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NASA NTRS2007

Advances in Scanning Reflectarray Antennas Based on Ferroelectric Thin Film Phase Shifters for Deep Space Communications

Though there are a few examples of scanning phased array antennas that have flown successfully in space, the quest for low-cost, high-efficiency, large aperture microwave phased arrays continues. Fixed and mobile applications that may be part of a heterogeneous exploration communication architecture will benefit from the agile (rapid) beam steering and graceful degradation afforded by phased array antennas. The reflectarray promises greater efficiency and economy compared to directly-radiating varieties. Implementing a practical scanning version has proven elusive. The ferroelectric reflectarray, under development and described herein, involves phase shifters based on coupled microstrip patterned on Ba(x)Sr(1-x)TiO3 films, that were laser ablated onto LaAlO3 substrates. These devices outperform their semiconductor counterparts from X- through and K-band frequencies. There are special issues associated with the implementation of a scanning reflectarray antenna, especially one realized with thin film ferroelectric phase shifters. This paper will discuss these issues which include: relevance of phase shifter loss; modulo 2(pi) effects and phase shifter transient effects on bit error rate; scattering from the ground plane; presentation of a novel hybrid ferroelectric-semiconductor phase shifter; and the effect of mild radiation exposure on phase shifter performance.

Romanofsky, Robert R.↗

NASA NTRS2010

Cellular Reflectarray Antenna

The cellular reflectarray antenna is intended to replace conventional parabolic reflectors that must be physically aligned with a particular satellite in geostationary orbit. These arrays are designed for specified geographical locations, defined by latitude and longitude, each called a "cell." A particular cell occupies nominally 1,500 square miles (3,885 sq. km), but this varies according to latitude and longitude. The cellular reflectarray antenna designed for a particular cell is simply positioned to align with magnetic North, and the antenna surface is level (parallel to the ground). A given cellular reflectarray antenna will not operate in any other cell.

Romanofsky, Robert R.↗

NASA NTRS2010

Cellular reflectarray antenna and method of making same

A method of manufacturing a cellular reflectarray antenna arranged in an m by n matrix of radiating elements for communication with a satellite includes steps of determining a delay .phi.m,n for each of said m by n matrix of elements of said cellular reflectarray antenna using sub-steps of: determining the longitude and latitude of operation, determining elevation and azimuth angles of the reflectarray with respect to the satellite and converting theta.sub.0 (.theta..sub.0) and phi.sub.0 (.phi..sub.0), determining .DELTA..beta..sub.m,n, the pointing vector correction, for a given inter-element spacing and wavelength, determining .DELTA..phi..sub.m,n, the spherical wave front correction factor, for a given radius from the central element and/or from measured data from the feed horn; and, determining a delay .phi.m,n for each of said m by n matrix of elements as a function of .DELTA..beta..sub.m,n and .DELTA..phi..sub.m,n..

Romanofsky, Robert R↗

NASA NTRS2011

Cellular reflectarray antenna and method of making same

Romanofsky, Robert R↗

NASA NTRS2002

Modulation Study for Beam Steerable Reflectarray Antennas

The reflectarray antenna is a power-efficient antenna but with an inherent intersymbol interference (ISI) problem with digital modulations. The composite signal model of a reflectarray is established. The ISI is characterized by the signal components delays. The feed-to-element distance and the element-to-observation distance contribute to the total delay, with the latter having the major effect. The effect of typical phase shifters' phase errors is analyzed and evaluated. Simulations are performed. The analytical and simulation results for an example reflectarray at f(sub c) = 26.5 GHz and bit rate of 1.325 Gbps show that the BER degradation due to ISI is proportional to the symbol rate and the loss ranges from less than 1 dB to around 2 dB in E(sub b)/N(sub o), depending on original E(sub b)/N(sub o), for BPSK, QPSK, 8PSK and 16QAM. The phase error effect is negligible for lower order modulations and is unacceptable for higher order modulations such as 64 and 256QAM.

