EP2545644A1 - A decomposition transmitting system and method for improving efficiency and linearity - Google Patents

A decomposition transmitting system and method for improving efficiency and linearity

Info

Publication number
EP2545644A1
EP2545644A1 EP10847574A EP10847574A EP2545644A1 EP 2545644 A1 EP2545644 A1 EP 2545644A1 EP 10847574 A EP10847574 A EP 10847574A EP 10847574 A EP10847574 A EP 10847574A EP 2545644 A1 EP2545644 A1 EP 2545644A1
Authority
EP
European Patent Office
Prior art keywords
block
signal
digital processing
transmitting system
amplifying
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10847574A
Other languages
German (de)
French (fr)
Other versions
EP2545644A4 (en
Inventor
Paul Gareth Lloyd
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ZTE Corp
ZTE Wistron Telecom AB
Original Assignee
ZTE Corp
ZTE Wistron Telecom AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ZTE Corp, ZTE Wistron Telecom AB filed Critical ZTE Corp
Publication of EP2545644A1 publication Critical patent/EP2545644A1/en
Publication of EP2545644A4 publication Critical patent/EP2545644A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H03F1/0205—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers
    • H03F1/0288—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers using a main and one or several auxiliary peaking amplifiers whereby the load is connected to the main amplifier using an impedance inverter, e.g. Doherty amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/30—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/32—Modifications of amplifiers to reduce non-linear distortion
    • H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
    • H03F1/3247—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits using feedback acting on predistortion circuits
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/189—High-frequency amplifiers, e.g. radio frequency amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
    • H03F3/211—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only using a combination of several amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F3/24—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
    • H03F3/245—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages with semiconductor devices only
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2201/00—Indexing scheme relating to details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements covered by H03F1/00
    • H03F2201/32—Indexing scheme relating to modifications of amplifiers to reduce non-linear distortion
    • H03F2201/3209—Indexing scheme relating to modifications of amplifiers to reduce non-linear distortion the amplifier comprising means for compensating memory effects
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2201/00—Indexing scheme relating to details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements covered by H03F1/00
    • H03F2201/32—Indexing scheme relating to modifications of amplifiers to reduce non-linear distortion
    • H03F2201/3212—Using a control circuit to adjust amplitude and phase of a signal in a signal path
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2201/00—Indexing scheme relating to details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements covered by H03F1/00
    • H03F2201/32—Indexing scheme relating to modifications of amplifiers to reduce non-linear distortion
    • H03F2201/3224—Predistortion being done for compensating memory effects
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2201/00—Indexing scheme relating to details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements covered by H03F1/00
    • H03F2201/32—Indexing scheme relating to modifications of amplifiers to reduce non-linear distortion
    • H03F2201/3233—Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/20—Indexing scheme relating to power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F2203/21—Indexing scheme relating to power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
    • H03F2203/211—Indexing scheme relating to power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only using a combination of several amplifiers
    • H03F2203/21106—An input signal being distributed in parallel over the inputs of a plurality of power amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/20—Indexing scheme relating to power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F2203/21—Indexing scheme relating to power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
    • H03F2203/211—Indexing scheme relating to power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only using a combination of several amplifiers
    • H03F2203/21142—Output signals of a plurality of power amplifiers are parallel combined to a common output

