In modern local area networks, the communication signals sent from one
computer to another across the lines of transmission are degraded because of reflection at
the receiver. This reflection can be characterized through the impedances of the
transmitter and the receiver, and is defined by the Institute of Electrical and Electronic
Engineers (IEEE) as the S11 return loss. The specifications for S11 return loss in Gigabit
Ethernet are given in terms of magnitude only in the IEEE 802.3 guidelines. This does
not fully take into account, however, the effects of frequency dependant impedances
within the bandwidth of interest. With a range of 30% error in the category 5, or CAT5,
transmission line impedance used in this specification and no further requirements for
individual components within the Gigabit Ethernet port, such as the RJ45 magjack or the
physical layer, the system can easily be out of tolerance for return loss error. A simple
impedance matching circuit could match the CAT5 cable to the physical layer such that
the return loss is minimized and the S21 transmission is maximized.
The first part of the project was commissioned by Dell Computer to characterize
the return loss of all of its platforms. This thesis goes further in the creation of a system
that can balance these two impedances so that the IEEE specification failure rate is
reduced with the lowest implementation cost, size, power and complexity. The return
loss data were used in the second phase of the project as the basis for component ranges
needed to balance the impedance seen at the front of the physical layer to the CAT5 transmission line. Using the ladder network theory, an impedance matching circuit was
created that significantly reduced the S11 return loss in the passband of the equivalent
ladder network. To manage this iterative process, a control loop was also designed.
While this system does not produce the accuracy that a programmable finite impulse
response (FIR) filter could, it does improve performance with relatively minimal cost,
power, area and complexity.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/5856 |
| Date | 17 September 2007 |
| Creators | Kamprath, Richard Alan |
| Contributors | Silva-Martinez, Jose |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 3674998 bytes, electronic, application/pdf, born digital |
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