Abstract: A radar target simulator front end, configured to simulate at least one radar target for testing a radar device under test is provided. The radar target simulator front end comprises at least two antenna units, arranged along a first angle under investigation. The at least two antenna units are configured to be selectively activated and deactivated. Whereby each antenna unit of the at least two antenna units generates a simulated radar target along the first angle under investigation, when activated.

Abstract: A miniature radar target simulator (MRTS) and a system comprising a plurality of MRTS's are described. The MRTS and system are useful for emulating echo signals for a radar DUT with reduced interference. Illustrative radar test systems desirably generate the intended (emulated) radar targets and reduce unwanted (“ghost”) signals, which can result in “ghost targets,” and errant/ambient electromagnetic radiation that reduces the performance and reliability of known re-illuminators and systems including same.

Abstract: A testing device for testing a distance sensor that operates using electromagnetic waves includes: a receiving element for receiving an electromagnetic free-space wave as a receive signal (SRX); and a radiating element for radiating an electromagnetic output signal (STX). In a test mode, a test signal unit generates a test signal (Stest), and the radiating element is configured to radiate the test signal (Stest) or a test signal (S?test) derived from the test signal (Stest) as the electromagnetic output signal (STX). In the test mode, an analysis unit is configured to analyze the receive signal (SRX) or the derived receive signal (S?RX) in terms of its phase angle (Phi) and/or amplitude (A) and store a determined value of phase angle (Phi) and/or amplitude (A) synchronously with the radiation of the test signal (Stest) or of the derived test signal (S?test) as the electromagnetic output signal (STX).

Abstract: A transmission apparatus according to an embodiment includes a power amplifier, an antenna switch, and a control circuit. The power amplifier amplifies and outputs a transmission signal. The antenna switch switches, among at least two or more antennas, an antenna configured to output the transmission signal from the power amplifier. The control circuit performs output power control of the power amplifier when the control circuit outputs to the antenna switch a switching control signal for switching the antenna.

Abstract: A simulation system for use in testing a radar system comprises a coarse delay module, a fine delay module, and a doppler shift module. The coarse delay module is configured to receive a first stream of digital data samples that are sampled from a radar signal at a sample time period or a second stream of digital data samples that are processed by another simulation system component and delay the digital data samples by a selectable first delay time that is greater than or equal to the sample time period. The fine delay module is configured to receive the digital data samples and filter the digital data samples to represent delay by a selectable second delay time that is less than the sample time period. The doppler shift module is configured to receive the digital data samples and adjust a value of a frequency content of the fine delayed samples.

Abstract: A system for testing vehicular radar is described. The system include a diffractive optical element (DOE) configured to diffract electromagnetic waves incident on a first side from a radar device under test (DUT). The system also includes a re-illumination element adapted to receive the electromagnetic waves diffracted from the DOE from a second side. The re-illumination element being adapted to transmit apparent angle of arrival (AoA) electromagnetic waves back to the DOE.

Abstract: A radar sensor head for a radar system. The radar sensor head includes at least one transmitting antenna for generating and at least one receiving antenna for receiving radar waves; a preprocessing unit for defined preprocessing of received data; an interface for connecting the radar sensor head to a data line; and a calibration data unit for at least partially calibrating the transmitting antenna and/or the receiving antenna, calibration data for the transmitting antenna and the receiving antenna being stored using the calibration data unit.

Abstract: Methods and systems for generating and utilizing an emulated radar data cube are disclosed. An emulated radar transmission waveform is defined based on expected radar performance. A virtual real world scenario comprising one or more virtual target objects is constructed. The virtual target objects emulate reflection and scattering properties to an input radar wave of real world objects. Operations of radar transmit and receive channels including an antenna array and free space propagation are emulated to obtain emulated raw radar data. Data processing is performed on the emulated raw radar data to build an emulated radar data cube. The emulated radar data cube is utilized to test a radar perception algorithm.

Abstract: An improved superheterodyne receiver for a portable radio is provided. The receiver includes a frequency controller that applies pulse-shaped modulation to first and second LO signals in a synchronized manner. The frequency controller is steered by Artificial Intelligence (AI) based machine learning (ML) to determine first and second LOs that minimize image interference in the baseband signal.

