WO2016050273A1 - Wideband transmit signal generation - Google Patents

Wideband transmit signal generation Download PDF

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Publication number
WO2016050273A1
WO2016050273A1 PCT/EP2014/070857 EP2014070857W WO2016050273A1 WO 2016050273 A1 WO2016050273 A1 WO 2016050273A1 EP 2014070857 W EP2014070857 W EP 2014070857W WO 2016050273 A1 WO2016050273 A1 WO 2016050273A1
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WO
WIPO (PCT)
Prior art keywords
transmit signal
signal generation
generation circuits
transmit
circuit
Prior art date
Application number
PCT/EP2014/070857
Other languages
French (fr)
Inventor
Bjoern Jelonnek
Marko FLEISCHER
Frank DECHEN
Original Assignee
Nokia Solutions And Networks Oy
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 Nokia Solutions And Networks Oy filed Critical Nokia Solutions And Networks Oy
Priority to PCT/EP2014/070857 priority Critical patent/WO2016050273A1/en
Priority to EP14777321.2A priority patent/EP3202046A1/en
Publication of WO2016050273A1 publication Critical patent/WO2016050273A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/005—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
    • H04B1/0053—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges with common antenna for more than one band
    • H04B1/0057—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges with common antenna for more than one band using diplexing or multiplexing filters for selecting the desired band
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H04B1/0483—Transmitters with multiple parallel paths

Definitions

  • the present invention relates to wideband transmit signal generation. More specifically, the present invention relates to an apparatus for wideband transmit signal generation, a method of operating the same, and a computer program product for carrying out the method of operating the same .
  • radio freguency (RF) units for modern/future mobile communication entities support transmission of such wideband transmit signals even with low power usage .
  • a wideband-enabled transmit signal path including e.g. a wideband digital pre-distortion (DPD) and a wideband power amplifier (PA), together with a single antenna.
  • DPD digital pre-distortion
  • PA wideband power amplifier
  • power amplifiers capable of supporting such wideband transmit signals are under development, these have to cope with several challenges such as reduced efficiency and higher freguency dependency of their non-linearity operation with a higher transmit signal bandwidth.
  • the complexity and implementation effort of the DPD increases in more than a guadratic manner with regard to transmit signal bandwidth. For example, with PA transistors having resonances in the region of 250 MHz, a significant degradation of the digital pre-distortion result is expected for a transmit signal with 400 MHz bandwidth.
  • an apparatus comprising a plurality of transmit signal generation circuits configured to generate a plurality of transmit signals having different freguency bands, a combination circuit configured to combine the plurality of transmit signals to generate an output transmit signal, the combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits, and a control circuit configured to control the plurality of transmit signal generation circuits in accordance with operating characteristics of the combination circuit.
  • the operating characteristics of the combination circuit may comprise the freguency responses of the bandpass filter circuits of the combination circuit.
  • each of the plurality of transmit signal generation circuits may comprise a power amplification circuit .
  • control circuit may be configured to control an input signal of the power amplification circuit of each of the transmit signal generation circuits for an overlap region of the freguency responses of the plurality of bandpass filter circuits .
  • control circuit may be configured to control the input signal of the power amplification circuit of each of the transmit signal generation circuits such that the resulting output signals are adjusted to combine with each other so as to produce a desired output transmit signal in the overlap region.
  • control circuit may be configured to control a digital pre- distortion circuit or an adaptive filter circuit arranged on an input side of the power amplification circuit.
  • control circuit may be configured to control one or more of the plurality of transmit signal generation circuits to switch off generation of the respective one or more transmit signals.
  • the combination circuit may be configured to generate a wideband output transmit signal using at least two of the plurality of transmit signals, wherein said wideband output transmit signal has a freguency band involving the freguency bands of the at least two transmit signals, or one or more narrowband output transmit signals respectively using one of the plurality of transmit signals, wherein said narrowband output transmit signal has a freguency band involving the freguency band of the one transmit signal.
  • control circuit may be configured to select the one or more transmit signals to be used for generating the output transmit signal in accordance with a loss of each of the transmit signal generation circuits in a predetermined freguency region.
  • control circuit may be configured to control the plurality of transmit signal generation circuits using at least one of measurements of each of the transmit signals and the output transmit signal.
  • control circuit may be configured to identify a transformation network in each of the plurality of transmit signal generation circuits, and to control the plurality of transmit signal generation circuits using the identified transformation network of each of the transmit signal generation circuits.
  • the apparatus may further comprise a plurality of circulators arranged on an output side of each of the plurality of transmit signal generation circuits, each circulator being configured to transfer the generated transmit signal to a respective bandpass filter in the combination circuit.
  • the control circuit may be configured to detect a loss of each of the transmit signal generation circuits in a predetermined freguency region of the freguency response of the respective bandpass filter using a reflected signal transferred from the respective bandpass filter by the respective circulator, and to control the plurality of transmit signal generation circuits using the detected loss of each of the transmit signal generation circuits.
  • the apparatus may further comprises a load modulation detection circuit configured to detect a load modulation between the plurality of transmit signal generation circuits, wherein the control circuit may be configured to control the plurality of transmit signal generation circuits using the detected load modulation.
  • the apparatus may comprise or be comprised by a radio freguency unit of a mobile communication entity.
  • a method of operating an apparatus comprising a plurality of transmit signal generation circuits and a combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits, the method comprising causing the plurality of transmit signal generation circuits to generate a plurality of transmit signals having different freguency bands, causing the combination circuit to combine the plurality of transmit signals to generate an output transmit signal, and controlling the plurality of transmit signal generation circuits in accordance with operating characteristics of the bandpass filter circuits.
  • the method may further comprise causing the combination circuit to generate a wideband output transmit signal using at least two of the plurality of transmit signals, wherein said wideband output transmit signal has a freguency band involving the freguency bands of the at least two transmit signals, or generate one or more narrowband output transmit signals respectively using one of the plurality of transmit signals, wherein said narrowband output transmit signal has a freguency band involving the freguency band of the one transmit signal.
  • a computer program product comprising computer-executable computer program code which, when the computer program code is executed on a computer, is configured to cause the computer to carry out a method according to the above method-related example aspect.
  • a technigue for generation of wideband transmit signals (or, stated in other words, support of transmission of wideband transmit signals) is provided.
  • the technigue according to exemplifying embodiments of the present invention is capable of avoiding deficiencies such as increased cost and/or size as well as reduced efficiency and/or increased complexity due to increased transmit signal bandwidth.
  • FIG. 1 shows a simplified block diagram of a basic structure of an apparatus according to exemplifying embodiments of the present invention
  • Figure 2 shows a diagram illustrating the principle of wideband coherent combining according to exemplifying embodiments of the present invention
  • Figure 3 shows diagrams illustrating different operation modes under the principle of wideband coherent combining according to exemplifying embodiments of the present invention
  • Figure 4 shows a block diagram of a first exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention
  • Figure 5 shows a block diagram of a second exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention
  • Figure 6 shows a block diagram of a third exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention.
