JP2001237723A - Transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control transmitter, without having to increase the quantized noise of a D/A conversion part by installing a digital multiplier and an attenuator, and making the coefficient of the multiplier to be equal to that of the attenuator. SOLUTION: A power calculation part 302 calculates an amplitude value 303 of a transmission signal by using a transmission digital orthogonal base band signal 301. A digital multiplier 304 multiplies it by a prescribed coefficient and performs attenuation. An attenuated amplitude value 305 is turned into an address and a reference table for nonlinear distortion compensation is referred to. Nonlinear distortion compensation data 307, obtained by making nonlinear distortion compensation data having the inverse characteristics of the nonlinear distortion characteristics of a transmission system to be orthogonal, are obtained. In a nonlinear distortion compensation part 308, the complex product of the base band signal 301 and nonlinear distortion compensation data 307 is obtained and an orthogonal base band signal 309, on which nonlinear distortion compensation is performed, is outputted. The orthogonal base band signal 309 is modulated orthogonally, and an attenuator 316 attenuates the signal by the same rate as the coefficient used in the multiplier 304 and is amplified by an amplifier 318 of the transmission system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitting apparatus provided with a nonlinear distortion compensating circuit for compensating for nonlinear distortion generated in a transmitting system, which is used for a communication device of a radio communication system using a digital modulation system.

[0002]

2. Description of the Related Art Conventionally, in a transmission apparatus, if the efficiency of a transmission system amplifier is increased in order to save power of a radio terminal, a large amount of nonlinear distortion in the transmission system is likely to occur. For this reason, it is necessary to perform nonlinear distortion compensation by some method. One method is to perform nonlinear distortion compensation of amplitude and phase by referring to a distortion compensation table using the value of a transmission baseband signal. Have been.

FIG. 8 shows a block diagram of a conventional transmitting apparatus. Reference numeral 801 denotes a transmission digital orthogonal baseband signal. Reference numeral 802 denotes a lookup table for nonlinear distortion compensation.
3 is amplitude distortion compensation data, and 804 is phase distortion compensation data. Reference numeral 805 denotes a D / A converter for converting digital data into an analog value, and 806 denotes a converted analog quadrature baseband signal. Reference numeral 807 denotes a low-pass filter for limiting the band of the transmission signal, and reference numeral 808 denotes a band-limited orthogonal baseband signal. 809 is a quadrature modulator, 810
Is a modulation signal. 811 is a gain control amplifier for compensating for amplitude distortion, 812 is a modulation signal for which amplitude distortion has been compensated, 813 is a phase shifter for compensating for phase distortion, 814 is a modulation signal for which amplitude and phase shift distortion have been compensated, and 815 is a transmission system. 816 is a transmission modulation signal.

[0004] The operation of the transmitting apparatus configured as described above will be described below. First, the transmission digital quadrature baseband signal 801 is transmitted to the D / A converter 80.
5, the signal is converted to an analog value, band-limited by a low-pass filter 807, and then quadrature-modulated by a quadrature modulator 809 to become a modulated signal 810. At the same time, the amplitude distortion compensation data 803 and the phase distortion compensation data 804 are obtained by referring to the reference table 802 using the value of the transmission digital orthogonal baseband signal 801 as an address. Next, the gain control amplifier 811
Performs amplitude distortion compensation using the amplitude distortion compensation data 803,
The phase shifter 813 performs phase distortion compensation using the phase distortion compensation data 804, and modulates the amplitude and phase distortion of the modulated signal 8
Get 14. Finally, the modulated signal 814 having undergone the amplitude and phase distortion compensation is amplified by a transmission system amplifier 815, and a transmission modulated signal 816 is output.

[0005]

In this transmitting apparatus, a nonlinear distortion compensation characteristic is deteriorated due to a DC offset generated in a D / A conversion section and a quadrature modulation section. SUMMARY OF THE INVENTION It is an object of the present invention to provide a transmission apparatus for controlling transmission power without increasing quantization noise of a D / A converter.

[0006]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides a multiplier for multiplying an output of the power calculator by a constant coefficient, and a nonlinear distortion prepared in advance using the output of the multiplier. A table reference unit that refers to a compensation table, a nonlinear distortion compensator that performs nonlinear distortion compensation on the transmission orthogonal baseband signal using an output of the table reference unit, and a quadrature modulator that orthogonally modulates the output of the nonlinear distortion compensator And an attenuator for attenuating the output of the quadrature modulator.

This has the effect of controlling the transmission power without increasing the quantization noise of the D / A converter by making the coefficients of the multiplier and the attenuator equal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is provided in a communication device of a radio communication system using a digital modulation system, and calculates a power of a digitally modulated transmission quadrature baseband signal by calculation. A multiplier that multiplies the output of the power calculation unit by a constant coefficient, a table reference unit that refers to a nonlinear distortion compensation table prepared in advance using the output of the multiplier, and the transmission quadrature baseband signal. A non-linear distortion compensator that performs non-linear distortion compensation using the output of the table reference unit, a D / A converter that converts the output of the non-linear distortion compensator into analog,
A transmission device comprising a transmission system nonlinear distortion compensation circuit including: a quadrature modulation unit that quadrature modulates an output of an A conversion unit; and an attenuator that attenuates the output of the quadrature modulation unit. Has the effect of controlling the transmission power without increasing the quantization noise of the D / A converter.

