WO2007055676A1 - Procede et systeme de mesure de distance dans une boucle de communications en semi-duplex en frequence intermediaire faible ou nulle - Google Patents

Procede et systeme de mesure de distance dans une boucle de communications en semi-duplex en frequence intermediaire faible ou nulle Download PDF

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Publication number
WO2007055676A1
WO2007055676A1 PCT/US2003/018590 US0318590W WO2007055676A1 WO 2007055676 A1 WO2007055676 A1 WO 2007055676A1 US 0318590 W US0318590 W US 0318590W WO 2007055676 A1 WO2007055676 A1 WO 2007055676A1
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WIPO (PCT)
Prior art keywords
signal
frequency
digital
frequency signal
phase
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Application number
PCT/US2003/018590
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English (en)
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WO2007055676A8 (fr
Inventor
Shlomo Berliner
Alan Bensky
Reuven Amsalem
Gil Sever
Dani Aljadeff
Original Assignee
Bluesoft Inc.
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.)
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Publication date
Application filed by Bluesoft Inc. filed Critical Bluesoft Inc.
Priority to PCT/US2003/018590 priority Critical patent/WO2007055676A1/fr
Publication of WO2007055676A1 publication Critical patent/WO2007055676A1/fr
Publication of WO2007055676A8 publication Critical patent/WO2007055676A8/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/82—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Definitions

