Method and apparatus for providing feeder cable insertion loss detection in a transmission system without interfering with normal operation
First Claim
1. A method for measuring the insertion loss of a cable having first and second cable ends respectively connected between a signal source and a narrowband device, comprising:
- injecting a non-interfering signal at a first predetermined frequency outside a frequency band of the narrowband device onto the cable proximate the first cable end, wherein injecting the non-interfering signal occurs contemporaneously with a transmission of normal operating signals to the narrowband device at a second predetermined frequency within the frequency band of the narrowband device;
proximate to the signal source, measuring an amplitude of the injected signal;
proximate to the signal source, measuring the amplitude of a reflected signal, the injected signal being reflected by the narrowband device; and
calculating a current insertion loss for the cable, wherein calculating the current insertion loss includes determining a median of the difference between the measured amplitudes of the injected and reflected signals.
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Accused Products
Abstract
A method and apparatus for measuring a change in the insertion loss of a transmission line in a communication system is disclosed. The method provides feeder cable insertion loss detection in a transmission system without interfering with normal operation. The method includes injecting a non-interfering signal at a predetermined frequency onto a cable providing normal operating signals to a narrowband device at a predetermined frequency, measuring the amplitude of the injected signal, measuring the amplitude of a reflected signal, the injected signal being reflected by the narrowband device and processing the amplitude of the injected signal and the amplitude of the reflected signal to derive a current insertion loss for the cable. In addition, the method further includes comparing the current insertion loss to a prior insertion loss and determining the cable to be defective when the current insertion loss differs from the prior insertion loss by a predetermined amount and replacing the cable when the current insertion loss differs from the prior insertion loss by the predetermined amount. The injecting further includes selecting a signal for injection having a frequency and power that does not interfere with the normal operating signals and which causes the signal to reflect back from the narrowband device. The frequency of the selected signal for injection causes the narrowband device to appear to the selected signal for injection as a short or an open. The narrowband device is an antenna, a low noise amplifier, a power amplifier, a filter or a RF-to-light converter for a fiber optic distribution network.
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Citations
22 Claims
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1. A method for measuring the insertion loss of a cable having first and second cable ends respectively connected between a signal source and a narrowband device, comprising:
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injecting a non-interfering signal at a first predetermined frequency outside a frequency band of the narrowband device onto the cable proximate the first cable end, wherein injecting the non-interfering signal occurs contemporaneously with a transmission of normal operating signals to the narrowband device at a second predetermined frequency within the frequency band of the narrowband device;
proximate to the signal source, measuring an amplitude of the injected signal;
proximate to the signal source, measuring the amplitude of a reflected signal, the injected signal being reflected by the narrowband device; and
calculating a current insertion loss for the cable, wherein calculating the current insertion loss includes determining a median of the difference between the measured amplitudes of the injected and reflected signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A transmission system providing operating signals to a narrowband device over a cable, comprising:
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an injection coupler disposed proximate a first end of the cable opposite a second end of the cable coupled to the narrowband device, the coupler injecting a signal onto the cable, the injected signal being selected to have a frequency and power that does not interfere with the existing operating signals and which causes the injected signal to reflect back from the narrowband device;
a forward port, coupled to the cable proximate the injection coupler, the forward port allowing an amplitude of the injected signal to be measured;
a reflection port, coupled to the cable proximate the injection coupler, the reflection port allowing an amplitude of the reflected signal to be measured; and
an insertion loss processor coupled to the forward port and the reflection port to calculate a current insertion loss for the cable, wherein calculating the current insertion loss includes determining an average of the amplitude losses of the injected and reflected signals. - View Dependent Claims (13)
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14. A cellular network, comprising:
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a switching center for controlling the routing of calls in the cellular network;
a plurality of a base stations, coupled to the switching center, each base station comprising a base station transceiver, a narrowband device, and a feeder cable coupling the narrowband device and the base station transceiver via first and second cable ends respectively, wherein each of the plurality of base stations further comprise;
an injection coupler disposed at the base station at a position relative to the feeder cable opposite to the narrowband device, the coupler injecting a signal onto the feeder cable, the injected signal being selected to have a frequency outside a frequency band of the narrowband device that does not interfere with existing operating signals of the narrowband device and which causes the injected signal to reflect back from the narrowband device;
a forward port, coupled to the feeder cable proximate the injection coupler, the forward port allowing an amplitude of the injected signal to be measured;
a reflection port, coupled to the feeder cable proximate the injection coupler, the reflection port allowing an amplitude of the reflected signal to be measured; and
an insertion loss processor coupled to the forward port and the reflection port to calculate a current insertion loss for the cable, wherein calculating the current insertion loss includes determining an average of the amplitude losses of the injected and reflected signals. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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Specification