Antenna patterns with ultra-low sidelobes have been obtained for an experimental receiving array designed with timemodulated slot radiators. The technique utilizes on-off RF switches which are programmed in a predetermined sequence to produce the desired pattern.The results of tests on an experimental eight-element slot array designed for sidelobe reduction are presented. Two examples are considered: 1) an initial static pattern with 30-db sidelobes which are reduced to about 40 db by sequential switching and 2) an initial static pattern with 13-db sidelobes which are reduced directly to about 44 db by a m e r e n t sequence of switching. Measured patterns illustrating the sidelobe reduction are included.The applicability of the sidelobe reduction technique to large electronically steerable phased arrays is considered briefly and it is concluded that it is compatible with such systems.
This paper studies the scattering of a plane wave by an active corrugated structure in which each slot region is connected to a microwave solid-state amplifier. Consequently, not only are we able to control the phase of the reflected wave but also its power gain. An exact solution to this problem has been obtained by the residue calculus method under the assumption that only the TEM wave propagates and is amplified in the slot region. Numerical results are presented for illustrating the scattering properties as a function of the slot dimension and the amplifier gain. An approximate but much simplified analytical expression for the reflection coefficient is derived and it should be found useful in other scattering problems (such as the design of a reflector antenna) by the ray-tracing method. A related problem of surface wave propagation on the active corrugated structure and its potential application as a high-power amplifier are also discussed.
The relative contributions of leaky, surface, and space waves are studied for an open-ended dielectric-loaded waveguide structure using Wiener-Hopf technique with the key step in factorizing the kernel being carried out numerically. The relative field contributions are evaluated by both ordinary saddle-point and modified saddle-point integration methods, and the. accuracy of each method in different spatial regions is examined.
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