| 1. |
- Bengtsson, Olof, 1969-
(författare)
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Design and Characterization of RF-Power LDMOS Transistors
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In mobile communication new applications like wireless internet and mobile video have increased the demand of data-rates. Therefore, new more wideband systems are being implemented. Power amplifiers in the base-stations that simultaneously handle these wideband signals for many terminals (handhelds) need to be highly linear with a considerable band-width. In the past decade LDMOS has been the dominating technology for use in these RF-power amplifiers. In this work LDMOS transistors possible to fabricate in a normal CMOS process have been optimized and analyzed for RF-power applications. Their non-linear behavior has been explored using load-pull measurements. The mechanisms of the non-linear input capacitance have been analyzed using 2D TCAD simulations. The investigation shows that the input capacitance is a large contributor to phase distortion in the transistor. Computational load-pull TCAD methods have been developed for analysis of RF-power devices in high-efficiency operation. Methods have been developed for class-F with harmonic loading and for bias-modulation. Load-pull measurements with drain-bias modulation in a novel measurement setup have also been conducted. The investigation shows that the combination of computational load-pull of physical transistor structures and direct measurement evaluation with modified load-pull is a viable alternative for future design of RF-power devices. Simulations and measurements on the designed LDMOS shows a 10 to 15 % increase in drain efficiency in mid-power range both in simulations and measurements. The computational load-pull method has also been used to investigate the power capability of LDMOS transistors on SOI. This study indicates that either a low-resistivity or high-resistivity substrate should be used in manufacturing of RF-power LDMOS transistors on SOI to achieve optimum efficiency. Based on a proper substrate selection these devices exhibit a 10 % higher drain-efficiency mainly due to lower dissipated power in the devices.
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| 2. |
- Landin, Per Niklas, 1983-, et al.
(författare)
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Sideband asymmetries in RF power LDMOS before and after digital predistortion
- 2009
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The merging of the fields of RF engineering and signal processing has introduced concepts such as behavioral modeling and enabled digital linearization schemes for wireless devices, such as power amplifiers (PAs). Despite that this process has been going on for a number of years much work remains to be done. The links between physical behavior and mathematical models are far from well-understood as are the optimum strategies for device design. This study focus on digital predistortion properties of a one-stage PA consisting of a power transistor mounted in a test fixture. The device under test (DUT) is an Infineon PTF210451E, a 45W transistor intended for usage in the frequency bands 2010-2025 MHz and 2110-2170 MHz. The test fixture is also designed by Infineon Technologies. The signal types used in the measurements are single and double carrier wideband code division multiple access (WCDMA) signals. The double carrier WCDMA signals have tone-spacings of 5, 10 and 15 MHz. Normal two-tone measurements are also presented.
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| 3. |
- Tornblad, Olof
(författare)
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Physical modeling of on-state losses in bipolar Si and SiC power devices
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Power losses affect both the installation- and long-term cost of power electronic systems. The installation cost is related to the fatt that power losses in silicon power devices generate heat and make installation of heat sinks and water cooling necessary. If self-heating effects are strong, lotal overheating can eventually lead to device failure. To improve the design of power device systems, more accurate calculations of the Safe Operating Area (SOA) of power devices are desirable. Power semiconductor devices with lower losses are also needed. With the emerg ing SiC technology, much higher drift temperatures can be tolerated and much lower power losses can be achieved for the very high voltage range. In this thesis, on-state losses in bipolar Si and SiC power devices have been studied by comparing measurements to numerical simulations. Carrier distributions under high-leve1 injection were mesured utilizing the technique of Free Carrier Absorption (FCA). Measurements were performed for elevated temperatures under static equilibtium for Si power diodes and Insulated Gate Bipolar Transistors (IGBTs). Potential distributions in power diode structures were meas ured by contacting the samples with a tungsten probe tip. A set of physical models for accurate simulation of bipolar Si power devices is proposed; special attention was drawn to the modeling of minority carrier transport in emitters. Measurements of carrier distributions were canied out also for 4H-SiC power diode structures and the results were compared with simulation. Physical models for simulation of 4H- and 6H- SiC bipolar power devices are suggested. It was found that anisotropic material properties are important for the operation of bipolar 6H-SiC devices.Finally, various contributions to the heat generation term of a recently improved theory were evaluated under extreme, but realistic conditions. It was concluded that heat generation in bipo lar Si power devices, both stationary and transient, can be modeled accurately by only taking the Joule heat and the recombination heat terms into account.
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