JPH10285067A - Satellite broadcast receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the deterioration of bit error rate caused by the undesired waves and to secure the excellent detection characteristic for a satellite broadcast receiver by preparing an LPF part at the preceding stage of a detection part. SOLUTION: The high frequency signal inputted from an input terminal 1 is converted into an intermediate frequency signal at a tuner part 4 and inputted to a detection part 6 via an LPF part 7 after undergoing the band limitation via an SAW(surface acoustic wave) filter 5. This input signal is inputted to the I and Q signal mixing circuits 12 and 13 respectively. The filter 5 transmits a desired signal and also its double, triple or quadruple signal. The cut-off frequency of the part 7 is previously set a level higher than the intermediate frequency and lower than the double of intermediate frequency. In other words, a case where the high frequency component signals other than the passing desired signal are leaked to the part 6 due to the characteristic of the filter 5 can be prevented. Thus, it's possible to improve the deterioration of bit error rate caused by the high frequency component signals and to secure the excellent detection characteristic.

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 used for a satellite broadcast front aid, for example.
In particular, a frequency conversion unit and a surface acoustic wave filter (hereinafter referred to as S
AW) and a satellite broadcast receiver provided with at least a detecting means.

[0002]

2. Description of the Related Art In satellite broadcast reception, the FM modulation method has been mainly used as a signal modulation method for transmitting a video signal. As a conventional receiver, a technical report of the Institute of Television Engineers of Japan (Jan. 1990, vol. 14, no.
Satellite broadcast receivers such as those described in pages 53 to 58, "IC-Compact Front End for Satellite Broadcast Tuners") are known.

[0003]

The above-mentioned conventional satellite broadcast receiver uses a so-called analog satellite broadcast in which the signal modulation method is F even if a signal other than the desired signal is input to the input of the FM detection circuit.
Since the modulation is M, the influence on the detection output signal is small. Also, even if output, the image quality does not significantly deteriorate due to visual problems.

However, in a so-called digital satellite broadcast in which a video signal is PCM-coded and a QPSK modulation system is used as a signal modulation system, a detection output bandwidth is about 5 MHz in an analog satellite broadcast, whereas it is 20 MHz.
The interference signal has a large effect on the detection characteristics, and has a problem that it directly leads to bit error rate degradation.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the drawbacks of the prior art, prevent leakage of unnecessary waves to a detection circuit, and perform good satellite broadcast reception without bit error rate and image quality deterioration. It is to provide a satellite broadcasting receiver capable of.

[0006]

In order to achieve the above object, a first aspect of the present invention is to select a desired signal from a plurality of digitally modulated input signals such as four-phase phase modulation. Amplifying and mixing with the first local oscillation signal to convert it to an intermediate frequency signal, a surface acoustic wave filter for band limiting the intermediate frequency signal, and distributing the band limited intermediate frequency signal. Detecting means for directly mixing with the second local oscillation signal and mixing the I signal with a signal obtained by shifting the phase of the second local oscillation signal by 90 degrees to output a Q signal; and the surface acoustic wave filter and the detecting means. And a low-pass filter disposed therebetween.

In order to achieve the above object, a second invention is to select and amplify a desired signal from a plurality of digitally-modulated input signals such as four-phase phase modulation and the like, A frequency converting means for converting to an intermediate frequency signal by mixing with the oscillation signal, a surface acoustic wave filter for band-limiting the intermediate frequency signal, and distributing the band-limited intermediate frequency signal to form a second local oscillation signal; Direct mixing and I
Detecting means for mixing the signal with a signal obtained by shifting the second local oscillation signal by 90 degrees to output a Q signal; and inputting the I signal and the Q signal output from the detecting means,
Binary encoding means for encoding and outputting a base number, digital demodulation means for receiving the encoded signal, performing digital demodulation and outputting a digital demodulated signal, and disposed between the surface acoustic wave filter and the detection means. And a low-pass filter.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention provides a low-pass filter in front of a detection circuit and attenuates unnecessary waves with the low-pass filter to prevent unnecessary waves from leaking to the detection circuit. Thus, it is possible to perform good satellite broadcast reception without deterioration in bit error rate and image quality.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a satellite broadcast receiver according to the first embodiment of the present invention.

In FIG. 1, 1 is a high frequency signal input terminal,
2 is an I signal output terminal, 3 is a Q signal output terminal, 4 is a tuner section for selecting a high frequency input signal and converting it to an intermediate frequency signal, 5 is a SAW, 6 is a detection section for detecting a modulated wave, and 7 is a low band. This is a pass filter unit.

The tuner section 4 includes a high-frequency amplifier section 8, a mixer section 9, an intermediate frequency amplifier section 10, a first local oscillator 11
It has. The detection unit 6 includes an I signal mixing circuit 1
2, Q signal mixing circuit 13, second local oscillation circuits 14, 9
A zero-degree phase circuit 15 is provided.

