Optimisation of a Doherty power amplifier based on dual-input characterisation

The success of the Doherty architecture compared to other efficiency enhancement techniques derives mainly from its simple design and full-RF nature, not requiring complex digital signal processing to achieve high back-off efficiency. In this work we propose a design strategy for the optimisation of a Doherty power amplifier to mitigate the typical practical issues of this architecture related to inaccuracy of the non-linear model and of the manufacturing. The approach is based on the experimental characterisation of a dual-input Doherty prototype without input section. This test structure is obtained from a single-input Doherty amplifier, designed only through non-linear simulations, by removing the input section and allowing for separate control of the two RF inputs. From the collected data, approximated functions for the phase shift and power splitting versus frequency are identified to be realizable in hardware with RF networks. Compared to the reference single-input Doherty stage, a significantly improved behavior is registered in terms of output power (up to 2.7 dB), efficiency at saturation and back-off (30 % and 15 % respectively) and power gain (2 dB)

Design Product-Service Systems by Using a Hybrid Approach: The Fashion Renting Business Model

As is known, sustainability issues represent one of the main challenges companies have to face. Among all, the fashion industry is considered one of the most impactful, both in terms of resource utilization and pollution. Fashion renting is a recent business model for companies to reduce their environmental footprint, following a circular economy approach. The study aims to develop and discuss the proposed hybrid approach to effectively support fashion companies in designing new business models, taking into account both the customer and the company perspective. On the one hand, agent-based modeling (ABM) allow us to represent customers’ behaviour and interaction. On the other hand, discrete event simulation (DES) paradigm is used to model fashion renting processes. Because customers’ attitude to that service reflects its successful implementation, motivators and barriers have been investigated to be included in the model. The practical implication is defining a model to support fashion companies in designing rental business models before implementing them. From a theoretical point of view, it overcomes the literature gap about the definition of a unique model for fashion renting, including processes, customers and interactions between agents. Follow-up research will include the presentation of simulation results

A Simple Method to Identify Parametric Oscillations in Power Amplifiers Using Harmonic Balance Solvers

A qualitative method to verify the presence of parametric oscillations at f_0/2 in power amplifiers (PAs) is presented and validated. It relies on the simultaneous application of fundamental and subharmonic tones to trigger possible parametric oscillations and can be implemented in any commercial harmonic balance solver without requiring any external software that may be expensive or however not available to the designer. Wide applicability is guaranteed by the fact that this method does not require access to any internal node of the circuit. In fact, the amplifier is handled as a black-box where only the input and output ports are accessible. The stability check is first demonstrated on a simplified case study and then validated on a real K-band integrated PA, where it correctly reproduces with simulations the parametric oscillations observed by measurements. On the redesigned amplifier, the proposed test predicted the absence of oscillations, which has been confirmed by the experimental characterization

Evaluation of a stacked-FET cell for high-frequency applications

This paper presents the design, electromagnetic simulation strategies and experimental characterisation of a two-stage stacked-FET cell in a 100 nm GaN on Si technology around 18.8 GHz, suited for Ka band satellite downlink applications. A good agreement is found between the electromagnetic simulations and the measured performance on the manufactured prototype, thus demonstrating that a successful voltage combining architecture can be obtained in the frequency range of interest with the selected topology, based on a symmetric fork-like connection between the transistors. This proves the effectiveness of an appropriate electromagnetic simulation set-up in correctly predicting the crosstalk, which typically affects this structure, leading to a correct stacking operation

A Novel Stacked Cell Layout for High Frequency Power Applications

This letter presents an innovative stacked cell, where the common source device is split in two smaller devices leading to a more compact and symmetric structure, with almost negligible parasitics associated to the transistors connection. This novel configuration is rigorously compared, for the first time, with the two classical approaches commonly adopted to physically connect the two devices. The three different layouts are fabricated in Gallium Nitride technology for high frequency power applications, and experimentally compared by means of an extensive measurement campaign performed on several loads and in different bias conditions, ranging from class AB to C. The proposed novel configuration outperforms the other two in all conditions, thanks to the advantages of adopting two smaller devices with reduced parasitics, higher gain and higher power density. These features are common to different technologies, thus making the novel topology widely applicable for the design of high frequency stacked cells

Effect of Hypnotic Group Treatment on Distress Psychopathology in Mixed-group Outpatients with Depression and Anxiety

Background: There is evidence of hypnosis being effective in reducing both emotional distress, anxiety, and depression. Hypnosis as a technique promotes enhanced mental mastery over the body. This may result in hypnosis being particularly salient in treating distress associated with somatic and psychological symptoms. Objective: This research aims at verifying the effectiveness of a group treatment, which provides for the use of hypnosis-related techniques in mixed-group outpatients with anxiety or depression. Methods: Participants. 31 outpatients (average age= 49.005; DS =12.1) including 13 with mild-moderate depression (average age= 49.17; DS=12.20) and 18 with mild-moderate anxiety (average age=48.84; DS=13.02). Procedure. The group treatment comprised 8 sessions, during which a hypnotic state was induced, aimed at generating a sensation of profound wellbeing in the participants. They could share their experience in a penultimate group session, and were provided with individualised recommendations on nutrition and lifestyle in the last individual session. Patients were prescribed to practice self-hypnosis every day at home with the support of a CD-ROM. Psychopathological symptomatology (SCL-90R), depression (BDI), and anxiety (STAI-Y1, SAS) were assessed at pre, post, and 3-month follow-up. Statistical analysis. Friedman, Kruskal-Wallis and Mann-Whitey tests were used. The Bonferroni\u2019s correction was applied as needed. The effect size (Cohen\u2019s d) was also measured. Results: For the total sample, for all tests, significant differences were observed in the phases. The effect size was found to vary from \u201csmall\u201d at pre to \u201dmedium\u201d at post. A \u201clarge\u201d effect size was observed when comparing pre and follow-up phases. An overall reduction in the symptoms of distress measured by the SCL-90 R \u2013 with the anxiety group showing better outcomes \u2013 alongside with an improvement in the symptoms of depression and anxiety were observed in all participants. Conclusion: The clinical impact appears to be relevant, as shown by the values for d. The treatment is cost-effective for highly prevalent disorders in outpatients. The outcomes of this study support the effectiveness of hypnotic group treatment

Safe and selective operation of fine chemical reactions through the semi batch recycle reactor (SBRR)

In the fine chemical industry, a number of exothermic reaction processes are better performed under reflux conditions. Such an operating regime of the reactor allows for removing the reaction heat at a self-controlling temperature, hence preventing peaks of the conversion rate with their related thermal effects. Moreover, when the desired reaction generates a low volatility product, which can further react with a non-selective reactant, dosing such a reactant under reflux conditions potentially allows for removing the target species from the reactor, hence subtracting it from its further degradation. However, there exist also a number of processes that must be operated at temperature values lower than the normal boiling point of the low volatility product and for which vacuum conditions cannot be adopted, because of a number of process constraints. This prevents the possibility of taking advantage, from a safety point of view, of the aforementioned self-controlling feature of the processes operated under reflux conditions. The semibatch recycle reactor allows for achieving both a satisfactory process selectivity and productivity (strictly connected with the operating temperature range defined by the recipe) as well as the safer process conditions related to the reflux conditions thanks to its intrinsic possibility of operating even at atmospheric pressure the reaction vessel and the boiler at different temperature values

Parameterized Complexity of the k-anonymity Problem

The problem of publishing personal data without giving up privacy is becoming increasingly important. An interesting formalization that has been recently proposed is the $k$-anonymity. This approach requires that the rows of a table are partitioned in clusters of size at least $k$ and that all the rows in a cluster become the same tuple, after the suppression of some entries. The natural optimization problem, where the goal is to minimize the number of suppressed entries, is known to be APX-hard even when the records values are over a binary alphabet and $k=3$, and when the records have length at most 8 and $k=4$ . In this paper we study how the complexity of the problem is influenced by different parameters. In this paper we follow this direction of research, first showing that the problem is W[1]-hard when parameterized by the size of the solution (and the value $k$). Then we exhibit a fixed parameter algorithm, when the problem is parameterized by the size of the alphabet and the number of columns. Finally, we investigate the computational (and approximation) complexity of the $k$-anonymity problem, when restricting the instance to records having length bounded by 3 and $k=3$. We show that such a restriction is APX-hard.Comment: 22 pages, 2 figure

Evaluating GaN Doherty architectures for 4G Picocells, WiMax and microwave backhaul links

This paper evaluates the Doherty power amplifier architecture in terms of linearity, efficiency and design solutions. As case study four different prototypes are presented, one for 4G Picocells at 2.1 GHz, one for WiMax applications at 3.5 GHz and two for point-to-point microwave backhaul radiolinks at 7 GHz. Experimental results together with design guidelines are discussed addressing strengths and weaknesses of the Doherty architectur

The effect of pregnancy on subsequent relapse from Graves' disease after a successful course of antithyroid drug therapy.

OBJECTIVE: Pregnancy and the postpartum (PP) period are associated with profound changes of the immune system, which largely influence the clinical activity of autoimmune diseases. The aim of this study was to evaluate the effect of pregnancy and/or the PP period in driving a clinical relapse of hyperthyroidism in patients with Graves' disease (GD) who are in remission after antithyroid drug (ATD) treatment. Data were retrospectively collected from 150 female patients with GD, who were assigned to two groups according to the occurrence of a successful pregnancy after ATD withdrawal. RESULTS: Relapsing Graves' hyperthyroidism was observed in 70 of 125 patients in group I (no pregnancy after ATD withdrawal) (56.0%) and 21 of 25 patients in group II (pregnancy after ATD withdrawal) (84.0%) (P < 0.05). Logistic regression analysis (dependent variable: relapse/nonrelapse; covariates: age, positive family history for autoimmune thyroid disease, duration of treatment with ATD, number pregnancies at diagnosis, number of pregnancies after ATD withdrawal) showed a significant effect only for the number of pregnancies after ATD withdrawal [4.257 (1.315-13.782)]. The effect was ascribed to the PP period rather than to pregnancy itself because in 20 of 21 patients of group II (95.2%), the relapse of Graves' hyperthyroidism occurred between 4 and 8 months after delivery. CONCLUSIONS: The PP period is significantly associated with a relapse of hyperthyroidism in GD patients being in remission after ATD. We therefore recommend that patients with GD in remission after a course of ATD should have their thyroid function tested at 3 and 6 months after delivery