Abstract: A system for testing automobile radar sensor configurations includes multiple probe arrays, multiple enclosures, a channel emulator and a test controller. The enclosures each enclose one of the probe arrays together with a corresponding different automobile radar sensor. Each probe array is configured to receive radar signals from the corresponding automobile radar sensor and emulate echo signals back to the corresponding automobile radar sensor. The channel emulator is configured to supply the echo signals to each of the probe arrays. The test controller includes a memory that stores instructions and a processor that executes the instructions. The test controller controls the channel emulator and is configured to perform performance testing on an automobile radar sensor configuration that includes the automobile radar sensors and an automobile driving controller that reacts to the echo signals received by each of the automobile radar sensors.

Abstract: An automotive testing method includes acquiring radar sensor data responsive to a radar excitation signal generated by a radar transmitting unit, forwarding the acquired radar sensor data to an electronic system of a radar receiving unit, generating radar data from the forwarded radar sensor data, and processing the radar data, wherein the step of acquiring radar sensor data includes generating synthetic radar data, the synthetic radar data being forwarded as radar sensor data to the electronic system of the radar receiving unit, where the synthetic radar data includes reflection signals, preferably all reflection signals, in a complex time series, that succeed each other and have the same temporal behavior within a synthetic period that lasts at least an order longer than a time period of the radar excitation signal.

Abstract: A device for simulating at least one echo signal of a signal is described, said device comprising an input for receiving the signal, a signal manipulation unit and an output for transmitting the signal processed by said signal manipulation unit. Said signal manipulation unit is configured to add a delay to the signal, to change the frequency of the signal and/or to change the amplitude of the signal. Said device further comprises at least one bandwidth changing unit. Said bandwidth changing unit is configured to change the frequency bandwidth of the signal. In addition, a system and a method for simulating at least one echo signal of a signal are described.

Abstract: A wireless communication system, in some embodiments, comprises: a receiver; one or more tunable elements, coupled to the receiver, to adjust an impedance of the system; and a processor, coupled to the one or more tunable elements, to tune said one or more tunable elements based on the strength of a received signal.

Abstract: An electromagnetic radiation measuring device includes a test antenna module and a main processor electrically connected to the test antenna module. The test antenna module includes a plurality of pre-test antennas and at least one final test antenna, which have predetermined polarities and are positioned at predetermined heights, respectively. The pre-test antennas and the final test antenna respectively receive wireless signals sent from an electronic device. The main processor measures and records a frequency of the strongest wireless signal received by selected ones of the pre-test antennas that have the same polarity, and further determines whether power of wireless signals at the recorded frequency received by the final test antenna polarized to have the same polarity as that of the selected ones of the pre-test antennas exceeds a predetermined acceptable range.

Abstract: A calibration system for a dual polarization radar system with built in test couplers has been developed. The system includes a dual polarization radar transmitter antenna that generates a transmission pulse. A test coupler is located behind the antenna that reads a sample of the transmission pulse a test signal. A calibration circuit receives the sample of the transmission pulse and generates a test signal that simulates a desired atmospheric condition. Finally, a test antenna transmits the test signal to the dual polarization radar transmitter antenna for calibration of the system.

Abstract: According to one embodiment, simulating the mutual performance of an antenna array coupled to an electrical drive circuit includes receiving one or more cross-coupling matrices and a number of electrical circuit parameters. Each cross-coupling matrix comprises matrix elements that each represent a cross-coupling factor of one antenna element to another antenna element of the antenna array. The electrical circuit parameters model one or more characteristics of the electrical drive circuit. Performance of the microwave antenna array and the electrical drive circuit in a far-field environment is modeled according to the electrical circuit parameters and the cross-coupling matrices.

Abstract: A system for testing radio frequency (RF) communications of a device capable of such communications is provided. The system includes a chamber for isolating the device from RF interference, an antenna that is suitable for RF communications with the device wherein the antenna is capable of communications over a range of frequencies, the antenna being located within the chamber, and a digital communication link for providing non-RF communications with the device.

Abstract: The present invention provides a method and system of analyzing radar information of a radar system. According to certain embodiments of the invention, the method comprises: providing radar information including at least a portion modified in response to an EWE (electronic-warfare) action; obtaining position data corresponding to at least a position of a target associated with the EW action with respect to the radar system; and analyzing the radar information for comparing it with the position data, thereby allowing to determine at least one effect of the EW action on the radar information.