  • Figure 7 shows a flowchart of a method of operating an apparatus according to exemplifying embodiments of the present invention.
  • lines/arrows interconnecting individual blocks or entities are generally meant to illustrate an operational coupling there-between, which may be a physical and/or logical coupling, which on the one hand is implementation-independent (e.g. wired or wireless) and on the other hand may also comprise an arbitrary number of intermediary functional blocks or entities not shown.
  • Figure 1 shows a simplified block diagram of a basic structure of an apparatus according to exemplifying embodiments of the present invention.
  • an apparatus 100 comprises a plurality of transmit signal generation circuits 110 and 120, a combination circuit 130 and a control circuit 140.
  • Each of the transmit signal generation circuits 110, 120 is configured to generate a transmit signal, i.e. a narrowband transmit signal, wherein the thus generated transmit signals have different freguency bands.
  • the freguency bands of two narrowband transmit signals may partly overlap or adjoin each other.
  • the combination circuit 130 is configured to combine the plurality of transmit signals to generate an output transmit signal, and comprises a plurality of bandpass filter circuits BPFl, BPF2 having mutually overlapping freguency responses for - li
  • the control circuit 140 is configured to control the plurality of transmit signal generation circuits. Such control may be performed in accordance with operating characteristics of the combination circuit, such as e.g. the freguency responses of the bandpass filter circuits of the combination circuit 130. While the exemplary structure of Figure 1 illustrates two transmit signal generation circuits, it is to be noted that the present invention is not limited to such configuration. Rather, there may be an arbitrary number of transmit signal generation circuits, such as e.g. three or more. In such case, the freguency responses of a pair of bandpass filter circuits for two of the transmit signal generation circuits are mutually overlapping, respectively.
  • the combination circuit 140 is operable to combine the plurality of transmit signals to generate an output transmit signal under the principle of wideband coherent combining (CC) .
  • the principle of wideband coherent combining (CC) refers to a freguency- dependent combination of narrowband transmit signals using bandpass filter circuits with overlapping freguency responses.
  • the narrowband signals can be combined such that a desired output transmit signal in the overlap region can be generated.
  • the transmit signal generation circuits each comprise a power amplification circuit such as a power amplifier (PA)
  • PA power amplifier
  • the control circuit may control an input signal of the power amplification circuit of each of the transmit signal generation circuits for an overlap region of the freguency responses of the plurality of bandpass filter circuits. More specifically, the control circuit may control the input signal of the power amplification circuit of each of the transmit signal generation circuits such that the resulting output signals are adjusted to combine with each other so as to produce a desired output transmit signal in the overlap region.
  • the control of the plurality of transmit signal generation circuits may be based on various parameters, such as at least one of measurements of each of the transmit signals and the output transmit signal.
  • the control may be based on (a measurement of) one or more of the transmit signals, or may be based on (a measurement of) the output transmit signal, or may be based on both (a measurement of) one or more of the transmit signals and (a measurement of) the output transmit signal.
  • Figure 2 shows a diagram illustrating the principle of wideband coherent combining according to exemplifying embodiments of the present invention.
  • the horizontal axis represents the freguency
  • the dashed curve represents the freguency response of a first bandpass filter circuit denoted by BPFl corresponding to (the frequency band of the narrowband transmit signal of) a first transmit signal generation circuit
  • the chain line represents the frequency response of a second bandpass filter circuit denoted by BPF2 corresponding to (the frequency band of the narrowband transmit signal of) a second transmit signal generation circuit.
  • the rectangles represent individual frequency carriers, wherein the solid rectangles represent carriers in the frequency band of the first transmit signal generation circuit, and the hatched rectangles represent carriers in the frequency band of the second transmit signal generation circuit.
  • the principle of coherent combining (CC) is applied in the overlap region between the two frequency responses, which is represented by the dotted oval.
  • CC principle of coherent combining
  • the combination circuit 140 is operable in different operation modes, as outlined below.
  • Figure 3 shows diagrams illustrating different operation modes under the principle of wideband coherent combining according to exemplifying embodiments of the present invention .
  • the combination circuit operates in a first operation mode, in which a wideband output transmit signal is generated using two transmit signals (in general, at least two of a plurality of transmit signals) .
  • the resulting wideband output transmit signal has a freguency band involving the freguency bands of both (in general, the at least two) transmit signals.
  • the combination operates in a second operation mode, in which a narrowband output transmit signal is generated using one of the two (in general, the plurality of) transmit signals.
  • the resulting narrowband output transmit signal has a freguency band involving the freguency band of the one transmit signal.
  • the resulting narrowband output transmit signal may comprise a part of the other transmit signal in the overlap region, respectively. This is specifically effective when the same data signal is transmitted via both transmit signal paths.
  • the control circuit may control one or more of the plurality of transmit signal generation circuits to switch off generation of the respective one or more transmit signals. Namely, the control circuit may select one or more transmit signals to be used for generating the output transmit signal (i.e. switch on or activate generation thereof), thus setting the respective transmit signal/signals in a high power or switch-on state. Stated the other way round, deselect one or more transmit signals not to be used for generating the output transmit signal (i.e. switch off or deactivate generation thereof), thus setting the respective transmit signal/ signals in a low power or switch-off state.
  • such de-/selection may be made in accordance with a loss of each of the transmit signal generation circuits (or e.g. its power amplifier) in a predetermined freguency region such as the overlap region.
  • both transmit signal generation circuits can be used for the generation/provision of the output transmit signal in a freguency region in which both of them are effectively operable in view of their loss characteristics (e.g. when both transmit signal generation circuits or e.g. their power amplifiers exhibit a similar loss) .
  • a freguency region in which only one of the transmit signal generation circuits is effectively operable in view of their loss characteristics (e.g. when one of the transmit signal generation circuits or e.g.
  • the transmit signal generation circuit with the lower loss can be used for the generation/provision of the output transmit signal.
  • one or more of the plural transmit signal generation circuits may be controlled to be switched off when its/their freguency band/bands is/are not reguired for generation/provision of the output transmit signal .
  • each of the transmit signal generation circuits comprises a power amplifier PA and a digital pre-distortion circuit DPD (which could also be replaced or accompanied by any type of adaptive filter circuit) arranged on an input side of the power amplifier PA.
  • each of the transmit signal generation circuits exemplarily also comprises a digital-to-analog converter DAC, a local oscillator and a low-power transmit signal TX .
  • DAC digital-to-analog converter
  • TX low-power transmit signal
  • an exemplary RF unit comprises two transmit signal generation circuits (indicated by dashed boxes), a filter combiner and a control circuit, like the apparatus of Figure 1, as well as a circulator at the output of the filter combiner, and a duplex filter towards an antenna.