Xiong, Fuqin↗

NASA NTRS1996

A High-gain Circularly Polarized Ka-band Microstrip Reflectarray

A half-meter, 32 GHz, circularly polarized microstrip reflectarray antenna has been developed. Excellent efficiency, good bandwidth, and low average sideglobe and cross-pol levels are achieved. It is believed that this is electrically the largest microstrip reflectarray (6924 elements) that has ever been developed, and it is the first time that circular polarization has been demonstrated using microstrip elements.

reflectarray antenna microstrip Ka-band circular p↗

NASA NTRS1997

(abstract) Microstrip Reflectarray and its Applications

The microstrip reflectarray antenna, being in the form of a flat reflector, has recently been investigated by several antenna researchers. To demonstrate that such an antenna can be developed with relatively large electrical aperture, a half-meter-diameter microstrip array has been designed and constructed at 32 GHz with circular polarization. It is believed that this is the largest microstrip reflectarray ever built.

antenna reflectarray microstrip↗

NASA NTRS1997

(abstract) A Ka-Band 0.5 m Circularily Polarized Microstrip Reflectarray

The microstrip reflectarray antenna, being in the form of a flat reflector, has recently been investigated by several antenna researchers. This antenna, when compared to the conventional parabolic reflector, not only has the potential advantages of achieving smaller mass, smaller volume, simpler deployment mechanism, but also has the capability of scanning its main beam to larger angles from the broadside direction. Without any power divider and its associated large insertion loss, a phased reflectarray may not need the high cost T/R modules and can still remain to be an efficient array antenna.

antennas reflectarray parabolic reflector↗

NASA NTRS2006

A Cassegrain Offset-Fed Dual-Band Reflectarray

An X/Ka dual-band microstrip reflectarray with circular polarization (CP) has been constructed using thin membranes and Cassegrain offset-fed configuration. It is believed that this is the first Cassegrain reflectarray ever been developed. This antenna has a 75-cm-diameter aperture and uses metallic subreflector and angular-rotated annular ring elements. It achieved a measured -3dB-gain bandwidth of 700 MHz at X-band and 1.5 GHz at Ka-band, as well as a CP bandwidth (3dB axial ratio) of more than 700 MHz at X-band and more than 2 GHz at Ka-band. The measured peak efficiencies are 49.8% at X-band and 48.2% at Ka-band.

offset fed↗

NASA NTRS2015

Integrated Solar Array and Reflectarray Antenna for High Bandwidth Cubesats

The Integrated Solar Array and Reflectarray Antenna (ISARA) mission will demonstrate a reflectarray antenna that increases downlink data rates for Cube- Sats from the existing baseline rate of 9.6 kilobits per second (kbps) to more than 100 megabits per second (Mbps). The ISARA spacecraft is slated for launch no earlier than Dec. 1, 2015.

Downlink data rates for CubeSats↗

NASA NTRS2017

Integrated Solar Array and Reflectarray Antenna for High Bandwidth Cubesats

The Integrated Solar Array and Reflectarray Antenna (ISARA) mission will demonstrate a reflectarray antenna that increases downlink data rates for CubeSats from the existing baseline rate of 9.6 kilobits per second (kbps) to more than100 megabits per second (Mbps). A secondary payload called the CubeSat Multispectral Observation System (CUMULOS), is an experimental remote sensing payload also being demonstrated on this mission. A launch date for the ISARA spacecraft is currently pending.

ISARA↗

NASA NTRS1996

Microstrip Reflectarray with Elements Having Variable Rotation Angles

A novel means of achieving cophasal far-field radiation has been demonstrated for a curcularly polarized microstrip reflectarray with elements having variable rotation angles. Two Ka-band, half meter microstrip reflectarrays have been fabricated and tested.

reflectarray↗

DOE OSTI2016

MAcro-Electro-Mechanical Systems (MÆMS) based concept for microwave beam steering in reflectarray antennas

