CN1246979C - Coupling structure of high-temperature superconductive filter for adjusting-free satellite communication and making process - Google Patents

Abstract

The present invention relates to a coupling structure and a manufacture technology thereof of a high-temperature superconductive filter for adjusting-free satellite communication, which belongs to the technical field of communication. The coupling structure is characterized in that two L-shaped transmission wires are respectively inserted between one of two resonators and a third resonator, wherein the two resonators connected with a leading wire are arranged on both sides of a band pass filter, the third resonator faces the two resonators obliquely, and the transmission wire made by the same manufacture technology as that of the resonators and a tap is finished by one-time processing. The present invention is suitable for the design of a frequency preselector at the front end of the radio frequency of a satellite communication receiving system or at the front end of a base station in a mobile communication system. When the present invention is used for a satellite receiving system, the reflection loss in a passband is reduced to-20dB from original-15dB, and the transmission coefficient S21 is also improved. Meantime, the present invention replaces all tuning screws, lowers the cost of a wave filter and shortens development cycle, and is suitable for mass production.

Description

The adjusting-free satellite communication coupled structure of high temperature superconduction wave filter

Technical field

The adjusting-free satellite communication belongs to analog and communication technical field with the coupled structure of high temperature superconduction wave filter, relate in particular to satellite communication receiving system radio-frequency front-end or mobile communication system in the frequency preselection device technical field of base station front end.

Background technology

The filter synthesis method of traditional low-pass prototype that constitutes based on lumped-parameter element is when doing the logical frequency translation of low pass one band, only at centre frequency f ₀The place is accurately, and error is all arranged on all the other frequencies, especially has very mistake in stopband.On the other hand, when substituting lumped-parameter element, also can introduce error with microwave structure, such as: adopt the microstrip line of semi-open structure to constitute resonator, because propagation is accurate TEM ripple, have longitudinal electric field, the magnetic-field component of non-zero, therefore at frequency nf ₀There is intrinsic parasitic passband near (n is the positive integer greater than 1).Generally speaking, adopt tuning screw to be revised, promptly add the tuning screw of metal or sapphire material in the appropriate location of the lid of shielding box.But for the high temperature superconduction wave filter of (77K) work under cryogenic conditions, tuning with screw will be very difficult, waste time and energy and the cost height.

In order to realize higher frequency selectivity, to make that promptly transition band is narrow as far as possible, the topological structure of at present popular band pass filter is: introduce cross-couplings (cross coupling) between non-adjacent resonator, cry non-adjacent coupling again, can near the upper and lower edge of passband, respectively produce a transmission zero.With the corresponding low-pass prototype of this topological structure (is example with order N=8) as shown in Figure 1, the elliptic function frequency response that is referred to as to be as the criterion of corresponding transfer function.J among the figure ₃₆The cross-couplings that i.e. expression is introduced into.

The external sort factor of coupling coefficient between the resonator and input, output resonator, can be by the component value of low-pass prototype and the parameter in the design objective and determine that relational expression is as follows:

${\mathrm{<figure-callout\; id="1"\; label="Q\; e"\; filenames="C0310487300071.png"\; state="\{\{state\}\}">Q</figure-callout>}}_e=\frac{g_0{\mathrm{<figure-callout\; id="1"\; label="g"\; filenames="C0310487300071.png"\; state="\{\{state\}\}">g</figure-callout>}}_1}{\mathrm{FBW}}$

$Q_{\mathrm{eN}}=\frac{g_N{g}_{N+1}}{\mathrm{FBW}}$

$M_{\mathrm{ij}}=\frac{\mathrm{FBW}}{\sqrt{g_i{g}_j}}{J}_{\mathrm{ij}}$

Q wherein _E1And Q _ENBe respectively the external sort factor of input, output resonator, M _IjIt is the coupling coefficient between the resonator i resonator j.FBW is a fractional bandwidth, is defined as FBW=BW/f ₀, BW is a pass band width.From g ₀To g _N+1Be the normalized capacitance of low-pass prototype, J _IjIt is the characteristic admittance (referring to Fig. 1) of the admittance inverter between the resonator i resonator j.

The present similar high-temperature superconductor band pass filter of reporting on the pertinent literature, from measured result, voltage standing wave ratio is still waiting to improve, because the reflection loss in the band is all about-15dB, in addition bigger.This has not only directly caused power loss, requires relatively harsher occasion at some, also may cause the instability of prime element circuit.

