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A compact S-band auto-tracking antenna feed for 6 m mono-pulse auto-tracking ground station is presented. It is designed to reduce the effect of blockage of the antenna systems and modify the orientation angle of the main reflector to align antenna boresight with a satellite. A circular waveguide is designed to connect to the septum polarizer for communication between the earth and LEO satellite. Based on the circular waveguide as an inner metal, a cylindrical metal is added as an outer metal to form a coaxial line for tracking LEO satellite. The uplink band of the antenna feed is from 2.025 to 2.12 GHz and the downlink band is from 2.2 to 2.3 GHz. The results show that the antenna gain of 6 m reflector is about 39.7 dBic and the 1-dB-beamwidth is 1 degree. The polarization isolation between sum and difference patterns is larger than 30 dB, and the axial ratio is lower than 1.1 dB within ± 0.5 degree range.

TMs paper proposes a novel single-stage three-phase to single-phase current-fed high step-up ac-dc matrix converter for high voltage dc applications. The proposed converter inserts a boost matrix converter, which is formed by three boost inductors and six bidirectional switches, between a three-phase ac source and a Cockcroft-Walton voltage multiplier (CW-VM) circuit. By using this topology associated with power factor correction technique, the proposed converter not only achieves almost unity power factor and sinusoidal input phase currents with low distortion but also obtains high voltage gain at the output end. Moreover, the matrix converter generates an adjustable-frequency and adjustable-amplitude current which injects into the CW-VM to regulate the dc output voltage and smooth its ripple. With this flexible injection current, the performance of the proposed converter is superior to the conventional CW-VM, which is usually energized by a single-phase ac source. Sourced by three-phase ac source, the proposed converter is quite suitable for high-power and high voltage applications. Both operation principle and control strategy of the proposed converter are detailed in this paper. Finally, simulation results demonstrate the performance of the proposed converter and the experimental work will be conducted in the near future.

This paper proposes a transformerless single-phase single-stage high step-up ac-dc converter based on symmetrical Cockcroft-Walton voltage multiplier (CW-VM) with only adding two bidirectional switches and two boost inductors. With the help of the boost structure, not only the voltage gain can be higher than that of the conventional symmetrical CW-VM but also the power factor correction (PFC) methods for conventional boost ac-dc converter can apply to the proposed topology to achieve high quality of line conditions and regulated dc output. In this paper, a commercial average-current controller (ICE1PCS01) based on quasi-steady-state approach by using one cycle control technique is used to implement the PFC function. By this way, the multiplier and line-voltage sensor are unnecessary as compared with the multiplier approach; it simplifies the controller design and reduces the circuit components and cost. A 250W laboratory prototype is built for testing, and experimental results demonstrate the validity of the proposed converter.

This paper proposes a soft-switching technique applying to a single-stage single-phase ac to high voltage dc converter based on Cockcroft-Walton (CW) voltage multiplier circuit. Originally operating under hard-switching, the proposed converter improves switching characteristics by adding an auxiliary circuit for achieving soft-switching. The circuit operation principle of the proposed converter is presented in this paper. The design consideration for determining the values of circuit components used in the implementation is driven as well. For improving the line condition, power factor correction is applied to the proposed converter. Some conventional PFC control methods can be easily adapted to the proposed converter with few modifications. For convenience, this paper employs a commercial PFC IC to implement the controller for the proposed converter. The PWM signal generated form the PFC IC is modified by a simple digital circuit and then sends to the main and auxiliary switches in the power stage. A 500W/1200V prototype is built for test, measurement and evaluation. Finally, the experimental results demonstrate the validity of the proposed converter.

Asynchronous motor is a multi-variables, nonlinear, strong coupling and time-varying system, in order to eliminate the coupling impact of the stator current, design the current decoupling controller to achieve the stator current torque component and the excitation component nonlinear decoupling by non-linear compensation method, it make PI controller parameters setting simplified. According to this method, design the parameters of the current PI regulator and the speed PI regulator, Experiments proved this controller has good dynamic performance.