Definitions

  • the present invention relates to communication system and especially to a transmitting system in the communication system.
  • Transmitting system in the communication system comprises a number of different subsystems.
  • the performance of the transmitting system can be measured according to various metrics, including efficiency and linearity.
  • efficiency and linearity Usually, the primary performance of the transmitting system is limited by a power amplifier.
  • Linearity requirements for the transmitting system are usually defined in the specification of the transmitting system.
  • Efficiency requirements for the transmitting system are usually, and increasingly, influenced by the market.
  • the goal for improving the performance of the transmitting system is to achieve the minimum required signal quality (linearity) with the minimum wasted power (efficiency).
  • FIG. 1 A typical architecture for improving the efficiency of the transmitting system is showed in figure 1.
  • This architecture is called "fixed RF input split Doherty-type amplifier with pre-distortion", in which the system is linearized by digital pre-distortion (or, DPD).
  • efficiency-improving techniques e.g. Doherty
  • Doherty require amplifiers to output amplified signals to a combiner with the characteristic required by the combiner.
  • These characteristic required by the combiner are well defined in theory, but in practice, they are difficult to produce and maintain.
  • the system is used to realize amplifiers (e.g. Doherty amplifier) that are not able to auto-generate the complex characteristic required by the combiner.
  • amplifiers e.g. Doherty amplifier
  • the present invention provides a decomposition transmitting system and method, which can simultaneously improve efficiency and linearity of the transmitting system, as well as improve featurebility and stability of the transmitting system, compared with the prior art.
  • efficiency is the ratio of the useful signal level generated by the transmitting system to the signal level input into the transmitting system
  • linearity is generally the ratio of the useful signal level to unwanted or distorted signal level
  • featurebility means the suitability for manufacturing the transmitting system, while meeting the specification at lower or lowest cost
  • stability means the capability to maintain specified performance of the transmitting system throughout the lifetime of the product and/or in various operating conditions of the product.
  • An object of the present invention is to provide a decomposition transmitting system comprising a data source block, a digital processing block, an amplifying block, a combining block, and an outputting
  • the digital processing block comprises: one or more digital processing sub-blocks, each digital processing sub-block being configured to perform a mathematical transformation on its input signal, to decompose a signal from the data source block into a plurality of transformed signals, and each of the plurality of transformed signals being output to a corresponding input of the amplifying block, whereby the efficiency and linearity of the decomposition transmitting system are improved.
  • the mathematical transformation is designed to realize desired characteristics of amplifiers in the amplifying block.
  • some or all of the one or more digital processing sub-blocks in the digital processing block perform the mathematical transformation by using a feedback signal from the outputting block/monitor.
  • the amplifying block and the combining block are designed for Doherty type operation.
  • the plurality of transformed signals comprise the signal from the data source block.
  • the amplifying block comprises one or more splitters, each splitter is configured to split one of the plurality of transformed signals from the digital processing block.
  • one of the one or more splitters is configured to split the signal from the data source block into more than one split signals and output one of the split signals to a main amplifier in the amplifying block and the other split signai(s) to corresponding peaking amplifier(s) in the amplifying block.
  • each of the one or more splitters are configured to split one of the plurality of transformed signals except the signal from the data source block into more than one split signals and output the split signals to corresponding peaking amplifiers in the amplifying block.
  • one of the one or more digital processing sub-blocks is a digital pre-distortion sub-block
  • the digital pre-distortion sub-block is configured to receive the signal from the data source block and output a digital pre-distorted signal to other digital processing sub-blocks and the amplifying block.
  • the amplifying block comprises one or more splitters, each splitter is configured to split one of the plurality of transformed signals from the digital processing block.
  • one of the one or more splitters is configured to split the digital pre-distorted signal from the digital pre-distortion sub-block into more than one split signals and output one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
  • each of the one or more splitters are configured to split one of the plurality of transformed signals except the digital pre-distorted signal from the digital pre-distortion sub-block into more than one split signals and output the split signals to corresponding peaking amplifiers in the amplifying block.
  • An object of the present invention is to provide a decomposition transmitting method, the method comprises: performing a mathematical transformation on an input signal of each digital processing sub-block of a digital processing block in a transmitting system, to decompose a signal from a data source block in the transmitting system into a plurality of transformed signals; outputting each of the plurality of transformed signals to a
  • the mathematical transformation is designed to realize desired characteristics of amplifiers in the amplifying block.
  • the step of performing a mathematical transformation further comprises: performing the mathematical transformation by using a feedback signal from an outputting block/monitor in the transmitting system.
  • the method further comprises: designing the amplifying block and a combining block in the transmitting system for Doherty type operation.
  • the plurality of transformed signals comprise the signal from the data source block.
  • the method further comprises: splitting one or more of the plurality of transformed signals from the digital processing block.
  • the method further comprises: splitting the signal from the data source block into more than one split signals; and outputting one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
  • the method further comprises: splitting respectively one or more of the plurality of transformed signals except the signal from the data source block into more than one split signals; and outputting the split signals to corresponding peaking amplifiers in the amplifying block.
  • one of the digital processing sub-blocks is a digital pre-distortion sub-block
  • the method further comprises: pre-distorting the signal from the data source block into a digital pre-distorted signal; and outputting the digital pre-distorted signal to other digital processing sub-blocks and the amplifying block.
  • the method further comprises: splitting one or more of the plurality of transformed signals from the digital processing block.
  • the method further comprises: splitting the digital pre-distorted signal from the digital pre- distortion sub-block into more than one split signals; and outputting one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
  • the method further comprises: splitting respectively one or more of the plurality of transformed signals except the digital pre-distorted signal from the digital pre- distortion sub-block into more than one split signals; and outputting the split signals to corresponding peaking amplifiers in the amplifying block.
  • Figure 1 shows a system of the prior art which comprises a digital pre- distortion sub-block
  • Figure 2 shows a decomposition transmitting system for improve efficiency and linearity of the system
  • Figure 3(a) shows a "3-way Doherty-type amplifier with two channel inputs" decomposition transmitting system with pre-distortion function according to one embodiment of the present invention
  • Figure 3(b) shows a "3-way Doherty-type amplifier with two channel inputs" decomposition transmitting system with pre-distortion function according to another embodiment of the present invention
  • Figure 4 shows a "2-way Doherty-type amplifier with two channel inputs" decomposition transmitting system with pre-distortion function according to one embodiment of the present invention
  • Figure 5 shows a flow chart with which the embodiments of figure 3(a), 3(b) and 4 operate;
  • Figure 6(a) shows a "3-way Doherty-type Amplifier with two channel inputs" decomposition transmitting system without pre-distortion function according to one embodiment of the present invention
  • Figure 6(b) shows a "3-way Doherty-type Amplifier with two channel inputs" decomposition transmitting system without pre-distortion function according to another embodiment of the present invention
  • Figure 7 shows a "2-way Doherty-type amplifier with two channel inputs" decomposition transmitting system without pre-distortion function according to one embodiment of the present invention
  • Figure 8 shows a flow chart with which the embodiments of figure 6(a), 6(b) and 7 operate.
  • the improved transmitting system can solve the intrinsic problems of the prior art by introducing a concept of "decomposition".
  • the improved transmitting system of the present invention can be called a decomposition transmitting system.
  • the reference output from the data source block or (optional) digital pre-distortion sub-block is copied into two or more paths, which in turn are modified independently and differently in the digital processing block.
  • the individual outputs from the digital processing block (which have of course been converted into analog form and undergone any necessary frequency conversion, as per the prior art), passed to the amplifying block and combining block, usually exhibit little correlation with the desired output.
  • one or more digital processing sub-blocks are included in the digital processing block. It is noted that one of the one or more digital processing sub-blocks may be a digital pre-distortion sub-block as in the prior art.
  • the function of the digital pre-distortion sub-block is the same with that in the prior art.
  • the digital pre-distortion sub-block can ensure that the whole transmitting system is linear.
  • the digital pre-distortion sub-block has two inputs, that is, a signal from the data source block and a signal fed back from the outputting block/monitor. The digital pre-distortion sub-block will attempt to correlate these two inputs.
  • the overall characteristic of the amplifier can be modified by other digital processing sub-blocks except the digital pre-distortion sub-block.
  • the extent, to which the characteristic of the amplifier is modified depends on the algorithm used, which will be discussed in detail.
  • the characteristic of the amplifier might be modified by the other digital processing sub-blocks to increase the efficiency of the amplifier.
  • the resultant, modified amplifier characteristic is automatically and subsequently linearized by the digital pre-distortion sub-block.
  • the other digital processing sub-blocks might be used to reduce the level of distortion from the amplifier, that is, improve the linearity together with the digital pre-distortion sub-block, in still another example, the other digital processing sub-blocks might actually add distortion to the amplifier, but in such a way that
  • the digital pre-distortion sub-block linearization is more easily achieved by the digital pre-distortion sub-block.
  • the other digital processing sub-blocks might actually be used to completely linearize the system by itself, thus removing the need for the digital pre-distortion sub-block.
  • the function of the digital processing sub- blocks depends on actual application needs.
  • the efficiency and linearity of the transmitting system can be improved by the one or more digital processing sub-blocks with or without the digital pre-distortion sub-block.
  • the specific embodiments for improving the efficiency and linearity of the transmitting system which comply with the principle of the present invention will be discussed in detail below.
  • the decomposition transmitting system sequentially comprises a data source block, a digital processing block, an amplifying block, a
  • the reference signal is output from the data source block.
  • This reference signal enters the digital processing block where the signal is processed to produce a number of outputs.
  • These outputs are passed to an amplifying block with two or more independent amplifying channels.
  • the signals are subsequently passed to a combining block which combines the signals output from the amplifying block, so as to reconstruct an amplified version of the reference input, with a high signal level suitable for transmission.
  • the data source block is the source of the reference signal for the system.
  • the digital processing block receives the reference signal from the data source block, and optionally, receives feedback signal from the outputting block/monitor (which itself might be frequency shifted, but anyway is digitized and processed, as known to those skilled in the art).
  • the feedback signal from the outputting block/monitor may be used by none, some or all of the digital processing sub-blocks in the digital processing block.
  • the feedback signal from the outputting block/monitor can be used by the training
  • the reference signal is processed in the digital processing block, and the processed signal is output to the amplifying block.
  • the digital processing block comprises one or more digital processing sub-blocks. Each digital processing sub-block may perform a fixed or adaptable transformation on the signal input to it. Specifically, each digital processing sub-block transforms its own input signal by applying a mathematical transformation.
  • transformation applied might be adapted according to the feedback signal from the outputting block/monitor. The transformation will be discussed in detail with reference to figures 5 and 8.
  • the first input digital processing block which receives the signal from the data source block, may be a digital pre- distortion (DPD) sub-block, which usually performs a linearization function.
  • DPD digital pre- distortion
