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As research and development of renewable and clean energy based systems is advancing rapidly, the nonlinear source emulator (NSE) is becoming very essential for testing of maximum power point trackers or downstream converters. Renewable and clean energy sources play important roles in both terrestrial and nonterrestrial applications. However, most existing NSEs have only been concerned with simulating energy sources in terrestrial applications, which may not be fast enough for testing of nonterrestrial applications. In this paper, a high-bandwidth NSE is developed that is able to simulate the behaviors of a typical nonlinear source under different critical conditions that can happen during their operations. The proposed 200-W NSE, which consists of a fourth-order output filter buck converter and a novel nonlinear small-signal reference generator, can quickly react not only to an instantaneous change in the input source but also to a load step between nominal and open circuit. Moreover, all of these operation modes have a very fast settling time of only 10 $\mu$ s, which is hundreds of times faster than that of existing works. This attribute allows for higher speed and a more efficient maximum power point tracking algorithm. The proposed NSE, therefore, offers a superior dynamic performance among devices of the same kind.

In this paper, we present flicker noise measurements of two X-band direct conversion mixers implemented in a SiGe:C BiCMOS technology. Both mixers use a ring structure with either Schottky diodes or diode-connected HBTs for double balanced operation. The mixers are packaged in a metal casing on an Arlon 25N substrate to shield the sensitive noise measurement. Conversion loss measurements of both mixers is performed both for on-wafer and packaged versions. The experimental results shows that the Schottky diode mixer exhibits a 1/f noise corner frequency of 250 kHz, while the diode connected HBT circuit demonstrates a 1/f noise corner frequency around 10 kHz.

This paper describes modeling, fabrication and high power optical characterization of thin gold films embedded in silicon dioxide. The propagation vector of surface plasmon polaritons has been calculated by the effective index method for the wavelength range of 750-1700 nm and film thickness of 15, 30 and 45 nm. The fabrication process of such plasmonic waveguides with width in the range of 1-100 μm and their quality inspection are described. The results of optical characterization of plasmonic waveguides using a high power laser with the peak power wavelength 1064 nm show significant deviation from the linear propagation regime of surface plasmon polaritons at the average input power of 100 mW and above. Possible reasons for this deviation are heating of the waveguides and subsequent changes in the coupling and propagation losses.

A new type of Marchand balun is presented in this paper, which has the property of complex impedance transformation. To allow the Marchand balun to transform between arbitrary complex impedances, three reactances should be added to the circuit. A detailed analysis of the circuit gives the governing equations. To verify the theory, a design and electromagnetic simulation of a lumped element Marchand balun is made in a SiGe BiCMOS technology. The lumped element impementation is favorable because capacitors are placed where the additional reactances should be added. Thus it is possible to absorb a positive reactance by reducing a capacitor. At the design frequency of 10.5 GHz it matches 50Ω to 50 - j66Ω. It has an insertion loss of 5.1 dB, an input reflection of −20.8 dB, as well as phase and magnitude imbalance better than 0.2° and 0.12 dB, respectively.

The conventional method of modeling CMUTs use the isotropic plate equation to calculate the deflection, leading to deviations from FEM simulations including anisotropic effects of around 10% in center deflection. In this paper, the deflection is found for square plates using the full anisotropic plate equation and the Galerkin method. Utilizing the symmetry of the silicon crystal, a compact and accurate expression for the deflection can be obtained. The deviation from FEM in center deflection is

