In-building CATV system, and up-converter and down-converter for use therein

• US 6,615,407 B1
• Filed: 02/18/2000
• Issued: 09/02/2003
• Est. Priority Date: 02/19/1999
• Status: Expired due to Fees

• Current Assignee: Masprodenkoh Kabushikikaisha.
• Original Assignee: Masprodenkoh Kabushikikaisha.
• Inventors: Inaguma, Mitsuhiko
• Primary Examiner(s): Miller, John
• Assistant Examiner(s): BELIVEAU, SCOTT E
• Application Number:
  US09/507,712
• Time in Patent Office: 1,292 Days
• Field of Search: 725/71, 725/78, 725/74, 725/80, 725/111, 725/118, 725/126, 725/127, 725/128, 725/148, 725/149, 725/83
• US Class Current: 725/78
• CPC Class Codes: H04H 60/97 using uplink of the CATV systems
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence

Abstract

A down-converter comprises a frequency division circuit, PLL, and local oscillation circuit to convert a signal from a reference oscillation circuit to a converting reference signal with a constant frequency, and uses this signal to frequency-convert an in-building upward signal to an upward signal able to be transmitted in an external bi-directional CATV system. When the frequency of the converting reference signal deviates from the frequency of the converting reference signal on the side of an up-converter for converting the upward signal to the in-building upward signal on a terminal side, the upward signal cannot be accurately restored. Therefore, the down-converter uses the frequency division circuit to convert the converting reference signal to a transmitting reference signal with a low frequency, and outputs the transmitting reference signal to the terminal side.

Claims

1. An in-building CATV transmission system for communicating a downward signal input from a CATV system to an in-building terminal and for transmitting an upward signal from the terminal to the CATV transmission system, comprising:

an in-building transmission line,

a down-converter, and

an up-converter,

the down-converter connected with the CATV system for receiving the downward signal in a first frequency range and transmitting a corresponding in-building downward signal through the in-building transmission line to the up-converter, the up-converter being connected with the terminal and providing a corresponding downward signal to the terminal,

the up-converter being connected to the terminal for receiving the upward signal from the terminal and transmitting a corresponding in-building upward signal to the down-converter through the in-building transmission line, and

the down-converter receiving the in-building upward signal and providing the corresponding upward signal to the CATV system,

the down-converter including

a frequency generator for generating a first converting reference signal and a reference signal generator for generating a transmitting reference signal wherein the transmitting reference signal frequency is lower than a lowest frequency of the downward signal,

a down-mixer for generating the in-building downward signal by adding the transmitting reference signal to the downward signal, so that the downward signal in the in-building downward signal is in the first frequency range, and

an up-signal receiving mixer connected from the first converting reference signal for extracting the upward signal from an in-building upward signal in a second frequency range and providing the upward signal to the CATV system,

the up-converter including

a receiving filter for extracting the downward signal from the in-building downward signal and providing the downward signal to the terminal and a phase-locked loop circuit for extracting the transmitting reference signal from the in-building downward signal and generating a second converting reference signal having the same frequency as the first converting reference signal, and

an up-signal sending mixer connected from the second converting reference signal for frequency converting the upward signal into the in-building upward signal in the second frequency range and transmitting the in-building upward signal to the up-signal receiving mixer of the down-converter.

2. The in-building CATV transmission system of claim 1 for communicating downward signal input from a CATV system to an in-building terminal and for transmitting an upward signal from the terminal to the CATV transmission system, wherein:

the reference signal generator comprises;

a frequency division circuit for deriving the transmitting reference signal from the first converting reference signal.

3. The in-building CATV transmission system of claim 1 for communicating a downward signal input from a CATV system to an in-building terminal and for transmitting an upward signal from the terminal to the CATV transmission system, wherein:

the frequency generator further comprises;

a pilot regenerator for generating a pilot reference signal from a CATV pilot signal from the downward signal for use as the first converting reference signal for extracting the upward signal from the in-building upward signal, and

a transmission reference signal selector for selecting the CATV pilot signal in the downward signal as the transmitting reference signal of the in-building downward signal.

