CN105337012A - Double-frequency coupler based on step-type impedance transformer - Google Patents

Abstract

The invention discloses a double-frequency coupler based on a step-type impedance transformer. The double-frequency coupler comprises two groups of double-frequency impedance transformers. Each group of double-frequency impedance transformers comprises two double-frequency impedance transformers. The four double-frequency impedance transformers are arranged alternately according to different groups and are in head-to-tail connection in sequence to form an annular structure; and meanwhile, ports are formed at the connection places of the four double-frequency impedance transformers, and thus double-frequency coupling is realized. Each double-frequency impedance transformer is formed by a symmetrical three-section step impedance transmission line. The double-frequency coupler not only solves the problems of large structure size and narrow work bandwidth, and meanwhile, can be realized through planar transmission lines of microstrip lines and band-shape lines and the like; and the cost is relatively low.

Description

A kind of double frequency coupler based on notch cuttype impedance transformer

Technical field

The present invention relates to a kind of microwave double frequency coupler, it belongs to multi-frequency microwave coupler field.

Background technology

At present, the implementation of microwave double frequency coupler generally has following several:

1. based on the design of the converter with double-frequency of composite right/left-handed transmission line.This kind of scheme is the Transmission line analogy based on lumped parameter, and load lumped capacity on the transmission line, inductance builds left hand transmission line, produces negative permittivity and the negative magnetoconductivity of equivalence.Owing to there is inevitable parasitic right hand effect, thus this kind of transmission line has left hand and right-handed transmission characteristic.Utilize controllable dispersion and the negative electricity length characteristic structure double frequency impedance transformer of this transmission line.

2. based on the design of the double frequency impedance transformer of loading minor matters line.This kind of scheme lays particular emphasis on the various loading minor matters line structure of design, and representative have Τ type or Π type or Γ type or E type structure and modified node method thereof, or be loading stepped type minor matters line, short circuit coupling line etc.Because the design loading minor matters line structure is varied, make the way of realization of double frequency coupler very flexible, be used widely.

3. based on the design of coupled resonators structure.This scheme is the impedance or the admittance inverter that traditional quarter-wave transmission line are equivalent to two ends connection parallel resonator, makes the double frequency coupler designed have certain band-pass filtering property.

Summary of the invention

Goal of the invention: in order to overcome the deficiencies in the prior art, the invention provides a kind of double frequency coupler based on notch cuttype impedance transformer, it is larger that this coupler not only solves double frequency coupler implementation structure size, the problem that bandwidth of operation is narrower, microstrip line can be used simultaneously, the planar transmission line forms such as strip line realize, and cost is lower.

Technical scheme: for achieving the above object, the technical solution used in the present invention is:

A kind of double frequency coupler based on notch cuttype impedance transformer, comprise first, second group double frequency impedance transformer, first group of double frequency impedance transformer comprises two the first double frequency impedance transformers, second group of double frequency impedance transformer comprises two the second double frequency impedance transformers, first double frequency impedance transformer is alternately arranged with the second double frequency impedance transformer by grouping is different and is connected to form circulus from beginning to end successively, draw port from the junction of the first double frequency impedance transformer and the second double frequency impedance transformer simultaneously, thus realize double frequency coupler; Wherein, described first double frequency impedance transformer comprises two first pair of impedance transmission lines and second pair of impedance transmission lines, and the two ends that described first pair of impedance transmission lines is arranged at second pair of impedance transmission lines form symmetric form three-section type stepped impedance transmission line; Described second double frequency impedance transformer comprises the 3rd pair of impedance transmission lines and the 4th pair of impedance transmission lines, and the two ends that described 3rd pair of impedance transmission lines is arranged at the 4th pair of impedance transmission lines form symmetric form three-section type stepped impedance transmission line.

Preferred: described first double frequency impedance transformer is alternately arranged with the second double frequency impedance transformer by grouping is different and is connected to form ring-type square structure from beginning to end successively.

Preferred: two Frequency point places of described first double frequency impedance transformer are all equivalent to K impedance transformer; Two Frequency point places of described second double frequency impedance transformer are all equivalent to K impedance transformer.

