GB2263045A - Satellite broadcast reception system with signal processing dependent on noise and gain - Google Patents
Satellite broadcast reception system with signal processing dependent on noise and gain Download PDFInfo
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- GB2263045A GB2263045A GB9226798A GB9226798A GB2263045A GB 2263045 A GB2263045 A GB 2263045A GB 9226798 A GB9226798 A GB 9226798A GB 9226798 A GB9226798 A GB 9226798A GB 2263045 A GB2263045 A GB 2263045A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/14—Picture signal circuitry for video frequency region
- H04N5/21—Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
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Abstract
A satellite broadcast reception system comprises a signal converting circuit 10 for converting a first IF signal into a second IF signal and automatically controlling the gain of the second IF signal in response to a gain control signal, a demodulator 20 for demodulating the second IF signal to base band, a noise level detecting circuit 30 for detecting the noise level in the output signal of the demodulator 50, a comparison unit 60 for comparing the gain control signal with a reference and the detected noise level with a reference, and generating a control signal in accordance with the compared results, and a video signal processing circuit 70 for modifying the video signal or processing it normally in response to the control signal. <IMAGE>
Description
SATELLITE BROADCASTING RECEPTION SYSTEM
The present invention relates in general to a satellite broadcasting reception system, and more particularly to a satellite broadcasting reception system for prevention of degradation in a picture quality which may be caused due to attenuation of a carrier/noise ratio and a reception sensitivity of a received satellite broadcasting signal resulting from bad weather conditions such as a rainfall.
Referring to Fig. 1, there is shown a block diagram of a conventional satellite broadcasting reception system. As shown in this figure, the conventional satellite broadcasting reception system comprises a tuner 1 for converting a first intermediate frequency signal inputted therein into a second intermediate frequency signal of a band lower than that of the first intermediate frequency signal, an automatic gain control (AGC) circuit 2 for automatically controlling a gain of the second intermediate frequency signal from the tuner 1 in response to a gain control signal, an amplifier 3 for amplifying the gain-controlled second intermediate frequency signal from the automatic gain control circuit 2 by a predetermined amplification degree, a rectifier 4 for rectifying an output signal from the amplifier 3, an amplifier 5 for amplifying an output signal from the rectifier 4 by a predetermined amplification degree and outputting the amplified signal as the gain control signal to the automatic gain control circuit 2, a demodulator 6 for demodulating the output signal from the amplifier 3 into a frequency signal corresponding to an original base band of a received satellite broadcasting signal, a signal detecting circuit 7 for detecting a video signal and an audio signal from an output signal from the demodulator 6, an audio signal processing circuit 8 for processing the detected audio signal from the signal detecting circuit 7 to be audible, a video signal processing circuit 9 for processing the detected video signal from the signal detecting circuit 7 to be displayable, a telop signal generating circuit 10 for generating a predetermined telop signal, and a switch 11 for selectively outputting one of output signals from the telop signal generating circuit 10 and the video signal processing circuit 9 in response to the output signal from the amplifier 5.
The operation of the conventional satellite broadcasting reception system with the above-mentioned construction will hereinafter be described.
The satellite broadcasting signal received through a parabolic antenna (not shown) is first converted into the first intermediate frequency signal of 1.035 to 1.336GHz in a down converter (not shown). The first intermediate frequency signal from the down converter is converted into the second intermediate frequency signal of 402.78MHz in the tuner 1.
The automatic gain control circuit 2 automatically controls the gain of the second intermediate frequency signal from the tuner 1 in response to the output signal from the amplifier 5.
The gain-controlled second intermediate frequency signal from the automatic gain control circuit 2 is amplified by a predetermined amplification degree in the amplifier 3 and then demodulated into the frequency signal of the original base band of 27MHz in the demodulator 6.
On the other hand, the output signal from the amplifier 3 is converted into a direct current (DC) signal in the rectifier 4 and then amplified by a predetermined amplification degree in the amplifier 5. The output signal from the amplifier 5 is applied as the gain control signal to the automatic gain control circuit 2, which automatically controls the gain of the second intermediate frequency signal from the tuner 1 in response to the gain control signal from the amplifier 5.
The signal detecting circuit 7 detects the video signal and the audio signal from the output signal from the demodulator 6. The audio signal processing circuit 8 performs a digital demodulation with respect to the detected audio signal from the signal detecting circuit 7 to process the detected audio signal to be audible. The video signal processing circuit 9 removes from the detected video signal from the signal detecting circuit 7 a low frequency signal or an energy diffusion signal which is mixed upon band width compression, to obtain the displayable video signal. The telop signal generating circuit 10 generates a character signal such as, for example, "bad reception condition.
