JP3230928B2 - Transmission power control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission power control circuit used for controlling the transmission power of a CDMA type automobile telephone, portable telephone or the like.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing an example of a conventional transmission power control circuit of this type. In the drawing, reference numeral 1 denotes a transmission input terminal, 2 denotes a transmission-side variable gain amplifier, 3 denotes a power amplifier, and 4 denotes a power amplifier. A transmission output terminal, 5 is a reception input terminal, 6 is a variable gain amplifier on the reception side, 7 is a reception output terminal, 8 is a power detection circuit, 9 is a comparison signal input terminal, 10 is a comparator, 11 is a control signal input terminal,
12 is an adder. Note that the variable gain 2 on the transmission side and the variable gain amplifier 6 on the reception side have the same characteristics.

Next, the operation will be described. First, a reception signal input from the reception input terminal 5 is amplified by the reception-side variable gain amplifier 6 and received as a reception output signal by the reception output terminal 7.
Is output to Also, this output signal output is
The power is detected by the power detection circuit 8 and guided to the comparator 10 as a detection signal. The comparator 10 receives a reference power value from a comparison signal input terminal 9. The detection signal is compared with the reference power value, and the comparison result is used as a reception AGC signal as the reception-side variable gain. The gain is applied to the amplifier 6 so that the detection signal and the reference power value become equal.

[0004] The received AGC signal is supplied to an external transmission power control signal input to a control signal input terminal 11 and an adder 12.
And is added to the transmission-side variable gain amplifier 2 as a transmission power control signal. In the transmission-side variable gain amplifier 2, the transmission signal input from the transmission input terminal 1 is amplified with a gain based on the transmission power control signal, and further amplified by the power amplifier 3 and transmitted from the transmission output terminal 4. Take it out as a signal.

Generally, the variable gain amplifiers 2 and 6 on the transmission side and the reception side do not have linearity with respect to the control by the control signals (the output signal of the adder 12 and the reception AGC signal in this conventional example). Normal, and therefore the control signal input terminal 11
When an external transmission power control signal is not input to the receiver, a change in the level of the reception signal input from the reception input terminal 5 causes a constant reception output signal to be obtained from the reception output terminal 7 in response to the change. Since the received AGC signal is generated at this time, and the received AGC signal is equal to the transmission power control signal for controlling the transmission side variable gain amplifier 2, the output signal of the transmission side variable gain amplifier 2 is The relationship of (Equation 1) is established with respect to the received signal input from.

[0006]

Po = A−Pi (Po: transmission power, Pi: reception power, A: constant) However, when an external transmission power control signal is input to the control signal input terminal 11, the adder 12 outputs Since the transmission power control signal and the reception AGC signal are added to the transmission-side variable gain amplifier 2 in the added form, the transmission power control signal is controlled by the nonlinearity of the control signal versus gain change of the transmission-side variable gain amplifier 2. Cannot be changed in proportion to the transmission power.

[0007]

As described above, the conventional transmission power control circuit can change the transmission power in proportion to the external transmission power control signal due to the nonlinearity of the gain change of the variable gain amplifier. Even if there is a change in gain due to frequency characteristics of a power amplifier or the like that further amplifies transmission power,
There was a problem that this could not be corrected.

An object of the present invention is to solve such a conventional problem and to provide a transmission power control circuit that outputs transmission power proportional to a control signal by performing feedback control based on transmission power. And

[0009]

SUMMARY OF THE INVENTION The present invention provides a variable gain amplifier on the receiving side for amplifying a received input signal, a power detecting circuit for detecting a power value of an output signal of the variable gain amplifier on the receiving side, and the power detecting circuit. A comparator for comparing the detection signal with a reference power value, a transmission-side variable gain amplifier for amplifying a transmission signal, a power amplifier for amplifying an output signal of the transmission-side variable gain amplifier, and branching the output of the power amplifier. A directional coupler, a detector for detecting a signal branched by the directional coupler, a control-side variable gain amplifier whose gain is controlled by an output of the comparator and a reference voltage is input, and the control-side gain. A comparison circuit configured to compare the output of the variable amplifier with the output of the detector, and an adder configured to add the output of the comparison circuit, the output of the comparator, and an external transmission power control signal; Output As a control signal of the transmitting-side variable gain amplifier, in which the output of the comparator and a control signal of the reception-side variable gain amplifier.

