Sector Neutral Portfolios: Long Memory Motifs Persistence in Market Structure Dynamics

We study soft persistence (existence in subsequent temporal layers of motifs from the initial layer) of motif structures in Triangulated Maximally Filtered Graphs (TMFG) generated from time-varying Kendall correlation matrices computed from stock prices log-returns over rolling windows with exponential smoothing. We observe long-memory processes in these structures in the form of power law decays in the number of persistent motifs. The decays then transition to a plateau regime with a power-law decay with smaller exponent. We demonstrate that identifying persistent motifs allows for forecasting and applications to portfolio diversification. Balanced portfolios are often constructed from the analysis of historic correlations, however not all past correlations are persistently reflected into the future. Sector neutrality has also been a central theme in portfolio diversification and systemic risk. We present an unsupervised technique to identify persistently correlated sets of stocks. These are empirically found to identify sectors driven by strong fundamentals. Applications of these findings are tested in two distinct ways on four different markets, resulting in significant reduction in portfolio volatility. A persistence-based measure for portfolio allocation is proposed and shown to outperform volatility weighting when tested out of sample

Design and Realization of a MEMS Tunable Reflectarray for mm-Wave Imaging Application

Electronic beam scanning reflectarrays represent a very interesting solution to obtain reconfigurable antennas at mm-wave frequencies. The potentialities of such systems could be further increased in terms of costs and performance by employing MEMS devices. In this paper we present the design and the simulated results of a two-layer MEMS tuneable reflectarray. This antenna is designed for outdoor passive mm-waves imaging applications (35 GHz). The target is to realize a low cost, fast, small and light antenna system to be implemented in portable devices. The manufacturing of the prototype is on the way at the ITC-irst (Trento – IT) laboratories

Combined Liquid Crystal and MEMS Phase Shifter: Preliminary Measurement Results

This paper presents preliminary measurement results of a reflection phase shifter realized in a hybrid MEMS and Liquid Crystal technology. The MEMS switch part of the phase shifter is undesirably affected by Liquid Crystal, leading to a higher actuation voltage and the absence of a sudden switching operation. Nevertheless, measurements of the LC filled MEMS switch could achieve the desired 180° phase shift

MEMS and combined MEMS/LC technology for mm-wave Electronic Scanning Reflectarrays

This paper presents the most recent advances within ARASCOM project (MEMS & Liquid Crystal based’ Agile Reflectarray Antennas for Security & COMmunication). One of the objectives of the project is the exploitation of MEMS and Liquid Crystal (LC) technology in mm-wave electronic scanning reflectarrays. In particular two solutions have been investigated: a MEMS-only approach, where the switches are used to obtain reconfigurable elementary cells with 1-bit of phase resolution - an efficient method applicable in large antennas; and a LC/MEMS combined solution, where the LCs provide a continuous phase-shift up to 180° and a MEMS is used to add another 180° when necessary. Preliminary results validate the proposed approach and give indications for future steps

MEMS and combined MEMS/LC technology for mm-wave Electronic Scanning

This paper proposes two innovative solutions for the exploitation of MEMS and Liquid Crystal (LC) technology in mm-wave electronic scanning reflectarrays: a MEMS-only approach, where the switches are used to obtain reconfigurable elementary cells with 1-bit of phase resolution and a LC/MEMS combined solution, able to provide a continuous phaseshift up to 180°