James A. Nessel

A novel nanoionics-based switch for microwave applications

This paper reports the development and characterization of a novel switching device for use in microwave systems. The device utilizes a switching mechanism based on nanoionics, in which mobile ions within a solid electrolyte undergo an electrochemical process to form and remove a conductive metallic “bridge” to define the change of state. The nanoionics-based switch has demonstrated an insertion loss of ∼0.5dB, isolation of ≫0dB, low voltage operation (1V), low power (∼¼W) and low energy (∼nJ) consumption, and excellent linearity up to 6 GHz. The switch requires fewer bias operations (due to non-volatile nature) and has a simple planar geometry allowing for novel device structures and easy integration into microwave power distribution circuits.

Demonstration of a X-band multilayer Yagi-like microstrip patch antenna with high directivity and large bandwidth

The feasibility of obtaining large bandwidth and high directivity from a multilayer Yagi-like microstrip patch antenna at 10 GHz is investigated. A measured 10-dB bandwidth of ~20% and directivity of ~11 dBi is demonstrated through the implementation of a vertically-stacked structure with three parasitic directors, above the driven patch, and a single reflector underneath the driven patch. Simulated and measured results are compared and show fairly close agreement. This antenna offers the advantages of large bandwidth, high directivity and symmetrical broadside patterns, and could be applicable to satellite as well as terrestrial communications

Frequency estimator performance for a software-based beacon receiver

As propagation terminals have evolved, their design has trended more toward a software-based approach that facilitates convenient adjustment and customization of the receiver algorithms. One potential improvement is the implementation of a frequency estimation algorithm, through which the primary frequency component of the received signal can be estimated with a much greater resolution than with a simple peak search of the FFT spectrum. To select an estimator for usage in a Q/V-band beacon receiver, analysis of six frequency estimators was conducted to characterize their effectiveness as they relate to beacon receiver design.

Predicting Sparse Array Performance From Two-Element Interferometer Data

Widely distributed (sparse) ground-based antenna arrays are being considered for deep space communications applications with the development of the proposed Next Generation Deep Space Network. However, atmospheric-induced phase fluctuations can impose daunting restrictions on the performance of such an array, particularly during transmit and particularly at Ka-band frequencies, which have yet to be successfully resolved. In this paper, an analysis of the uncompensated performance of a sparse antenna array, in terms of its directivity and pattern degradation, is performed utilizing real data. The theoretical derivation for array directivity degradation is validated with interferometric measurements (for a 2-element array) recorded at Goldstone, CA, from May 2007-May 2008. With the validity of the model established, an arbitrary 27-element array geometry is defined at Goldstone, CA, to ascertain its theoretical performance in the presence of phase fluctuations based on the measured data. Therein, a procedure in which array directivity performance can be determined based on site-specific interferometric measurements is established. It is concluded that a combination of compact array geometry and atmospheric compensation is necessary to minimize array loss impact for deep space communications.

Preliminary results from the AFRL-NASA W/V-band terrestrial link experiment in Albuquerque, NM

Atmospheric propagation models and the measurements that train them are critical to the design of efficient and effective space-ground links. As communication systems advance to higher frequencies in search of higher data rates and open spectrum, a lack data at these frequencies necessitates new measurements to properly develop, validate, and refine the models used for link budgeting and system design. In collaboration with the Air Force Research Laboratory (AFRL), NASA Glenn Research Center has deployed the W/V-band Terrestrial Link Experiment (WTLE) in Albuquerque, NM to conduct a measurement campaign at 72 and 84 GHz, among the first atmospheric propagation measurements at these frequencies. WTLE has been operational since October 1, 2015, and the system design shall be herein discussed alongside preliminary results and performance.

W/V-band terrestrial link experiment, an overview

The Air Force Research Laboratory in partnership with NASA Glenn Research Center and the University of New Mexico have initiated the W/V-band Terrestrial Link Experiment (WTLE) to conduct propagation analysis at W/V-band frequencies. An overview is provided of the system and ancillary equipment to facilitate the propagation experiment.

