Jiahui Fu

Modeling and design of the novel MEMS phase shifter for Ka band applications

The paper presents a model which describes the stage circuit of a distributed MEMS transmission line (DMTL) phase shifter at Ka band and an approach for DMTL design utilizing the saw-shaped coplanar waveguide (SCPW). The results of circuit simulation and full wave analysis prove that the model is in good agreement with theoretical analysis. The model can effectively simplify the design complexity after optimization. Simulation results show that S/sub 11/ and S/sub 21/ can achieve -20 dB and -2.5 dB, respectively, at Ka band. Comparing with literature data, it has been predicted that S/sub 11/ improves about 8 dB.

An efficient modeling technique for RF MEMS phase shifter based on RBF neural network

A modeling technique based on RBF neural network is presented for the design of RF MEMS phase shifter. Three sensitive parameters are selected according to complicated three-dimensional structure design of an RF MEMS phase shifter and used as inputs of neural network. Experiments show that the proposed approach in this paper is a high efficiency modeling for the RF characteristics analysis for RF MEMS phase shifter. The training of the RBF neural network is accomplished within 30 minutes using 27*51 samples. The trained RBF neural network is able to predict the outputs for 51 test samples within 1 minute. Comparison between RBF neural network predictions and HFSS simulations show that the root mean square relatively errors, mean absolute relatively errors and maximize absolute relatively errors are less than 0.0368, 0.0417 and 0.0442 respectively.

An Improved Design for Ka-Band Phase Shifter Using Distributed MEMS Transmission Line Structure

The paper presents a model which describes the stage circuit of Distributed MEMS Transmission Line (DMTL) phase shifter at Ka band and an approach for DMTL design utilizing the saw-shaped coplanar waveguide(CPW). The result of circuit simulation and full wave analysis prove that the model is in good agreement with theoretical analysis. The model can effectively simplify the design complexity after optimization. Simulation results show that the S11 and S21 can achieve -20 dB and -2.5 dB, respectively, and the phase shift arrives at −180 ◦ at Ka band. Comparing with literature data, it has been predicted that S11 improves about 8 dB and the phase shift can increase about 100 ◦ in the same condition.

RF characteristics investigation of MEMS phase shifter with CPW discontinuities

The operating principle of the RF MEMS phase shifter is described. Two improved design approaches based on the CPW discontinuities to decrease the return loss are proposed. By using network theory and CST microwave studio simulation tool, the proposed RF MEMS phase shifters are modeled. Simulation results for the two designs are compared and discussed based on the analysis. Simulation results show that less than -10 dB return loss and more than -2 dB insertion loss is achieved for over 1 GHz bandwidth range for the proposed models. At least 6 dB return loss decrease is realized compared with the conventional MEMS phase shifter design methods.

A novel experimental validation method of dynamic X-parameters includes long-term memory effects

A novel experimental validation method for the modeling of amplifier with long-term memory effects of dynamic X-parameters is proposed in this paper. The basic idea of this method is by applying the narrow step signal as stimulus signal to replace the classical two-tone measurements. The comparison results between the measured and the measurement-based model have a perfect agreement, and it proves the validity of theory.

Modeling approach for distributed RF MEMS phase shifter based on IA-BP neural network

An Efficient modeling technique based on immune algorithm and BP neural network is presented for the design of RF MEMS phase shifter. Three sensitive parameters are selected according to complicated three-dimensional structure design of an RF MEMS phase shifter and used as inputs of neural network. In the model, immune algorithm is first used for global search and then BP algorithm for local search. Experiments show that the proposed approach in this paper is a high efficiency modeling for the RF characteristics analysis for up/down-state of RF MEMS phase shifter. Comparison between improved BP neural network predictions and HFSS simulations show that the root mean square errors, mean absolute errors and maximize absolute errors are less than 1.77dB(5.34o), 2.24dB(5.93o) and 2.60dB(6.19o) respectively. Also, improved BP neural network reduces the training time at least 30 minutes.

Quasi-static parameter analysis for arbitrary metallization thickness of RF MEMS coupled microstrip lines

The paper describes a method to analyze arbitrary metallization thickness on a coupled microstrip line for RF MEMS passive device design. Using a conformal mapping technique, closed-form expression quasi-static parameters for the metallization thickness of coupled microstrip lines are determined. They are found to be accurate compared with simulation tools. By using this method, the even-odd mode impedance of coupled microstrip lines for arbitrary metallization thickness can be obtained.

An approach to shielding effectiveness estimation of electronic equipment enclosures

In this paper, an approach to the shielding effectiveness evaluation of electronic enclosures with small apertures or slots is discussed. We use transmission line theory to analyze the equipment enclosures or boxes with small apertures or slots. The enclosure was represented by a length of coplanar strip transmission line. The effect of frequency, the dimensions of the enclosure and the size of the apertures in the enclosure are taken into account in the shielding effectiveness calculation. A computer simulation is used for the evaluation. Simulation results are in good agreement with tested data.

High precision RF linearizer by digital predistortion technique

This paper presents a new adaptive digital predistortion linearization technique and algorithm for high linearity RF power amplifier used for transmitters of IMT-2000 band mobile communication base station. Simulation results show an improvement of -63 dB for the third-order intermodulation distortion suppression. This technique is easy to realize adaptive control and suitable for circuit integration.