JP2586188Y2 - Tuner for satellite broadcasting reception - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite broadcast receiving tuner for converting a high frequency signal output from a BS converter into an intermediate frequency signal in a television receiver for receiving satellite broadcasts.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram showing a configuration example of a satellite broadcasting system. In this figure, 1 and 2 are broadcast satellites, respectively, which transmit satellite broadcast signals of a plurality of broadcast channels having the bands shown in FIGS. 5 (a) and 5 (b), respectively. Numerals 3 and 4 are parabolic antennas for reception, which are installed outdoors, and numerals 5 and 6 are arranged near parabolic antennas 3 and 4, respectively. , A BS converter 7 for converting a high frequency signal of about 1 to 2 GHz into a satellite broadcast receiving tuner (hereinafter simply referred to as a tuner) which is provided indoors and converts a high frequency signal to an intermediate frequency signal.

Next, FIG. 6 shows an example of the configuration of a tuner 7. In this figure, 8 and 9 are input terminals to which the high-frequency signals output from the BS converters 5 and 6 are input, respectively, 10 and 11 are switches each constituted by a PIN diode or the like, and 12 is a switch control circuit. Switching signal S output from a control circuit (not shown)
_The switches 10 and 11 are turned on / off according to _C.

[0004] 13 RF amplifier, 14 a tracking filter, the pass frequency characteristic is controlled in a frequency band of the channel selected by the tuning voltage V _T output from the channel selection circuit (not shown). Fifteen
Is a local oscillator for oscillating a local oscillation signal, the frequency of the local oscillation signal by the tuning voltage V _T output from the channel selection circuit (not shown) is controlled. Further, 16 is a mixer for mixing the output signal of the tracking filter 14 with the local oscillation signal and converting it to an intermediate frequency signal, and 17 is a band pass filter (hereinafter, referred to as a SAW (Surface Acoustic Wave) device) for passing the intermediate frequency signal. BPF), 18 is BP
This is an output terminal from which the output signal of F17 is output.

In such a configuration, in order to receive, for example, a satellite broadcast signal of a channel in a shaded band shown in FIG. 5A transmitted from the broadcast satellite 1, a switching signal is transmitted from a control circuit (not shown). to turn on the switch 10 outputs a S _C, while turning off the switch 11, the pass frequency characteristic and local tracking filter 14 outputs a tuning voltage V _T corresponding to the channel corresponding the channel selection circuit (not shown) The frequency of the local oscillation signal output from the oscillator 15 is controlled.

[0006] Thus, the satellite broadcast signal received by the parabolic antenna 3 is amplified by the BS converter 5, converted into a high-frequency signal of about 1 to 2 GHz, and input to the tuner 7 via the input terminal 8. . Next, the high-frequency signal input to the input terminal 8 is
0, is amplified by the high-frequency amplifier 13, passes through the tracking filter 14, is mixed with the local oscillation signal in the mixer 16, and is converted into an intermediate frequency signal.
The signal is output from an output terminal 18 via a line 17.

[0007]

An invention is the way, in the conventional satellite broadcast receiving tuner described above, heavy as the channel frequency band of the broadcast satellite 1 and 2 are shown in FIG. 5
Input from the BS converter to input terminals 8 and 9
The high-frequency signals to be superposed also overlap. Therefore, the isolation in the switches 10 and 11 requires about 40 dB or more. However, the switches 10 and 11 have a frequency of about 1 to 2 G
Since the frequency is as high as Hz, there is a disadvantage that it is difficult to secure sufficient isolation unless a complicated and expensive configuration is used.

In a satellite broadcasting system, the signal level of each channel is substantially the same, so that, unlike a normal television system using terrestrial waves, when a certain channel is received, the tracking filter 14 is set to a narrow band and the other channels are set to a narrow band. Is not required to be sufficiently attenuated, but it is necessary to sufficiently attenuate the image signal and the local oscillation signal, so that the configuration of the tracking filter 14 is complicated. The present invention has been made under such a background, and a satellite broadcast capable of sufficiently securing isolation of a switch unit with a simple configuration and sufficiently attenuating an image signal and a local oscillation signal of a reception channel. An object is to provide a tuner for reception.

