CN107968240B - Adjustable plasma photonic crystal frequency-selecting filter - Google Patents
Adjustable plasma photonic crystal frequency-selecting filter Download PDFInfo
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- CN107968240B CN107968240B CN201711472734.XA CN201711472734A CN107968240B CN 107968240 B CN107968240 B CN 107968240B CN 201711472734 A CN201711472734 A CN 201711472734A CN 107968240 B CN107968240 B CN 107968240B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/2005—Electromagnetic photonic bandgaps [EPB], or photonic bandgaps [PBG]
Abstract
The invention relates to an adjustable plasma photonic crystal frequency-selecting filter, which comprises a support box and a plasma generating device arranged in the support box, wherein the top surface and the bottom surface of the support box are respectively provided with a first interface and a second interface, the interior of the first interface and the interior of the second interface are both connected with the plasma generating device, one of the exterior of the first interface and the exterior of the second interface is connected with a driving power supply, the other one of the exterior of the first interface and the exterior of the second interface is connected with the ground, the left side surface of the support box is provided with a rectangular waveguide, the right side surface of the support box is provided with a photoelectric signal conversion device, and the photoelectric signal conversion device comprises a photoelectric detector and a signal output interface connected with the photoelectric detector. The filter made of the plasma photonic crystal has good filtering effect, good transmitted frequency component unicity and high matching degree of actual effect and design in a forbidden band range; the manufacturing cost is low; by adjusting the plasma, adjustable narrow-band frequency selection is realized.
Description
Technical Field
The invention relates to the technical field of microwave communication, in particular to an adjustable plasma photonic crystal frequency-selective filter.
Background
Microwave Communication (Microwave Communication) is Communication using microwaves, which are electromagnetic waves having a wavelength of 1mm to 1 m. Microwave communication can be used for the transmission of various telecommunication services due to its wide frequency band and large capacity. Such as telephone, telegraph, data, fax, and color television, may be transmitted via microwave circuits. In microwave communication systems, the filter is a wavelength selective device, simply a device that separates useful and unwanted signals, and has an important role in multiplexing equipment. With the increasing development of microwave communication, frequency resources are more and more strained, and the development of a wavelength division multiplexing system can fully utilize bandwidth and expand transmission capacity. In a wavelength division multiplexing system, a narrow band frequency selective filter directly affects the quality of the entire communication. In high quality communications, low loss and high quality waveform response filters are necessary.
Development of narrow-band filters: traditional narrow-band filters are often made on the basis of basic LC and RC low-pass filters, and the most applied microwave filters at present are circuit filters and waveguide filters:
1. the earliest filters were LC filters invented in 1917 by scientists in the united states and germany, belonging to circuit filters. The simplest LC filter is formed by connecting an inductance device L and a capacitance device C in series or in parallel, the basic principle is that the characteristics of low frequency passing and high frequency resisting of the inductance device and the characteristics of high frequency passing and low frequency resisting of the capacitance device are utilized, and the combined impedance of the inductance device, the capacitance device and the capacitance device is utilized in series and in parallel to enable the combined impedance of the inductance device and the capacitance device to be maximum or minimum to certain specific frequencies, so that the frequency selection effect is achieved. By reasonable design, the LC filter can show good and stable filtering performance, including a larger frequency band and low insertion loss, and is generally used in a higher frequency (2-4 GHz) circuit. In practical application, however, the small inductor is not easy to manufacture, and the influence of distribution parameters is difficult to estimate, so that the manufacturing cost is high generally, and the wide application of the small inductor is limited;
2. RC filters, which appeared in the 70's of the 20 th century, also belong to circuit filters. The simplest RC filter is formed by connecting a capacitor device C in parallel across a load L. The characteristic of 'high frequency pass and low frequency stop' of a capacitor device is utilized, and the capacitor device is limited by frequency, so that the capacitor device is generally used in a low-frequency circuit and is often combined with an operational amplifier to form an active filter. But because of the existence of the resistor R, the resistor R can not be used in a large-current circuit, the loss is also caused by the existence of the resistor R, and the filtering effect is not ideal due to the existence of the absolute value tolerance of the element;
