CN203644914U - Coaxial cavity dual-band filter based on step impedance structure - Google Patents

Abstract

The utility model discloses a coaxial cavity dual-band filter based on step impedance structures. The coaxial cavity dual-band filter is formed by coupling a plurality of step impedance coaxial cavity resonator units. Each step impedance coaxial cavity resonator unit is composed of two rod-shaped solid metal conductors, a cylindrical metal wall and a filler. The filler is air, and is positioned in a resonant cavity among the cylindrical metal wall and the rod-shaped solid metal conductors. An upper end and a lower end of the cylindrical metal wall are provided with outer-layer covering plates which enclose the resonant cavity. The plurality of step impedance coaxial cavity resonator units is in a linear parallel structure. The two rod-shaped solid metal conductors are two coaxial cylinders having different diameters, and are divided into a lower conductor column and an upper conductor column, wherein the two conductor columns are vertically connected in series. The lower conductor column is electrically connected with a feeder line of an input port or an output port. The coaxial cavity dual-band filter adopts the step impedance coaxial cavity resonator units and realizes two passbands which have a passband frequency having a larger adjustable scope, and is small in size and simple and reasonable in structure.

Description

Coaxial cavity double frequency filter based on Stepped Impedance structure

Technical field

The utility model relates to the dual frequency filter in wireless communication field, is specifically related to a kind of coaxial cavity double frequency filter based on Stepped Impedance structure.

Background technology

Due to developing rapidly and people need to day by day increase radio communication of wireless communication technology, current market 2G, 3G, 4G network are also deposited, many wireless terminals, such as mobile phone, panel computer etc., in the time of design, all wish the compatible multiple communication standards of energy, this just can allow terminal use enjoy the service that different operators provides simultaneously.Multiband filter is realized multiple passbands or stopband on a circuit simultaneously, and can significantly reduce circuit size and reduce costs, be therefore the focus of a research.In actual industrial production, the most frequently used is cavity body filter, because compared with flat filter, cavity body filter has higher power capacity.In cavity body filter, the filter that uses coaxial cavity to make generally can be realized higher bandwidth, and communication speed is being required to more and more higher society, and this is an obvious advantage.In addition, with respect to waveguide filter, coaxial cavity filter has minimum dispersion, and the signal passing through can produce distortion hardly.Therefore, coaxial cavity filter has very high actual application value.

In prior art, the most direct method of design double frequency filter is that each frequency range is designed to an independently resonator, then they is combined into a double frequency filter.But interact for fear of two resonators, between resonator, must have enough distances, must cause like this filter size to become large, and cost is also very high.2010, Xiaoguang Liu, Linda P.B.Katehi, Dimitrios Peroulis delivers the article that is entitled as " Novel Dual-Band Microwave Filter Using Dual-Capacitively-Loaded Cavity Resonators " on the art periodical " IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS ", and it produces two passbands with two resonators respectively while proposing design double frequency filter.Not only volume is larger to use the filter of this structural design, and first parasitic passband is positioned at the frequency tripling place of the first passband, therefore from the second passband close to, easily introduce and disturb.

In prior art, another one mentality of designing is in a passband, to insert to realize two passbands zero point, as two examples below: 2006, Giuseppe Macchiarella and Stefano Tamiazzo deliver the article that is entitled as " Design Techniques for Dual-Passband Filters " on the art periodical " IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES ", it uses coaxial cavity to design double frequency band-pass filter while proposing design double frequency filter, and this filter uses uniform resonator; Chinese Patent Application No. is 201310062624.1, patent name is the technical scheme of SIR coaxial cavity double-passband filter, uses equally coaxial cavity to design double frequency band-pass filter, and this filter uses the resonator of Stepped Impedance structure.Thisly in a passband, insert the method that realizes two passbands zero point, cause band connection frequency less than adjustable extent; And need to design the strict structure that forms side by side matrix of numerous resonators, thereby make that filter volume is large, profile can not be adjusted flexibly.

Utility model content

The purpose of this utility model is to overcome the deficiencies in the prior art, and the coaxial cavity double frequency filter based on Stepped Impedance structure that a kind of band connection frequency is larger than adjustable extent, volume is little, simple and reasonable and cost is low is provided.

