WO1997023034A1 - Modulateur agile en frequence - Google Patents

Modulateur agile en frequence Download PDF

Info

Publication number
WO1997023034A1
WO1997023034A1 PCT/US1996/019989 US9619989W WO9723034A1 WO 1997023034 A1 WO1997023034 A1 WO 1997023034A1 US 9619989 W US9619989 W US 9619989W WO 9723034 A1 WO9723034 A1 WO 9723034A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
channel
modulator
controller
transmission path
Prior art date
Application number
PCT/US1996/019989
Other languages
English (en)
Inventor
Joseph P. Preschutti
Steven Lee Flickinger
James Ray Fetterolf
Elwood D. Nonnemacher
Original Assignee
The Whitaker Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Whitaker Corporation filed Critical The Whitaker Corporation
Priority to JP9522941A priority Critical patent/JP2000502525A/ja
Priority to AU14212/97A priority patent/AU1421297A/en
Priority to EP96944393A priority patent/EP0868775A1/fr
Publication of WO1997023034A1 publication Critical patent/WO1997023034A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J1/00—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general
    • H03J1/0008—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor
    • H03J1/0041—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor for frequency synthesis with counters or frequency dividers
    • H03J1/005—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor for frequency synthesis with counters or frequency dividers in a loop
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/16—Multiple-frequency-changing
    • H03D7/161—Multiple-frequency-changing all the frequency changers being connected in cascade
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/10—Adaptations for transmission by electrical cable
    • H04N7/106—Adaptations for transmission by electrical cable for domestic distribution

