Abstract: A portable test system is arranged to enable testing of an aircraft-mounted radar system. Simulated radar returns are transmitted via a test antenna positioned a short distance from an aircraft parked on an airport surface. The varying amplitude of received radar pulses is analyzed as the test antenna is illuminated by the main beam and side lobes of the radar antenna pattern as the radar beam is scanned. By controlling the amplitude of the simulated radar returns in inverse relation to the amplitude of received radar pulses, simulated radar returns inserted off beam center line are interpreted by the radar system as received on the beam center line. Test system transmissions, which may incorporate windshear effect test data, are thus enabled to create simulated effects usable for testing radar system response to a variety of airborne conditions, such as windshear. Test methods are also described.

Abstract: An apparatus for producing an electromagnetic signal which simulates the radar signature of a vertical takeoff and landing vehicle is disclosed. The apparatus contains a means for receiving a radar signal, modulation means for modifying the radar signal, means for dividing the modulated signal into at least a first divided signal and a second divided signal, means for producing a Doppler composite signal, means for mixing the composite Doppler signal with the first divided signal, means for attenuating the second divided signal, and means for combining the attenuated second divided signal and the composite Doppler signal.

Abstract: A wavefront simulator that emulates plane wave propagation from multiple nsmitting antennas is used to evaluate, in both a static and a dynamic manner, an array processor used in RF communications to determine the location of transmitting antennas and possibly to perform beamforming for cancelling the energy of an interfering transmitter. The wavefront simulator generates time delay signals, giving the appearance of being emitted from different transmitters or sources, and simulates those signals as being received by an antenna array associated with the array processor. The array processor utilizes the time delay signals to calculate, e.g., the angle of arrival of the signals from the emitting antennas.

Abstract: A loop simulator is provided for testing radar altimeter systems. Several accurately calibrated delay lines and attenuation elements can be switched into and out of the signal path. Using these elements, the loop simulator can be configured to provide several common tests for radar altimeters. Switching of the various elements is controlled by a microprocessor, which determines the appropriate configuration based upon a mode input, and automatically switches the correct elements into the signal path. The controller automatically compensates for attenuation of the various elements.

Abstract: A radar performance monitor (RPM) receives a transmitted radar signal from a radar system being monitored and couples the signal to a recirculating loop comprising a SAW delay line in order to produce a series of simulated radar return signals of equal amplitude and by using the same frequency as the received radar signal providing the frequency falls within a predetermined bandwidth of the SAW delay line. The simulated radar return signals are displayed at the radar system and used to evaluate the operation and calibration of a transmitter and the sensitivity and calibration of a transmitter and the sensitivity and calibration of a receiver in the radar system. The radar performance monitor is actuated at the option of a radar operator.

Abstract: A moving target simulator is provided for testing a wide variety of radars ithout the need for a direct connection between the simulator and the radar under test. The simulator accurately replicates the pulse width and amplitude of transmitted radar signals and provides a delay feature that permits simulated target scenarios to be presented to a radar under test. The simulator incorporates control features that allow Doppler frequency changes to be accounted for and that permit signal level changes to be made as in accordance with inverse 4th law distance-dependent target-return power variation.

Abstract: An optical acoustic charge transport (ACT) device provides a variable and continuous delay for RF signals. Received RF signals are converted to light and focused onto an optical ACT device. The continous delay is utilized to generate a false radar return.

Abstract: A programmable fiber optic delay system employs multiple programmable fiber optic delay lines, and switches among the delay lines for inclusion in an overall delay path. Switching among the delay lines is coordinated with the programming of those lines so that only a delay line with a settled delay program is included in the overall delay path. Each delay line consists of a plurality of fiber optic segments of varying length. The line's delay is programmed by switching in particular segments whose aggregate lengths correspond to a desired delay period. The multiple delay lines are used to simulate target speed and distance for use in testing a radar system. The programming of each individual delay line and the switching between lines is preferably controlled by a computer resident in the target simulator.

