WO2013162444A2 - Agencement et procédé de récupération de signal de porteuse - Google Patents

Agencement et procédé de récupération de signal de porteuse Download PDF

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Publication number
WO2013162444A2
WO2013162444A2 PCT/SE2013/050386 SE2013050386W WO2013162444A2 WO 2013162444 A2 WO2013162444 A2 WO 2013162444A2 SE 2013050386 W SE2013050386 W SE 2013050386W WO 2013162444 A2 WO2013162444 A2 WO 2013162444A2
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WO
WIPO (PCT)
Prior art keywords
signal
frequency
data
recovery
arrangement
Prior art date
Application number
PCT/SE2013/050386
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English (en)
Other versions
WO2013162444A3 (fr
Inventor
Zhongxia HE
Original Assignee
He Zhongxia
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 He Zhongxia filed Critical He Zhongxia
Publication of WO2013162444A2 publication Critical patent/WO2013162444A2/fr
Publication of WO2013162444A3 publication Critical patent/WO2013162444A3/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
    • H04L27/0014—Carrier regulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0044—Control loops for carrier regulation
    • H04L2027/0046—Open loops
    • H04L2027/0051—Harmonic tracking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0044—Control loops for carrier regulation
    • H04L2027/0053—Closed loops
    • H04L2027/0055—Closed loops single phase
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H04L27/22—Demodulator circuits; Receiver circuits
    • H04L27/227—Demodulator circuits; Receiver circuits using coherent demodulation
    • H04L27/2271—Demodulator circuits; Receiver circuits using coherent demodulation wherein the carrier recovery circuit uses only the demodulated signals
    • H04L27/2273—Demodulator circuits; Receiver circuits using coherent demodulation wherein the carrier recovery circuit uses only the demodulated signals associated with quadrature demodulation, e.g. Costas loop
    • 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

