JPH07297866A - Transmission control method - Google Patents

Abstract

PURPOSE:To provide a transmission control method for operating a high frequency amplifier in low distortion at a high efficiency. CONSTITUTION:A continuous I.Q signal generated by an I.Q signal generator 11 comprising a discrete I.Q data signal generator and a roll-off filter is given to a signal conversion circuit 12, in which the amplitude or phase of the continuous I.Q signal is converted optimizingly by taking distortion of a phase characteristic of an input output characteristic in the high frequency amplifier 15 into account so that the high frequency amplifier 15 is operated at a high efficiency and low distortion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission control method for improving the efficiency of a high frequency amplifier used in a radio device of a digital modulation method.

[0002]

2. Description of the Related Art In recent years, wireless devices are required to be digital and highly efficient. In particular, when using multi-level QPSK modulation as a digital modulation method, it is necessary for the wireless circuit to be linear. In particular, the high frequency amplifier using the FET is used in the region where the linearity is lowered because it is operated in the vicinity of the saturation region of the output characteristic for high efficiency. An example of the above-described conventional transmission control method will be described below with reference to the drawings.

FIG. 11 is a block diagram of a conventional transmission control circuit. In FIG. 11, 1 is discrete IQ
I / Q consisting of data signal generator and roll-off filter
A signal generator, 2 is a digital modulator, and 3 is a high frequency amplifier. The operation of the transmission control circuit configured as described above will be described below.

Conventionally, the I / Q signal generator 1 generates a continuous I / Q signal according to discrete transmission information, and the digital modulator 2 synthesizes a carrier wave into a digital modulated signal using the I / Q signal. The high frequency amplifier 3 amplifies the digitally modulated signal up to the power required to be transmitted from the antenna.

[0005]

However, the above-mentioned structure has a problem that the linearity of the amplifier is deteriorated in the design of the high frequency amplifier in which high efficiency is emphasized. Here, the cause of the linearity deterioration will be described with reference to the drawings.

FIG. 12 is a diagram showing the input / output characteristics of a high-frequency amplifier using a commonly used FET. In order to perform the transmission at the highest efficiency point, the peak of the efficiency curve is designed to be the operating point of the amplifier as shown in FIG. At this time, the power of the input signal fluctuates in the shaded operation area b1 around the operation point. The linearity of the amplifier decreases due to the saturation of the output and the steep advance of the phase.In such an amplifier with a high efficiency design, however, the modulation signal is distorted because the phase of the input signal fluctuates sharply in the over-input region. Will be lost.

In view of the above problems of the conventional transmission control method, it is an object of the present invention to provide a transmission control method for operating a high frequency amplifier in a highly efficient state with further improved linearity. is there.

[0008]

The present invention according to claim 1 is based on I
In the transmission control method of modulating the carrier wave by the digital modulator with the amplitude of the composite vector component of the IQ signal generated by the Q signal generator and amplifying the power of the modulated signal by the high frequency amplifier, The amplitude is
This is a transmission control method for controlling to be smaller than a predetermined value determined in consideration of the distortion of the phase characteristic of the input / output characteristic in the high frequency amplifier.

According to a fourth aspect of the present invention, a carrier wave is modulated by a digital modulator with the amplitude of a composite vector component of an IQ signal generated in a predetermined phase by the IQ signal generator, and the modulated signal of the modulated signal is modulated. In a transmission control method for amplifying power by a high frequency amplifier, when the phase of the I / Q signal is larger than a predetermined value determined by considering the distortion of the phase characteristic of the input / output characteristics in the high frequency amplifier,
This is a transmission control method in which the amplitude is delayed compared to the case where the amplitude is smaller than a predetermined value.

[0010]

According to the present invention, the amplitude of the combined vector component of the I and Q signals is controlled to be smaller than a predetermined value determined in consideration of the distortion of the phase characteristic of the input / output characteristic of the high frequency amplifier, so that the input modulation to the high frequency amplifier is performed. Signal over-input can be reduced.

Further, according to the present invention, when the amplitude of the composite vector component of the phase of the I / Q signal is larger than a predetermined value determined in consideration of the distortion of the phase characteristic of the input / output characteristic in the high frequency amplifier, the amplitude is a predetermined value. By delaying as compared with the case where it is smaller, a steep advance in the phase characteristic of the high frequency amplifier can be alleviated.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

FIG. 1 is a block diagram showing a circuit configuration for realizing a transmission control method according to the first embodiment of the present invention. In FIG. 1, 11 is an I / Q signal generator including a discrete I / Q data signal generator and a roll-off filter,
Reference numeral 12 is a signal conversion circuit that converts the amplitude and phase of the I / Q signals generated by the I / Q signal generator 11, 13 is a conversion control circuit that controls the signal conversion circuit 12, and 14 is the signal conversion circuit 12. The digital modulator 15 modulates the carrier wave with the I / Q signals, and 15 is a high frequency amplifier for high frequency amplifying the modulation signal from the digital modulator 14.

