JPH1093875A - Tuner for satellite broadcasting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tuner for satellite broadcasting, which can obtain the satisfactory signal of an S/N ratio with a simple circuit. SOLUTION: A first intermediate frequency signal inputted to the tuner for satellite broadcasting 20 and the output signal of a local oscillation circuit 22 are mixed in a mixing circuit 24. It is converted to become the frequency of not less than 1.5GHz. The signal of the specified frequency is taken out from the signal which is frequency-converted by a band pass filter 26. The obtained signal is inputted to an S/N enhancer 30 through an amplification circuit 28 and the S/N ratio of the signal is improved. The output signal of the S/N enhancer 30 is inputted to a demodulation circuit 32 and it is demodulated into a video signal and a sound signal. The frequency can be converted so that it becomes the frequency of a second intermediate frequency signal before the signal is inputted to the demodulation circuit 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tuner for receiving satellite broadcasting, and more particularly to a satellite for selecting a signal of a desired channel from a first intermediate frequency signal transmitted from a BS converter attached to a receiving antenna. The present invention relates to a broadcast receiving tuner.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a circuit of a conventional tuner for receiving satellite broadcasting. The satellite broadcast receiving tuner 1 includes a local oscillation circuit 2 for oscillating a signal having a frequency corresponding to a signal of a selected channel. The first intermediate frequency signal sent from the BS converter attached to the receiving antenna 3 is mixed with the output signal of the local oscillation circuit 2 by the mixing circuit 4 and frequency-converted to a second intermediate frequency signal. Further, the bandpass filter 5 extracts a signal of a desired frequency from the second intermediate frequency signal. The output signal of the band-pass filter 5 is amplified by an amplifier circuit 6 having an automatic gain adjustment circuit (AGC circuit), and then demodulated by a subsequent demodulation circuit 7 into a video output and an audio output.

When such a satellite broadcast receiving tuner 1 is used, as shown in FIG. 5, a circuit using an S / N enhancer is added in order to increase the S / N ratio of a signal.
The first intermediate frequency signal is mixed with the output signal of the local oscillation circuit 11 by the mixing circuit 10 and frequency-converted. The local oscillation circuit 11 oscillates a signal having a frequency corresponding to the channel selection signal obtained from the satellite broadcast receiving tuner 1. The output signal of the mixing circuit 10 is input to the band-pass filter 12, and only the signal of the selected channel is output. The output signal of the bandpass filter 12 is input to the S / N enhancer 14 via the amplifier circuit 13,
Here, the S / N ratio is increased. At this time, the output signal of the mixing circuit 10 is set to be 1.5 GHz or more so that the frequency at which the S / N enhancer 14 operates stably is set. The output signal of the S / N enhancer 14 is mixed with the output signal of the local oscillation circuit 11 by the mixing circuit 15 and frequency-converted again to the first intermediate frequency signal. The first intermediate frequency signal thus obtained is input to the satellite broadcast receiving tuner 1.

As shown in FIG. 6, a first intermediate frequency signal is input to a variable band-pass filter 16, and only a signal of a selected channel is extracted by a channel selection signal from a tuner 1 for receiving satellite broadcasting. Is also good. Then, the selected signal is amplified by the amplifier circuit 13, the S / N ratio is further increased by the S / N enhancer 14, and then input to the satellite broadcast receiving tuner 1. Further, as shown in FIG. 7, the first intermediate frequency signal may be selected by the satellite broadcast receiving tuner 1 through the amplifier circuit 13 and the S / N enhancer 14 without frequency selection.

