EP1958405A2 - Creation d'un signal de porteuse rf module a bande passante modulee en largeur d'impulsion - Google Patents

Creation d'un signal de porteuse rf module a bande passante modulee en largeur d'impulsion

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Publication number
EP1958405A2
EP1958405A2 EP06842209A EP06842209A EP1958405A2 EP 1958405 A2 EP1958405 A2 EP 1958405A2 EP 06842209 A EP06842209 A EP 06842209A EP 06842209 A EP06842209 A EP 06842209A EP 1958405 A2 EP1958405 A2 EP 1958405A2
Authority
EP
European Patent Office
Prior art keywords
signal
phase
carrier signal
modulated carrier
class
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Withdrawn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
EP06842209A
Other languages
German (de)
English (en)
Inventor
Jukka Varis
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.)
Nokia Oyj
Original Assignee
Nokia Oyj
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 Oyj filed Critical Nokia Oyj
Priority to EP06842209A priority Critical patent/EP1958405A2/fr
Publication of EP1958405A2 publication Critical patent/EP1958405A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
    • H04L25/40—Transmitting circuits; Receiving circuits
    • H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
    • H04L25/4902—Pulse width modulation; Pulse position modulation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C5/00—Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal
    • 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
    • H03F3/19—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
    • H03F3/191—Tuned 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
    • H03F3/217—Class D power amplifiers; Switching amplifiers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/36—Modulator circuits; Transmitter circuits
    • H04L27/361—Modulation using a single or unspecified number of carriers, e.g. with separate stages of phase and amplitude modulation

Definitions

  • the present invention relates to a modulator for generating a modulated carrier signal from an input signal with a time-varying envelope according to claim 1 , respective methods according to claims 20 and 22, and a mobile communications terminal according to claims 24 and 25.
  • the present invention relates generally to a transmitter structure with high efficiency power amplifiers, wherein a bandpass pulse width modulation (BP-PWM) for generation of the modulated carrier signal is used.
  • BP-PWM bandpass pulse width modulation
  • 4G fourth-generation
  • 4G fourth-generation
  • 4G fourth-generation
  • 4G fourth-generation
  • 4G quaternary phase-shift keying
  • CDMA code division multiplex access
  • Bandwidth is expected to be higher than 20 MHz to support the demand for multimedia services.
  • QPSK-CDMA systems are usually realized using direct up-conversion transmitters.
  • a QPSK-CDMA system generates a varying envelope signal, which must be linearly amplified to high power lev- els for long-range communications.
  • a linear amplifier is required to avoid amplitude as well as phase distortion through AM/PM conversion in the amplified variable envelope modulated signal.
  • the requirement for a linear amplification for a variable envelope modulated signal generally results in a less efficient amplifier than in the case of amplifying constant envelope modulated signal.
  • a known approach is to use high efficiency amplifier configurations together with appropriate modulation formats that can provide envelope variation. That is, a high efficiency non-linear amplifier driven by a dedicated control signal results in a high efficiency amplifier, which behaves, quasi-linear.
  • the main concern is the generation of the required driving signal for a switching mode power amplifier (SMPA).
  • SMPA switching mode power amplifier
  • pulse width modulation may be a promising approach to provide both efficiency and linearity in power amplification.
  • Fig. 1 shows schematically the modulator 100, wherein input modulation signals I and Q, e.g. a OQPSK (Offset Quaternary Phase Shift Keying) signal as used in CDMA, are input to a converter 110, which outputs phase and amplitude modulation signals.
  • I and Q e.g. a OQPSK (Offset Quaternary Phase Shift Keying) signal as used in CDMA
  • phase and amplitude modulation signals are fed to digitally driven ⁇ -modulators 121 and 122, operated at a carrier frequency fc, e.g. 900MHz for cellular band communication.
  • the carrier frequency fc is derived by frequency dividing means 135 from a local oscillator 130.
  • the PM ⁇ -modulator 121 provides a digital output word corresponding to predetermined digital values for pulse position.
