Low-frequency reactance amplifier

This work presents the theory and experimental demonstrations of frequency-controlled energy absorption in parametric mixing circuits which may find applications in the design of tunable notch filters and frequency-selective surfaces. A time-varying capacitance model is used to describe the energy exchange among the pump, signal, and idler frequencies in parametric mixing circuits. Analytical derivations reveal that under specific frequency ordering, the system exhibits a positive conductance at the signal frequency that is correlated with the pump frequency, leading to measurable energy absorption. A fabricated on-chip circuit operating between 1.3 and 2.3 GHz serves as a physical representation of the theoretical model, experimentally validating the predicted energy transfer behavior. The results establish a unified framework linking circuit-level phenomena to the fundamental physics of energy redistribution in parametric systems.

مقدمه: در سیستم‌های کاشت حلزون، واژه کانال به تعداد محل‌های تحریکی در گوش داخلی و یا حلزون دلالت داشته و به این شکل دامنه فرکانسی و یا زیر و بمی تعیین می‌گردد. سیستم‌های کاشت حلزون چند کاناله برخلاف کاشت حلزون تک کاناله، سیگنال ورودی را به باندهای فرکانسی متفاوتی تقسیم کرده و به مکان‌های مختلف تحریکی معین در گوش داخلی انتقال می‌دهد. داشتن محل‌های تحریکی بیشتر، 2 هدف اصلی را به دنبال دارد: 1- از آن‌جایی که فیبرهای عصب شنوایی در حلزون به صورت تونوتوپیک سازمان‌دهی شده است، تعداد الکترود بیشتر تفکیک فرکانسی بهتری را ارایه می‌کند. 2- اگر در حلزون مناطقی وجود داشته باشد که به تحریک الکتریکی به طور نامناسب و یا به هیچ وقت پاسخ ندهد، در برنامه‌ریزی دستگاه از تحریک آن مکان‌ها اجتناب می‌شود و اجزای فرکانسی ورودی پردازش شده، با تحریک همراه می‌شود. هدف از انجام مطالعه حاضر، مقایسه کاشت حلزون تک کاناله با چند کاناله از نظر استراتژی کدگذاری فرکانسی و اثر آن بر درک گفتار افراد دریافت کننده سیستم‌های کاشت حلزون بود. مواد و روش‌ها: مطالعه حاضر به وسیله بررسی پایگاه‌های علمی (Pubmed، Science direct، Google scholar) در بازه زمانی 2016-1965 با استفاده از واژگان مرتبط با موضوع انجام شد و مقالات با توجه به معیارهای ورود و خروج انتخاب گردید. یافته‌ها: کاشت حلزون‌های تک کاناله فرکانس را بر اساس سرعت شلیک ایمپالس‌های الکتریکی کدبندی می‌کند. کاشت حلزون‌های چند کاناله از نظریه استراتژی مکانی برای کدبندی فرکانسی استفاده می‌کند که در آن فرکانس‌های مختلف سیگنال شنوایی جداسازی شده و به شکل تونوتوپیک در طول در ازای حلزون، از طریق آرایه الکترودی ارایه می‌شود. کدگذاری مکانی و زمانی فرکانس‌های صدا می‌تواند تا حدودی به وسیله تحریک چند کاناله عصب شنوایی، حفظ و تکرار شود. در کاشت حلزون چند کاناله استراتژی کدگذاری دارای 2 مدل استخراج ویژگی و شکل موج می‌باشد. همچنین، درک گفتار حاصل از سیستم‌های تک کاناله و چند کاناله بررسی شد. نتیجه‎گیری: با توجه به یافته‌ها، می‌توان نتیجه گرفت که سیستم‌های کاشت حلزون تک کاناله با کدگذاری زمانی فرکانسی، نمی‌تواند به میزان کافی اطلاعات گفتاری را منتقل کند؛ در حالی که کاشت حلزون‌های چند کاناله به اندازه کافی شباهت به نقشه تونوتوپیک حلزون داشته و فهم گفتار در آن نسبت به وسایل تک کاناله بیشتر است.

