The millimeter wave (mmWave) has gotten a lot of attention recently due to its prominence in the operation of 5G wireless technology.
Millimeter waves lie in the band of spectrum between 30 Ghz and 300 Ghz right above the microwave band. It’s also known as extremely high frequency (EHF) or very high frequency (VHF) by the International Telecommunications Union (ITU).
Millimeter waves are being used to power high-speed wireless broadband communications because there are only two ways to increase the speed of wireless data transmission: increase the spectrum utilization, or increase the spectrum bandwidth.
Compared to the first approach, increasing the spectrum bandwidth is simpler and more direct. Without changing the spectrum utilization, increasing the available bandwidth several times over can increase data transmission speeds by a similar amount. The problem is that the commonly used frequencies below 5 GHz are already extremely crowded. Consequently, 5G’s use of millimeter waves uses the second of the two methods to increase transmission speeds.
Based on communication principles, the maximum signal bandwidth in wireless communication is about 5% of the carrier frequency. Therefore, the higher the carrier frequency, the greater the signal bandwidth. That’s why, among the millimeter-wave frequencies, 28 GHz and 60 GHz are the most promising frequencies for 5G. The 28 GHz band can provide an available spectrum bandwidth of up to 1 GHz, while each channel in the 60 GHz band can provide an available signal bandwidth of 2 GHz (a total available spectrum of 9 GHz divided between four channels).
Comparatively, the maximum carrier frequency of the 4G-LTE band, 2 GHz, provides an available spectrum bandwidth of only 100 MHz. Therefore, using millimeter wave frequencies can easily increase the spectrum bandwidth by a factor of 10, allowing for a massive increase in transmission speeds.
The downside is that mmWaves have short wavelengths that range from 10 millimeters to 1 millimeter. They also have high atmospheric attenuation and are absorbed by gases in the atmosphere, which reduces the range and strength of the waves. Rain and humidity can impact performance and reduce signal strength as well — a condition known as rain fade.
Due to its short range of about a kilometer, millimeter waves travels by line of sight, so its high-frequency wavelengths can be blocked by physical objects like buildings and trees.
Want to know more? Tonex offers mmWave Training, a 3-day course that covers mmWave analysis, design and testing.