JPH0428183B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a satellite broadcast receiver having features in an audio signal processing circuit.

BACKGROUND TECHNOLOGY Conventionally, the bandwidth of the audio tuning circuit of a satellite broadcasting receiver has often been manually switched, and in some cases, the band width has been automatically switched by detecting the degree of modulation.

Problems to be Solved by the Invention However, with a method that automatically switches the band depending on the degree of modulation, it is difficult to accurately determine the degree of modulation when the signal is modulated by a signal with a large dynamic range, such as classical music. Things are difficult in a short period of time. If the bandwidth is improperly set, distortion will occur. In addition, if the band is selected to be wider than necessary, it will cause distortion due to adjacent voices, and if it is narrow, it will cause distortion due to overdeviation, which is more problematic.

Means for Solving the Problems The present invention solves the above-mentioned problems by storing all the audio carrier waves sent along with one video signal, and storing the currently tuned audio carrier wave and both sides thereof. The configuration is such that the bandwidths of the first and second audio tuning circuits are switched in response to the frequency difference between the audio carrier wave and the audio carrier wave.

Effect The present invention has the above configuration, calculates the frequency difference between the tuned audio carrier wave and the carrier wave closest to the carrier wave, narrows the bandwidth when the frequency difference is smaller than a preset frequency difference, and narrows the bandwidth when the frequency difference is wide. By changing the characteristics of the band waver to widen the width, it is possible to extract an audio signal without distortion.

Embodiment A satellite direction receiver according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of a satellite broadcast receiving system equipped with the audio circuit of the present invention, and shows an example of C-band reception in the United States. In Figure 2, 1 is a parabolic antenna, 2 is an LNB (a block converter that converts all 4GHz band signals to 1GHz band), 3 is a support for LNB2, and cable 4 is a support for support 3.
The output of the LNB 2 is transmitted to the 2nd mixer 5 via the cable 4. In addition, 5 to 8 below are satellite broadcast receivers or
It is called an IDU (indoor unit). The 2nd mixer 5 tunes to a desired video carrier wave and converts it to an intermediate frequency (for example, 510 MHz). 6 is an IF (intermediate frequency) amplifier, 7 is an FM wideband detector, and the band is flat up to about 9MHz. 8 is an audio processing circuit that selects, tunes, and detects an audio carrier wave of 5.5 to 8.5 MHz from the output of the FM wideband detector 7;
is capable of stereo reception, with left (C) and right (R) outputs available.

Next, the main parts of the present invention will be explained using FIG. 1 and FIG. 3. In FIG. 1, 9 is A for audio reception.
System switching circuit for switching the tuning of system (12, 13, 14, 15, 16, 17, 18) and B system (23, 24, 25, 26, 27, 28, 29), 10 is a switch for starting the sertor operation and search start circuit for automatic search start;
Reference numeral 11 denotes a preset type search counter, which is not shown, but if the tuning frequency is to be directly specified using three or four digits, this counter may be preset. 12 is an OR gate, 13 is a PLL phase detector, and the phase detection output is transmitted to a local oscillator (OSC) 14 via a low-frequency wave detector. 15 is a mixer (MIX), which measures the difference between the output of the FM wideband detector 7 and the output of the local oscillator 14, which is 10.7M in this case.
Outputs Hz. 16 is an SIF circuit including a band waver whose bandwidth can be switched, and 17 is an audio detection circuit.

23 is an OR gate, 24 is a PLL phase detector,
25 is a local oscillator, 26 is a mixer, 27 is a
The SIF circuit 28 is a voice detection circuit, which operates in the same manner as the components in the A system.

Here, normal operation will be described. One possible method is to first select a video carrier wave and then automatically search for the A-system audio. This can be done by configuring so that the output of the system switching circuit 9 automatically becomes the high level of the A system after a so-called channel (also called a transponder in a satellite broadcasting receiver) is specified. At the same time as the output of the system switching circuit 9 becomes high level for the A system, the output of the search start circuit 10 and the search counter 11 are made to count up. The search counter 11 counts pulses of 100 Hz, for example, and writes the output to the PLL circuit. Local frequency is 5.5+10.7~8.5+10.7, i.e. 16.2M~
Varies between 19.2MHz. PLL resolution 20KHz
Then, 19.2M=20×960 (steps),
Search counter 11 may be a 10-bit counter.
The standard oscillation is 2MHz, and the frequency is divided by 1/100 to 20KHz.
The local output of the local oscillator 14 is set to 1/n (maximum
960) Compare the divided frequencies and control the local frequency of the local oscillator 14 so that they are equal. Assuming that the A system is tuned to f ₁ =5.6M, the local frequency is 16.3MHz and the frequency division ratio is 815.
In other words, the search counter is 815 in 10-bit binary.
is output, and the phase detector 13 of the PLL is preset to 815 via the OR gate 12. The search counter 11 counts only from 810 to 960, and is forcibly preset to 810 after 960.

