Television – Receiver circuitry – Tuning
Reexamination Certificate
1998-08-24
2002-03-05
Kostak, Victor R. (Department: 2611)
Television
Receiver circuitry
Tuning
C348S725000, C348S678000
Reexamination Certificate
active
06353463
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a TV receiver which receives both an analog broadcasting signal and a digital broadcasting signal and then processes the received analog and digital broadcasting signals. The present invention relates, more particularly, to a TV receiver having an analog/digital dual tuner and control unit for automatically controlling the radio frequency (RF) gain of the dual tuner.
2. Description of the Related Art
A general automatic gain control (AGC) circuit automatically controls the gain of an amplifier so that the level of an output signal is constant although the level of an input signal varies. The AGC circuit used in a TV receiver automatically controls an RF gain of the RF amplifier employed in a tuner and the intermediate frequency (IF) gain of an IF amplifier connected to an output end of the tuner, and thus maintains the level of a restored video signal to be constant although the level of a received broadcasting signal varies.
Meanwhile, an advanced TV receiver can receive and signal-process both an analog broadcasting signal in an analog broadcasting mode and a digital broadcasting signal in a digital broadcasting mode, and restores the received broadcasting signal into an original video signal to then be displayed on a screen.
Referring to
FIG. 1
, a conventional advanced TV receiver having an analog tuner and a digital tuner, where the RF gain of each is individually controlled, will be described.
The TV receiver of
FIG. 1
includes a block for receiving and signal-processing a digital broadcasting signal to be restored into a baseband digital video signal, and a block for receiving and signal-processing an analog broadcasting signal to be restored into an analog composite video signal.
A digital tuner
10
A receives a digital broadcasting signal and then selects a channel corresponding to a channel select control signal output from a controller
18
. The tuner amplifies an RF signal of the selected channel according to a digital automatic gain control signal AGC
d
feedback from a digital automatic gain controller
14
A, and converts the amplified RF signal into an IF signal. A digital IF processor
12
A amplifies and detects the IF signal from the digital tuner
10
A and restores the resultant signal into a baseband digital video signal. The digital automatic gain controller
14
A generates a digital automatic gain control signal AGC
d
for lowering an amplification factor of a high-frequency amplifier (not shown) employed in the digital tuner
10
A if the output level of the digital IF processor
12
A is higher than a predetermined value. The controller
14
A also generates a digital automatic gain control signal AGC
d
for increasing an amplification factor of the high-frequency amplifier (not shown) if the output level of the digital IF processor
12
A is lower than a predetermined value. The generated digital automatic gain control signal is supplied to the digital tuner
10
A.
Meanwhile, an analog tuner
10
B receives a analog broadcasting signal, selects a channel corresponding to a channel select control signal output from the controller
18
. It then amplifies an RF signal of the selected channel according to an analog automatic gain control signal AGG
a
feedback from an analog automatic gain controller
14
B, and converts the amplified RF signal into an IF signal. An analog IF processor
12
B amplifies and detects the IF signal from the analog tuner
10
B and restores the resultant signal into an analog composite video signal. The analog automatic gain controller
14
B generates an analog is automatic gain control signal AGC
a
for lowering an amplification factor of a high-frequency amplifier (not shown) employed in the analog tuner
10
B if the output level of the analog IF processor
12
B is higher than a predetermined value. Alternatively, the controller
14
B generates an analog automatic gain control signal AGC
a
for increasing an amplification factor of the high-frequency amplifier (not shown) if the output level of the analog IF processor
12
B is lower than the predetermined value. The generated analog automatic gain control signal is supplied to the analog tuner
10
B.
A signal processor
15
converts a baseband digital video signal supplied from the digital IF processor
12
A and an analog composite video signal supplied from the analog IF processor
12
B into a luminance signal and a chrominance signal, respectively, and converts the luminance signal and the chrominance signal into a predetermined display format, to then be displayed on a CRT screen
16
. Since the above signal processing method is well known to those skilled in the art, the detailed description thereof will be omitted.
The controller
18
applies a channel select control signal for selecting a corresponding channel to the digital tuner
10
A if the channel selected by a user is a digital broadcasting mode, and applies a channel select control signal for selecting a corresponding channel to the analog tuner
10
B if the channel selected by a user is an analog broadcasting mode. Accordingly, the digital tuner
10
A or analog tuner
10
B selects a corresponding channel according to the channel select control signal output from the controller
18
.
As described above, since the conventional TV receiver shown in
FIG. 1
includes the broadcasting signal processing blocks for respective broadcasting modes independently, there is no close operational relationship between the broadcasting signal processing blocks. The structure of the system is complicated and thereby contributes to production costs. Also, since the TV receiver of
FIG. 1
controls the tuners
10
A and
10
B according to the broadcasting modes of the channels to be viewed, respectively, the control method is complicated and inefficient.
SUMMARY OF THE INVENTION
To solve the above problems, it is the object of the present invention to provide a TV receiver having a dual tuner capable of receiving and selecting an analog broadcasting signal or a digital broadcasting signal and a controller for automatically controlling the radio frequency (RF) gain of the dual tuner, in which the system is simplified and the structure is well organized.
To accomplish the above object of the present invention, there is provided a TV receiver for receiving and signal-processing an analog broadcasting signal and a digital broadcasting signal, the TV receiver has a dual tuner for selecting the channel of a corresponding broadcasting mode according to an applied channel select control signal, from among the received broadcasting signals. The dual tuner also controls the gain of a radio frequency (RF) signal of the selected channel according to an applied automatic gain control signal, and converts the gain-controlled RF signal into an intermediate frequency (IF) signal. The TV receiver also has a signal distributor for distributing the IF signal output from the dual tuner according to a broadcasting mode. It also includes an analog processor for amplifying and detecting the analog IF signal output from the signal distributor to be restored into an analog composite video signal and generating an analog automatic gain control signal for controlling the RF gain of the dual tuner in response to the level of the restored signal and a digital processor for amplifying and detecting the digital IF signal output from the signal distributor to be restored into a baseband digital video signal and generating a digital automatic gain control signal for controlling the RF gain of the dual tuner in response to the level of the restored signal. The TV receiver has a switching portion for selecting one of the automatic gain control signals, output from the respective processors, according to an applied AGC select signal and supplying the selected automatic gain control signal to the dual tuner. The TV receiver also has a controller for applying the channel select control signal of each broadcasting mode to the dual tuner and applying the AGC select signal of each broadcasting
Kostak Victor R.
Samsung Electronics Co,. Ltd.
Sughrue & Mion, PLLC
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