KR101436926B1 - Concurrent dual-band digital pre-distortion apparatus and method for power amplifier - Google Patents

Abstract

The present invention relates to a pre-correction apparatus for the power amplification signal of different dual bands and a method thereof. A concurrent dual-band digital pre-distortion apparatus for a power amplifier and a method thereof according to the present invention include performing an IF frequency conversion and a sampling process by coupling the output of the power amplifier signal of different dual bands, digitalizing the same, performing a signaling process on a transmitted/received signal, and performing concurrent pre-correction process.

Description

[0001] The present invention relates to a simultaneous dual-band digital predistortion apparatus and method for a power amplifier,

The present invention relates to a power amplifier, and more particularly to a Concurrent Dual-band Digital Pre-Distortion (DPD) device and method for a power amplifier that linearizes the output of a power amplifier having nonlinear characteristics. will be.

In recent years, the complexity and multi-functionalization of terminal systems have been demanded in accordance with the provision of various wireless communication services. Accordingly, the emergence of multi-band, multi-mode and multi-standard Various research and development are proceeding in accordance with the dual-band RF component and the low power and miniaturization.

In particular, dual-band amplifiers are required to achieve higher levels of SDR (Software Defined Radio) by reducing hardware complexity and providing system re-configurability for the system .

Due to the rapid development of communication technology, high-speed data transmission becomes possible, and the data transmission capacity increases. As the data transmission capacity increases, the Peak to Average Power Ratio (PAPR) value of the transmission signal increases and the bandwidth of the transmission signal increases. However, due to the high PAPR value and the wide transmission bandwidth, the nonlinear characteristic occurring in the power amplifier is a decisive factor that deteriorates the performance of the communication system.

Since the nonlinear problem of the power amplifier acts as a main factor that deteriorates the performance of the communication system, a pre-distortion technique is used as a solution to the nonlinear problem occurring in the power amplifier.

Predistortion is a technique that makes the output of a power amplifier be a desired signal by distorting the signal in advance in the baseband region so as to be opposite to the characteristics of the power amplifier. The predistorter can effectively compensate the nonlinear problem of the power amplifier .

On the other hand, digital predistortion (DPD) is a digital technology for processing nonlinear characteristics of a power amplifier in a digital baseband instead of an analog RF. A digital predistortion (DPD) device converts a digital baseband input signal and a non- The input signal is pre-distorted so that there is no distortion in the output component of the final power amplifier as compared to the frequency down conversion and analog-to-digital converted digital baseband signal.

Therefore, in order to support a high-linearity dual-band power amplifier, a dual-band linearization device is required.

Accordingly, it is an object of the present invention to provide a simultaneous dual-band digital predistorter for a power amplifier for supporting a high-linearity dual-band power amplifier and a method thereof To provide.

In accordance with another aspect of the present invention, there is provided a digital predistortion type dual band power amplifier comprising: a digital predistortion type dual band power amplifier for merging the dual band input signals into one, And then applies the filtered signal to the dual band power amplifier after demerge, DAC (digital-to-analog conversion) and frequency conversion (IF-to-RF) (RF-to-IF) and then ADC (Analog-to-Digital Conversion) coupling the signals output to the power amplifier, and merge the two signals into one signal and apply the signals to the DPD , It is possible to achieve linearization for both bands at the same time.

According to another aspect of the present invention, there is provided a simultaneous dual band digital predistorter comprising: a processing unit for merging the dual band input signal into one signal; a nonlinear component A mixer and a filter for demodulating a signal passed through the DPD to each signal, a digital-to-analog converter (DAC) for converting the signal into an analog signal, A dual-band power amplifier for receiving and amplifying the RF signal, a coupler for monitoring the signal, a coupler for coupling the signal coupled in the coupler, To an IF, an analog-to-digital converter (ADC) for converting the IF signal into a digital signal, and a demultiplexer (Merge) provides a simultaneous dual-band digital predistortion device, it characterized in that the processing unit provided with a to.

