JPS62112407A - Booster for television receiver - Google Patents

Abstract

PURPOSE:To always keep an excellent reception state regardless of an electric field strength by switching a changeover means for a signal amplifier path of a booster and a through-path automatically in response to an AGC voltage outputted from a tuner of a receiver. CONSTITUTION:In a control means of the changeover means between the signal amplifier path of the booster 1 and the through-path, the changeover means is switched to the through-path when an AGC voltage outputted from a TV tuner VIF circuit 3 is the 1st switching voltage or below at the operating state of the amplifier path. In the operating state of the through-path, when the AGC voltage reaches the 2nd switching voltage or over higher than said voltage, the changeover means is switched to the amplifier path. Thus, in selecting the 1st and 2nd switching voltages corresponding nearly to the difference from the AGC voltage depending on the presence of the gain of the amplifier path, the changeover from the amplifier path into the through-path and vice versa are attained automatically depending on a slight difference from the TV broadcast electric field.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides an amplification system that automatically amplifies a signal according to the strength of the electric field of a television broadcast radio wave tuned by a television tuner/VIS circuit. The present invention relates to a booster for a television receiver that can appropriately switch either a path or a through path that does not amplify signals into an operating state.

(Prior art) Conventional boosters for general television receivers are used in areas where there is a lot of radio wave interference, such as mountainous areas, or where the electric field strength of television broadcast waves is weak, such as in areas that are far from the television receiver. In regions with weak electric fields, the antenna input is appropriately amplified and inputted to the television tuner/VIS circuit in order to improve the reception condition of the television receiver. However, in areas with strong electric fields where the electric field strength of television broadcast radio waves is strong, if the antenna input is amplified more than necessary and input to the television tuner VIS circuit, cross-modulation will occur, which will adversely affect the reception of the television receiver. tends to worsen. Therefore, conventional boosters for television receivers are provided with an amplification path that amplifies the signal and a through path that does not amplify the signal.
It is configured so that either one of the amplification path and the through path is manually switched to the operating state by a switching means, and the television program whose tuning is selected]/
It is possible to switch the gain according to the electric field strength of the broadcasting wave (Problem 13 to be solved by the invention).
7. ) By the way, if you are in an area where the electric field strength of each television broadcast wave to be received is about the same, when installing the television receiver, you should first connect the booster to the amplification path that amplifies the signal and the signal amplification path. It is sufficient to use a switching means to set the operating state between the through route and the through route, and there is no problem even if the booster is for a conventional television receiver. In areas where the field strength of television broadcast waves is strong but the field strength of other television broadcast waves is weak, in order to maintain good reception of the television receiver, it is necessary to Each time the channel is switched according to the electric field strength of There is a problem that the process is complicated.

An object of the present invention was to solve the problems of the conventional booster for television receivers as described above, and the present invention is based on the electric field strength of the television broadcast radio waves tuned to and selected by the television tuner/VIS circuit. Therefore, it is an object of the present invention to provide a booster for a television receiver that can automatically switch to either an amplification path that amplifies a signal or a through path that does not amplify a signal.

(Means for Solving the Problem) In order to achieve the above object, the booster for a television receiver of the present invention is provided with an amplification device that is interposed between the antenna and the television tuner/VIS circuit to amplify the signal. In a booster for a television receiver, the booster is provided with a path and a through path in which the signal is not amplified, and in which only one of the amplification path and the through path is switched into an operating state by a switching means, wherein the switching means control means for controlling the television tuner V in the operating state of the amplification path;
When the AGC voltage output from the IS circuit becomes equal to or lower than the first switching voltage, the switching means is switched to the through path, and in the operating state of the through path, the AG
The switching means is configured to switch to the amplification path when the C voltage becomes equal to or higher than a second switching voltage higher than the first switching voltage.

(Function) The control means for controlling the switching means switches the switching means to the through path when the AGC voltage output from the television tuner/VIS circuit becomes equal to or lower than the first switching voltage in the operating state of the amplification path; In the operating state of the through path, the switching means is switched to the amplification path when the AGC voltage exceeds the second switching voltage, which is higher than the first switching voltage, so the difference in AGC voltage due to the presence or absence of gain in the amplification path is By setting the pressures of the first and second 9J converters 1 approximately corresponding to the above, it is possible to switch from the amplification path to the through path operating state and from the through path to the amplification path operating state. It can be automatically switched based on the same field strength of television broadcast waves. Therefore, a good reception condition can always be maintained regardless of the field strength of television broadcast waves without requiring manual switching.

