JP2004048122A - Down converter for satellite broadcasting reception - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To equalize overall gains even when the deviation of gains in each band of a low-noise amplifier or an intermediate frequency amplifier is not corrected, and to improve the overall gains without increasing the number of stages of the amplifier. <P>SOLUTION: This down converter for satellite broadcasting reception is provided with a low-noise amplifier 1 which amplifies a satellite broadcasting signal in a satellite broadcasting band; a mixer 3 which is provided on the following stage of the amplifier 1 and block-converts the satellite broadcast signal into n intermediate-frequency band being a band lower than the satellite broadcasting band and having the same bandwidth as that of the satellite broadcasting band: an oscillator 21 which supplies a local oscillation signal having a fixed frequency to the mixer 3; and an intermediate-frequency amplifier 4 which amplifies an intermediate frequency signal in an intermediate-frequency band. The frequency of the local oscillation signal is made higher than the maximum frequency in the satellite broadcasting band. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a satellite broadcast receiving downconverter.
[0002]
[Prior art]
FIG. 7 shows a configuration of a conventional down converter for receiving satellite broadcasting. FIG. 7 shows a configuration in which satellite broadcast signals converted from circular polarization into horizontal polarization H and vertical polarization V are block-converted into intermediate frequency signals by circuits of different systems. In the example of US specifications, the band in which satellite broadcast signals are arranged (hereinafter referred to as satellite broadcast band) is from 12.2 GHz to 12.7 GHz, and the band in which intermediate frequency signals are arranged (hereinafter referred to as intermediate frequency band) is It is from 0.95 GHz to 1.45 GHz. Hereinafter, the configuration will be described in detail.
[0003]
First, the horizontally polarized satellite broadcast signal rf is input to a low-noise amplifier 31 including a plurality of stages of amplifiers 31a and 31b. The amplified horizontal polarization H is input to the mixer 33 via the band-pass filter 32. The local oscillation signal Lo is supplied from the oscillator 51 to the mixer 33. Since the frequency of the local oscillation signal Lo is fixed at 11.25 GHz, the mixer 33 outputs an intermediate frequency signal if which is block-converted into an intermediate frequency band of 0.95 GHz to 1.45 GHz. The intermediate frequency signal if of the horizontal polarization H is amplified by an intermediate frequency amplifier 34 including a plurality of stages of amplifiers 34a and 34b, and input to the switching means 52.
[0004]
On the other hand, the vertically polarized satellite broadcast signal rf is also input to the low-noise amplifier 41 including a plurality of stages of amplifiers 41a and 41b. The amplified vertical polarization V is input to the mixer 43 via the band pass filter 42. Since the local oscillation signal Lo having the same frequency of 11.25 GHz is also supplied from the oscillator 51 to the mixer 43, the intermediate frequency signal if which is block-converted into an intermediate frequency band of 0.95 GHz to 1.45 GHz from the mixer 43. Is output. The intermediate frequency signal if of the vertically polarized wave V is amplified by an intermediate frequency amplifier 44 including a plurality of stages of amplifiers 44a and 44b, and input to the switching means 52.
[0005]
The switching means 52 has two output terminals, and the switching operation thereof is controlled by means (not shown), and an intermediate frequency signal if of the horizontal polarization H or an intermediate frequency signal if of the vertical polarization V is supplied to either output terminal. It is to be taken out.
[0006]
Here, the frequency relationship among the satellite broadcast band, the intermediate frequency band, and the local oscillation signal Lo will be described with reference to FIG. Assuming that the lowest frequency 12.2 GHz of the satellite broadcast band is RF1 and the highest frequency 12.7 GHz is RF2, the intermediate frequency signal if is obtained by the frequency difference between the satellite broadcast signal rf and the local oscillation signal Lo, and the local oscillation signal Lo is obtained. Since it is lower than the satellite broadcasting band, the lowest frequency IF1 of the intermediate frequency band is 0.95 GHz and the highest frequency IF2 is 1.45 GHz. That is, the lowest frequency RF1 of the satellite broadcasting band is converted to the lowest frequency IF1 of the intermediate frequency band, and the highest frequency RF2 of the satellite broadcasting band is converted to the highest frequency IF2 of the intermediate frequency band.
[0007]
Next, the relationship between each gain of the low noise amplifier 31 and the intermediate frequency amplifier 34 and the overall gain will be described with reference to FIGS. The content of the relationship between each gain of the low-noise amplifier 41 and the intermediate frequency amplifier 44 and the overall gain is the same, and a description thereof will be omitted.
