C/N performance of broadband two-way transmission of RF signals over transmission mediums with limited bandwidth

• US 6,353,490 B1
• Filed: 05/12/1999
• Issued: 03/05/2002
• Est. Priority Date: 05/12/1999
• Status: Expired due to Fees

• Current Assignee: Quintech Electronics & Communications, Inc. (Evertz Technologies Limited)
• Original Assignee: Quintech Incorporated
• Inventors: Singer, Samuel, Krasnikoff, Harry, Morales, Maximo V.
• Primary Examiner(s): Chan, Jason
• Assistant Examiner(s): Bello, Agustin
• Application Number:
  US09/310,510
• Time in Patent Office: 1,028 Days
• Field of Search: 359/162, 359/124, 359/154, 359/125, 359/145, 370/480, 455/103
• US Class Current: 398/66
• CPC Class Codes: H04B 10/271 Combination of different networks, e.g. star and ring configuration in the same network or two ring networks interconnected
• CPC Class Codes: H04B 10/275 Ring-type networks
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications
• CPC Class Codes: H04N 7/22 Adaptations for optical transmission

Abstract

The bandwidth of a two-way broadband signal transmission system is expanded by frequency stacking shared band signals. The up conversion (stacking) and down conversion (destacking) systems utilize matched filters, preferably in a multiplexer configuration, which are directly connected, without a combiner, to output the stacked frequency signal in the case of the up conversion system, and without a splitter to separate the frequency stacked signals in the down conversion system. A single base local oscillator signal is used to generate all of the local oscillator signals needed in the system for up and down conversion. In a coax/HFC cable system in which shared band signals from multiple groups of subscribers are frequency stacked in service area nodes for transmission to a headend containing the down conversion system, the single base local oscillator signal is generated by a redundant high quality local oscillator in the headend and transmitted to all of the service area nodes in the broadband downstream signal. A comb generator in each service area node and in the headend generates the local oscillator signals needed for up/down conversion as harmonics of the base local oscillator signal for system wide frequency stability. The frequency stacked signals can be further frequency stacked for hub-to-hub and hub-to-headend interactive broadband signal transport.

Claims

1. RF block conversion apparatus for processing n shared band RF signals in a broadband two-way communication system, said apparatus comprising:

n signal inputs;

means for receiving a signal of a selected RF frequency for use as a base local oscillator signal;

means for generating from said base local oscillator signal, n−

1 local oscillator signals, each of a different RF frequency;

n−

1 mixers for up/down frequency conversion of n−

1 of said n shared band RF signals between said shared band and n−

1 different frequency bands, to each of which mixers one of said n−

1 local oscillator signals is applied, to convert between one of said shared band RF signals and one of said n−

1 different frequency bands, each mixer connected to a signal input such that there is one signal input that is not connected to a mixer; and

n bandpass filters including n−

1 bandpass filters for each of said n−

1 different frequency bands, each of said n−

1 bandpass filters connected to one of said mixers and one bandpass filter connected to the signal input that is not connected to a mixer, all n of said bandpass filters being connected to a common node at which a frequency stacked RF signal having said n RF signals stacked in n frequency bands is present, said bandpass filters not being connected to a combiner or a splitter.

2. The RF block conversion apparatus of claim 1 wherein n equals at least 2.

3. The RF block frequency conversion apparatus of claim 2 where n is equal to 4 and said bandpass filters comprise a four channel quadraplexer filter.

4. The RF block frequency conversion apparatus of claim 1 wherein said mixers generate inverted outputs used as said n−

1 bands.

5. The RF block frequency conversion apparatus of claim 1 wherein said n−

1 local oscillator signals are harmonics of said base local oscillator signal.

6. The RF block frequency conversion apparatus of claim 5 wherein said means generating said harmonics of said base local oscillator signal comprises a comb generator.

7. The RF block frequency conversion apparatus of claim 1 wherein said apparatus acts as a frequency stacker, further comprising n−

1 shared band bandpass filters to which n−

1 of said n shared band RF signals are applied, each of said n−

1 shared band bandpass filters having an output coupled to an input of one of said mixers.

8. The RF block frequency conversion apparatus of claim 7 wherein said mixer means includes multicarrier amplifiers between said shared band additional bandpass filters and said mixers.

9. The RF block frequency conversion apparatus of claim 8 including an impedance matching pad coupled to an input of one bandpass filter.

10. An RF block conversion apparatus for processing an input RF signal formed by combining n RF signals each of said RF signals being within a frequency band distinct from a frequency band of all other RF signals that were combined to form said input RF signal, said apparatus comprising:

a signal input for receiving said input signal,

n bandpass filters each having an input connected to the signal input and an output, all bandpass filters having a bandwidth such that the bandwidth of each filter corresponds to a bandwidth of one of the signals from which the input signal was formed,

n−

1 mixers, each mixer connected to an output of one of the n bandpass filters, such that there in one bandpass filter not connected to a mixer, wherein each of the bandpass filters has a bandwidth that does not overlap a bandwidth of any of the other bandpass filters; and

means for generating n−

1 oscillator signals, each of a different RF frequency and connected to the mixers such that each mixer receives a different one of the n−

1 oscillator signals and converts a signal from the bandpass filter to which the mixer is connected.

