JPH11205170A - Digital satellite broadcasting receiver - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent a bit error rate from deteriorating due to an unnecessary wave near a digital satellite broadcast signal of a desired channel such as a digital satellite broadcast signal of an adjacent channel or a high-frequency noise. SOLUTION: An RF of a received digital satellite broadcast signal is provided.
The signal is supplied to the high-frequency direct quadrature detection means 5 via the HPF 3 and the preamplifier 4, and the carriers from the local oscillator 8 by the multipliers 7a and 7b and the carrier shifted by the 90-degree phase shifter 9, respectively. The signals are multiplied and converted into baseband demodulated I and Q signals. These demodulated I and Q signals pass through LPFs 11a and 11b, respectively, and the A / D converter 1
2 is supplied. When the user specifies a desired channel, the control microcomputer 21 sends control data to the frequency synthesizer 14, and sets the pass bandwidth of the LPFs 11a and 11b to be optimal for demodulated I and Q signals in the desired channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital satellite broadcast receiver used for a digital satellite broadcast front end for receiving digital satellite broadcasts having different transmission bandwidths.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing an example of a conventional digital satellite broadcasting receiver, wherein 1 is a front end, 2 is a high frequency signal input terminal, 3 is a high-pass filter, 4 is a preamplifier, 5 is high frequency direct quadrature detection means, 6
Are RF / AGC (high frequency variable gain) amplifiers, 7a and 7b
Is a multiplier, 8 is a local oscillator, 9 is a 90-degree phase shifter, 10
a and 10b are baseband amplifiers, 11a 'and 11b'
Is a low-pass filter, 12 is an analog-digital conversion circuit, 13 is a digital demodulator, 14 is a frequency synthesizer, 15 is a digital demodulated signal output terminal, 16 is a power supply terminal, 17, 18 are power terminals, and 19 is a clock. Terminal,
Reference numeral 20 denotes a data terminal, and reference numeral 21 denotes a control microcomputer.

In FIG. 1, a front end 1 is supplied with a power supply voltage from a power supply terminal 17 to be in an operation state. The front end 1 is received by an antenna (not shown) installed outdoors, and received by an outdoor unit (not shown) at 1 GHz. A digitally modulated high frequency (in this case, radio frequency) digital satellite broadcast signal in a band is input from the input terminal 2. A power supply voltage is supplied from the power supply terminal 16 to the external unit via the input terminal 2. Further, a power supply voltage for channel selection is supplied from the power supply terminal 18.

In this front end 1, the input R
An F (radio frequency) signal is converted to a high-pass filter (hereinafter, HP).
F) 3 and a preamplifier 4 perform processing such as unnecessary wave removal and amplification, and then the level is adjusted by an RF / AGC amplifier 6 controlled by an AGC voltage generated by a digital demodulation means 13 to obtain a high frequency direct quadrature. The signal is supplied to the detection means 5.

[0005] In the high frequency direct quadrature detection means 5, the R output from the local oscillator 8 and the RF / AGC amplifier 6 is output.
A carrier having a fixed phase at a frequency equal to the center frequency of a digital satellite broadcast signal of a desired channel (hereinafter, referred to as a desired channel signal) in the F signal is output.

The RF supplied from the RF / AGC amplifier 6
On the one hand, the signal is multiplied by the carrier from the local oscillator 8 in a multiplier 7a and converted into a baseband signal. This baseband signal is supplied as a demodulated I signal to a low-pass filter (hereinafter, referred to as LPF) 11a 'via a baseband amplifier 10a. RF / AG
The RF signal supplied from the C amplifier 6 is also
At b, the carrier is shifted by 90 degrees by the 90-degree phase shifter 9 to be converted into a baseband signal. This baseband signal is supplied as a demodulated Q signal to the LPF 11b 'via the baseband amplifier 10b.

The oscillation frequency of the local oscillator 8 (ie, the oscillation frequency of the local oscillator 8)
The frequency of the above carrier) is
Is controlled as follows.

