38.0 GHz Band
Understanding the 38.0 GHz Band
Before the invention of 5G, the idea of using a 38 GHz frequency to communicate with a moving smartphone was considered science fiction. The 38.0 GHz Band was strictly the domain of Fixed Microwave Backhaul.
The Legacy: Point-to-Point Backhaul
If an enterprise business or a hospital needed a 1 Gigabit internet connection, but there was no fiber-optic cable in the street, they used 38 GHz.
- Engineers would bolt a 1-foot diameter parabolic dish to the roof of the hospital and point it directly at a telecom tower 2 miles away.
- Because the 38 GHz wave is so tiny (7.8 millimeters), the 1-foot dish provides massive Antenna Gain, focusing the energy into an incredibly tight, laser-like beam (usually less than 1.5 degrees wide).
- As long as there was perfect, flawless Line-of-Sight between the two dishes, the 38 GHz link could push Gigabit speeds through the air. However, a single heavy rainstorm would violently absorb the 7.8mm waves, causing temporary 'Rain Fade' outages.
The 5G mmWave Revolution (Band n260)
When 5G needed massive chunks of empty spectrum to achieve true multi-gigabit speeds, regulators looked at the 38 GHz band. Because it was only used for narrow point-to-point links, there was a massive amount of empty space.
The FCC auctioned the 37.0 to 39.5 GHz block to cellular carriers (creating 5G Band n260). To overcome the extreme fragility of the signal, carriers abandoned traditional broadcasting and deployed Massive MIMO Beamforming. A 38 GHz 5G streetlamp dynamically focuses its energy into tight beams, tracking individual users to punch through the atmospheric loss and deliver speeds exceeding 4 Gigabits per second to compatible smartphones.
Key Equations
The 38.0 GHz Band (specifically spanning the 37.0 to 39.5 GHz range) is a critical block of millimeter-wave (mmWave) spectrum that serves a dual purpose...
Key specifications:
38.0 GHz | 39.5 GHz | 38 GHz
Power: P(dBm) = 10log(PmW), 0dBm = 1mW
Comparison
| Band | Range | Wavelength | Application | Standard |
|---|---|---|---|---|
| 38.0 GHz Band | 38 GHz region | 7.9 mm | Primary use | ITU allocation |
| Adjacent lower | 34.2 GHz | 8.8 mm | Related band | Shared spectrum |
| Adjacent upper | 41.8 GHz | 7.2 mm | Related band | Guard band |
| Harmonic 2f | 76.0 GHz | 3.9 mm | Spurious | Filter required |
| Sub-harmonic | 19.0 GHz | 15.8 mm | LO option | Mixer design |
Frequently Asked Questions
Does 38 GHz interfere with 39 GHz?
They are functionally the exact same band. In the United States, the FCC mathematically grouped the 37 GHz, 38 GHz, and 39 GHz blocks together during 'Auction 103,' treating them as one massive, continuous 3,400 MHz playground for 5G mmWave deployments. Carriers will often bond channels across these arbitrary boundaries to maximize speed.
Why use 38 GHz instead of 80 GHz E-Band for backhaul?
Distance and rain fade. The 80 GHz E-band can push a massive 10 Gigabits per second, but because the frequency is so high, it is violently destroyed by rain. An 80 GHz link is usually limited to less than 1.5 miles. A 38 GHz link has lower capacity (usually 1 to 2 Gbps) but survives rain much better, allowing it to reliably cover longer distances up to 3 or 4 miles.
Does 38 GHz require a special smartphone?
Yes. To connect to a 38 GHz network, your smartphone must have a specialized 'mmWave' antenna module built into the side of the glass frame. Because 38 GHz signals are easily blocked by the human hand, modern phones often embed three or four of these tiny antenna arrays around the perimeter of the phone to ensure at least one is always exposed to the cell tower.