SI4701 데이터 시트보기 (PDF) - Silicon Laboratories
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SI4701 Datasheet PDF : 69 Pages
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AN383
L = ----o-------eI--r-N----2---A--
Equation 4. Ferrite Loop Inductance Calculation
Where µe = Effective relative permeability of antenna
Signal receiving capability of an antenna is defined by its antenna height. Antenna height of a loop antenna is
derived from Equation by replacing the flux with the inner product of the magnetic field and the surface area of the
coil and is expressed as follows:
he
=
2--------N-----A--------e
Equation 5. Simplified Ferrite Loop Inductance Calculation
Where:
he = Effective antenna height
N = Number of turns in coil
A = Cross-sectional area of ferrite rod
µe = Relative effective permeability of antenna
= Wavelength of signal
Equation 6 is used to rewrite the antenna height in terms of antenna inductance as follows:
he = 2-----c---f--L--o-a--N-n---t--l-r
Equation 6. Effective Antenna Height Calculation
Where:
f = Signal frequency
Lant = Antenna inductance
lr = Length of ferrite rod
c = speed of light
µo = Permeability of air/free space
N = Number of turns in coil
Equation 6 tells us the relationship between antenna height and the factors that affect antenna height. The induced
voltage can be calculated simply by multiplying the antenna height with the electric field strength for an AM signal
(denoted by E) with dimensions of Volts/unit length. Equation 7 expresses this relationship:
Vinduced = E 2-----c---f--L--o-a--N-n---t--l-r
Equation 7. Induced Voltage Calculation
64
Rev. 0.8
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