Stan Skafidas

IEEE 802.15.3c Medium Access Controller Throughput for Phased Array Systems

This paper studies the impact of phased array antennas directivity onto the throughput performance of WPANs adopting the IEEE 802.15.3 MAC standard in the 60 GHz band. High gain directional transmission is desirable in the 60 GHz band to overcome the high signal attenuation typical of these frequencies and improve the wireless channel reliability in order to achieve data rates up to 5 Gbps. In our antenna system model, directional transmission at both transmitter and receiver side is accomplished through a simplified scheme of direction of arrival estimation and beamsteering. We have implemented the antenna system and the antenna control protocol within 802.15.3 MAC in ns2. Our simulation analysis shows that the accuracy of the antenna pointing direction must increase with the antenna directivity otherwise significant throughput degradation is experienced.

Emergence of competitive control in a memristor-based neuromorphic circuit

Recent work in neuroscience is revealing how the blowfly rapidly detects orientation using neural circuits distributed directly behind its photo receptors. These circuits like all biological systems rely on timing, competition, feedback, and energy optimization. The recent realization of the passive memristor device, the so-called fourth fundamental passive element of circuit theory, assists with making low power biologically inspired parallel analog computation achievable. Building on these developments, we present a memristor-based neuromorphic competitive control (mNCC) circuit, which utilizes a single sensor and can control the output of N actuators delivering optimal scalable performance, and immunity from device variation and environmental noise.

A simple voltage reference with ultra supply independency

An ultra wide dynamic range voltage reference operating with power consumption of pico-watt has been designed for a retinal prosthesis device using IBM 65nm CMOS process. The temperature coefficient is zeroed at 37 °C while achieving 2.5 ppm/°C over the range from 25 °C to 75 °C. A perfect suppression of the supply voltage dependence is realised to provide line sensitivity of 0.04%/V with ultra low input voltage of 0.5 V up to 3.5 V. The power supply noise attenuation is simulated to maintain at -100 dB across whole frequency band up to 100GHz. The occupied chip area is maintained as low as 0.003 mm2 with size of 35μm by 75μm.

Performance Enhanced Butt Coupling for Effective Interconnection Between Fiber and Silicon Nanowire

A performance enhanced butt coupling structure incorporating a vertically and laterally tapered SiON polymer core on silicon (Si) to tunnel and widen propagating optical modes of adiabatic taper is proposed. The proposed structure can effectively overcome the strong back reflections caused at the interface between fiber and Si nanowire to enable higher coupling efficiency. The placement of the SiON polymer core is chosen to restrict the passage of light through the bottom cladding to avoid unnecessary leakage. The performance of the structure is characterized for distinct features, including taping length, coupling efficiency, and coupling bandwidth for both single as well as cacaded configurations, compared with the state-of-the-art grating coupler. It is found that, with the right set of design specifications, butt couplers can outperform grating couplers in both coupling efficiency and bandwidth, although grating couplers are considered friendlier for wafer-level testing.

Nanosensors for next generation drug screening

One promising path for future drug screening technologies is to examine the binding of ligands to target proteins at the single molecule level by passing them through nanometer sized pores and measuring the change in pore current during translocation. With the aim of evaluating such technologies we perform virtual experiments on the translocation of proteins through silicon nitride nanopores. These simulations consist of large scale, fully atomistic models of the translocation process that involve steering a test protein through the nanopore on a timescale of tens of nanoseconds. We make a comparison between theoretically expected and simulated values of the current drop that is seen when the protein occupies the pore. Details of the stability of the protein and the preservation of its function as measured by its secondary and tertiary structure will be presented to validate both the simulation results and the fundamental design of the proposed device. Finally, the results will be placed in the context of experimental work that combines nanofabrication and microuidics to create a high throughput, low cost, drug screening device.

