Abstract: A method for estimating signal/noise ratio is provided. The method comprises calculating a first signal/noise ratio (SNR) estimate using a technique with a first response time, calculating a second SNR estimate using a technique with a second, slower response time, and blending the first SNR estimate with the second SNR estimate.

Abstract: A rotating antenna is used in a wireless system to impart a phase onto a received signal by electronically moving the effective receiving antenna location along a circular path such that the modulation phase angle indicates the bearing of the radio transmission and the gain of a signal transmitted by the antenna is increased in the direction of the received signal to enhance the link between transmitter and receiver. In order to simulate a rotating antenna, the antenna preferably comprises an antenna array having a plurality of antennae for use by one receiver. During reception of a signal from a remote transmitter, a scanner is adapted to scan through the plurality of antennae and in turn provide a signal received from each of the plurality of antennae to the receiver in the wireless system. The signal is modulated by virtue of the antenna rotation to include a Doppler frequency component.

Abstract: A positioning apparatus that measures a current position by using measurement basis codes carried on satellite waves from a plurality of positioning satellites includes: a first phase error information generating unit that generates first phase error information indicating an error of a first phase on the basis of a frequency difference between a first frequency which is an estimated value of a receiving frequency of the satellite wave and a second frequency which is a frequency corresponding to a maximum value of a correlation value under a condition of the estimated phase; a second phase information generating unit that generates second phase information indicating a second phase by correcting a first phase information on the basis of the first phase error information; and a positioning unit that measures the current position on the basis of the second phase information on at least three of the positioning satellites.

Abstract: A position determination method including a step of transmitting a periodic signal having a carrier frequency, a step of sequentially receiving the periodic signal having the carrier frequency at various locations using at least one antenna, and a step of determining a first coordinate of the object location on the basis of a zero crossing of a Doppler frequency response which may be associated with the first coordinate of the object location, the first coordinate of the object location corresponding to a coordinate of that location of the at least one antenna which it has when receiving the periodic signal at the zero crossing in relation to the object location.

Abstract: A system for enhancing the performance of a wireless communication device (WCD) while executing a direction of arrival (DoA) estimation. The performance may be improved through device management, and may include the collection of information from one or more sensors installed within the WCD. The sensor information may initially be used to determine an appropriate configuration for the device. Further, the sensor information may also be used to affect the behavior of the device while performing the DoA estimation.

Abstract: A system and method for determining a position of a moving platform are provided. The method includes transmitting a carrier signal from one of the moving platform and a stationary platform, receiving a received signal at the other of the moving and stationary platforms, deriving a frequency shift between the carrier signal and the received signal, and calculating the apparent closing velocity using the frequency shift and a frequency of the carrier signal.

Abstract: A reception level measuring system in which a base station in a code division multiple access (CDMA) mobile communication system measures a reception level of a signal from a mobile station. The reception level measuring system has an approximate-line estimating device, a phase-rotation estimating device; a Doppler-frequency estimating device and a reception signal power estimating device. The approximate-line estimating device provides an approximate line by linearly approximating signal amplitudes of a demodulated data stream in I- and Q-channels from a reception signal, in a time interval which is set in accordance with an estimated Doppler frequency. The phase-rotation estimating device estimates an amount of phase rotation based on a gradient of the approximated line. The Doppler-frequency estimating device estimates the estimated Doppler frequency based on the amount of phase rotation; and the reception signal power estimating device estimates a reception signal power based on said approximate line.

Abstract: The present invention pertains to a robotic wash cell including a six-axis robotic arm and end effector equipped with nozzles that spray unheated, solvent free, pure water at high-pressure to clean or debur objects by maintaining the nozzles in close proximity and substantially normal to each surface being cleaned or edge being deburred. The robotic cell wash is particularly useful for cleaning contaminants such as oil and grease from items having more complex shapes. The six-axis robotic arm positions the nozzles and their sprays substantially normal to each surface being cleaned or deburred. The nozzles produce a multi-zone spray pattern with a continuous effective cleaning zone. A water recycling and pressurizing system collects the used water, separates out the oil and grease contaminants to a level of about 5 ppm, and pressurizes the pure water to about 3,000 psi for washing operations or about 6,000 psi for deburring operations.