4. The in-building CATV transmission system of claim 3 for communicating a downward signal input from a CATV system to an in-building terminal and for transmitting an upward signal from the terminal to the CATV transmission system, the frequency generator further comprises:

a pilot signal generator for generating a pseudo pilot reference signal,

a pilot signal detector for generating a pilot detect signal when a pilot signal is present in the downward signal,

a pilot reference signal selector responsive to the pilot detect signal for selecting the pilot reference signal as the first converting reference signal when a pilot signal is present in the downward signal and for selecting the pseudo pilot reference signal as the first converting reference signal when a pilot signal is not present in the downward signal,

transmission reference signal selector being responsive to the pilot detect signal for selecting the transmitting reference signal generated by the reference signal generator as the transmitting reference signal of the in-building downward signal.

5. The in-building CATV transmission system of claim 4, wherein:

the pilot signal generator generates the pseudo pilot reference signal from an output of the frequency generator.

6. The in-building CATV transmission system of claim 4 for communicating downward signal input from a CATV system to an in-building terminal and for transmitting an upward signal from the terminal to the CATV transmission system, wherein:

the reference signal generator comprises;

a circuit for deriving the transmitting reference signal from the output of a pilot signal generator.

7. An in-building CATV transmission system for communicating a downward signal input from a CATV system to an in-building terminal and for transmitting an upward signal from the terminal to the CATV transmission system, comprising:

a down-converter connected with the CATV system for

receiving the downward signal in a first frequency range and transmitting a corresponding in-building downward signal through an in-building transmission line to an up-converter connected with the terminal, and

receiving an in-building upward signal from the transmission line in a second frequency range and providing a corresponding upward signal to the CATV system, and

an up-converter connected to the transmission line for

receiving the in-building downward signal and transmitting a downward signal to the terminal, and

converting an upward signal from the terminal to a corresponding in-building upward signal to the down-converter in the second frequency range,

the down-converter including;

a first frequency generator for generating a transmitting reference signal derived from a first converting reference signal wherein the transmitting reference signal frequency is lower than a lowest frequency of the downward signal,

an in-building downward signal generator for generating the in-building downward signal, wherein the in-building downward signal includes the downward signal and the transmitting reference signal, and

an up-signal converter for converting the in-building upward signal to an upward signal,

the up-converter including

a receiving filter for extracting the downward signal and the transmitting reference signal from the in-building downward signal,

a second signal generator generating a second converting reference signal having the same frequency as the first converting reference signal based on the transmitting reference signal, and

an in-building up-signal generator for generating the in-building upward signal by frequency converting the upward signal into the second frequency range using the second converting reference signal.

8. The in-building CATV transmission system of claim 7 for communicating a downward signal input from a CATV system to an in-building terminal and for transmitting an upward signal from the terminal to the CATV transmission system, wherein:

the frequency generator further comprises;

a pilot regenerator for generating a pilot reference signal from a CATV pilot signal from the downward signal for use as the first converting reference signal for extracting the upward signal from the in-building upward signal, and

a transmission reference signal selector for selecting the CATV pilot signal in the downward signal as the transmitting reference signal of the in-building downward signal.

9. The in-building CATV transmission system of claim 8 for communicating a downward signal input from a CATV system to an in-building terminal and for transmitting an upward signal from the terminal to the CATV transmission system, the frequency generator further comprises:

a pilot signal generator for generating a pseudo pilot reference signal,

a pilot signal detector for generating a pilot detect signal when a pilot signal is present in the downward signal,

a pilot reference signal selector responsive to the pilot detect signal for selecting the pilot reference signal as the first converting reference signal when a pilot signal is present in the downward signal and for selecting the pseudo pilot reference signal as the first converting reference signal when a pilot signal is not present in the downward signal,

transmission reference signal selector being responsive to the pilot detect signal for selecting the transmitting reference signal generated by the reference signal generator as the transmitting reference signal of the in-building downward signal.