Abstract: A stabilizing method of a synthetic aperture radar and a position determining method by the radar. At least three repeaters are arranged in mutually different positions on the ground or the sea and a radio frequency signal having a predetermined frequency is transmitted from the radar mounted on a radar platform such as an aircraft to the repeaters. Each repeater frequency-modulates and amplifies the received signal to return the signal to the radar. The radar receives the signal returned from each repeater. The radar calculates a distance between the radar platform and each repeater on the basis of a time required for the transmitting and the receiving and phase information of the received signal. When the position of each repeater is known, by using the positions of the repeaters and the calculated distances, the position of the radar platform can be calculated. On the basis of the obtained position of the radar platform, a reference signal for phase compensation is generated.

Abstract: A route predicting apparatus for monitoring a flying target and predicting a route thereof. Even if the target is hidden by mountains or other obstacles thus preventing observation for a certain time, a reliable route prediction is carried out by utilizing the fact that a route of the target is restricted by geographical features. The apparatus comprises an observation unit for observing a target and outputting an observed value thereof, a terrain information unit for outputting characteristic parameters of stored terrain information, a prediction unit coupled to receive the observed value and the characteristic parameters of terrain information for performing a fuzzy inference to output a predicted observed value of the target, and a learning adjustment unit coupled to receive an error signal between a predicted observed value at the current time predicted a unit time before and a real observed value at the current time for adjusting the prediction unit by using a neural network.

Abstract: A synthetic aperture radar system is mounted in a moving platform. The synthetic aperture radar system includes a multi-beam antenna having a plurality of reception beams different in direction from one another, the multi-beam antenna being adapted to receive radar echoes from objects. The width of each of the reception beams is selected such that the band width of a Doppler shift contained in the radar echo of a moving object is broader than that of a Doppler shift contained in the radar echo of a stationary object. The radar echo is pulse compressed to improve the range resolution before the frequency thereof is shifted such that the center frequency of the Doppler shift due to the velocity of the moving platform becomes zero. After the frequency shifting, the radar echo is filtered to separate the radar echoes of the moving and stationary objects from each other.

Abstract: An unwanted signal suppression device is disclosed for suppressing unwanted signals in input signals containing desired and unwanted signals. The input signals are divided into segments in the time domain. The device includes a unit for detecting the segment having maximum power, a unit for computing reflection coefficients on the basis of the segments except the detected power segment, and a lattice filter for suppressing the unwanted signals by using the computed reflection coefficients. A second device includes a reflection coefficient computing unit, a median filter and a lattice filter. A third device includes a unit for estimating unwanted signals frequency, a filter for computing filter weights on the basis of the estimated frequency and filter coefficients and for applying the computed weights to the input signals so as to suppress the unwanted signals.

Abstract: A pulsed Doppler radar system comprises a transmitter for generating and transmitting a pulse signal having expanded frequency bandwidth, an antenna apparatus for sending the output of the transmitter to a target and for receiving a signal which was sent by the transmitter and reflected by the target, a receiver for processing the received signal to obtain a complex video signal, a pulse compressing circuit including a pulse Doppler processor responsive to the complex video signal for detecting a relative speed of the target and a storage device for storing a reference signal which includes a compensation factor by which an influence of the Doppler effect is compensated in accordance with the speed of the target.

Abstract: A radar system having a phased array antenna for transmission and a digital beam forming antenna for reception for observing a plurality of targets by transmitting transmission pulses to the respective targets comprises a subtraction control circuit, a transmission timing control circuit and a transmission beam direction control circuit. The substraction control circuit calculates a required number of transmission pulses (beams) to be transmitted for each of transmission cycles in accordance with detected Doppler frequencies of the targets, so as not to cause ambiguity on the detected Doppler frequencies, and determines a beam direction for each of transmission beams. The timing control circuit and beam direction control circuit control transmission timing and direction of the beams.

Abstract: A synthetic aperture radar system wherein a plurality of beams is formed for receiving echo signals and the spectra of the received signals are synthesized in an azimuth compression unit to improve the cross-range resolution.

Abstract: The receiving apparatus of a spotlight mapping radar system is provided with a digital beamforming antenna capable of converting the echo signals received by a plurality of antenna elements into corresponding digital signals and processing them by DFT and forming a plurality of reception beams oriented in different directions at the same time to enhance the cross-range resolution without reducing the distance measurement capability and the measurable range. Pulse compressors, azimuth compressors, display buffers and reference signal generators are provided respectively for each of the outputs of the digital beamforming antenna for outputting the plurality of reception beams. An output picture synthesizing apparatus synthesizes signals representing the picture information from the respective display buffers and outputs the synthesized signals to a display to display thereon the synthesized picture of an object to be observed.