Now, if 5.6MHz is not the desired audio carrier wave, manually operate the search start circuit 10,
The search counter 11 is moved again. When the local frequency changes, the tuning detection circuit 18 detects the change in the level of the audio carrier wave of the SIF circuit 16, and at the tuning point,
The search counter 11 is stopped. If the tuning peak is difficult to find in the tuning detection circuit 18, the search counter 11 is preset to the average (or intermediate) value before and after the peak, or the search counter 11 is
As an up/down counter, return to the peak after the peak, and set the search counter 11 at the tuning point.
to be fixed. Let us assume that we are tuned to f ₂ =6.26MHz in Figure 3, and that this is stereo L. Assuming that the range memory 20 is configured to write the frequency division ratio at that time when searching the A system, 6.26M, that is, 848, is stored in the range memory 20 at the address of the A system. If f ₂ is the desired carrier wave, then the system switching circuit 9 is operated to designate a search for system B. At this time, it is assumed that all the frequency division ratios of the tuned carrier waves are written from the range memory 20 to the carrier memory 22 via the arithmetic processing circuit 21 while the A system is specified.

When you specify the search for the B system, the search counter 11 counts 100Hz as in the case of the A system.
Tunes to f ₃ = 6.44MHz, which is next to f ₂ . Below, sequentially f ₄ =
6.62MHz, _f5 = 6.800MHz, _f6 = 7.600MHz, _f7 =
8. It tunes to 200MHz and writes its frequency division ratio to the carrier memory 22. In this case, since the output of the system switching circuit 9 is at a low level in the A system, the phase detector 13 of the PLL has a fixed frequency division ratio (tuned to _f2 ), and the OR gate 12 is prohibited from operating. When f ₁ is about to be written to the carrier memory 22, the memory control circuit 31 writes f ₁
It is detected that the frequency division ratio has already been written somewhere in the carrier memory 22, it is assumed that all the carriers have been written to the carrier memory 22, the mute of the audio detection circuit 28 is canceled, and the data from the carrier memory 22 is The frequency division ratios of f ₁ , f ₂ , and f ₃ are sequentially read out and the search counter 11 is stored in a preset memory. In system B, even if the search start circuit 10 is operated, the frequency division ratios of all carriers are memorized, and each time the search start circuit 10 is operated, the search counter 11 is sequentially updated at each frequency division ratio.
Preset. In this case, a tuned output is always produced. First, a tuned output is produced at _f1 . Audio detection circuit 28
When the R output is heard but it is not the desired carrier wave, when the search start circuit 10 is operated, the search counter 11
is set to the division ratio of f ₂ , but the range memory 20
The A system and B system are the same, and the arithmetic processing circuit 2
1, it is determined that they are the same, and from the carrier memory 22,
Output the following frequency division ratio of f ₃ . This process is repeated, and if _f6 is the desired R voice, the search is left stopped at this point. At this time, the frequency division ratios of f ₂ and f ₆ are stored in the range memory 20. When the search start circuit 10 is not operated for a long period of time after synchronization, the carrier memory 2
The frequency difference detection circuit 30 compares the contents of the range memory 20 with the contents of the range memory 20. In this case, the frequency difference detection circuit 30 detects the frequency difference between f ₁ , f ₃ , f ₄ , f ₅ , and f ₇ with respect to f ₂ and f ₆ , that is, the difference in frequency division ratio. As is clear from FIG. 3, the difference between f ₂ and f ₃ is 180KHz, which is a difference of 9 in the frequency division ratio. Temporarily change the type of audio band waver to ±
Assuming three types: 60KHz, ±120KHz, and ±240KHz,
A bandwidth of ±60 KHz is sufficient to clearly distinguish carrier waves based on the difference between f ₂ and f ₃ . Assuming that the setting error (tuning point detection error) is one step,
When the difference in frequency division ratio is 6, the frequency interval is 120KHz, and if there is an error of 1 step, or 20KHz, then f ₂ + 60 + 20 = f ₂ + 80KHz, and the modulation is nearly half the difference between f ₂ and f ₃ . think about things. That is, if the difference is 6 steps or less, the band needs to be ±60KHz. In the frequency difference detection circuit 30, if the difference in frequency division ratio is 6 steps or less,
Both SIF circuits 16 and 27 are limited to a band of ±60KHz. If the difference in frequency division ratio is less than 12 steps and more than 7 steps, the band will be switched to ±120KHz. If the difference in frequency division ratio is 13 steps or more, set the bandwidth to ±240KHz. These calculations are performed by the frequency difference detection circuit 3.
0, thereby supplying three types of output signals to the SIF circuits 16 and 27. It is well known that SIF band switching can be achieved relatively easily by switching capacitance or inductance. In addition, the B system, that is,
The operation of the tuning detection circuit 29 that detects the tuning point of the SIF circuit 27 is the same as that of the tuning detection circuit 18. As mentioned above, when the switch 10 switches the bandwidth after a certain period of time after tuning B, at the same time, the search start circuit 10 sends an output to the system switching circuit 9,
Both the A/B systems are fixed, the OR gates 12 and 23 are shut off, and the frequency division ratios of the phase detectors 13 and 24 of the PLL are fixed. With this configuration, both the A and B systems are tuned to the correct frequency. Although the outputs of the audio detection circuits 17 and 28 in FIG. The circuit configuration shown in Figure 1 can be used as is. or,
Frequency difference detection does not need to be performed for all frequencies, but if there is a division ratio difference of 6 steps or less, it will be ±60KHz.
Needless to say, it is sufficient to limit the bandwidth.