At this time, provided that a level of the gain control signal from the amplifier 5 becomes lower than a predetermined reference voltage, due to variation in an electric field resulting from bad weather conditions such as a rainfall, as shown in Fig. 2 which is a graph illustrating a variation of the gain control signal, the switch 11 outputs the output signal from the telop signal generating circuit 10 as the final video signal. On the contrary, when the level of the gain control signal is higher than the predetermined reference voltage, the switch 11 outputs the output signal from the video signal processing circuit 9 as the final video signal.
In other words, the video signal of the received satellite broadcasting signal is displayed when the reception condition of the received satellite broadcasting signal is good, while the telop signal such as "bad reception condition is displayed instead of the received video signal when the reception condition of the received satellite broadcasting signal is bad due to bad weather conditions such as a rainfall.
However, the above-mentioned conventional satellite broadcasting reception system has the following disadvantages:
First, in the case where the reception condition of the received satellite broadcasting signal is bad due to the bad weather conditions such as the rainfall, there is not provided any apparatus for compensating for the satellite broadcasting signal of the bad reception condition, except that the characters such as bad reception condition" are displayed.
Second, since the reception condition of the received satellite broadcasting signal is discriminated based on the automatic gain control (AGC) signal, the reception condition cannot be discriminated accurately. This is because there is little variation of the gain control signal according to the rainfall. In fact, a carrier/noise (C/N) ratio becomes very small due to the rainfall.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a satellite broadcasting reception system which is capable of compensating for a video signal of a received satellite broadcasting signal when a reception condition of the received satellite broadcasting signal is bad due to bad weather conditions such as a rainfall.
In accordance with the present invention, the above and other objects can be accomplished by a provision of a satellite broadcasting reception system, comprising: signal converting means for obtaining a gain control signal, converting a first intermediate frequency signal inputted therein into a second intermediate frequency signal of a band lower than that of the first intermediate frequency signal and automatically controlling a gain of the second intermediate frequency signal in response to the gain control signal; demodulating means for demodulating the second intermediate frequency signal from said signal converting means into a frequency signal corresponding to an original base band of a received satellite broadcasting signal; said signal converting means obtaining the gain control signal from an output signal from said demodulating means; noise level detecting means for detecting a noise level from the output signal from said demodulating means; signal detecting means for detecting a video signal fran the output signal from said demodulating means; comparison means for comparing the gain control signal from said signal converting means with a predetermined reference gain control signal and the detected noise level from said noise level detecting means with a predetermined reference noise level, respectively, and generating a control signal for control of the processing of the detected video signal from said signal detecting means in accordance with the compared results; and video signal processing means for compensating for the video signal from said signal detecting means or processing it normally in response to the control signal from said comparison means and then processing the video signal to be displayable.
Examples of embodiments of the present invention will now be described with reference to the drawings, in which:
Fig. 1 is a block diagram of a conventional satellite broadcasting reception system;
Fig. 2 is a graph illustrating a variation of a gain control signal;
Fig. 3 is a schematic block diagram of a satellite broadcasting reception system in accordance with the present invention;
Fig. 4 is a detailed block diagram of the satellite broadcasting reception system in Fig. 3 in accordance with an embodiment of the present invention;
Fig. 5 is a flowchart illustrating an operation of a comparison unit in accordance with the present invention;
Fig. 6 is a graph illustrating states of a carrier and a noise contained in a received satellite broadcasting signal;;
Fig. 7 is a detailed block diagram of the satellite broadcasting reception system in Fig. 3 in accordance with an alternative embodiment of the present invention;
Fig. 8 is a detailed block diagram of a filtering circuit of a video signal processing circuit in the system in Fig. 7; and Fig. 9 is a circuit diagram of a umi luminance signal processor and the filtering circuit of the video signal processing circuit in the system in Fig. 7.
