JP2001057522A - Transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust a transmission output by allowing a controlling means to calculate the difference between the level of a signal detected by a detecting means and a prescribed value stored in a storing means and to control a level adjusting means in accordance with the calculated difference. SOLUTION: A directional coupler 8 fetches a part of an output of a power amplifier (PA) 7, and a detection circuit 28 detects it. An A/D converter 10 performs A/D conversion of this detected signal and sends the signal to a control circuit 2'. The circuit 2' checks whether or not the amplitude value of the sent detection signal is the specified amplitude value of an output level of the PA 7 stored in a transmission output level table 29. When the amplitude value of the detection signal is not the specified amplitude value, the circuit 2' makes the attenuation quantity of a feedback side attenuator 9 plus α dB and detects an output of the coupler 8 again. It is possible to easily adjust a transmission output because this operation is repeated until the amplitude value of the detection signal becomes the specified amplitude value in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in adjustment of a transmission output of a transmitter using a feedback system.

[0002]

2. Description of the Related Art In a conventional digital radio system, a linear modulation system such as a π / 4 shift QPSK modulation system represented by a cellular phone and a PHS system is adopted from the viewpoint of improving frequency use efficiency. However, in the conventional linear modulation method, when a transmission signal is amplified by a power amplifier, an unnecessary spectrum is generated due to a deviation from the linear characteristic (non-linear characteristic) of a circuit including the power amplifier, which affects adjacent channel leakage power. To reduce this effect,
It is necessary to compensate for non-linearity related to the amplitude or phase distortion of the linear operation power amplifier. One of the means for achieving this is a Cartesian feedback type compensation circuit.

A conventional Cartesian feedback type compensation circuit is used.
The linear operation transmitter used will be described with reference to FIG. FIG.
Is a transmitter using a Cartesian feedback compensation circuit.
FIG. 3 is a block diagram illustrating a configuration. 27 emits baseband signal
Raw circuit, 12-1 and 12-2 adder, 3-1 and 3-2 loop fill
4 is a quadrature modulator, 5-1 and 5-2 are D / A converters, and 7 is
Power amplifier (PA), 8 is directional coupler, 9 is Attenuator on feedback side
Data, 11 is a quadrature demodulator, 1 is an output terminal, 22 is an oscillator, 2 is
Control circuit, 23 is a temperature table, 24 is a temperature sensor, 13 is
Filter 3-1 and 3-2, quadrature modulator 4, PA7
Circuit, 14 is directional coupler 8, feedback-side attenuator 9, quadrature
This is a feedback circuit including the demodulator 11 and the temperature sensor 24. Ma
First, the function as a normal transmitter will be described below. base
In-phase component of baseband signal from band signal generation circuit 27
I_FWAnd the quadrature component Q_FWIs output. In-phase component I_FWIs D / A
After D / A conversion by the converter 5-1, the adder 12-1
The signal is input to the quadrature modulator 4 via the filter 3-1. Similarly,
Intersection Q_{F W}Was also D / A converted by the D / A converter 5-2.
After that, quadrature modulation via adder 12-2 and loop filter 3-2
Input to the container 4. Oscillator 22 generates a reference frequency signal,
The signals are sent to the quadrature modulator 4 and the quadrature demodulator 11. Quadrature modulator 4
Forced in-phase component I_FWAnd the quadrature component Q_FWOf the reference frequency
Quadrature-modulates based on the signal and outputs the quadrature-modulated signal PA7
I do. This quadrature modulated signal is amplified by PA7,
It is output via the combiner 8 and the output terminal 1.

On the other hand, a part of the output of the PA 7 is taken out by the directional coupler 8 and inputted to the feedback-side attenuator 9. The feedback-side attenuator 9 attenuates the input signal and outputs the signal to the quadrature demodulator 11. Quadrature demodulator 11 quadrature demodulation, are output as the feedback in-phase component I _FB and the feedback quadrature component Q _FB of the baseband signal.

[0005] The feedback common-mode component I _FB of the baseband signal is
Input to the adder 12-1, the adder 12-1 is negative added to the in-phase component I _FW inputted from the D / A converter 5-1, and outputs a signal that has been subjected to the negative feedback loop Input to quadrature modulator 4 via filter 3-1. The feedback common-mode component Q _FB of the baseband signal is input to the adder 12-2, and the adder 12-
2 is negatively added to the quadrature component Q _FW inputted from the D / A converter 5-2, and outputs a signal that has been subjected to the negative feedback input to the quadrature modulator 4 via the loop filter 3-2 I do.

