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Abstract-Many problems in radar and communication signal processing involve radio frequency (RF) signals of very high bandwidth. This presents a serious challenge to systems that might attempt to use a high-rate analog-to-digital converter (ADC) to sample these signals, as prescribed by the Shannon/Nyquist sampling theorem. In these situations, however, the information level of the signal is often far lower than the actual bandwidth, which prompts the question of whether more efficient schemes can be developed for measuring such signals. In this paper we propose a system that uses modulation, filtering, and sampling to produce a low-rate set of digital measurements. Our "analog-to-information converter" (AIC) is inspired by the recent theory of Compressive Sensing (CS), which states that a discrete signal having a sparse representation in some dictionary can be recovered from a small number of linear projections of that signal. We generalize the CS theory to continuous-time sparse signals, explain our proposed AIC system in the CS context, and discuss practical issues regarding implementation.

Abstract-We develop a framework for analog-to-information conversion that enables sub-Nyquist acquisition and processing of wideband signals that are sparse in a local Fourier representation. The first component of the framework is a random sampling system that can be implemented in practical hardware. The second is an efficient information recovery algorithm to compute the spectrogram of the signal, which we dub the sparsogram. A simulated acquisition of a frequency hopping signal operates at 33× sub-Nyquist average sampling rate with little degradation in signal quality.

In this paper, we present a low-loss plasmonic Bragg reflector structure with high light-confinement. We show that periodic changes in the dielectric materials of the metal-insulator-metal waveguides can be utilized to design efficient subwavelength Bragg reflectors and micro-cavities. FDTD simulation results of the designed Bragg reflector using realistic material parameters justify that the transfer matrix calculations are adequate for the design purposes.

The authors present an optical range resonator based on single mode metal-insulator-metal plasmonic gap waveguides. Complete transmission at 90° bends would enable the design of rectangular structures with cross-section area less than 500nm2, which consequently leads to easing the fabrication process. The resonator exhibits a free spectral range of 270nm. We show that a small bridge between the resonator and the input waveguide can be used to tune the resonance frequency. In addition, ultracompact add/drop directional couplers are realizable using the presented ring resonator structure.

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In this paper, we present a modeling and design methodology based on characteristic impedance for plasmonic waveguides with Metal-Insulator-Metal (MIM) configuration. Finite-Difference Time-Domain (FDTD) simulations indicate that the impedance matching results in negligible reflection at discontinuities in MIM heterostructures. Leveraging the MIM impedance model, we present a general Transfer Matrix Method model for MIM Bragg reflectors and validate our model against FDTD simulations. We show that both periodically stacked dielectric layers of different thickness or different material can achieve the same performance in terms of propagation loss and minimum transmission at the central bandgap frequency in the case of a finite number of periods.

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