7,078 research outputs found
Novel concept for pulse compression via structured spatial energy distribution
We present a novel concept for pulse compression scheme applicable at RF,
microwave and possibly to optical frequencies based on structured energy
distribution in cavities supporting degenerate band-edge (DBE) modes. For such
modes a significant fraction of energy resides in a small fraction of the
cavity length. Such energy concentration provides a basis for superior
performance for applications in microwave pulse compression devices (MPC) when
compared to conventional cavities. The novel design features: larger loaded
quality factor of the cavity and stored energy compared to conventional
designs, robustness to variations of cavity loading, energy feeding and
extraction at the cavity center, substantial reduction of the cavity size by
use of equivalent lumped circuits for low energy sections of the cavity,
controlled pulse shaping via engineered extraction techniques. The presented
concepts are general, in terms of equivalent transmission lines, and can be
applied to a variety of realistic guiding structures.Comment: 18 pages, 10 figure
High Frequency Quantum Admittance and Noise Measurement with an On-chip Resonant Circuit
By coupling a quantum detector, a superconductor-insulator-superconductor
junction, to a Josephson junction \textit{via} a resonant circuit we probe the
high frequency properties, namely the ac complex admittance and the current
fluctuations of the Josephson junction at the resonant frequencies. The
admittance components show frequency dependent singularities related to the
superconducting density of state while the noise exhibits a strong frequency
dependence, consistent with theoretical predictions. The circuit also allows to
probe separately the emission and absorption noise in the quantum regime of the
superconducting resonant circuit at equilibrium. At low temperature the
resonant circuit exhibits only absorption noise related to zero point
fluctuations, whereas at higher temperature emission noise is also present.Comment: 15 pages, 15 figure
Synthesis of high-order bandpass filters based on coupled-resonator optical waveguides (CROWs)
We present a filter design formalism for the synthesis of coupled-resonator optical waveguide (CROW) filters. This formalism leads to expressions and a methodology for deriving the coupling coefficients of CROWs for the desired filter responses and is based on coupled-mode theory as well as the recursive properties of the coupling matrix. The coupling coefficients are universal and can be applied to various types of resonators. We describe a method for the conversion of the coupling coefficients to the parameters based on ring resonators and grating defect resonators. The designs of Butterworth and Bessel CROW filters are demonstrated as examples
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