JP5634830B2 - Frequency converter - Google Patents

Description

  The present invention relates to a frequency conversion device, and more particularly to a frequency converter for converting a television broadcast signal.

  An example of an agile type frequency converter that receives a television broadcast signal, for example, a terrestrial digital broadcast signal, and converts the frequency into another frequency is disclosed in Patent Document 1. In the technique of Patent Document 1, the UHF band terrestrial digital television broadcast signal supplied to the input-side mixer is frequency-converted into an intermediate frequency signal by the input-side local oscillation signal supplied to the input-side mixer, and this is output. The signal is supplied to the side mixer, and is converted into an output terrestrial digital television broadcast signal having a desired frequency in the UHF band by the output side local oscillation signal supplied to the output side mixer.

JP 2007-295334 A

  In such a technique, the center frequency of the first intermediate frequency signal may be set to 57 MHz, for example. This is because it is possible to use a relatively inexpensive SAW filter. In this case, the output-side local oscillation signal is a value obtained by adding or subtracting 57 MHz to the center frequency of the output terrestrial digital television broadcast signal. This second local oscillation signal may leak and be included in the output signal of the output side mixer. If this second local oscillation signal is to be removed from the output signal, the center frequency of the output terrestrial digital television broadcast signal and the frequency of the output side local oscillation signal are only 57 MHz apart, so a filter with a steep selection characteristic is output. This must be provided on the output side of the side mixer, resulting in high costs. In particular, in an agile type frequency converter, the center frequency of the output terrestrial digital television broadcast signal is not fixed at the time of shipment from the factory, and filters of various frequencies must be prepared. For example, if the center frequency of the intermediate frequency signal is in the GHz band, it is not necessary to use a filter having a steep characteristic, but it is likely to be affected by phase noise degradation and frequency deviation of the local oscillation signal.

  In the present invention, the filter provided on the output side of the mixer used in the final stage can use a filter having a gradual selection characteristic, and the output television broadcast signal is affected by the phase noise degradation and frequency deviation of the local oscillation signal. An object of the present invention is to provide a frequency converter that is difficult to receive.

The frequency conversion device according to one aspect of the present invention converts an input television broadcast signal into an output television broadcast signal having a predetermined center frequency. As the input television broadcast signal and the output television broadcast signal, those having a center frequency in the UHF band can be used. A first frequency converting means converts the frequency of the input television broadcast signal into a first intermediate frequency signal having a frequency lower than that of the input television broadcast signal by using a first local oscillation signal. For example, the first intermediate frequency signal may have a center frequency in the UHF band or the VHF band. The first local oscillating means has the first local oscillating signal having a frequency obtained by adding or subtracting the center frequency of the first intermediate frequency signal to the center frequency of the input television broadcast signal. 1 It supplies to frequency conversion means. It is desirable that the first intermediate frequency signal has a center frequency in the VHF band. The second frequency converting means converts the first intermediate frequency signal into a second intermediate frequency signal having a frequency higher than the first intermediate frequency signal and lower than a center frequency of the output television broadcast signal by a second local oscillation signal. Convert frequency. The second intermediate frequency signal may have a center frequency between the input television broadcast signal and the first intermediate frequency signal. Alternatively, it may have a higher center frequency than the input television broadcast signal . However, the GHz band is not used. A second local oscillating means having the second local oscillation signal having a frequency obtained by adding or subtracting the center frequency of the first intermediate frequency signal to the center frequency of the second intermediate frequency signal; Two frequency conversion means are supplied. The third frequency conversion means converts the second intermediate frequency signal into the output television broadcast signal by the third local oscillation signal. The third local oscillation means has a frequency of a value obtained by adding or subtracting the center frequency of the second intermediate frequency signal to the center frequency of the output television broadcast signal for the third local oscillation signal; This is supplied to the third frequency conversion means. The frequencies of the first to third local oscillation signals exist in the VHF band to the UHF band. That is, the first and second intermediate frequency signals exist in the VHF band to the UHF band. Filter means for passing the output television broadcast signal is provided on the output side of the third frequency conversion means .