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

(Embodiment 1) FIG. 1 is a block diagram of a transmitting apparatus according to an embodiment of the present invention. Reference numeral 301 denotes a transmission digital orthogonal baseband signal, 302 denotes a power calculation unit, 303 denotes an amplitude value calculated by the power calculation unit 302, 304 denotes a digital multiplier, 305 denotes a corrected amplitude value, and 306 denotes a lookup table for nonlinear distortion compensation. , 307 are orthogonalized nonlinear distortion compensation data, 308 is a nonlinear distortion compensator, 309 is an orthogonal baseband signal with nonlinear distortion compensated, 310 is a D / A converter, 311 is an analog orthogonal baseband signal, 312 is band limiting. 313 is a band-limited analog quadrature baseband signal, 314 is a quadrature modulator, 315 is a modulation signal, 316
Is an attenuator, 317 is an attenuated modulation signal, 318 is a transmission system amplifier, and 319 is an amplified transmission modulation signal.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. First, the power calculator 302 calculates the amplitude value 303 of the transmission signal using the transmission digital orthogonal baseband signal 301. Next, the calculated amplitude value 303 of the transmission signal is multiplied by a constant coefficient by the digital multiplier 304 and attenuated.
With the attenuated amplitude value 305 as an address, the nonlinear distortion compensation data 307 obtained by orthogonalizing the nonlinear distortion compensation data having the inverse characteristic of the nonlinear distortion characteristic of the transmission system calculated in advance is obtained by referring to the lookup table 306 for nonlinear distortion compensation. .

The nonlinear distortion compensator 308 performs a complex product of the transmission digital orthogonal baseband signal 301 and the orthogonalized nonlinear distortion compensation data 307, and outputs a nonlinear distortion compensated orthogonal baseband signal 309.

[0013] The D / A converter 310 converts the orthogonal baseband signal 309 subjected to the nonlinear distortion compensation into an analog signal.
The band is limited by the low-pass filter 312, and an analog quadrature baseband signal 313 is obtained. Then, after performing quadrature modulation by the quadrature modulator 314 to produce a modulated signal 315, the signal is attenuated by the attenuator 316 at the same ratio as the coefficient used in the multiplier 304, and then amplified by the transmission system amplifier 318 and transmitted. The modulation signal 319 is output.

As described above, according to the embodiment of the present invention, by providing the digital multiplier 304 and the attenuator 316 and equalizing the coefficients of the multiplier and the attenuator, the quantization noise of the D / A conversion unit is obtained. Can be controlled without increasing transmission power.

(Embodiment 2) FIG. 3 shows a block diagram of a transmitting apparatus. 101 is a transmission digital quadrature baseband signal, 102 is a transmission system non-linear distortion compensator, 103 is a non-linear distortion-compensated quadrature baseband signal, 104 is DC
A compensation signal generator for generating a signal for offset compensation;
05 is a transmission quadrature baseband signal or DC offset compensation signal, 106 and 126 are digital adders, 107
And 127 are orthogonal baseband signals with DC offset compensation, 108 is a D / A converter, 109 is an analog orthogonal baseband signal, 110 and 122 are low-pass filters for band limitation, and 111 and 123 are band-limited. Analog quadrature baseband signal, 112 is a quadrature modulator, 113 is a modulation signal, 114 is a transmission system amplifier, 115 is an amplified transmission modulation signal, 116 is a distributor, 117 is a distributed transmission modulation signal, and 118 is an attenuator , 119 is an attenuated transmission modulation signal, 120 is a quadrature detector, 121 is a quadrature detected quadrature baseband signal, 124 is an A / D converter, 125
Is a digital orthogonal baseband signal, 128 is a DC offset estimator, 129 is a DC offset compensation signal of a transmission modulation system, 130 is a DC offset compensation signal of a transmission demodulation system, 131 is a control signal for controlling a compensation signal unit, and 132 is attenuation. This is a control signal for controlling the vessel.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. First, the nonlinear distortion compensator 102 performs nonlinear distortion compensation on the transmission digital orthogonal baseband signal 101, and outputs the orthogonal distortion-compensated orthogonal baseband signal 103. Compensation signal generation section 104 outputs quadrature baseband signal 103 for which nonlinear distortion has been compensated as it is or generates and outputs a signal for DC offset compensation according to control signal 131 from DC offset estimation section 128. Select The DC output compensation data 129 is added to the selectively output signal 105 by the digital adder 106, and the D
Compensate for C offset. The D / A converter 108 converts the DC offset-compensated quadrature baseband signal 107 into an analog signal, and performs band limitation by a low-pass filter 110 to obtain an analog quadrature baseband signal 111. Then, after performing quadrature modulation by the quadrature modulator 112 to obtain a modulated signal 113, the signal is amplified by a transmission system amplifier 114 to a required size and a transmission modulated signal 115 is output. At this time, the transmission modulation signal 115 is distributed by the distributor 116.

The distributed transmission modulation signal 117 is attenuated by the attenuator 11.
After being attenuated by 8, the quadrature detection section 120 performs quadrature detection, passes through a low-pass filter 122 for band limitation, and then converts the digital signal by an A / D conversion section 124 to obtain a digital quadrature baseband signal 125. . Digital adder 126
Then, the DC offset compensation data 130 is added to compensate for the DC offset of the transmission demodulation system.

On the other hand, the DC offset estimating unit 128
The DC offsets of the transmission modulation system and the transmission demodulation system are independently estimated. First, the amount of attenuation of the attenuator 118 is made sufficiently large by the control signal 132 to cut off the input signal of the quadrature detector 120. At this time, D is set such that the DC offset-compensated orthogonal baseband signal 127 of the transmission demodulation system becomes 0.
The C offset compensation data 130 is updated. Next, the attenuation of the attenuator 118 is reduced by the control signal 132,
After enabling the input signal of the quadrature detection unit 120, the compensation signal generation unit 104 outputs a signal for DC offset compensation by the control signal 131. At this time, the transmission demodulation system D
The DC offset compensation data 130 is updated based on the orthogonal baseband signal 127 on which the C offset has been compensated.

