A Dielectric-loaded Leaky Wave Antenna
The design and the measured performance are described of a flat, leaky-wave antenna in which the inductive, leaky surface is backed with a slab of dielectric. The analysis is based on a transverse resonance analysis which determines the physical dimensions of the antenna for a certain specified aperture distribution. An antenna was built to compare the theoretical behavior with the measured performance. Two ways of forming the dielectric to the antenna were tested. When the dielectric was molded in place the radiation pattern agreed very well with the theoretically predicted pattern, but high losses in the casting resin gave a lower gain for the antenna than anticipated. For a machined piece of dielectric, the radiation pattern was not as close to the predicted pattern as for the molded sample, but the gain was close to the predicted value. The antenna consists of a 28-by-18-inch through filled with a dielectric material over which a sheet of parallel wires is strung. At the design frequency, 4.75 gc, the antenna radiates a pencil beam 9.4 by 8.3 degrees wide at an angle of 54 degrees measured from the normal to the inductive surface. The beam can be scanned from approximately 75 degrees down to 12 degrees from the normal to the aperture by changing the frequency from 5.25 gc to 4.20 gc. (Author).
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Calculated and Measured Performance of LeakyWave Antenna
Comparison of Measured Patterns for the Antennas with Molded
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8.3 degrees aluminum cone ANTENNAS WITH MOLDED attenuation constant BEAM POSITION beamwidth calculated Cd/a coaxial line conical antenna CONICAL LEAKY-WAVE ANTENNA conical surface contour coth cut-off frequency describes the design DESIGN DATA design frequency dielectric casting resin dielectric constant dielectric loaded dielectric material DIELECTRIC MEDIA dielectric-filled waveguide dielectric-loaded leaky-wave antenna digital computer dissipation factor E-plane feed horn flat antenna frequency range gain factor grid spacing inches input inside the waveguide interface kd/kd launcher leaky surface machined to fit MEASURED PATTERNS MOLDED DIELECTRIC MODEL normal nulls filled outer conductor parallel wires phase constant phase distribution phase variations phase velocity plane plotted in Fig Polystyrene predicted pattern predicted value present antenna propagation radiated beam radiation pattern rectangular waveguide refractive index scan angle second model shown in Fig side-lobes SKETCH Stanford Research Institute Table III DESIGN TE10 mode transmission line transverse resonance equation trough wavelength width wire diameter zero