Topic
Fundamental frequency
About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.
Papers published on a yearly basis
Papers
More filters
Patent•
06 Oct 1939TL;DR: In this paper, the authors describe a system of the kind described in Specification 474,021 which employs two modulation stages, the first carrier frequency and the several second carrier frequencies being multiples of the same fundamental frequency and being such that the upper and lower side-bands resulting from the second modulation fall in two distinct frequency ranges one of which is eliminated by a common high-pass or low-pass filter.
Abstract: 519,264. Multiplex systems. MEYER, L. W. (Naamlooze Vennootschap Philips, Gloeilampenfabrieken). Oct. 10, 1938, No. 29358. Drawings to Specification [Class 40 (iv)] In a system of the kind described in Specification 474,021 which employs two modulation stages, the first carrier frequency and the several second carrier frequencies being multiples of the same fundamental frequency and being such that the upper and lower side-bands resulting from the second modulation fall in two distinct frequency ranges one of which is eliminated by a common high-pass or low-pass filter, loss of energy due to the parallel connection of the second modulators is reduced by the provision in each output circuit of a band-pass filter of a simple nature passing the appropriate side-band.
75 citations
TL;DR: The superconducting substrate is modeled as a perfect magnetic conductor, greatly reducing the STAR emitter power and modifying its angular dependence, especially parallel to the substrate, based upon this substrate model, existing Bi(2)Sr( 2)CaCu(2),O(8 + δ) crystals atop perfect electric conductors could have STAR emitters power in excess of 5 mW, acceptable for many device applications.
Abstract: The angular dependence of the radiation-zone output power and electric polarization of stimulated terahertz amplified radiation (STAR) emitted from a dc voltage applied across cylindrical and rectangular stacks of intrinsic Josephson junctions is calculated. The boundary conditions are obtained from Love’s equivalence principles. During coherent emission, a spatially uniform ac Josephson current density in the stack acts as a surface electric current density antenna source, leading to a harmonic radiation frequency spectrum, as in experiment, but absent in all cavity models of cylindrical mesas. Spatial fluctuations of the ac Josephson current allow its fundamental mode to lock onto the lowest finite energy cylindrical cavity mode, causing it to resonate, leading to a non-uniform magnetic surface current density radiation source, and a non-trivial combined fundamental frequency output power with linear polarization for general radiation directions, which may be fully or partially coherent. The higher ac Josephson harmonics do not excite other cylindrical cavity modes. For rectangular mesas, the lowest energy modes are empirically not excited, but the non-uniform ac Josephson current can excite the harmonic sequence of modes with spatial variation across the rectangular widths, leading to combined radiation outputs both for the fundamental and the higher harmonics, which combinations also may be either fully or partially coherent. The superconducting substrate is modeled as a perfect magnetic conductor, greatly reducing the STAR emitter power and modifying its angular dependence, especially parallel to the substrate. Based upon this substrate model, existing Bi2Sr2CaCu2O8+δ crystals atop perfect electric conductors could have STAR emitter power in excess of 5 mW, acceptable for many device applications. (Some figures in this article are in colour only in the electronic version)
75 citations
TL;DR: The elastic constants of singlecrystal KCl and NaI have been measured by means of the ultrasonic pulse echo method using a wideband amplifier to display the unrectified echo pattern directly as mentioned in this paper.
Abstract: The elastic constants of single‐crystal KCl and NaI have been measured by means of the ultrasonic pulse echo method using a wide‐band amplifier to display the unrectified echo pattern directly. The experimental results agree with previous measurements made using other techniques. From detailed observations of successive echoes, made possible by the wide‐band receiving unit, it was determined that the pulse was attenuated at the front, and at the same time elongated, due to reflection from the specimen‐transducer interface. This effect turns out to be just what one would expect theoretically, and is responsible for the so‐called ``transit‐time error.'' The transit‐time error may be as large as one vibration period of the fundamental frequency in the pulse, and is most pronounced for crystal samples in which the acoustic impedance is the same as that of the quartz transducer.
75 citations
TL;DR: In this paper, the authors determine the optimum tapering of a cantilever carrying an end mass, i.e., the shape which yields the highest possible value of the first fundamental frequency of harmonic bending vibrations in the vertical plane.
Abstract: We determine the optimum tapering of a cantilever carrying an end mass, i.e., the shape which, for a given total mass, yields the highest possible value of the first fundamental frequency of harmonic bending vibrations in the vertical plane.
75 citations
TL;DR: In this paper, a novel method to suppress harmonic responses of parallel-coupled bandpass filters is proposed, where the coupling coefficient at fundamental resonant frequency can be tuned to desirable values whereas it is zero at the second harmonic.
Abstract: This letter presents a novel method to suppress harmonic responses of parallel-coupled bandpass filters. The harmonic suppression is based on discriminating coupling. The coupling coefficient at fundamental resonant frequency can be tuned to desirable values whereas it is zero at the second harmonic. Hence, the coupling region blocks the second harmonic but still allows the transmission of signals at passband frequency. Benefiting from this feature, the second harmonic can be suppressed without degrading the passband performance. Furthermore, no additional circuit is needed. For demonstration purpose, two example filters are implemented. The experimental results are presented to verify the proposed method.
74 citations