High Performance Integrated Beam-Steering Techniques for Millimeter-Wave Systems
Abdellatif, Ahmed Shehata Mohamed
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Recently, the research and development of low cost and highly efficient millimeter-wave (mmWave) systems with beam-steering capabilities have significantly advanced to address the ever-increasing demand for future wireless ultra-broadband applications. These applications include, but are not limited to, automotive anti-collision surveillance radar, smart navigation systems, improved wireless tracking, satellite communication, imaging, 5G wireless communication, and 60GHz multi-gigabit wireless personal and local area network (WPAN/WLAN). In general, beam-steering capability significantly relaxes the overall system power budget and minimizes the interference. In communication applications, it enhances the link robustness through multi-path mitigation and increases the channel and the aggregated channel throughput by exploiting the spatial dimension. In imaging/radar systems, beam-steering is essential for achieving the required resolution (angle-of-arrival). In this work, I have proven many beam-steering advantages in this work through the development of a ray-tracing based wireless channel model, which has been used to extract the antenna system requirements and to quantitatively illustrate the usefulness of the presented beam-steerable systems. Despite the advantages it provides, the realization of this electronic beam-steerable mmWave antenna system is quite challenging. In general, the mmWave components' design, integration, fabrication and testing processes are far more complex than their lower frequency counterparts. This can be attributed to the significant losses and parasitics experienced at mmWave frequencies, as well as the lack of reliable design models. Systems with fully integrated (on-chip) antennas and passives have been widely studied and presented at mmWave range; however, the performance (low antenna gain, high phase noise, etc…), the cost (die size is huge), and thermal problems are still major issues for these systems. Hybrid integration tackles these problems by combining a compact and low power consumption die (or multiple dies) with high performance off-chip passives (antenna, feed network, passive phase shifters, resonators, etc…); however, this integration is costly. In addition, there is a challenge associated with the implementation of high performance components at mmWave range. This is mainly due to the use of advanced/non-standard types of fabrication technologies and complex integration/packaging techniques. Investigation, optimization, development of a highly efficient and yet very low cost mmWave beam-steering solution calls for a multi-disciplinary approach which involves EM theory, optimization techniques, microwave circuits, wireless communications, Silicon micro-fabrication, layout design, parasitics modeling/extraction and MEMS technology. The proposed study introduces a high performance beam-steering mmWave antenna system along with its integration with the active components with special consideration to the fabrication cost. The new high resistivity Silicon (HRS) dielectric waveguide (DWG) based platform, which has recently been developed at CIARS (Centre for Intelligent Antenna and Radio Systems), is extended and used for wireless mmWave systems with beam-steering antennas. Electronic beam-steering can be implemented through beam-switching configurations (simple, fast but coarse) or phase array configurations (complex but high performance for large arrays). A novel low cost, highly efficient and compact switched-beam antenna is proposed for the automotive radar application. The design optimization along with the fabrication and measurement details have been discussed. For phased array applications, various HRS DWG-based antenna designs have been proposed and discussed in this study. Among them is the novel pixelated antenna which represents a new systematic procedure for designing a compact and low cost dielectric antenna for mmWave/sub-THz applications. I have developed a method using Genetic Algorithm to optimize the shape of the antenna in a compact space for any given specifications. The other important component is the phase shifter. Low-cost, compact and easily integrated phase shifters with low insertion loss and low power consumption are highly desirable for a wide range of applications. In addition, minimal insertion loss variations for the full range of phase shift over a wide frequency band is a critical requirement. I have carefully studied the effects of phase shifters non-idealities, taking into consideration the phased array system level requirements and presented two novel HRS DWG-based phase shifters. Among the proposed phase shifters is a structure that changes the phase of the propagating mode by varying the propagation constant using a high dielectric constant (40-170) slab of Barium Lanthanide Tetratitanates. This leads to a compact phase shifter design. The additional advantage of this phase shifter is that it focuses the fields in a lossless air gap (new low loss guiding structure). Different types of the proposed phase shifter have been developed and successfully tested including electrically controlled ones. Finally, I present new techniques for low cost and efficient integration for the proposed high quality mmWave passives with active components.