  • the output of the PM ⁇ -modulator 121 controls a digital pulse delay modulator 140, which acts on the input periodic pulse train to produce a phase modulated output pulse train. Then, this phase modulated pulse train is fed to a pulse width modulator 150, which selects a pulse width value from predetermined digital values, in accordance with the output by the AM ⁇ -modulator 122.
  • the output of the modulator 100 is a full pulse modulated signal with a constant envelope for driving a switching power amplifier in the output for a quasi-linear amplification of the input signal with time- varying envelope.
  • two ⁇ -modulators are necessary in addition to the pulse position modulator (PPM) and pulse width modulator (PWM).
  • the PPM and PWM modulators 121 , 122 require a digital clock, which has to be approximately 7 GHz. Moreover, there is high quantization noise outside the signal band due to the ⁇ -modulation, which is folded back into the frequency band of interest by residual nonlinearity.
  • the transmitter 200 for generating the bandpass RF signal comprises a modulator for the two orthogonal input signals I, Q of a time-varying envelope signal comprises a low frequency portion 201 , a high frequency portion 202, a local oscillator 210 for generating the carrier signal, a SMPA 204 for amplifying the modulated carrier signal and a bandpass filter 206 for delivering the respective radio frequency (RF) output signal RFout.
  • the modulator low-frequency portion 201 includes control means 205 for determining amplitude and phase, respectively, related information content of the modulation signal encoded in the input signals I and Q and for generating respective amplitude and phase related control signals. These control signals are used to encode the desired BP-PWM signal.
  • the modulator high-frequency RF portion 202 comprises the local oscillator 210 generating a substantially sinusoidal RF frequency signal, which is fed to two identical branches each having respective phase modulators 241 and 242 which are controlled by respective control signals generated from the amplitude and phase related modulation signals.
  • the RF signal output from the respective phase modulators 241 and 242 have phase information corresponding to the amplitude and phase related modulation signal.
  • the respective pulse position modulated (PPM) signals are used for driving the SMPA 204 and at the same time are combined and bandpass filtered by the bandpass filter 206 such that the desired radio frequency (RF) output signal RFout is present.
  • the PM and AM processes are executed simultaneously by means of two parallel and identical branches that are controlled by dedicated control signals.
  • the structure of the modulator in Fig. 2 is called herein paral- IeI BP-PWM as acronym.
  • the two branches, which are used in parallel of the transmitter structure have to be strictly identical to avoid distortion caused by amplitude and phase imbalances.
  • both branches have to have identical components as identical phase modulators.
  • phase modulators should be replaced with, for instance, standard FM-synthesizers, additional processing is needed beside two separate and strictly similar synthesizers.
  • a modulator for generating a pulse width modulated carrier signal from an input signal with time-varying envelope.
  • the modulator comprises control means arranged for generating from said input signal respective modulator control signals related to phase and amplitude information content of the input signal.
  • Generator means provide a carrier signal to first phase modulating means for phase modulation of the carrier signal.
  • the first phase modulating means are controlled by a first phase control signal from the control means.
  • the phase modulated carrier signal is input to a first and a second branch.
  • the second phase modulating means are controlled by a second phase control signal from the control means.
  • Signal combiner means are arranged for combining the phase modulated signal from the first branch and said phase modulated carrier signal from the second branch to provide at a output of the combiner means the pulse width modulated carrier signal.
  • the input signal consists of two orthogonal input signals.
  • These input signals may be orthogonal I- and Q-signals, so called In-phase and Quadrature- phase components of the input signal with time-varying envelope.
  • the modulator further comprises converter means for deriving amplitude and phase information related signals from said orthogonal input signals.
  • the respective amplitude and phase information related signals are input to first control means, which comprise pre-distortion means adapted to pre- distort said amplitude information signal.
  • control means are arranged to generate the first phase control signal as combination of the phase information related signal from said input signals and the pre-distorted amplitude information related signal from said input signals modified by a first compensation factor and to generate the second phase control signal from the pre-distorted amplitude information related signal.
  • the first phase control signal corresponds to the actual value of the phase information related signal reduced by half of the actual value of the pre- distorted amplitude information related signal. That is, the actual value of the phase information related signal of the input signal is reduced by half of the phase that corresponds to the momentary value of the amplitude information related signal.