Abstract: Provided is a Doppler based automated direction finding system that detects radio frequency (RF) leaks in a cable television plant. During a ride-out, the system detects leaks and stores leak data, such as amplitude, location, and bearing. The stored data is uploaded to a computer that performs a leak analysis. The leak analysis isolates the leaks using Doppler-based bearing information and separates cable leaks from other RF sources, such as power sources and noise. Erroneous information that results from RF reflections (multi path) may be eliminated while processing the data using triangulation. After the leak analysis, the computer generates work orders and maps, makes the data available to users, and may also compile information and file reports based on the data.

Abstract: A method determines range from a moving platform to an emitter. The method receives a RF signal from the emitter; counts a number of phase reversals of the received RF signal during a period of time; measures a Doppler frequency during the period of time; and determines the range to the emitter based on both the number of counted phase reversals and the measured Doppler frequency.

Abstract: A method and apparatus for determining the position and/or the orientation of a movable object using a Doppler shift of electromagnetic signals. The apparatus includes a transmitter for transmitting a periodic electromagnetic signal, a sensor mountable on the object for receiving the signal transmitted by the transmitter and a controller in communication with the transmitter and the sensor for determining the position and/or orientation of the sensor relative the transmitter.

Abstract: Provided is a Doppler based automated direction finding system that detects radio frequency (RF) leaks in a cable television plant. During a ride-out, the system detects leaks and stores leak data, such as amplitude, location, and bearing. The stored data is uploaded to a computer that performs a leak analysis. The leak analysis isolates the leaks using Doppler-based bearing information and separates cable leaks from other RF sources, such as power sources and noise. Erroneous information that results from RF reflections (multi path) may be eliminated while processing the data using triangulation. After the leak analysis, the computer generates work orders and maps, makes the data available to users, and may also compile information and file reports based on the data.

Abstract: A method of determining an azimuth and elevation of a radiation emission source using a single-axis direction finding system is provided. The method includes receiving a plurality of radiation signals at the single-axis direction finding system. The plurality of radiation signals are emitted from the radiation source, each of the plurality of radiation signals being received at one of a plurality of attitudes of the single-axis direction finding system. The method also includes measuring an angle of arrival of each of the plurality of radiation signals with respect to the single-axis direction finding system. Additionally, the method includes calculating an azimuth angle of each of the plurality of radiation signals with respect to the single-axis direction finding system using the respective measured angle of arrival. Further, the method includes calculating a respective vector corresponding to each of the azimuth angles at different elevation angles within a predetermined range.

Abstract: A system for locating electromagnetic signal sources via the rotational Doppler effect whereby a radar station generating electromagnetic signals, such as radar frequency signals, initially scans the sky for aircraft. An aircraft having the system operationally installed thereon and utilizing apparatus or navigational systems already present on the aircraft receives radar signals. The system is programmed to capture radar signal parameters and extract the rotational Doppler frequencies induced by the motion of the aircraft. The angular velocity of the host platform is often the dominant source of this frequency; however, lateral velocity is not detrimental to the process. The measurement of the rotational Doppler frequency is accomplished through antennas presently installed on large numbers of military aircraft with no requirement for phase calibration of the electrical paths between antennas and receiver.

Abstract: The invention is a method of calibrating the sensor system of a wideband direction finder using a noise source. The sensor system includes at least two wideband tuners, and an analog/digital (A/D) converter connected to each wideband tuner. The calibration method involves selecting a common set of center frequencies for each of the wideband tuners. The wideband tuners receive a signal from the noise source on a per data frame basis. The passband of the received signal is then divided into a number of time-sampled data frames. For each time-sampled data frame, both a gain variation and a phase variation are calculated for the noise received at each wideband tuner. Gain and phase differences between the signal received by each wideband tuner within the same frame are compared. Based on the time-sampled data collected, the phase and gain differences for the signals received at the tuners which have not been previously mapped can be determined.

Abstract: A frequency management scheme for a hybrid communications/positioning device, such as a cellular/GPS or other combined device, generates a local clock signal for the communications portion of the device, using a crystal oscillator or other part. The oscillator output may be delivered to a phase locked loop to drive a high-frequency clock for the cellular or other communications portion of the hybrid device. A processor may determine frequency error between the phase locked loop and base station or other reference, to derive a digital frequency tracking message. A Doppler search or other logical control message may likewise be communicated from the processor to a GPS or other positioning receiver. The GPS receiver circuitry may consequently adjust Doppler center, window width or other parameters to enhance time to first fix or other performance.

