Browsing by Author "Ala-Laurinaho, Juha, Dr., Aalto University, Department of Electronics and Nanoengineering, Finland"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Millimeter-Wave Antennas on Flexible Substrates: Roll-to-Roll Reverse-Offset Printing and Probe Station-Based Characterization
    (Aalto University, 2020) Zheng, Jianfang; Ala-Laurinaho, Juha, Dr., Aalto University, Department of Electronics and Nanoengineering, Finland; Elektroniikan ja nanotekniikan laitos; Department of Electronics and Nanoengineering; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Räisänen, Antti V., Prof., Aalto University, Department of Electronics and Nanoengineering, Finland; Taylor, Zachary D., Prof., Aalto University, Department of Electronics and Nanoengineering, Finland
    Upcoming generations of millimeter-wave (mm-wave) communication systems present significant challenges on traditional fabrication paradigms, and the characterization of antennas in such systems. To meet the next generation mm-wave systems requirements, the antenna manufacturing must be low cost, high resolution, and suitable for mass production. Further, characterization method for these antennas must be developed that are compatible with a probe station environment. This dissertation studies roll-to-roll reverse-offset (R2R-RO) printing based fabrication of mm-wave antennas on flexible substrates and investigates the antenna radiation performance characterization methods for mm-wave probe-fed on-wafer antennas. The first part of the dissertation presents the R2R-RO printing technique and its application in the fabrication of mm-wave antennas. Printing technology offers a viable option for mass production. At mm-wave frequencies, the structure feature sizes are on the order of a few 10s of microns making fabrication with conventional printing methods unfeasible. R2R-RO printing enables the fabrication with the resolution of less than 10 µm making it sufficient for the future mm-wave electronics manufacturing. The principle of R2R-RO printing is presented, and a customized design structure is proposed to enable large-area printing. Coplanar waveguide (CPW) and microstrip patch antenna structures are designed and printed with the R2R-RO technique, and measured in a probe station environment. The results demonstrate print ink layer conductivity sufficient for mm-wave antennas. The second part of the dissertation is devoted to the systematic study of methods to quantify antenna radiation performance (gain and radiation pattern). Traditional antenna gain measurement methods require a second antenna to probe the antenna under test (AUT) which substantially increases measurement system complexity and can be impractical in a probe station measurement. The one-antenna gain measurement requires only the AUT and specular conductor plate (reflector). This reduced set of equipment enables characterization of probe-fed antennas in cluttered environments. The effect of reflector size on the measurement is studied with the physical optics (PO) method. A standard gain horn (SGH) and a microstrip patch antenna were measured by the one-antenna gain measurement method with the application of time-gating on frequency domain data. In addition, the antenna gain measurement method is extended to characterize the radiation pattern by adding a rotator to measure gain values at different angles. The radiation pattern and gain of several mm-wave antennas with different designed beam directions were measured by the proposed method in the probe station environment. Good agreement was observed between experiments and simulation.
  • Thumbnail Image
    Item
    Millimeter-wave techniques for the detection of corneal water content
    (Aalto University, 2023) Baggio, Mariangela; Ala-Laurinaho, Juha, Dr., Aalto University, Department of Electronics and Nanoengineering, Finland; Tamminen, Aleksi, Dr., Aalto University, Department of Electronics and Nanoengineering, Finland; Elektroniikan ja nanotekniikan laitos; Department of Electronics and Nanoengineering; Millimeter-wave and THz techniques; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Taylor, Zachary D., Prof., Aalto University, Department of Electronics and Nanoengineering, Finland
    This thesis concerns the study of millimeter-wave and THz reflectometry for corneal sensing. Human cornea is a lossy thin film at millimeter wave frequencies. It sits on top of a material of known properties: water and its physical thickness can be measured with ultrasound and optical techniques. Two key features render it a great match to millimeter wave imaging. First, the thickness ranges from 0.4 mm up to 0.7 mm falling right in the middle of the submillimeter range: 0.1 mm to 3 mm. Second the permittivity at millimeter-wave and THz frequencies is a strong function of water content. Therefore, the water content of the cornea and even the water gradient can be studied by illuminating cornea with millimeter waves and solving the inverse scattering problem.An effective medium theory and multilayer T-matrices is proposed as a model for the cornea reflection coefficient. A Montecarlo sensitivity analysis is also performed to investigate the possibility of solving the inverse scattering problem with presence of additive white Gaussian noise and to extract the water gradient and thickness of cornea with a particle swarm optimization algorithm. The analysis reveals that corneal parameter extraction might suffer from ambiguity and an additional thickness measurement might be needed. This technique has also been implemented in two experiments with two different millimeter-wave systems. First, a Gaussian beam telescope was used to perform corneal phantom reflectivity measurements in the WR 3.4 waveguide band (220-330 GHz). The Gaussian beam telescope was chosen because it allows to create a Gaussian beam with a certain beam waist and radius of curvature evolution. The phantoms were aligned to the optics, their reflectivity was measured, and their thickness and water gradient were also extracted. Another WR-3.4 quasioptical system was built, which used an axicon-hyperbolic lens as focusing objective. This system is less sensitive to distance deviation than the Gaussian beam telescope as the axicon has a long depth of field. The corneal phantom reflectometry experiment was repeated. The phantom thickness and water extraction results were performed. Other quasioptical systems are studied to integrate millimeter-wave reflectometry with an adjunct system to assist the corneal alignment in real-time. A first solution is to use a fast-scanning submillimeter wave adjunct imaging system that creates coupling coefficient maps. Anterior segment optical coherence tomography is also explored as a possible adjunct system by integrating it with dual reflector objectives.
  • Thumbnail Image
    Item
    Multi-band 5G Antenna Designs for Smartphones
    (Aalto University, 2024) Chen, Quangang; Lehtovuori, Anu, Dr., Aalto University, Department of Electronics and Nanoengineering, Finland; Ala-Laurinaho, Juha, Dr., Aalto University, Department of Electronics and Nanoengineering, Finland; Elektroniikan ja nanotekniikan laitos; Department of Electronics and Nanoengineering; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Viikari, Ville, Prof., Aalto University, Department of Electronics and Nanoengineering, Finland
    In the pursuit of increasing data transmission rates, mobile communications have rapidly evolved into the 5G era. With more and more frequency bands being specified and utilized, one of the longstanding challenges in mobile phone antenna design has been to cover multiple communication bands within the limited internal space of a phone. The introduction of Multiple-Input Multiple-Output (MIMO) technology and millimeter-wave (mm-wave) technology, together with the attractive visual appearance of handsets, has presented new challenges for mobile phone antenna design. The first part of this thesis concentrates on frequency-reconfigurable antennas, specifically utilizing lumped components. A full metal-rimmed model serves as a basis in the antenna designs covering hepta-band of 4G and C-band of 5G. A decoupling method of 5G MIMO antennas is also proposed based on the current suppression in a ring slot. Subsequent designs in this part focus on the frequency-reconfigurable antennas in the mm-wave frequency band. Required capacitance is first studied in the frequency band from 24 to 43.5 GHz, and practical antenna design is then implemented with commercially available tunable components, covering a frequency band from 23.2-30.2 GHz with total efficiency larger than -2.5 dB. A novel cluster array concept is introduced in the second part for frequency tunability through the adjustment of feeding weights. Realized gains of antenna arrays are maximized using eigenvalues of electric-field results. The proposed approach can be applied to various antenna designs to improve the spherical coverage in a wide frequency range. For instance, diverse patch and dipole elements, which can be seen as multiple-resonance circuits, are employed to illustrate this concept. The third part presents a dual-polarized end-fire antenna array as a supplement to broadside antennas achieving full spherical coverage required for the 5G mm-wave applications. Multiple resonant modes are generated through the use of a novel stacked antenna with a low profile for vertical polarization. The overlapped bandwidth of the vertical polarization and horizontal polarization ranges from 24 to 43.5 GHz. The methods developed in this thesis achieve the multiple frequency bands for 5G mobile communications. This work contributes to the antenna designs for modern smartphones, incorporating the research between practical applicability and innovative approaches.