WO2004034666A1 - Modulateur multiporteuses qam a conversion-elevation directe - Google Patents

Modulateur multiporteuses qam a conversion-elevation directe Download PDF

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Publication number
WO2004034666A1
WO2004034666A1 PCT/IB2003/004066 IB0304066W WO2004034666A1 WO 2004034666 A1 WO2004034666 A1 WO 2004034666A1 IB 0304066 W IB0304066 W IB 0304066W WO 2004034666 A1 WO2004034666 A1 WO 2004034666A1
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WO
WIPO (PCT)
Prior art keywords
signals
signal
adder
combined
phase
Prior art date
Application number
PCT/IB2003/004066
Other languages
English (en)
Inventor
Hendricus T. G. M. Penning De Vries
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.
Priority to AU2003260864A priority Critical patent/AU2003260864A1/en
Publication of WO2004034666A1 publication Critical patent/WO2004034666A1/fr

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Classifications

    • 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
    • H04L27/362—Modulation using more than one carrier, e.g. with quadrature carriers, separately amplitude modulated

Definitions

  • the invention relates to a method for creating intermediate frequency (IF) output signals within a quadrature amplitude modulator (QAM), with the steps of, creating an in-phase (I) signal and a quadrature (Q) phase signal of input signals, creating a pair of IF signals of said I-signal, and creating a pair of IF signals of said Q-signal.
  • the invention further relates to an integrated circuit comprising mapping means for mapping an input signal onto an in-phase path and a quadrature phase path, said in-phase path comprising upconversion means for converting in-phase path signals into a pair of IF signals, and said quadrature path comprising upconversion means for converting quadrature phase path signals into a pair of IF signals.
  • the invention also relates to the use of such a method and such an integrated circuit.
  • quadrature amplitude modulated (QAM) carriers are used.
  • WO 01/03440 Al discloses a method that allows the combination of intermediate frequency (IF) QAM signals for two or more different channels in a cable television system so that the resulting composite signal can be upconverted to a radio frequency by a single upconversion circuit for broadcast.
  • IF intermediate frequency
  • QAM modulators are provided, each receiving, respectively, a video signal for a separate channel, and each outputting, respectively, a QAM signal at a different IF carrier frequency.
  • the QAM signals comprise signal components referred to as the in-phase (I) and quadrature (Q) phase signals.
  • the I- and Q-phase signals are modulated onto a single carrier.
  • the I-phase signal is multiplied by a cosine wave at the carrier frequency, and the Q-phase signal by a sine wave at carrier frequency.
  • the I- and Q-phase signals are combined to form a composite I/Q modulated signal.
  • the composite I/Q modulated signals are then converted from the digital to the analog domain. Further a combiner is provided, for combining the D/A converted QAM signals output by the at least two QAM modulators. For upconverting the composite IF carrier signal output by the combiner, a single upconverter is required.
  • Upconversion from IF to RF frequency may be implemented in the analog domain.
  • the commonly used superheterodyne upconvertor uses two mixers and several image filters. This upconvertor architecture is not suited for integration.
  • An alternative class of upconvertor architectures uses Hilbert transforms and or complex filtering techniques.
  • the combined signal is send to a single sideband (SSB) modulator in the analog domain.
  • a SSB modulator may be implemented by Hilbert transformer, multipliers and an adder.
  • the Hilbert transformer implements a 90 degree phase shift to the input signal. This 90 degree phase shift makes it possible to reject mirror frequencies in the output signal.
  • the multipliers shift the intermediate frequency carrier to a radio frequency at center frequency.
  • a wideband SSB modulator which is able to upconvert signals comprising a plurality of IF carrier signals is difficult to implement.
  • the Hilbert transformer has to work properly over a wide frequency band. As requirements on the Hilbert transformer are serious in case of a composite signal comprising multiple QAM IF signals, implementation becomes more difficult in the analog domain.
  • first IF signals of said I- and said Q-signals are combined within a first adder and put out as a first combined IF signal
  • second IF signals of said I- and said Q-signals are combined within a second adder and put out as a second combined IF signal.
  • a complex IF output signal is generated, which can be easily upconverted into a desired radio frequency, even when multiple QAM signals have to be upconverted into a single carrier.
  • An input signal is first split into an in-phase signal and an quadrature phase signal.
  • the in-phase signal is then split and upconverted into a pair of LF signals. This may be carried out by multipliers, multiplying the in-phase signal with +/-cos( ⁇ 1 t) for generation of a first IF signal and +/-sin( ⁇ t) for generation of a second IF signal, with an the local oscillator frequency.
  • This signal is also split and upconverted into a pair of IF signals by multiplying +/-cos( ⁇ t) +/-sin( ⁇ 1 t) to the quadrature phase signal, respectively.
  • the first signals generated from the in-phase signal and the quadrature phase signal are fed to a first adder, which combines these signals. Also the second intermediate frequency signals generated from the in-phase signal and the quadrature phase signal are fed to a second adder, which combines these signals.
  • the whole splitting, upconversion to intermediate frequency and adding may be carried out in the digital domain, which makes integration easier.
  • the output from the adders may then be shifted to radio frequency in the analog domain without the use of a Hilbert transformer.