According to another aspect of the present invention, there is provided a simultaneous dual band digital predistortion method comprising: merging a dual band signal input from a frame unit; Passing the merged input signal through a crest factor reduction unit (CFR) and a digital predistortion unit (DPD); Demerging the passed signal through a filter and re-demodulating the received signal into respective signals; Converting the demodulated signal into an analog signal from a digital-analog converter (DAC) and performing frequency conversion (IF-to-RF) through a radio unit; A step of amplifying the frequency-converted signal by applying the frequency-converted signal to a dual-band power amplifier; Converting a signal output from the dual-band power amplifier to RF-to-IF and converting the digital signal to an analog-to-digital converter; A step of merging the two signals converted into the digital signal into one signal; And applying the merged signal to the digital predistortion unit to compensate for the nonlinear component generated in the amplifying process of the dual band power amplifier.

At this time, in the simultaneous dual-band digital predistortion method according to the present invention, the radio unit is any one of a mixer and a modulator.

In addition, the simultaneous dual-band digital predistortion method according to the present invention is characterized in that before the process of merging the two signals converted into the digital signal into one signal, the two signals passed through the ADC are aligned between paths through delay and gain adjustment Further comprising the steps of:

Also, in the simultaneous dual-band digital predistortion method according to the present invention, the digital-analog conversion and the analog-digital conversion are performed for each frequency band.

According to another aspect of the present invention, there is provided a digital predistortion type dual band power amplifier comprising: a digital predistortion type dual band power amplifier for merging a dual band signal input from a frame unit into a single signal, a first merge unit for merge the first merge unit; A simultaneous dual band digital predistorter for compensating for nonlinear components of the dual band power amplifier; A first mixer and a filter that demerge a signal having passed through the predistortion unit into respective signals; A digital-analog converter (DAC) for converting the demodulated signal into an analog signal; A radio unit for converting the converted analog signal into a radio frequency (RF) signal; A dual band power amplifier receiving and amplifying the RF signal; A coupler for monitoring an output signal of the dual band power amplifier; A second mixer for converting the coupled signal in the coupler into an intermediate frequency (IF) signal; An analog-to-digital converter (ADC) for converting the IF signal into a digital signal; And a second merge unit for merging the two signals through the ADC into one signal.

In this case, the radio unit of the simultaneous dual-band digital predistorter according to the present invention is characterized by being a mixer and a modulator.

Further, the second merger of the simultaneous dual-band digital predistorter according to the present invention is characterized in that the two signals passed through the ADC are aligned with each other through delay and gain adjustment.

Also, in the simultaneous dual-band digital predistorter according to the present invention, the digital-analog converter (DAC) and the analog-digital converter (ADC) are provided for respective frequency bands.

The present invention having the above-mentioned solution and structure has a very useful effect in ensuring linearity of a dual-band power amplifier requiring high linearity by simultaneous predistortion of a dual-band signal.

The present invention is also advantageous in lowering the cost of a dual-band power amplifier and a communication system including the same.

FIG. 1 is a block diagram of a system using a single-band power amplifier to which a digital predistorter according to the related art is applied.
FIG. 2 is a block diagram of a system for transmitting signals of two bands using a dual-band power amplifier to which a simultaneous dual-band digital predistorter according to the present invention is applied;
FIG. 3 is a detailed block diagram of a simultaneous dual-band digital predistorter according to the present invention and a signal form at each stage,
4A to 4C are characteristic graphs measured after applying the simultaneous dual band digital predistorter according to the present invention.

Hereinafter, a detailed description of preferred embodiments of the present invention will be given with reference to the accompanying drawings. It should be noted that the same configurations of the drawings denote the same reference numerals as possible whenever possible. Specific details are set forth in the following description, which is provided to provide a more thorough understanding of the present invention. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

FIG. 1 is a block diagram of a system using a single-band power amplifier to which a digital predistorter according to the related art is applied. FIG. 1 is a block diagram illustrating a system using a single-band power amplifier using a digital predistorter according to the related art. And shows a block diagram that can be generally applied when transmitting.

