Respuesta :
When we consider unguided wireless communications, we must understand the signal attenuation that occurs between transmit and receive antennas.
The information, or message, that we wish to transmit, is modulated onto a frequency carrier, which is then emitted from a transmit antenna in the form of an electromagnetic (EM) wave.
The signal power (watts) received by the antenna is much less than the transmitted power due to attenuation loss. The Friis equation (also known as the Free Space Loss, FSL equation) describes this attenuation loss.Attenuation, as treated in the Friis equation, is the spreading of power over an ever increasing surface area as it propagates away from the transmit antenna.
We can measure how much power resides in a 1 meter2 area as a function of distance from the isotropic antenna.
Power Density, Pd = Pt/(4πd2)
where the (λ/4πd)2 term is sometimes referred to as the path loss or free space loss. The following definitions are assumed:
Pt - The transmitted signal power.
λ - The wavelength of the carrier (i.e., the center frequency of the radiated signal)
d - The distance between the transmitting and receiving antennas.
We can also place the above equation into decibel format:
FSLdB = [FSL] = 20log10(4πd/l) = 20log10(4π) + 20log10(d) - 20log10(l)
Learn more about friis equation from here: https://brainly.com/question/28147107
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