  In the frequency conversion device configured as described above, the frequency of the third local oscillation signal is separated from the center frequency of the output television broadcast signal by the center frequency of the second intermediate frequency signal, and the center frequency of the second intermediate frequency signal. Is a frequency between the first intermediate frequency signal and the input television broadcast signal, or higher than the input television broadcast signal, so that the output television broadcast signal and the third local oscillation signal are sufficiently separated from each other. Even if the third local oscillation signal is included in the output signal of the third frequency conversion means, the third local oscillation signal is removed by providing a filter with a gentle characteristic on the output side of the third frequency conversion means. Can do.

  The input television broadcast signal is present in the UHF band, the output television broadcast signal is present in the VHF band, the mid band, the super high band or the UHF band, and the second intermediate frequency signal is present in the UHF band. can do. With this configuration, the third local oscillation signal is sufficiently separated in frequency from the output television broadcast signal, and the filter on the output side of the third frequency conversion means is surely used with a slow selection characteristic. can do.

  Further, the VHF band, mid band, super high band and UHF band filters can be connected in parallel to the output side of the third frequency converting means. With this configuration, the center frequency of the output television broadcast signal can be easily changed to any of the VHF band, mid band, super high band, and UHF band by converting the oscillation frequency of the third local oscillation means. can do.

  As described above, according to the present invention, it is possible to use a filter having a gradual selection characteristic as a filter provided on the output side of the frequency conversion means for outputting an output television broadcast signal. Further, since it is not necessary to set the frequency of the local oscillation signal to be used in the GHz band, the output television broadcast signal is not easily affected by the phase noise degradation and the frequency deviation of the local oscillation signal.

It is a block diagram of the frequency converter of one embodiment of the present invention. It is a figure which shows the frequency relationship of the signal of each part in the frequency converter of FIG. It is a figure which shows the frequency relationship of the signal of each part in the conventional frequency converter. It is a block diagram of a frequency conversion device according to the present invention related art. It is a figure which shows the frequency relationship of the signal of each part in the frequency converter of FIG.

Frequency conversion apparatus of one embodiment of the present invention, an input television broadcast signal supplied thereto, for example, an input digital terrestrial television broadcasting signal of a predetermined channel of the UHF band, a plurality of frequency bands, for example the UHF band, VHF radio The frequency conversion is performed to an output television broadcast signal of an output channel having a center frequency at a predetermined frequency in a frequency band selected from the mid band and the super high band, for example, an output terrestrial digital television broadcast signal. The channels of the input terrestrial digital television broadcast signal and the output terrestrial digital television broadcast signal are set, for example, at the construction site of this frequency converter.

  This frequency converter has an input terminal 2 to which the above-mentioned input terrestrial digital television broadcast signal f1 is supplied. A high frequency blocking coil 3 for removing unnecessary high frequency components is connected between the input terminal 2 and a reference potential point, for example, a ground potential point. The input terrestrial digital television broadcast signal f 1 supplied to the input terminal 2 is supplied to an amplifying means, for example, an amplifier 8 through a DC blocking capacitor 4 and a frequency variable filter (VF) 6. The input terrestrial digital television broadcast signal f1 amplified by the amplifier 8 is supplied to the amplifier 14 via the gain controller (GC) 10 and the frequency variable filter 12, amplified there, and then passed through the frequency variable filter 16. The first frequency conversion means, for example, the input side mixer 18 is supplied.

  In the frequency variable filters 6, 12, and 16, the pass frequency of these frequency variable filters 6, 12, and 16 is determined based on a selection frequency control signal supplied from the control unit, for example, the microcomputer 20 via the D / A converter 22. The belt is changed. The selection frequency control signal is generated by the microcomputer 20 in accordance with the channel of the input terrestrial digital broadcast signal set by the input / output channel setting switch 24 in the microcomputer 20. The image signal of the input terrestrial digital broadcast signal f1 is removed by the frequency variable filters 6, 12, 16 in which the selection frequency is controlled.

