WO2006023012A2 - Multiplexage a division de distance - Google Patents

Multiplexage a division de distance Download PDF

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Publication number
WO2006023012A2
WO2006023012A2 PCT/US2005/021082 US2005021082W WO2006023012A2 WO 2006023012 A2 WO2006023012 A2 WO 2006023012A2 US 2005021082 W US2005021082 W US 2005021082W WO 2006023012 A2 WO2006023012 A2 WO 2006023012A2
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WO
WIPO (PCT)
Prior art keywords
sources
subband
signals
signal
spectral
Prior art date
Application number
PCT/US2005/021082
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English (en)
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WO2006023012A3 (fr
Inventor
Venkata Guruprasad
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Venkata Guruprasad
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
Priority claimed from US11/069,152 external-priority patent/US7106801B1/en
Application filed by Venkata Guruprasad filed Critical Venkata Guruprasad
Priority to EP05760863A priority Critical patent/EP1782593A4/fr
Priority to CA2575981A priority patent/CA2575981C/fr
Priority to JP2007529836A priority patent/JP4824026B2/ja
Publication of WO2006023012A2 publication Critical patent/WO2006023012A2/fr
Publication of WO2006023012A3 publication Critical patent/WO2006023012A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/02—Channels characterised by the type of signal
    • H04L5/06—Channels characterised by the type of signal the signals being represented by different frequencies
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity

Definitions

  • This invention generally pertains to communication of information between a source and a receiver More particularly, it concerns the use of source distance information at the receiver to ensure maximum bandwidth of communication and avoid noise and interference from other sources operating over the same frequencies
  • Such a separation is available for sources located at different directions from the receiver using phased array antennae as remarked, but not for sources along roughly the same direction and differing only in distance
  • the method would be also useful for detecting the presence of multiple sources, i e of interference, so as to enable a receiver to lock on to and track a selected source SUMMARY OF THE INVENTION
  • a primary object of the present invention is to provide a very general mechanism, whirh would be largely independent of signal form and content, for separating signals from multiple sources even when the sources are located along roughly the same direction from the receiver
  • Another object is to enable, at a receiver, most if not the entire physical bandwidth between a source and the receiver to be made available for communication between them, without interfering with communication from other sources or receivers
  • a secondary object is to provide a general means for detecting such interference and determining the causative source distance distribution
  • W 3 ⁇ [F 3 ] — L[F 3 ] will denote the respective bandwidths, so that
  • a nominal bandwidth W > W 3 can be assumed as non overlapping portions of the spectra would be separable by filters
  • the inventive procedure for extracting a specific signal F 1 then comprises the steps of A optionally first splitting the combined received signal into n > 1 subbands of successive widths ⁇ ⁇ W , ⁇ iW , ⁇ ⁇ W , i e into subbands n— 1 n
  • G ⁇ t ⁇ G ⁇ denotes corresponding baseband filters of bandwidths ⁇ ⁇ W;
  • Steps D and E can be interchanged, i.e. the subbands can be summed before applying the reverse mechanism, if the a ⁇ are equal. These steps form successive stages of signal processing in the receiver.
  • the essence of the separation, contained in Steps B through D, is summarized by the following process flow:
  • the utility of the method lies in the fact that the H operations depend only on ⁇ ⁇ which are independent of the signal sources, the latter being distinguished by the indices i or j in the above equations.
  • the separation is obtained spectrally via the transformed filters G ⁇ x ⁇ H ⁇ G ⁇ (equation 7), applied in the transformed space as H ⁇ i G ⁇ H ⁇ , per equation (9), instead of baseband filters G ⁇ , which per se cannot provide the separation.
  • the design of G ⁇ can be derived from that of G ⁇ by frequency scaling it by a ⁇ r x using known principles of filter design, the estimation of r, for this purpose will be described shortly.
  • the separation is nevertheless useful as the separated parts comprise t he lower frequency band [C, C + ⁇ W] from the nearer source and the higher frequency band [H - ⁇ W, Ti] from the farther source, which will likely contain much of the information
  • the separated high frequency band ⁇ - ⁇ W, H] would serve as a strong reference tor autocorrelative separation of the remainder of the signal bandwidth [C, ⁇ — ⁇ W) With subband processing, however, the conditions (15) become
  • the secondary object of detecting interference and estimating the source distribution may be achieved by a simple variation of this procedure, comprising, after Step B, the alternative steps of
  • n( ⁇ ) - ⁇ V S - ⁇ W/2 1 J ⁇ V 2 - ⁇ W/2 1 J and r max ( ⁇ ) a _ 1 f n[H(a)(S o F)( ⁇ ) ⁇ ⁇ Q - ⁇ W/2 - 1 * ⁇ -i f tt[ ⁇ r JXS[I + HH _ ⁇ (24) I, Q - ⁇ W/2 respectively, as a function of the subband centre frequency ⁇ We may likewise compute
  • the above inventive procedures are independent of the physical nature of the signals and their wavelength range
  • An equally general method for inducing the frequency shifts in the received waveforms, per equation (23) and orthogonally to their modulated information so as to be suitable for the objects of this invention, is provided by the copending application as mentioned
  • the method concerns the spectral phase distribution of a signal, which can be obtained using any appropriate spectromet ⁇ c means, such as resonant cavities or circuits, diffraction gratings for optical signals, and digital signal processing for electronic media
  • it involves scanning the gradient of this phase distribution over the signal spectrum by continuously varying the instantaneous tuning ⁇ of the resonant cavity or circuit, the intervals d ⁇ n ⁇ sm ⁇ (for any given diffraction angle ⁇ ) of the giating, or the sampling interval T ⁇ 1/ ⁇ of the digital processing system, each at the same normalized rate ⁇ ⁇ 1 d ⁇ /dt ⁇ ⁇ ⁇ d ⁇ /dt ⁇ T
  • a receiver embodying the present invention would thus generally include
  • the receiver would additionally include either
  • a fixed or vaiiablc means for setting either a or G, or both, in order to select a desired signal F 1 and reject interfering signal or noise sources, according to Steps A through E, or
  • a receiver may use a single tunable subband filter S( ⁇ ) and one set of spectral bound detector means applied to H(a)(SoF)( ⁇ ) per equation (24) to continually scan the entire signal bandwidth W using the modified inventive procedure oi Steps A* through C*
  • Both of the inventive functions, of separating the signal from a desired source and of detecting interference withm the signal band, may be implemented within a given receiver, for use one at a time or in parallel
  • the spectral bound detectors may be also applied to the unshifted spectra for accuracy of measurement, in which case the same threshold a th (equation ]) must be employed
  • the subband filters should suffice to ensure that spectral discontinuities withm a subband do not matter - it should be sufficient to scan inward from the extremities of the spectrum to the first crossing of the threshold magnitude ⁇ o t/ ,
  • one or more of the following schemes ould be generally necessary set the threshold above a sufficiently high empirically determined value, compare several successive samples to skip over narrower noise spikes, or average over several successive frames, which is common in spectral measurements
  • More sophisticated techniques involving smoothening, interpolation or autocorrelation over the spectrum may also be used None of these schemes is usually an option for Steps C and D for selecting
  • ⁇ basic receiver need not employ subba ⁇ dmg at all, and thus skip Steps A and E
