KR100633481B1 - Improving circuit for inter modulation distortion of multi-signal input - Google Patents

Abstract

A circuit for improving an IMD(Inter Modulation Distortion) property is provided to enable a strong electric field signal, inputted to the transistor of an amplifier, to be inputted as a normal electric field signal after decreasing the level of the signal and enable a weak electric field signal and the normal electric field signal to be inputted without decreasing the level of the signals, thereby preventing signal distortion and normally receiving the signals irrespective of the inputted signal level. A control unit(140) determines the level of a multi-channel input signal and supplies control power if the level is higher than a reference level and does not supply the control power if the level is lower than the reference level. A selecting unit(110) decreases the level of the multi-channel input signal when connecting to the control unit(140) and receiving the control power and passes the multi-channel input signal without decreasing the level when not receiving the control power. An amplifying unit(100) receives a signal outputted from the selecting unit(110) and amplifies the signal, and inputs the signal to a tuned circuit(130).

Description

Improving circuit for inter modulation distortion of multi-signal input

1 is an overall block diagram of a conventional multi-channel RF receiver.

2 is a detailed circuit diagram of the amplifier of FIG.

3 is a detailed circuit diagram of an amplifier circuit of an embodiment of the present invention.

FIG. 4 is a flowchart for describing an operation of the circuit of FIG. 3.

Explanation of symbols for main parts of the drawings

100: amplifier 110: selection circuit, 120: divider

130: tuning circuit 140: control unit D1, D2: diode

TR1: transistor

The present invention relates to a circuit for improving an intermodulation distortion (IMD) characteristic for a strong signal when a multichannel signal is input.

IMD means that two or more frequency signals interfere with each other to generate an unwanted parasitic signal. When IMD becomes large, reception quality decreases significantly during synchronization. In particular, an active element such as an amplifier has a small distortion because the IMD is not large in the weak electric field or the normal electric field, but the active IMD becomes large in the strong electric field, resulting in severe distortion, thereby greatly reducing the reception quality.

1 is an overall block diagram of a conventional multichannel RF receiver, and FIG. 2 is a detailed circuit diagram of the amplifier of FIG.

As shown in FIG. 1, the RF signal received by the antenna 10 is amplified by the amplifier 30 by passing only a signal having a predetermined bandwidth through the filter 20, and the amplified signal is distributed. And input to the TV and tuning circuit 40.

As shown in FIG. 2, the amplifier 30 is configured around the transistor TR, and a capacitor C1 and a resistor R1 are connected in series between the output terminal of the filter 20 and the base and the base of the transistor TR. A resistor R4 is connected between the connection point of the capacitor C1 and the resistor R1 and the ground, and a resistor R2 and a resistor between the connection point of the capacitor C1 and the resistor R1 and the bias power supply Vcc. R7 is connected. An inductor (choke coil L1) is connected between the connection point of the resistor R2 and the resistor R7 and the collector of the transistor TR, and the capacitor C2 and the resistor R3 are connected between the collector and the base of the transistor TR. Is connected, the capacitor (C5) is connected between the collector and the distributor 50 formed of a 1: 1 balun transformer, the resistor (R5), (R6), the capacitor (C3) is connected between the emitter and the ground. The signal input to the splitter 50 is divided into two, one is input as a TV signal, and one is input to the tuning circuit 40.

In such a circuit configuration, the bias DC power supply Vcc is dropped by the resistor R7, and the dropped voltage is distributed by the resistors R2 and R4 and applied to the base to bias the transistor. The signal from which the Citizen band of 0 to 30 MHz is removed from the filter 20 passes through the condenser C1, and the DC component is removed. The signal is lowered by the resistor R1 and input to the base, and the signal amplified by the transistor TR. Is output to the tuning circuit 40 and the TV via the distributor 50 composed of 1: 1 balun transformer via the condenser C5.