Abstract: Determining the angle of arrival of a signal by providing a plurality of antennae, sampling, in turn, the output from each of the antennae to obtain a set of samples, each of the samples relating to different points in time, performing a Fourier transform on the set of samples, thereby producing a sequence of spectral lines, identifying a signal impinging on the antennae from the configuration of the spectral lines, and calculating, from phase and amplitude data gathered from at least a subset of the spectral lines, the direction of arrival of the signal at the antennae.

Abstract: A location system includes a plurality of beacon transmitters each positioned at a respective location. Each beacon transmitter includes a plurality of antennas positioned in a circular arrangement. Each beacon transmitter is configured to transmit an identification signal having a plurality of reference data and to transmit a directional signal from the plurality of antennas by selecting one of the antennas at a time in sequence around the circular arrangement to simulate a rotating antenna. The location system further includes a receiver configured to receive the identification signals and a plurality of Doppler-shifted directional signals each corresponding to one of the directional signals, wherein the receiver is configured to generate a plurality of time data for each received Doppler-shifted directional signal, and wherein the receiver is configured to determine a location of the receiver using each received Doppler-shifted directional signal, each time data, and each identification signal.

Abstract: A method of determining the angle of arrival of a signal, the method comprising the steps of: providing a plurality of antennae; sampling, in turn, the output from each of the antennae, to obtain a set of samples, each of the samples relating to different points in time; performing a Fourier transform on the set of samples, thereby producing a sequence of spectral lines; identifying a signal impinging on the antennae from the configuration of the spectral lines; and calculating, from phase and amplitude data gathered from at least a subset of the spectral lines, the direction of arrival of the signal at the antennae.

Abstract: A radio direction finding system for a low signal quality transmission signal performs a Fast Fourier Transform (FFT) on an entire received RF band into a number of FFT bins, each serving as an IF filter. The contents of each FFT bin are demodulated to decode a frequency signature from the encoded RF signal. A signal-to-noise ratio comparator receives the FFT baseband samples and determines the signal level from the known frequency signature. The FFT baseband buffer with the greatest SNR corresponding to a particular FFT frequency bin is outputted as a direction finding metric.

Abstract: An autonomously movable cleaning robot comprising a platform and motive force to autonomously move the robot on a substantially horizontal surface having boundaries. The robot further has a computer processing unit for storing, receiving and transmitting data, and a cleaning implement operatively associated with the robot. The robot receives input data from an external source. The external source may be physical manipulation of the robot, remote control, or by triangulation from at least three external transmitters.

Abstract: An enhanced Doppler type direction finding system uses two antennas or antenna pairs (1 & 7) that are rotated in two mutually orthogonal circular paths (8 & 13) to intercept incoming RF from an emitting source, whose direction is to be determined.

Abstract: A communications system for determining the position and velocity of an object using a plurality of GPS signals transmitted by a plurality of GPS sources includes an interrogator remote from the object and responsive to the plurality of GPS signals. The interrogator transmits an RF signal including GPS source information and at least one of frequency information and time and code phase information of at least one of the GPS signals. The system also includes a transponder positioned on the object and responsive to the RF signal and the plurality of GPS signals. The transponder tracks one of the plurality of GPS signals in response to the GPS source information and the frequency information and time and code phase information. The transponder generates a correlation snapshot and transmits the snapshot to the interrogator.

Abstract: A GPS receiver and associated method that embodies high-dynamic, fast acquisition, and interference-suppressing capabilities for the reception and processing of GPS signals from a plurality of GPS satellites to produce GPS signal time and frequency parameters and navigation fixes. The GPS receiver includes an antenna and an analog front-end to intercept the incoming radio-frequency signal, band-limiting amplify the signal, and to convert it to an appropriate intermediate frequency so that it may be converted to digital form. One or more high-speed digital signal processors (DSP) constitute an all digital software baseband processor that process the sampled and quantified signals to form a two-dimensional delay-Doppler map of correlation power and to extract the signal time and frequency parameters and navigation data. The baseband processor is organized into functionally identical channels, each dynamically assigned to a different satellite visible.