Definitions

  • the present invention relates to an arrangement for carrier signal recovery having the features of the first part of claim 1.
  • the invention also relates to a method for carrier recovery having the features of the first part of claim 10.
  • Carrier signal recovery and demodulation are needed to be able to estimate and compensate for frequency and phase differences between for example the local oscillator of a receiver in a communication system and the carrier wave of the received signal modulated in a transmitter, particularly such that coherent demodulation can be provided.
  • a carrier wave is modulated by a baseband signal.
  • the baseband information is extracted from the modulated waveform in a signal received at the receiver.
  • the oscillator carrier frequencies of the transmitter and the receiver would be matched perfectly as far as both frequency and phase are concerned, which in turn would allow for a perfect coherent demodulation of the modulated baseband signal.
  • the carrier frequencies of the oscillators of the transmitter and the receiver are not the same since the receivers and the transmitters normally are completely independent and they have their own oscillators with frequency and phase offsets, frequency instabilities, phase instabilities etc .
  • One of the methods in a first category is based on using a closed-loop compensation structure with a phase extraction block and a loop filter LF, which is schematically illustrated in Fig. 1, and by means of which phase and frequency offset are detected, and the offset is compensated for by tuning the local oscillator, VCO (Voltage Control Oscillator), of the receiver.
  • VCO Voltage Control Oscillator
  • Fig. 2 illustrates an example of the other category which is based on an open-loop compensation structure which, instead of implementing a feedback-loop, a closed-loop, uses an open loop, a forward feed-loop, for cancelling the frequency offset by means of a derotator.
  • a first method is based on data aided extraction which comprises transmitting known data at certain time instants (pilot data) , and to, based on this known information, enable extraction of
  • ⁇ Other methods that do not use data aided extraction are also known.
  • a multiply- filter-divide method non-data-aided carrier recovery
  • a non- linear operation is applied to a modulated signal to create harmonics of the carrier frequency with the modulation removed.
  • the carrier harmonic is then band-pass filtered and frequency divided to recover the carrier frequency, a PLL (Phase Locked Loop) may then follow.
  • Multiply-filter-divide is an example of open-loop carrier recovery, which is favored in burst transactions since the acquisition time is typically shorter than for closed-loop synchronizers.
  • the unknown data-related phase is normalized into n2n.
  • the signal is then divided by four, and GO F can be obtained (see Fig. 3) : HPF indicates a high pass filter, LPF low pass filter.
  • a Costas Loop is a phase-locked loop used for carrier phase recovery from suppressed-carrier modulation signals, such as from double- sideband suppressed carrier signals.
  • the main application of Costas loops is in wireless receivers. Its advantage over the PLL-based (Phase Locked Loop) detectors is that at small deviations the Costas loop error voltage is sin (2 (6i-6 f ) ) instead of sin(6i-6 f ) . This doubles the sensitivity and also makes the Costas loop uniquely suited for tracking Doppler-shifted carriers.
  • decision directed carrier recovery In modern DSP (Digital Signal Processor) based receivers a decision directed method is often adopted.
  • decision directed carrier recovery the output of a symbol decoder is fed to a comparison circuit and the phase difference/error between a decoded symbol and a received signal is used to control the local oscillator.
  • a common form of decision directed carrier recovery begins with quadrature phase correlators producing in-phase and quadrature signals representing a symbol coordinate in the complex plane. This point should correspond to a location in the modulation constellation diagram.
  • the phase error between the received value and nearest/decoded symbol is calculated using arctangent (or an approximation) . However, arctangent can only compute a phase correction between 0 and n/2.
  • QAM Quadratture Amplitude Modulation
  • a receiving arrangement including such an arrangement for carrier signal recovery is also provided, as well as a method for carrier signal recovery, which has the features of the characterizing part of claim 10.
  • an arrangement is provided which is capable of handling high data rates and high carrier frequencies while still being easy to design and fabricate. It is also an advantage that an arrangement is provided which can be used for high modulation formats without requiring any modification and which, in advantageous embodiments, even removes the need for using any frequency multipliers and enables the use of comparatively simple frequency dividers.
  • Fig. 1 shows a state of the art closed loop carrier recovery compensation structure
  • Fig. 2 shows a state of the art open loop carrier recovery compensation structure
  • Fig. 3 shows a state of the art carrier recovery structure based on multiplication, filtering and division for performing a phase extraction
  • Fig. 4 shows a carrier signal recovery arrangement according to a first embodiment of the invention
  • Fig. 5 shows a carrier signal recovery arrangement according to a second embodiment of the invention
  • Fig. 6 shows a receiving arrangement with a carrier signal recovery arrangement according to one embodiment of the invention
  • Fig. 7 shows a recovery arrangement according to the invention included in a closed loop structure
  • Fig. 8 shows a carrier recovery arrangement according to one embodiment of the invention included in an open loop structure
  • Fig. 9 is a schematic flow diagram describing a procedure for carrier signal recovery according to one embodiment of the invention.
  • Fig. 4 shows a block diagram of a first embodiment of the invention wherein a distorted signal R.Q(t) is received in an arrangement 100.
  • the distorted signal is here a signal which has been down-converted in (here) an IQ direct converting mixer and by means of a local oscillator a sinusoid source has been provided at a receiver carrier frequency.
  • any down- converted, distorted, signal or particularly any output distorted signal from the mixer may form the input signal to the arrangement 100, i.e. it could also have been the Ri(t) which had been input and it would then be recovered in a similar manner as shown in Fig. 4.
  • a delay means 14 Ro(t) is delayed ( ⁇ ) and in a mixer 4 the time delayed signal is multiplied by the distorted down-converted signal Ro(t) giving an adjusted output signal R ad (t) which then is input to a low pass filter (LPF) 5.