[0010]

According to the above construction, the transmission power proportional to the control signal can be output, and the transmission power of a mobile station such as a car phone or a mobile phone can be accurately set and controlled, and the transmission power can be further amplified. Even if there is a change in gain due to the frequency characteristics of a power amplifier or the like, this can be corrected.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the figure, the same parts as those in the conventional example are denoted by the same reference numerals. FIG. 1 is a circuit diagram showing one embodiment of the transmission power control circuit of the present invention. In the figure, 1 is a transmission input terminal, 2 is a transmission side variable gain amplifier, 3 is a power amplifier, 4 is a transmission output terminal, 5 is a reception input terminal, 6 is a reception side variable gain amplifier, 7 is a reception output terminal, and 8 is a reception output terminal. The power detection circuit, 9 is a comparison signal input terminal, 10 is a comparator, 11 is a control signal input terminal, and 12 is an adder. 13 is a directional coupler, 14 is a detector, 15
Is a comparison circuit, 16 is a control-side variable gain amplifier, and 17 is a reference voltage. The variable gain amplifiers 2, 6, and 16 on the transmission side, the reception side, and the control side have the same characteristics.

Next, the operation will be described. First, a reception signal input from the reception input terminal 5 is amplified by the reception-side variable gain amplifier 6 and is received as a reception output signal by the reception output terminal 7.
Is output to The power of the output signal is detected by the power detection circuit 8 and the detected signal is guided to the comparator 10 as a detection signal. The comparator 10 receives a reference power value from a comparison signal input terminal 9, compares the detection signal with the reference power value, and compares the comparison result as a received AGC signal with the reception-side variable gain amplifier. In addition, the gain is controlled so that the detection signal and the reference power value become equal. The operation up to this point for the received signal is the same as that of the conventional example. However, in this embodiment, as described above, the directional coupler 13, the detector 14, A circuit comprising a circuit 15, a control-side variable gain amplifier 16, and a reference voltage 17 is added, and these operate as follows.

First, a part of the output signal of the power amplifier 3 is branched by the directional coupler 13, which is detected by the detector 14, and the detection output is led to the comparison circuit 15. Meanwhile, the reference voltage
17 is amplified by the control-side variable gain amplifier 16, the obtained reference signal is led to the comparison circuit 15, and this is compared with the detection output to obtain a correction signal. Note that the gain of the control-side variable gain amplifier 16 is controlled based on the received AGC signal, and the output signal of the reference signal is
It is proportional to the output signal of the variable gain amplifier 2 when no external transmission power control signal is input to the control signal input terminal 11. Therefore, when the difference between the detection output and the reference signal is obtained by the comparison circuit 15, a change in the transmission output due to the frequency characteristic of the power amplifier 3 and a change in the transmission output due to the external transmission power control signal appear in the difference. , Which is the correction signal. By adding this correction signal to the adder 12, it is possible to correct an error in the control signal due to a change in the transmission output due to the frequency characteristic of the power amplifier 3 or a change in the transmission output due to the external transmission power control signal.

[0014]

As is apparent from the above embodiments, the present invention provides a transmission power control circuit of this kind which can perform error-free control even when there is nonlinearity in gain change with respect to a control signal of a variable gain amplifier. Can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a transmission power control circuit according to the present invention.

FIG. 2 is a circuit diagram illustrating an example of a conventional transmission power control circuit.

[Explanation of symbols]

1 ... transmission input terminal, 2 ... transmission side variable gain amplifier, 3
... power amplifier, 4 ... transmission output terminal, 5 ... reception input terminal, 6 ... reception side variable gain amplifier, 7 ... reception output terminal, 8 ... power detection circuit, 9 ... comparison signal input terminal,
10… Comparator, 11… Control signal input terminal, 12… Adder,
13 ... directional coupler, 14 ... detector, 15 ... comparison circuit,
16: Variable gain amplifier on control side, 17: Reference voltage.

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/02-1/04 H04B 1/38-1/58 H04B 7/24-7/26 H04Q 7 / 00-7/04

Claims (1)

(57) [Claims] A variable gain amplifier for amplifying a reception input signal; a power detection circuit for detecting a power value of an output signal of the variable gain amplifier on the reception side; a detection signal of the power detection circuit and a reference power value; A comparator that amplifies a transmission signal, a power amplifier that amplifies an output signal of the transmission-side gain variable amplifier, a directional coupler that branches an output of the power amplifier, A detector for detecting a signal branched by the directional coupler, a control-side variable gain amplifier whose gain is controlled by an output of the comparator and a reference voltage is input, an output of the control-side variable gain amplifier, and the detector And an adder for adding the output of the comparison circuit, the output of the comparator, and the external transmission power control signal. The output of the adder is controlled by the transmission-side variable gain amplifier. Faith Wherein the output of the comparator is a control signal of the variable gain on the receiving side.