WO2001031932A2 - Procede et dispositif de reception permettant de traiter un signal produit selon le procede de numerotation multifrequence - Google Patents

Procede et dispositif de reception permettant de traiter un signal produit selon le procede de numerotation multifrequence Download PDF

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Publication number
WO2001031932A2
WO2001031932A2 PCT/DE2000/003751 DE0003751W WO0131932A2 WO 2001031932 A2 WO2001031932 A2 WO 2001031932A2 DE 0003751 W DE0003751 W DE 0003751W WO 0131932 A2 WO0131932 A2 WO 0131932A2
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WO
WIPO (PCT)
Prior art keywords
sample
processing module
frequency
signal
sequence
Prior art date
Application number
PCT/DE2000/003751
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German (de)
English (en)
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WO2001031932A3 (fr
Inventor
Gonzalo Lucioni
Original Assignee
Siemens Aktiengesellschaft
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Publication date
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Publication of WO2001031932A2 publication Critical patent/WO2001031932A2/fr
Publication of WO2001031932A3 publication Critical patent/WO2001031932A3/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
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/30—Systems using multi-frequency codes wherein each code element is represented by a combination of frequencies
    • 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
    • H04L2027/0063—Elements of loops
    • H04L2027/0065—Frequency error detectors

Definitions

  • the invention relates to a method for processing a signal generated by the multi-frequency selection method and a receiving device for performing the method.
  • the multi-frequency dialing method is a signaling method in which signaling characters such as e.g. Dialing digits, hereinafter referred to briefly as DTMF characters, are transmitted via analog voice channels.
  • DTMF symbols are defined by the combination of two tone signals, the frequencies of which come from two different frequency groups. Four frequencies are contained in each of the lower and m of the upper frequency group. The lowest frequency of the upper frequency group is larger than the highest frequency of the lower frequency group.
  • the maximum number of DTMF signs that can be displayed results from the number of possible combinations according to which distinguishable frequency pairs can be formed, each consisting of a frequency of the lower frequency group and a frequency of the upper frequency group. With four frequencies and frequency group, sixteen DTMF characters can be displayed.
  • the signaling information on which the character is based must first be recovered from the signal in the receiving device. This is usually done taking into account specified target values, which are specified for DTMF signals, for example, by the Q.24 standard of the International Telecommunication Union, ITU-T for short.
  • For the reception of DTMF signals methods are known from the prior art which are based on comparatively complicated algorithms, so that the receiving devices which operate on them are technically complex. So need so- most conventional receiving devices operating terbänken with bandpass Fil ⁇ , as well as those that perform a digital Fourier transform in accordance with the Goertzel algorithm, eight individual recipients that are assigned to the distributed to the two frequency groups of eight frequencies. This high level of technical complexity has hitherto made it difficult to design such a receiving device by means of a microprocessor with a comparatively simple processor architecture, such as is frequently used in digital private branch exchanges, for example.
  • the object of the invention is to provide a method or a receiving device operating according to this method, with which a DTMF signal can be received and processed efficiently with less technical effort than before.
  • the invention solves this problem by a method for processing a signal generated by the multi-frequency selection method, in which the signal is sampled and a time-discrete sequence of samples is generated, from this sequence a first digitally filtered sequence of samples, the permitted frequencies of which lie in a first frequency group , and at least one further, second digitally filtered sequence of samples, the permitted frequencies of which lie in a second frequency group and are greater than the frequencies of the first frequency group, are determined for the samples of the first filtered sequence in each case the phase difference compared to a previous sample as a measure of the signal frequency falling in the first frequency group and a measure of the signal amplitude present at this signal frequency, the phase difference in each case compared to a previous sample value as M for the sample values of the second filtered sequence ate for the signal frequency falling in the second frequency group and a measure for the signal amplitude present at this signal frequency, the measures determined from the samples of the first filtered sequence and the samples from the second ) co M h- »
  • the sampled values of the first filtered sequence are advantageously fed to a first processing module, which generates a complex sampled value from the sampled values by assigning the respective sampled value unchanged to the real part and phase-shifted to the imaginary part of the complex sampled value, and which measures the phase difference as a measure of the signal frequency complex sample value and as a measure of the signal amplitude, the absolute value of the complex sample value is determined.
  • the samples of the second filtered sequence are fed to a second processing module, which generates a complex sample from the samples in each case by assigning the respective sample unchanged to the real part and out of phase with the imaginary part of the complex sample, and that as The phase difference of the complex sample value is determined as a measure of the signal frequency and the absolute amount of the complex sample value is determined as a measure of the signal amplitude.
  • Tr z disregards cn O
  • N P 3 ; v ⁇ ⁇ P n ⁇ P ⁇ t-i - rt O P- p P P. P, p- d p- u? ⁇
  • NPP li P rt ⁇ 1 cn pj P- ⁇ cn tr tr d ⁇ rt t ⁇ cn t-pj dö Hl ⁇ Hl p j cn ⁇ P- tr d ⁇ J ti cn ⁇ cn PP P- PJ li P- g ⁇ ⁇ p
