What Are Microwaves?
Microwaves are a form of electromagnetic radiation with wavelengths ranging from about 30 centimeters down to one millimeter, corresponding to frequencies between 300 MHz (0.3 GHz) and 300 GHz. The inherent properties of microwaves make them suitable for applications such as wireless communications, radar systems, navigation, heating and cooking food, and even studying the universe.
Microwave Spectrum Allocations
| Band | Frequency Range | Wavelength Range | Typical Applications |
|---|---|---|---|
| L band | 1 – 2 GHz | 30 – 15 cm | GPS, mobile phones |
| S band | 2 – 4 GHz | 15 – 7.5 cm | Weather radar, microwave ovens |
| C band | 4 – 8 GHz | 7.5 – 3.8 cm | Satellite communication |
| X band | 8 – 12 GHz | 3.8 – 2.5 cm | Military & civil radar |
| Ku band | 12 – 18 GHz | 2.5 – 1.7 cm | Satellite TV broadcasting |
Frequency allocations may vary by country.[1]
As this table shows, different frequency bands within the microwave range are assigned to various applications by government regulators. Higher microwave frequencies allow for faster communication and better radar resolution.
Brief History
The existence of radio waves was predicted by James Clerk Maxwell‘s famous equations in the 1860s. But it was German physicist Heinrich Hertz who first experimentally generated and detected radio waves in 1887. By improving spark gap generator circuits, Hertz produced the first microwaves wavelengths as short as 66 cm, or a frequency of 455 MHz.
However, Hertz failed to find applications for them at the time. The subsequent development of radio communications relied on the longer wavelength ranges. It was not until the 1940s that microwave generation technology like the cavity magnetron made shorter wavelengths more usable.
Global Microwave Device Sales Revenue
| Year | Revenue (billion USD) |
|---|---|
| 2005 | 17.3 |
| 2010 | 32.6 |
| 2018 | 48.4 |
| 2025 (predicted) | 102.7 |
Source: Stratistics MRC[2]
The market size for microwave devices like radar systems and satellite communications has rapidly grown in recent decades as microwave technologies become integral across modern telecommunications infrastructure. In fact, total industry revenues are forecasted to double over the next 5 years due to expanding 5G wireless network rollouts.
Major Uses and Applications
Communications
Microwaves became essential for modern wireless communications because their small wavelength allows the use of conveniently sized directional antennas to precisely focus signals between two points. Their ability to carry vast amounts of telephone, television, internet and other data traffic relies on several technologies:
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Additional sections on science & research, transportation, military updated below…
Comparing Old and New Radar Systems
1960s Radar Array
- Single large parabolic antenna
- Output power: 1 MW
- Range: 100 nautical miles
- Unable to track while scanning
- Prone to clutter & interference
Modern Phased Array
- Hundreds of small antenna elements
- Output power: 10 kW
- Range: 250 nautical miles
- Track while scan capability
- Advanced digital signal processing
Early microwave radar systems relied on a single large transmission dish spinning mechanically to scan an area. But modern phased array radars can electronically steer their beam rapidly using banks of small antenna elements coordinated by phase shifters. This allows advanced capabilities like tracking incoming missiles during flight.
Particle Physics Experiments
Beyond applications sending beams through air, high-power microwaves focused into compact cavities can accelerate charged subatomic particles like electrons to nearly the speed of light.
Facilities called linear particle accelerators are enabling cutting-edge physics experiments searching for exotic new particles and forces. For example, the Linac Coherent Light Source in California provides researchers with intense X-rays by colliding microwave-accelerated electron beams into special targets.
Are Microwaves Safe?
While occasional exposure to low-levels from common devices like phones and WiFi routers show no clear health impacts in science studies so far, we still must take care regarding microwave safety. Extremely high-intensity beams like radar facilities utilize can cause severe tissue damage by rapidly heating human skin just as in an oven.
Regular users of microwave-emitting equipment are advised to maintain a reasonable distance from active antenna sources. Engineering controls like shielding microwave ovens helps limit unnecessary exposure. Fortunately, incorporating adequate safeguards has made consumer and commercial microwave devices safe for operators during ordinary use.
Conclusion
In closing, microwave radiation has transformed technology infrastructure critical to modern life – enabling wireless connectivity, precise navigation, defense systems and scientific research. As new high-frequency 5G networks roll out across the world, our exploitation of microwaves‘ unique capabilities is only slated to grow. Maintaining basic safety limits and precautions for these invisible energy beams remains reasonable public policy.
References
[1] Ofcom – United Kingdom Frequency Allocation Table, August 2022[2] Microwave Devices Market – Global Forecast to 2025, Stratistics MRC, January 2020
