Domenic Belgiovane

Temperature coefficient of multijunction space solar cells as a function of concentration

Measurements of multijunction space solar cells were taken as a function of temperature for low intensity operation (down to 0.02 suns), and also at high intensities (up to 60 suns). Cells from two vendors were tested. The effect of intensity on the measured temperature coefficient was analyzed. The temperature coefficient of the short circuit current was directly proportional to the intensity, while the temperature coefficient of the open circuit current decreased proportionally to the open circuit voltage. Commercial triple-junction space cells were tested to temperatures as high as 400°C, showing a slight deviation from linear performance but no catastrophic degradation.

77 GHz radar scattering properties of pedestrians

Using radars for detecting and tracking pedestrians has important safety and security applications. Most existing human detection radar systems operate in UHF, X-band, and 24GHz bands. The newly allocated 76-77 GHz frequency band for automobile collision avoidance radar systems has once again raised great interest in pedestrian detection and tracking at these frequencies due to its longer detection range and better location accuracy. The electromagnetic scattering properties must be thoroughly understood and analyzed so a catalog of human scattering can be utilized for intensive automotive radar testing. Measurements of real human subjects at these frequencies is not a trivial task. This paper presents validation between the measured radar cross section (RCS) patterns of various human subjects and a full-wave EM simulation. The RCS of a human is shown to depend on a number of factors, such as posture, body shape, clothing type, etc.

Radar characteristics of pedestrians at 77 GHz

Studying pedestrian radar scattering features will lead to development of more reliable pedestrian collision avoidance radar algorithms. In this paper, the study of backscattering features of 77 GHz radar from a pedestrian in different postures is discussed. Radar scattering patterns were collected from 9 human subjects to investigate possible radar signatures associated with pedestrian at 77 GHz. Measured backscattering changes for the standing and walking postures. Full-wave simulation and measurement are shown to be in agreement. Doppler frequency shift associated with pedestrian motion was also studied at 77 GHz. The time-varying RCS from walking to standing posture is extracted from these measurements.

Engineering the Input Impedance of Electric Planar Metamaterials Analogue of Dipole Array

Since the demand of metamaterial (MM) based devices for practical applications is increased, the method with input impedance of dipole aims to produce fast results with reasonable accuracy for its design proposed. In this work, the unit of MM is equivalent to a dipole and then MM could be treated as a dipole array. An analysis is performed based on classical microwave dipole and numerical simulation by using the finite-difference time-domain for different MM configurations in the form of dipoles array. Additionally, a quality factor (Q-factor) based analysis is shown to yield simulation results which are in good agreement with the experiment. In essence, this shows that we could use antenna theory and numerical method to analyze MM thus opening the doors for a more efficient parameter optimization method.

Surrogate Bicycle Design for Millimeter-Wave Automotive Radar Pre-Collision Testing

This paper discusses the development of a surrogate bicycle target for evaluating the effectiveness of vehicular autonomous emergency braking (AEB)/ pre-collision systems (PCSs) that uses 77-GHz radar systems in detecting bicyclists on the road. The design objective of the surrogate bicycle is to produce similar optical appearance and radar response in a 76–78 GHz band as a real bicycle selected based on its popularity (in 2014) in the United States. In addition, the surrogate bicyclist needs to be able to withstand the impact of the test vehicle traveling at 30 mph (or 48 kph) should it fail to detect the surrogate target. Our design approach differs from the only other surrogate bicyclist developed by a European research group in that our surrogate bicyclist produces similar radar response as a real bicyclist over the entire 360° of azimuth angles. Our design approach began with experimental characterizing the radar cross section (RCS) patterns of real bikes of different types as well as identifying RCS contributions of different parts on a bike via accurate simulations, which were also used for design optimizations. The RCS performance of the fabricated surrogate bicycle was verified via 360° azimuth pattern measurement comparison with a real bicycle. Its physical performance was tested via actual field testing on a test track with two commercial vehicles equipped with AEB and PCS systems.

Radar scattering properties of bicycles at 77 GHz

Collision avoidance systems are becoming a common a standard safety feature in newer or future cars. Some radars operating at 24 GHz have been successfully used in parking, lane changing, and blind spot detection. Newer 76-78 GHz radars are being developed and tested by car makers for their superior range and resolution. However, using cost effective vehicular radars in reliably detecting pedestrian and bicyclist with low false alarm rate still poses challenging due to many possible variations of these targets as well as the presence of other road objects. This paper focuses on studying the radar scattering characteristics of common bikes in stationary in the 76-78 GHz band with a goal of being able to design a more effective bicycle detection radar and detection algorithm.

500–2000-MHz Brightness Temperature Spectra of the Northwestern Greenland Ice Sheet

An ultra-wideband radiometer has been developed to measure subsurface properties of the cryosphere including ice sheets and sea ice. The radiometer measures brightness temperature spectra from 0.5 to 2 GHz using 12 channels, each of which measures scene brightness temperatures over an ~88-MHz bandwidth resolved into 0.24-MHz intervals. The instrument was flown over northwestern Greenland in September 2016 and acquired the first, wideband, low-frequency brightness temperature spectra over the ice sheet and coastal region. The results reveal strong spatial and spectral variations that correlate well with the physical properties of the surface encountered along the flight path, which started over ocean, then passed the rock near the coast, and then up onto the ablation, wet, percolation, and dry snow zones of the interior ice sheet. In particular, strong spectral responses in percolation and dry snow zones are observed and plausibly explained by varying the distribution of horizontal density layers and isolated icy bodies in the upper portion of the firn. The success of the airborne deployment of the instrument and subsequent implementation of algorithms to limit radio frequency interference in unprotected bands is motivating continued airborne investigations as well as stimulating research into the feasibility of a spaceborne instrument.

The Ultra-Wideband Software Defined Microwave Radiometer (UWBRAD) for Ice sheet subsurface temperature sensing: Calibration and campaign results

The Ultra-Wideband Microwave Radiometer is a novel pseudo-correlation radiometer design measuring scene brightness temperatures from 0.5–2 GHz created under NASAs Instrument Incubator Program. This document analyzes the design and operation of the radiometer, the accuracy and stability of the brightness temperatures it produces, and presents initial results from a field campaign conducted in Greenland in September 2016.

Conical log spiral antenna development for the UWBRAD ice sheet internal temperature sensing

The Ultra-wideband Software Defined Radiometer (UWBRAD) for ice sheet internal temperature sensing is designed to provide observations of ice sheet brightness temperatures from 500-2000 MHz. This paper reports antenna design considerations for the UWBRAD radiometer. A prototype 4 channel radiometer and antenna were deployed in Antarctica, and the full 12 channel radiometer has been planned for airborne deployment over Greenland in September 2016. Deployment in Antarctica requires careful material considerations which will function at very low temperatures. Airborne deployment requires the antenna pass aircraft certifications and be able to withstand the drag forces without failure. The conical logarithmic spiral antenna design was selected, fabricated, and tested for the radiometry applications discussed.

The Ultra-wideband Software-Defined Radiometer (UWBRAD) for ice sheet internal temperature sensing: Results from recent observations

The Ultra-wideband Software Defined Radiometer (UWBRAD) for ice sheet internal temperature sensing is designed to provide observations of ice sheet brightness temperatures from 500-2000 MHz. This presentation reports on current status of the instrument development, experimental results obtained to date, and plans for a September 2016 airborne deployment over Greenland.