  • the present invention relates generally to distance measuring systems, and more specifically, to a method and system for measuring a distance between transceivers having a low or zero intermediate frequency.
  • BLUETOOTH devices provide a wireless network operating in the 2.4 Ghz Industrial Scientific and Medical band and be enhanced to provide a measurement of distance between connected devices without adding a separate infrastructure as is required with systems such as the
  • GPS Global Positioning System
  • BLUETOOTH is a trademark of Bluetooth SIG, Inc., which is an acronym for Bluetooth Special Interest Group - a consortium of wireless device manufacturers.
  • the half-duplex techniques described in the above-incorporated patent application are techniques that require synchronization of a pair of transceivers to retain phase coherency between reception and transmission intervals of a half-duplex signal. Without synchronization, a phase measurement cannot be made and therefore no distance measurement. In a direct conversion half-duplex system or a half-duplex low IF system where synchronization is impractical, implementation of the known distance measurement techniques is impossible. Therefore, it would be desirable to provide a method and system for measuring distance within a low or zero IF transceiver loop, so that distance between wireless devices may be made without requiring additional infrastructure and without synchronization of local oscillators between wireless devices.
  • the above objective of providing a distance measurement in a low or zero intermediate frequency half-duplex communications loop is achieved in a method and system.
  • the method is embodied in a system that transmits a radio- frequency (RF) signal from a measuring device to a measured device.
  • the measured device receives the RF signal during a reception interval and demodulates the received RF signal with a local oscillator having a predetermined frequency differing from the local oscillator frequency of the measuring device.
  • the resulting down-converted signal phase and frequency information is stored during the reception interval and retained until after the end of the reception interval.
  • the measured device up-converts a signal having a phase and frequency in conformity with the stored phase and frequency information using the measurement device local oscillator and transmits the up-converted signal.
  • the resulting signal transmitted from the measured device is of the same frequency as the received RF signal and is synchronized to the measurement device local oscillator.
  • the transmitted signal is received at the measuring device and is used to measure the distance between the measuring device and the measured device.
  • Figure 1 is a pictorial diagram depicting a wireless network in which an embodiment of the invention is practiced.
  • Figure 2 is a block diagram depicting a communications loop within which the present- invention is embodied.
  • Figure 3 is a block diagram depicting a phase-frequency hold circuit in accordance with an embodiment of the invention.
  • Figure 4 is a block diagram depicting a phase-frequency hold circuit in accordance with an alternative embodiment of the invention.
  • Figure 5A is a schematic diagram depicting a selectable modulator/demodulator circuit that may be used within transceivers 1OA and 1OB of Figure 2.
  • Figure 5B is a schematic diagram depicting phase detector and loop filter circuit that may be used within the phase-frequency hold circuit of Figure 3.
  • FIG. 6 is a flowchart depicting a method in accordance with an embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • a wireless network within which the present invention is embodied is depicted in a block diagram.
  • a plurality of wireless devices 10A-10D inter-communicate via radio-frequency (RF) signals (for example 12A and 12B illustrating a communication between devices 1OA and 10B) transmitted and received via antennas 14A and 14B.
  • Wireless devices 10A-10D may be mobile telephones, personal digital assistants (PDAs), laptop computers with wireless modems, pagers, or other portable or non-portable devices that include wireless communications capability.
  • PDAs personal digital assistants
  • laptop computers with wireless modems, pagers, or other portable or non-portable devices that include wireless communications capability.
  • Some devices in the associated wireless network may be receive-only or broadcast only, but in order to implement the distance measuring techniques of the present invention, a pair of transceivers is used, as a signal must be transmitted from a "measuring” device to a “measured” device and a second signal is then returned from the measured device.
  • Wireless devices 10A-10D are transceivers capable of communicating using a common protocol and frequency band of operation.
  • transceivers 10A-10D may be BLUETOOTH devices communicating in a band centered around 2.4Ghz and having a bandwidth of approximately 80 Mhz. 79 channels are provided with a lMhz bandwidth each, and the devices frequency hop at a rate of 1600 hops per second.
  • a complete protocol, including communications control protocols and transport layer protocols are defined by the BLUETOOTH specification, providing a complete wireless networking solution. While the BLUETOOTH specification is of particular interest in wireless networking, it should be understood that the techniques of the present invention apply to wireless communication systems in general, and in particular to half-duplex communication systems using either direct conversion (zero IF) or low frequency IF signals.
  • the present invention measures distance using techniques similar to those described in the above- incorporated patent applications.
  • the slope of phase versus frequency as measured around a communications loop and over a plurality of frequencies is used to determine the distance between a pair of transceivers.
  • the ambiguities due to an unknown number of wavelengths between the transceivers and due to multipath distortion is resolved by the use of multiple frequency measurements.
  • the techniques and apparatus of the present invention further encompass distance measuring within systems using a continuously varying frequency (such as a linear "chirp" profile or other time-variant frequency profile) within a half-duplex communications system, as the techniques of the present invention provide a transceiver that is capable of transmitting a response signal that is coherent with a received signal without synchronization of local oscillators and it is this method and structure to which the invention particularly pertains.
  • a continuously varying frequency such as a linear "chirp" profile or other time-variant frequency profile
  • the far end of a communications loop using direct conversion cannot transmit a signal coherent with a signal received from the originating end of the communications loop.
