WO2011088774A1

WO2011088774A1 - Outdoor unit and method for improving output performance of outdoor unit

Info

Publication number: WO2011088774A1
Application number: PCT/CN2011/070342
Authority: WO
Inventors: 王伟; 许少峰; 宋亮
Original assignee: 华为技术有限公司
Priority date: 2010-01-19
Filing date: 2011-01-18
Publication date: 2011-07-28
Also published as: CN101771441A; CN101771441B

Abstract

An outdoor unit (ODU) and a method for improving output performance of the outdoor unit are disclosed by the present invention. The method comprises that: the ODU receives a first analog signal transmitted by an indoor unit (IDU), then down-converts the first analog signal to a first digital baseband signal (11); the ODU receives a second analog signal output from a power amplifier (PA), then down-converts the second analog signal to a second digital baseband signal (12); the ODU obtains a digital predistortion coefficient according to the first digital baseband signal and the second digital baseband signal (13); and the ODU performs digital predistortion processing for the first digital baseband signal by employing the digital predistortion coefficient, obtains a signal processed by the digital predistortion, and transmits the signal to the PA (14). With the present invention, the linearization of transmission links can be achieved without requirement that the PA works in a linear mode.

Description

The present invention claims the priority of the Chinese patent application filed on Jan. 19, 2010, with the application number of 201010003387.8, entitled "Outdoor Unit and Method for Improving Output Performance", The entire contents of this application are incorporated herein by reference. TECHNICAL FIELD The present invention relates to data processing techniques, and more particularly to an outdoor unit and method for improving output performance.

Background technique

As a backbone transmission network device, a microwave transmission device can be used to connect the base station and the base station controller. A corresponding microwave transmission device may be separately disposed on the base station side and the base station controller side, and the microwave transmission devices on both sides generally include an outdoor device and an indoor device, wherein the outdoor device includes a microwave antenna and an Out Door Unit (ODU). Indoor equipment includes an In Door Unit (IDU). The signal sent from the IDU on one side passes through the ODU and the microwave antenna on the side and is sent to the other side. In order to make the transmitted signal undistorted, it can be realized by ensuring that the transmission link is linear. In the prior art, the power amplifier (PA) in the ODU is operated in a linear mode to ensure the linearity of the transmission link. The prior art has at least the following problems: When the PA operates in the linear mode, its working efficiency is too low. If the PA does not work in the linear mode, the distortion is large, that is, the output performance of the existing scheme is poor.

SUMMARY OF THE INVENTION Embodiments of the present invention provide an outdoor unit and a method for improving output performance thereof, which solve the existing The problem of poor output performance in technology.

An aspect of the present invention provides a method for improving an output performance of an outdoor unit, including: an outdoor unit receiving a first analog signal sent by an indoor unit, and down-converting the first analog signal to a first digital baseband signal;

The outdoor unit receives the second analog signal output by the power amplifier, and downconverts the second analog signal into a second digital baseband signal;

The outdoor unit obtains a digital pre-distortion coefficient according to the first digital baseband signal and the second digital baseband signal;

The outdoor unit performs digital predistortion processing on the first digital baseband signal by using the digital predistortion coefficient to obtain a digital predistortion processed signal for transmission to the power amplifier.

Another aspect of the present invention provides an outdoor unit, including:

a first receiving module, configured to receive a first analog signal sent by the indoor unit, and down-convert the first analog signal into a first digital baseband signal;

a second receiving module, configured to receive a second analog signal output by the power amplifier, and downconvert the second analog signal into a second digital baseband signal;

a calculating module, configured to obtain a digital pre-distortion coefficient according to the first digital baseband signal and the second digital baseband signal;

And a digital predistortion module, configured to perform digital predistortion processing on the first digital baseband signal by using the digital predistortion coefficient to obtain a digital predistortion processed signal for transmission to the power amplifier.

Since the digital pre-distortion technology can realize the linearization of the link, it can be known from the above technical solution that the ODU in the embodiment of the present invention performs digital pre-distortion processing on the signal sent by the IDU, so that the PA can be operated in the linear mode without requiring the PA to operate in the linear mode. To achieve linearization of the transmit link and thus Improve output performance. DRAWINGS

FIG. 1 is a schematic flowchart diagram of a method according to a first embodiment of the present invention;

2 is a schematic structural diagram of an ODU according to a first embodiment of the present invention;

3 is a schematic flowchart of a method according to a second embodiment of the present invention;

FIG. 4 is a schematic structural diagram of an ODU according to a second embodiment of the present invention. detailed description

The technical solution of the present invention will be further described in detail below through the accompanying drawings and embodiments. FIG. 1 is a schematic flowchart of a method according to a first embodiment of the present invention, including:

Step 11: The ODU receives the first analog signal sent by the IDU, and downconverts the first analog signal into a first digital baseband signal.

