Abstract: A sensor system that provides an adjustable threshold level for the sensed quantity is described. The adjustable threshold allows the sensor to adjust to ambient conditions, aging of components, and other operational variations while still providing a relatively sensitive detection capability for hazardous conditions. The adjustable threshold sensor can operate for extended periods without maintenance or recalibration. In one embodiment, the sensor is self-calibrating and runs through a calibration sequence at startup or at periodic intervals. In one embodiment, the adjustable threshold sensor is used in an intelligent sensor system that includes one or more intelligent sensor units and a base unit that can communicate with the sensor units. When one or more of the sensor units detects an anomalous condition (e.g., smoke, fire, water, etc.) the sensor unit communicates with the base unit and provides data regarding the anomalous condition.

Abstract: A real time emergency response surveillance system, a method, and a computer readable medium for storing a computer program for responding to an emergency situation are disclosed. The real time emergency response surveillance system includes one or more surveillance stations communicatively coupled to an operations center. Each surveillance station includes a controller, a video camera, a communication module and a display screen. The surveillance station is placed in one of a surveillance mode and an emergency response mode. Real time video data is transmitted from the surveillance station to the operations center in both the surveillance mode and the emergency response mode. Real time video data is received from the operations center at the surveillance station in emergency response mode. The real time video data received at the surveillance station is displayed on a display screen in emergency response mode.

Abstract: A tamper-resistant remotely monitorable electronic seal including a shaft portion, a sensor, a socket arranged to engage the shaft portion and the sensor in a monitorable manner and a wireless communicator associated with at least one of the shaft portion, the sensor and the socket and being operative to provide a remotely monitorable indication of at least one monitorable event, the sensor being operative to sense application of force to the electronic seal in an attempt to separate the shaft portion from the socket and to indicate the application of force as one of the at least one monitorable event.

Abstract: A vehicular electronic key system includes an on-board device that mutually communicates with a portable device, and operates control equipment installed on a vehicle when specific information from the portable device is authenticated. The on-board device includes a distance storage section for storing travel distances of the vehicle, and a warning section for warning that the portable device disappeared when communication was stopped between the on-board device and the portable device. The on-board device communicates with the portable device each time a predetermined distance is travelled, stores the travel distance at each communication time point into the distance storage section, and drives, upon detection that a signal transmitted from the portable device was disrupted, the warning section to warn an undetected region between the last travel distance stored immediately before the transmitted signal was disrupted and a travel distance at a time point at which the transmitted signal was disrupted.

Abstract: Methods and systems are presented to provide wireless features with a property security system. A detected alarm, which is incapable of being communicated externally by the property security system, is passed to a wireless communication device for processing. In response to the alarm, the wireless communication device communicates an emergency message to an emergency call center service via a wireless transmission.

Abstract: The Owner Aware Object represents a new class of Physical Objects that mimic the awareness of the presence or absence in their immediate surroundings of their rightful owner. The system is composed of an Owner Private Space Generator, one or multiple Owner Private Space Sensors and an optional Super Owner Aware Object which is a Computer connected Owner Aware Object. The Generator and the Sensor Objects work together to establish within a three dimensional space, a volume of Object and Owner Security. While within this volume, the Sensor is maintaining ciphered communication link with the Generator and thus establishes a Secure Volume. Should these two components lose this link, a breach of security event is triggered and both units attempt Owner Notification of the new state of the system. Should two or more Owner Private Spaces intersect or collide, all Owners are notified of the new system status.

Abstract: An enhanced object tracking system for tracking and controlling access to a plurality of objects such as keys is disclosed. The object tracking system implements many improvements including automated user identification using biometric data extracted from the user with a minimum of user interaction, tracking of objects both inside and outside their storage units, the locking of objects within slots of their storage unit to guard against illicit removal and return of keys and to insure random slot rotation, image and visual based inventory verification methodologies, and tracking of objects during times when they are checked out of the system. The result is an intelligent object tracking system with automated control functions and high reliability.

Abstract: Methods and devices are provided for identifying, locating and provisioning individual RFID devices in a network. According to some implementations of the invention, a combination of EPC code information and existing networking standards form the basis of identifying and provisioning methods. For example, MAC address information and EPC information can be combined to identify a particular device and its location in a network. For implementations using the Dynamic Host Configuration Protocol (“DHCP”), DHCP Options may be used to pass provisioning information. Some implementations employ Domain Name Service (“DNS”) and dynamic DNS (“DDNS”) to allow easy identification of RFID devices.

