DEVICE FOR ELECTRICALLY MEASURING AT LEAST ONE PARAMETER OF A MAMMAL'S TISSUE
The device measuring a parameter p that depends on the real and/or imaginary parts of the permittivity of body tissue operates at a frequency f where a temperature change affects the permittivity of free water only weakly. If the parameter p depends on the real part of the permittivity only, the frequency f should be between 6.2 and 10.1 GHz. If the parameter p depends on the imaginary part of the permittivity only, the frequency f should be between 25.5 and 36 GHz. If parameter p depends on the real and imaginary parts of the permittivity, the derivative of the parameter in respect to the real and imaginary parts of permittivity can be used to calculate an optimum frequency range.
1 . A device for measuring at least one parameter p depending on the real part ε′ and/or imaginary part ε″ of the permittivity of body tissue, in particular skin, of a mammal, said device comprising
a signal generator ( 6 ) generating an AC voltage at a frequency f,
an electrode arrangement ( 1 , 2 , 4 ) connected to said signal generator ( 6 ) for generating an alternating electric field in said tissue,
a measuring unit ( 7 , 8 , 10 ) connected to said electrode arrangement ( 1 , 2 , 4 ) for determining said parameter p, wherein said parameter p is a function p (ε′, ε″) depending on the real part ε′ and/or the imaginary part ε″ of said permittivity,
characterized in that said frequency f is such that
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for a temperature T=34° C., a temperature deviation ΔT=4° C. and a threshold value B not larger than 0.05, wherein ε′ H20 (T,f) and ε″ H20 (T, f) are functions describing real and imaginary parts of the permittivity of water as a function of temperature T and frequency f.
2 . The device of claim 1 , wherein said threshold value B is not larger than 0.01.
3 . A device, according to claim 1 , for measuring at least one parameter p depending on the real part ε′ of the permittivity of body tissue, in particular skin, of a mammal, wherein said parameter p is substantially independent of the imaginary part ε″ of said permittivity, wherein said device comprises
a signal generator ( 6 ) generating an AC voltage at a frequency f,
an electrode arrangement ( 1 , 2 , 4 ) connected to said signal generator ( 6 ) for generating an alternating electric field in said tissue,
a measuring unit ( 7 , 8 , 10 ) connected to said electrode arrangement ( 1 , 2 , 4 ) for determining said parameter p,
wherein said frequency f is in a range between 6.2 and 10.1 GHz.
4 . The device of claim 3 , wherein said frequency f is between 7.2-9.2 GHz.
5 . A device according to claim 1 , for measuring at least one parameter p depending on the imaginary part ε″ of the permittivity of body tissue, in particular skin, of a of a mammal, wherein said parameter is substantially independent of the real part ε′ of said permittivity, wherein said device comprises
a signal generator ( 6 ) generating an AC voltage at a frequency f,
an electrode arrangement ( 1 , 2 , 4 ) connected to said signal generator ( 6 ) for generating an alternating electric field in said tissue,
a measuring unit ( 7 , 8 , 10 ) connected to said electrode arrangement ( 1 , 2 , 4 ) for determining said parameter p,
wherein said frequency f is in a range between 25.5 and 36 GHz.
6 . The device of claim 5 , wherein said frequency f is between 27.5 and 32.5 GHz, in particular 29.0 and 31.3 GHz.
7 . The device of claim 1 , wherein said electrode arrangement ( 1 , 2 , 4 ) comprises at least one coplanar waveguide.
8 . A method for operating the device of claim 1 , comprising the step choosing said frequency f such that
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′
p
(
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,
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T
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2
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·
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T
p
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,
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<
B
for a temperature T=34° C., a temperature deviation ΔT=4° C. and a threshold value B not larger than 0.05, wherein ε′ H20 (T,f) and ε″ H20 (T, f) are functions describing real and imaginary parts of the permittivity of water as a function of temperature T and frequency f.
9 . The device of claim 3 , wherein said frequency f is between 7.7 and 8.7 GHz.