Picture signal transmitting system using CATV network in which the local oscillator is transmitted separately

• US 6,184,920 B1
• Filed: 01/23/1998
• Issued: 02/06/2001
• Est. Priority Date: 07/17/1997
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Arai, Koji, Masuda, Shigefumi, Yatsuka, Hiroyuki
• Primary Examiner(s): Flynn, Nathan
• Assistant Examiner(s): VU, NGOC K
• Application Number:
  US09/012,502
• Time in Patent Office: 1,110 Days
• Field of Search: 455/70, 455/71, 455/5.1, 455/6.3, 348/6, 348/8, 348/11-13
• US Class Current: 725/127
• CPC Class Codes: H04N 5/38 Transmitter circuitry for the transmission of television signals according to analogue transmission standards H04N5/14 takes precedence
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence
• CPC Class Codes: H04N 7/104 Switchers or splitters
• CPC Class Codes: H04N 7/20 Adaptations for transmission via a GHz frequency band, e.g. via satellite

Abstract

A picture signal transmitting system using a CATV network sends a picture signal from a transmission path to subscribers by using a radio transmitter and receiver, and in the picture signal transmitting system, there is no physical wire connection from a tap off of the transmission path to subscribers. The picture signal transmitting system using a CATV network includes a CATV center, a first radio transmitter and receiver connected to said CATV center through a CATV transmission path, and provided near a subscriber'"'"'s house for concurrently sending out a side band signal obtained by up-converting a picture signal of a frequency bandwidth including a plurality of channels with a local oscillation signal of which level is larger than that of said side band signal, and the local oscillation signal, and a second radio transmitter and receiver provided in the subscriber'"'"'s house for separately receiving the picture signal and the local oscillation signal sent out from the first radio transmitter and receiver, and down-converting the frequency bandwidth of the received picture signal with the received local oscillation signal to an intermediate frequency bandwidth.

Claims

1. A picture signal transmitting system using a CATV network comprising:

a CATV center;

a first radio transmitter and receiver connected to said CATV center through a CATV transmission path, and provided near a subscriber'"'"'s house for sending out a side band signal obtained by up-converting of a picture signal having a frequency bandwidth including a plurality of channels with a local oscillation signal, and the local oscillation signal of which level is larger than that of said side band signal, separately; and

a second radio transmitter and receiver provided in said subscriber'"'"'s house for separately receiving the side band signal and the local oscillation signal sent out from the first radio transmitter and receiver, and mixing the received side band signal with the received local oscillation signal to down-convert the received side band signal to an intermediate frequency bandwidth.

2. The picture signal transmitting system according to claim 1,

wherein said second radio transmitter and receiver modulates a control signal with the received local oscillation signal and sends the modulated control signal to the first radio transmitter and receiver.

3. The picture signal transmitting system according to claim 1,

wherein the second radio transmitter and receiver superposes a modulation signal with a narrow frequency bandwidth over the received local oscillation signal, and sends out the superposed local oscillation signal as a control signal.

4. The picture signal transmitting system according to claim 3,

wherein said first radio transmitter and receiver receives the control signal as a channel selection request, and controls to select channels according to the received control signal.

5. The picture signal transmitting system according to claim 3,

wherein said first radio transmitter and receiver includes a modulator for modulating the picture signal with the local oscillation signal, and a controller for controlling the frequency of the local oscillation signal according to the control signal sent from the second radio transmitter and receiver, so that the frequency bandwidth of the modulated picture signal is shifted.

6. The picture signal transmitting system according to claim 5,

Wherein the first radio transmitter further includes a band pass filter having a fixed pass frequency bandwidth, connected to an output of the modulator for passing the modulated signal from the modulator within the fixed pass frequency bandwidth.

7. The picture signal transmitting system according to claim 6,

Wherein the fixed pass frequency bandwidth is assigned to each of subscribers, differently.

8. The picture signal transmitting system according to claim 1,

Wherein the second radio transmitter and receiver includes an injection synchronizing oscillator, to which the received local oscillation signal is injected.