Abstract: A system and method for determining a round trip delay of signals transmitted between first and second objects, such as a satellite and a mobile telephone, that move relative to each other. A first signal is transmitted from the first object to the second object. The first signal is received at the second object after a propagation delay D1, the delay D1 being the time taken by the first signal to traverse from the first object to the second object. A frequency of the first signal is measured at the second object. The second object then transmits to the first object a second signal containing a report of the measured first frequency. The second signal is received at the first object after a propagation delay D2, D2 being the time taken by the second signal to traverse from the second object to the first object. The first object measures a frequency of the second signal.

Abstract: A system for locating electromagnetic signal sources via the rotational Doppler effect whereby a radar station generating electromagnetic signals, such as radar frequency signals, initially scans the sky for aircraft. An aircraft having the system operationally installed thereon and utilizing apparatus or navigational systems already present on the aircraft receives radar signals. The system is programmed to capture radar signal parameters and extract the rotational Doppler frequencies induced by the motion of the aircraft. The angular velocity of the host platform is often the dominant source of this frequency; however, lateral velocity is not detrimental to the process. The measurement of the rotational Doppler frequency is accomplished through antennas presently installed on large numbers of military aircraft with no requirement for phase calibration of the electrical paths between antennas and receiver.

Abstract: An array antenna includes two sub-arrays. Each sub-array has at least three elements with at least one unshared element. Samplers sample elements separately for the sub-arrays. A direction-of-arrival estimator uses sampling from the samplers to make a separate direction-of-arrival estimate for each sub-array for direction of arrival of a signal from a source. A source location estimator estimates distances from the source to each element based on the separate direction-of-arrival estimates from the direction-of-arrival estimator. A sampling adjuster adjusts timing of sampling performed by the samplers based on the distances from the source location estimator.

Abstract: Array elements 111-1 to 111-n of array antenna 101 are arranged at respective different heights from a ground so as not to overlap to each other in a vertical direction. Received frequency conversion section 102 converts a radio frequency signal received at each of the array elements 111-1 to 111-n of array antenna 101 into an intermediate frequency signal or baseband signal. A/D conversion section 103 converts an analog signal output from received frequency conversion section 102 into a digital signal using a proper sampling frequency. Direction estimating section 105 estimates directions of an arrival radio signal in a horizontal plane and vertical plane using received digital signals obtained in A/D conversion section 103. It is thereby possible to suppress increases in the number of array elements and computation amount, and to improve estimation accuracy in the vertical direction and resolution at the time a plurality of signals arrive.

Abstract: A system for calculating the bearing of a signal source, with a directional antenna, provides corrections for distortion, such as due to a small fuselage of the monitoring aircraft and the elevation angle of an intruder aircraft with respect to the monitoring aircraft. A correction is applied to the bearing estimate that is based on relevant factors, such as the fuselage size and the elevation angle of the intruder aircraft. The correction can be calculated or applied through the use of a look-up table, which may be either pre-selected or selected after calculation of the elevation angle of the intruder aircraft.

Abstract: A system for calculating the bearing of a signal source, with a directional antenna, provides corrections for distortion, such as due to a small fuselage of the monitoring aircraft and the elevation angle of an intruder aircraft with respect to the monitoring aircraft. A correction is applied to the bearing estimate that is based on relevant factors, such as the fuselage size and the elevation angle of the intruder aircraft. The correction can be calculated or applied through the use of a look-up table, which may be either pre-selected or selected after calculation of the elevation angle of the intruder aircraft.

Abstract: In a satellite communication system (20), a method (50) and system of locating terrestrial-based user terminals (UTs). A UT (23) is located by a two-tier estimation procedure. Under this procedure, an initial estimate of the UT location is performed based on absolute signal propagation delay and Doppler shift measured from a communication link between a satellite and the UT. A second, refined estimate of the UT location is then performed based on the results of the initial estimate. The second estimate can be a function of the absolute propagation delay and absolute Doppler, as well as differential delay and differential Doppler measured from transmissions from two or more satellites (21-22) to the UT (23).

Abstract: A method and apparatus is disclosed for measurement processing of Satellite Positioning System (SPS) signals. A plurality of SPS signals from a corresponding plurality of SPS satellites are received in an SPS receiver. The signal environment corresponding to the location in which the SPS receiver is located is characterized to produce signal environment data. In one exemplary embodiment, an information source, such as a cellular network based database, is searched to retrieve the signal environment data given an approximate location of the GPS receiver. This approximate location may be specified by a location of a cell site which is in cellular radio communication with a cellular communication device which is co-located with the GPS receiver. One or more parameters related to signal characteristics of the satellite signals are defined. Threshold values for the parameters are determined using the signal environment data.