  • the signal transmitted by the originating end is not available at the far end of the communications loop at the time of transmission by the far end of the communications loop and therefore phase information must be held until the time of transmission from the far end of the communications loop.
  • This objective is accomplished by the method and structure disclosed in the above-reference patent application, but when implemented in a direct conversion system or system having a very low IF frequency, the locking of a local oscillator at the measured device is not possible as the phase comparison time for just one cycle of difference frequency can consume a large part of the reception interval.
  • the present invention concerns the structure and method by which the storing of phase information corresponding to the signal transmitted by the originating end of the communications loop (and thus the local oscillator and modulation source of the originating end) is achieved.
  • Transceiver 1OA and transceiver 1OB are coupled by a wireless communication 12 through antennas 14A and 14B.
  • Transceiver 1OA is the "measuring" device for the purposes of illustration and transceiver 1OB is the "measured” device, but the functional blocks, circuits and software/firmware required to implement the invention may be present in both transceivers or may be implemented in separate fashion as shown.
  • enhancements the measured device are required over prior art receivers, but the measurement device may be implemented in a fashion bimilar to the half-duplex transceiver described in the above-referenced patent application.
  • Modulation source 23A provides the source signal S m i of frequency F m that is up-converted by modulator 26A to provide RF transmit signal S Tx i that is broadcast through antenna 14A during a transmit time interval (time slot) as selected by T/R switch 22A.
  • Local oscillator 24A provides the upconversion signal at frequency F LO i and therefore the transmitted RF signal S Tx i has a frequency of F Lo i ⁇ F m (where the sign is determined by selection of either upper sideband or lower sideband selected by a processor 29A) .
  • the techniques of the present invention may be applied to a sinusoidal waveform having a simple frequency as illustrated by the above equations, or to a more complex spectrum having discrete or continuous bandwidth for which F m represents a band of frequencies .
  • Transceiver 1OB receives the RF signal corresponding to the S Tx i signal as received signal S RX ⁇ , which has the same frequency characteristics as S Tx ⁇ ,and a phase determined in part by the distance between transceiver 1OA and transceiver 1OB.
  • Signal S R ⁇ is downconverted by a demodulator 27B producing demodulated signal S d2 which has a frequency F m ⁇ (F L OI - F L02 ) , where F L02 is the frequency of local oscillator 24B used to demodulate signal S R ⁇ .
  • the sign of the frequency equation above is again determined by a selection of upper/lower sideband demodulation which may be selected by processor 29B.
  • Subsequent distance measurement signaling is then conducted by selecting upper or lower sideband modulation via the USB/LSB select signal.
  • a counter or an FFT algorithm may be used to determine the frequency offset between the local oscillators (of the measuring device and measured device) at the measured device and this frequency offset information may be transmitted to the measuring device for use in correcting the phase measurements.
  • this measurement is needed in one embodiment to determine the delay of the storage and conversion elements and is information already available .
  • Upper or lower sideband modulation is chosen to ensure that the frequency of S d2 which has a frequency F m ⁇ (F LO i - F L o 2 ) sufficiently high to carry out the measurement.
  • F m 75Khz
  • F m 75Khz
  • the demodulated frequency will be 75Khz, for deviations of 75Khz the sideband yielding a demodulated 150Khz (rather than zero) can be chosen and so forth, guaranteeing a 75Khz minimum frequency from the output of demodulator 27B.
  • the proper sideband for modulation chosen as described above to yield a minimum demodulated frequency at the measured device, can be chosen in several ways.
  • One mechanism is to transmit a request from the measuring device to the measured device (using a command protocol) that causes the measured device to send a binary representation of a measurement: of the difference frequency between the local oscillator reference clocks (for example, by measuring the deviation between the demodulated frequency and the expected demodulated frequency for a predetermined RF frequency) .
  • the estimated deviation is returned to the measuring device to inform the measuring device of the deviation between the local oscillators.
  • upper sideband or lower sideband modulation is selected by the measuring device to guarantee a minimum demodulated frequency within the measured device.
  • the frequency deviation may be measured using an FFT algorithm, counter chain or other frequency measurement technique.
  • An alternative mechanism for selecting operating an sideband for modulation is for the measuring device to send a request (via a command protocol) to the measured device requesting that the measured device return one time interval of upper sideband demodulation and then one interval of lower sideband transmission (based on a fixed modulating reference within the measured device) .
  • the average of the two received frequencies at the measuring device yields the offset between the local oscillators, since the modulation deviation will subtract to remove contribution from the modulating source.
  • phase/frequency hold circuit 28 The output of demodulator 27B is measured (sampled) during the reception interval by a phase/frequency hold circuit 28.
  • Phase/freq hold circuit 28 may be an analog system or a digital system as will be described in particular embodiments below.
  • the phase and frequency information corresponding to the S d2 signal is held until the transmission interval and the output of phase/ freq hold 28 is upconverred by modulator 26B to produce a transmit signal S Tx2 , which has a carrier frequency of F LO i ⁇ F m corresponding exactly to signal S TX2 transmitted from transceiver 1OA and having a phase determined in part by the distance between transceiver 1OA and transceiver 1OB.
  • Transceiver 1OA receives the signal transmitted from transceiver 1OB during a reception interval as selected by T/R switch 22A and received signal S RXI is demodulated by demodulator 27A to produce demodulated signal Sai which has a frequency of F m exactly the same as modulation source 23A output signal S m i .
  • the output of modulation source 23A and demodulated signal S d i are then compared by signal processing block 25 to determine a phase for that particular channel frequency. Multiple hop phase measurements are then used to determine a measured distance eliminating the effects of multipath and other path delays .