[0005]

By using the circuit shown in FIG. 5, the frequency at which the S / N enhancer operates most stably (1.5 GHz or more) can be obtained, and the S / N ratio can be increased. However, the external circuit of the satellite broadcast receiving tuner becomes complicated. The circuit shown in FIG. 6 can have a simpler structure than the circuit shown in FIG. 5, but since the first intermediate frequency signal is processed at the same frequency, the S / N operating in a wide band is used. An enhancer is required. Further, in the circuit shown in FIG. 7, the channel selection signal from the satellite broadcast receiving tuner becomes unnecessary, and the circuit becomes simpler. However, since no frequency selection is performed, a plurality of signals are input to the amplifier circuit. Therefore, in addition to an S / N enhancer that operates in a wide band, a high-performance amplifier circuit that does not easily generate intermodulation (IM) is required.

SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a tuner for receiving a satellite broadcast capable of obtaining a signal having a good S / N ratio with a simple circuit.

[0007]

SUMMARY OF THE INVENTION The present invention provides a local oscillation circuit for oscillating a signal having a frequency corresponding to a signal of a channel selected from among first intermediate frequency signals, a first intermediate frequency signal and a local oscillation circuit. A mixing circuit for frequency-converting a signal of a channel selected by mixing the output signal of the mixer to a frequency of 1.5 GHz or more, and a band-pass for extracting a signal of the selected channel from the output signal of the mixing circuit A filter, an amplifier circuit for amplifying the output signal of the band-pass filter, and S
An S / N enhancer for increasing the / N ratio and a demodulation circuit for demodulating an output signal of the S / N enhancer.
This is a tuner for receiving satellite broadcasting. The satellite broadcast receiving tuner includes a local oscillation circuit and a mixing circuit for converting the output signal of the S / N enhancer into a second intermediate frequency signal, and the second intermediate frequency signal is demodulated by a demodulation circuit. Is also good. Also, the present invention mixes a local oscillation circuit that oscillates a signal having a frequency corresponding to a signal of a channel selected from the first intermediate frequency signal, and a first intermediate frequency signal and an output signal of the local oscillation circuit. Circuit for frequency-converting the signal of the selected channel into a second intermediate frequency signal, a band-pass filter for extracting a signal of the selected channel from the output signal of the mixing circuit, and an output signal of the band-pass filter Frequency conversion circuit for converting the frequency to 1.5 GHz or more, an amplification circuit for amplifying the output signal of the frequency conversion circuit, and an S / N enhancer for increasing the S / N ratio of the output signal of the amplification circuit And another frequency conversion circuit for converting the output signal of the S / N enhancer into the second intermediate frequency signal again, and a demodulation circuit for demodulating the output signal of another frequency conversion circuit. And a circuit, a satellite broadcasting receiving tuner.

By incorporating an S / N enhancer into a tuner for receiving satellite broadcasting, the S / N ratio of a signal can be increased without using an external circuit. At this time, by setting the signal input to the satellite broadcast receiving tuner to 1.5 GHz or more, the S / N enhancer can be operated efficiently. The signal passed through the S / N enhancer is
By converting the frequency to the frequency of the normal second intermediate frequency signal, the subsequent demodulation circuit can be made the same circuit as the conventional one. Further, only a signal of a desired channel is selected by a band-pass filter, and
By passing through the / N enhancer, the S / N enhancer can be used in the most stable operation range.

[0009]

According to the present invention, the S / N ratio of a signal can be increased without using an external circuit by incorporating an S / N enhancer in a tuner for receiving satellite broadcasting.
Moreover, since a circuit conventionally incorporated in a tuner for satellite broadcast reception can be used, the circuit configuration can be simplified as compared with a case where an external circuit is provided. Further, since the signal is converted to a frequency of 1.5 GHz or more and input to the S / N enhancer, the S / N enhancer can be used in a stable operation range, and the S / N enhancer having a wide operation bandwidth can be used. No need to develop. Furthermore, if only the signal of the selected channel is passed through the S / N enhancer, the performance of the S / N enhancer can be maximized and a good signal can be obtained.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings.

