JP3350800B2 - Composite electronic tuner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite electronic tuner mounted on a video tape recorder (VTR) or the like.

[0002]

2. Description of the Related Art In recent years, a composite electronic tuner has been developed in which peripheral circuits are combined with an electronic tuner and integrated so as to reduce costs and downsize the electronic tuner.

As a combination, as shown in FIG. 5, a baseband signal (video signal / audio signal) is supplied to an electronic tuner circuit 41 having a built-in PLL circuit and having a UHF tuner and a VHF tuner. For a 2-in-1 tuner 40 integrated by combining a modulator circuit 43 for modulating and generating an RF signal, or as shown in FIG. 6, an electronic tuner circuit 41 incorporating a PLL circuit 42, not only the modulator circuit 43 but also the RF circuit.
There is a 3-in-1 tuner 50 that combines and integrates a detection circuit 44 that demodulates a signal into a baseband signal. Other than this, there is an electronic tuner circuit that integrates a low noise amplifier (LNA), and an electronic tuner circuit. There is one that integrates a booster RF switch.

[0004] As described above, the modulator circuit converts a baseband signal including a video signal and an audio signal into an RF signal transmitted from a broadcasting station. For example, when a recorded video tape is reproduced in a VTR, the modulator circuit converts the frequency of the reproduced video signal and audio signal into an RF signal so that the television signal can be received by a television receiver.
The signal is output from the F output terminal to the RF input terminal of the television receiver. Thus, the video / audio reproduced by the VTR can be viewed on the television receiver.

[0005] As is well known, at present, there are almost no conventional electronic tuners of the voltage tuning type using a conventional mechanical switch or variable resistor, and a P-controller which can be controlled by a microcomputer.
The LL tuning system is becoming mainstream. But,
In many cases, mechanical switches are still used for peripheral circuits. The same applies to a mechanical switch circuit (not shown: see 29 in FIG. 3) for operating the channel switching unit in the modulator circuit 43. This is because the control of the peripheral circuit is simple on / off compared to the electronic tuner circuit, and it is costly to use a dedicated IC for controlling the microcomputer with one or two control circuits. Because there is no merit.

FIG. 3 is a block diagram showing the configuration of a conventional 2-in-1 type composite electronic tuner 20. As shown in FIG.
3, reference numeral 21 denotes an electronic tuner circuit. The electronic tuner circuit 21 includes a PLL circuit 22 and the PLL circuit 22.
UHF circuit 23 selected by circuit 22, VHF-
A HIGH circuit 24 and a VHF-LOW circuit 25 are provided. Reference numeral 26 denotes a modulator circuit that modulates a baseband signal (video signal / audio signal) to generate an RF signal.
The modulator circuit 26 includes a channel switching unit 27. The PLL circuit 22 includes a microcomputer 28
, And the channel switching unit 27 is configured to be controlled by a mechanical switch circuit 29.

The PLL circuit 22 controlled by the microcomputer 28 is constituted by an IC.
The functions of the LL circuit 22 are roughly divided into two functions. One is a frequency control function which is an original function of a PLL (Phase Locked Loop), and the other is a function of controlling band division in an electronic tuner. The frequency control function controls the frequency of the oscillator etc. based on the data of the desired channel sent from the microcomputer,
A corresponding frequency (local oscillation frequency) is generated, and a desired channel is selected.

The band division control function includes generally known VHF (Very High Frequency), UHF
(Ultra High Frequency), which is a method necessary for a device that receives a wide frequency band.

For example, in the United States CATV (Cable Televisi)
on) is 55.25-88.
5.25 MHz is the entire reception band. Reception of this signal by a single circuit requires a considerably expensive and complicated circuit. Therefore, it is divided into several bands as described below, and each circuit is provided in an electronic tuner.

1) VHF-LOW band: 55.25 to 83.25 MHz 2) VHF-MID band: 91.25 to 211.25 MHz 3) VHF-HYPER band: 217.25 to 469.25 MHz 4) UHF band: 471.25 to 885.25 MHz In order to switch such a band, four band switches as changeover switches are usually built in an IC (PLL-IC) constituting a PLL circuit. The band switching by the band switch is a band division control function.