  • a delay means such as a signal delay block, for a delay of the respective second phase control signal from said control means.
  • PM and AM processes can be executed at the same time.
  • the PM and AM processes could as well be implemented in reverse order, so that the PM process is delayed.
  • the modulator comprises further in the first branch third phase modulating means for additional phase modula- tion of the phase modulated carrier signal.
  • the third phase modulating means are controlled by a third phase control signal from the control means.
  • the control means are arranged to generate the first phase control signal from the phase information related signal, the second phase control signal from the pre-distorted amplitude information related signal, and the third phase control signal from the pre-distorted amplitude information related signal modified by a second compensation factor.
  • the first phase control signal corresponds to the actual value of the phase information related signal
  • the second phase control signal corresponds to the actual value of the pre-distorted amplitude information related signal
  • the third phase control signal corresponds to the actual value of the pre-distorted amplitude information related signal with reversed sign.
  • delay compensation may be needed for equalizing the time differences between PM and AM processes.
  • delay compensation between the amplitude modulation process, which is performed by the first phase modulating means for phase modulation of the carrier signal, and the phase modulation processes, which is performed by the second phase modulating means for the additional phase modulation of the phase modulated carrier signal in the second branch there may be provided respective delay means for a delay of the respective second phase control signal from said control means and the respective third phase control signal from said control means, respectively.
  • the generated carrier signal may be a sinusoidal signal and the modulator may consist of substantially analog circuitry.
  • the modulator further comprises signal limiters in the first and second branch before the signal combiner means.
  • the carrier base signal may be a pulse signal and the modulator may consist substantially of digital circuitry.
  • parts of the modulator according to the invention consist of digital circuitry as well as analog circuitry.
  • the control means may be implemented as digital circuitry and the carrier signal gener- ating means together with the respective phase modulators and the combiner may be implemented in analog circuitry.
  • a method for generating a pulse width modulated carrier signal from a input signal with a time-varying envelope comprises the steps: generating a carrier signal; generating a first modulated car- rier signal by phase modulating the carrier signal corresponding to first phase control signal and generating a second modulated carrier signal by phase modulating the first modulated carrier signal corresponding to second control signal; and combining the first modulated carrier signal with the second modulated carrier signal to the pulse width modulated carrier signal.
  • the first phase control signal corresponds to the actual value of the phase information of the input signal reduced by half of the actual value of pre- distorted amplitude information of the input signal
  • the actual value of the phase related information of the input signal is reduced by half of the phase that corresponds to the momentary value of the amplitude related information.
  • a method for generating a pulse width modulated carrier signal from a input signal with a time-varying envelope comprises the steps: generating a carrier signal; generating a first modulated carrier signal by phase modulating the carrier signal corresponding to a first phase control signal and generating a second modulated carrier signal by additionally phase modulating the first phase modulated carrier signal corresponding to a second control signal; generating a third modulated carrier signal by additionally phase modulating the first modulated carrier signal corresponding to a third control signal; and combining the second modulated carrier signal with the third modulated carrier signal to the pulse width modulated carrier signal.
  • the first phase control signal corresponds to the actual value of phase information of the input signal
  • the second phase control signal corresponds to the actual value of pre-distorted amplitude information of the input signal
  • the third phase control signal corresponds to the actual value of the pre-distorted amplitude information with reversed sign.
  • a mobile communication terminal comprises a transmitter having a modulator for generating a radio frequency modu- lated carrier signal for transmission according to the first aspect of the present invention.
  • a mobile communication terminal comprises a transmitter having circuitry arranged for generating a radio frequency modulated carrier signal for transmission by use of a method according to one of the second or third aspect of the present invention.
