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

• US 6,674,396 B2
• Filed: 09/21/2001
• Issued: 01/06/2004
• Est. Priority Date: 05/26/1998
• Status: Expired due to Term

• Current Assignee: Humatics Corporation
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Fullerton, Larry W., Richards, James L.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US09/960,278
• Publication Number:
  US 20020118132A1
• Time in Patent Office: 837 Days
• Field of Search: 342/118, 342/125, 342/175, 342/194, 342/195, 342/134, 342/135, 342/27, 342/28, 342/29-32, 342/450, 342/458, 342/463-465, 356/4.01, 356/5.01, 356/5.05, 356/5.08, 356/5.09
• 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 inphase (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 distance measurement using a radio system having first and second radio transceivers, said first radio transceiver having a transmit time base and a receive time base and said second radio transceiver having a further time base, comprising the steps of:

transmitting a first pulse train using the transmit time base from the first radio transceiver, the first pulse train having N pulses, where N is an integer number;

receiving the first pulse train at the second radio transceiver and synchronizing its time base with the first pulse train;

transmitting a second pulse train from the second radio transceiver, the second pulse train having N pulses;

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

determining a time delay between the transmit and receive time bases, the time delay indicating the total time of flight of the first and second pulse trains;

determining a coarse distance between the first and second radio transceivers from the time delay, the coarse range distance representative of the distance between the first and second radio transceivers in coarse resolution, by generating a transmit timing signal using the transmit time base;

receiving the transmit timing signal at a first latch and outputting a first timing (TX(I)) signal;

receiving the TX(I) signal at a first code position counter and outputting a first count value;

generating a receive timing signal using the receive time base;

dividing the receive timing signal by K at a counter, K being an integer number, and outputting a second timing (RX) signal;

receiving the RX signal at a second code position counter and outputting a second count value;

receiving the first count value at the data input port of a second latch and the second count value at the enable port of the latch, and outputting a code delay value, and determining a coarse distance value from the code delay value and a base count value, the base count value being representative of the number of pulses in the first or second pulse train;

generating an in-phase (I) and a quadrature (Q) signal from the time delay;

determining a fine distance between the first and second transceivers from the I and 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 generation of each of said transmit timing signal and receive timing signal comprises the steps of:

generating a base clock signal having a first frequency from a voltage controlled oscillator;

dividing the base clock signal using a counter to a second frequency, the second frequency being lower than the first frequency;

generating a reference signal having the second frequency from a reference signal generator;

determining a phase difference between the divided base clock signal and the reference signal at a phase detector;

receiving the phase difference at a phase locked loop (PLL) filter and outputting an error signal; and

receiving the error signal at the voltage controlled oscillator to thereby adjust the voltage controlled oscillator, and

wherein said divided base clock signal is utilized as the receive or transmit timing signal.

3. The method of claim 1, wherein said step of determining the fine distance comprises:

receiving the transmit timing signal at an inverter, inverting the transmit timing signal, and outputting an inverted transmit timing signal;

receiving the inverted transmit timing signal at a third latch and outputting a TX(Q) signal, the TX(Q) signal having a duty cycle proportional to the phase difference between the transmit timing signal and the TX(I) signal;

receiving the TX(I) signal and the RX signal at a first gate, comparing the phase of the TX(I) signal to the phase of the RX signal, and outputting the I signal, wherein the I signal has a duty cycle proportional to the phase difference between the TX(I) signal and the RX signal; and

receiving the TX(Q) signal and the RX signal at a second gate, comparing the phase of the TX(Q) signal to the phase of the RX signal, and outputting the Q signal, wherein the Q signal has a duty cycle proportional to the phase difference between the TX(Q) signal and the RX signal.

4. The method of claim 3, wherein said step of determining the fine distance further comprises:

receiving the I signal at a first low pass filter, removing the ac component from the I signal, and outputting an I_dc signal, the I_dc signal having an average dc value of the I signal;

receiving the Q signal at a second low pass filter, removing the ac component from the Q signal, and outputting a Q_dc signal having an average dc value of the Q signal; and

determining the fine distance from the I_dc and Q_dc signals.

