XRA RF Input Power Levels

This document discusses the recommended power levels at the XRA RF input ports for optimal operation.

The XRA provides two downstream and 1 upstream RF input ports (75 Ω).

Automatic gain control of the XRA ensures that downstream channel power levels stay within their optimal bounds at different stages of the internal processing chain (analog ADC input, digital FPGA input). The employed full-band-capture technology implies that the total RF input power (and not the individual channel power) is the relevant metric for downstream.

In general, the following rule applies:

A downstream RF input signal with total input power between 30 dBmV (-19 dBm) and 51 dBmV (2 dBm) is considered optimal.

If the above condition is not satisfied, the XRA generates a warning (for small deviations) or error message (for large deviations) in the corresponding connector state, along with a recommendation to help you remedy the situation.

Notes

• Exceeding the optimal input power level might permanently damage the XRA.
• For a limited input spectrum (e.g. a few SC-QAM channels), warnings or errors regarding a very low input level can be safely ignored (if the reported MER is acceptable). This is a known issue that might be solved in a future release.

Also, here automatic gain control regulates the internal upstream power levels.

In general, the following rule applies:

An upstream RF input signal with average upstream channel power density between 7 dBmV/1.6 MHz and 28 dBmV/1.6 MHz is considered optimal.

If the above condition is not satisfied, the XRA generates a warning (for small deviations) or error message (for large deviations) in the upstream connector state, along with a recommendation to help you remedy the situation.

Notes

• The average upstream channel power spectral density is estimated from all locked upstream channels (weighted by their active channel bandwidth).
• If no upstream channels are configured on the XRA, no input level information is available and hence, the reported connector status is "OK". This arguably undesirable (or misleading) behavior might be solved in a future release.