Since the transmitter using the Cartesian type feedback compensation circuit as described above has a negative feedback configuration,
It can be considered as an equivalent circuit as shown in FIG. FIG. 3 illustrates the relationship between the stability of the output of the transmitter and the change in gain with respect to the stability of the amount of improvement in distortion. FIG. 3 is a block diagram showing an equivalent circuit of the negative feedback circuit of FIG. 31 is the input terminal, 32
Is an adder, 13-1 is a main circuit, 33 is an adder, 34 is an output terminal,
14-1 is a feedback circuit. In FIG. 3, only the in-phase component side is considered, the main circuit 13-1 is the in-phase component side (loop filter 3, quadrature modulator 4, power amplifier 7) of the main circuit 13 in FIG. 2, and the feedback circuit 14-1 is FIG. 3 shows the orthogonal component side (directional coupler 8, feedback-side attenuator 9, and quadrature demodulator 11) of the feedback circuit 14 in FIG.
Now, the gain of the main circuit 13-1 is A, the gain of the feedback circuit 14-1 is β, the power of the signal input to the input terminal 31 is X, the power of the signal output from the output terminal 34 is Y, Assuming that the amount of nonlinear distortion is D, the input-output relational expression can be expressed as Expression (1). Here, assuming that Aβ≫1, Y = ｛A / (1 + Aβ)｝ X + D / (1 + Aβ) = (1 / β) X + D / Aβ Equation (1) Main circuit 13-1 and feedback When the product Aβ of the gain with the circuit 14-1 is sufficiently large (Aβ≫1), the input signal is multiplied by 1 / β, and the main circuit 1
The non-linear distortion D of 3-1 is output after being multiplied by 1 / Aβ. Therefore, by applying the negative feedback, the nonlinear distortion D is improved to 1 / Aβ. That is, the compensation of the nonlinear distortion D is determined by the gain of the main circuit and the gain of the feedback circuit.

In a transmitter using such a Cartesian feedback type compensation circuit, a change in the transmission output with respect to a temperature change is, for example, as shown in FIG. That is,
The temperature of the feedback circuit 14 is detected by the temperature sensor 24, and the temperature information is sent to the control circuit 2. The control circuit 2 adjusts the attenuation of the attenuator 9 using the temperature table 23, thereby coping with the change in the transmission output due to the temperature. The operation is as in the following procedures (1) and (2). (1) The temperature sensor 24 detects the temperature of the feedback circuit 14 and sends the temperature information to the control circuit 2.

(2) Based on the temperature information sent from the temperature sensor 24, the control circuit 2 obtains the amount of attenuation of the feedback-side attenuator 9 corresponding to each temperature stored in the temperature table 23. By adjusting the amount of attenuation of the side attenuator 9, the feedback gain is adjusted to suppress a change in the transmission output due to a temperature change.

[0009]

The above-mentioned prior art includes the following:
In response to a change in the output level of the transmitter due to temperature, the temperature of the feedback circuit is detected by a temperature sensor, and the attenuation of the feedback-side attenuator stored in the temperature table is calculated based on the temperature information. This has been addressed by adjusting the amount of attenuation. However, the temperature table stored in the temperature table is the attenuation amount of the attenuator corresponding to the temperature characteristic of the feedback circuit having a certain representative characteristic. Since the temperature characteristics of the feedback circuit differ from circuit to circuit due to variations in circuit elements, the transmitter adjusts the transmission output level to the specified level even if the attenuation amount in the temperature table of a certain characteristic is used as is in another feedback circuit. Can not do it. In addition, when individual temperature characteristics of each circuit are used, there is a disadvantage that measurement for creating a temperature table takes time. Further, there is a disadvantage that it cannot cope with aging.

An object of the present invention is to provide a transmitter which can eliminate the above-mentioned drawbacks and can easily adjust the transmission output.

[0011]