Abstract: A millimeter wave radar target simulation system and method. The system includes a down-converter that converts a millimeter wave radar signal to an intermediate frequency, an electrical-to-optical modulator that modulates an optical signal based on the down-converted signal, an optical-to-electrical demodulator that demodulates an optical signal to an electrical signal, an optical delay line serving to delay a signal passing from the electrical-to-optical modulator to the optical-to-electrical demodulator, and an up-converter that converts the electrical signal from the optical-to-electrical demodulator to a frequency that simulates a millimeter wave target return.

Abstract: The invention discloses a simulating measurement apparatus. The simulating measurement apparatus comprises a storing module, a controlling module, and a simulating module. The storing module is used for storing simulating parameter information. The simulating parameter information comprises at least one emitting simulating parameter, at least one receiving simulating parameter, and a radio beam channel transmitting simulating parameter. The controlling module generates a controlling signal according to the simulating parameter information. The simulating module generates a simulating measurement result of radio beams transmitted in the space between an emitting antenna and a receiving antenna by simulating the transmitting behavior of a plurality of RF signals according to the controlling signal.

Abstract: A distributed test system for implementing enhanced BIT (Built-In-Test) within an ESM (Electronic Surveillance Monitoring) or RF receiver system. The distributed test system includes a system processor, a programmable RF source element or other comparable test signal generating arrangement, and switched path coupled elements and various measurement elements, each embedded at strategic locations within the ESM system so as to effect maximum path coverage and test benefit.

Abstract: The invention concerns a method and apparatus for estimating a height of a target object using radar signals reflected from the target object wherein a receiver detects a plurality of radar signals reflected from the target object, respectively, at a plurality of different ranges, resolves the amplitudes of the plurality of reflected signals at the respective plurality of different ranges to generate an amplitude data set, and determining if the amplitude data set correlates to a particular height.

Abstract: An apparatus for use in controlling a simulated target position in a millimeter wave, hardware-in-the-loop system includes a pair of horns and a conditioning circuit. The conditioning circuit is capable of generating a pair of output millimeter wave signals, each to be broadcast from a respective one of the horns, the output millimeter wave signals being out of phase by a predetermined amount, and capable of attenuating at least one of the output millimeter wave signals to control the position of the simulated target in a first and a second region. A method for use in controlling a simulated target position in a millimeter wave, hardware-in-the-loop system includes generating a pair of output millimeter wave signals that are out of phase by a predetermined amount; attenuating at least one of the output millimeter wave signals to control the position of the simulated target in a first and a second region; and broadcasting the millimeter wave signals.

Abstract: An apparatus for use in controlling a simulated target position in a millimeter wave, hardware-in-the-loop system includes a pair of horns and a conditioning circuit. The conditioning circuit is capable of generating a pair of output millimeter wave signals, each to be broadcast from a respective one of the horns, the output millimeter wave signals being out of phase by a predetermined amount, and capable of attenuating at least one of the output millimeter wave signals to control the position of the simulated target in a first and a second region. A method for use in controlling a simulated target position in a millimeter wave, hardware-in-the-loop system includes generating a pair of output millimeter wave signals that are out of phase by a predetermined amount; attenuating at least one of the output millimeter wave signals to control the position of the simulated target in a first and a second region; and broadcasting the millimeter wave signals.

Abstract: The present invention relates to a method for calibrating the phase of a microwave source, in which: a calibration circuit is closed, the calibration circuit comprising an injection channel connected to a measurement channel via the source to be calibrated; a test signal is injected through the source to be calibrated, the test signal being injected on the injection channel, the phase ?m of the signal having passed through the source to be calibrated is measured, the phase of the signal being measured on the measurement channel, wherein: the amplitude Am of the signal having passed through the source to be calibrated is measured, the amplitude of the signal being measured on the measurement channel; The calibration circuit is opened at the source to be calibrated; the test signal is injected on the injection channel; the phase ?f and the amplitude Af of the signal present on the measurement channel is measured; a corrected phase value ?c is determined, this corrected phase being the phase of a complex number

Abstract: Systems and methods enable numerically creating a flat field in a compact radar range with a curved reflector, and without use of a separate phased array of elements, at frequencies lower than those that are possible with currently known, reflector-only compact radar ranges. A compact radar range is calibrated to enable weighting factors to be computed. The weighting factors may be computed by performing an optimization algorithm. The weighting factors are used to weight separate target signals sequentially returned from a target zone such that, when combined, a numerically composite measurement has a substantially constant magnitude across the target zone.

