JPH0514903A - Mobile satellite receiver - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a device suitable for being applied to a mobile body that receives satellite broadcasting, and prevents a synchronous flow at the time of switching between an input video signal and a video signal from a memory, thereby making a sense of discomfort. The present invention is intended to provide a receiving device that does not include the above. [Structure] Satellite broadcasting receiving antenna 1, circuit 3 for selecting and demodulating BS-IF signal, circuit for amplifying and detecting CN ratio, circuit 4 for demodulating video, and digitally storing video signal Memory 8, a switch 11 for switching an input video signal and a video signal from the memory, and a circuit 12 for controlling the switch, and an optimal switching pulse depending on a voltage value corresponding to the CN ratio and a fixed or variable threshold voltage value. Is output, which is a switching style. [Effects] With the above configuration, it is possible to prevent a synchronization flow at the time of switching, and to provide a satellite broadcast receiving device with no discomfort.

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 such as an automobile.

[0002]

2. Description of the Related Art In recent years, the demand for satellite broadcasting has been increasing due to the expansion of broadcasting satellites and the diversification of program contents. It is considered that satellite broadcast waves, which are free from the effects of multipath and ghost and have a wide service area, are suitable for reception on mobile bodies such as automobiles. For satellite broadcasting reception on ships and trains where the propagation conditions are relatively good and there is no fast tracking operation, there are systems that are already in use or are being developed for practical use.

An example of the above-mentioned conventional satellite broadcast mobile receiving device will be described below with reference to the drawings. FIG. 6 shows the configuration of a conventional satellite broadcast mobile receiving device. In FIG. 6, 1 is a BS antenna for automatic tracking, and 2
Is the antenna controller. 3 selects a BS-IF signal, demodulates it, and 4 performs a video signal process. Reference numeral 5 is a video signal sync separation circuit, and 6 is a sync detection circuit. Reference numeral 7 is an A / D converter for periodically sampling and A / D converting a video signal, 8 is a memory for temporarily storing, and 9 is a D / A converter. Reference numeral 10 is a timing generation circuit for generating signals for controlling these circuits. The controller 12 uses the output from the synchronization detection circuit to switch 11
In this, the input video signal and the video signal temporarily stored in memory are switched. The switched video signal is displayed on the CRT 15 via the chroma circuit 13 and the video output circuit 14. The operation of the satellite broadcast mobile receiving device configured as described above will be described below. First, the BS-IF signal from the satellite broadcasting antenna installed on the roof of the moving body and controlled in multiple axes by the geomagnetic sensor, gyro, or the phase difference of the incoming satellite broadcasting radio wave is 3 channel selection, demodulation circuit, 4 video signal. It becomes a video signal through the processing circuit. The video signal is separated by a sync separation circuit 5 into horizontal and vertical signals or a composite sync signal. On the other hand, the signal output from the video signal processing circuit 4 is sampled at regular intervals,
It is D and temporarily stored in the memory as a digital signal. This digital signal is D / A converted and input to the switch 11 as an analog video signal. The timing generation circuit is based on the sync signal generated by the sync separation circuit.
It generates clocks for the / D converter, the memory, and the D / A converter, and write and read pulses. Now, when the mobile body enters a tunnel in a city area or in a mountainous area and the radio wave of the satellite is blocked by the tunnel, the video signal disappears and the output of the sync separation becomes 0 level. If the sync detection circuit 6 monitors the output of the sync separation circuit, the reception state of satellite broadcasting can be grasped. According to the synchronization detection circuit 6, the controller 12 selects the input video signal when the reception condition is good, and when the radio wave is blocked, selects and displays the still screen stored in the memory 8 when the reception condition is good. It is possible to eliminate the unsightly appearance of the noise screen when the radio wave is cut off, and to receive the satellite broadcast mobile body reception without any discomfort.

