Television – Receiver circuitry – Tuning
Reexamination Certificate
1999-09-07
2002-11-19
Miller, John (Department: 2614)
Television
Receiver circuitry
Tuning
C348S706000
Reexamination Certificate
active
06483554
ABSTRACT:
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C § 119 from an application entitled Method Of Designing Tuner Circuit earlier filed in the Korean Industrial Property Office on the day of Sep. 5
th
, 1998, and there duly assigned Ser. No. 98-36625 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to image signal processing and image signal circuits, and, more particularly, to tuning signal processing and tuning circuits with small output drive currents exhibiting increased drive current capacitance at an output terminal.
2. Description of the Related Art
Typically, a tuning circuit in a video tape recorder (i.e., a VCR) includes an radio frequency converter, a tuner and a demodulator. A broadcasting signal received by an antenna is output to a radio frequency amplifier and an output mode switch through a distributor. The RF converter includes the distributor, an output switch, and a modulator. The tuner includes the RF amplifier, a mixer, and a local oscillator while the demodulator includes a surface acoustic wave (i.e., a SAW) filter, a demodulator, an output buffer, and frequently, an external buffer that is often necessary to provide a current necessary to drive some external appliances that is larger than can be obtained with the output buffer included in the integrated circuit.
In the operation of a typical tuning circuit constructed as an integrated circuit, a broadcast signal is amplified at its radio frequency, mixed with a local oscillation frequency signal of a channel predetermined by the local oscillator in order to convert the broadcast signal into an intermediate frequency. The intermediate frequency is then demodulated. The demodulated video signal is applied through the internal output buffer that provides a small drive current of between approximately 0.5~1 milli-Amperes. A selection switch selects a video signal to apply to a video signal processor from between the video signal from the tuner circuit or a video input signal applied to an input video jack. When the tuner circuit is constructed as an integrated circuit, an externally connected circuit can be driven with a driving current of approximately 0.5~1 milli-Amperes; this range of amplitudes is common in integrated circuits. I have noticed that if a circuit connected to the integrated tuner circuit should happen to require a driving current of 10 milli-Amperes or more however, an external buffer must be incorporated into the tuner circuit between the output buffer in order to obtain a sufficiently large driving current from the integrated circuit. I have found that absent the external buffer, the ability of the integrated tuning circuit deteriorates to the point that attenuation occurs in the high frequency signal components of the video signal, thereby markedly reduces the gain of the higher frequency characteristics of the video signal.
SUMMARY OF THE INVENTION
It is therefore, an object of the present invention to provide an improved tuning process and video image signal tuning circuit.
It is another object to provide tuning signal processing and tuning circuits able to increase drive current capacitance at an output terminal.
It is still another object to provide a process and tuning circuit able to increase drive current capacitance at an output terminal without resort to an external buffer circuit.
It is yet another object to provide a process and tuning circuit able to increase drive current capacitance at an output terminal without resort to an external buffer circuit.
It is still yet another object to provide a process and integrated tuning circuit able to reduce attenuation of the gain of the higher frequency components of a video signal.
It is a further object to provide a tuning signal process and tuning circuit having a small output drive current, that exhibits increased drive current capacitance at an output terminal.
It is a still further object to provide a process and integrated tuning circuit using a buffer that produces a small driving current while minimizing the attenuation of the higher frequency characteristics of video signals.
These and other objects may be attained with a tuning circuit and process that uses a buffer installed within an integrated circuit (IC) providing small-current drive at a video output terminal. The tuning circuit has an RF converter, a tuner and a demodulator. A video output signal from the buffer in the integrated circuit is input to an input circuit for processing a signal without an external buffer, and the amount of attenuation of the gain of the higher frequency components of the video signal due to the low amplitude of the small drive current improves the frequency characteristic of a video signal in the tuner circuit in proportion to the amount of attenuation.
REFERENCES:
patent: 4361854 (1982-11-01), Wolfe
patent: 4814874 (1989-03-01), Adachi
patent: 4947263 (1990-08-01), Yun
patent: 5673088 (1997-09-01), Nah
patent: 5706060 (1998-01-01), Ruitenburg
patent: 5737034 (1998-04-01), Rhee
patent: 5737035 (1998-04-01), Rotzoll
patent: 5742357 (1998-04-01), Griesbaum
patent: 6094229 (2000-07-01), Ohshima
Bushnell , Esq. Robert E.
Miller John
Shang Annan Q.
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