RE: [SI-LIST] : Definition of Hi-Speed (UC)

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From: Jian Zheng (jian@zeland.com)
Date: Tue Nov 02 1999 - 12:01:11 PST


Hi, Everybody:

I think "high speed" is a relative term. "Speed" in computer and
communication term is more how fast we can transmitt the signals to the
receivers. Just a constant V or I does not carry any signal. Even a signal
with constant pattern such as a sinusoidal signal does not carry any
message. In order to send some message to a receiver, we have to change the
signal. That is how we have the AM (changing the magnitude of the signal),
FM (changing the frequency of the signal), and 1/0 in the digital computer
or digital communications. The "speed" is on how fast you can change the
signal. The faster you can change the signal, the faster you can transmitt
the message to the receivers. However, you will need wider bandwidth.
Constant V or I is just one point at the origin in the frequency axis. A
pure sinusoidal signal is also one point in the frequency axis. Both of them
will not carry any message. A varying signal without a fixed pattern will
occupies a section in the frequency axis, and it will carry much message.
The faster this signal without a fixed pattern is changing. the wider
bandwidth the signal is, and the higher speed the signal can transmitt the
message to the receiver. How is "high speed"? It really depends upon what
system you are talking about. For CPU, 1 GHz is considered high speed. For
CPU bus, 150 MHz is high speed. For microwave communications, people are
talking about 10's of GHz or more than 100 GHz. Thanks!

Best regards,

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Jian-X. Zheng, Ph.D, jian@zeland.com, http://www.zeland.com
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