Abstract: The present invention relates to a monitoring device (1) with a transmitter unit (2) and a receiver unit (3) for monitoring an area. Slotted cables serve as antennas. According to the invention, a first slotted cable is arranged as a transmitting an antenna (4) for transmitting a pulsed high-frequency signal and a second slotted cable is arranged as a receiving antenna (9) for receiving the reflected signal. The slotted cables are arranged in association with each other and essentially parallel to each other, and the transmitter unit (2) is connected to the first slotted cable at one end of the antenna arrangement and the receiver unit (3) is connected to the second slotted cable at the other end of the antenna arrangement.

Abstract: A complex radar target emitter having independent control of three radio frequency (RF) radiation field characteristics, the radiation field characteristics being the real and imaginary components of the complex amplitude of the radiation field, the spatial derivative of the real and imaginary components of the complex amplitude in one of two orthogonal planes, and the spatial derivative of the real and imaginary components of the complex amplitude in the other of the two orthogonal planes.

Abstract: Apparatus and a method for radiometric temperature measurement comprises a radiometer receiver coupled to an antenna/calibration switch that has coupled thereto a brightness temperature signal. A driver coupled to the antenna/calibration switch controls the operation of the switch between an antenna mode and a calibration mode. An adjustable cold/warm noise source is coupled to the antenna/calibration switch to provide a calibration radiation temperature applied through the antenna/calibration switch in the calibration mode to the radiometer receiver. An output of the radiometer receiver is coupled to the adjustable cold/warm noise source and is adjusted in accordance with the output of the radiometer receiver for a null comparison measurement. Also coupled between the output of the radiometer receiver and the antenna/calibration switch is a mode selector switch that operates to a mode one position to couple the output of the radiometer receiver to the adjustable cold/warm noise source.

Abstract: A system for calibrating airborne direction finding antenna arrays eliminates the problem of trying to maintain a constant depression angle when flying an airplane directly over a calibration antenna to collect deep depression angle data. The deep depression angle data necessary for calibration is provided by data from a scale model of the aircraft having a direction-finding array which simulates the actual direction-finding array on the aircraft. In order to collect deep depression angle data, the model is pivoted through 360° while maintaining a controlled depression angle. Thus, it is unnecessary for calibration to actually fly a plane to attempt to obtain deep depression angle measurements. In the subject system, only a single depression set of data is required from the aircraft. Thus, with the exception of baseline shallow depression angle data from this plane, the calibration data comes strictly from the scale model, which is much more easily obtained.

Abstract: A device for generating a desired transit time delay of a pulsed radar signal is characterized in that a delay line (13) with signal input and signal output for the pulsed radar signal is provided whose transit causes time delay &tgr; of the pulsed radar signal, that a signal amplifier (14) is connected downstream of the delay line which increases the amplitude of the pulsed radar signal by a certain amplification factor f, and that a decoupling device (12) is provided which permits supply of at least part of the amplitude of the pulsed radar signal coming from the signal output of the signal amplifier to the signal input of the delay line again and which permits, after n times transit of the pulsed radar signal through the delay line, decoupling of at least part of the amplitude of the pulsed radar signal, wherein T=n·&tgr; and wherein n is a natural number.

Abstract: A method for simulating a Doppler signal under stationary conditions is described. The method includes sampling a radar return signal at an integer multiple of the return signal frequency plus a fraction of the return signal period and generating a base band signal from the samples.

Abstract: An apparatus for electronic warfare signal simulation which is used in an external test system to simultaneously test a plurality of “victim” communication systems for vulnerability to jamming. The test system includes a remote radiator of a signal free of jamming effects, and a remote radiator of one or more radio frequency control signals which represent one or more predetermined jamming threats in the low and mid bands.

Abstract: A device for generating a desired transit time delay of a pulsed radar signal is characterized in that a delay line (13) with signal input and signal output for the pulsed radar signal is provided whose transit causes time delay &tgr; of the pulsed radar signal, that a signal amplifier (14) is connected downstream of the delay line which increases the amplitude of the pulsed radar signal by a certain amplification factor f, and that a decoupling device (12) is provided which permits supply of at least part of the amplitude of the pulsed radar signal coming from the signal output of the signal amplifier to the signal input of the delay line again and which permits, after n times transit of the pulsed radar signal through the delay line, decoupling of at least part of the amplitude of the pulsed radar signal, wherein T=n·&tgr; and wherein n is a natural number.

