Millimeter wave (MMW) radiation is electromagnetic radiation with a wavelength in the millimeter band, which corresponds to frequencies between 30 and 300 GHz. MMW radiation falls in the extremely high frequency (EHF) range of the electromagnetic spectrum.
The term “millimeter wave” is used somewhat loosely, since there is no official definition for this frequency range. In general, however, MMW refers to frequencies that are too high for conventional radio waves and too low for infrared waves. The upper limit of the MMW range may be as high as 1 THz (1000 GHz), but most definitions place it at 300 GHz. The lower limit is more difficult to define, but wavelengths of 1 mm are generally considered to be within the MMW range.
MMW radiation has a number of unique properties that make it useful for a variety of applications. For example, MMW waves can penetrate fog and clouds better than lower-frequency waves, making them ideal for communications and weather sensing applications. Additionally, MMW waves can be generated using relatively small and inexpensive antennas, making them attractive for use in portable devices such as cell phones and laptops.
Because they have a short wavelength, MMW waves also interact strongly with matter. This property can be exploited for imaging purposes; by bouncing MMW waves off objects and analyzing the reflected signal, it is possible to create images with much higher resolution than what is possible with visible light or x-rays. This type of imaging is often referred to as millimeter wave radar or active electronically scanned array radar (AESA). Millimeter wave radar has a wide range of potential applications including airport security screening, police speed detection, military target identification/tracking, and weather monitoring.
One potential downside to using MMW radiation is its interaction with water vapor in the atmosphere. At frequencies above approximately 60 GHz, water vapor absorbs significant amounts of energy from MMW signals passing through the atmosphere. This absorption causes attenuation—a reduction in power—of the signal over distance traveled. As a result, long-distance propagation of MMW signals is generally not possible without some form of signal amplification (e Electromagnetic compatibility ies). However, recent advances in amplifier technology have made it possible to overcome this limitation to some extent; amplifiers capable of boosting signals by up to 1000 times their original strength are now available commercially .1
Despite these challenges ,M MW technology continues t o develop rapidly o wing t o its many potential advantages . For example , research teams i n Japan2 3and South Korea4 5have developed systems capable o f transmitting data at rates exceeding 100 Gbps over distances up t han 10 km using m illimeter wav es . These kinds o f speeds would enable ultrafast wireless internet connections , potentially eliminating th e need f or cables altogether . Other groups6 7are working on developing similar systems that could work even better i n rain or snow , thanks t o new techniques f or “ beam steering ” which direct m illimeter w av es around obstacles .8
In addition t o its uses i n telecommunications , millim eter wav e technol ogy also has promising implications f or medicine . One area where millim eter wav es could be particularly useful is cancer detection ;9 10 because they interact so strongly with matter , m illim eter w av es can provide detailed information about tissue density and composition 11 — information that could help doctors distinguish between healthy tissue and cancerous tumors . Additionally , m illim eter w av es can penetrate deep into th e body without causing harm 12 — meaning that they could potentially be used f or real -time imaging during surgery 13 —and they can be focused on very small areas 14 15to minimize damage t o healthy tissue . 16
While much research still needs t o be done before any definitive conclusions can b e drawn 17 18about th e medical benefits of mill imeter -wave therapy ,19the preliminary results look promising 20 21and suggest that thi s technology ma y one day play an important role in diagnosing and treating cancer patients