Referring to Fig. 3, there is shown a schematic block diagram of a satellite broadcasting reception system in accordance with an embodiment of the present invention. As shown in this figure, the sateillite broadcasting reception reception system of this embodiment comprises a signal converting circuit 10 for obtaining a gain control signal, converting a first intermediate frequency signal inputted therein into a second intermediate frequency signal of a band lower than that of the first intermediate frequency signal and automatically controlling a gain of the second intermediate frequency signal in response to the gain control signal, a demodulator 20 for demodulating the second intermediate frequency signal from the signal converting circuit 10 into a frequency signal corresponding to an original base band of a received satellite broadcasting signal, the signal converting circuit 10 obtaining the gain control signal from an output signal from the demodulator 20, a noise level detecting circuit 30 for detecting a noise level from the output signal from the demodulator 20, a signal detecting circuit 40 for detecting a video signal and an audio signal from the output signal from the demodulator 20, an audio signal processing circuit 50 for processing the detected audio signal from the signal detecting circuit 40 to be audible, a comparison unit 60 for comparing the gain control signal from the signal converting circuit 10 with a predetermined reference gain control signal stored therein and the detected noise level from the noise level detecting circuit 30 with a predetermined reference noise level stored therein, respectively, and generating a control signal for a process of the detected video signal from the signal detecting circuit 40 in accordance with the compared results, and a video signal processing circuit 70 for compensating for the video signal from the signal detecting circuit 40 or processing it normally y in response to the control signal from the comparison unit 60 and then processing the video signal to be displayable.
Referring to Fig. 4, there is shown a detailed block diagram of the satellite broadcasting reception system in Fig.
3 in accordance with an embodiment of the present invention.
As shown in this figure, the signal converting circuit 10 in
Fig. 3 includes a tuner 1Oa for converting the first intermediate frequency signal inputted therein into the second intermediate frequency signal of the band lower than that of the first intermediate frequency signal, an automatic gain control circuit lOc for automatically controlling the gain of the second intermediate frequency signal from the tuner 10a in response to the gain control signal, an amplifier 10d for amplifying an output signal from the automatic gain control circuit 10c by a predetermined amplification degree, and a rectifier 10b for rectifying the output signal from the demodulator 20 and outputting the rectified signal as the gain control signal to the automatic gain control circuit 10c.
The noise level detecting circuit 30 in Fig. 3 includes a filter 30a for filtering the output signal from the demodulator 20 to detect therefrom a desired frequency band of signal corresponding to a noise, an amplifier 30b for amplifying an output signal from the filter 30a by a predetermined amplification degree, and a peak detector 30c for detecting an envelope corresponding to a peak value of an output signal from the amplifier 30b. Herein, the peak detector 30c may include an integrator and the filter 30a may be a band pass filter having the upper limit value which is higher than that of the original base band of the received satellite broadcasting signal.
The signal detecting circuit 40 in Fig. 3 includes an audio signal detector 40a for detecting only the audio signal from the output signal from the demodulator 20 and a video signal detector 40b for detecting only the video signal from the output signal from the demodulator 20. Herein, the audio signal detector 40a may include a 5.73MHz band pass filter BPF and the video signal detector 40b may include a low pass filter LPF.
The video signal processing circuit 70 in Fig. 3 includes à first amplifier 70a for amplifying the detected video signal from the signal detecting circuit 40 by a predetermined amplification degree, a second amplifier 70b for amplifying an output signal from the first amplifier 70a by a predetermined amplification degree, a f filter 70c for filtering an output signal from the second amplifier 70b to remove therefrom a high frequency band of signal corresponding to a noise, and a switch 70d for inputting output signals from the first amplifier 70a and the filter 70c and selectively outputting one of the inputted signals in response to the control signal from the comparison unit 60.
Also as shown in Fig. 4, the satellite broadcasting reception system further comprises a first amplifying circuit 80 for amplifying the gain control signal from the rectifier 10b by a predetermined amplification degree, a first analog/digital (A/D) converter 90 for converting an output signal from the first amplifying circuit 80 into a digital signal and outputting the digital signal to the comparison unit 60, a second amplifying circuit 100 for amplifying the output signal from the noise level detecting circuit 30 by a predetermined amplification i f i degree, and a second A/D converter 110 for converting an output signal from the second amplifying circuit 100 into a digital signal and outputting the digital signal to the comparison unit 60.
Although not shown in detail in Figs. 3 and 4, the comparison unit 60 includes a microcomputer. The microcomputer pre-stores therein the reference gain control signal with respect to the gain control signal from the signal converting circuit 10 and the reference noise level with respect to the noise level from the noise level detecting circuit 30 and compares them with each other, respectively, on the basis of a preset system program. In accordance with the compared results, the microcomputer outputs the control signal for the process for removal of the noise from the video signal or for the normal process of the video signal, as will be described later in detail with reference to Fig. 9.
The filter 30a in the noise detecting circuit 30 is the band pass filter BPF, as mentioned above, which detects a noise component of a frequency band having the upper limit value which is higher by about 1-2MHz than that of the original base band of the received satellite broadcasting signal. For example, the upper limit value of the base band is 8MHz in a high vision and 6.5MHz in a normal vision, respectively. In this case, the filter 30a has the upper limit value of 9-10MHz.
