JP2000196549A - Method for modulating plurality of carriers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize a dynamic range of an amplifier by avoiding a defect of an amplifier input reaching a multiple of number of carriers resulting from sum of maximum values of instantaneous amplitude of the carriers when phases of the carriers are matched in the case of using a method of synthesizing a plurality of the carriers from one or a few reference oscillators to decrease a maximum input voltage possibly to be caused. SOLUTION: In the method for modulating a plurality of carriers, one or a few reference oscillators 1 generate a plurality of carriers and each modulator 8 for a transmitter for frequency multiplex communication or code multiplex communication that digitally modulates a plurality of the carriers gives an optional offset to each carrier as an initial phase so as to reduce a maximum amplitude of the input to a high frequency amplifier, Thus, the dynamic range of the amplifier 10 where a linear operating region is limited or a maximum input amplitude voltage has a limitation can effectively be utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to use of a dynamic range of a high-frequency amplifier for amplifying a plurality of digitally modulated carriers in a mobile radio base station transmitter or the like using frequency multiplex communication or code multiplex communication. It relates to a method for improving efficiency.

[0002]

2. Description of the Related Art Conventionally, in a transmitter of a mobile radio base station using frequency multiplex communication or code multiplex communication, a plurality of individual oscillators have been used to generate a plurality of carriers. Therefore, the correlation between the carriers is low, and the amplitude change of a signal obtained by frequency-multiplexing a plurality of carriers is almost the same as the change in noise, and the maximum amplitude voltage does not become a wave number multiple. The influence of the distortion due to the operation was able to be suppressed.

However, providing a plurality of individual oscillators as described above increases the size of the apparatus, so that a method of combining a plurality of carrier waves from one or a small number of reference oscillators has recently been adopted. In this method, since the correlation between the carrier waves is high, the phases between the carrier waves may be aligned. And
When the phases between the carriers are aligned, the instantaneous maximum value of the amplitude of each carrier is added to the maximum amplitude voltage at the input of the high-frequency amplifier, so that the number of times becomes equal to the number of carriers.

If the amplifier is used without distortion, the maximum input voltage must be adjusted to the maximum value of the linear range of the amplifier, so that the dynamic range of the amplifier is governed by the maximum possible input voltage. If it becomes too large, it is necessary to use an amplifier with a large rated output and operate at a low operating point where distortion is less likely to occur in order to suppress distortion during amplification.

[0005] The above circumstances are described in more detail below.

In a mobile radio base station and a satellite communication base station, a signal obtained by frequency-multiplexing (or code-multiplexing) a plurality of modulated waves is amplified by an amplifier such as a transmitter. When synthesizing a plurality of carriers for the frequency multiplexing by a synthesized method from one or a small number of reference oscillators so that the frequency can be arbitrarily selected, the mutual correlation between the carriers becomes high as described above, and the When the N-wave modulated signal is frequency-multiplexed, the amplitude voltage becomes N times at the maximum if the phases of the signals between the carrier waves are aligned. Therefore, the amplitude distribution of the multiplexed signal is widely distributed up to a high voltage range, and when used up to the non-linear operation range of the amplifier, deterioration due to distortion is greater than that of a signal having a small correlation. In some cases, the limitation of the maximum input voltage of the amplifier is relaxed by a time rate or the like (a large input that occurs momentarily is accepted as an error range). Relaxation of the voltage limit at the time rate cannot be expected.
In a method of synthesizing a carrier from one or a small number of reference oscillators by a synthesized method, the linearity of an amplifier at a rated output operating point of a transmitter used in a normal operating point setting or at an optimum operating point of power efficiency is not satisfied. It gets worse.
Therefore, in order to suppress signal degradation, it is required to lower the operating point of the amplifier so that the maximum voltage of the amplitude falls within a linear range. As a result, the output power is reduced. There was a problem that it had to be used.

This will be described below with reference to the drawings.