This paper proposes a high step-up dc-dc converter based on Cockcroft-Walton (CW) voltage multiplier without step-up transformer. Providing high step-up rate, the proposed converter is quite suitable for applying to low-input level dc generation systems. The proposed converter improves the impractical operation of the conventional boost dc-dc converter at high duty ratio due to non-ideal characteristics of the circuit components, such as the equivalent series resistance of the inductor. For easy design, a commercial average-current-control continuous conduction mode (CCM) integrated circuit (ICE1PCS01) and a complex programmable logic device (CPLD) LC4256V are used to implement the control strategy of the proposed converter. A modified switching function, which is built in CPLD, controls the switches to generate an alternating source to the CW voltage multiplier. Under CCM operation, the output voltage ripple of the proposed converter can be limited by the flexibly adjustable frequency. A 200W laboratory prototype is built for test and the experimental results demonstrate the validity of the proposed converter.

In this paper, a new compensation strategy for receiving clean power is proposed with a conventional 18-pulse AC/DC rectifier scheme. In the proposed strategy, the compensation currents are injected at the dc side in front of the inter-phase transformer. The injected currents generated by a three-phase current-controlled inverter effectively improve the total harmonic distortion (THD) of the ac main currents. Compared to the conventional active filters set at the ac side, the three-phase inverter used in the proposed method operates with a rather low kVA rating. Moreover, the 18-pulse AC/DC rectifier draws nearly sinusoidal currents from the ac source under the operation of the proposed compensation strategy. A digital-signal-processor (DSP, TMS320F2812) based digital controller is employed to calculate the desired compensation currents and deals with the trigger signals needed for the three-phase inverter. Simulation of the proposed system is conducted for evaluation and a 1.5kW laboratory prototype is built for test as well. Both the simulated and the experimental results are presented to show the validity of the proposed compensation strategy.

This paper proposes a new active interphase transformer for 24-pulse diode rectifier. The proposed scheme injects a compensation current into the secondary winding of either of the two first-stage interphase transformers. For only one of the first-stage interphase transformers being active, the inverter conducted the injecting current is with a lower kVA rating [1.26% pu (Po)] compared to conventional active interphase transformers. Moreover, the proposal scheme draws near sinusoidal input currents and the simulated and the experimental total harmonic distortion of overall line currents are only 1.88% and 2.27% respectively. When the inverter malfunctions, the input line current still can keep in the conventional 24-pulse situation. A digital-signal-processor (DSP) based digital controller is employed to calculate the desired compensation current and deals with the trigger signals needed for the inverter. Moreover, a 6kW prototype is built for test. Both simulation and experimental results demonstrate the validity of the proposed scheme.

This paper proposes a novel single-phase ac to high voltage dc converter based on Cockcroft-Walton cascade rectifier with only adding one bi-directional switch and one boost inductor. This paper also derives a new method of circuit representation for Cockcroft-Walton cascade rectifier, which simplifies the equivalent circuit and is convenient for simulation. Compared with conventional Cockcroft-Walton rectifier, the proposed converter provides half-wave symmetric and low-distorted line current, adjustable power factor at the ac source, and regulated dc output voltage. Unit power factor is achieved by the average-current method and the dc output voltage is regulated by a PI compensator. Moreover, this paper employs a digital signal processor to implement a digital controller for operating the proposed converter and a prototype with 500w rating is implemented for test. Both simulation and experimental results demonstrate the validity of the proposed converter.

Postural instability is an important measure of Parkinson's disease conditions. Because of the fluctuation of clinical symptoms and large inter-rater and intra-rater variation, traditional method of analyzing postural instability using its onset time measure can result in controversial conclusion of treatment benefit. We propose a Brownian motion based latent structure model to study treatment's effect on postural instability The new method not only incorporates patient's multiple onset times, but also the special covariate structure of postural instability process. The proposed model does not require even-spaced visiting schedules, and the correlation of the binary process is naturally built through the underlying latent Brownian motion process. Theoretical and computational properties of the proposed model are examined. A dataset from a double-blinded multicenter Parkinson's disease clinical trial is used to demonstrate the methodology.