The operation of the satellite broadcasting reception system with the construction mentioned above with reference to
Fig. 4 in accordance with the present invention will hereinafter be described in detail.
The satellite broadcasting signal received through a parabolic antenna (not shown) is first converted into the first intermediate frequency signal of 1.035 to 1.336GHz in a down converter (not shown), which typically brings the frequency down. In the signal converting circuit 10, the first intermediate frequency signal outputted from the down converter is converted into the second intermediate frequency signal of 402.78MHz in the tuner idea. The automatic gain control circuit lOc automatically controls the gain of the second intermediate frequency signal from the tuner 10a in response to the gain control signal from the rectifier 10b.
The gain-controlled second intermediate frequency signal from the automatic gain control circuit 10c is amplified by a predetermined amplification degree in the amplifier 10d and then applied to the demodulator 20. On the other hand, the rectifier 10b acts to rectify the output signal from the demodulator 20 and outputs the rectified signal as the gain control signal to the automatic gain control circuit lOc.
The demodulator 20 demodulates the output signal from the amplifier 10d in the signal converting circuit 10 into the frequency signal of 27MHz corresponding to the original base band of the received satellite broadcasting signal.
In the noise detecting circuit 30, the f filter 30a filters the output signal from the demodulator 20 to detect therefrom the desired frequency band of signal corresponding to the noise and the amplifier 30b amplifies the output signal from the filter 30a by a predetermined amplification degree. The peak detector 30c detects the envelope corresponding to the peak value of the output signal from the amplifier 30b. It is noted that the envelope is a direct current (DC) component representing the noise level. Namely, a carrier/noise (C/N) ratio is small when the envelope value is large, while it is large when the envelope value is small.
In the signal detecting circuit 40, the audio signal detector 40a detects only the audio signal from the output signal from the demodulator 20 and the video signal detector 40b detects only the video signal from the output signal from the demodulator 20. The audio signal processing circuit 50 processes the detected audio signal from the audio signal detector 40a in the signal detecting circuit 40 to be audible.
The detected video signal from the video signal detector 40b in the signal detecting circuit 40 is applied to the video signal processing circuit 70.
On the other hand, the gain control signal from the rectifier 1Db in the signal converting circuit 10 is also applied to the first amplifying circuit 80, which amplifies the applied gain control signal by a predetermined amplification degree and outputs the amplified signal to the first A/D converter 90. In result, the digital-converted gain control signal from the first A/D converter 90 is received by the comparison unit 60.
The noise level from the noise detecting circuit 30 is amplified by a predetermined amplification degree in the second amplifying circuit 100 and then converted into a digital signal in the second A/D converter 110. In result, the digital-converted noise level from the second A/D converter 110 is received by the comparison unit 60.
Noticeably, the satellite broadcasting reception system may also employ an analog manner in which the gain control signal and the noise level are applied directly to the comparison unit 60 with no conversion into the digital signals. Nevertheless, in order to compensate for degradation in a picture quality even in fine variations in the gain control signal and the noise level, this embodiment provides the satellite broadcasting reception system of the digital manner.
Referring to Fig. 5, there is shown a flowchart illustrating an operation of the comparison unit 60 in accordance with an embodiment of the present invention. As shown in this figure, the comparison unit 60 (for example, microcomputer) first compares the inputted gain control signal with the predetermined reference gain control signal. If the inputted gain control signal is higher than the predetermined reference gain control signal as a result of the comparison, the comparison unit 60 then compares the inputted noise level with the predetermined reference noise level. If the inputted noise level is greater than the predetermined reference noise level as a result of the comparison, the comparison unit 60 determines that much noise has been contained in the video signal and then outputs as the control signal a first logic level signal (for instance, high signal) for removal of the noise from the video signal. On the contrary, when the inputted noise level is smaller than or equal to the predetermined reference noise level, the comparison unit 60 determines that the picture quality of the received satellite broadcasting signal is good and then outputs as the control signal a second logic level signal (for example, low signal) for the normal process of the video signal.On the other hand, when the inputted gain control signal is not higher than the predetermined reference gain control signal, the comparison unit 60 outputs as the control signal the first logic level signal (for instance, high signal) for removal of the noise from the video signal, irrespective of the noise level.
