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Paramagnetic materials are attracted to magnetic fields, hence have a relative magnetic permeability greater than one (or, equivalently, a positive magnetic susceptibility). The magnetic moment induced by the applied field is linear in the field strength, and it is rather weak. It typically requires a sensitive analytical balance to detect the ...
In the high-frequency region, which extends from radio frequencies to the far infrared and terahertz region, the plasma frequency of the electron gas is much greater than the electromagnetic propagation frequency, so the refractive index n of a metal is very nearly a purely imaginary number. In the low frequency regime, the effective relative ...
Permittivity as a function of frequency can take on real or complex values. In SI units, permittivity is measured in farads per meter (F/m or A 2 ·s 4 ·kg −1 ·m −3). The displacement field D is measured in units of coulombs per square meter (C/m 2), while the electric field E is measured in volts per meter (V/m).
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency [1] range from around 20 kHz to around 300 GHz.
In physics, field strength is the magnitude of a vector-valued field (e.g., in volts per meter, V/m, for an electric field E). [1] For example, an electromagnetic field has both electric field strength and magnetic field strength.
Radio waves in this band have wavelengths from ten to one millimeter, so it is also called the millimeter band and radiation in this band is called millimeter waves, sometimes abbreviated MMW or mmWave. [3] Some define mmWaves as starting at 24 GHz, thus covering the entire FR2 band (24.25 to 71 GHz), among others. [4] [5]
This approximation assumes the Q_factor of the antenna is much greater than one; [note 3] in other words the stored energy is much larger than the feed energy per cycle which is equal to the radiated energy. This is a good approximation for a thin antenna driven at resonance.
From the gain factor G, one finds the gain in decibels as: G dBi = 10 log 10 ( G ) . {\displaystyle G_{\text{dBi}}=10\log _{10}\left(G\right).} Therefore, an antenna with a peak power gain of 5 would be said to have a gain of 7 dBi. dBi is used rather than just dB to emphasize that this is the gain according to the basic definition, in ...