5. The method of claim 4, wherein said step of determining the fine distance from the I_dc and Q_dc signals comprises:

receiving the I_dc signal at a first analog to digital (A/D) converter and outputting a first digital output having a value between a maximum value and a minimum value;

receiving the Q_dc signal at a second analog to digital (A/D) converter and outputting a second digital output having a value between the maximum value and the minimum value; and

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

6. The method of claim 5, wherein said step of determining the fine distance from the first and second digital outputs comprises:

generating an I triangular waveform from the first digital output; and

generating a Q triangular waveform from the second digital output.

7. The method of claim 6, further comprising the steps of:

dividing the I and Q triangular waveforms into four quadrants;

normalizing the I and Q triangular waveforms by a common mid point for the I and Q triangular waveforms; and

resolving the ambiguities of the first and second digital outputs from the I and Q triangular waveforms.

8. The method of claim 7, wherein said step of resolving the ambiguities of the first and second digital values comprises:

determining a quadrant location of the range from the I and Q triangular waveforms; and

determining the actual distance of the second transceiver from the I triangular waveform.

9. A system for distance measurement using a radio system, comprising:

a first radio transceiver having a first transmit time base for generating a first transmit timing signal and a first receive time base used for generating a first receive timing signal;

a second radio transceiver having a second transmit time base for generating a second transmit timing signal and a second receive time base for generating a second receive timing signal;

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

a coarse distance measurement circuit for measuring the coarse distance between the first and second radio transceivers from the time delay, the coarse range distance being representative of the distance between the first and second radio transceivers in coarse resolution, comprising a first latch for receiving the transmit timing signal and outputting a first timing signal, TX(I);

a first code position counter for receiving the TX(I) signal and outputting a first count value;

a counter for dividing the receive timing signal by K, K being an integer, and outputting a second timing RX signal;

a second code position counter for receiving the RX signal and outputting a second count value; and

a second latch for receiving the first count value and the second count value and outputting a code delay value, wherein the coarse distance is determined from the code delay value and a base count value, the base count value being representative of the number of pulses in the first or second pulse train; and

a fine distance measurement circuit for generating an I signal and a Q signal using the time delay and for determining a fine distance between the first and second radio transceivers using the I and Q signals, the fine distance indicating the distance between the first and second transceivers in fine resolution, and

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

10. The system of claim 9, wherein the fine distance measurement circuit comprises:

an inverter for receiving and inverting the transmit timing signal and outputting an inverted transmit timing signal;

a third latch for receiving the inverted transmit timing signal and outputting a TX(Q) signal, the TX(Q) signal having a duty cycle proportional to the phase difference between said transmit timing signal and the TX(I) signal;

a first gate for receiving the TX(I) signal and the RX signal, comparing the phase of the TX(I) signal to the phase of the RX signal, and outputting the I signal, wherein the I signal has a duty cycle proportional to the phase difference between the TX(I) signal and the RX signal; and

a second gate for receiving the TX(Q) signal and the RX signal, comparing the phase of the TX(Q) signal to the phase of the RX signal, and outputting the Q signal, wherein the Q signal has a duty cycle proportional to the phase difference between the TX(Q) signal and the RX signal.

11. The system of claim 10, further comprising:

a first low pass filter for receiving the I signal, removing the ac component from the I signal, and outputting an I_dc signal, the I_dc signal having an average dc value of the I signal;

a second low pass filter for receiving the Q signal, removing the ac component from the Q signal, and outputting a Q_dc signal having an average dc value of the Q signal;

a first analog to digital (A/D) converter for receiving the I_dc signal and outputting an I₁ signal; and

a second A/D converter for receiving the Q_dc signal and outputting a Q₁ signal, and wherein the fine distance is determined from the I₁ and Q₁ signals.

12. A transceiver for transmitting ultra wideband signals comprising:

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

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

wherein a final distance measurement between the transceiver and the second transceiver is determined by using the first distance measurement in conjunction with the second distance measurement.

13. The transceiver of claim 12, further comprising:

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

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

a time delay signal generator responsive to the transmit timing signal and to the receive timing signal and outputting a time delay signal; and

wherein the first distance measurement is determined using the time delay signal.