Referring again to Fig. 4, in the video signal processing circuit 70, the first amplifier 70a amplifies the detected video signal from the signal detecting circuit 40 by a predetermined amplification degree. For the purpose of compensation for the gain of the received satellite broadcasting signal attenuated due to bad weather conditions such as a rainfall, the output signal from the first amplifier 70a is again amplified in the second amplifier 70b. The filter 70c filters the output signal from the second amplifier 70b to remove therefrom the high frequency band of signal corresponding to the noise. For such a filtering operation, the filter 70c may be a band pass filter BPF having the upper limit value which is lower than that of the original base band of the received satellite broadcasting signal.Then, in response to the control signal from the comparison unit 60, the switch 70d selectively outputs one of the output signals from the amplifier 70a and the filter 70c, as the final video signal
That is, upon receiving the control signal of the first logic level from the comparison unit 60, i.e., when a reception sensitivity or the C/N ratio of the received satellite broadcasting signal is bad, the switch 70d outputs the output signal from the filter 70c at its input terminal b as the final video signal. On the contrary, upon receiving the control signal of the second logic level indicating that the reception sensitivity and the C/N ratio of the received satellite broadcasting signal are good, the switch 70d outputs the output signal from the amplifier 70a at its input terminal a as the final video signal.
Fig. 6 shows states of a carrier and a noise contained in the satellite broadcasting signal received through the parabolic antenna. In this drawing, the reference numeral A designates a main carrier of 402.78MHz, B a DC level of a noise in the case of a bad C/N ratio and C a DC level of a noise in the case of a good C/N ratio, respectively. It can be seen from Fig. 6 that there is a large difference between the DC levels of the good and bad C/N ratio conditions.
Referring to Fig. 7, there is shown a detailed block diagram of the satellite broadcasting reception system in Fig.
3 in accordance with an alternative embodiment of the present invention. The construction in Fig. 7 is substantially the same as that in Fig. 4, with the exception that the video signal processing circuit 70 is constructed differently from that in Fig. 4. Hence, only the construction and operation of the video signal processing circuit 70 in the system in Fig.
7 will hereinafter be described and a description of those of other components therein will be omitted.
In Fig. 7, the video signal processing circuit 70 includes a luminance/chrominance (Y/C) separator 70e for separating luminance and chrominance signals Y and C from the video signal from the signal detecting circuit 40, a luminance signal processor 70f for processing the separated luminance signal Y from the Y/C separator 70e to be displayable, a chrominance signal processor 70g for processing the separated chrominance signal C from the Y/C separator 70e to be displayable, a filtering circuit 70h for filtering an output signal from the luminance signal processor 70f in response to the control signal from the comparison unit 60 to remove therefrom a high frequency band of signal corresponding to a black noise, and an adder 70i for adding output signals from the filtering circuit 70h and the chrominance signal processor 70g and outputting the added signal as the final video signal.
Referring to Fig. 8, there is shown a detailed block diagram of the filtering circuit 70h of the video signal processing circuit 70 in the system in Fig. 7. As shown in this drawing, the filtering circuit 70h includes a first band pass filter 70hl for filtering the output signal from the luminance signal processor 70f to pass the frequency signal corresponding to the original base band of the received satellite broadcasting signal, a second band pass filter 70h2 for filtering the output signal from the luminance signal processor 70f to remove therefrom the high frequency band of signal corresponding to the black noise, thereby to pass only a signal of a frequency band having the upper limit value which is lower than that of the original base band of the received satellite broadcasting signal, and a switch 70h3 for selectively outputting one of output signals from the first and second band pass filters 70h1 and 70h2 in response to the control signal from the comparison unit 60.
In operation, upon receiving the control signal of the first logic level from the comparison unit 60, the switch 70h3 outputs as the final luminance signal the output signal from the second band pass filter 70h2 in which has been removed the high frequency band of signal corresponding to the black noise. On the contrary, upon receiving the control signal of the second logic level from the comparison unit 60, the switch Oh3 outputs as the final luminance signal the output signal from the first band pass filter 70h1 or the frequency signal corresponding to the original base band of the received satellite broadcasting signal.
Referring to Fig. 9, there is shown a circuit diagram of the luminance signal processor 70f and the filtering circuit 70h of the video signal processing circuit 70 in the system in
Fig. 7. As well-known, the first and second band pass filters 70hl and 70h2 include coils L1 and L2 and capacitors C2 and
C3, respectively.Also, the luminance signal processor 70f includes a DC voltage source Vcc, a capacitor C1 for inputting the luminance signal Y from the Y/C separator 70e, first and second resistors R1 and R2 connected in series between the DC voltage source Vcc and ground and connected in common to an output of the capacitor Cl, a NPN type transistor Q1 having its collector connected to the DC voltage source Vcc, its emitter connected to the ground and its base connected to the common connection point of the first and second resistors R1 and R2, and a third resistor R3 connected between the emitter of the NPN type transistor Q1 and the ground.