The output signal corresponding to the input signal of the amplifier is shown in FIG.
The characteristics shown in FIG. Since the signal A whose amplitude changes enters the non-linear region A of the amplifier, the distortion of the output becomes larger than that of the signal A whose amplitude changes little. In order to use the amplifier effectively, it is important to suppress the change in amplitude.

FIGS. 3 and 4 show the calculation results of the conventional method in the case of using π / 4 shift four-phase modulation. As can be seen, the correlation between a plurality of carriers synthesized in phase from the reference oscillator is high, and the amplitude distribution of the multiplexed signal is such that when 100 waves are multiplexed as shown in FIG.
It is widely distributed up to 0 times. Also, as shown in FIG. 4, since the carrier waves having correlation are multiplexed, it can be seen that a periodic change in amplitude voltage occurs.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method for combining a plurality of carriers from one or a small number of reference oscillators in a transmitter or the like of a mobile radio base station using the frequency multiplex communication or the code multiplex communication. In the case of using, the disadvantage that the maximum value of the carrier amplitude is added when the phase of each carrier is aligned and the maximum input voltage of the high-frequency amplifier becomes a wave number times the number of carriers, and the maximum input voltage that can occur is reduced. And a method for effectively utilizing the dynamic range of the amplifier.

[0011]

SUMMARY OF THE INVENTION A multi-carrier modulation method according to the present invention generates a plurality of carriers from one or a small number of reference oscillators, and the plurality of carriers are each digitally phase-modulated. In a multiplex communication transmitter or the like, when each modulator is phase-modulated by a digital signal in each modulator, an amplifier is provided by giving an arbitrary offset as an initial phase to each carrier distributed / supplied from the reference oscillator. It is characterized in that the maximum amplitude of the input is reduced and the dynamic range of the high-frequency amplifier is effectively used.

[0012]

FIG. 1 is a circuit diagram of a digital phase modulator used in the present invention. Upon receiving a reference signal from the reference oscillator 1, each carrier generation circuit 3 generates a carrier having a required frequency and distributes it to each modulator by the distributor 2. 2-4 The conversion circuit 5 converts the binary information of "0, 1" into quaternary information necessary for four-phase modulation. The digital filter circuit 7 creates phase change information necessary for modulation from the quaternary information. The quadrature modulator 4 performs four-phase modulation from the phase change information signal. The multi-wave modulator 9 frequency-multiplexes a plurality of modulator outputs. The amplifier 10 amplifies the multiplex signal to a predetermined voltage at a high frequency and outputs the amplified signal.

The above is the configuration of a general digital phase modulation circuit. In the present invention, a phase rotation circuit is added to this, so that an initial value of an arbitrary phase can be added to each carrier.

In a modulation method such as π / 4 shift four-phase modulation, an initial value of any of the eight phases can be set in units of 45 degrees by adding an arbitrary value to the quaternary information output from the 2-4 conversion circuit. Can be set. When collective modulation of a plurality of waves is performed by digital signal processing, it is necessary to convert numerical information into an analog signal (amplitude change). However, when the present invention is applied to modulation processing, the maximum voltage value can be suppressed. Maximize the resolution of the analog conversion circuit. Also, in the code multiplexing method, the method of the present invention has the same effect on the same principle as that of frequency multiplexing.

FIGS. 5 to 8 show calculation results when the multiple carrier modulation method of the present invention is used in the π / 4 shift four-phase modulation.

In a digital phase modulator, information is modulated as a change in phase with respect to a carrier wave. At this time, an arbitrary initial value (11 in FIG. 1) is added to individual information to perform modulation. FIG. 5 shows the amplitude distribution when an initial value is arbitrarily given to each carrier. FIG. 5 shows the calculated values when the initial value of the phase of each carrier is an arbitrary value in units of 1 degree. Compared to FIG. 3, the maximum amplitude input voltage is reduced to about 1/3 in this example, and the periodic change shown in FIG. 4 as shown in FIG. 6 is also eliminated. In addition, the duration of the voltage portion where the amplitude change is high is short, and the deterioration is reduced even if the voltage range is affected by nonlinearity. That is, since the correlation between the respective carriers is substantially eliminated, generation of a high input voltage as shown in FIG. Therefore, as shown in FIG. 5, the operating point may be determined by assuming that the maximum input voltage is at most 30 times the carrier voltage, and as shown in FIG. The operating point can be made much higher than in the case where the operating point is determined, and the output can be output accordingly, so that the power efficiency of the amplifier can be improved.