Referring to FIG. 1, a frame unit is used for data communication with an upper system. In the downlink, the frame unit operates as a de-framer to reproduce data sent from the upper system.

The de-framed data in the De-Framer passes through a Crest Factor Reduction (CFR) and a Digital Pre-Distortion (DPD) Is converted into an analog signal after passing through a digital-to-analog converter (DAC). The converted analog signal is frequency-converted into a radio frequency (RF) signal after passing through a radio transceiver (Trx). The frequency-converted RF signal is amplified through a power amplifier (PA) and then applied to a duplexer.

As described above, in the system using the single band power amplifier to which the digital predistorter (DPD) according to the prior art shown in FIG. 1 is applied, the above operation is performed for each frequency band, (Two in total), and the two frequency bands amplified in each block are combined in a duplexer and outputted through an antenna.

Each of the signals output from each of the power amplifiers PA is coupled and frequency-converted into an intermediate frequency (IF) signal after passing through the radio unit Trx, ADC: Analog-to-Digital Converter). Finally, the digitized signal is applied to the digital predistortion unit (DPD) and used for nonlinear component compensation calculation processing.

On the other hand, in an uplink, a signal received through an antenna is branched in frequency by a duplexer, and each branched frequency band signal is amplified and frequency-converted by a radio unit Trx. The amplified and frequency-converted signal is digitized through an analog-to-digital converter (ADC) and serialized to a promised format to send data from the framer to the host system.

Next, a simultaneous dual-band digital predistorter for a power amplifier and its method according to the present invention will be described in detail with reference to Figs. 2 and 3. Fig.

FIG. 2 is a block diagram of a system for transmitting signals of two bands using a dual-band power amplifier to which a simultaneous dual-band digital predistorter according to the present invention is applied. FIG. Band digital predistortion apparatus and a signal form at each stage. The IF output stage of the digital-analog conversion unit (DAC) and the analog-to-digital conversion unit (DAC) (ADC) to the IF input stage and the signal form of each stage.

In the simultaneous dual-band digital predistorter for a power amplifier according to the present invention, signals of two bands passing through a frame / de-framer and a crest factor reducing unit (CFR) are merged into a single signal, And applied to a concurrent dual band digital predistortion (DPD).

Here, the present invention deals with two frequency bands, but handles all two frequency bands in one simultaneous dual band digital predistortion (DPD). The signals that have passed through the concurrent dual band DPD are again demarcated into respective signals.

The signals demultiplexed into the respective signals are converted into analog signals through a digital-to-analog converter (DAC), frequency-converted into RF signals after passing through a radio unit Trx, Amplified and output to the antenna through a duplexer.

Also, the output signal of the dual-band power amplifier PA is coupled, passed through the radio unit Trx, frequency-converted into an IF signal, passed through an analog-to-digital converter (ADC) And then applied to a concurrent dual band digital predistortion unit (DPD) to be used for nonlinear component compensation calculation processing.

In order to process signals of two bands using one digital-analog converter (DAC) or one analog-digital converter (ADC), a wideband signal including both bands is converted into a digital- ) And an analog-to-digital converter (ADC).

In particular, in the case of an analog-to-digital converter (ADC), a sampling rate corresponding to twice the nonlinear distortion component bandwidth of the input signal is required. This generally corresponds to twice the bandwidth of the complex modulated signal 5 times, which means that a very high sampling rate is required.

Due to such a limitation due to the sampling rate, there is a limitation in implementing a dual-band digital predistorter with one digital-analog converter (DAC) and one analog-digital converter (ADC) in a conventional digital predistortion structure . Digital-to-analog converters (DACs) or analog-to-digital converters (ADCs) with high sampling rates are low resolution, power consuming and expensive.