  • gnale is impermeable. This allows low-frequency interference ⁇ signals, as for example, is on the fork of a remote ⁇ speaker reflected acoustic sound signal, easily and reliably be eliminated.
  • the DTMF signal can be evaluated in the identification unit for both frequency groups with the same sampling rate, that is, on a common time base.
  • a receiving device is provided for performing the method just explained.
  • FIG. 1 shows a receiving device for a DTMF signal
  • FIG. 2 shows an example of a processing module provided in the receiving device according to FIG. 1,
  • FIG. 3 shows another example of the processing module
  • FIG. 4 shows a special embodiment of the receiving device according to FIG. 1,
  • 5a and 5b show two bridge wave digital filters provided in the receiving device according to FIG. 4,
  • FIG. 1 is designed, for example, as part of a digital private branch exchange and for receiving DTMF signals.
  • the receiving device 10 has two processing branches 12, 14, each of which contains a processing module 16, for which two exemplary embodiments are shown in FIGS. 2 and 3.
  • the processing branch 12 processes the DTMF signal in a frequency range which is defined by a lower frequency group provided in the multi-frequency selection method and which contains four predetermined frequencies.
  • the second processing branch 14 processes the DTMF signal in a frequency range which is assigned to an upper frequency group.
  • the upper frequency group also contains four frequencies, which, however, are larger than the highest frequency of the lower frequency group.
  • the lower and the upper frequency group are m
  • Figure 6a shows a concrete example with reference to ge ⁇ and designated there with LG and HG.
  • the processing module 16 provided in the first processing branch 12 is preceded by a low-pass filter 18, which is permeable to the frequencies of the lower frequency group LG and impermeable to the frequencies of the upper frequency group HG. Accordingly, the processing module 16 provided in the second processing branch 14 is preceded by a high-pass filter 20 which is impermeable to the frequencies of the lower frequency group LG and permeable to the frequencies of the upper frequency group HG.
  • the processing module 16 of the first processing branch 12 determines, later to be explained, a measure of the frequency and a measure of the amplitude of the portion of the DTMF signal processed by the processing branch 12. These two measures are referred to below as frequency measure FM1 and as amplitude measure AMI. Accordingly, the processing module 16 of the second processing branch determines a frequency measure FM2 and an amplitude measure AM2 of the portion of the DTMF signal processed in the second processing branch 14.
  • the dimensions FM1, AMI and FM2, AM2 are fed to an identification unit 22, which evaluates these dimensions in order to thereby transmit a signaling information transmitted with the DTMF signal, i.e. a DTMF sign to identify.
  • the identification unit 22 compares the dimensions FM1, AMI with target values specified for the lower frequency group LG, while it compares the dimensions FM2, AM2 with target values specified for the upper frequency group HG. This comparison is carried out in the receiving device 10 presented here in accordance with the ITU-T standard Q.24 specified for the multi-frequency dialing method.
  • the setpoints used for evaluation in the identification unit 22 mean that for the m two frequency Group-assigned frequencies defined tolerance ranges within which the frequency measures FM1 and FM2 must lie so that the corresponding frequencies are recognized as being present in the received DTMF signal.
  • the setpoints stipulate minimum levels for the amplitude measures relating to the frequencies under consideration.
  • the identification unit 22 uses these setpoints to check whether the dimensions FM1, AMI or FM2, AM2 are within the predetermined tolerance ranges both for one of the four frequencies of the lower frequency group LG and for one of the frequencies of the upper frequency group HG. If this is the case, the received DTMF signal is identified as the transmission signal of that DTMF symbol which is determined by the combination of these two frequencies contained in the different frequency groups LG, HG.
  • FIG. 2 shows a first example of the processing module 16 used in the two processing branches 12, 14 of the receiving device 10.
  • the processing module 16 receives a sequence of samples x n , which has been generated in a manner known per se by sampling the DTMF signal at a predetermined sampling rate and then digitizing.
  • the sampled values x n are fed to a digital filter 24 of the processing module 16. From the respective sample value x n, this generates a complex sample value x ' n corresponding to this.
  • n is a running index which indicates that x n or x ' n is the nth sample within the time-discrete sequence of samples.
  • the complex sample x ' n is the nth sample within the discrete-time sequence of samples.
  • the complex sample x ' n is by the relationship
  • the received sample value x n is supplied on the one hand to a real branch 26 and on the other hand to an imaginary branch 28.
  • the sample value x n substantially unchanged as a real part x of the complex sample 'n output while the sample x n in the Imaginärteilz- weig 16 by a phase shift unit 30 by -90 ° with respect to the data transmitted via the real part branch 26 sample x n is phase shifted.
  • the digital filter 24 thus outputs a value via the imaginary part branch 28, which represents the imaginary part of the complex sample value x ' n .
  • a Hilbert transformer can be used as the digital filter 24, which carries out the above-described phase shift and thus the generation of the complex sampling values x ' n .
  • the digital filter 24 outputs the complex sample value x ' n, divided into the real part and the imaginary part, to a phase determination unit 32 and to an amplitude determination unit 34.
  • the phase determination unit 32 contains an arithmetic unit 34, which determines the phase p n from the complex sample x ′ ′′ for each sample n and outputs it.
  • the CORDIC algorithm known from the prior art can be used to determine the phase.