Here, a method of estimating the DC offset of the transmission modulation system will be described below. Signal from the compensation signal generator 104

[0020]

(Equation 1)

When the transmission quadrature baseband signal is output, the DC offset of the transmission modulation system is

[0022]

(Equation 2)

To be affected by

[0024]

(Equation 3)

## EQU1 ## The amplitude and phase characteristics of the path from the quadrature modulator 112 to the quadrature detection unit 120 are displayed in complex form,

[0026]

(Equation 4)

Then, the baseband signal orthogonally demodulated is

[0028]

(Equation 5)

Is

[0030]

(Equation 6)

## EQU1 ## Signal in the same way

[0032]

(Equation 7)

The baseband signal that has been quadrature demodulated when

[0034]

(Equation 8)

Is

[0036]

(Equation 9)

Is as follows. The square of each of the above two signals is

[0038]

(Equation 10)

The quadrature modulator 112 for each signal
Assuming that the amplitude and phase characteristics of the path from to the quadrature detector 120 are substantially equal,

[0040]

[Equation 11]

When the above is replaced by the following, the difference between the two square values is

[0042]

(Equation 12)

## EQU4 ## and the in-phase component of the DC offset is obtained. Also, as a transmission baseband signal

[0044]

(Equation 13)

And

[0046]

[Equation 14]

By using

[0048]

(Equation 15)

An orthogonal component is obtained in the form

According to the above method, the DC offset of the transmission modulator can be estimated without being affected by the phase characteristics of the path from the quadrature modulator 112 to the quadrature detector 120.

As described above, according to the present embodiment, the transmission system nonlinear distortion compensator 102, the compensation signal generator 104, the digital adders 106 and 126, the attenuator 118, and the DC offset estimator 128 are provided. 132, the amount of attenuation of the attenuator 118 is made sufficiently large so that the quadrature detector 120
, The DC offset compensation data 130 is updated such that the DC offset compensated orthogonal baseband signal 127 of the transmission demodulation system becomes 0 at this time, and the control signal 132 attenuates the attenuator 118. The input signal of the quadrature detection unit 120 is made effective by reducing the amount, and a signal for DC offset compensation is output from the compensation signal generation unit 104 by the control signal 131, and the DC offset compensated quadrature of the transmission demodulation system at this time is output. Baseband signal 127
, The DC offset of the transmission modulation system and the DC offset of the transmission demodulation system can be independently detected as digital data obtained by A / D conversion of a quadrature baseband signal of the transmission demodulation system. Thus, the DC offset is automatically compensated by a simple digital operation, and highly accurate transmission system nonlinear distortion compensation can be performed.

(Embodiment 3) FIG. 2 is a block diagram of a transmitting apparatus. 201 is a transmission digital orthogonal baseband signal, 202 is a transmission system nonlinear distortion compensator, 203 is a nonlinear baseband signal with nonlinear distortion compensated, and 204 is a DC
A compensation signal generator for generating a signal for offset compensation, 2
05 is a transmission quadrature baseband signal or DC offset compensation signal, 206 and 226 are digital adders, 207
And 227 are orthogonal baseband signals subjected to DC offset compensation, 208 is a D / A converter, 209 is an analog orthogonal baseband signal, 210 and 222 are low-pass filters for band limitation, and 211 and 223 are band-limited. Analog quadrature baseband signal, 212 a quadrature modulator, 213 a modulation signal, 214 a transmission system amplifier, 215 an amplified transmission modulation signal, 216 a distributor, 217 a distributed transmission modulation signal, 218 a connection switch 219, a transmission modulation signal that has passed through the switch; 220, a quadrature detection unit;
Is a quadrature baseband signal obtained by quadrature detection, 224 is A / D
The conversion unit 225 is a digital orthogonal baseband signal,
28 is a DC offset estimator, and 229 is the D of the transmission modulation system.
C offset compensation signal, 230 is a DC offset compensation signal of a transmission demodulation system, 231 is a control signal for controlling a compensation signal section, and 232 is a control signal for controlling a switch.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. First, the nonlinear distortion compensator 202 performs nonlinear distortion compensation on the transmission digital orthogonal baseband signal 201, and outputs the orthogonal distortion-compensated orthogonal baseband signal 203. The compensation signal generation unit 204 outputs the quadrature baseband signal 203 subjected to nonlinear distortion compensation as it is or generates and outputs a signal for DC offset compensation in accordance with the control signal 231 from the DC offset estimation unit 228. Select The DC output compensation data 229 is added to the selectively output signal 205 by the digital adder 206, and the D
Compensate for C offset. The D / A converter 208 converts the orthogonal baseband signal 207 having been subjected to the DC offset compensation into an analog signal, and performs band limitation by the low-pass filter 210 to obtain an analog orthogonal baseband signal 211. Then, after performing quadrature modulation by the quadrature modulator 212 to obtain a modulated signal 213, the signal is amplified by a transmission system amplifier 214 to a required size, and a transmission modulated signal 215 is output. At this time, the transmission modulation signal 215 is distributed by the distributor 216.