  • a more sophisticated receiver may use subbanding, and would need a multitude ol input subband filters ⁇ S ⁇ ⁇ With subbanding, it would be often also useful to use a smaller a ⁇ for the higher subbands, while using sufficiently high values for the low subbands, so as to keep the shifted spectra within the handling range of the circuits, this would not be a concern with digital signal processing
  • the shift parameter a may be alternatively fixed at a large enough value for the intended operating distance range Large values of a can be achieved using bhort time frames in the shifting mechanism, as also described in the copending application
  • the desired signal F 1 can then be selected by varying G, or switching between a set of fixed filters (G 1 )
  • the alternative would be to use a single fixed selection filter G, and to vary ⁇ in order to bring F 1 into the pass band of G In either case, the variation may be performed manually through suitably implemented
  • the detection module may use relatively narrow subbands to dynamically determine the coarsest subband partitioning of the signal spectrum to simplify the operating configuration of source selection module, and to thus ensure better performance or lower the total power consumption
  • Another variation would be to keep the inventive selection module on standby, so as to only activate it in the presence of interference
  • the onset of interference may be detected aut omat ically using the inventive Steps C and D', simplistically without partitioning into subbands, or more particularly with subbands, or more accurately using a single scanning subband, as in Steps A* through C*
  • An alternative arrangement could also be employed for the interference detection in order to activate the inventive source selection procedure
  • the inventive signal selection procedure may even be manually activated or turned off based on perception of interference If multiple antenna or aperture feeds are available, c g as
  • an automatic (non interactive) source selection system may use the phase differences between the feeds to discriminate in direction as well as distance
  • prcfiltering may be also employed to alter the spectral profile over the desired band in order to simplify, or correct for limitations in, the design of the selection filter G 1
  • the prefilte ⁇ ng could include compressing the signal spectrum, using frequency modulation say, and Step D could likewise be accomplished by "mixing" , i e by multiplying with a generated intermediate frequency signal, or by frequency modulation If the same value of ⁇ is used for each of the subbands in Step B, Step E could be performed before Step D, as mentioned, with the advantage that only one reverse shitting mechanism is needed, though it must then handle the combined shifted bandwidth of all of the subbands
  • the input signal spectrum may be expanded before Step B using frequency modulation to limit noise arising in the subsequent stages
  • the final stage may likewise comprise a more complex combination of mixing and spectral expanding or compacting
  • a receiver needing to monitor multiple sources may be designed using a common shift mechanism in Step B and multiple selectors G 1 , each differently designed and fed the same shift mechanism output in parallel, or using identical selectors but fed by differently designed or tuned shift mechanisms, the latter being each fed the same input combination of signals
  • Fig 1 illustrates the separability of wave-propagated signals from two or more sources at different distances irom the receiver, using a distance-dependent frequency shifting mechanism at a receiver
  • Fig 2 summarizes the simplified inventive procedure for selecting a desired signal in the scenario of Fig 1
  • Fig 3 demonstrates the problem of spectral shadow that occurs with closely located sources, or signals with low frequency content, or with inadequate distance-dependent frequency shifting
  • Fig 4 illustrates separability of the lower half of the signal bandwidth in the scenario of Fig 3
  • Fig 5 illustrates separability of the upper half of the signal bandwidth in the scenario of Fig 3
  • Fig 6 summa ⁇ zes the inventive procedure for selecting a desired signal in the strigiio of Fig 3
  • Fig 7 is a block diagram for a receiver implementing the inventive piocedure of Fig 6
  • Fig 8 is a block diagiam for a simpler version of the receiver of Fig ⁇
  • Fig 9 is a block diagram for a receiver implementing the simplified inventive procedure of Fig 2
  • Fig 10 shows the alternative steps in the simplified mvenl ive procedure to determine the spread of sources
  • Fig 11 shows the modified inventive procedure for measuring the spread of sources using a scanning filter
  • Fig 12 is a block diagram for a receiver implementing the modified inventive procedure of Fig 11
  • Fig 13 illustrates the "scatter plot" approach for displaying the spread of sources
  • Step B of the inventive procedure the receiver causes the spectra of these component signals to be shifted in proportion to the source distances using the method described in the copendmg application, i e by frequency factors (1 + ⁇ r) [220] and (1 + ⁇ 1 ) [230]
  • Fig 3 illustrates the problem of spectral shadow, which arises whenever the sources are too close ( ⁇ r, ⁇ r,), the applied temporal parallax (a) is too small, or the signal contains very low frequencies (£ « HOr £ s; 0), so that equation (13) is not satisfied
  • the figure shows that under any of these conditions, the shifted spectra overlap and cannot be separated using a band-pass filter If, further the sources are of nearly equal strength, the shifted spectrum of the nearer source, F i ( ⁇ 1 ) [320], in effect casts a shadow [322] over the shifted spectrum F 2 (w 2 ) [330] of the farther source, i e that portions of the latter, F2(w2) [330], that fall within this shadow will suffer interference from the nearer source If the signals are frequency or spread-spectrum modulated for which a receiver typically recovers the carrier coherently using a phase-lock circuit, the faithcr or otherwise weaker source would be likely rejected altogether, regardless of which source was desired Further,
  • the inventive solution for the spectral shadow problem is to partition the incoming combined signal into two or more subbands, to then apply the procedure of Fig 2 separately to each of the subbands, and lastly, recombine the subbands to obtain the separated signal spectrum
  • the shadow [322] covers roughly half of the second source spectrum [330]
  • separation can be achieved by partitioning the input signal into two subbands, as illustrated in Figs 4 and 5, showing the results of applying Step B to the lower and the upper subbands, respectively
