This paper presents a theoretical and experimental analysis of the capabilities of the dual-input Doherty power amplifier (DPA) architecture to mitigate efficiency and output power degradations when used in a mismatched load environment. Following a simplified linear piecewise approach, an analytical demonstration is proposed to derive optimal radio frequency drives applied to the Auxiliary path of the DPA to restore power performances while avoiding large signal voltage clipping of active cells. The proposed analytical study is corroborated with harmonic balance simulated results of a C-band, 20-W GaN DPA prototype. The fabricated dual-input DPA prototype has been measured under 1.5-VSWR mismatch configurations to validate the proposed analysis.

The design of agile active antennas requires an efficient modeling methodology in order to quantify the impact of other components on the array radiation pattern, and especially the influence of power amplifiers (PA). Therefore, the performance prediction of PA on TX chains is of prime importance. This article describes two different approaches for active antenna applications. The first one concentrates on PA macro-modeling, which takes into account a large output load impedance mismatch with a voltage standing wave ratio up to 4:1. A PA behavioral model based on nonlinear scattering functions was developed and extracted from CW measurements. The model validity was checked by comparison with the measured data. The second one describes a novel technique for synthesizing a given radiation pattern, whereas taking into account the mutual coupling and calculated matching impedances (ZL ≠ 50 Ω) of each antenna in the array according to frequency and pointing angle.

We have studied the interaction of soft X-ray thermal radiation with foam-layered metal targets. The X-radiation was produced by focusing a high energy laser inside a small size hohlraum. An increment in shock pressure was observed with the foam layer as compared to bare metal targets.