  • Fig. 1 shows a RF pulsewidth modulator utilizing delta-sigma ( ⁇ ) modulators in the prior art for generating a BP-PWM signal, in which AM and PM processes are executed separately and controlled by separate ⁇ -modulators;
  • Fig. 2 shows a modulator structure of the prior art using PWM and PPM for generating a BP-PWM signal, in which AM and PM processes are executed simultaneously in two parallel and identical branches;
  • Fig. 3A shows a modulator structure according to a first embodiment of the present invention
  • Fig. 3B illustrates the control means of Fig. 3A in more detail
  • Fig. 4A shows a modulator structure according to a second embodiment of the present invention.
  • Fig. 4B illustrates the control means of Fig. 4A in more detail.
  • T 1//
  • f the frequency of which is equal to the desired RF-frequency or a base frequency of the desired RF-frequency.
  • a sinusoidal carrier signal may be used, which when applied to a limiter comes close to the required two-state signal for driving the SMPA.
  • the SMPA does not cause significant phase distortion, but due to its two-state behavior, it is very non-linear as to the amplitude.
  • the driving signal is processed such that neither phase nor amplitude information of the modulation signal is embedded in the amplitude of the driving signal. Consequently, both phase and amplitude information of the input signal is to be modulated to the transition times, i.e. the edges, of the pulse train for driving the SMPA.
  • the coding approach of the invention divides the required modulation into a phase modulation (PM) part and an amplitude modulation (AM) part.
  • the PM part may be realized in any of a number of known methods to generate a phase modulated constant envelope signal and for adding the phase information to the carrier signal.
  • the AM part then adds the amplitude information by controlling the width of the resultant pulses of the carrier signal.
  • PM and AM are related to the information content of the original modulation signal, i.e. the respective phase and amplitude information related content.
  • the essence of these so-called outphasing techniques lies in the realization that any envelope and phase-modulated signal can be represented by the summation of two components with fixed envelope but varying in phase.
  • BW-PWM signals the basic principle behind BW-PWM signals is that the durations of individual pulses are proportional to the amplitude of the modulated signal, and that the locations of the individual pulses are pulse-position modulated (PPM) according to the phase content of the modu- lated signal.
  • PPM pulse-position modulated
  • the modulator structures 301 and 302 comprise a low frequency part 400 and a high frequency part 500 by which the modulated carrier signal is provided to an amplifier 304. Then, at the output of a bandpass filter 306, which lets the desired frequency band for transmission pass through, the BP- PWM carrier signal RFout is present.
  • the output can be a two-state signal or tri-state signal.
  • the tri-state signal does not contain spectral components in the vicinity of DC, since the time average of the pulses is zero.
  • the bandpass filter (BPF) may be replaced by a low pass filter (LPF).
  • LPF low pass filter
  • the BPF may be required.
  • the amplifier 304 may be a switching mode power amplifier, which may be supplied by a switching mode power supply based on a DC-to-DC converter design and used to control the output power of the transmitter.
  • the limited minimum width of pulses may cause dynamic range degeneration.
  • tuning the supply volt- age(s) of the amplifier 304 may be used for control of output power.
  • the SMPA may be of any now-known amplifier configuration for future-developed amplifiers having operational properties to carry out the intended functions of the present in- vention.
  • the SMPA is a high efficiency amplifier design such as class-D, class-E or class-S.
  • the invention is not limited to such configurations and may also include, for example, class-C or saturated class-B amplifiers.
  • the input signal with a time-varying envelope is input to the low frequency part 400.
  • said input signals consist of two orthogonal signals, an In-phase input signal I and a Quadrature-phase input signal Q, which present the In-phase and Quadrature-phase components of the input modulation signal.
  • a converter 410 derives the amplitude and phase information related content from the l-input signal and the Q-input signal. In other words, the converter 410 performs a conversion from Cartesian coordinates I and Q into polar coordinates represented by amplitude and phase information.
  • the phase information related signal is provided at 411 and the amplitude information related signal is provided at 412.
  • Fig. 3A shows a first embodiment of the present invention.
  • the amplitude and phase information sig- nals at 411 , 412 are delivered to a first control unit 420a for generating respective first and second control signals provided at 421 and 422.
  • both the converter 410 and first control unit 420a are built with digital circuitry and thus controlled by a common clock signal CLK provided by any now-known clock signal generation means (not shown in Fig. 3A).
