JPH07283798A - Movable receiver for satellite broadcast - Google Patents

Abstract

PURPOSE:To switch the dynamic image/still image without displaying the scramble image in receiving the scramble satellite broadcast by a moving body. CONSTITUTION:The satellite broadcasting radiowave accepted by an antenna 1 is selected and demodulated by a CS/BS tuner 3. An FM detection signal 4, voice bit stream signal 5, C/N ratio 6 are detected to allow a scramble decoder 7 to perform descramble picture processing. A video signal 10 and a descramble data signal 8 are outputted. The video signal 10 and a still picture 12 by a memory 11 are inputted to a video signal switching circuit 14. A controller 9 controls switching the dynamic image/still image based on the C/N ratio 6 and the descramble status signal 8.

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 device in a mobile body.

[0002]

2. Description of the Related Art In recent years, many broadcasting satellites (BS) and communication satellites (CS) have been launched, and the demand for satellite broadcasting is increasing with the increase in the number of channels and diversification of program contents. It is considered that satellite broadcast waves with a wide service area without the effects of multipath and ghosts are suitable for reception by moving bodies such as cars and trains, and there are systems that have already been put to practical use in some ships and trains. is there. For example, it is proposed in JP-A-5-14903.

An example of a conventional satellite broadcast mobile receiver will be described below with reference to FIG. In FIG. 3, reference numeral 1 denotes a satellite antenna for automatic tracking, which is equipped with a frequency converter (hereinafter, converter). Reference numeral 2 is a CS / BS-IF signal, 3 is a CS / BS tuner, which selects and demodulates the CS / BS-IF signal 2 and outputs an FM detection signal 4, an audio bit stream signal 5, and a carrier-to-noise ratio ( Below C /
N ratio) 6 is output. Reference numeral 24 denotes a pay system satellite broadcast scramble decoder (hereinafter referred to as scramble decoder), which outputs the descrambled video signal 10. A memory 11 digitally processes the video signal 10 and temporarily stores it, and outputs the video signal 12 which is a still image. Two
Reference numeral 5 is a controller for outputting a control signal 13 for switching between moving image / still image depending on the value of the C / N ratio 6, 14 is a video signal switching circuit, which controls the moving image signal 10 and the still image signal 12 by the control signal 13. Switch over. 15
Is a monitor for displaying moving images / still images.

The operation of the satellite broadcast mobile receiving apparatus configured as described above will be described below with reference to FIG. First, CS and BS scrambled broadcast radio waves are installed on the roof of a moving body and received by a geomagnetic sensor, a gyro, or a satellite broadcast antenna 1 that is multi-axis controlled by the phase difference of incoming satellite broadcast radio waves, and then received by a converter. The signal is converted into the CS / BS-IF signal 2 and input to the CS / BS tuner 3. In the CS / BS tuner 3, after channel selection, FM demodulated FM demodulated signal 4, QPSK demodulated (quadrature phase demodulated) audio bit stream signal 5,
C / N ratio 6 is output. The scramble decoder 24 performs descramble image processing using the FM detection signal 4 and the audio bit stream signal 5 output from the CS / BS tuner 3 to restore the original video signal. A part of the video signal 10 output from the scramble decoder 24 is stored in the memory 11 after digital processing, and the video signal 12 which is a still image is output from the memory 11. The video signal 10 and the video signal 12 that has become a still image are input to the video signal switching circuit 14.

On the other hand, the controller 25 outputs the video selection control signal 13 to the video signal switching circuit 14 depending on the strength of the C / N ratio 6 output from the CS / BS tuner 3. That is, based on the value of the C / N ratio at which the image is recognized as good, a moving image is output when the C / N ratio is higher than that value, and a still image is output when the C / N ratio is low. Control to. Therefore, when the reception condition is good, a moving image is displayed, and when the reception condition is bad and the reception condition is bad, a still image is selected and displayed on the monitor 15, so that unsightly noise at the time of the interruption of the radio wave is eliminated and the satellite broadcasting is performed without a feeling of discomfort. Can be seen.

[0006]

However, in the above-mentioned configuration, when the BS or CS scrambled broadcast is received, the mobile body passes through the support line of the overhead line, the bridge girder of the overpass, the tunnel, etc., and the electric wave is temporarily blocked. Then, the video / still image is switched depending on the strength of the C / N ratio, but each time the C / N ratio rises and exceeds the descrambling limit, the scramble decoder uses the individually contracted keys necessary for descrambling. Process the reference number and descramble it. Since this processing time is delayed from the time when a still image is switched to a moving image, there is a problem that a scrambled image is temporarily displayed during this processing.

