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Patent Issued for Method and Arrangement for Measuring Delay of a Signal between Two Stations of the Arrangement

June 18, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Gierlich, Roland (Rheinbach, DE); Huttner, Jorg (Munchen, DE); Ziroff, Andreas (Passau, DE), filed on July 13, 2010, was published online on June 3, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8742978 is assigned to Siemens Aktiengesellschaft (Munich, DE).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The invention relates to communication signal processing and, more particularly, to a method and an arrangement for determining the propagation delay of a signal between a first and second station in the arrangement with to determine the spatial distance between the stations.

"The industrial domain is an instance of where precisely determining a radio transmitter's position or, as the case may be, its distance from a base station or such is of significance. Besides meeting the demand for cost- and energy-saving measuring systems, particularly for applications in closed spaces or halls it is therein necessary owing to possible multipath reflections to employ high-resolution measuring systems to obviate errors in distance measuring. For instance, Ultra Wide Band (UWB) signals offer a large signal bandwidth and thereby promise a relatively high resolution and high degree of accuracy.

"Various methods that employ, for example, optical signals, ultrasound signals, or radio sensor technology, are known for determining a position or, as the case may be, distance. In particular, the methods for determining a distance bistatically with the aid of radio signals can be divided into three categories.

"The first category is communication-based systems. Here, the distance is determined additionally from the communication signal. The degrees of accuracy achievable in distance measurements are not expected to be high because less stringent demands are placed on synchronizing in many communication systems or, as the case may be, only a very narrowband radio channel is available.

"The second category is Frequency Modulated Continuous Frequency-Stepped Continuous Wave (FMCW/FSCW) solutions. These systems operate in the Industrial, Scientific, and Medical (ISM) bands and enable a distance value to be determined in a manner similar to classical FMCW radar by tuning a transmitting frequency. Transponder-based or, as the case may be, backscatter solutions are therein employed on the one hand and, on the other, receivers that can synchronize themselves therewith.

"The third category is ultra wideband (UWB) systems. These systems exploit new regulations allowing the emission of ultra wideband signals which, though, have a very low spectral power density. The receiver architectures can be, for example, power detectors having a moderate capacity or coherent receivers that require either very long correlation times or an extremely fast sampling rate.

"These solutions have cost implications specifically for one-dimensional distance measuring between two radio stations because complex signal-processing steps are necessary in at least one of the two stations.

"FIG. 1A shows a conventional principle of measuring distance between a transmitting/receiving station 10 and an object 20. Transmitting/receiving station 10 has a phase-locked loop (PLL) 11 that drives a first 12 and second pulse generator 13. First pulse generator 12 thereupon generates a first series TX-series of signal pulses TX-puls(i), where i=0, 1, 2, 3, . . . , at a pulse-repetition rate f.sub.0. Second pulse generator 13 correspondingly generates a second series RX-series of signal pulses RX-puls(j), where j=0, 1, 2, 3, . . . , at a pulse-repetition rate f.sub.0+.DELTA.f. It can therein be assumed that, for example, signal pulses TX-puls(0) and RX-puls(0) are generated simultaneously.

"Because pulse-repetition rates differ by the amount .DELTA.f, signal pulses of first series TX-series and second series RX-series regularly coincide at time intervals 1/.DELTA.f, meaning at instants T.sub.TX/RX(a)=a*1/.DELTA.f+c, where a=0, 1, 2, 3 . . . c is therein only a constant that depends on how instant t=0 is established (for example c=0 in the case of FIG. 1B).

"First series TX-series is then emitted by an antenna 14 of transmitting/receiving station 10 and reflected on object 20 whose distance from transmitting/receiving station 10 is to be ascertained.

"First series TX-series or, as the case may be, its signal pulses TX-puls(i) is/are reflected on object 20 and received by a second antenna 15 of transmitting/receiving station 10. Another series REC-series of signal pulses REC-puls(i) which, like first series TX-series, has a pulse-repetition rate f.sub.0, but which is time-shifted relative to series TX-series in keeping with signal propagation delay .tau., will thus be available at antenna 15. Signal propagation delay .tau. is therein defined such that .tau. indicates the length of time a signal takes to travel from transmitting/receiving station 10 to object 20 and back. Received series REC-series has accordingly been shifted by .tau. relative to transmitted series TX-series.