Now, a point of difference between the video signal processing circuits 70 in Figs. 4 and 7 will be described.
In the case where the reception sensitivity or the C/N ratio of the received satellite broadcasting signal is bad due to the bad weather conditions such as the rainfall, the video signal processing circuit 70 in Fig. 4 amplifies the video signal on the basis of the carrier center frequency to increase the attenuated reception sensitivity and then removes the noise from the amplified video signal to increase the quality of the video signal. Namely, the video signal processing circuit 70 in Fig. 4 processes the luminance and chrominance signals Y and C simultaneously, resulting in the following problem. Generally, in the case where the C/N ratio of the received satellite broadcasting signal is bad, the black noise is placed on the high frequency band of the received satellite broadcasting signal. The black noise results in only degradation of the luminance signal Y.For this reason, when the simultaneous process of the luminance and chrominance signals Y and C is performed, the video signal of poor color may be obtained since the chrominance signal C of the high frequency band is unnecessarily removed. For the purpose of improvement in the video signal processing circuit 70 in Fig. 4, the video signal processing circuit 70 in Fig.
7, when the reception sensitivity and the C/N ratio of the received satellite broadcasting signal are bad, separates the luminance and chrominance signals Y and C from the video signal and then removes from the separated luminance signal Y only the high frequency band of signal corresponding to the black noise. Therefore, in accordance with the video signal processing circuit 70 in Fig. 7, there can be obtained the video signal of clean color in which the black noise has been removed without a color damage.
As hereinbefore described, embodiments of the present invention can provide the following advantages:
First, the reception sensitivity and picture quality conditions of the received satellite broadcasting signal are discriminated on the basis of the gain control signal and the noise level which are obtained from the frequency signal demodulated corresponding to the original base band of the received satellite broadcasting signal. If it is discriminated that the conditions are bad, the attenuated reception sensitivity is elevated and the noise is removed.
Therefore, the good picture quality can be obtained from the received satellite broadcasting signal regardless of the weather conditions.
Second, the gain control signal and the noise level are converted into the digital signals, which are then compared with the reference gain control signal and the reference noise level, respectively. The control signal for the process of the video signal is generated in accordance with the compared results. Therefore, the video signal can be compensated for even in fine variations in the gain control signal and the noise level.
Third, the reception sensitivity and picture quality conditions of the received satellite broadcasting signal are checked on the basis of both of the gain control signal and the noise level. This enables an accurate compensation for the video signal.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (20)
1. A satellite broadcasting reception system, comprising:
signal converting means for obtaining a gain control signal, converting a first intermediate frequency signal inputted therein into a second intermediate frequency signal of a band lower than that of the first intermediate frequency signal and automatically controlling a gain of the second intermediate frequency signal in response to the gain control signal;
demodulating means for demodulating the second intermediate frequency signal from said signal converting means into a frequency signal corresponding to an original base band of a received satellite broadcasting signal;
said signal converting means obtaining the gain control signal from an output signal from said demodulating means;
noise level detecting means for detecting a noise level from the output signal from said demodulating means;;
signal detecting means for detecting a video signal from the output signal from said demodulating means;
comparison means for comparing the gain control signal from said signal converting means with a predetermined
reference gain control signal and the detected noise level from said noise level detecting means with a predetermined
reference noise level, respectively, and generating a control
signal for control of the processing of the detected video signal from said signal detecting means in accordance with the compared results; and
video signal processing means for compensating for the video signal from said signal detecting means or processing it normally in response to the control signal from said
comparison means and then processing the video signal to be displayable.
2. A satellite broadcasting reception system as set forth
in Claim 1, wherein said signal converting means includes:
a tuner for converting the first intermediate frequency
signal inputted therein into the second intermediate frequency
signal of the band lower than that of the first intermediate
frequency signal;
an automatic gain control circuit for automatically
controlling the gain of the second intermediate frequency signal from said tuner in response to the gain control signal;
an amplifier for amplifying an output signal from said automatic gain control circuit by a predetermined
amplification degree; and
a rectifier for rectifying the output signal from said demodulating means and outputting the rectified signal as the gain control signal to said automatic gain control circuit.
3. A satellite broadcasting reception system as set forth in Claim 2, further comprising:
a first amplifying circuit for amplifying the gain control signal from said rectifier by a predetermined amplification degree; and
a first analog/digital converter for converting an output signal from said first amplifying circuit into a digital signal and outputting the digital signal to said comparison means.