[0008]
In general, the gain of an amplifier is high at low frequencies and is low at higher frequencies. Further, it is desirable that the entire gain including the intermediate frequency amplifier 34 be flat over the entire intermediate frequency band. Therefore, conventionally, the gain of the low noise amplifier 31 and the gain of the intermediate frequency amplifier 34 are corrected so as to be flat in each band by a correction circuit (not shown). That is, when the low-noise amplifier 31 has such a characteristic that the gain gradually decreases from the gain G1 at the lowest frequency RF1 to the gain G2 at the highest frequency RF2 as indicated by the dotted line in FIG. Is corrected as follows.
[0009]
Similarly, when the intermediate frequency amplifier 34 has such a characteristic that the gain gradually decreases from the gain G3 at the lowest frequency IF1 to the gain G4 at the highest frequency IF2 as shown by the dotted line in FIG. Is corrected to Therefore, if the conversion loss of the mixer 33 is ignored, the overall gain G5 becomes (G2 + G4) as shown in FIG. The number of stages of each of the amplifiers 31 and 34 is determined so that this gain satisfies the specification.
[0010]
[Problems to be solved by the invention]
In the above configuration, since the low noise amplifier and the intermediate frequency amplifier are each provided with a correction circuit for flattening the frequency characteristics, an extra circuit is required for each amplifier, which complicates the configuration. Further, in order to flatten the frequency characteristics, the gain at the lowest frequency of the satellite broadcasting band in the low noise amplifier and the gain at the lowest frequency of the intermediate frequency band in the intermediate frequency amplifier are sacrificed, and the required gain is obtained. Therefore, the number of constituent stages of each amplifier had to be increased.
[0011]
According to the present invention, the entire gain can be leveled in the band without correcting the gain deviation in each band of the low noise amplifier and the intermediate frequency amplifier, and the overall gain can be increased without increasing the number of amplifier stages. The purpose is to:
[0012]
[Means for Solving the Problems]
In order to solve the above problem, a down converter for receiving satellite broadcasting according to the present invention includes a low noise amplifier for amplifying a satellite broadcasting signal in a satellite broadcasting band, and a downstream stage provided with the low noise amplifier. A mixer for performing block conversion to an intermediate frequency band having a lower band than the band and having the same bandwidth as the bandwidth of the satellite broadcasting band; an oscillator for supplying a local oscillation signal having a fixed frequency to the mixer; An intermediate frequency amplifier for amplifying an intermediate frequency signal in a frequency band, wherein the frequency of the local oscillation signal is higher than the highest frequency in the satellite broadcast band.
[0013]
Further, the deviation between the gain of the highest frequency and the gain at the lowest frequency in the satellite broadcasting band of the low noise amplifier and the deviation between the gain of the highest frequency and the gain of the lowest frequency in the intermediate frequency band of the intermediate frequency amplifier are substantially equal to each other. Made equal.
[0014]
Further, the frequency of the local oscillation signal is set to be approximately 1 GHz higher than the highest frequency in the satellite broadcasting band.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The down converter for receiving satellite broadcasting according to the present invention will be described with reference to FIGS. FIG. 1 shows a circuit configuration of a satellite broadcast receiving downconverter of the present invention, FIG. 2 shows a frequency relationship among a satellite broadcast band, an intermediate frequency band, and a local oscillation signal, and FIGS. FIG.
[0016]
FIG. 1 shows a configuration in which satellite broadcast signals converted from circular polarization into horizontal polarization H and vertical polarization V are block-converted into intermediate frequency signals by circuits of different systems. This configuration is basically the same as the conventional configuration (FIG. 7). In the example of US specifications, the band in which satellite broadcast signals are arranged (hereinafter referred to as satellite broadcast band) is from 12.2 GHz to 12.7 GHz, and the band in which intermediate frequency signals are arranged (hereinafter referred to as intermediate frequency band) is It is from 0.95 GHz to 1.45 GHz. Hereinafter, the configuration will be described in detail.
[0017]
First, the horizontally polarized satellite broadcast signal rf is input to a first low-noise amplifier 1 including a plurality of stages of amplifiers 1a and 1b. The amplified horizontal polarization H is input to the first mixer 3 via the first bandpass filter 2. The first mixer 3 is supplied with a local oscillation signal Lo from the oscillator 21. The frequency of the local oscillation signal Lo is approximately 1 GHz higher than the highest frequency of the satellite broadcasting band. Specifically, it is set to 13.65 GHz, which is 0.95 GHz higher. Then, the first mixer 3 outputs an intermediate frequency signal if block-converted into an intermediate frequency band of 0.95 GHz to 1.45 GHz. The intermediate frequency signal if of the horizontally polarized wave H is amplified by the first intermediate frequency amplifier 4 including a plurality of stages of amplifiers 4a and 4b, and input to the switching means 22.
