arXiv subjects

Sandy Cochran

Publications and source records attributed to Sandy Cochran.

3 recordsLinked to original sources

arXiv2025

Bio-integrated ${\mu}$Bots with Overtone Ultra-Wideband Magnetoelectric Antennas for Wireless Telemetry

Implantable and wearable devices require antennas that are both miniaturized and efficient, yet conventional designs are constrained by narrow bandwidth and orientation sensitivity. We report overtone ultra-wideband magnetoelectric (OUWB-ME) antennas that exploit higher order acoustic modes in polished silicon substrates to achieve a 22.6 GHz bandwidth in the 3-4 GHz range. Packaged into "${\mu}$Bots," these magnetoelectric heterostructures bonded with silver nanoparticle inks maintain stable operation under biological loading. In vitro assays confirm the biocompatibility of AlN and the protective role of parylene encapsulation for FeGa. Ex vivo rat and human tissues reshape transmission spectra, identifying reproducible frequency windows near 3.3 and 3.9 GHz. ${\mu}$Bots enable real-time audiovisual telemetry using software-defined radios and exhibit compatibility with 7T MRI. By combining wideband response, robustness to misalignment, and biocompatible packaging, OUWB-ME ${\mu}$Bots provide a scalable platform for wireless bio-integrated communication and telemetry.

physics.app-ph↗

arXiv2025

An AI-driven EDA Algorithm-Empowered VCO and LDO Co-Design Method

Traditionally, the output noise and power supply rejection of low-dropout regulators (LDOs) are optimized to minimize power supply fluctuations, reducing their impact on the low-frequency noise of target voltage-controlled oscillators (VCOs). However, this sequential design approach does not fully address the trade-offs between high-frequency and LDO-induced low-frequency phase noise. To overcome this limitation, this paper presents a co-design method for low phase-noise LC-tank VCOs powered by LDOs. It is difficult to carry out the co-design using traditional manual design techniques. Hence, an efficient AI-driven EDA algorithm is used. To validate the proposed method, a 5.6 GHz LC-tank VCO with an integrated LDO is designed using a 65 nm CMOS process. Simulations show that the co-design method improves phase noise by 1.2 dB at a 1 MHz offset and reduces dynamic power consumption by 28.8%, with FoM increased by 2.4 dBc/Hz compared to the conventional sequential design method.

eess.SP↗

arXiv2018

Measuring the phase velocity of twisted wavefronts

Traditionally one defines the speed of a wave as a property of the medium. Recent studies in photonics have challenged this idea, indicating that spatial shaping of the optical wavefront has can alter the arrival time of single photons when compared to an entangled reference photon. However, relying only on time of flight measurements leads to ambiguity in the measurement. Unlike photonics, one can directly measure the phase and intensity of sound, permitting unambiguous measurements. We developed a bespoke 28-element ultrasonic phased array transducer to generate short pulses that carrying orbital angular momentum. Through spatial mapping, we observed pulse modulation that indicates a localised change in phase velocity by over 10 m/s. We present a geometrical argument for this effect, proposing that the phase velocity varies to compensate for the effective path length increase arising from spatial wavefront shaping. We expect that this pulse dispersion is a general effect for any spatially shaped wavefront and that it could be utilised to manipulate readings from pulse based sensor technologies such as SONAR, medical ultrasound, and underwater communication systems.

physics.class-ph↗