JP2001068956A - Amplifier for antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably output a high frequency input signal to a tuner respectively in the case that an antenna reception terminal power is strong or weak. SOLUTION: A detection circuit 14 detects an RF input signal from an antenna and outputs a DC signal in response to an antenna receiving end power to a 1st changeover on/off circuit 15. When a voltage of the DC signal is higher than a prescribed threshold voltage, the 1st changeover on/off circuit 15 is closed and a 2nd changeover on/off circuit 16 is open. Thus, only a signal via an attenuator 12 or the like is outputted to a tuner. When the voltage of the DC signal is a prescribed threshold voltage or below, the 1st changeover on/off circuit 15 is open and the 2nd changeover on/off circuit 16 is closed. Thus, only a signal via an amplifier 13 or the like is outputted to the tuner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna amplifying device for outputting a high frequency signal from an antenna to a tuner.

[0002]

2. Description of the Related Art Conventionally, as an amplifying device for an antenna, for example, Japanese Patent Application Laid-Open No.
What is described in 12118 gazette is known. These conventional amplifying devices for antennas include an amplifying circuit using active elements in order to improve the sensitivity of the antenna. In the weak / medium electric field region, a high-frequency signal having a weak power at the antenna receiving end is suitably amplified by this amplifier circuit and output to the tuner to ensure good reception performance.

[0003]

By the way, in an area with a strong electric field, for example, a large number of extremely strong high-frequency signals may exist. As described above, when a plurality of extremely high-frequency signals having extremely high power at the antenna receiving end are input to the above-described amplifier circuit, active elements in the circuit are saturated, and the amplification characteristics exhibit nonlinearity. Then, modulation occurs between the input high-frequency signals and the like, and the signal output from the amplifier circuit to the tuner causes distortion. Due to the occurrence of such distortion, (1) the tuner search is stopped at a frequency other than the frequency of the broadcast station. (2) the sound of the broadcast wave with weak power at the antenna receiving end is taken over by the sound of the strong broadcast wave. There is a problem.

[0004] In order to deal with such a problem,
For example, it is conceivable to expand the dynamic range of the amplifier circuit, but this is technically possible but inappropriate in practical use. This is because an upper limit input level is set for a tuner connected to such an antenna amplifying device so as not to damage the tuner.

An object of the present invention is to provide an antenna amplifying apparatus that can output a high-frequency input signal from an antenna to a tuner appropriately when the power at the antenna receiving end is high and when the power is low.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 is an antenna amplifying apparatus for outputting a high-frequency input signal from an antenna to a tuner. Detecting means, and amplifying means for amplifying a high-frequency input signal from the antenna,
When the detected antenna receiving end power is weak, a high-frequency input signal from the antenna is output to the tuner via the amplifying means, and when the detected antenna receiving end power is strong, the antenna Switching means for outputting a high-frequency input signal from the tuner to the tuner without passing through the amplifying means.

According to a second aspect of the present invention, in the antenna amplifying apparatus according to the first aspect, when the detected antenna receiving end power is strong, a high frequency input signal from the antenna is passed through an attenuating means. Output to the tuner.

According to a third aspect of the present invention, in the antenna amplifying apparatus according to the first aspect, when the detected power at the receiving end of the antenna is strong, the high frequency input signal from the antenna is subjected to impedance matching means. The gist is to output to the tuner via the interface.

According to the first aspect of the present invention, when the power at the receiving end of the antenna is weak, the high frequency input signal from the antenna is suitably amplified via the amplifying means and output to the tuner. Is done. Therefore, the reception performance of the tuner is suitably secured.

On the other hand, when the power at the receiving end of the antenna is strong, the high-frequency input signal from the antenna is output to the tuner without passing through the amplifying means. Therefore, it is possible to prevent the active element in the amplifying unit from being saturated due to the input of a high-frequency input signal having a high power at the antenna receiving end to the amplifying unit, thereby preventing the output signal from being distorted.

According to the second aspect of the present invention, when the power at the antenna receiving end is high, the high-frequency input signal from the antenna is passed through the attenuating means, for example, to such an extent that the active element in the path is not saturated. Is suitably attenuated.

According to the third aspect of the present invention, when the power at the receiving end of the antenna is high, the high-frequency input signal from the antenna is efficiently output to the tuner via the impedance matching means.