"Receive signal RX-series having pulse-repetition rate f.sub.0 is fed to a mixer 16 in which it is correlated with second series RX-series of signal pulses RX-puls(j) at a pulse-repetition rate f.sub.0+.DELTA.f. The signal will be detectable in the baseband if the two series' signal pulses coincide, meaning that a series BB-series having signal pulses BB-puls(k) and then having in each case a signal pulse BB-puls(k) will be generated in mixer 16 if a signal pulse RX-puls(j) of RX-series coincides in time with a signal pulse REC-puls(i) of REC-series. That occurs at instants T.sub.REC/RX(b)=b*1/.DELTA.f-.tau.*f0/.DELTA.f+c, where b=0, 1, 2, 3, . . . and c=constant (see above).

"The time distance .DELTA. between an instant T.sub.TX/RX(a) at which two pulses of series TX-series and RX-series coincide in time and an instant T.sub.REC/TX(b) at which two pulses of series of REC-series and RX-series coincide in time, .DELTA.=.tau.*f0/.DELTA.f, will then with a=b be proportional to propagation delay .tau. and hence also to the distance between transmitting/receiving station 10 and object 20.

"FIG. 1B shows the time characteristics of the different pulse series TX-series, RX-series, RX-series, and BB-series. Signal pulses TX-puls(0) and RX-puls(0) were generated simultaneously. Receive signal REC-series has been time-shifted relative to first pulse series TX-series due to propagation delay .tau.. The result BB-series for series REC-series and RX-series correlating that occur in mixer 16 is shown at the bottom of the chart. Comparing instant T.sub.REC/RX(1) with T.sub.TX/RX(1) will supply signal propagation delay .tau.. It should be appreciated that the same applies to comparing instants T.sub.REC/RX(2) with T.sub.TX/RX(2), etc., meaning that comparing instants T.sub.REC/RX(a) with T.sub.TX/RX(a) will supply the propagation delay being sought.

"The conventional method that is presented assumes, however, that the transmitter and receiver are accommodated in one and the same station or, as the case may be, that a common time scale for the different signal series is established by PLL 11, meaning that the transmitter and receiver are synchronized. Only the distance from an object can accordingly be measured with this method, not the distance between two stations. If the transmitter and receiver are mutually separate and not fed by a shared PLL, for example, synchronizing will first need to be established for measuring the distance between the transmitter and receiver."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "It is therefore the object of the present invention to provide a method and an arrangement for determining the propagation delay of a signal between a first and second station.

"This and other objects and advantages are achieved in accordance with the invention by providing the possibility to synchronize UWB pulses which thus enables the distance between two stations to be determined.

"In accordance with the invention, a first series TX100-ser of first signal pulses is first generated in a first station at a first pulse-repetition rate f1 to determine the signal propagation delay .tau. between the first station and the second station. Generated thereupon in the second station are a second series TX200-serP of second signal pulses at a second pulse-repetition rate f2 and a third series TX200-serM of third signal pulses at a third pulse-repetition rate f3, with f2=f1+.DELTA.f and f3=f1-.DELTA.f applying to the pulse-repetition rates in the second station. Second series TX200-serP and third series TX200-serM are then transmitted by the second station to the first station and received there, whereupon series REC100-serP, REC100-serM received at the first station will be fed to a correlator, in particular a mixer. The series will be correlated there with the first series, with a resultant series BB100-ser of signal pulses being generated. Signal propagation delay .tau. is finally determined from the time distance .DELTA. between two successive signal pulses of resulting series BB100-ser.

"A signal pulse of resulting series BB100-ser will be generated in the correlator whenever a signal pulse of first series TX100-ser coincides in time with a signal pulse of received series REC100-serP, REC100-serM.

"The second and third series are advantageously first mutually superimposed to form a further series particularly by adding the second and third series. The second and third series are then transmitted to the first station as the further series and received there.