[0018]
On the other hand, the vertically polarized satellite broadcast signal rf is also input to the second low-noise amplifier 11 including a plurality of stages of amplifiers 11a and 11b. The amplified vertical polarization V is input to the second mixer 13 via the second band-pass filter 12. Since the local oscillation signal Lo having the same frequency of 13.65 GHz is also supplied from the oscillator 21 to the second mixer 13, the second mixer 13 performs block conversion to an intermediate frequency band of 0.95 GHz to 1.45 GHz. The output intermediate frequency signal if is output. The intermediate frequency signal if of the vertically polarized wave V is amplified by the second intermediate frequency amplifier 14 including a plurality of stages of amplifiers 14a and 14b, and input to the switching unit 22.
[0019]
The switching means 22 has two output terminals, and the switching operation thereof is controlled by means not shown, and an intermediate frequency signal if of the horizontal polarization H or an intermediate frequency signal if of the vertical polarization V is applied to any output terminal. It is to be taken out. A tuner unit (not shown) is provided after the switching unit, and an arbitrary intermediate frequency signal in an intermediate frequency band is selected by the tuner unit.
[0020]
Here, the frequency relationship among the satellite broadcast band, the intermediate frequency band, and the local oscillation signal Lo will be described with reference to FIG. Assuming that the lowest frequency 12.2 GHz of the satellite broadcasting band is RF1 and the highest frequency 12.7 GHz is RF2, the intermediate frequency signal if is obtained by the frequency difference between the satellite broadcasting signal rf and the local oscillation signal Lo, and the local oscillation signal Lo is obtained. Since it is higher than the satellite broadcasting band, the lowest frequency IF1 of the intermediate frequency band is 0.95 GHz and the highest frequency IF2 is 1.45 GHz. That is, the lowest frequency RF1 of the satellite broadcasting band is converted to the highest frequency IF2 of the intermediate frequency band, and the highest frequency RF2 of the satellite broadcasting band is converted to the lowest frequency IF1 of the intermediate frequency band.
[0021]
Next, the relationship between each gain of the first low noise amplifier 1 and the first intermediate frequency amplifier 4 and the overall gain will be described with reference to FIGS. The contents of the relationship between the respective gains of the second low-noise amplifier 11 and the second intermediate frequency amplifier 14 and the overall gain are the same, and a description thereof will be omitted.
[0022]
The present invention uses the fact that the frequency of the local oscillation signal Lo is higher than that of the satellite broadcasting band to equalize the overall gain within the band. That is, unless a special frequency characteristic correction circuit is provided, the gain of the first low noise amplifier 1 is as high as G1 at the lowest frequency RF1 and as low as G2 at the highest frequency RF2 as shown in FIG. . Therefore, the gain in the intermediate frequency band subjected to the block conversion by the first mixer 3 is shown in FIG. 4 if the insertion loss of the first bandpass filter 2 and the conversion loss by the first mixer 3 are ignored. As described above, the lowest frequency IF1 is as low as G2, and the highest frequency is as high as G1.
[0023]
On the other hand, the gain of the first intermediate frequency amplifier 4 is as high as G3 at the lowest frequency IF1 and as low as G4 at the highest frequency IF2 unless a special frequency characteristic correction circuit is provided, as shown in FIG. The deviation is B. Here, if the gain deviation A of the first low-noise amplifier 1 in the satellite broadcasting band and the gain deviation B of the first intermediate-frequency amplifier 4 in the intermediate frequency band are made substantially equal, the overall gain G5 is shown in FIG. As described above, (G1 + G4 = G2 + G3) can be obtained over the entire range of the intermediate frequency band.
[0024]
In this configuration, since the gain of the lowest frequency in the first low noise amplifier 1 and the first intermediate frequency amplifier 4 is not sacrificed, the overall gain is increased, and in some cases, the number of amplification stages of each amplifier is reduced. Is also possible.
Also, by increasing the frequency of the local oscillation signal Lo by 0.95 GHz higher than the highest frequency RF2 of the satellite broadcast band, the intermediate frequency signal if can be converted from the conventional 0.95 GHz to the intermediate frequency band of 1.45 GHz, The local oscillation signal Lo is not limited to a frequency higher by 0.95 GHz.
