Fig. 1 is a schematic structural diagram of a microwave frequency selecting device based on a bandgap closed loop according to an embodiment of the present invention. As shown in fig. 1, the microwave frequency-selective device is composed of two identical rectangular waveguides and a square metal rectangular waveguide box. The rectangular waveguide is 42.09mm wide and 63.13mm high (x direction), and filled with polytetrafluoroethylene material (epsilon r1 is 2) (the purpose of filling polytetrafluoroethylene in the rectangular waveguide of the incident and exit ports is to obtain a lower cut-off frequency of the square metal rectangular waveguide box, so that electromagnetic waves of 2.376GHz can be normally transmitted); the square rectangular waveguide box structure plays a role in frequency selection, the side length of the metal box is 172.72mm, and the height (x direction) of the metal box is 63.13 mm; the boundaries of the entire structure are metal. In the TE10 wave mode, the cut-off frequency of the metal cavity is 2.376GHz (λ 0 is 126.26mm, 2 times higher than the metal box), and at the cut-off frequency point, the space in the metal cavity can be equivalent to an ENZ medium, and at this time, electromagnetic waves with a frequency higher than 2.376GHz can pass through the metal cavity smoothly. Then, a square metal block is placed in the metal cavity, the side length of the metal block is 168mm, the height (x direction) of the metal block is 63.13mm, and the sectional area (yoz surface) of the metal block is 94.6% of that of the metal box, so that a narrow closed-loop air band gap is formed between the metal box and the filled metal block, the structure is equivalent to a good EMNZ medium at the frequency point of 2.376GHz, and the electromagnetic wave of 2.376GHz can completely pass through the structure through the simulation result. Further, the transmission coefficient of the structure in the frequency band of 2.32-2.42GHz is 0dB (namely, full transmission) by adopting the numerical calculation result of the transmission coefficient of the full-wave simulation calculation software COMSOL, and the transmission peak is very sharp, namely, once the transmission coefficient deviates from the frequency point, the transmission coefficient of the structure is rapidly reduced, and a good frequency selection effect is achieved.
Because the height of the outer frame is 63.13mm (in the x direction) (half of the wavelength of the frequency selection point for determining the frequency selection point), the inner frame and the outer frame are equal in height and also have a square section, and the sectional area (hollow area) is S1(168mm is multiplied by 168mm), the sectional area of the outer frame is S172.72mm is multiplied by 172.72mm), the inner frame and the outer frame are placed in the middle (namely the central points of the two frames are superposed), an air band gap with uniform width is formed between the inner frame and the outer frame, the upper surface and the lower surface (the lower surface is positioned on a YOZ surface, the upper surface is parallel to the YOZ surface, and the height is 63.132mm) of the band gap are sealed by adopting a metal cover plate, and at1S) still 94.6%. The structure is provided with a rectangular input port and a rectangular output port, the bottom edges of which are designated as aoAnd a1Respectively connected to the input waveguide and the output waveguide. Assuming that the characteristic impedances of the input and output waveguides are both Z0The input impedance of the input end of the structure is Z1。
According to the microwave transmission theory, if the electromagnetic wave is to pass through the structure smoothly, the input impedance of the structure should match the characteristic impedance of the waveguide, Z1＝Z0. It is found by derivation that the input resistance Z of the structure at this time1The equation for the calculation of the resistance is:
Z1＝Z0ao/a1-jωμ0(1-S1/S)S/a1
wherein Z is0Characteristic impedance of microwave frequency-selective device, aoIs the width of the input port, a1Is the width of the output port, S1Is the cross-sectional area of the inner ring of the closed-loop band gap structure, S is the cross-sectional area of the outer ring of the closed-loop band gap structure, omega is the frequency of the microwave passing through the microwave frequency-selecting device, mu0The closed loop with closed loop band gap structure has filled medium magnetic permeability.
By S in the example of FIG. 11The imaginary part in the input impedance calculation formula is about zero, theoretically Z1 is approximately equal to Z0, theoretically matching conditions are met, and according to theoretical derivation, the electromagnetic transmission capacity of the structure is determined by the sectional area ratio of the inner ring and the outer ring and is independent of the shape of the rings, so that the sectional shape of the closed air band gap ring is changed, and the height of the ring (used for determining the frequency selection point) and the sectional area ratio of the inner ring and the outer ring are kept unchanged.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. The microwave frequency-selecting device is characterized by comprising a closed-loop band gap structure, an input waveguide and an output waveguide, wherein the closed-loop band gap structure is a closed-loop columnar structure formed by an inner-loop metal sheet, an outer-loop metal sheet, an upper metal sheet and a lower metal sheet which are connected end to end in a surrounding mode, the ratio of the inner-loop cross-sectional area to the outer-loop cross-sectional area of the closed-loop band gap structure is larger than 90%, an input port and an output port are arranged on the side edge of the closed-loop band gap structure respectively, the input port is connected with a port of the input waveguide, and the output port is connected with a port of the output waveguide.