  • the first phase control signal at 421 and second phase control signal at 422 are input to the high frequency part 500 of the modulator 301. The generation of the first and second phase control signal will be explained in more detail below.
  • a generator 510 for generating a carrier signal, which may be at the center frequency of the re- quired RF-frequency or a base frequency thereof.
  • the generator 510 may be realized as any now-known local oscillator which may also be incorporated as a modulator sub-block, for example in the first phase modulator 521 , which will be described below.
  • any known analog circuitry as well as digital circuitry for implementation of an oscillator may be used. For instance, in "CMOS Wireless Phase-Shifted Transmitter", IEEE Journal of solid-state circuits, vol. 39, no. 8, August 2004, which is herewith incorporated by reference, S. Hamedi-Hagh at al. disclose a possible implementation for an analog local oscillator.
  • the carrier signal generated by the generator 510 is input to the first phase modulator 521 for a phase modulation of the carrier signal in accordance to the first phase control signal provided by the first control unit 420a in the low frequency part 400 at 421. Then the phase modulated carrier signal is output from the first phase modulator 521 and split into a first and a second branch 531 and 532. In the second branch 532, there is a second phase modulator 522 for an additional phase modulation of the already phase modulated carrier signal by the first phase modu- lator 521. The second phase modulator 522 carries out an additional phase modu- lation in accordance to the second phase control signal provided from the first control unit 420a.
  • both the phase modulated carrier signal of the first branch 531 and the twice phase modulated carrier signal of the second branch 532 are combined to the desired pulse width modulated carrier signal by a signal combiner 540, whose output corresponds to the output of the high frequency part 500 of the modulator 301.
  • the generated carrier signal is a digital signal
  • that is the digital signals are pulse-position modulated, which is equivalent to the phase-modulation of a sinusoidal signal.
  • mainly digital circuitry can be used and the combination of the phase modulated carrier signal of the first branch and the twice phase modulated carrier signal of the second branch 531 , 532 can be got either by using arithmetic operations alike subtraction or summation or logical operations alike AND-, OR-, or XOR-operations and their linear counterparts. It would also be possible to use sequential circuits as RS- and T-flip-flops. Preferred combining method depends on the specific application.
  • limiters 551 , 552 which are to be used, if the generated carrier signal is a analog, in particular a sinusoidal, signal, for instance, provided by an analog local oscillator. Since the input signals for the combiner 540 has to be digital in any case, such limiters 551 , 552 are preferably located before the signal combiner 540.
  • limiters 551 , 552 may also be used to enhance the operation of the used amplifier 304 and/or the signal combiner 540.
  • the combined signals of the first and second branch 531 , 532 constitute the desired radio frequency modulated carrier signal for transmission, which has a varying duty-cycle and is then power amplified by the amplifier 304.
  • Preferred power amplifier arrangements depend on the specific application. For instance, in US 2004/0251962 of the same inventor as the present application, which is related to a "Power Control for Switching Mode Power Amplifier" and incorporated herewith by reference, a possible configuration for a SMPA with power control is provided that may also be used together with the modulator of the present invention.
  • the above-mentioned class-E power amplifiers are critical with signals having a varying duty-cycle.
  • respective power amplifiers in the first branch 531 as well as the second branch 532 located before the signal combiner 540 instead of the location of the amplifier 304 or in addition to the amplifier 304.
  • CMOS Wireless Phase-Shifted Transmitter IEEE Journal of solid-state circuits, vol. 39, no. 8, August 2004, also a possible implementation is disclosed for applicable power amplifiers together with the realization of a signal combiner as well as a bandpass filter circuit.
  • the signals in the first and second branch 531 , 532 are digital signals and the respective power amplifiers are located before combination of the signals of the first and second branch 531 , 532, then the signals passing the respective amplifiers have constant duty-cycle.
  • class-E power amplifiers with very high gain can be used and can be driven in switching mode without strictly pulsed control.
  • the pulse width modulated carrier signal it is, depending on the application, also possible to utilize the existing variable gain amplifiers and linear power amplifiers.
