Non-disruptive sweep measurement using coherent detection
Non-disruptive sweep measurements using low power coherent signals overcome the limitations of prior art frequency response systems for cable networks. Modulated or unmodulated, e.g. continuous wave (CW), test signals are transmitted into the network at a first or input point (input point is in the head end for forward sweep; input point is in the field for reverse sweep). The test signals are transmitted continuously at multiple frequencies, so as a composite they form a wideband, OFDM-like (orthogonal frequency-division multiplexing) waveform. A receiver at a second or output point generates power reading measurements, from which the frequency response of the network is produced.
1. An apparatus operable to test a cable network, the apparatus comprising:
an interface to receive a multi-frequency test signal injected into the cable network at a first point, the test signal injected at a power level below that of active signals on the cable network, so as to substantially not disrupt transmission of the active signals; and
a signal processor to detect power readings of the received multi-frequency test signal received at a second point in the cable network, wherein a frequency response of the cable network is operable to be generated based on the power readings.
2. The apparatus of claim 1 , wherein the second point in the cable network is upstream from the first point.
3. The apparatus of claim 1 , wherein the second point in the cable network is downstream from the first point.
4. The apparatus of claim 1 , wherein the multi-frequency test signal is at least 30 dB below the active signals in the cable network.
5. The apparatus of claim 1 , wherein the multi-frequency test signal is at or below a noise floor of the active signals on the cable network.
6. The apparatus of claim 1 , wherein the multi-frequency test signal comprises a continuous sweep of carrier signals.
7. The apparatus of claim 1 , wherein the multi-frequency test signal comprises a sweep of at least 100 carrier signals.
8. An apparatus operable to test a cable network, the apparatus comprising:
a transmitter to transmit a multi-frequency test signal to the cable network at first point thereof at a power level below that of active signals on the cable network, so as to substantially not disrupt the transmission of the active signals, wherein a receiver is to detect power readings of the multi-frequency test signal to determine a frequency response of the cable network.
9. The apparatus of claim 8 , wherein the receiver is to receive the multi-frequency test signal at a second point in the cable network that is upstream from the first point.
10. The apparatus of claim 8 , wherein the receiver is to receive the multi-frequency test signal at a second point in the cable network that is downstream from the first point.
11. The apparatus of claim 8 , wherein the multi-frequency test signal is at least 30 dB below the active signals in the cable network.
12. The apparatus of claim 8 , wherein the multi-frequency test signal is at or below a noise floor of the active signals on the cable network.
13. The apparatus of claim 8 , wherein the multi-frequency test signal comprises a continuous sweep of carrier signals.
14. The apparatus of claim 8 , wherein the multi-frequency test signal comprises a sweep of at least 100 carrier signals.
15. The apparatus of claim 8 , wherein the multi-frequency test signal comprises unmodulated carrier signals.
16. The apparatus of claim 8 , wherein the multi-frequency test signal comprises modulated carrier signals.
17. A system for testing a cable network, the system comprising:
a transmitter to insert a multi-frequency test signal into the cable network at a first point at a power level below that of active signals on the cable network, so as to substantially not disrupt transmission of the active signals; and
a receiver to detect power readings of the multi-frequency test signal received at a second point of the cable network, wherein the frequency response is operable to be generated based on the power readings.
18. The system of claim 17 , wherein the multi-frequency test signal is at least 30 dB below the active signals in the cable network.
19. The system of claim 17 , wherein the multi-frequency test signal is at or below a noise floor of the active signals on the cable network.
20. The system of claim 17 , wherein the multi-frequency test signal comprises a continuous sweep of carrier signals spaced between 100 kHz and 500 KHz apart.