GB578406A - Improvements in the control of modulated radio waves - Google Patents

Abstract

578,406. Radiolocation. ROST, H. F., THUNELL, K. H., VIGREN, S. D., and CLAESSON, P. H. E. Nov. 24, 1942, No. 16625. [Class 40 (v)] [Also in Groups XXXV and XXXVI] Oscillation frequency.- The basic frequency or the degree of modulation of a frequency modulated transmitter of ultra-short waves is manually or automatically controlled by passing a portion of the radiation from a transmitter 101, for example, through a wave guide comprising two channels 95, 96 of different lengths so that they produce normally a beat frequency to which a cavity resonator into which they feed is tuned. One output passes through a detector 98 and amplifier 99 to a filtering and rectifying device 100 to produce a voltage on a grid leak 115, or measuring instrument,' which is the difference between the voltage developed in the filter circuits, these being respectively tuned to frequencies as slightly above and below the desired beat frequency. As shown, a correction of the degree of modulation of the transmitter 101 is obtained bv an electron tube 116, whereby an anode voltage of variable value is applied to a relaxation oscillator generator 127, but any suitable kind of regulator may be employed. To obtain small dimensions for the channels 95, 96, harmonics of the transmitted radiation may be used. The invention is described as applied in apparatus for measuring distances to an object by.measurement of the beat frequency between direct reception from the transmitter and reception of radiation reflected from the object, the apparatus comprising means for automatically scanning the sky by transmitted waves until reflected reception causes automatic following of the object. Alignment.-The transmitter 101 and a receiver 103 are mounted on a horizontal shaft 110 which may be turned by an A.C. reversible motor 15 having split fields controlled by valves 33, 34, the grid voltages of which are phase shifted for selective operation. The shaft 110 is carried by a vertical shaft 111 which is similarly operated by a motor 14. These motors may be manually controlled by a switch 89 to determine a given direction of radiation, after which intermittent and alternate action of the motors produces automatic and progressive scanning of a definite field, until the receiver 103 is energized by reflected waves to a degree sufficient to energize a relay R1, whereupon the motors are automatically controlled to cause the radiation to follow the reflecting object. To achieve this, a shaft 108 is constantly driven to rotate an aperture 106 in front of the receiver and to operate commutators 21 ... 24 so that filter networks such as 46, associated with the separate motor control circuits by operation of a relay R2 at the same time as R1, in turn receive radiation from opposite sides of two planes normal to each other and parallel with the receiver axis. If the energy received on appropriate sides of these planes is not equal, the motors operate to restore equality and the object is accordingly followed. Specification 578,420, [Group XXXVI], is referred to.