In view of the above problems, the present invention eliminates this temporary scrambled image and provides a more comfortable satellite broadcast reception.

[0008]

In order to solve the above problems, a satellite broadcast mobile receiver according to the present invention is installed on the roof of a mobile such as a car or a train, and is a multi-axis controlled automatic tracking satellite. CS / B that outputs a video signal, an audio signal, and a C / N ratio by selecting and demodulating a broadcasting antenna and a CS / BS-IF signal output from a converter attached to the antenna
S tuner, scramble decoder that outputs descrambled video signal and descramble status signal when receiving scrambled broadcast, memory that digitally stores video signal and outputs still image, and switches between video / still image A video signal switching circuit, a controller that detects the C / N ratio and the descramble status signal, and outputs a control signal for switching the video / still image depending on the strength of the C / N ratio and the value of the descramble status signal, It is equipped with a monitor that displays still images.

[0009]

According to the present invention, the scramble decoder has a function of outputting a signal (descramble status signal) indicating whether or not the video signal is in the descramble state, and the controller has only the strength of the C / N ratio. Not only the video / considering the descramble status signal
The scrambled image is not displayed on the monitor because the still image is switched to the moving image after the descrambling state is confirmed by outputting the still image switching signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a satellite broadcast mobile receiver according to the present invention. 1 is a satellite broadcasting antenna for multi-axis controlled automatic tracking, which is installed on the roof of a moving body and is equipped with a converter. 2 is CS / BS-I
F signal. 3 is a CS / BS tuner, CS / BS-IF
The signal 2 is selected and demodulated, and the FM detection signal 4, the audio bit stream signal 5, and the C / N ratio 6 are output. A scramble decoder 7 outputs a descrambled video signal 10 and a descramble status signal 8. A memory 11 digitally processes the video signal 10 and temporarily stores it, and outputs the video signal 12 which is a still image. Reference numeral 9 is a controller that outputs a control signal 13 for switching between moving and still images according to the value of the C / N ratio 6 and the value of the descrambling status signal 8. Reference numeral 14 is a video signal switching circuit, which controls the video signal 1 of the moving image by the control signal 13.
0 and the video signal 12 of the still image are switched. A monitor 15 displays a moving image / still image.

The operation of the satellite broadcast mobile receiving device configured as described above will be described below with reference to FIGS. 1 and 2. First, in FIG. 1, CS and BS scrambled broadcast waves are received by a satellite broadcast antenna 1. The satellite dish 1 is installed on the roof of the moving body,
Multi-axis control is performed by the geomagnetic sensor, the gyro, or the phase difference of the incoming satellite broadcast waves. The received radio waves are converted into CS / BS-IF signal 2 by the converter and CS
/ Input to the BS tuner 3. CS / BS tuner 3
Now, after channel selection, FM demodulated FM detection signal 4,
QPSK demodulated audio bitstream signal 5, C / N
The ratio value 6 is output. CS / in the scramble decoder 7
Descramble image processing is performed using the FM detection signal 4 and the audio bit stream signal 5 output from the BS tuner 3 to restore the original video signal. At the same time, a descramble status signal 8 indicating whether or not it is in the descramble state is transmitted to the controller 9. A part of the video signal 10 output from the scramble decoder 7 is stored in the memory 11 after digital processing, and the video signal 12 which is a still image is output from the memory 11. The original video signal 10 and the still video signal 12 are input to the video signal switching circuit 14. On the other hand, the controller 9 detects the C / N ratio 6 sent from the CS / BS tuner 3 and the descramble status signal 8 sent from the scramble decoder 7, and when the reception condition is good, a moving image is displayed.
When the radio wave is blocked and the reception condition is poor, the control signal 13 is sent to the video signal switching circuit 14 so as to select a still image.