Objective To observe the effect of TOMATIS auditory training on improving cognitive and post-traumatic stress disorder in patients after breast cancer chemotherapy. Methods Eighty invasive ductal carcinoma of breast cancer patients with cognition and psychological disorders were selected in the breast department of Tangshan People's Hospital from October 2016 to September 2017.All patients were randomly divided into control group (n=40) and experimental group (n=40). The experimental group was given the TOMATIS high and low audio frequency auditory training, and the control group was given ordinary music training.Before and after the intervention, the Chinese version of the Montreal cognitive assessment scale (MoCA) and the post-traumatic stress disorder scale (PTSD-SS) were evaluated for both groups of patients. Results After the intervention, the experimental group had significantly higher scores in visual structure skills((3.83±0.71)vs(2.68±0.57)), executive function ((2.23±0.53)vs(1.55±0.50)), attention and concentration((1.55±0.78)vs(1.23±0.53)), language((1.50±0.75)vs(1.08±0.47)), calculation((2.00±0.60)vs(1.45±0.75)), abstract thinking((1.63±0.54)vs(1.00±0.51)), memory((4.68±0.47)vs(2.70±0.72)), directive force((5.25±0.54)vs(3.90±0.81)) and total score((22.65±2.89)vs(15.58±2.10))than the control group(all P<0.05). After intervention, the scores of subjective assessment of traumatic events((2.60±0.63)vs(3.98±0.62)), repeated recurring experiences((24.05±2.72)vs(26.70±2.28)), avoidance symptoms((24.35±1.64)vs(26.40±1.19)), increased alertness((24.23±1.80)vs(25.45±1.20)), impaired social function((7.28±1.01)vs(8.68±0.66)), and total scores((85.85±5.13)vs(94.63±2.92)) in the experimental group were significantly lower than those in the control group, and the differences were statistically significant (all P<0.01). Conclusion TOMATIS auditory training can effectively improve the cognitive function and psychological state in breast cancer chemotherapy patients, which is worthy of popularization and application. Key words: TOMATIS auditory training; Breast cancer; Chemotherapy; Cognitive dysfunction; Post-traumatic stress disorder

A Superconducting QUantum Interference Device (SQUID) modulated by a fast oscillating magnetic flux can be used as a parametric amplifier, providing gain with very little added noise. Here, we develop linearized models to describe the parametrically flux-pumped SQUID in terms of an impedance. An unpumped SQUID acts as an inductance, the Josephson inductance, whereas a flux-pumped SQUID develops an additional, parallel element which we have coined the ``pumpistor.'' Parametric gain can be understood as a result of a negative resistance of the pumpistor. In the degenerate case, the gain is sensitive to the relative phase between the pump and signal. In the nondegenerate case, gain is independent of this phase. We develop our models first for degenerate parametric pumping in the three-wave and four-wave cases, where the pump frequency is either twice or equal to the signal frequency, respectively. We then derive expressions for the nondegenerate case where the pump frequency is not a multiple of the signal frequency, where it becomes necessary to consider idler tones which develop. For the nondegenerate three-wave case, we present an intuitive picture for a parametric amplifier containing a flux-pumped SQUID where current at the signal frequency depends upon the load impedance at an idler frequency. This understanding provides insight and readily testable predictions of circuits containing flux-pumped SQUIDs.

In Part I of this paper, we introduce useful analysis that leads to a simple signal flow graph (SFG), which captures the FET-R-C circuit's action completely across a wide range of design parameters. Part I focuses on the analysis of a single-path FET-R-C circuit's signal transfer characteristics and gives us guidelines for sample-and-hold (S/H) and passive sampling mixer (P-M) designs. Part II extends the analysis to multi-path FET-R-C circuit configurations, e.g., a complex I-Q passive mixer that is common in RF applications. Then the noise and driving-point impedance analyses are carried out to provide valuable insights of practical S/H and P-M designs.

Unusually low noise, combined with high stable gain over fairly wide bands, has been obtained with electron beam amplifiers of a new kind. This paper explains how this performance is achieved by the action of a transverse quadrupole field upon a fast cyclotron wave. The first two sections give a qualitative description of the device and of the amplifying mechanism. A physical picture of the fast cyclotron wave is used to explain the interchange of signal and noise in the input coupler and the mechanism of parametric amplification in the quadrupole region. The third section presents a detailed analysis of the amplification process. It shows that the fast cyclotron wave is amplified in accordance with a cosh function of distance traveled through the quadrupole, and that a new cyclotron wave at idler frequency (difference between pump and signal frequencies) is generated which grows as a sinh function of distance. The fourth section describes experimental tubes built to date. These operate on frequency bands between 400 and 800 mc. Typical bandwidth is 40 to 50 mc independent of gain, which may be adjusted to 20 or 30 db. Residual noise temperature of the electron beam in good specimens within this experimental lot is 70°K; input coupler loss raises this figure to about 100°K. This is equivalent to a noise figure of 1.4 db if the device is used, for instance, in radio astronomy.