  • signals are passed between the digital processing sub-blocks according to the connection relationship between the digital processing sub-blocks.
  • the digital processing sub-blocks can be connected in various manners according to actual needs.
  • the digital processing sub-blocks may be, for example, linear or non-linear, time- dependent or time-independent, and implemented as mathematical formula or look up tables (LUTs) or other means, which are well known to those skilled in the art.
  • the amplifying block may contain one or more "linear input splitter" sub-blocks, which will be discussed hereinafter. There are two or more interfaces between the digital processing block and the amplifying block. There are two or more interfaces between the amplifying block and the combining block.
  • the combining block combines the signals from the amplifying block according to the design of the combining block.
  • the combining block has at least two inputs from the amplifier block and one output to the output/monitor.
  • the combining block is Doherty type.
  • the Doherty type combining block demands particular signals from the amplifying block.
  • Other types of combining block will place different demands on signals from the amplifying block.
  • the outputting block/monitor is a subsystem for further transmitting the amplified signal.
  • the outputting block/monitor can be used to take a sample of output signal back to the digital processing block, and the signal fed back to the digital processing block is distributed to one or more sub-blocks of digital processing blocks for adaptation.
  • the outputting block/monitor can also be used by the system for other monitoring purposes, before passing the signal into the transmission medium.
  • m is equal to 1 or equal to n (n>1). While in the present invention, in certain embodiments, m is larger than 1 and m may be equal to or less than n. Ideally, m is equal to 2 for minimum complexity.
  • a person skill in the art can easily construct a "n-way Doherty-type amplifier with m channel inputs (m ⁇ n)" decomposition transmitting system. In fact, efficiency increases as n increases, but in a rapidly diminishing manner. In some applications, higher values of n are advantageous; for example, where very high output signal levels are required from the transmitter.
  • a "3-way Doherty-type amplifier with two channel inputs" decomposition transmitting system with pre-distortion function is showed.
  • the digital pre-distortion sub-block performs a pre- distortion on the reference signal, which is common to all channels in the amplifying block.
  • the digital processing sub-block performs a transformation on the pre-distorted signal, so as to improve the performances of the decomposition transmitting system, for example, linearity, linearizability, efficiency or combination of these or other performances.
  • embodiments have corresponding advantages, such as improved efficiency, linearity, featurebility and stability.
  • the output from the digital pre-distortion sub-block is input into a linear input splitter, the output from which is input into a first peaking amplifier and a main amplifier; the output from the digital processing sub-block is input into a second peaking amplifier.
  • the output from the digital pre-distortion sub-block is input into a main amplifier; the output from the digital processing sub-block is input into a linear input splitter, the output from which is input into a first peaking amplifier and a second peaking amplifier.
  • the output from the digital pre-distortion sub-block is also input into the digital processing sub- block.
  • Figures 3(a) and 3(b) are the same in that there being two different outputs from the digital processing block compared with the prior art.
  • the feedback signal from the outputting block/monitor is fed back to the digital processing block. In this way, the signal from the digital processing sub-block is fed back to the digital pre-distortion sub-block.
  • a "2-way Doherty-type amplifier with two channel inputs" system with pre- distortion function is showed.
  • the digital processing block is the same with that in figures 3(a) and 3(b).
  • figures 3(a) and 3(b) there is no linear input splitter in the amplifying block. Therefore, the number of the inputs to the amplifying block equals to the number of the outputs to the combining block.
  • the signal output from the digital pre-distortion sub-block is also input into the digital processing sub-block.
  • the combining block and the outputting block/monitor in figure 4 are the same with those in figures 3(a) and 3(b).
  • a digital processing sub-block which is unique to one channel in the amplifying block, applies a transformation to the pre-distorted signal, so as to improve the performances of the decomposition transmitting system, for example, linearity, linearizability, efficiency or combination of these or other
  • This embodiment has corresponding advantages, such as improved efficiency, linearity, featurebility and stability, as discussed before.
  • the digital processing sub-blocks in the digital processing block implement a procedure showed by the flow chart of figure 5.
  • Figure 5 describes a flow chart that the digital processing sub-blocks in the digital processing block of figure 3(a), 3(b) and 4 might operate with.
  • step 501 the procedure starts, then the procedure proceeds to step
  • step 502 select a training frequency and target_gain, which may be a scalar or a vector, a relative value or an absolute value. Then set the signal output from the digital pre-distortion sub-block to a low level, and set the multiplier (which may be a scalar or a vector) of another digital processing sub-block to 0. And monitor the signal output from the outputting
  • a maximum value for the small signal "gain" may be
  • the target_gain is usually decided by a designer when designing the system. The designer decides the target_gain according to the desired result and the type and characteristic (which will never be ideal) of the amplifier. Then the procedure proceeds to step 503.
  • step 503 increase the level of the signal output from the digital pre- distortion sub-block by a fixed amount or ratio, and monitor the signal output from the outputting block/monitor. Then calculate a gain which is a ratio of the level of the signal output from the outputting block/monitor to the level of the signal output from the pre-distortion sub-block. Then the procedure proceeds to step 504.
  • the procedure assesses whether the absolute value of the calculated gain is less than the absolute value of target_cjain. If the absolute value of the calculated gain is less than the absolute value of target_gain, then the procedure proceeds to step 505; otherwise, the procedure returns to step 503.
  • step 505 increase the level of the signal output from the digital pre- distortion sub-block by a fixed amount or ratio. Then the procedure proceeds to step 506.
  • step 506 adjust/search the multiplier of the digital processing sub- block. Then monitor the signal output from the outputting block/monitor and calculate the gain. Then the procedure proceeds to step 507.
  • the procedure decides whether the calculated gain is equal to target_gain. If the gain is equal to target_gain, then the procedure proceeds to step 508; otherwise, the procedure proceeds to step 510.
  • the procedure decides whether the desired appropriate multiplier of the digital processing sub-block has been found. It should be noted that the desired appropriate multiplier is predetermined according to the desired result and the characteristic the amplifier. In one example, the desired appropriate multiplier is chosen to have the lowest magnitude. In another example, the desired appropriate multiplier is chosen to give the desired output signal level with the highest efficiency. If the appropriate multiplier of the digital processing sub-block has been found, then the procedure proceeds to step 509; otherwise, the procedure returns to step 506.
  • step 509 store e.g. the signal level output from the digital pre- distortion sub-block, the training frequency etc. (the independent variables) and the corresponding multiplier of the digital processing sub-block (the dependent variable) in a look up table, for example. Then the procedure returns to step 505.
  • the procedure decides whether maximum output level of any of the sub-blocks in the digital processing block or the amplifying block has been reached. Typically, when no more output level can be extracted, i.e. the decomposition transmitting system has reached its "saturated output level", the maximum output level is reached. If the maximum output level of any of the sub-blocks in the digital processing block and the amplifying block has been reached, then the procedure proceeds to step 511 ; otherwise, the procedure returns to step 506.
  • the procedure decides whether training has completed. The decision depends on the characteristics of the actual system. In most cases, training would take place over a number of discrete frequencies and perhaps also temperature. A first frequency and/or temperature are
  • step 512 If training has completed, then the procedure ends at step 512; otherwise, the procedure returns to step 502.
  • the distortion exhibited by the amplifier may have different effects on the different signal being transmitted.
  • An amplifier which exhibits some distortion may not actually distort a signal being transmitted. For example, if the signal being transmitted has only large signal levels, and the amplifier only exhibits distortion on small signal, then the large signal will not experience any distortion; and vice versa.
  • AM-AM means “amplitude modulation to amplitude modulation conversion”
  • AM-PM means “amplitude modulation to phase modulation conversion”.
  • Table 1 target_gain is a constant and a scalar
  • pre-distortion & pre-distortion & signal transformation performed by transformation other digital processing sub- performed by other biock(s) digital processing sub-block(s) target_gain is a constant and a vector
  • the decomposition transmitting system will have both higher efficiency and better linearity than the transmitting system in the prior art. This is primarily because the Doherty (prior art) amplifiers in the prior art system are not able to reproduce (i.e. output to the combiner) the precise signals required to operate as a true Doherty amplifier. With the invention, the precise output signals from the amplifiers, required for Doherty operation, can be created in an arbitrarily accurate manner.
  • the digital processing sub-blocks do not comprise a digital pre-distortion sub-block.
  • a "3-way Doherty-type Amplifier with two channel inputs" decomposition transmitting system without digital pre-distortion function is showed.
  • the amplifying block in figure 6(a) is the same with that in figure 3(a)
  • the amplifying block in figure 6(b) is the same with that in figure 3(b).
  • the digital processing sub-block implements a procedure showed by the flow chart of figure 8.
  • Figure 8 describes a flow chart the digital processing sub-blocks in the digital processing block of figure 6(a), 6(b) and 7 operate with. Variations to the flow chart are obvious to those skilled in the art. Alternatively, other procedures for realize the same purpose can be used. The procedure is as follows.
  • step 801 the procedure starts, then the procedure proceeds to step
  • step 802 select a training frequency and target gain, which may be a scalar or a vector, and an absolute value. Then set the signal output from the data source block to a specific level, and set the multiplier (which may be a scalar or vector) of the digital processing sub-block to 0.
  • the target_gain should usually be set to a lower magnitude value.
  • the target_gain is usually decided by a designer when designing the system. The designer decides the target_gain according to the desired result and the type and characteristic (which will never be ideal) of the amplifier. Then the procedure proceeds to step 803.
  • step 803 increase the level of the signal output from the data source block by a fixed amount or ratio, and monitor the signal output from the outputting block/monitor. Then calculate a gain which is a ratio of the level of the signal output from the outputting block/monitor to the level of the signal output from the data source block. Then the procedure proceeds to step 804.
  • step 804 adjust/search the multiplier of the digital processing sub- block. Then monitor the signal output from the data source block and calculate the gain. Then the procedure proceeds to step 807.
  • the procedure decides whether the calculated gain is equal to target_gain. If the gain is equal to target__gain, then the procedure proceeds to step 806; otherwise, the procedure proceeds to step 808.
  • the procedure decides whether the desired appropriate multiplier of the digital processing sub-block has been found.
  • the desired appropriate multiplier is chosen to have the lowest magnitude.
  • the desired appropriate multiplier is chosen to give the desired output signal level with the highest efficiency. If the appropriate multiplier of the digital processing sub-block has been found, then the procedure proceeds to step 807; otherwise, the procedure returns to step 804.
  • step 807 store e.g. the signal level output from the data source block, the training frequency etc. (the independent variables) and the corresponding multiplier of the digital processing sub-block (the dependent variable) in a look up table, for example. Then the procedure returns to step 803.
  • the procedure decides whether maximum output level of any of the sub-blocks in the digital processing block and the amplifying block has been reached. Typically, when no more output level can be extracted, i.e. the decomposition transmitting system has reached its "saturated output level", the maximum output level is reached. If the maximum output level of any of the sub-blocks in the digital processing block and the amplifying block has been reached, then the procedure proceeds to step 809; otherwise, the procedure returns to step 804.
  • the procedure decides whether training has completed. The decision depends on the characteristics of the actual system. In most cases, training would take place over a number of discrete frequencies and perhaps also temperature. A first frequency and/or temperature are
  • step 810 If training has completed, then the procedure ends at step 810; otherwise, the procedure returns to step 802.
  • the digital processing sub-block will simultaneously improve the overall efficiency and linearity of the decomposition transmitting system and reduce the complexity of the digital pre-distortion sub-block.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Amplifiers (AREA)

