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    Design and Validation of a Concurrent Dual-Band GaN Doherty Power Amplifier
    (2023) Ur Rasool Haider, Jamal; Chalmers tekniska högskola / Institutionen för mikroteknologi och nanovetenskap (MC2); Chalmers University of Technology / Department of Microtechnology and Nanoscience (MC2); Fager, Christian; Saad, Paul; Hou, Rui; Zhou, Han
    In the current era characterized by rapid advancements in wireless communication, the demand for high data rates, multi-band operation and low power consumption in communication systems like mobile base stations, poses significant challenges. To address these challenges, it is imperative to explore and devise new power amplifier (PA) solutions that conform to these stringent requirements. This thesis presents a comprehensive solution in the form of a dual-band Doherty PA (DB-DPA) to meet these pressing requirements. DPAs have gained considerable popularity due to their ability to achieve high back-off efficiency across a wide range of output power levels. The primary objective of this research is to design and simulate a symmetrical DB-DPA using state-of-the-art GaN-HEMT technology, for the frequency bands of 1.85 and 2.65 GHz. The load modulation network comprises a wideband combiner followed by a Chebyshev transformer. Subsequently, the designed DB-DPA is fabricated, measured, and the obtained results are presented and analyzed in detail. Through extensive measurements, this study demonstrates that the proposed DBDPA design delivers satisfactory performance in terms of drain efficiency (DE) and power gain for both the lower and upper-frequency bands of 1.85/2.65 GHz with a bandwidth of 100 MHz each. At a peak power of 47.9/47.3 dBm, the DB-DPA achieves a DE of 55.6/54.5%. Furthermore, at a 6 dB back-off level, the DB-DPA exhibits a DE of 41.2/44.6% and a gain of 19.5/15 dB for the desired frequencies. These characteristics position this design as a promising candidate for communication applications. The findings presented in this research emphasize the potential of the proposed DB-DPA design and provide a viable solution that meets the growing requirements of the wireless industry. The comprehensive investigation conducted through simulations and measurements contributes to the body of knowledge in the field and provides valuable insights for further advancements in DB-DPA design.
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    Anyon Colliders: A time-dependent quantum Hall particle collider to reveal fractional statistics in the Laughlin sequence
    (2023) Varada, Sushanth; Chalmers tekniska högskola / Institutionen för mikroteknologi och nanovetenskap (MC2); Chalmers University of Technology / Department of Microtechnology and Nanoscience (MC2); Splettstoesser, Janine; Acciai, Matteo; Spånslätt, Christian
    Elementary particles in nature (3+1 dimensions) are classified into bosons and fermions based on their exchange statistics. However, more general statistics, intermediate be- tween fermionic and bosonic, are possible in 2+1 dimensions. Quasiparticles obeying this intermediary statistics are called anyons. A particularly relevant phase of matter hosting anyons is the fractional quantum Hall effect, where anyonic statistics has recently been demonstrated. Generally, exchange statistics is expected to be accessible in interference experiments, such as in the Hong-Ou-Mandel effect. In this setup, fermions show van- ishing current correlations due to anti-bunching caused by the Pauli exclusion principle. Bosons, instead, bunch together due to Bose-Einstein statistics causing a surge in the current correlations. Can Hong-Ou-Mandel interferometry be extended to probe the frac- tional statistics of anyons? In this thesis, we investigate this question in a fractional quantum Hall setup in the Laughlin sequence (filling factor ν = 1/(2n + 1), n ∈ Z+), where two anyons collide at a quantum point contact with a tunable time delay. Previous studies investigating sim- ilar systems relate current correlations of quasiparticle collisions with braiding between injected anyons and quasi-particle-hole excitations at the tunneling quantum point con- tact, which emerge due to thermal or quantum fluctuations. However, it remains unclear whether the presently studied Hong-Ou-Mandel effect probes the universal exchange phase (θ) picked up by the quasiparticles or other parameters, such as the non-universal scaling dimension (δ). We show that θ accumulated by the incoming anyons due to interaction with quasi-particle-hole pairs at the quantum point contact cancel out in time-sensitive two-particle interferometry. Instead, the key quantity measured through current correla- tions is the non-universal δ of the quasi-particle-hole excitations.
  • Post
    Miniaturized high-energy radiation drain filters for quantum computing applications
    (2023) Andersson, Linus; Chalmers tekniska högskola / Institutionen för mikroteknologi och nanovetenskap (MC2); Chalmers University of Technology / Department of Microtechnology and Nanoscience (MC2); Gasparinetti, Simone; Rehammar, Robert
    Quantum Processing Units (QPUs) using superconducting qubits are known for their sensitivity to various types of radiation and many different aspects are being worked on in order to increase their resilience against noise. Superconducting qubits are especially sensitive frequencies with energy exceeding twice the superconducting energy gap of the superconductor. Above this frequency, Copper-pairs start to break, which partially disrupts superconductivity and degrades the performance of the QPU. In order to tackle this problem, a new type of low pass filtering technique called High Energy Radiation Drain (HERD) has been developed at at Chalmers University of Technology. Unlike previously employed filters relying on absorptive materials and resonant circuits to block high-frequency photons, this novel filtering technique overcomes the trade-off between low losses in the passband and high attenuation in the stopband. However, the filter is relatively large compared other filtering techniques, which makes it less suitable for high qubit density systems. In this thesis, we focus on the miniaturization of the HERD filtering technology and present two devices which have a reduced size of 32-57% and 47% respectively compared to their predecessor. The first device, implemented in printed circuit board technology, is manufactured and characterized with a resulting insertion loss of more than 40 dB above 80 GHz and an insertion loss of less than 0.29 dB below 8 GHz, measured at 77 K. The results show good agreement between measurements and simulations. In addition, a software is developed for performing eigenmode field decomposition of the filtering structure, which is used to better understand how the field couples to the filtering structure inside the prototype. The insights obtained from simulations and the field decomposition is then used to design the second device, a miniaturized coaxial HERD filter. The results shows that the HERD filtering technique can be made suitable for high qubit density systems where further miniaturization beyond this thesis should be possible.
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    Development of a triboelectrically powered intracranial pressure sensor and a brain phantom test rig
    (2023) Afshar, Shabir; Chalmers tekniska högskola / Institutionen för mikroteknologi och nanovetenskap (MC2); Chalmers University of Technology / Department of Microtechnology and Nanoscience (MC2); Lundgren, Per; Asplund, Maria
    Intracranial pressure (ICP) monitoring is crucial for diagnosing and treating neurological disorders. This master thesis focuses on developing a self-powered pressure sensor for wireless pressure monitoring inside the skull. The sensor design is based on triboelectric technology, aiming to overcome the limitations of conventional ICP sensors such as power supply requirements, complex fabrication, and mechanical inflexibility. The primary goal of this study is to explore the potential of triboelectric pressure sensors for monitoring ICP. A test rig and brain phantom are also constructed to simulate pressure variations of the actual brain in vitro. Triboelectric sensors convert mechanical pressure into electrical signals through electrostatic induction. First, the literature is reviewed on ICP and conventional invasive pressure sensors. Then, simulations of the modelled sensor are conducted by COMSOL software. Achieved results provide valuable insights into the implementation and feasibility of triboelectric pressure sensors for ICP monitoring. Additionally, the project successfully achieved the construction of a simplified brain phantom with a pressure-tight ventricle void. This was accomplished by casting silicone rubber into a 3D-printed mould, serving as the project’s secondary goal. In conclusion, this thesis presents extensive research on developing and evaluating triboelectric sensing mechanisms for ICP monitoring. The findings contribute to the advancement of less invasive pressure sensors, holding potential significance in neurology and healthcare.
  • Post
    GaN MMIC Oscillator Design for Low Phase Noise Using a Tunable Cavity Resonator
    (2020) Karlsson, Johan; Shehryar, Usman; Chalmers tekniska högskola / Institutionen för mikroteknologi och nanovetenskap (MC2); Chalmers University of Technology / Department of Microtechnology and Nanoscience (MC2); Kuylenstierna, Dan; Lidström, Niklas
    One of the main limiting factors that prevents higher data rates in the communication systems of today is the phase noise of oscillators. To reach lower phase noise, the most effective improvement is to use resonators with higher quality factor (Q). On-chip resonators typically have poor quality factor so an external resonator is preferred from a performance perspective. Another way of lowering phase noise is to increase the power inside the oscillator, e.g., by using a high-power device technology. This thesis presents simulation and design of two Gallium Nitride (GaN) MMIC based reflection type oscillators with integrated phase shifters, designed in the WIN Semiconductors NP15 GaN HEMT technology. The integrated phase shifter can be used for compensating interconnect parasitics as well as phase locking with a PLL. The designs are intended for high-Q mechanically tunable cavity resonators for two different frequency bands, 11.6 to 13.0 GHz and 13.3 to 14.7 GHz. The thesis also presents transistor-model port de-embedding, required to extract a three-port transistor model from the two-port common-source model available in the design kit. Simulations based on WIN’s design kit, the de-embedded device model, and simulated cavity S parameters indicate minimum phase noise of -142 dBc/Hz at 100 kHz offset for the low-frequency band and -133 dBc/Hz at 100 kHz offset for the high-frequency band.