Two Conductors in Parallel (Unbalanced) Above Ground Plane
For D << d, h
Z0= (69/ε½) log10{(4h/d)[1+(2h/D)2]-½}

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Single Conductor Above Ground Plane
For d << h
Z0= (138/ε½) log10(4h/d)

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Two Conductors in Parallel (Balanced) Above Ground Plane
For D << d, h1, h2
Z0= (276/ε½) log10{(2D/d)[1+(D/2h)2]-½}

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Two Conductors in Parallel (Balanced) Different Heights Above Ground
Plane
For D << d, h1, h2
Z0= (276/ε½)log10{(2D/d)[1+(D2/4h1h2)]-½}

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Single Conductor Between Parallel Ground Planes
For d/h << 0.75
Z0= (138/ε½) log10(4h/πd)

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Two Conductors in Parallel (Balanced) Between Parallel Ground Planes
For d << D, h
Z0= (276/ε½) log10{[4h tanh(πD/2h)]/πd}

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Balanced Conductors Between Parallel Ground Planes
For d << h
Z0= (276/ε½) log10(2h/πd)

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Two Conductors in Parallel (Balanced) of Unequal Diameters
Z0= (60/ε½) cosh-1
(N)
N = ½[(4D2/d1d2) - (d1/d2) - (d2/d1)]

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Balanced 4-Wire Array
For d << D1, D2
Z0= (138/ε½) log10{(2D2/d)[1+(D2/D1)2]-½}

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Two Conductors in Open Air
Z0= 276 log10(2D/d)

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5-Wire Array
For d << D
Z0= (173/ε½) log10(D/0.933d)

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Single Conductor in Square Conductive Enclosure
For d << D
Z0≈ [138 log10(ρ) +6.48-2.34A-0.48B-0.12C]/ε½
A = (1+0.405ρ-4)/(1-0.405ρ-4)
B = (1+0.163ρ-8)/(1-0.163ρ-8)
C = (1+0.067ρ-12)/(1-0.067ρ-12)
ρ= D/d

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Air Coaxial Cable with Dielectric Supporting Wedge
For d << D
Z0≈ [138 log10(D/d)]/[1+(ε-1)(θ/360)]½)
ε = wedge dielectric constant
θ= wedge angle in degrees

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Two Conductors Inside Shield (sheath return)
For d << D, h
Z0= (69/ε½) log10[(ν/2σ2)(1-σ4)]
ν = h/d σ = h/D

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Balanced Shielded Line
For D>>d, h>>d
Z0=
(276/ε½) log10{2ν[(1-σ2)/(1+σ2)]}
ν = h/d σ = h/D

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Two Conductors in Parallel (Unbalanced) Inside Rectangular Enclosure
For d << D, h, w
∞
Z0= (276/ε½) {log10[(4h tanh(πD/2h)/πd)-
∑ log10[(1+μm2)/(1-νm2)]}
m=1
μm=sinh(πD/2h)/cosh(mπw/2h)
νm=sinh(πD/2h)/sinh(mπw/2h)

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