US 2001/0033607 A1 · Spread spectrum localizers

Abstract

A network of localizers determines relative locations in three-dimensional space to within 1 cm by cooperatively measuring propagation times of pseudorandom sequences of electromagnetic impulses. Ranging transmissions may include encoded digital information to increase accuracy. The propagation time is determined from a correlator circuit which provides an analog pseudo-autocorrelation function sampled at discrete time bins. The correlator has a number of integrators, each integrator providing a signal proportional to the time integral of the product of the expected pulse sequence delayed by one of the discrete time bins, and the non-delayed received antenna signal. With the impulses organized as doublets the sampled correlator output can vary considerably in shape depending on where the autocorrelation function peak falls in relation to the nearest bin. Using pattern recognition the time of arrival of the received signal can be determined to within a time much smaller than the separation between bins. Because operation of standard CMOS circuitry generates noise over a large frequency range, only low-noise circuitry operates during transmission and reception. To provide the time accuracy necessary for distancing, a high-frequency clock operates during inter-localizer communications. The high-frequency clock uses a phase-lock loop circuit to increase the clock rate and a programmable delay to provide still finer time graduations. A stage in the low-frequency clock uses low-noise circuitry during transmissions and receptions, and standard circuitry at other times.

Claims71

Dependent claims

A receiver for reception of nonsinusoidal spread spectrum radio communications comprising:

a spread spectrum radio antenna for receiving a nonsinusoidal communication signal impingent thereon during a reception time window;
a code-sequence generator to generate a digital pseudorandom impulse sequence resembling said communication signal;
a time-integrating correlator to calculate integrals of a product of said communication signal and delayed versions of said digital pseudorandom impulse sequence;
and
a processor for determining an arrival time of said communication signal by evaluating said integrals.

2 more elements

A timebase of a spread spectrum transceiver providing a first communication triggering signal having a beginning communication time, comprising:

a low-frequency clock signal source providing a low-frequency clock signal having a sequence of low-frequency clock pulses;
a low-noise phase-lock loop for generating a high-frequency clock signal from said low-frequency clock signal;
a stage-one low-noise counter maintaining a first count of clock impulses of said high-frequency clock signal;
a stage-one event register for storing a high-frequency portion of said beginning communication time;
a stage-one low-noise comparator for providing said first communication triggering signal when said first high-frequency portion of said beginning communication time is equal to said first count;
a stage-one low-noise switching means for activating said stage-one low-noise counter, and stage-one low-noise reception comparator when a stage-one enable signal is received;
and
a stage-two low-noise counter for maintaining a second count of said low-frequency clock pulses when active;
a stage-two standard-circuitry counter for maintaining a third count of said low-frequency clock pulses when active;
a stage-two event register for storing an intermediate-frequency portion of said beginning communication time;
a stage-two low-noise comparator for sending said stage-one enable signal to said stage-one low-noise switching means when said intermediate-frequency portion of said beginning communication time corresponds to said second count;
a stage-two switching means for activating said stage-two low-noise counter and said stage-two low-noise comparator, and inactivating said stage-two standard-circuitry counter, after a stage-two enable signal is received;
and
a stage-three standard-circuitry counter for maintaining a fourth count of terminal counts from said stage-two low-noise counter and said stage-two standard-circuitry counter;
a stage-three event register for storing a reception low-frequency portion of said beginning communication time;
and
a stage-three standard-circuitry comparator for sending said stage-two enable signal-to said stage-two reception switching means when said low-frequency portion of said beginning communication time corresponds to said fourth count.

14 more elements

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

(a) determining an approximate separation distance between said first and second transceivers;
(b) choosing a first transmission time for transmitting a first distancing communication from said first transceiver to said second transceiver;
(c) choosing a first delay time for said second transceiver to wait from a first central time of a first reception window before transmitting a second distancing communication back to said first transceiver, said first central time of said first reception window being equal to said first transmission time plus said approximate separation distance divided by the speed of light;
(d) transmitting said first distancing communication from said first transceiver to said second transceiver at said first transmission time;
(e) receiving said first distancing communication at said second transceiver during said first reception window;
(f) transmitting said second distancing communication from said second transceiver to said first transceiver after said first delay time;
(g) determining a first arrival time of said first distancing communication at said second transceiver subsequent to step (f);
(h) receiving said second distancing communication at said first transceiver during a second reception window, a second central time of said second reception window being equal to said second transmission time plus said approximate separation distance divided by the speed of light;
(i) determining a second arrival time of said second distancing communication at said first transceiver;
and
(j) calculating a first updated separation distance between said first and second transceivers based on said first and second arrival times.

8 more elements

A method for determining a separation distance and a ratio of clock rates of a first and a second localizer, said first localizer having a first clock and said second localizer having a second clock, comprising the steps of:

determining an approximate separation distance between said first and second transceivers;
choosing a first transmission time for transmitting a first distancing communication from said first transceiver to said second transceiver;
choosing a first delay time for said second transceiver to wait from a first reception window before transmitting a second distancing communication back to said first transceiver;
transmitting said first distancing communication from said first transceiver to said second transceiver at said first transmission time according to said first clock;
receiving said first distancing communication at said second transceiver during said first reception window;
transmitting said second distancing communication from said second transceiver to said first transceiver after said first delay time according to said second clock;
determining a first arrival time of said first distancing communication at said second transceiver according to said second clock;
receiving said second distancing communication at said first transceiver during a second reception window;
determining a second arrival time of said second distancing communication at said first transceiver according to said first clock;
choosing a third transmission time for transmitting a third distancing communication from said second transceiver to said first transceiver;
choosing a second delay time for said first transceiver to wait from a third reception window before transmitting a fourth distancing communication back to said second transceiver;
transmitting said third distancing communication from said second transceiver to said first transceiver at said third transmission time according to said second clock;
receiving said third distancing communication at said first transceiver during said third reception window;
transmitting said fourth distancing communication from said first transceiver to said second transceiver after said second delay time according to said first clock;
determining a third arrival time of said third distancing communication at said first transceiver according to said first clock;
receiving said fourth distancing communication at said second transceiver during a fourth reception window;
determining a fourth arrival time of said fourth distancing communication at said second transceiver according to said second clock;
calculating said separation distance and said ratio of clock rates from said first, second, third and fourth transmission times and said first, second, third and fourth arrival times.