[0009]

SUMMARY OF THE INVENTION The present invention provides a frequency band.
Multiple signals that are input separately from multiple types of shared signals
Signal input terminal, connected to the plurality of signal input terminals,
Switching means for selectively outputting one of a plurality of types of signals
And a high frequency for amplifying the signal output from the switching means
An amplifier and the disconnection corresponding to each of the plurality of input terminals.
Conversion means and an input terminal of the high-frequency amplifier.
A plurality of variable traps, and
Corresponding to the signal input terminal to which the selected signal is input
The variable trap frequency to the receiving channel of the signal.
Local transmission frequency or the corresponding reception channel
Reduce reception interference according to the image frequency corresponding to
And the frequency of the other variable trap is
Other signal input terminals and the high-frequency amplifier according to the
Of the receiving channel of the signal between
The feature is to increase the Solation .

[0010]

According to the above arrangement, in order to receive a certain channel of a satellite broadcasting signal having a plurality of satellite broadcasting signals, the corresponding switching means is turned on, the other switching means are turned off, and the variable trap control is performed. By means, while controlling the frequency characteristic of the variable trap provided at the output terminal or the input terminal of the switched switching means to the characteristic of blocking the local oscillation frequency or image frequency of the receiving channel,
The frequency characteristic of the variable trap provided at the output terminal or the input terminal of the turned off switching means is controlled to the characteristic of blocking the center frequency of the receiving channel.

[0011]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of a satellite broadcast receiving tuner according to an embodiment of the present invention.
In this figure, parts corresponding to the respective parts in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted. In the tuner for receiving satellite broadcasting shown in this figure, a variable trap 19 is newly provided between the switch 10 and the high-frequency amplifier 13, and a variable trap 20 is newly provided between the switch 11 and the high-frequency amplifier 13. These variable trap 19 and 20 is constituted by a varactor or the like, the variable traps based on tuning voltage V _T output from the switching signal S _C and not shown channel selection circuit is output from the control circuit (not shown) The frequency characteristic is controlled by the control circuit 21.

That is, in the variable trap on the side where the switch is turned on, _assuming that the local oscillation frequency is f _L , the center frequency of the receiving channel is f ₀ , the intermediate frequency is f _IF , and the image frequency is image, FIG. ), The local _trapping frequency (f _L = f ₀ + f _IF ) or the image frequency (f image = f ₀ + 2f _IF ) of the receiving channel is blocked, and the variable trap on the side where the switch is turned off is shown in FIG. As shown in (b), the frequency characteristic is controlled so as to block the center frequency f ₀ of the reception channel.

In such a configuration, in order to receive a satellite broadcast signal transmitted from the broadcast satellite 1 in, for example, a channel in a band in a hatched portion shown in FIG. to turn on the switch 10 outputs a S _C, while turning off the switch 11, the pass frequency characteristic and local tracking filter 14 outputs a tuning voltage V _T corresponding to the channel corresponding the channel selection circuit (not shown) The frequency of the local oscillation signal output from the oscillator 15 is controlled. The variable trap control circuit 21 controls the respective frequency characteristic variable trap 19 and 20 based on the switching signal S _C and tuning voltage V _T mentioned above, the characteristics shown by the broken line in FIG. 3 (a) and (b) I do.

Thus, the satellite broadcast signal received by the parabolic antenna 3 is amplified by the BS converter 5, converted into a high-frequency signal of about 1 to 2 GHz, and input to the tuner 7 via the input terminal 8. . Next, the high-frequency signal input to the input terminal 8 is
After being amplified by the high-frequency amplifier 13 through 0 and the variable trap 19, it is passed through the tracking filter 14,
The signal is mixed with the local oscillation signal in the mixer 16, converted into an intermediate frequency signal, and output from the output terminal 18 via the BPF 17.

