JP2000307455A - Satellite broadcast receiving tuner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an IF signal from being distorted or abnormally oscillating when amplified by a 2nd and a 3rd amplifier. SOLUTION: This tuner is equipped with a frequency conversion part 1 which inputs multiple satellite broadcast signals having mutually different bandwidths and converting the frequencies of the satellite broadcast signals to output an intermediate-frequency signal, the 1st amplifier 2 which amplifies and outputs the intermediate-frequency signal, SAW filters 3 and 4 which have mutually different passing characteristics, and amplifiers 5 and 6 which input the IF signal and amplify level attenuation components of the IF signal by the SAW filters; and the 1st amplifier 2 is provided between the output end of the frequency conversion part 1 and the input ends of the SAW filters 3 and 4 and the amplifiers 5 and 6 are provided at the output ends of the SAW filters 3 and 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a satellite broadcast receiving tuner capable of receiving a plurality of satellite broadcasts having different bandwidths.

[0002]

2. Description of the Related Art A conventional satellite broadcast receiving tuner will be described with reference to FIG. The satellite broadcast receiving tuner converts first and second satellite broadcast signals having different bandwidths (for example, bandwidths of 36 MHz and 18 MHz) into an intermediate frequency signal (hereinafter, IF).
Frequency conversion unit 2 that converts the frequency into a signal (abbreviated as a signal) and outputs the converted signal.
1, the IF signal output from the frequency converter 21 is input, the first to third amplifiers 22, 23, and 24 for amplifying and outputting the level, and the IF signal are input.
The first and second SAW filters 25 and 2 which output only the frequency band of the desired channel out of the F signal
6.

Here, a first amplifier 22 amplifies an input IF signal to a desired signal level, and second and third amplifiers 23 and 24 operate as first and second SAW filters 2.
The IF signal is amplified by an attenuation of the level of the IF signal generated when the IF signal passes through 5, 26.

[0004] A satellite broadcast signal transmitted from a broadcast satellite is received by a parabolic antenna (not shown) and input to a frequency converter 21. Here, the frequency converter 21 includes a PLL circuit 27 that outputs a local oscillation signal having a constant frequency, and a mixer 28 that converts the frequency of a received satellite broadcast signal and outputs an IF signal.

The PLL circuit 27 has a voltage controlled oscillator 29 for outputting an oscillation signal, a variable frequency divider 30, and a phase comparator 31 for controlling a voltage supplied to the voltage controlled oscillator 29. The voltage controlled oscillator 29 is connected to the phase comparator 31 and the mixer 28.
The connection point between the mixer 9 and the mixer 28 is connected to the phase comparator 31 via the variable frequency divider 30. The oscillation signal output from the voltage controlled oscillator 29 is input to the mixer 28 and the variable frequency Input to the container 30.

Here, the variable frequency divider 30 converts the oscillation signal output from the voltage controlled oscillator 29 into a phase comparator 3 described later.
1, for dividing the signal into a signal having a frequency that can be compared with the reference signal. Although not shown, for example, a control signal is input from a microcomputer provided in a satellite broadcast receiving tuner. Depending on the signal, for example, when receiving the first satellite broadcast signal, the frequency division ratio is 1 /
N1 (N1: positive number), and when the second satellite broadcast signal is received, the frequency division ratio can be switched so as to be 1 / N2 (N2: positive number). The oscillation signal input to the variable frequency divider 30 is frequency-divided by the variable frequency divider 30 and input to the phase comparator 31.

Although not shown, the phase comparator 31 receives a reference signal output from a crystal oscillator, and compares the frequency-divided oscillation signal with the reference signal. Thus, the voltage supplied to the voltage controlled oscillator 29 is controlled so that the oscillation signal is output at a constant frequency. The phase comparator 31 is also connected to second and third amplifiers 23 and 24, which will be described later. When receiving the first satellite broadcast signal, the second comparator 23 transmits the second satellite broadcast signal to the second amplifier 23. When receiving, the base voltage is supplied to the third amplifier 24.

