GB577455A - Improvements in and relating to amplifiers for electric wave signals - Google Patents

Abstract

577,455. Wireless receiving systems. ROBINSON, J. April 19, 1939, Nos. 8923/40 and 8924/40. Divided out of 577,453. [Class 40 (v)] Incoming signals are mixed with local frequency-changing oscillations, which are derived from the signals and vary in amplitude with them, so that the output from the frequency-changer is proportional in amplitude to the product of the applied signals and the local oscillations. The amplifier output of harmonic frequency may be made proportional -to the square, cube, or higher power of the input, or to a fractional power of it. The harmonic of the signal may be obtained by passing the latter through a distorting device such as a leaky-grid detector. As shown, the signals are applied to an amplifier 11 having two outputs in parallel. One passes through an amplifier 12 to the frequency-changer 16, whilst the other passes first through a filter 13, and a harmonic-producer 14, and an amplifier 15 tuned to the desired harmonic. The output from the converter 16 may be converted back to the original frequency in a second converter 17, which is also coupled to the amplifier 15. Alternatively, both parallel paths may include harmonic-producers. The rectified resultant current may be used for automatic volume control. The output from 17 may be fed back to the amplifier 11 at any desired phase angle to give either positive or negative reaction. As applied to. a direction finder, an output corresponding to a high power of the input may be used to give an increased directional sensitivity, especially for " maximum " readings. By using negative feed-back, the minimum critical point would sharpen.