Preferred: the parameter of described double frequency impedance transformer:

$\left\{\begin{array}{c}\frac{1}{{\tan }^2{\mathrm{\θ}}_{f1}}-1=r+1/r\\ \frac{1}{{\tan }^2\left({\mathrm{\θ}}_{f2}\right)}-1=r+1/r\\ {\mathrm{sin\θ}}_{f1}(2{\cos }^2{\mathrm{\θ}}_{f1}+(1/r){\cos }^2{\mathrm{\θ}}_{f1}-r{\sin }^2{\mathrm{\θ}}_{f1})=\±Z_T/Z_1\\ \sin \left({\mathrm{\θ}}_{f2}\right)\left(2{\cos }^2\right({\mathrm{\θ}}_{f2})+(1/r\left){\cos }^2\right({\mathrm{\θ}}_{f2})-r{\sin }^2({\mathrm{\θ}}_{f2}\left)\right)=\±Z_T/Z_1\end{array}\right.;$

Wherein, θ _f1, θ _f2that transmission line is in frequency f respectively ₁, f ₂the electrical length at place, and θ _f2/ θ _f1=f ₂/ f ₁=m, m are operating frequency ratio, r=Z ₂/ Z ₁, Z ₁, θ ₁characteristic impedance and the electrical length of the impedance transmission lines at two ends, Z ₂, θ ₂characteristic impedance and the electrical length of middle impedance transmission lines, Z _tit is the resistance value of K converter.

Preferred: the frequency ratio between two groups of double frequency impedance transformers is 5.2, wherein characteristic impedance 45.2 Ω, 27.7 Ω of transmission line of a group, corresponding electrical length 29.0deg1.0GHz, 29.0deg1.0GHz; Characteristic impedance 64.0 Ω, 39.1 Ω of another group transmission line, corresponding electrical length 29.0deg1.0GHz, 29.0deg1.0GHz; Characteristic impedance 50 Ω of the port of export.

A kind of double frequency coupler based on notch cuttype impedance transformer provided by the invention, compared to existing technology, has following beneficial effect:

(1). the present invention can realize double frequency coupler, and its novel structure;

(2). the structure of double frequency coupler is simple, and overall dimensions is less, is conducive to the Integrated design of circuit;

(3). the matching at two frequency places is good, and insertion loss is lower, and isolation is high.

Accompanying drawing explanation

Fig. 1 conventional orthogonal 3dB directional coupling structure figure.

The structure chart of the single-frequency impedance transformer of Fig. 2 classics.

The structure chart of Fig. 3 double frequency stepped impedance code converter.

Fig. 4 is based on the double frequency coupler structure figure of stepped impedance code converter.

The insertion loss (S21, S31) of Fig. 5 double frequency coupler (frequency ratio is 5.2) and return loss (S11) curve chart.

The phase curve figure of the insertion loss (S21, S31) of Fig. 6 double frequency coupler (frequency ratio is 5.2).

Isolation (S41) curve chart of Fig. 7 double frequency coupler (frequency ratio is 5.2).

Embodiment

Below in conjunction with accompanying drawing, the present invention is further described.

A kind of double frequency coupler based on notch cuttype impedance transformer, as shown in Figure 4, comprise first, second group double frequency impedance transformer, first group of double frequency impedance transformer comprises two the first double frequency impedance transformers, second group of double frequency impedance transformer comprises two the second double frequency impedance transformers, described first double frequency impedance transformer is alternately arranged with the second double frequency impedance transformer by grouping is different and is connected to form ring-type square structure from beginning to end successively, draws port (P from the junction of the first double frequency impedance transformer and the second double frequency impedance transformer simultaneously ₁, P ₂, P ₃, P ₄), thus realize double frequency coupler; Wherein, as shown in Figure 3, described first double frequency impedance transformer comprises two first pair of impedance transmission lines and second pair of impedance transmission lines, and the two ends that described first pair of impedance transmission lines is arranged at second pair of impedance transmission lines form symmetric form three-section type stepped impedance transmission line; Described second double frequency impedance transformer comprises the 3rd pair of impedance transmission lines and the 4th pair of impedance transmission lines, and the two ends that described 3rd pair of impedance transmission lines is arranged at the 4th pair of impedance transmission lines form symmetric form three-section type stepped impedance transmission line.

Two Frequency point places of described first double frequency impedance transformer are all equivalent to K impedance transformer; Two Frequency point places of described second double frequency impedance transformer are all equivalent to K impedance transformer.

Fig. 1 gives conventional orthogonal 3dB directional coupling structure figure.Wherein, as shown in Figure 2, be the core of design, it should meet impedance transformation function to impedance transformer, realizes each port Impedance coupling, subtracts low power reflection loss, also will meet phase deviation function, realizes the orthogonality of straight-through arm and coupling arm signal.Its network characteristic can represent by matrix parameter.

Its abcd matrix is:

$A=\left(\begin{array}{cc}0& \±{\mathrm{jZ}}_T\\ \±\frac{1}{{\mathrm{jZ}}_T}& 0\end{array}\right)---\left(1\right)$

Wherein, Z _tbe the resistance value of K converter, j is imaginary unit, and A is the transmission matrix of K converter.

