Abstract: A method of locating a terrestrial emitter of electromagnetic radiation in the midst of a plurality of emitters in a satellite in orbit about the earth which utilizes a location estimation and location probability determination process with respect to each possible emitter site and its corresponding error region and then using both feedback and feed forward interaction between location and phase ambiguity resolution processes to generate resolved phase from emitter location, update emitter location or some or all of the emitters, and subsequently utilizing the probabilities thus determined to produce a single estimate of the desired emitter's location.

Abstract: In one embodiment, the disclosure relates to a method for estimating and predicting a target emitter's kinematics, the method including the steps of: (a) passively sampling, at a first sampling rate, an emitter signal to obtain at least one passively measured signal attribute for estimating the target kinematics; (b) inputting the passively measured signal attribute to an estimator at a first sampling rate; (c) determining a radar duty cycle for active radar measurements as a multiple of the first sampling rate, the multiple defining a duration between radar transmissions; (d) directing a radar system to make active target measurements at the determined duty cycle; (e) inputting to the estimator the active target measurements at the determined duty cycle, while continuously inputting the passively measured signal attributes.

Abstract: A method of locating a terrestrial emitter of electromagnetic radiation in the midst of a plurality of emitters in a satellite in orbit about the earth which utilizes a location estimation and location probability determination process with respect to each possible emitter site and its corresponding error region and then using both feedback and feed forward interaction between location and phase ambiguity resolution processes to generate resolved phase from emitter location, update emitter location or some or all of the emitters, and subsequently utilizing the probabilities thus determined to produce a single estimate of the desired emitter's location.

Abstract: A method of locating a terrestrial emitter of electromagnetic radiation in the midst of a plurality of emitters in a satellite in orbit about the earth which utilizes a location estimation and location probability determination process with respect to each possible emitter site and its corresponding error region and then using both feedback and feed forward interaction between location and phase ambiguity resolution processes to generate resolved phase from emitter location, update emitter location or some or all of the emitters, and subsequently utilizing the probabilities thus determined to produce a single estimate of the desired emitter's location.

Abstract: The present invention uses feedback 300 from RF carrier frequency measurements 301 to disassociate the emitter angle-of-arrival component 313 in the ambiguous phase measurement 312 from the initially unknown phase measurement integer ambiguities 314; to then process 302 resolve the ambiguities; and finally to process 303 to obtain the correct emitter AOA. The present invention does this by converting the actual interferometer baselines 315 on which the unassociated pulse 308 phase measurements 304 were made at different emitter frequencies to a baseline set 305 for a single-frequency equivalent interferometer array. This conceptual array has the following property: the phase measurement 306 that would be made on it at the fixed frequency for a signal at the same direction-of-arrival 307 are identical to the actual phase measurements made on the physical array. Because of this equivalency the conceptual array is called the E(equivalent)-array.

Abstract: A method and apparatus for determining from a moving observer the location, in terms of latitude, longitude, altitude, and velocity, of a stationary or moving radar emitting a pulsed or continuous-wave signal. The moving observer extracts from the radar signal significant electronic support measures (ESM) parameters, including frequency, pulse repetition interval, and pulse width, and determines from those parameters whether a radio frequency (RF) or pulse repetition frequency (PRF) measurement technique is appropriate, and whether the radar signal angle-of-arrival (AOA) must be computed. The emitter location is computed using a ratio of sequential frequency measurements, and the moving observer continues to collect frequency measurements until the location of the emitter can be established to within a predetermined degree of certainty.

Abstract: A method and apparatus for determining from a moving observer the location, in terms of latitude, longitude, altitude, and velocity, of a stationary or moving radar emitting a pulsed or continuous-wave signal. The moving observer extracts from the radar signal significant electronic support measures (ESM) parameters, including frequency, pulse repetition interval, and pulse width, and determines from those parameters whether a radio frequency (RF) or pulse repetition frequency (PRF) measurement technique is appropriate, and whether the radar signal angle-of-arrival (AOA) must be computed. The emitter location is computed using a ratio of sequential frequency measurements, and the moving observer continues to collect frequency measurements until the location of the emitter can be established to within a predetermined degree of certainty.

Abstract: A method and system for determining the geolocation--i.e., the latitude, longitude, and altitude--of a stationary RF signal emitter from two or more moving observer aircraft. The observers receive signals from the emitter and the system measures the phase difference between the signals. The observers then perform pulse time of arrival (TOA) measurements over a predetermined clock interval, and calculate the time difference of arrival (TDOA) of corresponding, same-pulse, emitter signals. Based on geometric relationships, the system creates a series of circular lines of position (LOPs) for each observer, and computes hyperbolic LOPs based on the TDOA calculations. The system determines emitter location from the intersection of the hyperbolic LOPs and the circular LOPs.

Abstract: A method for determining the geolocation--i.e., the latitude, longitude, and altitude--of a stationary emitter emitting an RF signal. The method employs at least one moving observer to measure electrical phase change of the emitter over two or more successive dwell intervals, and at least two observers, moving or stationary and of known position, to determine the pulse time of arrival of the emitter signal. The phase change measurements are taken using a long baseline interferometer (LBI), and the pulse time of arrival measurements are calculated using short baseline interferometers (SBI). Circles of position are generated from bearing change measurements ascertained from the LBI phase change measurements, and hyperbolic lines of position are generated based on the SBI measurements. The position of the emitter is then determined from the intersection of the circles and lines of position.