After passing the distributed transmission modulation signal 217 through the connection switch 218, the quadrature detection section 220 performs quadrature detection.
After passing through a low-pass filter 222 for band limitation, A /
The signal is converted into a digital signal by the D conversion unit 224, and a digital orthogonal baseband signal 225 is obtained. Digital adder 2
At 26, the DC offset of the transmission demodulation system is compensated by adding the DC offset compensation data 230.

On the other hand, the DC offset estimating section 228
The DC offsets of the transmission modulation system and the transmission demodulation system are independently estimated. First, the connection switch 21 is controlled by the control signal 232.
8, the input signal to the quadrature detector 220 is cut off.
At this time, the DC offset compensation data 230 is updated so that the DC offset compensated orthogonal baseband signal 227 of the transmission demodulation system becomes zero. Next, the control signal 232
The connection switch 218 is closed by the
After enabling the input signal to the control signal 231, the compensation signal generation unit 204 outputs a signal for DC offset compensation by the control signal 231. At this time, the DC offset compensation data 229 is updated based on the DC offset compensated orthogonal baseband signal 227 of the transmission demodulation system.

The method of estimating the DC offset of the transmission modulation system is the same as in the second embodiment.

As described above, according to the present embodiment, the transmission system nonlinear distortion compensator 202, the compensation signal generator 204, the digital adders 206 and 226, the connection switch 218, and the DC
An offset estimating unit 228 is provided, the connection switch 218 is opened by the control signal 232, and the input signal of the quadrature detecting unit 220 is cut off, so that the DC offset-compensated quadrature baseband signal 227 of the transmission demodulation system at this time becomes zero. Then, the connection switch 218 is closed by the control signal 232 to enable the input signal of the quadrature detection unit 120, and the control signal 231 is used to update the DC offset compensation signal from the compensation signal generation unit 204. And outputs a signal based on the orthogonal baseband signal 227 with the DC offset compensated for the transmission demodulation system at this time.
By updating the C offset compensation data 230, the DC offsets of the transmission modulation system and the transmission demodulation system can be independently detected as digital data obtained by A / D conversion of the orthogonal baseband signal of the transmission demodulation system. DC offset can be automatically compensated by simple digital operation, and highly accurate nonlinear distortion compensation of the transmission system can be performed.

(Embodiment 4) FIG. 4 shows a block diagram of a transmitting apparatus. 401 is a transmission digital orthogonal baseband signal, 402 is a transmission system nonlinear distortion compensator, 403 is a nonlinear distortion compensated orthogonal baseband signal, 404 is a signal controller that controls the orthogonal baseband signal, and 405 is a transmission orthogonal baseband signal. Or DC offset compensation signals, 406 and 428 are digital adders, 407 and 429
Are the quadrature baseband signals with DC offset compensation, 4
08 is a D / A converter, 409, 411 and 433 are analog quadrature baseband signals, 410 and 424 are changeover switches for controlling the path of analog baseband signals, 412
And 422 are low-pass filters for band limiting and 413 and 4
23 is a band-limited analog quadrature baseband signal,
414 is a quadrature modulator, 415 is a modulation signal, 416 is a transmission system amplifier, 417 is an amplified transmission modulation signal, 418 is a distributor, 419 is a distributed transmission modulation signal, 420 is a quadrature detection unit, and 421 is quadrature detection. 425 is an analog quadrature baseband signal selected by the changeover switch, 426 is an A / D converter, 427 is a digital quadrature baseband signal, 430 is a DC offset estimator, and 431 is a DC of a transmission modulation system. The offset compensation signal 432 is a DC offset compensation signal of the transmission demodulation system.
34 is a control signal for controlling the signal control unit, and 435 and 436
Is a control signal for controlling the changeover switch.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. First, the nonlinear distortion compensator 402 performs nonlinear distortion compensation on the transmission digital orthogonal baseband signal 401, and outputs the orthogonal distortion-compensated orthogonal baseband signal 403. Signal control unit 4
In the step 04, in response to the control signal 434 from the DC offset estimating section 430, whether to output the orthogonal baseband signal 403 with the nonlinear distortion compensated as it is or to output a digital signal in which both the in-phase component and the quadrature component are 0 Select The selectively output signal 405 is output to the digital adder 40.
In step 6, the DC offset compensation data 431 is added to compensate for the DC offset of the transmission modulation system. The DC offset compensated orthogonal baseband signal 407 is converted to a D / A converter 4
After conversion into an analog signal at 08, the changeover switch 410 is switched by the control signal 435 to control the signal path. At the time of transmitting the modulated signal, the band is limited by the low-pass filter 412, the quadrature modulation is performed by the quadrature modulator 414 to make the modulated signal 415, and then the transmission system amplifier 416
Then, the transmission modulation signal 417 is amplified after being amplified to a required size. At this time, the transmission modulation signal 417 is distributed by the distributor 418.

The distributed transmission modulation signal 419 is subjected to quadrature detection by the quadrature detection section 420, and the low-pass filter 4
After passing through 22, the signal is input to the changeover switch 424. DC
When estimating the offset, the signal is directly input from the changeover switch 410 to the changeover switch 424. The signal input to the changeover switch 424 is converted into a digital signal by the A / D converter 426, and a digital orthogonal baseband signal 427 is obtained.
In the digital adder 428, the DC offset compensation data 4
32 is added to compensate for the DC offset of the transmission demodulation system.

On the other hand, the DC offset estimating section 430
The DC offsets of the transmission modulation system and the transmission demodulation system are independently estimated. First, the changeover switch 42 is controlled by the control signal 436.
4, the input signal of the A / D converter 426 is cut off.
At this time, the DC offset compensation data 432 is updated so that the DC offset compensated orthogonal baseband signal 429 becomes 0. Next, the changeover switch 424 is closed by the control signal 436 to enable the input signal of the A / D converter 426, and the changeover switch 4 is changed by the control signal 435.
10 to control the analog quadrature baseband signal 409
Is directly input to the changeover switch 424, and then a digital signal having both in-phase and quadrature components of 0 is output from the signal control unit 404 by the control signal 434. At this time, the orthogonal baseband signal 429 becomes 0,
The DC offset compensation data 431 is updated.

As described above, according to the present embodiment, the transmission system nonlinear distortion compensator 402, the signal controller 404, the digital adders 406 and 428, the changeover switches 410 and 424,
A DC offset estimating unit 430 is provided, and a changeover switch 424 is opened by a control signal 436 to open an A / D converting unit 426.
Is cut off so that the DC offset-compensated quadrature baseband signal 429 at this time becomes zero.
The offset compensation data 432 is updated, and then the changeover switches 410 and 424 are controlled by the control signals 435 and 436 so that the analog quadrature baseband signal 409 is input to the A / D converter 426 as a baseband signal. When the control signal 434 outputs a digital signal in which both the in-phase component and the quadrature component are 0 from the signal control unit 404, the DC offset compensation data 431 is updated so that the quadrature baseband signal 429 becomes 0. The DC offset of the analog-to-digital converter of the transmission modulation system and the transmission demodulation system can be detected independently as digital data obtained by A / D conversion of the orthogonal baseband signal of the transmission demodulation system, and simple digital calculation can be performed. In D
It is possible to automatically compensate for the C offset and perform highly accurate transmission system nonlinear distortion compensation.

(Embodiment 5) FIG. 5 shows a block diagram of a transmitting apparatus. 501 is a modulation baseband signal, 5
02 is a signal generation unit, 503 is a modulation system digital orthogonal baseband signal, 504 is a modulation system vector adder, 505
Is a modulation digital orthogonal baseband signal with offset compensation, 506 is a D / A converter, 507 is a modulation analog quadrature baseband signal, 508 is a modulation band limiting filter, 509 is a modulation analog quadrature base band limited. Band signal, 510 is a quadrature modulator, 511 is a modulation signal, 512 is an amplifier, 513 is an amplified modulation signal, 51
4 is a distributor, 515 is a transmission modulation signal, 516 is a feedback modulation signal, 517 is a quadrature demodulator, 518 is a demodulation analog quadrature baseband signal, 519 is a demodulation system band limiting filter, and 520 is a band limited demodulation analog. 521 is an A / D converter, 522 is a demodulation system digital orthogonal baseband signal, 523 is a demodulation system vector adder, 524 is a demodulation system baseband signal, and 525 is a DC.
The offset estimator 526 includes a reference signal output control signal,
27 is a modulation system DC offset estimated value, 528 is a demodulation system D
The C offset estimated value 529 is a conversion frequency control signal,
Reference numeral 30 denotes a modulation system oscillator, 531, a demodulation system oscillator, 532, a modulation system frequency conversion signal, and 533, a demodulation system frequency conversion signal.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. Demodulation system D
During the C offset estimation operation, the DC offset estimation unit 525
Controls the signal generation unit 502 to output a reference signal through the reference signal output control signal 526, and the modulation system D
The C offset estimation value 527 and the demodulation system DC offset estimation value 528 both output 0. The reference signal is modulated signal 5
11 is a signal having a constant frequency and a constant amplitude. Further, through the conversion frequency control signal 529, the frequency of the demodulation system oscillator 531 is controlled so that the modulation system oscillator 530 generates a frequency higher by a certain frequency (hereinafter, referred to as a difference frequency).

The reference signal 503 output from the signal generator 502 is directly input to the D / A converter 506 because the estimated value of the DC offset 527 of the modulation system is 0, and becomes the analog quadrature baseband signal 507 of the modulation system. The modulation system analog baseband signal 507 is
08, and is converted into a modulated signal 511 in the carrier frequency band by the modulation frequency conversion signal 532 in the quadrature modulator 510. Amplifier 512 has modulated signal 511.
And the splitter 514 amplifies the modulated signal 51
3 becomes a feedback modulation signal 516.

The orthogonal demodulation unit 517 converts the feedback modulation signal 516 into a demodulation analog quadrature baseband signal 518 by the demodulation system frequency conversion signal 533, and this signal is band-limited by the demodulation system band limiting filter 519.
Demodulated analog baseband signal 520 with band limitation
Is converted into a demodulation system digital orthogonal baseband signal 522 by the A / D conversion unit 521, and is output as it is as the demodulation system baseband signal 524 because the demodulation system DC offset estimated value 528 is 0.

Since the conversion frequencies of the modulation system and the demodulation system are different, a signal obtained by primary-transforming the signal of the modulation system and a signal further rotated by the difference frequency are output as the demodulation system baseband signal 524. The center vector of this rotation is nothing but the DC offset of the demodulation system, and the DC offset estimating unit 525 estimates the DC offset of the demodulation system by finding the center of rotation of the demodulation baseband signal 524.

After estimating the DC offset of the demodulation system, the DC offset estimating unit 525 outputs the demodulation system DC offset estimation value 528, sets the difference frequency to 0 through the conversion frequency control signal 529, and sets the reference signal to a constant frequency and an average. 0
Give a signal that is If the difference frequency is 0,
The demodulation system digital quadrature baseband signal 522 can be regarded as a signal obtained by linearly converting the reference signal and adding a DC offset of the demodulation system.
3 removes the DC offset component of the demodulation system, so that the demodulated system baseband signal 524 is obtained by linearly converting the reference signal. The reference signal is a constant frequency,
Since the average is 0, if the center of the rotation is shifted from the origin, the center vector is obtained by linearly transforming the DC offset of the modulation system, and the DC offset estimating unit 525 outputs the signal of the modulation system DC offset estimated value 527. , While sequentially updating the demodulation baseband signal 524 such that the center of the demodulation baseband signal 524 is at the origin, it is possible to estimate the transmission system DC offset.

Although the demodulation system oscillator 531 has a higher frequency than the modulation system oscillator 530, the same effect can be obtained if the frequencies are different from each other. Regardless of the magnitude of the frequency of 531, the modulation system oscillator 531 may be controlled.

Although the reference signal has been described as having a constant amplitude in the modulated signal 511, if the amplifier 512 has a sufficiently linear characteristic with respect to amplitude fluctuations from the modulation system to the demodulation system, The amplitude need not be constant.

The reference signal for DC offset compensation has been described as having a constant amplitude, but it goes without saying that this includes the case where the output is in a no-signal state.
If the reference signal is set to no signal, DC
By performing the offset compensation, there is an excellent feature that there is no possibility of affecting other devices without adding a special circuit or the like for preventing a reference signal from leaking outside.

As described above, according to the present embodiment, since the center point is obtained by averaging, not only the calculation is simple, but also in addition to features such as absorbing extraneous noise and conversion errors, orthogonal deviation is obtained. Also, it is not affected by the gain balance of IQ. Therefore, the DC offset can be obtained with high accuracy. In addition, since the configuration only needs to control the conversion frequencies of the modulation system and the demodulation system, the DC offset can be obtained with high accuracy without changing the conventional configuration.

(Embodiment 6) FIG. 6 is a block connection diagram of a transmitting apparatus according to the present embodiment. 601 is a modulation system baseband signal, 602 is a signal generation unit, 603 is a modulation system digital orthogonal baseband signal, 604 is a modulation system vector adder, 605 is an offset-compensated modulation system digital orthogonal baseband signal, and 606 is D / D A conversion unit 607 is a modulation analog quadrature baseband signal;
08 is a modulation system band limiting filter, 609 is a band-limited modulation analog quadrature baseband signal, 610 is a quadrature modulation unit, 611 is a modulation signal, 612 is an amplifier, 613 is an amplified modulation signal, 614 is a distributor, 615 Is a transmission modulation signal, 616 is a feedback modulation signal, 617 is a quadrature demodulation unit, 6
18 is a demodulation system analog quadrature baseband signal, 619 is a demodulation system band limiting filter, 620 is a band limited demodulation system analog baseband signal, 621 is an A / D converter,
622 is a demodulation system digital quadrature baseband signal;
3 is a demodulation system vector adder, 624 is a demodulation system baseband signal, 625 is a DC offset estimation unit, 626 is a reference signal output control signal, 627 is a modulation system DC offset estimation value, 628 is a demodulation system DC offset estimation value, and 629. Is a sampling timer control signal, 630 is a modulation system timer section,
631 is a demodulation system timer section, 632 is a D / A conversion signal,
33 is an A / D conversion signal.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. Demodulation system D
At the time of the C offset estimation operation, the DC offset estimation unit 625
Controls the signal generation unit 602 to output the reference signal through the reference signal output control signal 626, and the modulation system D
The C offset estimation value 627 and the demodulation system DC offset estimation value 628 both output 0. The reference signal is modulated signal 6
11 is a signal having a constant frequency and a constant amplitude. In addition, through the sampling timer control signal 629, the conversion cycle of the demodulation system timer section 631 is controlled so that the modulation system timer section 630 generates a conversion cycle larger by a fixed value (hereinafter, referred to as a difference cycle).

The reference signal 603 output from the signal generator 602 is input to the D / A converter 606 as it is because the DC offset estimation value 627 of the modulation system is 0. D
The / A conversion unit 606 receives the D / A signal from the modulation system timer unit 630.
The digital-to-analog conversion is performed according to the A-converted signal 632, and a modulation analog quadrature baseband signal 607 is output. The modulation system analog baseband signal 607 is band-limited by the band-limiting filter 608, and is converted by the quadrature modulator 610 into a modulated signal 611 in the carrier frequency band. The amplifier 612 amplifies the modulated signal 611, and
As a result, a part of the amplified modulated signal 613 becomes a feedback modulated signal 616.

The quadrature demodulator 617 outputs the feedback modulated signal 616
Is converted into a demodulation analog quadrature baseband signal 618, and this signal is band-limited by a demodulation band limiting filter 619. The A / D converter 621 performs analog-to-digital conversion of the demodulated analog baseband signal 620 whose band has been limited in accordance with the A / D converted signal 633 from the demodulator timer 631, and outputs the demodulated digital orthogonal baseband signal. 622 is output. Demodulation system vector adder 6
23 is a demodulation system digital quadrature baseband signal 622
The demodulation system DC offset estimation value 628 is added to the demodulation system DC offset estimation value 628, and the demodulation system DC offset estimation value 628 is 0. The band signal 622 is output as it is.

Since the conversion periods of the D / A conversion of the modulation system and the A / D conversion of the demodulation system are different, the demodulation system baseband signal 62
As No. 4, a signal obtained by performing a primary conversion on a signal in the modulation system and a signal further rotated by a difference cycle are output. The center vector of this rotation is nothing but the DC offset of the demodulation system.
The offset estimator 625 outputs the demodulated baseband signal 6
The DC offset of the demodulation system is estimated by finding the center of rotation of 24.

After estimating the DC offset of the demodulation system, the DC offset estimating unit 625 outputs a demodulation system DC offset estimation value 628, sets the difference cycle to 0 through the sampling control signal 629, and sets the reference signal to a constant frequency and an average of 0.
Give a signal that is When the difference cycle is 0, the demodulation system digital orthogonal baseband signal 622 can be regarded as a signal obtained by linearly converting the reference signal and adding a DC offset of the demodulation system.
As a result, the DC offset component of the demodulation system is removed, so that the demodulated baseband signal 624 is obtained by primary-converting the reference signal. The reference signal is a constant frequency,
Since the average is 0, if the center of rotation is shifted from the origin, the center vector is obtained by linearly transforming the DC offset of the modulation system, and the DC offset estimating unit 625 outputs the signal of the estimated DC offset value 627 of the modulation system. , While sequentially updating the demodulation baseband signal 624 such that the center of the demodulation baseband signal 624 comes to the origin, the transmission system DC offset can be estimated.

Here, the demodulation system timer unit 631 has a longer conversion period than the modulation system timer unit 630, but the same effect can be obtained if the conversion periods are different from each other.
Frequency of modulation timer section 630 and demodulation timer section 631
Irrespective of the size of the conversion cycle of the
1 may be controlled.

Although the reference signal has been described as having a constant amplitude in the modulated signal 611, if the amplifier 612 has a sufficiently linear characteristic with respect to amplitude fluctuations from the modulation system to the demodulation system, The amplitude need not be constant.

The reference signal for DC offset compensation has been described as having a constant amplitude, but it goes without saying that this includes the case where the output is in a no-signal state.
If the reference signal is set to no signal, DC
By performing the offset compensation, there is an excellent feature that there is no possibility of affecting other devices without adding a special circuit or the like for preventing a reference signal from leaking outside.

As described above, according to the present embodiment, since the center point is obtained by averaging, not only the calculation is simple, but also in addition to features such as absorbing extraneous noise and conversion errors, orthogonal deviation Also, it is not affected by the gain balance of IQ. Therefore, the DC offset can be obtained with high accuracy. In addition, since the configuration only needs to control the conversion cycle of the D / A conversion unit and the A / D conversion unit, the DC offset can be obtained with high accuracy without changing the conventional configuration.

(Embodiment 7) FIG. 7 is a block diagram of a transmitting apparatus. 701 is a modulation system digital orthogonal baseband signal, 702 is a signal generation unit, 703 is a modulation system digital orthogonal baseband signal, 704 is a modulation system vector adder, 705 is an offset-compensated modulation system digital orthogonal baseband signal, and 706 is D / A converter, 70
7 is a modulation analog quadrature baseband signal, 708 is a modulation band limiting filter, 709 is a modulation analog quadrature baseband signal whose band is limited, 710 is a quadrature modulator,
711 is a modulation signal, 712 is an amplifier, 713 is an amplified modulation signal, 714 is a distributor, 715 is a transmission modulation signal, 7
16 is a feedback modulation signal, 717 is a quadrature demodulation unit, 718 is a demodulation system analog quadrature baseband signal, 719 is a demodulation system band limiting filter, 720 is a band limited demodulation system analog baseband signal, and 721 is an A / D conversion unit. , 722 is a demodulation system baseband signal, 723 is a demodulation system vector adder, 724 is a demodulation system baseband signal, 725 is a DC offset estimator, 726 is a reference signal output control signal,
7 is an estimated value of a modulation DC offset, and 728 is a DC offset of a demodulation system.
This is the estimated offset value.

The operation of the transmitting apparatus configured as described above will be described with reference to FIG. Modulation system D
During the C offset estimation operation, the DC offset estimation unit 725
Controls the signal generation unit 702 to output a reference signal through the reference signal output control signal 726, and the modulation system D
0 is output to the C offset estimated value 727. The reference signal has a constant frequency and a constant amplitude in the modulation signal 711 and a signal having an average of 0 in the modulation system digital quadrature baseband signal 703.

The modulation system digital quadrature baseband signal 703 is output from the signal generation unit 702 as a reference signal. However, since the modulation system DC offset estimated value 727 is 0, the reference signal is directly used by the D / A conversion unit 706. It becomes an input and becomes a modulation system analog quadrature baseband signal 707. The modulation system analog baseband signal 707 is band-limited by the band-limiting filter 708,
At 10, it is converted into a modulated signal 711 in the carrier frequency band.
The amplifier 712 amplifies the modulated signal 711 and outputs the signal to the divider 714.
Thus, a part of the amplified modulation signal 713 becomes a feedback modulation signal 716.

The quadrature demodulator 717 outputs the feedback modulated signal 716
Is converted into a demodulation analog quadrature baseband signal 718, and this signal is band-limited by a demodulation band limiting filter 719. The band-limited demodulated analog baseband signal 720 is converted into a demodulated baseband signal 722 by the A / D converter 721. The demodulation baseband signal 722 can be regarded as a signal obtained by linearly converting the reference signal. Since the reference signal has a constant frequency and a constant amplitude, the demodulation system baseband signal 722 has IQ
A circle or a fixed point is drawn on a plane, and the vector of the center of rotation or the fixed point (hereinafter referred to as a center vector 1) is obtained by linearly converting the average of the modulation signal 711. Since the average is 0, the D / A conversion unit 706 and subsequent modulation systems generate
This is the same as the linearly transformed C offset vector.

Next, modulation system DC offset estimating section 725
Outputs a specific vector as the modulation system DC offset estimated value 727. Then, the demodulation baseband signal 722
Draws a circle or a fixed point on the IQ plane in the same manner as the previous time, but the center of rotation or the vector of the fixed point (hereinafter, referred to as center vector 2) is converted by the modulation system after the D / A conversion unit 706. The sum of the generated DC offset vector and the specific vector output as the modulation system DC offset estimated value 727 is linearly transformed.

Since the conversion function is obtained from the center vector 1, the center vector 2, and the specific vector, the D / A converter 7
It is possible to calculate a DC offset vector generated in the modulation system after 06. Thus, DC offset estimating section 725 estimates the modulation system DC offset.

Here, the reference signal has been described as having a constant amplitude in the modulated signal 711. However, if the amplifier 712 has a sufficiently linear characteristic with respect to amplitude fluctuations from the modulation system to the demodulation system, , The amplitude need not be constant.

Although the reference signal for DC offset compensation has been described as having a constant amplitude, it goes without saying that this includes the case where the output is in a no-signal state.
If the reference signal is set to no signal, DC
When the offset compensation is performed, it has excellent features such that there is no possibility of affecting other devices without adding a special circuit or the like for preventing the reference signal from leaking outside.

The size and direction of the specific vector are not limited as long as the linearity is maintained, but if the size is 1 and the direction is the axial direction, the transformation is performed. When a function is obtained, it has a feature that it can be configured only by an adder / subtractor.

As described above, according to the present embodiment, since the center point is obtained by averaging, not only the calculation is simple, but also there are features such as absorbing external noise and conversion errors. Therefore, the DC offset can be obtained with high accuracy.

[0093]

As described above, according to the present invention, by providing a digital multiplier and an attenuator and making the coefficients of the multiplier and the attenuator equal, the quantization noise of the D / A converter can be increased. It is possible to control the transmission power without any need.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transmission device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a transmission device.

FIG. 3 is a block diagram of a transmission device.

FIG. 4 is a block diagram of a transmission device.

FIG. 5 is a block diagram of a transmission device.

FIG. 6 is a block diagram of a transmission device.

FIG. 7 is a block diagram of a transmission device.

FIG. 8 is a block diagram of a conventional transmission device.

[Explanation of symbols]

 Reference Signs List 102 Nonlinear distortion compensator for transmission system 104 Compensation signal generator 106 Digital adder 108 D / A converter 110 Low-pass filter 112 Quadrature modulator 114 Amplifier for transmission system 116 Divider 118 Attenuator 120 Quadrature detector 122 Low-pass Filter 124 A / D converter 126 Digital adder 128 DC offset estimator 202 Transmission nonlinear distortion compensator 204 Compensation signal generator 206 Digital adder 208 D / A converter 210 Low-pass filter 212 Quadrature modulator 214 Transmission system 216 Distributor 218 Connection switch 220 Quadrature detector 222 Low-pass filter 224 A / D converter 226 Digital adder 228 DC offset estimator 302 Power calculator 304 Digital multiplier 306 Non-linear distortion compensation lookup table 308 Non line Distortion compensator 310 D / A converter 312 Low-pass filter 314 Quadrature modulator 316 Attenuator 318 Transmitter amplifier 402 Transmitter nonlinear distortion compensator 404 Signal controller for controlling quadrature baseband signal 406 Digital adder 408 D / A conversion unit 410 changeover switch 412 low-pass filter 414 quadrature modulator 416 transmission system amplifier 418 distributor 420 quadrature detection unit 422 low-pass filter 424 changeover switch 426 A / D conversion unit 428 digital adder 430 DC offset estimation Unit 502 compensation signal generation unit 504 digital adder 506 D / A conversion unit 508 low-pass filter 510 quadrature modulator 512 transmission system amplifier 514 divider 517 quadrature detection unit 519 low-pass filter 521 A / D conversion unit 523 digital Adder 52 DC offset estimator 530 Modulation oscillator 531 Demodulator oscillator 602 Compensation signal generator 604 Digital adder 606 D / A converter 608 Low-pass filter 610 Quadrature modulator 612 Transmitter amplifier 614 Divider 617 Quadrature detector 619 Low Band-pass filter 621 A / D converter 623 Digital adder 625 DC offset estimator 630 Modulation timer 631 Demodulation timer 702 Compensation signal generator 704 Digital adder 706 D / A converter 708 Low-pass filter 710 Quadrature Modulator 712 Transmitter amplifier 714 Divider 717 Quadrature detector 719 Low-pass filter 721 A / D converter 723 Digital adder 725 DC offset estimator

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 27/20 H04L 27/00 F (72) Inventor Kenichi Takahashi 3-10 Higashi-Mita, Tama-ku, Kawasaki City, Kanagawa Prefecture No. 1 Matsushita Giken Co., Ltd. (72) Inventor Kimihide Mihozu 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama City, Kanagawa Prefecture, Matsushita Communication Industrial Co., Ltd.

Claims (1)

[Claims] A power calculator for calculating the power of a digitally modulated transmission quadrature baseband signal;
A multiplier that multiplies the output of the power calculation unit by a constant coefficient, a table reference unit that refers to a nonlinear distortion compensation table prepared in advance using the output of the multiplier, and the transmission quadrature baseband signal, the table A transmission system comprising: a nonlinear distortion compensator that compensates for nonlinear distortion using an output of a reference unit; a quadrature modulator that quadrature modulates an output of the nonlinear distortion compensator; and an attenuator that attenuates an output of the quadrature modulator. A transmission device including a nonlinear distortion compensation circuit.