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A steady-state 3-D large-signal model of the beam–wave interaction (BWI) in folded-waveguide (FW) traveling-wave tubes (TWTs) has been developed. The model used a three-port network representation of the circuit and a set of discrete rays representation of the 3-D electron beam. Values of the impedance elements that characterize the model are determined by a 3-D finite-element code, high-frequency circuit simulator (HFCS). Besides, the RF fields inside the beam tunnel are represented with the digitized field profile obtained from HFCS. A new circuit attenuation model is described by introducing only one parameter. The model has been implemented in the BWISFW-3-D code. The results of the code predictions agree well with the measured data for an FW-TWT operating in the $W$ -band. The effect of uniform focusing magnetic field on BWI is also studied. [ABSTRACT FROM AUTHOR]

In this paper, a new Doherty amplifier architecture along with an analytical based design methodology is proposed. The proposed architecture uses novel three-port network as the output matching/combining network (OMCN). The three-port OMCN performs the power combining for any arbitrary output power ratios from the two transistors of the Doherty amplifier. It also performs the impedance matching from any arbitrary complex load impedance to the optimum impedances for both transistors at peak output power. Commonly in Doherty amplifiers, an optimum performance at peak power and a sub-optimum performance at power back-off are often obtained. Using the proposed output network, optimum performance can be reached at power back-off, as well as at peak power. Another three-port network is proposed for input matching/dividing network (IMDN) at the input of the proposed Doherty amplifier. The three-port IMDN is designed to perform the power division with any arbitrary division ratio, adjust the arbitrary phase difference between the input signals to the two transistors, and provide the impedance matching from any arbitrary complex source impedance to the optimal source impedances for the two transistors. To verify the provided theory, two prototype amplifiers are designed and tested. A 12-W amplifier is designed for a 50-\Omega source and load impedances at 1 GHz. Another 12-W amplifier is designed at 1 GHz for complex source and load impedances. Both amplifiers have efficiency of higher than 50% at 7-dB output power range. [ABSTRACT FROM PUBLISHER]