[0013]

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a circuit diagram showing an amplifying device for an antenna. As shown in FIG. 1, the antenna amplifying device includes an RF (high frequency) input signal terminal 10 connected to an antenna line, an attenuator 12 as an attenuating unit, an amplifier 13 as an amplifying unit, and a detecting unit. Constituting detection circuit 14
And a first switching ON / OFF (on / off) circuit 15 constituting the switching means, a second switching ON / OFF (on / off) circuit 16 constituting the switching means, and connected to the tuner via a coaxial cable. RF output signal terminal 17
Etc. are provided.

The RF input signal terminal 10 is connected to the attenuator 12. The attenuator 12 is arranged in a π-shape by a resistor 23 connected to the RF input signal terminal 10 and resistors 24 and 25 each having one end connected to one side and the other side of the resistor 23 and having one end grounded. Have been. The attenuator 12 attenuates the signal level of the RF input signal by a fixed ratio.

The attenuator 12 is connected to the RF output signal terminal 17 via a bias cut capacitor 26, the first switching ON / OFF circuit 15, and a bias cut capacitor 27. The RF input signal is output to the RF output signal terminal 17 via the attenuator 12 and the like when the first switching ON / OFF circuit 15 is on, and the first switching ON / OFF circuit 15 is off. It is shut off at the time.

Further, the RF input signal terminal 10 is connected to a bias cut capacitor 31 and the second switching ON / O.
The FF circuit 16 is connected to the amplifier 13. This amplifier 13 is connected to the RF output signal terminal 17. The RF input signal is supplied to the amplifier 1 when the second switching ON / OFF circuit 16 is on.
3 to the RF output signal terminal 17 via the
When the switching ON / OFF circuit 16 is in the off state, it is shut off.

Further, the RF input signal terminal 10
Are connected to the detection circuit 14 via a bias cut capacitor 32. The detection circuit 14 includes a detection circuit section 33 and a delay circuit section 34.

The detection circuit section 33 includes a diode 36 whose anode is connected to the bias cut capacitor 32 and a diode 37 whose cathode is connected to the bias cut capacitor 32 and whose anode is grounded.
And The detection circuit unit 33 detects the RF input signal and outputs a direct current (DC) signal corresponding to the signal level (amplitude) corresponding to the power at the antenna receiving end.

The delay circuit section 34 includes the diode 3
6 comprises a resistor 38 connected to the cathode, a resistor 39 connected to the resistor 38 and a capacitor 40 connected in parallel to each other and grounded. The delay circuit section 34 (capacitor 40) is connected to the first switching ON / OFF circuit 15, and applies the charging voltage of the capacitor 40 to the first switching ON / OFF circuit 15.

The first switching ON / OFF circuit 15 includes a first diode 41 and an N-channel field effect transistor (N-channel FET) 42. The anode of the first diode 41 is connected to the attenuator 12 via the bias cut capacitor 26. Incidentally, the attenuation factor of the attenuator 12 is set so that the first diode 41 is not saturated by the RF input signal. The cathode of the first diode 41 is connected to the RF output signal terminal 17 via the bias cut capacitor 27.

The anode of the first diode 41 is connected to a battery power supply Vcc via a high-frequency choke coil (hereinafter referred to as "RFC") 43 and a resistor 44. This resistor 44 is connected to the first diode 41 by RFC.
Adjustment is made so that an appropriate current flows through 43.

The cathode of the first diode 41 is connected to the drain of the N-channel FET 42 via the RFC 45. The drain of the N-channel FET 42 is connected to the battery power supply Vcc via the resistor 46. The source of the N-channel FET 42 is grounded, and the gate is connected to the detection circuit 14 (capacitor 40).

When the voltage (charging voltage of the capacitor 40) applied to the gate of the N-channel FET 42 is at an H (high) level higher than a predetermined threshold voltage, the N-channel FET 42 is turned on. , A resistor 46 and an N-channel FET from the battery power supply Vcc.
A current flows through 42. The threshold voltage is set so that the DC signal output from the detection circuit unit 33 according to the signal level (antenna receiving end power) of the RF input signal corresponds to a strong level of the antenna receiving end power or a weak level. Is set to a suitable value for classifying whether or not it corresponds to That is, when the voltage applied to the gate of the N-channel FET 42 is at an H level higher than a predetermined threshold voltage, it is assumed that the voltage corresponds to a high level of the power at the antenna receiving end, and the voltage is equal to the predetermined threshold voltage. When it is at the L (low) level below the voltage, it is assumed that it corresponds to a weak level of the antenna receiving end power.

When the N-channel FET 42 is turned on, the resistor 46 and the N-channel FET 4
2 through the N-channel FET 42
Is at the L level, the cathode of the first diode 41 connected to the drain via the RFC 45 is also at the L level, and the first diode 41 is turned on. That is, the first switching ON / OFF circuit 15 is turned on, and the RF input signal is output to the RF output signal terminal 17 via the attenuator 12 and the like.

