JPH04240989A - Satellite broadcast receiver - Google Patents

Abstract

PURPOSE:To reduce the provision of a sense of unpleasant to a viewer when the reception is interrupted by an obstacle in the case of employing the satellite broadcast receiver with a mobile body. CONSTITUTION:A video signal 6 and an FM detection output 11 are obtained from a reception signal 2 of an antenna 1, the video signal signal 6 is stored in a picture memory 8 and a signal outputted as a still picture is fed to a switch 10, a noise detection output of the FM detection output 11 is compared respectively with setting voltages 16, 16 by comparators 14, 15, the result of comparison controls the storage operation of the picture memory 8 and controls the changeover of the switch 10. When a reception signal is interrupted, since the video signal just before the shielding is displayed on a monitor 20 as a still picture when the reception signal is in sealing state, no sense of unpleasant is given to a viewer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite broadcast receiving apparatus in a moving body having a satellite tracking mechanism, and more particularly to a satellite broadcast receiving apparatus that obtains still images based on noise detection during radio wave shielding.

0002

[Prior Art] Conventionally, as a satellite broadcasting receiving device having a satellite tracking mechanism for receiving satellite broadcasting on a mobile body,
A configuration as shown in FIG. 3 is well known. In the receiving apparatus shown in the figure, a reception signal 2 of a satellite broadcast wave received by an antenna 1 including a satellite tracking mechanism is frequency-converted into an intermediate frequency (IF) signal 4 by an LNB 3, and inputted to a tuner 5. The tuner 5 selects a desired channel, outputs the video signal 6, and displays the image on the monitor 20.

0003

[Problems to be Solved by the Invention] However, in such conventional satellite broadcasting receiving devices, when the radio waves are blocked by buildings, tunnels, etc., the received image provided to the viewer becomes a noise-only image (generally , this is called a sandstorm). In particular, the pattern of occurrence during the shielding period varies greatly depending on the environment. For example, intermittent shielding of radio waves that occurs when driving on a bridge etc. has the problem of causing discomfort to the viewer. SUMMARY OF THE INVENTION An object of the present invention is to provide a satellite broadcast receiving apparatus that reduces discomfort to viewers when reception is interrupted by a blocking object.

0004

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a detection means for detecting a received signal of a satellite broadcast wave and outputting a detected output signal, as well as extracting a video signal from the received signal. and noise detection means that outputs a noise detection signal according to the noise level included in the detection output signal, and a noise detection means that compares the noise detection signal with a predetermined reference level, and determines whether or not the satellite broadcast wave is blocked based on the comparison result. a comparison/detection means that detects the state and outputs a shielding state detection signal; and a comparison/detection means that stores the video signal as a still image, outputs the stored video signal, and detects the shielding state of the satellite broadcast wave based on the shielding state detection signal. video signal storage control means for controlling the storage operation according to the detection signal; and switching to select either the video signal from the video signal storage means or the video signal extracted from the detection output signal based on the shielding state detection signal. It is equipped with a switching selection means and an image display means for displaying an image of the signal selected by the selection means, and when the satellite broadcast waves are in a shielded state,
The present invention is characterized in that the video signal immediately before the shielding state from the video signal storage means is displayed as a still image on the image display means.

[0005]

[Operation] In the present invention, a switching selection means is provided for selecting between a video signal extracted from a received signal from a satellite broadcast wave and a signal in which the video signal is made into a still image in a storage means, and the detection output signal includes By comparing the noise level with a reference signal and controlling the switching selection means and storage means based on the comparison result, when the received signal is blocked, a still image from the storage means can be displayed, thereby causing discomfort to the viewer. I won't give anything.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings. FIG. 1 shows the configuration of an embodiment of a satellite broadcast receiving apparatus according to the present invention. The device of the above embodiment is LN
B3, tuner 5, noise detection section 12, comparator 14, 1
5, a comparison detection unit 2 detects the shielding state of broadcast waves.
2. A video signal storage control unit 24 that includes an A/D converter 7, a memory 8, and a D/A converter 9 and controls the storage of video signals;
It is comprised of a switching section 10 that switches between the detected video signal and the stored video signal.

In the figure, a received signal 2 received by an antenna 1 is frequency-converted by an LNB 3 into an IF signal 4, and is input to a tuner 5. The tuner 5 selects a desired channel and outputs a video signal 6 and an FM detection signal 11. This video signal 6 is obtained by de-emphasizing the FM detection output, removing the 15 Hz triangular wave, and passing it through an LPF in the video signal band.

