JPH0514902A - Mobile satellite receiver - Google Patents

Abstract

PURPOSE:To eliminate abnormal sound by detecting the state of radio wave at the time interruption by means of a CN ratio and executing muting at a level which is one before reproduction cannot be executed. CONSTITUTION:When a travelling object comes to a city, a ravine or a tunnel and the radio wave of a satellite is interrupted, the CN ratio outputted from AMP 23 becomes low and a signal indicating that the ratio comes to under a threshold voltage being set before sound becomes erroneous is outputted by a CN ratio detecting circuit 24. A controller 25 interlocks the analog mute of a sound output by checking the signal. The reception state of a satellite broadcasting is immediately grasped and noise being the error of PCM data occurred in the neighborhood of a threshold is always eliminated by monitoring the output of AMP 23. Thus, abnormal sound occurred whenever radio wave is interrupted is eliminated so that the satellite broadcasting which is natural without strange feeling is received.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite broadcast receiver in a mobile body.

[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. 4 shows the configuration of a conventional satellite broadcast mobile receiving device. In FIG. 4, 1 is a BS antenna for automatic tracking, and 2
Is the controller of the BS antenna. 3 is BS-IF
Signal selection, demodulation, and 4 perform video signal processing. Reference numeral 5 is a video signal sync separation circuit, and 6 is a sync detection circuit. 7 is an A / D that periodically samples and A / D converts the video signal
Converter, 8 is memory for temporary storage, 9 is D / A
It is a converter. Reference numeral 10 is a timing generation circuit for generating signals for controlling these circuits. The controller 12 switches the original video signal and the video signal temporarily stored in the switch 11 by the output from the synchronization detection circuit. The switched video signal is passed through the chroma circuit 13 and the video output circuit 14 to the CRT 15
Is displayed in. On the other hand, an audio carrier signal is extracted from the demodulated signal with 16 BPFs and converted into an analog signal by an audio signal processing circuit of four-phase DPSK demodulation 17, PCM demodulation 18, and analog audio processing 19, and a mute circuit 20 is set. Then, the sound is output to the speaker 21. 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 and A / D at regular time intervals and temporarily stored in a memory as a digital signal. This digital signal is D / A converted and converted into an analog video signal by the switch 1
Input to 1. 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. In addition, a voice carrier signal is extracted from the demodulated signal by the BPF, converted into digital by 17 four-phase DPSK demodulation, error-corrected and PCM-demodulated, converted into an analog signal, and output to the speaker 21 as voice. To be done. At the same time, the mute signal is output from the PCM demodulation by the control from the controller 12 and as the number of PCM data errors increases.
0 is operated. 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 original video signal when the reception state is good, and when the radio wave is blocked, the still screen when the reception state is good stored in the memory 8 and the PCM demodulation circuit 18
When the error rate of the PCM data increases, the mute 20 is operated by both the mute and the control signal from the controller 12 to remove the unsightly noise screen after the satellite radio wave is cut off and the voice noise to eliminate the satellite broadcast mobile reception. can do.

[0004]

However, in the above-mentioned conventional configuration, the audio mute is performed after detecting a certain error rate in the PCM data, or the analog mute is performed when the synchronizing signal of the video signal is lost. Therefore, when the satellite signal is cut off, P has already passed the audio threshold point.
An error has occurred in the CM data, and a "buzzing noise", which is an error signal of the PCM data, is generated momentarily each time the satellite radio wave is cut off, giving a feeling of strangeness to the person watching the television.

The present invention solves the above-mentioned conventional problems, and eliminates a feeling of strangeness and followsability by detecting and muting voice PCM data before an error occurs in the voice PCM data due to interruption of radio waves. The purpose is to provide a satellite broadcast mobile receiver that achieves good voice cancellation.

[0006]

In order to achieve the above-mentioned object, the present invention provides a satellite broadcasting antenna, a circuit for selecting and FM demodulating a BS-IF signal output from the antenna, and a C
A circuit for amplifying and detecting the N ratio, a circuit for demodulating voice,
It is necessary to have a circuit configuration for muting the audio output and eliminating noise before the CN ratio becomes low and the PCM data signal becomes erroneous and the data cannot be reproduced.