15 more elements

A method for synchronization of communications of a first localizer and a second localizer, comprising the steps of:

said second localizer transmitting a series of beacon signals at beacon transmission times separated by a prearranged time interval;
said first localizer repeatedly attempting to receive one of said beacon signals during a reception window at a time equal to a previous time a failed attempt was made to receive one of said beacon signals plus said prearranged time interval plus a width of said reception window, until an initial success time when one of said beacon signals is successfully received;
said first localizer making an initial estimate of a distance of separation between said first and second localizers equal to half the speed of light multiplied by said width of said reception window;
said first localizer setting said current estimate of said distance equal to said initial estimate;
said first localizer setting said current success time equal to said initial success time;
said first localizer repeatedly transmitting a contact transmission at said current success time;
said first localizer repeatedly attempting to receive an acknowledgement communication from said second localizer at an acknowledgement reception time equal to said current success time plus an acknowledgement delay time minus said current estimate of said distance divided by the speed of light, until an acknowledgement acheived time when said first localizer receives said acknowledgement communication from said second localizer indicating that said distance is approximately equal to said current estimate of said distance;
said first localizer incrementing said current estimate of said distance by the speed of light multiplied by said width of said reception window following each of said repeatedly attempting to receive said acknowledgement communication steps;
said first localizer repeatedly incrementing said current success time by said prearranged time interval minus a prearranged turnaround delay time minus twice said current estimate of said distance divided by the speed of light following each of said repeatedly attempting to receive said acknowledgement communication steps;
said second localizer receiving one of said contact transmissions during a reception window said turnaround time prior to one of said beacon transmission times;
said second localizer determining an arrival time of said one of said contact transmissions;
and
said second localizer transmitting said acknowledgement communication said acknowledgement delay time after said one of said beacon transmission times.

10 more elements

An iterative method for determining a separation distance between a first transceiver and a second transceiver, comprising the steps of:

said first transceiver transmitting a first distancing communication at a first transmission time;
said second transceiver receiving said first distancing communication during a first reception window centered about said first transmission time plus a current estimate of said separation distance divided by the speed of light;
said second transceiver transmitting a second distancing communication after a first turnaround delay time from said first reception window;
said second transceiver determining a first arrival time of said first distancing communication subsequent to the previous step;
said first transceiver receiving said second distancing communication during a second reception window centered about said second transmission time plus said current estimate of said separation distance divided by the speed of light;
said first transceiver determining a second arrival time of said second distancing communication;
and
said first transceiver transmitting a third distancing communication at a third transmission time equal to said first transmission time plus a first prearranged waiting time;
said second transceiver receiving said third distancing communication during a third reception window centered approximately about said third transmission time plus said current estimate of said separation distance divided by the speed of light;
said second transceiver transmitting a fourth distancing communication at a second turnaround delay time from said third reception window, said fourth distancing communication having a first polarity if said first communication arrived in a first half of said first reception window, said fourth distancing communication having a second polarity if said first communication arrived in a second half of said first reception window;
said second transceiver determining a third arrival time of said third distancing communication subsequent to the previous step;
said first transceiver receiving said fourth distancing communication during a fourth reception window centered about said fourth transmission time plus said current estimate of said separation distance divided by the speed of light;
said first transceiver determining a fourth arrival time of said fourth distancing communication;
and
said first transceiver transmitting a fifth distancing communication at a fifth transmission time, said fifth transmission time being equal to said third transmission time plus a second prearranged waiting time minus an iteration increment if said fourth transmission had said first polarity, and said fifth transmission time being equal to said third transmission time plus said second prearranged waiting time minus said iteration increment if said fourth transmission had said second polarity;
said second transceiver receiving said fifth distancing communication during a fifth reception window centered approximately about said fifth transmission time plus said current estimate of said separation distance divided by the speed of light;
said second transceiver transmitting a sixth distancing communication at a third turnaround delay time from said sixth reception window, said sixth distancing communication having a first polarity if said third communication arrived in a first half of said third reception window, said sixth distancing communication having a second polarity if said third communication arrived in a second half of said third reception window;
said first transceiver receiving said sixth distancing communication during a sixth reception window, said sixth reception window being centered about said sixth transmission time plus said current estimate of said separation distance divided by the speed of light plus said iteration increment if said fourth distancing communication arrived in a second half of said fourth reception window, and said sixth reception window being centered about said sixth transmission time plus said current estimate of said separation distance divided by the speed of light minus said iteration increment if said fourth distancing communication arrived in a first half of said fourth reception window;
said first transceiver determining a sixth arrival time of said sixth distancing communication;
and
said first transceiver updating said current estimate of said separation distance based on said fifth transmission time, said sixth arrival time, and said third turnaround time.

18 more elements

Dependencies are inferred from the claim text.

Spread spectrum localizers

Life of this patent

Spread spectrum localizers

Life of this patent

Abstract

Claims71