In the configuration described above, the discrete I / Q signal is converted into a continuous I / Q signal by the I / Q signal generator 11 and input to the signal conversion circuit 12. Signal conversion circuit 1
At 2, I in response to the control signal from the conversion control circuit 13
-The amplitude of the Q signal is converted (details will be described later) and output to the digital modulator 14. The digital modulator 14 modulates a carrier by the input I / Q signal and outputs the modulated signal to the high frequency amplifier 15. The high frequency amplifier 15 power-amplifies the input modulated signal and transmits it from an antenna (not shown).

FIG. 2 is a diagram showing conversion characteristics of the I / Q signals which are the modulator inputs converted by the signal conversion circuit 12 in the above embodiment. Like this conversion characteristic, I
By suppressing the peak of the amplitude of the Q signal from A to B, it is possible to prevent the high input to the high frequency amplifier 15 and improve the linearity of the high frequency amplifier 15.

Next, the operation of the transmission control method of the above embodiment will be described with reference to FIGS. 2, 3 and 12.

First, FIG. 3 shows a general FE as in FIG.
It is a figure which shows the input-output characteristic of the high frequency amplifier using T,
As a result of the maximum amplitude of the input power being suppressed from A to B as shown in FIG. 2 by the signal conversion circuit 12 of FIG. 1, the power of the input signal fluctuates within the shaded operating region 31. ing. Next, comparing FIG. 12 and FIG. 3,
By suppressing the maximum amplitude of the input power, the variation area b1 of the input power of the conventional high frequency amplifier becomes the variation area 31 that does not include the input power in the area where the phase of the phase characteristic of the high frequency amplifier causing the distortion steeply advances. High frequency amplifiers can be used that are compressed and have improved linearity at maximum efficiency operating points.

Next, a transmission control method according to the second embodiment of the present invention will be described with reference to the drawings. Here, the basic circuit configuration of this embodiment is similar to that of FIG. 1 of the first embodiment.

FIG. 4 is a diagram showing the conversion characteristic of the I / Q signal of the modulator input which is converted by the signal conversion circuit 12 in the second embodiment. In this embodiment, the amplitude of the combined vector component of the I and Q signals is equal to or greater than the reference input power B, and the phase of the combined vector component is delayed. Here, the amplitude and phase of the I and Q signals will be described with reference to FIG. Considering a composite vector S of the Q signal that is orthogonal to the I signal, the magnitude of this S is used as the amplitude, and the angle between the positive axis of the I signal and S is used as the phase.

Further, FIG. 5 adds the effect of adding a signal subjected to control such as the conversion characteristic shown in FIG. 4 to the input / output characteristic of the high frequency amplifier using the general FET of FIG. It is a figure which shows the input-output characteristic at the time of doing. Comparing FIG. 12 and FIG. 5, by performing control such that the phase is delayed with an increase in input power as in the conversion characteristic of FIG. 4, the amplitude is larger than the input power fluctuation region 51 of the high frequency amplifier. The phase characteristic of the high-frequency amplifier is improved so that the phase characteristic is deteriorated (that is, the position where the steep advance of the phase occurs is outside the variable region 51), and the first embodiment is improved.
Similarly, the high-frequency amplifier can be used with improved linearity at the maximum efficiency point.

Next, a transmission control method according to the third embodiment of the present invention will be described with reference to the drawings. Here, the basic circuit configuration of this embodiment is similar to that of FIG. 1 of the first embodiment.

FIG. 6 is a diagram showing conversion characteristics of the signal conversion circuit 12 in the third embodiment. As shown in FIG. 6, in this embodiment, when the reference input power B is exceeded, a constant value B
It is possible to obtain the same effect as that of the first embodiment by controlling so as to suppress the above.

Next, a transmission control method according to the fourth embodiment of the present invention will be described with reference to the drawings. Here, the basic circuit configuration of this embodiment is similar to that of FIG. 1 of the first embodiment.

FIG. 7 is a diagram showing conversion characteristics of the signal conversion circuit 12 in the fourth embodiment. As shown in FIG. 7, when the reference input power C is exceeded, a quadratic function is used to smoothly control the input power until the maximum value reaches the reference input power B, thereby achieving the same effect as that of the first embodiment. It is possible to obtain.

Next, a transmission control method according to the fifth embodiment of the present invention will be described with reference to the drawings. Here, the basic circuit configuration of this embodiment is similar to that of FIG. 1 of the first embodiment.

FIG. 8 is a diagram showing conversion characteristics of the signal conversion circuit 12 in the fifth embodiment. As shown in FIG. 8, when the reference input power B is exceeded, the phase is linearly delayed, so that the same effect as that of the second embodiment can be obtained.

Next, a transmission control method according to the sixth embodiment of the present invention will be described with reference to the drawings. Here, the basic circuit configuration of this embodiment is similar to that of FIG. 1 of the first embodiment.

