Advanced Antenna Array Development for mm-Wave Communications: Advanced Antenna Array Development for mm-Wave Communications.pdf

Electronically controlled antenna arrays, such as reconfigurable and phased antenna arrays, are essential elements of high-frequency 5G communication hardware. These antenna arrays are aimed at delivering specified communication scenarios and channel characteristics in the mm-wave parts of the 5G spectrum. At the same time, several challenges are associated with the development of such antenna structures, and these challenges mainly originate from their intended mass production, contemporary manufacturing technologies, integration with active RF chains, compact size, dense circuitry, and limitations in postmanufacturing tuning. Consequently, 5G antenna array designers are presented with contradictory design requirements and constraints. Furthermore, these designers need to handle large numbers of designable parameters of the antenna array models, which can be computationally expensive, especially for repetitive and adaptive simulations that are required in design optimization and tuning. Antenna array synthesis, namely, the process of finding positions, orientation, and excitation of the array radiators, is a challenging yet crucial part of antenna array development. This process ensures that the performance requirements of the antenna array are met. Therefore, there is a need for reliable yet fast automated computer-aided design (CAD) and synthesis tools that can support the development of 5G antenna array solutions, from the initial prototyping stage to the final manufacturing tolerance analysis. This paper presents an overview of recent advances in antenna array synthesis from the viewpoint of their applicability to the design of electronically reconfigurable and phased antenna arrays for wireless communications and remote sensing.

Phased antenna arrays play a pivotal role in the development of upcoming 5G communication systems. Owing to spatial filtering and real-time pattern adaption capabilities, antenna arrays exhibit excellent wireless channel characteristics that are instrumental in achieving high data rates and reliable quality of service, especially in the millimeter-wave frequency range of the 5G spectrum . For decades, the phased arrays have been developed as rather bulky, expensive, stationary, or onboard antenna systems for radars, satellite, and cellular wireless communications.

Recent advances in electromagnetic (EM) computer-aided design (CAD) software , antenna manufacturing technologies , solid-state electronics in silicon-based technologies , millimeter-wave test instrumentation, and computational tools such as graphics processing units, allow for the development and industrialization of compact and cost-effective active phased antenna arrays with integrated electronically controllable beamformers. These products are suitable for 5G applications that are not just associated with base stations of network cells but also with extenders, repeaters, access points, and mobile terminals . Each application requires a tailored antenna array performance.

Thus, antenna designers need reliable and versatile array design procedures that can address challenging problems relevant to the synthesis of radiation patterns based on different masks, while handling multiple antenna performance parameters simultaneously, with a reasonable demand in terms of computational resources and time. Robust techniques should be able to perform syntheses with array models for different levels of complexity, ranging from distributions of isotropic uncoupled radiators to rigorous electromagnetically characterized models of array apertures where antenna mutual coupling effects are properly addressed. The use of a specific antenna array synthesis technique can be maximized by implementing a user-friendly interface and enabling software integration with commonly used electromagnetic computer-aided design (CAD) tools .

The antenna array synthesis is an automated process of identification or optimization of a specific antenna array model, namely, a procedure for determining the dimensional parameters and the (amplitude and/or phase) excitation tapers across the array aperture and terminals that are useful to meet given performance requirements. This ensures that the performance requirements, associated with the radiation pattern masks, are met in a certain antenna operational state. These requirements are usually essential in instances such as those occurring when pointing the main lobe along a certain direction in transmit (Tx) mode or while enforcing pattern nulls in specific angular sectors in the receive (Rx) mode.

The antenna characteristics considered in the framework of an array synthesis procedure include but are not limited to Radiation pattern properties over spatial directions, such as the main lobe half-power beamwidth (HPBW), null-to-null beamwidth, sidelobe level (SLL), grating lobe intensity, and front-to-back ratio (FBR) Power-related figures of merit such as peak directivity, gain, total efficiency, effective aperture, and antenna temperature Circuital characteristics at the array terminals, such as scattering parameters (input reflection and coupling coefficients) and active (apparent) impedance

Depending on the selected synthesis method or its particular realization, one or a few antenna parameters affect the array design goal function. Other characteristics can be controlled by incorporating specific constraints in the problem formulation. While certain antenna array features, primarily main lobe shape and sidelobe levels, can be evaluated using simple analytical techniques, total efficiency and scattering parameters can only be evaluated using full-wave electromagnetic modeling.

The development, realization, and applications of antenna array synthesis is an expanding research area, and several novel studies have emerged in the technical literature and new dedicated CAD tools have been introduced in the market. Therefore, providing an up-to-date detailed overview of this subject could be a rather ambitious task. Nevertheless, in this study, we have attempted to review the performance of phased antenna arrays in 5G applications through the perspective of an engineer.