11. The RF block frequency conversion apparatus of claim 10 including multicarrier amplifiers before and after said mixers.

12. The RF block frequency conversion apparatus of claim 11 including an impedance matching pad coupled to the output of said one bandpass filter not connected to a mixer.

13. A broadband two-way communication system comprising:

a headend;

at least one service area node;

a two-way transmission system connecting said at least one service area node with said headend for simultaneous two-way communication, said service area node comprising n branches each carrying a shared bandwidth RF subscriber signal and an up conversion system frequency stacking all of said shared bandwidth RF subscriber signals into a frequency stacking all of said shared bandwidth RF subscriber signal in which said n shared bandwidth RF subscriber signals are incorporated into n separate frequency bands, said frequency stacked RF return signal being transmitted over said two-way transmission system to said headend, said up conversion system including up converters using local oscillator signals to generate said separate frequency bands, and up converter local oscillator means generating said local oscillator signals for up conversion from a base local oscillator signal transmitted from said headend over said two-way transmission system, said headend having means generating a broadband downstream signal which is transmitted over said two-way transmission system to said at least one service area node which distributes said broadband RF downstream signal over each of said n branches, said headend also having a down conversion system for extracting said shared bandwidth RF subscriber signals from said frequency stacked RF return signals as separate signals, said down conversion system comprising bandpass filter means extracting each of said n separate frequency bands from said frequency stacked RF return signal, down converters using n−

1 local oscillator signals to extract said shared bandwidth RF subscriber signals from said separate frequency bands, down converter local oscillator means generating said local oscillator signals for down conversion from said base local oscillator signal; and

oscillator means, located at said headend, for generating said base local oscillator signal.

14. The system of claim 13 comprising a plurality of said service area nodes and wherein said base local oscillator signal is transmitted to each of said plurality of service area nodes over said two-way transmission system.

15. The system of claim 13 wherein said two-way transmission system comprises an optical fiber system, each of said branches comprises a coaxial cable, said service area node includes electro/optic conversion means modulating a carrier light beam on said optical fiber system with said frequency stacked RF return signal for transmission to said headend, and said headend comprises optic/electric conversion means demodulating said carrier light beam and extracting said frequency stacked RF return signal for destacking by said down conversion system.

16. The system of claim 15 wherein said optical fiber system comprises first optic fiber means for transmitting said broadband RF downstream signal, and second optic fiber means for transmitting said frequency stacked RF return signal, said base local oscillator signal being incorporated into said broadband downstream signal and said up converter local oscillator means comprising means extracting said base local oscillator signal from said broadband downstream signal.

17. The system of claim 16 wherein said local oscillator means includes means for generating additional local oscillator signals as harmonics of said base local oscillator signal.

18. The system of claim 17 wherein said means for generating said harmonics of said base local oscillator signal comprises a comb generator and local oscillator filters.

19. The system of claim 16 comprising a plurality of said service area nodes each generating a frequency stacked RF return signal, wherein said second optic fiber means transmits said frequency stacked RF return signals from said plurality of service area nodes to said headend and wherein said headend includes a down conversion system for extracting said shared bandwidth signals as separate RF subscriber signals from each of said frequency stacked RF return signals.

20. RF block conversion means for processing n shared band RF signals, said apparatus comprising:

means for receiving a signal of a selected RF frequency for use as a base local oscillator signal;

means for generating from said base local oscillator signal, n−

1 local oscillator signals, each of a different RF frequency;

n−

1 mixers to each of which one of said n−

1 local oscillator signals is applied to convert between one of said shared band RF signals and n−

1 different frequency bands; and

n bandpass filters including n−

1 bandpass filters for each of said n−

1 different frequency bands converted to said mixer means and one bandpass filter for said shared band, all n of said bandpass filters being connected to a common node at which a frequency stacked RF signal having said n RF signals stacked in n frequency bands is present.

21. The RF block frequency conversion means of claim 20 wherein n−

1 local oscillator signals are harmonics of said base local oscillator signal.

22. The RF block frequency conversion apparatus of claim 21 wherein said means generating said harmonics of said base local oscillator signal comprises a comb generator and filters for each desired local oscillator.

23. The RF block frequency conversion apparatus of claim 22 wherein said shared band is 5-42 MHz.

24. The RF block frequency conversion apparatus of claim 20 wherein n is equal to 4 and said four bandpass filters comprise a quadraplexer filter arrangement or 4 filters in quadraplexer configuration.

