High definition television system compatible with NTSC system

A HDTV system compatible with NTSC is accomplished by employing two channels for transmitting data. Since the channel I has low spatial definition+high time definition and the channel II has high spatial definition+low time definition, associating the channel I with the channel II produces high spatial definition+high time definition.

BACKGROUND OF THE INVENTION 
The present invention relates to a high definition television system (HDTV 
System), particularly compatible with NTSC system. 
Presently, the HDTV systems are largely classified into four classes, i.e., 
a system with one channel compatible with NTSC system, a 
spectrum-compatible system, a system with 1.5 or 2 channels compatible 
with NTSC system, and a system not compatible with NTSC system. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a HDTV system compatible 
with NTSC system, wherein an additional signal of one channel is added to 
the NTSC signal. 
According to one aspect of the present invention, the transmission part of 
a HDTV system comprises a television camera used for 60 Hz field frequency 
and 1050 lines two to one interlaced scanning, a matrix unit for 
transforming the red (R), green (G), and blue (B) signals of said camera 
into color difference signals (Y, I, Q), a first scan converter connected 
to the matrix unit to convert the 1050 lines two to one interlaced 
scanning signal to 525 lines two to one interlaced scanning signal, low 
pass filters for filtering the 525 interlaced scanning signal of the first 
scan converter, a second scan converter connected to the low pass filters 
to convert the 525 lines two to one interlaced scanning signal to the 1050 
lines two to one interlaced scanning signal, a side panel rejector 
connected to the low pass filters to divide a side panel signal from a 
central panel signal, a time expanding and signal reproducing means 
connected to the side panel rejector for time expanding the separated 
signal of the rejector to reproduce a signal, a first NTSC encoder for 
encoding the output signal of the time expanding and signal reproducing 
means, a second NTSC encoder for encoding the output signal of the side 
panel rejector, multiple subtractors for subtracting the output signals of 
the second scan converter from the output signals of the matrix unit, a 
first frequency shifter for shifting the output frequencies of 
subtractors, a first signal reproducing means for reproducing the 
frequency-shifted signals from the first frequency shifter, and a third 
NTSC encoder for encoding the output signal of the first signal 
reproducing means. 
According to another aspect of the present invention, the receiving part of 
the HDTV system comprises a first RF modulator for quadrature-modulating 
the output signals of the first and second NTSC encoders to transmit 
through channel I, a second RF modulator for quadrature-modulating the 
output signal of third NTSC encoder to transmit through channel II, a 
first RF demodulator for quadrature-demodulating the signal received 
through the channel I, a first NTSC decoder for decoding the side panel 
signal outputted from the first demodulator, a second NTSC decoder for 
decoding the central panel signal outputted from first demodulator, a 
time-compressing/signal reproducing means for time-compressing the output 
signal of the first decoder to reproduce a signal, a side panel injector 
for combining the output signals of the second decoder and the 
time-compressing/signal reproducing means, a third scan converter 
connected to the injector to convert the 525 lines two to one interlaced 
scanning signal to the 1050 lines two to one interlaced scanning signal, a 
second RF demodulator for quadrature-demodulating the signal received 
through the channel II, a third NTSC decoder for decoding the output 
signal of the second demodulator, a second signal reproducing means 
connected to the third NTSC decoder to convert the decoded 525 lines two 
to one interlaced scanning signal to the 1050 lines two to one interlaced 
scanning signal, a second frequency shifter for shifting the frequency of 
the output signal of the second signal reproducing means, multiple adders 
for adding the output signals of the third scan converter and second 
frequency shifter to produce Y, I, Q signals, a dematrix unit for 
transforming the Y, I, Q signals of the adders into R, G, B signals, and a 
display unit for displaying the R, G, B signals of dematrix unit. 
The present invention will now be described more specifically with 
reference to the drawings attached only by way of example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a television camera 10 used for 60 Hz field frequency 
is to produce 1050 lines two to one interlaced scanning signal. A matrix 
unit 12 is to transform the Red (R), Green (G), and Blue (B) signals of 
the camera 10 into color difference signals (Y, I, Q). A first scan 
converter 14 is to convert the 1050 lines two to one interlaced scanning 
signal to 525 lines two to one interlaced scanning signal. A low pass 
filter 16 is to filter the Y signal of the output of the first scan 
converter 14, while a low pass filter 17 is to filter the I, Q signals 
thereof. A second scan converter 18 is to convert the 525 lines two to one 
interlaced scanning signal into the 1050 lines two to one interlaced 
scanning signal. A side panel rejector 20 is to divide a side panel signal 
from a central panel signal. A time expanding and signal reproducing means 
22 is to time-expand the side panel signal to reproduce a signal. First, 
second and third NTSC encoders 24, 26 and 32 are to encode the signal. 