  • the circulators in the narrowband transmit signal paths are illustrated as part of the respective transmit signal generation circuits, it is to be noted that such illustration is made for explanatory purposes only without any limitation to such configuration. Namely, the circulators in the narrowband transmit signal paths may be also be arranged outside of the respective transmit signal generation circuits, as long as being arranged on an output side of each of the plurality of transmit signal generation circuits. That is, the circulator in each narrowband transmit signal path is configured to transfer the generated narrowband transmit signal to a respective bandpass filter in the filter combiner representing a combination circuit.
  • control of the transmit signal generation circuits may be based on various control inputs .
  • control inputs may comprise one or more of measurements of each of the narrowband transmit signals (as indicated by angled arrows between PA 0 /PA ! and the respective circulator) and a measurement of the output transmit signal (as indicated by an angled arrow between the adder in the filter combiner and the following circulator) .
  • a measurement of the output transmit signal i.e. the combined transmit signal, can be effectively used for ensuring a flat frequency characteristic, i.e. a (nearly) constant power, voltage or the like over the entire frequency band including the overlap region.
  • control inputs may comprise one or more of losses of the transmit signal generation circuits (e.g. PA 0 /PAi, the respective circulator, or the like) in a predetermined frequency region of the frequency response (such as the frequency region thereof) of the respective bandpass filter.
  • a loss of a transmit signal generation circuit e.g. PA 0 /PAi
  • PA 0 /PAi a transmit signal generation circuit
  • Such a loss of a transmit signal generation circuit may be obtained using a reflected signal transferred from the respective bandpass filter (to the control circuit) by the respective circulator (as indicated by arrows from between the respective circulator and the control block) . Based on the thus detected loss/losses, a loss-related control can be performed, as outlined above.
  • FIG. 5 shows a block diagram of a second exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention.
  • the exemplary RF unit of Figure 5 is basically similar to that of Figure 4. Accordingly, the description of similar parts and functionalities is omitted, and only differences are described below.
  • an exemplary RF unit comprises two transmit signal generation circuits (indicated by dashed boxes), a filter combiner and a control circuit, like the apparatus of Figure 1, wherein the filter combiner is integrated with a duplex filter.
  • Figure 6 shows a block diagram of a third exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention.
  • an exemplary RF unit comprises two transmit signal generation circuits (indicated by dashed boxes), a filter combiner and a control circuit, like the apparatus of Figure 1, as well as a circulator at the output of the filter combiner, and a duplex filter towards an antenna.
  • a load modulation detection circuit is provided in the control block or, stated in other words, load modulation detection means is realized by the control block.
  • load modulation detection circuit is configured to detect a load modulation between the plurality of transmit signal generation circuits (as indicated by angled arrows between PA 0 /PAi and the respective bandpass filter), and the control of the plurality of transmit signal generation circuits may be based on the detected load modulation.
  • Such load modulation may be based on transmit signals transferred between respective transmit signal generation circuits (such as a transfer of the transmit signal from PAi to PA 0 , and vice versa) and/or a reflected signal transferred from the respective bandpass filter back to the generating transmit signal generation circuit (such as a reflection of a signal from bandpass filter 0 to PA 0 , or the like) .
  • the load point/level of the respective transmit signal generation circuit e.g. the load resistance of PAo/PAi
  • a control similar to the above-outlined loss- related control can be performed. Taking into consideration one or more transferred signals in the control can be effectively used for generation/provision of an output transmit signal capable of compensating for such ( undesired/leaked) transfer or transfers.
  • control of the transmit signal generation circuits may be based on various control inputs, such as one or more of measurements of each of the narrowband transmit and a measurement of the output transmit signal, as described above in connection with Figure 4.
  • the control of the transmit signal generation circuits may additionally or alternatively be based on characteristics of a transformation network in any one of the transmit signal generation circuits (i.e. the transformation network in ⁇ 0 / ⁇ ) .
  • the control circuit in any one of Figures 4 to 6 may be configured to identify a transformation network in the transmit signal generation circuits, and to control the transmit signal generation circuits using the identified transformation network, respectively.
  • Figure 7 shows a flowchart of a method of operating an apparatus according to exemplifying embodiments of the present invention.
  • Such operating method is applicable for any apparatus comprising a plurality of transmit signal generation circuits and a combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits .
  • the plurality of transmit signal generation circuits are caused to generate a plurality of transmit signals having different freguency bands.
  • the combination circuit is caused to combine the plurality of transmit signals to generate an output transmit signal.
  • the plurality of transmit signal generation circuits are controlled in accordance with operating characteristics of the combination circuit, such as e.g. the frequency responses of the bandpass filter circuits . Details of such operating method are evident from the functional description of Figures 1 to 6 above .
  • Figure 7 merely shows an exemplary flowchart for illustrative purposes, in which an exemplary sequence of processes is illustrated.
  • the present invention is however not limited to the illustrated sequence of processes. Rather, the process 730 may precede or (at least partly) overlap with the process 720, or all of the processes 710 to 730 may be performed simultaneously or in parallel or may (at least partially) overlap. Also, two or more of the processes may be performed in a mutually adaptive/dependent manner.
  • An operating method may be implemented by respective functional elements, entities, modules, units, processors, or the like, as described below.
  • it may be implemented by any kind of controller, processor, or the like, by hardware or software (and/or firmware) or any combination thereof. That is, such operating method may be embodied as a computer program product, e.g. computer code instructions stored in a computer-readable memory.
  • the technigue according to exemplifying embodiments of the present invention is capable of avoiding deficiencies such as increased cost and/or size as well as reduced efficiency and/or increased complexity due to increased transmit signal bandwidth.
  • liguid radio concepts for wider bandwidths such as transmit signals with a bandwidth of several hundred MHz, e.g. 400 MHz or more, can be implemented .
  • the principle of wideband coherent combining (CC) is efficiently adopted for generating wideband transmit signals, especially in an overlapping region of freguency responses of respective bandpass filter circuits used in the signal combination.
  • exemplifying embodiments of the present invention enable an adeguate signal combination of different signals (e.g. signals for different freguency bands) being transmitted via plural transmit signal paths (without degradation DPD results, inaccurate impedance levels, additional load, etc., for example) .
  • respective functionalities, functional blocks or elements described above can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts .
  • the mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.
  • any structural means such as a portion or other circuitry of an amplifier may refer to one or more of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of circuits and software (and/or firmware), such as (as applicable) : (i) a combination of processor(s) or (ii) portions of proces sor ( s )/ software (including digital signal processor ( s )) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) circuits, such as a microproces sor ( s ) or a portion of a microprocessor ( s ) , that reguire software or firmware for operation, even if the software or firmware is not physically present. Also, it may also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware, any integrated circuit, or the like.
  • Any procedural step or functionality is suitable to be implemented as software/firmware or by hardware without changing the idea of the present invention.
  • Such software may be software code independent and can be specified using any known or future developed programming language, such as e.g. Java, C++, C, and Assembler, as long as the functionality defined by the method steps is preserved.
  • Such hardware may be hardware type independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components.
