KR900006262B1 - Transmitting circuit of carphone - Google Patents

Abstract

An AGC circuit has a main amplifier (12), a power amplifier (14), a comparator (16), a reference power level section (18), a voltage follow circuit (26), a peak detector (22), a strip line (20) and a rectifyling circuit (28) for temperature compensation. The rectifying circuit comprises a resister (R6) and diodes (D3,D4) directly connected with power supply and capacitors (C3,C4) for voltage bypass and high frequency bypass. The temperature compensation voltage through a diode (D2) is provided to the peak detector.

Description

Transmitter output circuit of car phone with rectifier for temperature compensation

1 is a block diagram of a conventional transmission output stage.

2 is a block diagram of a car phone transmission output stage according to the present invention.

3 is a detailed circuit diagram of FIG.

* Explanation of symbols for the main parts of the drawings

12: Main AMP 14: Power Amplifier

16: second comparator 18: reference power level section

20: strip line 22: peak detector

24: first comparator 26: voltage FoUow circuit

28: temperature compensation rectifier circuit R1-R6: low

C1-C4: Capacitor Dl-C4: Diode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic gain control (AGC) circuit for transmitting output stages in a car phone, and more particularly to a Sungshin output stage AGC circuit having a rectifying circuit for temperature compensation.

In general, in order to prevent a decrease in the transmission output level as the ambient temperature rises in the AGC circuit of the car phone, the AGC circuit is driven by inducing the output of the main amplifier to a predetermined level using a stall line. A block diagram showing such a conventional transmission output only configuration is shown in FIG. Here, various radio wave disturbances induced at high frequency output may cause car phone transmission power level to become somewhat unstable and affect peripheral circuits. In addition, the decrease of the output level due to the rise in the degree of output causes the minimum output level of the transmission to cause an output indicator error, thereby causing a malfunction of the system.

Accordingly, an object of the present invention is to provide a circuit capable of minimizing the influence on the stability of the transmission output level and the peripheral circuit by inducing a minimum output capable of driving the AGC furnace in the AGC furnace of the car output transmitter.

It is still another object of the present invention to provide a transmission output stage AGC furnace which can prevent an output indicator error due to a temperature rise at the lowest output level.

In order to achieve the above object, the present invention provides an automatic gain control circuit for a car-outside transmission output stage including a main amplifier, a power amplifier, a comparator, a reference power level unit, a voltage fall-toe circuit, a peak detector, and a strip line. A temperature formed by connecting a resistor and a plurality of diodes in series, grounding them through a voltage bypass capacitor and a high frequency bypass capacitor in parallel from the anode side of the diode, and connecting the anode side of another diode from the anode side. The rectifying circuit for compensation is characterized in that it is connected to the strip line and the peak detection period.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 2 is a block diagram of a car phone transmission output stage according to the present invention, which includes a main amplifier 12, a stripline 20, a peak detector 22, a voltage follower circuit 26, a reference power level unit 18, and a second circuit. In the car output AGG circuit of the car phone comprising the comparator 16 and the power amplifier 14, the output of the temperature compensating rectifier circuit 28 is connected between the strip line 20 and the peak detector 22. Minimize the output modulated signal from the stripline. The modulated output induced in the stripline is detected by the peak detector 22 and compared with an out-of-reference reference voltage level Vref at the first comparator 24 connected between the peak detector and the voltage flow circuit 26. The output instruction signal P'VR corresponding to the result is output. In the figure, reference numeral MOD denotes a modulation signal from a modulation driving amplifier, and an RF output from a stripline corresponds to a radio frequency output. The reference power leveling section 18 also provides the second comparator 16 with a predetermined reference power level (e.g., 0-7 level) to set the reference for gain control in the AGC circuit.

FIG. 3 is a circuit diagram showing an embodiment of the present invention, showing a concrete circuit of the temperature compensation rectifying circuit 28 and the peak detector 22 in the second diagram. The temperature compensation rectifier circuit 28 connects a resistor R6 and a diode D3 and D4 in series from a power supply voltage VCC, and capacitors C4 and C3 connected in parallel from an anode side of the diode D3. Ground), and the anode side of another diode D2 is connected from the anode side. The cathode side of the diode D2 is connected to a peak detector 22 composed of a diode Dl, a capacitor C2 and a resistor R2 and R3 as an output terminal of the temperature compensation rectifier circuit. Although the resistance values of the resistors R1-R6 shown in the drawings can be increased or changed slightly within the scope not departing from the spirit of the present invention, in the description of the embodiments herein, R1 = 68! &, R2 = 22k! &, The case where R3 = 15K! &, R4 = 27K! &, R5 = 910! &, And R6 = 3.9K! & Has been described as an example. Capacitors C3 and C4 are for voltage bypass and high frequency bypass, respectively, and their values are 0.01 μF and 1000 pF, respectively, and the power supply voltage VCC is 5V.

Therefore, the operation relationship of the present invention will be described with reference to the above-described drawing configuration.

By adding the temperature compensation rectifier circuit 28 in the AGC circuit shown inside the dotted line, the output of the main amplifier 12 can be minimized in the strip line 20. Looking at the minimum value, the voltage applied to the node point (a) by the forward voltage of the diode Dl and the resistors R2 and R3 is about 0.1V higher than the voltage of the node point (b) (0 14 ≒ R4 // R5). When the predetermined minimum output level is induced to the capacitor Cl through the strip line, the node point (poly) voltage is about 0.7V. As the power level is gradually raised, the node point (C) has a voltage of about 5 volts, and the AGC loop can be driven. Next, when the car is operating and the output from the main ampo 12 is lowered due to the increase of the silver at the minimum output level, and the node point (e) voltage becomes lower than 0.7V, the node point in the absence of the temperature compensation rectifier circuit. (A) The voltage becomes smaller than the node point (B) voltage, so that the output of the first comparator 24 becomes an output indicator error with a low level, and it is induced in the AGC loop and is referred to in the second comparator 16. The potential difference with the voltage is generated a lot, the power level in the main amplifier 12 is more than the minimum output level, causing a malfunction of the system. However, if the rectifier circuit for temperature compensation is added, the voltage of (C) at the output minimum level gradually decreases with temperature at 0.7V, so that (A) the potential decreases until it is close to or equal to (B) potential. C) The voltage at point is about 0.55V, while in the temperature compensation rectifier circuit (D) the potential is represented by the forward voltage by Schottky diodes (D3) and (D4), which is about 0.7V. Therefore, when the (C) potential becomes lower than the (D) potential due to the decrease in temperature, the Schottky diode D2 becomes conductive and drives the AGC circuit through the diode Dl with the signal emitted from the strip line.

The double-sheet diodes (Dl, D2, D3, D4) are the same Schottky diodes, but the forward voltage is about 0.15V less in the diodes D1 and D2 than the diodes D3 and D4 due to voltage and load resistance. . Due to this difference, the voltage of about 0.15V and the voltage induced in the stripline pass through the capacitor C2 and detect peak value together with the diode Dl. The voltage drop at point (A) prevents the phenomenon of being equal to or lower than the potential at point (B), and the difference of the difference voltage with respect to the reference voltage in the second comparator of the AGC loop is reduced. It will keep the system and prevent the malfunction of the system.

(C) The voltage is gradually attenuated by the temperature and (D) is lower than the potential. In this case, the minimum voltage at point (C) is about 0.3-0.35V. Even if there is no output from the main amplifier, the rectifier circuit for temperature compensation will operate, but the double-sided potential will be lower than the (b) potential, so the output indicator will be at the 'low' level. do.

As described above, the present invention induces the high frequency output from the main amplifier to the AGC circuit through the stripline at a minimum level, thereby stabilizing operating points of various elements of the output AGC loop, and minimizing radio wave interference in the peripheral circuit. Can be. In addition, the damping time of the AGC circuit is minimized by compensation of the temperature rise, thereby stabilizing the output of the main amplifier through the AGC loop, thereby improving the call quality of the car phone.

Claims (2)

A car phone having a main amplifier 12, a power amplifier 14, a comparator 16, a reference power example bell unit 18, a voltage flow circuit 26, a peak detector 22 and a strip line 20, etc. In a transmission output stage automatic gain control circuit, a resistor R6 and a diode D3 and a D4 are connected in series from a power supply voltage VCC, and a capacitor for voltage bypass having a parallel configuration from an anode side of the diode D3. C3) and the high frequency bypass capacitor C4 are grounded, and the anode side of another diode D2 is connected from the anode side so that a predetermined temperature compensation voltage is applied to the peak detector when the diode D2 conducts. Circuitry characterized in that it is supplied. The transmission output circuit as claimed in claim 1, wherein the diodes (Dl, D2, D3, D4) of the temperature compensation rectifier circuit (28) are Schottky diodes.

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