Leading the research study, Dr Clive Alabaster (pictured) of the Radar Systems Group at Cranfield University, says: “This research study is important because MMW frequencies are increasingly being used in a large number of applications…including airport security check-points.  

“To date, only predictive studies have attempted to describe human skin at these very high frequencies. This research study is for the first time collecting hard data in order to assess the potential risks associated with this technology. 

“The simple fact is that skin exposed to these very high frequencies bears the brunt of radiation exposure. As a result, the skin absorbs MMW frequencies and is heated on the surface with very little power penetrating to other tissue types which are deeper in the body,” explains Dr Alabaster. 

The research programme, sponsored by Japanese measurement equipment manufacturer Anritsu, has arrived at some preliminary results.  

Using the safety benchmark set by the National Radiological Protection Board (NRPB) of 10 milliWatts per square centimetre, Dr Alabaster calculated the temperature rise of skin exposed to this level of MMW radiation over a 30 second period.  

“The initial results on a single skin sample showed that this exposure would cause the surface of the skin to heat by only 0.2°C. The body will hardly notice this increase in temperature and so we can conclude that current legislation will avoid any burning hazard. Our future work in this area will reaffirm these results and seek to extend the study to a much wider variety of skin samples,” adds Dr Alabaster.  

Millimetre waves are radio frequency signals between 30 GHz and 300 GHz (one giga Hertz is 1 000 000 000 cycles per second). They are so-called because the wavelength of such signals is in the order of millimetres ie 10mm at 30 GHz to 1mm at 300 GHz. As such they are exceedingly high in frequency but are beginning to be exploited in a few specialist applications.