  • a Q r and I r pair of quadrature signals are received from demodulator 27B.
  • the input signal is filtered by a low-pass filter 32A and introduced to a phase comparator 41 that compares the phase of the demodulated signal with the output of a voltage-controlled oscillator (VCO) 43.
  • Loop filter amplifier 42 filters the output of phase comparator 41 to provide a control voltage V c to set the frequency of VCO 43, thus forming a phase-lock loop.
  • Phase comparator 41 and loop filter amplifier 42 include enable inputs coupled to a time slot detector 31A that disables the output of phase comparator 41 and puts loop filter amplifier in a "hold" state during the transmission interval (i.e., when Q r and I r are invalid because no signal is received during this interval) .
  • phase/freq hold circuit thus holds the phase and frequency of the demodulated signal received during the reception interval until the transmission interval begins.
  • Oscillator 43 provides a quadrature pair of output signals for input to modulator 26B and upconversion for transmission from the measured device.
  • the Q r signal could be used alternatively or in conjunction with the I r signal (For example, phase comparator 41 could be a quadrature multiplier and both signals in the pair could be used for phase comparison after low-pass filtering) .
  • time slot detect circuit 31A output may be supplied as an input signal from another block within a transceiver, as the detection of the time divisions are common to many other circuits within a typical transceiver.
  • Time slot detection based on the detected quadrature output may or may not be preferable and is include as only an example of a mechanism for deriving synchronization to time slots.
  • both quadrature signals Q r and I r are filtered by lowpass filters 32A and 32B and are subsequently sampled by A/D converters 33A and 33B.
  • a control logic 36 controls the sampling process, which is synchronized to the reception time slot detected by time slot detect 31B.
  • the sampled demodulated signals Q r and I t are stored in first-in-first-out (FIFO) memories 34A and 34B by control logic 36.
  • FIFO first-in-first-out
  • phase and frequency information of the demodulated signals Q r and I r are stored (as complete sampled waveforms of Q r and I r ) in FIFOS 34A and 34B until the transmission time interval.
  • a phase delay through the conversion system and FIFO memories 34A is compensated within the distance measurement by one of a variety of means.
  • a counter or an FFT algorithm may be used to determine the frequency offset between the local oscillators (of the measuring device and measured device) at either device and this frequency offset information may be transmitted from the measured device (in response to a request from the measuring device) to the measuring device for use in correcting the phase measurements.
  • the time delay of the sampling system is a design parameter and can be taken into account as well as the conversion component delays, or this information may be stored within the measured device and transmitted to the measuring device.
  • An alternative is to transmit a modulated signal from the measured device (during a specially designated time slot) and the processing subsystem within the measuring device can then determine the delay from the received modulated signal.
  • phase/freq hold 28A may use a "digital" phase comparator or a full digital phase-lock loop or phase/freq hold 28B may use an analog phase/frequency detection scheme and store values corresponding to frequency and phase rather than waveform samples .
  • the present invention concerns: 1) demodulating the received signal with a reference frequency other than the reference frequency of the originating source, 2) storing the resulting intermediate frequency signals' phase and frequency information for later transmission, and 3) modulating a signal having a phase and frequency in conformity with the stored phase and frequency information with the same reference frequency used to demodulate the received signal to produce a signal for transmission.
  • FIG. 5A an exemplary modulator/demodulator circuit 27C that may be used within transceivers 1OA and 1OB of figure 2 is depicted.
  • the signals are shown as configured for a demodulator, but it should be understood that a corresponding modulator circuit may be implemented by exchanging the RF In signal with a modulation input signal and demodulator output signals with RF Output signals.
  • USB/LSB select signal controls switch Sl which determines which of the quadrature local oscillator output signals is applied to the local oscillator input nodes of mixer Ml.
  • the RF in signal (which is the modulation input signal for a modulator) is applied to mixer Ml providing a demodulated quadrature output at the Output signal pins.
  • Figure 5A The illustration of Figure 5A is provided as an example and it should be understood that other forms of selectable mixer circuits can be used in accordance with embodiments of the invention, such as BJT and FET mixers, as well as digital implementations such as XOR gate mixers .
  • Phase detector 45 includes an edge comparator that produces a signed output based on whether the VCO Out signal leads or lags the Sig In signal.
  • buffer 47 enables the signed output to charge or discharge loop filter 48.
  • the switch in loop filter 48 opens, placing loop filter 48 in a hold state (because the capacitor voltage can only change due to leakage) .
  • any appropriate loop filter/phase detector can be used to implement the phase/frequency hold circuit as long as sufficient frequency agility and hold stability are achieved.
  • a command is transmitted to the measured device to return a 150KHz deviation signal (step 50) .
  • the deviation signal is transmitted from the measured device, received by the measuring device and the deviation is detected (step 51) . If the local oscillator of the measured device has a higher frequency than the local oscillator of the measuring device (decision 52) , the lower sideband is selected for subsequent distance measurement signaling (step 54) . Otherwise the upper sideband is selected (step 53) .
  • the distance measuring signal is transmitted from the measuring device to the measured device (step 55) and the measured device stores frequency and phase information during the reception interval (step 56B) . Then, the measured device transmits a return signal that is reconstructed from the stored frequency and phase information (step 57) . The measuring device receives and detects the phase of the return signal (step 58) . Steps 55 through 58 are repeated for multiple frequencies and the phase information is compensated for phase folding due to roll-overs of phase that occur (step 59) . After all of the measuring frequencies have been sampled, the distance between the measured device and the measuring device is determined by the slope of phase versus frequency (step 60) .

