Television – Special applications – Manufacturing
Reexamination Certificate
1998-06-08
2001-04-10
Flynn, Nathan (Department: 2711)
Television
Special applications
Manufacturing
C348S192000
Reexamination Certificate
active
06215514
ABSTRACT:
1. Field of the Invention
This invention relates to systems for determining the quality of a communication network. It is disclosed in the context of a CATV system having a return path from each subscriber's terminal, but is believed to have utility in other applications as well.
2. Background Art
The importance of leakage detection and repair in CATV systems is well documented. See, for example, U.S. Pat. No. 4,072,899 and U.S. Pat. No. 5,608,428. The invention relates to a continuous ingress monitoring system which performs ingress detection. The system can be configured to detect total, peak RF power in the return path frequency spectrum. This permits detection of the conditions that cause laser clipping in cable systems that include fiber optic legs. The system further can be configured to detect peak ingress power within specific bands. This permits detection of ingress of the frequencies most likely to disrupt transmissions through, for example, the fiber optic return path of a CATV network.
DISCLOSURE OF THE INVENTION
According to the invention, a noise monitoring system comprises a detector circuit coupled to a signal source. The detector circuit provides an output signal indicative of the signal coupled from the source. A peak follower circuit is coupled to the detector circuit for storing a peak detected output signal from the detector circuit.
According to an illustrative embodiment of the invention, the peak follower circuit is coupled to the detector circuit through a filter circuit having a defined frequency range, or passband. The peak follower circuit stores a peak detected output signal within the defined frequency range.
Further according to an illustrative embodiment of the invention, the filter circuit comprises a low pass filter circuit.
Additionally according to an illustrative embodiment, the system further comprises a mixer for mixing the signal from the signal source with a local oscillator frequency to produce a mixed signal, and for supplying the mixed signal to the detector circuit.
According to an illustrative embodiment, the mixed signal is supplied to the detector circuit through a low pass filter.
Additionally according to an illustrative embodiment, the peak follower circuit has a characteristic attack time so that the peak follower circuit stores a peak detected output signal having a defined minimum duration from the detector circuit.
Further according to an illustrative embodiment, the system comprises a controller coupled to the peak follower circuit and configured to receive the amplitude of the stored peak signal.
According to an illustrative embodiment, the controller is configured to receive the amplitude of the stored peak signal periodically.
Additionally according to an illustrative embodiment, the controller is further configured to generate a message if the amplitude of the stored peak signal exceeds a defined threshold.
Further according to an illustrative embodiment, the system comprises a plurality of detectors and a plurality of peak follower circuits. The controller comprises a controller for sequentially interrogating the plurality of peak follower circuits, for receiving the amplitudes of the stored peak signals from the peak follower circuits in response to the sequential interrogation, for deleting the amplitudes of the stored peak signals after their respective amplitudes have been received, and then for repeating this cycle.
According to illustrative embodiments, the signal source is the return path of a two-way CATV system.
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Barnes & Thornburg
Flynn Nathan
Trilithic, Inc.
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