  The input-side mixer 18 is supplied with a first local oscillation signal 1stLO from a first local oscillation means, for example, an input-side local oscillation circuit 26. The input side local oscillation circuit 26 includes a voltage controlled oscillator 26a and a PLL circuit 26b. The first local oscillation signal 1stLO is converted into an input terrestrial digital television broadcast signal f1 so that the frequency of the input terrestrial digital television broadcast signal f1 can be converted into a first intermediate frequency signal fIF1 preset at a center frequency of 57 MHz, for example. , 57 MHz is added to the frequency.

  For this setting, the microcomputer 20 sets a frequency division ratio in the PLL circuit 26b in accordance with the channel of the input terrestrial digital television broadcast signal set by the input / output channel setting switch 24. The reference signal is supplied from the reference signal generating circuit 28 to the PLL circuit 26b. Since the frequency of the first local oscillation signal 1stLO is set in this manner, the input-side mixer 18 down-converts the input terrestrial digital television broadcast signal to the first intermediate frequency signal fIF1 lower than that frequency.

  The output signal of the input side mixer 18 is supplied to a branching unit, for example, one branching unit 42, through a band pass filter (BPF) 30, an amplifier 32, a SAW filter 34, an amplifier 36, a SAW filter 38, and an amplifier 40. The bandpass filter 30 and the SAW filters 34 and 38 remove unnecessary signals other than the first intermediate frequency signal fIF1 from the output signal of the input side mixer 18. The first intermediate frequency signal fIF1 is amplified to a predetermined level by the amplifiers 36 and 40. There are commercially available 57 MHz SAW filters 34 and 38, and only the first intermediate frequency signal fIF1 can be extracted at low cost with high selectivity.

  The first intermediate frequency signal fIF1 branched by the one branching device 42 is amplified by an amplifier 44 and then detected by a level detection means, for example, a detector (DET) 46. The detected signal is compared with a predetermined AGC reference signal by a comparison means, for example, a comparator 48. The comparator 48 generates an AGC control signal representing the difference between the detection signal and the AGC reference signal, which is supplied to the gain controller 10 so that the value of the detection signal matches the AGC reference signal. The level of f1 is adjusted.

  The first intermediate frequency signal fIF1 that is the output signal of the one branching device 42 is supplied to the second frequency conversion means, for example, the intermediate mixer 52, via the low-pass filter 50. The intermediate mixer 52 is also supplied with a second local oscillation means, for example, a second local oscillation signal 2ndLO from the intermediate local oscillation circuit 54. The intermediate side local oscillation circuit 54 includes a voltage controlled oscillator 54 a and a PLL circuit 54 b, and a reference signal is supplied from the reference signal generation circuit 28. The intermediate mixer 52 converts the first intermediate frequency signal fIF1 into a second intermediate frequency signal fIF2 whose center frequency is preset to a frequency higher than that of the first intermediate frequency signal fIF1 by the second local oscillation signal 2ndLO. . That is, up-conversion is performed.

  The center frequency of the second intermediate frequency signal fIF2 is preset to 130 MHz when the channel of the output terrestrial digital television broadcast signal fc is the UHF band and the super high band, and is preset to 250 MHz when the channel is the VHF band and the mid band. Is set. Therefore, the frequency of the second local oscillation signal 2ndLO becomes a value 73 MHz or 193 MHz obtained by subtracting the center frequency 130 MHz or 250 MHz of the second intermediate frequency signal fIF2 from the frequency 57 MHz of the first intermediate frequency signal fIF1. Depending on the frequency band (UHF band or other band) of the output channel set by the input / output channel setting switch 24, the voltage controlled oscillator 54a oscillates the second local oscillation signal 2ndLO of 73 MHz or 193 MHz. A frequency division ratio is set from the microcomputer 20 to the PLL circuit 54b.

