JP2003298431A - Automatic power control circuit - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide an automatic power control circuit capable of performing power control on signals of a plurality of frequencies. SOLUTION: Each output of a GSM band amplifier 12 and a DCS band amplifier 22 is input to a power detection circuit 14 and selectively switched by a control signal from a switching control terminal 17. The output of the selected signal is compared with a reference voltage by a comparison circuit 16 for the GSM band or a comparison circuit 26 for the DCS band, and the gain of the amplifier 12 for the GSM band or the amplifier 22 for the DCS band is determined by the comparison output. Control. The power detection circuit 14 includes a current switching circuit that can generate two different currents from one constant current by an amount corresponding to a change in the detection current for each frequency band.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic power control circuit applicable mainly to a wireless communication device, and particularly to controlling the output power of an amplifier in a wireless communication device that can be used in two or more frequency bands. Therefore, the present invention relates to an automatic power control circuit for controlling the bias voltage of an amplifier.

[0002]

2. Description of the Related Art In mobile phones and car phones, it is important to control transmission power in order to suppress power consumption as much as possible and to enable stable communication. Especially, in a wireless communication system such as a mobile phone, transmission output is controlled. In order to stabilize at a certain level, automatic control of the transmission output (Automatic Power
er Control) is often performed.

FIG. 5 shows an example of a conventional automatic power control circuit. The RF signal to be transmitted, which is input from the input terminal 1, is amplified by the amplifier 2 and then output to the next stage from the output terminal 3 while being input to the power detection circuit 4. The detection signal of the voltage corresponding to the output signal of the output terminal 3 extracted from the output terminal 5 of the power detection circuit 4 is supplied to the comparison circuit 6 and is supplied from the reference voltage input terminal 7 of the output power control, for example, a base station. It is compared with a control signal whose level depends on the distance to the station. Then, the output power of the amplifier 2 is controlled by the comparison output output from the comparison circuit 6.

As shown in FIG. 6, for example, the power detection circuit in the conventional example has limiter amplifiers 1 of the first to third stages.
The output of each stage of the multistage amplifier consisting of 00 to 102 is detected by the detection circuits 103 to 105 of the first to third stages, and the constant current is subtracted from the total of the detected current waveforms of the respective stages to obtain the reference input power. In contrast, the power information was output by making it possible to obtain the standard output voltage determined by the specifications.

More specifically, for example, as shown in FIG. 7, for a signal input from the output terminal 3 of the amplifier 2, transistors Q3 and Q4, resistors R4 and R5, and a first constant current source I1 are provided. Stage limiter amplifier 100, transistors Q5 and Q6, resistors R6 and R7, constant current source I2
The output of each of the second-stage limiter amplifier 101, the transistors Q7 and Q8, the resistors R8 and R9, and the third-stage limiter amplifier 102 including the constant current source I3 is converted into a transistor Q9 to Q12, a constant voltage source V1, and a constant current A first stage detection circuit 103 composed of a source I4, transistors Q13 to Q16,
A second stage detection circuit 104 including a constant voltage source V2 and a constant current source I5, transistors Q17 to Q20, a constant voltage source V3,
Detection is performed using the detection circuit 105 of the third stage including the constant current source I6, and the detection current waveform of each stage is detected by Q21 and Q2.
By supplying the current I11 obtained by subtracting the correction current I10 from what is inverted by the current mirror composed of 2, R10 and R11 to the load resistor R12, the detection output Vout corresponding to the input power is taken out from the output terminal 5.

In the configuration of FIG. 7, the detection output Vout increases in proportion to the input power (dB), becomes 0 when there is no input, and when the input power is sufficiently large, the voltage determined by the product of the maximum value of I11 and the load resistance. Up to The slope of Vout with respect to the input power is determined by the input / output characteristics of each detection circuit and the load resistance value, and the input dynamic range is determined by the product of the gain of each limiter amplifier and the number of limiter amplifier stages.

On the other hand, recently, a terminal capable of supporting a plurality of communication systems with one terminal has become widespread, for example, from 880 MHz.
Global S using the 915 MHz frequency band
system for Mobile Communic
ations (hereinafter GSM) and 1.710 GHz-
Digita using the 1.785 GHz frequency band
l Communication System (hereinafter D
There are mobile phones compatible with both (CS). In such a mobile phone, it is necessary to be able to control the output power in both of the two frequency bands of 880 MHz to 915 MHz and 1.710 GHz to 1.785 GHz.

