A Study of Low-Noise Broadband VLF Receiving Techniques

Rorden, L. H.

doi:10.21236/ad0660050

Cited by 2 publications

(3 citation statements)

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“…For all subjects, the hippocampi were manually outlined using the freeware software program MRIcron (Rorden, 2007) by two observers who were blinded to all subject information. The delineation protocol, the hippocampal boundaries, and the correction for brain volume are described in detail elsewhere (Jeukens et al, 2009).…”

Section: Volumetrymentioning

confidence: 99%

Memory processes and prefrontal network dysfunction in cryptogenic epilepsy

et al. 2011

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Deficits in the processes involved in transient working memory, and to a lesser extent in short-term memory, in patients with localization-related epilepsy of both temporal and extratemporal origin cannot be attributed to hippocampal atrophy or function only, but are also related to reduced functional connectivity in the prefrontal brain. Because patients with symptomatic lesions or mesiotemporal sclerosis were excluded from this study, the results cannot be explained by structural lesions. Therefore, the current findings highlight the influence of epilepsy on the prefrontal network integrity as a possible underlying problem of memory impairment.

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Section: Volumetrymentioning

confidence: 99%

Memory processes and prefrontal network dysfunction in cryptogenic epilepsy

et al. 2011

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“…On the other hand, active matching networks for antennas with transistors or parametric amplifiers have been attempted by many since 1960s [14], [15], [16], [17], [18], [19], [20]. The noise performance of directly connecting electrically small antennas to an amplifier, whether it is a Bipolar transistor (BJT), Field effect transistor (FET) or a parametric amplifier have been analyzed since 1965 [21]. Unfortunately, neither those experiments or analyses led to insights on how such receivers should be designed toward the best noise and bandwidth performance that are comparable or even superior to the traditional impedance matched designs.…”

Section: Introductionmentioning

confidence: 99%

“…Some existing theoretical treatments of noise contribution of amplifiers in the antenna system are based on a constant LNA noise figure assumption which implies a constant amount of noise power is added in the receiver front-end [25], [27], [29] while in reality the amount of the noise added by the front-end is significantly impacted by the antenna's own impedance. Other classical treatments of transistor noises use an optimum noise impedance formulation derived from equivalent voltage and current noise sources observed through measurements [21]. However, the formulation has neither linked to the known scalable physical parameters of transistors such as gate periphery and transition frequencies, nor considered the practical constraints of the ESA impedance such as those imposed by Harrington-Chu's limit or Gustafsson's limit [11], [12], [13].…”

Section: Introductionmentioning

confidence: 99%

Theory of Broadband Noise Matching for HF/VHF Receivers With Electrically Small Antennas

Wang

2023

IEEE Access

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A general theory on noise matching performance of receivers with electrically small antennas (ESAs) emphasizing HF (3MHz to 30MHz) and VHF (30MHz to 300MHz) applications is presented through theoretical analyses, discussions, and circuit simulations with practical device models from a state-of-the art semiconductor technology. The theory considers all the noise sources and their interplay. The impact on the noise performance from both the physical constraint of the ESA in terms of its radiation quality factor and the scaling of transistor technology and periphery such as gate resistance, gate cutoff frequency and transition frequency has been discussed. Two receiver examples, one with electrically small dipole and the other with electrically small loop are studied with full-wave simulations. The antenna equivalent models are then connected to low noise amplifiers designed with the state-of-the-art Gallium Nitride (GaN) transistor models to evaluate the noise performance of the systems and compared against the theory. It is demonstrated that both the noise figure and its bandwidth can be significantly improved over traditional matching strategy when optimized active direct matching is applied at the price of increased device periphery and power consumption. In particular, the bandwidth of such low noise matching can be orders of magnitude wider than the antenna's conjugate impedance matching bandwidth that is defined by Harrington-Chu's limit.INDEX TERMS Broadband matching, electrically small antennas, GaN transistors, HF antennas, low noise matching, receivers, VHF antennas.

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A Study of Low-Noise Broadband VLF Receiving Techniques

Cited by 2 publications

References 0 publications

Memory processes and prefrontal network dysfunction in cryptogenic epilepsy

Memory processes and prefrontal network dysfunction in cryptogenic epilepsy

Theory of Broadband Noise Matching for HF/VHF Receivers With Electrically Small Antennas

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