Spread spectrum localizers
First Claim
1. A receiver for reception of nonsinusoidal spread spectrum radio communications from a nonsinusoidal spread spectrum radio transmitter comprising:
- a spread spectrum radio antenna having an ultra-wide bandwidth for receiving a nonsinusoidal communication signal impingent thereon during a reception time window;
a code-sequence generator to generate a digital pseudorandom sequence resembling a portion of said nonsinusoidal communication signal;
a time-integrating correlator to calculate values of integrals of a product of said communication signal and delayed versions of said digital pseudorandom sequences, said communication signal being an analog waveform derived from a digital signal generated at said nonsinusoidal spread spectrum radio transmitter; and
a processor for determining an arrival time of said communication signal from said values of said integrals.
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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.
160 Citations
16 Claims
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1. A receiver for reception of nonsinusoidal spread spectrum radio communications from a nonsinusoidal spread spectrum radio transmitter comprising:
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a spread spectrum radio antenna having an ultra-wide bandwidth for receiving a nonsinusoidal communication signal impingent thereon during a reception time window; a code-sequence generator to generate a digital pseudorandom sequence resembling a portion of said nonsinusoidal communication signal; a time-integrating correlator to calculate values of integrals of a product of said communication signal and delayed versions of said digital pseudorandom sequences, said communication signal being an analog waveform derived from a digital signal generated at said nonsinusoidal spread spectrum radio transmitter; and a processor for determining an arrival time of said communication signal from said values of said integrals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A receiver for reception of nonsinusoidal spread spectrum radio communications comprising:
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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 sequence resembling a portion of said communication signal; a time-integrating correlator to calculate values of integrals of a product of said communication signal and delayed versions of said digital pseudorandom squence, where said nonsinusoidal communication signal, denoted as Φ
e (t), has the form
space="preserve" listing-type="equation">Φ
.sub.e (t)=σ
t/δ
t!*γ
.sub.e (t mod δ
t),where square brackets indicates that an argument inside said square brackets is to be taken as a greatest integer less than or equal to said argument, γ
e is a received chip waveform, δ
t is a chip duration, and σ
is a pseudorandom sequence, and said digital pseudorandom sequence, denoted as Φ
i (t), has the form
space="preserve" listing-type="equation">Φ
.sub.i (t)=σ
t/δ
t!*γ
.sub.i (t mod δ
t),where γ
i is a digital chip waveform, and said received chip waveform and said digital chip waveform are similar enough that ##EQU20## integrating from 0 to δ
t, is on the order of unity; and
a processor for determining an arrival time of said communication signal from said values of said integrals. - View Dependent Claims (12)
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13. A receiver for reception of nonsinusoidal spread spectrum radio communications comprising:
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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 sequence resembling a portion of said communication signal, said code-sequence generator having a first low-coupled-noise circuit in use during said reception time window; a time integrating correlator to calculate values of integrals of a product of said communication signal and delayed versions of said digital pseudorandom sequence, said time-integrating correlator having a second low-coupled-noise circuit in use during said reception time window; a processor for determining an arrival time of said communication signal from said values of said integrals; a low-frequency clock which provides a low-frequency clock signal, said low-frequency clock having a first standard-logic circuit which is inactive during said reception time window, a third low-coupled-noise circuit which is active during said reception time window, and a means for inactivating and activating said first standard-logic circuit and said third low-coupled-noise circuit; and a high-frequency clock which processes said low-frequency clock signal from said third low-coupled-noise circuit to provide a high-frequency clock signal supplied to said code-sequence generator and said time-integrating correlator, said high-frequency clock having a fourth low-coupled-noise circuit in use during said reception time window. - View Dependent Claims (14)
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15. A receiver for reception of nonsinusoidal spread spectrum radio communications comprising:
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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 sequence resembling a portion of said communication signal, said code-sequence generator having a first low-coupled-noise circuit in use during said reception time window; a time-integrating correlator to calculate values of integrals of a product of said communication signal and delayed versions of said digital pseudorandom sequence, said time-integrating correlator having a second low-coupled-noise circuit in use during said reception time window; a processor for determining an arrival time of said communication signal from said values of said integrals; a high-frequency clock which provides a high-frequency clock signal supplied to said code-sequence generator and said time-integrating correlator, said high-frequency clock having a third low-coupled-noise circuit in use during said reception time window; and a low-frequency clock which derives a low-frequency clock signal from said high-frequency clock signal, and provides said low-frequency clock signal to said processor, said low-frequency clock having a first standard-logic circuit which is inactive during said reception time window, and a means for inactivating said first standard-logic circuit during said reception time window.
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16. A receiver for reception of nonsinusoidal spread spectrum radio communications comprising:
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a spread spectrum radio antenna for receiving an ultra-wide bandwidth nonsinusoidal communication signal impingent thereon during a reception time window; and a monolithic integrated signal processor for processing said nonsinusoidal communication signal impingent on said spread spectrum radio antenna, said monolithic integrated signal processor including a code-sequence generator to generate a digital pseudorandom sequence resembling said communication signal; a time-integrating correlator to calculate values of integrals of a product of said communication signal and delayed versions of said digital pseudorandom sequence; and means for determining an arrival time of said communication signal from said values of said integrals.
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Specification