| 释义 |
high ˈfrequency
[f. high a. + frequency 4.]
1. a. A frequency (see frequency 4 b) having a relatively large number of cycles in a second. Applied esp. to an electric current or voltage, an electromagnetic wave or a sound wave. Abbrev. , esp. in radio and telecommunications, where it also refers specifically to electromagnetic waves of 3–30 MHz. Often attrib.
1893[see frequency 4 b]. 1923Nature 7 July 12/2 The vibrations are of frequency 200,000 per second, such as are commonly used in wireless telegraphy and telephony. Such high frequencies are neither seen nor heard, but can be detected by special methods. 1934S. G. B. Stubbs Electr. Encycl. II. 612/2 High frequency (H.F.), refers to alternating currents, the frequency of which is reckoned in thousands. There is no definite line of demarcation between high and low frequency, but in general an alternating current is reckoned as of high frequency when the number of periods is greater than 10,000 per second. 1960H. Carter Dict. Electronics 127 High frequency. (1) A general term used to distinguish signals of radio frequency from those of audio frequency. (2) A relative term used to describe frequencies at the upper end of a particular frequency band. (3) Term of specific application to radio waves in the frequency range between 3 and 30 Mc/s, i.e. of wavelengths from 100 m down to 10 m. 1962A. Nisbett Technique Sound Studio iii. 79 High frequencies can be lost in a variety of ways. 1962M. G. Say Newnes' Conc. Encycl. Electr. Engin. 360/1 Fig. 1 (b) and (c) show that at high frequencies above 1,000 c/s there is an increasing tendency for the current to flow in a shallow surface layer of the conductor.
b. transf. A high rate of occurrence, in space or in time.
1935Huxley & Haddon We Europeans ix. 267 Our picture of the human species will be like a contour-map, a region of high frequency for, say, round-headedness being separated from another similar peak by a ‘valley’ of low frequency. 1971Sci. Amer. Oct. 21/1 A high frequency of kwashiorkor is now being found among the East Pakistan refugees in India.
2. attrib. (usu. with hyphen).
a. In sense 1 a, implying an applicability to an oscillation with a high frequency, as high-frequency formula, or an action or manner of working that involves such an oscillation.
1892Heaviside Electr. Papers II. 279 The high-frequency formulae are not so generally applicable as in the case of cores. 1893Jrnl. Soc. Arts 5 May 624/1 The phosphorescent glow of the novel high-frequency, high-voltage, high-vacuum lamps. 1902Proc. R. Soc. LXX. 341 The special manner in which a core or rod of iron or steel placed in a varying magnetic field is affected by high-frequency oscillations transmitted from considerable distances. 1903Daily Chron. 14 Nov. 5/2 High-frequency apparatus and superb laboratories are beside the point compared with air and light. 1914R. Stanley Text-bk. Wireless Telegr. xii. 149 Do high and low frequency waves travel at the same speed? 1921Jrnl. Industrial & Engin. Chem. July 639/2 High frequency voltage (10,000 to 20,000 cycles) is applied at the terminals of the coil. 1928Nature 21 Apr. 623/1 High frequency sound waves of low intensity passed through these cells cause the protoplasm to rotate. 1955F. E. Terman Electronic Radio Engin. (ed. 4) xxiv. 937 These requirements are usually more difficult to meet at the high-frequency end of the modulation range. 1960R. W. Marks Dymaxion World of B. Fuller 23/1 The high-frequency hiss of the surf. 1962A. Nisbett Technique Sound Studio iv. 80 Another example of high-frequency attenuation will occur in recording if the tape is in imperfect contact with the head. Ibid., Where the high frequency losses are progressive, measures may be taken to equalize for them. Ibid. 81 For a recording head the effect of high-frequency bias is to narrow the effective gap width.
b. In sense 1 b, meaning ‘occurring often or involving a rapid succession of events’.
1957D. L. Bolinger in Publ. Amer. Dialect Soc. xxviii. 89 Contrast the high-frequency suppose with the lower-frequency suspect. 1965English Studies Feb. 75 It is hard to judge of the size of the corpus..but it seems to be adequate at least for high-frequency items.
