GB577453A - Improvements in and relating to amplifiers for electric wave signals - Google Patents

Abstract

577,453. Directive wireless signalling. ROBINSON, J. April 19, 1939, Nos. 11822/39 and 5566/40. [Class 40 (v)] In a directional receiving system, the signals from two or more aerials are combined in a " mixer " valve or other non-linear device to give a resultant of harmonic frequency which varies in amplitude or phase with the direction of the incoming signals, the resultant being fed back to the aerial to influence the operation of an associated indicating device. The arrangement is designed to increase the normal directive effect, to cut out interfering signals even of the same frequency, and to provide automatic volume control. The aerials may include a frame aerial or a spaced array, and one aerial may be more directional than the other. As shown in Fig. 1, signals from a non-directive aerial 20 and a directive aerial 21 are combined, after amplification at 23 and 24, in a frequencychanger 22. For feed-back purposes the output from the latter is proportional in amplitude to the product of the two input signals, and of double their frequency, if both signals are alike. The output frequency may be restored to its original value by feeding signals from a third aerial 25 to a frequency changer 26, together with the output from the frequency changer 22, the resultant then being fed back to the amplifier 23 of the aerial 20. The phase of the feed-back will vary with the orientation of the frame aerial 21. The directional indicator 27 is connected to the aerial 20. Instead of using a third aerial 25, the feed-back frequency may be restored to its original value by the rectifying action of the valves 22 or 23. If the aerial 21 is uni-directional and no change of phase occurs, the feed-back then varies only in amplitude with the direction of the connecting signal, to give increased directional sensitivity. With a frame aerial, the feed-back will vary not only in amplitude but also in phase as the frame is rotated, so that positive or negative feed-back can be applied according to the direction of the incoming signals, the negative feed-back serving to eliminate undesired signals. The original frequency for feed-back purposes may also be obtained by distorting the signal from each receiver, so as to obtain harmonics, which are then recombined to produce the fundamental (Figs. 2 and 3, not shown). Specification 577,455 is referred to.