Subtractors 38, 40, 42 are to subtract the output signal of the second 
scan convertor 18 from the output signal of the matrix unit 12. A first 
frequency shifter 28 is to shift the output frequency of subtractors 38, 
40, 42. A first signal reproducing means 30 is to reproduce the 
frequency-shifted signals of the first frequency shifter 28. A first RF 
modulator 36 is to quadrature-modulate the output signals of the first and 
second NTSC encoders 24, 26 to transmit through channel I. A second RF 
modulator 34 is to quadrature-modulate the output signal of the third NTSC 
encoder 32 to transmit through channel II. 
Referring to FIG. 2, a first RF demodulator 44 is to quadrature-demodulate 
the signal received through the channel I into an RF signal. A 
time-compressing/signal reproducing means 50 is to time-compress the 
output signal of the first NTSC decoder 46 to reproduce a signal. A side 
panel injector 52 is to combine the output signals of the second NTSC 
decoder 48 and the time-compressing/signal reproducing means 50. A third 
scan converter 54 is to convert the 525 lines two to one interlaced 
scanning signal into the 1050 lines two to one interlaced scanning signal. 
A second RF demodulator 56 is to demodulate the signal received through 
the channel II into an RF signal. A third NTSC decoder 58 is to decode the 
RF demodulated signal of the second demodulator 56. A second signal 
reproducing means 60 is to reproduce the output signal of the third NTSC 
decoder 58. A second frequency shifter 62 is to shift the frequency of the 
output signal of the second signal reproducing means 60. Adders 64, 66, 68 
are to mix the signals outputted from the third scan convert 54 and second 
frequency shifter 62. A dematrix unit 70 is to transform the signals 
outputted from the adders 64, 66, 68 into the R. G. B signals. A display 
unit 72 is to display the R, G, B signals of the dematrix unit 70. 
Describing more specifically the embodiment with reference to FIGS. 1 to 5, 
the 1050 lines two to one interlaced scanning signals R, G, B outputted 
from the camera 10 are transformed by the matrix unit 12 into the Y, I, Q 
signals as follows: 
##EQU1## 
The Y, I, Q signals of the matrix unit 12 are converted by the first scan 
converter 14 from the 1050 lines two to one interlaced scanning format 
into the 525 lines two to one interlaced scanning format. The output 
signal Y.sub.1 of the first scan converter 14 is filtered by the 5.46 MHz 
low pass filter 16, while the output signals I.sub.1 and Q.sub.1 of the 
first scan converter 14 are filtered by the 0.65 MHz low pass filter 17. 
The output signals Y.sub.2, I.sub.2, Q.sub.2 of the low pass filters 16, 
17 are applied to the second scan converter 18, while also applied to the 
side panel rejector 20 to be separated as shown in FIG. 4. 
Namely, referring to FIG. 4, if the signal b is input to the side panel 
rejector 20, the portions of 0 to 7 .mu.s and 45 .mu.s to 52 .mu.s of the 
signal are applied to the time-expanding/signal reproducing means 22, 
while the other portion of 6 to 46 .mu.s is time-expanded as shown in FIG. 
4c. The bandwidth of this time-expanded signal is, respectively, 4.2 MHz, 
0.5 MHz and 0.5 MHz, and applied to the second NTSC encoder 26 from the 
side panel rejector 20. 
Meanwhile, the portions of 0 to 7 .mu.s and 45 to 52 .mu.s applied to the 
time-expanding/signal reproducing means 22 are respectively time-expanded 
into the portions of 0 to 26 .mu.s and 26 to 52 .mu.s as shown in FIG. 4a, 
input to the first NTSC encoder 24. The first RF modulator 36 
quadrature-phase-modulates the output signals of the first and second NTSC 
encoders 24 and 2 into a same phase, transmitting through the channel I. 
The output signals of the matrix unit 12 are applied to subtractors 38, 40, 
42, having the bandwidths of Y=36 MHz, Q=4.3 MHz and I=4.3MHz. The second 
scan converter 18 converts the output signals Y.sub.2, I.sub.2, Q.sub.2 of 
the low pass filters 16, 17 into the 1050 lines two to one interlaced 
scanning signals. Namely, the frequency bands of the output signals of the 
second scan converter respectively have two times the output signals of 
the low pass filters, so that Y.sub.4 is 10.92 MHz, and I.sub.4 and 
Q.sub.4 are 1.3 MHz. The subtractors 38, 40 and 42 subtract the output 
signal of the second scan converter 18 from the output signal of the 
matrix unit 12. Thus, the output signals Y.sub.5, I.sub.5 and Q.sub.5 of 
the subtractors 38, 40 and 42 respectively have the values of 36MHz-10.92 
MHz, 4.3MHz-1.3MHz and 4.3MHz-1.3MHz, inputted to the first frequency 
shifter to produce an output of which Y.sub.6 is 0-25 MHz, and I.sub.6 and 
Q.sub.6 are 0-3 MHz. 
The output signals of the first frequency shifter are vertically 
sub-sampled by the first signal reproducing means 30 to transform the 1050 
lines two to one interlaced scanning signals into the 525 lines two to one 
interlaced scanning signals so as to produce signals as shown in FIG. 3. 