  • the modulated output power including tuning of the l-and Q-signals, tuning pulse positions in connection with pulse width modulation or tuning pulse widths in connection with pulse position modulation, tuning the supply voltage of the power amplifier switches using a (slow) DC/DC- converter, and using a tunable attenuator after the power amplifier.
  • the first control unit 420a of the low frequency part 400 in the modulator 301 according to the present invention will be described in more detail. Therefore, reference is made to Fig. 3B. Accordingly, the phase information related signal at 411 and the amplitude information related signal at 412 are input to the first control unit 420a provided by the converter 410.
  • the amplitude information related signal is pre-distorted by a pre-distortion circuit 424a.
  • the respective pre-distorted amplitude information signal is used as the second phase control signal at 422.
  • the pre-distorted amplitude information signal or second phase control signal at 422, respectively is modified by a compensation circuit 426a and then combined with the phase information related signal at 411 by a signal combiner 428 which provides as output the first phase control signal at 421.
  • the combiner may be as mentioned above, for instance, an arithmetic summation circuit.
  • the modulator of the present invention for generating the modulated carrier signal as a bandpass pulse width modulated sig- nal the required phase modulation (PM) and amplitude modulation (AM) processes are performed separately in a serial manner, wherein in a first part of the high frequency section 500 the generated carrier signal is phase modulated in a respective phase modulation section PM and then with respect to the resultant BP-PWM carrier signal, in the amplitude modulation section AM a "single-edge" pulse width modulation is performed by only pulse position modulation in the second branch 532. Finally, by combining the signals from the first and second branch 531 , 532 the desired pulse width modulated signal is formed.
  • the required phase modulation (PM) and amplitude modulation (AM) processes are performed separately in a serial manner, wherein in a first part of the high frequency section 500 the generated carrier signal is phase modulated in a respective phase modulation section PM and then with respect to the resultant BP-PWM carrier signal, in the amplitude modulation section AM
  • An important feature of the present invention is the avoidance of unwanted phase modulation due to the fact that only one edge of pulses are modulated by only modulating the carrier signal in the second branch 532 in accordance with the second control signal, i.e. the amplitude information signal. That is a shift of the middle points of the pulses in the resultant signal would be present after the combining means 540.
  • Such unwanted phase shifting or phase modulation, respectively is entirely compensated according to the present invention by shifting the "original" phase modulated pulses by half of the momentary pulse width. Hence, the middle points of the resultant pulse width modulated signal after the combiner 540 do not drift according to the amplitude modulation any more.
  • Fig. 4A shows a second embodiment of the serial BP-PWM according to the present invention. It is to be noted that only differences of the second embodiment to the first embodiment have to be described in detail. Further, alike components are designated same reference signs.
  • the modulator 302 according to the second embodiment consists of the low frequency part 400 and a high frequency part 500, which provides the desired bandpass pulse width modulated signal to the respective amplifier 304 and bandpass filter 306 at the output of which the desired radio frequency bandpass pulse width modulated signal RFout is provided.
  • the main difference between the first and second embodiment is that in the amplitude modulation section AM of the high frequency part 500, additionally a third phase modulator 523 for phase modulation of the phase modulated carrier signal is provided in the first branch 531.
  • the third modulator 523 is controlled by a third phase control signal provided by the second control unit 420b of the low frequency part 400.
  • the first control unit 420a is replaced by a second control unit 420b, which is described in more detail with reference to Fig. 4B in the following.
  • the second control unit 420b has as input signals the phase information signal at 411 and the amplitude information signal at 412 provided by the converter 410 described above.
  • the second control unit 420b is arranged to generate the first phase control signal at 421 from the phase information signal.
  • the first phase control signal at 421 corresponds to the actual value of the phase information signal at 411.
  • the second control unit 420b is arranged to generate the second phase control signal at 422 from the amplitude information signal at 412 pre-distorted by a respective pre-distortion circuit 424b.
  • the second phase control signal at 422 corresponds to the actual value of the pre-distorted amplitude information signal at 412.