Abstract: In one aspect, the present invention discloses a communication device (see, for example, FIG. 5), such as a mobile unit (e.g., a cellular telephone handset) or a stationary unit (e.g., a cellular telephone base station). The communication device utilizes global positioning system (GPS) information 560 within a Doppler profile generator 540. For example, in a mobile unit, the GPS information would typically be generated at the device. A receiver 520 is coupled to the Doppler profile generator 550. The receiver 520 utilizes Doppler profile information in translating a received wireless signal into user information.

Abstract: A Doppler Direction Finder comprises at least one antenna (52) spaced from a location point (53). The at least one antenna (52) is arranged in use to be rotated about the rotation point (53). The at least one antenna (52) is arranged to provide a first output signal comprising a signal received by said at least one antenna (52) combined with the Doppler Shift component. There are means (70) for providing a second output signal comprising the received signal without the Doppler Shift component. Processing means (54-82) process the first and second signals to obtain the Doppler Shift component. Determining means (88) determine from the Doppler Shift component the direction from which the received signal is received.

Abstract: A method and system for calculating the range between a source which emits electromagnetic energy having an unknown frequency and a first receiver of electromagnetic energy at at least three points along a portion of a source trajectory. The source trajectory portion is a substantially straight line which has two end points. The first receiver moves along a first, substantially straight-line receiver trajectory so that the frequency of the electromagnetic energy is Doppler-shifted. The first receiver measures the Doppler-shifted frequency at at least three predetermined times. Next, at least two ratios of frequencies are calculated, the ratios being functions of the Doppler-shifted frequencies and bearing angles. Finally, the range between the first receiver and the source is calculated from the frequency ratios at the at-least-three points. In a first preferred embodiment the source is stationary.

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 direct sequence spread spectrum receiver samples an incoming signal and stores the sample in memory. Prior to sampling and storage, the incoming signal is translated to an IF signal. Also prior to storage, the IF signal is corrected for a frequency offset signal. The frequency offset may be caused by many sources, Doppler shift or local oscillator error, for example. Once the signal is corrected for the frequency offset, the signal sample is stored in memory. The signal sample is read from memory as necessary to process the signal. Such a receiver is useful in global positioning satellite (GPS) signal processing where the incoming signal contains several satellite transmissions encoded with CDMA encoding.

Abstract: The present invention is a system and method for accurately determining the distance (range) between one or more satellites and a user terminal and the rate of change (range rate) of that distance. When accurately determined according to the present invention, these quantities can be used to determine the location of the user terminal with a high degree of accuracy. When one satellite is available, the present invention determines the range and range rate based on the Doppler frequency shift that a signal experiences between the satellite and the user terminal, the round trip delay a signal experiences during transmission from the satellite to the user terminal and back via a satellite to a gateway, the Doppler frequency shift a signal experiences between the satellite and the gateway, and the timestamps of the measurements.

Abstract: Level crossing number counter section 115 obtains the Doppler frequency caused by fading by counting the number of times of a received signal crossing an averaged received signal level. Corresponding to the Doppler frequency, reference signal correlation integration control section 116 controls reference signal correlation integration section 311 to suspend and restart the processing of integrating the correlation data of the received signal obtained in reference signal correlation section 306 with a reference signal.

Abstract: The mobile cellular telephony terminal includes a radio transmitter/receiver (1) for communicating with base stations of a cellular network, measuring the Doppler velocity of the transmissions originating from the stations and accordingly operating circuits (2) for estimating the velocity of the terminal, by composition of the Doppler velocities, and updating circuits (4, 5) are provided for updating an inertial unit (10) supplying the radio circuit (1) with the position of the terminal, by comparison between a terminal velocity supplied by the unit (10) and the estimated velocity.

