System and method for distance measurement by inphase and quadrature signals in a radio system

• US 6,295,019 B1
• Filed: 01/14/2000
• Issued: 09/25/2001
• Est. Priority Date: 05/26/1998
• Status: Expired due to Term

• Current Assignee: Humatics Corporation
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Richards, James L., Fullerton, Larry W., Meigs, David C., Cowie, Ivan A., Stanley, Randall S.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US09/482,681
• Time in Patent Office: 620 Days
• Field of Search: 342/118, 342/120, 342/123, 342/125, 342/127, 342/134, 342/135, 342/145, 342/194, 342/195, 342/450, 342/451, 342/453, 342/458, 342/463, 342/464, 342/465, 342/29, 342/30, 342/36, 342/37, 342/42, 342/43, 342/46, 342/51, 342/86, 342/98, 342/103, 342/456, 342/357-1-3
• US Class Current: 342/125
• CPC Class Codes: G01S 13/08 Systems for measuring distance only indirect measurement G01S13/46
• CPC Class Codes: G01S 13/76 wherein pulse-type signals are transmitted
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/913 for landing purposes

Abstract

A system and a method for distance measurement utilizes a radio system. The distance is measured by determining the time it takes a pulse train to travel from a first radio transceiver to a second radio transceiver and then from the second radio transceiver back to the first radio transceiver. The actual measurement is a two step process. In the first step, the distance is measured in coarse resolution, and in the second step, the distance is measured in fine resolution. A first pulse train is transmitted using a transmit time base from the first radio transceiver. The first pulse train is received at a second radio transceiver. The second radio transceiver synchronizes its time base with the first pulse train before transmitting a second pulse train back to the first radio transceiver, which then synchronizes a receive time base with the second pulse train. The time delay between the transmit time base and the receive time base can then be determined. The time delay indicates the total time of flight of the first and second pulse trains. The time delay comprises coarse and fine distance attributes. The coarse distance between the first and second radio transceivers is determined. The coarse distance represents the distance between the first and second radio transceivers in coarse resolution. An in phase (I) signal and a quadrature (Q) signal are produced from the time delay to determine the fine distance attribute. The fine distance indicates the distance between the first and second transceivers in fine resolution. The distance between the first and second radio transceivers is then determined from the coarse distance and the fine distance attributes.

Claims

1. A method for measuring the distance between a first transceiver and a second transceiver, comprising the steps of:

determining a time delay that represents the total time taken for a first pulse train signal to travel from the first transceiver to the second transceiver and a second pulse train signal to travel from the second transceiver back to the first transceiver;

determining a coarse distance between the first and second transceivers based on the time delay, the coarse distance representative of the distance between the first and second transceivers in coarse resolution;

generating an in phase (I) and quadraphase (Q) signal from the time delay;

determining a fine distance between the first and second transceivers from the in phase (I) and quadraphase (Q) signals, the fine distance indicating the distance between the first and second transceivers in fine resolution; and

determining the distance between the first and second transceivers from the coarse distance and the fine distance.

2. The method of claim 1, wherein the first pulse train includes N pulses, and wherein the step of determining the time delay comprises the steps of:

determining a pulse count value by counting a number of pulses that occur between a time that the first transceiver begins to transmit the first pulse train signal to the second transceiver and a time that the first transceiver begins to receive the second pulse train signal from the second transceiver; and

determining the time delay by subtracting N pulses from the pulse count value.

3. The method of claim 1, wherein the first transceiver has a transmit time base and a receive time base, and wherein the step of determining the time delay comprises the steps of:

transmitting the first pulse train signal from the first transceiver using the transmit time base;

receiving the second pulse train signal at the first transceiver and synchronizing the receive time base with the second pulse train signal;

determining the time delay by determining a delay between the transmit time base and the receive time base.

