Vector delay lock loop processing of radiolocation transmitter signals

• US 5,398,034 A
• Filed: 03/29/1993
• Issued: 03/14/1995
• Est. Priority Date: 03/29/1993
• Status: Expired due to Term

• Current Assignee: Exelis Incorporated (L3Harris Technologies, Inc.)
• Original Assignee: Stanford Telecommunications, Inc. (Nokia Corporation)
• Inventors: Spilker, James J. Jr.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US08/038,931
• Time in Patent Office: 715 Days
• Field of Search: 342/357, 455/12.1, 455/13.2
• US Class Current: 342/357.27
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence

Abstract

A position, time location receiving system deriving its output position estimates from received inputs from a distributed array of pseudonoise multiplexed transmitter channels at determinable spatial positions. The receiving system has a plurality of delay lock loops, one for each transmitter channel. Control signals for the delay lock loops of each transmitter channel are derived from a current estimated location vector (x, y, z) and time.

Claims

1. A location and time estimation receiver which estimates its own location from signals received simultaneously from a multiplicity of code-modulated remote transmitters whose instantaneous locations can be determined, comprising:

signal receiving and conditioning means including an antenna and frequency conversion circuitry,

a plurality of delay controllable pseudo-noise oscillators,

a plurality of signal correlators, each signal correlator receiving an input from said signal receiving and conditioning means and a second input from one of said delay-controllable pseudo-noise oscillator,

a plurality of signal filters and demodulators, each deriving its input from one of said signal correlators, each producing an output representing distance and velocity measures of one transmitter to the receiver, respectively,

computational circuits that convert said distance and velocity measures, together with information on transmitter locations, into a single estimate of the instantaneous location of the receiver, using geometric techniques to derive estimates and averaging to produce a single estimate from redundant inputs,

an output filter whose response is representative of the process that constraints the relative motion of receiver and transmitter, and

a feedback circuit for determining the time rate of change of the receiver position as a first vector, and combines said first vector with further vectors representing the known direction and velocity of each said code modulated remote transmitter, and transmits the results as a plurality of scalar delay control signals fed to said delay-controllable pseudorandom noise oscillators to improve the accuracy, threshold performance and stability of the position estimates output by the receiver in the presence of redundant received signal data, data, additive receiver noise, and jamming or nonintentional interference.

2. A location and time estimation receiver as defined in claim 1 wherein the signal correlators produce separate outputs representing respectively the range and the relative velocity between each remote transmitter and said receiver.

3. A location and time estimation receiver as defined in claim 1 wherein there are more than four each of correlators, filters, demodulators, and said feedback-computational circuits.

4. A location and time estimation receiver as defined in claim 1 wherein the computational circuit has a loop gain and the loop gain of said feedback computational circuit is continually varied using signals derived from said series of position estimates.

5. A pseudonoise code multiplexed location-estimation receiver adapted for simultaneous reception of signals from multiple transmitters of determinable location and motion and transmitting a repeating code sequence, comprising

signal receiving and conditioning circuits,

a plurality of delay controllable reference pseudo-noise signal oscillators, and

a like plurality of signal correlators driven by said plurality of delay-controllable reference pseudo-noise signal oscillators, respectively, each signal correlator producing the repeating code sequence employed in a particular transmitter,

means for combining said signal correlator signals to compute an estimated location of the receiver in three dimensions, along with a timing estimate, and

a feedback circuit for converting said location output estimate into phase-delay signals for each reference pseudo-noise oscillator proportional to the direction, range and relative velocity of the transmitter whose signals it is processing.

6. A pseudonoise code multiplexed location-estimation receiver as defined in claim 5, wherein the sequence of location estimates is used adaptively to alter the computational parameters of said feedback circuit so that said location output estimate is constrained in the same way as is the physical movement of said receiver.

7. A side tone ranging multiplexed location-estimation receiver adapted for simultaneous reception of signals from multiple transmitters of determinable location and motion, each transmitter-transmitting a uniquely repeating code sequence, comprising

signal receiving and conditioning circuits,

a plurality of delay controllable reference pseudo-noise signal oscillators, and

a like plurality of signal correlators driven by said plurality of delay-controllable reference pseudo-noise signal oscillators, respectively, each signal correlator producing the repeating code sequence employed in a particular transmitter, respectively,

means for combining said signal correlator signals to compute an estimated location of the receiver in three dimensions and produce a location estimate output, and a timing estimate output,

a feedback circuit for converting said location estimate output and timing estimate output into phase-delay signals for each reference oscillator proportionate to the direction, range and relative velocity of the transmitter whose signals it is processing,

whereby the sequence of location estimate and timing estimate outputs is used adaptively to alter said phase-delay signals from said feedback circuit so that the estimated position sequence is constrained in the same way as is the physical movement of said receiver.

8. In a position-estimation receiver deriving its output estimates from received inputs from a remote, distributed array of four or more pulse-code multiplexed transmitters at determinable spatial positions, the improvement comprising, four or more delay-lock loop trackers, each measuring and indicating range data between the receiver and each transmitter, respectively, computational circuits for combining all said range data to determine an estimated receiver position based on said four or more transmitter-receiver ranges measured, an additional computation circuit to estimate, from the estimated receiver position and transmitter positions determined from initial information and transmitted data, a set of tracking delays appropriate to optimally track each transmitter through its associated tracker, and circuit means to feed the set of estimated tracking delays to the delay lock loop trackers, these elements acting collectively as a single integrated closed-loop position estimator.

9. In a position, time location receiving system deriving its output position estimates from received inputs from a remote, distributed array of at least four pseudonoise transmitter channels at determinable spatial positions, said receiving system having a plurality of delay lock loops, one for each transmitter, a method of enabling said system to tolerate a larger amount of intentional jamming or nonintentional interference comprising deriving control signals for said delay lock loops of each transmitter channel, respectively from a current estimated location vector (x, y, z) and time signal for said receiving system and applying said estimated location vector (x, y, z) and time signal as control signals to said delay lock loops.