Fig. 3 is the structure chart of double frequency K impedance transformer.Double frequency impedance transformer is saved by symmetric form three that stepped impedance transmission line forms, and it all can be equivalent to K impedance transformer at two Frequency point places, and the equivalent relation namely by Fig. 3 structure and original K converter is analyzed.

$A_t=\left(\begin{array}{cc}{A}_1& B_1\\ C_1& D_1\end{array}\right)---\left(2\right)$

$\left\{\begin{array}{c}{A}_1=D_1={\cos }^2{\mathrm{\θ}}_1{\mathrm{cos\θ}}_2-\left(\frac{Z_2}{Z_1}+\frac{Z_1}{Z_2}\right){\mathrm{sin\θ}}_2{\mathrm{sin\θ}}_1{\mathrm{cos\θ}}_1-{\sin }^2{\mathrm{\θ}}_1{\mathrm{cos\θ}}_2\\ B_1=j2Z_1{\mathrm{cos\θ}}_2{\mathrm{sin\θ}}_1{\mathrm{cos\θ}}_1+j{\mathrm{sin\θ}}_2\left(Z_2{\cos }^2{\mathrm{\θ}}_1-\frac{Z_1^2}{Z_2}{\sin }^2{\mathrm{\θ}}_1\right)\\ C_1=j2{\mathrm{cos\θ}}_2{\mathrm{sin\θ}}_1{\mathrm{cos\θ}}_1/Z_1+j{\mathrm{sin\θ}}_2\left({\cos }^2{\mathrm{\θ}}_1-\frac{Z_2}{Z_1^2}{\sin }^2{\mathrm{\θ}}_1\right)\end{array}\right.---\left(3\right)$

Wherein, Z ₁, θ ₁characteristic impedance and the electrical length of the impedance transmission lines at two ends, Z ₂, θ ₂characteristic impedance and the electrical length of middle impedance transmission lines, A _tfor the transmission matrix of Fig. 3 structure, A ₁, B ₁, C ₁, D ₁for transmission matrix element.

θ can be made to simplify the analysis ₁=θ ₂, r=Z ₂/ Z ₁, consider at two Frequency point f ₁, f ₂=mf ₁place, the equal i.e. A of two matrix parameter ₁=A _t, following equation can be obtained through deriving:

$\left\{\begin{array}{c}\frac{1}{{\tan }^2{\mathrm{\θ}}_{f1}}-1=r+1/r\\ \frac{1}{{\tan }^2\left({\mathrm{\θ}}_{f2}\right)}-1=r+1/r\\ {\mathrm{sin\θ}}_{f1}(2{\cos }^2{\mathrm{\θ}}_{f1}+(1/r){\cos }^2{\mathrm{\θ}}_{f1}-r{\sin }^2{\mathrm{\θ}}_{f1})=\±Z_T/Z_1\\ \sin \left({\mathrm{\θ}}_{f2}\right)\left(2{\cos }^2\right({\mathrm{\θ}}_{f2})+(1/r\left){\cos }^2\right({\mathrm{\θ}}_{f2})-r{\sin }^2({\mathrm{\θ}}_{f2}\left)\right)=\±Z_T/Z_1\end{array}\right.---\left(4\right)$

Wherein, θ _f1, θ _f2that transmission line is in frequency f respectively ₁, f ₂the electrical length at place, and θ _f2/ θ _f1=f ₂/ f ₁=m, m are operating frequency ratio.

Two operating frequencies are respectively to the double frequency coupler of 1GHz and 5.2GHz (frequency ratio is 5.2), structure as shown in Figure 4, solves (4) formula by numerical analysis, thus obtains and work as Z _t=50 Ω, the electrical length of stepped impedance code converter structure suitable during 35.35 Ω and characteristic impedance parameter, characteristic impedance and the electrical length parameter of the final each transmission line obtained are as shown in the table:

z 1(Ω)	45.2	θ 3(deg1.0GHz)	29.0
				z 2(Ω)	27.7	θ 2(deg1.0GHz)	29.0
z 3(Ω)	64.0	θ 3(deg1.0GHz)	29.0
				z 4(Ω)	39.1	θ 4(deg1.0GHz)	29.0
z 0(Ω)	50

Wherein, z ₀it is the impedance of port.