3. a microstrip filter, whose equivalent circuit is similar to an LC filter, is distinguished from the use of elements. In the microstrip filter, each capacitor C is replaced by an open-circuit parallel stub having a characteristic impedance of 1/C, and each inductor L is replaced by a short-circuit series stub having a characteristic impedance of L. The equivalent circuit and the conductive material are printed on a circuit board to manufacture the planar circuit filter. The microstrip filter is characterized by large filtering range, generally measured in GHz, but has the greatest defect that the higher harmonics of the working frequency of the microstrip filter often have obvious false response, and in addition, some unnecessary couplings often exist in the microstrip filter, and the couplings which are not considered in the design often influence the actual frequency response of a circuit;
4. a waveguide filter belongs to an optical filter. The waveguide filter is composed of a discontinuous structure and a transmission line section, wherein the discontinuous structure provides equivalent impedance, and the transmission line section is equivalent to a resonant cavity. Often applied as a band pass filter in the 0.5-10GHz band. Has low insertion loss, good standing wave characteristic of the pass band and high out-of-band attenuation. The disadvantage is that it is not modulatable;
5. a photonic band gap filter is a novel filter based on photonic crystals, particularly a microwave band, and belongs to a starting stage. The photonic crystal is an artificial periodically arranged medium and is characterized by having a photon forbidden band, namely, electromagnetic waves in a certain frequency cannot be transmitted in the photonic crystal. Photonic crystals have their unique advantages as filters: first, the loss is low, and in general, the dielectric loss constituting the photonic crystal structure is small. Second, the "forbidden band" is its own property, and filtering can be achieved without other circuit elements, similar to a waveguide. In addition, due to the existence of forbidden bands, when the periodicity of the photonic crystal is enough, signals at the band stop edge of the photonic crystal are quickly attenuated, so that the photonic crystal can effectively resist electromagnetic interference and has an ideal filtering effect. When point defects are introduced into the photonic crystal, the photonic crystal is used as a narrow-band-pass filter with a resonant cavity, and electromagnetic waves with specific frequency and wavelength can be directly selected from complicated electromagnetic waves. Through reasonable design, the frequency-selective filter can have wide forbidden band width and good frequency-selective characteristic, and the working frequency range can be greatly extended. However, the biggest disadvantage of the conventional photonic crystal filter is that it cannot be tuned, and once designed, its operating frequency cannot be changed unless it is recombined. Some mechanical methods, such as adding a perturbation medium into the resonant cavity, changing the size of the dielectric column, etc., are not practical, and some methods, such as changing the refractive index of the material by temperature or introducing a magnetic material to control the forbidden band of the photonic crystal, are limited by the surrounding environment.
The traditional circuit filter belongs to a digital filter, and when filtering, an electromagnetic wave signal received by an antenna needs to be converted into an electric signal through digital-to-analog conversion, so that the resolution of the digital-to-analog conversion often needs to be very high. Secondly, when processing information in the electric signal domain, the circuit filter often has the defects of large loss, large filtering effect and design access, high manufacturing cost and the like. In comparison, the optical filter directly processes the optical signal, the filtering effect is often ideal, and especially the photonic crystal filter with "forbidden band" has good filtering characteristics, including low loss, electromagnetic interference resistance, wide working frequency range, etc., but the traditional photonic crystal filter often has the defect of non-modulation.
Disclosure of Invention
The invention overcomes the defects of the prior art and provides an adjustable plasma photonic crystal frequency-selecting filter.
In order to achieve the purpose, the invention adopts the technical scheme that: the utility model provides an adjustable plasma photonic crystal frequency-selecting filter, includes the supporting box, locates support the plasma generating device of incasement, the top surface and the bottom surface of supporting box are provided with first interface and second interface respectively, the inside of first interface and the inside of second interface all with plasma generating device is connected, one of them is connected with drive power supply in the outside of first interface and the outside of second interface, and another is connected with ground, the left surface of supporting box is provided with rectangular waveguide, the right flank of supporting box is provided with photoelectric signal conversion device, photoelectric signal conversion device include photoelectric detector, with the signal output interface that photoelectric detector is connected.
In a preferred embodiment of the present invention, the tunable plasmonic crystal frequency selective filter further comprises a width of the rectangular waveguide is 17mm to 30mm, and a width of the rectangular waveguide is 5mm to 15 mm.
In a preferred embodiment of the present invention, the tunable plasmonic crystal frequency selective filter further comprises the support box in a rectangular parallelepiped structure.