Further, in the case of FIG. 5, the initial phase of each carrier is changed in units of 1 degree, but it is found that the effect is the same even if the initial phase is changed in units of 45 degrees. Figure 7
And FIG. As can be seen from the figure, the addition of a phase in units of 45 degrees can provide a sufficient effect similar to that shown in FIGS.

[0018]

As described above, the multi-carrier modulation system of the present invention has the following effects. -It is possible to improve the use efficiency of the transmitters of the mobile radio base station and the satellite communication base station, and it is expected that the size of the apparatus can be reduced. Further, the periodic amplitude change is eliminated and the duration of the high voltage range is shortened, so that even if the instantaneous maximum amplitude voltage exceeds the allowable maximum input voltage of the amplifier, there is an effect that occurrence of trouble is reduced. -Since the change in amplitude is reduced, the change in power supply current in a power-efficient amplifier such as a satellite transmitter is reduced. -In a relay system such as a satellite, the use efficiency of the transmitter of the base station can be improved, and the use efficiency of the transmitter mounted on the satellite can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a digital phase modulation circuit used in the present invention.

FIG. 2 is a diagram illustrating an example of input / output characteristics of an amplifier.

FIG. 3 is a diagram showing a case where carrier phase initial values are set to the same phase;
It is a figure which shows the histogram of the amplitude value (calculation value) at the time of 0 wave multiplexing.

FIG. 4 is a diagram showing a case where carrier phase initial values are set to the same phase;
It is a figure which shows the time change (calculated value) of the amplitude at the time of 0 wave multiplexing.

FIG. 5 is a diagram illustrating a histogram of amplitude values (calculated values) when an initial value of each carrier wave phase is arbitrarily set in units of one degree.

FIG. 6 is a diagram illustrating a temporal change (calculated value) of amplitude when an initial value of each carrier phase is arbitrarily set in units of one degree.

FIG. 7 is a diagram illustrating a histogram of amplitude values (calculated values) when an initial phase value of each carrier is arbitrarily set in units of 45 degrees.

FIG. 8 is a diagram showing a temporal change (calculated value) of amplitude when an initial phase value of each carrier is arbitrarily set in units of 45 degrees.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reference oscillator 2 Divider 3 Carrier synthesis circuit 4 Quadrature modulator 5 2-4 converter 6 Phase rotation circuit 7 Digital filter circuit 8 Digital four-phase modulator 9 Multiplexer 10 Amplifier

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Osamu Takeda 2-12-5 Iwamotocho, Chiyoda-ku, Tokyo Research Institute for Next-Generation Satellite Communications and Broadcasting Systems Co., Ltd. (72) Inventor Yoichi Kawakami Chiyoda-ku, Tokyo 2-12-5 Iwamotocho F-term (Reference) 5K004 AA05 FA05 FE07 FF01 FF02 FF05 5K022 AA04 AA10 AA12 AA17

Claims (1)

[Claims] 1. A transmitter for frequency multiplex communication or code multiplex communication in which a plurality of carriers are generated from one or a small number of reference oscillators and the plurality of carriers are digitally phase-modulated. When each carrier is phase-modulated by a digital signal, the maximum amplitude of the high-frequency amplifier input is reduced by giving an arbitrary offset as an initial phase to each carrier distributed and supplied from the reference oscillator,
A multi-carrier modulation method characterized by effectively utilizing a dynamic range of a high-frequency amplifier.