131,844 research outputs found
Democracy and Green Political Thought: Sustainability, Rights and Citizenship
No full textContains fulltext :
151317.pdf (Publisher’s version ) (Closed access)B. Doherty Democracy and Green Political Thought: Sustainability, Rights and Citizenship : ,199
A fully matched N-way Doherty amplifier with optimized linearity
No full textThis paper presents a new fully matched N-way Doherty amplifier. The basic principles of operation and important features are described. For the experimental verification, 2.14-GHz Doherty amplifiers,having two-, three-, and four-way structures are implemented using silicon LDMOSFETs and tested using down-link WCDMA signal. The linearity performances of the two-, three-, and four-way Doherty amplifiers are optimized for better efficiency versus linearity by a bias adjustment of the peaking amplifiers. For, simultaneously improving the efficiency and linearity to achieve maximum efficiency versus linearity, the gate biases of the peaking amplifiers for the N-way Doherty amplifier are optimized. As a result, the efficiency versus linearity characteristics are drastically improved by N-way extension of the Doherty amplifier.X11138sciescopu
Optimum design for linearity and efficiency of a microwave Doherty amplifier using a new load matching technique
No full textA Doherty amplifier with full load matching circuits of the carrier and peaking amplifiers at both low and high power levels is demonstrated for the first time. In the circuit design, sections of transmission lines are inserted in the load matching, network for power-level-dependent load impedances. The circuit elements and bias points are designed and optimized using a large-signal harmonic balance simulation to offer simultaneous improvements in linearity and efficiency. Two 1.4 GHz Doherty amplifiers have been implemented using silicon LDMOS FETs. The RF performances of the Doherty amplifier-I (a combination of a class B carrier amplifier and a bias-tuned class C peaking amplifier) have been compared with those of a class B amplifier alone. The Doherty amplifier-II (a combination Of a class AB carrier amplifier and a bias-tuned class C peaking amplifier) has been compared with a class AB amplifier alone. The new Doherty amplifiers show an improved linearity as well as higher efficiency.X11103sciescopu
Helping children think: Gaze aversion and teaching
No full textLooking away from an interlocutor's face during demanding cognitive activity can help adults answer challenging arithmetic and verbal-reasoning questions (Glenberg, Schroeder, & Robertson, 1998). However, such `gaze aversion' (GA) is poorly applied by 5-year-old school children (Doherty-Sneddon, Bruce, Bonner, Longbotham, & Doyle, 2002). In Experiment 1 we trained ten 5-year-old children to use GA while thinking about answers to questions. This trained group performed significantly better on challenging questions compared with 10 controls given no GA training. In Experiment 2 we found significant and monotonic age-related increments in spontaneous use of GA across three cohorts of ten 5-year-old school children (mean ages: 5;02, 5;06 and 5;08). Teaching and encouraging GA during challenging cognitive activity promises to be invaluable in promoting learning, particularly during early primary years
Optimised Doherty power amplifier with auxiliary peaking cell
No full textThe Doherty power amplifier has the most attractive architecture to improve the efficiency for amplifying a signal with a high peak-to-average power ratio. However, the ideal Doherty operation is difficult to be achieved because the g(m) of the peaking amplifier should be two times larger than that of the carrier amplifier. The gm mismatch between the carrier and peaking amplifiers hinders the proper load modulation at the peak power region. The Doherty power amplifier with an auxiliary drive cell for the peaking amplifier is introduced to solve the problem. The auxiliary peaking cell drives the main peaking amplifier with higher input power, solving the gain and output power reduction problem. Experimental results show that the proposed Doherty power amplifier can enhance gain, output power and power-added efficiency.X1195sciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Design of Doherty Power Amplifiers for Handset Applications
No full textIn this paper, we analyze the power drive of a Doherty power amplifier (PA), and introduce a technique for proper input dividing without a coupler. For the proper Doherty operation, we place a phase compensation circuit at the input of the carrier amplifier. We also propose an output matching of Doherty PA to reduce the number of matching components, and to match the output impedances to enhance efficiency and linearity in consideration of the uneven input drive. The PA circuit is fabricated using a 2-mu m InGaP/GaAs heterojunction bipolar transistor process and combined for Doherty operation using merged lumped components. For the IEEE 802.16e m-WiMAX signal, which has a 9.54-dB crest factor and 8.75-MHz bandwidth, the PA has an error vector magnitude of 3% and a power-added efficiency of 40.2% at an output power of 26 dBm.X113232sciescopu
A Saturated Doherty Power Amplifier Based On Saturated Amplifier
No full textA saturated Doherty power amplifier (PA) based on the saturated PA tuned by the self-generated harmonic currents is presented. When driven with mobileWiMAX 1FA signal, this Doherty PA demonstrates high efficiency performance (average 57%) over the WiMAX band from 2.5 GHz to 2.7 GHz. Simulated and experimental results allow the evaluation for the load modulation behavior of the saturated PA and bandwidth correlation between the Doherty and saturated unit PAs. The linearity requirement of the WiMAX signal is met using the digital feedback predistortion linearization technique.X1117sciescopu
Impact of Nonlinear C-bc on HBT Doherty Power Amplifiers
No full textTheoretically, the load modulation of carrier amplifiers in Doherty power amplifiers (PAs) achieves a 3-dB higher gain and a higher power-added efficiency (PAE) at a 3-dB back-off power due to the two times larger load impedance (2R(opt)), compared to those at the peak power. In this paper, we analyze the impact of nonlinear C-bc on the gain behavior of heterojunction bipolar transistors (HBT) that shows nearly identical gain and a lower PAE with 2R(opt). In the environment, the gain distribution of carrier and peaking amplifiers is explained for the linear operation of the Doherty PA with the imperfect load modulation. We also explore harmonic controls for the Doherty PA using class-F matching network to enhance efficiency at a given back-off power and propose a method using a second-harmonic short circuit at the input of the carrier amplifier to compensate for the signal distortion caused by nonlinear C-bc. To validate the efficiency improvement while achieving high linearity, a Doherty PA is fabricated and tested using a long-term evolution signal having a 10-MHz bandwidth and a 16-quadrature amplitude modulation (16-QAM) 7.5-dB peak-to-average power ratio. The proposed Doherty PA achieves a PAE of 45% and an adjacent channel leakage ratio of -34 dBc at an average output power of 29 dBm. The total consumed power of the proposed PA at this output power represents a reduction by 4.5% and 29%, respectively, to that of a conventional class-F-type Doherty and a class-AB PA.X111113sciescopu
Compact N-Way Doherty Power Combiners for mm-wave 5G Transmitters
No full textThis paper presents a design procedure for compact lumped-element 3-/4-/5-way Doherty power combiners suitable for mm-wave 5G transmitters. Among them, the 3-way Doherty power combiner is favored due to its low complexity, compact layout, and average drain efficiency at 12 dB power back-off (PBO) when implemented using lossy lumped elements. Based on the metal stack of a 40nm CMOS process, a 3-way Doherty power combiner can provide a simulated passive efficiency of more than 60% at 12 dB PBO and a 10% drain-efficiency bandwidth power bandwidth of 8/15 GHz at 30 GHz
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