(Description of Embodiments) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a block diagram of a television receiver using a booster for a television receiver according to the present invention, and FIG. 2 is a circuit diagram of a booster for a television receiver according to the present invention. FIG. 3 is an AGC voltage characteristic diagram output from the television tuner/VIS circuit in the operating state of the amplification path and the through path.

In FIG. 1, a booster 1 for a television receiver according to the present invention includes an antenna 2 and a television tuner/VIS.
It is interposed between the antenna input terminal 3a of the circuit 3, and provides the antenna input of the antenna 2 to the antenna input terminal 3a of the television tuner/VIS circuit 3 with or without amplifying the antenna input of the antenna 2. V
An AGC voltage is applied from the AGC terminal 3b of the IS circuit 3 to the AGC voltage input terminal 15.

Hereinafter, the booster 1 for a television receiver according to the present invention will be explained in detail. In FIG. 2, a multi-stage amplifier is interposed in series between an input terminal 4 and an output terminal 5, and an amplification path 6 where the antenna input is amplified and outputted, and an amplification path 6 where the antenna input is outputted without being amplified. A through path 7 is provided in parallel. Switching diodes 8 and 9 are interposed in reverse connection between the input terminal 4 and the amplification path 6, and other switching diodes 10 and 11 are connected in reverse between the input terminal 4 and the through path 7. When a forward current flows from the power supply terminal 12 to the switching diode 8.9 through one PNP transistor 13 and conducts, the other switching diode 10.11
is reverse biased and becomes non-conductive, and conversely, when a forward current flows from the power supply terminal 12 to the other switching diode 10.11 through the other PNP transistor 14 and becomes conductive, the switching diode 8.9 becomes non-conductive. It is configured so that it becomes non-conductive upon receiving a reverse bias, and only one of the amplification path 6 and the through path 7 is in an operating state. These switching diodes 8°9.1
0.11 and PNP) transistors 13 and 14 constitute switching means. Furthermore, the AG to which the AGC voltage is applied from the television tuner/VIS circuit 3
The C voltage input terminal 15 is connected to one input terminal of a comparator 17 via a resistor 16. One input terminal of the comparator 17 is grounded via a resistor 18, and is also grounded via a resistor 18 and an NPN transistor 20 connected in series. A reference voltage 21 is applied to the other input terminal of the comparator 17. Note that the comparator 17 may have a structure that includes a reference voltage,
At this time, the reference voltage 21 is unnecessary. The output terminal of the comparator 17 is connected to the base of one PNP transistor 13 via an inverter 22 and a resistor 23 in series, and is connected to the base of the other PNP transistor 13 via a resistor 24.
Connected to the base of 4. Furthermore, the other PNP
The collector of the transistor 14 is connected to the NP via a resistor 25.
N) Connected to the base of transistor 20. This N
PN) The base of the transistor 20 is grounded via the resistor 2B. Note that the comparator 17 and the reference voltage 21 constitute a comparison switching means, and the resistors 113 and 18.

19 and the NPN) transistor 20 constitute attenuation adjustment means, and the comparison switching means and attenuation adjustment means constitute control means for controlling the switching means.

In this configuration, when the reference voltage 21 is set to 1.25V and the AGC voltage of 3V, which is the first switching voltage, is applied to the AGC voltage input terminal 15 with the NPN transistor 20 non-conducting, the voltage of the resistor 18.18 is 1 to comparator 17 due to pressure.
．． Resistor 18.18 is set to provide an attenuated AGC voltage of 25V. Furthermore, when the NPN) transistor 20 is conductive and the resistor 18 is connected in parallel with the resistor 18, the AGC
When the AGC voltage of 7V, which is the second switching voltage, is applied to the voltage input terminal 15, the resistor 19 is connected so that an attenuated AGC voltage of 1.25V is applied to the comparator 17 by the voltage division of the resistor IEi, 18.19. Set.