A precise charge balancing and compliance voltage monitoring stimulator front-end for 1024-electrodes retinal prosthesis

In this paper, we present a precise charge balancing and compliance voltage monitoring stimulator front-end for 1024-electrode retinal prosthesis. Our stimulator is based on current mode stimulation. To generate a precisely matched biphasic current pulse, a dynamic current copying technique is applied at the stimulator front-end. A compliance voltage monitoring circuitry is included at the stimulator front-end to detect if a voltage across electrode-tissue interface goes beyond a predefined compliance voltage. Simulation results show the mismatch of a biphasic current pulse (at a maximum stimulation current of 476μA) is less than 0.1%. Also, the stimulator issues alarm signals, when a voltage compliance occurs during stimulation due to high tissue impedance. Our stimulator is implemented using a 65nm low voltage (LV) CMOS process, which helps reducing implementation area and power consumption.

A low-power, small-area and programmable bandgap reference

In this paper, we present a low-power, small-area and programmable bandgap reference, based on the reverse bandgap reference concept. It is implemented in a 65nm digital CMOS process with 1.2V power supply. It employs two switched capacitor amplifiers to weight temperature dependent voltages with opposite polarity. Programmability is achieved by adjusting a closed-loop gain of these two amplifiers. The implemented BGR generates three reference voltages, such as 0.591V (V_REF1), 0.872V (V_REF2) and 1.189V (V_REF3). In simulation, with ±10% supply voltage variation, the temperature coefficient (TC) of V_REF1, V_REF2 and V_REF3 is less than 43ppm/°C, 28ppm/°C and 33ppm/°C, respectivley, in the temperature range from -40°C to 100°C. The average power consumption is less than 40μW for V_REF1, 60μW for V_REF2 and 110μW for V_REF3. The layout area (excluding bonding pads) is 200μm by 190μm.

Provisioning in-house mobility for FTTH customers by incorporating modifications in optical network unit (ONU)

A modified ONU provisioning in-house mobility for FTTH customers is proposed and demonstrated. This scheme, in addition to fixed point access, distributes FTTH services wirelessly, potentially at equal speeds.

Millimeter-wave integrated radar systems and techniques

Abstract Recent advances in semiconductor fabrication are providing the opportunity to build very small and cost-effective single chip integrated radar systems operating at millimeter-wave frequencies and beyond. These tiny radar systems will enable a wide range of new applications such as automotive radar, safety helmet radar, robot guidance radar, UAV collision avoidance and mapping radar, bicycle safety radar, and many other possibilities. Considerable progress has been made in designing and building such systems; however, many challenges remain related to limitations imposed by radio frequency IC technology such as Complementary Metal Oxide Semiconductors (CMOS) including modest dynamic range and modest noise figure for low noise amplifies (LNAs), oscillator phase noise, limited transmit power, etc. There is also likely to be a significant interference challenge arising from large numbers of small radars operating in close spatial and spectral proximity in many of the envisioned applications. In this chapter we present an overview of some of the design challenges facing millimeter-wave radar, and shed light on recent advances in system design and signal processing techniques, including adaptive waveform scheduling and interference mitigation. Advances in signal processing will allow multiple radars to operate in an uncoordinated manner with limited processing power using adaptive waveform scheduling, that leads to better interference mitigation and higher ranging performance. We present some properties of the millimeter-wave spectrum and investigate ray-tracing methods as an efficient, accurate, and rapid testing platform for consumer radars applications, where we develop a ray-tracing propagation model for automotive radar operating in an urban environment. Also, we introduce novel tools from stochastic geometry to characterize the statistics of the interference resulting from many radars sharing the same spectrum in a particular location. Specifically, we study automotive radar applications and obtain interference statistics and the estimated detection performance. Finally, we briefly discuss certain fundamental limitations imposed on radar system capabilities, by CMOS technology and by the information carrying capacity of electromagnetic waves.

Compact Silicon Photonic Grating Coupler With Dual-Taper Partial Overlay Spot-Size Converter

A compact silicon photonic grating coupler enabling fiber-to-chip light coupling at a minimized footprint is proposed. The proposed coupler, which is partially overlaid at the tapered region, downsizes the effective length of the spot-size converter to 60 μm while reducing the lateral height and width adiabatically to 220 nm and 320 nm, respectively. The incorporation of such a coupler in a photonic integrated circuit requires a total physical length and width of 75 μm and 14 μm, respectively, to enable effective interfacing with single mode fiber. The coupling efficiency and bandwidth of the structure at the light wavelength of 1550 nm are quantified as 68% and 67 nm, respectively, which outperform most recent demonstrations.