Alliedsignal Inc.

Arezki Manseur

Ruy L Brandao

William C Weist

Randall C Spires

Steven R Sweet

Henri Baran

Philip R Hermann

Phillip R Hermann

A method for removing clutter related frequency components from power spectrums generated from weather radar return signals to provide improved windshear detection capability. Weather radar return signals are synchronously detected and digitized to provide i and q time domain sample sequences. The i and q time domain sample sequences are passed through a window function and then transformed to frequency domain sequences by a Fast Fourier Transform. A power spectrum is generated from the frequency domain sequences. The spectrum is subjected to a Spectral Gaussian Envelope Discrimination (SGED) process in which the spectral envelope is scanned to identify any lobe therein having a slope greater than a predetermined minimum. A first pseudo-Gaussian sigma, calculated from the width and maximum amplitude of any such lobe, is compared with a second pseudo-Gaussian sigma, calculated from known conditions. If the first sigma is less than the second sigma, the lobe is deemed to be clutter related and is edited from the spectral envelope.

Weather radar using spectral gaussian envelope discrimination for

A radar utilizes an antenna stabilization error correction system to automatically estimate and correct attitude sensor errors in pitch, roll and elevation. The radar system includes an antenna, an antenna positioner, a transmitter receiver, a signal processor, an antenna controller and stabilization processor and the antenna stabilization error correction system. As part of the normal signal processor sub function, ground clutter signals are extracted from the received signals. These signals are the primary input to the antenna stabilization error correction system. Other inputs are received from the signal processor, antenna controller and stabilization processor and an external aircraft radio altimeter. The antenna stabilization error correction system processes the signals and estimates pitch, roll and elevation errors which are passed back to the antenna controller and stabilization processor.

Antenna stabilization error correction system for radar

The invention comprises a weather radar system in which a magnetron transmitter is controlled in frequency by injecting therein a low power locking signal from a stable frequency source. Frequency lock between the source and the magnetron is maintained without requiring injection signals of excessive power by an automatic frequency control (AFC). The AFC determines the frequency and phase error between the injection signal and the magnetron output and adjusts the frequency of the source so as always to be within a narrow band of frequencies centered about the natural frequency of the magnetron. Over the long term, therefore, the frequency of the source will vary by an amount equal to the change in the natural frequency of the magnetron occurring during that time. Over the short term, however, the difference in frequency between the injection signal and the magnetron output is zero, while the phase difference is less than 90.degree.. The frequency source controlling the magnetron also serves as a frequency source for generating the several local oscillator frequencies required by the system receiver. Thus, the pulse to pulse transmitted signals, return signals and receiver i.f. signals all possess a high degree of phase coherence, readily permitting detection and determination of the doppler frequencies contained in the return signals.

Crystal controlled magnetron

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Boca Raton, FL, United States of America

Arezki Manseur