Rudi Paolo Paganelli

Theoretical and Numerical Design of a Wireless Power Transmission Link With GaN-Based Transmitter and Adaptive Receiver

In this paper, we describe a rigorous theoretical approach to the circuit-level nonlinear design of an entire inductive resonant wireless power transfer (IR-WPT) system, including the transmitter and receiver nonlinear subsystems. Starting from a novel analytical characterization of the inductive resonant link, the system efficiency is parametrically computed as a function of a set of circuital parameters, including the power levels to be transferred. These quantities are then used as design goals inside the nonlinear optimization of the transmitter and receiver blocks. By adopting the last generation miniaturized enhanced-mode AlGaN/GaN-power field-effect transistor and fast Schottky diodes, a Class-D amplifier and a full-bridge rectifier followed by a switching dc-dc Buck converter that acts as load impedance transformer are designed in a single optimization process at 6.78 MHz. Thus, the transmitter and the receiver are directly connected by the IR two-port network, and the system is capable to adapt to variable distances between the resonators of the IR-WPT link. The choice of the Class-D topology for the transmitter and the adaptability of the active receiver enable to get rid of inter-stage matching networks, which can severely reduce the overall efficiency, especially in high power transfer environments. With the proposed IR-WPT system, up to 44 W of transferred power and a peak of 73% dc-to-dc efficiency were obtained with an input dc voltage VDC=30 V at a link distance D=5 cm. Numerical and experimental results are discussed, demonstrating the accuracy of the proposed design procedure.

Envelope Tracking of an RF High Power Amplifier With an 8-Level Digitally Controlled GaN-on-Si Supply Modulator

This paper presents an envelope tracking (ET) transmitter architecture based on the combination of a novel 3-bit (N = 3) supply modulator and digital predistortion (DPD). The proposed power converter is based on a direct digital-to-analog conversion architecture that implements the binary-coded sum of N isolated dc voltages, allowing the synthesis of an output waveform with L = 2N voltage levels, with a binary distribution in the range ΔV = VM - VO (maximum voltage VM, offset voltage Vo). This solution provides a better voltage resolution VS = ΔV/(2N-1) with respect to typical multilevel switched-sources topologies (VS = ΔV/N). The improved voltage resolution enables the correction of the residual discretization error in the ET transmitter by means of DPD of the RF signal without the need of an auxiliary linear envelope amplifier. The proposed ET solution has been tested with an L-band 30-W lateral-diffused MOS RF high power amplifier (RF HPA) with 1.4- and 10-MHz long-term-evolution signals. In these conditions the converter demonstrated 92% and 83% efficiency, respectively, whereas the congregate efficiency of the transmitter are 38.3% and 23.9% at 5.5 and 1.9 W of average RF output power, respectively. These performances correspond to an improvement of 17.2 and 17.9 points for the power-added efficiency of the RF HPA and to 13.4 and 13 points of improvement for the efficiency of the entire transmitter with respect to fixed bias operation.

Joint Modeling of Piezoelectric Transducers and Power Conversion Circuits for Energy Harvesting Applications

In this paper, we describe a reliable modeling technique for piezoelectric transducers and a procedure for fast model parameters identification using inexpensive hardware and standard laboratory equipment. This technique is suitable for evaluating the performance of actively controlled power conversion circuits with custom input vibrations in the early phases of design. Direct measurements were taken on commercial Q220-A4-303YB cantilevered piezoelectric transducers from Piezo Systems with tip masses between 7 and 16 g and with two types of synchronized switch energy harvesters. The model describes, with a good degree of accuracy, both the response of the transducers to vibrations and their behavior with nonlinear power conversion circuits, including also the damping effects associated with the use of synchronized switch techniques.

Joint modeling of piezoelectric transducers and power conversion circuits for energy harvesting applications

This paper describes a reliable modeling technique for piezoelectric transducers and a procedure for identifying model parameters with few simple measurements and standard laboratory equipment. Direct measurements were taken on commercial Q220-A4-303YB piezoelectric transducers from Piezo Systems in a cantilever configuration with tip masses from 6 g to 18 g. For validation purposes, the behavior of the equivalent electromechanical circuits was simulated and compared to direct observations in real operating conditions. The model showed to predict with a high degree of accuracy both the frequency response of the transducers and the effects due to the presence of non-linear power converters which are usually ignored by conventional models presented in literature.

12-W

The chip-set for the transmitting power lineup of satellite SAR antenna T/R modules has been designed and implemented exploiting a 2- μm GaInP-GaAs heterojunction bipolar transistor (HBT) technology suitable for space applications. The HBT technology features an integrated emitter ballast resistor that enables high-power density operation without suffering thermal runaway phenomena. Two monolithic microwave integrated circuit (MMIC) driver amplifiers and a MMIC HPA are described: the drivers exhibit small-signal gains exceeding 21 dB and P1 dB output power of about 28 and 29 dBm, respectively, in a 2-GHz bandwidth and CW condition. The HPA delivers more than 40-dBm power at about 2.5-dB gain compression and power-added efficiency (PAE) exceeding 36% in a 700-MHz bandwidth in pulsed operation. Its peak performance at the center of the band are 40.9-dBm output power and 45% PAE. These performance are obtained within tight de-rating conditions for space applications.

X

This paper presents the design of miniaturized bond wire transformers assembled with standard IC bonding wires and NiZn and MnZn ferrite toroidal cores. Several prototypes are fabricated on a printed circuit board substrate with various layouts in a 4.95 mm × 4.95 mm area. The devices are modeled by analytical means and characterized with impedance measurements over a wide frequency range. Experimental results on 1:38 device show that the secondary self-inductance increases from 0.3 μH with aircore to 315 μH with ferrite core; the coupling coefficient improves from 0.1 with air-core to 0.9 with ferrite core; the effective turns ratio enhances from 0.5 with air-core to 34 with ferrite core. This approach is cost effective and enables a flexible design of efficient micromagnetics on top of ICs with dc inductance to resistance ratio of 70 μH/Ω and an inductance per unit area of 12.8 μH/mm2 up to 0.3 MHz. The design targets the development of bootstrap circuits for ultralow voltage energy harvesting. In this context, a low-voltage step-up oscillator suitable for thermoelectric generator sources is realized with a commercial IC and the proposed microtransformers. Experimental measurements on a discrete prototype report that the circuit bootstraps from voltages down to 260 mV and outputs a dc voltage of 2 V.

-Band MMIC HPA and Driver Amplifiers in InGaP-GaAs HBT Technology for Space SAR T/R Modules

This paper presents a design study of a new topology for miniaturized bondwire transformers fabricated and assembled with standard IC bonding wires and toroidal ferrite (Fair-Rite 5975000801) as a magnetic core. The microtransformer realized on a PCB substrate, enables the build of magnetics on-top-of-chip, thus leading to the design of high power density components. Impedance measurements in a frequency range between 100 kHz to 5 MHz, show that the secondary self-inductance is enhanced from 0.3 μH with an epoxy core to 315 μH with the ferrite core. Moreover, the micro-machined ferrite improves the coupling coefficient from 0.1 to 0.9 and increases the effective turns ratio from 0.5 to 35. Finally, a low-voltage IC DC-DC converter solution, with the transformer mounted on-top, is proposed for energy harvesting applications.

Modeling, Design, and Fabrication of High-Inductance Bond Wire Microtransformers With Toroidal Ferrite Core

This paper describes the modeling of startup circuits in battery-less micropower energy harvesting systems and investigates the use of bond wire micromagnetics. The analysis focuses on step-up Meissner oscillators based on magnetic core transformers operating with input voltages down to ≈100 mV, e.g, from thermoelectric generators. As a key point, this paper examines the effect of core losses and leakage inductances on the startup requirements obtained with the classical Barkhausen criterion, and demonstrates the minimum transconductance for oscillations to occur. For validation purposes, a step-up oscillator IC is fabricated in a STMicroelectronics 0.32 μm technology, and connected to two bond wire microtransformers, respectively, with a 1:38 MnZn ferrite core and with a 1:52 ferromagnetic low-temperature co-fired ceramic (LTCC) core. Coherently with the proposed model, experimental measurements show a minimum startup voltage of 228 mV for the MnZn ferrite core and of 104 mV for the LTCC core.

Design and fabrication of a 315 μΗ bondwire micro-transformer for ultra-low voltage energy harvesting

A simple method for the full characterization of passive n-port microwave monolithic integrated circuit (MMIC) structures using standard two-port vector network analyzer (VNA) measurements is presented. Its main advantages are: it does not require to perform measurements from all the ports of the network, no special calibration procedure is needed, the auxiliary terminations required by the procedure can be integrated at the border of the structure under test with minimal area increase, and it can be easily implemented in commercial CAD software. The method was applied to a nine-port microstrip structure corresponding to the output power combiner and impedance matching network of an X-band MMIC high power amplifier (HPA). The full S-parameter matrix was derived from two-port measurements and compared to the circuit–as well as electromagnetic (EM)-based simulations of the structure.