[0008] This video signal is converted into a digital signal by the A/D converter 7 and stored in the image memory 8. Furthermore, this image memory 8 outputs a signal as a still image, and the D/A converter 7 outputs the signal as a still image.
A converter 9 converts it into an analog signal. The output of the D/A converter 9 and the video signal are applied to a switch 10, and one of the signals is selected and displayed on the monitor 20. On the other hand, the FM detection output 11 is input to a noise detection circuit 12 to obtain a noise detection output 13 which is a voltage corresponding to the noise level.

FIG. 2 shows how the voltage of the noise detection output 13 changes during the process of shielding radio waves. As time t progresses and the shielding begins, the voltage of the noise detection output 13 increases. Comparators 14 and 15 compare with predetermined comparison voltages 16 and 17, and when noise detection output 13 exceeds the level of comparison voltage 16 (time t1),
The comparator 14 outputs a write enable (WE) signal 18, and when the noise detection output 13 exceeds the level of the comparison voltage 17 (time t2), the comparator 15 outputs a select (SE) signal 19.

Here, the reason why the WE signal 18 and the SE signal 19 are operated at different noise levels of the comparison voltages 16 and 17 will be explained. When the WE signal 18 and SE signal 19 are operated with the same comparison voltage, and the comparison voltage is set to a relatively low noise level, the reception level will drop momentarily due to rolling, pitching, etc. of the moving object rather than shielding. However, if the comparison voltage is set to a high noise level, the noise level of the image provided as a still image will increase, reducing the image quality. This is to become.

This WE signal 18 operates to inhibit writing into the image memory 8. That is, the image memory 8
For example, the video signal for one screen is stored while being constantly updated up to time t1. Therefore, at time t2,
Image data before time t1 is obtained.

The SE signal 19 also operates to control the selection operation of the switch 10. That is, when the voltage of the noise detection output 13 exceeds the comparison voltage 17, it is determined that a shielding state has occurred, and the output of the switch 10 is switched from the video signal from the tuner 5 to the output signal from the image memory 8 using the SE signal 19. At this time, since writing into the image memory 8 is already prohibited by the WE signal 18, the signal read out from the image memory 8 becomes a still image before time t1.

Note that these WE signal 18 and SE signal 19
It is desirable to switch during the vertical retrace period, considering the disturbance of the synchronization of the monitor 20.

[0014]

As described above, according to the present invention, in a satellite broadcast receiving device having a mobile tracking mechanism, when radio waves are blocked by a shielding object when receiving satellite broadcasts on a mobile body, By replacing the noise image (sandstorm) with a still image immediately before being occluded, it is possible to provide a still image with less noise.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of a satellite broadcast receiving device according to the present invention.

FIG. 2 is a diagram illustrating the operation of FIG. 1;

FIG. 3 is a configuration diagram of a conventional satellite broadcast receiving device.

[Explanation of symbols]

1 Antenna 5 Tuner 6 Video signal 8 Image memory 10 Switch 11 FM detection output 12 Noise detection circuit 14,15 Comparator 18 Write enable signal 19 Select signal 20 Monitor 22 Comparison detection section 24 Video signal storage control section

Claims (2)

[Claims] 1. Detecting means for detecting a received signal of a satellite broadcast wave and outputting a detected output signal, and extracting a video signal from the received signal; noise detection means for outputting a detection signal; and a comparison unit for comparing the noise detection signal with a predetermined reference level, detecting a state of shielding of the satellite broadcast wave based on the comparison result, and outputting a shielding state detection signal.・Detecting means, and a video signal that stores the video signal as a still image, outputs the stored video signal, and controls a storage operation according to the shielding state of the satellite broadcast wave based on the shielding state detection signal. a storage control means; a switching selection means for selectively selecting either the video signal from the video signal storage means or the video signal extracted from the detection output signal based on the shielding state detection signal; image display means for displaying an image of the signal selected by the means, when the satellite broadcast wave is in a shielding state, the video signal from the video signal storage means immediately before the shielding state is displayed as a still image on the image display means. A satellite broadcast receiving device characterized by displaying a display. 2. The comparison/detection means compares the noise detection signal with predetermined first and second reference levels, and when the noise detection signal exceeds the first reference level,
A control signal is output to the video signal storage control means to detect that the shielding is in the initial stage and prohibit storage of the video signal, and the noise detection signal is higher than the first reference level. When the second reference level is exceeded, the shielding state is detected and a control signal is sent to the switching selection means so as to select the video signal stored in the video signal storage control means immediately before the shielding state. The satellite broadcast receiving apparatus according to claim 1, comprising means for outputting.