Solid State Technology Branch of NASA Lewis Research Center

A collection of papers written by the members of the Solid State Technology Branch of NASA LeRC from Jun. 1991 - Jun. 1992 is presented. A range of topics relating to superconductivity, Monolithic Microwave Circuits (MMIC's), coplanar waveguides, and material characterization is covered

A true-time-delay networks design technique

This paper proposes a technique to design wide band switched-line (SL) true-time-delay (TTD) networks, commonly used for phased array antenna (PAA) applications. This study investigates the constant-delay behavior of switched-line phase shifters based on single-pole double-throw (SPDT) switches. Circuit sizing starts by considering the effective S-parameters of the switches, to use their non-idealities as an integral part of the phase shift linearly dependent to the frequency and by considering, from the beginning, the possible spatial positioning of elements that allows the circuit feasibility as a design target. The aim of this study is to provide a technique suitable for the design of well-matched TTD networks with a flat delay in wide bandwidth. In this paper, we propose new design formulas for which we show a single-frequency implementation. A computational strategy is used to obtain numerical solutions of the derived equations with this study. Finally, a monolithic X-band TTD circuit example is shown

Hybrid Precoding With Time-Modulated Arrays for Mmwave MIMO Systems

[Abstract]: We consider the utilization of time-modulated arrays (TMAs) as a simple and cost-effective approach to hybrid digital–analog precoding in millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems. Instead of conventional variable phase shifters (VPSs), our proposed TMA hybrid precoders use radio frequency (RF) switches followed by 1-bit VPSs in the analog part. We study the insertion losses at mmWave of a TMA analog precoding network in terms of sideband radiation and hardware efficiency. In addition, we present different algorithms for the design of both the baseband and RF parts of a TMA hybrid precoder. The proposed methods exhibit different tradeoffs between performance, complexity, and power efficiency. Finally, TMA precoders are compared to those implemented with conventional VPSs in terms of insertion losses, chip area, and cost, concluding that precoding with TMAs is a competitive solution for mmWave MIMO systems.This work was supported in part by the Xunta de Galicia under Grant ED431C 2016-045, Grant ED341D R2016/012, and Grant ED431G/01, in part by the AEI of Spain under Grant TEC2015-69648-REDC and Grant TEC2016-75067-C4-1-R, and in part by ERDF funds under Grant AEI/FEDER, EU.Xunta de Galicia; ED431C 2016-045Xunta de Galicia; ED341D R2016/012Xunta de Galicia; ED431G/0

A tunable millimeter-wave phase shifter driven by dielectric elastomer actuators

We present the successful operation of the first dielectric elastomer actuator (DEA) driven tunable millimeter-wave phase shifter. The development of dynamically reconfigurable microwave/millimeter-wave (MW/MMW) antenna devices is becoming a prime need in the field of telecommunications and sensing. The real time updating of antenna characteristics such as coverage or operation frequency is particularly desired. However, in many circumstances currently available technologies suffer from high EM losses, increased complexity and cost. Conversely, reconfigurable devices based on DEAs offer low complexity, low electromagnetic (EM) losses and analogue operation. Our tunable phase shifter consists of metallic strips suspended a fixed distance above a coplanar waveguide (CPW) by planar DEAs. The planar actuators displace the metallic strips (10 mm in length) in-plane by 500 μm, modifying the EM field distribution, resulting in the desired phase shift. The demanding spacing (50 ±5 μm between CPW and metallic strips) and parallel alignment criteria required for optimal device operation are successfully met in our device design and validated using bespoke methods. Our current device, approximately 60 mm x 60 mm in planar dimensions, meets the displacement requirements and we observe a considerable phase shift (~95° at 25 GHz) closely matching numerical simulations. Moreover, our device achieves state of the art performance in terms of phase shift per EM loss ~235°/dB (35 GHz), significantly out performing other phase shifter technologies, such as MMIC phase shifters

Adaptive Millimeter-Wave and THz Antenna Devices Based on Dielectric Elastomer Actuators

