Non-Foster acoustic radiation from an active piezoelectric transducer

The quality factor of a passive, linear, small acoustic radiator is fundamentally limited by its volume normalized to the emitted wavelength, imposing severe constraints on the bandwidth and efficiency of compact acoustic sources and of metamaterials composed of arrangements of small acoustic resonators. We demonstrate that these bounds can be overcome by loading a piezoelectric transducer with a non-Foster active circuit, showing that its radiation bandwidth and efficiency can be largely extended beyond what is possible in passive radiators, fundamentally limited only by stability considerations. Based on these principles, we experimentally observe a threefold bandwidth enhancement compared to its passive counterpart, paving the way toward non-Foster acoustic radiation and more broadly active metamaterials that overcome the bandwidth constraints hindering passive systems.

Design of Active Microstrip Semi-Circular Patch for UWB Applications

In this paper, we have proposed a semi-circular patch antenna with a slot in the patch and a ground plane with a notch. The proposed antenna is designed using FR-4 substrate with a dielectric constant of 4.4 and the height of the substrate is 1.6mm. We simulated the antenna using HFSS and obtained the S11 < -10dB in the range of 3GHz to 15GHz, which covers the UWB range of 3.1GHz to 10.6GHz. An active circuit is designed and simulated using ADS to improve the gain of the antenna when working in a lossy medium other than air.

CMOS active inductors and transformers for wireless applications

This thesis first reviews existing work in CMOS active inductors focusing on two implementations, Wu gyrator-C and differential floating active inductors. It then proposes a new method of quantifying the performance of active inductors by introducing a figure of merit called "mean quality factor" that is better suited to the large signal behavior of active inductors. New CMOS constant-Q active inductors are proposed that are intended specifically for applications where a large signal operation in required. The thesis then proposes CMOS active transformers that are active circuit equivalents of two magnetically coupled coils. Four applications of constant-Q active inductors and active transformers namely a 2.4 GHz voltage-controlled oscillator with -119.5dBc/Hz phase noise at 1 MHz offset, a 2.4 GHz current-mode phase-locked loop with -116dBc/Hz phase noise at 1 MHz offset and 80ns lock time, a 5 MHz 100X oversampled current-mode sigma-delta modulator with 50dB dynamic range and 65dB SNR, and a 1.6 GHz QPSK phase modulator with -101dBc/Hz phase noise at 1 MHz offset are presented.

CMOS active inductors and transformers for wireless applications

This thesis first reviews existing work in CMOS active inductors focusing on two implementations, Wu gyrator-C and differential floating active inductors. It then proposes a new method of quantifying the performance of active inductors by introducing a figure of merit called "mean quality factor" that is better suited to the large signal behavior of active inductors. New CMOS constant-Q active inductors are proposed that are intended specifically for applications where a large signal operation in required. The thesis then proposes CMOS active transformers that are active circuit equivalents of two magnetically coupled coils. Four applications of constant-Q active inductors and active transformers namely a 2.4 GHz voltage-controlled oscillator with -119.5dBc/Hz phase noise at 1 MHz offset, a 2.4 GHz current-mode phase-locked loop with -116dBc/Hz phase noise at 1 MHz offset and 80ns lock time, a 5 MHz 100X oversampled current-mode sigma-delta modulator with 50dB dynamic range and 65dB SNR, and a 1.6 GHz QPSK phase modulator with -101dBc/Hz phase noise at 1 MHz offset are presented.

Implementation of Passive and Active Circuit Elements in Cylindrical Finite-Difference Time-Domain Formulation

The implementation of passive and active linear circuit elements in cylindrical finite-difference time-domain technique (CFDTD) is developed. The updating equations for active element such as a voltage sources and passive elements such as resistors, capacitors and inductors are represented for elements located along one of the cylindrical coordinate’s independent parameters. The analytical solutions for simple circuit configurations are computed and used as a reference to verify and confirm the accuracy of the developed CFDTD formulation and numerical results.

Synaptic communication mediates the assembly of a self-organizing circuit that controls reproduction

Migration of gonadotropin-releasing hormone (GnRH) neurons from their birthplace in the nasal placode to their hypothalamic destination is critical for vertebrate reproduction and species persistence. While their migration mode as individual GnRH neurons has been extensively studied, the role of GnRH-GnRH cell communication during migration remains largely unexplored. Here, we show in awake zebrafish larvae that migrating GnRH neurons pause at the nasal-forebrain junction and form clusters that act as interhemisphere neuronal ensembles. Within the ensembles, GnRH neurons create an isolated, spontaneously active circuit that is internally wired through monosynaptic glutamatergic synapses into which newborn GnRH neurons integrate before entering the brain. This initial phase of integration drives a phenotypic switch, which is essential for GnRH neurons to properly migrate toward their hypothalamic destination. Together, these experiments reveal a critical step for reproduction, which depends on synaptic communication between migrating GnRH neurons.

Adjustment of the Early Meets Late Module to Differentiate the Active Circuit of a Dual Loop Reentrant Atrial Tachycardia

In dual loop reentrant ATs, the differentiation of the active circuit from the passive circuit in a dual loop reentry is still challenging. In such complicated AT cases, entrainment pacing is useful for determining the dominant circuit. However, we differentiated the active circuit by an AT activation map with an adjustment of the lower threshold value in the early meets late module. We also detected the gap of the previous PVI line by the same map with a further adjustment of the lower threshold value. The adjustment of the lower threshold might be advantageous for differentiating an active circuit of a dual loop reentry as well as gaps along the PVI line.

A distributed interpolative sigma-delta interface for fluxgate sensor

This paper presents a sigma-delta interface for fluxgate sensor based on a single-loop high-order modulation. A feedforward summation loop structure can reduce the linearity overload in integrators and the swing of integration signals. A Local feedback branch is proposed to realize the zero of noise transfer function (NTF) optimization and enhance noise shaping performance within signal band. The interface is fabricated in a standard 0.5 [Formula: see text]m CMOS process and the active circuit area is about 13 mm2. The chip consumes 120 mW from a 10 V supply with a sampling clock of 250 k Hz. The average noise floor of the digital fluxgate is about −115 dBV/Hz[Formula: see text] over a 100 Hz bandwidth.