WO2000062545A1 - Method and apparatus for using rf detector and delay circuit to reduce noise buildup in rf return systems - Google Patents
Method and apparatus for using rf detector and delay circuit to reduce noise buildup in rf return systems Download PDFInfo
- Publication number
- WO2000062545A1 WO2000062545A1 PCT/US2000/008825 US0008825W WO0062545A1 WO 2000062545 A1 WO2000062545 A1 WO 2000062545A1 US 0008825 W US0008825 W US 0008825W WO 0062545 A1 WO0062545 A1 WO 0062545A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- top terminal
- return system
- output
- selective
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/61—Network physical structure; Signal processing
- H04N21/6106—Network physical structure; Signal processing specially adapted to the downstream path of the transmission network
- H04N21/6118—Network physical structure; Signal processing specially adapted to the downstream path of the transmission network involving cable transmission, e.g. using a cable modem
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/61—Network physical structure; Signal processing
- H04N21/6156—Network physical structure; Signal processing specially adapted to the upstream path of the transmission network
- H04N21/6168—Network physical structure; Signal processing specially adapted to the upstream path of the transmission network involving cable transmission, e.g. using a cable modem
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/10—Adaptations for transmission by electrical cable
- H04N7/102—Circuits therefor, e.g. noise reducers, equalisers, amplifiers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/173—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
- H04N7/17309—Transmission or handling of upstream communications
Definitions
- the present invention relates to the field of cable television systems. More particularly, the present invention relates to the field of minimizing noise buildup in RF return systems by which the set -top terminals of individual cable subscribers communicate with the cable signal headend.
- the RF return systems involved with the present invention may be either wired or wireless .
- the cable television service provider establishes a signal headend from which television signals are distributed over the cable system to the population of subscribers.
- each subscriber receives a set-top terminal that is connected between an outlet to the cable system and the subscriber's television set.
- the set-top terminal allows the subscriber's television to make use of the cable television signal.
- the set-top terminal also sends signals to communicate with the headend. These signals are typically radio frequency (RF) signals.
- RF radio frequency
- the system by which the set-top terminal communicates with the headend is known as an RF return system.
- the return signals are generated by the set -top terminal and are sent to the headend via an RF transmitter in a wireless return system, or over an RF wire-line link in a wired return system.
- the RF transmitters generate a small amount of random noise or other spurious signals that propagate upstream over the RF return system.
- This unwanted signal noise is generated even if the RF transmitter is inactive, i.e., not transmitting a signal.
- Spurious noise can also be created in wired return systems by signal leakage or interference caused by over-the-air short wave or two-way radio or other signal broadcasts.
- the amount of noise generated by or through any one set-top terminal may be almost negligible, particularly with careful design, shielding and construction.
- the buildup of noise from the totality of set- top terminals of all the subscribers to the cable system creates a substantial problem in the RF return system.
- a set-top terminal (101) is provided for each subscriber and connected between the cable system and the subscriber's television set (not shown) .
- the set-top terminal (101) is connected by an RF signal cable (105) to the RF return system (106) .
- an RF switch (102) is interposed along the cable (105) between the set-top terminal (101) and the RF return system (106) .
- the switch (102) is opened when the set-top terminal (101) is not signaling the headend thereby preventing any noise generated from propagating into the RF return system (106) .
- the set-top terminal (101) is also provided with a separate wire connection (301) for controlling the switch (102) .
- the terminal (101) When the set-top terminal (101) needs to signal the headend, the terminal (101) generates a switch control
- the switch (102) opens to again prevent noise from the terminal (101) from reaching the RF return system (106) .
- Fig. 4 illustrates a solution to noise buildup using the same principles in a wireless cable system.
- the set-top terminal (101) is connected via cable (105) with a transverter (201) .
- the transverter (201) is an RF transmitter for wirelessly signaling the headend as an RF return system (116) .
- the set-top terminal (101) has a separate wired connection (401) over which an ON/OFF signal is sent to the transverter (201) to shut the transverter (201) down when the set- top terminal (101) is not using the RF return system (116) to signal the head end. While these arrangements limit the noise buildup in the RF return system, they also raise several problems. It must be noted that the transverter (201) (Fig. 4) , or the RF switch (102) (Fig. 3) , is typically mounted outside the subscriber's house remote from the set-top terminal (101) . Thus, the systems of Figs.
- 3 and 4 require additional wiring between the set -top terminal (101) and the components exterior to the subscriber's home in order to provide the control connections (301) and (401) . Additionally, there is a delay required to signal the switch (102) or the transverter (201) over the connections (301) or (401) , respectively, before the set-top terminal can begin using the RF return system (106) or (116) .
- the present invention may be embodied and described as an apparatus for minimizing noise buildup in a signal return system of
- the apparatus of the present invention includes: a signal detector connected to the output of a set-top terminal; and a selective link between the set-top terminal and the signal return system.