A method for making Vector Flow Images using the transverse oscillation (TO) approach on a convex array is presented. The paper presents optimization schemes for TO fields for convex probes and evaluates their performance using Field II simulations and measurements using the SARUS experimental scanner. A 3 MHz 192 elements convex array probe (pitch 0.33 mm) is used in both simulations and measurements. An F-number of 5 is used in transmit and two 32 element wide peaks are used in receive separated by 96 elements between peaks. Parabolic velocity profiles are simulated at beam-to-flow angles from 90 to 45 degrees in steps of 15 degrees. The optimization routine changes the lateral oscillation period lx to yield the best possible estimates based on the energy ratio between positive and negative spatial frequencies in the ultrasound field. The basic equation for lx gives 1.14 mm at 40 mm, and 1.51 mm from the simulated point spread function. This results in a bias of 35% as lx directly scales the estimated velocities. Optimizing the focusing yields a lx of 1.61 mm. The energy ratio is reduced from -12.8 dB to -20.1 dB and the spectral bandwidth from 115.1 m􀀀1 to 96.5 m􀀀1. lx is maintained between 1.47 and 1.70 mm from 25 mm to 70 mm and is increased to 2.8 mm at a depth of 100 mm. Parabolic profiles are estimated using 16 missions. The optimization gives a reduction in std. from 8.5% to 5.9% with a reduction in bias from 35% to 1.02% at 90 degrees (transverse flow) at a depth of 40 mm. Measurements have been made using the SARUS experimental ultrasound scanner and a BK Medical 8820e convex array transducer. Sixty-four elements was used in transmit and 2 x 32 elements in receive for creating a color flow map image of a flow rig phantom with a laminar, parabolic flow. At 75 degrees a bias of less than 1% was obtained.

Instead of using frequency multipliers before a fundamental mixer, subharmonic mixers can be used. In order to develop novel subharmonic mixer architectures it is necessary to know the exact signal phase at the nonlinear element. The purpose of this paper is to generalize the description of the small-signal admittance in a Schottky-diode mixer where the phase can be set arbitrarily. It is shown that only for the case of a fundamental frequency mixer this admittance becomes a purely real valued conductance. To test the theory a ×4 subharmonic sub-millimeter wave mixer is designed and simulated. With an RF frequency of 640 GHz, this design achieves a conversion gain of −13.5 dB with a LO-power of only −2.5 dBm.

Conventional color flow images are limited in velocity range and can either show the high velocities in systole or be optimized for the lower diastolic velocities. The full dynamics of the flow is, thus, hard to visualize. The dynamic range can be significantly increased by employing synthetic aperture flow imaging as demonstrated in this paper. Synthetic aperture, directional beamforming, and cross-correlation are used to produce B-mode and vector velocity images at high frame rates. The frame rate equals the effective pulse repetition frequency of each imaging mode. Emissions for making the B-mode images and velocity maps are interleaved in a 1-to-1 ratio. This provides continuous data allowing a wide range of velocities to be estimated. Two cases are considered in the flow estimation: In the first case, the angle of the flow is determined from the B-mode image. In the other case, the angle is determined by estimating the flow velocity in all directions and choosing the one with the strongest correlation. The method works for all angles, including fully axial and fully transverse flows. Field II simulations with a 192 element, 7 MHz linear array are made of laminar, transverse flow profiles. For a simulated peak velocity of 0.5 m/s, the relative bias is -6.8% and the relative standard deviation is 6.1%. The bias on the angle is 0.98 degrees with a standard deviation of 2.39 degrees when using the flow estimator to determine the angle. For a peak velocity of 0.05 m/s, the relative bias of the velocity estimation is -1.8% and the relative standard deviation 5.4%. The approach can thus estimate both high and low velocities with equal accuracy and thereby makes it possible to present vector flow images with a high dynamic range. Measurements are made using the SARUS research scanner, a linear array transducer similar to the simulated one, and a recirculating flow rig with a blood mimicking fluid and a parabolic flow profile with a peak velocity of approximately 0.3 m/s. The relative bias of the velocity estimation is 0.19% and the mean relative standard deviation 4.9%. For the direction estimation, the bias is 3.2 degrees with a standard deviation of 1.6 degrees.

In this paper a 24 GHz integrated front-end transceiver for vital signs detection (VSD) radars is described. The heterodyne radar transceiver integrates LO buffering and quadrature splitting circuits, up- and down-conversion SSB mixers and two cascaded receiver LNA's. The chip has been manufactured in a 0.25 µm SiGe:C BiCMOS technology and its size is 1390 × 2690 µm2. The transmitter demonstrates a maximum output power at 24 GHz of approximately −30 dBm with an externally applied LO power of 3 dBm. The receiver demonstrates a peak gain of 13.3 dB at 22.15 GHz with >10 dB return loss. The power consumption of the entire transceiver is approximately 164 mW.