[0025]
In the present invention, since the frequency of the local oscillation signal is higher than that of the satellite broadcast signal, the arrangement order of the intermediate frequency signals in the intermediate frequency band is opposite to that of the prior art. Needless to say, it is necessary to change the configuration of the tuner section that selects the intermediate frequency signal if and generates the baseband signal.
[0026]
【The invention's effect】
As described above, in the satellite broadcast receiving downconverter of the present invention, a low-noise amplifier for amplifying a satellite broadcast signal in a satellite broadcast band and a low-noise amplifier are provided at a subsequent stage, and the satellite broadcast signal is transmitted to the satellite broadcast band. A mixer that performs block conversion into an intermediate frequency band having a lower bandwidth than the bandwidth of the satellite broadcasting band, an oscillator that supplies a local oscillation signal having a fixed frequency to the mixer, and an intermediate frequency band in the intermediate frequency band. An intermediate frequency amplifier that amplifies the frequency signal is provided, and the frequency of the local oscillation signal is set higher than the highest frequency in the satellite broadcasting band, so that the gain deviation in each band of the low noise amplifier and the intermediate frequency amplifier is not corrected. However, the overall gain can be leveled within the band, and the overall gain can be increased without increasing the number of amplifier stages.
[0027]
Also, since the deviation between the gain of the highest frequency and the gain at the lowest frequency in the satellite broadcasting band of the low noise amplifier and the deviation between the gain of the highest frequency and the gain of the lowest frequency in the intermediate frequency band of the intermediate frequency amplifier were substantially equal, The gain in the band can be made substantially uniform.
[0028]
In addition, since the frequency of the local oscillation signal is approximately 1 GHz higher than the highest frequency in the satellite broadcasting band, the intermediate frequency signal can be output in the same band as the conventional intermediate frequency band.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing the configuration of a satellite broadcast receiving downconverter of the present invention.
FIG. 2 is a diagram showing a frequency relationship among a satellite broadcast band, an intermediate frequency band, and a local oscillation signal in the satellite broadcast receiving downconverter of the present invention.
FIG. 3 is a frequency characteristic diagram of a gain of a low noise amplifier in a satellite broadcast receiving downconverter of the present invention.
FIG. 4 is a frequency characteristic diagram of an intermediate frequency signal output from a mixer in the satellite broadcast receiving downconverter of the present invention.
FIG. 5 is a frequency characteristic diagram of the gain of the intermediate frequency amplifier in the satellite broadcast receiving downconverter of the present invention.
FIG. 6 is a frequency characteristic diagram of overall gain in the satellite broadcast receiving downconverter of the present invention.
FIG. 7 is a circuit diagram showing a configuration of a conventional down converter for receiving satellite broadcasting.
FIG. 8 is a diagram showing the frequency relationship among a satellite broadcast band, an intermediate frequency band, and a local oscillation signal in a conventional satellite broadcast receiving downconverter.
FIG. 9 is a frequency characteristic diagram of gain of a low noise amplifier in a conventional satellite broadcast receiving downconverter.
FIG. 10 is a frequency characteristic diagram of a gain of an intermediate frequency amplifier in a conventional satellite broadcast receiving downconverter.
FIG. 11 is a frequency characteristic diagram of the overall gain in a conventional satellite broadcast receiving downconverter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st low noise amplifier 2 1st band pass filter 3 1st mixer 4 1st intermediate frequency amplifier 11 2nd low noise amplifier 12 2nd band pass filter 13 2nd mixer 14 2nd Intermediate frequency amplifier 21 oscillator 22 switching means

Claims (3)

A low-noise amplifier that amplifies a satellite broadcast signal in a satellite broadcast band, and a low-noise amplifier that is provided at a stage subsequent to the low-noise amplifier. A mixer that performs block conversion into an intermediate frequency band having the same bandwidth, an oscillator that supplies a local oscillation signal having a fixed frequency to the mixer, and an intermediate frequency amplifier that amplifies the intermediate frequency signal in the intermediate frequency band, A downconverter for receiving satellite broadcasting, wherein a frequency of the local oscillation signal is higher than a highest frequency in the satellite broadcasting band. The deviation between the gain of the highest frequency and the lowest frequency in the satellite broadcasting band of the low-noise amplifier and the difference between the highest frequency gain and the lowest frequency gain of the intermediate frequency amplifier in the intermediate frequency band were made substantially equal. 2. The down converter for receiving satellite broadcasting according to claim 1, wherein 3. The down converter for receiving satellite broadcasting according to claim 1, wherein the frequency of the local oscillation signal is set to be approximately 1 GHz higher than the highest frequency in the satellite broadcasting band.

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