The satellite broadcast signal input to the frequency converter 21 is mixed with an oscillation signal in a mixer 28,
The frequency is converted and output as an IF signal. In addition,
When a satellite broadcast signal is received from voltage-controlled oscillator 29, a local oscillation signal higher than the satellite broadcast signal by the frequency of the IF signal is output. Then, the frequency converter 21
Is output to the first amplifier 22, and its level is amplified and output. Then, the IF signal whose level has been amplified is supplied to the second or third amplifier 2.
3 and 24 are input.

The second and third amplifiers 23 and 24 are connected to IF
The second and third amplifiers 23 and 23 are provided to amplify the level attenuation when the signal passes through the first and second SAW filters 25 and 26 (described later).
24 is connected to the output of the first amplifier 22 and the output of the second amplifier 23 is connected to the first S
The input terminal of the AW filter 25 and the output terminal of the third amplifier 24 are connected to the input terminal of the second SAW filter 26, respectively. And second and third amplifiers 23, 24
The base voltage from the above-described PLL circuit section 27 is supplied to the second amplifier 23 when receiving the first satellite broadcast signal, and the third amplifier 24 when receiving the second satellite broadcast signal.
It is supplied to.

The IF signal is amplified by the second or third amplifiers 23 and 24 and then input to the first or second SAW filters 25 and 26. Here, the first and second SAW filters 25 and 26 each have different pass characteristics. The pass characteristics of the first and second SAW filters 25 and 26 are almost the same as the bandwidths of the first and second satellite broadcast signals, respectively. Only the channels pass through and are output.

The first and second SAW filters 2
The output terminals 5 and 26 are connected to the IF signal output terminal 32. The IF signals output from the first or second SAW filters 25 and 26 are connected to the IF signal output terminal 32 (not shown). The signal is input to the connected demodulator.

[0012]

As described above, in the conventional satellite broadcast receiving tuner, the received satellite broadcast signal is converted into an IF signal, then amplified by the first amplifier 22, and further downstream. First or second SAW filter 2 with connected second or third amplifiers 23, 24
After being amplified by the amount attenuated by 5 and 26, only the desired channel is passed through the first or second SAW filters 25 and 26 and output. Therefore, when the IF signal is already amplified by the second and third amplifiers 23 and 24, the level of the IF signal is already high when the IF signal is input to the second and third amplifiers 23 and 24. However, there has been a problem in that distortion occurs or abnormal oscillation occurs.

The present invention has been made to solve this problem.
The object of the present invention is to prevent distortion and abnormal oscillation from occurring when the signals are amplified in 3, 24.

[0014]

In order to solve the above-mentioned problems, a satellite broadcast receiving tuner of the present invention receives a plurality of satellite broadcast signals, each having a different bandwidth, and converts the plurality of satellite broadcast signals into frequency signals. A frequency converter that converts and outputs an intermediate frequency signal, a first amplifier that amplifies and outputs the intermediate frequency signal, a plurality of SAW filters each having a different pass characteristic, and an IF signal,
A plurality of amplifiers for amplifying the level attenuation of the IF signal by the plurality of SAW filters, wherein a first amplifier is provided between an output terminal of the frequency conversion unit and an input terminal of the plurality of SAW filters; Each of multiple SAW
Provided at the output end of the filter.

Also, in the satellite broadcast receiving tuner of the present invention, the plurality of satellite broadcast signals are first and second satellite broadcast signals having different bandwidths, and the plurality of amplifiers include second and third amplifiers. The plurality of SAW filters includes first and second SAW filters.

Further, in the satellite broadcast receiving tuner of the present invention, the frequency converter and the first amplifier are built in the same IC.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

The satellite broadcast receiving tuner of the present invention will be described with reference to FIG. The satellite broadcast receiving tuner converts first and second satellite broadcast signals having different bandwidths (for example, bandwidths of 36 MHz and 18 MHz) into an intermediate frequency signal (hereinafter, IF).
Frequency conversion unit 1 that converts the frequency into a signal (abbreviated as a signal) and outputs it.
And a first amplifier 2 to which an IF signal output from the frequency conversion unit 1 is input, and amplifies and outputs the level.
First and second SAW filters 3 and 4 to which an IF signal is input and only a frequency band of a desired channel out of the IF signal is output; Second and third amplifiers 5 and 6 are a plurality of amplifiers that amplify the level of the IF signal by an amount corresponding to the attenuation of the level of the IF signal generated when the signal passes through the third and fourth levels.

