WO2006137007A1 - Emetteur pour un systeme de communication sans fil - Google Patents

Emetteur pour un systeme de communication sans fil Download PDF

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Publication number
WO2006137007A1
WO2006137007A1 PCT/IB2006/051973 IB2006051973W WO2006137007A1 WO 2006137007 A1 WO2006137007 A1 WO 2006137007A1 IB 2006051973 W IB2006051973 W IB 2006051973W WO 2006137007 A1 WO2006137007 A1 WO 2006137007A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
digital
transmitter
carrier frequency
harmonics
Prior art date
Application number
PCT/IB2006/051973
Other languages
English (en)
Inventor
Xuecheng Qian
Original Assignee
Koninklijke Philips Electronics N.V.
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 Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2006137007A1 publication Critical patent/WO2006137007A1/fr

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/16—Multiple-frequency-changing
    • H03D7/165—Multiple-frequency-changing at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature
    • 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
    • H04B1/0475—Circuits with means for limiting noise, interference or distortion

Definitions

  • the invention relates to a transmitter for use in a wireless communication system, more particularly, as defined by the preamble of claim 1.
  • Such a transmitter is generally known.
  • digital user signal is usually at first converted into analog domain and then modulated to radio frequency by one or two steps.
  • Conventional dual up-conversion transmitter usually employs an intermediate frequency (IF) mixer and a radio frequency (RF) mixer to convert baseband user signal to IF and RF in sequence .
  • IF intermediate frequency
  • RF radio frequency
  • an IF filter and a RF filter are used to attenuate unwanted harmonics or interference respectively.
  • lowpass filter, automatic-gain-control and power amplifier are often used in order to have a clean modulated signal within certain dynamic range.
  • the performance depends much on the linearity of the mixer used for up-conversion and the selectivity of filters.
  • the cost of a transmitter depends much on the mentioned analog circuits.
  • FIG. 1 is a block schematic diagram of a direct up-conversion transmitter 100.
  • the digital users signals comprising in-phase component and quadrature component are converted to analog baseband signals by digital-to-analog converters 104 and 114, which are followed by lowpass filters 106 and 116 for removing harmonics at unwanted frequencies.
  • the analog signals are modulated directly to a carrier frequency signal in IF mixers 108 and 118 by multiplying the analog signals with quadrature local oscillating signals generated by a carrier frequency local oscillator 112 and 90° phase shifter 110.
  • the modulated signals are added up in a summator 120 to form a real signal, which is filtered by a RF filter 122 for attenuating out-of-band noise and spurious interference.
  • Automatic gain contol 124 and PA 126 might be used to tune the signal power within certain dynamic range. After that the antenna 128 transmits the modulated signal at carrier frequency.
  • the direct up-conversion transmitter still suffers many problems similar to conventional dual up-conversion transmitter.
  • the existing analog RF mixer is expensive for good performance.
  • the lowpass filter located between digital-to-analog converter and RF mixer needs to have a low cutoff frequency and is difficult to be re-dimensioned for other modes.
  • there exists other problems including local oscilator pulling, leakage of local oscilator signal to output of RF mixers and I/Q phase and amplitude mismatching.
  • the invention provides a transmitter comprising a first and a second digital-to-analog converters, for converting a first and a second digital signal to a first and a second anolog signal, the first and the second digital signal being the in-phase component and the quadrature component of a digital baseband signal, a summator and a band pass filter, characterized in that said first and second digital-to-analog converters operate at the same operating rate f s but with a time shift ⁇ , for keeping 90° phase difference between the harmonics at the carrier frequency in the first and second analog signal, the summator adding up the first and second analog signal to form a third signal, the band pass filter suppressing harmonics in the third signal while passing the harmonic at a predetermined carrier frequency f c as a modulated signal, whereby the carrier frequency f c is a multiple N of the operating rate f s of said first and second digital-to-analog converters.
  • the carrier frequency f c is a multiple N of the