  • MOS Metal Oxide Semiconductor
  • CMOS Complementary MOS
  • BiMOS Bipolar MOS
  • BiCMOS BiCMOS
  • ECL Emitter Coupled Logic
  • TTL Transistor-Transistor Logic
  • ASIC Application Specific IC
  • FPGA Field-programmable Gate Arrays
  • CPLD Complex Programmable Logic Device
  • DSP
  • a device/apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device/apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor.
  • a device may be regarded as a device/apparatus or as an assembly of more than one device/apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example.
  • Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.
  • Apparatuses and/or means or parts thereof can be implemented as individual devices, but this does not exclude that they may be implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person.
  • the present invention also covers any conceivable combination of method steps and operations described above, and any conceivable combination of nodes, apparatuses, modules or elements described above, as long as the above- described concepts of methodology and structural arrangement are applicable.
  • Such technigue exemplarily comprise an apparatus comprising a plurality of transmit signal generation circuits configured to generate a plurality of transmit signals having different freguency bands, a combination circuit configured to combine the plurality of transmit signals to generate an output transmit signal, the combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits, and a control circuit configured to control the plurality of transmit signal generation circuits in accordance with operating characteristics of the combination circuit, such as e.g. the freguency responses of the bandpass filter circuits of the combination circuit .

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Abstract

There is provided a technique of wideband transmit signal generation. Such technique exemplarily comprise an apparatus comprising a plurality of transmit signal generation circuits configured to generate a plurality of transmit signals having different frequency bands, a combination circuit configured to combine the plurality of transmit signals to generate an output transmit signal, the combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping frequency responses for the plurality of transmit signal generation circuits, and a control circuit configured to control the plurality of transmit signal generation circuits in accordance with operating characteristics of the combination circuit, such as e.g. the frequency responses of the bandpass filter circuits of the combination circuit.

Description

Title
Wideband transmit signal generation Field
The present invention relates to wideband transmit signal generation. More specifically, the present invention relates to an apparatus for wideband transmit signal generation, a method of operating the same, and a computer program product for carrying out the method of operating the same .
Background
In modern/future telecommunication systems, high throughput is a customer reguirement which gains more and more attention. Due to this, modern/future telecommunication systems show an increasing demand of transmit signal bandwidth. As a result of this development, a transmit signal bandwidth of several hundred MHz is currently expected for modern/future telecommunication systems. At the same time, environmental, commercial and technological aspects ask for low power consumption.
Accordingly, it is reguired that radio freguency (RF) units for modern/future mobile communication entities support transmission of such wideband transmit signals even with low power usage .
As one approach for enabling support of such wideband transmit signals, it may be conceivable to utilize separated RF units and antennas for transmitting separate narrowband transmit signals such that these combine on air. Yet, as plural RF units and antennas are reguired, such approach implies a strong impact to cost and size of mobile communication entities.
As another approach for enabling support of such wideband transmit signals, it may be conceivable to utilize a wideband-enabled transmit signal path, including e.g. a wideband digital pre-distortion (DPD) and a wideband power amplifier (PA), together with a single antenna. Yet, although power amplifiers capable of supporting such wideband transmit signals are under development, these have to cope with several challenges such as reduced efficiency and higher freguency dependency of their non-linearity operation with a higher transmit signal bandwidth. In order to achieve the same level of intermodulation suppression, the complexity and implementation effort of the DPD increases in more than a guadratic manner with regard to transmit signal bandwidth. For example, with PA transistors having resonances in the region of 250 MHz, a significant degradation of the digital pre-distortion result is expected for a transmit signal with 400 MHz bandwidth.
Accordingly, there is a demand for enabling/realizing generation of wideband transmit signals (or, stated in other words, support of transmission of wideband transmit signals) while avoiding the deficiencies of the aforementioned approaches.
Summary
Various exemplifying embodiments of the present invention aim at addressing at least part of the above issues and/or problems and drawbacks . Various aspects of exemplifying embodiments of the present invention are set out in the appended claims .
According to an example aspect of the present invention, there is provided an apparatus comprising a plurality of transmit signal generation circuits configured to generate a plurality of transmit signals having different freguency bands, a combination circuit configured to combine the plurality of transmit signals to generate an output transmit signal, the combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits, and a control circuit configured to control the plurality of transmit signal generation circuits in accordance with operating characteristics of the combination circuit.
According to a variant of the above example aspect, the operating characteristics of the combination circuit may comprise the freguency responses of the bandpass filter circuits of the combination circuit. According to a variant of the above example aspect, each of the plurality of transmit signal generation circuits may comprise a power amplification circuit .
According to a variant of the above example aspect, the control circuit may be configured to control an input signal of the power amplification circuit of each of the transmit signal generation circuits for an overlap region of the freguency responses of the plurality of bandpass filter circuits . According to a variant of the above example aspect, the control circuit may be configured to control the input signal of the power amplification circuit of each of the transmit signal generation circuits such that the resulting output signals are adjusted to combine with each other so as to produce a desired output transmit signal in the overlap region.
According to a variant of the above example aspect, the control circuit may be configured to control a digital pre- distortion circuit or an adaptive filter circuit arranged on an input side of the power amplification circuit.
According to a variant of the above example aspect, the control circuit may be configured to control one or more of the plurality of transmit signal generation circuits to switch off generation of the respective one or more transmit signals.
According to a variant of the above example aspect, the combination circuit may be configured to generate a wideband output transmit signal using at least two of the plurality of transmit signals, wherein said wideband output transmit signal has a freguency band involving the freguency bands of the at least two transmit signals, or one or more narrowband output transmit signals respectively using one of the plurality of transmit signals, wherein said narrowband output transmit signal has a freguency band involving the freguency band of the one transmit signal.
According to a variant of the above example aspect, the control circuit may be configured to select the one or more transmit signals to be used for generating the output transmit signal in accordance with a loss of each of the transmit signal generation circuits in a predetermined freguency region.
According to a variant of the above example aspect, the control circuit may be configured to control the plurality of transmit signal generation circuits using at least one of measurements of each of the transmit signals and the output transmit signal.
According to a variant of the above example aspect, the control circuit may be configured to identify a transformation network in each of the plurality of transmit signal generation circuits, and to control the plurality of transmit signal generation circuits using the identified transformation network of each of the transmit signal generation circuits. According to a variant of the above example aspect, the apparatus may further comprise a plurality of circulators arranged on an output side of each of the plurality of transmit signal generation circuits, each circulator being configured to transfer the generated transmit signal to a respective bandpass filter in the combination circuit.
According to a variant of the above example aspect, the control circuit may be configured to detect a loss of each of the transmit signal generation circuits in a predetermined freguency region of the freguency response of the respective bandpass filter using a reflected signal transferred from the respective bandpass filter by the respective circulator, and to control the plurality of transmit signal generation circuits using the detected loss of each of the transmit signal generation circuits. According to a variant of the above example aspect, the apparatus may further comprises a load modulation detection circuit configured to detect a load modulation between the plurality of transmit signal generation circuits, wherein the control circuit may be configured to control the plurality of transmit signal generation circuits using the detected load modulation.