Here, first, if the electric field strength of the television broadcast radio wave selected for tuning in the television tuner VIS circuit 3 is extremely strong, and the AGC voltage output from the television tuner VIS circuit 3 is 3V or less of the first switching voltage. Ba,
Ov is output from the comparator 17, and the other PNP transistor 14 becomes conductive, and one PNP transistor 13, which is inverted and applied by the inverter 22, becomes non-conductive. Therefore, a forward current flows through the other switching diodes 10.11, making them conductive and making the through path 7 active, while the switching diodes 8.9 receive a reverse bias and become non-conducting, making the amplification path 6 inactive. . In addition,
When the other PNP transistor 14 becomes conductive and the through path 7 becomes operational, the NPN transistor 20 becomes conductive, greatly attenuating the AGC voltage applied to the AGC voltage input terminal 15 and applying it to the comparator 17.

Next, the electric field strength of the television broadcast radio wave to which the tuning is selected is weakened while the operating state of the through path 7 remains i-ho, and the AGC voltage from the television tuner VIS circuit 3 changes to the second switching voltage of 7V (7V). When the voltage reaches point a) in Figure 3, the comparator 17 inverts and outputs 12V, which is the power supply voltage, to the output terminal. Therefore, the other PNPI transistor 14 becomes non-conductive, and one PNP transistor 13, which is inverted and provided by the inverter 22, becomes conductive.

Therefore, a current flows through the switching diode 8.9, making it conductive and the amplification path 6 becomes operational, while the other switching diodes 10.11 receive reverse bias and become non-conductive, causing the through path 7 to become inactive. state.

Note that when the other PNP transistor 14 becomes non-conductive and the through path 7 becomes inactive, the NPN transistor 20 becomes non-conductive and reduces the amount of attenuation of the AGC voltage applied to the AGC voltage input terminal 5. For this reason, even if the operation of the amplification path 6 (the antenna input is amplified and the AGC voltage output from the television tuner and VIS circuit 3 drops significantly (point b in Fig. 3), the comparator I
The attenuated AGC voltage applied to 7 is greater than the reference voltage 21 and the amplification path 6 continues to operate.

Then, while the amplification path 6 remains in the operating state, the electric field strength of the television broadcast radio wave for which tuning is selected becomes stronger.
When the AGC voltage from the television tuner/VIS circuit 3 becomes less than the first switching voltage of 3V (point 0 in FIG. 3), the comparator 17 is inverted and outputs Ov to the output terminal. Therefore, the through path 7 becomes active and the amplification path 6 becomes inactive. At the same time, NPN transistor 20 becomes conductive and greatly attenuates the AGC voltage applied to AGC voltage input terminal 15. Therefore, even if the AGC voltage rises by switching from the amplification path 6 to the through path (point d in FIG. 3), the attenuated AGC voltage applied to the comparator 17 is smaller than the reference voltage 21, and the through path increases. The route remains operational.

In this way, switching from the amplification path 6 to the operating state of the through path 7 and switching from the through path 7 to the operating state of the amplification path 6 are performed depending on the electric field strength of the television broadcast radio waves, as is clear from FIG. This can be done with slight differences in . The difference in electric field strength of this television broadcast radio wave is determined by the amplification degree of the amplification path 6 (for example, 20 dB) and the AG
It is determined by setting the amount of attenuation of the C voltage. Amplification path 6
The degree of amplification is set such that the AGC voltage that changes when the switching means is switched becomes a voltage between the first and second switching voltages.

In addition, in the above embodiment, the switching means is configured by a semiconductor element, but is not limited to this, and may be configured to include a mechanical switch such as a relay. Further, the attenuation adjusting means constituting the control means may have any structure that increases the amount of attenuation of the AGC voltage when the through path 7 is in the operating state. Furthermore, instead of the damping adjustment means, A
An amplifier may be interposed between the GC voltage input terminal 15 and the comparator 17 so that its gain becomes small when the through path 7 is in the operating state. Furthermore, the attenuation adjustment means is omitted from the control means, and the reference ``weight pressure 2'' of the comparator 17 is
1, the first and second switching voltages A
The switching means may be configured to be switched by the GC voltage.