Here, the timing of switching the video signal will be specifically described with reference to FIG. FIG. 2A shows an example of the C / N ratio corresponding to the strength of the radio wave, and 16 is the allowable limit value of the C / N ratio at which the image is recognized as good, and the times at that time are t ₁ and t ₄ . To do. Reference numeral 17 denotes a C / N ratio threshold value that can be descrambled by the scramble decoder, and the times at that time are t ₂ and t ₃ . FIG. 2B shows a descramble status signal, which has a signal level Hig.
During periods 18 and 20 of h (hereinafter "H"), the video signal is descrambled, and during period 19 of level Low (hereinafter "L"), the video signal 10 is scrambled. Further, time t ₅ indicates the time when the video signal 10 output from the scramble decoder 7 changes from the scrambled state to the descrambled state, and t _{3 to} t ₅ are for the processing of individually contracted keys and collation numbers. It is time. FIG. 2C shows a control signal output from the controller for switching a video signal. Signal level "H"
The images are moving images in the periods 21 and 23, and the images are still images in the period 22 of the level "L". Further, time t ₆ indicates the time at which the still image is switched to the moving image.
(However, t ₁ <t ₂ <t ₃ <t ₄ ≦ t ₅ ≦ t ₆ ) For example, consider the case where a mobile body enters a tunnel. As shown in 2 (a), the C / N ratio sharply decreases. On the other hand, the controller 9 constantly monitors the descrambling status signal 8 and the value of the C / N ratio 6, and at the time t ₁ when the value of the C / N ratio 6 reaches the limit value 16 at which the image is considered to be good, as shown in FIG. "L" to switch the video from video to still as shown in c)
Of the control signal 13 of the above to the video signal switching circuit 14,
The still image 12 is displayed on the monitor 15. By the way, C
When the / N ratio is extremely reduced and the descrambling limit 17 is reached at time t ₂ , the scramble decoder 7 outputs the descramble status signal 8 as shown in FIG.
Is switched from "H" to "L" to notify the controller 9 that the video signal 10 output from the scramble decoder 7 is in the "scrambled state". However, at this time point t ₂ , the image has already been switched to the still image 12 at time t ₁ as shown in FIG. 2C, and therefore the still image in the descrambled state is displayed on the monitor 15. No scrambled image is displayed. Eventually, when the mobile unit exits the tunnel and the C / N ratio recovers rapidly, the scramble decoder 7 exceeds the descramble limit 17 at the time t ₃ and the processing of the key and the reference number is completed. After that, at time t ₅ when a descrambled image can be completely output, the descrambling status signal 8 is switched from “L” to “H” to notify the controller 9 that it is in the “descramble state”. . on the other hand,
The C / N ratio further increases and exceeds the limit value 16 at which the image is recognized as good at time t ₄ . In the controller 9,
The value of C / N ratio of 6 is higher than the limit value 16, and at time t ₆ was confirmed to be descrambled state, the control signal of "H" to switch to the video images from the still images 13
Is sent to the video signal switching circuit 14. Therefore, the descrambled moving image can be displayed on the monitor 15.

In this embodiment, the scramble decoder 7 can output a completely descrambled image as shown in FIG. 2 (b).
The time t ₅ of is set after the time t ₄ of FIG. 2 (a) at which the C / N ratio recovers and the image reaches the limit value at which the image is considered to be good, but in some cases, the reverse may occur. obtain.

[0014]

As described above, according to the satellite broadcast mobile receiving apparatus of the present invention, both the C / N ratio value and the descramble status signal are used for the determination of the moving image / still image switching, and the satellite broadcast radio wave is used. You can eliminate unsightly noise by switching from video to still image when the reception status of is poor.
In addition, when trying to switch from a still image to a video when the reception condition has improved, the descrambling status is checked before switching to a video, so when switching from a still image to a video, the display is temporary but unavoidable. The scrambled image can also be removed, and satellite reception in the mobile can be made more natural and comfortable.

[Brief description of drawings]

FIG. 1 is a block diagram of the configuration of a satellite broadcast mobile receiver according to an embodiment of the present invention.

2 (a) C corresponding to the strength of the radio wave in FIG.
(B) Waveform diagram showing switching timing of descramble status signal in FIG. 1 (c) Waveform diagram showing switching timing of moving image / still image switching control signal in FIG. 1

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

[Explanation of symbols]

 1 Mobile Satellite Antenna 2 CS / BS-IF Signal 3 CS / BS Tuner 4 FM Detection Signal 5 Audio Bitstream Signal 6 C / N Ratio 7 Scramble Decoder 8 Descramble Status Signal 9 Controller 10 Video Signal 11 Memory 12 Stationary Image 13 Video / still image switching control signal 14 Video signal switching circuit 15 Monitor 16 C / N ratio allowable limit value at which image is recognized to be good 17 Descrableable C / N ratio threshold value 18, 20 Video data Scramble period 19 Video scramble period 21, 23 Video display period 22 Still image display period

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04N 7/20 // H04N 7/167

Claims (1)

[Claims] 1. An antenna, a CS / BS tuner, a scramble decoder, and a memory for outputting a still image,
A video signal switching circuit for switching between moving images / still images, a controller for outputting a control signal for switching between moving images / still images depending on the value of the signal indicating whether the ratio of carrier to noise is strong or not and the descrambling state, A satellite broadcast mobile receiving device comprising a monitor for displaying moving images / still images.