Bijan Tehrani

Multilayer Inkjet Printing of Millimeter-Wave Proximity-Fed Patch Arrays on Flexible Substrates

Flexible inkjet-printed proximity-fed patch antennas, designed for the 24-GHz Industrial, Scientific, and Medical (ISM) band, are demonstrated in this letter for the first time featuring a multilayer inkjet deposition process. Inkjet printing of antennas allows for the low-cost, noncontact, and additive fabrication of RF components onto nearly any host substrate or package. The inkjet-printing process exhibited in this leter is the first inkjet process to demonstrate multilayer printed antennas, enabled by a new printable dielectric ink that allows for the deposition of thick dielectric layers. Printed coupled patch antennas with realized gains of over 4 dBi and four-element coupled patch arrays with gains of over 7 dBi are demonstrated on a flexible liquid crystal polymer (LCP) substrate. The antenna gain, return loss, and pattern are presented and demonstrate the repeatability and design flexibility of the novel inkjet-deposition process.

Additively Manufactured Nanotechnology and Origami-Enabled Flexible Microwave Electronics

Inkjet printing on flexible paper and additive manufacturing technologies (AMT) are introduced for the sustainable ultra-low-cost fabrication of flexible radio frequency (RF)/microwave electronics and sensors. This paper covers examples of state-of-the-art integrated wireless sensor modules on paper or flexible polymers and shows numerous inkjet-printed passives, sensors, origami, and microfluidics topologies. It also demonstrates additively manufactured antennas that could potentially set the foundation for the truly convergent wireless sensor ad-hoc networks of the future with enhanced cognitive intelligence and “zero-power” operability through ambient energy harvesting and wireless power transfer. The paper also discusses the major challenges for the realization of inkjet-printed/3-D printed high-complexity flexible modules as well as future directions in the area of environmentally-friendly “Green”) RF electronics and “Smart-House” conformal sensors.

Inkjet-printed, vertically-integrated, high-performance inductors and transformers on flexible LCP substrate

Vertically-integrated inkjet-printed inductors and transformers are demonstrated for the first time with high levels of performance and repeatability. The inductive components are fabricated using a well-characterized multi-layer inkjet printing process which is substrate independent and has been optimized for the fabrication of RF components. Printed spiral inductors with values of 10 nH and 25 nH are demonstrated with a maximum Q of over 20 at 1 GHz, which is the highest Q value reported to date for printed components, and a repeatability of within 5% between fabrication runs. Printed inductively coupled transformer-based baluns are also demonstrated which operate at 1.4 GHz with a maximum available gain of -1.7 dB.

Fully inkjet-printed multilayer microstrip and T-resonator structures for the RF characterization of printable materials and interconnects

A vertically-integrated, fully inkjet-printed microwave structure is demonstrated for the first time, where both the metallic elements and the platform substrate are completely fabricated with the additive inkjet printing process. The surface uniformity of SU-8 polymer ink is outlined as a function of layer deposition to provide a desirable profile for a thick RF substrate application. Inkjet-printed vias are demonstrated and realized as microwave substrate interconnects within SU-8. Microstrip and T-resonator structures are developed to demonstrate the application of these inkjet-printed platforms for the RF characterization of a printable material, where the relative permittivity of the substrate is extracted as a function of frequency from 1-30 GHz.

Inkjet Printing of Multilayer Millimeter-Wave Yagi-Uda Antennas on Flexible Substrates

This letter presents two high-gain, multidirector Yagi-Uda antennas for use within the 24.5-GHz ISM band, realized through a multilayer, purely additive inkjet printing fabrication process on a flexible substrate. Multilayer material deposition is used to realize these 3-D antenna structures, including a fully printed 120- μm-thick dielectric substrate for microstrip-to-slotline feeding conversion. The antennas are fabricated, measured, and compared to simulated results showing good agreement and highlighting the reliable predictability of the printing process. An endfire realized gain of 8 dBi is achieved within the 24.5-GHz ISM band, presenting the highest-gain inkjet-printed antenna at this end of the millimeter-wave regime. The results of this work further demonstrate the feasibility of utilizing inkjet printing for low-cost, vertically integrated antenna structures for on-chip and on-package integration throughout the emerging field of high-frequency wireless electronics.

Inkjet-printed 3D interconnects for millimeter-wave system-on-package solutions

This work outlines the development, fabrication, and measurement of fully inkjet-printed 3D interconnects for wireless mm-wave packaging solutions. Conductive silver nanoparticle and dielectric polymer-based inks are utilized to fabricate die attach, dielectric ramp, and CPW transmission line interconnect structures in order to interface a silicon die with a packaging substrate. Insertion and return loss are measured and compared with simulations over the range of 0-40 GHz. An inkjet-printed mm-wave bow-tie slot antenna is integrated with the IC die in order to highlight the highly versatile nature of this 3D interconnect technology for integration with emerging SoP technology.

Fully inkjet-printed multilayer microstrip patch antenna for Ku-band applications

A fully inkjet-printed multi-layer microstrip patch antenna with a CPW to microstrip line transition is designed and demonstrated for the first time in this paper. Both metallic layers and SU-8 substrate are fabricated with an additive inkjet printing process. The patch antenna is designed to operate at 14 GHz, and the operation of the antenna is confirmed in measurement validating that fully additively-processed RF devices are a new option for post processing RF devices with substrate independence.

Additively Manufactured RF Components and Modules: Toward Empowering the Birth of Cost-Efficient Dense and Ubiquitous IoT Implementations

In this review, the particular importance and associated opportunities of additively manufactured radiofrequency (RF) components and modules for Internet of Things (IoT) and millimeter-wave ubiquitous sensing applications is thoroughly discussed. First, the current advances and capabilities of additive manufacturing (AM) tools are presented. Then, completely printed chipless radio-frequency identification (RFID) systems, and their current capabilities and limitations are reported. The focus is then shifted toward more complex backscattering energy autonomous RF structures. For each of the essential components of these structures, that encompass energy harvesting and storage, backscattering front ends, passive components, interconnects, packaging, shape-chaging (4-D printed) topologies and sensing elements, current trends are described and representative stateof- the-art examples reported. Finally, the results of this analysis are used to argue for the unique appeal of AM RF components and systems toward empowering a technological revolution of costefficient dense and ubiquitous IoT implementations.

Post-process fabrication of multilayer mm-wave on-package antennas with inkjet printing

This work outlines and demonstrates for the first time the utilization of inkjet printing processes for the fabrication of on-package mm-wave antenna structures. A multilayer, fully printed 30 GHz square patch antenna with a 120 μm thick dielectric substrate is fabricated directly onto an IC chip package through the use of metallic and dielectric inks. A probe station is used to measure the return loss of the fabricated on-package antenna, showing excellent agreement with simulations. This well defined process of fully additive antenna fabrication demonstrates the integrity of the inkjet printing process for on-package and on-chip antenna fabrication up to mm-wave frequency ranges.

Inkjet Printing of a Wideband, High Gain mm-Wave Vivaldi Antenna on a Flexible Organic Substrate

A wideband, high gain mm-Wave Vivaldi antenna on a flexible substrate operating above 40 GHz with a realized gain greater than 9 dBi is demonstrated in this paper. This work presents both the highest frequency and highest gain antenna fabricated through inkjet printing to date. Inkjet printing allows for a rapid, low-cost, and environmentally advantageous fabrication of electronic components compared to traditional techniques and is currently advancing into mm-Wave operation for applications in high data-rate wireless communications.