Abstract: A dual port memory waveform generator system uses a clock-based system whose pulse durations and separations were set by counters that use the same fundamental clock frequency of the radar to be simulated. This pulse generator is loaded from a laptop computer. The output pulses are used to control pin switches to switch various frequencies, amplitudes, or phases as required for the particular radar being simulated. The result is a system with very good fidelity that will fit in a suitcase, and is very portable.

Abstract: The method of controlling travel speed of a vehicle includes controlling vehicle travel speed according to a set vehicle speed given by a driver of the controlled vehicle in a speed control mode; detecting at least one object present in front of the controlled vehicle and measuring distance to and relative speed of the at least one object when present in front of the controlled vehicle; determining whether or not a preceding vehicle is among the at least one object present in front of the controlled vehicle; controlling the vehicle travel speed according to a set distance to the preceding vehicle in a distance control mode when the preceding vehicle is present in front of the controlled vehicle; establishing whether or not a stationary object is among the at least one object present in front of the controlled vehicle; when a stationary object is found to be present, calculating a predicted travel path of the controlled vehicle and determining if the stationary object is located in the predicted travel path; w

Abstract: An antenna test range uses direct spread-spectrum based test signals to test the performance of an antenna. Since a spread spectrum waveform has high autocorrelation properties with itself and high cross-correlation properties with signals other than itself, in the receiver coupled to the antenna it is possible to effectively electronically reject all unwanted signals that may be present in the test range, and thereby allow both main beam and off-axis performance of the antenna to be completely and accurately measured.

Abstract: A method and device for testing the function of a radar. A diode (21) with variable radar radiation impedance is arranged in the beam path (23) inside the antenna unit (4, 6) of the car radar and is fed with alternating current for simulating a radar target at a distance from the antenna unit. The obtained target data for the simulated target are compared to the expected target data for testing the function.

Abstract: A linear phase detector circuit enables locking of two frequency sources which can operate in the range of 10 GHz with a minimal frequency offset, such as from 0 Hz to 50 KHz. With the frequency sources operating at frequencies F1 and F2 with an offset F2−F1 or F1−F2, the phase detector generates a DC signal indicating a phase offset between a signal F2−F1 or F1−F2 derived from the frequency sources and a reference operating at the desired offset F2−F1 or F1−F2, while eliminating any 2(F2−F1) or 2(F1−F2) component. In this way, the phase detector allows a substantially higher loop bandwidth than the offset F2−F1 or F1−F2, and allows phase tracking independent of the offset. The phase locking circuitry is useful in applications such as providing a variable Doppler shift in a radar signal.

Abstract: An automated simulator for radar and sonar applications. The inventive simulator is implemented in hardware and generates current parameters with respect to a simulated target in response to a plurality of initial values with respect thereto. In the illustrative embodiment, the initial values include range, velocity, and acceleration and are stored in first, second and third register respectively. In the best mode, the invention is implemented in a field-programmable gate array. The inventive target simulator also includes a range delay circuit for generating a simulated return from the simulated target. The range delay circuit includes logic for determining whether a simulated pulse train to be received is ambiguous or unambiguous and adjusting the pulse repetition rate of the pulse train accordingly. The range delay circuit calculates die initial time that a packet needs to make the trip to and from the target.

Abstract: A system is disclosed for generating simulated radar targets that eliminates the necessity for large outdoor test ranges and is relatively low in cost. The simulated radar target generating system provides complex targets of given simulated dimensions at given simulated distances when stimulated by signals emitted by the radar sensor in the sensor's operational frequency. The dimensions are simulated by the use of multi-tap delay device while the distances (or, range) are simulated by routing the signal, in the form of light, through a fiber optic delay of a desired length. This system, which costs less than $50 thousand, can be located as close as eight feet to the sensor under test.