Abstract

The present invention discloses a decomposition transmitting system comprising a data source block, a digital processing block, an amplifying block, a combining block, and an outputting block/monitor, the digital processing block comprising: one or more digital processing sub-blocks, each digital processing sub-block being configured to perform a mathematical transformation on its input signal, to decompose a signal from the data source block into a plurality of transformed signals, and each of the plurality of transformed signals being output to a corresponding input of the amplifying block, whereby the efficiency and linearity of the decomposition transmitting system are improved. A decomposition transmitting method is also disclosed.

Description

A decomposition transmitting system and method for improving efficiency and linearity
Technical Field
The present invention relates to communication system and especially to a transmitting system in the communication system.
Background
Transmitting system in the communication system comprises a number of different subsystems. The performance of the transmitting system can be measured according to various metrics, including efficiency and linearity. Usually, the primary performance of the transmitting system is limited by a power amplifier.
Linearity requirements for the transmitting system are usually defined in the specification of the transmitting system. Efficiency requirements for the transmitting system are usually, and increasingly, influenced by the market. The goal for improving the performance of the transmitting system is to achieve the minimum required signal quality (linearity) with the minimum wasted power (efficiency).
To this end, a number of architectures for improving the efficiency of the transmitting system have been proposed (e.g. Doherty architecture), these architectures typically reduce the wasted energy/power under some operation conditions.
A typical architecture for improving the efficiency of the transmitting system is showed in figure 1. This architecture is called "fixed RF input split Doherty-type amplifier with pre-distortion", in which the system is linearized by digital pre-distortion (or, DPD).
Usually, efficiency-improving techniques (e.g. Doherty) require amplifiers to output amplified signals to a combiner with the characteristic required by the combiner. These characteristic required by the combiner are well defined in theory, but in practice, they are difficult to produce and maintain.
As a result, there are two intrinsic problems with the prior art. First, the system is used to realize amplifiers (e.g. Doherty amplifier) that are not able to auto-generate the complex characteristic required by the combiner.
Second, there exist natural variations in the manufacturing processes, causing further performance degradations, in the industrial environment.
For example, in the case of Doherty architecture, there is a need for the Doherty architecture to realize a non-continuously differentiable function which has a "hockey stick" or "dog leg" characteristic. In the prior art, a very coarse approximation to this required characteristic was achieved by biasing "peak" amplifier(s) in class C (or more practically, deep class AB) mode, which further besets the system with problems (e.g. degraded amplifier reliability or in the case of class C, reducing output level as conduction angle decreases).
Therefore, there is a need for the amplifiers in the transmitting system to output signals with desired characteristic required by the combiner^ so as to improve the efficiency and linearity of the transmitting system. Disclosure of Invention
The present invention provides a decomposition transmitting system and method, which can simultaneously improve efficiency and linearity of the transmitting system, as well as improve industriability and stability of the transmitting system, compared with the prior art. As it is known to a person skilled in the art, efficiency is the ratio of the useful signal level generated by the transmitting system to the signal level input into the transmitting system; linearity is generally the ratio of the useful signal level to unwanted or distorted signal level; industriability means the suitability for manufacturing the transmitting system, while meeting the specification at lower or lowest cost; and stability means the capability to maintain specified performance of the transmitting system throughout the lifetime of the product and/or in various operating conditions of the product. An object of the present invention is to provide a decomposition transmitting system comprising a data source block, a digital processing block, an amplifying block, a combining block, and an outputting
block/monitor, the digital processing block comprises: one or more digital processing sub-blocks, each digital processing sub-block being configured to perform a mathematical transformation on its input signal, to decompose a signal from the data source block into a plurality of transformed signals, and each of the plurality of transformed signals being output to a corresponding input of the amplifying block, whereby the efficiency and linearity of the decomposition transmitting system are improved.
In accordance with a certain embodiment of the invention, the mathematical transformation is designed to realize desired characteristics of amplifiers in the amplifying block.
In accordance with a further embodiment of the invention, some or all of the one or more digital processing sub-blocks in the digital processing block perform the mathematical transformation by using a feedback signal from the outputting block/monitor.
In accordance with a further embodiment of the invention, the amplifying block and the combining block are designed for Doherty type operation.
In accordance with a further embodiment of the invention, the plurality of transformed signals comprise the signal from the data source block.
In accordance with a further embodiment of the invention, the amplifying block comprises one or more splitters, each splitter is configured to split one of the plurality of transformed signals from the digital processing block.
In accordance with a further embodiment of the invention, one of the one or more splitters is configured to split the signal from the data source block into more than one split signals and output one of the split signals to a main amplifier in the amplifying block and the other split signai(s) to corresponding peaking amplifier(s) in the amplifying block.
In accordance with a further embodiment of the invention, each of the one or more splitters are configured to split one of the plurality of transformed signals except the signal from the data source block into more than one split signals and output the split signals to corresponding peaking amplifiers in the amplifying block.
In accordance with a further embodiment of the invention, one of the one or more digital processing sub-blocks is a digital pre-distortion sub-block, the digital pre-distortion sub-block is configured to receive the signal from the data source block and output a digital pre-distorted signal to other digital processing sub-blocks and the amplifying block.
In accordance with a further embodiment of the invention, the amplifying block comprises one or more splitters, each splitter is configured to split one of the plurality of transformed signals from the digital processing block.
In accordance with a further embodiment of the invention, one of the one or more splitters is configured to split the digital pre-distorted signal from the digital pre-distortion sub-block into more than one split signals and output one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
In accordance with a further embodiment of the invention, each of the one or more splitters are configured to split one of the plurality of transformed signals except the digital pre-distorted signal from the digital pre-distortion sub-block into more than one split signals and output the split signals to corresponding peaking amplifiers in the amplifying block.
An object of the present invention is to provide a decomposition transmitting method, the method comprises: performing a mathematical transformation on an input signal of each digital processing sub-block of a digital processing block in a transmitting system, to decompose a signal from a data source block in the transmitting system into a plurality of transformed signals; outputting each of the plurality of transformed signals to a
corresponding input of an amplifying block in the transmitting system, whereby the efficiency and linearity of the transmitting system are improved.
In accordance with a certain embodiment of the invention, the mathematical transformation is designed to realize desired characteristics of amplifiers in the amplifying block. In accordance with a further embodiment of the invention, the step of performing a mathematical transformation further comprises: performing the mathematical transformation by using a feedback signal from an outputting block/monitor in the transmitting system.
In accordance with a further embodiment of the invention, the method further comprises: designing the amplifying block and a combining block in the transmitting system for Doherty type operation.
In accordance with a further embodiment of the invention, the plurality of transformed signals comprise the signal from the data source block.
In accordance with a further embodiment of the invention, the method further comprises: splitting one or more of the plurality of transformed signals from the digital processing block.
In accordance with a further embodiment of the invention, the method further comprises: splitting the signal from the data source block into more than one split signals; and outputting one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
In accordance with a further embodiment of the invention, the method further comprises: splitting respectively one or more of the plurality of transformed signals except the signal from the data source block into more than one split signals; and outputting the split signals to corresponding peaking amplifiers in the amplifying block.
In accordance with a further embodiment of the invention, one of the digital processing sub-blocks is a digital pre-distortion sub-block, the method further comprises: pre-distorting the signal from the data source block into a digital pre-distorted signal; and outputting the digital pre-distorted signal to other digital processing sub-blocks and the amplifying block.
In accordance with a further embodiment of the invention, the method further comprises: splitting one or more of the plurality of transformed signals from the digital processing block.
In accordance with a further embodiment of the invention, the method further comprises: splitting the digital pre-distorted signal from the digital pre- distortion sub-block into more than one split signals; and outputting one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
In accordance with a further embodiment of the invention, the method further comprises: splitting respectively one or more of the plurality of transformed signals except the digital pre-distorted signal from the digital pre- distortion sub-block into more than one split signals; and outputting the split signals to corresponding peaking amplifiers in the amplifying block.
Brief Description of the Drawings
Figure 1 shows a system of the prior art which comprises a digital pre- distortion sub-block;
Figure 2 shows a decomposition transmitting system for improve efficiency and linearity of the system;
Figure 3(a) shows a "3-way Doherty-type amplifier with two channel inputs" decomposition transmitting system with pre-distortion function according to one embodiment of the present invention;
Figure 3(b) shows a "3-way Doherty-type amplifier with two channel inputs" decomposition transmitting system with pre-distortion function according to another embodiment of the present invention;
Figure 4 shows a "2-way Doherty-type amplifier with two channel inputs" decomposition transmitting system with pre-distortion function according to one embodiment of the present invention;
Figure 5 shows a flow chart with which the embodiments of figure 3(a), 3(b) and 4 operate;
Figure 6(a) shows a "3-way Doherty-type Amplifier with two channel inputs" decomposition transmitting system without pre-distortion function according to one embodiment of the present invention;
Figure 6(b) shows a "3-way Doherty-type Amplifier with two channel inputs" decomposition transmitting system without pre-distortion function according to another embodiment of the present invention;