A satellite broadcast signal transmitted from a broadcast satellite is received by a parabolic antenna (not shown) and input to the frequency converter 1. Here, the frequency conversion unit 1 includes a PLL circuit 7 that outputs a local oscillation signal having a fixed frequency, and a mixer 8 that converts the frequency of a received satellite broadcast signal and outputs an IF signal.

The PLL circuit 7 has a voltage-controlled oscillator 9 for outputting an oscillation signal, a variable frequency divider 10, and a phase comparator 11 for controlling a voltage supplied to the voltage-controlled oscillator 9. The voltage controlled oscillator 9 is connected to the phase comparator 11 and the mixer 8, and a connection point between the voltage controlled oscillator 9 and the mixer 8 is connected via the variable frequency divider 10 to the phase comparator 11.
The oscillation signal output from the voltage controlled oscillator 9 is input to the mixer 8 and the variable frequency divider 10
Is input to

Here, the variable frequency divider 10 converts the oscillation signal output from the voltage controlled oscillator 9 into a phase comparator 11 described later.
In order to divide the signal into a signal having a frequency that can be compared with the reference signal, a control signal is input from a microcomputer provided in a satellite broadcast receiving tuner (not shown). For example, when the first satellite broadcast signal is received, the frequency division ratio is 1
/ N1 (N1: positive number), and when receiving the second satellite broadcast signal, the frequency division ratio can be switched so as to be 1 / N2 (N2: positive number). The oscillation signal input to the variable frequency divider 10 is divided by the variable frequency divider 10 and input to the phase comparator 11.

Although not shown, the phase comparator 11 receives a reference signal output from a crystal oscillator, and compares the frequency-divided oscillation signal with the reference signal. The voltage supplied to the voltage controlled oscillator 9 is controlled so that the oscillation signal is output at a constant frequency. The phase comparator 11 is also connected to second and third amplifiers 5 and 6, which will be described later. When receiving the first satellite broadcast signal, the second comparator 5 transmits the second satellite broadcast signal to the second amplifier 5. When receiving, a base voltage is supplied to the third amplifier 6.

The satellite broadcast signal input to the frequency conversion unit 1 is mixed with an oscillation signal in a mixer 8, frequency-converted and output as an IF signal. When a satellite broadcast signal is received from the voltage controlled oscillator 9,
A local oscillation signal that is higher than the satellite broadcast signal by the frequency of the IF signal is output. . Then, the IF signal output from the frequency conversion unit 1 is input to the first amplifier 2, and its level is amplified and output. The IF signal whose level has been amplified is supplied to the first and second SAW filters 3 and 4.
Is input to

The first and second SAW filters 3 and 4 are:
Each has different pass characteristics. The pass characteristics of the first and second SAW filters 3 and 4 are substantially the same as the bandwidths of the first and second satellite broadcast signals, respectively. Is passed through the first or second SAW filter 3, 4 and input to the second and third amplifiers 5, 6.

The second and third amplifiers 5 and 6 are for amplifying the level attenuation when the IF signal passes through the first and second SAW filters 3 and 4, respectively. , The amplification degree of the IF signal due to the provision of the first and second SAW filters (for example, 20 dB). The input terminals of the second and third amplifiers 5 and 6 are connected to the output terminals of the first and second SAW filters 3 and 4, respectively. The terminal is connected to the IF signal output terminal 12. The second and third amplifiers 5 and 6 receive the second satellite broadcast signal by the second amplifier 5 when the base voltage is received from the phase comparator 11 and the first satellite broadcast signal is received. Sometimes it is supplied to a third amplifier 6.

As described above, the second and third amplifiers 5 and 6 amplify the attenuation of the level of the IF signal caused by passing the IF signal through the first and second SAW filters 3 and 4.
Is provided after the first and second SAW filters 3 and 4, the level of the IF signal is amplified in the first amplifier 2, but is attenuated by the first and second SAW filters 3 and 4. Since the signal is input to the second and third amplifiers 5 and 6 after that, when the IF signal is input to the second and third amplifiers 5 and 6, the level of the IF signal is low. Therefore, the second and third amplifiers 5, 6
No distortion or abnormal oscillation occurs.

