Television – Receiver circuitry – Tuning
Reexamination Certificate
1999-05-14
2002-11-19
Miller, John (Department: 2614)
Television
Receiver circuitry
Tuning
C348S725000, C348S726000, C348S554000, C348S558000, C348S555000, C375S327000, C375S345000, C455S234100, C455S245100
Reexamination Certificate
active
06483553
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a TV, and more particularly, to a combined TV receiver which can receive and process an analog broadcasting signal as well as a digital broadcasting signal.
2. Background of the Related Art
The TV receiver is an appliance for decoding a broadcasting signal transmitted from a broadcasting station into an image signal and presenting image information to TV watchers. There are different standards of TV systems depending on scanning lines, frames per second, modulation type, channel bandwidth, video signal bandwidth, and audio channel modulation of a broadcasting signal transmitted from the broadcasting station, inclusive of the NTSC(National Television System Committee), PAL(Phase Alternation by Line), SECAM(Sequential Couleur a Memoire). The NTSC system is a standard system of a broadcasting signal having 525 scanning lines and transmitting 30 frames per second used in the north America, Japan and Korea. The NTSC system is compatible with black and white TV and has a simple driving circuit compared to other systems. The PAL system is a standard system of a broadcasting signal used in most European countries except some eastern European countries starting from France, in which a phase of one of two color difference signals are inverted at every scanning line in modulation. Though the PAL system has a somewhat poor compatibility with a black and white TV, a video signal of the PAL system is less influenced by a phase distortion caused by recording or transmission. The SECAM system is a standard system of a broadcasting signal developed in France and used in France, the old soviet union, east Europe and some African countries, in which a color subcarrier is frequency modulated and overlapped with a luminance signal while the two color difference signals are cut off in a sequence before transmission. Though the SECAM system is advantageous in small amplitude and phase distortions during transmission, a vertical resolution is poor.
FIG. 1
illustrates a block diagram of a related art analog TV receiver circuit schematically, of which operation will be explained. A tuning data is received at a tuner
1
. Then, a VIF(Video Intermediate Frequency)
2
provides a video signal, of which synchronizing signal is detected by a synchronizing signal detector
3
. If a synchronizing signal is contained in the signal received from the antenna, the signal is an analog signal, if there is no synchronizing signal, the signal is not an analog signal. An analog broadcasting receiver determines the presence of a broadcasting signal according to existence of a synchronizing signal, and stores a channel number having a broadcasting signal in a memory.
In the meantime, there have been research and other efforts for replacing a related art analog transmission type TV system with a digital transmission type TV gradually as digital technologies and video and audio data compression and restoring technologies are developed. In such a digital terrestrial TV broadcasting transmission system, there is a system of the USA and a system of Europe. The USA system is a VSB transmission system in which a single carrier is used and the European system is a COFDM(Coded Orthogonal Frequency Division Multiplexing) transmission system in which multi carriers are used. Particularly, because the multi carriers are used, the COFDM system is strong against interference and ghost in multiple path channel and allows to construct an SFN(Single Frequency Network) which can make a wide band transmission in a signal frequency. Because the present carrier condition is sensed in the COFDM system for making a Viterbi decoding with reference to the channel condition, an interference between channels or a selective fading of a frequency affect system performance, seriously. Therefore, as shown in
FIG. 2
, in the COFDM system, a signal called pilot
5
having a predictable value is added at every fixed intervals both in frequency axis Nf and time axis Nt directions between carriers of data at a transmitter side before transmission, which is used in synchronization or equalizing required in reception for restoring data at a receiver side. Together with this, the related art COFDM transmitter side transmits TPS(Transmission Parameter Signaling) including information on various transmission modes, and the receiver side decodes the TPS for use in demodulation. That is, the COFDM system is characterized in the use of multi carrier intransmission as well as the addition of pilots before transmission for use at the receiver side.
FIGS. 3
a
and
3
b
illustrate reception blocks in a COFDM system. As shows, signals (t) received through an antenna is amplified as necessary through a transmission channel
11
and the amplification terminal
12
. An amplification gain is controlled through an AGC(Auto Gain Controller)
16
. The amplified signal is digitized at an A/D converter
13
, provided to an I & Q demodulator
14
, and converted into of an I signal and a Q signal. The I signal and Q signal are subjected to adjustment of frequencies and powers as they pass through an FFT(Fast Fourier Transformer) block
15
and an equalizer
31
, and are restored into an original data as they pass through a demapper
32
, deinterleavers
33
and
36
and FEC(Forward Error Corrector)(not shown). At first, the received data is provided to a course timing block
17
for being divided into an effective data interval and a guard interval. The course timing block
17
shifts data by one interval to obtain correlation between data, and provides the correlation to an FFT start window generator
18
for establishing an interval of the data appropriate for subjecting to FFT. After the I & Q composite signals are converted at the FFT block
15
, TPS information is demodulated. The TPS demodulator
19
analyzes the pilot signals, and corrects frequency and time basis distortions of the received data using a result of the analysis, to decode a correct TPS signal. The pilot signals are detected from the signal subjected FFT at a scattered pilot extractor
20
and analyzed at an IFFT block
21
and a narrow & fine frequency controller
22
for obtaining a correct frequency band of the signal. The signal subjected to FFT is provided to a continual pilot extractor
23
for being frequency synchronized by which an error in a received frequency is corrected. And, the fine timing block
24
receives the data subjected to FFT and decodes a pilot signal in the data, for finding an exact timing of conversion of the FFT. The signal having frequency synchronized and frequency band corrected through the IFFT block
21
, the narrow & fine frequency controller
22
, and the fine timing block
24
is provided to the FFT block
15
, again. The signal provided to the FFT block
24
is corrected for an error in a data carrier by hard or soft decision. The FFT
15
should be provided in a COFDM demodulating system for receiving an I signal and a Q signal and transform into frequency components. The signal transformed into the frequency components at the FFT is provided to a TPS(Transmission Parameter Signalling) decoder
19
.
A memory
2
stores a signal from the FFT block
15
and provides the stored signal to the equalizer
31
, and the equalizer
31
compensates for a distortion in a frequency response signal caused in a transmission channel. The demapper
32
receives both the signal having distortion compensated at the equalizer
31
and a TPS signal from the TPS decoder
19
, and analyzes a mapped signal. The internal deinterleaver
33
subjects the signal analyzed at the demapper
32
to internal deinterleave, and provides the result to a Viterbi decoder
34
. The Viterbi decoder
34
receives both
20
a signal from the internal deinterleaver
33
and the TPS signal, and subjects to viterbi decoding. An external deinterleaver
36
subjects the signal subjected to internal interleave to external interleave with reference to a synchronizing signal detected at a synchronizing signal detector
35
. RS
Birch & Stewart Kolasch & Birch, LLP
LG Electronics Inc.
Miller John
Natnael Paulos
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