In a preferred embodiment of the present invention, the tunable plasmonic crystal frequency selective filter further comprises the size of the support box is (180) 220mm x (90-110) mm x (40-60 mm).
In a preferred embodiment of the present invention, the tunable plasmonic crystal frequency selective filter further comprises that the supporting box is made of an aluminum alloy material.
In a preferred embodiment of the present invention, the tunable plasmonic crystal frequency selective filter further includes a support plate disposed on both the inner top surface and the inner bottom surface of the support box, and the support plate has an array of holes disposed thereon.
In a preferred embodiment of the present invention, the tunable plasmonic crystal frequency selective filter further comprises a thickness of the supporting plate is 2-4 mm.
In a preferred embodiment of the present invention, the tunable frequency selective filter further comprises a support plate made of acrylic or teflon.
In a preferred embodiment of the present invention, the tunable plasma photonic crystal frequency selective filter further comprises a high frequency high voltage ac power supply as the driving power supply.
The invention solves the defects in the background technology, and has the following beneficial effects:
(1) the filter made of the plasma photonic crystal has good filtering effect, good transmitted frequency component singleness and high matching degree between the actual effect and the design within the range of forbidden band;
(2) the manufacturing cost is low, and the whole filter only needs an adjustable power supply with low price to supply power to the filter;
(3) by adjusting the plasma, adjustable narrow-band frequency selection is realized.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a schematic structural diagram of a preferred embodiment of the present invention;
FIG. 2 is a top view of a preferred embodiment of the present invention;
FIG. 3 is a forbidden band diagram generated by a complete photonic crystal without introduction of a plasma;
FIG. 4 is a graph of the transmittance of the filter without the introduction of plasma;
FIG. 5 is a graph of the real and imaginary components of the dielectric constant of a plasma as a function of plasma density for a constant wavelength of an electromagnetic wave;
FIG. 6 is a graph of the change in filter frequency selection for different plasma densities;
fig. 7 is a graph of the actual frequency response of the filter of the preferred embodiment of the present invention.
Detailed Description
The invention will now be described in further detail with reference to the accompanying drawings and examples, which are simplified schematic drawings and illustrate only the basic structure of the invention in a schematic manner, and thus show only the constituents relevant to the invention.
As shown in fig. 1, an adjustable plasma photonic crystal frequency-selective filter includes a support box 10 and a plasma generating device disposed in the support box 10, a first interface 12 and a second interface 14 are respectively disposed on a top surface and a bottom surface of the support box 10, an interior of the first interface 12 and an interior of the second interface 14 are both connected to the plasma generating device, one of an exterior of the first interface 12 and an exterior of the second interface 14 is connected to a driving power supply (not shown), the other is connected to ground, a rectangular waveguide 18 is disposed on a left side surface of the support box 10, a photoelectric signal conversion device 20 is disposed on a right side surface of the support box 10, and the photoelectric signal conversion device 20 includes a photodetector 22 and a signal output interface 24 connected to the photodetector 22.
In the invention, the length A of the wide side of the rectangular waveguide 18 is preferably 17-30mm, the length B of the narrow side of the rectangular waveguide 18 is preferably 5-15mm, and the rectangular waveguide is made of aluminum alloy and is used for guiding the transmission of TM electromagnetic waves.
The preferred support box 10 of the present invention is a rectangular parallelepiped structure. The size of the support box 10 is (180-. The support box 10 is made of an aluminum alloy material and is used for shielding electromagnetic waves and structurally supporting the filter. The support box 10 is provided with support plates 26 on both the inner top and bottom surfaces, and the support plates 26 are provided with an array of holes (not shown). It is further preferred that the thickness of the support plate 26 is 2-4 mm. The support plate 26 is preferably made of acrylic material, but is not limited to acrylic material, and may also be made of teflon.
The invention preferably adopts a high-frequency high-voltage alternating current power supply as the driving power supply, and further preferably adopts a high-frequency high-voltage alternating current power supply with the working frequency of 20kHz and the adjustable voltage amplitude of 0-30 kV.