4. The method of claim 3, wherein the step of generating the in phase (I) and quadraphase (Q) signals comprises the steps of:

generating a transmit timing signal using the transmit time base;

generating a first timing (TX(I)) signal using the transmit timing signal;

generating a receive timing signal using the receive time base;

generating a second timing (RX) signal using the receive timing signal;

generating a TX(Q) signal by comparing a phase of the transmit timing signal to a phase of the TX(I) signal, wherein a duty cycle of the TX(Q) signal is proportion a difference between the phase of the transmit timing signal and the phase of the TX(I) signal;

generating the in phase (I) signal by comparing the phase of the TX(I) signal and a phase of the RX signal, wherein a duty cycle of the in phase (I) signal is proportion to a different between the TX(I) signal and the RX signal; and

generating the quadraphase (Q) signal by comparing the phase of the TX(Q) signal and the RX signal, wherein a duty cycle of the quadraphase (Q) signal is proportional to a difference between the phase of the TX(Q) signal and the RX signal.

5. The method of claim 4, wherein the step of determining the fine distance comprises the steps of:

converting the inphase (I) signal into a direct current signal I_dc;

converting the quadraphase (Q) signal into a direct current signal Q_dc;

converting the I_dc signal to a first digital output having a value between a maximum and minimum value;

converting the Q_dc signal to a second digital output having a value between the maximum and minimum value; and

determining the fine distance from the first and second digital outputs.

6. The method of claim 5, wherein the step of determining the fine distance further comprising the steps of:

determining the fine distance based on the first and second digital outputs and I and Q triangular waveforms, wherein

the I triangular waveform relates to a plurality of I_dc signal readings taken as the distance between the first and second transceivers was varied, and

the Q triangular waveform relates to a plurality of Q_dc signal readings taken as the distance between the first and second transceivers was varied.

7. The method of claim 6, wherein the step of determining the distance between the first and second transceivers from the coarse distance and the fine distance comprises:

adjusting the coarse distance, if necessary, to produce an adjusted coarse distance; and

determining the distance between the first and second transceivers by adding the fine distance to the adjusted coarse distance.

8. A transceiver comprising:

a transmit time base generator for generating a transmit timing signal;

a receive time base generator for generating a receive timing signal;

a time delay circuit for determining a time delay between the transmit and receive time base generators;

a coarse distance measurement circuit for measuring a coarse distance between the transceiver and a second transceiver, the coarse distance representing a distance between the transceiver and the second transceiver in coarse resolution; and

a fine distance measurement circuit for generating an I signal and a Q signal from the time delay and for determining a fine distance between the transceiver and the second transceiver, the fine distance measurement indicating the distance between the transceiver and the second transceiver in fine resolution,

wherein the distance between the transceiver and the second transceiver is determined from the coarse distance and the fine distance.

9. The transceiver of claim 8, further comprising:

a means for transmitting a first pulse train signal to the second transceiver; and

a means for receiving a second pulse train signal from the second transceiver, wherein the receive time base is synchronized with the second pulse train.

10. The transceiver of claim 9, wherein the first pulse train signal includes N pulses, and wherein the time delay circuit comprises:

a counter for counting a number of pulses that occur between a time that the first transceiver begins to transmit the first pulse train signal to the second transceiver and a time that the first transceiver begins to receive the second pulse train signal from the second transceiver; and

a subtracter for determining the time delay by subtracting N pulses from the counted number of pulses.

11. The transceiver of claim 8, further comprising:

a means for generating a first timing (TX(I)) signal using the transmit timing signal;

a means for generating a second timing (RX) signal using the receive timing signal;

a first comparator for generating a TX(Q) signal by comparing a phase of the transmit timing signal to a phase of the TX(I) signal, wherein a duty cycle of the TX(Q) signal is proportion a difference between the phase of the transmit timing signal and the phase of the TX(I) signal;

a second comparitor for generating the inphase (I) signal by comparing the phase of the TX(I) signal and a phase of the RX signal, wherein a duty cycle of the inphase (I) signal is proportion to a different between the first timing signal TX(I) and the second timing signal RX; and

a third comparitor for generating the quadraphase (Q) signal by comparing the phase of the TX(Q) signal and the RX signal, wherein a duty cycle of the quadraphase (Q) signal is proportional to a difference between the phase of the TX(Q) signal and the RX signal.

12. The transceiver of claim 11, wherein the fine distance measurement circuit comprises:

a first filter for converting the inphase (I) signal into a direct current signal I_dc;

a second filter for converting the quadraphase (Q) signal into a direct current signal Q_dc;

a first analog to digital converter for converting the I_dc signal to a first digital output having a value between a maximum and minimum value;

a second analog to digital converter converting the Q_dc signal to a second digital output having a value between the maximum and minimum value; and

means for determining the fine distance from the first and second digital outputs.