Abstract: Doppler correction system and method comprising receiving a Doppler effected signal comprising a preamble signal (32). A delayed preamble signal (48) may be generated based on the preamble signal (32). The preamble signal (32) may be multiplied by the delayed preamble signal (48) to generate an in-phase preamble signal (60). The in-phase preamble signal (60) may be filtered to generate a substantially constant in-phase preamble signal (62). A plurality of samples of the substantially constant in-phase preamble signal (62) may be accumulated. A phase-shifted signal (76) may also be generated based on the preamble signal (32). The phase-shifted signal (76) may be multiplied by the delayed preamble signal (48) to generate an out-of-phase preamble signal (80). The out-of-phase preamble signal (80) may be filtered to generate a substantially constant out-of-phase preamble signal (82). A plurality of samples of the substantially constant out-of-phase signal (82) may be accumulated.

Abstract: An apparatus and method for target-angle determination using lower-frequency radars having compact non-moving antennas over broad viewing sectors. Use of direction finding (DF) in place of beam forming and scanning eliminates the need for conventional, physically large phased-array antenna systems. The described DF algorithm advances the art over previously described least-squares DF by allowing numerically efficient and robust resolution of multiple targets at closely spaced angles. When used with coastal HF ocean surface current and wave monitoring radars where sea echo is the target, the method extracts complex current patterns. The high degree of singularity of the antenna signal covariance matrix is exploited and used as the basis for extracting angles with minimal averaging. More receive antenna elements can be added at convenient locations to handle more complex target angle scenarios.

Abstract: An automatic frequency control system for use in satellite communications is provided that is pre-programmed with an initial acquisition Doppler offset frequency. The system includes a search mode for accurately determining the satellite's initial frequency translation error before the initiation of data transmission and also for determining the Doppler rate of change. The system further includes a tracking mode, in which the frequency variation is continuously monitored. Depending on the frequency characteristics of the transmission, the system is capable of re-entering the search mode to determine a new frequency translation error, if necessary.

Abstract: An encoded marker is transmitted as a paging signal for mobile satellite telephones. The signal is susceptible to Doppler effects, and the processing procedures are arranged to determine the Doppler characteristics of subsequent signals. The marker takes the form of a first frequency sweep occurring in a first direction followed by a second frequency sweep occurring in the opposite direction. The markers are correlated against sweep signatures to produce amplitude peaks. The mid-point between the peaks and the spacing between the peaks allows timing offsets and frequency shifts to be accurately calculated, thereby facilitating the processing of subsequent data signals.

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: A method of reducing the effects of interference on a radio receiver having access to multiple transmission sources including the steps of monitoring the signals received from all available sources, utilising information derived from the received signals from each source to compute the most likely frequency band of the interference, determining from said most likely frequency in conjunction with known ephemeris for the receiver and the current Doppler shift of the source signals which sources are least susceptible to interference at said most likely frequency, and passing the identities of said least susceptible sources to the receiver acquisition software.

Abstract: A method and apparatus for locating and tracking a portable transmitter that may be deposited with currency or other items desired to be tracked, comprising a doppler antenna array, analog antenna switching, radio frequency and intermediate frequency circuitry and a digital signal processor, exhibiting increasing sensitivity, accuracy, and range.

Abstract: In a satellite mobile communication system in which at least one mobile earth station communicates with a land earth station which is coupled with a network, through a satellite, the land earth station measures frequency offset in a request signal and/or a response signal in a received signal from the mobile earth station due to frequency offset by a transponder in the satellite and/or a local oscillator of said mobile earth station, and doppler shift due to movement of the satellite. The measured frequency offset is forwarded to the mobile earth station through a singalling channel or a communication channel through a satellite. The mobile earth station compensates frequency offset by adjusting oscillation frequency of a local oscillator in the mobile station based upon the measured frequency offset sent from the land earth station.

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: A Doppler position locator for determining the bearing of a signal source from a moving receiver. The signal source encodes a digital signal indicating its actual transmitting frequency on a transmitted carrier. The moving receiver such as an airplane receives a Doppler shifted carrier frequency and the digital information on what the actual transmitted frequency was. Comparison of the received frequency to the digital information on the transmitted frequency yields a Doppler frequency (the increase or decrease caused by the relative motion, i.e., the numerical difference between the transmitted and received frequencies). From the aircraft velocity and the two frequencies, the bearing can be determined using the formula .crclbar.=cos.sup.-1 (d*c)/(f*v) where .crclbar. is the bearing angle, f is the transmitted frequency, d is the Doppler shift or change in frequency, c is the speed of light and v is the magnitude of the receiver velocity.