[0008]

However, when the automatic power control circuit having the above-mentioned conventional configuration is used, the input signal having a high frequency such as 900 MHz and 1.7 GHz and a significantly different frequency band due to frequency characteristics is used. As a result, the limiter amplifier of the power detection circuit behaves as a limiter amplifier having a different gain depending on the frequency. In particular, when a signal in the higher frequency band is input, the gain of the limiter amplifier is lower than when a signal in the lower frequency band is input. As a result, the detection voltage is output at a low level. Therefore, even if signals of the same power intensity are input, the detection signal of the power detection circuit differs depending on the frequency, and power control cannot be performed on signals of different frequencies.

An object of the present invention is to solve such a problem, and an object thereof is to provide an automatic power control circuit capable of performing power control for signals of a plurality of frequencies by itself.

[0010]

To achieve this object, the automatic power control circuit of the present invention comprises a power detection circuit capable of performing accurate power detection for a plurality of frequency bands. Characterize. Further, the power detection circuit is characterized in that it is provided with a current switching circuit capable of producing, from one constant current, two currents which differ by the change amount of the detection current due to the frequency characteristic of the gain of the limiter amplifier.

By including the above power detection circuit,
One automatic power control circuit can perform accurate power control for two frequencies.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (Embodiment 1) FIG. 1 is a circuit diagram of an automatic power control circuit according to Embodiment 1 of the present invention. 11 is an input terminal for the GSM band, 12 is an amplifier for the GSM band, 13 is an output terminal for the GSM band, 21 is an input terminal for the DCS band, 22 is an amplifier for the DCS band, and 23 is D.
Output terminal for CS band, 14 is a power detection circuit capable of accurately detecting power in two bands, 15 is an output terminal of the power detection circuit, 17 is a control terminal for switching GSM / DCS band, and 18 is an output Reference voltage input terminal for power control,
Reference numeral 16 is a GSM band comparison circuit, and 26 is a DCS band comparison circuit.

Next, the operation of the first embodiment will be described. In FIG. 1, in the GSM band, the input terminal 11
A transmission signal is input from and is amplified by the GSM band amplifier 12. The output signal of the GSM band amplifier 12 is output from the GSM band output terminal 13 and at the same time input to the power detection circuit 14. Power detection circuit 14
Can operate for the GSM band when the potential of the switching control terminal 17 is LO, and can output a detection signal corresponding to the output power level of the GSM band amplifier 12 to the output terminal 15. The detection signal output from the power detection circuit 14 is compared in the GSM band comparison circuit 16 with a control signal supplied from the reference voltage input terminal 18, for example, a level corresponding to the distance to the base station, The gain of the GSM band amplifier 12 is controlled by the comparison output of the band comparison circuit 16.

Next, in the DCS band, the transmission signal is input from the input terminal 21 and amplified by the DCS band amplifier 22. The output signal of the DCS band amplifier 22 is output from the DCS band output terminal 23 and at the same time input to the power detection circuit 14. Power detection circuit 14
Can operate for the DCS band when the potential of the switching control terminal 17 is HI, and can output a detection signal according to the output power level of the amplifier 22 for the DCS band to the output terminal 15. The detection signal output from the power detection circuit 14 is compared in the DCS band comparison circuit 26 with a control signal supplied from the reference voltage input terminal 18 and having a level corresponding to the distance from the base station, for example, and DCS The output power of the DCS band amplifier 22 is controlled by the comparison output of the band comparison circuit 26.

As described above, according to the first embodiment,
By providing the power detection circuit capable of performing accurate power detection for a plurality of frequencies, one automatic power control circuit can perform power control for signals in two bands.

In the first embodiment, the band is GS.
Although there are two bands of the M band and the DCS band, it is obvious that the number of bands may be three or more.

The power detection circuit according to the first embodiment will be described in more detail. FIG. 2 shows the configuration of the power detection circuit. First, in the GSM band, when a voltage lower than the reference voltage Vref is applied to the switching control terminal 17, the GSM side of the changeover switch 29 is turned on,
A signal in the GSM band is input to the limiter amplifier 100 via the first matching circuit 27. At the same time, the transistors Q23 to Q26 and Q27 to Q3 connected to the constant current source I13 are connected.
0, the transistors Q23 to Q26 are turned on, and the correction current value is (3 /
4 × I13) + I12. Limiter amplifier 100-
The detection current Vout corresponding to the input power level of the GSM band is output to the output terminal 15 by supplying the load resistor R13 with a current obtained by subtracting the above-mentioned correction current from the detection current generated by 102 and the detection circuits 103 to 105. Is output.