  • the lower subband So ⁇ F 3 [105] of the combined incoming signal obtained from the lower subband filter S 0 in Step A separates, under the inventive operation H (a), into the shifted component spectra SQHF
  • Fig 5 shows the corresponding separation of the upper subband Si ⁇ j F 3 [106] of the combined incoming signal, obtained from the lower subband filter S ⁇ in Step A, into the shifted component spectra SiHFi [326] and SiHF 2 [336]
  • the shifted lower bound [337] of the second signal will coincide with the shifted upper bound [323] of the first
  • the shadow would range from the shifted lower bound [327] to the shifted upper bound [323], and fails to cover the shifted subband [336] of the second source
  • Step E recombination
  • Step E can be pel formed before applying the reveise shift, i e before Step D, which would be useful for reducing the number of operations
  • narrower filters could be used for the source selection, in the place of Gi [420], and that a could be made smaller as well
  • Fig 7 is a block diagram of a receiver incorporating the complete inventive procedure described in Fig 6 It shows incoming electromagnetic (or acoustic) waves [610] being collected by an antenna (or microphone)
  • Step A This combined signal is fed to a bank of input subband filters [630] to produce the combined subband signals S ⁇ ⁇ F j ⁇ as Step A
  • Step B These combined subband signals are then subjected to Step B using a bank of frequency shifting mechanisms [640] per the copendmg application, to get the shifted subband signals 11(CiI 11 )S 11 [F j ), in which the contributions from the individual sources are already separated in frequency as shown in the preceding figures
  • these shifted subband signals H(a ⁇ )S ⁇ ⁇ F j ⁇ are then fed to the band-pass selection filter bank [650], as Step C, to obtain the shifted subbands G ⁇ H(ot ⁇ )S ⁇ ⁇ F j ⁇ as
  • Step D H(—a ⁇ )H(a ⁇ )S ⁇ F ⁇ sa S ⁇ F ⁇ t the subbands of the desired signal, and recombmed by a summing device [670], which can be as simple as an operational amplifier (op-amp), to obtain ⁇ ⁇ S ⁇ F ⁇ — F 1 , the desired signal
  • Fig 8 is a simpler version of the receiver of Fig 7, in which the summing device is applied before down ⁇ shifting, which is only possible when the same value ol o is used in each of the frequency shifting mechanisms [640]
  • Fig 9 shows an even simpler receiver that treats the entire signal bandwidth W as one subband, and thus skips both Steps A and E Such a receiver would be adequate, as already explained, when the sources are well separated from one another and the signal bandwidth W does not include d c It would be generally sufficient for broadcast radio and also mobile (cellular) telephones, since the base stations would be typically spread far apart The more complex receiver of Fig 7 would be generally needed at the cellular base stations, however, as the mobile (cellular) phones could even be situated side by side
  • Step C then consists of seeking, from the low frequency end of the measured domain, the first crossings of the obtained distributions above a suitably chosen threshold ⁇ (/ , [700], as indicated by the arrows [710] and [720], thereby obtaining the values £[ ⁇ F, ⁇ ] and £[7-/( ⁇ ) ⁇ F j ⁇ ] as the respective abscissae
  • ⁇ suitably chosen threshold
  • An estimate of the distance r mm to the nearest source is then computed from the relation
  • Step D' which is the specialisation of equation (17) to a single subband encompassing the full signal bandwidth W Step D' correspondingly consists of seeking, from the high frequency end of the measured domain, the first crossings of the obtained distributions above the same threshold a t h [700], as indicated by the a ⁇ ows [730] and [740], to obtain the values ⁇ [ ⁇ -F, ⁇ ] and Tt[H[Q)[F 3 ]) as the respective abscissae
  • the distance r max to the farthest source is then estimated using the relation
  • Steps A* through C* given in the Summary
  • a single subband filter [450] with a very narrow passband ⁇ W -C W is used to scan the received signal spectrum F( ⁇ ) [100], to obtain the filtered signal (5 o F)( ⁇ ) [150] at each instantaneous position of the filter [450]
  • the threshold frequency bound detectors are again applied, as shown by the arrows [710] and [730] to determine the low and high frequency bounds of the shifted distribution,
  • Fig 12 is a block diagram of a receiver incorporating the scanning procedure of Fig 11
  • the received signal (or combination of signals) from the antenna [620] is first subjected to narrow band filtering, in accordance with Step A*, by a subband filter [450], whose centre frequency is made to periodically sweep over the input band of frequencies by a sweep controller [634]
  • the resulting filtered signal is then input to the frequency shift mechanism [642], per Step B*, and its frequency bounds are measured, per Step C*, by the high [732] and the low [712], respectively
  • the bound values obtained are used to compute ⁇ m m and ⁇ ii ax , applying equation (24), or other related statistics, by the source distribution computer [680]
  • the difference between the "scatter plot" and a diffractive interference pattern is that the plot represents the actvial spatial distribution of sources, albeit with multiple aliases whereas diffractive interlerence is only representative of their spectral distribution This is because the plot starts with the spectral distribution, whereas in diffraction theory, one starts with a spatial distribution of sources or slits The method is in this sense an inverse of diffractive interference
  • Step D could be replaced by a down-converter, optionally with a modulation- demodulation stage to scale back the bandwidth by the factor (1 + Q ⁇ )
  • the scaling down may be obviated by moving the modulation-demodulation stage before Steps A or B, so that the bandwidth is already scaled down by an estimate of the (1+ ⁇ r) factor for the
  • the present invention may be enhanced with direction- sensitive antenna technology to also provide separation of signals from sources at almost the same distance from the receiver, but differing in their directions
  • the inventive method may be conversely employed as an alternative to directional antennae in order to separate sources that are too close in direction
  • the present invention may likewise be combined with content-based separation methods including, but not limited to, amplitude, frequency, phase and spread-spectrum modulations, or TDM, and autocorrelative methods All such modifications, generalizations and variations are intended within the scope and spirit of the invention as defined in the claims appended hereto