Figure 7 shows a "2-way Doherty-type amplifier with two channel inputs" decomposition transmitting system without pre-distortion function according to one embodiment of the present invention; and Figure 8 shows a flow chart with which the embodiments of figure 6(a), 6(b) and 7 operate.
Detailed Description of the Invention
In the present invention, an improved transmitting system is presented.
The improved transmitting system can solve the intrinsic problems of the prior art by introducing a concept of "decomposition". Thus, the improved transmitting system of the present invention can be called a decomposition transmitting system.
In the decomposition transmitting system provided by the present invention, the reference output from the data source block or (optional) digital pre-distortion sub-block is copied into two or more paths, which in turn are modified independently and differently in the digital processing block. As a result, the individual outputs from the digital processing block, (which have of course been converted into analog form and undergone any necessary frequency conversion, as per the prior art), passed to the amplifying block and combining block, usually exhibit little correlation with the desired output.
To decompose the reference signal, one or more digital processing sub-blocks are included in the digital processing block. It is noted that one of the one or more digital processing sub-blocks may be a digital pre-distortion sub-block as in the prior art.
The function of the digital pre-distortion sub-block is the same with that in the prior art. The digital pre-distortion sub-block can ensure that the whole transmitting system is linear. The digital pre-distortion sub-block has two inputs, that is, a signal from the data source block and a signal fed back from the outputting block/monitor. The digital pre-distortion sub-block will attempt to correlate these two inputs.
However, in the present invention, the overall characteristic of the amplifier can be modified by other digital processing sub-blocks except the digital pre-distortion sub-block. The extent, to which the characteristic of the amplifier is modified, depends on the algorithm used, which will be discussed in detail. For example, in one example, compared with the prior art, the characteristic of the amplifier might be modified by the other digital processing sub-blocks to increase the efficiency of the amplifier. The resultant, modified amplifier characteristic is automatically and subsequently linearized by the digital pre-distortion sub-block. In another example, the other digital processing sub-blocks might be used to reduce the level of distortion from the amplifier, that is, improve the linearity together with the digital pre-distortion sub-block, in still another example, the other digital processing sub-blocks might actually add distortion to the amplifier, but in such a way that
linearization is more easily achieved by the digital pre-distortion sub-block. In yet another example, the other digital processing sub-blocks might actually be used to completely linearize the system by itself, thus removing the need for the digital pre-distortion sub-block. The function of the digital processing sub- blocks depends on actual application needs.
Therefore, the efficiency and linearity of the transmitting system can be improved by the one or more digital processing sub-blocks with or without the digital pre-distortion sub-block. The specific embodiments for improving the efficiency and linearity of the transmitting system which comply with the principle of the present invention will be discussed in detail below.
With reference to figure 2, which shows a primary model of the invention, the decomposition transmitting system sequentially comprises a data source block, a digital processing block, an amplifying block, a
combining block, and an outputting block/monitor. The reference signal is output from the data source block. This reference signal enters the digital processing block where the signal is processed to produce a number of outputs. These outputs are passed to an amplifying block with two or more independent amplifying channels. After amplification, the signals are subsequently passed to a combining block which combines the signals output from the amplifying block, so as to reconstruct an amplified version of the reference input, with a high signal level suitable for transmission.
The blocks in the decomposition transmitting system are discussed in detail.
The data source block is the source of the reference signal for the system. The digital processing block receives the reference signal from the data source block, and optionally, receives feedback signal from the outputting block/monitor (which itself might be frequency shifted, but anyway is digitized and processed, as known to those skilled in the art). The feedback signal from the outputting block/monitor may be used by none, some or all of the digital processing sub-blocks in the digital processing block. The feedback signal from the outputting block/monitor can be used by the training
procedure with reference to figures 5 and 8, which will be discussed in detail with reference to figures 5 and 8.
The reference signal is processed in the digital processing block, and the processed signal is output to the amplifying block. The digital processing block comprises one or more digital processing sub-blocks. Each digital processing sub-block may perform a fixed or adaptable transformation on the signal input to it. Specifically, each digital processing sub-block transforms its own input signal by applying a mathematical transformation. The
transformation applied might be adapted according to the feedback signal from the outputting block/monitor. The transformation will be discussed in detail with reference to figures 5 and 8.
In the digital processing block, the first input digital processing block, which receives the signal from the data source block, may be a digital pre- distortion (DPD) sub-block, which usually performs a linearization function. Within the digital processing block, signals are passed between the digital processing sub-blocks according to the connection relationship between the digital processing sub-blocks. And the digital processing sub-blocks can be connected in various manners according to actual needs. The digital processing sub-blocks may be, for example, linear or non-linear, time- dependent or time-independent, and implemented as mathematical formula or look up tables (LUTs) or other means, which are well known to those skilled in the art.
The amplifying block may contain one or more "linear input splitter" sub-blocks, which will be discussed hereinafter. There are two or more interfaces between the digital processing block and the amplifying block. There are two or more interfaces between the amplifying block and the combining block.
The combining block combines the signals from the amplifying block according to the design of the combining block. The combining block has at least two inputs from the amplifier block and one output to the output/monitor.
In the present invention, the combining block is Doherty type. Here, the Doherty type combining block demands particular signals from the amplifying block. Other types of combining block will place different demands on signals from the amplifying block.
The outputting block/monitor is a subsystem for further transmitting the amplified signal. The outputting block/monitor can be used to take a sample of output signal back to the digital processing block, and the signal fed back to the digital processing block is distributed to one or more sub-blocks of digital processing blocks for adaptation. The outputting block/monitor can also be used by the system for other monitoring purposes, before passing the signal into the transmission medium.
In the transmitting system, there may be "m" interfaces between the digital processing block and the amplifying block and "n" interfaces between the amplifying block and the combining block.
In the prior art, m is equal to 1 or equal to n (n>1). While in the present invention, in certain embodiments, m is larger than 1 and m may be equal to or less than n. Ideally, m is equal to 2 for minimum complexity. A person skill in the art can easily construct a "n-way Doherty-type amplifier with m channel inputs (m<n)" decomposition transmitting system. In fact, efficiency increases as n increases, but in a rapidly diminishing manner. In some applications, higher values of n are advantageous; for example, where very high output signal levels are required from the transmitter.
The preferred embodiments showed in figure 3(a), 3(b) and 4 are specific implementations of the primary model in figure 2.
Specifically, in some exemplary embodiments, with reference to figure 3(a) and 3(b), a "3-way Doherty-type amplifier with two channel inputs" decomposition transmitting system with pre-distortion function is showed. There are two sub-blocks in the digital processing block; and the two sub- blocks comprises a digital pre-distortion sub-block and a further digital processing sub-block. The digital pre-distortion sub-block performs a pre- distortion on the reference signal, which is common to all channels in the amplifying block. The digital processing sub-block performs a transformation on the pre-distorted signal, so as to improve the performances of the decomposition transmitting system, for example, linearity, linearizability, efficiency or combination of these or other performances. These
embodiments have corresponding advantages, such as improved efficiency, linearity, industriability and stability.
With reference to figure 3(a), the output from the digital pre-distortion sub-block is input into a linear input splitter, the output from which is input into a first peaking amplifier and a main amplifier; the output from the digital processing sub-block is input into a second peaking amplifier. With reference to figure 3(b), the output from the digital pre-distortion sub-block is input into a main amplifier; the output from the digital processing sub-block is input into a linear input splitter, the output from which is input into a first peaking amplifier and a second peaking amplifier. In figures 3(a) and 3(b), the output from the digital pre-distortion sub-block is also input into the digital processing sub- block. Figures 3(a) and 3(b) are the same in that there being two different outputs from the digital processing block compared with the prior art.
After the three signals from the amplifying block are combined in the combining block and the combined signal is input into the outputting block/monitor, the feedback signal from the outputting block/monitor is fed back to the digital processing block. In this way, the signal from the digital processing sub-block is fed back to the digital pre-distortion sub-block.
Therefore, within the "digital pre-distortion" loop, there exists another nested "digital processing" loop. In order that the whole system is linear, only one of the two loops needs to be linear. Alternatively, the task of linearizing the system may be shared between the two loops, that is, the "digital pre- distortion" loop and the nested "digital processing" loop. A more detailed description of linearizing the system is provided with reference to the flow chart of Figure 5. Furthermore, in this embodiment, there is a linear input splitter in the amplifying block which is splitting the signal input into the linear input splitter into two signals. Therefore, the number of the inputs to the amplifying block is different from the number of the outputs to the combining block (i.e. m<n).
Specifically, in one exemplary embodiment, with reference to figure (4), a "2-way Doherty-type amplifier with two channel inputs" system with pre- distortion function is showed. The digital processing block is the same with that in figures 3(a) and 3(b). Compared with figures 3(a) and 3(b), there is no linear input splitter in the amplifying block. Therefore, the number of the inputs to the amplifying block equals to the number of the outputs to the combining block. In figure 4, there are two outputs from the digital processing block. The signal output from the digital pre-distortion sub-block is also input into the digital processing sub-block. The combining block and the outputting block/monitor in figure 4 are the same with those in figures 3(a) and 3(b). A digital processing sub-block, which is unique to one channel in the amplifying block, applies a transformation to the pre-distorted signal, so as to improve the performances of the decomposition transmitting system, for example, linearity, linearizability, efficiency or combination of these or other
