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This study describes the Ku -band 70- and 30-W-class internally matched gallium nitride (GaN) power amplifiers (PAs) for multi-carrier satellite communications (SatComs). The GaN PAs maintain low third-order intermodulation distortion (IMD3) over a wide offset frequency range of up to 400 MHz, whereas in the Ku -band, one PA can deliver a high peak output power of approximately 70 W and the other PA, a peak output power of higher than 30 W. To realize a wide offset frequency operation, our proposed output-matching circuit includes three different types of difference-frequency short circuits, two of which are embedded into a tournament-shaped output-matching circuit inside the PA package and the rest is embedded into the drain bias feed placed outside the package. To verify the short-circuit design and its effectiveness, two different power classes (70 and 30 W), Ku -band GaN PAs, were designed and fabricated, and then, their output transfer characteristics focusing on IMD3 were measured. The measurements show that the 70-W-class GaN PA achieves a peak output power of 48.6 dBm while maintaining a linear output power of over 40 dBm and an IMD3 of less than −26 dBc over wide offset frequencies ranging from 1 to 400 MHz. The 30-W-class GaN PA maintains a linear output power of over 36.3 dBm and an IMD3 of less than −27 dBc over wide offset frequencies of up to approximately 600 MHz. To the best of the authors’ knowledge, these PAs have a record output power level over a wide frequency range of 1–400 MHz or higher under the condition of a low IMD3 of less than −25 dBc, compared to previously reported Ku -band GaN PAs used for multi-carrier SatComs.

Effects of wetting on wireless power transmission by an open-ring resonator coupling (ECOR) were investigated. Using sheets of paper wetted with deionized, tap, and sea waters as intervening materials, s-parameters were measured between two open-ring resonators on separated printed boards designed for 2.45GHz power transmission. The peak s21 degraded and the bandwidth shrank as the number of wet paper sheets increased. The results are compared with electromagnetic simulation using the complex dielectric constants and the conductivity of the waters.

Reduction of ON resistance and OFF capacitance of GaN microwave rectifying diode is realized by applying T-shaped anode wiring together with increase of donor concentration in the active layer. The time constant defined by the product of ON resistance and OFF capacitance is reduced from 2.72ps to 0.79ps while the breakdown voltage decreased from 108V to 50V.

Comparing circuit simulation results, an analytical model for the efficiency of single shunt rectenna circuits is developed. The model estimates the DC output power and loss power in rectenna circuits and gives good agreements with circuit simulation results. With this model, the effect of signal frequency and the diode capacitance is clarified.

Open-ring resonator coupling is used for the wireless power transmission through 1.6mm thick epoxy-glass plate. Microwave signal is emitted from one circuit board where an open-ring resonator is placed and the signal is received by another board with also an open-ring resonator and GaN Schottky barrier diode. At 2.3 GHz, RF to DC conversion efficiency of 37.1 % is obtained at the input power of 3.01 W and the output voltage of 8.75 V.