In order to achieve the above object, a transmitter according to the present invention detects an output level, and adjusts the attenuation of a feedback-side attenuator in accordance with the detected level, thereby changing temperature and temperature. This realizes a transmitter that can cope with fluctuations in transmission output due to factors other than changes and can cope with aging.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a transmitter using a Cartesian feedback type compensation circuit. For the reference numerals used in the description, the same components as those in FIG. In addition, 2 'is a control circuit, 28 is a detection circuit, 10 is an A / D converter, 29 is the transmission output level,
Table, 14 'is directional coupler 8, return side attenuator
9, a feedback circuit including the quadrature demodulator 11. FIG. 4 shows a flowchart of the operation. The operation of the transmitter is the same as the circuit described in FIG. In the present invention, how the control circuit 2 'controls the amount of attenuation of the feedback signal partially extracted from the directional coupler 8 by the feedback attenuator 9 will be described. 1 and 4, first, in step 41, a part of the output of the PA 7 is extracted by the directional coupler 8, and this is detected by the detection circuit 28 (output: W
1 (dBm)). Next, in step 42, the detected signal is A / D converted by the A / D converter 10 and sent to the control circuit 2 '.
The control circuit 2 'checks whether or not the amplitude value of the sent detection signal is a specified amplitude value (W (dBm)) of the output level of the PA7 stored in the transmission output level table 29 (for example,
For a transmitter with 5W output power, 5W + 20% and 5W-50% are acceptable.) If the amplitude value of the detection signal does not reach the specified amplitude value, the process proceeds to step 43, and if the amplitude value of the detection signal is the specified amplitude value, the operation is terminated. In step 43, since the amplitude value of the detected signal is not the specified amplitude value, the control circuit
2 ′, the attenuation of the feedback-side attenuator 9 is + α dB.
In step 44, the output of the directional coupler 8 is detected again (output: W2 (dBm)). In step 45, again
It is checked whether the amplitude value of the transmitted detection signal is a specified amplitude value (W (dBm)) of the output level of PA7 stored in the transmission output level table 29. If the amplitude value of the detected signal does not reach the specified amplitude value, the process proceeds to step 46, and if the amplitude value of the detected signal is the specified amplitude value, the operation is terminated. In step 46, | W2−W |> | W1−W | is calculated, and the difference from the specified amplitude value is greater when the attenuation of the feedback-side attenuator 9 is set to + α dB than before. If is smaller, the process returns to step 43, and this operation is repeated until the amplitude value of the detected signal reaches the specified amplitude value. Conversely, if the difference from the specified amplitude value is large, the process proceeds to steps 47 to 49, where the control circuit 2 'sets the attenuation of the feedback-side attenuator 9 to -α dBm (step 47), and sets the output of the directional coupler 8 to Detection is performed (step 48), and this operation is repeated until the amplitude value of the detected signal reaches the specified amplitude value (step 49). It is assumed that the temperature change of the detection circuit 28 is sufficiently small.

[0013]

As described above, according to the present invention, in a transmitter using a feedback system, the transmitter always follows a change in the transmitter output level due to temperature change and aging, and keeps a transmission output at a specified value. A transmitter capable of performing such operations.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a configuration of a transmitter according to the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a transmitter according to the related art.

FIG. 3 is an explanatory diagram of an equivalent circuit of a negative feedback circuit.

FIG. 4 is a flowchart of one embodiment of the processing operation of the control circuit of the present invention.

[Explanation of symbols]

1: output terminal, 2, 2 ': control circuit, 3-1 and 3-2: loop filter, 4: quadrature modulator, 5-1 and 5-2: D / A converter, 7: power amplifier (PA ), 8: directional coupler,
9: Feedback side attenuator, 10: A / D converter, 1
1: Quadrature demodulator, 12-1, 12-2: Adder, 13, 13-1: Main circuit, 14, 14-1, 14 ': Feedback circuit, 22: Oscillator, 2
3: temperature table, 24: temperature sensor, 27: baseband signal generation circuit, 28: detection circuit, 29: transmission output level table, 31: input terminal, 32, 33: adder,
34: output terminal

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H03F 3/24 H03F 3/24 H04L 27/20 H04L 27/20 CF term (Reference) 5J090 AA01 AA41 CA02 CA03 CA21 DN02 FA17 GN03 GN06 HA43 HN03 HN08 KA00 KA23 KA26 KA32. 5K060 BB05 CC04 DD04 HH06 HH31 JJ16

Claims (2)

[Claims] 1. A transmitter for compensating for non-linear distortion of a power amplifier operating in a linear manner, comprising a compensation circuit of a negative feedback system, detecting means for detecting a level of a negative feedback signal, and adjusting a level of the negative feedback signal. Storage means for storing a predetermined value for collating with the level of the negative feedback signal detected by the detection means, and control means for controlling the level adjustment means. By calculating the difference between the level of the signal detected by the detection means and the predetermined value stored in the storage means, by controlling the level adjustment means according to the calculated difference, A transmitter for adjusting a fluctuation of an output level of the transmitter. 2. A transmitter having a negative feedback type compensation circuit for compensating for nonlinear distortion of a power amplifier operating linearly, comprising: a directional coupler for extracting a part of an output of the power amplifier;
An attenuator for attenuating the level of the output signal of the directional coupler, a quadrature demodulator for demodulating the output signal of the attenuator, and negative feedback of two signals of an in-phase component and a quadrature component output from the quadrature demodulator A transmitter having a feedback circuit for compensating for nonlinear distortion of a power amplifier, comprising: a detection circuit for detecting a level of the output signal extracted by the directional coupler; and an A / D converter for A / D converting the detected signal. A D converter, a transmission output level table storing a specified amplitude value of the level of the output signal of the power amplifier, and control for determining whether the level of the output signal is within the range of the specified amplitude value. And an output level of the transmitter is adjusted by adjusting an attenuation amount of the attenuator according to a command from the control circuit. Machine.