RFWavelength vs. Frequency: Understanding the Relationship
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This page explains the difference between wavelength and frequency.
Where:
- λ = Wavelength in meters
- F = Frequency in Hertz
- ε = Dielectric constant of the propagation medium
- c = Velocity of light, i.e., 3 x 108 m/s
Frequency typically refers to the number of cycles of an electromagnetic wave per second. Wireless systems are often specified to operate at a certain frequency.
Wavelength primarily determines the size of an antenna. Lower frequencies correspond to higher wavelengths, and higher frequencies correspond to lower wavelengths. Shorter wavelengths are useful for concentrating signals in a narrow region, while longer wavelengths are useful for covering a broader area.
Generally, for communication from a satellite to the ground (point-to-multipoint link), a longer wavelength is preferred to cover a larger area. Conversely, for communication from the ground to a satellite (point-to-point link), a shorter wavelength is preferred to more precisely target the receiving system.
The wavelength of a microwave signal ranges from 75cm (at 400MHz) to 1mm (at 300GHz). This is why frequencies above 20GHz are often referred to as millimeter-wave frequencies.
The dielectric constant of the medium significantly impacts the relationship between frequency and wavelength.
The dielectric constant (ε) is a property of the medium through which the electromagnetic wave propagates. For a perfect vacuum, ε = 1; for dry air, ε ≈ 1 (approximately 1.006); and for Teflon, ε ≈ 2-11.
The wavelength of an 18GHz microwave signal in air is about 0.17m, while in Teflon it’s about 0.0053m. This demonstrates that changing the medium can considerably affect the wavelength.