[0011]

FIG. 1 is a block diagram showing an example of a tuner for receiving satellite broadcasting according to the present invention. The satellite broadcast receiving tuner 20 includes a local oscillation circuit 22 and a mixing circuit 24 for converting the frequency of the first intermediate frequency signal.
The mixing circuit 24 is connected to the band pass filter 26. The output signal of the bandpass filter 26 is amplified by an amplifier circuit 28 having an automatic gain control circuit (AGC circuit).
The signal is input to the S / N enhancer 30. Further, the output signal of the S / N enhancer 30 is demodulated by the demodulation circuit 32 into a video signal and an audio signal.

A signal from an antenna 34 is input to the satellite broadcast receiving tuner 20. A BS converter is attached to the antenna 34, and the received signal in the 12 GHz band is converted to 1035 MHz to 13
It is converted to a 35 MHz first intermediate frequency signal. This first
The intermediate frequency signal is input to the satellite broadcast receiving tuner 20.

In the satellite broadcast receiving tuner 20, a signal having a frequency corresponding to the selected channel is output from the local oscillation circuit 22. The output signal of the local oscillation circuit 22 and the first intermediate frequency signal are mixed by the mixing circuit 24. In a conventional tuner for receiving satellite broadcasting, the mixing circuit 24
At 134.26 MHz provisionally determined
Alternatively, the signal is converted into a second intermediate frequency signal of 402.78 MHz.
The conversion is performed so that the frequency becomes higher than GHz.

From the frequency-converted signal, only a signal of a desired frequency is extracted by the band-pass filter 26. The output signal of the band pass filter 26 is
The signal is amplified at 8, but a signal of a certain level is input to the S / N enhancer 30 because the AGC circuit is built in the amplifier circuit 28. The S / N enhancer 30 raises the S / N ratio of the signal, and the demodulation circuit 32 demodulates the signal into a video signal and an audio signal.

In this satellite broadcast receiving tuner 20, S
/ N enhancer 30 is incorporated, so that signal S
/ N ratio can be improved. In addition, since the input first intermediate frequency signal is converted to a frequency of 1.5 GHz or more, which is a stable operation band of the S / N enhancer 30, the S / N ratio can be efficiently improved. . In this satellite broadcast receiving tuner 20, the demodulation circuit 3
2 is different from the conventional second intermediate frequency signal, the demodulation circuit 32 has a higher frequency than the conventional tuner.
However, the circuit configuration has a simple configuration in which the S / N enhancer 30 is incorporated in the conventional configuration.

As shown in FIG. 2, a local oscillation circuit 36 and a mixing circuit 38 are provided after the S / N enhancer 30.
And the output signal of the S / N enhancer 30 is
It may be converted to the frequency of the intermediate frequency signal. In this satellite broadcast receiving tuner 20, a second tuner similar to the conventional tuner is used.
Since the intermediate frequency signal is input to the demodulation circuit 32, there is no need to adjust the demodulation circuit 32 so that a signal of a special frequency can be processed.

Further, as shown in FIG. 3, a local oscillation circuit 40 and a mixing circuit 42 are provided after the band-pass filter 26.
May be provided. Then, the output signal of the mixing circuit 42 is sent to the S / N
The data is input to the enhancer 30. The output signal of the S / N enhancer 30 is input to another frequency conversion circuit including the local oscillation circuit 40 and the mixing circuit 44, and the output signal of the mixing circuit 44 is input to the demodulation circuit 32.

In the satellite broadcast receiving tuner 20, the input first intermediate frequency signal is converted into a normal second intermediate frequency signal by the local oscillation circuit 22 and the mixing circuit 24. This second intermediate frequency signal is supplied to a bandpass filter 2
6 to extract only a signal of a specific frequency.
The obtained signal is converted by a frequency conversion circuit including the local oscillation circuit 40 and the mixing circuit 42 to have a frequency of 1.5 GHz or more. The frequency-converted signal is amplified by the amplifier circuit 28, and the S / N enhancer 30 increases the S / N ratio. The output signal of the S / N enhancer 30 is again converted to the frequency of the second intermediate frequency signal by the frequency conversion circuit formed by the local oscillation circuit 40 and the mixing circuit 44. This second intermediate frequency signal is input to the demodulation circuit 32.