The IDU can send the first analog signal to the ODU through a multiplexer (multiplexer) with the ODU. The multiplexer can transmit signals in a variety of frequency bands and is isolated from each other, usually,

A multiplexer connection is used between the IDU and the ODU. Of course, it can be understood that other devices having the same function as the multiplexer can be used.

Step 12: The ODU receives the second analog signal output by the PA, and down-converts the second analog signal into a second digital baseband signal.

Wherein, a coupler can be used to split the signal output by the PA into two channels, one for the duplexer, and then sent to the microwave antenna through the duplexer for transmission to the other side; the other can be fed back from the PA output. .

Step 13: The ODU obtains the number according to the first digital baseband signal and the second digital baseband signal. Word predistortion coefficient.

The principle of Digital Predistortion (DPD) technology is as follows: Before the signal enters the PA, the signal is first pre-distorted by the DPD coefficient. The distortion curve of the predistortion is opposite to the distortion curve of the PA, thus achieving the 4th cancellation. The purpose of PA distortion.

The DPD coefficient can be implemented by using a plurality of models, and the DPD coefficient can be obtained by using one of the prior art, which is not limited herein.

Step 14: The ODU performs digital predistortion processing on the first digital baseband signal by using the digital predistortion coefficient to obtain a digital predistortion processed signal for transmission to the PA.

In this embodiment, by performing digital predistortion processing in the ODU, linearization of the transmission link can be achieved without requiring the PA to operate in the linear mode. Therefore, the PA of the embodiment can work not only in the class A working mode belonging to the linear mode, but also in the class B working mode or the class AB working mode, which improves the working efficiency of the PA. Therefore, in this embodiment, the linearization of the link can be realized and the working efficiency of the PA can be improved, and the output performance can be improved.

FIG. 2 is a schematic structural diagram of an ODU according to a first embodiment of the present invention, including a first receiving module

21. A second receiving module 22, a computing module 23 and a digital predistortion module 24. The first receiving module 21 is configured to receive the first analog signal sent by the IDU, and down-convert the first analog signal into a first digital baseband signal; the second receiving module 22 is configured to receive the second analog signal output by the power amplifier, Downconverting the second analog signal to a second digital baseband signal; calculating module 23 and first receiving module

21 is connected to the second receiving module 22, configured to obtain a digital pre-distortion coefficient according to the first digital baseband signal and the second digital baseband signal; and the digital pre-distortion module 24 is configured to adopt the digital pre-distortion coefficient pair A digital baseband signal is subjected to digital predistortion processing to obtain a digital predistortion processed signal for transmission to the power amplifier.

In this embodiment, the linearity of the transmission link can be realized by performing digital predistortion processing in the ODU. The PA of the embodiment can work in the A type working mode, the B type working mode or the AB type working mode to improve the working efficiency of the PA. Since the linearization of the link can be achieved and the PA linearity is not required, it is possible to ensure that the signal is not distorted and that the specific working efficiency of the PA is improved, and the output performance is improved.

In order to better adapt to changes in the environment, the working mode of the PA in this embodiment can also adopt an adaptive adjustment mode.

FIG. 3 is a schematic flowchart of a method according to a second embodiment of the present invention, and FIG. 4 is a schematic structural diagram of an ODU according to a second embodiment of the present invention.

Referring to FIG. 4, the ODU provided in this embodiment includes a first receiving module 41, a second receiving module 42, a calculating module 43, and a digital pre-distortion module 44. For the specific functions of the foregoing modules, refer to the first embodiment.

The embodiment further includes a processing module 45 and a PA 46. The processing module 45 is configured to perform digital-to-analog conversion and modulation frequency shifting on the digital pre-distortion processed signal to obtain a third analog signal. The PA 46 is configured to receive the After the third analog signal is subjected to power amplification processing on the third analog signal, the second analog signal is obtained.

