Enhancing efficiency of single, large-aperture antennas

Numerical analysis method provides means of describing energy distribution in focal plane of parabolic surface in terms of phase and wavelength. Two approaches for enhancing antenna efficiency include single, large reflector focused to feeding element, and array of smaller apertures whose individual outputs are summed

Highly efficient impulse-radio ultra-wideband cavity-backed slot antenna in stacked air-filled substrate integrated waveguide technology

An impulse-radio ultra-wideband (IR-UWB) cavity-backed slot antenna covering the [5.9803; 6.9989] GHz frequency band of the IEEE 802.15.4a-2011 standard is designed and implemented in an air-filled substrate integrated waveguide (AFSIW) technology for localization applications with an accuracy of at least 3 cm. By relying on both frequency and time-domain optimization, the antenna achieves excellent IR-UWB characteristics. In free-space conditions, an impedance bandwidth of 1.92 GHz (or 29.4%), a total efficiency higher than 89%, a front-to-back ratio of at least 12.1 dB, and a gain higher than 6.3 dBi are measured in the frequency domain. Furthermore, a system fidelity factor larger than 98% and a relative group delay smaller than 100 ps are measured in the time domain within the 3 dB beamwidth of the antenna. As a result, the measured time-of-arrival of a transmitted Gaussian pulse, for different angles of arrival, exhibits variations smaller than 100 ps, corresponding to a maximum distance estimation error of 3 cm. Additionally, the antenna is validated in a real-life worst-case deployment scenario, showing that its characteristics remain stable in a large variety of deployment scenarios. Finally, the difference in frequency-and time-domain performance is studied between the antenna implemented in AFSIW and in dielectric filled substrate integrated waveguide (DFSIW) technology. We conclude that DFSIW technology is less suitable for the envisaged precision IR-UWB localization application

New Applications of Radio Frequency Identification Stations for Monitoring Fish Passage through Headwater Road Crossings and Natural Reaches

Within the Ouachita National Forest, roads and streams intersect each other thousands of times. Many of these road crossings alter stream hydrology and potentially limit longitudinal fish movement. To investigate the potential impacts of these road crossings on fish passage, we monitored movements of 3 native fish species (n = 2,171) individually tagged with radio frequency identification (RFID) tags in 2012 and 2013. We installed solar-powered RFID stations in 2 streams with road crossings and 2 reference streams without road crossings. Each of the 4 monitoring stations included a pair of antennas bracketing a road crossing (or similarly-sized natural reach) to continuously detect upstream or downstream passage. To monitor natural reference streams, we avoided full-duplex RFID technology, which would have required rigid in-stream structures. Alternatively, we utilized new applications of RFID technology such as direct in-stream installation of half-duplex wire antennas and figure-eight crossover antenna designs. These techniques appear promising, but technical difficulties limited the consistency of fish passage detection and consequently limited the strength of ecological conclusions. Even so, we report evidence that fish passed at significantly higher rates across reference reaches than reaches with road crossings. Furthermore, Creek Chub (Semotilus atromaculatus) passed reference reaches at significantly higher rates than Highland Stonerollers (Campostoma spadiceum), which passed at higher rates than Longear Sunfish (Lepomis megalotis). Stream intermittency appeared to exacerbate reduced passage rates associated with the road crossings

DSS-13 26-meter antenna upgraded radiometer system

The Deep Space Station (DSS)-13 26-m antenna radiometer system was upgraded with an IBM-compatible computer-controlled configuration with improved supporting hardware and software. Software was generated to analyze results and correct for antenna mispointing, tropospheric loss, and other observing errors. This total power radiometer configuration provides a prototype for the new DSS-13 34-m antenna. The radiometer system is described in terms of the theory, instrumentation hardware, computer configuration, and operational features and performance. The system is used to obtain antenna efficiency and pointing model data and is useful for radio source calibrations required for radio astronomy. Some recent results are given

DSS-13 beam-waveguide antenna performance in the bypass mode

A new 34-meter beam-waveguide (BWG) antenna that contains two microwave paths, a centerline feed system, and a bypass feed system, was built at the Deep Space Station 13 (DDS 13) at Goldstone, California. Previous articles have described the test results from the evaluation of the centerline BWG feed system in the receive mode as well as the test package hardware used to perform these tests. The test results from the evaluation of the bypass BWG feed system on the DSS-13 antenna in the receive mode, including the operating noise-temperature and the antenna-area-efficiency measurements, are presented

Double-layer Perfect Metamaterial Absorber and Its Application for RCS Reduction of Antenna

To reduce the radar cross section (RCS) of a circularly polarized (CP) tilted beam antenna, a double-layer perfect metamaterial absorber (DLPMA) in the microwave frequency is proposed. The DLPMA exhibits a wider band by reducing the distance between the three absorption peaks. Absorbing characteristics are analyzed and the experimental results demonstrate that the proposed absorber works well from 5.95 GHz to 6.86 GHz (relative bandwidth 14.1%) with the thickness of 0.5 mm. Then, the main part of perfect electric conductor ground plane of the CP tilted beam antenna is covered by the DLPMA. Simu¬lated and experimental results reveal that the novel antenna performs well from 5.5 GHz to 7 GHz, and its monostatic RCS is reduced significantly from 5.8 GHz to 7 GHz. The agreement between measured and simulated data validates the present design