Small satellites provide low cost access to space and they have historically been used for flight technology demonstrations and limited function space science activities. Novel antenna technologies have enabled high performance smallsat telecom, science in earth orbit, and the first Cubesat mission to Deep Space. Over the past 5 years, technologists at the Jet Propulsion Laboratory have designed, tested and successfully flown these innovative and enabling Smallsat antennas. This paper describes these innovations and their impact on smallsat performance for recent and future NASA missions.

Abstract-Thiswork presents a comprehensive characterization of the frequency dependence of the effective complex permittivity of bundled carbon nanotubes considering different densities over a broadband of frequencies from 10 MHz to 50 GHz using only one measurement setup. The extraction technique is based on rigorous modeling of coaxial and circular discontinuities using mode matching technique in conjunction with inverse optimization method to map the simulated scattering parameters to those measured by vector network analyzer. The dramatic values of complex permittivity obtained at low frequencies are physically explained by the percolation theory. The effective permittivity of a mixture of nano-particles of alumina and carbon nanotubes versus frequency and packing density is studied to verify the previously obtained phenomenon.

This paper presents a submillimeter-wave 500–550-GHz MEMS-reconfigurable phase shifter, which is based on loading a micromachined rectangular waveguide with 9 E-plane stubs. The phase shifter uses MEMS-reconfigurable surfaces to individually block/unblock the E-plane stubs from the micromachined waveguide. Each MEMS-reconfigurable surface is designed so that in the nonblocking state, it allows the electromagnetic wave to pass freely through it into the stub, while in the blocking state, it serves as the roof of the main waveguide and blocks the wave propagation into the stub. The phase-shifter design comprises three micromachined chips that are mounted in the H-plane cuts of the rectangular waveguide. Experimental results of the first device prototypes show that the microelectromechanical system (MEMS)-reconfigurable phase shifter has a linear phase shift of 20° in ten discrete steps (3.3 bits). The measured insertion loss is better than 3 dB, of which only 0.5–1.5 dB is attributed to the MEMS surfaces and switched stubs, and the measured return loss is better than 15 dB in the design frequency band of 500–550 GHz. It is also shown that the major part of the insertion loss is attributed to misalignment and assembly uncertainties of the micromachined chips and the waveguide flanges, shown by simulations and reproducibility measurements. The MEMS-reconfigurable phase shifter is also operated in an analog tuning mode for high phase resolution. Furthermore, a detailed study has been carried out identifying the reason for the discrepancy between the simulated (90°) and the measured (20°) phase shift. Comb-drive actuators with spring constant variations between 2.13 and 8.71 N/m are used in the phase shifter design. An actuation voltage of 21.94 V with a reproducibility better than σ=0.0503 V is measured for the actuator design with a spring constant of 2.13 N/m. Reliability measurement on this actuator was performed in an uncontrolled laboratory environment and showed no deterioration in the functioning of the actuator observed over one hundred million cycles.

QC 20170201

No abstract

-Electrical properties of nano-composite materials are extracted to investigate the possibility to engineer novel material for microwave applications. A measurement setup is developed to characterize material in a powder form. The developed measurement technique is applied on nano-particles of alumina, carbon nanotubes (CNTs), and composite mixture of carbon nanotubes and alumina. The effect of packing density on dielectric constant and loss tangent is thoroughly characterized experimentally. The obtained results show that the real part of effective permittivity may be considerably enhanced by increasing the percentage of conducting nano-particles. In addition, it is possible to decrease the loss in a material by mixing low-loss dielectric nano-particles powder in a lossy material.