The signal input to the tuning circuit 40 maintains a normal signal because the IMD of the amplifier 30 for the signal of the normal level (60 dB μV, 0 dB mV) or the weak field signal is small. However, in the case where the signal input to the amplifier 30 is a strong electric field signal, the signal distortion is largely generated by the harmonic components generated by the transistor TR, and thus the IMD becomes large. 40) to significantly reduce the reception quality.

In this circuit, when the strong field signal is input to the amplifier 30, to reduce signal distortion, the resistor R7 connected to the bias power supply Vcc is reduced to increase the collector current, and the resistor connected to the base of the transistor TR. Increasing (R1) to reduce the level of the input signal reduces the signal distortion, thereby reducing the IMD.

However, this method may be a method of reducing IMD with respect to a strong electric field input signal, but the level is further lowered with respect to the input of the normal signal level or the input of the low signal level so that the normal signal and the low level signal input cannot be received. do.

The present invention is to solve the above problems, and to provide an IMD characteristic improvement circuit for receiving a multi-channel RF signal without signal distortion for weak and strong field signals.

A characteristic of the present invention for achieving the above object is an inter-modulation distortion (IMD) characteristic improvement circuit for amplifying a multi-channel input signal and inputting it to a tuning circuit: determining a level of the multi-channel input signal to determine a reference value. A control unit applying control power in the case of a larger electric field and not applying control power when the level is less than or equal to the reference value; A selection unit connected to the control unit to reduce the level of the multi-channel input signal when the control power is applied and to pass the multi-channel input signal without reduction when the control power is not applied; And an amplifying unit receiving the signal output from the selecting unit and amplifying the signal to be input to the tuning circuit.

Further, in the present invention, the selector is connected to the signal input terminal of the amplification unit and at least one diode connected by the control power supply, and is connected between the diode and the ground to emit an input signal to ground when the diode is in a conductive state. It is preferable to include a capacitor.

In the present invention, the amplifying unit is composed of a transistor, the multi-channel input signal is input to the base of the transistor through the selection unit, the selection unit is the multi-channel input only when the control power is applied from the control unit It is preferable to reduce the level of the signal and input the signal to the base.

The selector may include at least one diode having a cathode connected to a line connected to the signal input terminal of the amplifier and a control power applied to an anode.

In addition, in the present invention, it is preferable to further include a capacitor connected between the anode and ground.

Hereinafter, an embodiment of the present invention according to the accompanying drawings will be described in detail.

3 is a detailed circuit diagram of an amplifier circuit of an embodiment of the present invention.

In the amplifier 100 illustrated in the embodiment of FIG. 3, an RF signal received from an antenna is input to an input through a filter, a bias power is applied from a bias DC power supply Vcc, and is input to an input. The input signal is input to the controller 140. The controller 140 senses the level of the input signal and applies the control power to the amplifier 100 through the resistor R14. The output of the amplifier 100 is distributed by the internal divider 120 to be output to the tuning circuit 130 and the TV (TV output).

The capacitor C1, the selector 110, the resistor R1, and the capacitor C10 are connected in series between the input terminal of the amplifier 100 and the base of the transistor TR1, and between the base and the bias power supply Vcc. A resistor R2 and a resistor R7 are connected in series, and a resistor R4 is connected between the base and the ground. An inductor (choke coil L1) is connected between the collector (R2) and the resistor (R7) and the collector, and the resistor (R3) and capacitor (C2) are connected between the collector and the base. The condenser C5 is connected between the divider 120, and a signal is output from the divider 120 to the tuning circuit 120 and the TV, respectively, and the resistor R5 and the resistor R6 between the emitter and the ground. , The capacitor C3 is connected in parallel.