performances. This embodiment has corresponding advantages, such as improved efficiency, linearity, industriability and stability, as discussed before.
In these embodiments, the digital processing sub-blocks in the digital processing block implement a procedure showed by the flow chart of figure 5. Figure 5 describes a flow chart that the digital processing sub-blocks in the digital processing block of figure 3(a), 3(b) and 4 might operate with.
Variations to the flow chart are obvious to those skilled in the art.
Alternatively, other procedures for realize the same purpose can be used. The procedure is as follows.
At step 501 , the procedure starts, then the procedure proceeds to step
502.
At step 502, select a training frequency and target_gain, which may be a scalar or a vector, a relative value or an absolute value. Then set the signal output from the digital pre-distortion sub-block to a low level, and set the multiplier (which may be a scalar or a vector) of another digital processing sub-block to 0. And monitor the signal output from the outputting
block/monitor. A maximum value for the small signal "gain" may be
established at this step. The target_gain is usually decided by a designer when designing the system. The designer decides the target_gain according to the desired result and the type and characteristic (which will never be ideal) of the amplifier. Then the procedure proceeds to step 503.
At step 503, increase the level of the signal output from the digital pre- distortion sub-block by a fixed amount or ratio, and monitor the signal output from the outputting block/monitor. Then calculate a gain which is a ratio of the level of the signal output from the outputting block/monitor to the level of the signal output from the pre-distortion sub-block. Then the procedure proceeds to step 504.
At step 504, the procedure assesses whether the absolute value of the calculated gain is less than the absolute value of target_cjain. If the absolute value of the calculated gain is less than the absolute value of target_gain, then the procedure proceeds to step 505; otherwise, the procedure returns to step 503.
At step 505, increase the level of the signal output from the digital pre- distortion sub-block by a fixed amount or ratio. Then the procedure proceeds to step 506.
At step 506, adjust/search the multiplier of the digital processing sub- block. Then monitor the signal output from the outputting block/monitor and calculate the gain. Then the procedure proceeds to step 507.
At step 507, the procedure decides whether the calculated gain is equal to target_gain. If the gain is equal to target_gain, then the procedure proceeds to step 508; otherwise, the procedure proceeds to step 510.
At step 508, the procedure decides whether the desired appropriate multiplier of the digital processing sub-block has been found. It should be noted that the desired appropriate multiplier is predetermined according to the desired result and the characteristic the amplifier. In one example, the desired appropriate multiplier is chosen to have the lowest magnitude. In another example, the desired appropriate multiplier is chosen to give the desired output signal level with the highest efficiency. If the appropriate multiplier of the digital processing sub-block has been found, then the procedure proceeds to step 509; otherwise, the procedure returns to step 506.
At step 509, store e.g. the signal level output from the digital pre- distortion sub-block, the training frequency etc. (the independent variables) and the corresponding multiplier of the digital processing sub-block (the dependent variable) in a look up table, for example. Then the procedure returns to step 505.
At step 510, the procedure decides whether maximum output level of any of the sub-blocks in the digital processing block or the amplifying block has been reached. Typically, when no more output level can be extracted, i.e. the decomposition transmitting system has reached its "saturated output level", the maximum output level is reached. If the maximum output level of any of the sub-blocks in the digital processing block and the amplifying block has been reached, then the procedure proceeds to step 511 ; otherwise, the procedure returns to step 506.
At step 511 , the procedure decides whether training has completed. The decision depends on the characteristics of the actual system. In most cases, training would take place over a number of discrete frequencies and perhaps also temperature. A first frequency and/or temperature are
characterized until the maximum output level is reached. Then the next frequency and/or temperature are characterized. This is repeated. Exactly how much training is required depends on the characteristics of the
components - especially the sub-blocks in the amplifying block. If training has completed, then the procedure ends at step 512; otherwise, the procedure returns to step 502.
It is noted that the distortion exhibited by the amplifier may have different effects on the different signal being transmitted. An amplifier which exhibits some distortion may not actually distort a signal being transmitted. For example, if the signal being transmitted has only large signal levels, and the amplifier only exhibits distortion on small signal, then the large signal will not experience any distortion; and vice versa.
Therefore, for different signals, that is, large signal and small signal, we have different processing. In table 1 below, "AM-AM" means "amplitude modulation to amplitude modulation conversion", "AM-PM" means "amplitude modulation to phase modulation conversion".
Table 1 target_gain is a constant and a scalar
transformation
AM-AM AM-PM magnitude small pre-distortion pre-distortion domain signal
large pre-distortion & pre-distortion & signal transformation performed by transformation other digital processing sub- performed by other biock(s) digital processing sub-block(s) target_gain is a constant and a vector
transformation
AM-AM AM-PM magnitude small pre-distortion pre-distortion domain signal
large pre-distortion & pre-distortion & signal transformation performed by transformation other digital processing sub- performed by other blocks) digital processing sub-block(s) Once the system has been trained using the flow chart with reference to figure 5, the decomposition transmitting system will have both higher efficiency and better linearity than the transmitting system in the prior art. This is primarily because the Doherty (prior art) amplifiers in the prior art system are not able to reproduce (i.e. output to the combiner) the precise signals required to operate as a true Doherty amplifier. With the invention, the precise output signals from the amplifiers, required for Doherty operation, can be created in an arbitrarily accurate manner.
in other embodiments, the digital processing sub-blocks do not comprise a digital pre-distortion sub-block.
The preferred embodiments showed in figure 6(a), 6(b) and 7 are specific implementations of the primary model in figure 2.
Specifically, in some exemplary embodiments, with reference to figure 6(a) and 6(b), a "3-way Doherty-type Amplifier with two channel inputs" decomposition transmitting system without digital pre-distortion function is showed. There is only one digital processing sub-block in the digital processing block, which is not a digital pre-distortion sub-block. The amplifying block in figure 6(a) is the same with that in figure 3(a), the amplifying block in figure 6(b) is the same with that in figure 3(b).
Specifically, in one exemplary embodiment, with reference to figure 7, a "2- way Doherty-type amplifier with two channel inputs" decomposition
transmitting system without digital pre-distortion function is showed. There is only one digital processing sub-block in the digital processing block, and this is not a digital pre-distortion sub-block. The amplifying block in figure 7 is the same with that in figure 4.
In these embodiments, the digital processing sub-block implements a procedure showed by the flow chart of figure 8. Figure 8 describes a flow chart the digital processing sub-blocks in the digital processing block of figure 6(a), 6(b) and 7 operate with. Variations to the flow chart are obvious to those skilled in the art. Alternatively, other procedures for realize the same purpose can be used. The procedure is as follows.
At step 801 , the procedure starts, then the procedure proceeds to step
802. At step 802, select a training frequency and target gain, which may be a scalar or a vector, and an absolute value. Then set the signal output from the data source block to a specific level, and set the multiplier (which may be a scalar or vector) of the digital processing sub-block to 0. The target_gain should usually be set to a lower magnitude value. The target_gain is usually decided by a designer when designing the system. The designer decides the target_gain according to the desired result and the type and characteristic (which will never be ideal) of the amplifier. Then the procedure proceeds to step 803.
At step 803, increase the level of the signal output from the data source block by a fixed amount or ratio, and monitor the signal output from the outputting block/monitor. Then calculate a gain which is a ratio of the level of the signal output from the outputting block/monitor to the level of the signal output from the data source block. Then the procedure proceeds to step 804.
At step 804, adjust/search the multiplier of the digital processing sub- block. Then monitor the signal output from the data source block and calculate the gain. Then the procedure proceeds to step 807.
At step 805, the procedure decides whether the calculated gain is equal to target_gain. If the gain is equal to target__gain, then the procedure proceeds to step 806; otherwise, the procedure proceeds to step 808.
At step 806, the procedure decides whether the desired appropriate multiplier of the digital processing sub-block has been found. In one example, the desired appropriate multiplier is chosen to have the lowest magnitude. In another example, the desired appropriate multiplier is chosen to give the desired output signal level with the highest efficiency. If the appropriate multiplier of the digital processing sub-block has been found, then the procedure proceeds to step 807; otherwise, the procedure returns to step 804.
At step 807, store e.g. the signal level output from the data source block, the training frequency etc. (the independent variables) and the corresponding multiplier of the digital processing sub-block (the dependent variable) in a look up table, for example. Then the procedure returns to step 803. At step 808, the procedure decides whether maximum output level of any of the sub-blocks in the digital processing block and the amplifying block has been reached. Typically, when no more output level can be extracted, i.e. the decomposition transmitting system has reached its "saturated output level", the maximum output level is reached. If the maximum output level of any of the sub-blocks in the digital processing block and the amplifying block has been reached, then the procedure proceeds to step 809; otherwise, the procedure returns to step 804.
At step 809, the procedure decides whether training has completed. The decision depends on the characteristics of the actual system. In most cases, training would take place over a number of discrete frequencies and perhaps also temperature. A first frequency and/or temperature are
characterized until the maximum output level is reached. Then the next frequency and/or temperature are characterized. This is repeated. Exactly how much training is required depends on the characteristics of the
components - especially the sub-blocks in the amplifying block. If training has completed, then the procedure ends at step 810; otherwise, the procedure returns to step 802.
In reality, the digital processing sub-block will simultaneously improve the overall efficiency and linearity of the decomposition transmitting system and reduce the complexity of the digital pre-distortion sub-block. These advantages are achieved by: ensuring that the inputs to the Doherty-type combining block are arbitrarily accurate for Doherty operation; and reducing variations in the overall characteristic of the amplifier in time domain and frequency domain, which is known in the art as "memory effect".
While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims

1. A decomposition transmitting system comprising a data source block, a digital processing block, an amplifying block, a combining block, and an outputting block/monitor, the digital processing block comprising:
one or more digital processing sub-blocks, each digital processing sub- block being configured to perform a mathematical transformation on its input signal, to decompose a signal from the data source block into a plurality of transformed signals, and each of the plurality of transformed signals being output to a corresponding input of the amplifying block,
whereby the efficiency and linearity of the decomposition transmitting system are improved.
2. A decomposition transmitting system according to claim 1 , wherein the mathematical transformation is designed to realize desired characteristics of amplifiers in the amplifying block.
3. A decomposition transmitting system according to claim 1 , wherein some or all of the one or more digital processing sub-blocks in the digital processing block perform the mathematical transformation by using a feedback signal from the outputting block/monitor.
4. A decomposition transmitting system according to claim 1 , the amplifying block and the combining block are designed for Doherty type operation.
5. A decomposition transmitting system according to any one of claims 1-4, wherein the plurality of transformed signals comprise the signal from the data source block.
6. A decomposition transmitting system according to claim 5, wherein the amplifying block comprises one or more splitters, each splitter is configured to split one of the plurality of transformed signals from the digital processing block.
7. A decomposition transmitting system according to claim 6, one of the one or more splitters is configured to split the signal from the data source block into more than one split signals and output one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
8, A decomposition transmitting system according to claim 6, each of the one or more splitters are configured to split one of the plurality of transformed signals except the signal from the data source block into more than one split signals and output the split signals to corresponding peaking amplifiers in the amplifying block.
9. A decomposition transmitting system according to any one of claims 1-4, wherein one of the one or more digital processing sub-blocks is a digital pre-distortion sub-block, the digital pre-distortion sub-block is configured to receive the signal from the data source block and output a digital pre-distorted signal to other digital processing sub-blocks and the amplifying block.
10. A decomposition transmitting system according to claim 9, the amplifying block comprises one or more splitters, each splitter is configured to split one of the plurality of transformed signals from the digital processing block.
11. A decomposition transmitting system according to claim 10, one of the one or more splitters is configured to split the digital pre-distorted signal from the digital pre-distortion sub-block into more than one split signals and output one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
12. A decomposition transmitting system according to claim 10, each of the one or more splitters are configured to split one of the plurality of transformed signals except the digital pre-distorted signal from the digital pre- distortion sub-block into more than one split signals and output the split signals to corresponding peaking amplifiers in the amplifying block.
13. A decomposition transmitting method, comprising:
performing a mathematical transformation on an input signal of each digital processing sub-block of a digital processing block in a transmitting system, to decompose a signal from a data source block in the transmitting system into a plurality of transformed signals;
outputting each of the plurality of transformed signals to a
corresponding input of an amplifying block in the transmitting system,
whereby the efficiency and linearity of the transmitting system are improved.
14. A decomposition transmitting method according to claim 13, wherein the mathematical transformation is designed to realize desired characteristics of amplifiers in the amplifying block.
15. A decomposition transmitting method according to claim 13, wherein the step of performing a mathematical transformation further comprises:
performing the mathematical transformation by using a feedback signal from an outputting block/monitor in the transmitting system.
16. A decomposition transmitting method according to claim 13, further comprising:
designing the amplifying block and a combining block in the transmitting system for Doherty type operation.
17. A decomposition transmitting method according to any one of claim 13-16, wherein the plurality of transformed signals comprise the signal from the data source block.
18. A decomposition transmitting method according to claim 17, further comprising:
splitting one or more of the plurality of transformed signals from the digital processing block.
19. A decomposition transmitting method according to claim 18, further comprising:
splitting the signal from the data source block into more than one split signals; and
outputting one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
20. A decomposition transmitting method according to claim 18, further comprising:
splitting respectively one or more of the plurality of transformed signals except the signal from the data source block into more than one split signals; and
outputting the split signals to corresponding peaking amplifiers in the amplifying block.
21. A decomposition transmitting method according to any one of claim 13-16, wherein one of the digital processing sub-blocks is a digital pre- distortion sub-block, the method further comprises:
pre-distorting the signal from the data source block into a digital pre- distorted signal; and
outputting the digital pre-distorted signal to other digital processing sub-blocks and the amplifying block.
22. A decomposition transmitting method according to claim 21 , further comprising:
splitting one or more of the plurality of transformed signals from the digital processing block.
23. A decomposition transmitting method according to claim 22, further comprising:
splitting the digital pre-distorted signal from the digital pre-distortion sub-block into more than one split signals; and
outputting one of the split signals to a main amplifier in the amplifying block and the other split signal(s) to corresponding peaking amplifier(s) in the amplifying block.
24. A decomposition transmitting method according to claim 22, further comprising:
splitting respectively one or more of the plurality of transformed signals except the digital pre-distorted signal from the digital pre-distortion sub-block into more than one split signals; and
outputting the split signals to corresponding peaking amplifiers in the amplifying block.
EP10847574.0A 2010-03-12 2010-03-12 A decomposition transmitting system and method for improving efficiency and linearity Withdrawn EP2545644A4 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE2010/050279 WO2011112129A1 (en) 2010-03-12 2010-03-12 A decomposition transmitting system and method for improving efficiency and linearity