According to a variant of the above example aspect, the apparatus may comprise or be comprised by a radio freguency unit of a mobile communication entity.
According to an example aspect of the present invention, there is provided a method of operating an apparatus comprising a plurality of transmit signal generation circuits and a combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits, the method comprising causing the plurality of transmit signal generation circuits to generate a plurality of transmit signals having different freguency bands, causing the combination circuit to combine the plurality of transmit signals to generate an output transmit signal, and controlling the plurality of transmit signal generation circuits in accordance with operating characteristics of the bandpass filter circuits.
According to a variant of the above example aspect, the method may further comprise causing the combination circuit to generate a wideband output transmit signal using at least two of the plurality of transmit signals, wherein said wideband output transmit signal has a freguency band involving the freguency bands of the at least two transmit signals, or generate one or more narrowband output transmit signals respectively using one of the plurality of transmit signals, wherein said narrowband output transmit signal has a freguency band involving the freguency band of the one transmit signal.
According to an example aspect of the present invention, there is provided a computer program product comprising computer-executable computer program code which, when the computer program code is executed on a computer, is configured to cause the computer to carry out a method according to the above method-related example aspect.
Further developments and/or modifications of the aforementioned example aspects of the present invention are set out in the following.
By way of exemplifying embodiments of the present invention, a technigue for generation of wideband transmit signals (or, stated in other words, support of transmission of wideband transmit signals) is provided. The technigue according to exemplifying embodiments of the present invention is capable of avoiding deficiencies such as increased cost and/or size as well as reduced efficiency and/or increased complexity due to increased transmit signal bandwidth.
Brief description of the drawings
In the following, the present invention will be described in greater detail by way of non-limiting examples with reference to the accompanying drawings, in which Figure 1 shows a simplified block diagram of a basic structure of an apparatus according to exemplifying embodiments of the present invention,
Figure 2 shows a diagram illustrating the principle of wideband coherent combining according to exemplifying embodiments of the present invention,
Figure 3 shows diagrams illustrating different operation modes under the principle of wideband coherent combining according to exemplifying embodiments of the present invention,
Figure 4 shows a block diagram of a first exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention,
Figure 5 shows a block diagram of a second exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention,
Figure 6 shows a block diagram of a third exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention, and
Figure 7 shows a flowchart of a method of operating an apparatus according to exemplifying embodiments of the present invention.
Detailed description
The present invention is described herein with reference to particular non-limiting examples and to what are presently considered to be conceivable embodiments of the present invention. A person skilled in the art will appreciate that the present invention is by no means limited to these examples and embodiments, and may be more broadly applied.
It is to be noted that the following description of the present invention and its embodiments mainly refers to explanations being used as non-limiting examples for exemplifying purposes. As such, the description of exemplifying embodiments given herein specifically refers to terminology which is related thereto. Such terminology is only used in the context of the presented non-limiting examples, and does naturally not limit the present invention in any way. Rather, any other structures, elements, modules, functionalities, etc. may also be utilized as long as complying with what is described herein and/or exemplifying embodiments described herein are applicable to it.
Hereinafter, various exemplifying embodiments and implementations of the present invention and its aspects are described using several variants and/or alternatives. It is generally noted that, according to certain needs and constraints, all of the described variants and/or alternatives may be provided alone or in any conceivable combination (also including combinations of individual features of the various variants and/or alternatives). In this description, the words "comprising" and "including" should be understood as not limiting the described exemplifying embodiments and implementations to consist of only those features that have been mentioned, and such exemplifying embodiments and implementations may also contain features, structures, elements, modules, functionalities etc. that have not been specifically mentioned . In the drawings, it is noted that lines/arrows interconnecting individual blocks or entities are generally meant to illustrate an operational coupling there-between, which may be a physical and/or logical coupling, which on the one hand is implementation-independent (e.g. wired or wireless) and on the other hand may also comprise an arbitrary number of intermediary functional blocks or entities not shown.
According to exemplifying embodiments of the present invention, in general terms, there is provided a technigue for generation of wideband transmit signals (or, stated in other words, support of transmission of wideband transmit signals ) .
Figure 1 shows a simplified block diagram of a basic structure of an apparatus according to exemplifying embodiments of the present invention.
As shown in Figure 1, an apparatus 100 according to exemplifying embodiments of the present invention comprises a plurality of transmit signal generation circuits 110 and 120, a combination circuit 130 and a control circuit 140. Each of the transmit signal generation circuits 110, 120 is configured to generate a transmit signal, i.e. a narrowband transmit signal, wherein the thus generated transmit signals have different freguency bands. For example, the freguency bands of two narrowband transmit signals may partly overlap or adjoin each other. The combination circuit 130 is configured to combine the plurality of transmit signals to generate an output transmit signal, and comprises a plurality of bandpass filter circuits BPFl, BPF2 having mutually overlapping freguency responses for - li
the plurality of transmit signal generation circuits, i.e. one bandpass filter circuit for each transmit signal generation circuit. As indicated by dashed arrows, the control circuit 140 is configured to control the plurality of transmit signal generation circuits. Such control may be performed in accordance with operating characteristics of the combination circuit, such as e.g. the freguency responses of the bandpass filter circuits of the combination circuit 130. While the exemplary structure of Figure 1 illustrates two transmit signal generation circuits, it is to be noted that the present invention is not limited to such configuration. Rather, there may be an arbitrary number of transmit signal generation circuits, such as e.g. three or more. In such case, the freguency responses of a pair of bandpass filter circuits for two of the transmit signal generation circuits are mutually overlapping, respectively.
According to exemplifying embodiments of the present invention, the combination circuit 140 is operable to combine the plurality of transmit signals to generate an output transmit signal under the principle of wideband coherent combining (CC) . In this regard, the principle of wideband coherent combining (CC) refers to a freguency- dependent combination of narrowband transmit signals using bandpass filter circuits with overlapping freguency responses. Thereby, the narrowband signals can be combined such that a desired output transmit signal in the overlap region can be generated.
In a non-limiting example (as exemplified in Figures 4 to 6 below) , in which the transmit signal generation circuits each comprise a power amplification circuit such as a power amplifier (PA) , for the overlap region, the PA input signals are controlled so that the phase of the PA output signals will combine to the desired output signal. Accordingly, the control circuit may control an input signal of the power amplification circuit of each of the transmit signal generation circuits for an overlap region of the freguency responses of the plurality of bandpass filter circuits. More specifically, the control circuit may control the input signal of the power amplification circuit of each of the transmit signal generation circuits such that the resulting output signals are adjusted to combine with each other so as to produce a desired output transmit signal in the overlap region. According to exemplifying embodiments of the present invention, the control of the plurality of transmit signal generation circuits may be based on various parameters, such as at least one of measurements of each of the transmit signals and the output transmit signal. For example, the control may be based on (a measurement of) one or more of the transmit signals, or may be based on (a measurement of) the output transmit signal, or may be based on both (a measurement of) one or more of the transmit signals and (a measurement of) the output transmit signal. Figure 2 shows a diagram illustrating the principle of wideband coherent combining according to exemplifying embodiments of the present invention.
