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+ a! g/ D- K; p! H5 P传输线 巴伦# c6 g! Y! L. F7 W' u
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; s+ s. V" C( g- o. ?- D! m4 s1.基本原型:
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( m, V, o7 t$ [1 D2.最佳传输条件:
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2.2 传输线长度l应尽可能地小,工程设计中一般取<λ/8
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3.相关公式. I7 l; t5 X1 R( s; H i7 y" G
3.1传输损耗公式:9 P) q" K: [6 h" y8 y# l2 U
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$ x4 P1 p- j$ _0 J5 `4 k, v3.2反射损耗公式为:
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式中。Rg为源阻抗。L0为空芯绕组电感,μ’为磁导率实部, μ”为磁导率虚部。磁损耗角正切tanδm=μ”/μ’。选择μ’高、tanδm大的材料能够 同时满足传输损耗、反射损耗的指标要求。 . u8 Y" }# `$ e
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3.3磁导率
) f0 x1 |( m: }8 Q2 E铁氧体磁芯磁导率随频率变化的影响:
' S. x$ f) ?# T% \磁导率随频率 变化的公式为
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式中,S为斯诺克常数,,fr为截止频率。 ; C) G% n, x, m( }! H0 M" |
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将上式代人传输损耗公式进行分析得知应选择截止频率低、斯诺克常数高的磁芯材料。 ]* @& M- a$ N; T, A/ `6 ~
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综上所述,可以得出磁芯材料的选取原则是要求低频初始磁导率μ’高、截止频率fr低、斯诺克常数S 高、损耗大tanδm的材料。
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* }, P/ B* z! I* }4.ADS 中低端巴伦模型* s, \' e4 n0 W) a. v
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BALUN1 (Balanced-to-Unbalanced Transformer (Ferrite Core)) ) {. H4 p. i5 d) N. J
Symbol
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Range of Usage - N; F1 ^( N0 k) M3 W; S
Z > 0, Len > 0, AL > 09 ?+ R2 |! d: Q6 Z5 a
K ≥ 10 A& h, R: \: m& M, e, V
A ≥ 04 ^% w$ T" X" X) h6 b. e9 T
F ≥ 0
8 n K4 ~7 J$ U$ l) N! bN ≥ 1 ( a5 p v p, B3 n" R; e: \/ s/ @/ }
Parameters * |+ Y5 r+ d4 x2 ?
| Name | Description | Units | Default | | Z | Characteristic impedance of transmission line | Ohm | 50.0 | | Len | Physical length of transmission line | mil | 12.0 | | K | Effective dielectric constant(有效介电常数) | None | 2.0 | | A | Attenuation (per unit length) of transmission line | dB/meter | 0.0 | | F | Frequency for scaling attenuation | GHz | 1.0 | | N | Number of turns | None | 5.0 | | AL | Inductance index(电感指数) | nH | 960.0 | | TanD | Dielectric loss tangent (介质损耗角正切) | None | 0 | | Mur | Relative permeability (相对磁导率) | None | 1 | | TanM | Magnetic loss tangent(磁损耗正切) | None | 0 | | Sigma | Dielectric conductivity (介电导电率) | None | 0 | | Temp | Physical temperature | °C | None | - Q) F6 C9 j, O3 q R
· This component is a length of transmission line(specified by Z, Len, K, A and F) coiled around a ferrite core. % ]& {: X. F2 h4 J9 S) {
Choking inductance Lc accountsfor low-frequency roll-off and is given by
4 b- x! g# B x( tLc = N2 × AL' F& n2 h/ C$ d
A(f) = A (for F = 0)
* \/ @* |( R- [, _+ f1 n6 H# [1 {A(f) = A(F) × file:///C:/Users/wanghai/AppData/Local/Temp/msohtmlclip1/01/clip_image013.png
6 C) l" K7 i0 x2 N# w(for F ≠ 0)
6 b, W( E; j( c8 N pwhere
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F = reference frequency for attenuation
6 m3 Y7 V2 o5 M( _( U4 K" HFor time-domain analysis, an impulseresponse obtained from the frequency-domain analytical model is used. Thiscomponent has no default artwork associated with it.
6 {) w, S9 ~0 W0 F' G" T· The "Temp" parameter is only used in noisecalculations. ( v6 A) R9 w$ Y/ O1 V3 U
· For noise to be generated, the transmission line must belossy (loss generates thermal noise). 4 v* g4 K. h8 E1 i
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& O$ @1 v9 E! q: ?/ z( R5.小节:
A& s, j5 d* _. b7 z' V* S4 ]调节ADS 中的参数可以仿真出巴伦对应的传输损耗; # t" V2 _9 N; i% z. B, y% h: J- T
介电常数环节需要进一步讨论;. " |" \0 e. V' w1 D
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