[0004]

However, in the above-mentioned conventional configuration, since the presence or absence of the sync signal is detected, the level of the video signal is about to drop when the satellite radio wave is cut off, and the screen is out of sync and the screen is displayed. As a result, the whole screen is dancing before and after the screen stands still, and the response is slow. Also, since the input video signal and the video signal from the memory are switched uniformly depending on the presence or absence of the sync signal, it can be stored in a good image state and kept still in an area where satellite reception is strong or in an environment with good weather conditions. The present invention, which was not provided, solves the above-mentioned conventional problems, and when radio waves are blocked and a still image is displayed, it is possible to prevent screen dancing and smoothly change from a moving image to a still image without discomfort and with good followability. Another object of the present invention is to provide a satellite broadcast mobile receiver that stores the best image state in memory according to the satellite broadcast reception state and freezes it.

[0005]

In order to achieve the above-mentioned object, the present invention is installed on the roof of a mobile body and has a multi-axis controlled satellite broadcasting antenna, an antenna controller for controlling the antenna, and an output from the antenna controller. BS-I
Circuit for F signal selection and FM demodulation, circuit for amplifying and detecting CN ratio, circuit for demodulating video and audio, and periodically A / D converting the video signal, memory, D / A conversion Circuit, a timing circuit for generating write / read pulses, a switch for switching between the input video signal and the D / A converted video signal, and when the CN ratio is high, the input video signal is output and when the CN ratio is low, Is a circuit that controls the switch to output the video signal from the memory, and the threshold level that switches between the input video signal and the video signal from the memory is changed to store the best image status according to the satellite broadcast reception status. It has a configuration of a controller circuit that makes it stand still.

[0006]

[Operation] When satellite broadcast waves are blocked by this configuration,
Detect the CN ratio, switch to a still image while the level is below a certain level and the sync signal is stable,
Ensuring image stability and tracking, and varying the threshold level that switches between the input video signal and the video signal from the memory according to the reception status of satellite broadcast waves Memory in the image state,
The object is to provide a satellite broadcast mobile receiver that reduces the state in which the image is stationary by sacrificing a little memory for the image in a bad state.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A satellite broadcast mobile receiving apparatus according to a preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a satellite broadcast mobile receiver according to the first embodiment of the present invention. In FIG.
An antenna controller installed on the roof of a moving body, which controls a multi-axis controlled satellite broadcasting antenna and an antenna, a circuit for selecting and demodulating a BS-IF signal output from the antenna controller, an FM demodulation, and a CN ratio amplification, A circuit for detecting, a circuit for demodulating video and audio, a circuit for periodically A / D converting a video signal to perform memory / D / A conversion, a timing circuit for generating a write / read pulse,
A switch for switching the original video signal and the D / A converted video signal, and a circuit for controlling the switch to output the input video signal when the CN ratio is high and output the video signal from the memory when the CN ratio is low. have.

FIG. 2 shows a controller circuit in which the threshold level for switching between the input video signal and the video signal from the memory is varied to store the best image state in memory according to the satellite broadcast reception state and to make it stand still. The operation of the satellite broadcast mobile receiving device configured as described above will be described below with reference to FIGS.