On the other hand, when the voltage applied to the gate of the N-channel FET 42 is at the L level below a predetermined threshold voltage, the N-channel FET 42 turns off and the drain of the N-channel FET 42 goes to the H level. . Therefore, the cathode of the first diode 41 connected to the drain via the RFC 45 also becomes H level, and the first diode 41 is turned off. That is, the first switching ON / OFF circuit 15 is turned off, and the RF input signal is cut off.

The drain voltage of the N-channel FET 42 is output to the second switching ON / OFF circuit 16. The second switching ON / OFF circuit 16 includes the second diode 5
1 and an NPN transistor 52.

The anode of the second diode 51 is connected to the RF input signal terminal 10 via the bias cut capacitor 31, and the cathode is connected to the RF output signal terminal 17 via the amplifier 13. I have.

The anode of the second diode 51 is connected to a battery power supply Vc via an RFC 53 and a resistor 54.
c. The resistor 54 is adjusted so that an appropriate current flows through the second diode 51 via the RFC 53.

The cathode of the second diode 51 is RF
It is connected to the collector of the NPN transistor 52 via C55. The collector of the NPN transistor 52 is connected to a battery power supply Vcc via a resistor 56. The emitter of the NPN transistor 52 is grounded, and the base is connected to the drain of the N-channel FET 42 via a resistor 57. In addition,
A bias resistor 58 having the same base is connected between the base and the emitter of the NPN transistor 52.

Here, when the base of the NPN transistor 52, that is, the drain of the N-channel FET 42 is at L level, the NPN transistor 52 is turned off and the collector of the NPN transistor 52 becomes H level. Therefore, the cathode of the second diode 51 connected to the collector via the RFC 55 also becomes H level, and the second diode 51 is turned off. That is, the second switching ON / OFF circuit 16 is turned off, and the RF input signal is cut off.

On the other hand, when the base of the NPN transistor 52, that is, the drain of the N-channel FET 42 is at the H level, a current flows from the battery power supply Vcc via the resistor 56 and the NPN transistor 52. At this time, since the collector of the NPN transistor 52 is at the L level, the cathode of the second diode 51 connected to the collector via the RFC 55 is also at the L level, and the second diode 51 is turned on. That is, the second switching ON / OFF circuit 16 is turned on, and the RF input signal is supplied to the R
The signal is output to the F output signal terminal 17.

As described above, when the voltage applied to the gate of the N-channel FET 42 is at the H level higher than the predetermined threshold voltage, the first switching ON / OF
F circuit 15 is turned on, while the second switching ON / OFF
The circuit 16 is turned off. Therefore, the RF input signal terminal 1
The RF input signal input to 0 is output to the RF output signal terminal 17 via the attenuator 12 and the like.

When the voltage applied to the gate of the N-channel FET 42 is at an L level below a predetermined threshold voltage, the first switching ON / OFF circuit 15 is turned off, while the second switching ON / OFF circuit 15 is turned off. The ON / OFF circuit 16 is turned on. Accordingly, the RF input signal input to the RF input signal terminal 10 is transmitted to the RF input signal through the amplifier 13 and the like.
Output to the output signal terminal 17.

Next, the operation of the antenna amplifying device will be described. The RF input signal input to the RF input signal terminal 10 from the antenna is
2 to the detection circuit 14. Here, the RF input signal is detected, and a DC signal (charge voltage of the capacitor 40) corresponding to a signal level (amplitude) corresponding to the power at the antenna receiving end is output to the N-channel FET 42 of the first switching ON / OFF circuit 15. You. At this time, when the voltage of the DC signal is higher than a predetermined threshold voltage, the N-channel FET 42 is turned on on the assumption that the voltage corresponds to a strong signal level of the power at the antenna receiving end. Then, since the first diode 41 is turned on, the RF input signal is applied to the attenuator 1
The signal is output to the first diode 41 via 2 or the like. At this time, the level (amplitude) of the RF input signal is
Thereby, the first diode 41 is suppressed to the extent that it does not saturate. The first diode 41 has D
A current in which the C current and the RF current corresponding to the RF input signal are superimposed flows. This current is output to the RF output signal terminal 17 after the DC component is cut by the bias cut capacitor 27.

Further, since the N-channel FET 42 is on, the drain of the N-channel FET 42 goes low, and the NPN transistor 52 of the second switching ON / OFF circuit 16 turns off. Therefore, the second diode 51
Turns off. Therefore, the RF input signal is not output to the RF output signal terminal 17 via the amplifier 13.