  The output signal of the intermediate mixer 52 is amplified by the amplifier 60 via the two second intermediate frequency band-pass filters 56 and 58 connected in parallel, and supplied to the third frequency converter, for example, the output mixer 62. Is done. The second intermediate frequency band-pass filter 56 is for the case where the center frequency of the second intermediate frequency signal fIF2 is 130 MHz, and the second intermediate frequency band-pass filter 58 is the center frequency of the second intermediate frequency signal fIF2. For 250 MHz case. The second intermediate frequency signal fIF2 obtained by removing unnecessary signals from the output signal of the intermediate mixer 52 by the second intermediate frequency band-pass filters 56 and 58 is amplified by the amplifier 60 and supplied to the output mixer 62. Supplied.

  The output-side mixer 62 is also supplied with third local oscillation means, for example, a third local oscillation signal 3rdLO from the output-side local oscillation circuit 64. The output-side local oscillation circuit 64 also includes a voltage-controlled oscillator 64a and a PLL circuit 64b, and a reference signal is supplied from the reference signal generation circuit 28. The output-side mixer 62 converts the frequency of the second intermediate frequency signal fIF2 into the output terrestrial digital television broadcast signal fc by the third local oscillation signal 3rdLO.

  The frequency of the third local oscillation signal 3rdLO is a value obtained by adding the center frequency 130 MHz or 250 MHz of the second intermediate frequency signal fIF2 to the center frequency of the output terrestrial digital television broadcast signal fc. The PLL circuit 54b has a frequency dividing ratio from the microcomputer 20 so that the voltage controlled oscillator 64a oscillates the third local oscillation signal 3rdLO in accordance with the output channel set by the input / output channel setting switch 24. Is set.

  The output signal of the output side mixer 62 includes a series circuit of a band pass filter 66 for UHF band and a frequency variable filter 68, a band pass filter 70 for mid band, a band pass filter 72 for super high band, and a band for VHF band. The signal is supplied to the amplifier 76 through a parallel circuit with the pass filter 74. The frequency band that the frequency variable filter 68 passes is changed by the microcomputer 20 via the D / A converter 69.

  When the output terrestrial digital television broadcast signal fc is in the UHF band, an unnecessary signal is removed from the output signal of the output side mixer 62 by the band pass filter 66 for UHF band and the variable filter 68 and supplied to the amplifier 76. When the output terrestrial digital television broadcast signal fc is midband, an unnecessary signal is removed from the output signal of the output side mixer 62 by the midband band pass filter 70 and supplied to the amplifier 76. When the output terrestrial digital television broadcast signal fc is a super high band, an unnecessary signal is removed from the output signal of the output side mixer 62 by the super high band band pass filter 72 and supplied to the amplifier 76. When the output terrestrial digital television broadcast signal fc is in the VHF band, an unnecessary signal is removed from the output signal of the output-side mixer 62 by the VHF band band-pass filter 74 and supplied to the amplifier 76.

  The output signal of the amplifier 76 is supplied to the amplifier 82 via the gain controller 78 and the attenuator (ATT) 80 and the parallel circuit of the filter. This parallel circuit includes a series circuit of a frequency variable filter 68a similar to the frequency variable filter 68, an attenuator 84, a midband bandpass filter 70a, a super high band bandpass filter 72a, and a VHF band. It consists of a pass filter 74a. The frequency variable filter 68 a is controlled from the microcomputer 20 via the D / A converter 69 in the same manner as the frequency variable filter 68.

  The amplifier 76, the gain controller 78, and the amplifier 82 are controlled by a squelch signal (SQ). This squelch signal is generated when the detection signal of the detector 46 is compared with the squelch reference signal in the comparator 86 and the detection signal of the detector 46 is smaller than the squelch reference signal.

  The output signal of the amplifier 82 is supplied to the output terminal 92 through the high pass filter 88 and the DC blocking capacitor 90. Also, a DC +5 V voltage supplied from the outside to the output terminal 92 is supplied to each active device of the frequency converter via the high frequency blocking coil 94 to operate them.

  FIG. 2A shows the frequency relationship of the input terrestrial digital television broadcast signal f1, the first local oscillation signal 1stLO, and the first intermediate frequency signal fIF1. FIG. 4B shows the frequency relationship of the first intermediate frequency signal fIF1, the second intermediate frequency signal fIF2, and the second local oscillation signal 2ndLO. FIG. 4C shows the frequency relationship of the second intermediate frequency signal fIF2, the output terrestrial digital television broadcast signal fc, and the third local oscillation signal 3rdLO. Since the center frequency of the output terrestrial digital television broadcast signal is 550 MHz, the frequency of the third local oscillation signal is 680 MHz. There is a difference of 130 MHz which is the same as the center frequency of the second local oscillation signal fIF2.