Abstract: A position indicating system includes: a position indicating device, a first reference device, and a second reference device. The position indicating device includes: a first position indicating module for outputting a first signal; a second position indicating module for outputting a second signal; and a selecting module coupled to the first position indicating module and the second position indicating module for selectively driving the first position indicating module to output the first signal or driving the second position indicating module to output the second signal. The first reference device is corresponding to the first position indicating module for receiving the first signal and generating first position information according to a position of the position indicating device. And the second reference device is corresponding to the second position indicating module for receiving the second signal and generating second position information according to a position of the position indicating device.

Abstract: A RFID related system and method for tracking articles that are not individually labeled with RFID tags. A transporter with an RFID reader identifies a carrier with an RFID tag as it is disposed onto the transporter. The location and/or number of the disassociated articles, once removed or otherwise disassociated with the carrier are transmitted to a computer on the transporter. Tagged carriers that continue to have articles associated therewith are removed from the transporter and placed back into storage. The computer may transmit data regarding the carrier and articles to a database.

Abstract: An apparatus and method for automatically tracking each individual vehicle, of a plurality of vehicles, in a race around a track. The device employs RFID tags on each of the vehicles being tracked and at gates adapted to cause the RFID to energize and broadcast the vehicle's identity when a pass through the gate is determined. Collisions of data transmission and resulting loss of identification data are reduced through commands to RFIDs responding and remedied with an inventory command based on most likely respondents. The device can be employed to both track the individual vehicle participants in a race and also to register the participants in the race. Races can be tracked on different courses in different geographic locations by placing the RFID tags on all participants and tracking their progress on the individual remote tracks from a central location.

Abstract: There is disclosed an information processing system having plural IC tags (e.g. RFID tags), each of which transmits back a signal in response to an interrogatory signal sent from a cell phone acting as an interrogator. The information processing system includes the RFID tags and the cell phone. The cell phone transmits an interrogatory signal to the tags to read information from the tags. Each tag receiving the interrogatory signal transmits positional information stored in the tag to the cell phone in response to the interrogatory signal. The cell phone transmits a specific interrogatory signal including at least one of the transmitted sets of positional information. Each tag receiving the specific interrogatory signal makes a decision as to whether the positional information contained in the specific interrogatory signal matches the positional information stored in the tag itself.

Abstract: An electronic article surveillance (EAS) tag 20 having a metal attaching member 34 located therein and adapted to securely and releasably receive a shaft 52 of a pin therein, whereby a predetermined arcuate probe is inserted through an opening and applies a requisite force to the attaching member 34 to release the shaft 52. There are no channels leading the authorized arcuate probe to the attaching member 34. A plurality of partitions 58 and pillars 62 are interspersed within tag 20 to deflect any unauthorized probes from engaging and detaching attaching member 34.

Abstract: An integrated system for tracking assets (tools and materials) and personnel associated with a work site. Personnel are equipped with tracking devices having at least geolocation capability. Assets are tagged with RFID tags, which are interrogated at portals, by mobile scanners, or by personnel tracking devices having RFID reading capability. The tag readers and tracking devices are all in communication with a common “information backbone” and all data is delivered to, and processed by, a common command and control subsystem.

Abstract: A wireless tracking system and method with a tag removal detection feature is disclosed herein. The system and method utilize a tag attached to an asset which includes a processor, a motion sensor (such as an accelerometer), a transceiver, a tag removal sensor and a power source having a limited supply of power. The tag removal sensor is an optical sensor which is activated only when the motion sensor detects motion. In this manner, the tag conserves power since the tag is typically only in motion ten percent of the day. If the tag is removed from the asset, the optical sensor confirms the removal and an alert is activated by the system.

Abstract: Rendering data stored within an electronic data tag unreadable. A receptacle receives an article with the data tag, detects the presence of the electronic data tag, and decommissions the electronic data tag. The receptacle further modifies a label on the article to remove data printed thereon.

Abstract: One or more inertially controlled switches may be coupled to a radio frequency identification (RFID) tag, so that the response of the RFID tag indicates the state of the switch(es). The RFID tag and the switch(es) may be coupled together in various ways so that the state of the switches affects the response of the RFID tag to an RFID reader.