Definitions

  • This invention relates to modulators for television signals and, more particularly, to a frequency agile modulator controllable to modulate input baseband video and audio signals to a selected defined television channel .
  • a particular application of such a system is the distribution of television programs within a school, which may have a number of classrooms and administrative offices, each having a television monitor. At a given time, it may be desired to provide a television program to selected ones of the classrooms and offices, originating either from a source within one of the classrooms or offices, such as a VCR or video camera, or from an outside source, such as a local cable system.
  • Each of the classrooms and offices is therefore provided with an outlet having an input port and an output port and, when a program originating in a particular office or classroom is to be distributed, the source is connected to the input port of the outlet in that particular room. Since several programs may be distributed throughout the school at a given time, each program must be assigned to a specific and unique television channel so that there is no interference therebetween. It is therefore an object of the present invention to provide a frequency agile modulator by means of which baseband video and audio signals may be modulated onto a selected television channel .
  • the foregoing and additional objects are attained in accordance with the principles of this invention by providing a frequency agile modulator which provides at an output terminal a modulated signal in a selected frequency band corresponding to a defined television channel.
  • a modulator stage receives input baseband video and audio signals and modulates a carrier signal with the input baseband video and audio signals to provide a modulated carrier signal .
  • An up converter stage mixes the modulated carrier signal with a fixed frequency oscillation signal to provide a modulated intermediate frequency signal
  • a down converter stage including a controllable variable frequency oscillator mixes the modulated intermediate frequency signal with the output of the variable frequency oscillator to provide a modulated radio frequency signal in a selected frequency band corresponding to a defined television channel.
  • the modulator also includes a transmission path coupled between the down converter stage and the modulator output terminal, with the transmission path being selectively switchable to an off state wherein the modulated radio frequency signal is prevented from passing therethrough.
  • the modulator further includes a selector by means of which a user can identify a selected television channel, and a controller coupled to the selector for controlling the variable frequency oscillator and the transmission means. The controller is effective in response to the selector changing its identification of a selected television channel for changing the frequency of the variable frequency oscillator to correspond to the newly selected television channel and for causing the transmission path to switch to its off state for a predetermined period of time.
  • the selector includes a first user influenced switch which is selectively actuatable for indicating that the selected television channel is to be incremented and a second user influenced switch which is selectively actuatable for indicating that the selected television channel is to be decremented.
  • the modulator further includes a low pass filter and a high pass filter, each coupled between the output of the transmission means and the output terminal, and switch coupled to the filters for causing only a selected one of the filters to be in the circuit path between the output of the transmission means and the output terminal. The controller controls the switch in accordance with the selected television channel.
  • the drawing shows a frequency agile modulator, designated generally by the reference numeral 10, constructed in accordance with the principles of this invention which is operative for providing at its output terminal 12 a modulated signal in a selected frequency band corresponding to a defined television channel.
  • These television channels, and their corresponding frequency bands are in accordance with a standard specified by the National Television System Committee (NTSC) , as is well known in the art.
  • the input terminals 14 and 16 receive the input baseband video and audio signals, respectively, which are to be so modulated. These baseband signals may originate, for example, from a VCR or television camera, or may be demodulated television program signals received from a local cable company or other source which are to be remodulated to a selected channel .
  • Operation of the modulator 10 is under the control of the controller 18, which is preferably a programmed microprocessor.
  • Inputs to the controller 18 include a channel selector having a user influenced "channel up" push-button switch 20 and a user influenced “channel down” push-button switch 22. These two switches 20, 22 comprise the sole means by which the user can control the modulator 10, other than by applying power thereto, so that such control does not require a technical background.
  • a channel display 24 is provided, which is under the control of the controller.
  • the channel display 24 comprises a two place seven segment light emitting diode display which responds to signals provided by the controller 18 over the leads 26 for displaying a visual representation, in alphanumeric form, of the selected television channel.
  • the user actuates the switches 20, 22 to step through the available channels, as shown on the display 24.
  • the user Upon reaching the desired channel, the user merely ceases actuation of the switches 20, 22.
  • the controller 18 senses lack of actuation of the switches 20, 22 for a predetermined period of time as an indication that the desired channel has been selected.
  • the input baseband video and audio signals received at the input terminals 14 and 16, respectively, are applied as inputs to the modulator stage 28 which includes a carrier frequency oscillator 30.
  • the oscillator 30 provides a carrier signal at a frequency of 45.75 MHz and the baseband video and audio signals are used to modulate this carrier signal.
  • the modulated carrier signal is then provided as an output on the lead 32 to the up converter stage 34 after passing through the bandpass filter 36 which insures that the modulated signal on the output lead 32 is a single vestigial signal.
  • the up converter stage 34 mixes the modulated carrier signal on the lead 32 with a fixed intermediate frequency signal from the oscillator 38, which preferably has a frequency of 200 MHz, to provide a modulated intermediate frequency signal.
  • This signal is passed through the filter 40, which preferably is a bandpass filter centered at 245.75 MHz.
  • the output of the up converter stage 34 on the lead 42 is provided as an input to the down converter stage 44.
  • the function of the down converter stage 44 is to shift the frequency band of the signal on the lead 42 into the frequency band of the television channel selected by the user via the switches 20, 22 and displayed on the display 24.
  • These frequency bands and the alphanumeric representations thereof are standards set by the NTSC.
  • the down converter stage 44 includes a controllable variable frequency oscillator 46, preferably a phase locked loop oscillator, controllable by the controller 18 to provide an oscillation signal which is mixed with the modulated intermediate frequency signal on the lead 42 to provide a modulated radio frequency signal in the selected frequency band corresponding to the selected television channel.
  • This signal is passed to the output lead 48 through the filter 50, which is preferably a low pass filter to eliminate high frequency out of band spurious noise signals.
  • no signals are applied to the output terminal 12 until the modulator 10 has been set to a selected channel for a predetermined period of time.
  • This is accomplished by providing an amplifier stage 52 which is controlled by the controller 18 to block signal transmission therethrough for a predetermined period of time after each operation of the channel up selector switch 20 or the channel down selector switch 22, as will be described in full detail hereinafter.
  • the normal function of the amplifier stage 52 is to amplify the signal to overcome losses in the distribution network.
  • the amplified signal on the lead 54 passes to the filter stage 56 which includes the low pass filter 58 and the high pass filter 60.
  • the filters 58, 60 are coupled between the output of the amplifier stage 52 and the output terminal 12, through the equalizer 62.
  • a switch 64 Connected between the outputs of the filters 58, 60 and the output terminal 12 is a switch 64 which is controlled by the controller 18 so that only one of the filters 58, 60 is connected in the signal path at any given time.
  • the selected filter is chosen in accordance with the selected channel. If a low frequency channel is selected, then the low pass filter 58 is in the signal path. Conversely, if a high frequency channel is selected, then the high pass filter 60 is in the signal path.
  • the purpose of the filters 58, 60 is for noise limiting.
  • the equalizer 62 is provided.
  • the equalizer 62 is a frequency dependent attenuator which attenuates the signal passing therethrough as a monotonically decreasing function of the signal frequency.
  • high frequency signals are attenuated less than low frequency signals.
  • the lower frequency signals are transmitted at a lower level than the higher frequency signals. Accordingly, once the overall gain of the modulator 10 is set, the power level of the signal received at an outlet is substantially frequency independent.
  • the modulator 10 is arranged to block signal transmission during channel changing.
  • the controller 18 causes the amplifier stage 52 to selectively block transmission therethrough by means of the switch 66 which controls the application of power to the amplifier stage 52.
  • the switch 66 controls the application of power to the amplifier stage 52.
  • the controller 18 determines that the user has selected a desired channel due to there being no actuation of the switches 20, 22 for a predetermined period of time, a channel lock signal is transmitted on the lead 68.
  • This channel lock signal causes the switch 66 to close and provide power to the amplifier stage 52, allowing the modulated signal to appear on the output terminal 12.
  • the channel lock signal is received by the channel lock indicator 70, which illustratively includes a light emitting diode which is then energized to inform the user that the channel number shown on the display 24 has been selected and is being used for distributing the program provided at the input terminals 14, 16.
  • the light emitting diode is not energized, this indicates that there is no transmission by the modulator 10. Accordingly, there has been disclosed an improved frequency agile modulator. While an illustrative embodiment of the present invention has been disclosed herein, it is understood that various modifications and adaptations to the disclosed embodiment will be apparent to those of ordinary skill in the art and it is intended that this invention be limited only by the scope of the appended claims .