25. The RF block conversion apparatus of claim 22 adapted for processing m sets of said n shared band RF signals, said apparatus comprising m sets of mixer means and m sets of bandpass filters each having a common node at which a frequency stacked RF signal having n RF signals stacked in n frequency bands is present;

and

additional mixer means for up/down conversion of m−

1 of said frequency stacked RF signals, said additional mixer means including means generating m−

1 additional oscillator signals each of an RF frequency different from all the other oscillator signals, and m−

1 additional mixers to each of which one of said m−

1 additional oscillator signals is applied to convert between the n frequency bands of one of said stacked frequency RF signals and m−

1 additional different frequency bands; and

m additional bandpass filters including m−

1 additional bandpass filters one for each of said m−

1 additional different frequency bands connected to said additional mixer means and one additional bandpass filter for the mth frequency stacked RF signal, all m of said additional bandpass filters connected to a single node at which a multiple frequency stacked RF signal having said m frequency stacked RF signals stacked in m distinct frequency bands is present.

26. The RF block conversion apparatus of claim 25 wherein n−

1 and said m−

1 local oscillator signals are harmonics of said base local oscillator signal.

27. A method of broadband two-way communication between a headend and a large number of subscribers comprising:

generating a broadband RF downstream signal at the headend;

transmitting said broadband RF downstream signal over a two-way transmission system to a number of service area nodes;

distributing said broadband RF downstream signal from each service area node to associated groups of subscribers over a plurality of branches between the service area node and said groups of subscribers;

sending shared bandwidth RF subscriber signals from each group of subscribers back to the associated service area node over said branches;

frequency stacking said shared bandwidth RF subscriber signals from said plurality of branches in each service are node into a stacked frequency RF return signal using a common base local oscillator signal transmitted from said headend to each of said local nodes via said two-way transmission system;

transmitting said stacked frequency RF return signals from each service area node to said headend;

frequency destacking said stacked frequency RF return signals in said headend to extract said plurality of shared bandwidth RF subscriber signals;

generating said base local oscillator signal; and

distributing said base local oscillator signal to said headend for said frequency destacking and to each of said plurality of subscriber units for said frequency stacking of said shared bandwidth RF subscriber signals.

28. The method of claim 27 wherein,

said step of frequency stacking further includes frequency stacking numbers of said stacked frequency RF return signals into multiple frequency stacked RF return signals;

said step of transmitting said stacked frequency RF return signals comprises transmitting said multiple frequency stacked RF return signals to said headend; and

said step of frequency destacking comprising destacking said multiple frequency stacked RF return signals in said headend to extract said plurality of shared bandwidth RF subscriber signals.

29. The method of claim 28 where said step of frequency stacking numbers of said stacked frequency RF return signals into multiple frequency stacked RF return signals, and said step of destacking said double frequency stacked RF return signals employ said common base local oscillator signal.

30. The method of claim 27 wherein said step of frequency stacking further includes multiple stages of frequency stacking frequency stacked RF return signals for transmission to said headend and multiple stages of frequency destacking at said headend to extract said shared bandwidth RF subscriber signals.

31. The method of claim 30 wherein said multiple stages of frequency stacking and destacking all employ said common base local oscillator signal.

32. The method of claim 27 wherein said step of frequency stacking further comprises frequency converting a stacked frequency RF return signal from a first frequency band to a second frequency band.

33. An RF block conversion apparatus for processing n shared band RF signals in a broadband two-way communication system, said apparatus comprising:

n signal inputs, one for each of the n shared band RF signals,

n−

1 mixers, each mixer attached to one of the n signal inputs,

at least one generator for generating n−

1 oscillator signals, each of a different RF frequency and connected to the mixers such that each mixer receives a different one of the n−

1 oscillator signals and converts one of said shared band RF signals; and

n bandpass filters each having an input and an output, the input of one bandpass filter connected directly to a signal input and each of the other of said bandpass filters having their input connected to one of the mixers such that each mixer is connected to one of the bandpass filters, the outputs of all bandpass filters being connected to a common node and not connected to a combiner or splitter wherein each of the bandpass filters has a bandwidth that does not overlap a bandwidth of any of the other bandpass filters.

34. An RF block conversion apparatus for processing four shared band RF signals in a broadband two-way communication system, said apparatus comprising:

four signal inputs, one for each of the four shared band RF signals,

three mixers, each mixer attached to one of the four signal inputs,

at least one generator generating three oscillator signals, each of a different RF frequency and connected to the mixers such that each mixer receives a different one of the three oscillator signals and converts one of said shared band RF signals; and

four bandpass filters each having an input and an output, the input of one bandpass filter connected directly to a signal input and each of the other of said bandpass filters having their input connected to one of the mixers such that each mixer is connected to one of the bandpass filters, the outputs of all bandpass filters being connected to a common node and not connected to a combiner or splitter wherein each of the bandpass filters has a bandwidth that does not overlap a bandwidth of any of the other bandpass filters.