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Noise Elimination (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
  • Circuits Of Receivers In General (AREA)

Abstract

L'invention concerne un procédé général d'extraction d'un signal électromagnétique ou propagé par onde d'une source souhaitée à partir de l'ensemble de la forme d'onde reçue qui contient la somme des signaux émanant d'une multitude de sources, indépendamment, des contenus et de la modulation des signaux. Ce procédé consiste, dans un premier temps, à étendre le spectre de la somme reçue de signaux proportionnellement à leurs distances de source de manière à isoler spectralement le signal de la source souhaitée, à sélectionner le spectre de signal isolé au moyen d'un filtre passe bande et, finalement, à comprimer spectralement le signal sélectionné et à le ramener à sa bande d'origine de fréquences. L'expansion dépendante de la distance est réalisée par balayage du gradient de phase du spectre de signal. Si les sources sont trop proches les unes des autres ou si leurs signaux occupent des fréquences très faibles, la somme reçue des signaux peut être divisée en au moins deux sous-bandes, l'expansion et le filtrage de sélection étant appliqués individuellement à chaque sous-bande et les sous-bandes de signal sélectionnées étant ensuite recombinées en vue d'obtenir le signal souhaité. Un procédé associé de calcul de la diffusion des distances de source par mesure des limites de fréquences élevées et faibles de la somme étendue de signaux ou de sous-bandes ou par tracé de la somme étendue de signaux ou de sous-bandes sur un graphe.
PCT/US2005/021082 2004-08-24 2005-06-15 Multiplexage a division de distance WO2006023012A2 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP05760863A EP1782593A4 (fr) 2004-08-24 2005-06-15 Multiplexage a division de distance
CA2575981A CA2575981C (fr) 2004-08-24 2005-06-15 Multiplexage a division de distance
JP2007529836A JP4824026B2 (ja) 2004-08-24 2005-06-15 距離分割多重化

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US60368804P 2004-08-24 2004-08-24
US60/603,688 2004-08-24
US11/069,152 US7106801B1 (en) 2005-03-01 2005-03-01 Distance division multiplexing
US11/069,152 2005-03-01

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WO2006023012A2 true WO2006023012A2 (fr) 2006-03-02
WO2006023012A3 WO2006023012A3 (fr) 2006-04-06

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JP (1) JP4824026B2 (fr)
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WO (1) WO2006023012A2 (fr)

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WO2014085936A1 (fr) * 2012-12-07 2014-06-12 Evolution Engineering Inc. Procédé et appareil pour télémétrie électromagnétique de fond de trou à canaux multiples
US9803473B2 (en) 2015-10-23 2017-10-31 Schlumberger Technology Corporation Downhole electromagnetic telemetry receiver

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014085936A1 (fr) * 2012-12-07 2014-06-12 Evolution Engineering Inc. Procédé et appareil pour télémétrie électromagnétique de fond de trou à canaux multiples
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US9803473B2 (en) 2015-10-23 2017-10-31 Schlumberger Technology Corporation Downhole electromagnetic telemetry receiver

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CA2575981C (fr) 2013-10-29
WO2006023012A3 (fr) 2006-04-06
CA2575981A1 (fr) 2006-03-02
JP4824026B2 (ja) 2011-11-24
EP1782593A2 (fr) 2007-05-09
JP2008511250A (ja) 2008-04-10
EP1782593A4 (fr) 2013-03-27

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