Fig. 5-Fig. 7 characterize work frequency ratio be 5.2 the performance curve that emulates of double frequency coupler, wherein S11 curve is port one coverage diagram, S21 and S31 curve is straight-through characteristic curve and coupling characteristic, and S32 is isolation curve.The corresponding S parameter of two frequency bins is:

f ₁＝1.0GHz,|S ₁₁|＝-52.8dB,|S ₂₁|＝|S ₃₁|＝-3.0dB,|S ₄₁|＝-52.8dB,∠S ₂₁-∠S ₃₁＝90°

f ₂＝5.2GHz,|S ₁₁|＝-41.7dB,|S ₂₁|＝|S ₃₁|＝-3.0dB,|S ₄₁|＝-41.7dB,∠S ₂₁-∠S ₃₁＝90°

The present invention adopts symmetric form three to save stepped impedance transmission line formation double frequency impedance transformer, this double frequency impedance transformer, should make to realize each port Impedance coupling at two working frequency points places, subtract low power reflection loss, meet phase deviation function again, realize the orthogonality of straight-through arm and coupling arm signal thus realize double frequency 3dB directional coupler.The circuit structure of this double frequency coupler is simple, and operating frequency is than adjustable, and overall dimensions is less, and owing to not loading the resonant elements such as any minor matters line, the planar transmission line forms such as thus bandwidth of operation is wider, and it can use microstrip line, strip line realize, and cost is lower.

The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (5)

1. the double frequency coupler based on notch cuttype impedance transformer, it is characterized in that: comprise first, second group double frequency impedance transformer, first group of double frequency impedance transformer comprises two the first double frequency impedance transformers, second group of double frequency impedance transformer comprises two the second double frequency impedance transformers, first double frequency impedance transformer is alternately arranged with the second double frequency impedance transformer by grouping is different and is connected to form circulus from beginning to end successively, draw port from the junction of the first double frequency impedance transformer and the second double frequency impedance transformer simultaneously, thus realize double frequency coupler; Wherein, described first double frequency impedance transformer comprises two first pair of impedance transmission lines and second pair of impedance transmission lines, and the two ends that described first pair of impedance transmission lines is arranged at second pair of impedance transmission lines form symmetric form three-section type stepped impedance transmission line; Described second double frequency impedance transformer comprises the 3rd pair of impedance transmission lines and the 4th pair of impedance transmission lines, and the two ends that described 3rd pair of impedance transmission lines is arranged at the 4th pair of impedance transmission lines form symmetric form three-section type stepped impedance transmission line.

2. the double frequency coupler based on notch cuttype impedance transformer according to claim 1, is characterized in that: described first double frequency impedance transformer is alternately arranged with the second double frequency impedance transformer by grouping is different and is connected to form ring-type square structure from beginning to end successively.

3. the double frequency coupler based on notch cuttype impedance transformer according to claim 1, is characterized in that: two Frequency point places of described first double frequency impedance transformer are all equivalent to K impedance transformer; Two Frequency point places of described second double frequency impedance transformer are all equivalent to K impedance transformer.

4. the double frequency coupler based on notch cuttype impedance transformer according to claim 1, is characterized in that: the parameter of described double frequency impedance transformer:

$\left\{\begin{array}{c}\frac{1}{{\tan }^2{\mathrm{\θ}}_{f1}}-1=r+1/r\\ \frac{1}{{\tan }^2\left({\mathrm{\θ}}_{f2}\right)}-1=r+1/r\\ {\mathrm{sin\θ}}_{f1}(2{\cos }^2{\mathrm{\θ}}_{f1}+(1/r){\cos }^2{\mathrm{\θ}}_{f1}-r{\sin }^2{\mathrm{\θ}}_{f1})=\±Z_T/Z_1\\ \sin \left({\mathrm{\θ}}_{f2}\right)\left(2{\cos }^2\right({\mathrm{\θ}}_{f2})+(1/r\left){\cos }^2\right({\mathrm{\θ}}_{f2})-r{\sin }^2({\mathrm{\θ}}_{f2}\left)\right)=\±Z_T/Z_1\end{array}\right.;$

Wherein, θ _f1, θ _f2that transmission line is in frequency f respectively ₁, f ₂the electrical length at place, and θ _f2/ θ _f1=f ₂/ f ₁=m, m are operating frequency ratio, r=Z ₂/ Z ₁, Z ₁, θ ₁characteristic impedance and the electrical length of the impedance transmission lines at two ends, Z ₂, θ ₂characteristic impedance and the electrical length of middle impedance transmission lines, Z _tit is the resistance value of K converter.

5. the double frequency coupler based on notch cuttype impedance transformer according to claim 1, it is characterized in that: the frequency ratio between two groups of double frequency impedance transformers is 5.2, wherein characteristic impedance 45.2 Ω, 27.7 Ω of transmission line of a group, corresponding electrical length 29.0deg1.0GHz, 29.0deg1.0GHz; Characteristic impedance 64.0 Ω, 39.1 Ω of another group transmission line, corresponding electrical length 29.0deg1.0GHz, 29.0deg1.0GHz; Characteristic impedance 50 Ω of the port of export.