  FIG. 3 shows the frequency relationship when the first intermediate frequency signal fIF1 is directly converted into an output terrestrial digital television broadcast signal fc having a center frequency of 550 MHz. In this case, the local oscillation signal LO is 607 MHz. There is a frequency difference between the output terrestrial digital television broadcast signal fc and the local oscillation signal LO only at the same frequency 57 MHz as the center frequency of the first intermediate frequency signal fIF1. Therefore, in order to remove the local oscillation signal LO leaked to the output signal of the mixer, a filter having a relatively high selectivity that can remove the local oscillation signal having a frequency difference of only 57 MHz is used on the output side of the mixer. There is a need.

  On the other hand, after the frequency conversion of the first intermediate frequency signal fIF1 into a second intermediate frequency signal having a higher frequency than the first intermediate frequency signal fIF1 as in this frequency conversion device, the second intermediate frequency signal is output to the output terrestrial digital television broadcast signal fc. When the frequency conversion is performed, a frequency corresponding to the center frequency of the second intermediate frequency signal having a high frequency is generated between the output terrestrial digital television broadcast signal fc and the third local oscillation signal 3rdLO corresponding to the local oscillating signal 3rdLO. There is a difference. Therefore, since there is a frequency difference about twice that shown in FIG. 3, the band pass filter 66 for UHF band, frequency variable filters 68 and 68a, band pass filters 70 and 70a for mid band, and the band for super high band Even if a moderate frequency characteristic filter composed of an inductance and a capacitor is used for the pass filters 72 and 72a and the band pass filters 74 and 74a for the VHF band, the third local oscillation signal is output from the output signal of the output side mixer 62. Can be removed. In addition, since the first to third local oscillation signals are not in the GHz band, the output terrestrial digital television broadcast signal is not easily affected by the phase noise degradation and the frequency deviation of the local oscillation signal.

A frequency conversion device according to the present invention is shown in FIGS. In the frequency converter according to the first embodiment, the input side mixer 18, the input side local oscillation circuit 26, the intermediate side mixer 52, the intermediate side oscillation circuit 54, the output side mixer 62, and the output side oscillation circuit 64 are used. In the frequency conversion device of the second embodiment, the input side mixer 18, the input side local oscillation circuit 26, the output side mixer 62, and the output side oscillation circuit 64 are provided as shown in FIG. Used to perform two-stage frequency conversion.

  As shown in FIG. 5A, when the center frequency of the input terrestrial digital television broadcast signal f1 is 500 MHz, the center frequency of the first intermediate frequency fIF1 is 190 MHz, which is lower than the frequency of the input terrestrial digital television broadcast signal f1. The first local oscillation signal 1stLO is set to 690 MHz obtained by adding the center frequency of the input terrestrial digital television broadcast signal f1 and the center frequency of the first intermediate frequency fIF1. The frequency of the second local oscillation signal of the output side local oscillation circuit 64 is the center frequency of the output terrestrial digital television broadcast signal fc, as shown in FIG. Assuming that the center frequency is 500 MHz, the center frequency of the first intermediate frequency signal and the center frequency of the output terrestrial digital television broadcast signal fc are set to 690 MHz. Since other configurations are the same as those of the frequency conversion device according to the first embodiment, a detailed description thereof will be omitted.

  In this frequency conversion device, the first intermediate frequency signal is frequency-converted to a frequency lower than that of the input terrestrial digital television broadcast signal, and is converted to an output terrestrial digital television broadcast signal having a frequency higher than that. The frequency difference between the two local oscillation signal and the output terrestrial digital television broadcast signal can be increased. As a result, the second local oscillation signal is output from the output-side mixer 62 even if a filter having a gentle frequency characteristic composed of an inductance and a capacitor is used for the UHF band pass filter 66 and the frequency variable filters 68 and 68a. It can be removed from the output signal. In addition, since the first and second local oscillation signals are not in the GHz band, the output terrestrial digital television broadcast signal is not easily affected by the phase noise degradation and the frequency deviation of the local oscillation signal.