  • the second control unit 420b is arranged to generate the third phase control signal at 423 from the actual value of the pre-distorted amplitude information signal by modification with a second compensation factor applied by a compensation circuit 426b.
  • the second phase control signal at 422 corresponds to the actual value of the pre-distorted amplitude information signal and the third phase control signal at 423 corresponds to the actual value of the pre-distorted amplitude information signal with reversed sign, i.e. the pre-distorted amplitude information signal is multiplied with -1.
  • the pulse width modulation of the pulses of the car- rier signal is performed by a "double-edge" pulse width modulation.
  • the PWM process is realized by respective pulse position modulations (PPM) in both the first and second branch 531 , 532 of the amplitude modulation section AM.
  • PPM pulse position modulations
  • the third phase modulator 523 is needed in the amplitude modulation section AM.
  • the amplitude modulation section AM is now symmetrically.
  • the two PPM processes in the first and second branch 531 , 532 allow effectively two amplitude modulation controls: one for controlling the leading-edges, in the second branch 532 of the amplitude modulation section AM, and another for controlling the trailing-edges, in the first branch 531 of the ampli- tude modulation section AM.
  • the edges are shifted to opposite directions causing symmetrical double-edge modulation.
  • both edges are symmetrically modulated and phase fluctuation caused by amplitude modulation does not exist any more and phase correction is not needed.
  • time compensation means between the PM and AM processes may be necessary. This may be easily effected to the first embodiment (Fig. 3A) and second embodiment (Fig. 4A) of the invention by implementation of respective delay blocks 431 and 432, respectively, to the respective AM process phase control signal lines 422 and 423, respectively.
  • the BP-PWM according to the present invention provides several advantages vis- a-vis the prior art solutions. Since phase modulation and amplitude modulation processes are executed separately, the phase modulators have not to be identical any more. Moreover, the first phase modulating means 521 may be implemented separately, e.g. using an IQ-modulator or included in the frequency generator 510, i.e. merely, for example, a FM-synthesizer is needed.
  • the second phase modulator 522 in the first embodiment can be replaced with a phase shifter, for example a passive delay-line type phase modulator.
  • the control range will be 0 ⁇ a * ⁇ t) ⁇ ⁇ /2.
  • the second and third phase modulators 522, 523 in the second embodiment (Fig. 4A) can be replaced with phase shifters.
  • CMOS Wireless Phase-Shifted Transmitter IEEE Journal of solid-state circuits, vol. 39, no. 8, August 2004, also a solution for applicable phase shifters is disclosed.
  • the maximum needed local frequency generated by the frequency generation means 510 can be equal or lower than the desired center frequency of the generated modulated carrier signal. It is also possible to modulate directly other than the first pulse width modulation harmonic, which is explained in more detail in US 6,993,087 of the same inventor, which is incorporated herewith by reference.
  • the modulator of the present invention it is possible to utilize higher harmonics of the modulator output as well. Since the amplitude of the n-th harmonic is proportional to sin(n - ⁇ ) , where ⁇ denotes a parameter related to the first harmonic, by dividing in the pre-distortion part of the control units 420a or 420b, respectively, the pre-distorted amplitude by n, a distortion less amplitude can be arranged for the n-th harmonic. Likewise, it is also that the angle of the n-th harmonic of a sinusoidal signal passing a non-linear device exhibits similar expansion, that is, it will be multiplied by n. By diving the angle related to the input IQ- signals by n, it is possible to arrange the correct phase modulation for the n-th harmonic.
  • the modulator at a lower frequency then would otherwise be possible.
  • the benefit is exceptionally high for a fully digital modulator by allowing a lower clock frequency.
  • the use of sub-harmonics can be used to advantageously avoid mixing of the transmitting signal with the local oscillator.
  • the amplifier 304 still preserves the good efficiency provided that the unwanted harmonics may be terminated with high impedance to gain good power efficiency.
  • Other harmonics could also be filtered to meet spurious emission re- quirements.
  • the strong first harmonic should be filtered to produce an acceptable modulated output signal.
  • the serial structure of the bandpass pulse width modulator according to the present invention offers many possible embodiments to practical implementations.
