The professional auto body painter works in an extreme environment, where the painter faces constant movement, ever-changing working situations and pressure to deliver a flawless paint job: the paint booth. The temperature in the paint booth is high, often around 30˚ Celsius. The floor is very hard, made of metal grid or concrete, and the painter usually has to move around a lot, at least 9 km per day. For this project I chose to focus on the painter’s work footwear as a major part of the personal protective equipment. My goal is to create a new standard in working shoes, specifically made for this environment and context. A comfortable shoe that could withstand heat, paint dust and wear. A shoe that is made for its users: the FRM AIRCON.

Sojourns at high altitude are often accompanied by weight loss and changes in body composition. The aim was to study body composition before and after 40 days high-altitude exposure. The subjects were four women and six men, non-smoking, healthy and active students and a scientist from Mid Sweden University in Östersund with a mean (SD) age of 26 (10) years. All subjects volunteered for a six-week trek to the Mount Everest Base Camp via Rolwaling in Nepal. Before the sojourn subject’s height was 177 (10) cm and weight was 71.9 (10) kg. Body composition was measured with Lunar iDXA at the Swedish Winter Sports Research Centre in Östersund before and after the trek. Total body mass (SD) decreased from 71.8 (10.0) kg before to 69.7 (9.4) kg after the trek (P=0.00). Total fat mass decreased from 14.7 (5.9) kg to 13.8 (4.6) kg (P=0.01). Fat percent decreased from 21.6 (7.9) % to 21.0 (7.2) % (P=0.03). Total lean mass decreased from 54.0 (10.0) kg to 52.9 (9.7) kg (P=0.01). Bone mineral content was unchanged, 3.04 (0.5) kg before and 3.03 (0.5) after (P=0.13). Thus both total body mass and total lean mass had decreased after a six week trekking in Nepal.

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As the oil and gas industry continues to explore higher temperature environments, electronics that operate at those temperatures without additional cooling become critical. Additionally, current communications systems cannot support the higher data-rates being offered by advancements in sensor technology. An RF modem would be capable of supplying the necessary bandwidth to support the higher data-rate. A voltage-controlled oscillator is an essential part of an RF modem. This thesis presents a 2.336-2.402 GHz voltage-controlled oscillator constructed with 0.25 μm GaN-on-SiC technology high electron mobility transistor (HEMTs). The measured operating temperature range was from 25°C to 225°C. A minimum tuning range of 66 MHz, less than 20% variation in output power, and harmonics more than 20 dB down from the fundamental is observed. The phase noise is between -88 and -101 dBc/Hz at 100 kHz offset at 225°C. This is the highest frequency oscillator that operates simultaneously at high temperatures reported in literature. / Master of Science / The oil and gas industry require communications systems to transmit data collected from sensors in deep wells to the surface. However, the temperatures of these wells can be more than 210 °C. Traditional Silicon based circuits are unable to operate at these temperatures for a prolonged period. Advancements in wide bandgap (WBG) semiconductor devices enable entrance into this realm of high temperature electronics. One such WBG technology is Gallium Nitride (GaN) which offers simultaneous high temperature and high frequency performance. These properties make GaN an ideal technology for a high temperature RF modem. A voltage-controlled oscillator is an essential part of a RF modem. This thesis demonstrates a GaN-based 2.36 GHz voltage-controlled oscillator (VCO) whose performance has been measured over a temperature range of 25°C-225°C. This is the highest frequency oscillator that operates simultaneously at high temperatures reported in literature.

The decline of easily accessible reserves pushes the oil and gas industry to explore deeper wells, where the ambient temperature often exceeds 210 °C. The need for high temperature operation, combined with the need for real-time data logging has created a growing demand for robust, high temperature RF electronics. This thesis presents the design of an intermediate frequency (IF) variable gain amplifier (VGA) for downhole communications, which can operate up to an ambient temperature of 230 °C. The proposed VGA is designed using 0.25 μm GaN on SiC high electron mobility transistor (HEMT) technology. Measured results at 230 °C show that the VGA has a peak gain of 27dB at center frequency of 97.5 MHz, and a gain control range of 29.4 dB. At maximum gain, the input P1dB is -11.57 dBm at 230 °C (-3.63 dBm at 25 °C). Input return loss is below 19 dB, and output return loss is below 12 dB across the entire gain control range from 25 °C to 230 °C. The variation with temperature (25 °C to 230 °C) is 1 dB for maximum gain, and 4.7 dB for gain control range. The total power dissipation is 176 mW for maximum gain at 230 °C. / Master of Science / The oil and gas industry uses downhole communication systems to collect important information concerning the reservoirs such as rock properties, temperature, and pressure, and relay it back to the surface. The electronics in these communication systems have to withstand temperatures exceeding 210 °C. Current high temperature electronics are not able to handle such temperatures for extended periods of time. Advancements in semiconductor technologies allow for fabrication of semiconductors that withstand high temperatures, such as GaN (Gallium Nitride). This thesis describes the design of a VGA (variable gain amplifier), which is an essential part of a downhole communication system. The VGA is designed using GaN semiconductor technology. Measured results show that the VGA shows good performance from 25 °C to 230 °C without the use of any cooling techniques, and can thus be used to design nextgeneration robust, high speed downhole communication systems.

Decreasing reserves of natural resources drives the oil and gas industry to drill deeper and deeper to reach unexploited wells. Coupled with the demand for substantial real-time data transmission, the need for high speed electronics able to operating in harsher ambient environment is quickly on the rise. This paper presents a high temperature VCO for downhole communication system. The proposed VCO is designed and prototyped using 0.25 μm GaN on SiC RF transistor which has extremely high junction temperature capability. Measurements show that the proposed VCO can operate reliably under ambient temperature from 25 °C up to 230 °C and is tunable from 328 MHz to 353 Mhz. The measured output power is 18 dBm with ±1 dB variations over entire covered temperature and frequency range. Measured phase noise at 230 °C is from -121 dBc/Hz to -109 dBc/Hz at 100 KHz offset. / Master of Science / The oil and gas industry are drilling deeper and deeper to reach unexploited wells due to decreasing reserves of easily available natural resources. In addition, high speed electronics able to operating in harsher ambient environment is required to meet the demand for substantial realtime data transmission. This work presents a high temperature VCO for downhole communication system which can meet the requirement aforementioned. The proposed VCO is designed and prototyped to meet the harsh temperature and high speed requirement. Measurements show that, under ambient temperature from 25 °C up to 230 °C, the proposed VCO can operate reliably from 328 MHz to 353 Mhz, as required by the communication system.

The objective of the proposed research is to characterize the safe-operating-area of silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) under radiofrequency (RF) operation and extreme environments. The degradation of SiGe HBTs due to mixed-mode DC and RF stress has been modeled for the first time. State-of-the-art 200 GHz SiGe HBTs were first characterized, and then DC and RF stressed. Excess base leakage current was modeled as a function of the stress current and voltage. This physics-based stress model was then designed as a sub-circuit in Cadence, and incorporated into SiGe power amplifier design to predict the DC and RF stress-induced excess base current. Based on these studies, characterization of RF safe-operating-area for SiGe HBTs using devices and circuits is proposed.

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Natural resources are always collected from harsh environments, such as mines and deep wells. Currently, depleted oil wells force the gas and oil industry to drill deeper. As the industry drills deeper, temperatures of these wells can exceed 210 °C. Contemporary downhole systems have reached their depth and temperature limitations in deep basins and are no longer meet the high requirements in harsh environment industries. Therefore, robust electronic systems that can operate reliably in harsh environments are in high demand. This thesis presents a high temperature reference voltage generator that can operate reliably up to 250 °C for a downhole communication system. The proposed reference voltage generator is designed and prototyped using 4H-SiC bipolar transistors. Silicon carbide (SiC) is a semiconductor material that exhibits wide bandgap, high dielectric breakdown field strength, and high thermal conductivity. Due to these properties, it is suitable for high-frequency, high-power, and high-temperature applications. For bypassing the lack of high temperature p-type SiC transistors (pnp BJT, PMOS) and OpAmp inconvenience, an all npn voltage reference architecture has been developed based on Widlar bandgap reference concept. The proposed reference voltage generator demonstrates for the first time a functional high temperature discrete reference voltage generator that uses only five 4H-SiC transistors to achieve both temperature and supply independent. Measurement results show that the proposed voltage reference generator provides an almost constant negative reference voltage around -3.23 V from 25 °C to 250 °C regardless of any change in power supply with a low temperature coefficient (TC) of 42 ppm/°C. / Master of Science

As the oil industry continues to drill deeper to reach previously untapped wells, the operating environments for electronic systems become harsher, especially due to high temperatures. It is essential to design electronic circuits and systems to be able to withstand these extreme temperatures. The proposed power amplifier (PA) has been designed for a downhole communication system operating at an ambient temperature of 230oC. GaN technology was chosen primarily due to its ability to function at a high junction temperature. The proposed PA was designed with Qorvo's T2G6003028-FL HEMT as it operates reliably at a high junction temperature (T_J) and also the package offers low junction to case thermal resistance . The proposed PA can operate reliably up to an ambient temperature of 230oC using passive cooling opposed to active cooling. At 230 C it operates in class A with a peak PAE of 25.03%, maximum output power of 1.66 W, peak gain of 24.5 dB, center frequency of 255 MHz with 1dB ripple in the passband over a 60 MHz bandwidth, 1dB output compression of approximately 32 dBm, and OIP3 of 37.9dBm. CW measurements were taken for all parameters. / Master of Science