First, FIG. 1 shows the configuration of a satellite broadcast mobile receiver, which is installed on the roof of a mobile and is multi-axis controlled by a geomagnetic sensor, a gyro, or the phase difference of incoming satellite broadcast radio waves. BS-I from broadcast antenna
The F signal is FM demodulated by the channel selection and demodulation circuit of 3. Demodulation output is FM by 16 band pass filters (BPF)
Wide area noise generated in the demodulation circuit is selected, amplified and corrected by the AMP 17, and becomes a signal corresponding to the CN ratio. (Special public H
The CN ratio detection of 18) is to preset the threshold voltage value of the CN ratio corresponding to the allowable limit of the image quality, and output an ON / OFF signal with the value as a boundary. The video signal output from the video signal processing circuit 4 is separated by a sync separation circuit 5 into horizontal, vertical, or composite sync signals. Also, when satellite broadcast waves can be received normally, the video signal is switch 11, chroma circuit 1
3. Displayed on the CRT 15 via the video output circuit 14 and determined in consideration of visibility-A / D converted at a sampling rate of twice or more of the color carrier at a constant time and temporarily stored as a digital signal. Memorized in. This digital signal is D / A converted and input to the switch 11 as a still image analog video signal. The timing generation circuit generates a clock, a write and a read pulse for the A / D converter, the memory and the D / A converter based on the sync signal generated by the sync separation circuit. Now, when the mobile unit enters a tunnel in a city or mountainous area and the radio waves from the satellite are blocked, the CN output from the AMP 17
The ratio is lowered, and the CN ratio detection circuit 18 outputs a signal indicating that the voltage has fallen below the threshold voltage. When the controller 12 sees this signal, the timing circuit 10 is instructed to read the signal for prohibiting the write pulse output to the memory 8 and the normal still image signal before the CN ratio is lowered, and the switch 11 is set to the memory side. Switch. If the AMP output of 17 is monitored by the CN ratio detection circuit of 18, the reception state of satellite broadcasting can be grasped. When the reception state is good, the original video signal is selected, and when the radio wave is blocked, the memory is selected. By selecting and displaying the still screen stored in 8 when the reception state is good, it is possible to eliminate unpleasantness of the noise screen at the time of blocking the radio wave and to receive the satellite broadcast mobile reception without feeling uncomfortable.

Next, a concrete circuit embodiment of (claim 5) will be described with reference to FIG. 2a. 30 is a CN ratio detection signal, 31 is an emitter resistance, 32 and 42 are transistors, 33 is a diode, 34 is an input resistance, 40 and 41 are division resistances, 36
Is a threshold adjustment volume, 38 is an operational amplifier, 3
9 is a feedback resistance of the operational amplifier, 43 is a collector resistance, 44
Is a controller output, 45 is a B voltage, 11 is a switch for switching between an input video signal 47 and a video signal 48 from a memory, and 49 is a selected video signal.

In the circuit configured as described above, the CN ratio detection signal received by the buffer transistor 32 is applied to the plus side of the operational amplifier 38 via the resistor 34. This CN ratio detection signal is smoothed by the capacitor 35 to suppress a minute fluctuation, and when the CN ratio becomes low, the diode 3
3. Discharge through the transistor 32 to quickly follow the decrease in CN ratio. On the other hand, the comparison voltage is finely adjusted by the volume 36 placed between the B voltage 45 and the GND, and is input to the minus side of the operational amplifier 38 via the resistor 37. The output of the operational amplifier is high level when the value of the CN ratio is higher than the reference voltage according to the level change of the CN ratio, and is low level in the opposite case. This output is a transistor 4
Inverted by 2, switch 1 as control signal 44
In 1, the input video signal 47 and the video signal 48 from the memory are switched.

Next, a concrete circuit embodiment of claim 6 will be described with reference to FIG. 2b. 30 is a CN ratio detection signal, 31 is an emitter resistance, 35 and 53 are capacitors, 32 and 42 are transistors, 33, 50 and 52 are diodes, 34 is an input resistance, 40, 41, 51 and 54 are dividing resistors, and 36 is Threshold adjustment volume, 38 operational amplifier, 39 operational amplifier feedback resistance, 43 collector resistance, 44 controller output, 45 B voltage, 11 input video signal 4
7 and switch for switching video signal 48 from memory, 4
Reference numeral 9 is a selected video signal.

In the circuit configured as described above, the CN ratio detection signal received by the buffer transistor 32 is applied to the plus side of the operational amplifier 38 through the resistor 34. The CN ratio detection signal is smoothed by the capacitor 35 to suppress fine fluctuations, and when the CN ratio becomes low, the CN ratio detection signal is discharged through the diode 33 and the transistor 32 to quickly follow the decrease in the CN ratio. On the other hand, the CN ratio signal is applied to the resistor 5
The signal divided by 1 and 54 is charged in the capacitor 53. At this time, divide the CN ratio by about half, and
The time constant of 3 is set to several times that of the capacitor 35, the average level of the CN ratio is held, the volume 36 is finely adjusted and set, and added through the diode 52. The diode 52 is set to cut off the discharge route of the capacitor 53. The output of the operational amplifier is high level when the value of the CN ratio is higher than the reference voltage according to the level change of the CN ratio, and is low level in the opposite case. This output is inverted by the transistor 42, and as the control signal 44, the input video signal 47 and the video signal 48 from the memory are input to the switch 11 at the switch 11.
Switch.