A voltage is independently applied to each band switch in accordance with data sent from the microcomputer, and one of the band switches is turned on to select a circuit of a corresponding band.

Although an example of band division has been described above, in recent years, as the performance of components (particularly diodes) has been improved, an electronic tuner that divides and uses all reception bands into four parts has hardly been developed. And usually
The development of electronic tuners that divide the entire reception band into three, and in some cases, divide it into two has become the majority. When dividing into three, for example, there is the following band division.

VHF-LOW band: 55.25 to 127.25 MHz VHF-HIGH band: 133.25 to 361.25 MHz UHF band: 367.25 to 885.25 MHz Thus, the number of band divisions was reduced from 4 to 3. As a result, P
One band switch among the four band switches of the LL-IC is left. When the number of band divisions is reduced from four to two, two band switches are left.

The composite electronic tuner 20 shown in FIG.
The UHF circuit 23 in the electronic tuner circuit 21 corresponds to the above, the VHF-HIGH circuit 24 corresponds to the above, and the number of band divisions is reduced to 3.
The VHF-LOW circuit 25 corresponds to the above. In the composite electronic tuner 20, one band switch is left in the PLL-IC constituting the PLL circuit 22. If the number of band divisions is two, the number of surplus band switches in the PLL-IC becomes two.

FIG. 4 is a circuit diagram showing a configuration of a mechanical switch circuit 29 for a channel switching section 27 (not shown) in the modulator circuit 26. 4, reference numeral 26a denotes a modulator IC constituting the modulator circuit 26, and reference numeral 30 denotes a PN in the mechanical switch circuit 29.
P-type switching transistors, 31, 32, and 33 are resistors, and 34 is a slide switch. The emitter of the switching transistor 30 is connected to a 5 V DC power supply 35, the collector is connected to the channel switching terminal 26b of the modulator IC 26a, and is connected to the ground GND via the resistor 31. The resistor 32 is connected, the base is connected to one end of the slide switch 34 via the resistor 33, and the other end of the slide switch 34 is connected to the ground GND.

The modulator circuit 26 is usually provided with two or more output channels having different frequencies in order to avoid the influence of beats and the like. A means for switching the output channel is a channel switching unit 27,
Often composed of For example, it is assumed that the modulator IC 26a is designed to be 3ch when the channel switching terminal 26b is at 0V and to be 4ch when the channel switching terminal 26b is at 5V. Slide switch 34
Is turned off and opened, the switching transistor 30 is non-conductive and the modulator IC 26
The voltage applied to the channel switching terminal 26b is 0 V
Therefore, the modulator IC 26a outputs 3ch. When the slide switch 34 is turned on and short-circuited to the ground GND, the switching transistor 30
Is conducted, and 5 V is applied to the channel switching terminal 26b of the modulator IC 26a.
6a outputs 4ch. Usually, it is set to a so-called empty channel.

[0017]

In the case of the above-mentioned prior art, as a switch means for operating the channel switching section 27, a mechanical type comprising a switching transistor 30, three resistors 31 to 33 and a slide switch 34 is used. A switch circuit 29 is employed. The slide switch 34 is a switch that has a fixed electrode and a movable electrode, and is turned on / off by sliding the movable electrode to contact / separate from the fixed electrode. This slide switch is inexpensive compared to an electronic switching element controlled by a microcomputer using a semiconductor such as a transistor, but on the other hand, it is susceptible to deterioration and failure due to wear due to the presence of mechanical contacts There is a problem that. Further, since a switching transistor and three resistors are used, the number of parts is large, the circuit configuration is complicated, and the cost is increased.

On the other hand, since electronic tuners with four band divisions are still manufactured, the number of PLL-IC band switches is four in some IC manufacturers.
The PLL-IC of the three-band system and the PLL-IC of the two-band system both use the PLL-IC of the four-band system so as not to increase the cost. Therefore, in the PLL-IC used in the electronic tuner circuit of the three-band system or the two-band system, the remaining one or two band switches are not deleted and are built in without being used. It is in. If the number of band divisions is reduced from 4 to 3, P
One band switch among the four band switches of the LL-IC is left. When the number of band divisions is reduced from four to two, two band switches are left.