The frequency synthesizer 14 includes a control microcomputer 2 for controlling the operation of the entire digital satellite broadcast receiver.
1 is operated by a clock supplied through a clock terminal 19. When a desired channel is specified by the user, the control microcomputer 21 sends control data corresponding to the specified desired channel to the frequency synthesizer 14 via the data terminal 20. Therefore, the frequency synthesizer 14 captures the control data, detects the oscillation frequency of the local oscillator 8, and refers to the control data to make the oscillation frequency equal to the center frequency of the RF signal in the desired channel signal. As shown in FIG.
By controlling the power supply voltage supplied from the oscilloscope, the oscillation frequency of the local oscillator 8 is controlled. Thereby, the oscillation frequency of local oscillator 8 is set to a frequency at which a desired channel signal can be received.

The baseband signal output from the multiplier 7a is amplified as a demodulated I signal by a baseband amplifier 10a, and is then digital-broadcast satellite signal of an adjacent channel (hereinafter referred to as an adjacent channel signal) by an LPF 11a '.
Such unnecessary waves are suppressed, and further supplied to an analog / digital conversion circuit (hereinafter, referred to as an A / D conversion circuit) 12 to be encoded into a binary number. The baseband signal output from the multiplier 7b is amplified as a demodulated Q signal by the baseband amplifier 10b, and unnecessary waves such as adjacent channel signals are suppressed by the LPF 11b '.
The signal is supplied to the A / D conversion circuit 12 and is encoded into a binary number.

[0010] The encoded demodulated I and Q signals are supplied to digital demodulation means 13 and digitally demodulated, and the demodulated digitally demodulated signal is output from an output terminal 15.

In some cases, error correction is also performed by the digital demodulation means 13.

The digital demodulation means 13 is connected to the control microcomputer 2 via a clock terminal 19 and a data terminal 20.
The internal information (for example, transmission rate and bit) indicating the setting of the processing operation inside the digital demodulation unit 13 (for example, transmission rate, modulation method, etc.) and the reception state of the signal received by the digital demodulation unit 13 It also has a function of transmitting and receiving information such as an error rate and the presence or absence of a synchronization signal.

Here, in such digital satellite broadcast reception, interference caused by an adjacent channel signal, which is one of the causes of deterioration of the reception state, will be described.

Normally, the digital satellite broadcast signals of each channel are arranged continuously by frequency division as shown in FIG. When a digital satellite broadcast signal arranged in this manner is received, the received RF signal is received as in the above-described conventional example.
In a digital satellite broadcast receiver using a method of directly converting a signal to a baseband signal (so-called direct conversion method), the output of the high-frequency direct quadrature detection means 5 is
As shown in FIG. 5, in addition to the baseband signal whose center frequency of the desired channel signal is 0, an adjacent channel signal arranged adjacent thereto is included as a baseband signal at a frequency position separated by the signal interval. ing. A part of the baseband signal of the adjacent channel signal is converted by the A / D conversion circuit 12 into a frequency band of the desired channel signal to become an interference signal, which has an adverse effect on the demodulation characteristics of the digital demodulation means 13 and is most affected by digital signal transmission. This causes deterioration of the bit error rate, which is an important characteristic, and causes deterioration of image quality and the like.

[0015] Of course, a similar problem is caused by unnecessary waves such as noise near the digital satellite broadcast signal of the desired channel.

In order to suppress such an adverse effect due to the interfering signal, in the conventional digital satellite broadcasting receiver shown in FIG. 6, the high frequency direct quadrature detection means 5 and the A / D conversion circuit 12 are used.
And LPFs 11a 'and 11b' are arranged between
By setting the passbands of the PFs 11'a and 11b 'to have a specific passband corresponding to the transmission characteristics (for example, the transmission bandwidth) of the digital satellite broadcast signal, the above-described interference signal is suppressed, and the adjacent channel signal and the like are suppressed. This prevents the bit error rate from deteriorating due to interference signals near the desired channel signal.

