Waveguide manufacturing technologies for next-generation millimeter-wave antennas

Some recent waveguide-based antennas are presented in this paper, designed for the next generation of communication systems operating at the millimeter-wave band. The presented prototypes have been conceived to be manufactured using different state-of-the-art techniques, involving subtractive and additive approaches. All the designs have used the latest developments in the field of manufacturing to guarantee the required accuracy for operation at millimeter-wave frequencies, where tolerances are extremely tight. Different designs will be presented, including a monopulse antenna combining a comparator network, a mode converter, and a spline profile horn; a tunable phase shifter that is integrated into an array to implement reconfigurability of the main lobe direction; and a conformal array antenna. These prototypes were manufactured by diverse approaches taking into account the waveguide configuration, combining parts with high-precision milling, electrical discharge machining, direct metal laser sintering, or stereolithography with spray metallization, showing very competitive performances at the millimeter-wave band till 40 GHzThis work was supported by the Spanish Government under Grant TEC2016-76070- C3-1/2-R (ADDMATE); in part under Grant PID2020-116968RB-C32/33 (DEWICOM), Agencia Estatal de Investigación MCIN/AEI/10.13039/501100011033, Fondo Europeo de Desarrollo Regional: AEI/FEDER, UE. This work was also partially supported under Grant S2013/ICE3000 (SPADERADARCM), Madrid Regional Governmen

Mechanically reconfigurable linear phased array antenna based on single-block waveguide reflective phase shifters with tuning screws

This work presents the design and prototyping of a reconfigurable phased array in Ku band (16 to 18 GHz) implemented in waveguide technology. The design is based on the use of a novel seamless waveguide module integrating four reconfigurable phase shifters to adjust the relative phase shift between the unitary elements of a linear array, which are illuminated uniformly by a corporate waveguide feeding network. The phase shifters are implemented by a 90º hybrid coupler in waveguide technology where two of its ports are loaded with a tunable reactive load, implemented in this proof of concept with a tuning screw. The four phase shifters have been manufactured in a single part using direct metal laser sintering, avoiding the losses related to bad electric contacts and misalignments associated to multipart devices. This also simplifies the assembly of the full phased array, leading to a modular approach with three parts whose design can be addressed separately. The experimental results for the complete array antenna show great performance and demonstrate that the main-lobe of the radiation pattern can be effectively scanned continuously between the angles - 25º and 25º, with a high efficiency in the whole design band thanks to the proposed waveguide implementationThis work was supported by the Spanish Government, Agencia Estatal de Investigación, Fondo Europeo de Desarrollo Regional: AEI/FEDER, UE, under Grant TEC2016-76070-C3-1-

Low cost fabrication processing for microwave and millimetre-wave passive components

Microwave and millimetre-wave technology has enabled many commercial applications to play a key role in the development of wireless communication. When dissipative attenuation is a critical factor, metal-pipe waveguides are essential in the development of microwave and millimetre-wave systems. However, their cost and weight may represent a limitation for their application. In the first part of this work two 3D printing technologies and electroless plating were employed to fabricate metal pipe rectangular waveguides in X and W-band. The performance for the fabricated waveguides was comparable to the one of commercially available equivalents, showing good impedance matching and low attenuation losses. Using these technologies, a high-performance inductive iris filter in W-band and a dielectric flap phase shifter in X-band were fabricated. Eventually the design and fabrication of a phased antenna array is reported. For microwave and millimetre-wave applications, system-on-substrate technology can be considered a very valuable alternative, where bulky coax and waveguide interconnects are replaced by low-loss transmission lines embedded into a multilayer substrate, which can include a wide range of components and subsystems. In the second part of this work the integration of RF MEMS with LTCC fabrication process is investigated. Three approaches to the manufacture of suspended structures were considered, based on laser micromachining, laser bending of aluminium foil and hybrid thick/thin film technology. Although the fabrication process posed many challenges, resulting in very poor yield, two of the solution investigated showed potential for the fabrication of low-cost RF MEMS fully integrated in LTCC technology. With the experience gained with laser machining, the rapid prototyping of high aspect ratio beams for silicon MEMS was also investigated. In the third part of this work, a statistical study based on the Taguchi design of experiment and analysis of variance was undertaken. The results show a performance comparable with standard cleanroom processing, but at a fraction of the processing costs and greater design flexibility, due to the lack of need for masks.Open Acces

high performance microwave waveguide devices produced by laser powder bed fusion process