In order to achieve the above object, the technical solution adopted in the utility model is, a kind of coaxial cavity double frequency filter based on Stepped Impedance structure, formed by several Stepped Impedance coaxial cavity resonator element couplings, each Stepped Impedance coaxial cavity resonator unit is made up of two shaft-like solid metallic conductor, tubular metallic walls (4) and charges (5) three parts, charges (5) are air, in resonant cavity between tubular metallic walls and shaft-like solid metallic conductor, the two ends up and down of tubular metallic walls arrange outer capping plate, and resonant cavity is airtight.Described several Stepped Impedance coaxial cavity resonator unit are wire parallel construction, and described two shaft-like solid metallic conductor are two sections of coaxial cylinders that diameter is different, are divided into lower conductor post (1) and upper conductor post (2), and two sections of conductor pins are connected up and down.Due to the diameter difference of two sections of conductor pins, be also characteristic impedance difference, so, by changing its impedance ratio, the frequency ratio that can realize first and second passbands is controlled.Lower conductor post (1) is electrically connected with first feed line (6) of input port or second feed line (8) of output port.

More specifically, described tubular metallic walls (4) is square metal shell; Described lower conductor post (1) and upper conductor post (2) are equal in length, and coaxial with described tubular metallic walls (4).

More specifically, between adjacent two Stepped Impedance coaxial cavity resonator unit, tuning screw (3) is set, tuning screw is connected on outer capping plate, and its length can flexible, for filter is finely tuned, thereby reduce the impact that mismachining tolerance produces final result.

More specifically, between adjacent two Stepped Impedance coaxial cavity resonator unit, coupling window (7) is set, can adjusts the size of coupling coefficient, it is divided into upper and lower two windows, window width is adjustable, is mainly in order to control more neatly capacitive coupling and inductive coupled; Window above (is that width is W ₂window) there is stronger capacitive coupling and inductive coupled simultaneously, and window below (is that width is W ₁window) take inductive coupled as main.Due to the introducing of hybrid coupled, in the middle of two passbands, produce a zero point, improve the local edge of passband.

More optimize, described Stepped Impedance coaxial cavity resonator unit has 3, structure is arranged in a linear, the feed line of its input port and output port is electrically connected with the lower conductor post (1) at linear array structure two ends respectively, because double-end feed linear distance is far away, input and output signal interferes with each other few.

More optimize, any one metal in described coaxial cavity double frequency filter employing aluminium, copper, iron, gold or silver based on Stepped Impedance structure or the alloy of any several metals are made.

More optimize, the material of the inner surface of the tubular metallic walls (4) of the described coaxial cavity double frequency filter based on Stepped Impedance structure, tuning screw coating and shaft-like solid metallic conductor coating be silver-colored, to reduce loss.

The operation principle of the coaxial cavity double frequency filter of the utility model based on Stepped Impedance structure:

The frequency of two passbands, mainly by resonator control, can regulate the frequency ratio of two passbands easily by adjusting resonator impedance ratio.

Referring to Fig. 1, the relation of impedance ratio and frequency ratio can represent by following formula, and wherein Rz is that the characteristic impedance of upper conductor post (2) is than the characteristic impedance of lower conductor post (1), f ₁and f ₂be respectively the frequency of first, second passband.

$\frac{f_2}{{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HDA0000410620520000031.png"\; state="\{\{state\}\}">f</figure-callout>}}_1}=\frac{\mathrm{\&pi;}}{\arctan \sqrt{R_Z}}-1---\left(1\right)$

Can see (D in the time that impedance ratio Rz is greater than 1 from formula (1) ₂<D ₁), frequency ratio is less than 3; (D in the time that impedance ratio Rz is less than 1 ₂>D ₁), frequency ratio is greater than 3.

In design, choose L ₂=L ₃, the characteristic impedance of conductor is used formula below to carry out approximate calculation, wherein Z ₀₁for the characteristic impedance of lower conductor post (1), Z ₀₂for the characteristic impedance of upper conductor post (2), ε _rfor the relative electric medium constant of charges in cavity.

$Z_{01}=\frac{60}{\sqrt{{\mathrm{\&epsiv;}}_r}}\ln \left(\frac{L_2}{D_1}\right),Z_{02}=\frac{60}{\sqrt{{\mathrm{\&epsiv;}}_r}}\ln \left(\frac{L_2}{D_2}\right)---\left(2\right)$

According to above twice formula, under different lower upper conductor column diameter ratios, the frequency ratio (partial data) obtaining as shown in Figure 4.

