JPH10303995A - Modulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the modulating device which is reduced in power consumption without any deterioration in modulation precision. SOLUTION: The modulating device is equipped with a mapping means 2 which converts input data into in-phase signal and quadrature signal, a root Nyquist filters 3 and 4 which limit the bandwidths of the in-phase signal and the quadrature signal, and provided with a level detecting means 5 which evaluates the level suppression value based on the level detected values of the signals outputted by the root Nyquist filters, a level suppressing means 6 which suppresses the output levels of the root Nyquist filters by using the level suppression values, filters 7 and 8 which limits the bands of the level- suppressed signals, and a quadrature modulating means 9 which imposes quadrature modulation on the filter outputs and outputs a modulated signal. The peak values of the output signals from the root Nyquist filters are suppressed corresponding to their levels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulator for use in digital mobile communication and the like, and more particularly, to realizing low power consumption.

[0002]

2. Description of the Related Art In a conventional modulator for modulating a digital signal, power consumption is reduced by suppressing the amplitude of a signal in a time section other than a data identification point. As shown in FIG. 5, this conventional modulation device includes a mapping circuit 25 for converting data applied to a data input terminal 24 into an in-phase signal and a quadrature signal, and a Nyquist filter 26 for limiting the band of a baseband signal. , 27,
A waveform shaping signal generator 30 that generates a waveform that has a maximum value at the time of data identification and has a smaller value at other times.
And multipliers 28 and 29 for multiplying the outputs of the Nyquist filters 26 and 27 by the signal output from the waveform shaping signal generator 30,
Data output terminal after quadrature modulating the output signals of multipliers 28 and 29
32, a quadrature modulator 31 for outputting a modulation signal.

In this modulation device, data applied to a data input terminal 24 is input to a mapping circuit 25 and is mapped to a value corresponding to a digital modulation method, and an in-phase signal having the same phase as the input data and a signal orthogonal thereto. It is converted to a quadrature signal. The in-phase signal and the quadrature signal are sent to Nyquist filters 26 and 27, respectively, where the band is limited so as to satisfy the Nyquist criterion.

The amplitude of the signal waveform output from the Nyquist filters 26 and 27 is 1 or -1 at data identification points P1 to P6, for example, as shown in FIG. , The amplitude at the data identification points P1 to P6.

The band-limited in-phase signal and quadrature signal are input to multipliers 28 and 29, respectively.

On the other hand, from the waveform shaping signal generator 30, FIG.
As shown in (b), a waveform is generated in which the amplitude at the data identification time point is 1 and the amplitude at the intermediate time point is 0,
The output is output to multipliers 28 and 29. Multipliers 28 and 29 individually multiply the waveform shaping signal by the in-phase signal and quadrature signal input from Nyquist filters 26 and 27, respectively. As a result of this multiplication,
As shown in FIG. 6C, the amplitudes of the signals of the outputs of the multipliers 28 and 29 are suppressed in a time section other than the data identification point.

The outputs of the multipliers 28 and 29 are quadrature-modulated by the quadrature modulator 31 and output from the data output terminal 32 as a modulation signal.

As described above, in this modulation device, power consumption is reduced and interference with other signals is reduced by suppressing the amplitude of the modulated signal in a time section other than the data identification point.

[0009]

However, in this conventional modulator, since the transmitting side has full Nyquist characteristics, it is possible to reduce power consumption by such a method. In a modulation device in which the transmission side and the reception side share half each, and each of the transmission side and the reception side has a root Nyquist characteristic, when this method is applied, there is a problem that modulation accuracy is deteriorated. . This is because, in the case of a modulator having the root Nyquist characteristic, the amplitude at the data discrimination point of the band-limited baseband signal is not completely converged to 1 or −1, so that the waveform shaping shown in FIG. This is because, when the signals are multiplied, the vacancy of the eye pattern in FIG. 6C is reduced, and the number of determination errors on the receiving side increases.

The present invention solves such a conventional problem, and reduces power consumption without deteriorating modulation accuracy even in a system in which a transmitting side and a receiving side each have a root Nyquist characteristic. It is an object of the present invention to provide a modulation device that can perform the modulation.

[0011]

SUMMARY OF THE INVENTION Therefore, in the modulation apparatus of the present invention, a level detecting means for calculating a level suppression value based on a level detection value of a signal output from a root Nyquist filter, and using this level suppression value Level suppression means for performing level suppression control of the signal output from the root Nyquist filter.

In this device, since the level suppression amount is controlled according to the amplitude of the modulated wave, the peak of the modulated wave can be suppressed without lowering the modulation accuracy.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides a mapping means for converting input data into an in-phase signal and an orthogonal quadrature signal having the same phase as the input data, and a converted in-phase signal and quadrature signal. And a root Nyquist filter for limiting the band of the baseband signal,
Level detection means for calculating a level suppression value based on the level detection value of the signal output from the root Nyquist filter, and level suppression means for performing level suppression control of the signal output from the root Nyquist filter using the level suppression value And a filter for limiting the band of the signal subjected to the level suppression control by the level suppression means, and a quadrature modulation means for quadrature modulating the output of the filter and outputting a modulation signal, wherein the output from the root Nyquist filter is provided. The peak value of the signal is suppressed according to the level.