- the selective link is activated by the signal detector so as to operatively connect the set-top terminal with the signal return system when the signal detector detects a signal output by the set-top terminal.
- a delay circuit is preferably used for delaying deactivation of the selective link for a predetermined period of time after the signal detector no longer detects the signal output by the set-top terminal .
- the selective link includes a switch for selectively coupling the set-top terminal with the signal return system.
- the signal detector closes the switch so as to connect the set-top terminal to the signal return system when the signal detector detects a signal output by the set-top terminal.
- the signal detector also signals the switch to open when the output signal from the set-top terminal is no longer detected.
- the delay circuit maintains the switch in a closed state for a predetermined period of time after the signal detector stops detecting the signal output by the set-top terminal. This is particularly important if the output signal from the set-top terminal is time division multiplexed and comprises a series of spaced signal bursts.
- the selective link preferably includes a transverter for transmitting signals from the set-top terminal to the headend.
- the signal detector turns the transverter on when the signal detector detects a signal output by the
- the signal detector also signals the transverter to deactivate when the output signal from the set-top terminal is no longer detected.
- the delay circuit maintains the transverter in an on state for a predetermined period of time after the signal detector stops detecting the signal output by the set-top terminal. Again, this is particularly useful if the output signal from the set -top terminal is time division multiplexed.
- the present invention also encompasses a method for minimizing noise buildup in a signal return system of a cable television system through which a set-top terminal signals a cable system headend.
- the method includes activating a selective link between the set- top terminal and the signal return system in response to detection of a signal output by the set -top terminal.
- the method also includes delaying deactivation of the selective link for a predetermined period of time after the signal output by the set-top terminal ceases.
- FIG. 1 is a block diagram of a device for preventing unwanted noise in a wired RF return system of a cable television network according to the present invention.
- Fig. 2 is a block diagram of a device for preventing unwanted noise in a wireless RF return system of a cable television network according to the present invention.
- Fig. 3 is a block diagram of a conventional device for preventing unwanted noise in a wired RF return system of a cable television network.
- Fig. 4 is a block diagram of a conventional device for preventing unwanted noise in a wireless RF return system of a cable television network.
- Fig. 1 illustrates the principles of the present invention as applied to a wired cable television network with a wired RF return system (106) .
- a set-top terminal (101) is connected via a cable (105) to an RF return system (106) .
- An RF switch (102) is employed between the set -top terminal (101) and the RF return system (106) to prevent spurious noise from the set-top terminal (101) from entering the RF return system (106) when the set-top terminal (101) is not using the RF return system (106) .
- the set-top terminal (101) has no direct control over the open/closed status of the switch (102) . Rather, an RF signal detector (103) is connected to the cable
- the detector (103) detects an RF signal from the set-top terminal (101), it signals the switch (102) to close, thereby connecting the set-top terminal (101) to the RF return system (106) .
- This arrangement eliminates the need for additional wiring between the set-top terminal (101) and the RF switch (102) which is usually located on the exterior of a subscriber's house remote from the set-top terminal (101) .
- the link between the RF detector (103) and the RF switch (102) also includes a delay circuit (104) .
- a typical RF return system (106) uses time-based multiplexing to accommodate the large number of
- TDMA time division multiple access
- the turn-off delay circuit (104) keeps the switch (102) closed, i.e. keeps the set-top terminal (101) connected to the RF return system (106), for a predetermined period of time after the RF detector (103) has ceased detecting an RF signal on the cable (105) .
- the predetermined period during which the turn-off delay circuit (104) maintains the link between the set- top terminal (101) and the RF return system (106) should be minimized. For example, if the transmission bursts in the TDMA scheme being used are separated by 10 seconds, the delay circuit (104) will hold the switch (102) closed for 10 seconds or more after the RF detector (103) ceases to detect an RF signal on the cable (105) . In this manner, only the first transmission burst may experience a delay in the activation of the switch (102) . All the transmission bursts in the signal thereafter will find the switch (102) held closed by the turn-off delay circuit (104) .
- Fig. 2 illustrates the principles of the present invention as applied to a cable system with a wireless RF return system (116) .
- a set-top terminal (101) is connected via a cable (105) to a wireless RF return system (116) .
- a transverter (201) is used to wirelessly transmit signals from the terminal (101) over the RF return system (116) .
- spurious noise from the transverter (201) from propagating over the RF return system (116)
- the set-top terminal (101) has no direct control over the ON/OFF status of the transverter (201) . Rather, an RF signal detector (103) is connected to the cable (105) . When the detector (103) detects an RF signal from the set-top terminal (101) , it turns on the transverter (201) , thereby enabling transmissions from the set-top terminal (101) to the RF return system (116) .
