Ming Hui

Behavior modeling for multi-carrier multi-mode power amplifiers using real-valued time-delay RBF networks

This paper proposes a real-valued time-delay radial basis function (RVTDRBF) networks suitable for dynamic modeling of the baseband nonlinear behaviors of the multi-carrier multi-mode power amplifiers (MMPA). Parameters (weights and centers) of the proposed model are identified using the orthogonal least square (OLS) algorithm. In order to verify the model ability for modeling the nonlinearity of MMPA, a 110-W LDMOS class-AB PA and three different test signals are used. The three different test signals are three-carrier CDMA2000, one-carrier WCDMA and twelve-carrier CDMA2000, respectively. The accuray of the proposed model is investigated with the normalized mean square error (NMSE), the amplitude and the output spectrum. The validation results demonstrate the accuracy of the RVTDRBF model.

Electronically Tunable Impedance-Matching Networks for Intelligent RF Power Amplifiers in Cognitive Radio Systems

This paper presents the simulation and optimization design of the electronically tunable impedance matching networks for intelligent RF power amplifiers in a cognitive radio system. Reconfigurable elements, such as varactors and RF switches are utilized to achieve the dynamic impedance matching both in the input and output matching circuit, providing coarse and fine tuning of the target impedances with low loss and excellent impedance coverage from 500MHz to 800MHz. The topology of varactor model is illustrated to ensure the precision of simulation. In addition, high-precision bias voltage controlling system is designed to improve the nonlinear problem caused by the varactor. The simulation results demonstrate the excellent performance of the tunable networks, satisfying the requirement of the cognitive radio systems.

Pre-compensation for RF Optical Transceiver Using Memory Polynomial Pre-distorters

In this paper, a memory polynomial nonlinear model-based predistorter is utilized to linerize a ROF system which is comprised of RF optical transceiver. The nonlinear model of the system is described as AM-AM character and AM-PM character. In addition, the compensation results of nonlinear distortions with memory effects have demonstrated that the memory polynomial nonlinear model-based predistorter exhibits good performance in suppressing the spectrum re-growth caused by the memory effects of the ROF system which is comprised of RF optical transceiver.

Nonlinear characteristics for simultaneous transmission of multiband and multimode RF signals in radio-Over-fiber systems

In this paper, we have proposed a multiband multimode ROF system which is experimentally demonstrated with the simultaneous generation and transmission of the CDMA (f0=830MHz), WCDMA (f0=1950mHz) and WIMAX (f0=2400MHz) signals. The dependence of the static nonlinear properties of the system on the applied signals has been discussed to illustrate the necessity for extracting the static nonlinear properties in real time when the real modulated signals are applied. The dynamic exponential weighted moving average method is used to extract the static nonlinear properties of the multiband multimode ROF system which consist of the AM/AM and AM/PM characteristics. The spectrum of the input signal is compared with the spectrum of the output signal to illustrate the nonlinear distortion in frequency domain.