[0015] At this time, the reception channel of the local oscillation frequency _{(f L = f 0 + f} IF) or image frequency _(f imege =
f ₀ + 2f _IF ) is sufficiently attenuated by the variable trap 19. Further, the high frequency signal in the vicinity of the receiving channel leaked from the switch 11 is sufficiently attenuated by the variable trap 20. In addition, high-frequency signals other than those near the reception channel cannot be sufficiently attenuated by the variable trap 20, but the tracking filter 14 and the BPF 1
7 provides sufficient attenuation so that it is not disturbed by this signal.

As described above, the high-frequency signal in the vicinity of the receiving channel, which is the signal on the non-receiving side, is sufficiently attenuated by the variable trap on the non-receiving side. The amount of attenuation is small. For example, if the isolation in the variable trap is 20 dB, the isolation in the switch may be 20 dB. Therefore, the switch can be easily configured. In addition, the local oscillation frequency of the receiving channel (f _L = f ₀ +
Since the sufficiently attenuated by f _IF) or image frequency _{(f imege f 0 + 2f IF} ) side of the variable trap receives the performance of the tracking filter 14 is correspondingly reduced. Therefore, the circuit configuration of the tracking filter 14 and its adjustment can be simplified. The frequency characteristic of the variable trap on the non-receiving side does not need to be narrow, and if sufficient attenuation is obtained for the high frequency signal near the receiving channel, as shown in FIG. Since the characteristics may be sufficient, tracking with the local oscillator 15 is also facilitated.

In the above-described embodiment, the variable traps 19 and 1 are connected to the output terminals of the switches 10 and 11 respectively.
Although the example in which 0 is provided is shown, variable traps 19 and 10 may be provided at the input terminals of the switches 10 and 11. Also, in one embodiment described above,
Although an example in which satellite broadcast signals transmitted from two broadcast satellites 1 and 2 are received has been described, a satellite broadcast receiving tuner according to the present invention provides two types of satellite broadcast signals transmitted from one broadcast satellite, for example, It goes without saying that the present invention can be applied to the case of receiving vertically and horizontally polarized satellite broadcast signals.

[0018]

As described above, according to the present invention, there is an effect that sufficient switch isolation can be ensured with a simple configuration. Further, there is an effect that the image signal and the local oscillation signal of the reception channel can be sufficiently attenuated with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a satellite broadcast receiving tuner according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of characteristics of variable traps 19 and 20.

FIG. 3 is a diagram for explaining the operation of the satellite broadcast receiving tuner according to one embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating a configuration example of a satellite broadcasting system.

FIG. 5 is a diagram showing an example of the band of each broadcast channel of broadcast satellites 1 and 2;

FIG. 6 is a block diagram showing a configuration example of a conventional satellite broadcast receiving tuner.

[Explanation of symbols]

 10, 11 switch 12 switch control circuit 13 high-frequency amplifier 14 tracking filter 15 local oscillator 16 mixer 17 BPF 19, 20 variable trap 21 variable trap control circuit

Claims (1)

(57) [Scope of request for utility model registration] A plurality of kinds of signals sharing a frequency band are respectively
A plurality of signal input terminals that are separately input, and a plurality of signal input terminals connected to the plurality of signal input terminals.
Switching means for selectively outputting one of them, and a high-frequency amplifier for amplifying a signal output from the switching means
And a switching device corresponding to each of the plurality of input terminals.
Multiple variable resistors inserted between the input terminals of the high-frequency amplifier
A trap, wherein a signal selected by the switching means is inputted.
The frequency of the variable trap corresponding to the signal input terminal,
There is a local oscillation frequency corresponding to the reception channel of the signal
Or match the image frequency corresponding to the receiving channel.
Reduce the interference and reduce the frequency of the other variable traps to the reception channel of the signal
According to other signal input terminals and the input of the high-frequency amplifier.
Isolation of the receiving channel of the signal between the
A tuner for receiving satellite broadcasts , characterized by increasing the size of the tuner.