High Performance Integrated Beam-Steering Techniques for Millimeter-Wave Systems

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.4 month

An N-bit digitally variable ultra wideband pulse generator for GPR and UWB applications

This paper presents a low-cost Ultra Wideband (UWB) pulse generator that can vary the pulse duration digitally by using a Step Recovery Diode (SRD), microstrip transmission lines and PIN diodes. First, a sharp edge is generated by using a SRD circuitry. Then a pulse is formed from the sharp edge through the use of transmission lines and the PIN diodes. Based on the number of transmission lines (N), the duration of the pulse can be varied in steps. The UWB pulse generator circuits are implemented on an FR-4 substrate using microstrip line technology and UWB pulses with durations of 550 to 2400 psec are measured. N2 Ke

Phase Shifter for Millimeter-Wave Frequency Range Based on Glide Symmetric Structures

The use of glide symmetry in radiofrequency devices to introduce dispersive effects has been recently proposed and demonstrated. One of these effects is to control the propagation constant of the structure. Here, we propose a mm-wave phase shifter whose elements have a glide-symmetric configuration to achieve a greater phase shift in the same waveguide space than the non-glide-symmetric case. The glide-symmetric phase shifter is implemented in waveguide technology and is formed by rows of metallic pins that produce the desired phase shift. To assess the better performance of the glide-symmetric phase shifter, it is compared to its non-glide-symmetric version whose metallic pins are located only in one of the broad sides of the waveguide. The operating frequency range of the phase shifter is 67 to 75 GHz. Results show a 180 degree phase shift in regard to the reference waveguide without pins, and 50 degrees more than the non-glide-symmetric version.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Small Footprint Multilayered Millimeter-Wave Antennas and Feeding Networks for Multi-Dimensional Scanning and High-Density Integrated Systems

This paper overviews the state-of-the-art of substrate integrated waveguide (SIW) techniques in the design and realization of innovative low-cost, low-profile and low-loss (L3) millimeter-wave antenna elements, feeding networks and arrays for various wireless applications. Novel classes of multilayered antenna structures and systems are proposed and studied to exploit the vertical dimension of planar structures to overcome certain limita-tions in standard two-dimensional (2-D) topologies. The developed structures are based on two techniques, namely multi-layer stacked structures and E-plane corners. Differ-ent E-plane structures realised with SIW waveguide are presented, thereby demonstrating the potential of the proposed techniques as in multi-polarization antenna feeding. An array of 128 elements shows low SLL and height gain with just 200g of the total weight. Two versions of 2-D scanning multi-beam are presented, which effectively combine frequency scanning with beam forming networks. Adding the benefits of wide band performance to the multilayer structure, two bi-layer structures are investigated. Different stacked antennas and arrays are demonstrated to optimise the targeted antenna performances in the smallest footprint possible. These structures meet the requirement for developing inexpensive compact millimeter-wave antennas and antenna systems. Different structures and architectures are theoretically and experimentally studied and discussed for specific space- and ground-based appli-cations. Practical issues such as high-density integration and high-volume manufacturability are also addressed

Hybrid Beamforming for Large Antenna Arrays with Phase Shifter Selection

This paper proposes an asymptotically optimal hybrid beamforming solution for large antenna arrays by exploiting the properties of the singular vectors of the channel matrix. It is shown that the elements of the channel matrix with Rayleigh fading follow a normal distribution when large antenna arrays are employed. The proposed beamforming algorithm is effective in both sparse and rich propagation environments, and is applicable for both point-to-point and multiuser scenarios. In addition, a closed-form expression and a lower-bound for the achievable rates are derived when analog and digital phase shifters are employed. It is shown that the performance of the hybrid beamformers using phase shifters with more than 2-bits resolution is comparable with analog phase shifting. A novel phase shifter selection scheme that reduces the power consumption at the phase shifter network is proposed when the wireless channel is modeled by Rayleigh fading. Using this selection scheme, the spectral efficiency can be increased as the power consumption in the phase shifter network reduces. Compared to the scenario that all of the phase shifters are in operation, the simulation results indicate that the spectral efficiency increases when up to 50% of phase shifters are turned off.Comment: Accepted to Transactions on Wireless Communications, 201

Variable High Precision Wide D-Band Phase Shifter

This paper proposes a new concept of designing compact high precision millimeter-wave wideband variable phase shifters. The phase shifter is implemented with a stacked shim with extremely short length of 0.9 mm and two waveguide flange adaptors with length of 0.5 mm. High precision phase shifting is achieved over entire D-band (110-170 GHz) by rotating the shim 90 degrees from aligned to perpendicular with consistent impedance matching performance. In addition, a glide-symmetric holey electromagnetic bandgap (EBG) structure is adopted to avoid wave leakage from the gap between the shim and the flange adaptors. A proof-of-concept (PoC) demonstrator is designed, manufactured, and tested. The measured results show that the designed stacked shim phase shifter with embedded EBG structure ensures return loss higher than 10 dB across 110-170 GHz with a 75 mu m airgap between waveguide flanges. The studied phase shifter provides a 0.88ffi phase shifting with each degree of mechanical rotation. The fabricated PoC phase shifter has a worst-case insertion loss of 0.92 dB and a return loss of 20 dB across the entire 110-170 GHz band and a maximum phase shift of 30 degrees. At 10 degrees phase shifting, the measured insertion loss is lower than 0.52 dB, and return loss is higher than 23 dB, respectively