Abstract: An active radar target device is disclosed. This device contains a means receiving a radar signal, a means for decreasing the frequency of the radar signal received, at least one means for delaying the reduced frequency radar signal, means for increasing the frequency of the delayed signal, and means of modulating the delayed signal. The modulated and delayed signal is transmitted to an antenna, from which it may be radiated to a radar detector.

Abstract: A simulated burst echo signal (artificial target), corresponding to a deld and conditioned version of an RF burst signal from an associated radar under test, is presented to the associated radar under test by coupling a portion of the RF burst signal into a shipboard sensor exerciser apparatus in which the present invention is employed to feed an attenuated facsimile of the RF burst signal into a phase-locked loop portion thereof. The phase-locked loop locks on to the attenuated facsimile of the RF burst signal and generates an error signal in response thereto. The error signal is then digitized and stored in an error storage unit portion where it is delayed for a predetermined time associated with the desired selected range of the artificial target.

Abstract: Both a system and a method for simulating targets for a radar system is disclosed herein which generally comprises a test target generator having an input slaved to the pulse transmit frequencies of the radar system for generating a target simulating signal, a horn antenna for emitting the target simulating signal back to the radar receiver, a laser-operated optical transmission link having a single mode fiber optic cable for transmitting the target simulating signal from the test target generator to the horn antenna via optical carrier, and an amplification and processing circuit system connected between the output of the optical transmission link and the input of the horn antenna for increasing the amplitude of the target simulating signal to a level that is detectable by the radar receiver, and for further processing the signal.

Abstract: A transmit pulse delay processor for simulating delayed radar reflections from a target and a method for simulating delayed radar reflections. The pulse delay process utilizes a counter, an adder, a FIFO and a comparator. The pulse delay processor maintains input pulse width and features a programmable delay. The depth selected for the FIFO determines the number of transmit pulses that can be simultaneously delayed. The frequency of the resolution clock clocking the counter and the number of bits in the counter can be selected both to accommodate the length of delay required and to achieve better output pulse accuracy. The pulse delay processor has various applications, but is particularly useful in radar simulation where multiple input pulses must be simultaneously delayed.

Abstract: The present invention provides a radar simulation system with at least two counters. The first counter is a coarse counter 20/30 that counts a transmit pulse interpulse periods to provide a coarse return delay at the beginning of a radar look. The second counter is a fine counter 22/36 which counts, after the coarse counter has counted down to zero, from each subsequent transmit pulse to the time for the return pulse. Once the coarse counter has finished counting, the fine counter, which can be reset and reloaded during the look responsive to each transmit pulse, can provide return targets repeating at the same distance at the pulse repetition frequency. A cyclic counter 24 can also be added that produces the return pulses by cyclically counting the interpulse period one the fine counter has timed out. If the cyclic counter is used the fine counter is not reloaded during the look.

Abstract: A radar test set target which is co-located with the radar and produces a faithful replica of the radar signal substantially delayed in time. The radar signal modulates a laser light which is controllable delayed in time by transmitting the modulated laser light through a fiber optic delay line. The output of the delay line is demodulated and the extracted and delayed radar signal is returned to the radar as a test signal.

Abstract: A sweep frequency, continuous wave (CW) radar tank gauge (3) providing measurement of the level of tank contents or ullage (19), having greatly improved accuracy through improved methods of processing calibrate and return signals directed toward the surface of tank contents (20). Use of sweep synchronous measurement (46) of time domain calibrate/return difference signals (42) and time domain of a virtual "carrier" fundamental in the frequency domain, provide highly accurate measure of tank signal return times. The entire range of return signals is made available for processing and analysis (5), including distinguishable tank bottom reflections.