According to a second aspect of the present invention, the level detecting means includes an envelope calculating means for calculating the square root of the sum of the square value of the in-phase signal and the square value of the quadrature signal output from the root Nyquist filter. A level ratio calculating means for calculating a level ratio between the value calculated by the envelope calculating means and the reference value, and a table describing a relationship between the level ratio and the level suppression value. The suppression value is output to the level suppression means, and the level suppression value can be obtained with a simple configuration.

According to a third aspect of the present invention, the level detecting means calculates the sum of the square value of the in-phase signal and the square value of the quadrature signal output from the root Nyquist filter.
A square calculating means, a square level ratio calculating means for calculating a level ratio between the value calculated by the envelope square calculating means and the reference value, and a table describing the relationship between the level ratio and the level suppression value. The level suppression value read from this table is output to the level suppression means. Since the calculation of the square root is not required as compared with the level detection means of claim 2, the configuration is simpler. It can be.

According to a fourth aspect of the present invention, the level suppression means includes a multiplier for multiplying the level suppression value read from the table by each of the in-phase signal and the quadrature signal output from the root Nyquist filter. Things,
By multiplying the output of the root Nyquist filter by the level suppression value, the peak value of the output of the root Nyquist filter can be suppressed, and the ratio of the average power value to the peak power value of the modulated wave can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(First Embodiment) As shown in FIG. 1, a modulator according to a first embodiment converts a data applied to a data input terminal 1 into an in-phase signal and a quadrature signal. 2, a root Nyquist filter 3 for band-limiting the in-phase signal output from the mapping circuit 2, a root Nyquist filter 4 for band-limiting the quadrature signal output from the mapping circuit 2, and outputs of the root Nyquist filters 3, 4. A level detection circuit 5 for detecting the envelope of the signal and calculating a level suppression value; a level suppression circuit 6 for suppressing a peak in the envelope of the root Nyquist output based on the calculation result of the level detection circuit 5; 6
And a quadrature modulator 9 for quadrature-modulating the outputs of the filters 7 and 8 and outputting a modulated signal to a data output terminal 10.

The level detection circuit 5, as shown in FIG.
An envelope calculating circuit 11 for calculating the square root of the sum of the square value of the root Nyquist filter output of the in-phase signal and the square value of the root Nyquist filter output of the quadrature signal; a preset reference value 12 and an envelope calculating circuit A level ratio calculation circuit 13 for calculating a ratio (level ratio) to the output value of 11 is provided, and a table 14 describing a relationship between the level ratio and the level suppression value is described.

As shown in FIG. 3, the level suppression circuit 6 includes a multiplier 16 for multiplying a root Nyquist filter output of the in-phase signal by a level suppression value 18 inputted from the level detection circuit 5, and a quadrature signal. A multiplier 17 for multiplying the output of the root Nyquist filter by the level suppression value 18 is provided.

In this modulator, data applied to a data input terminal 1 is input to a mapping circuit 2 and is mapped to a value corresponding to a digital modulation method, and an in-phase signal having the same phase as input data and a quadrature orthogonal to the input data. Is converted to a signal. The in-phase signal and the quadrature signal are sent to root Nyquist filters 3 and 4, respectively, where the band of the baseband signal is limited.

The band-limited in-phase signal and quadrature signal are input to a level detection circuit 5 and a level suppression circuit 6.

In the level detecting circuit 5, an envelope calculating circuit 11
The signals output from the root Nyquist filters 3 and 4 are used to calculate the output of each root Nyquist filter.
The square root of the sum of the power values is calculated, and the calculation result is output to the level ratio calculation circuit 13. The level ratio calculation circuit 13 calculates a level ratio between a preset reference value 12 and an output value of the envelope calculation circuit 11, reads a level suppression value corresponding to the level ratio from the table 14, and outputs the level suppression circuit. 6 is output.

In the level suppression circuit 6, the multiplier 16 multiplies the output of the root Nyquist filter of the in-phase signal by the level suppression value 18 output from the level detection circuit 5, and the multiplier 17 outputs the quadrature signal. The output of the root Nyquist filter is multiplied by the level suppression value 18 output from the level detection circuit 5 to suppress the peak level of the output of the root Nyquist filters 3 and 4.

The output of the level suppression circuit 6 is such that the in-phase signal and the quadrature signal are band-limited by filters 7 and 8 and quadrature-modulated by a quadrature modulator 9, and then output to a data output terminal.
Output from 10.

As described above, in this modulator, the envelope peak is detected from the root Nyquist filter output of the in-phase signal and the root Nyquist filter output of the quadrature signal, and the peak level of the root Nyquist filter output is determined according to the detected value. And the band is further restricted. Therefore, the envelope peak value generated at the intermediate point between the data identification points can be suppressed without deteriorating the modulation accuracy, and the ratio of the average power to the peak power of the modulated wave can be reduced.

