JPH0127304Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tuner for receiving satellite broadcasts, and more particularly to a tuner for receiving satellite broadcasts that can be applied to both individual and communal reception frequency bands.

Conventionally, there are four types of systems for receiving satellite broadcasting, as shown in FIGS. 1 to 4 a and b, respectively. Figure 1 shows public reception (HE) U/M (AM)
This shows the transmission method. This method is mainly for medium to large public listening facilities, and uses the FM transmission method.
Existing CATV (Cable Television), which is converted to AM transmission format and transmitted, has a relatively large number of distributions.
Or, in the case of distribution via terrestrial broadcasting, all reception channels are demodulated and then re-modulated and sent to each home, where each home receives it using an existing receiver. Also, Figure 2 shows the building public listening reception.
This refers to the UHF (FM) transmission system, which is used for public listening systems with a relatively small number of distribution terminals, such as building public listening systems. Signal transmission involves converting the 12 GHz band signal received by receiving antenna 1 into a 1.0 to 1.3 GHz frequency band signal using converter (ODU: outdoor unit) 2, and transmitting the signal to another SHF.
After converting the signal into a UHF (470-770MHz) frequency band signal using the S-U converter 3, which converts the frequency band from the band to the UHF band, the signal is transmitted within a building, etc., and distributed to each house. At this point, the U-S converter 4 converts the signal back into the frequency band of 1.0 to 1.3 GHz. And Chuyuna (IDU: outdoor unit) 5
The desired channel is selected and supplied to the receiver, and the signal is FM transmission. Next, Figure 3 is almost the same as the building common reception UHF (FM) transmission system shown in Figure 2, but the difference is that
Tuner (IDU) 5 with UHF band input terminal
470~770MHz UHF
It is supplied by transmission. Also, Figure 4 a, b
1A and 2B show individual reception methods, respectively: a shows television reception, and b shows audio reception. This individual reception method is the most commonly used,
1.0~ from antenna 1 and converter (ODU) 2
The 1.3GHz FM signal is supplied to the tuner 5 as is.

In each of these systems, the tuner unit is basically designed with input from either the 1.0 to 1.3 GHz frequency band or the 470 to 770 MHz UHF frequency band.

Therefore, if a user moves, for example, from a house of the type shown in Figure 2 to an apartment house of the type shown in Figure 3,
Since the tuner units use different frequency bands,
The tuner unit you have will become unusable.
Furthermore, even if a tuner unit is purchased exclusively for communal listening, it is impossible to switch to individual listening in the future.

The present invention was developed in view of the above circumstances, and its purpose is to provide an inexpensive satellite broadcast reception tuner that has a simple configuration and can be used in both individual reception and communal reception frequency bands. That's true.

An embodiment of the present invention will be described below with reference to the drawings. As explained above, the input signals for the tuner include the 1 GHz band (1.0 to 1.3 GHz) and the lower TV UHF band (470 to 770 MHz). Here, for convenience of explanation, the former is assumed to be _H and the latter is assumed to be _L.
When receiving these signals, a so-called superheterodyne method is usually used, in which the signals are tuned by a tuner and converted into intermediate frequency signals using a local oscillator and a mixer. Now, the local oscillation frequency for _H is F _H , that for _L is F _L , and the intermediate frequency is
F _I. And in general, considering that _L , _H , F _L , F _H , and F _I are positive numbers, and that F _I is lower (smaller) than _L and _H , | _L −F _L |=F _I …(1) | _H −F _H |=F _I …(2) The following relationship holds true.

On the other hand, _L and _H are usually determined so that their sum becomes a constant frequency F _C as shown in the following equation.

_L + _H = F _C ...(3) For example, in the case shown in Figure 5, for _H = 1 GHz = 1000 MHz, _L = 770 MHz, and for _H = 1.3 GHz = 1300 MHz, _L = 470 MHz. , the sum of _H and _L should be 1770MHz. That is, F _C =1770MHz, and even at frequencies between these, the sum of _H and _L is set to F _C .

When determined in this way, the relationship between local oscillation frequencies F _L and F _H is obtained from equations (1) and (2) as follows: F _L = ( _L + _H ) −2F _I −F _H …(4) F _L = ( _L + _H ) − F _H …(5), and add the numerical values F _C = _L + _H = 1770MHz and
Substituting F _I = 430 (MHz) and rearranging, F _L = 910 − F _H …(6) F _L = 1770 − F _H …(7), and subtracting F _H from the specific frequencies of 910 MHz and 1770 MHz. It turns out that the result is F _L.
This is a specific frequency (in this case 910MHz or
1770MHz) and a local oscillation signal with a frequency of _FH using a frequency mixer, a signal with a local oscillation frequency of _FL can be obtained.

