Low-pass step attenuator

A bidirectional communications system having a forward path to a subscriber and a return path from a subscriber, forward path signals being transmitted along the forward path and return path signals being transmitted along the return path, further comprising:

• a filter circuit comprising a first branch that passes forward path signals between a first node and a second node with relatively little or no attenuation, a blocking capacitor connected between the second node and an output terminal, an attenuating branch that uniformly attenuates return path signals connected between the first node and the second node in a first frequency range, and a second branch that passes return path signals connected between the first node and the second node in a second frequency range with relatively little or no attenuation.

A step attenuator for use in CATV applications with bidirectional communications having a forward path to a CATV subscriber and a return path from the CATV subscriber, the step attenuator including a circuit, in a first branch between a first node and a second node, that applies flat loss to frequencies below a first frequency on said return path and passes frequencies above a second frequency higher than said first frequency on said forward path, the step attenuator further comprising a second branch allowing signals from a CATV subscriber to pass without attenuation, the step attenuator further comprising a block capacitor connected between the second node and an output terminal.

A circuit comprising a first branch, a second branch, and a third branch connected between a first node and a second node and a blocking capacitor connected between the second node and an output terminal, said first branch providing a no-attenuation path for signals lower than a first frequency;

• said second branch providing attenuation between a second frequency and a third frequency;
• and said third branch providing a no-attenuation path for signals higher than a fourth frequency.