Therefore, in the simultaneous dual-band digital predistorter for a power amplifier according to the present invention, as shown in FIG. 2, two digital-to-analog converters (DAC) and analog- Signal.

FIGS. 4A to 4C are characteristic graphs measured after applying the simultaneous dual band digital predistortion (DPD) apparatus according to the present invention. FIG. 4A is a graph measured in a wide band from 1800 MHz to 2100 MHz, Zoom measurement at 1800Mhz and 2100Mhz, respectively.

4A to 4C, blue is a spectrum including a nonlinear component of the amplifier before the predistortion is performed, and yellow is a spectrum after removing the nonlinear component after the predistortion. As shown, the present invention is a predistortion device for supporting dual-band power amplifiers due to the emergence of multi-band and multi-standard. By using a simultaneous dual-band digital predistorter, And the desired goal can be achieved while reducing the cost.

As described above, the simultaneous dual-band digital predistorter for a power amplifier according to the present invention has a structure as shown in FIG. 2, so that two frequency band signals of a dual- Band digital predistortion (Concurrent Dual band DPD), which can be expected to be cost-effective when compared with the conventional method.

Further, in the simultaneous dual-band digital predistorter for a power amplifier according to the present invention, only one lookup table is used. The reason why only one look-up table is used in the present invention is that it is advantageous to use one look-up table because the characteristics of the two bands are independent of each other and have dependency characteristics.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should not be limited by the described embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

Claims (8)

CLAIMS 1. A method for simultaneous dual band digital predistortion of a digital predistortion type dual band power amplifier,
A process of merging the dual band signals input from the frame unit into one;
Passing the merged input signal through a crest factor reduction unit (CFR) and a digital predistortion unit (DPD);
Demerging the passed signal through a filter and re-demodulating the received signal into respective signals;
Converting the demodulated signal into an analog signal from a digital-analog converter (DAC) and performing frequency conversion (IF-to-RF) through a radio unit;
A step of amplifying the frequency-converted signal by applying the frequency-converted signal to a dual-band power amplifier;
Converting a signal output from the dual-band power amplifier to RF-to-IF and converting the digital signal to an analog-to-digital converter;
A step of aligning the two signals through the analog-to-digital converter (ADC) through paths by delay and gain adjustment;
Merging the two signals arranged in the path into one signal; And
Applying the merged signal to the digital predistortion unit (DPD) to compensate for the non-linear component generated in the amplification process of the dual-band power amplifier;
Band digital predistortion method for a power amplifier.
The wireless communication system according to claim 1,
Wherein the digital predistorter is one of a mixer and a modulator.
delete The method of claim 1, wherein the digital-to-analog conversion and the analog-to-digital conversion are performed for each frequency band.
A digital predistortion type dual band digital power predistorter for a dual band power amplifier,
A first merge unit for merging the dual band signals input from the frame unit into one signal;
A simultaneous dual band digital predistorter for compensating for nonlinear components of the dual band power amplifier;
A first mixer and a filter that demerge a signal having passed through the predistortion unit into respective signals;
A digital-analog converter (DAC) for converting the demodulated signal into an analog signal;
A radio unit for converting the converted analog signal into a radio frequency (RF) signal;
A dual band power amplifier receiving and amplifying the RF signal;
A coupler for monitoring an output signal of the dual band power amplifier;
A second mixer for converting the coupled signal in the coupler into an intermediate frequency (IF) signal;
An analog-to-digital converter (ADC) for converting the IF signal into a digital signal;
A second merge unit for aligning the two signals through the analog-to-digital converter (ADC) through paths by delay and gain adjustment, and merging the signals into one signal;
Band digital predistortion device for a power amplifier.
6. The wireless communication system according to claim 5,
Wherein the digital predistorter is one of a mixer and a modulator.
delete 6. The dual-band digital predistorter for a power amplifier according to claim 5, wherein the digital-analog converter (DAC) and the analog-digital converter (ADC) are provided for respective frequency bands.

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