Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.

Detection of bridge tap using frequency domain analysis

Abstract: A method for detecting the presence of a bridge tap and other types of fault in a transmission line. Initially, test signals of predetermined frequencies are transmitted into a transmitting end of the transmission line. The test signals are received at a receiving end of the transmission line and the amplitudes of the received signal are measured. A frequency response of the transmission line is computed based on the measured amplitudes. The frequency response is then analyzed for the presence of a frequency-domain signature that corresponds to one of the detectable types of fault. The presence of a bridge tap or another type of fault is identified based on the detected frequency-domain signature. The frequency-domain signature associated with a bridge tap can comprise a set of one or more attenuation dips in the frequency response, with each attenuation dip corresponding to a local minima in the frequency response. The length of the bridge tap can be estimated based on a fundamental frequency of the set of harmonically related attenuation dips. Also, the location of the bridge tap in the transmission line can be estimated by performing a time domain reflectometer (TDR) test.

A 0.28 THz Power-Generation and Beam-Steering Array in CMOS Based on Distributed Active Radiators

Abstract: In this paper, we present a scalable transmitter architecture for power generation and beam-steering at THz frequencies using a centralized frequency reference, sub-harmonic signal distribution, and local phase control. The power generation and radiator core is based on a novel method called distributed active radiation, which enables high conversion efficiency from DC to radiated terahertz power above fmax of a technology. The design evolution of the distributed active radiator (DAR) follows from an inverse design approach, where metal surface currents at different harmonics are formulated in the silicon chip for the desired electromagnetic field profiles. Circuits and passives are then designed conjointly to synthesize and control the surface currents. The DAR consists of a self-oscillating active electromagnetic structure, comprising of two loops which sustain out-of-phase currents at the fundamental frequency and in-phase currents at the second harmonic. The fundamental signal, thus gets, spatially filtered, while the second harmonic is radiated selectively, thereby consolidating signal generation, frequency multiplication, radiation of desired harmonic and filtration of undesired harmonics simultaneously in a small silicon footprint. A two-dimensional 4×4 radiating array implemented in 45 nm SOI CMOS (without high-resistivity substrate) radiates with an EIRP of +9.4 dBm at 0.28 THz and beam-steers in 2D over 80° in both azimuth and elevation. The chip occupies 2.7 mm × 2.7 mm and dissipates 820 mW of DC power. To the best of the authors' knowledge, this is the first reported integrated beam-scanning array at THz frequencies in silicon.

Pitch Extraction and Fundamental Frequency: History and Current Techniques

Abstract: Pitch extraction (also called fundamental frequency estimation) has been a popular topic in many fields of research since the age of computers. Yet in the course of some 50 years of study, current techniques are still not to a desired level of accuracy and robustness. When presented with a single clean pitched signal, most techniques do well, but when the signal is noisy, or when there are multiple pitch streams, many current pitch algorithms still fail to perform well. This report presents a discussion of the history of pitch detection techniques, as well as a survey of the current state of the art in pitch detection technology.

Correct tonotopic representation is necessary for complex pitch perception

Abstract: The ability to extract a pitch from complex harmonic sounds, such as human speech, animal vocalizations, and musical instruments, is a fundamental attribute of hearing. Some theories of pitch rely on the frequency-to-place mapping, or tonotopy, in the inner ear (cochlea), but most current models are based solely on the relative timing of spikes in the auditory nerve. So far, it has proved to be difficult to distinguish between these two possible representations, primarily because temporal and place information usually covary in the cochlea. In this study, “transposed stimuli” were used to dissociate temporal from place information. By presenting the temporal information of low-frequency sinusoids to locations in the cochlea tuned to high frequencies, we found that human subjects displayed poor pitch perception for single tones. More importantly, none of the subjects was able to extract the fundamental frequency from multiple low-frequency harmonics presented to high-frequency regions of the cochlea. The experiments demonstrate that tonotopic representation is crucial to complex pitch perception and provide a new tool in the search for the neural basis of pitch.