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传输线 巴伦
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1.基本原型:0 C# P' d! C/ E0 ]* h9 X
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2.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
# C/ g& t6 I1 ~8 @5 l4 @. V! |* j3.1传输损耗公式:5 u. v0 k' D% S' k+ {
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J0 V+ a, A( ~' Z# u0 V3.2反射损耗公式为: ( l& K P8 a) p6 r/ Q' @9 u
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5 n5 O+ O- N7 o# {1 G4 K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。 2 w7 g# _! X2 m, n
1 f. J2 g& t9 e7 n1 o3 S; m3.3磁导率
7 t7 j: V1 n$ F$ _) R1 l铁氧体磁芯磁导率随频率变化的影响: , K8 M1 b4 y( q+ d) M( S( H
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。
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8 E, n2 U7 Y3 s6 \! C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。 2 |: {& c s* T" ]
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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。 0 L+ r8 u4 n5 l
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4.ADS 中低端巴伦模型
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& g+ D( b5 T- O) g" y( x/ }# Z: q& JBALUN1 (Balanced-to-Unbalanced Transformer (Ferrite Core)) ' o/ c v. ^& |' m
Symbol 2 m, {. J) t( K% h
, j# D# H: r" ^& E/ q: _Range of Usage
0 H0 d, ~1 U' s( ~2 y* d# IZ > 0, Len > 0, AL > 0: t" n9 b3 c1 o2 M: y/ K
K ≥ 1
* J! `7 Q! s, r2 n5 i# KA ≥ 0, M% ~" s$ y" ?) c' \
F ≥ 07 E% K- K( h5 v6 }7 d# Y
N ≥ 1
" T$ k: |0 ~9 j: `Parameters $ m/ F6 `" S5 y% i0 U6 E: ]
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 | 6 b A& s/ [4 |7 s/ I6 y0 f
· This component is a length of transmission line(specified by Z, Len, K, A and F) coiled around a ferrite core.
* o9 w8 w9 Y9 G" gChoking inductance Lc accountsfor low-frequency roll-off and is given by
; z# v1 _7 G1 ? J2 b& K2 [8 C% yLc = N2 × AL" m/ [2 f6 L, Y% U% N
A(f) = A (for F = 0)$ b+ H6 d! m. u6 j8 _% G. h) m
A(f) = A(F) × file:///C:/Users/wanghai/AppData/Local/Temp/msohtmlclip1/01/clip_image013.png9 l9 F, D4 j# L9 D2 u6 N, e
(for F ≠ 0)
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f = simulation frequency5 v* X$ d4 W5 l- v5 R" P* |
F = reference frequency for attenuation
. S2 c& d$ x8 E" }For time-domain analysis, an impulseresponse obtained from the frequency-domain analytical model is used. Thiscomponent has no default artwork associated with it. ' B, t6 U7 p4 C; ^$ k
· The "Temp" parameter is only used in noisecalculations.
) o* k% V" h1 @2 e* q% Z: ], C· For noise to be generated, the transmission line must belossy (loss generates thermal noise).
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5.小节:7 f; a- c* O& _; | O( g* I
调节ADS 中的参数可以仿真出巴伦对应的传输损耗; - W8 L! D; s/ H" O0 a$ i" x
介电常数环节需要进一步讨论;.
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