  • the upconverted analog signals may then be easily added by a third adder in the analog domain. Thus implementation becomes less complicated.
  • a method according to claim 2 is preferred.
  • the output of the two adders represents one complex IF signal in the digital domain.
  • the adders may add intermediate frequency signals from a plurality of input signals. All these intermediate frequency signals should have different intermediate frequencies provided by their local oscillators.
  • the output of multiple QAM modulators may be combined into a single complex IF signal, which may be upconverted after D/A conversion onto a radio frequency without the need of a Hilbert transformer. This is a reason for easy implementation.
  • a method according to claim 5 enables interfacing between the digital QAM modulator and an analog upconvertor.
  • the signals may be upconverted to the desired RF output frequency to be transmitted.
  • the combination of the radio frequency signals is best carried out with a method according to claim 7.
  • a method according to claim 8 is proposed.
  • An optimum transmit filter within the in-phase and the quadrature phase path coming from the input signal is provided by a method according to claim 9.
  • a method according to claim 10 is advantageous.
  • a method according to claim 11 is proposed.
  • distortion might be introduced to the signal.
  • the signal distortion such as phase and/or amplitude error
  • a further aspect of the invention is an integrated circuit.
  • the objects of the invention are solved when a first adder is provided for combining first IF signals from said pairs of IF signals and a second adder is provided for combining second IF signals from said pairs of IF signals.
  • the QAM modulator may be implemented with two integrated circuits.
  • a first integrated circuit generates a complex, digital IF signal.
  • the second integrated circuit implements digital/analog conversion and upconversion.
  • Yet a further aspect of the invention is the use of a pre-described method or a pre-described integrated circuit to generate a plurality of QAM signals as is required in headends for CATN, Voice over IP, Video over IP, Video on Demand, DVB, DOCISIS related applications.
  • the QAM modulator according to the invention generates a complex intermediate frequency output in such a way that this signal can be easily upconverted to the desired radio frequency.
  • Multiple QAM signals can be added and send to the single upconverter.
  • FIG. 1 shows a QAM modulator capable of combining QAM signals of a plurality of input signals.
  • the QAM converter comprises a symbol mapper 2, half raised cosine filters 8, a first adder 14, a second adder 16, digital analog converters 22, a third adder 24, and multipliers 9.
  • the QAM converter works as follows:
  • An input signal x (t) may comprise a stream of bits representing a video signal or a voice signal or any other data in the digital domain.
  • the signal ⁇ t) is fed to symbol mapper 2.
  • Symbol mapper 2 maps the bits from the input signal x ⁇ t) into QAM symbols. These QAM symbols are provided as in-phase signals on in-phase path 4 and quadrature phase signals on quadrature phase path 6.
  • In-phase signals and quadrature phase signals are filtered by half raised cosine filters 8, allowing optimal transmission.
  • the filtered in-phase and quadrature phase signals are fed to multipliers 9 a-d.
  • said in-phase signal is multiplied with cos( ⁇ 1 t) at multiplier 9a and with -sin( ⁇ it) (inverted sin( ⁇ x t)) at multiplier 9b.
  • the output of multiplier 9a is a first intermediate frequency signal 10a.
  • the output of multiplier 9b is a second intermediate frequency signal 12a.
  • quadrature phase signal is multiplied with sin( ⁇ ⁇ t) at multiplier 9c and with cos ⁇ t) at multiplier 9d.
  • the output of multiplier 9c is a first intermediate frequency signal 10b.
  • the output of multiplier 9d is a second intermediate frequency signal 12b.
  • the first intermediate frequency signals 10 are fed to first adder 14.
  • the second intermediate frequency signals 12 are fed to second adder 16.
  • Adder 14 allows to add more intermediate frequency in-phase signals 10c, lOd, ....
  • the adder 14 combines all intermediate frequency signals 10 onto one IF signal 18. It should be noted, that the IF signals 10c, lOd from different input signals should have different intermediate frequencies.
  • Adder 16 allows to add more intermediate frequency signals 12c, 12d, ....
  • the adder 16 combines all intermediate frequency signals 12 onto one IF signal 20. It should be noted, that the IF signals 12c, 12d from different input signals should have different intermediate frequencies.
  • the IF signals 18 and 20 represent one complex IF signal in the digital domain. This signal is digital/analog converted within D/A converters 22, respectively.
  • the D/A converted signals are upconverted onto the radio frequency ⁇ r by the multipliers 9e and 9f, respectively. This is done by multiplying the D/A converted signal 18 by cos( ⁇ x t) and D/A converted signal 20 by sin( ⁇ x t).
  • the upconverted radio frequency signals 18 and 20 are then fed to adder 24 which combines the signals and puts out a combined QAM radio frequency signal in the analog domain.
  • the desired radio frequency QAM signal can be written as
  • QAM(t) x(t) * [cos( ⁇ > ⁇ t) cos( ⁇ x t) - sin( ⁇ ! t) sin( ⁇ x t)] +y(t) * [sin( ⁇ ! t) cos( ⁇ x t) + cos( ⁇ 1 1) sin( ⁇ x t)], which is implemented by an integrated circuit according to figure 1.
  • This implementation may be within two separate integrated circuits.
  • the first integrated circuit generates a complex, digital IF signal and the second integrated circuit implements D/A and upconversion.
  • the invention can be applied to generate a plurality of QAM signals as is required in headends for CATV, Voice over IP, Video over IP, Video on Demand, DVB, DOCISIS related applications.