4. A satellite broadcasting reception system as set forth in any preceding claim, wherein said noise level detecting means includes:
a filter for filtering the output signal from said demodulating means to detect therefrom a desired frequency band of signal corresponding to a noise;
an amplifier for amplifying an output signal from said filter by a predetermined amplification degree; and
a peak detector for detecting an envelope corresponding to a peak value of an output signal from said amplifier.
5. A satellite broadcasting reception system as set forth in Claim 4, wherein said peak detector includes an integrator for integrating the output signal from said amplifier to obtain the envelope of DC level representing the noise level.
6. A satellite broadcasting reception system as set forth in Claim 4 or 5, wherein said filter is a band pass filter.
7. A satellite broadcasting reception system as set forth in Claim 6, wherein said band pass filter has the upper limit value which is higher by 1-2MHz than that of the original base band of the received satellite broadcasting signal.
8. A satellite broadcasting reception system as set forth in any one of Claims 4 to 7, further comprising:
a second amplifying circuit for amplifying the output signal from said peak detector by a predetermined amplification degree; and
a second analog/digital converter for converting an output signal from said second amplifying circuit into a digital signal and outputting the digital signal to said comparison means.
9. A satellite broadcasting reception system as set forth
in any preceding Claim, wherein said video signal processing means
includes:
a first amplifier for amplifying the detected video signal from said signal detecting means by a predetermined amplification degree;
a second amplifier for amplifying an output signal from said first amplifier by a predetermined amplification degree;
a filter for filtering an output signal from said second amplifier to remove therefrom a high frequency band of signal corresponding to a black noise; and
a switch for inputting output signals from said first amplifier and said filter and selectively outputting one of the inputted signals in response to the control signal from said comparison means.
10. A satellite broadcasting reception system as set forth in Claim 9, wherein said filter is a band pass filter having the upper limit value which is lower than that of the original base band of the received satellite broadcasting signal
11. A satellite broadcasting reception system as set forth in any preceding claim, wherein said video signal processing means includes::
a luminance/chrominance separator for separating luminance and chrominance signals from the video signal from said signal detecting means;
a luminance signal processor for processing the separated luminance signal from said luminance/chrominance separator to be displayable;
a chrominance signal processor for processing the separated chrominance signal from said luminance/chrominance separator to be displayable;
a filtering circuit for filtering an output signal from said luminance signal processor in response to the control signal from said comparison means to remove therefrom a high frequency band of signal corresponding to a black noise; and
an adder for adding output signals from said filtering circuit and said chrominance signal processor and outputting the added signal as the final video signal.
12. A satellite broadcasting reception system as set forth in Claim 11, wherein said filtering circuit includes:
a first band pass filter for filtering the output signal from said luminance signal processor to pass the frequency signal corresponding to the original base band of the received satellite broadcasting signal;
a second band pass filter for filtering the output signal from said luminance signal processor to remove therefrom the high frequency band of signal corresponding to the black noise, thereby to pass only a signal of a frequency band having the upper limit value which is lower than that of the original base band of the received satellite broadcasting signal; and
a switch for selectively outputting one of output signals from said first and second band pass filters in response to the control signal from said comparison means.
13. A satellite broadcasting reception system as set forth in Claim 12, wherein said first and second band pass filters each includes a capacitor and a coil.
14. A satellite broadcasting reception system as set forth in any one of claims 11 to 13, wherein said luminance signal processor includes:
a DC voltage source;
a capacitor for inputting the luminance signal from said luminance/chrominance separator;
first and second resistors connected in series between said DC voltage source and ground and connected in common to an output of said capacitor;
a NPN type transistor having its collector connected to said DC voltage source, its emitter connected to the ground and its base connected to the common connection point of said first and second resistors; and
a third resistor connected between said emitter of said
NPN type transistor and the ground.
15. A satellite broadcasting reception system further including audio signal detecting means for detecting an audio signal from the demodulating means.
16. A satellite broadcasting reception system as set forth in any preceding claim, wherein said signal detecting means includes:
an audio signal detector for detecting only the audio signal from the output signal from said demodulating means; and
a video signal detector for detecting only the video signal from the output signal from said demodulating means
17. A satellite broadcasting reception system as set forth in Claim 16, wherein said audio signal detector includes a band pass filter and said video signal detector includes a low pass filter.
18. A satellite broadcasting reception system as set forth in any preceding claim, wherein said demodulating means includes a band pass filter.
