206 research outputs found
A double stub impedance tuner with SiC diode varactors
No full textDesign and characterization of a double-stub impedance tuner at 1.4 GHz, based on SiC varactors, fabricated at the Chalmers University, is presented. Preliminary studies are carried out to evaluate the capacitance range required to reach the desired impedance coverage, extending from 15 to 80Ω. Accurate optimization is then completed through RF CAD simulation adopting a reliable nonlinear varactor model. The circuit, that to the authors' knowledge is the first example of a generic tuner based on SiC varactors, represents a good compromise between coverage range and losses, the most important figures of merit of a tuner, that besides will be shown to exhibit very good agreement between measurements and simulations. Tuner performances, layout compactness and simplicity, together with the high voltage that can be handled by SiC varactors make it a viable solution for the tunable output networks required in reconfigurable RF power amplifiers
Kit Preparation with Cobot-Supported Sorting in Mixed Model Assembly
No full textKitting is a common approach of materials supply with mixed-model assembly, by which components are supplied to the assembly process in pre-sorted kits. With kitting, the kit preparation is a labour intensive process and order batching is often applied to enhance efficiency. Here, improved quality and efficiency by means of automation is desirable, but knowledge of the potential of collaborative robots to support kit preparation with order batching is lacking. The purpose of this paper is to identify the potential of cobots to support time-efficient kit preparation with order batching, when the pick task is performed manually and a cobot carries out the sort task. A modelling approach is applied with experimental data from laboratory experiments to compare the cycle time between fully manual and cobot-supported kit preparation with order batching. The findings suggest that a cobot-supported sort task leads to a comparable average cycle time, with less variability of the cycle time, when compared to the fully manual setup. The paper contributes several insights on the application of cobots to support kit preparation, and the model developed in the paper can be used by practitioners to assess the potential of cobots to support their processes for kit preparation. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved
Design and characterization of SiC varactor-based phase shifters
No full textDesign and realization of two continuously tunable phase shifters for 1.4 GHz band is presented. Both circuits are based on SiC varactors, conceived to enable high-voltage, high-power operation, and suitable for application in the transmitter chain of reconfigurable radios. Experimental characterization shows, for the loaded line phase shifter, 74° maximum phase shift with insertion loss lower than 1 dB, and, for the reflective phase shifter, 90° maximum phase shift and insertion loss lower than 0.6 d
Design method for quasi-optimal multiband branch-line couplers
No full textIn this article, the design approach, the implementation, and experimental results of multiband branch-line couplers operating at arbitrary frequencies are presented.
The conventional branch-line coupler structure is adapted to multiband operation by shunting its four ports with multiband reactive networks. The performance of the proposed multiband couplers is theoretically analyzed and optimized through the even-odd mode circuit analysis. Dual-band (2.4–3.5 GHz), triple-band (1.5–2.4–4.2 GHz), and quad-band (1.5–2.4–3.5 GHz) microstrip branch-line couplers have been realized and tested to verify the design method. The good experimental results (input return loss greater than 15 dB and amplitude imbalance lower than 0.7 dB) show excellent agreement with theoretical and simulated ones, thus validating the proposed approach
Design of a concurrent dual-band 1.8-2.4-GHz GaN-HEMT doherty power amplifier
No full textIn this paper, the design, implementation and experimental
results of a high efficiency dual-band GaN-HEMT
Doherty power amplifier (DPA) are presented. An extensive
discussion about the design of the passive structures is presented
showing different possible topologies of the dual-band DPA. One
of the proposed topologies is used to design a dual-band DPA in
hybrid technology for the frequency bands 1.8GHz and 2.4GHz
with the second efficiency peak at 6 dB output power backoff
(OBO). For a continuous wave output power of 20W, the
measured power added efficiency is 64% and 54% at 1.8GHz
and 2.4GHz, respectively. At 6 dB OBO, the resulting measured
Power-Added Efficiency (PAE) were 60% and 44% in the two
frequency bands. Linearized concurrent modulated measurement
using 10MHz LTE signal with 7 dB Peak-to-Average-Ratio (PAR)
at 1.8GHz and 10MHz WiMAX signal with 8.5 dB PAR at
2.4GHz shows an average PAE of 34%, at an adjacent channel
leakage ratio of -48 dBc and -46 dBc at 1.8GHz and 2.4GHz,
respectively
Efficiency optimization for phase controlled multi-source microwave oven
No full textA solid-state microwave generators system is considered as an alternative to the magnetron, in order to inject electromagnetic energy into the cavity of a microwave oven for domestic use. Over current devices, the use of solid state technology allows one to control the frequency and phase of the electromagnetic field generated.
Considering a simplified cavity with 2 solid state sources, the influence of the electrical parameters on maximum efficiency obtainable in the process of microwave heating is investigated. By varying the frequency, different values of optimal phases and different values of maximum efficiency are detected.
Moreover, the procedure is repeated with varying the position of one source port and the influence of geometry on the system performance is evaluated.
Our results demonstrate that the ability to control the electrical quantities of a microwave heating process makes it possible to obtain better results in terms of energy efficiency over the current poorly controllable systems
Branch-line coupler design operating in four arbitrary frequencies
No full textThis letter deals with a GaAs MMIC Doherty Power
Amplifier (DPA) for X-Band systems. To the best of authors’
knowledge, it represents the first DPA realisation in the X-Band
frequency range. Experimental results shown a 30dBm saturated
output power and a drain efficiency greater than 53% at 9.5GHz.
Moreover, in the 6dB of power back-off (from 18dBm to 24dBm
input power), an AM/AM distortion lower than 1dB is also
demonstrated with an average efficiency greater than 50%
Nonideality sources and implementation considerations in polar transmitters
No full textIn this paper, the main nonidealities appearing in polar transmitters will be addressed, together with several implementation considerations. Special attention will be paid to the role of AM modulation nonlinearity and parasitic AM-to-PM conversion, once architecture mechanisms such as time-delay mismatch between branches or limited bandwidth in the amplitude path are controlled. The device limiting factors for a highly efficient switched mode operation and a linear amplitude modulation will be identified. Some circuit design and implementation guidelines for the RF modulating stage and the envelope amplifier will be discussed, to finish with system-level analysis considerations under two-tone and real communication signal excitations
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