[0017]

By the way, even in a digital satellite broadcast signal received via the same satellite, the transmission bandwidth is not always the same in all channels. Normally, the transmission bandwidth of the broadcast signal is different. In the above-mentioned conventional digital satellite broadcast receiver, when receiving such digital satellite broadcast signals having different transmission bandwidths, the pass bandwidths of the LPFs 11a 'and 11b' are received in order to prevent information loss of the transmission signals. The characteristic is set to correspond to the digital satellite broadcast signal of the channel having the widest transmission bandwidth among the digital satellite broadcast signals.

However, in such a conventional digital satellite broadcast receiver, the LPFs 11a 'and 11b'
When receiving a digital satellite broadcast signal having a transmission bandwidth narrower than the pass bandwidth of the digital satellite broadcast signal, although there is no signal loss, the bit error rate due to unnecessary waves near the desired channel signal such as an adjacent channel signal or high frequency noise is reduced. Deterioration occurs, resulting in deterioration of image quality and the like.

Also, digital satellite broadcast signals having different transmission bandwidths are often transmitted from different satellites, and an antenna is required for each satellite in order to receive them. In such a receiver, it is necessary to connect these antennas to the input terminal 2 of the front end 1 according to each reception, which requires a great deal of trouble.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem, and to prevent a bit error rate from deteriorating even when a channel desired to be received is switched, so that a good image quality can be obtained. Is to provide.

Another object of the present invention is to provide a digital satellite broadcast receiver capable of automatically receiving digital satellite broadcast signals from different satellites.

[0022]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for transmitting a digital satellite broadcast signal between a high frequency direct quadrature detection means and an A / D conversion circuit, the plurality of transmission paths corresponding to transmission characteristics. An LPF having a bandwidth is arranged, and the pass bandwidth of the LPF is controlled so as to always become an optimum pass bandwidth according to the transmission characteristics of a received signal.

Also, the present invention provides a receiving means for receiving a group of digital satellite broadcast signals from n different satellites (where n is an integer of 2 or more), and Selecting means for selecting a digital satellite broadcast signal group including the desired channel signal, and selecting the desired channel signal, and setting the LPF pass bandwidth according to the desired channel signal.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of a digital satellite broadcast receiver according to the present invention.
Reference numerals a and 11b denote LPFs, and parts corresponding to those in FIG.

In the figure, the received digital satellite broadcast signals are from the same satellite in the first embodiment, and generally the same transmission characteristics (transmission bandwidth, transmission rate, etc.) for each channel. However, depending on the channel, for example, the transmission bandwidth may be different from other channels.

Therefore, the LPFs 11a and 11b have a plurality of pass bandwidths corresponding to the transmission bandwidths of these channel signals.
An optimum pass bandwidth is set according to the transmission bandwidth of the desired channel signal to be received. For example, if the transmission bandwidth BW of the received desired channel signal is 27 MHz, the frequency bandwidth of the demodulated I and Q signals output from the high-frequency direct quadrature detection means 5 is, as shown in FIG. 13.5 MHz, which is 1/2 of BW. Therefore, in this case, the pass bandwidth of these LPFs 11a and 11b is 1
It is set to 3.5 MHz.

The control microcomputer 21 stores data indicating the transmission characteristics (transmission bandwidth, transmission rate, center frequency of RF signal, etc.) for each channel of the digital satellite broadcast signal. Is specified, the control microcomputer 21 refers to the data for the specified desired channel, and sends control data for setting the oscillation frequency of the local oscillator 8 and the pass bandwidth of the LPFs 11a and 11b from the data terminal 20 to the frequency synthesizer 14. send. Upon receiving the control data, the frequency synthesizer 14 controls the oscillation frequency of the local oscillator 8 so as to match the center frequency of the desired channel signal in the RF signal as described above, and also controls the low-pass frequencies of the LPFs 11a and 11b. The width is set so as to match the frequency band of the demodulated I and Q signals output from the multipliers 7a and 7b at this time.

Here, the pass bandwidths of the LPFs 11a and 11b are controlled via the frequency synthesizer 14, but may be directly controlled by the control microcomputer 21.