19. A satellite broadcasting reception system as set forth in any preceding claim, wherein said comparison means outputs the control signal of a first logic level for compensation for the video signal when the inputted gain control signal is lower than the predetermined reference gain control signal or when the inputted noise level is higher than the predetermined reference noise level although the inputted gain control signal is higher than the predetermined reference gain control signal and outputs the control signal of a second logic level for the normal process of the video signal when the inputted gain control signal is higher than the predetermined reference gain control signal and the inputted noise level is lower than the predetermined reference noise level.
20. A satellite broadcasting reception system as claimed in any one of claims 15 to 18 further including audio signal processing means for processing the detected audio signal from the signal detecting means to be audible.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1019910024548A KR940008909B1 (en) | 1991-12-27 | 1991-12-27 | Apparatus for improving quality of image signal of sattelite transmission system |
| KR1019910024549A KR950001576B1 (en) | 1991-12-27 | 1991-12-27 | Rainfall Reduction Compensation Circuit of Satellite Broadcasting Receiver |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9226798D0 GB9226798D0 (en) | 1993-02-17 |
| GB2263045A true GB2263045A (en) | 1993-07-07 |
| GB2263045B GB2263045B (en) | 1996-03-20 |
Family
ID=26628880
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9226798A Expired - Lifetime GB2263045B (en) | 1991-12-27 | 1992-12-23 | Satellite television broadcasting reception system |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH05268501A (en) |
| DE (1) | DE4244357A1 (en) |
| GB (1) | GB2263045B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4042959A (en) * | 1976-05-07 | 1977-08-16 | Gte Sylvania Incorporated | Noise suppression circuit |
| US4926261A (en) * | 1988-02-10 | 1990-05-15 | Sony Corporation | Video noise reduction circuit |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2330628B2 (en) * | 1973-06-15 | 1976-09-30 | Siemens AG, 1000 Berlin und 8000 München | RECEIVING DEVICE FOR THE PROCESSING OF MULTI-CHANNEL TELEVISION PROGRAMS BROADCASED ON A SATELLITE |
| JPS5532072A (en) * | 1978-08-29 | 1980-03-06 | Asahi Optical Co Ltd | Compound type digital electric shutter facilitating operation for iris correction |
| JPS6119261A (en) * | 1984-07-05 | 1986-01-28 | Toshiba Corp | Frequency converting circuit |
| CA1329640C (en) * | 1987-07-24 | 1994-05-17 | Miyoshi Yamauchi | Outdoor unit low noise converter for satellite broadcast reception use |
| JPS6449377A (en) * | 1987-08-19 | 1989-02-23 | Mitsubishi Electric Corp | Automatic noise removing circuit |
| JPS6449375A (en) * | 1987-08-19 | 1989-02-23 | Seiko Epson Corp | Automatic picture quality control circuit |
| JPS6450693A (en) * | 1987-08-21 | 1989-02-27 | Hitachi Ltd | Noise reducer |
| US5014350A (en) * | 1988-04-28 | 1991-05-07 | Sanyo Electric Co., Ltd. | Apparatus for and method of improving the AFC of a television broadcast satellite receiver |
| DE3837130A1 (en) * | 1988-11-02 | 1990-05-03 | Thomson Brandt Gmbh | SATELLITE BROADCAST RECEIVER |
| DE3909685A1 (en) * | 1989-03-23 | 1990-09-27 | Kathrein Werke Kg | Method for frequency conversion, especially for communal satellite receiver systems, and associated frequency converter |
| DE4025241A1 (en) * | 1990-08-09 | 1992-02-13 | Thomson Brandt Gmbh | Microwave reception device with antenna dish - has function control data signals fed to antenna dish via antenna cable |
| MY108617A (en) * | 1990-11-15 | 1996-10-31 | Thomson Consumer Electronics Inc | Audio level equalization of broadcast fm and narrow frequency deviation fm radio signals |
| DE4125995A1 (en) * | 1991-06-08 | 1992-12-10 | Licentia Gmbh | RECEIVER ARRANGEMENT |
-
1992
- 1992-12-22 JP JP4342723A patent/JPH05268501A/en active Pending
- 1992-12-23 GB GB9226798A patent/GB2263045B/en not_active Expired - Lifetime
- 1992-12-28 DE DE4244357A patent/DE4244357A1/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4042959A (en) * | 1976-05-07 | 1977-08-16 | Gte Sylvania Incorporated | Noise suppression circuit |
| US4926261A (en) * | 1988-02-10 | 1990-05-15 | Sony Corporation | Video noise reduction circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2263045B (en) | 1996-03-20 |
| GB9226798D0 (en) | 1993-02-17 |
| JPH05268501A (en) | 1993-10-15 |
| DE4244357A1 (en) | 1993-07-01 |
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