In design, choose lower conductor post (1) and the equal in length of upper conductor post (2) (is L ₄=L ₅), establish upper and lower conductor pin at f ₁electrical length under frequency is θ, has following formula:

$\mathrm{\&theta;}=\arctan \left(\sqrt{R_Z}\right)---\left(3\right)$

Owing to there being capacity effect in resonant cavity, these are only approximate formula.In design, should utilize the initial value of formula to be optimized again design.

As for the bandwidth of passband, mainly by external sort factor and coupling coefficient control.External sort factor is to be determined by the feed placement of feed line, and coupling coefficient can (change W by adjusting coupling window ₁and W ₂size) regulate.

With respect to prior art, the beneficial effects of the utility model are:

(1) the utility model adopts Stepped Impedance coaxial cavity resonator unit to realize two passbands, has reduced the volume of circuit and has reduced cost of manufacture.

(2) the utility model can regulate the frequency ratio of two passbands easily by adjusting resonator impedance ratio, and band connection frequency is larger than adjustable extent.

(3) some resonator elements of the present utility model are wire parallel construction, can form the various shape such as straight line, curve, simple and reasonable, can facilitate, be applied to flexibly various actual working environment.

Accompanying drawing explanation

Fig. 1 is the overall structure schematic diagram of the utility model embodiment.

Fig. 2 is the generalized section of the utility model embodiment.

Fig. 3 is the top cross-sectional view of the utility model embodiment.

Fig. 4 be in the resonant cavity of the utility model embodiment two sections of coaxial conductor column diameters than with the graph of a relation of band connection frequency ratio.

Fig. 5 is the simulation result figure of the utility model embodiment.

Embodiment

Further illustrate the utility model below in conjunction with drawings and Examples, but the claimed scope of the utility model is not limited to the scope of embodiment statement.The other changes and modifications that those skilled in the art is made in the situation that not deviating from spirit of the present utility model and protection range, are still included in the scope of claims protection.

Embodiment

The present embodiment, a kind of coaxial cavity double frequency filter based on Stepped Impedance structure, as shown in Figure 1, there are 3 Stepped Impedance coaxial cavity resonator unit linear array structures, first feed line (6) of its input port and second feed line (8) of output port are separately positioned on linear array structure two ends, because double-end feed linear distance is far away, input and output signal interferes with each other few.

Described Stepped Impedance coaxial cavity resonator unit is made up of two shaft-like solid metallic conductor, tubular metallic walls (4) and charges (5) three parts, charges (5) are air, in resonant cavity between tubular metallic walls and shaft-like solid metallic conductor, the two ends up and down of tubular metallic walls arrange outer capping plate, and resonant cavity is airtight.Two shaft-like solid metallic conductor are two sections of coaxial cylinders that diameter is different, are divided into lower conductor post (1) and upper conductor post (2), and two sections of conductor pins are connected up and down.

Described tubular metallic walls (4) is square metal shell (L ₂=L ₃); Described lower conductor post (1) and upper conductor post (2) (L equal in length ₄=L ₅), and coaxial with described tubular metallic walls (4).

Between adjacent two Stepped Impedance coaxial cavity resonator unit, tuning screw (3) is set, tuning screw is connected on outer capping plate, its length can flexible, for filter is finely tuned, thereby reduces the impact that mismachining tolerance produces final result.

Between adjacent two Stepped Impedance coaxial cavity resonator unit, coupling window (7) is set, it is divided into upper and lower two windows, window width (W ₁and W ₂) adjustable.

The present embodiment adopts metallic aluminium to make.

The material of the inner surface of the tubular metallic walls (4) of the present embodiment, tuning screw coating and shaft-like solid metallic conductor coating is silver, to reduce loss.

The present embodiment each several part size, as shown in Figure 1:

Given band connection frequency index is f ₁=900MHz, f ₂=1800MHz, the impedance ratio that can obtain resonant cavity by formula (1)-(3) is 3, upper lower conductor is at f ₁the electrical length at place is θ=1.05.Afterwards, determine external sort factor by adjusting distributing point, determine coupling coefficient by adjusting coupling window, just can obtain required bandwidth.After optimizing, each several part dimensional parameters is: L ₁=111.3mm, L ₂=L ₃=50mm, L ₄=L ₅=50.5mm, L ₆=50.5mm, L ₇=28.6mm, W ₁=9.6mm, W ₂=10mm, W ₃=3mm, D ₁=22.74mm, D ₂=4mm, H=6.5mm.