14. The transceiver of claim 13, further comprising:

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

a means for generating a second timing signal, RX, using the receive timing signal; and

a means for generating a third timing signal, TX(Q), using at least one of the transmit timing signal and TX(I).

15. The transceiver of claim 14, further comprising:

an in-phase (I) signal generator responsive to the TX(I) and RX signals;

a quadrature (Q) signal generator responsive to the TX(Q) and RX signals; and

a means for determining the second distance measurement using the in-phase (I) signal and the quadrature (Q) signal.

16. The transceiver of claim 15, wherein the means for determining the second distance measurement using the in-phase (I) signal and the quadrature (Q) signal comprises:

a first converter for converting the I signal into a I_dc signal having an average dc value of the I signal; and

a second converter for converting the Q signal into a Q_dc signal having an average dc value of the Q signal; and

wherein the second distance measurement is determined using the I_dc and Q_dc signals.

17. The transceiver of claim 16, wherein the first converter comprises:

a low pass filter for receiving the I signal, removing the ac component from the I signal, and outputting said I_dc signal.

18. The transceiver of claim 16, wherein the second converter comprises:

a low pass filter for receiving the Q signal, removing the ac component from the Q signal, and outputting said Q_dc signal.

19. The transceiver of claim 16, wherein the means for determining the second distance measurement comprises:

a first A/D converter responsive to the I_dc signal and outputting a first digital output (I₁) signal; and

a second A/D converter responsive to the Q_dc signal and outputting a second digital output (Q₁) signal; and

wherein the second distance measurement is determined using the I₁ and Q₁ signals.

20. The transceiver of claim 19, further comprising:

a processor for evaluating an I_z variable from the I₁ signal and a Q_z variable from the Q₁ signal, wherein the I_z and Q_z variables are evaluated as a function of distance.

21. A transceiver for transmitting ultra wideband signals comprising:

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 comprising a transmit time base generator to generate a transmit timing signal;

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

a time delay signal generator responsive to the transmit timing signal and to the receive timing signal and outputting a time delay signal wherein the coarse distance is determined using the time delay signal; and

a fine distance measurement circuit to measure a fine distance between the transceiver and the second transceiver, the fine distance representing the distance between the transceiver and the second transceiver in fine resolution comprising a means for generating a first timing signal, TX(I), using the transmit timing signal, a means for generating a second timing signal, RX, using the receive timing signal and a means for generating a third timing signal, TX(Q), using at least one of the transmit timing signal and TX(I); and

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

22. The transceiver of claim 21, further comprising:

an in-phase (I) signal generator responsive to the TX(I) and RX signals;

a quadrature (Q) signal generator responsive to the TX(Q) and RX signals; and

a means for determining the fine distance using the in-phase (I) signal and the quadrature (Q) signal.

23. The transceiver of claim 22, wherein the means for determining the fine distance using the in-phase (I) signal and the quadrature (Q) signal comprises:

a first converter for converting the I signal into a I_dc signal having an average dc value of the I signal; and

a second converter for converting the Q signal into a Q_dc signal having an average dc value of the Q signal; and

wherein the fine distance is determined using the I_dc and Q_dc signals.

24. The transceiver of claim 23, wherein the first converter comprises:

a low pass filter for receiving the I signal, removing the ac component from the I signal, and outputting said I_dc signal.

25. The transceiver of claim 24, wherein the second converter comprises:

a low pass filter for receiving the Q signal, removing the ac component from the Q signal, and outputting said Q_dc signal.

26. The transceiver of claim 25, wherein the means for determining the fine distance comprises:

a first A/D converter responsive to the II_dc signal and outputting a first digital output (I₁) signal; and

a second A/D converter responsive to the Q_dc signal and outputting a second digital output (Q₁) signal; and

wherein the fine distance is determined using the I₁ and Q₁ signals.

27. The transceiver of claim 26, further comprising:

a processor for evaluating an I_z variable from the I₁ signal and a Q_z variable from the Q₁ signal, wherein the I_z and Q_z variables are evaluated as a function of distance.