Summary of the invention

Coupled structure of the present invention is characterised in that: respectively two of band pass filter both sides connecting lead-in wire resonator and and their another resonators of tiltedly facing toward between the appropriate location respectively insert one section L type transmission line, wherein:

The live width of L type transmission line is 240 μ m;

The line length of L type transmission line horizontal segment is 4.6mm;

The L type transmission line vertically line length of section is 4.6mm;

Above-mentioned horizontal segment is 0.8mm with the spacing that is being connected between two resonators that go between;

Above-mentioned vertical section be connected the lead-in wire two resonators between spacing be 1.0mm.

The manufacturing process of coupled structure of the present invention is characterized in that: same manufacture craft is adopted in described L type transmission line and resonator and tap, and time processing forms.

Experimental results show that: the reflection loss in the passband reduces, and transmission coefficient also improves simultaneously.In addition, cancelled whole tuning screws, shortened the construction cycle, be suitable for producing in batches.

Description of drawings

Fig. 1: the topological structure of low-pass prototype (order N=8).

Fig. 2: the initial domain of band pass filter.

Fig. 3: improved band pass filter domain.

Fig. 4: the comparison of passband internal reflection coefficient S 11 curves before and after improving: the curve before the representative improves; Curve after zero representative improves.

Fig. 5: the comparison of transmission coefficient S21 curve before and after improving: the curve before the representative improves; Curve after zero representative improves.

Embodiment

For the symmetrical structure of Fig. 1, can adopt strange, the even theory of modules to carry out comprehensively.Reflection coefficient S11, transmission coefficient S21 and strange mould reflectioncoefficient _o, even mould reflectioncoefficient _eBetween relational expression be:

$S_{11}=\frac{{\mathrm{\&Gamma;}}_e+{\mathrm{\&Gamma;}}_o}{2}$

$S_{21}=\frac{{\mathrm{\&Gamma;}}_e-{\mathrm{\&Gamma;}}_o}{2}$

Strange mould reflectioncoefficient _o, even mould reflectioncoefficient _eWith strange mould normalization input admittance y _o, even mould normalization input admittance y _eThe pass be:

${\mathrm{\&Gamma;}}_o=\frac{1-y_o}{1+y_o}$

${\mathrm{\&Gamma;}}_e=\frac{1-y_e}{1+y_e}$

So have

$S_{11}=\frac{1-y_e{y}_o}{(1+y_e)(1+y_o)}$

$S_{21}=\frac{y_o-y_e}{(1+y_e)(1+y_o)}$

And y _oAnd y _eCan use about the continued fraction of low-pass prototype component value and represent.Then can obtain S ₂₁(Ω) and | S ₂₁(Ω) | ²With the relational expression of low-pass prototype component value, Ω is the normalized radian frequency of low pass filter.

The power transmission factor that can establish 8 rank low pass filters shown in Figure 1 is:

${\left|S_{21}\left(\mathrm{\&Omega;}\right)\right|}^2=\frac{1}{1+{\mathrm{\&epsiv;}}^2\frac{{({\mathrm{\&Omega;}}^2-{\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="C0310487300071.png"\; state="\{\{state\}\}">Z</figure-callout>}}_1^2)}^2{({\mathrm{\&Omega;}}^2-Z_2^2)}^2{({\mathrm{\&Omega;}}^2-Z_3^2)}^2{({\mathrm{\&Omega;}}^2-Z_4^2)}^2}{{({\mathrm{\&Omega;}}^2-P^2)}^2}}$

$=\frac{{({\mathrm{\&Omega;}}^2-P^2)}^2}{{\mathrm{\&epsiv;}}^2{({\mathrm{\&Omega;}}^2-{\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="C0310487300071.png"\; state="\{\{state\}\}">Z</figure-callout>}}_1^2)}^2{({\mathrm{\&Omega;}}^2-Z_2^2)}^2{({\mathrm{\&Omega;}}^2-Z_3^2)}^2{({\mathrm{\&Omega;}}^2-Z_4^2)}^2+{({\mathrm{\&Omega;}}^2-P^2)}^2}$

In the formula ± P is the normalization transmission zero in the low-pass prototype, can be a certain greater than 1 real number according to the requirement of transition band being established P, and Z ₁, Z ₂, Z ₃, Z ₄For less than 1 nonnegative real number.ε ²It is the constant that characterizes ripple in the passband.To then | S ₂₁(Ω) | ²Write as about Ω equally with the relational expression of low-pass prototype component value ²The form of fraction.With the following formula contrast, equal again according to the coefficient of respective items, can list equation group about the low-pass prototype component value.So far, just can by the characteristic function of power transmission factor zero, limit, comprehensively go out corresponding low-pass prototype.