  • the low pass filter 5 is so designed that only one signal is selected, namely the second harmonic of the distortion term of the distorted signal, which is only related to 2 ⁇ , ⁇ being difference between the frequency of the down-converted distorted signal cod, the frequency of the received carrier signal ⁇ ⁇ and the frequency of the local oscillator of the receiver, COLO ⁇ i.e. the second harmonic of the distortion term, the second order of the difference signal, which is achieved by giving the low pass filter a cut-off frequency which is much lower than the data symbol rate so that the output only contains low frequency components and no data.
  • Fig. 5 shows an alternative implementation, similar means as in Fig. 4 are indicated by the same reference numerals but are given an index 1 and will therefore not be described any further herein to the extent that they perform the same function.
  • the difference is here that the requirements on the low pass filter 5i are somewhat less stringent, important being that it be given such a cut-off frequency that only the second harmonic of the distortion term of the noise (difference signal) is selected, but the output signal R' a dj(t> does still contain the modulated data.
  • an envelope detector 6i is introduced which has a time constant which is longer than the symbol period and so the data will be eliminated, and an output signal R" a dj ⁇ t) as described in the embodiment shown in Fig.
  • the envelope detector 6 that it responsible for removing the data, whereas in the embodiment of Fig. 4 the low pass filter 5 is carefully selected so that also the data is removed, avoiding the need for any envelope detector.
  • Fig. 6 shows a receiving arrangement 300A with a recovery arrangement 300 substantially as the arrangement shown in Fig. 5.
  • the receiver arrangement 300A contains an IQ direct down- converting mixer I 2 , and a local oscillator 2 2 providing a sinusoid source at carrier frequency.
  • a signal R(t) from a transmitter with its local oscillator is received (considered undistorted) , down-converted in mixer I 2 in a receiver with local oscillator 2 2 and a frequency COLO-
  • the distortion produced is o)d being the frequency of the down-converted distorted signal, wherein ⁇ ⁇ is the frequency of the receiver carrier signal, GOLO the frequency of the receiver local oscillator.
  • R.Q(t) and a delayed- by-T version thereof are both input to a mixer 4 2 , where they are multiplied to provide an output signal R a d (t) .
  • R ad j (t) Passing R ad j (t) through a low-pass filter 5 2 , the output will be R' adj(t) as explained below.
  • R' ad j(t) is fed to an envelope detector 6 2 .
  • the output R"adj (t) from the low-pass filter 6 2 represents the second harmonic of the frequency offset between a transmitter oscillator, not shown, and which does not form part of the present invention, and a receiver oscillator 2 2 .
  • a balun 8 2 is used to convert a single-end signal to two differential signals which are 180° out of phase. These out-of-phase signals are then input to frequency dividers 9 2 , 10 2 , giving outputs cos (Aoot) and sin(Aoot) .
  • phase detectors lli,ll 2 the modulated I and Q signals can be extracted, thus demodulation is achieved.
  • a mathematic expression of the demodulation process is given according to the following:
  • R Q (t) cos(ct»t + ⁇ ) ⁇ cos[(ct» + ⁇ ) ⁇ ]
  • R j (t) cos(cot + (p) x sin [(ct> + ⁇ ) ⁇ ]
  • R. Q (t) or Ri(t) can be used for carrier recovery.
  • R. Q (t) is taken as input to the mixer 2 .
  • R. Q (t) of the mixer 2 is provided to a delay element 3 2 , which provides a real time delay to the signal, the output thus being:
  • R Q (t + T) cos[o(t + ⁇ ) + ⁇ ] ⁇ cos[(o + ⁇ )( ⁇ + T)]
  • T is an certain fixed true time delay, which satisfies T « T Sym , so that ⁇ in R Q (t) and Ri(t) can be considered to the same.
  • the output of the mixer 42 can then be calculated as follows:
  • the output of the filter will contain only really low frequency components.
  • the output of the LPF can be represented as (A being the amplitude) :
  • a balun 8 2 provides two outputs with 180° phase difference:
  • R B ' alun (t) A x cos[2A(oT + n] [9] and passing these signals through frequency dividers 9 2 , IO 2 gives :
  • Fig. 7 schematically illustrates an implementation of a recovery arrangement 400 in a closed loop recovery compensation structure 400A in which it acts as a phase extraction arrangement. Similar components are given the same reference numerals as in the preceding figures but with an index 3. It is schematically illustrated how the recovery signal, with the extracted phase, from the envelope detector 6 3 is input to a loop filter 15 3 in a compensation structure similar to the one discussed with reference to the state of the art structure of Fig. 1.
  • Fig. 8 illustrates an implementation of a recovery arrangement comprising an arrangement for phase extraction 500 as implemented in an open loop carrier recovery compensation structure 500A. Again components which have been discussed earlier in the description are given the same reference numerals, but with an index 4.
  • the signal output from the envelope detector 6 4 is here input to a loop filter 15 and to a derotator I6 4 which uses the signals from the envelope detector and the loop filter to perform a derotation .
  • Fig. 9 is a schematical flow diagram describing the procedure for extracting a phase to be used for recovery of a distorted signal. It is supposed that a distorted input signal, for example from an IQ down converting mixer is received. A time delay, ⁇ , is introduced into the signal, 100, and the delayed, distorted signal is multiplied by the distorted signal (without delay) in a mixer, 101.
  • the second harmonic depending only on 2 ⁇ , the second order of the difference signal as explained above, is extracted, 102, by giving the filter a cut-off frequency which is so selected that only low frequencies are selected, 102.
  • modulated data is removed from the extracted signal to obtain a recovery signal.
  • the recovery signal from the envelope detector can be used for recovery of the distorted down-converted signal and data can be demodulated, 104.
  • the down-converted signal (and hereby distorted) does not have to be down-converted in an IQ down- converter, but the inventive concept is of course also applicable for otherwise distorted, down-converted, signals.
  • Another advantage is that the implementation complexity is very low and no constructional modification is needed for high modulation formats as long as the symbol rate is much higher than the frequency offset.
  • Another advantage is that it is suitable for high frequency or high data rates without demanding any high performance components, mixers, dividers, ADCs, which suffer from being extremely expensive and difficult to provide.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)