As shown in fig. 2, the plasma generating device includes a photonic crystal and a plasma discharge tube, and the photodetector 22 is used for detecting the electromagnetic wave signal filtered by the photonic crystal and converting the electromagnetic wave signal into an electrical signal, and outputting the electrical signal to the photoelectric amplifying circuit through the signal output interface 24. The photonic crystal is formed by arranging alumina ceramic rods 28 (dielectric constant is 9.4) with the diameter of 6mm in an XY plane according to a regular hexagonal lattice, wherein the arrangement period a =12mm, and the arrangement period a refers to the distance between the centers of circles of the adjacent alumina ceramic rods 28. The TM wave (electric field polarized axially along the alumina ceramic rod 28) enters the photonic crystal through the rectangular waveguide 18 and the electromagnetic wave in the 6.5GHz to 10GHz range is completely blocked by the photonic crystal. An alumina ceramic rod 28 is removed from the center of the photonic crystal, and the plasma discharge tube is placed at the center to form a point defect, thereby forming a resonant cavity. The plasma discharge vessel comprises a discharge vessel 30 and two electrodes (not shown in the figure) enclosed within the discharge vessel 30, one of which is connected to the interior of the first interface 12 and the other of which is connected to the interior of the second interface 14. In this embodiment, the outside of the first port 12 is connected to a driving power source, the outside of the second port 14 is connected to ground, and preferably, the discharge tube 30 is a quartz tube (having a dielectric constant of 3.8), and the discharge tube 30 has a thickness of 1mm and an inner diameter of 14 mm. It is further preferred that the discharge vessel 30 is a commercial low pressure mercury lamp, model number clapet ZW15S15Y-Z380, with a small amount of mercury and shielding gas being charged into the discharge vessel 30. The array of holes provided in the support plate 26 cooperate with the array of holes formed by the plurality of alumina ceramic rods 28 and the discharge tubes 30 to facilitate the confinement of the plurality of alumina ceramic rods 28 and the discharge tubes 30.
Fig. 3 shows the forbidden band generated by the complete photonic crystal without introducing plasma, which is simulated by the COMSOL software. Fig. 4 is a transmission spectrum of the filter without plasma introduction, simulated using COMSOL software. In the simulations of fig. 3 and 4, perfect magnetic conductor boundaries were applied in the X-axis direction, i.e. infinite period of the alumina ceramic rods in the X-axis direction, and 7 lines of alumina ceramic rods in the Y-axis direction, for simplicity of calculation.
As can be seen from fig. 3, the photonic crystal has a forbidden band width of about 6.5GHz to 10GHz, a transmittance of less than 0.05, a band-pass edge which is extremely steep, and a signal decays very fast. As can be seen from fig. 4, when a point defect is introduced, there is an extremely narrow transmission peak around 8.873GHz, the transmittance is equal to 1, the Q value is calculated to be about 3000, and if no other means is used, the filter can only obtain a signal with one frequency in the forbidden band range, and cannot be tuned.
The driving power is turned on and plasma 32 is generated in the discharge tube 30. When a plasma is introduced into the cavity, due to the dispersive nature of the plasma, the refractive index of the medium in the cavity will decrease slightly after the plasma density is changed, and cause the transmission peak to shift to high frequencies. FIG. 5 is a graph showing the relationship between the real part and imaginary part of the dielectric constant of plasma and the plasma density under the condition that the wavelength of the electromagnetic wave is constant, and FIG. 6 is a graph showing the change of the frequency selection of the filter under different plasma densities.
In the simulation, the plasma collision frequency (the cause of generation of the imaginary part) was set to 1GHz, and the imaginary part of the dielectric constant of the plasma was 0.005 in the band of 6GHz-11GHz, and was so minute that it was not shown in FIG. 5. As can be seen from fig. 5, as the plasma density increases, the dielectric constant of the plasma will slowly decrease in the filter selection frequency band and cause the resonant cavity resonant frequency to shift to a high frequency. As can be seen from FIG. 6, when the plasma density n is higheFrom 0 to 1X 1011cm-3In which n ise=0 corresponds to no plasma, transmission peak in the figureThe frequency was varied from 8.873GHz to 8.985 GHz, with a tuning range of up to 100MHz, and indeed, by continuously adjusting the plasma density, the frequency shift of the transmission peak could theoretically be varied up to 10 GHz.
