| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
|
Based on some offline discussion, I would like to reopen comment R1-25 (TCI return loss) to additionally close out the mixing segment return loss issue. I would propose that we add the following to the existing ACCEPT IN PRINCIPLE. === Add the following to close related mixing segment return loss issue === Replace 188.8.2 Return loss (P119 L1-51) with the following: 188.8.2 Return loss and characteristic impedance Mixing segment return loss is specified by the TCI return loss and the characteristic impedance of the cabling used in the mixing segment. See 188.9.1.2 for specification of TCI return loss. Where the mixing segment is comprised of separable cabling segments, the characteristic impedance requirement applies to each individual separable segment longer than 5 cm.
Assemblies of cabling where the segments are shorter than 5 cm may be treated as a connected group until the length exceeds 5 cm. The characteristic impedance shall be 100 ohms +/- 5 ohms at 10 MHz. The most important part of this is the principle of specifying the cabling separate from the TCI loading, and then to cover the matching of the cabling segments when they might be separable (i.e., there is
a chance they come from different batches). 5% is certainly sufficient for our needs (10% peak-to-peak mismatch). +/-10% is probably OK too, but could matter in a worst-case (20% peak-to-peak mismatch) George Zimmerman, Ph.D. President & Principal CME Consulting, Inc. Experts in Advanced PHYsical Communications 310-920-3860 To unsubscribe from the STDS-802-3-SPMD list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-SPMD&A=1 |