Television – Receiver circuitry – Tuning
Reexamination Certificate
2000-10-20
2004-09-28
Miller, John (Department: 2614)
Television
Receiver circuitry
Tuning
C725S151000
Reexamination Certificate
active
06798463
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a television receiving apparatus capable of receiving a television broadcasting signal in correspondence to two different kinds of channel plans, and more particularly to a television receiving apparatus having an automatic discrimination auto-search function for two kinds of channel plans.
Conventionally, a television receiving apparatus has been provided which is capable of receiving selectively either the TV (television wave) broadcasting or the CATV (cable television) broadcasting. This television receiving apparatus may have an automatic discrimination auto-search function for automatically discriminating whether the receivable channel plan is for TV broadcasting or for CATV broadcasting (e.g., the Unexamined Japanese Patent Application Publication No. Hei 11-4388).
As disclosed in this publication, noticing that the CATV broadcasting has the channels assigned in a specific frequency band (e.g., 300 MHz to 400 MHz) in which none of the TV broadcasting channels are assigned, a CATV mode is discriminated if any broadcasting station exists in the specific frequency band, or a TV mode is discriminated if no broadcasting station exists in the specific frequency band. And in accordance with a result of discrimination, the channel preset is executed, and the channel tuning control is performed, based on the content of the channel preset.
In this way, the conventional television receiving apparatus discriminates a CATV mode or a TV mode in such a manner that the CATV mode is discriminated if a station exists in a specific frequency band in which the TV broadcasting channel is not assigned.
However, with such a conventional discrimination method, since a station may be discriminated to be present due to the influence of the noise, in spite of the station being absent, there is the possibility that a false discrimination may occur by falsely discriminating the CATV mode in spite of the TV mode in essence. Therefore, to reduce such false discrimination as least as possible, the CATV mode may be discriminated in the case where two or more stations exist in a specific frequency band, but in anyway, it is impossible to eliminate the influence of the noise completely.
SUMMARY OF THE INVENTION
This device has been created to solve the above-mentioned problems, and its objective is to provide a television receiving apparatus having improved discrimination accuracy in an automatic discrimination auto-search mode.
In order to solve the above-mentioned problems, a television receiving apparatus of this device capable of receiving signals of a desired frequency in correspondence to a first channel plan having predetermined channel frequencies assigned, and a second channel plan containing the channel frequencies assigned to this first channel plan and having other channel frequencies assigned in a frequency band not assigned to this first channel plan, comprising channel number counting means for counting up the number of station present channels in the channel plan to which a station belongs, if it is judged that the channel frequency of the station is within a fixed frequency range from a center frequency.
In the present device having the above feature, the channel number counting means judges whether or not the channel frequency of a station is within a fixed frequency range from the center frequency, and counts up the number of station present channels in the channel plan to which the station belongs, if the channel frequency of the station is within the fixed frequency range from the center frequency. In this way, in this device, the number of station present channels contained in each channel plan is counted by judging whether or not the channel frequency of the station is within the fixed frequency range from the center frequency during the automatic discrimination auto-search for the channel plan, so that the number of channels can be counted more correctly.
A television receiving apparatus of this device which is capable of receiving signals of a desired frequency in correspondence to a first channel plan having predetermined channel frequencies assigned, and a second channel plan containing the channel frequencies assigned to the first channel plan and having other channel frequencies assigned in a frequency band not assigned to the first channel plan, comprising:
station presence judging means for judging whether a broadcasting station is present or not at a channel frequency assigned to each channel plan by searching all or part of the frequency bands contained in the first channel plan or the second channel plan;
channel number counting means for judging whether or not the channel frequency of the broadcasting station is within a fixed frequency range from a center frequency, if the station presence judging means judges that the broadcasting station is present, and counting up the number of station present channels in the channel plan to which the broadcasting station belongs, if the channel frequency of the broadcasting station is within the fixed frequency range from the center frequency, for all the broadcasting stations which are judged that station is present; and
channel plan discriminating means for comparing the number of channels for the first channel plan and the number of channels for the second channel plan which are counted by the channel number counting means, discriminating a first channel plan mode, if the count number for the first channel plan is greater than or equal to the count number for the second channel plan, or discriminating a second channel plan mode, if the count number for the first channel plan is smaller than the count number for the second channel plan.
In this device having the above feature, the station presence judging means searches all the frequency bands contained in the first channel plan or the second channel plan substantially continuously, and judges whether or not a broadcasting station exists at a channel frequency assigned to each channel plan. When this station presence judging means judges that the broadcasting station is present, the channel number counting means judges whether or not the channel frequency of that broadcasting station is within a fixed frequency range from the center frequency, and counts up the number of station present channels in the channel plan to which the broadcasting station belongs, if the channel frequency of the broadcasting station is within the fixed frequency range from the center frequency, for all the stations which are judged that station is present. Thereafter, the channel plan discriminating means compares the number of channels for the first channel plan and the number of channels for the second channel plan which are counted by the channel number counting means, discriminates a first channel plan mode, if the count number for the first channel plan is greater than or equal to the count number for the second channel plan, or discriminates a second channel plan mode, if the count number for the first channel plan is smaller than the count number for the second channel plan. In this way, in this device, since the number of station present channels contained in each channel plan is counted during the automatic discrimination auto-search for the channel plan, and ultimately the channel plan is discriminated depending on whether the total number of channels for the first channel plan is greater than or equal to the total number of channels for the second channel plan or not, whereby it is possible to eliminate the influence of the noise and discriminate the channel mode at high accuracy.
In the television receiving apparatus of this device, the first channel plan is ground wave broadcasting, and the second channel plan is cable television broadcasting. In a channel plan (TV channel plan) for ground wave broadcasting and a channel plan (CATV channel plan) for CATV broadcasting, the channel frequencies of the channel numbers “2” to “13” for TV broadcasting are the same as the channel frequencies of the channel numbers “2” to “13” for CATV br
Beliveau Scott
Crowell & Moring LLP
Funai Electric Co. Ltd.
Miller John
LandOfFree
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