- This arrangement eliminates the need for additional wiring between the set-top terminal (101) and the transverter (201) which is typically mounted on the exterior of a subscriber's house remote from the set-top terminal (101) .
- the link between the RF detector (103) and the transverter (201) also includes a delay circuit (104) .
- the turn-off delay circuit (104) keeps the transverter (201) turned on for a predetermined period of time after the RF detector (103) has ceased detecting an RF signal on the cable (105) .
- the predetermined period during which the turn-off delay circuit (104) maintains the transverter (201) in the "on" state should be minimized. As in the preceding example, if the transmission bursts in the TDMA scheme being used are separated by 10 seconds, the delay circuit
- the present invention allows optimal control of the RF switch (102) or transverter (201) so as to minimize spurious noise in the return system (106 or 116) without a control connection between the set- top terminal (101) and the return system (106 or 116) .
- the delay circuit (104) avoids the problem of delay in activating the selective link between the set-top terminal (101) and the return system (106 or 116) .
- communication from the set-top terminal (101) to the headend is made swift, efficient and free of noise.
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP00920071A EP1173976A1 (en) | 1999-04-14 | 2000-04-03 | Method and apparatus for using rf detector and delay circuit to reduce noise buildup in rf return systems |
AU40665/00A AU4066500A (en) | 1999-04-14 | 2000-04-03 | Method and apparatus for using rf detector and delay circuit to reduce noise buildup in rf return systems |
CA002370516A CA2370516A1 (en) | 1999-04-14 | 2000-04-03 | Method and apparatus for using rf detector and delay circuit to reduce noise buildup in rf return systems |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US29129099A | 1999-04-14 | 1999-04-14 | |
US09/291,290 | 1999-04-14 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2000062545A1 true WO2000062545A1 (en) | 2000-10-19 |
Family
ID=23119711
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2000/008825 WO2000062545A1 (en) | 1999-04-14 | 2000-04-03 | Method and apparatus for using rf detector and delay circuit to reduce noise buildup in rf return systems |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1173976A1 (en) |
AU (1) | AU4066500A (en) |
CA (1) | CA2370516A1 (en) |
TW (1) | TW488166B (en) |
WO (1) | WO2000062545A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2385248A (en) * | 2001-10-06 | 2003-08-13 | Technetix Plc | Signal filtering apparatus for a cable distribution network |
EP1382203A4 (en) * | 2001-04-23 | 2006-09-27 | Scientific Atlanta | Burst-mode digital transmitter |
EP2415260A1 (en) | 2009-04-01 | 2012-02-08 | David Zilberberg | System for reducing noise in a catv home amplifier upstream path and a method thereof |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2316590A (en) * | 1996-08-13 | 1998-02-25 | Motorola Inc | Data communication apparatus and method thereof |
EP0859514A2 (en) * | 1997-02-18 | 1998-08-19 | NextLevel Systems, Inc. | Cable television communication systems |
WO1998039921A1 (en) * | 1997-03-04 | 1998-09-11 | Com21, Inc. | Catv network and cable modem system having a wireless return path |
-
2000
- 2000-04-03 AU AU40665/00A patent/AU4066500A/en not_active Abandoned
- 2000-04-03 EP EP00920071A patent/EP1173976A1/en not_active Withdrawn
- 2000-04-03 WO PCT/US2000/008825 patent/WO2000062545A1/en not_active Application Discontinuation
- 2000-04-03 CA CA002370516A patent/CA2370516A1/en not_active Abandoned
- 2000-04-14 TW TW89107030A patent/TW488166B/en not_active IP Right Cessation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2316590A (en) * | 1996-08-13 | 1998-02-25 | Motorola Inc | Data communication apparatus and method thereof |
EP0859514A2 (en) * | 1997-02-18 | 1998-08-19 | NextLevel Systems, Inc. | Cable television communication systems |
WO1998039921A1 (en) * | 1997-03-04 | 1998-09-11 | Com21, Inc. | Catv network and cable modem system having a wireless return path |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1382203A4 (en) * | 2001-04-23 | 2006-09-27 | Scientific Atlanta | Burst-mode digital transmitter |
GB2385248A (en) * | 2001-10-06 | 2003-08-13 | Technetix Plc | Signal filtering apparatus for a cable distribution network |
GB2385248B (en) * | 2001-10-06 | 2005-08-10 | Technetix Plc | Signal filtering apparatus |
EP2415260A1 (en) | 2009-04-01 | 2012-02-08 | David Zilberberg | System for reducing noise in a catv home amplifier upstream path and a method thereof |
Also Published As
Publication number | Publication date |
---|---|
TW488166B (en) | 2002-05-21 |
AU4066500A (en) | 2000-11-14 |
EP1173976A1 (en) | 2002-01-23 |
CA2370516A1 (en) | 2000-10-19 |
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