13. The transceiver of claim 12, wherein the means for determining the line distance comprises:

means for determining the fine distance based on the first and second digital outputs and I and Q triangular waveforms, wherein

the I triangular waveform relates to a plurality of I_dc signal readings taken as the distance between the first and second transceivers varies, and

the Q triangular waveform relates to a plurality of Q_dc signal readings taken as the distance between the first and second transceivers varies.

14. The transceiver of claim 13, further comprising:

means for adjusting the coarse distance, if necessary, to produce an adjusted coarse distance; and

means for adding the fine distance to the adjusted coarse distance, wherein the sum is the distance between the transceiver and second transceiver.

15. A method for measuring the distance between a first transceiver and a second transceiver, comprising the steps of:

generating a transmit timing signal using a transmit time base of the first transceiver;

transmitting a first pulse train signal, using the transmit time base, from the first transceiver to the second transceiver;

receiving the first pulse train signal at the second transceiver and synchronizing a second transceiver time base with the first pulse train signal;

transmitting a second pulse train, using the second transceiver time base that is synchronized with the first pulse train signal, from the second transceiver to the first transceiver;

receiving the second pulse train signal at the first transceiver and synchronizing a receive time base of the first transceiver with the second pulse train signal;

generating a receive timing signal using the receive time base that is synchronized with the second pulse train signal;

determining a time delay between the transmit time base and the receive time base;

determining a coarse distance measurement from the time delay.

16. The method of claim 15, further comprising the steps of:

determining a fine distance between the first transceiver and the second transceiver based on the transmit timing signal and the receive timing signal; and

determine the distance between the first and second transceivers from the coarse distance and the fine distance.

17. The method of claim 16, wherein the step of determining the fine distance comprises:

generating a first timing (TX(I)) signal using the transmit timing signal;

generating a second timing (RX) signal using the receive timing signal;

generating a TX(Q) signal by comparing a phase of the transmit timing signal to a phase of the TX(I) signal, wherein a duty cycle of the TX(Q) signal is proportion a difference between the phase of the transmit timing signal and the phase of the TX(I) signal;

generating an inphase (I) signal by comparing the phase of the TX(I) signal and a phase of the RX signal, wherein a duty cycle of the inphase (I) signal is proportion to a different between the TX(I) signal and the RX signal;

generating a quadraphase (Q) signal by comparing the phase of the TX(Q) signal and the RX signal, wherein a duty cycle of the quadraphase (Q) signal is proportional to a difference between the phase of the TX(Q) signal and the RX signal; and

determining the fine distance between the first transceiver and the second transceiver from the inphase (I) signal and the quadraphase (Q) signal.

18. A transceiver comprising:

a transmit time base generator that generates a transmit timing signal;

a receive time base generator that generates a receive timing signal;

a time delay circuit that determines a delay between the transmit and receive time bases;

a coarse distance measurement circuit that measures a coarse distance between the transceiver and a second transceiver based on the delay, the coarse distance representing the distance between the transceiver and the second transceiver in coarse resolution; and

a fine distance measurement circuit that determines a fine distance between the first transceiver and the second transceiver based on the transmit timing signal and the receive timing signal,

wherein the distance between the transceiver and the second transceiver is determined from the coarse distance and the fine distance.

19. The transceiver of claim 18, wherein the fine distance measurement circuit comprises:

a circuit that generates a first timing (TX(I)) signal using the transmit timing signal;

a circuit that generates a second timing (RX) signal using the receive timing signal;

a circuit that generates a TX(Q) signal by comparing a phase of the transmit timing signal to a phase of the TX(I) signal, wherein a duty cycle of the TX(Q) signal is proportion a difference between the phase of the transmit timing signal and the phase of the TX(I) signal;

a circuit that generates an inphase (I) signal by comparing the phase of the TX(I) signal and a phase of the RX signal, wherein a duty cycle of the inphase (I) signal is proportion to a different between the TX(I) signal and the RX signal;

a circuit that generates a quadraphase (Q) signal by comparing the phase of the TX(Q) signal and the RX signal, wherein a duty cycle of the quadraphase (Q) signal is proportional to a difference between the phase of the TX(Q) signal and the RX signal; and

a circuit that determines the fine distance between the first transceiver and the second transceiver from the inphase (I) signal and the quadraphase (Q) signal.

