Passive discrete-time systems with a Pontryagin state space

Passive discrete-time systems with Hilbert spaces as an incoming and outgoing space and a Pontryagin space as a state space are investigated. A geometric characterization when the index of the transfer function coincides with the negative index of the state space is given. In this case, an isometric (co-isometric) system has a product representation corresponding to the left (right) Krein-Langer factorization of the transfer function. A new criterion, based on the inclusion of reproducing kernel spaces, when a product of two isometric (co-isometric) systems preserves controllability (observability), is obtained. The concept of the defect function is expanded for generalized Schur functions, and realizations of generalized Schur functions with zero defect functions are studied

An Analog Baseband Approach for Designing Full-Duplex Radios

Recent wireless testbed implementations have proven that full-duplex communication is in fact possible and can outperform half-duplex systems. Many of these implementations modify existing half-duplex systems to operate in full-duplex. To realize the full potential of full-duplex, radios need to be designed with self-interference in mind. In our work, we use an experimental setup with a patch antenna prototype to characterize the self-interference channel between two radios. In doing so, we form an analytical model to design analog baseband cancellation techniques. We show that our cancellation scheme can provide up to 10 dB improved signal strength, 2.5 bps/Hz increase in rate, and a 10,000 improvement in BER as compared to the RF only cancellation provided by the patch antenna.Comment: 5 pages, 8 figures, to appear in 2013 Asilomar Conference proceeding

Generalized Schur–Nevanlinna functions and their realizations

Pontryagin space operator valued generalized Schur functions and generalized Nevanlinna functions are investigated by using discrete-time systems, or operator colligations, and state space realizations. It is shown that generalized Schur functions have strong radial limit values almost everywhere on the unit circle. These limit values are contractive with respect to the indefinite inner product, which allows one to generalize the notion of an inner function to Pontryagin space operator valued setting. Transfer functions of self-adjoint systems such that their state spaces are Pontryagin spaces, are generalized Nevanlinna functions, and symmetric generalized Schur functions can be realized as transfer functions of self-adjoint systems with Kreĭn spaces as state spaces. A criterion when a symmetric generalized Schur function is also a generalized Nevanlinna function is given. The criterion involves the negative index of the weak similarity mapping between an optimal minimal realization and its dual. In the special case corresponding to the generalization of an inner function, a concrete model for the weak similarity mapping can be obtained by using the canonical realizations.The Author(s) 2020. CC BY 4.0fi=vertaisarvioitu|en=peerReviewed

Minimal Passive Realizations of Generalized Schur Functions in Pontryagin Spaces

Passive discrete-time systems in Pontryagin space setting are investigated. In this case the transfer functions of passive systems, or characteristic functions of contractive operator colligations, are generalized Schur functions. The existence of optimal and *-optimal minimal realizations for generalized Schur functions are proved. By using those realizations, a new definition, which covers the case of generalized Schur functions, is given for defects functions. A criterion due to D.Z. Arov and M.A. Nudelman, when all minimal passive realizations of the same Schur function are unitarily similar, is generalized to the class of generalized Schur functions. The approach used here is new; it relies completely on the theory of passive systems.©TheAuthor(s)2020. CC BY 4.0fi=vertaisarvioitu|en=peerReviewed

Passive discrete-time systems with a Pontryagin state space

Passive discrete-time systems with Hilbert spaces as an incoming and outgoing space and a Pontryagin space as a state space are investigated. A geometric characterization when the index of the transfer function coincides with the negative index of the state space is given. In this case, an isometric (co-isometric) system has a product representation corresponding to the left (right) Kreĭn–Langer factorization of the transfer function. A new criterion, based on the inclusion of reproducing kernel spaces, when a product of two isometric (co-isometric) systems preserves controllability (observability), is obtained. The concept of the defect function is expanded for generalized Schur functions, and realizations of generalized Schur functions with zero defect functions are studied.fi=vertaisarvioitu|en=peerReviewed

Household consumption reduction during the crisis years:a gateway to sustainable consumption?

Abstract. The disruption in household consumption presented by the COVID-19 pandemic has sparked marketing scholars to speculate whether the crisis times have accelerated progression towards more sustainable consumption. In addition, very recently Europe has faced a severe energy crisis and rising inflation rates resulting in rapidly increased living costs. Consequently, the objective of this master’s thesis is to study how the recent crisis years have influenced household consumption reduction and identify which drivers have motivated households to reduce consumption during the crisis times. The theoretical framework of this thesis explores the phenomenon of anticonsumption, which is a marketing research orientation interested in consumers’ ways and motivation to reduce consumption. Furthermore, household consumption and what is already known about the pandemic’s repercussions are reviewed to form a framework for the research. The empirical part of this thesis applies qualitative research method in form of focus group interviews which are recorded, transcribed, and finally coded for further analysis to provide the empirical findings. The findings conclude that the crisis years have increased household consumption reduction, implying of more sustainable consumption. Seven different categories consisting of variety of methods to reduce consumption during the crisis years were identified from the data. Especially increased planning, reconsidering what is necessary consumption, and changes in buying process demonstrated of reduced consumption during the crisis times. While the pandemic had mainly targeted specific consumption categories, the cost-of-living crisis had affected households in a more holistic way considering daily activities. Saving money was found to be the most significant driver to reduce consumption, but the crisis years had also increased households’ motivation for sustainable consumption and crisis preparedness for the future. Consumption reduction drivers that were found to be characteristic to crisis times included sense of security, preparing for the future, and solidarity. The research findings contribute to the anticonsumption research field in relation to the recent crisis years. The findings indicate that in pursuit of more effective sustainable marketing and demarketing strategies, instead of emphasizing the negative effects of overconsumption, highlighting the positive individual level outcomes that consumption reduction can generate, may prove to be more efficient. Consumers are aware of the harmfulness of overconsumption and demonstrate increased motivation to reduced materialism and investing more in product quality, which underlines the importance of quality in product design and used materials. The findings also provide support for the effectiveness of price-based environmental policies, when aiming at decreased consumption on a household level