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A novel enlarging fractional bandwidth (FBW) technique for acoustic‐wave‐lumped‐element resonator (AWLR)‐based bandpass filters is presented. The new technique is based on a series of matching inductors that replace the parallel or series acoustic wave (AW) resonators of AW filters to beak the bandwidth constraint of the ladder‐type structure. In addition, the transmission response analysis of the proposed AWLR‐based filter is provided. A prototype of the AWLR‐based filter is fabricated and tested to validate the proposed FBW widening technique. The measured insertion loss, FBW, and out‐of‐band rejection are 1.5 dB, 1.63kt2 (kt2 is the electromechanical coupling coefficient of the AWR), and 38 dB, respectively. [ABSTRACT FROM AUTHOR]

For spatial multibody systems, the dynamic equations of multibody systems with compound clearance joints have a high level of nonlinearity. The coupling between different types of clearance joints may lead to abundant dynamic behavior. At present, the dynamic response analysis of the spatial parallel mechanism considering the three-dimensional (3D) compound clearance joint has not been reported. This work proposes a modeling method to investigate the influence of the 3D compound clearance joint on the dynamics characteristics of the spatial parallel mechanism. For this purpose, 3D kinematic models of spherical clearance joint and revolute joint with radial and axial clearances are derived. Contact force is described as normal contact and tangential friction and later introduced into the nonlinear dynamics model, which is established by the Lagrange multiplier technique and Jacobian of constraint matrix. The influences of compound clearance joint and initial misalignment of bearing axes on the system are analyzed. Furthermore, validation of dynamics model is evaluated by ADAMS and Newton–Euler method. This work provides an essential theoretical basis for studying the influences of 3D clearance joints on dynamic responses and nonlinear behavior of parallel mechanisms.

In this study, the dynamics behaviors analysis of parallel mechanism considering joint clearance and flexible links are investigated using a computational methodology. The nonlinear dynamic model of 4-UPS-RPS spatial parallel mechanism with clearance in spherical joint and flexible links is established by combining KED method and Lagrange method. The dynamic responses including collision force and motion characteristics of the moving platform are obtained. Chaos and bifurcation are analyzed. The effects of different clearances on the dynamics behaviors of the parallel mechanism are studied. The results show that 4-UPS-RPS spatial parallel mechanism is very sensitive to joint clearance and flexible links, and small variations in the clearance value can cause the mechanism change from periodic motion to chaotic motion. This research provides a methodology for forecasting the dynamics behavior of parallel mechanisms with clearance and flexible links.

In this paper, an accurate parasitic parameters extraction method based on full wave electromagnetic for 0.1 μm GaN high electron mobility transistors (HEMTs) small-signal equivalent circuit up to 110 GHz is presented. To describe the distribution effects of HEMTs electrodes at extremely high frequency, a 2-stage distributed transmission line equivalent circuit model is also presented. To minimize the distribution effects, a shorter gate-width device, called partial transistor model, is used to extract the second stage ( N = 2) parasitic capacitance before extracting the first stage ( N = 1) parameters. An AlGaN/GaN HEMT with gate length of 0.1 μm is used for validation, and the experimental results show that good agreement has been achieved between measured and simulated scattering (S) parameters up to 110 GHz. [ABSTRACT FROM AUTHOR]

ABSTRACT The compact UWB flexible filter with low loss and excellent stop band suppression on ultrathin liquid crystal polymer substrate is presented firstly. A uniform microstrip line connected with five pairs of stubs is used. The flexible filter with the pass band of 4.1-10.6 GHz. The measured minimum insertion loss is 0.76 dB at 5.4 GHz and the return loss is better than 11.3 dB. While the frequency is higher than 12.1 GHz, excellent high resistance band suppression is obtained. The bending behavior of the UWB flexible filter is analyzed. In case of R = 17.5 mm, the insertion loss is only improved by 0.004 dB and the return loss is optimized by 0.45dB. Good agreement is obtained between the flat and the bending. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:194-197, 2017 [ABSTRACT FROM AUTHOR]