The band pass filter that is made of N coupled resonators is carried out circuit analysis as can be known: the transmission coefficient of filter and reflection coefficient can be by the external sort factor Q of coupling matrix [M], input resonator _E1, output resonator external sort factor Q _ENThese three parameters are definite fully, are shown below:

$S_{21}=\frac{2}{\sqrt{q_{e1}{q}_{\mathrm{eN}}}}[A{]}_{N1}^{-1}$

$S_{11}=1-\frac{2}{q_{e1}}[A{]}_{11}^{-1}$

Q in the formula _E1=Q _E1FBW, q _EN=Q _ENFBW, [A] _Ij ^-1The capable j column element of i of the inverse matrix of representing matrix [A], [A]=[q]+P[U]-j[m].Wherein for matrix [q]: [q] ₁₁=1/q _E1, [q] _NN=1/q _EN, all the other elements are zero; P=j Ω; [U] is N rank unit matrix; [m] is the normalization coupling matrix, is defined as [m]=[M]/FBW, and [m] is coupling matrix, and the capable j column element of its i is coupling coefficient M _Ij

Mini strip line resonator adopts square open-loop structure (openloop), and the initial designs domain of band pass filter as shown in Figure 2.In low-pass prototype, think only to exist by J ₃₆The cross-couplings of expression, and do not have other cross-couplings.And through frequency translation, and with behind the alternative lumped-parameter element of microwave structure, new non-adjacent coupling has appearred.Although stiffness of coupling is very weak, can cause the deterioration of band pass filter performance to a certain extent.Therefore we will manage to eliminate this non-adjacent coupling (unwanted crosscoupling).In fact exactly some element in the coupling matrix [M] of microwave band-pass filter is revised, thereby avoided the deterioration of transmission coefficient and reflection coefficient as far as possible.

In the initial domain, just there is non-adjacent coupling between No. 1 and No. 3 resonators, investigates these two resonators now separately.Insert one section L type transmission line when the appropriate location between these two resonators, can find immediately: double resonance peak coupling characteristic has originally become the single resonance peak, illustrates that this section L molded lines has played the effect of decoupling really.So on the basis of initial domain, add two sections L type transmission lines, as shown in Figure 3 (mark 0 expression lead-in wire).Wherein, the live width of L type transmission line is 200 μ m, and the line length of horizontal segment is 4.6mm, and vertically the line length of section is 4.6mm, and vertical section of the L type transmission line spacing with resonator 1 (perhaps 8) is 1mm, and the spacing of horizontal segment and resonator 1 (perhaps 8) is 0.8mm.

This high-temperature superconductor band pass filter is applied to the radio-frequency front-end of satellite communication receiving system, between reception antenna and low noise amplifier.Centre frequency is 1615MHz (L-band), and pass band width is 10MHz.The filter 2 inches diameter, the LaAlO that 0.5mm is thick ₃Substrate is made, LaAlO ₃The two-sided thick high temperature superconducting materia YBa of 0.6 μ m that applies of substrate ₂Cu ₃O ₇(YBCO), adopt the ion sputtering manufacturing process.

Same manufacturing process is adopted in L type transmission line and resonator and tap (i.e. lead-in wire), and time processing forms.

Through such improvement, the reflection loss in the passband is reduced to-20dB by original-15dB, as shown in Figure 4.While transmission coefficient S ₂₁Also improve, be mainly reflected in that insertion loss in the passband reduces and transition band narrows down, as shown in Figure 5.Such corrective measure has also replaced all tuning screws, has not only reduced the manufacturing cost of filter, and has shortened the construction cycle, is suitable for producing in batches.

This filter is equally applicable to the base station radio-frequency front end of mobile communication system.

Claims (1)

1. the adjusting-free satellite communication is with the coupled structure of high temperature superconduction wave filter, contain the square open-loop structure that mini strip line resonator adopts in the band pass filter, it is characterized in that: respectively two of band pass filter both sides connecting lead-in wire resonator and and their another resonators of tiltedly facing toward between the appropriate location respectively insert one section L type transmission line, wherein:

The live width of L type transmission line is 240 μ m;

The line length of L type transmission line horizontal segment is 4.6mm;

The L type transmission line vertically line length of section is 4.6mm;

Above-mentioned horizontal segment is 0.8mm with the spacing that is being connected between two resonators that go between;

Above-mentioned vertical section be connected the lead-in wire two resonators between spacing be 1.0mm.

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