Fig. 7 is a graph of the actual frequency response of the filter of the preferred embodiment of the present invention. The position of the transmission peak is slightly shifted due to the uneven thickness of the alumina ceramic rod, approximately at 8.838GHz, and the Q value is calculated to be about 480. The electromagnetic wave signal at the forbidden band is attenuated very weakly, compared with the transmission peak, the signal intensity is far lower than that of the transmission peak, and the stronger signal appears only after the signal lasts for about 10GHz, which is very good in accordance with theoretical analysis. When the adjustable voltage is applied to the two ends of the discharge tube 30, the density of the plasma begins to change and the position of the transmission peak is controlled, the current in the discharge is measured by the current probe, when the current is increased from 2.21mA to 8.13mA, the position of the transmission peak is slowly moved from 8.838GHz to 8.913GHz, and the higher transmissivity and the narrower frequency range are kept all the time, and finally the adjustment range of the bandwidth of 75MHz is realized, which shows the good wave adjusting capability of the filter of the invention.
In light of the foregoing description of the preferred embodiment of the present invention, it is to be understood that various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (5)
1. An adjustable plasma photonic crystal frequency-selective filter is characterized in that: the plasma generation device comprises a support box and a plasma generation device arranged in the support box, wherein the support box is of a cuboid structure, the size of the support box is 180-220mm x 90-110mm x 40-60mm, support plates are arranged on the inner top surface and the inner bottom surface of the support box, a hole array is arranged on each support plate, a first connector and a second connector are respectively arranged on the top surface and the bottom surface of the support box, the inside of each first connector and the inside of each second connector are connected with the plasma generation device, the plasma generation device comprises photonic crystals and plasma discharge tubes, the photonic crystals are arranged in an XY plane according to a regular hexagonal lattice by alumina ceramic rods, one alumina ceramic rod is removed from the center of each photonic crystal, and the plasma discharge tubes are placed into the center to form point defects, the photoelectric conversion device comprises a photoelectric detector and a signal output interface connected with the photoelectric detector, one of the outside of the first interface and the outside of the second interface is connected with a driving power supply, the other one of the outside of the first interface and the outside of the second interface is connected with the ground, the left side surface of the supporting box is provided with a rectangular waveguide, the length of the wide side of the rectangular waveguide is 17-30mm, the length of the narrow side of the rectangular waveguide is 5-15mm, the right side surface of the supporting box is provided with the photoelectric signal conversion device, and the photoelectric signal conversion device comprises the photoelectric detector and the signal output interface connected with the photoelectric detector.
2. The tunable plasmonic crystal frequency-selective filter of claim 1, wherein: the supporting box is made of an aluminum alloy material.
3. The tunable plasmonic crystal frequency-selective filter of claim 1, wherein: the thickness of the supporting plate is 2-4 mm.
4. The tunable plasmonic crystal frequency-selective filter of claim 1, wherein: the supporting plate is made of acrylic or polytetrafluoroethylene materials.
5. The tunable plasmonic crystal frequency-selective filter of claim 1, wherein: the driving power supply is a high-frequency high-voltage alternating current power supply.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201741777U (en) * | 2010-02-26 | 2011-02-09 | 电子科技大学 | Metal photonic crystal filter |
| CN103715480A (en) * | 2014-01-20 | 2014-04-09 | 吉林大学 | Single-band-pass tunable microwave photonic filter with ultrahigh quality factor |
| CN106028614A (en) * | 2016-07-28 | 2016-10-12 | 苏州大学 | Device for producing continuous tunable defect mode plasma photonic crystals and method thereof |
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| KR100640694B1 (en) * | 2004-04-27 | 2006-10-31 | 일진소재산업주식회사 | Method of manufacturing filter for EMI Shield |
| KR20090069972A (en) * | 2007-12-26 | 2009-07-01 | 삼성코닝정밀유리 주식회사 | Filter for display apparatus and plasma display apparatus comprising the same |
| CN102269842A (en) * | 2011-07-18 | 2011-12-07 | 北京邮电大学 | Realization method of photonic crystal micro-cavity with high-quality factor |
| CN103296343B (en) * | 2012-03-01 | 2017-02-15 | 深圳光启创新技术有限公司 | Filter |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201741777U (en) * | 2010-02-26 | 2011-02-09 | 电子科技大学 | Metal photonic crystal filter |
| CN103715480A (en) * | 2014-01-20 | 2014-04-09 | 吉林大学 | Single-band-pass tunable microwave photonic filter with ultrahigh quality factor |
| CN106028614A (en) * | 2016-07-28 | 2016-10-12 | 苏州大学 | Device for producing continuous tunable defect mode plasma photonic crystals and method thereof |
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