The present invention has been made in view of such circumstances, and uses a band switch that has not been used in the PLL-IC until now as a changeover switch for a modulator circuit. The purpose is to achieve simplification of the circuit configuration and cost reduction by using it.

[0020]

According to a first aspect of the present invention, there is provided a composite electronic tuner comprising: a PLL circuit comprising an IC; and a plurality of band selection circuits selected by the PLL circuit . And booster RF
A modulator circuit comprising an IC that has a built-in amplifier circuit for converting a baseband signal to an RF signal, and when the number of the plurality of band selection circuits is smaller than the number of band switches in the PLL-IC, the remaining Of the booster RF amplifier circuit
It is characterized in that it is configured to also be used as an on / off switch. If the signal from the broadcasting station is weak,
It is common to use a star and use it for this booster
The RF amplifier circuit has a built-in modulator IC.
As an on / off switch for the RF amplifier circuit,
Band switch that has been left as a result of
The conventional technology is needed because the switch is also used.
Since the number of parts is large, the circuit configuration is complicated, and there are mechanical contacts
Mechanical switch circuits, which are prone to
This can simplify the circuit configuration and reduce the cost as a whole.

[0021]

[0022]

[0023]

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a composite electronic tuner according to the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 shows a 2 in 1 type composite electronic tuner 1 in a VTR according to a first embodiment.
FIG. 3 is a block diagram showing a configuration of a 0. This composite-type electronic tuner 10 is obtained by combining and integrating an electronic tuner circuit 11 and a modulator circuit 16. The electronic tuner circuit 11 includes a PLL circuit 12 having four band switches therein, and a UHF circuit 13, a VHF-HIGH circuit 14, and a VHF-LOW circuit 15 selected by the PLL circuit 12. The modulator circuit 16 modulates a baseband signal (video signal / audio signal) into an RF signal, and includes a channel switching unit 17 for selecting a vacant channel when connecting to a television receiver. The PLL circuit 12 is configured to be controlled by a microcomputer 18. That is, in the PLL circuit 12, the UHF
A band switch corresponding to the circuit 13 and a VHF-HIG
A band switch corresponding to the H circuit 14 and a VHF-LO
The microcomputer 18 controls on / off of a band switch corresponding to the W circuit 15.

This PLL circuit 12 has a band division number of 4
It is manufactured for one electronic tuner circuit and is shown in FIG.
In the case of the three-band system having the configuration described above, one of the four band switches inside the PLL circuit 12 is left unused without being used. However, in the first embodiment, the extra band switch inside the PLL circuit 12 is not left unused, and the channel built in the modulator circuit 16 necessary to avoid the influence of beats and the like is used. It is configured to be used for controlling the switching unit 17.
That is, one of the output ports of the microcomputer 18
And the input side of the band switch, which has been determined to be left in the PLL circuit 12, is connected, and the output side of the band switch is connected to the control terminal of the channel switching unit 17. In response to a command, the channel switching unit 1 is switched through the band switch.
7 is set, and the output channel of the modulator circuit 16 is set to an empty channel so that no beat or the like occurs.

FIG. 2 is a block diagram showing the structure of the main part. An output terminal 12a connected to a band switch of the PLL circuit 12 is connected to a channel switching terminal 16b of a modulator IC 16a constituting the modulator circuit 16, and the channel switching terminal 16b is connected to the modulator IC 16a.
It is connected to a channel switching unit 17 (not shown) inside 16a.

As described above, in the first embodiment, in order to set the modulator circuit 16 to the state of the vacant channel output, the slide switch 34, the switching transistor 30 and the resistor 31 which are complicated, expensive and easily worn are used.
Mechanical switch circuit 2 having a complicated configuration of
9 instead of using a dedicated IC that has no merit in terms of cost.
Since the band switch, which has been considered to be left behind in the L circuit 12, is configured to be controlled by the microcomputer, the circuit configuration can be simplified and the cost can be reduced.