3. Comb., as high-frequency amplifier, high frequency choke, high frequency cinematography, high frequency condenser microphone, high frequency current, high frequency photography, high frequency response, high frequency transformer; high-frequency alternator, any of several kinds of alternator designed to give an alternating current with a frequency greater than about 10 kHz; high-frequency amplification, the amplification of signals of high frequency; in Radio applied spec. to amplification at the carrier frequency in a radio receiver; high-frequency heating, the heating of a substance by placing it in an alternating electric field (dielectric heating) or magnetic field (induction heating) with a frequency above that of the mains electricity supply; high-frequency induction furnace (see quot. 1958); high-frequency resistance, (a) the increased electrical resistance of a conductor at high frequencies, owing to the skin effect; (b) a resistance for use at high frequencies; high-frequency treatment, (a) Med. (see quot. 1931); (b) Metallurgy, the hardening of metals by heating them inductively and quenching.
1901Proc. R. Soc. LXVIII. 514 (heading) The *high frequency alternator. 1935J. B. Moore in K. Henney Radio Engin. Handbk. (ed. 2) 564 The high-frequency alternator is one of the most used types of transmitter for long-wave transoceanic code communication.
1919Wireless World Nov. 448 An eight valve amplifier, comprising five stages of *high-frequency amplification, one stage of rectification, and two stages of audio-frequency amplification with transformer coupling. 1934S. O. Pearson in S. G. B. Stubbs Electr. Encycl. II. 612/1 The magnification of electrical variations at the signal—or radio—frequency of the received oscillations, that is, before they are applied to the detector of a wireless receiver, is termed high-frequency amplification.
1919Wireless World Feb. 628 (heading) The use of impedance, capacity and resistance couplings in *high-frequency amplifiers.
1928*High frequency choke [see choke 6].
1958Van Nostrand's Sci. Encycl. (ed. 3) 812/1 High-frequency photography includes both still and motion-picture photography... In *high-frequency (slow-motion) cinematography the exposing rate may range from 32 to several thousand frames per sec.
1940Chambers's Techn. Dict. 188/1 *High-frequency condenser microphone, a condenser microphone in which the polarising voltage is alternating at a high radio-frequency, amplitude modulation of which is detected by a de-modulator and used for audio-frequency transmission.
1896McClure's Mag. VI. 414/2 A *high frequency current. 1923E. W. Marchant Radio Telegr. ii. 13 When we come to deal with the high-frequency currents that are employed in Radio, their behaviour is quite different.
1925Jrnl. Iron & Steel Inst. CXII. 73 *High-frequency heating may be found useful in the forging and heat treatment of steel. 1967A. K. Osborne Encycl. Iron & Steel Ind. (ed. 2) 218/1 The polarity of this field changes many times per second with the alternation of the current necessary for high frequency heating.
1920Trans. Amer. Electrochem. Soc. XXXV. 158 Since the presentation of the above paper a development into commercial form of *high-frequency induction furnaces of the oscillatory current type has been actively continued. 1958A. D. Merriman Dict. Metallurgy 125/1 A high-frequency induction furnace is a melting furnace in which currents at a frequency above 500 c./sec. are used to induce eddy currents in the charge, which in turn generate heat in the material.
1958Van Nostrand's Sci. Encycl. (ed. 3) 813/1 High-frequency photography which consists of a number of high-speed photographs made in rapid succession.
1892Heaviside Electr. Papers II. 193 The *high-frequency resistance is independent of the steady resistance, and must be much greater than it. 1951A. Hund High-Frequency Measurements (ed. 2) ii. 96 Any amplitude differences are balanced out by properly chosen high-frequency resistances. Ibid. ix. 310 In all cases, the high-frequency resistance is that quantity which, when multiplied by the square of the effective value of the high-frequency current, gives the energy dissipated in the conductor.
1930Wireless World 17 Dec. 686/2 (heading) *High frequency response.
1923E. W. Marchant Radio Telegr. iv. 56 This change in voltage may be passed on..by means of a small *high-frequency transformer, to the grid of a second valve.
1931S. R. Roget Dict. Electr. Terms (ed. 2) 146/2 *High frequency treatment, curative treatment involving the use of interrupted trains of damped high frequency oscillations. 1967A. K. Osborne Encycl. Iron & Steel Industry (ed. 2) 202/2 High-frequency treatment. |