Next, in the DCS band, a voltage higher than the reference voltage Vref is applied to the switching control terminal 17,
The DCS side of the changeover switch is turned on, and the signal in the DCS band passes through the second matching circuit 28 and the limiter amplifier 10
Input to 0. At the same time, among the transistors Q23 to Q26 and Q27 to Q30 connected to the constant current source I13, the transistors Q27 to Q30 are turned on and the transistor Q2 is turned on.
The correction current is (2/4 × I13) depending on 9 to Q30.
It becomes + I12. A current obtained by subtracting the above correction current from the detection current generated by the limiter amplifiers 100 to 102 and the detection circuits 103 to 105 is supplied to the load resistor R13, so that the detection signal Vout corresponding to the input power level in the DCS band is obtained. It is output to the output terminal 15.

Assuming that the gain difference of the limiter amplifier with respect to the GSM band and the DCS band is ΔG, as shown in FIG. 3, the GSM band and the DCS band when the input power is the same.
The output current (before correction) with respect to the band differs by a current value ΔI determined by the slope of the detection characteristic and ΔG. Therefore,
Regarding the correction current value Igsm in the GSM band and the correction current value Idcs in the DCS band, Igsm = (3/4 × I13) + I12 Idcs = (2/4 × I13) + I12 ΔI = (1/4 × I13) By setting the constant current values I12 and I13 so that the above condition holds, the power detection circuit of FIG. 2 can have the same power detection characteristics in both the GSM band and the DCS band.

Igsm, Idcs, I1 listed here
Although the ratio of 2, I13, and I13 to be divided into 3/4 and 2/4 is an example, when actually designing, ΔI obtained by actual measurement or simulation and Igsm obtained from the specification of the power detection characteristic Or from the value of Idcs, I
By setting the values of 12, I13 and the number of transistors in the portions of Q23 to Q26 and Q27 to Q30 for determining the distribution ratio of I13, it is possible to correct the deviation of the power detection characteristics between the GSM band and the DCS band.

(Second Embodiment) FIG. 4 shows a power detection circuit according to a second embodiment of the present invention. As in the case of the first embodiment, when a voltage lower than the reference voltage Vref is applied to the switching control terminal 17 in the GSM band, the transistors Q23 to Q23 connected to the constant current source I13.
Transistors Q23 to Q of Q26 and Q27 to Q30
26 is turned on, and the transistors Q23 to Q25 cause
The correction current value is (3/4 × I13) + I12. At the same time, the GSM side of the changeover switch is turned on, so that the limiter amplifiers 100 to 102 and the detection circuit 103 to
A current obtained by subtracting the above correction current from the detection current generated in 105 is supplied to the load resistor R13,
Detection signal Vout according to the input power level of the GSM band
Is output to the output terminal 15.

Next, in the DCS band, a voltage higher than the reference voltage Vref is applied to the switching control terminal 17,
Transistors Q23 to Q2 connected to constant current source I13
6, transistors Q27 to Q30 among Q27 to Q30
Is turned on, and the correction current becomes (2/4 × I13) + I14 by the transistors Q29 to Q30. at the same time,
When the DCS side of the changeover switch is turned on, a current obtained by subtracting the correction current from the detection current generated by the limiter amplifiers 200 to 202 and the detection circuits 203 to 205 is supplied to the load resistor R23. The detection signal Vout according to the input power level of the band is output to the output terminal 15.

Here, as in the case of the first embodiment, GS
By setting the correction current value Igsm in the M band and the correction current value Idcs in the DCS band, the power detection circuit in FIG. 4 can have the same power detection characteristics in both the GSM band and the DCS band. Needless to say.

[0024]

As described above, according to the present invention,
By providing a power detection circuit that can perform accurate power detection for multiple frequency bands, it is possible to realize an excellent automatic power control circuit that can perform power control for multiple frequency bands by itself. is there.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an automatic power control circuit according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a power detection circuit according to the first embodiment of the present invention.

FIG. 3 is an input power-output current characteristic diagram of the power detection circuit according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a power detection circuit according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional automatic power control circuit.

FIG. 6 is a configuration diagram of a power detection circuit in a conventional example.

FIG. 7 is a more specific circuit diagram of FIG.