Prototype antenna elements for the next-generation TDRS enhanced multiple-access array

This paper summarizes a study performed to produce prototype antenna elements for the next-generation enhanced Tracking and Data Relay Satellite Continuation (TDRS-C) multiple-access (MA) S-band phased-array antenna. Compared to the multiple-access antenna on the current class of TORS, the enhanced multiple-access antenna requires elements that achieve greater on-axis gain, simultaneous circular polarization capability, and increased beamwidth. To demonstrate that array elements could be realized meeting these requirements, designs that were successful in simulation were fabricated and tested. These included a helical antenna; a novel short backfire antenna, excited with a circular waveguide (cup waveguide) with integrated polarizer and orthomode transducer (OMT); and a corrugated-horn antenna with integrated polarizer and OMVT. The paper describes the design process for the novel elements, and compares measured and simulated results. It also compares the elements in terms of performance, size, and mass.

Performance of the NASA beacon receiver for the Alphasat Aldo Paraboni TDP5 propagation experiment

NASA Glenn Research Center (GRC) and the Politecnico di Milano (POLIMI) have initiated a joint propagation campaign within the framework of the Alphasat propagation experiment to characterize rain attenuation, scintillation, and gaseous absorption effects of the atmosphere in the 40 GHz band. NASA GRC has developed and installed a K/Q-band (20/40 GHz) beacon receiver at the POLIMI campus in Milan, Italy, which receives the 20/40 GHz signals broadcast from the Alphasat Aldo Paraboni Technology Demonstration Payload (TDP) #5 beacon payload. The primary goal of these measurements is to develop a physical model to improve predictions of communications systems performance within the Q-band. Herein, we describe the design and preliminary performance of the NASA propagation terminal, which has been installed and operating in Milan since June 2014. The receiver is based upon a validated Fast Fourier Transform (FFT) I/Q digital design approach utilized in other operational NASA propagation terminals, but has been modified to employ power measurement via a frequency estimation technique and to coherently track and measure the amplitude of the 20/40 GHz beacon signals. The system consists of a 1.2-m K-band and a 0.6-m Q-band Cassegrain reflector employing synchronous open-loop tracking to track the inclined orbit of the Alphasat satellite. An 8 Hz sampling rate is implemented to characterize scintillation effects, with a 1-Hz measurement bandwidth dynamic range of 45 dB. A weather station with an optical disdrometer is also installed to characterize rain drop size distribution for correlation with physical based models.

A microstrip patch-fed short backfire antenna for the tracking and data relay satellite system-continuation (TDRSS-C) multiple access (MA) array

A novel microstrip patch-fed short backfire antenna has been presented here for the first time as a candidate antenna element for the next generation TDRSS-C MA array. This design meets nearly all the specifications required for the enhanced MA array antenna element and promises to provide a lightweight low cost alternative over other designs presently being considered (i.e., corrugated horn, helix, waveguide-fed SBA). Simulations performed using IE3D and MWS agree with measured data, thus far, and indicate an 11% 15-dB bandwidth and a maximum directivity of 15.2 dBi. Future work involves further optimization of the radiation characteristics and the construction of the complete short backfire antenna structure to verify simulated results

Design of a K/Q-band Beacon Receiver for the Alphasat TDP#5 Experiment

This paper describes the design and performance of a coherent K/Q-band (20/40GHz) beacon receiver developed at NASA Glenn Research Center (GRC) that will be installed at the Politecnico di Milano (POLIMI) for use in the Alphasat Technology Demonstration Payload #5 (TDP#5) beacon experiment. The goal of this experiment is to characterize rain fade attenuation at 40GHz to improve the performance of existing statistical rain attenuation models in the Q-band. The ground terminal developed by NASA GRC utilizes an FFT-based frequency estimation receiver capable of characterizing total path attenuation effects due to gaseous absorption, clouds, rain, and scintillation. The receiver system has been characterized in the lab and demonstrates a system dynamic range performance of better than 58dB at 1Hz and better than 48dB at 10Hz rates.