The carrier frequency of the first analog signal may be the intermediate frequency F0, and the first receiving module 41 may include a first digital down converter (DDC) 411, and the first DDC 411 is configured to receive the first simulation sent by the IDU. The signal, and the intermediate frequency F0 is taken as the local oscillation frequency Lol, and the first analog signal is down-converted into the first in-phase digital signal II and the first orthogonal digital signal Q1 by using the intermediate frequency.

The digital predistortion processed signal is a digital predistortion processed in-phase digital signal Ι and a digital predistortion processed orthogonal digital signal Q2'; the processing module 45 includes a first digital to analog converter (Digital Analog Converter) , DAC ) 451, first low pass filter ( Low Pass Filter, LPF) 452, second DAC 453, second LPF 454, IQ modulator 455, and first mixer 456. The first DAC 451 is configured to perform digital-to-analog conversion on the digital pre-distortion processed in-phase digital signal to obtain a first transmit analog signal; the first LPF 452 is configured to perform low-pass filtering on the first transmit analog signal to obtain a first low pass filtered processed signal; a second DAC 453 for performing digital to analog conversion on the digital predistortion processed orthogonal digital signal to obtain a second transmitted analog signal; a second LPF 454 for The second transmit analog signal is low-pass filtered to obtain a second low-pass filtered processed signal; the IQ modulator 455 is configured to directly modulate the signal to the intermediate frequency F0, and the first low pass filter is processed by using the intermediate frequency The post signal and the second low pass filtered signal are modulated into a fourth analog signal having a frequency of the intermediate frequency; a first mixer (Mixer) 456 converts the intermediate frequency to a microwave frequency Lo2, and the Lo2 is used as a microwave. The local oscillator frequency is used to upconvert the fourth analog signal to the third analog signal, and the carrier frequency of the third analog signal is the microwave frequency Lo2.

The second receiving module 42 may include a second mixer 421, a band pass filter (BPF) 422 and a second DDC 423, and the second mixer 421 is configured to receive a second analog signal output by the power amplifier. Specifically, the signal outputted by the PA can be split into two paths by the coupler 47, and sent to the second mixer 421, and the second mixer 421 converts the RF frequency to the intermediate frequency, where Lo2 is used as the local oscillator frequency. The radio frequency converts the second analog signal into a fifth analog signal, and the carrier frequency of the fifth analog signal is the intermediate frequency F0 (here, the same frequency F0 as the transmitting frequency can be selected, and the local oscillator can be shared a frequency source); a band pass filter 422 is configured to perform band pass processing on the fifth analog signal to obtain a band pass filtered analog signal; and a second DDC 423 is configured to directly down convert the intermediate frequency F0. A second in-phase digital signal 12 and a second quadrature digital signal Q2 are obtained.

The embodiment may further include a correction module 48 for pre-distorting the digital The processed signal is subjected to Analog Quadrature Modulation (AQM) and correction processing. The calculation module 43, the digital predistortion module 44, and the correction module 48 may be integrated on a Field Programmable Gate Array (FPGA) 49.

For the connection relationship between the above modules, refer to FIG. 4 . The above F0 and Lol may be specifically 350M.

Referring to FIG. 3, the method provided in this embodiment includes:

Step 301: The first DDC in the ODU receives the first analog signal sent by the IDU, and the carrier frequency of the first analog signal is the intermediate frequency F0.

Step 302: The first DDC in the ODU uses the intermediate frequency F0 as a local oscillator frequency to downconvert the first analog signal into a first in-phase digital signal II and a first quadrature digital signal Q1.

Step 303: The digital predistortion module in the ODU performs digital predistortion processing on the first inphase digital signal II and the first quadrature digital signal Q1 to obtain a digital predistortion processed in-phase digital signal II' and digital predistortion. The processed quadrature digital signal Q1'.

Step 304: The first DAC in the ODU performs digital-to-analog conversion on Ι to obtain a digital-to-analog converted signal.

Step 305: The first LPF in the ODU performs low-pass filtering on the digital-to-analog converted signal to obtain a low-pass filtered signal.

Step 306: The second DAC in the ODU performs digital-to-analog conversion on Q1' to obtain another digital-to-analog converted signal.

Step 307: The second LPF in the ODU performs low-pass filtering on the other digital-to-analog converted signal to obtain another low-pass filtered signal.

Steps 304-305 and steps 306-307 have no timing constraint relationship. Step 308: The modulator in the ODU uses the intermediate frequency F0 as the local oscillator frequency of the modulator, and modulates the two analog signals obtained in steps 305 and 307 into a fourth analog signal whose carrier frequency is the intermediate frequency.

