| 摘要 |
871,656. Radar. MARCONI'S WIRELESS TELEGRAPH CO. Ltd. July 2, 1959 [Oct. 16, 1958], No. 33094/58. Class 40(7) Relates to airborne speed and/or distance measuring radar utilizing the Doppler effect on earth reflections. According to the invention transmissions are made at a number of different angles of depression relative to the plane containing the pitch and roll axes of the aircraft and the strengths of derived signals each dependent on the magnitude of the echo signal corresponding to a differently-directed transmission are compared to derive information for calibrating or correcting the measurements. The echo spectrum is distorted by the increase of echo power with depression angle and it is stated that known measuring devices may give an incorrect velocity indication. Aerials 21, 31 are switched to receiver 5 synchronously with transmitter 1 output to aerials 2, 3. The receiver output, which is at frequencies corresponding to the beat frequencies between transmitted and received signals, is fed via filter R, K amplifier 8, rectifier 9 and synchronous switch 411 to amplitude comparator 10, 11 whose output controls motor 16 to adjust the filter characteristic so as to yield a correct velocity measurement by known device 7. The comparator is arranged to adjust the filter until the comparator inputs are in a predetermined relationship which may be equality. More than two differentlydirected beams may be used, and simultaneous transmission effected. The invention may be applied to Doppler-effect systems in which a number of beams of different directions relative to the aircraft heading are used for speed and drift measurements. Manual control of the filter may be employed. |
