Michael Haider

Quantum theory of the dissipative Josephson parametric amplifier

Recent research in superconducting quantum circuits operating close to the quantum limit results in the need of a quantum mechanical treatment of losses. Of special interest is the dynamic behaviour of an open quantum system. As an example, a negative-resistance Josephson parametric amplifier is treated. The DC bias voltage is chosen such that a strong interaction between the Josephson junction and the two resonant circuits, the signal and the idler circuit, is achieved. Power exchange occurs between the two considered resonator modes and also between the resonator modes and the DC power supply. Losses in the resonators are modeled by the quantum Langevin method, which describes the losses by coupling the resonators to a heat bath representing a photon gas in thermal equilibrium. The derived dynamic behaviour does not provide signal energy saturation, like classically expected for parametric amplifiers. Introducing a phenomenological multi-photon coupling approach, saturation of the amplified signal is ensured. The time evolution of the signal and noise energy is calculated and numerically evaluated for a specific example in cases of both, the quantum Langevin method with and without the phenomenological multi-photon coupling approach. Copyright

An extension of the iransverse wave formulation to model stochastic electromagnetic fields

In this work we present the Correlation Transverse Wave Formulation (CTWF) method for direct computation of the auto- and cross correlation functions (ACFs and CCFs) of stationary stochastic electromagnetic fields. The transverse wave formulation, in performing a modal expansion of the electromagnetic fields in the homogeneous parts of the calculation domain and solving the near field continuity on both sides of the circuit surfaces, provides a direct derivation of the ACFs and CCFs without hypothesis on the structure of radiated fields.

Solution processing of silver nanowires for transparent heaters and flexible electronics

We present the solution-based synthesis of silver nanowires (AgNWs) with an aspect ratio over 400 in a short growth time of 20 min. The addition of potassium chloride (KCl) during the growth regulates the supply of silver atoms and leads to an agglomerate-free and well-dispersed solution. Via a facile and scalable deposition technique, i.e. spray-coating, the AgNWs are deposited to transparent electrodes (TEs) on flexible or glass substrates. Without any post-treatment such as sintering that can harm the substrate, the films show a high transparency at a low sheet resistance. The TEs are characterized as transparent heaters in terms of their infrared, transient thermal and electrical properties up to a working temperature of 130 deg. C. For the use in flexible electronics, an AgNW-film on a polyvinyl chloride (PVC) substrate is tested under operation for 10,000 bending cycles and shows only a slight increase in resistance.

Generalized Langevin theory for Josephson parametric amplification

Superconducting quantum circuits exhibit an extraordinary potential for future electronic applications. The most important element in superconducting quantum circuits is the Josephson junction, built by nanofabricated superconducting electrodes separated by a thin insulating layer. Superconducting devices allow mixing and parametric amplification up to the terahertz range under low energy consumption and ultra-low noise. High frequency signals at low temperatures exhibit a photon energy exceeding the thermal energy, resulting in the need of a quantum mechanical treatment of the electromagnetic field at millimeter-wave frequencies. In this work, we investigate the dynamic behaviour of a negative-resistance, dissipative DC biased Josephson parametric amplifier. The Langevin theory is used for modeling of the dissipation in the resonant circuits. We investigate Markovian dynamics for modeling the dissipative Josephson parametric amplifier in a correct manner, neglecting memory effects. We derive the equations of motions of the resonator operators and numerically evaluate the time evolution of the signal and noise energies. Applying a phenomenological multi-photon coupling approach, a correction of the Markovian assumption is achieved providing an expected saturation in the dynamical behaviour of the circuit.

Network methods for full-wave modeling of stochastic electromagnetic fields

Stochastic electromagnetic (EM) fields with Gaussian amplitude probability distribution can be represented by correlation dyadics. The analytic treatment of such stochastic EM fields using Greens functions and correlation dyadics allows to compute the spectral energy density distribution of stochastic EM fields. Applying the Method of Moments we convert the field problem into a networklike problem described by algebraic equations.

The correlation transmission line matrix (CTLM) method

Modeling of field propagation for noisy electromagnetic (EM) fields requires consideration of auto- and cross-correlation field spectral densities. The correlation transmission line matrix (CTLM) method is an extension of the TLM method allowing for the time-domain modeling of stochastic EM fields. In this contribution, the CTLM method is treated, and its application in combination with established full-wave solvers, and a numerical study is presented.

Field modeling of dynamic inductive power supply of electric vehicles on the road

In this work we report the simulation of the properties of a MFIPT system based on the numerical field modeling of the inductive coupling. The coupled coil arrangement is modeled by CST under consideration of the losses due to the road material and the enclosing metallic structure of the electric vehicle. We study the effect of shielding on the mutual coupling between a primary coil embedded in the road and a secondary coil in the electric vehicle, and evaluate resulting magnetic field levels in the passenger area.

Time-domain far-field measurements for cross-correlation analysis

In this work the scanned contribution of a pseudo random noise signal generated in a printed circuit board (PCB) is correlated with the radiated electromagnetic interference (EMI) in the near-field as well as in the far-field. Far-field measurements were performed inside the anechoic chamber for the DUT installed on a rotating table. The proposed cross-correlation spatial-time analysis allows to localize the path of the generated pseudorandom source over the PCB surface and to predict the angular distribution of the radiated emissions from the electronic devices.

Characterization of EM field above a single aperture or air-vents of an enclosure for a variable degree of correlation between stochastic sources inside

In this paper, an electromagnetic field distribution above a single aperture or an array of apertures (so-called air-vent) of a metal enclosure with two monopole sources inside is considered. Based on the previously developed approach that uses the S-parameter description of a multi-port network model of sources and near-field probes, incorporated into the correlation matrix calculation, the electromagnetic field above the aperture is characterized for a variable degree of correlation between considered sources. Height at which the aperture field is sampled and the type of aperture on enclosure lid are also taken into account. Experimental and numerical data have accompanied the analysis carried out in the paper.

Time-domain characterization of probes for two-point measurements of stochastic EM fields

Due to the internal switching processes high-bit-rate digital devices emit radiated electromagnetic interference (EMI). Scanning of the near-field of the radiated EMI of devices and printed circuit boards (PCBs) with ultra-wideband probes allows to record the EMI field correlations as a basis for modeling the EMI radiated into the environment. Accurate near-field measurements require a de-embedding process that removes the influence of the probes, transmission lines and measurement circuits on the measurement results. In this work we describe a de-embedding methodology based on the measured S-parameters of a test setup consisting of a microstrip test structure and the scanning probe.