Our first encounters with signals were in the time domain for 1-D signals and the spatial domain for 2-D images. We have seen time domain signals as a graph or as a trace on an oscilloscope. Undergraduate engineers have usually used a spectrum analyzer in the laboratory to characterize signals in the frequency domain. However, almost everyone has seen a graphical representation of an acoustic frequency spectrum when they observe the flashing lights on the spectrum displays of graphic equalizers on higher quality stereo systems. The display shows the observer the relative power of the signal in various frequency ranges. The interpretation in the frequency domain of audio signals is aided by the fact that the ear is basically a spectrum analyzer. It is easy to interpret the terms high and low frequency when applied to audio signals. We have no difficulty thinking of a rumble as a low-frequency sound, or a screech as a high-frequency sound. We will have to work a bit to achieve the same associations of visual phenomena with frequency bands. However, be assured that the effort is worthwhile. Among the interpretations that will be shown are that edges are associated with higher frequencies; shading is associated with lower frequencies; blurring is basically a low pass filter, while differentiation is a high pass operation.

Noise analysis of imagers with a-Si:H pin diode pixels

Mechanical damping, tan delta, of lead metaniobate was determined experimentally over a wide range of frequency. Damping at audio and sub-audio frequency was lower than at ultrasonic frequency. The experiments were conducted in torsion and bending using an instrument capable of determining viscoelastic properties over more than 10 decades of time and frequency. Mechanical damping was higher in bending than torsion at all frequencies. Damping observed in this study at the highest frequencies approach the high value 0.09 previously observed at ultrasonic frequency.

The effect of inverse-squared frequency dependence of the apparent resistance of varactor diodes is discussed in the optimization of the noise figure of negative resistance and up-converter parametric amplifiers. Optimum idler frequency for a given signal frequency for minimum noise figure is calculated. It is also shown that about twofold improvement in the noise figure is obtained if the proper idler frequency is used for negative resistance amplifiers. It is also shown that the value of the optimum loading changes for upconverter amplifiers.

A low-mass sound generator with particularly good performance at low audio frequencies (i.e. 30 to 300 Hz) has been developed. The actuation component is a Thunder actuator (Face Int. Corp.). This actuator is coupled to a resonant compliant diaphragm to increase output in the low frequency band. The modal response of various 28 cm diameter prototypes was monitored using laser Doppler vibrometry and nearfield acoustic holography. The first mode appears near 40 Hz, with a maximum displacement of 3.4 microns per volt. Sound pressure levels measured in the farfield using 200 volts peak drive found nominal levels of 74+/- 6 dB(at 25 cm) over the band from 38 to 330 Hz. Near 45 and 100 Hz the SPL reaches 80 dB. (Above 330 Hz the output is higher, but remains well behaved to at least 2 kHz.) Higher outputs can be obtained by using a higher drive voltage and multiple devices. Because of its low mass, this device is particularly interesting for aerospace applications. This work was developed in the NRL/ONR Smart Blanket program, which is exploring the use of active controlled surface covers for reducing sound levels in payload fairing regions.

The emerging applications of the parametric loudspeaker, such as 3D audio, require both directivity control and high fidelity at the audible frequency (i.e., the difference frequency of the primary frequencies generated by the parametric loudspeaker). Although the phased array techniques have been applied and proved adequate to adjust the steering angles of the parametric loudspeaker, and preprocessing methods have been studied to reduce the harmonic distortions, there is no published work on the effectiveness of the combination of the beamsteering method and the preprocessing methods for the broadband steerable sound beam system. This paper aims to investigate on this unexplored problem. First, the relation between the phases of the primary waves and the difference frequency wave is explored to prove the feasibility of achieving a broadband steerable sound beam from the parametric loudspeaker with preprocessing methods. Second, based on the derived relation, the beamsteering structure is proposed. Lastly, preprocessing methods are proposed for the steerable parametric loudspeaker using double sideband modulation (DSBAM) and square root amplitude modulation (SRAM) methods. Spatial performances of the steerable parametric loudspeaker with preprocessing methods are presented in this paper.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Meena Singh, Sanjay Roy, B. P. Singh; On Demand Realization of Input and Output Resistances of MOSFET Amplifier. AIP Conference Proceedings 26 December 2011; 1414 (1): 266–270. https://doi.org/10.1063/1.3669970 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

A precision current sensing circuit with chopper amplifier of symmetric topology

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