Abstract: An electrical surveillance measures system for measuring direction of arrival (DOA), i.e., both azimuth and elevation, of a pulsed or continuous wave radar signal from a moving emitter. Either carrier frequency or pulse repetition interval (PARI) Doppler shift are used whereby the ratio of the Doppler shift is measured by a moving observer. The DOA is measured as a unit vector having basis vectors formed from a linearly independent set of observer's velocity vectors. The DOA unit vector has a linear part where the coefficients of the basis vectors are derived directly from the ratios of frequency or PARI measurements taken in three contiguous dwells. The DOA unit vector has a nonlinear part formed from the requirement that the DOA vector have unit magnitude. The unit vector is resolved in the system coordinates in which emitter azimuth and elevation are defined to allow computation of the latter two values.

Abstract: Radar emitter carrier frequency or pulse time-of-arrival measurements are used to resolve the differential phase measurement ambiguities on a long baseline interferometer (LBI) used to passively locate the emitter. The LBI requires only two pulses to precisely measure the change in signal angle of arrival caused by observer motion relative to the emitter, whereas frequency Doppler needs tens of pulses, and time Doppler may need hundreds of pulses, to estimate the same change to the same accuracy. Therefore Doppler measurements are made only to the accuracy needed to estimate the angle change accurately enough to differentially resolve the LBI.

Abstract: Method and apparatus for passive emitter location which overcomes the time to range and other restrictive limitations of passive tracking systems by combining pulse frequency, time of arrival and bearing or angle of arrival measurements to obtain a range measurement at each parameter update. No specific observer motion is required and relatively few restrictions on emitter motion are present in order to obtain an accurate determination.

Abstract: A method and apparatus for locating a pulse echo radar emitter in both angle and range using a single antenna and minimal use of the observer platform's navigation instruments are described. The emitter's rest frequency and pulse repetition frequencies are extracted. Using the emitter signal DOA and measurements of pulse TOA and emitter frequency, the observer's acceleration and velocity along the emitter DOA path are found. Combining observer velocity with the above kinematic quantities allows emitter range and bearing to be determined. No observer platform heading or angular attitude information is required.

Abstract: An apparatus for determining a spatial angular reference to an emitter of RF signals, such as direction of arrival or angle of arrival, from phase measurements made between two antennas is described. The apparatus uses at least a pair of dual polarized antennas having non-parallel boresights. Like polarized outputs from the antennas produce phase information which is stored and then summed to remove bias error in favor of the sin (AOA) component, while the phase information from the like polarized antennas is also differenced producing a signal indicative of the bias error. It is shown that the bias error can be uniquely related to emitter angle and azimuth. The latter information is obtained without the need for making emitter frequency measurements.

Abstract: A method is described modifying initially linear or planar interferometer arrays such that the arrays can be placed in conformal installations. The method commences with a conventional linear or planar array design and then using certain techniques and relationships allows for the possibility of antenna placement with materially reduced restrictions. A plurality of phase equivalent antenna locations obeying prescribed relationships are generated. These positions lie on the conformal surface on which the array is to be mounted. This permits an optimal set of antenna positions to be chosen based on operational requirements.

Abstract: Method and apparatus for enabling a pulse echo radar to generate a false signal in both time and frequency based passive Doppler ESM location systems. The latter false signal causes the ESM system to mislocate the radar. The radar's reference oscillator frequency is varied to create false passive Doppler information at an intercept receiver. These variations are predetermined changes in RF and PRF frequencies for the radar and are relatively small compared to those frequencies.

Abstract: A method and apparatus for controlling the output characteristics of a radar emitter for thereby preventing the location of the emitter using Doppler techniques. The emitter's RF frequency and PRF are under the control of a random signal generator which causes the emitter to emulate common signal corrupting influences.

Abstract: A method for determining a constant classification parameter for a radar is described; this parameter uniquely characterizes and identifies the radar being monitored. The method does not require the use of navigation or orientation information concerning the observer platform. The emitter pulse repetition frequency (PRF) provides a clock signal to allow measurement of the number of cycles of emitter carrier occurring in a predetermined interval. This value is the same at the emitter and at the observer and forms the aforementioned classification parameter. The classification parameter is additionally used to detect the presence of countermeasures designed to defeat passive Doppler emitter location.

Abstract: Bearing rate of change, or equivalently bearing differences, are used to estimate emitter geolocation, in contrast to using such rates or differences to estimate only range. In using the bearing differences, it is not necessary to maintain the same relative bearing to compensate for DOA dependent errors. Nor does the invention require a precise fully resolved and calibrated interferometer to generate DF measurements. Furthermore, it can be used with currently implemented amplitude DF systems that employ no phase interferometry at all. By making minimal changes, these systems will produce accurate geolocation. The invention will also work with any system that can be modified to produce an accurate bearing rate-of-change. Therefore, it can be used with time-difference-of-arrival (TDOA) systems also. If bearing measurements are also produced by such systems, the magnitude of the bias on that bearing measurement is not important.

Abstract: The invention provides a method for using single linear arrays for making AOA measurements only in sensor coordinates to perform emitter direction finding from an observing aircraft.