Television – Basic receiver with additional function – For display of additional information
Reexamination Certificate
2001-08-01
2004-08-03
Lee, Michael H. (Department: 2614)
Television
Basic receiver with additional function
For display of additional information
C348S553000, C348S569000, C348S725000, C348S726000, C455S226400, C455S025000, C375S324000
Reexamination Certificate
active
06771318
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a digital broadcasting demodulation apparatus which demodulates digital data of digital broadcasting which are received by an antenna.
BACKGROUND ART
In recent television broadcasting, services using satellites or CATV (Cable Television) have been performed with digital compression technology, digital modulation/demodulation technology and the like. Video is coded according to MPEG 2 (Motion Picture Experts Group 2). As a digital modulation scheme, a QPSK (Quadrature Phase Shift Keying) scheme is adopted in satellite broadcasting and a QAM (Quadrature Amplitude Modulation) scheme is adopted in CATV. In the US, the ground wave digital broadcasting (DTV) was started in the Autumn of 1998, and video compression using MPEG 2 is executed and services are performed in a digital modulation 8VSB (Vestigial Side Bands) scheme.
At present, in ordinary households in the US, loop-type or dipole-type simple indoor antennas are generally used in receiving the NTSC (National Television System Committee) analog ground wave broadcasting, and relatively good video can be viewed on television. It is also expected that the digital ground wave broadcasting will be received with the simple indoor antennas in many households. Hereinafter, an example of the digital ground wave broadcasting receiving apparatus is described with reference to the drawings.
FIG. 6
is a block diagram illustrating a structure of a conventional digital broadcasting demodulation apparatus.
The conventional ground digital broadcasting demodulation apparatus
1000
comprises a tuner
302
for selecting a signal of a channel from a RF signal which is received by a loop-type or dipole-type indoor antenna
1
, a SAW (Surface Acoustic Wave) filter
303
for subjecting the selected modulated signal to the band limitation, an AMP
304
for amplifying the signal, an orthogonal detector
305
for executing orthogonal detection to the amplified signal using a-mixer, a first low-pass-filter (hereinafter, referred to as LPF)
306
, an A/D converter
307
for converting an analog signal into a digital signal, a synchronization establishment unit
308
for reproducing a clock and detecting a Sync signal of packet data, a waveform equalizer
309
, a forward error corrector
311
, a data output terminal
311
, an AGC (Automatic Gain Control) signal detector
312
, a second LPF
313
, and a Voltage Control Oscillator (hereinafter, referred to as VCO)
321
.
The operation of the so-constructed conventional digital broadcasting demodulation apparatus is described.
The broadcasting station compresses coded digital video data and audio data, multiplexes the compressed data with various types of information, converts the data into data in a packet format (hereinafter, referred to as packet data), subjects the packet data to RF modulation, and transmits the data to viewers.
The viewer manually changes the direction of the simple indoor antenna
1
so as to obtain a received power having a good C/N (Carrier to Noise Ratio). The antenna
1
receives the RF demodulated signals and transmits the signals to the tuner
302
of the digital broadcasting modulation apparatus.
The tuner
302
selects a signal of a channel which is selected by the viewer from the RF modulated signals, subjects the selected signal to gain control, and outputs an intermediate frequency (IF) signal.
The SAW filter
303
imposes band limitation on the IF signal which is output by the tuner
302
so as to obtain a predetermined frequency characteristics, and outputs the signal to the AMP
304
.
The AMP
304
receives a control signal from the AGC signal detector
312
(which is described later), amplifies the signal which is transmitted by the SAW filter
303
, and outputs the amplified signal to the orthogonal detector
305
.
The orthogonal detector
305
subjects the signal which is output by the AMP
304
to orthogonal detection, and obtains a baseband signal.
The first LPF
306
removes excess higher harmonic components of the baseband signal. The baseband signal whose higher harmonic components are removed is transmitted to the A/D converter
307
and the AGC signal detector
312
.
The AGC signal detector
312
detects an envelope of the baseband signal.
The envelope which is detected by the AGC signal detector
312
is transmitted to the AMP
304
via the second LPF
313
as the AGC signal and the amplitude of the received modulated signal is controlled by the AMP
304
. In addition, the AGC signal is supplied by the AMP
304
to the tuner
302
to control the operation of the tuner
302
. That is, the AGC signal executes feedback control for both of the tuner
302
and the AMP
304
.
On the other hand, the baseband signal which is input to the A/D converter
307
is converted in a digital signal and supplied to the synchronization establishment unit
308
.
The synchronization establishment unit
308
extracts a clock reproduction control signal from the baseband signal and outputs the clock reproduction control signal to the VCO
321
while detecting a Sync signal of the packet data and outputting the packet data to the waveform equalizer
309
.
The waveform equalizer
309
controls frequency characteristics of the data, removes distortion of the data occurring due to interference such as ghost or multi-path, and outputs the data to the Forward Error Corrector (FEC)
310
.
The Forward Error Corrector
310
corrects errors in the packet data which are output from the waveform equalizer
309
, and outputs the corrected data to the output terminal
311
as MPEG transport data. The transport data which are output from the output terminal
311
are subjected to decoding processing by a decoder (not shown), and video data are displayed on a predetermined monitor (not shown) and audio data are output from a predetermined audio output unit (not shown).
The VCO
321
feeds back an oscillated frequency signal in accordance with the clock reproduction signal to the A/D converter
307
. Here, the signal which is fed back to the A/D converter
307
is generated by a PLL.
However, changes in the image quality of video of the digital ground wave broadcasting are steeper near thresholds of C/N which indicates whether the video display is sufficiently possible or not, as compared with changes in the image quality of video of the analog ground wave broadcasting such as NTSC. That is, in the digital broadcasting, when the C/N is within the thresholds, video having certain image quality can be displayed under all conditions of a received radio wave. However, when the C/N is outside the thresholds even slightly, the video is interrupted or frozen.
When the digital ground wave broadcasting is received using the loop-type or dipole-type simple indoor antenna, the direction of the antenna is changed manually, thereby finding an optimum value of the directivity or receiving sensitivity. At this time, it is required that the received radio wave is displayed on a monitor as video when manually moving the antenna and that the image quality of video on the monitor is judged every time the antenna is moved. However, it is very complicated to manually decide the receiving direction or position of the antenna, and it is difficult to decide the optimum direction and position of the antenna.
DISCLOSURE OF THE INVENTION
To solve the above-mentioned problems, a digital broadcasting demodulation apparatus which demodulates signals of digital broadcasting received by an antenna, comprises a signal demodulation unit for demodulating a signal of a desired channel from the digital broadcasting; and an indication unit for indicating a parameter which is affected by a condition of a radio wave received by the antenna among parameters associated with processing of the signal demodulation unit, to viewers.
According to the digital broadcasting demodulation apparatus of the present invention, even when video is not displayed on a monitor during reception of the broadcasting with a simple indoor antenna or the like, the parameter which is affected by the condition of th
Desir Jean W.
Lee Michael H.
Matsushita Electric - Industrial Co., Ltd.
LandOfFree
Digital broadcasting demodulation apparatus with a direction... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Digital broadcasting demodulation apparatus with a direction..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digital broadcasting demodulation apparatus with a direction... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3339016