As multimedia devices advance, current high-speed wireless standards may soon struggleto support their growing demand for data speeds. This results in limitations in bandwidthfor applications, notably affecting activities like streaming high-definition television andultra-high-definition video. The proposed solution is to go up in frequency (millimeterwaves) allowing for use of greater bandwidths, in new bands. A problem is, however,that the path loss at mmWave frequencies is substantially greater than at frequencies below6GHz, currently the main frequency range used by both cellular and Wi-Fi. In order tocompensate for the increase in pathloss, wireless systems operating at mmWave frequenciesneed to use high gain antennas e.g. antenna arrays. Such arrays operate using digital oranalog beamforming. In this thesis the design, fabrication and verification of an analogbeamforming network connected to a four-antenna element patch array implemented at26GHz on a four-layer printed circuit board is presented. The components of the structuresof the Butler matrix beamforming network were designed and evaluated in simulationsusing CST. The stack up is a four-layer PCB-board with antenna elements and feedingnetwork on opposite outer layers. All structures in the Butler matrix were constructedin micro strip line with characteristic impedance of 50 ohm on Rogers RT-duroid 5880substrate to reduce dielectric losses. The designed 4x4 Butler matrix aimed at four set stateswith progressive phase differences ±45 and ±135 resulting in main lobes with direction -40,-15, 14 and 39 degrees. In the simulation, a progressive phase difference up to a deviationof up to 8.6 degrees was observed for all states. The fabricated Butler matrix was verified onan antenna measurement range to have main lobe directions of -45, -15, 15 and 40 degreesand with half power beam widths (HPBW) of 27.5, 25, 25 and 27.5 degrees respectively.The nulls between each lobe in the radiation pattern had a relative gain compared to peakvalue of -12.2 dBi resulting in similar magnitude as noise floor. The side lobe suppressionwere evaluated to minimum of 6.3 dB. The high directivity and well-defined nulls confirmthe hybrid couplers properties of equal power division as well as phase difference betweenoutput ports. The patch antennas were verified to have a dominant linear polarization butthe peak value for all lobes shows a deviation of -4.1 dB for all measurements comparedto simulation. In conclusion the final patch antenna array and Butler matrix performed asexpected from the simulation. Indicating that the proposed analog beam forming antennadesign is robust and well suited to be used in e.g. Open RAN applications.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:umu-223870 |
| Date | January 2024 |
| Creators | Lindbergh, Marcus |
| Publisher | Umeå universitet, Institutionen för fysik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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