Further, the received digital satellite broadcast signal contains data indicating the above-described transmission characteristics, and by using this, the LPFs 11a and 11b are used.
May be optimally set.

For example, the control microcomputer 21 fetches the error-corrected digital demodulated signal demodulated by the digital demodulation means 13 through the data terminal 20 to extract the above-mentioned data. The transmission rate may be determined, and the control data may be sent from the data terminal 20 to the frequency synthesizer 14 or the LPFs 11a and 11b in accordance with the result of the determination to switch the pass bandwidth of the LPFs 11a and 11b.

If the digital demodulation means 13 can also detect the error rate of the encoded signal supplied from the A / D conversion circuit 12, the control microcomputer 2
1 fetches the error rate via the data terminal 20 and sequentially changes the bandpass widths of the LPFs 11a and 11b in a direction in which the error rate is improved while monitoring the error rate, so that the best error rate is obtained. It may be set to a pass band of a certain value. The pass bandwidth at this time is an optimum pass bandwidth for the demodulated I and Q signals output from the multipliers 7a and 7b.

Also in the first embodiment, since a system for directly converting a digital satellite broadcast signal as an RF signal to a baseband signal (so-called direct conversion system) is used, when a desired channel is switched, the adjacent channel is switched. In some cases, interference due to channel signals may occur. In this manner, the high-frequency direct quadrature detection means 5 and the A / D
LPFs 11a and 11b arranged between conversion circuits 12
Since the pass band width of the desired channel signal is optimally set according to the desired channel signal, unnecessary waves in the vicinity of the desired channel signal such as adjacent channel signals are sufficiently suppressed, and the bit error rate is reduced. Deterioration can be prevented.

Further, high-frequency noise output from the multipliers 7a and 7b can be reduced, and deterioration of the bit error rate at the time of a weak electric field or low C / N can be prevented.

FIG. 2 is a block diagram showing a second embodiment of a digital satellite broadcast receiver according to the present invention,
2b is a high frequency signal input terminal, 3a and 3b are HPFs,
a, 4b are preamplifiers, 22 is an input switching circuit, 16a,
Numeral 16b denotes a power supply terminal, and portions corresponding to those in FIG.

In the second embodiment, digital satellite broadcast signals from different satellites can be selectively received. In FIG. 2, an antenna (not shown) installed outdoors is used to receive from one satellite. Then, a digitally modulated digital satellite broadcast signal converted into a 1 GHz band by an outdoor unit (not shown) is input from an input terminal 2a, and the HPF 3a
After processing such as unnecessary wave removal and amplification is performed by the preamplifier 4a and the preamplifier 4a, the signal is supplied to the high frequency direct quadrature detection means 5. Similarly, it is received from the other satellite by an antenna (not shown) installed outdoors, and 1G by an outdoor unit (not shown).
The digitally modulated digital satellite broadcast signal converted to the Hz band is input from the input terminal 2b, and after being subjected to processing such as unnecessary wave removal and amplification by the HPF 3b and the preamplifier 4b, is supplied to the high frequency direct quadrature detection means 5. Is done.

Here, the preamplifiers 4a and 4b are ON / O
When switching data is supplied from the control microcomputer 21 to the input switching circuit 22 via the data terminal 20 and the frequency synthesizer 14, the input switching circuit 2
2 switches the preamplifiers 4a and 4b to O according to the switching data.
N, OFF control, one of them is turned on and the other is turned off. Thereby, the input terminals 2a, 2
One of the received RF signals from b is selected and supplied to the high frequency direct quadrature detection means 5.

Therefore, for example, a series of digital satellite broadcast signals having a transmission bandwidth of 27 MHz from one of the satellites (hereinafter, referred to as a series)
This is referred to as a first digital satellite broadcast signal group), and the other satellite has a transmission bandwidth of 36 MHz.
When an RF signal of a series of digital satellite broadcast signals (hereinafter, referred to as a second digital satellite broadcast signal group) is transmitted, an antenna for receiving the first digital satellite broadcast signal group and an outdoor unit are provided. The first and second digital satellite broadcast signals can be received by connecting the antenna for receiving the second digital satellite broadcast signal group and the outdoor unit to the input terminal 2b by connecting to the input terminal 2a. The first digital satellite broadcast signal group is input from the input terminal 2a, and the second digital satellite broadcast signal group is input from the input terminal 2b.