Namely, one of three samples is selected as shown in FIG. 3a in the first 
field so as to only transmit even line, while, in the second field, one of 
three samples is selected as shown in FIG. 3b so as to only transmit odd 
line. In this manner, if the data is transmitted up through the sixth 
field, the transmission of one frame data is completed. 
Hence, the signal is formed in the NTSC format without deteriorating the 
definition in the spatial direction although the definition is 
deteriorated in the direction of time. The signal thus constructed is 
transmitted via the third NTSC encoder 32 and second RF modulator 34 to 
the channel II. Consequently, the NTSC signal and side panel signal are 
transmitted through the channel I, and the definition component signal 
through the channel II, so that the HDTV receiver receives and combines 
all the signals through the both channels I and II to obtain the High 
Definition. The signal characteristics of the channel I show 
Y'=0.about.10.92 MHz, I'=Q'=1.3 MHz, and the frame frequency=30 Hz, while 
the signal characteristics of the channel II show Y"=36 MHz.about.10.92 
MHz, I"=Q"=4.3 MHz.about.1.3 MHz, and the frame frequency=10 Hz. Although 
the signals are separated from each other as described above, the image 
quality is hardly affected, for a definition exchange method is employed. 
Namely, since the channel I has low spatial definition+high time 
definition and the channel II has high spatial definition+low time 
definition, associating the channel I with the channel II produces high 
spatial definition+high time definition. 
The decoding part of FIG. 2 functions in opposite to the encoding part of 
FIG. 1. The signals of the channels I and II are respectively received by 
the first and second RF demodulators 44 and 56. The first RF demodulator 
44 quadrature-phase-demodulates the signal received through the channel I, 
applying the side panel signal to the first NTSC decoder 46 and the 
central panel signal to the second NTSC decoder 48. The first NTSC decoder 
46 decodes the received signal to transform it (see FIG. 4a) into the 
signal of 0-7 .mu.s and 45-52 .mu.s (see FIG. 4b) applied to the 
time-compressing/signal reproducing means 50. The output signal of the 
second NTSC decoder 48 is input to the side panel injector 52, so that the 
signal c of FIG. 4 is transformed into the signal b of 6 .mu.s to 46 
.mu.s. The side panel injector 52 combines the output signals of the 
second NTSC decoder 48 and time-compressing/signal reproducing means 50. 
Here, the portion of 6 .mu.s to 7 .mu.s and the portion of 45 .mu.s to 46 
.mu.s get overlapped. These portions are to prevent the image distortion 
caused by mismatching the side panel signal with the central signal. 
Hence, these portions are linearly compensated as shown in FIG. 5. 
The third scan converter 54 converts the 525 lines two to one interlaced 
scanning signal Y'.sub.1, I'.sub.1, Q'.sub.1 output from the side panel 
injector 52 into the 1050 lines two to one interlaced scanning signal 
Y'.sub.2, I'.sub.2, Q'.sub.2. Meanwhile, the second RF demodulator 56 
quadrature-phase-demodulates the signal received through the channel II. 
The output of the second RF demodulator is decoded by the third NTSC 
decoder 58 into the format as shown in FIG. 3. 
This signal is interlaced into the 525 lines two to one interlaced signal 
by the second signal reproducing means 60. Of the interlaced signal, the 
frequency band of the Y".sub.1 signal is 12.6 MHz, and that of the 
I".sub.1 and Q".sub.1 signals are 1.5 MHz. If the above signals are 
line-interpolated, the frequency band of the Y".sub.1 signal becomes 25.2 
MHz, and that of the I".sub.1 and Q".sub.1 signals become 3 MHz. The 
second frequency shifter 62 shifts the output signals Y".sub.1, I".sub.1 
and Q".sub.1 of the second signal reproducing means 60 to the signals of 
which the Y".sub.2 signal has the frequency band of 10.92 MHz to 36 MHz 
with the frequency band of the I".sub.2 and Q".sub.2 being 1.3 to 4.3 MHz. 
The first, second and third adders 64, 66, 68 add the output signals 
Y'.sub.2, I'.sub.2 and Q'.sub.2 of the third scan converter 54 and the 
output signals Y".sub.2, I".sub.2 and Q".sub.2 of second frequency shifter 
62 to produce the signal of which the Y.sub.0 signal has the frequency 
band of 0 to 36 MHz with the frequency band of the I.sub.0 and Q.sub.0 
signals being 0 to 4.3 MHz. The dematrix unit 70 transforms the Y.sub.0, 
I.sub.0, Q.sub.0 signals of the adders 64, 66, 68 into the R.sub.0, 
G.sub.0, B.sub.0 signals as follows: 
##EQU2## 
The output of the dematrix unit 70 is displayed by the display unit 72. The 
frame displayed comprises a highly defined 1050 lines two to one 
interlaced scanning signals whose luminance band and chrominance band are 
respectively 36 MHz and 4.3 MHz. 
As stated above, the present invention accomplishes a HDTV system 
compatible with NTSC by employing two channels for transmitting data.