FIG. 9 is a diagram showing conversion characteristics of the signal conversion circuit 12 in the sixth embodiment. As shown in FIG. 9, when the reference input power B is exceeded, a quadratic function is used to perform control so that the phase is smoothly delayed, and the same effect as that of the second embodiment can be obtained.

As described above, the high frequency amplifier is controlled by optimally converting the amplitude or phase of the composite vector of the I and Q signals so as to reduce the distortion of the high frequency amplifier after the continuous I and Q signals are generated. It is possible to avoid the region where the phase characteristics are deteriorated, and it is possible to operate the high frequency amplifier in a highly efficient and low distortion state.

In the fourth embodiment, the control for suppressing the input power is performed by using the quadratic function, but not limited to this, for example, a higher-order function of third or higher order, an exponential function, a logarithmic function,
The input power may be controlled so that the input power changes smoothly by using a trigonometric function or a combination thereof. Then, the same effect as that of the first embodiment can be obtained.

Further, in the sixth embodiment, the phase control is performed by using the quadratic function.
A higher-order function or higher order function, an exponential function, a logarithmic function, a trigonometric function, or a combination thereof may be used to control so as to improve the phase characteristics of the input / output characteristics of the high frequency amplifier. Then, the same effect as that of the second embodiment can be obtained.

Further, in the first, third and fourth embodiments, the method of controlling only the amplitude of the IQ signal is used, and in the second, fifth and sixth embodiments, the I / Q signal is controlled. Although the method of controlling only the phase of the Q signal is used, the present invention is not limited to this, and any combination of these may be used to control the phase and the amplitude at the same time. In that case, the effects of the first and second embodiments can be obtained at the same time.

[0033]

As is apparent from the above description, the present invention has the advantage that the high frequency amplifier can be operated in a highly efficient state with further improved linearity.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration for realizing a transmission control method according to a first example of the present invention.

FIG. 2 is an I diagram for explaining the operation in the first embodiment.
It is a Q signal conversion characteristic view.

FIG. 3 is an input / output characteristic diagram of the high-frequency amplifier for explaining the operation in the first embodiment.

FIG. 4 is an IQ signal conversion characteristic diagram for explaining the operation in the second embodiment according to the present invention.

FIG. 5 is an input / output characteristic diagram of a high frequency amplifier for explaining an operation in the second embodiment.

FIG. 6 is an IQ signal conversion characteristic diagram for explaining the operation in the third embodiment according to the present invention.

FIG. 7 is an IQ signal conversion characteristic diagram for explaining the operation in the fourth embodiment according to the present invention.

FIG. 8 is an IQ signal conversion characteristic diagram for explaining the operation in the fifth embodiment according to the present invention.

FIG. 9 is an IQ signal conversion characteristic diagram for explaining the operation in the sixth embodiment according to the present invention.

FIG. 10 is a diagram showing a relationship between amplitude and phase of a combined vector of I and Q signals.

FIG. 11 is a block diagram showing a circuit configuration of a conventional transmission control method.

FIG. 12 is an input / output characteristic diagram of a high frequency amplifier for explaining an operation in a conventional example.

[Explanation of symbols]

 1, 11 I / Q signal generator 12 Signal conversion circuit 13 Conversion control circuit 2, 14 Digital modulator 3, 15 High frequency amplifier

Claims (6)

[Claims] 1. An I.multidot.I generated by an I.Q signal generator.
In a transmission control method in which a carrier is modulated by a digital modulator with the amplitude of a composite vector component of a Q signal and the power of the modulated signal is amplified by a high frequency amplifier, the amplitude of the composite vector component is an input / output characteristic of the high frequency amplifier. The transmission control method is characterized by controlling to be smaller than a predetermined value determined by taking into consideration the distortion of the phase characteristic of. 2. The transmission control method according to claim 1, wherein controlling to be smaller than a predetermined value suppresses the amplitude by applying a predetermined function in a region where the amplitude of the combined vector component is a predetermined value or more. . 3. The control to be smaller than a predetermined value means that the amplitude of the combined vector component has a predetermined value in a region where the amplitude is equal to or larger than a predetermined value.
The described transmission control method. 4. A carrier wave is modulated by a digital modulator with the amplitude of a composite vector component of the IQ signal generated in a predetermined phase by the IQ signal generator, and the power of the modulated signal is amplified by a high frequency amplifier. In the transmission control method described above, when the amplitude of the composite vector component is larger than a predetermined value determined by taking into consideration the distortion of the phase characteristic of the input / output characteristic in the high frequency amplifier, the amplitude of the phase of the I / Q signal is A transmission control method characterized in that the transmission is delayed as compared with a case where it is smaller than a predetermined value. 5. The transmission control method according to claim 4, wherein the phase of the I / Q signal is delayed by applying a predetermined function. 6. The transmission control method according to claim 1 controls the amplitude of the combined vector component to be small, and the transmission control method according to claim 4 delays the phase of the IQ signal. Transmission control method.