Step 309: The first mixer in the ODU converts the fourth analog signal into a third analog signal by using the microwave frequency Lo2 as a local oscillator frequency, and the carrier frequency of the third analog signal is the microwave frequency Lo2. .

Step 310: The first mixer sends the third analog signal to the PA in the ODU.

Step 311: The PA performs power amplification processing on the third analog signal to obtain a second analog signal.

Step 312: The coupler in the ODU divides the second analog signal into two paths, one is sent to the duplexer, and then sent to the microwave antenna through the duplexer; the other is fed back to the second mixer in the ODU.

Step 313: The second mixer down-converts the second analog signal to a fifth analog signal by using the microwave frequency Lo2 as a local oscillator frequency, and a carrier frequency of the fifth analog signal is equal to the intermediate frequency F0.

Step 314: The BPF in the ODU performs band-pass processing on the fifth analog signal to obtain an analog signal processed by the band pass filter.

Step 315: The second DDC uses the intermediate frequency F0 as a local oscillator frequency, and down-converts the band-pass filtered analog signal into a second in-phase digital signal 12 and a second orthogonal digital signal Q2.

Step 316: The calculation module in the ODU obtains a digital pre-distortion coefficient according to the first digital baseband signal (11, Q1) and the second digital baseband signal (12, Q2).

Step 317: The digital predistortion module in the ODU performs digital predistortion processing on the first digital baseband signal by using the digital predistortion coefficient to obtain a digital predistortion processed signal.

Step 318: The correction module in the ODU performs amplitude on the digital predistortion processed signal. Quadrature modulation (AQM) and correction processing yield updated II' and Q1'. Of course, it can be understood that the correction processing can also be performed first, and then the digital pre-distortion processing is performed. Thereafter, steps 304-318 may be repeatedly performed to form a continuous closed-loop DPD, and adaptive processing may be implemented to adapt to changes in the environment. In this embodiment, the digital pre-distortion processing in the ODU can realize the linearization of the transmission link without requiring the PA to work in the linear mode. The PA of this embodiment can work in the B-type working mode or the AB-type working mode. Next, (or you can bias the class A power amplifier to class AB) to improve the efficiency of the PA and save energy. Moreover, in this embodiment, a closed-loop DPD can be formed through the above cycle, and the closed-loop DPD has a larger and more stable benefit than the open-loop DPD or the static DPD, and can be adaptively adjusted according to different output powers, thereby reducing The requirements for production commissioning, improve the straight-through rate and reduce the impact of the environment on the PA. Therefore, this embodiment can ensure the performance of the system and improve the competitiveness of the product. It will be understood by those skilled in the art that all or part of the steps of implementing the above method embodiments may be performed by hardware related to the program instructions. The descriptions of "first", "second" and the like in the embodiments of the present invention are only for making the description clearer, and do not indicate the advantages and disadvantages of the scheme.

It should be noted that the above embodiments are only intended to illustrate the technical solutions of the present invention and are not to be construed as limiting the embodiments of the present invention. The technical solutions of the present invention may be modified or equivalently substituted, and the modified technical solutions may not deviate from the spirit and scope of the technical solutions of the present invention.

Claims

Rights request

A method for improving output performance of an outdoor unit, comprising:

The outdoor unit receives the first analog signal sent by the indoor unit, and down converts the first analog signal into a first digital baseband signal;

2. The method according to claim 1, further comprising:

Performing digital-to-analog conversion and modulation frequency shifting on the digital pre-distortion processed signal to obtain a third analog signal;

Transmitting the third analog signal to the power amplifier;

After the power amplification process is performed on the third analog signal by the power amplifier, the second analog signal is obtained.

3. A method according to claim 1 or 2, characterized in that

The carrier frequency of the first analog signal is an intermediate frequency;

The downconverting the first analog signal to the first digital baseband signal comprises:

Using the intermediate frequency as the first digital downconverted local oscillator frequency, the first digital downconversion is used to downconvert the first analog signal to a first inphase digital signal and a first quadrature digital signal.

