January 17, 2012
Nippon Telegraph and Telephone Corporation
Nippon Telegraph and Telephone Corporation (NTT, CEO: Satoshi Miura, Tokyo) has successfully developed the world’s smallest wireless transceivers that cover all four of the channels*1 allocated in the 60-GHz band*2 (See Figure 1). They have a maximum transmission rate of 3.8 Gbit/s per channel. Simultaneous four channel transmissions makes the transmission rate about 15 Gbit/s.
The wireless transceiver technologies will be used to download gigabyte-class content from kiosk terminals in stations, convenience stores, and so on.
With the popularization of broad band networks, high-speed and large-capacity broadband wireless system have been researched and developed worldwide.
In order to achieve a noncontact high-speed download system which enables download of gigabyte-class content (e.g., a DVD of 4.7 GB) in about 10 seconds, NTT has worked in research and development of 60-GHz wireless transceivers.
In Japan, as per the revisions to the Radio Act in September 2011, four channels without licenses can be used (Figure 2 ).If these channels are used simultaneously, it will be possible to download gigabyte content within 10 seconds.
NTT has developed the world's smallest wireless transceivers which can use all four channels in the 60GHz-band.
We have realized the miniaturized transceivers by using our wireless module (Figure 3 ) in which a broadband antenna and MMICs*3 are integrated in the multi-layer LTCC*4 substrate. It can cover all four channels.
It is necessary to take into consideration not only the wireless access speed but also the speeds of storage and memory. Using PCs equipped with a high speed bus and storage, the read / write performances of the gigabyte-class HD video were tested. The result confirmed that a high-speed file transfer was possible in real time.
In the future, this wireless transceiver is expected to become a key technology for the non-contact high-speed transmission which can transmit gigabyte class content.
Wireless modules are realized by integration of broadband antenna and MMICs (Figure 3 ).
The antenna is a microstrip antenna with stacked rings formed on a multi-layer LTCC substrate. By using the metal ring as the metal wall and the parasitic element*5, the antenna obtains a high-gain and compact size. It has the antenna gain*6 of 10 dBi in the 60-GHz band.
A Frequency converter MMIC is one of the key devices for full coverage of the 60-GHz band. To make frequency bandwidth broad, we use 4-stage directional couplers. The lumped capacitor lies at the center point of the coupled line. This capacitor effectively increases the coupling, resulting in tight coupling. By properly choosing the physical shape, the bandwidth and the phase characteristics of the coupler are effectively improved. The converter has a relative bandwidth*7 of 15% at 60GHz band.
Since signal frequencies in the substrates in 60-GHz band wireless transceivers become high, coupling between elements or/and lines also becomes high, resulting in degraded signals. By using the stacked substrates and optimization of element arrangements, the coupling between elements and/or lines was suppressed, and high integration was realized.
Transmission rate verification tests of several gigabytes are demonstrated (Figure 4 ).
In this test, one channel of the 60-GHz band was used and read/write speeds in real time using the HD video were measured.
Aiming for smart phone implementation in the future, NTT will continue to miniaturize the transceiver further.
Moreover, NTT will advance the technology further towards implementations of non-contact high-speed transmission of gigabyte class content in kiosk terminals, recorders, home gateways, etc (Figure 5 ).
NTT Science and Core Technology Laboratory Group, PR Section
Information is current as of the date of issue of the individual press release.
Please be advised that information may be outdated after that point.