| 释义 |
frequency modulation Electr.
a. Modulation of a wave by variation of its frequency.
b. The system of transmission of radio waves, etc., using such modulation. Abbrev. F.M. Cf. amplitude modulation (amplitude 6 d).
1922J. R. Carson in Proc. Inst. Radio Engin. X. 59 It has been proposed..to employ an apparently radically different system of modulation which may be termed frequency modulation as distinguished from amplitude modulation, in the belief that the former system makes possible the transmission of signals by a narrower range of transmitted frequencies. 1943Electronic Engin. XV. 440/1 The ideal detector for frequency modulation is one which not only faithfully reproduces the true form of the f.m. components, but also is unresponsive to amplitude fluctuations of the carrier signal. 1955Times 29 July 5/4 The present system of amplitude modulation in the v.h.f. maritime services should be changed to one of frequency modulation. 1958N.Z. Listener 10 Oct. 21/1 The possibility of introducing FM (frequency modulation), a method of broadcasting that gives high fidelity reception. 1962Which? Feb. 36/2 On the VHF band the FM (frequency modulation) system is used.
Hence frequency-modulated ppl. a.; (as a back-formation) frequency-modulate v.
1936R. Glasgow Princ. Radio Engin. xi. 314 In order for a phase- or a frequency-modulated signal to become audible, it must be converted into an amplitude-modulated signal. 1950Gloss. Terms Radar (B.S.I.) 6 Frequency-modulated radar, a form of radar in which the radiated wave is frequency-modulated and the returning echo beats with the wave being radiated, thus enabling the range to be measured. 1962F. I. Ordway et al. Basic Astronautics vii. 322 The radio frequency carrier wave is modulated by a group of subcarriers... The subcarriers are frequency-modulated by the characteristics of the intelligence. |