Abstract

L'invention concerne un procédé permettant de créer des signaux de sortie de fréquence intermédiaire complexe (IF), à l'intérieur d'un modulateur d'amplitude en quadrature (QAM). Ce procédé comprend les étapes consistant à : créer un signal en phase (I) et un signal en phase de quadrature (Q) de signaux d'entrée, créer une paire de signaux IF du signal I, et créer une paire de signaux IF du signal Q. Pour permettre une intégration facile et une combinaison simple d'une pluralité de signaux QAM en une porteuse de diffusion unique, on propose que les premiers signaux IF du signal I et du signal Q soient combinés à l'intérieur d'un premier additionneur et en ressortent en tant que premier signal IF combiné. Des seconds signaux IF du signal I et du signal Q sont combinés à l'intérieur d'un second additionneur et ressortent en tant que second signal IF combiné.
PCT/IB2003/004066 2002-10-11 2003-09-12 Modulateur multiporteuses qam a conversion-elevation directe WO2004034666A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003260864A AU2003260864A1 (en) 2002-10-11 2003-09-12 Multi carrier qam modulator with direct up-conversion

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP02079216.4 2002-10-11
EP02079216 2002-10-11

Publications (1)

Publication Number Publication Date
WO2004034666A1 true WO2004034666A1 (fr) 2004-04-22

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AU (1) AU2003260864A1 (fr)
WO (1) WO2004034666A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2585394A (en) * 2018-11-06 2021-01-13 The Sec Dep For Foreign And Commonwealth Affairs Improved device and method for modulating information

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999035736A1 (fr) * 1998-01-07 1999-07-15 Qualcomm Incorporated Modulateur et demodulateur en quadrature
WO2000065799A1 (fr) * 1999-04-23 2000-11-02 Nokia Networks Oy Modulateur maq

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999035736A1 (fr) * 1998-01-07 1999-07-15 Qualcomm Incorporated Modulateur et demodulateur en quadrature
WO2000065799A1 (fr) * 1999-04-23 2000-11-02 Nokia Networks Oy Modulateur maq

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
RAZAVI B: "A 900-MHz/1.8-GHz CMOS transmitter for dual-band applications", VLSI CIRCUITS, 1998. DIGEST OF TECHNICAL PAPERS. 1998 SYMPOSIUM ON HONOLULU, HI, USA 11-13 JUNE 1998, NEW YORK, NY, USA,IEEE, US, 11 June 1998 (1998-06-11), pages 128 - 131, XP010291264, ISBN: 0-7803-4766-8 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2585394A (en) * 2018-11-06 2021-01-13 The Sec Dep For Foreign And Commonwealth Affairs Improved device and method for modulating information
US11463290B2 (en) 2018-11-06 2022-10-04 The Secretary Of State For Foreign And Commonwealth Affairs Device and method for improved demodulation of multiple modulation schemes
US11477063B2 (en) 2018-11-06 2022-10-18 The Secretary Of State For Foreign And Commonwealth Affairs Device and method for modulating information
GB2585394B (en) * 2018-11-06 2023-02-08 The Sec Dep For Foreign Commonwealth And Development Affairs Acting Through The Government Communica Improved device and method for modulating information

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Publication number Publication date
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