In addition, the selector 110 includes a capacitor C13 connected between the capacitor C1 and the resistor R1, a resistor R10 connected between the connection point of the capacitor C1 and the capacitor C13 and the ground, and a capacitor ( Diode (D1) connected between the connection point of C1) and capacitor (C13) and ground; resistor (R11) and capacitor (C13) connected between connection point of capacitor (C11) and capacitor (C13) and resistor (R1) and ground; Line connecting diode D2, capacitor C12, connection point of diode D1 and capacitor C11 and connection point of diode D2 and capacitor C12 connected between the connection point of resistor R1 and ground ( 11) and a resistor R12 connected between the controller 140. At this time, the cathodes of the diodes D1 and D2 are connected to the connection point of the capacitor C1 and the capacitor C13, and the connection point of the capacitor C13 and the resistor R1, and the anodes are respectively the capacitors C11 and ( C12).

FIG. 4 is a flowchart for describing an operation of the circuit of FIG. 3.

When the input signal is input to the input terminal of the amplifier 100 from the filter, the input signal is input to the selector 110 by removing the direct current component by the capacitor (C1) while the control unit 140 through the resistor (R14) It is input (S1). The controller 140 compares the input signal with a strong electric field reference level and determines that the input signal is larger than the reference level and determines that the input signal is a strong electric field input to the diodes D1 and D2 through the resistor R12. If the control power is applied (S2), (S3), (S4), (S5), and the input signal is smaller than the reference level, it is determined that it is not a strong electric field input and the control power is not applied (S2), (S3). ), (S6).

When the diodes D1 and D2 are in a conducting state, the signals input to the selection unit 110 through the capacitor C1 are distributed to the capacitors C11 and C12 to be discharged to ground, thereby reducing the input signal level. Will be reduced. However, since the control power is not applied from the controller 140, the diodes D1 and D2 are turned off so that the signal input to the selector 110 is input to the resistor R1 without reduction. That is, when the input signal is a strong electric field, it is discharged to the ground through the diodes D1 and D2, so that the input signal is reduced and the IMD generated by the transistor TR1 is reduced, thereby amplifying without signal distortion and tuning circuit ( Inputs an amplified signal. When the input signal is a weak or normal electric field, diodes D1 and D2 are turned off to input the input signal to the base without attenuation of the level, and this signal is amplified and input to the tuning circuit 130. (S7), (S8).

like this. The signal input to the transistor TR1 of the amplifier 110 is attenuated by the selector 110 in the case of a strong electric field, and is inputted without level attenuation for the normal electric field and the weak electric field signal, and thus a low IMD state regardless of the input signal. The signal can be amplified, and the tuning circuit is also tuned in the absence of signal distortion, thereby improving reception sensitivity (S9).

According to the present invention having the above object and configuration, the strong electric field input to the transistor of the amplifier is attenuated by the signal level and input into the normal electric field to prevent signal distortion, and the weak electric field and the normal electric field are inputted without attenuating the signal level. Thus, normal reception can be achieved regardless of the signal level input.

Claims (5)

An IMD characteristic improvement circuit for amplifying a multi-channel input signal and inputting it to a tuning circuit; A controller for determining a level of the multi-channel input signal and applying control power when the power is greater than a reference value and not applying control power when the level is less than or equal to the reference value; A selection unit connected to the control unit to reduce the level of the multi-channel input signal when the control power is applied and to pass the multi-channel input signal without reduction when the control power is not applied; And an amplifying unit which receives the signal output from the selecting unit and amplifies and inputs the signal to the tuning circuit. The method of claim 1, wherein the selector is connected to the signal input terminal of the amplification unit and at least one diode connected by the control power supply, and is connected between the diode and the ground to emit an input signal to the ground when the diode is in a conductive state IMD characteristic improvement circuit comprising a capacitor. The multi-channel input signal is input to the base of the transistor through the selector, the selector is the multi-channel only when the control power is applied from the controller. And reducing the level of the input signal and inputting it to the base. The method of claim 1, wherein the selector comprises a cathode connected to a line connected to the signal input terminal of the amplifier and at least one diode to which the control power is applied to an anode. IMD characteristic improvement circuit. 5. The IMD characteristic improvement circuit of claim 4, further comprising capacitors connected between the anode and ground.

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