(Effects of the Invention) As explained above, according to the booster for a television receiver according to the present invention, the control means for controlling the switching means is controlled to be connected to the television tuner @ in the operating state of the amplification path.
When the AGC voltage output from the VIS circuit becomes less than or equal to the first switching voltage, the switching means is switched to the through path, and in the operating state of the through path, the AGC voltage is equal to or higher than the second switching voltage, which is higher than the first switching voltage. Since the switching means is switched to the amplification path when Switching to the operating state of the through path and switching from the through path to the operating state of the amplification path can be automatically switched with the same intensity of television broadcast waves. Therefore, an excellent effect is achieved in that a good reception condition can always be maintained regardless of the electric field strength of television broadcast waves without requiring manual switching.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a television receiver using a booster for a television receiver according to the present invention, and FIG. 2 is a circuit diagram of a booster for a television receiver according to the present invention. FIG. 3 is an AGC voltage characteristic diagram output from the television tuner/VIS circuit in the operating state of the amplification path and the through path. 1: Booster for television receiver, 2: Antenna, 3: Television tuner VIS circuit, 4: Input terminal, 5: Output terminal, 6: Amplification path, 7: Through path. 8.9, 10, 11 Niswitching diode, 13.
14: PNP) transistor, 15: AGC voltage input terminal, 1B, 18.1!9: Resistor, 17: Comparator,
20: NPN transistor. Procedure Amendment Written January 27, 1986 Michibu Uga, Commissioner of the Patent Office1, Indication of the case Patent Application No. 252297 of 19852, Name of the invention Booster for Television Receiver 3, Amendment. Relationship with the Patent Case Patent Applicant Name (582) Matsushita Electric Industrial Co., Ltd. Name (675
) Yokoo Seisakusho Co., Ltd. 4, Agent address: 2-6, Kanda Kita Jomono-cho, Chiyoda-ku, Tokyo, Power of attorney subject to amendment, Claims in the specification and details of the invention 7, Contents of amendment (1) Power of attorney Replenish as shown in the attached sheet. (2) Amend the claims of the specification as shown in the attached sheet. (3) Second line of the specification, line 15, page 3, line 8 and line 13, page 5, line 5 and line 15, page 6, line 3 and lines 12-13, 7 Page lines 15 and 19,
Page 8, lines 2 and 3; page 9, line 9; page 11, line 4 and lines 6-7; page 12, line 3 and line 20; page 13, line 6, rVIsj on line 7 on page 15, line 9 on page 16, and line 13 on page 16 are each corrected by l'VIFJ. Attachment (Japanese Patent Application No. 60-252297) r Claims (1) An amplification path for amplifying a signal and an amplification path for amplifying a signal, which is interposed between an antenna and a television tuner/VIF circuit. A booster for a television receiver is provided with a through path and a through path, and only one of the amplification path and the through path is switched to an operating state by a switching means, further comprising a control means for controlling the switching means, and a control means for controlling the switching means. means switches the switching means to the through path when the AGC voltage output from the television tuner/VIF circuit becomes equal to or lower than the first switching voltage in the operating state of the amplification path; Then, the AGC voltage is the first
A booster for a television receiver, characterized in that the booster is configured to switch the switching means to the amplification path when the switching voltage reaches a second switching voltage higher than the switching voltage of the booster.

Claims (2)

[Claims] (1) An amplification path that amplifies the signal and a through path that does not amplify the signal are provided between the antenna and the television tuner/VIS circuit, and these amplification paths and the through path are used as switching means. In a booster for a television receiver in which only one of the switching means is switched to an operating state, a control means for controlling the switching means is provided, and the control means controls the output from the television tuner/VIS circuit when the amplification path is in the operating state. The switching means is switched to the through path when the AGC voltage to be applied becomes equal to or lower than the first switching voltage, and in the operating state of the through path, the AGC voltage is lower than the first switching voltage.
A booster for a television receiver, characterized in that the booster is configured to switch the switching means to the amplification path when the switching voltage reaches a second switching voltage higher than the switching voltage of the booster. (2) The control means includes an attenuation adjustment means that attenuates and adjusts the AGC voltage, and a comparison switching means that compares the attenuated AGC voltage with a reference voltage, and the attenuation amount of the attenuation adjustment means is determined by the attenuation of the amplification path. The AGC is adjusted to be larger in the operating state of the through path than in the operating state of the through path, and the comparison switching means is attenuated by the attenuation adjustment means
2. A booster for a television receiver according to claim 1, wherein said switching means is configured to switch said amplification path into an operating state when the voltage is higher than a reference voltage.