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

La présente invention a trait à procédé et système de mesure de distance dans une boucle de communications en semi-duplex en fréquence intermédiaire faible ou nulle fournissant un mécanisme permettant de mesurer la distance entre deux émetteurs-récepteurs sans synchronisation des oscillateurs locaux des deux récepteurs. La distance entre les émetteurs-récepteurs peut être mesurée dans des systèmes mettant en oeuvre la conversion directe (fréquence intermédiaire nulle) ou des fréquences intermédiaires si faibles que le bruit de phase réduit nettement la précision de la mesure de distance. La boucle de communications est fermée par la démodulation, la remodulation et la retransmission d'un signal reçu pour fournir un signal retransmis qui présente la même porteuse et la même fréquence de modulation que le signal reçu. Un circuit de maintien de phase fournit un système analogique pour une exploitation en semi-duplex qui maintient l'information de fréquence et de phase du signal reçu pour la retransmission dans un intervalle de temps ultérieur. En variante, une implantation numérique réalise le maintien de phase et de fréquence via un système d'échantillonnage et de temporisation comprenant un sous-système de conversion analogique-numérique, une mémoire de premier entré, premier sorti de temporisation et un convertisseur numérique-analogique.
PCT/US2003/018590 2003-06-13 2003-06-13 Procede et systeme de mesure de distance dans une boucle de communications en semi-duplex en frequence intermediaire faible ou nulle WO2007055676A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US2003/018590 WO2007055676A1 (fr) 2003-06-13 2003-06-13 Procede et systeme de mesure de distance dans une boucle de communications en semi-duplex en frequence intermediaire faible ou nulle

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Application Number Priority Date Filing Date Title
PCT/US2003/018590 WO2007055676A1 (fr) 2003-06-13 2003-06-13 Procede et systeme de mesure de distance dans une boucle de communications en semi-duplex en frequence intermediaire faible ou nulle

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WO2007055676A1 true WO2007055676A1 (fr) 2007-05-18
WO2007055676A8 WO2007055676A8 (fr) 2007-08-16

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3676865A (en) * 1971-01-06 1972-07-11 Sperry Rand Corp High frequency signal memory and regenerator
US3680092A (en) * 1970-03-30 1972-07-25 Ford Motor Co Ranging system using phase detection
US4011562A (en) * 1975-03-21 1977-03-08 Cubic Industrial Corporation Single frequency radio ranging system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3680092A (en) * 1970-03-30 1972-07-25 Ford Motor Co Ranging system using phase detection
US3676865A (en) * 1971-01-06 1972-07-11 Sperry Rand Corp High frequency signal memory and regenerator
US4011562A (en) * 1975-03-21 1977-03-08 Cubic Industrial Corporation Single frequency radio ranging system

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