By suppressing the envelope peak value, power consumption can be reduced and interference with other signals can be reduced. Also, by lowering the ratio of average power to peak power, the latter stage of the modulator can be obtained. Of the power amplifier connected to the power amplifier can be reduced.

(Second Embodiment) In the modulation device of the second embodiment, the configuration of the level detection circuit 5 is different from that of the first embodiment.

The level detection circuit in this modulation device is:
As shown in FIG. 4, an envelope square calculating circuit 19 for calculating the sum of the square value of the root Nyquist filter output of the in-phase signal and the square value of the root Nyquist filter output of the quadrature signal.
And a square level ratio calculating circuit 21 for calculating a level ratio between a preset reference value 20 and an output value of the envelope square calculating circuit 19.
And a table 22 in which the relationship between the level ratio and the level suppression value is described.

In this level detection circuit, an envelope square calculation circuit 19 calculates the sum of the square value of the output of the root Nyquist filter 3 and the square value of the output of the root Nyquist filter 4, and calculates the calculation result. The signal is output to the square level ratio calculation circuit 21. The square level ratio calculation circuit 21 calculates a predetermined reference value.
The level ratio between the output value of the square envelope calculation circuit 19 and the output value of the squared envelope calculation circuit 19 is calculated, and the level suppression value corresponding to this level ratio is calculated in the table 22
And outputs it to the level suppression circuit 6.

As described above, the level detection circuit obtains the level suppression value by comparing the envelope level with the reference value while maintaining the square level. Although the obtained level suppression value is the same as that of the first embodiment, it is not necessary to find the square root in the calculation process, so that the calculation load on the envelope square calculation circuit 19 is reduced, and the circuit scale can be reduced. .

[0032]

As is apparent from the above description, the modulation apparatus of the present invention suppresses the peak level of the modulation signal without deteriorating the modulation accuracy and reduces the ratio of the average power to the peak power of the modulated wave. can do. As a result, power consumption can be reduced, interference with other signals can be reduced, and power efficiency requirements for a power amplifier connected at a subsequent stage can be relaxed.

Further, in the modulation device for detecting the envelope level using the sum of the square values of the output of the root Nyquist filter, the size of the device can be further reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a modulation device according to a first embodiment of the present invention;

FIG. 2 is a block diagram showing a configuration of a peak detection circuit in the modulation device according to the first embodiment;

FIG. 3 is a block diagram illustrating a configuration of a peak suppression circuit in the modulation device according to the first embodiment;

FIG. 4 is a block diagram showing a configuration of a peak detection circuit in a modulation device according to a second embodiment of the present invention;

FIG. 5 is a block diagram showing a configuration of a conventional modulation device;

FIG. 6 is a diagram showing waveforms at various parts in a conventional modulation device.

[Explanation of symbols]

 1, 24 data input terminal 2, 25 mapping circuit 3, 4 root Nyquist filter 5 level detection circuit 6 level suppression circuit 7, 8 band limiting filter 9, 31 quadrature modulator 10, 32 data output terminal 11 envelope calculation circuit 12 level Ratio reference value 13 Level ratio calculation circuit 14, 22 Level suppression control table 15, 18, 23 Level suppression control value 16, 17, 28, 29 Multiplier 19 Envelope square calculation circuit 20 Square level ratio reference value 21 Square Level ratio calculation circuit 26, 27 Nyquist filter 30 Waveform shaping signal generator

Claims (4)

[Claims] 1. A mapping means for converting input data into an in-phase signal and an orthogonal signal orthogonal to the input data, and a root Nyquist filter for limiting a band of a baseband signal of the converted in-phase signal and the orthogonal signal. A modulation device comprising: a level detection unit that calculates a level suppression value based on a level detection value of a signal output from the root Nyquist filter; and a level of a signal output from the root Nyquist filter using the level suppression value. Level suppression means for performing suppression control, a filter for limiting the band of a signal subjected to level suppression control by the level suppression means, and quadrature modulation means for orthogonally modulating the output of the filter and outputting a modulation signal. A modulation device characterized by the above-mentioned. 2. An envelope calculating means for calculating a square root of a sum of a square value of an in-phase signal and a square value of a quadrature signal output from the root Nyquist filter; A level ratio calculating means for calculating a level ratio between the value calculated by the means and the reference value, and a table describing a relationship between the level ratio and the level suppression value, wherein the level suppression value read from the table is provided. 2. The modulation device according to claim 1, wherein the output of the modulation device is output to the level suppression unit. 3. An envelope square calculating means for calculating the sum of the square value of the in-phase signal and the square value of the quadrature signal output from the root Nyquist filter;
A square level ratio calculating means for calculating a level ratio between the value calculated by the envelope square calculating means and a reference value, and a table describing a relationship between the level ratio and the level suppression value, 2. The level suppression unit according to claim 1, wherein the level suppression value read from the table is output to the level suppression unit.
3. The modulation device according to claim 1. 4. The apparatus according to claim 1, wherein said level suppression means includes a multiplier for multiplying the level suppression value read from said table by each of an in-phase signal and a quadrature signal output from said root Nyquist filter. Claim 1
4. The modulation device according to any one of claims 1 to 3.