[Second Embodiment] In the first embodiment, the band switch, which has been considered to be left behind in the PLL circuit 12, is used for controlling the channel switching unit 17 of the modulator circuit 16. Although not shown in the composite electronic tuner according to the second embodiment,
The band switch is configured to be used as a system switch of the modulator circuit 16. There is a model that uses a modulator IC for the whole world as the modulator IC 16a. In such a case, the system differs depending on the country, so it is necessary to adjust the system for each country. In the case of the second embodiment, the configuration shown in FIG.
1, the output terminal 12a of the PLL circuit 12 is connected to a system switching terminal (not shown) of the modulator IC 16a. The band switch is configured to be controlled by the microcomputer as in the first embodiment. The effect is the same as that of the first embodiment.

[Embodiment 3] When a radio wave from a broadcasting station is weak, a booster is used.
An amplifier circuit is used. This RF amplifier circuit is built in the modulator IC 16a. The switch of the RF amplifier circuit is turned on in an area where the radio wave is weak, and if not, the switch of the RF amplifier circuit is turned off. Although not shown, the composite electronic tuner according to the third embodiment is configured such that the above-mentioned band switch, which is considered to be extra, is used as an on / off switch of the RF amplifier circuit. Things. In the configuration of the third embodiment, in FIG. 2, the output terminal 12a of the PLL circuit 12 is connected to the R terminal of the modulator IC 16a.
It is connected to a control terminal (not shown) of an on / off switch of the F amplifier circuit. The band switch is also configured to be controlled by the microcomputer. The effect is the same as that of the first embodiment.

The following can be cited as other embodiments. In the case of a composite electronic tuner in which all reception bands are divided into two and used, two band switches are left inside the PLL circuit 12, and these two band switches are connected to the modulator I.
Used as a channel changeover switch and a system changeover switch of C16a, used as a channel changeover switch of a modulator IC 16a and an on / off changeover switch of an RF amplifier circuit, or used as a modulator IC 16a.
There are various combinations of combinations, such as use as the system changeover switch a and the on / off changeover switch of the RF amplifier circuit.

Further, in the case of each of the above embodiments, 2 in
Although one type of composite electronic tuner has been described, the present invention may be applied to a 3 in 1 type composite electronic tuner as shown in FIG.

[0033]

According to the composite type electronic tuner according to claim 1 according to the present invention, radio waves from the broadcasting station to definitive band switch that surplus in the PLL-IC to the modulator IC
Of the booster RF amplifier circuit required when the
Since the switch is also used as an on / off switch, the mechanical switch circuit, which requires a large number of parts and has a complicated circuit configuration and mechanical contacts, which is liable to cause deterioration or failure, can be omitted. In addition, instead of using a dedicated IC that has no merit in terms of cost, it is possible to simplify the circuit configuration and reduce the cost as a whole.

[0034]

[0035]

[0036]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a composite electronic tuner according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a configuration of a main part in the first embodiment.

FIG. 3 is a block diagram showing a configuration of a composite electronic tuner according to a conventional technique.

FIG. 4 is a circuit diagram showing a configuration of a mechanical switch circuit for a channel switching unit of a modulator circuit in a composite electronic tuner according to the related art.

FIG. 5 is a block diagram showing a configuration of a general 2 in 1 type composite electronic tuner.

FIG. 6 is a block diagram showing a configuration of a general 3 in 1 type composite electronic tuner.

[Explanation of symbols]

 10 Composite electronic tuner 11 Electronic tuner circuit 12 PLL circuit 13 UHF circuit 14 VHF-HIGH circuit 15 VHF-LOW circuit 16 Modulator circuit 16a Modulator IC 16b Channel switching Terminal 17: Channel switching unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H03J 1/00-5/24 H04N 5/44 H04B 1/06-1/26

Claims (1)

(57) [Claims] 1. A PLL circuit comprising an IC and the PL circuit
An electronic tuner circuit including a plurality of band selection circuits selected by an L circuit , and a booster RF amplifier circuit ;
Path to convert baseband signal to RF signal
C, and when the number of the plurality of band selection circuits is smaller than the number of band switches in the PLL-IC, the remaining band switches are turned on / off of the RF amplifier circuit of the booster. Oh
Composite electronic tuner, characterized in that where the structure is also used in off change-over switch.