Next, the operation of the receiver will be described.
The high-frequency signal input from the input terminal 1 is transmitted to the tuner unit 4
After being converted to an intermediate frequency signal and band-limited by the SAW 5, the signal is input to the detection unit 6 via the low-pass filter unit 7. The input signals are input to the I signal mixing circuit 12 and the Q signal mixing circuit 13, respectively. The signal input to the I signal mixing circuit 12 is mixed with an in-phase signal with respect to the oscillation signal input from the second local oscillation circuit 14, converted into a baseband signal, and converted as an I signal from the I signal output terminal 2. Is output.

The signal input to the Q signal mixing circuit 13 is mixed with a signal obtained by changing the phase of the oscillating signal by 90 degrees from the second local oscillation circuit 14 by a 90-degree phase shifting circuit 15 to obtain a baseband signal. And output from the Q signal output terminal 3 as a Q signal.

Next, the pass characteristics of the SAW 5 will be described in detail. Due to its configuration principle, the SAW 5 is two times (960 MHz) and three times (1440 MHz) the desired signal other than the desired signal (in the case of a fundamental wave of 480 MHz) as shown in FIG.
z) or quadruple (1920 MHz) signals have the characteristic of passing through, and these high-order frequency component signals also pass through like the desired signal.

Next, the operation of the low-pass filter section 7 will be described. The cut-off frequency of the low-pass filter unit 7 is previously set to the intermediate frequency or more and twice or less of the intermediate frequency (for example, in the case of the intermediate frequency 480 MHz, 480 MHz
(z is not less than 960 MHz). That is, the characteristic of the SAW 5 prevents the higher-frequency component signal other than the desired signal passing therethrough from leaking to the detector 6. As a result, the degradation of the bit error rate due to the high-order frequency component signal is greatly improved, and a good detection characteristic is obtained.

FIG. 2 is a block diagram of a satellite broadcast receiver according to a second embodiment of the present invention. In the figure, the same operations as those in FIG. 1 are denoted by the same reference numerals, and the description is omitted. Reference numeral 16 denotes an analog-to-digital conversion circuit (hereinafter, abbreviated as an A / D conversion circuit) that inputs the I signal and the Q signal output from the detection unit 6 and encodes and outputs the binary signal.
Reference numeral 17 denotes a digital demodulation circuit that inputs a signal encoded in a binary number, performs digital demodulation, and outputs a digital demodulated signal.
Reference numeral 18 denotes a digital demodulation signal output terminal.

The operation of the receiver shown in FIG. 2 will be described. The operation of this receiver up to the detector 6 is the same as that of the receiver of FIG. The I signal and the Q signal output from the detection unit 6 are respectively input to the A / D conversion circuit 16, and are coded into binary numbers and output. The encoded signal is input to a digital demodulation circuit 17, digitally demodulated, and a digital demodulated signal is output via a digital demodulated signal output terminal 18. In some cases, the digital demodulation circuit 17 corrects the error and outputs a digital demodulated signal after the error correction.

In the receiver of the second embodiment shown in FIG. 2, the same SAW 5 as that of the receiver of the first embodiment shown in FIG. 1 is used. Although a problem occurs, since the low-pass filter 7 is inserted before the SAW 5 and the detector 6, higher-order frequency component signals other than the desired signal due to the characteristics of the SAW 5 are leaked to the detector 6. Bit error rate degradation and the like are greatly improved, and a good digital demodulated output is obtained.

FIG. 4 is a block diagram of a satellite broadcast receiver according to a third embodiment of the present invention. In the figure, the same operations as those in FIG. 1 are denoted by the same reference numerals, and the description is omitted. Reference numeral 19 denotes a SAW module in which the SAW 5 and the low-pass filter 7 are sealed in the same package.

In the receiver according to the present embodiment, since the SAW 5 and the low-pass filter 7 are enclosed in the same package, high-order frequency component signals other than the desired signal passing through the SAW 5 are blocked in the package. As a result, good detection characteristics can be obtained without being leaked to the detection unit 6 due to unnecessary coupling such as space and between patterns.

Further, the SAW 5 and the low-pass filter 7 can be reduced in size by one package, and the receiver can be reduced in size.
The degree of freedom in designing at the time of design is also increased. The packaging of the SAW 5 and the low-pass filter 7 can be applied to the receivers according to the first and second embodiments.

FIG. 5 is a block diagram of a satellite broadcast receiver according to a fourth embodiment of the present invention. In the figure, the same operations as those in FIG. 1 are denoted by the same reference numerals, and the description is omitted. Reference numeral 20 denotes an integrated circuit (IC) in which the detection unit 6 and the low-pass filter 7 are integrated and sealed in the same package.

In the receiver of this embodiment, FIG.
Since the same SAW 5 as that of the receiver of the first embodiment shown in FIG. 1 is used, the same problem as that of the receiver of FIG. 1 occurs, but a low-pass filter 7 is inserted before the SAW 5 and the detector 6. Therefore, bit error rate deterioration and the like due to leakage of higher-order frequency component signals other than the desired signal due to the characteristics of the SAW 5 to the detector 6 are greatly improved, and a good digital demodulated output is obtained.

