Chance Glenn

Observation of chaos in a microwave limiter circuit

Chaotic behaviour has been observed in a microwave limiter circuit that consists of a shunt p-i-n diode cascaded with a 0.68-dB/MHz rolloff bandpass filter. The chaos manifests itself as a broad-band power spectral density of the output signal. The chaos appears and disappears as the incident power to the limiter circuit is increased, suggesting bifurcations and periodic windows in the chaotic region. Data are included that illustrate classic characteristics of chaos such as period doubling and broad-band spectra.<<ETX>>

A modified shifted means-based segmentation approach to detect active regions and coronal holes in the solar dynamics observatory images

Solar images taken at different wavelengths enable scientists to visualize and analyze the suns activities. The Solar Dynamics Observatory (SDO) provides high-resolution images of the sun, with cadence in seconds, taken at varying wavelengths, resulting in finely detailed, almost continuous data for researchers examination. We propose an approach to find active regions and coronal holes that involves shifted means based segmentation, and voting based edge linking to link fragments combined with Moores neighbor tracing algorithm to highlight the regions of interest. This approach is illustrated by using the images taken by the AIA telescopes onboard of the SDO mission. We obtain a segmented image that clearly isolates the active regions. Moreover this method is comparatively faster than the commonly used fuzzy logic based methods. This method is capable of forming a foundation for the analysis of various other features of the sun like detection of prominences.

Mutually orthogonal chaotic multiplexing

This paper describes the formulation and analysis of a new digital multiplexing technique. Mutually orthogonal chaotic (MOC) multiplexing has its foundation in nonlinear dynamical systems and chaos theory. We outline the conceptualization and analysis of the algorithm. We show simulation results for the implementation and show that there is superior bandwidth efficiency and superior noise performance as compared to standard single carrier modulation techniques. We discuss potential applications of MOC multiplexing and the implications for digital communications and signal processing in general.

Trends in mixer damage

The dynamic damage properties of 74 pairs of 1N23 X-band mixer diodes have been measured using a train of 30 short pulses at a 1-p.p.s. repetition rate. The pulsewidths used were from 25 ns to 1 mu s and the pulse risetimes were less than 2 ns. A first 30- mu J pulse caused a 3-dB degradation of conversion loss. The damage of successive 16- mu J pulses asymptotically approached 3-dB.<<ETX>>