In the diagram of Figure 2, the horizontal axis represents the freguency, the dashed curve represents the freguency response of a first bandpass filter circuit denoted by BPFl corresponding to (the frequency band of the narrowband transmit signal of) a first transmit signal generation circuit, and the chain line represents the frequency response of a second bandpass filter circuit denoted by BPF2 corresponding to (the frequency band of the narrowband transmit signal of) a second transmit signal generation circuit. Also, the rectangles represent individual frequency carriers, wherein the solid rectangles represent carriers in the frequency band of the first transmit signal generation circuit, and the hatched rectangles represent carriers in the frequency band of the second transmit signal generation circuit.
According to exemplifying embodiments of the present invention, the principle of coherent combining (CC) is applied in the overlap region between the two frequency responses, which is represented by the dotted oval. As a result of the application of the principle of coherent combining (CC) in the overlap region, a wideband output transmit signal with a flat frequency characteristic, i.e. a (nearly) constant power, voltage or the like over the entire frequency band including the overlap region can be obtained .
Hence, by application of coherent combining in the in the overlap region between the two frequency responses of separate bandpass filter circuits, which realizes an appropriate addition of signal powers in the relevant frequency region, it is possible to utilize power amplifiers with a lower peak power than would be required otherwise . According to exemplifying embodiments of the present invention, the combination circuit 140 is operable in different operation modes, as outlined below.
Figure 3 shows diagrams illustrating different operation modes under the principle of wideband coherent combining according to exemplifying embodiments of the present invention .
In the first diagram of Figure 3, denoted by "common TX", the combination circuit operates in a first operation mode, in which a wideband output transmit signal is generated using two transmit signals (in general, at least two of a plurality of transmit signals) . In this case, which basically corresponds to the case illustrated in Figure 2, the resulting wideband output transmit signal has a freguency band involving the freguency bands of both (in general, the at least two) transmit signals.
In any one of the second and third diagrams of Figure 3, denoted by "TX0" and "TXl", the combination operates in a second operation mode, in which a narrowband output transmit signal is generated using one of the two (in general, the plurality of) transmit signals. In this case, the resulting narrowband output transmit signal has a freguency band involving the freguency band of the one transmit signal. As illustrated, the resulting narrowband output transmit signal may comprise a part of the other transmit signal in the overlap region, respectively. This is specifically effective when the same data signal is transmitted via both transmit signal paths.
It is to be noted that the operation modes illustrated in the second and third diagrams of Figure 3 can also be combined such that e.g. two narrowband output transmit signals are generated respectively using one of the two (in general, the plurality of) transmit signals.
According to exemplifying embodiments of the present invention, the control circuit may control one or more of the plurality of transmit signal generation circuits to switch off generation of the respective one or more transmit signals. Namely, the control circuit may select one or more transmit signals to be used for generating the output transmit signal (i.e. switch on or activate generation thereof), thus setting the respective transmit signal/signals in a high power or switch-on state. Stated the other way round, deselect one or more transmit signals not to be used for generating the output transmit signal (i.e. switch off or deactivate generation thereof), thus setting the respective transmit signal/ signals in a low power or switch-off state. For example, such de-/selection may be made in accordance with a loss of each of the transmit signal generation circuits (or e.g. its power amplifier) in a predetermined freguency region such as the overlap region. Based thereon, in the illustrated example, both transmit signal generation circuits can be used for the generation/provision of the output transmit signal in a freguency region in which both of them are effectively operable in view of their loss characteristics (e.g. when both transmit signal generation circuits or e.g. their power amplifiers exhibit a similar loss) . Otherwise, in a freguency region in which only one of the transmit signal generation circuits is effectively operable in view of their loss characteristics (e.g. when one of the transmit signal generation circuits or e.g. their power amplifiers exhibits a (significantly) lower loss than the other), the transmit signal generation circuit with the lower loss can be used for the generation/provision of the output transmit signal. In order to improve efficiency, one or more of the plural transmit signal generation circuits (such as power amplification circuits thereof) may be controlled to be switched off when its/their freguency band/bands is/are not reguired for generation/provision of the output transmit signal . In the following, exemplary structures according to exemplifying embodiments of the present invention are described with reference to Figures 4 to 6. Similar to the basic structure of Figure 1, two transmit signal generation circuits are again illustrated for explanatory purposes without limiting the configuration to such number. As indicated by dashed boxes in any one of Figures 4 to 6, each of the transmit signal generation circuits comprises a power amplifier PA and a digital pre-distortion circuit DPD (which could also be replaced or accompanied by any type of adaptive filter circuit) arranged on an input side of the power amplifier PA. Arranged in-between, each of the transmit signal generation circuits exemplarily also comprises a digital-to-analog converter DAC, a local oscillator and a low-power transmit signal TX . With reference to Figures 4 and 5 below, exemplifying embodiments of the present invention are described, in which circulators are used for controlling the transmit signal generation circuits . Figure 4 shows a block diagram of a first exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention.
As shown in Figure 4, an exemplary RF unit according to exemplifying embodiments of the present invention comprises two transmit signal generation circuits (indicated by dashed boxes), a filter combiner and a control circuit, like the apparatus of Figure 1, as well as a circulator at the output of the filter combiner, and a duplex filter towards an antenna.
While the circulators in the narrowband transmit signal paths are illustrated as part of the respective transmit signal generation circuits, it is to be noted that such illustration is made for explanatory purposes only without any limitation to such configuration. Namely, the circulators in the narrowband transmit signal paths may be also be arranged outside of the respective transmit signal generation circuits, as long as being arranged on an output side of each of the plurality of transmit signal generation circuits. That is, the circulator in each narrowband transmit signal path is configured to transfer the generated narrowband transmit signal to a respective bandpass filter in the filter combiner representing a combination circuit.
As shown in Figure 4, the control of the transmit signal generation circuits may be based on various control inputs . Specifically, such control inputs may comprise one or more of measurements of each of the narrowband transmit signals (as indicated by angled arrows between PA0/PA! and the respective circulator) and a measurement of the output transmit signal (as indicated by an angled arrow between the adder in the filter combiner and the following circulator) . A measurement of the output transmit signal, i.e. the combined transmit signal, can be effectively used for ensuring a flat frequency characteristic, i.e. a (nearly) constant power, voltage or the like over the entire frequency band including the overlap region.
Additionally or alternative, such control inputs may comprise one or more of losses of the transmit signal generation circuits (e.g. PA0/PAi, the respective circulator, or the like) in a predetermined frequency region of the frequency response (such as the frequency region thereof) of the respective bandpass filter. Such a loss of a transmit signal generation circuit (e.g. PA0/PAi) may be obtained using a reflected signal transferred from the respective bandpass filter (to the control circuit) by the respective circulator (as indicated by arrows from between the respective circulator and the control block) . Based on the thus detected loss/losses, a loss-related control can be performed, as outlined above. Taking into consideration one or more reflected signals in the control can be effectively used for generation/provision of an output transmit signal capable of compensating for such reflection or reflections . Figure 5 shows a block diagram of a second exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention.