Abstract: A combination ID/tag holder is disclosed. The holder comprises (i) a holder body, (ii) a first pouch for holding a traditional ID card, (iii) a second pouch for holding a tag container, (iv) a tag container, for placement in the second pouch, and (v) a tag, such as a RFID tag, for placement in the tag container. The present invention can be used in conjunction with an automated attendance monitoring system to monitor attendance of students or other individuals whose whereabouts need to be tracked.

Abstract: An RFID tag-containing apparatus which is capable of alerting a user to leakage of information stored in RFID tags without tailoring the RFID tags. At least one container section is capable of containing at least one article. A receiver section receives information transmitted from an RFID tag attached to the article contained in the container section. When the receiver section receives the information from the RFID tag, a notification signal is output for notifying a user that the information stored in the RFID tag has been be read.

Abstract: A patient activity monitoring system that allows caregivers of multiple patients to work more efficiently and with reduced cost, while increasing the quality and level of patient care. The system includes a plurality of remote monitoring subsystems, a plurality of user notification units, and a central monitoring unit with a Graphical User Interface (GUI) communicably coupled between the remote monitoring and user notification units. Each remote monitoring subsystem includes a remote monitoring unit, and a sensor device associated with a respective patient that detects one or more activity and/or physiological parameters of the patient. A simplified user interface including the GUI and the user notification units provides indications of the type and level of assistance required by one or more patients to caregivers at centralized and remote locations.

Abstract: A system and method for ensuring that a monitored individual is located within a designated area is provided. The system contains a monitoring band having a transmitter capable of transmitting a signal. A transceiver interface unit is also located within the system, which is capable of receiving the signal and determining if the signal is a signal indicating that the monitoring band has been cut or a signal indicating that the transmitter on the monitoring band is functional. The system also contains a monitoring station capable of performing an event if the monitoring station receives the cut-band signal, or if the monitoring station is monitoring the monitoring band, performing the event if the polling signal is not received by the monitoring station within a predefined period of time.

Abstract: A human locator system and method conducts long-range locating with components or steps that are not readily visible on the person of the lost human, and that is fully independent of external communications and power systems. The human subject is provided with a beacon that may be concealed on or in the body, which is activated to produce a signal which may be sensed by a sensor or receiver deployed to scan a field of search in which the human subject may be located. The beacon indicates a signal origination point that is indicative of the location of the human subject by differentiating the human subject in a pre-arranged manner from the background region in which the human subject is located.

Abstract: A device for the early detection and advanced warning that waste is backing up in a waste pipe line comprising: a tubular body member having an open lower portion, a central hollow core extending axially there through, and a closed upper portion. The open lower portion is dimensionally sized and configured to be removably yet sealably fitted and fixed into the waste pipe line. The closed upper portion is provided with a vent.

Abstract: A gas-measuring system is provided that is suitable for both mobile and stationary use. A mobile measuring device (2) with sensors (4, 5, 6, 7) for detecting gas concentrations and a base station (3) are provided for this purpose. The mobile measuring device (2) is inserted into a holder (31) of the base station (3) and the operating functions to the measuring device (2) are now switched over to the base station (3).

Abstract: A system that monitors at least a household electric user, in particular a household appliance, includes a monitoring device that is connected between a source of electric energy and the electric user, the monitoring device including a metering means for detecting one or more electric quantities being associated with the operation of said user, and further including a control means that is programmed for (i) comparing the electric quantity or quantities being measured through the metering means with reference values of said electric quantity or quantities which are stored within the control means; (ii) generating, in function of the comparison, information being representative of the current operating status or phase of operation of the electric user; and (iii) allowing for the reading or transmission of the information to the outside of said device.

Abstract: A device for monitoring a leakage current of a surge arrester has a measuring element for detecting a leakage current in a leakage current circuit. A filter assembly filters the leakage current in order to extract a third harmonic oscillation which is evaluated by an evaluation circuit with respect to the value thereof. The evaluation circuit delivers at least one warning signal to a display device. In a preferred embodiment, three display devices operating as a signaling light are provided. A power supply for the used circuits is obtainable by way of a transformer which extracts a necessary auxiliary zero-potential energy contained in the leakage current and with the aid of a main power supply unit connected to the transformer.