Next, the timing for preventing the synchronous flow at the time of switching a still image will be described with reference to FIG. FIG. 3A shows the intensity of the radio wave coming from the broadcasting satellite, and shows that the radio wave is blocked when the level is 0. Reference numeral 61 indicates a level at which the intensity of the radio wave is weakened and synchronization occurs. (B) shows the presence / absence of a synchronization signal, 62 and 64 show the sections where the synchronization signal exists, and 63 the sections where they do not exist. (C) is 65, 66, 6 when the output of (b) is used for the presence or absence of radio waves of satellite broadcasting.
7 shows a section where a synchronous flow may occur. (D) shows the CN ratio corresponding to the strength of the radio wave, 6
Numeral 8 is a threshold voltage value determined based on the allowable limit of the image. Judge the goodness of the image at this level,
(E) shows the switching timing. In this figure, 69 and 61 indicate sections when the radio wave is stable, and 60 indicates a section when the signal is cut off. As can be seen from this figure, the synchronization flow does not occur because the image is switched to the still image within the section where the synchronization is stable. Next, the characteristics and timing of the threshold change during reception of satellite broadcast radio waves will be described using FIG. 4 and FIG. Figure 4
The X-axis indicates the CN ratio, and the Y-axis indicates the CN ratio detection output voltage.
Reference numeral 80 indicates a CN ratio detection output voltage characteristic, 82 indicates a threshold fixed voltage, and 81 indicates a threshold characteristic obtained by adding a divided value of the CN ratio detection output voltage and the threshold fixed voltage. If this threshold characteristic 81 is used, when the satellite broadcast radio wave is cut off from 83 with a high CN ratio, it is stored in the CN ratio detection output voltage of 84, and when the satellite broadcast radio wave is cut off from 85 with a low CN ratio, it is CN of 86. The threshold level is changed according to the CN ratio in the satellite broadcast wave reception state so as to be stored in the ratio detection output voltage. As a result, (f) of FIG.
87 is (g) at a fixed threshold 89 with respect to the CN ratio in the satellite broadcasting radio wave reception state, and (h) is at a threshold obtained by adding a value obtained by dividing the CN ratio detection output voltage and the fixed threshold voltage, and this signal (5V Sometimes input video signal,
The video signal of the memory is shown at 0V) and the switch 1 in FIG.
If 1 is controlled, the image can be stored in a good image state when the satellite broadcast reception state is good, and in a bad state, the state in which the image is stationary can be reduced by sacrificing the image memory a little.

[0016]

As described above, according to this embodiment, a satellite broadcasting antenna that is installed on the roof of a moving body and is multi-axis controlled, an antenna controller that controls the antenna, and a BS output from the antenna controller. -A circuit for selecting and demodulating an IF signal, a circuit for amplifying and detecting a CN ratio, a circuit for demodulating video and audio, a circuit for periodically A / D converting a video signal, and a memory, D / A A circuit for converting, a timing circuit for generating write and read pulses,
A switch for switching between the input video signal and the D / A converted video signal; and a circuit for controlling the switch to output the input video signal when the CN ratio is high and output the video signal from the memory when the CN ratio is low. , By switching the input video signal and the video signal from the memory, by changing the threshold level, the controller circuit configuration that memorizes and freezes the best image state according to the satellite broadcast reception state is provided. In addition to preventing the synchronization flow that occurs, the threshold level that switches between the input video signal and the video signal from the memory is changed according to the reception status of satellite broadcast radio waves, and when the satellite broadcast reception status is good, memory is stored in a good image status. In a bad state, the image memory is sacrificed a little to reduce the state in which the image is static, which is natural and different. It is those that can be achieved with no sensitive satellite broadcast receiver.

[Brief description of drawings]

FIG. 1 is a block diagram of a device according to an embodiment of the present invention.