  • Delay elements 36 and an adder 38 are connected on the output side to the arithmetic unit 35.
  • the phase p n determined by the arithmetic unit 35 is supplied to the adder 38 directly on the one hand and on the other hand via the delay element 36.
  • the delay element 36 delays the phase p n by m times the sampling period T.
  • m is a positive integer and is equal to 1 in the example according to FIG. 2.
  • the signal p n _ m output by the delay element 36 is the phase of the ( nm) -th complex sample x ' n - m .
  • the adder 38 calculates the phase difference p n _ m between the nth complex Sample x ' n and the (nm) th complex sample x' n - m .
  • the result of the subtraction carried out by the adder 38 is output as frequency measure FM1 or FM2.
  • the amplitude determining unit 34 includes two multiplied as ⁇ rer 40, 42 and an adder 44.
  • the two inputs of the multiplier 40, the real part Re (x 'n) of the complex sample x' n is in each case supplied while the two inputs of the multiplier 42.jeweils the Imaginary part Im (x ' n ) of the complex sample x' n is supplied.
  • the multipliers 40, 42 each form the square of the values supplied to them and output the result to the adder 44. The addition carried out by this provides the square of the absolute value of the complex sample value x ' n and thus, as the amplitude measure AMI or AM2, the square of the constant amplitude A of the sinusoidal DTMF signal.
  • FIG. 3 shows a further example of the processing module 16. This differs from the processing module according to FIG. 2 only in the design of the digital filter used, which is designated 46 in FIG. 3, and in the two additional averaging units 48 and 50. The others Components are identical to those of the processing module according to FIG. 2, so that they are not described here.
  • the received sample value x n is supplied to a real branch 52 and to an imaginary branch 54, the structure of which is described in detail below.
  • the digital filter 46 are over the real part of branch 52 to the real part of the complex sample 'n réelle limbaden value Re (x' n) x, while it to the imaginary part of the complex sample value x on the Imaginärteilzweig 54 'n réelle relieden value Im (x ' n ).
  • tastratenverminderer 74 reduced in its sampling rate of 4 kHz to 2 kHz sequence of samples which the upper Fre ⁇ quenzrios associated processing module to 16th
  • the proces ⁇ criztungsmodul 16 determines a sampling rate of 2 kHz, the dimensions FM2 and AM2.
  • FM2 is fed to the sampling rate reducer 78 and AM2 to the sampling rate reducer 80. These each hide the second sample value and then feed the dimensions FM2 and AM2 to the identification unit 22 at a sampling rate of 1 kHz.
  • FIGS. 5a and 5b show specific embodiments of the two bridge wave digital filters 84 and 88. These embodiments are based on the prior art set out in "Explicit Formulas for Lattice Wave Digital Filters", L. Gazsi, IEEE Trans, on Circuits and Systems, Jan. 1985, pages 68 to 88, so that the mode of operation depends does not need to be discussed here.
  • the bridge wave digital filter 84 has three arithmetic blocks 92, 94 and 96, also referred to as adapters, whose coefficients ⁇ l, ⁇ 3 and ⁇ 5 are defined as follows:
  • the bridge wave digital filter 84 thus represents a filter of the seventh degree.
  • the bridge wave digital filter 88 is a filter of the fifth degree, the arithmetic blocks or adapters 98, 100 of which are assigned the following coefficients ⁇ i and ⁇ 3 :
  • both the bridge wave digital filter 84 and the bridge wave digital filter 88 each wells can be operated at the lower sampling rate, that is, the bridge wave digital filter 84 to 2 kHz, and the bridges ⁇ wave digital filter 88 at 1 kHz.
  • the sampling periods T shown in FIG. 5 also relate to these sampling rates.
  • FIG. 6 shows the frequency shifts of the two frequency groups LG and HG, which are caused by the signal processing of the DTMF signal in the receiving device 10 according to FIG. 4.
  • the diagram in FIG. 6a shows the frequency spectrum of the DTMF signal supplied to the first filter unit 82.
  • the length of the arrows is intended to illustrate the signal amplitudes occurring at the corresponding frequencies.
  • the sampling rate at this stage of the signal processing is 4 kHz.
  • FIG. 6b shows the frequency spectrum of the DTMF signal as it appears at the input of the processing module 16 provided in the first processing branch 12 of the receiving device 10. 6b that the audio signal HT has been removed from the frequency spectrum by the bridge wave digital filter 88, which acts as a high-pass filter.
  • FIG. 6 c shows the frequency spectrum which the DTMF signal shows at the input of the processing module 16 provided in the second processing branch 14.
  • the sampling rate reduction from 4 kHz to 2 kHz leads to a mirror-symmetrical "flipping" of the frequency spectrum of HG.
  • the mirror axis of this flip is determined by the sampling frequency of 2 kHz.
  • FIGS. 7a to 7c show simulation results which have been achieved with the receiving device 10 according to FIG. 4. The following boundary conditions have been taken into account in this simulation:
  • Pulse / pause ratio 40 ms / 40 ms DTMF transmission level for HG and for LG each -29 dBm nominal frequencies for the lower frequency group: 697 Hz, 770 Hz, 852 Hz, 941 Hz
  • FIGS. 7a and 7b show the time dependency of the frequency of a DTMF signal to be tested with the receiving device 10 according to FIG.
  • This DTMF signal is intended to transmit all sixteen possible DTMF characters in the time range shown.
  • the time diagram according to FIG. 7a is assigned to the lower frequency group, while the time diagram of FIG. 7b is assigned to the upper frequency group. Both the FIG. 7a and FIG. 7b clearly show the nominal frequencies of the respective frequency group.
  • FIG. 7c shows the simulation result as it is output by the identification unit 22 of the receiving device 10. It can be seen that all sixteen transmitted DTMF characters are recognized by the identification unit 22. Furthermore, the simulation shows that the receiver 10 according to FIG. 4 has to execute about 0.9 million commands per second in order to recognize the DTMF characters. Conventional DTMF receivers require 1.5 to 2.5 million commands per second for this.