  • the harmonics at the carrier frequency in the first and second analog signals can keep 90° phase difference exactly to remove the need of a 90° phase shifter.
  • the transmitter further comprises a lowpass filter, for suppressing harmonics at frequencies higher than the carrier frequency in the third signal.
  • the cutoff frequency of the lowpass filter is normally a bit higher than the carrier frequency and much higher than that in a direct up-conversion transmitter and thus the lowpass filter is very easy to be implemented in integrated circuits and re- dimensioned for other modes.
  • the invention further provides a communication system comprising a transmitter and a receiver, the transmitter being the transmitter according to the invention.
  • the invention provides a method of modulating digital signal to a predetermined carrier frequency, the method comprising: converting a first and a second digital signal to a first and a second analog signal via first and second digital-to-analog converters, the first and the second digital signal being the in-phase component and the quadrature component of a digital baseband signal, characterized in that said first and second digital-to-analog converters operate at the same operating rate f s but with a time shift ⁇ , for keeping 90° phase difference between the harmonics at the carrier frequency in the first and second analog signal, and the method further comprisng adding up the first and second annalog signal to form a third signal and suppresing harmonics in the third signal while passing the harmonic at a predetermined carrier frequency f c as a modulated signal, whereby the carrier frequency f c is a multiple N of the operating rate f s of said first and second digital-to-analog converters.
  • Fig. 1 is a block schematic diagram of a conventional direct up-conversion transmitter.
  • Fig. 2 is a block schematic diagram of a transmitter for use in a wireless communication system in accordance with the invention.
  • Fig.3 is a block schematic diagram of another embodiment of a transmitter in accordance with the invention.
  • Fig.4 is a block schematic diagram of a communication system comprising a transmitter in accordance with the invention.
  • Fig.5 is a flow chart illustrating a method of modulating a digital signal to a carrier frequency in accordance with the invention.
  • Fig.6 is a flow chart illustrating another embodiment of a method of modulating a digital signal to a carrier freqency in a transmitter provided in this invention.
  • Fig.2 is a block schematic diagram of a transmitter 200 for use in a wireless communication system in accordance with the invention.
  • the in-phase component DBS-I and quadrature component DBS-Q of a digital baseband signal are passed to digital-to- analog converters 204 and 214, where they are converted to a first and a second analog signal.
  • the first and the second analog signal are added up in a summator 220 to form a third signal having a plurality of harmonics.
  • the third signal is passed to a bandpass filter 236, which suppresses harmonics in the third signal while passing the harmonic at a predetermined carrier frequency ( f c ) as a wanted modulated signal (MS) to be transmitted.
  • f c predetermined carrier frequency
  • the operating rate f s should be selected in such a way that the carrier frequency f c is multiple of f s , that is wherein N is an integer and a wanted modulated signal is obtainable from the N - th harmonic of the first and second analog signal. Since the impulse response of a digital-to- analog converter is a rectangular function, there are period zeros in its amplitude frequency response. Hence, N shall be selected that the N - th harmonic in the first and the second analog signal is not located at the zeros of the frequency response.
  • the time difference between the digital-to-analog converters 204 and 214 shall be selected properly to keep 90° phase difference between the harmonics at the carrier frequency in the analog signals outputted by the digital-to-analog converters. This is explained below in detail.
  • I(t) and Q(t) are time-domain in-phase component and quadrature component of a digital baseband signal to be transmitted and /(/) and Q(f) are respectively spectrum signals, then/(/ + Nf s ) and Q(f + Nf s ) are their N - th harmonics at the carrier frequency f c in the first and second analog signal. Assuming all harmonics excepted the one at the predetermined carrier frequency have been suppressed by the bandpass filter 236. The signal processing could be concentrated on the harmonics at the carrier frequency.
  • the N - th harmonics of quadrature component is Q(f + Nf s )e ⁇ l2 ⁇ .
  • the first and second analog signal comprises harmonics at both/ c and -f c
  • the sum is further expressed as
  • n an integer and B is bandwidth of the baseband signal