[0007]

With this configuration, the condition when the satellite broadcast radio wave is blocked is detected quickly by the CN ratio, and the CN ratio becomes low, so that P
By muting the audio signal output at the level before the CM data signal is erroneous and the data cannot be reproduced, stable and reliable audio erasing can be performed.

[0008]

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 a BS antenna for automatic tracking, and 2 is a controller of the BS antenna. 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 switches the original video signal and the video signal temporarily stored in the switch 11 by the output from the synchronization detection circuit. The switched video signal is displayed on the CRT 15 via the chroma circuit 13 and the video output circuit 14. On the other hand, FM
Wide band noise generated in the demodulation circuit is selected by 22 band pass filters (BPF) and amplified by AMP 23, 24
The CN ratio is detected and the controller 25 outputs a mute signal. An audio carrier signal is extracted from the demodulated signal by 16 BPFs, the phase-modulated audio carrier signal is converted into a digital signal by the 4-phase DPSK demodulation 17 and the PCM demodulation 18, and the analog audio processing circuit 19,
After being D / A converted by, the sound is output as a sound that can be heard by the speaker 21 through the mute circuit of 20. Next, in FIG. 2, 30 is a CN ratio detection signal, 32 is a buffer transistor, 31 is an emitter resistor, and 34 is added to the operational amplifier 38 through the resistor. 35 is a smoothing capacitor. 33
Is a diode for improving transient characteristics, 36 is a threshold adjustment volume, 37 is an input resistance of a comparator, 39 is a feedback resistance of an operational amplifier, 40 and 41 are division resistances, 43 and 4
4 is a collector resistance, 46 is a base resistance, and transistor 4
Inversion at 2, the transistor 45 is driven and the transistors 49 and 50 are switched. 55 and 53 are audio L and R signal inputs, 56 and 54 are audio output signals, 47 and 51 are DC voltage cut capacitors, 48,
The operation of the satellite broadcast mobile receiving apparatus having the above-described configuration will be described with reference numeral 52 being a protective resistor and 57 being a DC power supply voltage. First, FIG. 1 shows the configuration of a satellite broadcast mobile receiving device, which is installed on the roof of a mobile and is a satellite broadcast antenna 1 which is multi-axis controlled by a geomagnetic sensor, a gyro, or the phase difference of incoming satellite broadcast radio waves. The BS-IF signals from 2 and 2 are FM demodulated by the channel selection and demodulation circuit of 3. 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. When the satellite broadcast wave can be normally received, the video signal is displayed on the CRT 15 through the switch 11, the chroma circuit 13, and the video output circuit 14, and after the video signal is A / D converted 7, the sampling is performed at regular time intervals. Then, the digital signal is temporarily stored in the memory 8. This digital signal is D / A converted 9 and input to the switch 11 as a still image analog video signal. The timing generation circuit 10 uses an A / D converter, a memory, and a sync signal generated by the sync separation circuit.
A clock for the D / A converter, a write pulse, and a read pulse are generated, and the switching of the video signal stored in the original video signal is performed by the controller 12 that has detected synchronization. On the other hand, a wide-band noise generated in the FM demodulation circuit is selected from the channel demodulated and demodulated signal by a bandpass filter (BPF), amplified by the AMP 23, and corrected.
The signal corresponds to the N ratio. (See Japanese Patent Publication H1-175487) 24 CN ratio detection corresponds to the allowable limit of voice.
The threshold voltage value of the ratio is set in advance, and an ON / OFF signal with that value as the boundary is output. On the other hand, an audio carrier signal is extracted from the demodulated signal by 16 BPFs, the phase-modulated audio carrier signal is converted into a digital signal by the 4-phase DPSK demodulation 17 and the PCM demodulation 18, and the analog audio processing circuit 19, At D / A
After being converted, the speaker 2 is passed through the mute circuit of 20.
1 outputs as audible voice. Next, reference numeral 32 in FIG. 2 is added to the plus side of the operational amplifier 38 through the buffer transistor resistor 34. This CN ratio detection signal plays a role in suppressing fine fluctuations with a smoothing capacitor, and
If the ratio suddenly decreases, the diode 33 and the transistor 32
The discharge is performed through to quickly follow the decrease in the CN ratio. The DC voltage applied to the plus side of the comparator is output after being compared with the DC voltage fixed by the threshold adjustment volume on the minus side, inverted by the transistor 42, drives the transistor 45, switches the transistors 49 and 50, and outputs the voice. Mutes the signal. Now, when the mobile unit enters a tunnel in a city area or in a mountainous area, and the radio waves from the satellite are blocked, the CN ratio output from the AMP 23 becomes low, and the voltage becomes below the threshold voltage set by the CN ratio detection circuit 24 before a voice error occurs. A signal indicating that it has become available is output. The controller 25 sees this signal and links the analog mute of the audio output. In this way, if the AMP output of 23 is monitored, the reception state of satellite broadcasting can be grasped quickly, and P that occurs near the threshold can be detected.
Noise, which is an error in CM data, is always eliminated.