Abstract

La présente invention concerne un agencement de récupération de porteuse (100) permettant de récupérer un signal d'entrée modulé (R(t)) abaissé en fréquence par un oscillateur local avec une fréquence différente de la fréquence de la porteuse du signal d'entrée modulé (R(t)) de manière à produire un signal déformé abaissé en fréquence (RQ(t)). L'agencement comprend : un moyen de retard (14) permettant d'introduire un retard temporel dans le signal déformé (RQ(t)); un mélangeur (4) conçu pour multiplier le signal déformé reçu (RQ(t)) par le signal déformé retardé et pour doter un signal de sortie ajusté (Radj(t)) d'un terme de déformation; un filtre passe-bas (5) conçu pour extraire un signal comprenant le deuxième harmonique du terme de déformation à partir du signal de sortie ajusté (Radj(t)) correspondant à deux fois la différence de fréquences (2Δω) entre l'oscillateur local et la fréquence de la porteuse du signal d'entrée modulé (R(t)), et; un moyen permettant de retirer les données modulées dudit signal de façon à produire un signal de récupération dépourvu de données modulées pouvant être utilisé pour supprimer la déformation.
PCT/SE2013/050386 2012-04-24 2013-04-10 Agencement et procédé de récupération de signal de porteuse WO2013162444A2 (fr)

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Application Number Priority Date Filing Date Title
SE1250404-9 2012-04-24
SE1250404A SE536593C2 (sv) 2012-04-24 2012-04-24 En anordning och ett förfarande för återhämtning av bärvågssignaler

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112565134A (zh) * 2020-11-27 2021-03-26 北京北广科技股份有限公司 一种接收端射频信号的载波相位固定补偿方法
CN113242199A (zh) * 2021-04-30 2021-08-10 杭州电子科技大学 自动识别系统载波恢复方法

Citations (1)

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Publication number Priority date Publication date Assignee Title
JP2000298165A (ja) * 1999-04-15 2000-10-24 Mitsubishi Electric Corp パルス変調信号識別装置及びレーダ信号識別装置

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000298165A (ja) * 1999-04-15 2000-10-24 Mitsubishi Electric Corp パルス変調信号識別装置及びレーダ信号識別装置

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FEIGIN J.: 'Practical Costas loop design' PRIMEDIA BUSINESS MAGAZINES & MEDIA vol. 25, no. 1, 01 January 2002, OVERLAND PARK, KS, US, pages 20 - 36 *
GUSTRAU J. ET AL.: 'VCO linearisation by frequency feedback' RADIO FREQUENCY INTEGRATED CIRCUITS (RFIC) SYMPOSIUM 07 June 1998, BALTIMORE, MD, USA, pages 135 - 138, XP010285115 *
IMBEAUX J. C.: 'Performances of the Delay-Line Multiplier Circuit for Clock and Carrier Synchronization in Digital Satellite Communications' IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, [Online] vol. 1, no. 1, pages 82 - 95 Retrieved from the Internet: <URL:http://ieeexplore.ieee.org/xpl/ articleDetails.jsp?arnumber=1145909> [retrieved on 2013-10-13] *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112565134A (zh) * 2020-11-27 2021-03-26 北京北广科技股份有限公司 一种接收端射频信号的载波相位固定补偿方法
CN112565134B (zh) * 2020-11-27 2022-03-15 北京北广科技股份有限公司 一种接收端射频信号的载波相位固定补偿方法
CN113242199A (zh) * 2021-04-30 2021-08-10 杭州电子科技大学 自动识别系统载波恢复方法

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WO2013162444A3 (fr) 2014-01-16
SE1250404A1 (sv) 2013-10-25
SE536593C2 (sv) 2014-03-18

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