Dynamic reconfiguration of antenna devices is becoming a prime need in emerging telecommunication and remote sensing systems operating in the portion of the electromagnetic (EM) spectrum spanning from millimeter-wave (MMW) to terahertz. Different techniques and materials are currently available for the implementation of a given EM reconfiguration in antenna systems at microwaves andMMW, such as semiconductors, RF-MEMS, Liquid Crystal, and ferroelectrics. However, a common feature to all these technologies is the significant increased loss and complexity with regard to the devices fixed counterpart. Both loss and complexity further increase when high-performance reconfiguration capabilities are addressed atMMWand above, constituting a major limitation to the future deployment of dynamically controllable systems. Advanced performance, low-complexity and low-cost are, therefore, the cornerstones in the development of new technologies for antenna reconfiguration. In this framework, the main objective of this thesis is to contribute to the advancement of low-cost and efficient technologies enabling antenna reconfiguration capabilities fromMMWto THz frequencies. Within this scope, it is proposed the analysis, design and implementation of mechanically reconfigurable devices using dielectric elastomer actuators (DEAs). DEAs are an emerging technology that possesses unique properties, and represents a potential alternative to conventionalmechanical reconfiguration schemes. DEAs are especially attractive for their large strain combined with low-costmaterials and fabrication, analog control and near-zero DC power consumption. These characteristics make them particularly suited to the realization of low-cost and low-loss reconfigurable antennas. The high potential of DEAs for the realization of adaptive devices is experimentally validated by the development of different prototypes operating atMMWand THz frequencies: i) a very low-loss true-time-delay phase shifter operating at Ka-band; ii) a Ka-band reconfigurable reflectarray with 1-D beam-scanning capability; iii) a stretchable and beam-scanning THz reflectarray exhibiting the uncommon potential for the implementation of conformal or reconfigurable devices based on mechanical stretching. The designs and concepts demonstrated in this thesis pave the way for the evolution of new DEA-based reconfigurable devices resulting in low-cost, low loss and compact structures

Solid State Technology Branch of NASA Lewis Research Center

Reprints of one year's production of research publications (June 1990 to June 1991) are presented. These are organized into three major sections: microwave circuits, both hybrid and monolithic microwave integrated circuits (MMICs); materials and device work; and superconductivity. The included papers also cover more specific topics involving waveguides, phase array antennas, dielectrics, and high temperature superconductors

Active and Reconfigurable Millimetre-Wave Antennas and Systems

PhDThe millimetre-wave (mm-wave) spectrum offers considerable advantages in terms of antenna form factor and spectrum availability. However, use of this region often requires reconfigurable antennas and systems. Initially, a review of the various applications which are taking hold in the lower regions of the mm-wave spectrum (30 to 100 GHz) is undertaken. Specifically, reconfigurable reflectarray technologies are selected for further research, and critical analysis of the reconfiguration techniques for including these in antennas is considered. Silicon as an optically activated semiconductor is chosen as the reconfiguration mechanism due to its low cost and the scope for improvement in this area. A new form of illumination is used, replacing traditional infra-red (IR) lasers with high power IR-LEDs enclosed in a cavity, increasing the efficiency of the silicon illumination. However, to make use of this novel illumination source, and subsequently integrate it into an antenna, the silicon response has to be characterised within Ka-band. This is done through measurements in a waveguide-based characterisation test cell, from which the complex electromagnetic properties of silicon under IR-LED illumination are retrieved with the aid of full-wave simulations. Using the measured conductivity properties of the illuminated silicon, reflectarrays with non-uniform amplitude distributions can be designed. Through variation of illumination intensities of IR-LEDs throughout the array, it is shown through measurements and full-wave simulations that unit cell reflections can be modified while phases are kept relatively constant. This theoretically allows switching between, for example a low side-lobe pattern binomial array, or a narrow beamwidth pattern Chebyshev array. To implement this, a novel multilayer unit-cell is designed, integrating the IR-LED. This is then used in a full reflectarray design which is measured. The key contributions of this work include the novel illumination mechanism and its integration into a reflectarray antenna, and the use of reconfigurable photoconductive materials to provide a mechanism for beam shaping and pattern synthesis at Ka-band.EPSRC DTC under grant number 135614

NASA developments in solid state power amplifiers

Over the last ten years, NASA has undertaken an extensive program aimed at development of solid state power amplifiers for space applications. Historically, the program may be divided into three phases. The first efforts were carried out in support of the advanced communications technology satellite (ACTS) program, which is developing an experimental version of a Ka-band commercial communications system. These first amplifiers attempted to use hybrid technology. The second phase was still targeted at ACTS frequencies, but concentrated on monolithic implementations, while the current, third phase, is a monolithic effort that focusses on frequencies appropriate for other NASA programs and stresses amplifier efficiency. The topics covered include: (1) 20 GHz hybrid amplifiers; (2) 20 GHz monolithic MESFET power amplifiers; (3) Texas Instruments' (TI) 20 GHz variable power amplifier; (4) TI 20 GHz high power amplifier; (5) high efficiency monolithic power amplifiers; (6) GHz high efficiency variable power amplifier; (7) TI 32 GHz monolithic power amplifier performance; (8) design goals for Hughes' 32 GHz variable power amplifier; and (9) performance goals for Hughes' pseudomorphic 60 GHz power amplifier