The exemplary RF unit of Figure 5 is basically similar to that of Figure 4. Accordingly, the description of similar parts and functionalities is omitted, and only differences are described below.
As shown in Figure 5, an exemplary RF unit according to exemplifying embodiments of the present invention comprises two transmit signal generation circuits (indicated by dashed boxes), a filter combiner and a control circuit, like the apparatus of Figure 1, wherein the filter combiner is integrated with a duplex filter.
With reference to Figure 6 below, exemplifying embodiments of the present invention are described, in which load modulation is used for controlling the transmit signal generation circuits.
Figure 6 shows a block diagram of a third exemplary structure of a RF unit comprising an apparatus according to exemplifying embodiments of the present invention.
As shown in Figure 6, an exemplary RF unit according to exemplifying embodiments of the present invention comprises two transmit signal generation circuits (indicated by dashed boxes), a filter combiner and a control circuit, like the apparatus of Figure 1, as well as a circulator at the output of the filter combiner, and a duplex filter towards an antenna.
Although not shown in Figure 6, a load modulation detection circuit is provided in the control block or, stated in other words, load modulation detection means is realized by the control block. Such load modulation detection circuit is configured to detect a load modulation between the plurality of transmit signal generation circuits (as indicated by angled arrows between PA0/PAi and the respective bandpass filter), and the control of the plurality of transmit signal generation circuits may be based on the detected load modulation. Such load modulation may be based on transmit signals transferred between respective transmit signal generation circuits (such as a transfer of the transmit signal from PAi to PA0, and vice versa) and/or a reflected signal transferred from the respective bandpass filter back to the generating transmit signal generation circuit (such as a reflection of a signal from bandpass filter 0 to PA0, or the like) . Namely, due to transfer of such undesired signals, the load point/level of the respective transmit signal generation circuit (e.g. the load resistance of PAo/PAi) may change, thus reguiring a corresponding control of the affected transmit signal generation circuit. Based on the thus detected load modulation, a control similar to the above-outlined loss- related control can be performed. Taking into consideration one or more transferred signals in the control can be effectively used for generation/provision of an output transmit signal capable of compensating for such ( undesired/leaked) transfer or transfers.
Irrespective of the above, the control of the transmit signal generation circuits may be based on various control inputs, such as one or more of measurements of each of the narrowband transmit and a measurement of the output transmit signal, as described above in connection with Figure 4.
According to exemplifying embodiments of the present invention, in the exemplary RF unit of any one of Figures 4 to 6, the control of the transmit signal generation circuits may additionally or alternatively be based on characteristics of a transformation network in any one of the transmit signal generation circuits (i.e. the transformation network in ΡΑ0/ΡΑχ) . Accordingly, the control circuit in any one of Figures 4 to 6 may be configured to identify a transformation network in the transmit signal generation circuits, and to control the transmit signal generation circuits using the identified transformation network, respectively.
Figure 7 shows a flowchart of a method of operating an apparatus according to exemplifying embodiments of the present invention.
As shown in Figure 7, an operating method 700 of an apparatus comprising or being comprised by a radio freguency unit, such as the apparatus illustrated in any one of Figures 1 and 4 to 6, according to exemplifying embodiments of the present invention comprises the following processes. Such operating method is applicable for any apparatus comprising a plurality of transmit signal generation circuits and a combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits .
In process 710, the plurality of transmit signal generation circuits are caused to generate a plurality of transmit signals having different freguency bands. In process 720, the combination circuit is caused to combine the plurality of transmit signals to generate an output transmit signal. In process 730, the plurality of transmit signal generation circuits are controlled in accordance with operating characteristics of the combination circuit, such as e.g. the frequency responses of the bandpass filter circuits . Details of such operating method are evident from the functional description of Figures 1 to 6 above .
It is to be noted that Figure 7 merely shows an exemplary flowchart for illustrative purposes, in which an exemplary sequence of processes is illustrated. The present invention is however not limited to the illustrated sequence of processes. Rather, the process 730 may precede or (at least partly) overlap with the process 720, or all of the processes 710 to 730 may be performed simultaneously or in parallel or may (at least partially) overlap. Also, two or more of the processes may be performed in a mutually adaptive/dependent manner.
An operating method according to exemplifying embodiments of the present invention may be implemented by respective functional elements, entities, modules, units, processors, or the like, as described below. For example, it may be implemented by any kind of controller, processor, or the like, by hardware or software (and/or firmware) or any combination thereof. That is, such operating method may be embodied as a computer program product, e.g. computer code instructions stored in a computer-readable memory.
Generally, the above-described methods, procedures and functions may be implemented by respective functional elements, entities, modules, units, processors, or the like, as described below.
By virtue of exemplifying embodiments of the present invention, as evident from the above, a technique for generation of wideband transmit signals (or, stated in other words, support of transmission of wideband transmit signals) is enabled/realized.
According to exemplifying embodiments of the present invention, it is possible to utilize a single set/path of conventional/available elements such as narrowband power amplifiers and digital pre-distortion circuits. Hence, the technigue according to exemplifying embodiments of the present invention is capable of avoiding deficiencies such as increased cost and/or size as well as reduced efficiency and/or increased complexity due to increased transmit signal bandwidth. For example, liguid radio concepts for wider bandwidths such as transmit signals with a bandwidth of several hundred MHz, e.g. 400 MHz or more, can be implemented . According to exemplifying embodiments of the present invention, the principle of wideband coherent combining (CC) is efficiently adopted for generating wideband transmit signals, especially in an overlapping region of freguency responses of respective bandpass filter circuits used in the signal combination. Hence, exemplifying embodiments of the present invention enable an adeguate signal combination of different signals (e.g. signals for different freguency bands) being transmitted via plural transmit signal paths (without degradation DPD results, inaccurate impedance levels, additional load, etc., for example) .
In general, it is to be noted that respective functionalities, functional blocks or elements described above can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts . The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.
Any structural means such as a portion or other circuitry of an amplifier may refer to one or more of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of circuits and software (and/or firmware), such as (as applicable) : (i) a combination of processor(s) or (ii) portions of proces sor ( s )/ software (including digital signal processor ( s )) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) circuits, such as a microproces sor ( s ) or a portion of a microprocessor ( s ) , that reguire software or firmware for operation, even if the software or firmware is not physically present. Also, it may also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware, any integrated circuit, or the like.
Any procedural step or functionality is suitable to be implemented as software/firmware or by hardware without changing the idea of the present invention. Such software may be software code independent and can be specified using any known or future developed programming language, such as e.g. Java, C++, C, and Assembler, as long as the functionality defined by the method steps is preserved. Such hardware may be hardware type independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components. A device/apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device/apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor. A device may be regarded as a device/apparatus or as an assembly of more than one device/apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example.
Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof. Apparatuses and/or means or parts thereof can be implemented as individual devices, but this does not exclude that they may be implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person.
The present invention also covers any conceivable combination of method steps and operations described above, and any conceivable combination of nodes, apparatuses, modules or elements described above, as long as the above- described concepts of methodology and structural arrangement are applicable.
In view of the above, there is provided a technigue of wideband transmit signal generation. Such technigue exemplarily comprise an apparatus comprising a plurality of transmit signal generation circuits configured to generate a plurality of transmit signals having different freguency bands, a combination circuit configured to combine the plurality of transmit signals to generate an output transmit signal, the combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits, and a control circuit configured to control the plurality of transmit signal generation circuits in accordance with operating characteristics of the combination circuit, such as e.g. the freguency responses of the bandpass filter circuits of the combination circuit .
Even though the invention is described above with reference to the examples according to the accompanying drawings, it is to be understood that the invention is not restricted thereto. Rather, it is apparent to those skilled in the art that the present invention can be modified in many ways without departing from the scope of the inventive idea as disclosed herein.
List of acronyms and abbreviations
3GPP 3r Generation Partnership Project
BP Bandpass
BPF Bandpass Filter BW Bandwidth
CC Coherent Combining
DAC Digital-to-Analog Converter
DPD Digital Pre-Distortion
LO Local Oscillator PA Power Amplifier
RF Radio Freguency
RX Receive/Reception
TX Transmit/Transmission
VSWR Voltage Standing Wave Ratio

Claims

Claims
1. An apparatus comprising a plurality of transmit signal generation circuits configured to generate a plurality of transmit signals having different freguency bands, a combination circuit configured to combine the plurality of transmit signals to generate an output transmit signal, the combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits, and a control circuit configured to control the plurality of transmit signal generation circuits in accordance with operating characteristics of the combination circuit.
2. The apparatus according to claim 1, wherein the operating characteristics of the combination circuit comprise the freguency responses of the bandpass filter circuits of the combination circuit.
3. The apparatus according to claim 1 or 2, wherein each of the plurality of transmit signal generation circuits comprises a power amplification circuit.
4. The apparatus according to claim 3, wherein the control circuit is configured to control an input signal of the power amplification circuit of each of the transmit signal generation circuits for an overlap region of the freguency responses of the plurality of bandpass filter circuits .
5. The apparatus according to claim 4, wherein the control circuit is configured to control the input signal of the power amplification circuit of each of the transmit signal generation circuits such that the resulting output signals are adjusted to combine with each other so as to produce a desired output transmit signal in the overlap region.
6. The apparatus according to claim 4 or 5, wherein the control circuit is configured to control a digital pre-distortion circuit or an adaptive filter circuit arranged on an input side of the power amplification circuit.
7. The apparatus according to any one of claims 1 to 6, wherein the control circuit is configured to control one or more of the plurality of transmit signal generation circuits to switch off generation of the respective one or more transmit signals.
8. The apparatus according to any one of claims 1 to 7, wherein the combination circuit is configured to generate a wideband output transmit signal using at least two of the plurality of transmit signals, wherein said wideband output transmit signal has a frequency band involving the frequency bands of the at least two transmit signals, or one or more narrowband output transmit signals respectively using one of the plurality of transmit signals, wherein said narrowband output transmit signal has a frequency band involving the frequency band of the one transmit signal.
9. The apparatus according to claim 8, wherein the control circuit is configured to select the one or more transmit signals to be used for generating the output transmit signal in accordance with a loss of each of the transmit signal generation circuits in a predetermined frequency region .
10. The apparatus according to any one of claims 1 to 9, wherein the control circuit is configured to control the plurality of transmit signal generation circuits using at least one of measurements of each of the transmit signals and the output transmit signa1. - Si
11. The apparatus according to any one of claims 1 to 10, wherein the control circuit is configured to identify a transformation network in each of the plurality of transmit signal generation circuits, and to control the plurality of transmit signal generation circuits using the identified transformation network of each of the transmit signal generation circuits.
12. The apparatus according to any one of claims 1 to 11, further comprising a plurality of circulators arranged on an output side of each of the plurality of transmit signal generation circuits, each circulator being configured to transfer the generated transmit signal to a respective bandpass filter in the combination circuit.
13. The apparatus according to claim 12, wherein the control circuit is configured to detect a loss of each of the transmit signal generation circuits in a predetermined freguency region of the freguency response of the respective bandpass filter using a reflected signal transferred from the respective bandpass filter by the respective circulator, and to control the plurality of transmit signal generation circuits using the detected loss of each of the transmit signal generation circuits.
14. The apparatus according to any one of claims 1 to 11, further comprising a load modulation detection circuit configured to detect a load modulation between the plurality of transmit signal generation circuits, wherein the control circuit is configured to control the plurality of transmit signal generation circuits using the detected load modulation.
15. The apparatus according to any one of claims 1 to 14, wherein the apparatus comprises or is comprised by a radio freguency unit of a mobile communication entity.
16. A method of operating an apparatus comprising a plurality of transmit signal generation circuits and a combination circuit comprising a plurality of bandpass filter circuits having mutually overlapping freguency responses for the plurality of transmit signal generation circuits, the method comprising causing the plurality of transmit signal generation circuits to generate a plurality of transmit signals having different freguency bands, causing the combination circuit to combine the plurality of transmit signals to generate an output transmit signal, and controlling the plurality of transmit signal generation circuits in accordance with operating characteristics of the bandpass filter circuits.
17. The method according to claim 16, further comprising causing the combination circuit to generate a wideband output transmit signal using at least two of the plurality of transmit signals, wherein said wideband output transmit signal has a freguency band involving the freguency bands of the at least two transmit signals, or generate one or more narrowband output transmit signals respectively using one of the plurality of transmit signals, wherein said narrowband output transmit signal has a freguency band involving the freguency band of the one transmit signal.
18. A computer program product comprising computer- executable computer program code which, when the computer program code is executed on a computer, is configured to cause the computer to carry out the method according to claim 16 or 17.
PCT/EP2014/070857 2014-09-30 2014-09-30 Wideband transmit signal generation WO2016050273A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4217661A (en) * 1975-10-14 1980-08-12 Kahn Leonard R Audio signal transmission system and method incorporating automatic frequency correction
US20090052556A1 (en) * 2007-08-23 2009-02-26 Fernandez Andrew D Frequency interleaving method for wideband signal generation
WO2011109128A1 (en) * 2010-03-02 2011-09-09 The Aerospace Corporation Increased capacity communication links with spectrum sharing

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4217661A (en) * 1975-10-14 1980-08-12 Kahn Leonard R Audio signal transmission system and method incorporating automatic frequency correction
US20090052556A1 (en) * 2007-08-23 2009-02-26 Fernandez Andrew D Frequency interleaving method for wideband signal generation
WO2011109128A1 (en) * 2010-03-02 2011-09-09 The Aerospace Corporation Increased capacity communication links with spectrum sharing

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