This paper presents an ultra‐wideband, high‐efficiency continuous resistive‐reactive class‐J power amplifier. The design space is extended by controlling the second harmonic with impedance component and multiple harmonics of a continuous class‐J PA, enabling it to achieve efficient output in multiple octave bandwidths. Based on this theory, a GaN HEMT transistor CGH40010F is used to achieve a 0.6 to 3.2 GHz, average efficiency of 65%, ultra‐wideband PA with output power greater than 40 dBm. The simulation results are consistence with the measurement results and respond to the expectations.

In this article, a novel electro-mechanical energy conversion model of power harvesting from the vibration-induced the piezoelectric stator of the traveling wave rotary ultrasonic motor was proposed. Based on the curvature basis approach, the relationship between the deduced voltage and the mechanical stain induced by piezoelectric polarization was formulated. In addition to the relationships between the maximum induced voltages at the resonance frequency, the conversion energy density and the dimensions of the piezoelectric stator were also derived. The analytical model shows that the vibration-induced voltage is proportional to the exciting electrical voltage magnitude and square of height of the piezoelectric ceramic (PZT) but is inversely proportional to the permittivity of PZT and the damping coefficient of the stator. Some simulations and experimental results demonstrate that the maximum output voltage coincides with the energy conversion analytical model.

This article presents a compact broadband high‐efficiency power amplifier (PA) with a filtering structure. Unlike the cascaded filter behind the traditional PA, the proposed cascaded branch load coupling microstrip line structure is used to design the output matching network (OMN) of the PA. It plays the roles of impedance matching and filtering, which is called a filtering OMN, the overall size of the circuit will be reduced. Two coupled microstrip lines cascaded are used to extend the working bandwidth, and a microstrip line is loaded to the port of the coupled microstrip lines to ensure high selectivity and good out‐of‐band performance. For verification, a broadband high‐efficiency PA is designed and manufactured by using CGH40010F GaN HEMT. Measurements demonstrate that in the range from 1.2 to 3.6 GHz, the saturated output power is from 39.8 to 41.8 dBm, the drain efficiency (DE) with a 62%–73%, and the gain is between 9.9 and 11.7 dB.

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