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Transmitters (AREA)

Abstract

Cette invention concerne un modulateur agile en fréquence qui module des signaux d'entrée vidéo ou audio en bande de base destinés à un canal sélectionné en mode NTSC. Ledit modulateur comporte un microprocesseur qui possède comme entrées un commutateur poussoir servant à incrémenter les canaux et un commutateur poussoir servant à décrémenter les canaux. Un étage d'amplification du modulateur est invalidé par le microprocesseur lorsque le canal est en cours de changement. Un filtre passe-bas réducteur de bruits et un filtre passe-haut réducteur de bruits sont montés en parallèles entre la sortie de l'étage d'amplification et la sortie du modulateur et, en fonction du canal sélectionné, l'un ou l'autre de ces deux filtres est inséré dans le chemin des signaux par le microprocesseur. Un circuit correcteur est prévu en sortie du modulateur de telle sorte que les signaux de fréquence inférieure puissent être transmis à un niveau inférieur à celui des signaux de fréquence supérieure.
PCT/US1996/019989 1995-12-18 1996-12-16 Modulateur agile en frequence WO1997023034A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP9522941A JP2000502525A (ja) 1995-12-18 1996-12-16 周波数エイジル変調器
AU14212/97A AU1421297A (en) 1995-12-18 1996-12-16 Frequency agile modulator
EP96944393A EP0868775A1 (fr) 1995-12-18 1996-12-16 Modulateur agile en frequence

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US874195P 1995-12-18 1995-12-18
US60/008,741 1995-12-18

Publications (1)

Publication Number Publication Date
WO1997023034A1 true WO1997023034A1 (fr) 1997-06-26

Family

ID=21733390

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1996/019989 WO1997023034A1 (fr) 1995-12-18 1996-12-16 Modulateur agile en frequence

Country Status (4)

Country Link
EP (1) EP0868775A1 (fr)
JP (1) JP2000502525A (fr)
AU (1) AU1421297A (fr)
WO (1) WO1997023034A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998017062A1 (fr) * 1996-10-11 1998-04-23 The Whitaker Corporation Regulation de niveau pour un systeme de distribution a large bande
WO2000033457A1 (fr) * 1998-11-30 2000-06-08 General Instrument Corporation Modulateur universel
US7043211B1 (en) 1998-11-30 2006-05-09 General Instrument Corporation Universal modulator
ES2272140A1 (es) * 2004-12-22 2007-04-16 Angel Iglesias, S.A. Modulador de television doble banda lateral.

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002325046A (ja) 2001-04-25 2002-11-08 Alps Electric Co Ltd フィルタ切替回路

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4527194A (en) * 1983-07-27 1985-07-02 Zenith Electronics Corporation Channel assignment for CATV system
US5038404A (en) * 1989-09-01 1991-08-06 General Instrument Corp. Low phase noise agile up converter
EP0582023A1 (fr) * 1992-08-06 1994-02-09 Fritz Fischer Elektronik Dispositif de télévision

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4527194A (en) * 1983-07-27 1985-07-02 Zenith Electronics Corporation Channel assignment for CATV system
US5038404A (en) * 1989-09-01 1991-08-06 General Instrument Corp. Low phase noise agile up converter
EP0582023A1 (fr) * 1992-08-06 1994-02-09 Fritz Fischer Elektronik Dispositif de télévision

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998017062A1 (fr) * 1996-10-11 1998-04-23 The Whitaker Corporation Regulation de niveau pour un systeme de distribution a large bande
WO2000033457A1 (fr) * 1998-11-30 2000-06-08 General Instrument Corporation Modulateur universel
US7043211B1 (en) 1998-11-30 2006-05-09 General Instrument Corporation Universal modulator
ES2272140A1 (es) * 2004-12-22 2007-04-16 Angel Iglesias, S.A. Modulador de television doble banda lateral.

Also Published As

Publication number Publication date
JP2000502525A (ja) 2000-02-29
AU1421297A (en) 1997-07-14
EP0868775A1 (fr) 1998-10-07

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