The IF signals output from the first and second SAW filters 3 and 4 are not shown in FIG.
The signal is input to a demodulator connected to the F signal output terminal 12.

Here, in the above-described example, the case where two types of satellite broadcast signals having different bandwidths are input has been illustrated, but the case where three or more types of satellite broadcast signals having different bandwidths are received is further described. Represents the S provided at the subsequent stage of the first amplifier 2.
By providing AW filters and amplifiers by the number of satellite broadcast signals, a plurality of satellite broadcast signals can be received by one satellite broadcast receiving tuner. In the above-described frequency conversion unit 1, the frequency conversion unit 1 and the first amplifier 2 are separate, but these may be formed into one IC, and the frequency conversion unit 1 and the first amplifier 2 By integrating them into one IC, a smaller satellite broadcast receiving tuner can be provided.

[0029]

As described above, the satellite broadcast receiving tuner of the present invention receives a plurality of satellite broadcast signals, each having a different bandwidth, and converts the frequency of the plurality of satellite broadcast signals into an intermediate frequency signal. A frequency converter for outputting, a first amplifier for amplifying and outputting the intermediate frequency signal,
A plurality of SAW filters, each having a different pass characteristic; and a plurality of amplifiers to which the IF signal is input and amplifying the level attenuation of the IF signal by the plurality of SAW filters. By providing between the output terminal and the input terminal of the plurality of SAW filters and providing each of the plurality of amplifiers at the output terminal of the plurality of SAW filters, the level of the IF signal is amplified in the first amplifier. Since the level of the IF signal is low when the IF signal is input to the second and third amplifiers because the signal is attenuated by the first and second SAW filters, the second and third amplifiers Distortion and abnormal oscillation do not occur.

In the satellite broadcast receiving tuner of the present invention, the plurality of satellite broadcast signals are first and second satellite broadcast signals having different bandwidths, and the plurality of amplifiers include first to third amplifiers. Since the plurality of SAW filters include the first and second SAW filters, the level of the IF signal is amplified by the fp first amplifier, but is attenuated by the first and second SAW filters. When the IF signal is input to the second and third amplifiers, the level of the IF signal is low, so that distortion and abnormal oscillation do not occur in the second and third amplifiers.

Further, the satellite broadcast receiving tuner of the present invention provides a satellite broadcast receiving tuner capable of receiving a plurality of satellite broadcast signals by incorporating a frequency converter and the first amplifier in the same IC. I can do it.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a main part of a conventional satellite broadcast receiving tuner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frequency conversion part 2 1st amplifier 3 1st SAW filter 4 2nd SAW filter 5 2nd amplifier 6 3rd amplifier 7 PLL circuit 8 Mixer 9 Voltage controlled oscillator 10 Variable frequency divider 11 Phase comparator 12 IF signal output terminal

Claims (3)

[Claims] 1. A frequency converter for receiving a plurality of satellite broadcast signals, each having a different bandwidth, converting the plurality of satellite broadcast signals into a frequency signal, and outputting an intermediate frequency signal, and amplifying the intermediate frequency signal. And a plurality of SAWs each having a different pass characteristic
A filter and the IF signal are input to the plurality of SAs.
A plurality of amplifiers for amplifying the level attenuation of the IF signal by the W filter, wherein the first amplifier is provided between an output terminal of the frequency conversion unit and an input terminal of the plurality of SAW filters. Wherein each of the amplifiers is provided at an output end of the plurality of SAW filters. 2. The plurality of satellite broadcast signals are first and second satellite broadcast signals having different bandwidths, the plurality of amplifiers include second and third amplifiers, and the plurality of SAW filters are second and third amplifiers. The satellite broadcast receiving tuner according to claim 1, further comprising first and second SAW filters. 3. The satellite broadcast receiving tuner according to claim 1, wherein the frequency converter and the first amplifier are built in the same IC.