Abstract Additive manufacturing technologies are currently envisaged to boost the development of a next generation of microwave devices intended for satellite telecommunications. Due to their excellent electromagnetic and mechanical properties, metal waveguide components are key building blocks of several radio frequency (RF) systems used in these applications. This article reports the perspectives deriving from the use of laser powder bed fusion (L-PBF) technology to the production of high-performance microwave waveguide devices. A robust design of filters has been implemented in several prototypes manufactured in AlSi10Mg alloy. The corresponding measured performance confirm the applicability of the L-PBF process to the intended application

Enabling Ridge Waveguide Technology for Wideband Millimeter-Wave Decoys

Emerging high power millimeter wave applications such as RF decoy repeaters require transmission line technologies operating over a wide bandwidth with the ability to carry hundreds of watts of continuous wave (CW) power. To develop such repeaters an enabling technology for integration of components such as dual-polarized antennas, filters, couplers, bends, and twists is needed. This thesis presents the analysis, design, and measurements of novel passive components for such repeaters in V- and W- bands. At these high frequencies, traditional techniques of design and fabrication are challenging due to small size, losses, and wide bandwidth.A high-power capable wideband 45 ‒ 110 GHz double-ridge waveguide (WRD45110) transmission line with low loss, low dispersion, and high theoretical power-handling is demonstrated first. Then, utilizing the designed cross-section a suite of passive waveguide components required for a typical decoy repeater system such as straight transmission lines, E- and H- plane bends, 90&deg; twists, and termination loads are developed. A quad-ridge horn antenna with consistent broadside gain and stable E- and H- plane radiation patterns over the desired frequency band is also demonstrated. All components are carefully designed across different physics-based domains (RF, thermal, air-breakdown, etc.) and fabricated with either a direct metal laser sintering (DMLS) 3D printing or a conventional CNC machining with special care taken to allow for easy interconnecting.The design of a dual polarized high power capable system over 45 ‒ 110 GHz band is also presented. To combine two polarizations into the same radiating aperture, an Orthomode Transducer (OMT) based upon WRD45110 is developed. In order to fabricate this prototype through DMLS process, this OMT is devised with all the guidelines of 3D metal printing.Also, in system level, a preliminary system integration of a decoy repeater is discussed. To enhance the isolation between the TX and RX antennas in a decoy repeater, reactive impedance surfaces (RIS) with 1D RIS (corrugations), and 2D RIS (mushroom structure) are designed and built. In addition, a switched-beam phased array system that uses a perforated gradient index flat lens for beam scanning in &plusmn;30&deg; elevation and 0&deg; ‒ 360&deg; azimuth is demonstrated over the entire 45 ‒ 110 GHz frequency range.</p

Additively Manufactured RF Components, Packaging, Modules, and Flexible Modular Phased Arrays Enabling Widespread Massively Scalable mmWave/5G Applications

The 5G era is here and with it comes many challenges, particularily facing the high frequency mmWave adoption. This is because of the cost to implement such dense networks is much greater due to the high propagation losses of signals that range from 26 GHz to 40 GHz. Therefore there needs to be a way to utilize a method of fabrication that can change with the various environments that 5G will be deployed in, be it dense urban areas or suburban sprawl. In this research, the focus is on making these RF components utilized for 5G at low cost and modular with a focus on additive manufacturing. Since additive manufacturing is a rapid prototyping technique, the technology can be quickly adjusted and altered to meet certain specifications with negligible overhead. Several areas of research will be explored. Firstly, various RF passive components such as additively manufactured antennas and couplers with a combination hybrid inkjet and 3D printing will be discussed. Passive components are critical for evaluating the process of additive manufacturing for high frequency operation. Secondly, various structures will be evaluated specifically for packaging mmWave ICs, including interconnects, smart packaging and encapsulants for use in single or multichip modules. Thirdly, various antenna fabrication techniques will be explored which enables fully integrated ICs with antennas, called System on Antenna (SoA) which utilizes both inkjet and 3D printing to combine antennas and ICs into modules. These modules, can then be built into arrays in a modular fashion, allowing for large or smaller arrays to be assembled on the fly. Finally, a method of calibrating the arrays is introduced, utilizing inkjet printed sensors. This allows the sensor to actively detect bends and deformations in the array and restore optimal antenna array performance. Built for flexible phased arrays, the sensor is designed for implementation for ubiquitous use, meaning that its can be placed on any surface, which enables widespread use of 5G technologies.Ph.D