Abstract: A closure for a container comprises means to secure the closure to the mouth of the container and an electronic device. The closure further comprises activation means operative to activate the electronic device when the closure is rotated relative to the container. The closure comprises a lower closure half comprising means to secure the closure to the container, and an upper closure half rotatably mounted on the lower closure half. A container comprising such a closure is also provided. The electronic device could comprise a sound-emitting device, a vibratory device or a light-emitting device.

Abstract: This invention provides a light emitting array apparatus for use in a video screen display or lighting device incorporating a panel having a plurality of LEDs. Such a panel provides a plurality of LEDs on the front face of the panel in close thermal proximity to the panel. Typically this would include LEDs mounted to a PCB that is then affixed to the panel such that heat may transfer from the LEDs into the support panel itself. The support panel can disperse the heat throughout the panel and the to the surrounding air, especially from the front face of the panel. Such a construction may alleviate the need for fans or other cooling apparatus behind the panel and allow for the panel to be fitted directly to a supporting wall or other structure and also reduce cost and bulk of construction.

Abstract: An audio visual homing marker includes a shock-resistant housing with a power supply, audio speaker and LED array inside the housing. A power switch is attached to the housing and the power supply. The housing includes a plurality of bulkheads that create a plurality of chambers. The power supply, the audio speaker and the LED array are each contained within separate chambers. The power switch is biased to the on position. The housing is a generally cylindrical polycarbonate structure and may be a transparent material. The LED array may include a plurality of LEDs attached around the perimeter of the housing. The audio speaker can be a siren or other loud speaker. The LED array may emit a visible or non-visible light. A variety of holders and dispensers make it easy to deploy the markers from a car or aircraft.

Abstract: A LED lighting system for reading multiple data matrix codes on device populated transport media with a line scan camera, includes a light housing, a plurality of LED circuit bars, having a plurality of LEDs, mounted to an inner surface of the light housing arranged to provide high angle lighting and low angle lighting and a light controller operatively connected to the light housing to selectively control the light intensity, the light distribution and the angle of the LEDs on each of the plurality of LED array bars, whereby the LED lighting system can reduce texture noise and detect contrast in color or contrast in texture on the device populated transport media. The LED lighting system includes a device cooling system having an air compressor for cooling the LEDs such that they can operate at an optimal level.

Abstract: A system for providing communication of information by modulating a magnetostatic field with a magnetostatic transmitter that modulates said magnetostatic field to contain the information and detecting the information in the modulated field at a distance with a magnetostatic detector that detects the modulated magnetic field containing the information.

Abstract: An inductive coupling system including a mandrel and an inner sleeve and outer housing that surround and rotate relative to the mandrel. The system also includes a mandrel electronics system and a housing electronics system that communicate electronically using a mandrel inductive coupler and a housing inductive coupler. The mandrel electronics system may also communicate with equipment on the surface. Alternatively, the system may include a mandrel and first and second mandrel electronics systems in different mandrel sections. The first and second mandrel electronics systems communicate electronically using a mandrel inductive coupler. Also alternatively, the system may include a mandrel and an inner sleeve and outer housing that surround and rotate relative to the mandrel. The system also includes a mandrel electronics system and a housing electronics system that communicate electronically using a housing inductive coupler.

Abstract: An automatic meter reading (AMR) system includes a fixed or mobile reader and an endpoint. The endpoint is interfaced to a utility meter and the fixed or mobile reader is capable of communicating with the endpoint via RF communication. In this system the fixed or mobile reader sends a message to the endpoint that includes a response mode direction; the response mode direction from the reader tells the endpoint to respond to the reader either in a mobile network mode or a fixed network mode.

Abstract: A remote energy meter system and method is provided having a meter server and a client module located remotely from the meter server. The meter server communicates with the client via a wireless communications link to recover energy production parameter values. The remote energy meter system preferably provides real-time and automated monitoring of, at least, energy production and system failure parameters.

Abstract: Temperature measurement data obtained by measuring the temperature of a cable clamp (31) by a temperature sensor (320) is radio-transmitted from a temperature sensing unit (32) at a predetermined timing, and the radio-transmitted temperature measurement data is received by a receiving station (5), classified by the temperature sensing unit number, and stored in a temperature measurement data storage area (502A). The temperature measurement data transmitted from twelve temperature sensing units (32) can be received by one receiving station (5).