20. The transceiver of claim 18, wherein the fine distance measurement circuit comprises:

means for generating a first timing (TX(I)) signal using the transmit timing signal;

means for generating a second timing (RX) signal using the receive timing signal;

means for generating a TX(Q) signal by comparing a phase of the transmit timing signal to a phase of the TX(I) signal, wherein a duty cycle of the TX(Q) signal is proportion a difference between the phase of the transmit timing signal and the phase of the TX(I) signal;

means for generating an inphase (I) signal by comparing the phase of the TX(I) signal and a phase of the RX signal, wherein a duty cycle of the inphase (I) signal is proportion to a different between the TX(I) signal and the RX signal;

means for generating a quadraphase (Q) signal by comparing the phase of the TX(Q) signal and the RX signal, wherein a duty cycle of the quadraphase (Q) signal is proportional to a difference between the phase of the TX(Q) signal and the RX signal; and

means for generating the fine distance between the first transceiver and the second transceiver from the inphase (I) signal and the quadraphase (Q) signal.

21. A method for measuring the distance between a first impulse radio transceiver and a second impulse radio transceiver that transmit ultra wide band signals, comprising the steps of:

determining a coarse distance measurement between the first impulse radio transceiver and the second impulse radio transceiver and a fine distance measurement between the first impulse radio transceiver and the second impulse radio transceiver; and

determine the distance between the first and second impulse radio transceivers from the coarse distance measurement and the fine distance measurement.

22. The method of claim 21, further comprising the steps of:

generating a transmit timing signal using a transmit time base of the first impulse radio transceiver;

transmitting a first ultra wide band (UWB) signal, using the transmit time base, from the first impulse radio transceiver to the second impulse radio transceiver;

receiving the first UWB signal at the second impulse radio transceiver and synchronizing a second transceiver time base with the first UWB signal;

transmitting a second UWB signal, using the second transceiver time base that is synchronized with the first UWB signal, from the second impulse radio transceiver to the first impulse radio transceiver; and

receiving the second UWB signal at the first impulse radio transceiver and synchronizing a receive time base of the first impulse radio transceiver with the second UWB signal;

generating a receive timing signal using the receive time base that is synchronized with the second UWB signal,

wherein said step of determining the coarse distance measurement and the fine distance measurement comprises the steps of;

determining the coarse distance measurement based on a time delay between the transmit time base and the receive time base; and

determining the fine distance measurement based on the transmit timing signal and the receive timing signal.

23. The method of claim 22, wherein the step of determining the fine distance comprises:

generating a first timing (TX(I)) signal using the transmit timing signal;

generating a second timing (RX) signal using the receive timing signal;

generating a TX(Q) signal by comparing a phase of the transmit timing signal to a phase of the TX(I) signal, wherein a duty cycle of the TX(Q) signal is proportion a difference between the phase of the transmit timing signal and the phase of the TX(I) signal;

generating an inphase (I) signal by comparing the phase of the TX(I) signal and a phase of the RX signal, wherein a duty cycle of the inphase (I) signal is proportion to a different between the TX(I) signal and the RX signal;

generating a quadraphase (Q) signal by comparing the phase of the TX(Q) signal and the RX signal, wherein a duty cycle of the quadraphase (Q) signal is proportional to a difference between the phase of the TX(Q) signal and the RX signal; and

determining the fine distance between the first transceiver and the second transceiver from the inphase (I) signal and the quadraphase (Q) signal.

24. A transceiver comprising:

a transmit time base to generate for generating a transmit timing signal;

a receive time base generator to generate a receive timing signal;

a time delay circuit to determine a time delay between the transmit and receive time base generators;

a coarse distance measurement circuit to measure a coarse distance between the transceiver and a second transceiver, the coarse distance representing a distance between the transceiver and the second transceiver in coarse resolution; and

a fine distance measurement circuit to generate an I signal and a Q signal from the time delay and to determining a fine distance between the transceiver and the second transceiver based on the I signal and Q signal, the fine distance measurement indicating the distance between the transceiver and the second transceiver in fine resolution,

wherein the distance between the transceiver and the second transceiver is determined from the coarse distance and the fine distance.