  • B than bandwidth of the baseband signal is based on the consideration of signal
  • Fig.3 is a block schematic diagram of another embodiment of a transmitter 300 in accordance with the invention.
  • the transmitter 300 further comprises a highpass filter 232, perferably formed by an AC coupling, for removing baseband components and suppressing harmonics at frequencies lower than the carrier frequency and a lowpass filter 234 for suppressing harnomics at frequencies higher than the carrier frequency.
  • the highpass filter 232 and lowpass filter 234 are arranged after the summator 220. They cooperate with the bandpass filter 236 for further removing or attenuating unwanted harmonics and out-of- band interference.
  • the transmitter 300 further comprises an automatic- gain-control 244, for tuning the power of the modulated signal with certain dynamic range, a power amplifier 246, for amplifying power of the modulated signal, and an antenna 248, for transmitting the modulated signal, wherein the the power amplifier 246 is arranged after the automatic-gain-control 244 and is followed by the antenna 248.
  • the duty-cycle is chosen to be 0.5, which causes a loss of about
  • the lowpass filter 234 is chosen to be a 3 rd -order Butterworth type and its 3- dB cutoff frequency is also f c . It has an attenuation of 28.5dB on the 3 rd -order harmonic at
  • the fig.4 is a block schematic diagram of a communication system 10 comprising a transmitter and a receiver.
  • the transmitter is a transmitter in accordance with the invention.
  • the transmitter provided by this invention has same functions as a conventional up-conversion transmitter but it removes the needs of any mixer or 90° phase shifter, thereby simplifies the analog circuits, reduces cost and increases the flexibility of integrateion.
  • Fig.5 is a flow chart illustrating a method of modulating a digital signal to a carrier frequency in a transmitter provided in this invention.
  • a first and a second digital signal are converted to a first and a second anolog signal in the first and second digital-to-analog converters 204 and 214, the first and the second digital signal being the in-phase component and the quadrature component of a digital baseband signal.
  • the first and second digital-to-analog converters operate at same operating rate f s but with a time shift ⁇ , keeping 90° phase difference between the harmonics at the carrier frequency in the analog signals.
  • step 303 the first and second analog signal are added up in a summator 220 to form a third signal having a plurality of harmonics.
  • the carrier frequency f c is multiple N of the operating rate f s of the first and second digital-to- analog converters 204 and 214 and the operating rate is selected in such a way that the third signal comprises harmonics at the carrier frequency and the harmonics at the carrier frequency are not located at its zeros of the amplitude frequency response of the digital-to- analog converters.
  • step 304 harmonics in the third signal are suppressed but the harmonic at the carrier frequency f c is passed as a wanted modulated signal through a band pass filter 236.
  • Fig.6 is a flow chart illustrating another preferred method of modulating a digital signal to a carrier frequency in a transmitter provided in this invention.
  • the processing in step 302 in fig.6 is the same as the one in fig.5.
  • step 303 in fig.6 is the same as the one in fig.5.
  • step 304' besides the same processing of step 304 in fig.5, the harmonics at frequencies higher than the carrier frequency in the third signal are further suppressed via a lowpass filter 234.
  • the cutoff frequency of the lowpass filter is the carrier frequency, which is much higher than that of lowpass filter in a conventional direct up-conversion transmitter 100, and thus easier to be implemented as integrated circuit and re- dimensioned for other modes.
  • step 304' the baseband components and harmonics at frequencies lower than the carrier frequency in the third signal are further suppressed via a highpass filter 232.
  • the highpass filter is preferably formed by a coupling capacitor, which is easy to be implemented.
  • step 305 the power of the modulated signal is tuned within a predetermined dynamic range in an automatic-gain-control 244.
  • step 306 the power of the modulated signal outputted by automatic- gain-control 244 is amplified in a power amplifier 246.
  • step 307 the amplified modulated signal is transmitted by an antenna 248.
  • the method of modulating a digital signal to a predetermined carrier frequency removes the needs of mixing and 90° phase shifting and is much simplier than that in a conventional up-conversion transmitter 100, and thus can reduce cost and improve flexiblity of a transmitter.