In the above embodiment , the case where the input terrestrial digital television broadcast signal supplied to the input terminal 2 is one wave has been described. However, a plurality of input digital terrestrial television broadcast signals are supplied to the input terminal 2 at the same time. A plurality of input terrestrial digital television broadcast signals can be frequency-converted.

In the above embodiment , the first local oscillation signal 1stLO is a value obtained by adding 57 MHz to the center frequency of the input terrestrial digital television broadcast signal f1, but 57 MHz is subtracted from the center frequency of the input terrestrial digital television broadcast signal f1. It is possible to have the value obtained as a frequency. Similarly, the second local oscillation signal 2ndLO can also have a frequency obtained by adding the center frequency of the first intermediate frequency signal fIF1 to the center frequency of the second intermediate frequency signal fIF2, or the third local oscillation signal 2ndLO. The signal 3rdLO can also have a frequency obtained by subtracting the center frequency of the second intermediate frequency signal fIF2 from the center frequency of the output terrestrial digital television broadcast signal fc.

In the above embodiment , in order to frequency-convert the input terrestrial digital television broadcast signal into an output terrestrial digital television broadcast signal in any one of the UHF band, the mid band, the super high band, and the VHF band, UHF band pass filter 66, mid band band pass filters 70 and 70a, super high band band pass filters 72 and 72a, and VHF band pass filters 74 and 74a are provided on the output side. When the frequency band of the John broadcast signal is predetermined in any one of the UHF band, the mid band, the super high band, and the VHF band, only the band pass filter for that frequency band can be provided.

18 Input side mixer (first frequency conversion means)
26 Input-side local oscillation circuit (first local oscillation means)
52 Intermediate mixer (second frequency conversion means)
54 Intermediate-side oscillation circuit (second local oscillation means)
62 Output side mixer (third frequency conversion means)
64 Output side oscillation circuit (third local oscillation means)

Claims (3)

A frequency converter that converts an input television broadcast signal into an output television broadcast signal having a predetermined center frequency,
First frequency converting means for converting the frequency of the input television broadcast signal by a first local oscillation signal into a first intermediate frequency signal having a frequency lower than that of the input television broadcast signal;
The first local oscillation signal is supplied to the first frequency conversion means as a frequency having a value obtained by adding or subtracting the center frequency of the first intermediate frequency signal to the center frequency of the input television broadcast signal. First local oscillation means;
A second frequency conversion that converts the first intermediate frequency signal by a second local oscillation signal into a second intermediate frequency signal that is higher in frequency than the first intermediate frequency signal and lower than the center frequency of the output television broadcast signal. Means,
The second local oscillation signal is supplied to the second frequency conversion means as a frequency having a value obtained by adding or subtracting the center frequency of the first intermediate frequency signal to the center frequency of the second intermediate frequency signal. A second local oscillation means;
Third frequency conversion means for converting the second intermediate frequency signal into the output television broadcast signal by a third local oscillation signal;
The third local oscillation signal has a frequency value obtained by adding or subtracting the center frequency of the second intermediate frequency signal to the center frequency of the output television broadcast signal, and supplies the third frequency signal to the third frequency conversion means A third local oscillation means for
And the frequencies of the first to third local oscillation signals exist in the VHF band to the UHF band,
A frequency converting device, provided on the output side of the third frequency converting means, is a filter means for passing the output television broadcast signal . 2. The frequency converter according to claim 1 , wherein the input television broadcast signal exists in a UHF band, and the output television broadcast signal exists in a VHF band, a mid band, a super high band, or a UHF band, The frequency signal is a frequency converter existing in the UHF band. 3. The frequency converter according to claim 2 , wherein filters for the VHF band, mid band, super high band, and UHF band are respectively connected in parallel to an output side of the third frequency converting means.

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