Upstream noise suppression circuits and related radio frequency subscriber drop equipment and methods
Upstream noise suppression circuits include a splitter and a combiner that are connected by first and second communications paths. An information signal removal circuit is provided on the second communications path and is configured to remove an upstream information signal therefrom. A phase shifter is also provided on the second communications path between the upstream information signal removal circuit and the combiner.
1. An upstream noise suppression circuit, comprising:
a radio frequency (“RF”) splitter having an input port, a first output port and a second output port;
an RF combiner having a first input port that is coupled to the first output port of the RF splitter, a second input port that is coupled to the second output of the RF splitter, and an output port;
an information signal removal circuit that is coupled between the second output of the RF splitter and the second input port of the RF combiner, the information signal removal circuit configured to selectively remove an upstream information signal from the second communications path and including a burst detector that is configured to detect the upstream information signal and a delay circuit that delays the upstream information signal by a predetermined amount of time; and
a phase shifter that is coupled between an output of the upstream information signal removal circuit and the second input of the RF combiner,
wherein the connection between the first output port of the RF splitter and the first input port of the RF combiner comprises a first communications path, and the connection between the second output port of the RF splitter and the second input port of the RF combiner comprises a second communications path.
2. The upstream noise suppression circuit of claim 1 , wherein the information signal removal circuit further includes a switching circuit that selectively diverts the upstream information signal from the second communications path in response to a control signal from the burst detector.
3. The upstream noise suppression circuit of claim 1 , wherein the information signal removal circuit further includes a filter circuit that selectively filters the upstream information signal from the second communications path in response to a control signal from the burst detector.
4. The upstream noise suppression circuit of claim 1 , wherein a ground path component of the second communications path is connected to the phase shifter and a signal carrying component of the second communications path is not connected to the phase shifter.
5. The upstream noise suppression circuit of claim 1 in combination with an RF signal amplifier that includes first and second diplexers that separate upstream and downstream communications that are transmitted between the first and second diplexers onto separate upstream and downstream communications paths, wherein the upstream noise suppression circuit is provided on the upstream communication path.
6. The upstream noise suppression circuit of claim 5 , wherein the upstream and downstream communications paths are part of a first communications path that amplifies the downstream signals, the RF signal amplifier further including a second communications path that is a passive, non-interruptible communications path, wherein a second upstream noise suppression circuit is provided on the passive, non-interruptible communications path.
7. The upstream noise suppression circuit of claim 1 in combination with an RF tap unit that includes an RF input port, an RF output port, a plurality of RF tap ports, a power divider network and a directional coupler having an input that is coupled to the RF input port, a first output that is coupled to the RF output port, and a second output that is coupled to the power divider network.
8. The upstream noise suppression circuit of claim 7 , wherein the upstream noise suppression circuit is between the directional coupler and the power divider network.
9. The upstream noise suppression circuit of claim 7 , wherein the upstream noise suppression circuit is one of a plurality of upstream noise suppression circuits, wherein each of the upstream noise suppression circuits is provided between a respective one of a plurality of outputs of the power divider network and a respective one of the RF tap ports.
10. An upstream noise suppression circuit, comprising:
an RF splitter having an input port, a first output port and a second output port;
an RF combiner having a first input port that is coupled to the first output port of the RF splitter, a second input port that is coupled to the second output of the RF splitter, and an output port, where the connection between the first output port of the RF splitter and the first input port of the RF combiner comprises a first communications path, and the connection between the second output port of the RF splitter and the second input port of the RF combiner comprises a second communications path; and
a selective phase shifter circuit that is coupled between the second output of the RF splitter and the second input of the RF combiner, the selective phase shifter circuit configured to selectively phase shift a signal on the second communications path and including a burst detector that is configured to detect the presence of an upstream information signal that is contained within the signal on the second communications path;
wherein the selective phase shifter circuit phase shifts the signal on the second communications path by approximately 180 degrees in response to the burst detector not detecting the presence of the upstream information signal; and
wherein the selective phase shifter circuit passes the signal on the second communications path without phase shifting the signal in response to the burst detector detecting the presence of the upstream information signal.
11. The upstream noise suppression circuit of claim 10 , further comprising a switching circuit that is controlled in response to an output of the burst detector.
12. The upstream noise suppression circuit of claim 10 in combination with an RF signal amplifier that includes first and second diplexers that separate upstream and downstream communications that are transmitted between the first and second diplexers onto separate upstream and downstream communications paths, wherein the upstream noise suppression circuit is provided on the upstream communication path.
13. The upstream noise suppression circuit of claim 10 , wherein the upstream and downstream communications paths are part of a first communications path that amplifies the downstream signals, the RF signal amplifier further including a second communications path that is a passive, non-interruptible communications path, wherein a second upstream noise suppression circuit is provided on the passive, non-interruptible communications path.
14. The upstream noise suppression circuit of claim 10 in combination with an RF tap unit that includes an RF input port, an RF output port, a plurality of RF tap ports, a power divider network and a directional coupler having an input that is coupled to the RF input port, a first output that is coupled to the RF output port, and a second output that is coupled to the power divider network.
15. The upstream noise suppression circuit of claim 14 , wherein the upstream noise suppression circuit is between the directional coupler and the power divider network.