Further, since the detection unit 6 and the low-pass filter 7 are integrated into one package, the size of the receiver can be reduced, and the degree of freedom in designing can be increased. The packaging of the detection unit 6 and the low-pass filter 7 can be applied to the receivers according to the first and second embodiments.

FIG. 6 is a perspective view showing an example of the low-pass filter 7. In this example, the low-pass filter 7 includes a substrate 23 made of glass epoxy resin or the like, a strip line 24 formed of copper foil thereon, a chip capacitor 25, and a ground pattern 26.

The signal input from the input terminal 21 is input to the chip capacitor 25 whose one side of the electrode is grounded via the grounding pattern 26 via the strip line 24, and is output from the output terminal 22. At this time, the cutoff frequency of the low-pass filter 7 is determined by the inductance component and the capacitance of the chip capacitor 25.

Since the low-pass filter 7 of FIG. 6 uses the strip line 24 instead of the air-core coil, the size of the low-pass filter 7 is reduced, so that the receiver can be downsized and the cost can be reduced. Can also be planned. In the low-pass filter 7 having the configuration shown in FIG. 6, the same characteristics and effects can be obtained with a so-called microstrip line in which a ground pattern is provided on the opposite side of the surface of the substrate 23 where the strip line 24 and the chip capacitor 25 are arranged. .

[0028]

As described above, according to the present invention, by providing a low-pass filter section in front of the detection section, the SA
Unnecessary waves such as high-order frequency component signals other than the desired signal that are not blocked by W are prevented from leaking to the detection unit, and bit error rate deterioration due to unnecessary waves is greatly improved. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a satellite broadcast receiver according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a satellite broadcast receiver according to a second embodiment of the present invention.

FIG. 3 is a graph showing the transmission characteristics of a surface acoustic wave filter.

FIG. 4 is a block diagram of a satellite broadcast receiver according to a third embodiment of the present invention.

FIG. 5 is a block diagram of a satellite broadcast receiver according to a fourth embodiment of the present invention.

FIG. 6 is a perspective view showing an example of a low-pass filter applied in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High frequency input terminal 2 I signal output terminal 3 Q signal output terminal 4 Tuner part 5 Surface acoustic wave filter 6 Detection part 7 Low pass filter part 8 High frequency amplification part 9 Mixer part 10 Intermediate frequency amplification part 11 1st local oscillator 12 I Signal mixing circuit 13 Q signal mixing circuit 14 2nd local oscillation circuit 15 90 degree phase shift circuit 16 A / D conversion circuit 17 Digital demodulation circuit 18 Digital demodulation signal output terminal 19 SAW module 20 Integrated circuit 21 Input terminal 22 Output terminal 23 Board 24 Strip Line 25 Chip Capacitor 26 Ground Pattern

Claims (7)

[Claims] 1. A frequency conversion means for selecting and amplifying a desired signal from a plurality of digitally modulated input signals and mixing the selected signal with a first local oscillation signal to convert the signal into an intermediate frequency signal; A surface acoustic wave filter that band-limits the frequency signal, distributes the band-limited intermediate frequency signal, and directly mixes with the second local oscillation signal to produce an I signal;
A satellite broadcast receiving apparatus comprising: a detection unit that outputs a Q signal by mixing with a signal that is phase-shifted by 0 degrees; and a low-pass filter disposed between the surface acoustic wave filter and the detection unit. Machine. 2. A frequency conversion means for selecting and amplifying a desired signal from a plurality of digitally modulated input signals, and converting the selected signal into an intermediate frequency signal by mixing the selected signal with a first local oscillation signal. A surface acoustic wave filter for band-limiting the signal; distributing the band-limited intermediate frequency signal; mixing the I signal with the second local oscillation signal directly;
Detection means for mixing the signal with the phase-shifted signal to output a Q signal; and binary coding means for inputting the I signal and the Q signal output from the detection means, encoding the binary signals, and outputting the binary signals. Digital demodulation means for receiving the encoded signal, performing digital demodulation and outputting a digital demodulated signal, and a low-pass filter arranged between the surface acoustic wave filter and the detection means. And a satellite broadcast receiver. 3. The satellite broadcast receiver according to claim 1, wherein a cut-off frequency of the low-pass filter is set to be equal to or higher than the intermediate frequency and equal to or lower than twice the intermediate frequency. 4. The satellite broadcast receiver according to claim 1, wherein a cutoff frequency of the low-pass filter is set to be equal to or higher than a second local oscillation frequency. 5. The satellite broadcast receiver according to claim 1, wherein said low-pass filter is integrated in a surface acoustic wave filter package. 6. A satellite broadcast receiver according to claim 1, wherein said low-pass filter is integrated with said detection means. 7. The satellite broadcast receiver according to claim 1, wherein said low-pass filter is constituted by a pattern inductor and a capacitor formed of a microstrip or a strip line.