Friday fragments - comms news from around the web for 6 December 2013

Avoiding a TV/LTE clash. In some countries, concern is mounting that television signals on the new digital frequencies could experience inference from LTE services in adjacent bands. LTE wasn't widespread when digital TV first started appearing, and some TV manufacturers chose to use inexpensive tuners that might not be capable of filtering out interfering LTE signals. In Japan, the cost of deploying filters or new tuners could run as high as $500 per household.

When delays are a good thing. Lengths of optical fibre are often used when there is a need to introduce a delay in the receipt of signals, such as in phased array radars. But marrying up optical fibre connections with photonic chips is an expensive, time-consuming and tricky operation. DARPA researchers have come up with an alternative - a photonic chip that has an in-built delay waveguide that can replace up to 50 metres of optical fibre. The device provides low loss and true time delay.

How high can you go? German researchers have demonstrated a wireless connection that transmitted signals between transmitter and receiver at a frequency of 237.5 GHz. The technology could lead to high-speed data-transfer systems with speeds of up to 100 gigabits per second. It has the potential to be used in remote regions when the cost of installing an optical fibre network would be prohibitive.

Terahertz, that's how high. Borrowing tools from the semiconductor and MEMS (microelectromechanical systems) fields, DARPA researchers have fabricated a terahertz-class vacuum power amplifier that could help reach those 100-gigabit-per-second rates. “Unlike lasers, the electronics … would be able to handle multiple missions with a single system. For applications like ultrahigh data rate digital communications, these technologies could enable wireless networks … orders of magnitude faster than today's networks."