Fujitsu's Millimeter-band Transmitter Exceeds 10Gbps Data

Tag : Fiber Transmitter

Fujitsu's Millimeter-band Transmitter Exceeds 10Gbps DataTransmission Speeds (Top News, 23 Jun 2008)

Fujitsu Laboratories Ltd and Fujitsu Ltd have developed atransmitter operating in the 70GHz to 100GHz band using impulseradio that is capable of transmitting data at speeds of more than10Gbps. This new development eliminates the need for oscillatorsand other hardware that had been required for use of earliermillimeter-band transmitters, thus enabling a smallermillimeter-band transmitter. As a substitute for fiber-optichigh-speed lines, the new transmitter could be used in wide rangeof applications geared to help bridge the digital divide, includingplatform networks and short-range wireless LANs.

This research was carried out as part of the Research andDevelopment Project for Expansion of Radio Spectrum Resources,which is sponsored by Japan's Ministry of Internal Affairs andCommunications.

Fujitsu and Fujitsu Laboratories developed the followingimpulse-radio technologies to enable the transmitter to achieve10Gbps data transfer speeds:
1. Ultra-short pulse generator
To obtain sufficiently high energy pulses in the 70GHz to 100GHzband, the pulses need to be very short. The smaller the full-widthis at half-maximum (FWHM) for a pulse, the higher the energy itcarries up to a high frequency; effectively, this requires a FWHMbelow 10 picoseconds (ps).

Fujitsu Laboratories' indium-phosphide high electron-mobilitytransistor (InP-HEMT) technology enabled the development of ashort-pulse generator, with a FWHM of 7.6psproven to carry enoughenergy for frequencies above 100GHz.

2. Low-loss filter
The millimeter-band pulse transmitter carries energy in a shortpulse across an extremely wide band, which must be able to extractonly that band needed for transmission. Because the millimeter bandis highly susceptible to losses caused by the skin effect, theresearchers created a multi-stage coupled-line filter using asubstrate of alumina, which is readily obtainable and offersexcellent high-frequency performance.

The result is that the filter passes a signal frequency range of78GHz to 93GHz, and losses within that range (insertion losses)were 1.5dB