Farr Fields (United States)

Social connections are crucial for today’s middle and high school students. We address this social need through a 3-H Social and Emotional Learning (SEL) Cycle. Through the Three Sisters Garden activity presented here, we teach secondary school students about biodiversity and sustainability as we integrate the arts into STEM (STEAM). Students investigate the growth and development of organisms from a crosscutting lens of systems. Students initiate the sensemaking process by paralleling their own need for companionship to plants. Students end the lesson by initiating a scientific argumentation for a Three (or Four) Brothers/Others Garden. The 3-H learning cycle begins and returns to social and emotional connections, giving equal weight of importance to the heart (social and emotional), hands (problem-solving), and heads (sensemaking). The lesson presented here exemplifies school garden-based learning and students’ ability to initiate sensemaking of the indigenous Three Sisters Garden intercropping method. Analyzing gardens from a systems lens allows students to make emotional and cognitive connections between their own need for social connections and plants increased growth and productivity in a polyculture. When students emotionally, socially, and cognitively participate in the process of science, they begin to see themselves as a part of the scientific process.

We derive here a simple function describing antenna performance in the time domain. This function describes antenna performance in both transmission and reception and in both the time and frequency domains. The resulting equations are as simple as possible. From this function one can simply derive such conventional frequency domain quantities as gain, realized gain, and antenna factor. It is hoped that this function will be adopted as an IEEE standard for time domain antenna performance.

We recently developed the concept of the impulse response of an antenna, in order to more simply characterize antenna performance in the time domain. This time domain waveform is analogous to antenna gain in the frequency domain. Using older methods, to fully characterize antenna performance on boresight in the time domain, one would need waveforms in both transmission and reception, and for various risetimes and/or pulse widths. The impulse response of an antenna is equally useful in the time and frequency domains, is equally useful in transmission and reception, and is simply related to the gain or realized gain of an antenna. Furthermore, the impulse response of an antenna is independent of the source risetime or incident field pulse width.

We study here three topics in Ultra-Wideband Antennas. First, we consider a standard for characterizing antenna performance in the time domain, We develop a single time domain function, called antenna impulse response, which fully describes antenna performance with equations that are as simple as possible in both the frequency and time domains. Next, we survey the available large UWB antennas, primarily consisting of variations of Impulse Radiating Antennas. These consist of a reflector and a wideband feed, and are capable of nearly two decades of bandwidth; or a 100:1 band ratio. Finally, we review the status of time domain UWB antenna ranges, which can be used to characterize both wideband and narrowband antennas in both the time and frequency domains. Such systems also measure the impulse response of an antenna.

A commercially available discone antenna is modified to improve the VSWR at low frequencies. The conical and ground plane elements were replaced with distributed load resistors based on work by T. T. Wu and R. W. P. King. The modifications were done in steps to determine the effect of each change. The overall effect is dramatic reduction and smoothing of the VSWR.

Reflector impulse radiating antennas (IRAs) are designed to have paraboloidal reflectors, and they are constructed so that the electrical feed point of the TEM feed line coincides with the focal point of the paraboloid. In many practical cases, the feed point and focal points are not exactly aligned, producing some defocus. The paraboloidal reflector converts the spherical wave emanating from the feed point into a plane wave (i.e. a spherical wave focused at ∞). Defocus can be approximated by a hyperboloidal reflector that converts the expanding spherical wave into a second expanding wave which appears to emanate from the second focal point of the hyperboloid, which is behind the reflector. Previous theoretical results predicted that the E- and H-plane responses from an in-focus IRA should be symmetric with respect to the temporal center of the response. The results shown here demonstrate that the defocusing causes these responses to become asymmetric. The new results are in better agreement with experimental measurements of IRAs.

A Multifunction IRA is an extension of a standard Impulse Radiating Antenna that has the additional flexibility of an adjustable beamwidth. This adjustability is implemented by defocusing the feed, in order to select between a narrow or broad beam. We provide here the theory of operation of the antenna, for both in-focus and out-of-focus situations. Furthermore, we built and tested a design with a 46 cm diameter. We found good agreement of the experiment with theory.

Recent results are reported that improve the prompt radiated response from reflector and lens impulse radiating antennas (IRAs) by improved control of the aperture fields of the TEM mode distribution. Both reflector and lens IRAs benefit from trimming the aperture to eliminate portions where the vertical component of the electric field is oriented in the wrong direction. Reflector IRAs can further benefit from reorientation of the TEM feed arm angles as well as the relative size of the feed arms to the maximum aperture radius. Significant improvements over 45-degree feed arms can be realized by making 200-Ohm reflector IRAs with feed arms at 30 degrees from the vertical with the circle of symmetry slightly inside the aperture outer boundary and small amounts of aperture trimming.