Therefore, when the user specifies a desired channel, the control microcomputer 21 determines which of the first and second digital satellite broadcast signal groups includes the specified desired channel, and furthermore, determines the RF signal. The center frequency and the transmission bandwidth of the signal are determined, and control data corresponding to the determination result is sent to the frequency synthesizer 14 and the input switching circuit 22. Based on the control data sent, the input switching circuit 22 turns on the preamplifier 4a and turns on the preamplifier 4b when the designated desired channel is included in the first digital satellite broadcast signal group. In the OFF state, the first digital satellite broadcast signal group input from the input terminal 2a is supplied to the high frequency direct quadrature detection means 5, and the designated desired channel is included in the second digital satellite broadcast signal group. In some cases, the preamplifier 4b is turned on and the preamplifier 4a is turned off, and the second digital satellite broadcast signal group input from the input terminal 2b is supplied to the high-frequency direct quadrature detection means 5.

When the designated desired channel is included in the first digital satellite broadcast signal group based on the data from the control microcomputer 21, the frequency synthesizer 14 sets the pass band of the LPFs 11a and 11b to the first. Of digital satellite broadcast signals in the digital satellite broadcast signal group
When the specified desired channel is set to 13.5 MHz, which is の of the transmission bandwidth of 7 MHZ, and is included in the second digital satellite broadcast signal group, the LPFs 11 a and 11
The pass band b is set to 18 MHz, which is の of the transmission bandwidth of 36 MHZ of the digital satellite broadcast signal in the second digital satellite broadcast signal group.

It should be noted that the transmission bandwidths of the digital satellite broadcast signals of the respective channels transmitted from the same satellite may not always be equal. In this case, if the control microcomputer 21 knows the transmission bandwidth in all the receiving channels, the user specifies the desired channel and
The control microcomputer 21 determines the transmission bandwidth in the designated desired channel, and according to the determination result, the LPF 11
What is necessary is just to set the pass bandwidth of a and 11b.

However, as in the first embodiment shown in FIG. 1, when the control microcomputer 21 sets the pass bandwidth of the LPFs 11a and 11b using the output of the digital demodulation means 13, the following is performed. What should I do?

That is, when the preamplifier 4a is turned on to select the first digital satellite broadcast group, the LPF 11a,
11b is once set to a predetermined value for the first digital satellite broadcast group, and then the first
The passband width is adjusted to the optimum passband for the designated desired channel by the same method as that of the embodiment. For example, in the first digital satellite broadcasting group, if the transmission bandwidth is 27 MHz as described above for most channels, or if the average transmission bandwidth is approximately 27 MHz, the preamplifier 4
Turn on a to select the first digital satellite broadcast group, and temporarily set the pass bandwidth of LPFs 11a and 11b to 13.
It is set to 5 MHz and then adjusted to the optimum pass bandwidth for the specified desired channel. The same applies to the case where the second digital satellite broadcast signal group is selected.
The pass band widths of a and 11b are once set to 18 MHz, and thereafter, the pass band width is adjusted to the optimum pass band width for the designated desired channel.

As described above, in the second embodiment, the same effects as those of the digital satellite broadcast receiver of the first embodiment shown in FIG. 1 can be obtained, and the digital satellite broadcast signals having different transmission characteristics can be obtained. In order to receive each broadcast signal, it is not necessary to replace the antenna or outdoor unit, and the user simply selects the desired channel and receives the digital satellite broadcast signal of this desired channel. Can be.

In the second embodiment, digital satellite broadcast signals from two satellites are received. In general, digital satellite broadcast signals from n satellites (where n is an integer of 2 or more) are received. The same applies to the case of receiving a satellite broadcast signal.