  • the modulator structure provided by the present invention can advantageously be used in mobile communication terminals where high power efficiency is mandatory to realize long battery life.
  • a modulator and method for generation of a bandpass pulse width modulated carrier signal for efficient wireless transmitters for transmission of varying envelope signals has been provided.
  • the new structure of the BP-PWM consists of the serial and separate execution of the required phase and amplitude modulation processes which could be provided in any order, i.e., amplitude modulation process after phase modulation process or vice versa.
  • a first solution with single-edge pulse width modulation has been disclosed in which unwanted phase shifting by the amplitude modulation process is entirely compensated by appropriate shifting of the original phase modulated signal by half of the momentary pulse width in the amplitude modulation process.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Amplifiers (AREA)
  • Transmitters (AREA)

Abstract

L'invention porte sur un modulateur et sur un procédé de création d'un signal de porteuse modulé en largeur d'impulsion permettant à des émetteurs sans fil de transmettre efficacement des signaux à enveloppe variable. D'une manière générale, la nouvelle structure du modulateur de largeur d'impulsion consiste en l'exécution sérielle et séparée du processus requis de modulation de la phase et de l'amplitude. Selon une première solution, on module la largeur d'impulsion en jouant sur un seul flanc, ce qui permet de compenser les déphasages indésirables dus au processus de modulation de l'amplitude. Selon une deuxième solution, on module la largeur d'impulsion en jouant sur les deux flancs, ce qui permet de compenser les fluctuations de phase dues au processus de modulation de l'amplitude et de réduire les efforts de correction de phase.
EP06842209A 2005-12-01 2006-11-27 Creation d'un signal de porteuse rf module a bande passante modulee en largeur d'impulsion Withdrawn EP1958405A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP06842209A EP1958405A2 (fr) 2005-12-01 2006-11-27 Creation d'un signal de porteuse rf module a bande passante modulee en largeur d'impulsion

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP05026267 2005-12-01
EP06842209A EP1958405A2 (fr) 2005-12-01 2006-11-27 Creation d'un signal de porteuse rf module a bande passante modulee en largeur d'impulsion
PCT/IB2006/003370 WO2007063387A2 (fr) 2005-12-01 2006-11-27 Creation d'un signal de porteuse rf module a bande passante modulee en largeur d'impulsion

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EP1958405A2 true EP1958405A2 (fr) 2008-08-20

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EP (1) EP1958405A2 (fr)
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US8098726B2 (en) * 2007-07-27 2012-01-17 Intel Corporation Subranging for a pulse position and pulse width modulation based transmitter
US20090036064A1 (en) * 2007-07-31 2009-02-05 Ashoke Ravi Digital integrated transmitter based on four-path phase modulation
EP2498397B1 (fr) 2011-03-11 2017-10-04 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Appareil d'amplification d'un signal d'entrée
CN104065360B (zh) * 2014-06-19 2017-01-04 航天科工惯性技术有限公司 一种宽温应用且频率稳定可控的近正弦载波发生器
US10069662B2 (en) * 2015-11-10 2018-09-04 Infineon Technologies Ag Mixed analog-digital pulse-width modulator
CN109510633B (zh) * 2018-12-05 2020-09-25 中国人民解放军国防科技大学 特定谐波消除多电平射频脉宽调制的功率均衡方法及调制器

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US6049248A (en) * 1998-12-23 2000-04-11 Lucent Technologies Inc. Method and apparatus for generating a driver signal for use by a non-linear class S amplifier for producing linear amplification
US6993087B2 (en) * 2001-06-29 2006-01-31 Nokia Mobile Phones Ltd. Switching mode power amplifier using PWM and PPM for bandpass signals
US6975177B2 (en) * 2003-06-09 2005-12-13 Nokia Corporation Method and system for a generation of a two-level signal

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See references of WO2007063387A3 *

Also Published As

Publication number Publication date
WO2007063387A3 (fr) 2007-09-27
CN101322368A (zh) 2008-12-10
WO2007063387A2 (fr) 2007-06-07

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