As described above, when an RF input signal corresponding to a strong signal level of the power at the antenna receiving end is input, only the signal via the attenuator 12 and the like is output to the RF output signal terminal 17. Since a high-frequency signal is not input to the amplifier 13, the occurrence of distortion in the signal output to the RF output signal terminal 17 (tuner) is avoided.

On the other hand, when the voltage of the DC signal (charging voltage of the capacitor 40) corresponding to the signal level (amplitude) corresponding to the power at the antenna receiving end is equal to or lower than a predetermined threshold voltage, the signal having the weak power at the antenna receiving end is output. Assuming that the level corresponds to the level, the N-channel FET turns off and the first diode 41 turns off. Therefore, the RF input signal is transmitted to the attenuator 1
2 is not output to the RF output signal terminal 17.

Since the N-channel FET 42 is off, the drain of the N-channel FET 42 goes to H level, and the NPN transistor 52 of the second switching ON / OFF circuit 16 turns on. Therefore, the second diode 51
Is turned on, the RF input signal is supplied to the second diode 51
Is output to The second diode 51 includes:
A current flows in which the DC current and the RF current corresponding to the RF input signal are superimposed. This current is output to the RF output signal terminal 17 via the amplifier 13.

As described above, when the RF input signal corresponding to the weak signal level of the antenna receiving end power is input, only the signal via the amplifier 13 and the like is output to the RF output signal terminal 17. Then, the RF output signal terminal 17
The signal output to the (tuner) is suitably amplified.

As described in detail above, according to the present embodiment, the following effects can be obtained. (1) In the present embodiment, an RF input signal having a high power at the antenna receiving end in a strong electric field area is output to the RF output signal terminal 17 (tuner) via the attenuator 12 and the like. Therefore, the active element in the amplifier saturates, for example, when an RF input signal with a strong antenna receiving end power is input to the amplifier, and the like.
The generation of distortion in the output signal is avoided. Therefore, it is possible to prevent the search of the tuner from being stopped at a frequency other than the frequency of the broadcasting station in the strong electric field area, or to prevent the sound of the broadcast wave with weak power at the antenna receiving end from being hijacked by the sound of the strong broadcast wave. be able to.

The RF input signal having a weak power at the antenna receiving end is suitably amplified through the amplifier 13 and the like and output to the RF output signal terminal 17 (tuner). Therefore, the reception performance of the tuner can be suitably secured.

(2) In this embodiment, an RF input signal having a high power at the antenna receiving end in a strong electric field area is converted into an attenuator 1
2, the first diode 41 can be attenuated to such an extent that the first diode 41 is not saturated.

(3) In this embodiment, the first and second switching ON / OFF circuits 15 and 16 constituting the switching means are provided with N-channel FETs 42 and N, which are semiconductor switches, respectively.
A PN transistor 52 was employed.

(4) In the present embodiment, the attenuator 12 can be configured extremely easily by the resistors 23 to 25 arranged in a π shape. (Second Embodiment) Hereinafter, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the attenuator 12 of the first embodiment is removed, and an impedance matching circuit is employed before the bias cut capacitor 27 of the first embodiment. Omitted.

As shown in FIG. 2, an impedance matching circuit 61 as an impedance matching means is connected to the capacitor 62 having one side connected to the first switching ON / OFF circuit 15 and the other side of the capacitor 62. And a coil 63 whose one end is grounded. The impedance matching circuit 61 matches the impedance up to the RF output signal terminal 17 including the antenna with the characteristic impedance of the coaxial cable to which the RF output signal terminal 17 is connected, for example, 75 ohms. With such matching, the RF input signal from the antenna is efficiently output to the tuner via the coaxial cable.

As described in detail above, according to this embodiment, the following effects can be obtained in addition to the effects (1) and (3) in the first embodiment. (1) In the present embodiment, an RF input signal from the antenna corresponding to a strong signal level of the antenna receiving end power can be efficiently output to the tuner (coaxial cable).

The embodiment of the present invention is not limited to the above embodiment, but may be modified as follows. In the first embodiment, the resistors 23, 24, 25
Employs an attenuator 12 arranged in a π-shape. On the other hand, an attenuator in which the resistors are arranged in a T-shape may be employed.
Further, the present invention is not limited to the attenuator having such a combination of resistors, and may employ an attenuator having another shape.

In the first embodiment, when the power at the antenna receiving end is high, the RF input signal input to the RF input signal terminal 10 is converted to the RF output signal terminal 17 (tuner) via the attenuator 12. Output to On the other hand, the attenuator 12 may be omitted, and the RF input signal input to the RF input signal terminal 10 may be output to the RF output signal terminal 17 (tuner) without passing through the attenuator. .

