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This paper presents a new design methodology for broadband Doherty architecture using the three-port input and output networks technique. The proposed topology was developed to overcome the Doherty power amplifier (DPA) bandwidth limitations. The output three-port network performs the impedance matching from any load impedance to the optimum loads for both main and peaking transistors and also combines the power delivered from the two devices at any power ratio. On the other hand, the input-splitting network is proposed for matching the input impedances of the two transistors to the source impedance. The freedom in choosing the power division ratio of the input network enables us to achieve a tradeoff between efficiency and linearity. Also, it provides a way to accomplish the phase compensation using an arbitrary phase difference between the two branches of the Doherty power amplifier and thus, helps obviate the need of the highly bandwidth limiting offset lines found in the Doherty design. A two-stage broadband Doherty power amplifier is implemented using 0.25-um GaN HEMT MMIC process to validate the proposed topology. The fabricated DPA was measured under both continuous wave (CW) and modulated signal at different operating frequencies. Across 3.3-3.7 GHz, the implemented DPA delivers a maximum output power exceeding 42 dBm, power added efficiency (PAE) over 52 % at the peak power and over 38 % in the back-off state over the operating 400 MHz bandwidth. The fully integrated circuit has a chip-size of 4.4 mm × 3.5 mm.

This paper presents a novel wideband filtering power divider. Instead of the T-junction in the traditional power divider design, a three coupled-line structure is utilized to provide the equal power division to every outputs. Together with the quarter-wavelength coupled line in each way, a wideband filtering response can be obtained. In order to enhance the frequency selectivity, a pair of half-wavelength open stubs are loaded between the three-line coupled structure and parallel coupled lines to produce a pair of transmission zeros on both sides of the passband. To enhance the upper stopband rejection, two additional open stubs are installed at output ports. A new three-port equivalent network for the three-line coupled structure is proposed, and the circuit model for the filtering power divider can be developed for illustrating the working mechanism and the design process. Furthermore, the generalized Chebyshev function is applied to synthesize and analyze the whole structure systematically. For demonstration, a prototype of the wideband filtering power divider operating at 3 GHz is designed and fabricated. The measured results show a 16-dB bandwidth of 62%, an isolation better than 16.5 dB, and a 29-dB wide stopband from 4.39 to 7.73 GHz (1.1f0).

A novel technique for characterizing reciprocal three-port networks is proposed. The approach is an extension of the conventional unterminating method for characterizing two-port networks: on the one hand, the latter extracts the parameters of a (reciprocal) two-port network from one-port measurements, and on the other hand, the presented generalization extracts the parameters of a (reciprocal) three-port network from two-port measurements. The technique is believed of interest particularly for those which occasionally need to perform three-port vector-corrected measurements of three-port test-bench components such as baluns and directional couplers but do not have access to multiport equipment and software. [ABSTRACT FROM AUTHOR]

A geometrical test for the unconditional stability of three-port networks is presented. The derivation is presented in full detail, starting from the concept of input mapping region as an indicator of unconditional stability. A novel set of (equivalent) parameters is then defined, which can serve to rapidly check the unconditional stability of a three-port network under test. Although the derivation is rather lengthy, the final part of the contribution shows that the practical application of the test is actually straightforward. [ABSTRACT FROM AUTHOR]

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]

Trilateral haptic systems can be modeled as three-port networks. Analysis of coupled stability of a three-port network can be accomplished in either the passivity or the absolute stability frameworks assuming all three ports are connected to passive but otherwise unknown terminations. This paper first introduces our recent results in terms of extending Raisbecks passivity criterion and Llewellyns absolute stability criterion to general three-port networks - both criteria are founded on the properties of a positive-real Hermitian matrix. Next, we show that the absolute stability criterion is less conservative than the passivity criterion. Then, to show how the two criteria may be utilized at the system design stage, we apply them to the problem of designing controllers for a dual-user haptic teleoperation system and a triple-user collaborative haptic virtual environment. Using the two criteria, controllers are then designed and compared in terms of conservatism in simulations and experiments. [ABSTRACT FROM AUTHOR]

A medium-voltage (MV) wind turbine generator (WTG)-battery energy storage (BESS) grid interface converter topology with medium-frequency (MF) transformer isolation is introduced in this paper. The system forms a three-port network in which several series stacked ac-ac converters transform the low-frequency (50/60 Hz) utility MV into MF (0.4 to 2 kHz) ac voltage by modulating it with MF square wave. This voltage is then fed to the MF transformer primary windings. The secondary and tertiary windings interface with the WTG side and the BESS side, respectively, after power conversion. The power generated by WTG is transferred to the MF transformer secondary windings through a three-phase pulse width modulation (PWM) rectifier and a three-phase PWM inverter, whereas the power transfer between the BESS and the tertiary winding occurs through a three-phase PWM inverter. It is shown that the utility grid sinusoidal currents, the battery current, and the WTG output currents can be controlled to be of good quality using PI and DQ control strategies. Thus, the proposed MF transformer-based three-port topology results in smaller converter weight/volume. Moreover, the control can handle voltage sags/swells and provide low voltage ride-through capability. Simulation waveforms along with experimental results are shown as proof of concept. [ABSTRACT FROM AUTHOR]

Trilateral haptic systems can be modeled as three-port networks. We present a criterion for absolute stability of a general class of three-port networks. Traditionally, existing (i.e., Llewellyn’s) criteria have facilitated the stability analysis of bilateral haptic systems modeled as two-port networks. If the same criteria were to be used for stability analysis of a three-port network, its third port termination would need to be assumed known for it to reduce to a two-port network. This is restrictive because, for absolute stability, all three terminations of the three-port network must be allowed to be arbitrary (while passive). Extending Llewellyn’s criterion, we present closed-form necessary and sufficient conditions for absolute stability of a general class of three-port networks. We first find a symmetrization condition under which a general asymmetric impedance (or admittance) matrix Z3\times 3 has a symmetric equivalent Zeq from a network stability perspective. Then, via the equivalence of passivity and absolute stability for reciprocal networks, an absolute stability condition for the original nonreciprocal network is derived. To demonstrate the convenience and utility of using this criterion for both analysis and design, it is applied to the problem of designing stabilizing controllers for dual-user haptic teleoperation systems, with simulations and experiments validating the criterion. [ABSTRACT FROM PUBLISHER]