Therefore, by providing a variable oscillator that generates the frequency F _H as a local oscillator and a fixed oscillator that generates 910 MHz or 1770 MHz, and by providing a frequency mixer that mixes these and converts the frequency, F _H can be changed. By simply changing the switch, it is possible to receive _L which corresponds to _FL .
In other words, 2 which is _L and _H in the relationship of equation (3)
In order to receive frequency band signals, only one local oscillator is required, and by using a changeover switch, for example, _L can be received as is at the local oscillation frequency used when receiving _H. be able to. In other words, the trouble of re-tuning can be saved.

Next, a specific embodiment of the present invention will be explained in detail with reference to FIG. This figure shows the configuration of a tuner for receiving satellite broadcasting according to the present invention. In the same figure, 21 is an input terminal, and this input terminal 21 has the aforementioned _H (1.0 to 1.3 GHz) and _L (470 to 770 MHz).
Two frequency band signals are input. This input terminal 21 is connected to a bandpass filter (BPF) 22 for passing the _H signal, and a UHF band, that is, _L (470
It is connected to each input terminal of a low-pass filter (LPF) 23 for passing signals of up to 770 MHz. The output terminal of the bandpass wave generator 22 is an amplifier A24.
One fixed contact 25 of the changeover switch 25 via
connected to a. In addition, the low-pass wave filter 23
The output terminal of is connected to the other fixed contact 25b of the changeover switch 25 via an amplifier B26. A movable contact 25c of the changeover switch 25 is connected to one input end of the frequency mixer A27.
This frequency mixer A27 has the above-mentioned frequency _H or _L.
Frequency conversion is performed by mixing each signal with a local oscillation signal of frequency F _H or F _L described later, and the frequency F _I
(430MHz) intermediate frequency signal. The output terminal of this frequency mixer A27 is connected to an output terminal 30 via an intermediate frequency amplifier 28 and an FM detector 29. The FM detector 29 demodulates the intermediate frequency signal subjected to FM (frequency modulation) into the original signal. The output end of this FM detector 29 is connected to a first local oscillator 32 via an AFC (Automatic Frequency Control) unit 31. This first local oscillator 32 is a variable frequency local oscillator, and has a predetermined frequency F _H set by a frequency setter (tuning knob) 32a.
The AFC unit 31 automatically controls the oscillation frequency of the first local oscillator 32. First local oscillator 3
The output end of No. 2 is the movable contact 33c of the changeover switch 33.
It is connected to the. One fixed contact 33b of this changeover switch 33 is connected to one input end of a frequency mixer B34. This frequency mixer B3
The other input terminal of 4 has a fixed frequency F _O (910MHz
The output terminal of a second local oscillator 35 that outputs an oscillation signal of 1770 MHz) is connected to the second local oscillator 35. That is, the frequency mixer B34 is the first local oscillator 3
The local oscillation signal of frequency F _H from 2 and the oscillation signal from the second local oscillator 35 are mixed, and the frequency
This outputs the F _L local oscillation signal. The output terminal of this frequency mixer B34 is a selector switch 36.
is connected to one fixed contact 36b.

Also, the other fixed contact 36 of the changeover switch 36
The other fixed contact 3 of the changeover switch 33 is shown at a.
3a is connected. Furthermore, the movable contact 36c of this changeover switch 36 is connected to the frequency mixer A2.
is connected to the other input terminal of 7. Note that the changeover switches 25, 33, and 36 are interlocked with each other.

Next, the operation of the satellite broadcast receiving tuner having the above configuration will be explained. Now, the input signal of the input terminal 21 is
If the frequency _H = 1.3 GHz = 1300 MHz, the corresponding UHF band frequency satisfies equation (3), so _L = 470 MHz.

First, when this _H = 1300 MHz input signal is received, this signal is selected by the band pass waver 22, amplified to a predetermined level by the amplifier A24, and then passed through the changeover switch 25 to the frequency mixer A2.
It is input to one input end of 7. In this case, each movable contact 25c of the changeover switch 25, 33, 36,
33c and 36c are fixed contacts 25a and 33, respectively.
It is closed on the a and 36a sides. On the other hand, the oscillation frequency of the first local oscillator 32 is set by the frequency setter 32a.
When F _H is set (tuned) to 870 MHz, this local oscillation signal is inputted to the other input terminal of the frequency mixer A27 via the changeover switches 33 and 36. The frequency mixer A27 mixes both the input signals and outputs a signal having the difference between the two signals, that is, the intermediate frequency F _I (430 MHz). This output signal is amplified to a predetermined level by an intermediate frequency amplifier 28, detected by an FM detector 29, and then outputted from an output terminal 30. This is a very ordinary superheterodyne method of reception.