Publications (2)

Publication Number Publication Date
EP2545644A1 true EP2545644A1 (en) 2013-01-16
EP2545644A4 EP2545644A4 (en) 2013-09-18

Family

ID=44563719

Family Applications (1)

Application Number Title Priority Date Filing Date
EP10847574.0A Withdrawn EP2545644A4 (en) 2010-03-12 2010-03-12 A decomposition transmitting system and method for improving efficiency and linearity

Country Status (4)

Country Link
EP (1) EP2545644A4 (en)
CN (1) CN102906996A (en)
RU (1) RU2012142252A (en)
WO (1) WO2011112129A1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9374041B2 (en) 2011-12-15 2016-06-21 Telefonaktiebolaget Lm Ericsson (Publ) Doherty power amplification apparatus and method
US8952754B2 (en) 2013-03-15 2015-02-10 Imagine Communications Corp. Linearization of heterogeneous power amplifier systems
EP2882097A1 (en) * 2013-12-09 2015-06-10 Alcatel Lucent Method for optimizing operation of a doherty amplifier and doherty amplifier
DE102019000324A1 (en) * 2019-01-20 2020-07-23 IAD Gesellschaft für Informatik, Automatisierung und Datenverarbeitung mbH Transmitting and receiving device with a broadband RF power amplifier, in particular N-way Doherty amplifier with active load modulation
US11218118B2 (en) 2020-03-30 2022-01-04 Analog Devices International Unlimited Company Linearity optimizer for a millimeter-wave beamforming system

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6472934B1 (en) * 2000-12-29 2002-10-29 Ericsson Inc. Triple class E Doherty amplifier topology for high efficiency signal transmitters
US20060001485A1 (en) * 2004-07-02 2006-01-05 Icefyre Semiconductor Corporation Power amplifier
US20080111622A1 (en) * 2006-11-14 2008-05-15 Roland Sperlich Hybrid Doherty Amplifier System and Method
US20080238544A1 (en) * 2007-03-30 2008-10-02 Nortel Networks Limited Amplifier pre-distortion systems and methods
US7619468B1 (en) * 2008-09-30 2009-11-17 Nortel Networks Limited Doherty amplifier with drain bias supply modulation

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05191178A (en) * 1992-01-16 1993-07-30 Japan Radio Co Ltd Power amplifier
US20070164818A1 (en) * 2004-06-18 2007-07-19 Kenichi Horiguchi High efficiency amplifier

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6472934B1 (en) * 2000-12-29 2002-10-29 Ericsson Inc. Triple class E Doherty amplifier topology for high efficiency signal transmitters
US20060001485A1 (en) * 2004-07-02 2006-01-05 Icefyre Semiconductor Corporation Power amplifier
US20080111622A1 (en) * 2006-11-14 2008-05-15 Roland Sperlich Hybrid Doherty Amplifier System and Method
US20080238544A1 (en) * 2007-03-30 2008-10-02 Nortel Networks Limited Amplifier pre-distortion systems and methods
US7619468B1 (en) * 2008-09-30 2009-11-17 Nortel Networks Limited Doherty amplifier with drain bias supply modulation

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO2011112129A1 *

Also Published As

Publication number Publication date
RU2012142252A (en) 2014-04-20
CN102906996A (en) 2013-01-30
EP2545644A4 (en) 2013-09-18
WO2011112129A1 (en) 2011-09-15

Similar Documents

Publication Publication Date Title
JP5205182B2 (en) Distortion compensation amplifier
CN101675584B (en) Amplifier pre-distortion systems and methods
JP5236661B2 (en) Method and system for linearizing baseband predistortion in multi-channel wideband communication system
CN101416382B (en) Method and equipment for reducing frequency memory effect of RF power amplifier
KR101679230B1 (en) Polynomial digital predistortion apparatus for compensation of non-linear characteristic of power amplifier and the method thereof
CN104363191B (en) A kind of digital pre-distortion method of frequency-hopping communication system
Staudinger et al. Memory fading Volterra series model for high power infrastructure amplifiers
US8564368B1 (en) Digital Predistorter (DPD) structure based on dynamic deviation reduction (DDR)-based volterra series
CA2817805A1 (en) Orthogonal basis function set for digital predistorter
CN102025327A (en) Amplifier apparatus and predistortion control method
JP2005117599A (en) High frequency amplifier
EP3665773A1 (en) Polyphase digital signal predistortion in radio transmitter
EP2545644A1 (en) A decomposition transmitting system and method for improving efficiency and linearity
Nader et al. Peak-power controlling technique for enhancing digital pre-distortion of RF power amplifiers
Rahati Belabad et al. An accurate digital baseband predistorter design for linearization of RF power amplifiers by a genetic algorithm based Hammerstein structure
Karimi et al. An analog/digital pre-distorter using particle swarm optimization for RF power amplifiers
US20190097589A1 (en) Circuit and method for predistortion
CN100512246C (en) Radio frequency distortion linearizing method
Pan et al. Digital linearization of multiple power amplifiers in phased arrays for 5G wireless communications
JP2008028746A (en) Distortion compensating device
KR20120054369A (en) Predistorter using memory polynomial model, predistorting method thereof, and system including the predistorter
Naraharisetti et al. 2D quasi exact inverse of PA model in digital predistorter for concurrent dual-band system
Rahmanian et al. Efficient fpga implementation of a digital predistorter for power amplifier linearization
KR102640792B1 (en) An apparatus and a operating method of pre-distorter with compensation
Byrne et al. Recursive pre-distorter for hardware efficient digital pre-distortion

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20121005

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR

DAX Request for extension of the european patent (deleted)
A4 Supplementary search report drawn up and despatched

Effective date: 20130821

RIC1 Information provided on ipc code assigned before grant

Ipc: H03F 1/32 20060101ALI20130815BHEP

Ipc: H03F 1/02 20060101AFI20130815BHEP

Ipc: H03F 3/189 20060101ALI20130815BHEP

Ipc: H03F 1/30 20060101ALI20130815BHEP

Ipc: H03F 3/24 20060101ALI20130815BHEP

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20140318