2. A bandgap closed-loop based microwave frequency selective device as claimed in claim 1, wherein the cut-off frequency of the microwave frequency selective device is adjusted by changing the height of the closed-loop bandgap structure.
3. A microwave frequency-selective device based on band-gap closed loop according to claim 1, characterized in that, the input impedance Z of the microwave frequency-selective device1The method specifically comprises the following steps:
Z1＝Z0ao/a1-jωμ0(1-S1/S)S/a1
wherein Z is0Is the characteristic impedance of the input waveguide, aoIs the width of the input port, a1Is the width of the output port, S1Is the cross-sectional area of the inner ring of the closed-loop band gap structure, S is the cross-sectional area of the outer ring of the closed-loop band gap structure, omega is the frequency of the microwave passing through the microwave frequency-selecting device, mu0The closed loop with closed loop band gap structure has filled medium magnetic permeability.
4. The microwave frequency-selective device based on band-gap closed loop as claimed in claim 1, wherein the equivalent permeability of the microwave frequency-selective deviceμeffThe method specifically comprises the following steps:
wherein S is1Is the cross-sectional area of the inner ring of the closed-loop bandgap structure, and S is the cross-sectional area of the outer ring of the closed-loop bandgap structure.
5. A microwave frequency-selective device based on band-gap closed loop according to claim 1, characterized in that the closed loop internal filling medium of the closed loop band-gap structure is air.
6. A microwave frequency-selective device based on band-gap closed loop according to claim 1, characterized in that the cut-off frequency of the microwave frequency-selective device is adjusted by changing the closed-loop internal filling medium of the closed-loop band-gap structure.
7. The microwave frequency-selecting device based on band-gap closed loop of claim 1, wherein the cross-sections of the inner ring and the outer ring of the closed-loop band-gap structure are rectangular, triangular or circular.
8. The microwave frequency-selecting device based on the closed loop with the band gap as claimed in claim 1, wherein the cross section of the inner ring and the cross section of the outer ring of the closed loop band gap structure are both square, wherein the dimension of the side of the cross section of the inner ring is 168mm, the dimension of the side of the cross section of the outer ring is 172.72mm, the height of the closed loop band gap structure is 63.13mm, and the filling medium inside the closed loop of the closed loop band gap structure is polytetrafluoroethylene.
9. The microwave frequency-selective device based on the band-gap closed loop of claim 8, wherein the cutoff frequency of the microwave frequency-selective device is 2.376 GHz.
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Citations (4)
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| RS20130133A1 (en) * | 2013-04-05 | 2014-10-31 | Institut Za Fiziku Beograd | Tuning of the tunneling frequency in foam epsilon-near-zero waveguide with narrowed channel |
| CN111029696A (en) * | 2019-11-20 | 2020-04-17 | 西安电子科技大学 | Second-order filter based on miniaturized stacking of slow-wave substrate integrated groove gap waveguide |
| CN111540990A (en) * | 2020-05-18 | 2020-08-14 | 中国人民解放军海军工程大学 | Microwave frequency-selecting device based on waveguide |
| US10833380B2 (en) * | 2015-05-08 | 2020-11-10 | Elwha Llc | Holographic mode conversion for transmission lines |
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- 2021-01-27 CN CN202110107314.1A patent/CN112952313B/en active Active
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RS20130133A1 (en) * | 2013-04-05 | 2014-10-31 | Institut Za Fiziku Beograd | Tuning of the tunneling frequency in foam epsilon-near-zero waveguide with narrowed channel |
| US10833380B2 (en) * | 2015-05-08 | 2020-11-10 | Elwha Llc | Holographic mode conversion for transmission lines |
| CN111029696A (en) * | 2019-11-20 | 2020-04-17 | 西安电子科技大学 | Second-order filter based on miniaturized stacking of slow-wave substrate integrated groove gap waveguide |
| CN111540990A (en) * | 2020-05-18 | 2020-08-14 | 中国人民解放军海军工程大学 | Microwave frequency-selecting device based on waveguide |
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| N. VOJNOVIC ET AL.: "Tunable Second-Order Bandpass Filter Based on Dual ENZ Waveguide", 《9TH INTERNATIONAL CONGRESS ON ADVANCED ELECTROMAGNETIC MATERIALS IN MICROWAVES AND OPTICS-METAMATERIALS 2015》 * |
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