Abstract: Proper operation of a system fault monitor is verified while the monitor is coupled on-line with the system and to an alarm line. During periods when actual system signals are produced, the monitor is coupled through one of two time delay circuits to the alarm line. During periods when no actual signals are produced by the system, the monitor input is switched to an error signal generator and the monitor output is coupled through the other time delay circuit to processing circuitry which detects the presence of the alarm signal after the circuit time delay. If no alarm signal is detected, a failure of the monitor and/or delay circuit is indicated.

Abstract: A sweep frequency, continuous wave (CW) radar tank gauge (3) providing measurement of the level of tank contents or ullage (19), having greatly improved accuracy through improved methods of processing calibrate and return signals directed toward the surface of tank contents (20). Use of sweep synchronous measurement (46) of time domain calibrate/return difference signals (42) and determination of a virtual "carrier" fundamental in the frequency domain, provide highly accurate measure of tank signal return times. The entire range of return signals is made available for processing and analysis (5), including distinguishable tank bottom reflections.

Abstract: A device for imparting a selected delay to a pulse emanating from a transmitter before the pulse is returned as a simulated radar echo to a radar altimeter receiver. The selected delay is obtained by recirculating the transmitted pulse through a fixed delay element a prescribed number of times. The system includes a control circuit, including a single-pole, double-throw electronic switch coupled to a presettable counter which may be preloaded with a count value corresponding to the number of iterations of the transmitted pulse through a closed loop including the delay elements. Upon each such traversal, the counter is decremented and when the counter generates a borrow signal, the electronic switch diverts the pulse to the altimeter's receiver. The recirculation loop also includes pulse amplifying and shaping circuitry for compensating for attenuation and distortion of the recirculating pulse.

Abstract: An FM-CW range measuring apparatus (1) to be tested generates a beat signal Fb at the frequency fb between transmitted and received waves. A simulator connected to this apparatus comprises a signal processing link, including a first HF interrupter (6), a circulator (7) and a second HF interrupter (8). A delay line (11) operating in the reflecting mode for producing the delay .tau. is connected to an input-output of the circulator means for controlling the interrupters (26, 28, 29, 33) effect opening thereof at a frequency f.sub.r (f.sub.r >2b), the first interrupter being opened during .delta. (.delta.<<1/f.sub.r), and the second interrupter during .delta.' (.delta.'.perspectiveto..delta.). The phase shift .tau.' between .delta. and .delta.' is such that the durations .delta. and .delta.' are separated from each other and that at least an echo of the order p in the delay line is defined by the equation:p.multidot..tau..perspectiveto.f/f.sub.r +.tau.'where k is a small integer.

Abstract: The invention concerns a method and an apparatus for measuring the level of a material with microwave signals. The apparatus consists of a signal processing unit (10) and a transmitter unit (1) of known type. The transmitter unit produces a measuring signal having a frequency (f.sub.m) corresponding to the distance (H) to be measured and a reference signal having a frequency (f.sub.r) corresponding to an accurately known length (L). In the signal processing unit (10) the reference signal is multiplied by a selectable number (AQ) which is proportional to the quotient of an assumed value for the distance divided by the known length (L), after which the frequency is divided by a fixed number (Z) so that the frequency of the signal after multiplication and division becomes equal to the expected frequency of the measuring signal.

Abstract: A simulator is provided for testing a radio altimeter of the type which emits a frequency-modulated wave, the modulation being according to linear segments of slope p, and which compares the frequencies of the emitted wave and of the wave which is received after reflection to provide a distance measurement. The simulator according to the invention is connected between the transmitting antenna and the receiving antenna of the altimeter, and comprises two signal-processing chains which are arranged, in parallel, between a receiving section and an SSB mixer, the output terminal of which is connected to a transmitting section. The first chain is formed by first devices, which generate a quantity G, which is proportional to p, and second devices, which generate a signal possessing a frequency f.sub.d, the ratio of f.sub.d and G assuming a predetermined, adjustable ratio, Q. The second chain is formed by a coupler which is connected to a variable attenuator.