Envelope tracking of a radio frequency amplifier for Long Term Evolution using a three-level class-G modulator

In this contribution, efficiency enhancement of a radio frequency (RF) power amplifier (PA) for Long Term Evolution (LTE) base stations using envelope tracking is investigated. The dynamically adapted drain bias voltage is provided by a three-level class-G modulator. The potential of this bias modulator is demonstrated with a class AB PA built in gallium nitride (GaN) technology with an operation frequency of 2.75 GHz, a maximum output power of 41 dBm and a peak power-added efficiency (PAE) of 60%. When driven by an LTE signal with a bandwidth of 20 MHz, overall system efficiency can be increased from 17% with a constant supply voltage up to 29% with envelope tracking. This is accompanied by a reduction of linearity. Adjacent channel leakage ratio (ACLR) decreases by 10 dB in the first and by 18 dB in the second adjacent channel, respectively. Error vector magnitude (EVM) increases from 9% up to 29%

Single waveguide silicon-organic hybrid modulator

We present a novel silicon-organic hybrid modulator based on an integrated dual-mode interferometer. The modulator offers a compact, simplified design and enhanced robustness to on-chip fluctuations of temperature compared to conventional Mach-Zehnder based systems. A prototype modulator showing a voltage dependent transmission spectrum is obtained by cladding a dual-mode waveguide in a 250 nm silicon-on-insulator technology with a customized organic electro-optic layer. Estimated phase shifts and corresponding figures of merit are discussed in this contribution. The used organic layer is based on the guest-host approach with customized donor-acceptor chromophore embedded and poled in a poly(methylmethacrylate) matrix. The presented prototype is to the best of the authors'' knowledge the first integrated single waveguide silicon-organic hybrid modulator

Rapidly Measuring the Speed of Unconscious Learning: Amnesics Learn Quickly and Happy People Slowly

BACKGROUND We introduce a method for quickly determining the rate of implicit learning. METHODOLOGY/PRINCIPAL FINDINGS The task involves making a binary prediction for a probabilistic sequence over 10 minutes; from this it is possible to determine the influence of events of a different number of trials in the past on the current decision. This profile directly reflects the learning rate parameter of a large class of learning algorithms including the delta and Rescorla-Wagner rules. To illustrate the use of the method, we compare a person with amnesia with normal controls and we compare people with induced happy and sad moods. CONCLUSIONS/SIGNIFICANCE Learning on the task is likely both associative and implicit. We argue theoretically and demonstrate empirically that both amnesia and also transient negative moods can be associated with an especially large learning rate: People with amnesia can learn quickly and happy people slowl

Program FFlexCom — High frequency flexible bendable electronics for wireless communication systems

Today, electronics are implemented on rigid substrates. However, many objects in daily-life are not rigid — they are bendable, stretchable and even foldable. Examples are paper, tapes, our body, our skin and textiles. Until today there is a big gap between electronics and bendable daily-life items. Concerning this matter, the DFG Priority Program FFlexCom aims at paving the way for a novel research area: Wireless communication systems fully integrated on an ultra-thin, bendable and flexible piece of plastic or paper. The Program encompasses 13 projects led by 25 professors. By flexibility we refer to mechanical flexibility, which can come in flavors of bendability, foldability and, stretchability. In the last years the speed of flexible devices has massively been improved. However, to enable functional flexible systems and operation frequencies up to the sub-GHz range, the speed of flexible devices must still be increased by several orders of magnitude requiring novel system and circuit architectures, component concepts, technologies and materials

Cerebellar-dependent delay eyeblink conditioning in adolescents with Specific Language Impairment

Cerebellar impairments have been hypothesized as part of the pathogenesis of Specific Language Impairment (SLI), although direct evidence of cerebellar involvement is sparse. Eyeblink Conditioning (EBC) is a learning task with well documented cerebellar pathways. This is the first study of EBC in affected adolescents and controls. 16 adolescent controls, 15 adolescents with SLI, and 12 adult controls participated in a delay EBC task. Affected children had low general language performance, grammatical deficits but no speech impairments. The affected group did not differ from the control adolescent or control adult group, showing intact cerebellar functioning on the EBC task. This study did not support cerebellar impairment at the level of basic learning pathways as part of the pathogenesis of SLI. Outcomes do not rule out cerebellar influences on speech impairment, or possible other forms of cerebellar functioning as contributing to SLI

Comparison of a single and a dual-gate GaN switching-amplifier for future communication systems

A high efficiency switch-mode amplifier with a dualgate configuration in the output stage is designed in a 250 nm GaN HEMT technology. Measurements are performed up to 8 Gbps using periodic square wave signals and bandpass delta sigma (BPDS) signals. The results are compared to a single-gate amplifier which uses the same driver stage and gate width. The dual-gate amplifier achieves a higher output power and shows a better RF-performance at bit rates above 2 Gbps. A broadband output power of 14 W and a PAE of 77.5 % at 0.9 Gbps are demonstrated. Furthermore, a 5.2 Gbps BPDS signal with an eye amplitude of about 50 V is measured. It is the first time that such high amplitudes are achieved in combination with bit rates above 5 Gbps. The presented measurement results demonstrate the importance of GaN devices for future switch-mode amplifiers

Tribologische Untersuchung von Siliciumnitrid für keramische Walzwerkzeuge

Das wichtigste Merkmal keramischer Werkstoffe für den Einsatz in der Umformtechnik ist ihre im Vergleich zu Umformwerkzeugen aus Stahl wesentlich höhere Verschleißbeständigkeit. Um höhere Standzeiten der Walzwerkzeuge zu erreichen, ist daher der Einsatz von keramischen Werkstoffen interessant. Im Rahmen eines Verbundprojekts werden keramische Walzen für verschiedene Anwendungen konzipiert, hergestellt und unter Einsatzbedingungen getestet. Ziel dieser Untersuchungen ist zunächst der Nachweis der Einsatzfähigkeit dieser Walzen. Weitere Optimierungsschritte sollen zeigen, welche Vorteile keramische Walzen in verschiedenen Einsatzgebieten wie Drückwalzen, Drahtwalzen und Bandwalzen bezüglich Standzeit, Produktqualität oder Kühlschmierstoffverbrauch bieten können. In diesem Beitrag werden aktuelle Arbeiten und Ergebnisse zur Werkstoffentwicklung und zum tribologischen Verhalten von Siliciumnitrid im Hinblick auf die Anwendung für Walzwerkzeuge vorgestellt. Bei dem unter den gegebenen Bedingungen vorherrschenden tribochemischen Verschleißmechanismus erweisen sich die untersuchten Siliciumnitridwerkstoffe als sehr verschleißbeständig, wobei sich durch die tribochemische Glättung der Oberflächen zusätzlich Vorteile ergeben

Technology potential of ceramic piston pins

What is the use potential of high performance ceramics for current and future requirements in engine manufacturing? The Fraunhofer-Institutes LBF and IWM are analysing this in close collaboration with industry partners from the motor and ceramics industry. The starting point of the ongoing investigations in this area is the piston pin used in diesel engines, because great development and sales potential are expected for this concept