"In an alternative embodiment, before being transmitted to the first station, the second and third series are fed to a switch belonging to the second station, with the switch being controlled to alternately select the second or third series, with the selected series being transmitted to the first station and received there.

"The switch is driven to change over at the instant in time at which the second-series and third-series pulses are generated simultaneously.

"Second series TX200-serP and third series TX200-serM are advantageously generated having a fixed mutual phase relationship.

"Second pulse-repetition rate f2 and third pulse-repetition rate f3 are controlled by a phase-locked loop belonging to the second station.

"Second series TX200-serP is therein generated by a pulse generator, with the pulse generator being controlled by the phase-locked loop such that second series TX200-serP will have second pulse-repetition rate f2. Third series TX200-serM is furthermore generated by a pulse generator, with the pulse generator being controlled by the phase-locked loop such that third series TX200-serM will have third pulse-repetition rate f3.

"First series TX100-ser is moreover initially transmitted by the first station to the second station and received there. Series REC200-ser received at the second station is fed to a correlator belonging to the second station where received series REC200-ser will be correlated with second series TX200-serP or third series TX200-serM. A signal BB200-ser is therein generated which is fed to the phase-locked loop. The phase-locked loop in turn makes second pulse-repetition rate f2 and third pulse-repetition rate f3 available based on signal BB200-sig.

"It is also an object to provide an arrangement for determining signal propagation delay .tau. between a first station in the arrangement and a second station in the arrangement, with the first station having a first pulse generator by which a first series TX100-ser of first signal pulses can be generated at a first pulse-repetition rate f1, the second station having a second and third pulse generator, with it being possible for the second pulse generator to generate a second series TX200-serP of second signal pulses at a second pulse-repetition rate f2 and it being possible for the third pulse generator to generate a third series TX200-serM of third signal pulses at a third pulse-repetition rate f3, with f2=f1+.DELTA.f and f3=f1-.DELTA.f applying to the pulse-repetition rates, the second station having a transmitting device for transmitting second TX200-serP and third series TX200-serM to the first station, the first station having a receiving device for receiving the transmitted series and a correlator for correlating received series REC100-serP, REC100-serM with first series TX100-ser, with a resultant series BB100-ser being generated during the correlation, and the first station having an evaluation unit by which a time distance .DELTA. between two successive signal pulses of the resultant series BB100-ser can be ascertained.

"The second station advantageously includes a switch that is connected to the second and third pulse generator and to the transmitting device. The switch is configured to select second series TX200-serP or third series TX200-serM for transmittal to the first station.

"The first station furthermore includes a transmitting device for transmitting first series TX100-ser to the second station. The second station also has a receiving device for receiving transmitted first series TX100-ser, as well as a correlator for correlating received first series REC200-ser with second series TX200-serP or with third series TX200-serM. A signal BB200-ser that can be fed to a phase-locked loop belonging to the second station is generated during the correlation. The phase-locked loop controls the second and third pulse generator based on signal BB200-ser.

"An advantage of the invention compared with the prior art is that a bistatic distance-measuring system can be produced from two pulse radars by slightly expanding the PLL circuit and receiving unit. The system is furthermore characterized by its simplicity in signal-processing terms. Fast sampling rates are obviated through successive sampling and a kind of time spreading is produced. Because suitable transmission will give the baseband signal a symmetric curve, distance evaluations are also simplified. Multi-channel reflections with a propagation delay of longer duration will be further apart. The complete PLL circuits can be implemented in a microcontroller. The method in accordance with the invention can thus be applied to different pulse-radar methods, for example, to methods in which successive noise sequences are correlated.

"Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein."

URL and more information on this patent, see: Gierlich, Roland; Huttner, Jorg; Ziroff, Andreas. Method and Arrangement for Measuring Delay of a Signal between Two Stations of the Arrangement. U.S. Patent Number 8742978, filed July 13, 2010, and published online on June 3, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8742978.PN.&OS=PN/8742978RS=PN/8742978

Keywords for this news article include: Electronics, Signal Processing, Siemens Aktiengesellschaft.

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Source: Electronics Newsweekly


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