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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)
  • Circuits Of Receivers In General (AREA)

Abstract

La présente invention concerne un procédé permettant de traiter un signal produit selon le procédé de numérotation multifréquence. Dans ce procédé, le signal est échantillonné et une suite à valeurs discrètes dans le temps de valeurs d'échantillonnage (xn) est produite. A partir de ces valeurs d'échantillonnage sont réalisées des mesures de fréquence et d'amplitude (FM1, FM2, AM1, AM2) qui correspondent à un groupe de fréquences inférieur (LG) ou un groupe de fréquences supérieur (HG). Les mesures (FM1, FM2, AM1, AM2) sont comparées à des valeurs théoriques prédéfinies. Si les mesures établies (FM1, FM2, AM1, AM2) concordent avec les valeurs théoriques, le signal est identifié comme porteur d'une information de signalisation.
PCT/DE2000/003751 1999-10-28 2000-10-24 Procede et dispositif de reception permettant de traiter un signal produit selon le procede de numerotation multifrequence WO2001031932A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE1999152027 DE19952027C2 (de) 1999-10-28 1999-10-28 Verfahren und Empfangseinrichtung zum Verarbeiten eines nach dem Mehrfrequenzwahlverfahren erzeugten Signals
DE19952027.5 1999-10-28

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WO2001031932A3 WO2001031932A3 (fr) 2002-02-07

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US10620298B2 (en) 2016-08-26 2020-04-14 Infineon Technologies Ag Receive chain configuration for concurrent multi-mode radar operation

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2234411A (en) * 1989-07-03 1991-01-30 Marconi Instruments Ltd Integrated circuit for digital demodulation
EP0547373A1 (fr) * 1991-11-25 1993-06-23 Motorola, Inc. Circuit et méthode de détection de signaux multifréquences à deux tonalités
EP0903899A2 (fr) * 1997-09-12 1999-03-24 Siemens Aktiengesellschaft Procédé et dispositif d'évaluation des signaux de tonalités multifréquences utilisant un filtre d'ondes numérique adaptatif à réjection

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1289281C (fr) * 1988-05-05 1991-09-17 Jerry Stroobach Detecteur de tonalites dtmf numeriques

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2234411A (en) * 1989-07-03 1991-01-30 Marconi Instruments Ltd Integrated circuit for digital demodulation
EP0547373A1 (fr) * 1991-11-25 1993-06-23 Motorola, Inc. Circuit et méthode de détection de signaux multifréquences à deux tonalités
EP0903899A2 (fr) * 1997-09-12 1999-03-24 Siemens Aktiengesellschaft Procédé et dispositif d'évaluation des signaux de tonalités multifréquences utilisant un filtre d'ondes numérique adaptatif à réjection

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DE19952027C2 (de) 2001-09-27
DE19952027A1 (de) 2001-05-10
WO2001031932A3 (fr) 2002-02-07

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