In this satellite broadcast receiving tuner 20, the input first intermediate frequency signal is converted to a second intermediate frequency signal, and only the signal selected by the band-pass filter 26 is frequency-converted to 1.5 GHz or more. . That is, since only the selected signal is input to the S / N enhancer 30, the S / N ratio can be efficiently increased.

As described above, in the tuner 20 for receiving satellite broadcasting according to the present invention, the S / N ratio can be increased by omitting the external circuit by incorporating the S / N enhancer 30. In addition, since a circuit included in a conventional tuner for receiving satellite broadcasting can be used, the circuit configuration can be simplified and the S / N ratio can be increased as compared with a conventional combination of a tuner and an external circuit. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a satellite broadcast receiving tuner of the present invention.

FIG. 2 is a block diagram showing another example of the satellite broadcast receiving tuner of the present invention.

FIG. 3 is a block diagram showing still another example of the satellite broadcast receiving tuner of the present invention.

FIG. 4 is a block diagram showing an example of a satellite broadcast receiving tuner as a background of the present invention.

FIG. 5 is a block diagram showing an example in which an external circuit is added to the satellite broadcast receiving tuner shown in FIG.

6 is a block diagram showing another example in which an external circuit is added to the satellite broadcast receiving tuner shown in FIG.

FIG. 7 is a block diagram showing still another example in which an external circuit is added to the satellite broadcast receiving tuner shown in FIG.

[Explanation of symbols]

 Reference Signs List 20 Tuner for satellite broadcast reception 22 Local oscillation circuit 24 Mixing circuit 26 Bandpass filter 28 Amplifying circuit 30 S / N enhancer 32 Demodulation circuit 36 Local oscillation circuit 38 Mixing circuit 40 Local oscillation circuit 42 Mixing circuit 44 Mixing circuit

Claims (3)

[Claims] 1. A local oscillation circuit that oscillates a signal having a frequency corresponding to a signal of a channel selected from among first intermediate frequency signals, and mixes the first intermediate frequency signal with an output signal of the local oscillation circuit. A mixing circuit for frequency-converting the signal of the selected channel into a frequency of 1.5 GHz or more, a band-pass filter for extracting the signal of the selected channel from an output signal of the mixing circuit, An amplifier circuit for amplifying an output signal of the filter; and an S / N for increasing an S / N ratio of an output signal of the amplifier circuit.
A tuner for receiving a satellite broadcast, comprising an N enhancer and a demodulation circuit for demodulating an output signal of the S / N enhancer. 2. An output signal of the S / N enhancer is output to a second
The tuner for receiving a satellite broadcast according to claim 1, further comprising a local oscillation circuit and a mixing circuit for converting the second intermediate frequency signal into an intermediate frequency signal, wherein the demodulation circuit demodulates the second intermediate frequency signal. 3. A local oscillation circuit for oscillating a signal having a frequency corresponding to a signal of a channel selected from among the first intermediate frequency signals, mixing the first intermediate frequency signal with an output signal of the local oscillation circuit. A mixing circuit for frequency-converting the signal of the selected channel into a second intermediate frequency signal, a band-pass filter for extracting a signal of the selected channel from an output signal of the mixing circuit, A frequency conversion circuit for converting an output signal to a frequency of 1.5 GHz or more; an amplification circuit for amplifying an output signal of the frequency conversion circuit; and an S / N for increasing an S / N ratio of an output signal of the amplification circuit.
An N enhancer, another frequency conversion circuit for converting an output signal of the S / N enhancer again to the second intermediate frequency signal, and a demodulation circuit for demodulating an output signal of the another frequency conversion circuit. Tuner for receiving satellite broadcasting.