FIG. 3 is a block diagram showing a third embodiment of a digital satellite broadcast receiver according to the present invention, in which 23 is a tunable filter, 24 is a tuner, 25 is a mixer,
26 is a local oscillator, 27 is an IF amplifier, 28 is a quadrature detection means, and 29 is a local oscillator.

Referring to FIG.
And 1 GH in which processing such as unnecessary wave removal and amplification is performed by the HPF 3, the preamplifier 4, and the tunable filter 23.
RF of z-band digitally modulated digital satellite broadcast signal
The signal is supplied to the tuner unit 24.

In the tuner section 24, the supplied RF
The signal is adjusted in level by the RF / AGC amplifier 6 and supplied to the mixer 25. In the mixer 25, the local oscillator 26 and the frequency synthesizer 14 form frequency conversion means. The frequency synthesizer 14 controls the local oscillator 26 according to control data supplied from the control microcomputer 21 via the data terminal 20, and sets the oscillation frequency to a value corresponding to the designated desired channel. Thus, the RF signal supplied by the mixer 25 is mixed with the carrier from the local oscillator 26, and the center frequency of the digital satellite broadcast signal of the desired channel is set to a predetermined frequency,
For example, it is converted to a 479.5 MHz IF signal. This IF signal is amplified by an IF amplifier 27 and then supplied to a quadrature detector 28.

In the quadrature detection means 28, the local oscillator 29 oscillates at a frequency (here, 479.5 MHz) equal to the center frequency of the supplied IF signal in the desired channel. Fixed carrier has occurred. On the other hand, the supplied IF signal is multiplied by this carrier in a multiplier 7a to be converted into a baseband signal, and further supplied to an LPF 11a to remove unnecessary waves such as adjacent channel signals. Is supplied to the A / D converter 10. In addition, multiplier 7
In (b), the IF signal is multiplied by the carrier from the local oscillator 29 whose phase has been shifted by 90 degrees by the 90-degree phase shifter 9 to be converted into a baseband signal, and supplied to the LPF 11b to remove unnecessary waves such as adjacent channel signals. After that, the signal is supplied to the A / D converter 10 as a demodulated Q signal.

The operation after the A / D converter 10 is the same as that of the first embodiment shown in FIG.
The pass band width of 11b is set in the same manner as in the embodiment shown in FIG.

Also in the third embodiment, the LPF 11a,
Since the pass bandwidth of 11b is always set to be optimal for any desired channel, even if the transmission characteristics of the digital satellite broadcast signal to be received are different, an unnecessary wave in the vicinity of the desired channel signal such as an adjacent channel signal may be generated. Weak electric field due to bit error rate deterioration and high frequency noise, low C /
It is possible to prevent the bit error rate from deteriorating at the time of N or the like.

Also, as in the third embodiment, the RF
Obtaining the baseband signal after converting the signal into an IF signal can be performed even when receiving transmission signals from a plurality of satellites as in the second embodiment shown in FIG. 2, the tuner unit 24 in FIG. 3 is used in place of the RF / AGC amplifier 6, and the present embodiment is applicable, and the same effect as that of the second embodiment can be obtained.

[0053]

As described above, according to the present invention,
A low-pass filter having a plurality of passbands corresponding to the transmission characteristics of the received digital satellite broadcast signal is arranged between the high-frequency direct quadrature detection means and the A / D conversion circuit, and according to the transmission characteristics of the received signal. By controlling the pass band width of the low-pass filter so that it always becomes the optimum pass band width for the desired channel signal, even when receiving digital satellite broadcasts with different transmission characteristics, unnecessary waves near the desired channel signal such as adjacent channel signals can be obtained. It is possible to obtain good reception characteristics without deterioration of the bit error rate due to deterioration of the bit error rate due to high frequency noise, weak electric field due to high frequency noise, and low C / N.

[Brief description of the drawings]

FIG. 1 is a first digital satellite broadcast receiver according to the present invention.
It is a block diagram showing an embodiment.

FIG. 2 shows a second digital satellite broadcast receiver according to the present invention.
It is a block diagram showing an embodiment.

