Page 8

MWEE MARAPR 2014

News Lasers allow ultra-sensitive detection of radio waves When detecting radio waves, ‘noise’ in the detector of the measuring instrument limits how sensitive and precise the measurements can be. Researchers at the Niels Bohr Institute have developed a method where they can avoid noise by means of laser light and can consequently achieve extreme precision of measurements. ‘Noise’ in the detector of a measuring instrument is first and foremost due to heat, that causes atoms and electrons to move chaotically, so the measurements become imprecise. The usual method to reduce noise in the detector of the measuring equipment is therefore to cool it down to 5-10 degrees Kelvin, which corresponds to around -265 °C. This is expensive and still does not enable the weakest signals to be measured. “We have developed a detector that does not need to be cooled down, but which can operate at room temperature and yet hardly has any thermal noise. The only noise that fundamentally remains is so-called quantum noise, which is the minimal fluctuations of the laser light itself,” explains Eugene Polzik, Professor and Head of the research center Quantop at the Niels Bohr Institute at the University of Copenhagen. The method, called optomechanics, is a complex interaction between a mechanical movement and optical radiation. The experiment comprises an antenna, Artists impression by Mette Høst. which picks up the radio waves, a capacitor and a laser beam. The antenna picks up the radio waves and transfers the signal to the capacitor, which is read by the laser beam, i.e., the capacitor and the laser beam make up the detector. However, the capacitor is not an ordinary pair of metal plates. “In our system, one metal plate in the capacitor is replaced by a 50 nanometer thick membrane. It is this nanomembrane that allows us to make ultrasensitive measurements without cooling the system, explains Research Assistant Professor Albert Schliesser, who Wearable ring for gesture control In the spirit of Lord of the Rings, could a ring, in this case a clever piece of technology, become a powerful tool for controlling everything. Ring from Logbar Inc., CA is a wearable input device that lets the user perform a multitude of tasks such as gesture control of smart appliances and devices, send texts, pay bills and so on. The company is currently running a kickstarter campaign and to get the device mass produced, with shipping expected to start in 2014. Ring uses a Bluetooth Low Energy signal to connect to smart devices. Basically Ring detects the movement of the finger that is inside and identifies the gesture being made. Gestures can be performed anytime and anywhere. A lot of the companies IP is in the development of this gesture recognition technology with a particular focus on the accuracy of recognition and power consumption. The device provides four functions: a gesture control function to control home appliances and apps; texting where gesturing of letters in the air enables the user to write a text; payment information transmission to settle payment of bills with a single gesture; and a receive/alert function to detect incoming transmissions/ alerts through built-in vibration and LED. Each application has its own unique gesture mark and is activated when the user performs the designated action. Gestures can also be edited and customised via a smartphone or tablet. Ring uses precise letter recognition software called Ring Font that enables users to type letters anywhere, anytime. has coordinated the the experiments in Quantop’s optomechanical laboratory at the Niels Bohr Institute. He explains that the capacitor is made up of three layers. At the bottom is a chip made of glass with a layer of aluminum, where the positive and negative poles are. The nanomembrane itself is made of silicon nitrate and is coated with a thin layer of aluminum, since there has to be a metallic substance to better interact with the electric field. The chip and the membrane are only separated by a micrometer. The radio wave signal produces fluctuations in the membrane, which in turn enables the signal to be read optically using a laser beam. This is done through a complex interaction between the membrane’s mechanical fluctuations, the electrical properties of the metallic layer and the light that is hitting the membrane. www.nbi.ku.dk/english This enables the use of Twitter, Facebook, or other social network features, sending of texts, and even changing the station on the TV, by performing a simple gesture. To control appliances and devices Ring connects via Bluetooth directly or via Hub pairing. Hub is basically a routing device that enables the sending and receiving of Infrared or WiFI signals to connect Ring to devices that do not support Bluetooth. Ring supports payments using IBeacon or GPS to enable fast payments at participating retails stores, restaurants and even between individuals. It supports direct number payment that only requires tracing a number with a finger or checkmark payment that allows quick payments by gesturing a checkmark. Currently, Ring has been tested with the iPhone, iPad, Andorid, PCs and wearable devices such as Google Glass and smart watches, home control devices, web services including Twitter, Facebook, Evernote, amongst others, and iOS native apps. 8 Microwave Engineering Europe March-April 2014 www.microwave-eetimes.com


MWEE MARAPR 2014
To see the actual publication please follow the link above