[Explanation of symbols]

11,21 Input terminals 12 GSM Band Amplifier 13,23 output terminals 14 Power detection circuit 15 Output terminal of power detection circuit 16 GSM band comparison circuit 17 Switching control terminal 18 Reference voltage input terminal 22 DCS band amplifier 26 Comparison circuit for DCS band 27, 28 Matching circuit 29 Changeover switch 31-34 Adder circuit 100-102, 200-202 Limiter amplifier 103-105, 203-205 Detection circuit

Continued front page    F term (reference) 5J100 JA01 LA00 LA08 LA09 LA10                       QA01 SA01 SA02                 5K060 CC11 DD04 HH06 HH39 JJ08                       JJ23 KK01 LL01 LL07

Claims (3)

[Claims] 1. An automatic power control circuit used for controlling output power of an amplifier of a wireless communication device usable in two or more frequency bands, wherein an input terminal for the first band and an output for the first band are provided. An amplifier for the first band having a terminal, an amplifier for the second band having an input terminal for the second band and an output terminal for the second band, and an output of the amplifier for the first band as a first input And the output of the amplifier for the second band as the second input,
A power detection circuit having a switching control terminal for selectively switching between the first input and the second input; and an output of the power detection circuit as a first input and a reference voltage as a second input. A first band comparison circuit for controlling the first band amplifier by an output, and an output of the power detection circuit as a first input, a reference voltage as a second input, and an output for the second band An automatic power control circuit comprising: a second band comparison circuit for controlling a band amplifier. 2. The power detection circuit includes a first matching circuit having a first input terminal, a second matching circuit having a second input terminal, and an output of the first matching circuit as a first matching circuit. The first input and the output of the second matching circuit as the second input,
Switch having a control terminal for selectively switching the input of the switch and the second input, an amplifier circuit in which limiter amplifiers are cascade-connected in multiple stages and their inputs are connected to the output of the switch, A plurality of detection circuits each having an output of a limiter amplifier of each stage in the circuit as input, a current addition means for sequentially adding detection currents of the plurality of detection circuits, a first constant current source, and a reference voltage source And a second constant current source,
A load resistor, an output terminal, a first transistor group in which emitters and bases of N transistors are commonly connected, and a second transistor group in which emitters and bases of M transistors are commonly connected,
The emitters of the first and second transistor groups are commonly connected to the first constant current source and the base of the first transistor group is connected to the control terminal.
The base of the second transistor group is connected to the reference voltage source, and the collectors of n transistors of the first transistor group and the collectors of m transistors of the second transistor group are connected. Are connected in common, and the collectors of the n transistors and the collectors of the m transistors that are connected in common, the output of the current adding means, the second constant current source, and the load resistor are respectively connected. The device is connected to the output terminal.
The described automatic power control circuit. 3. A power detection circuit, comprising: a first matching circuit having a first input terminal; and limiter amplifiers connected in cascade in a plurality of stages, the input of which is connected to the output of the first matching circuit. A first amplifying means, a first detecting means composed of a plurality of detecting circuits each having an output of a limiter amplifier of each stage in the first amplifying means as an input, and each detecting circuit of the first detecting means. A first current adding means composed of an adding circuit for adding detected currents in order, a first load resistor connected to the first current adding means, and a second matching circuit having a second input terminal, Second amplifying means, in which a plurality of limiter amplifiers are connected in cascade and the input thereof is connected to the output of the second matching circuit, and the output of the limiter amplifier of each stage in the second amplifying means is respectively input. From multiple detection circuits Second detection means, an addition circuit configured to add detection currents of the detection circuits of the second detection means in order, and a second current addition means connected to the second current addition means. And a first output taken from a connection point between the first current adding means and the first load resistance as a first input, and the second current adding means and the second load resistance. A second output extracted from the connection point of the second input, a second input, and a changeover switch having a control terminal and an output terminal for selectively switching the first input and the second input; and a first constant current. Source, a reference voltage source, a second constant current source, a third constant current source, a first transistor group in which emitters and bases of N transistors are commonly connected, and an emitter of M transistors And the base are commonly connected A second transistor group, the emitters of the first and second transistor groups are commonly connected to connect to the first constant current source, and the base of the first transistor group is connected to the control terminal. connection,
The base of the second transistor group is connected to the reference voltage source, and the collectors of n transistors of the first transistor group are commonly connected to connect the first input of the changeover switch to the first input of the changeover switch. To the second constant current source, and to commonly connect the collectors of m transistors in the second transistor group to the second input of the changeover switch and the third constant current source. The automatic power control circuit according to claim 1, wherein: