JPH0974371A - Radio equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the arithmetic errors of a nonlinear distortion correction amount and to improve a distortion compensation effect by comparing preamble demodulation data near a maximum amplitude value with preamble signals. SOLUTION: A part of transmission output signals outputted from an antenna 7 is attenuated in an attenuator 8 and then, fed back to a reception part by a switch 9. The signals are demodulated in a demodulator 10 and converted into digital data signals by an A/D converter 11. Among them, for the preamble demodulation data, respective amplitude values are compared and the maximum amplitude value is detected. The plural pieces of the preamble demodulation data with the maximum amplitude value as a center are tentatively stored in a maximum value reception memory 20. Then, the delay amount of demodulation data signals is corrected by outputting the preamble demodulation data near the maximum amplitude value stored in the maximum value reception memory 20 through a delay correction device 15, comparing them with the preamble signals on a transmission side (near the maximum amplitude) in a delay detection circuit 17 and controlling the delay amount of the delay correction device 15 by the error signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention compensates for non-linear distortion of a transmission amplifier by previously distorting a modulation input signal, and compares the amount of compensation with a demodulation signal obtained by demodulating the output of the transmission amplifier and the above modulation input signal. The present invention relates to an improvement of a wireless device having a predistorter type non-linear compensation circuit obtained by

[0002]

2. Description of the Related Art Generally, in a digitized radio for mobile communication, when a linear modulation method such as QPSK or multilevel QAM is used, the transmission spectrum is widened due to the non-linear distortion of a transmission amplifier, and the adjacent channel is disturbed as noise power. Therefore, linear compensation of the transmission amplifier is required. In a conventional radio transmitter, as a countermeasure against this, a so-called predistorter compensation method is often used in which the input signal of the transmission amplifier is pre-distorted so as to cancel the distortion at the output stage of the transmission amplifier. . In that case,
For example, "Linear Amplification Technique for Digit
al Mobile Communications '' CH2379-1 / 89/0000/0159 19
89 As described in IEEE PP.159, a demodulation circuit is provided in the transmitter, or a feedback signal obtained by demodulating a part of the output of the transmission amplifier using the receiver is compared with the modulation input signal.
Closed loop control is often used in which the distortion correction amount is obtained from the comparison value and compensated.

An example of a wireless device using this conventional compensation method is shown in FIG. As a communication method, a predetermined preamble signal having an amplitude change as shown in FIG. 3 is transmitted for each frame prior to the data signal as shown in FIG. ) Is used to perform an arithmetic process for distortion correction and delay correction as an example. In FIG. 2, in the transmitter, when a modulated input signal (transmission data signal) is input from the input terminal 1, the multiplier 2 multiplies it by the distortion correction value from the distortion correction value storage memory 13, and then the D / A It is converted into an analog signal by the converter 3. Next, the modulator 4 performs a predetermined modulation process, the transmission amplifier 5 amplifies the power to a predetermined power, and then outputs the power from the antenna 7 via the demultiplexer 6. A part of the transmission modulated wave signal is attenuated through the attenuator 8 and then fed back to the receiving section by the switch 9. The signal fed back to the receiving section is demodulated by the demodulator 10, converted into a digital signal by the A / D converter 11, and then temporarily stored in the reception memory 16. To correct the time delay of the demodulated data signal, the demodulated data signal of the preamble signal is output from the reception memory 16 via the delay compensator 15, and the delay detection circuit 17 compares the preamble signal with the preamble signal on the transmission side. This is performed by controlling the delay correction amount of the delay corrector 15 with a signal.

In this way, the preamble demodulated data signal whose delay amount has been corrected with respect to the transmission preamble signal is compared with the transmission preamble signal by the comparison and distortion correction value calculation circuit 12, and the distortion correction value of the nonlinear distortion of the transmission amplifier 5 is compared. Is calculated. Next, using the calculated distortion correction value,
The distortion correction values corresponding to the amplitude values of all the transmission data signals are obtained, and the distortion correction values are written in the respective addresses calculated by the memory address calculation circuit 14 in the distortion correction value storage memory 13. Furthermore, when the transmission data signal is input from the input terminal 1 in the next frame,
A distortion correction value corresponding to the amplitude value of the transmission data signal is read from the distortion correction value storage memory 13 and multiplied by the transmission data signal
The correction is made in advance so as to cancel the non-linear distortion of the transmission amplifier 5.

[0005]

In the above-mentioned prior art, from the vicinity of the transmission start time of the preamble signal,
Since it is configured to capture the demodulated data signal,
The threshold level for signal detection in the delay detection circuit 17 is set to a low level value near the rising edge of the preamble signal. Therefore, when noise is superimposed, the detection timing of the delay detection is deviated, which causes a problem that a large error occurs in the delay amount to be detected. The present invention has been made to solve this problem, and suppresses the detection error of the delay amount of the demodulated signal even in the situation where strong noise is superimposed, and greatly improves the accuracy of nonlinear distortion compensation of the transmission amplifier. The purpose of the present invention is to provide a wireless device.

[0006]

In order to achieve the above object, the present invention takes in demodulated data for a predetermined period and detects a maximum amplitude value of the demodulated data taken in, and a detected maximum amplitude value. And a maximum value receiving memory for storing the demodulated data before and after the demodulated data of (1), and is configured to perform delay detection on the transmitted preamble signal for the demodulated data near the maximum amplitude value of the preamble demodulated data. It was done. As a result, it is less likely to be affected by noise, and the error in the detected delay amount can be minimized.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. 1, 3 and 4. Similar to the above-mentioned conventional example, as a communication system, a predetermined preamble signal whose amplitude changes as shown in FIG.
An example will be described in which the data signal is transmitted for each frame prior to the data signal and the calculation processing for the distortion correction and the delay correction is performed using the idle time of the transmission (when another channel is connected).

In FIG. 1, a preamble signal and a data signal to be transmitted are input from an input terminal 1, multiplied by a distortion correction value from a distortion correction value storage memory 13 in a multiplier 2, and then D / A converter 3 Is converted into an analog signal.
Next, the modulator 4 performs a predetermined modulation process such as multi-level QAM, the transmission amplifier 5 amplifies the power to a predetermined power, and then outputs the power from the antenna 7 via the demultiplexer 6. A part of this transmission output signal is attenuated by the attenuator 8 and then fed back to the receiving section by the switch 9.

The signal fed back to the receiving section is demodulated by the demodulator 1.
It is demodulated by 0 and converted into a digital data signal by the A / D converter 11. Of these, the preamble demodulated data obtained by demodulating the preamble signal is the maximum amplitude value detection unit 2
It is given to 1 and is taken into a register or the like and temporarily held. The amplitude values of the fetched preamble demodulated data are compared with each other, and the maximum amplitude value is detected. Next, the preamble demodulation data including the preceding and succeeding data is extracted centering on the detected preamble demodulation data of the maximum amplitude value, and is supplied to the maximum value reception memory 20 including, for example, a shift register. A plurality (for example, three symbols) of preamble demodulation data centered on the maximum amplitude value is temporarily stored in the maximum value reception memory 20.

To correct the delay amount of the demodulated data signal, the preamble demodulated data in the vicinity of the maximum amplitude value stored in the maximum value reception memory 20 is output via the delay corrector 15, and the delay detection circuit 17 transmits the ( It is performed by comparing with a preamble signal (near the maximum amplitude value) and controlling the delay amount of the delay corrector 15 by the error signal. Therefore, even if noise is superimposed, the maximum amplitude level of the preamble signal is usually set to a value sufficiently higher than the noise level, so that the signal detection threshold level in the delay detection circuit 17 is sufficiently higher than in the conventional case. Since the value can be set to a high value, it is possible to remarkably reduce the deviation of the detection timing of the delay amount detection, and always to accurately detect and correct the delay amount of the demodulated signal.
In this way, the preamble demodulation data whose delay amount is accurately corrected is compared with the transmission preamble signal by the comparison and distortion correction value calculation circuit 12, and the distortion correction value of the transmission amplifier 5 is calculated from this difference signal. Next, using the calculated distortion correction values, distortion correction values corresponding to the amplitude values of all transmission data signals are obtained, and in the distortion correction value storage memory 13, the addresses calculated by the memory address calculation circuit 14 are stored. Each distortion correction value is written.

Further, as shown in FIG. 4, when the multiple access method between wireless stations is, for example, the TDMA method, the transmission data signal is input terminal 1 at the next transmission frame timing.
, The distortion correction value corresponding to the amplitude value of the transmission data signal is read from the distortion correction value storage memory 13 and is multiplied by the transmission data signal so that the transmission data signal is transmitted in advance. The non-linear distortion of the amplifier 5 is compensated so that the non-linear distortion of the transmission amplifier 5 can be adaptively corrected. Further, the present invention is not limited to only the TDMA system as described above, and in a communication system in which a preamble signal or a reference signal corresponding to the preamble signal is periodically transmitted, a multiple access system is an FDMA system or It is obvious that the CDMA system can be applied, and its application range is wide.

[0012]

According to the present invention, the maximum amplitude value of the preamble demodulated data is detected, the preamble demodulated data in the vicinity of the maximum amplitude value is stored, and the preamble demodulated data is compared with the transmitted preamble signal. At the time of detecting the delay amount, it is possible to remarkably reduce the deviation of the detection timing due to the ambient noise and the like, and it is possible to remarkably reduce the detection error of the delay amount, and hence the calculation error of the non-linear distortion correction amount. It can be greatly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a conventional wireless device.

FIG. 3 is a diagram showing an example of a transmission preamble signal.

FIG. 4 is a diagram showing an example of a TDMA transmission slot.

[Explanation of symbols]

1 ... Input terminal, 2 ... Multiplier, 3
... D / A converter, 4 ... Modulator, 5 ...
Transmission amplifier, 6 ... Demultiplexer, 7 ... Antenna, 8 ... Attenuator, 9 ... Switch, 10 ... Demodulator, 11 ... A
/ D converter, 12 ... Comparison and distortion correction value calculation circuit, 13 ... Distortion correction value storage memory, 1
4 ... Memory address calculation circuit, 15 ... Delay corrector,
16 ... Reception memory, 17 ... Delay detection circuit, 20 ... Maximum value reception memory, 21 ...
Maximum amplitude value detector.

Claims (2)

[Claims] 1. A modulator for performing a predetermined modulation process on a transmission data signal, a transmission amplifier for amplifying an output signal of the modulator at a predetermined amplification factor, and the transmission by predistorting the transmission data signal. Compensation means for compensating the non-linear distortion of the amplifier, demodulator for receiving a part of the output of the transmission amplifier and performing a predetermined demodulation process, and comparing the demodulated data signal with the transmission data signal and compensating by the compensation means. In a radio having a non-linear compensation circuit including a calculation means for calculating a distortion amount, a detection means for fetching the demodulated data signal for a predetermined period and detecting a maximum amplitude value of the demodulated data signal, and a demodulation of the detected maximum amplitude value A maximum value receiving memory for storing a predetermined number of demodulated data signals centered on data, and a radio device. 2. The radio device according to claim 1, wherein the multiple access system between the plurality of radio devices is a TDMA system.