FIG. 2 is a specific circuit configuration diagram of a device according to an embodiment of the present invention.

[Fig. 3] Timing diagram for preventing synchronous flow when switching still images

FIG. 4 is a timing diagram of a device according to an embodiment of the present invention.

FIG. 5 is a timing diagram of a device according to an embodiment of the present invention.

FIG. 6 is a block configuration diagram of a conventional device.

Claims (6)

[Claims] 1. A BS received by a satellite broadcast receiving antenna.
A circuit for selecting an IF signal and performing FM demodulation, a circuit for detecting a carrier-to-noise ratio (hereinafter referred to as a CN ratio) of the demodulated signal, a circuit for demodulating a video signal and an audio signal, and a digital signal for the video signal. In the mobile satellite broadcast receiving apparatus, the signal processing means, the signal processing means for writing to and reading from the memory, and the switch for switching between the video signal input from the antenna and the video signal read from the memory are used. A satellite broadcast receiving apparatus for a mobile body, characterized in that the input video signal and the video signal from the memory are switched by comparing the voltage values of a DC voltage corresponding to the above and a DC voltage of a predetermined threshold level. 2. A BS received by a satellite dish.
The ratio of carrier to noise of the demodulated signal of the IF signal (CN
Ratio) and a DC voltage set as a threshold level by adding a constant DC voltage to the DC voltage corresponding to the CN ratio, and comparing the voltage values with each other, an input video signal from the satellite broadcast receiving antenna is obtained. And a signal from a memory are switched, a satellite broadcast receiving apparatus for a mobile body. 3. B output from a satellite broadcast receiving antenna
A circuit for selecting an S-IF signal and performing FM demodulation, a circuit for amplifying and detecting a carrier-to-noise ratio (CN ratio) of the demodulated signal, a circuit for demodulating video and audio, and a demodulated video signal Means for digitally processing and writing to and reading from the memory, a switch for switching between an input video signal and a video signal read from the memory, and a voltage value of a DC voltage corresponding to the CN ratio and a voltage of a predetermined threshold level. A satellite broadcast receiving apparatus for a mobile body, comprising switching control means for comparing the sizes of the above and controlling the switch. 4. The B output from the satellite receiving antenna
A circuit for selecting an S-IF signal for FM demodulation, a circuit for amplifying and detecting a CN ratio, a circuit for demodulating video and audio, and a means for digitally processing a video signal and writing it to and reading it from a memory, A switch for switching an input video signal and a video signal read from a memory, a DC voltage corresponding to the CN ratio, and a threshold for setting a constant DC voltage to the DC voltage corresponding to the CN ratio as a threshold level voltage. A level setting means; and a switching control means for comparing the magnitude of the DC voltage corresponding to the CN ratio with the threshold level voltage and outputting a switching control signal for switching the switch according to the magnitude relationship of the voltage value. The input video signal from the satellite receiving antenna and the signal from the memory are switched by a switching control signal. And a mobile satellite broadcasting receiver. 5. The BS received by the satellite broadcast receiving antenna
The ratio of carrier to noise of the demodulated signal of the IF signal (CN
Ratio) for inputting a DC voltage corresponding to the input terminal to the input terminal, a smoothing capacitor for smoothing the CN ratio detection signal, and a bias voltage terminal and grounded for setting a predetermined threshold level. 2. The satellite for a mobile body according to claim 1, further comprising a voltage adjusting volume for controlling the video signal, a transistor for switching the video signal, and a circuit for switching between the input video signal and the signal from the memory according to the voltage of the predetermined threshold level. Broadcast receiver. 6. An input buffer transistor for receiving a DC voltage corresponding to a CN ratio, a smoothing capacitor, a diode for improving transient characteristics, a comparator, a comparison voltage adjusting volume, a transistor for switching a video signal, and the buffer transistor. 3. A circuit for switching between the input video signal and the signal from the memory is provided by means for resistance-dividing the output voltage of FIG. 1 and superimposing it on the comparison voltage, and a voltage of a threshold level corresponding to the CN ratio.
The satellite broadcast receiving device for a mobile body described.