Abstract

L'invention concerne un émetteur (200) pour un système de communication sans fil. Cet émetteur (200) comprend un premier et un second convertisseurs numérique-analogique (204, 214) servant à convertir un premier et un second signaux numériques en un premier et un second signaux analogiques, le premier et le second signaux numériques étant le composant I et le composant Q d'un signal en bande de base numérique, un sommateur (220) servant à additionner le premier et le second signaux analogiques afin de former un troisième signal et un filtre passe-bande (236) servant à supprimer les harmoniques du troisième signal tout en passant l'harmonique à une fréquence porteuse prédéterminée sous forme de signal modulé. Il est ainsi possible de se soustraire aux exigences d'un mélangeur et d'un compensateur de phase à 90° et de simplifier les circuits analogiques de façon à réduire le coût et à augmenter la flexibilité de mise en oeuvre d'un émetteur.
PCT/IB2006/051973 2005-06-24 2006-06-20 Emetteur pour un systeme de communication sans fil WO2006137007A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN200510079119 2005-06-24
CN200510079119.3 2005-06-24

Publications (1)

Publication Number Publication Date
WO2006137007A1 true WO2006137007A1 (fr) 2006-12-28

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PCT/IB2006/051973 WO2006137007A1 (fr) 2005-06-24 2006-06-20 Emetteur pour un systeme de communication sans fil

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WO (1) WO2006137007A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2020752A1 (fr) 2007-08-02 2009-02-04 SiRiFIC Wireless Corporation Système sans fil disposant d'une pureté spectrale élevée
CN110320663A (zh) * 2019-03-20 2019-10-11 华中科技大学 基于直接二元搜索算法设计的超小尺寸大带宽模式滤波器

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4855894A (en) * 1987-05-25 1989-08-08 Kabushiki Kaisha Kenwood Frequency converting apparatus
EP0817369A2 (fr) * 1996-06-25 1998-01-07 Harris Corporation Procédé pour élever en fréquence et élévateur en fréquence avec filtre à pré-compensation
WO1999067878A1 (fr) * 1998-06-24 1999-12-29 Conexant Systems, Inc. Procede et dispositif resserrant la precision de la modulation
US6507303B1 (en) * 2000-05-31 2003-01-14 3Com Corp Direct digital conversion of baseband signals to super-nyquist frequencies

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4855894A (en) * 1987-05-25 1989-08-08 Kabushiki Kaisha Kenwood Frequency converting apparatus
EP0817369A2 (fr) * 1996-06-25 1998-01-07 Harris Corporation Procédé pour élever en fréquence et élévateur en fréquence avec filtre à pré-compensation
WO1999067878A1 (fr) * 1998-06-24 1999-12-29 Conexant Systems, Inc. Procede et dispositif resserrant la precision de la modulation
US6507303B1 (en) * 2000-05-31 2003-01-14 3Com Corp Direct digital conversion of baseband signals to super-nyquist frequencies

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2020752A1 (fr) 2007-08-02 2009-02-04 SiRiFIC Wireless Corporation Système sans fil disposant d'une pureté spectrale élevée
JP2009038802A (ja) * 2007-08-02 2009-02-19 Sirific Wireless Corp 高スペクトル純度ワイヤレスシステム
EP2323268A1 (fr) * 2007-08-02 2011-05-18 Icera Canada ULC Système sans fil disposant d'une pureté spectrale élevée
CN110320663A (zh) * 2019-03-20 2019-10-11 华中科技大学 基于直接二元搜索算法设计的超小尺寸大带宽模式滤波器
CN110320663B (zh) * 2019-03-20 2020-12-01 华中科技大学 基于直接二元搜索算法设计的超小尺寸大带宽模式滤波器

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