An electronic scanning antenna (ESA) that uses a beamformer for scanning the beam has the advantage of being able to form multiple beams for multimode, sharedaperture applications. This scanning approach is achieved at a reduced parts count for the antenna subassembly and therefore at a lower cost than approaches utilizing phaseshifting elements for controlling the beam. This paper discusses our efforts to realize such a beamformer using Rotman lens geometry and details some of the technologies we investigated as well as some engineering tradeoffs encountered.
The energy distribution for field-current electrons from tungsten has been obtained. The distribution was obtained experimentally by the method of retarding potentials. It was possible to apply this method even at the high potentials necessary for field-current emission, since in this experiment the accelerating potential which liberated the electrons also served to decelerate them. This distribution exhibits three major features: (1) Only a minute portion of the electrons reach a copper collector unless the potential of the collector is positive by at least 4.5 volts with respect to the emitter; (2) the greatest number of electrons have energies very close to the maximum energy obtained; (3) the range of energies is at least 10 volts.
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