Abstract: An apparatus and method for generating an electromagnetic environment in which the free field, plane wave response of electronic systems of an electrically large (greater than several wavelengths in its longest dimension) object, or objects, under test can be measured in the electromagnetic radiating near field of the transmitter array apparatus. The apparatus comprises: (1) one or more transmitting station(s), each station home to an array of radiating elements; (2) a software operating system and computer that controls the electronic circuits of the apparatus and executes an optimizing algorithm based on a Genetic Algorithm to control the radiation of each transmitting station; and (3) mechanical and electrical circuits that enable the apparatus to conduct self calibration and adjustment as required. In operation, the apparatus is placed and distributed about an object under test.

Abstract: An antenna test range uses direct spread-spectrum based test signals to test the performance of an antenna. Since a spread spectrum waveform has high autocorrelation properties with itself and high cross-correlation properties with signals other than itself, in the receiver coupled to the antenna it is possible to effectively electronically reject all unwanted signals that may be present in the test range, and thereby allow both main beam and off-axis performance of the antenna to be completely and accurately measured.

Abstract: An antenna test range uses direct spread-spectrum based test signals to test the performance of an antenna. Since a spread spectrum waveform has high autocorrelation properties with itself and high cross-correlation properties with signals other than itself, in the receiver coupled to the antenna it is possible to effectively electronically reject all unwanted signals that may be present in the test range, and thereby allow both main beam and off-axis performance of the antenna to be completely and accurately measured.

Abstract: A digital radar landmass simulator (DRLMS) used for stimulation testing pulse radars, wherein the DRLMS operates by synthesizing time-overlapping chirp waveforms using finite impulse response filters. The DRLMS, thus, effectively generates many overlapping complex pulse signals from many radar reflectors representing a semi-infinite continuum of closely spaced targets. The DRLMS also allows the insertion/injection of the effects of Doppler shift and jamming into the synthesized modulated signal.

Abstract: A method and apparatus for testing an antenna control system. The antenna control system having an antenna control unit electrically coupled to an antenna pedestal. The present invention simulates the operational environment of the antenna control system and records the systems responses to the simulation. The responses are then analyzed and the antenna control system is adjusted to correct errors.

Abstract: A moving target simulator system for pulse Doppler radar includes a processor for processing received radar signal and transforming the signal into patterned pulses before subjecting the patterned pulses to an 180 degree phase-shift by a phase-shifter. The system also includes a reference signal provided by a corner reflector located in proximity of the simulator. The reference signal and a phase-shifted signal from the simulator are processed by the radar equipped with a phase corrector circuitry to correct a phase drift problem associated with the use of a small antenna with the simulator.

Abstract: The electromagnetic target generator of this invention is used to simulate radar target for the purpose of testing and experimenting on a variety of weapon systems radars. The weapon system radar being tested emits a radar signal which is received by the target generator. The target generator delays, doppler shifts, and reemits the signal for receipt by the weapon system antenna. The simulated target presented to the radar system under investigation has digitally controlled range, radial velocity, coordinated doppler and radar cross section. This provides a realistic radar target return without requiring real targets. The radar system is exercised in inflight and tactical operational configuration and no part of the weapons system radar is bypassed. Delayed radar target replicas are indistinguishable from real target waveforms. The electromagnetic target generator may be used in locations which preclude the use of real radar targets, such as anechoic chambers, and also may be used in the field.

Abstract: A system is tested for jamming resistance by supplying a simulated jamming ignal. The simulated jamming signal is produced by calculating a propagation path loss in the terrain between the system under test and a location where the jammer would be, predicting a jamming level in accordance with the propagation path loss, and generating a simulated jamming signal. The simulated jamming signal is supplied to the antenna port of the system under test. The testing does not require the use of either a real jammer or a pilot signal generator at the location where the jammer would be.

Abstract: A photonic radar decoy (50) is provided which simulates an aircraft to a radar having an interrogating signal. A plurality of receiving antenna (52, 54, 56, 58, 60) are attached to the decoy (50) with each of the receiving antenna (52, 54, 56, 58, 60) independently capable of receiving the interrogating signal from the interrogating radar system. Each signal received by an antenna (52, 54, 56, 58, 60) is transmitted to a signal combiner and amplifier (82) by delay lines (72, 74, 76, 78, 80). The combiner and amplifier (82) coherently adds the transmitted signals, thereby producing a coherent signal which is amplified and subsequently emitted by a non-directional transmission antenna 106, simulating a dynamic and complex radar signature of an aircraft.