The propagation of electromagnetic waves, such as radio waves, is influenced by their frequency. In general, lower frequency waves tend to travel farther than higher frequency waves. This phenomenon is primarily due to two factors:
a. Diffraction: Diffraction is the bending of waves around obstacles or the spreading of waves as they pass through openings. Lower frequency waves have longer wavelengths, making them less susceptible to diffraction. They can wrap around obstacles more effectively, allowing them to travel over longer distances and even penetrate through buildings and other obstructions.
b. Absorption and scattering: Higher frequency waves are more likely to be absorbed or scattered by various objects in their path, such as buildings, trees, and other environmental elements. This absorption and scattering can lead to a reduction in signal strength and range for higher frequency waves compared to lower frequency waves.
- Use of microwaves in cellular phones:
Microwaves are used in cellular phones for several reasons:
a. Spectrum availability: The radio frequency spectrum is a limited resource, and different frequency bands are allocated for various applications. The use of microwaves (typically in the 1-6 GHz range) for cellular communication allows for more efficient use of the available spectrum because higher frequencies can support higher data transfer rates. This is important for handling the increasing demand for mobile data services.
b. Data capacity: Microwaves have higher bandwidths, which means they can carry more data compared to lower frequency radio waves. This is crucial for supporting modern smartphone functionalities, such as video streaming, high-quality voice calls, and other data-intensive applications.
c. Antenna size: The higher frequency of microwaves allows for the use of smaller antennas in mobile devices, which is desirable for portable devices like cell phones.
d. Line-of-sight propagation: Microwaves exhibit a more line-of-sight propagation behavior, which can be advantageous in urban environments with many tall buildings. They can bounce off buildings and other structures to reach their destination, compensating for the reduced diffraction compared to lower frequency radio waves.
Overall, the choice of using microwaves in cellular phones is a trade-off between data capacity, spectrum efficiency, and practical considerations related to antenna size and urban propagation challenges. Different frequency bands are allocated for various applications to strike the right balance between these factors.