The present embodiment course of work is as follows in conjunction with the simulation result of full-wave simulation software HFSS:

In simulation process, from input port input test signal, can obtain through the present embodiment output signal after treatment from output port.As shown in Figure 5, transverse axis represents the signal frequency of input, and the longitudinal axis represents the amplitude size of scattering parameter, comprises insertion loss (S ₂₁) amplitude and return loss (S ₁₁) amplitude, S ₂₁represent that its corresponding mathematical function is: power output/input power (dB)=20*log|S by the relation between the input power of signal and the power output of signal of the present embodiment ₂₁|; In signals transmission, the Partial Power of signal is reflected back toward signal source, and the power being reflected becomes reflection power; S ₁₁represent that its corresponding mathematical function is as follows: reflection power/incident power=20*log|S by the relation between the input power of signal and the reflection power of signal of the present embodiment ₁₁|.The three dB bandwidth of two passbands of the present embodiment is respectively 0.894GHz to 0.905GHz(1.2%) and 1.793GHz to 1.807GHz(0.8%).That is to say, in work, need signal to be processed from input port input, so, frequency 0.894GHz between 0.905GHz and 1.793GHz can pass through the present embodiment to the signal between 1.807GHz, all the other signals all will obtain being greater than the power attenuation of half.

Above-described embodiment is preferably execution mode of the utility model; but execution mode of the present utility model is not restricted to the described embodiments; other any do not deviate from change, the modification done under Spirit Essence of the present utility model and principle, substitutes, combination, simplify; all should be equivalent substitute mode; for example change resistance value, the change coupling window shape of Stepped Impedance; or change rectangular cavities into other shapes etc., within being included in protection range of the present utility model.

Claims (7)

1. the coaxial cavity double frequency filter based on Stepped Impedance structure, formed by several Stepped Impedance coaxial cavity resonator element couplings, each Stepped Impedance coaxial cavity resonator unit is made up of two shaft-like solid metallic conductor, tubular metallic walls (4) and charges (5) three parts, charges (5) are air, in resonant cavity between tubular metallic walls and shaft-like solid metallic conductor, the two ends up and down of tubular metallic walls arrange outer capping plate, and resonant cavity is airtight; It is characterized in that: described several Stepped Impedance coaxial cavity resonator unit are wire parallel construction; Described two shaft-like solid metallic conductor are two sections of coaxial cylinders that diameter is different, are divided into lower conductor post (1) and upper conductor post (2), and two sections of conductor pins are connected up and down; Lower conductor post (1) is electrically connected with first feed line (6) of input port or second feed line (8) of output port.

2. the coaxial cavity double frequency filter based on Stepped Impedance structure according to claim 1, is characterized in that: described tubular metallic walls (4) is square metal shell; Described lower conductor post (1) and upper conductor post (2) are equal in length, and coaxial with described tubular metallic walls (4).

3. the coaxial cavity double frequency filter based on Stepped Impedance structure according to claim 1, it is characterized in that: between adjacent two Stepped Impedance coaxial cavity resonator unit, tuning screw (3) is set, tuning screw is connected on outer capping plate, and its length can flexible.

4. the coaxial cavity double frequency filter based on Stepped Impedance structure according to claim 1, is characterized in that: between adjacent two Stepped Impedance coaxial cavity resonator unit, coupling window (7) is set, it is divided into upper and lower two windows, and window width is adjustable.

5. according to the coaxial cavity double frequency filter based on Stepped Impedance structure described in claim 1-4 any one, it is characterized in that: described Stepped Impedance coaxial cavity resonator unit has 3, the structure that is arranged in a linear, the feed line of its input port and output port is electrically connected with the lower conductor post (1) at linear array structure two ends respectively.

6. according to the coaxial cavity double frequency filter based on Stepped Impedance structure described in claim 1-4 any one, it is characterized in that: any one metal in employing aluminium, copper, iron, gold or silver or the alloy of any several metals are made.

7. according to the coaxial cavity double frequency filter based on Stepped Impedance structure described in claim 1-4 any one, it is characterized in that: the material of the inner surface of tubular metallic walls (4), tuning screw coating and shaft-like solid metallic conductor coating is silver.

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