FIG. 3 shows a third digital satellite broadcast receiver according to the present invention.
It is a block diagram showing an embodiment.

FIG. 4 is a diagram showing an arrangement of transmission signals in satellite broadcasting.

FIG. 5 is a frequency spectrum diagram showing an output signal of a quadrature detector in a digital satellite broadcast receiver.

FIG. 6 is a block diagram showing an example of a conventional digital satellite broadcast receiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front end 2, 2a, 2b High frequency signal input terminal 4a, 4b Preamplifier 5 High frequency direct quadrature detection means 7a, 7b Multiplier 8 Local oscillator 9 90 degree phase shifter 11a, 11b Low pass filter 12 A / D Conversion circuit 13 Digital demodulation means 14 Frequency synthesizer 15 Digital demodulated signal output terminal 21 Control microcomputer 22 Input switching means 24 Tuner section 25 Mixer 26 Local oscillator 28 Quadrature detection means 29 Local oscillator

Claims (7)

[Claims] 1. A high-frequency signal of a received digital satellite broadcast signal of a plurality of channels is inputted, a demodulated I signal is detected by detecting a local oscillation signal having the same frequency as the center frequency of a desired channel, and the local oscillation signal is phase-shifted by 90 degrees. High-frequency direct quadrature detection means for detecting the shifted signal to generate a Q signal, respectively, and a pass band width is set according to the desired channel, and demodulated I and Q signals of a channel adjacent to the desired channel are removed. And a demodulation I, of the desired channel from the low-pass filter.
Binary encoding means for encoding Q into a binary number; and digital demodulation means for digitally demodulating and error-correcting the signal encoded by the binary encoding means and outputting a digital demodulated signal of the desired channel. A receiver for digital satellite broadcasting, comprising: 2. A frequency conversion means for converting a received high frequency signal of a plurality of channels of digital satellite broadcast signals into an intermediate frequency signal by mixing the high frequency signal with a first local oscillation signal; A quadrature detecting means for detecting a demodulated I signal by detecting the local oscillation signal of the second local oscillation signal and a signal obtained by shifting the second local oscillation signal by 90 degrees to generate a demodulated Q signal; A low-pass filter that is set according to the channel and has a variable pass bandwidth for removing demodulated I and Q signals of a channel adjacent to the desired channel, and demodulated I and I of the desired channel from the low-pass filter.
Binary encoding means for encoding Q into a binary number; and digital demodulation means for digitally demodulating and error-correcting the signal encoded by the binary encoding means and outputting a digital demodulated signal of the desired channel. A receiver for digital satellite broadcasting, comprising: 3. The digital satellite broadcast receiver according to claim 1, wherein a pass bandwidth of the low-pass filter is determined according to a transmission bandwidth of demodulated I and Q signals of the digital satellite broadcast signal of the desired channel. Digital satellite broadcasting receiver characterized by changing. 4. The digital satellite broadcast receiver according to claim 1, wherein a pass bandwidth of the low-pass filter changes according to a transmission rate of demodulated I and Q signals of the digital satellite broadcast signal of the desired channel. A receiver for digital satellite broadcasting. 5. A digital satellite broadcast receiver according to claim 1, wherein: a receiving means for receiving a group of digital satellite broadcast signals from n different satellites (where n is an integer of 2 or more); Selecting means for selecting a digital satellite broadcast signal group including the digital satellite broadcast signal of the desired channel from among the received digital satellite broadcast signal groups, and receiving the selected digital satellite broadcast signal group. Digital satellite broadcast receiver characterized by high frequency signals. 6. The digital satellite broadcast receiver according to claim 5, wherein the low-pass filter switches and sets a predetermined pass bandwidth for the digital satellite broadcast signal group selected by the selection unit. A receiver for digital satellite broadcasting. 7. The digital satellite broadcast receiver according to claim 5, wherein the low-pass filter has a predetermined pass bandwidth for the digital satellite broadcast signal group selected by the selection unit. A digital satellite broadcast receiver, which is set to be switched and thereafter adjusted from the specified pass bandwidth to an optimum pass bandwidth for the desired channel.