A repository & source of cutting edge news about emerging terahertz technology, it's commercialization & innovations in THz devices, quality & process control, medical diagnostics, security, astronomy, communications, applications in graphene, metamaterials, CMOS, compressive sensing, 3d printing, and the Internet of Nanothings. NOTHING POSTED IS INVESTMENT ADVICE! REPOSTED COPYRIGHT IS FOR EDUCATIONAL USE.
Terahertz (THz) Kiosk application offers ultrahigh downloads of digital information to users’ handheld devices. System configuration and multiple paths between the transmitter and receiver have important impact on the achievable data rates. In this paper, the propagation channel of THz Kiosk downloading application is investigated and a stochastic channel model is proposed. Based on channel measurements using a vector network analyzer, a 3-D ray-tracing simulator is calibrated to conduct simulations for an in-depth analysis of the different channel characteristics. Successively, the observed propagation paths are classified and the key channel parameters in time, frequency, and spatial domains are modeled for each type of ray. The resulting stochastic model is evaluated in terms of Rician K-factor and root mean square delay spread. Compared to the reference data, the mean absolute errors of these two metrics of the three investigated scenarios are less than 1.48 dB and 0.07 ns, respectively. The results show that the target 100 gigabits per second data rate is achievable at tens of gigahertz system bandwidth at proper communication distance and higher order modulation schemes. The developed channel model allows system design engineers to generate realizations of propagation channel efficiently for designing Kiosk-fashion close-proximity communication systems in the THz band.
This week, researchers at Hiroshima University showed off a new terahertz transmitter that is just as powerful as its predecessors, but should ultimately prove more affordable for commercial applications. In a demo at the International Solid-State Circuits Conference in San Francisco, they presented a device capable of delivering data at breathtaking speeds of more than 100 gigabits per second at a frequency of 300 gigahertz.
At its very best, the transmitter can shuttle data at 105 Gb/s, which is 2,100 times faster than the peak cellular speeds of 50 megabits per second available through LTE. After a successful demo, the transmitter could find its way into future wireless applications that require low latency and high bandwidth.
Though other transmitters have achieved speedy data rates in the terahertz range before, the group says theirs is the first to also be based on a CMOS integrated circuit, which means it’s potentially more viable for commercial base stations or devices.
“This is quite a step for this kind of technology, because it relies on something that is freely available and could be easily implemented, compared to all of the other techniques,” says Riccardo DegI’Innocenti, a researcher at the University of Cambridge who was not involved in the work.
Terahertz waves are shorter in length and are broadcast at much higher frequencies than the microwaves used today for smartphones, household devices, or military radar. For example, Wi-Fi devices emit waves that measure about 12 centimeters in length at a frequency of 2.4 GHz. Waves in the terahertz range span less than 1 millimeter and start at 100 GHz.
Other teams have demonstrated competing terahertz transmitters that deliver data at speeds even faster than those shown by the Hiroshima group. However, these systems often relied on technology that was bulky or which could not easily scale.
In contrast, the new transmitter has a 2-by-3-mm footprint, and was created using a 40-nanometer CMOS process. “There are many ways also to build a terahertz wireless system,” says DegI’Innocenti. “However, this is still progress because the CMOS technology was sort of lagging behind.”
Minoru Fujishima, a professor at Hiroshima University and a member of the team that developed the transmitter, says the primary advantage of fabricating the device with CMOS is that it will allow manufacturers to sell it at a competitive price if it is commercialized. However, the first run was still rather expensive. The tiny transmitter he demonstrated cost US $100,000 to build.
Fujishima’s group hopes their transmitter can be used in satellite communications, or to set up a wireless link between cellular base stations. “I think that is a very promising application because space cannot be linked by fiber optics,” he says.
Elsewhere, companies and researchers have developed extra-sensitive receivers to reliably detect terahertz waves, which are quickly absorbed as they travel through the atmosphere.
Thomas Küerner, who has worked at TU Braunschweig in Germany on projects in which terahertz transmitters have been developed, calls the new research “quite a milestone.” Alongside Iwao Hosako, who is a coauthor with Fujishima, Küerner is leading the IEEE 802.15 Task Group 3d; the group’s mission isto develop a standard for devices that will operate in the 300-GHz band.
Küerner says the task group is considering four primary applications for 300-GHz devices. One is as a replacement for the wires inside devices with high-speed terahertz links that can send data from one part of the device to another. The second is using terahertz waves to enable the creation of wireless kiosks in retail stores that will let customers instantly download films to their devices instead of having to take a DVD home with them. The third, says Küerner, is to create wireless connections for data centers that can replace fiber optic cables. And the final application is to use terahertz waves for fronthaul or backhaul in cellular networks.
Fiber-wireless transmission in the terahertz-wave band as well as in the millimeter-wave band is the key for a seamless integration of radio and optical networks in a physical layer. Advanced optical fiber communication technology enables a high precision direct waveform transfer between optical and radio domains. For realization of a seamless conversion, an optical-terahertz converter is configured with optical heterodyning for an optical-to-terahertz conversion. Analog optical modulation techniques by an input millimeter-wave signal and an intermediate frequency component after a frequency downconversion are utilized for a terahertz-to-optical conversion. A quadrature phase-shift keying signal transmission in an optical-fiber-to-radio-to-optical-fiber link (fiber-wireless bridge) is successfully demonstrated with the 90 and 300-GHz signals, simultaneously, using an optical frequency comb source. The possible transmission distance in severe weather conditions in these frequency bands is also discussed.