Effects of the Invention As described above, according to the present invention, the interval between audio carrier waves can be calculated without detecting the peak of the modulation degree,
Since the required bandwidth can be determined, the sound quality of the detected and reproduced sound is good. In addition, since all the audio carrier waves attached to one video signal are stored in memory, when the search switch is pressed, audio carrier waves can be selected one after another. After audio is output from system A, all carrier waves are searched using system B, so the sound can be heard on one channel, so there are few practical problems. B can also be set so that the sound comes out within 10 seconds.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the main parts of a satellite broadcasting receiver according to an embodiment of the present invention, Fig. 2 is a block diagram of a receiving system incorporating the audio circuit of the present invention, and Fig. 3 explains the same operation. FIG. 2 is a characteristic diagram showing a frequency spectrum for. 9...System switching circuit, 10...Search start circuit, 11...Search counter, 12...OR gate, 13...PLL phase detector, 14...Local oscillator, 15...Mixer, 16...SIF Circuit, 17... Audio detection circuit, 18... Tuning detection circuit, 19... Reference oscillator, 20... Range memory, 21... Arithmetic processing circuit, 22... Carrier memory, 23... OR gate, 24... PLL phase detector, 25... Local oscillator, 26... Mixer, 27... SIF circuit, 28... Audio detection circuit, 29... Tuning detection circuit, 30... Frequency difference detection circuit, 31... Memory output control circuit.

Claims (1)

[Claims] 1. A receiver for receiving satellite broadcast waves including two or more audio carrier waves accompanying one video carrier wave, the first receiver being tuned to the first audio carrier wave of the two or more audio carrier waves. a second audio tuning circuit that tunes to a second audio carrier of the two or more audio carrier waves; and a first audio tuning circuit that stores all carrier frequencies of the two or more audio carrier waves. a memory; a second memory for storing a tuning frequency of the first audio tuning circuit and a tuning frequency of the second audio tuning circuit; and a tuning frequency stored in the second memory and a tuning frequency of the second audio tuning circuit; A circuit that calculates a frequency difference with a stored carrier frequency, and determines whether the frequency difference between the currently tuned first or second audio carrier wave and an adjacent audio carrier wave is larger than a preset value. A satellite broadcasting receiver comprising means for switching the bandwidths of the audio bandpass filters of the first and second audio tuning circuits in response to the output of the calculation circuit indicating whether the output is small.