Abstract: A traffic control system and method, for expediting traffic flow across international border crossings, includes a traffic control center and a virtual traffic lane. The traffic control center is spaced apart from the border crossing, and monitors traffic flow through a border zone. The traffic control center receives border-bound traffic, or electronic information from such traffic, and evaluates it to determine a vehicle's preparedness level. The traffic control center includes facilities for temporarily holding vehicles, and assists vehicles preparing to cross the border. The virtual traffic lane is a preferred route between the traffic control center and the border crossing, and is changeable depending upon traffic conditions. The virtual traffic lane is selected from a number of available monitored routes. The traffic control center monitors traffic conditions in the border zone, and determines which preferred travel route is most appropriate for selection as the virtual lane at any given time.

Abstract: A method for monitoring a number of terminals, particularly parking meters, in which at least first and second adjacent terminals are able to communicate with each other and with a monitoring center, comprises a monitoring protocol according to which the first and second terminals must call each other and, if no call and/or reply is received from the second terminal, the first terminal calls the monitoring center to inform it of an abnormal situation concerning the second terminal.

Abstract: A rotary encoder exhibits a shaft, which can be coupled in torque-proof fashion to a rotating object to be measured. The shaft is connected at a true angle of rotation to a material measure and is divided axially into a drive section (10), which can be coupled to the measured object, and an output section (12), which is connected to the material measure. The drive section (10) and the output section (12) are connected in torsionally rigid but axially resilient fashion by an intermediate element (26), which takes the form of a disk.

Abstract: An object of the present invention is to provide an input apparatus and input key capable of reducing the number of operations on the input key for input of symbols and permitting a user to designate a symbol to be inputted, by a simpler operation. An input key 10a to which a plurality of symbols or marks are assigned, has a key top 30a to be pushed, a sensor part 32 for detecting a push position on a surface of the key top 30 by a finger or the like used to push the key top 30a, a moving direction detector 34 for detecting a change of the push position of the finger or the like detected by the sensor part 32 and for detecting a moving direction of the finger or the like during movement thereof on the surface of the key top 30, and a switch 40a to change a state with a push on the key top 30, and has a converter 50 for converting a state of the switch 40a and the moving direction detected by the moving direction detector 34, into symbol information.

Abstract: A modulation table for converting data with a basic data length of m bits into a variable length code (d,k;m,n;r) is provided. The modulation table includes a basic table for converting data patterns into code patterns and a replacement table for replacing data patterns with code patterns. The replacement table includes minimum-run-successive-occurrence limiting data patterns for limiting the number of times of successive occurrence of the minimum run to N (N>1) or less and minimum-run-successive-occurrence limiting code patterns corresponding to the minimum-run-successive-occurrence limiting data patterns. At least one of the minimum-run-successive-occurrence limiting code patterns includes an undetermined code.

Abstract: Sample rate converters (12) for converting input sample rates (F81) of signals into output sample rates (Fs4) are provided with sample rate adapters (3,6) for adapting (basic idea) intermediate sample rates (Fs2) such that output sample rates (Fs4) are larger (upsampling) or smaller (downsampling) than input sample rates (F81), to reduce their complexity and to avoid bookkeeping and structure switching problems. Sample rate adapters (3,6) in the form of variable sample rate decreasers (3) allow the sample rate converters (12) to be used in video applications requiring DC-out being equal to DC-in. Sample rate adapters (3,6) in the form of variable sample rate increasers (6) allow the sample rate converters (12) to be used in audio applications.

Abstract: A method for serially transmitting data between a first and a second station is provided, the first station unidirectionally transmitting at least two signals to the second station on two signal paths. In this method, a shift register is provided in each station, the two signal paths of the first station being routed in parallel into a shift register, and the data transmission to the second station being carried out by automatically clocking the shift register from a time base.

Abstract: Analog signals can be fully encoded as an asynchronous time sequence generated by a time encoding machine. With knowledge of the parameters of the time encoding machine, the asynchronous time sequence can be decoded using a non-linear time decoding machine. Such a system can be extended into an encoder/decoder in which a signal is processed in M separate channels. An input signal is applied to the encoder where the signal is provided to an M channel encoder circuit including a filter bank having a total bandwidth partitioned among M adjacent or overlapping filters. Each of the M filters are coupled to a corresponding one of M time encoding machines. The encoder output is represented by M sets of time encoded trigger values. The input signal can be recovered from the M sets of time encoded trigger values by applying the trigger signals to a corresponding M channel decoder which includes M TDMs and filters. The TDMs recover the continuous signal from each channel.

