A theory is presented giving far‐field radiation patterns and surface‐wave behavior for vertically polarized antennas located at zero height over flat ground, with a surface impedance which can be discontinuous along a radius from the antenna. The theory is based on the radiation from the surface electric and magnetic currents as determined by the Sommerfeld attenuation function. Both sky‐wave and surface‐wave solutions are obtained simultaneously, with applications to ground screens, recovery phenomena, Fresnel zones, and similar engineering problems discussed with examples. In general, the results agree with those obtained using the compensation theorem.
DYNAMIC RANGE in receiving and transmitting equipment, as well as modern signal-processing instrumentation, is becoming increasingly important. Schottky-barrier diodes and FET's are recognized as potential high dynamic range devices for frequncy converters or mixers; however, the reasons given for their selection are usually empirical or experimental, rather than carefully derived from device theory. Two types of mixers will be described here and an experimental verification of the dynamic range of the better one, using MOlSFET's, will be described.The standard four-diode bridge (or ring) mixer, shown in Figure 1 is presumed to be driven so that the diodes and in the off state for the next half period. The analysis are in the o n state for cne-half the local oscillator period then becomes very simple1a2. Proper termination of the sum and image frequencies can give very low conversion loss2.cates that the off state nonlinear q-v characteristic of the A careful time-domain analysis of such a mixer indidiodes is responsible for all of the intermodulation observed. (The on state does not contribute until the source and load impedance values become so low that the series loss resistance of the diodes gives intolerable conversion loss.) The same analysis allows the odd part of the nonlinear off-state q-v characteristic to be removed to the bridge terminals as shown in Figure 2.A straightforward analysis gives the two-tone intermodulation dynamic range, expressed as the ratio of two-tone power to intermod power, as where: R, = effective source (and load resistance) R, = series loss resistance of diode wS = signal frequency Pa, = single-tone power available from source and Q3 is determined from the expansion of the off-state q-w relation ___ tics and Space Administration Grant NGR 22-009-163.phone Systems". BSTJ, p. 305-337; April, 1939.
RESEARCH OBJECTIVESInvestigations of nonlinear, time-variant linear, and linear active circuits are aimed at a better understanding of the relations between theoretical models and physical devices. Current research includes:(a) theoretical investigations, design, and experimental behavior of parametric amplifiers and frequency multipliers (b) determination of the invariant properties of active network components under various kinds of embedding (c) studies of transistor and tunnel-diode circuits. It has been demonstrated (1, 2) that extra currents other than the fundamental and nth-harmonic currents must be present in abrupt-junction varactor frequency multipliers (except the doubler, n = 2). These extra currents are called "idler" currents.For the best multiplier efficiency, the impedance of the external network seen by an idler current should be pure imaginary (lossless impedance) and of the proper
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