4. A method according to any one of claims 1-3, characterized in that

The digital predistortion processed signal is an in-phase digital signal and number after digital predistortion processing Orthogonal digital signal after word predistortion processing;

After the digital pre-distortion processed signal is subjected to digital-to-analog conversion and modulation frequency shift, the third analog signal is obtained:

And performing the digital-to-analog conversion and the low-pass filtering on the digital pre-distortion processed in-phase digital signal and the digital pre-distortion processed orthogonal digital signal respectively to obtain two analog signals;

Using the intermediate frequency as the local oscillator frequency of the modulator, the modulator is used to modulate the two analog signals into a fourth analog signal having a frequency of the intermediate frequency;

Using the microwave frequency as the local oscillator frequency of the first mixer, the fourth analog signal is upconverted to the third analog signal by using the first mixer, and the carrier frequency of the third analog signal is The microwave frequency is described.

5. A method according to any one of claims 1-4, characterized in that

The downconverting the second analog signal to the second digital baseband signal comprises:

Using the microwave frequency as the local oscillator frequency of the second mixer, the second analog signal is down-converted to a fifth analog signal by using the second mixer, and the carrier frequency of the fifth analog signal is an intermediate frequency;

Performing band pass processing on the fifth analog signal by using a band pass filter to obtain an analog signal after band pass filtering;

Using the intermediate frequency as the second digital down-converted local oscillator frequency, and down-converting the band-pass filtered analog signal to the second in-phase digital signal and the second orthogonal digital signal by using the second digital down-conversion .

The method according to any one of claims 1 to 5, further comprising: performing analog quadrature modulation and correction processing on the digital predistortion processed signal.

7. An outdoor unit, comprising: a first receiving module, configured to receive a first analog signal sent by the indoor unit, and down-convert the first analog signal into a first digital baseband signal;

The outdoor unit according to claim 7, further comprising:

a processing module, configured to perform digital-to-analog conversion and modulation and frequency shifting on the digital pre-distortion processed signal to obtain a third analog signal;

And a power amplifier, configured to receive the third analog signal, and perform power amplification processing on the third analog signal to obtain the second analog signal.

9. An outdoor unit according to claim 7 or 8, characterized in that

The carrier frequency of the first analog signal is an intermediate frequency;

The first receiving module includes:

a first digital down-conversion, configured to receive a first analog signal sent by the indoor unit, and use the intermediate frequency as a demodulation frequency, and down-convert the first analog signal into a first in-phase digital signal and the first frequency by using the intermediate frequency An orthogonal digital signal.

The outdoor unit according to any one of claims 7-9, wherein the digital predistortion processed signal is a digital predistortion processed in-phase digital signal and a digital predistortion processed orthogonal number signal; The processing module includes:

a first digital-to-analog converter, configured to perform digital-to-analog conversion on the digital pre-distortion processed in-phase digital signal to obtain a first transmitted analog signal;

a first low pass filter, configured to perform low pass filtering on the first transmit analog signal to obtain a first low pass filtered processed signal;

a second digital-to-analog converter, configured to perform digital-to-analog conversion on the digital pre-distortion processed orthogonal digital signal to obtain a second transmit analog signal;

a second low pass filter, configured to perform low pass filtering on the second transmit analog signal to obtain a second low pass filter processed signal;

An IQ modulator, configured to use the intermediate frequency as a local frequency, and modulate the first low pass filtered signal and the second low pass filtered signal into a frequency of the intermediate frequency using the intermediate frequency Fourth analog signal;

a first mixer, configured to use a microwave frequency as a local oscillator frequency, and use the microwave frequency to upconvert the fourth analog signal to the third analog signal, where a carrier frequency of the third analog signal is Microwave frequency.

The outdoor unit according to any one of claims 7 to 10, wherein the outdoor unit further comprises: a coupler, configured to divide the second analog signal output by the power amplifier into two paths, one way Used to send to the opposite end, and the other is used to send to the second mixer;

The second receiving module includes:

a second mixer, configured to receive a second analog signal of another path outputted by the combiner, using a microwave frequency as a local oscillator frequency, and down-converting the second analog signal to a fifth simulation by using the microwave frequency a signal, the carrier frequency of the fifth analog signal is an intermediate frequency;

a band pass filter, configured to perform band pass processing on the fifth analog signal to obtain a band pass filter a second analog down signal, configured to use the intermediate frequency as a local oscillator frequency, and down-convert the analog signal processed by the band pass filter into a second in-phase digital signal and Two orthogonal digital signals.

The outdoor unit according to any one of claims 7-11, further comprising: a correction module, configured to perform analog quadrature modulation and correction processing on the digital predistortion processed signal.

13. The outdoor unit of claim 12, wherein

The computing module, the digital predistortion module, and the correction module are integrated on a field programmable gate array.