Next, the timing for preventing noise generation when the satellite broadcast wave is cut off 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 reception state of radio waves deteriorates and PCM data disappears. (B) shows the presence / absence of PCM data, 62 and 64 indicate sections where PCM data exists, and 63 indicates sections where there is no PCM data. (C) shows a section in which the PCM data may be erroneous in 65, 66, and 67 when the output of (b) is used for the presence or absence of a radio wave of satellite broadcasting. (D) shows the CN ratio corresponding to the strength of the radio wave, and 68 sets the threshold voltage value in the level range of the signal capable of reproducing the PCM data. (E) shows the timing at which the sound is judged to be good or bad at this level and the sound is switched.
Is. In this figure, 69 and 71 indicate sections when the radio wave is stable and 70 indicates a section when the signal is cut off. As you can see from this figure, if you mute the audio before the PCM data error starts,
There is no "click noise" due to the error.

[0010]

As described above, according to this embodiment, the satellite broadcasting antenna and the BS-IF output from the antenna are provided.
A circuit for channel selection and FM demodulation, a circuit for amplifying and detecting the CN ratio, a circuit for demodulating voice, and a channel carrier for extracting and demodulating a voice carrier signal with 16 BPF,
4-phase QPSK demodulation, PCM demodulation, analog audio processing, converted into an analog signal by an audio signal processing circuit, and outputs a sound through a mute circuit to a speaker, to a DC voltage corresponding to the CN ratio and a predetermined threshold level. The PCM data signal is erroneous depending on the voltage of the signal, and the satellite broadcast mobile reception circuit is configured by muting the audio signal within the signal level range where the data can be reproduced. It is possible to eliminate the "click noise" that occurs each time the signal is interrupted, and to realize natural and comfortable satellite broadcasting reception.

[Brief description of drawings]

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

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

FIG. 3 is a waveform configuration diagram of a conventional device.

FIG. 4 is a block configuration diagram of a conventional device.

Claims (3)

[Claims] 1. A satellite broadcasting antenna, a circuit for selecting and FM demodulating a BS-IF signal output from the antenna, a circuit for amplifying and detecting a carrier-to-noise ratio (hereinafter referred to as a CN ratio), and a voice signal. The PCM data signal is erroneous due to the demodulating circuit, the DC voltage corresponding to the CN ratio, and the voltage of a predetermined threshold level, and the audio signal is muted within a signal level range in which the data can be reproduced. Satellite receiver for mobile devices. 2. A satellite broadcasting antenna, a circuit for selecting and FM demodulating a BS-IF signal output from the antenna, a circuit for amplifying and detecting a CN ratio, a circuit for demodulating a voice, and the CN ratio. According to a circuit configuration characterized in that a PCM data signal is erroneous due to a DC voltage corresponding to the above and a voltage of a predetermined threshold level, and an audio signal is muted within a signal level range in which data can be reproduced. Item 1. A satellite broadcast receiving device for a mobile body according to item 1. 3. An input buffer transistor for receiving a DC voltage corresponding to the CN ratio, a smoothing capacitor, a diode for improving transient characteristics, a comparator, a comparison voltage adjusting volume, a transistor for switching an audio signal, and a predetermined circuit. 2. The satellite broadcast receiving apparatus for a mobile object according to claim 1, further comprising a circuit for muting an audio signal according to the threshold level voltage.