Television – Bandwidth reduction system – Format type
Reissue Patent
1999-02-12
2001-02-27
Hsia, Sherrie (Department: 2614)
Television
Bandwidth reduction system
Format type
C348S726000, C348S538000, C375S355000, C375S371000
Reissue Patent
active
RE037070
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a high definition television (HDTV) receiver, and more particularly, to a HDTV receiver which is improved in its overall performance and is simplified in its configuration, by improving a symbol timing restoring circuit.
FIG. 1
is a block diagram of a conventional 8-vestigial sideband (VSB) receiver, in which a high-frequency signal input from an antenna (ANT) is demodulated and is carrier-restored when a channel is a selected in a tuner
1
and a signal having a central frequency of 44 MHz is automatic-gain controlled and IF-bandpass filtered in an IF processor & carrier restoring portion
2
.
This signal is digitally sampled in an analog-to-digital conventer (ADC)
3
and precise symbol timing is detected by a timing restoring portion
4
, thereby controlling the timing of ADC
3
.
The output of ADC
3
is also input to a sync detector
5
to detect a data segment sync from a data segment sync pattern (
FIG. 3A
) and to detect a field sync from a field sync pattern being in the first line of a transmission format.
At this time, the data segment sync and field sync detected in sync detector
5
are used as the control signals of subsequent blocks
7
through
16
.
NTSC (National Television System Committee) interference detector
7
receives a signal passing through a post-comb filter
6
and a signal not passing therethrough and determines whether there is an identical channel interference with that of NTSC or not, to then transmit a comb control signal SC
1
.
If there is no NTSC identical channel interference, the signal not passing through post-comb filter
6
is selected by a multiplexer
8
. A channel equalizer
9
equalizes the incoming signal which is set to 8 levels to remove the intersymbol interference due to a ghost generated at the channel.
Also, a phase corrector
10
corrects the phase error remaining after signal-processing, setting the incoming signal to 8 levels. An optimal viterbi decoder
11
performs a 4-state viterbi decoding operation and the decoded output is output through multiplexer
13
.
If there is NTSC identical channel interference, the output of post-comb filter
6
is selected as the output of multiplexer
8
. At this time, post-comb filter
6
subtracts data delayed for 12 symbol period from the current data.
Therefore, the original 8 level data becomes 15 level data. The NTSC identical channel interference is removed. At this time, channel equalizer
9
and phase controller
10
operate assuming that the incoming signal is 15 level data, and multiplexer
13
selects and outputs the output of a partial response (PR) viterbi decoder
12
.
PR viterbi decoder
12
, an 8-state decoder, has much more complex structure than that of optimal viterbi decoder
11
.
The output of multiplexer
13
is dissipated in order to enhance the correction capability for burst errors in a deinterleaver
14
. An error controller
15
performs a Reed-Solomon decoding operation.
Also, a derandomizer
16
releases a signal randomly formed in a transmission port reversely. Timing restoring portion
4
is constituted by a data segment sync detector
4
a
and a phase locked loop (PLL)
4
b,
as shown in FIG.
2
. The digitally converted signal is concurrently output to data segment sync detector
4
a
and PLL
4
b.
At this time, data segment sync detector
4
a
detects a data segment sync, based on the data pattern “1001” for 4 symbol period of 2 levels shown in FIG.
3
A.
PLL
4
b
detects the phase error for the timing from a data segment sync pattern. The output of a phase detector is as shown as
FIG. 3B
, digitally, and as
FIG. 3C
, analogically.
The position of a sampling point
4
shown in
FIG. 3C
is a zero-crossing point, and a symbol timing is detected using the zero-crossing point.
However, the aforementioned conventional art adopting a post-comb filter for reducing the NTSC identical channel interference has a very complex configuration.
SUMMARY OF THE INVENTION
To solve these problems, it is an object of the present invention to provide a HDTV receiver, which allows a better symbol timing restoration even if there is an NTSC identical channel interference, by improving a symbol timing restoring circuit, and which is simplified in its configuration, by eliminating a post-comb filter.
To accomplish the above object, there is provided a HDTV receiver comprising: a tuner for selecting a necessary channel from input signals via an antenna; an IF processing & carrier restoring portion for performing an IF process & carrier restoration from the output of the tuner; an analog-to-digital converter (ADC) for converting the output of the IF processing & carrier restoring portion into a digital signal; a timing restoring portion for restoring a timing from the output of the ADC; a 2:1 down-sampler for 2:1 down-sampling the output of the ADC; a sync detector for detecting a sync from the output of the 2:1 down-sampler; a channel equalizer for performing a channel equalization from the output of the 2:1 down-sampler; a phase controller for correcting the phase error from the output of the channel equalizer; an optimal viterbi decoder for performing a viterbi decoding operation from the output of the phase controller; a deinterleaver for dissipating the output of the optimal viterbi decoder in order to enhance the correction capability due to burst errors; an error controller for performing a Reed-Solomon decoding operation with respect to the output of the deinterleaver; and a derandomizer for releasing the output of the error controller and restoring a signal randomly formed at a transmission port reversely.
REFERENCES:
patent: 4503453 (1985-03-01), Rougeolle
patent: 5363408 (1994-11-01), Polk
patent: 5425060 (1995-06-01), Roberts
patent: 5479449 (1995-12-01), Patel
patent: 5535252 (1996-07-01), Kokayashi
“VSB Transmission System”, Zenith Electronics Corporation, Dec. 17, 1993, pp 8-16, FIGS. 9, 12, 14.
Kim Dae-Jin
Kim Key H.
Kim Yung G.
Park Hee B.
Park Jung S.
Hsia Sherrie
LG Electronics Inc.
Long Aldridge & Norman
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