By Paul D. Brooks, Time Warner Cable
Many engineers regard the task of overcoming ingress as the most difficult in reliable operation of return plant. Because ingress levels are dependent only on source characteristics and physical coupling "receiving antenna" mechanisms, every dB of operating level is one additional dB of ingress immunity. Since the physical coupling mechanisms have historically been difficult to control, it is essential to operate signal sources at the highest possible levels in order to "buy margin" over ingress sources. This paper will introduce three techniques of ingress margin improvement:
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Leveling of tap port sensitivity through purposeful introduction of loss in the sub-low band.
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Leveling of tap port sensitivity by a new approach to selection of return amplifier input levels.
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A brief examination of the upper limits of existing terminal device output levels and power densities, and the implication of these limits on the selection of the operating points of return amplifiers as these operating points pertain to ingress margin.