Next, in the case of receiving a signal in the UHF band, _L = 470MHz as mentioned above, and in order to obtain an output signal with the same intermediate frequency as in the case of _H reception, that is, F _I = 430MHz, the frequency F _L = 900MHz. or F _L =40MHz
local oscillation signal is required. Here, the oscillation frequency of the second local oscillator 35 is F _O =910MHz or F _O
= 1770MHz, selector switch 25, 33,
When all 36 movable contacts 25c, 33c, and 36c are closed to the fixed contacts 25b, 33b, and 36b, the first local oscillator 32 has a frequency F _H of 870 MHz, and the second local oscillator 35 has a frequency F _O of 910 MHz. Alternatively, the 1770 MHz signal is mixed and frequency converted by the frequency mixer B34. This frequency mixer B34
If we extract the frequency of the difference between F _H and F _O from the output signal of , if F _O = 910MHz, then F _O −F _H = 910−870
= 40 (MHz), and in the case of F _O = 1770, F _O −F _H =
The signal has a frequency of 1770-870=900 (MHz).

In other words, the frequency F _L = 40 MHz or F _L = required to receive a signal with _L = 470 MHz in the UHF band.
A local oscillation signal of 900MHz can be obtained. However,
This local oscillation signal of frequency F _L and the received signal of frequency _L = 470 MHz, which has been amplified to a predetermined level by amplifier B26 selected by low-pass wave generator 23, are mixed by frequency mixer A27, and as a result, Similarly to the case where _{the H} signal is received, a signal with an intermediate frequency F _I =430 MHz is output. This signal is amplified to a predetermined level by an intermediate frequency amplifier 28, detected by an FM detector 29, and then outputted from an output terminal 30.

In this way, when receiving signals from the two frequency bands mentioned above, the signal from the other frequency band can be received by simply switching the switch while keeping the same local oscillation frequency as when the signal from one frequency band was received. be able to. In other words, normally it is necessary to have two systems of variable frequency local oscillators for _H and _L , but with this invention, only one system of variable frequency local oscillators is required.
The circuit and device become simple, and the cost can be reduced. In addition, handling and operations such as no need to re-tune are extremely easy.

As described above, according to the present invention, with a simple configuration,
It is possible to provide a satellite broadcast reception tuner that can be used in both individual reception and communal reception frequency bands and is easy to handle.

[Brief explanation of the drawing]

1 to 4 are block diagrams showing typical systems of conventional satellite broadcast reception modes, respectively, and FIG. 5 is a circuit block diagram of a tuner for satellite broadcast reception according to an embodiment of the present invention. 21...Input terminal, 22...Band pass wave generator,
23...Low pass wave generator, 24...Amplifier A, 2
5...Selector switch, 26...Amplifier B, 27...
...Frequency mixer A, 28...Intermediate frequency amplifier, 2
9...FM detector, 30...output terminal, 31...
AFC unit, 32...first local oscillator, 3
2a... Frequency setter, 33... Changeover switch,
34... Frequency mixer B, 35... Second local oscillator, 36... Changeover switch.

Claims (1)

[Scope of utility model registration request] Signal in the first receiving frequency band (1000-1300MHz)
_H and second reception frequency band (470-770MHz) signal
In a satellite broadcast reception tuner that receives signals of two frequency bands in which the sum of frequencies with f _L is a constant value F _C (1770MHz), an input terminal into which each input signal of the reception frequency band is input; a branching filter that selects and outputs input signals _H and _L in both frequency bands; a variable-frequency first local oscillator that outputs a first local oscillation signal F _H for the signal _H in the first receiving frequency band; a second local oscillator with a fixed frequency _that outputs an oscillation signal F _O of a predetermined frequency; and a second local oscillator with a fixed frequency that outputs an oscillation signal F _O of _a predetermined frequency; a frequency mixer B that outputs the second local oscillation signal F _L , and mixes the signal _H of the first receiving frequency band and the first local oscillation signal F _H , or the signal of the second receiving frequency band;
A frequency mixer A that mixes _L and a second local oscillation signal F _L to output an intermediate frequency signal F _I , an intermediate frequency amplifier that amplifies the intermediate frequency signal F _I , and the amplified signal F A detector for converting _I into a video signal or an audio signal, and a changeover switch A for switching the input of the signal _L or _H to the frequency mixer A.
, a changeover switch B for switching the input of the signal F _L or F _H to the frequency mixer A, and a changeover switch C for switching the input of the signal F _H to the frequency mixer A or frequency mixer B. When receiving the signal _H in the first receiving frequency band, the signal _H and the signal F _H are input to the frequency mixer A, and the signal _L in the second receiving frequency band is received. At times, the changeover switch A, changeover switch B, and changeover switch C are switched in conjunction so that the signal F _H is input to the frequency mixer B, and the signal _L and the signal F _L are input to the frequency mixer A. A tuner for satellite broadcast reception featuring: