KR930000726B1 - Apparatus for extending operation region of a mobile phone - Google Patents

Abstract

The output signal of a received signal strength indicator (RSSI) is fed back to gain control terminal of an IF amplifier to decrease the reception sensitivity of a receiver so that amplifiers in a reception stage are not saturated. The circuit includes an amplifier (1) for amplifying signals received from an antenna, an IF amplifier (4) for amplifying intermediate frequency signal, a deector (5) for generating RSSI signal and for filtering local oscillator signal, a feedback amplifier (6) for feeding the RSSI signal back to the amplifier (1), and an IF amplifier controller (9) for generating and transmitting control signal to the IF amplifier according to the magnitude of signal transmitted from the feedback amplifier (6).

Description

Active Area Expansion Circuits for Car Phone Transceivers

1 is a block diagram according to the prior art.

2 is a block diagram according to the present invention.

3 is a circuit diagram of FIG.

4 is a relationship between the output voltage of the RSSI and the RF input.

* Explanation of symbols for main parts of the drawings

1: low noise amplifier 2: mixer

3: band pass filter (BPF) 4: IF amplifier

5 detector IC 6 amplifier

7, 8: OP-amp 9: IF amplifier control unit

Q1: transistor

The present invention relates to a receiving active area extension circuit in a car phone transceiver. In particular, a negative feed back loop is formed as a gain control terminal of an IF amplifier by using an output signal of a received signal strength indicator (RSSI). In addition, the present invention relates to an active area extension circuit which further expands an area in which the respective amplification stages are not saturated, that is, the active area is lowered by lowering the overall reception sensitivity.

In the prior art, as shown in FIG. 1, a conventional car phone transceiver circuit includes a low noise amplifier 1 for amplifying a signal input through an antenna, an output of the low noise amplifier 10 and a local oscillator (not shown in the drawing). And a band pass filter (3) for filtering the output of the mixer (3), and the band pass filter (3). IF (intermediate frequency) amplifier 4, which is connected to an output terminal of the band pass filter 3 and performs an intermediate frequency amplification for the output of the band pass filter 3, and an output of the intermediate frequency amplifier 4, and receives a local oscillator (shown in the drawing). And a detector IC (5) for receiving the local oscillation frequency provided by the controller) and outputting the RSSI signal and the detected signal.

The RSSI simply sends an output signal to the A / D converter to check the relative signal strength, so that when the strong input signal enters the RF first stage, i.e., the low noise amplifier 1, through the antenna, each amplification stage saturates the detected signal. Due to the distortion, the small active area of the receiver, the small active area of the RSSI, and the receiving system is too sensitive to instantaneous changes in the field strength appearing through the forests of urban buildings. An instant imbalance in data and audio demodulation caused an error.

Accordingly, the present invention has been made to solve the above-described problems. In the car phone transceiver, the AGC circuit is added to the reception stage, the mixer, etc. using the RSSI output signal, and the active region of each amplifier stage for the wider RF input. An object of the present invention is to provide a circuit capable of improving characteristics.

In addition, another object of the present invention is to provide a circuit that can enhance the reliability of the system by eliminating the phenomenon in which the distortion of the detected signal is increased at the time of strong input, and automatically maintaining a proper gain at the input on the active area. It is.

In order to achieve the above object, the present invention provides a feedback amplifier (6) for receiving the RSSI output of the detector IC (5) and returning it to the low noise amplifier (1) in the conventional transceiver of FIG. It is characterized in that it further comprises an IF amplifier control unit 9 connected to the output terminal of (6) for providing a control signal according to the output of the feedback amplifier (6) to the IF amplifier (4).

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

2 is a block diagram of an embodiment according to the present invention, in which 6 is a feedback amplifier and 9 is an IF amplifier controller.

As shown in the drawing, the present invention provides a low noise amplifier (1) for amplifying a signal input through an antenna, and a local portion provided at the output of the low noise amplifier (1) and a local oscillator (not shown). A mixer (2) for synthesizing the oscillation frequency, a band pass filter (3) for filtering the output of the mixer (3), and an output terminal of the band pass filter (3) are connected to a band pass filter ( IF (intermediate frequency) amplifier 4 performing intermediate frequency amplification with respect to the output of 3), and local oscillation provided by a local oscillator (not shown in the drawing) by receiving the output of the intermediate frequency amplifier 4; A car phone transceiver having a detector IC (5) for receiving a frequency and outputting an RSSI signal and a detected signal, wherein the feedback amplifier receives the RSSI output of the detector (5) and returns it to the low noise amplifier (1). (6), and the feedback amplifier ( And an IF amplifier control unit 9 connected to an output terminal of 6) for providing a control signal according to the output of the feedback amplifier 6 to the IF amplifier 4.

3 is a circuit diagram of the present invention, which is a detailed circuit diagram of FIG.

The output signal of the RSSI demodulated by the detector IC 5 is applied to the negative terminal of the op amp 7 through the resistor R1 and set by the variable resistor VR1 by the input resistors R2 and R4 at the negative terminal. When a reference voltage is applied, a constant differential amplification voltage is output through its output stage. The output of the OF amplifier 7 is

At this time, this output voltage is inversely related to the output signal of the RSSI.

Therefore, since the OP amplifier 8 of the IF amplifier control unit 9 receives the output voltage of the OP amplifier 7 in which the variable resistor VR2 is adjusted through the (+) terminal, this is a resistor R5 connected in parallel with the inverting (-) terminal. And amplifies the input voltage by (1 + R6 / R5) by R6. As a result, the transistor Q1 connected to the output terminal of the OP amplifier 8 is driven to supply the power supply voltage B- to the IF amplifier 4.

On the other hand, since the output signal of the OP amplifier 7 is applied to the gate G2 of the FET 10 in the low noise amplifier 1 having the dual input terminal, the FET 10 is switched to forge the feedback voltage applied to the gate G2. As a result, the overall gain drops when the drain current decreases. The signal passing through the FET 10 is again applied to the IF amplifier 4 through the mixer 2 and the bandpass filter 3.

As a result, it formed through the double feedback loop and obtained the graph as shown in FIG.

That is, the OP amplifier 7 generates a voltage source inversely proportional to the RSSI output signal, and applies an extremely strong RF input by applying it to the gate G2 of the PET 10 of the amplifier 1 and the positive terminal of the OP amplifier 8. Even if the signal is received (typically -30 dB), the gain is automatically adjusted by the formation of the feedback loop to maintain a constant level.

Thus, according to the present invention, the gain control through the feed back loop expands the active area of the RSSI, does not cause distortion during large RF inputs, and is more effective than the instantaneous change of the input generated when passing between buildings in the city center. There is an effect that can provide a well-supported receiving system.

Claims (3)

A low noise amplifying means (1) for amplifying a signal input through an antenna, and a mixing for synthesizing the output of the low noise amplifying means (1) and a local (local) oscillation frequency provided by a local oscillator (not shown). A band pass filter means 3 connected to the means 2, to a band pass filter means 3 for filtering the output of the mixing means 3, and to an output end of the band pass filter means 3; IF (intermediate frequency) amplifying means (4) for performing intermediate frequency amplification with respect to the output of the signal, and a local oscillation provided by a local oscillator (not shown) by receiving the output of the intermediate frequency amplifying means (4). A car phone transceiver having a detection means (5) for receiving a frequency and receiving a RSSI (Received Signal Strength Indictor) signal and a detected signal wave, the low noise amplifying means receiving the RSSI output of the detection means (5) Bin feedback to (1) IF amplifier control means 9 which is connected to an amplifying means 6 and an output terminal of the feedback amplifying means 6 and provides another control signal to the IF amplifying means 4 at the output of the feedback amplifying means 6. An active area expansion circuit for a car phone transceiver, characterized in that it further comprises. 2. The feedback amplifier (60) according to claim 1, wherein the feedback amplifying means (60) receives an RSSI signal which is an output of the detecting means (5) to an inverting terminal (-) and supplies a reference voltage by the variable resistor VR1 at the non-inverting terminal (+). An active area expansion circuit in a car phone transceiver, characterized in that it comprises a receiving op amp (7) and a variable resistor (V R2) connected to an output terminal of the op amp (7). The OP amplifier (8) according to claim 1, wherein the IF amplifier control unit (9) has a non-inverting terminal (+) connected to an output terminal of the feedback amplifier means (6) and resistors R5 and R6 connected in parallel to an inverting terminal. And a transistor (Q1) connected to an output terminal of the OP amplifier (8).

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