We present a new approach to perform beam steering in reflecting type apertures such as reflectarray antennas. The proposed technique exploits macro-scale mechanical movements of parts of the structure to achieve two-dimensional microwave beam steering without using any solid-state devices or phase shifters integrated within the aperture of the antenna. The principles of operation of this microwave beam steering technique are demonstrated in an aperture occupied by ground-plane-backed, sub-wavelength capacitive patches with identical dimensions. We demonstrate that by tilting the ground plane underneath the entire patch array layer, a phase shift gradient can be created over the aperture of the reflectarray that determines the direction of the radiated beam. Changing the direction and slope of this phase shift gradient on the aperture allows for performing beam steering in two dimensions using only one control parameter (i.e., tilt vector of the ground plane). A proof-of-concept prototype of the structure operating at X-band is designed, fabricated, and experimentally characterized. Experiments demonstrate that small mechanical movements of the ground plane (in the order of 0.05λ{sub 0}) can be used to steer the beam direction in the ±10° in two dimensions. It is also demonstrated that this beam scanning range can be greatly enhanced to ±30° by applying this concept to the same structure when its ground plane is segmented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS1995

Analysis of a microstrip reflectarray antenna for microspacecraft applications

A microstrip reflectarray is a flat reflector antenna that can be mounted conformally onto a spacecraft's outside structure without consuming a significant amount of spacecraft volume and mass. For large apertures (2 m or larger), the antenna's reflecting surface, being flat, can be more easily and reliably deployed than a curved parabolic reflector. This article presents the study results on a microstrip reflect-array with circular polarization. Its efficiency and bandwidth characteristics are analyzed. Numerous advantages of this antenna system are discussed. Three new concepts using this microstrip reflectarray are also proposed.

Huang, J.↗

NASA NTRS1999

Ka-Band Beam Steering Reflectarray Study

A one-meter diameter, 32 GHz active microstrip reflectarray capable of electronic beam steering has been studied. The 15_500 element array consists of rnicrostrip patch antennas, microstrip phase shifters, and dc bias lines. Specifically, the study focused on the solid-state devices and dc bias layouts for scanning the beam linearly 45 from boresight using 2-bit phase shifters. Three configurations are recommended for the reflectarray with integrated 2-bit phase shifters where the total substrate and cladding mass varies from 8 kg to 14 kg. Additionally, dc power requirements for p-i-n diodes in 1-bit, 2-bit and 3-bit phase shifting circuits are approximately 19 W, 19 W, and 39 W, respectively. The dc power requirement for phase shifters using passive MESFETs is much less than 1 W.

McSpadden, James O.↗

NASA NTRS2006

An eight-meter inflatable reflectarray antenna and its inflatable/self-rigidizable booms

This paper presents the analysis and test results related to buckling capability, modal characteristics, and thermal expansion coefficient of STR aluminum laminate inflatable/self-rigidizable booms with lengths up to 10 metes. STR booms are fundamental building blocks of space inflatable/self-rigidizable reflectarray antennas. These boom characteristics are essential for analyzing structural integrity, in orbit dynamic response, and in orbit thermal distortion of the 8-mter reflectarray antenna. Distinct advantages of the STR booms will also be identified and presented by this paper.

membranes↗

NASA NTRS2000

Beam scanning reflectarray antenna with circular polarization

A novel means of scanning a circularly polarized reflectarray antenna. The reflectarray is an array of metallic elements arranged on a surface designed to compensate for the various path lengths of the optical rays from an illuminating feed to the reflecting surface and then to the antenna aperture. With appropriate design, the phase in the aperture can be made to vary linearly in any desired direction and also to produce a radiated beam normal to the constant phase surface. In the case of circular polarization, this path length compensation can be accomplished by rotation of the individual elements.

Huang, John↗

NASA NTRS2009

Wide-Angle-Scanning Reflectarray Antennas Actuated by MEMS

An effort to develop large-aperture, wide-angle-scanning reflectarray antennas for microwave radar and communication systems is underway. In an antenna of this type as envisioned, scanning of the radiated or incident microwave beam would be effected through mechanical rotation of the passive (reflective) patch antenna elements, using microelectromechanical systems (MEMS) stepping rotary actuators typified by piezoelectric micromotors. It is anticipated that the cost, mass, and complexity of such an antenna would be less than, and the reliability greater than, those of an electronically scanned phased-array antenna of comparable beam-scanning capability and angular resolution. In the design and operation of a reflectarray, one seeks to position and orient an array of passive patch elements in a geometric pattern such that, through constructive interference of the reflections from them, they collectively act as an efficient single reflector of radio waves within a desired frequency band. Typically, the patches lie in a common plane and radiation is incident upon them from a feed horn.

Fang, Houfei↗