A circuit for outputting the RF input signal input to the RF input signal terminal 10 to the RF output signal terminal 17 via the attenuator 12 and an output to the RF output signal terminal 17 without the attenuator And a circuit that performs the operations. Then, for example, when the antenna receiving end voltage is strong and slightly strong, the R
The F input signal is separately switched between output to the RF output signal terminal 17 (tuner) via the attenuator 12 and output to the RF output signal terminal 17 (tuner) without the attenuator. Such a circuit configuration may be adopted.

The impedance matching circuit 61 in the second embodiment uses, for example, a transformer.
Other forms of impedance matching circuits may be used. As the amplifier 13 in each of the above embodiments, an amplifier that can change and control the amplification factor stepwise or continuously according to the power at the antenna receiving end may be adopted. As such an amplifier, for example, there is an amplifier whose bias is changed according to the power at the antenna receiving end and whose amplification factor is controlled according to the bias. Further, for example, an amplifier having an automatic gain control (AGC) circuit may be used.

In each of the above embodiments, the switching of the circuit between the case where the power at the antenna receiving end is high and the case where the power at the antenna receiving end is low is performed by the semiconductor type switch using the N-channel FET 42 and the NPN transistor 52. On the other hand, for example, a mechanical switch using a relay may be used.

The detection circuit 14 employed in each of the above embodiments may be a detection circuit of another shape. The circuit configuration adopted in each of the above embodiments is an example. The point is that the RF input signal is switched between the case where the RF input signal is output to the RF output signal terminal 17 via the amplifier and the case where the RF input signal is output to the RF output signal terminal 17 without the amplifier according to the antenna receiving end power. Any circuit configuration may be used.

Next, technical ideas other than the claims that can be grasped from the above embodiments will be described below together with their effects. (A) The amplifying device for an antenna according to any one of claims 1 to 3, wherein the switching means is configured by a semiconductor switch.

According to this configuration, since the switching means is constituted by a semiconductor switch, the reliability and the response speed are improved as compared with, for example, a mechanical switch. (B) In the antenna amplifying device according to claim 2,
An amplifying device for an antenna, wherein the attenuating means is constituted by a resistor arranged in at least one of a π shape and a T shape.

According to this structure, the above-mentioned damping means is very simply constituted by the resistors arranged in at least one of the π type and the T type.

[0057]

As described in detail above, according to the first aspect of the present invention, a high-frequency input signal from an antenna is preferably output to a tuner when the power at the antenna receiving end is high and when the power is low. Can be provided.

According to the second aspect of the present invention, when the power at the receiving end of the antenna is high, the high-frequency input signal from the antenna is suitably attenuated via the attenuating means so that the active elements in the path are not saturated. can do.

According to the third aspect of the invention, when the power at the receiving end of the antenna is strong, the high frequency input signal from the antenna can be efficiently output to the tuner via the impedance matching means.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an antenna amplifying device according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the antenna amplifying device according to the present invention.

[Explanation of symbols]

Reference Signs List 12 Attenuator as attenuating means 13 Amplifier as amplifying means 14 Detection circuit constituting detecting means 15 First switching ON / OFF circuit constituting switching means 16 Second switching ON / OFF circuit constituting switching means 61 Impedance matching Impedance matching circuit as a means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor, English word Koide 2-1-1 Asahi-cho, Kariya-shi, Aichi, Japan F-term (reference) 5J100 JA01 KA05 LA00 LA10 QA01 QA02 SA02 5K062 AD03 AD07 AE02 AG01 BA02 BB09 BE09

Claims (3)

[Claims] 1. An antenna amplifying device for outputting a high-frequency input signal from an antenna to a tuner, a detecting means for detecting an antenna receiving end power, an amplifying means for amplifying a high-frequency input signal from the antenna, When the power at the antenna receiving end is weak, a high-frequency input signal from the antenna is output to the tuner via the amplifying means, and when the detected power at the antenna receiving end is strong, the high-frequency signal from the antenna is output. A switching unit that outputs an input signal to the tuner without passing through the amplifying unit. 2. The antenna amplifying device according to claim 1, wherein when the detected antenna receiving end power is strong, a high-frequency input signal from the antenna is output to the tuner via an attenuation unit. An amplifier device for an antenna, comprising: 3. The antenna amplifying device according to claim 1, wherein when the detected antenna receiving end power is strong, a high-frequency input signal from the antenna is output to the tuner via impedance matching means. An amplifier device for an antenna, comprising: