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PhD Defence Alireza Bagherimoghim | 28 GHz Gapwaveguide-based Phased ArrayAntennas for 5G Applications

28 GHz Gapwaveguide-based Phased ArrayAntennas for 5G Applications

The PhD Defence of Alireza Bagherimoghim will take place in the Waaier building of the University of Twente and can be followed by a live stream.
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Alireza Bagherimoghim is a PhD student in the department Radio Systems. Co)Promotors are prof.dr.ir. A.B.J. Kokkeler and dr. A. Alayón Glazunov from the faculty Electrical Engineering, Mathematics and Computer Science.

The fifth generation (5G) of mobile wireless communication aims to provide higher data capacity than the previous generations could. With large frequency bands already licensed at mmWaves, data rates of around 10 Gbit/s can be offered. However, these frequency bands lead to more free space path loss, for example, 20 dB more loss moving from 3 to 30 GHz. Phased array antennas integrated with low-loss antenna elements and high-power front-ends have drawn much attention to compensate for this increased loss.

State-of-the-art phased array antennas for mmWave 5G are designed with antenna elements based on a dielectric substrate and employ front-ends with CMOS and SiGe BiCMOS technology. The antenna elements based on a dielectric substrate typically show a high loss at mmWave frequencies and suffer from low bandwidth. The techniques to increase the bandwidth of such antenna elements usually add to the complexity of the structure by increasing the number of layers. This thesis aims to use gapwaveguide technology as the baseline for antenna element design, which is a low-loss, low-cost, and wideband transmission line at mmWave frequencies.

In this thesis, a phased array is designed with improved characteristics in terms of low antenna and front-end losses. The objective is to propose a cost-effective and scalable phased array while enhancing its complex structure. For 5G communication systems operating at 28 GHz, a high equivalent isotropic radiated power (EIRP) active phased array antenna is proposed.  The antenna design is based on the gapwaveguide technology and consists of 16×16 single 45° slant-polarized elements. The proposed design employs a low-complexity printed circuit board (PCB) structure with only six layers, i.e., half of existing wideband solutions.

Power amplifiers with high output power have interesting applications in fulfilling the need for high power at mmWave 5G. Designing a phased array with such characteristics requires addressing challenges including power handling, thermal dissipation, and temperature stability. Therefore, a cost-efficient, high EIRP (60 dBm), large-bandwidth (26.5-29.5 GHz) active phased array antenna system has been designed and experimentally verified.

Finally, the performance of hybrid digital-analog multi-beam systems employing the proposed phased array antennas is studied for 5G applications in indoor environments. Comprehensive numerical simulations focused on collocated and distributed phased array antenna deployments in indoor office environments are compared.

In summary, this thesis contributes to the field of phased array antenna designs for mmWave 5G communication. The research presents innovative designs, characterizes their performance, and analyzes their suitability for 5G applications. The findings provide valuable insights: such as the advantages of using gapwaveguide technology for antenna element design in mmWave phased arrays, improving design methodology by relaxing the complexity and cost, proposal of a cost-efficient, high-power phased array antenna system with large bandwidth and high EIRP, and validation of the benefits of distributed deployment for indoor environments.