Abstract: Circuits, methods, and apparatus for inhibiting non-monotonic output voltage behavior in an R-2R ladder digital to analog converter (DAC). Resistance values of selected resistors of the R-2R ladder are designed to compensate for finite resistances of switches and for variances within the resistances of the resistors and of the switches. The compensating resistance values dampen or eliminate the non-monotonic behavior in the DAC.

Abstract: The present disclosure relates to apparatus and methods for measurement of analog voltages in an integrated circuit. In particular, the apparatus includes an on-chip digital-to-analog converter configured to receive a variable digital input code and output a corresponding analog voltage corresponding to the variable digital input code. The apparatus also includes an on-chip comparator circuit configured to receive the analog voltage output by the digital-to-analog converter and a test analog voltage as inputs and to provide an output indicating the test analog voltage. Further, the apparatus includes an on-chip logic operative to determine the test analog voltage based on the output of the comparator circuit. A corresponding method is also disclosed.

Abstract: Polarity independent precision measurement of an input voltage signal is accomplished using a voltage integrating circuit that receives a first positive reference voltage and the input voltage signal, wherein the first positive reference voltage is greater in magnitude than the input voltage signal. A resetting circuit is coupled to the voltage integrating circuit for stabilizing its output. A pair of comparators, each connected to the output of the voltage integrating circuit, make voltage comparisons against a second reference voltage and a third reference voltage respectively, wherein the second and third reference voltages are greater in magnitude than the first reference voltage. A time interval measurement circuit receives the outputs of the pair of comparators, and operates to measure the time taken for the output of the voltage integrating circuit to transit to the second reference voltage level and the third reference voltage level.

Abstract: An image sensor may be improved by using ADCs that compensate for the effect of comparator input offset on comparator decisions. Offset compensation may be implemented in an ADC by using an amplifier section between the input of the ADC and a comparator section of the ADC to amplify the signals supplied to the comparator inputs and thereby reduce the effect of comparator offset on the comparator decision. The comparator section may be an autozeroing comparator section that is capable of performing an offset reduction operation to store offset compensation values at capacitors provided at its inputs. The amplifier section may be an autozeroing amplifier section having one or more amplifier stages that are capable of performing an offset reduction operation to store offset compensation values at capacitors provided at their inputs. Offset compensation may also be implemented using an autozeroing comparator section without a preceding amplifier section.

Abstract: The invention relates to an electromagnetic radiation absorber for a preselected frequency range, comprising: an absorbent sheet (10) located such that said electromagnetic radiation falls on it, and a conductive base (20) located under said absorbent sheet, wherein said absorbent sheet: has a total thickness e exceeding ?/(?)1/24, where ? is the wavelength of the incident electromagnetic radiation, and is made up of a dielectric material containing amorphous magnetic microwires, the magnetic permeability of which in the preselected frequency range has an imaginary part ?? which is at least 100 times greater than the corresponding real part ??, said microwires being distributed in a volume having a thickness e2 of at least ?/(?)1/216, where ? is the dielectric constant of the absorbent sheet and said volume is located a distance e3 from the conductive base that is not less than ?/(?)1/28.

Abstract: A radar decoy having radar reflectors disposed in the interior of the inflated canopy of a descending parachute as a first set of four corner reflectors, and a second set of corner reflectors disposed on the exterior of the canopy integral with the first set of corner reflectors, to form an octahedron of eight corner reflectors. The radar decoy is pliable and folded with the parachute for stowage in the interior of a canister. When loaded on a vehicle flying in a trajectory, the canister may open at a point P on the trajectory, to release the parachute, and thereby deploy the radar decoy to become operative.

Abstract: In a method for interferometric radar measurement, at least two side looking RADAR systems on satellite and/or missile-supported platforms illuminate a common surface area by means of microwave signals. A first side looking RADAR system sends a first radar signal on a first transmit frequency, and at least a second side looking RADAR system sends at least a second radar signal on at least a second transmit frequency. At least one of the at least two side looking RADAR systems receives the at least two interfering radar signals reflected on the common surface area, determines difference phases of the received radar signals from the interferograms, determines therefrom a drift of a system clock of the at least two side looking RADAR systems, and compensates the determined drift.