With the development of mobile communication technology, the demand for mobile devices continues to rise. Acoustic devices such as radio frequency (RF) filters and duplexers are widely used in mobile handsets because of their excellent electric performance characteristics. However, the key bottleneck is how to convert a lumped circuit model into the structure parameters of an acoustic resonator for RF circuit designers so that they can apply RF circuit design tools in designing surface acoustic wave (SAW) devices. The neural network (NN) has been widely applied in various science and management areas for its powerful learning and mapping capabilities. In this paper, a method of building a bridge between the lumped equivalent circuit (EC) model and structure parameters of a SAW resonator is proposed. The approach begins with establishing a database that shows the relationship between the values of the lumped EC and corresponding structure parameters of the SAW resonator. A four-layered NN with the back-propagation (BP) algorithm is adopted to determine the relationship between the structure parameters of the SAW resonator and the lumped EC. Then, other input/output pairs are presented to check if the estimated lumped EC matched with original circuit. Finally, as an example, the design of a long term evolution (LTE) transmitter (Tx) filter is developed to demonstrate the proposed approach.
The absorption of the helium 388.9 nm line by a high-pressure pulsed helium-neon laser discharge has been measured. The density and decay rate of density of He (2 3S) metastable atoms in the discharge have been estimated. While the accuracy of the decay rate measurements is of the order of 576, that of the density measurements is probably not better than 20%, because of the difficulty of determining the shape of the collision-broadened absorption line. The measured decay rates of He (2 3S) atoms are given for mixtures with helium and neon partial pressures in the range 80 to 260 torr and 4 to 30 torr respectively. T h e decay rate at a fixed neon pressure is shown to be independent of the helium pressure, and to be proportional to the neon pressure at a fixed helium pressure. Agreement with values obtained by extrapolating results from low-pressure measurements of Benton et al. in 1962 is good. 1Ieasurements of the peak density of He (2 Y-3) as a function of the pulsed excitation voltage of the laser discharge are gilven and agree well with calculated values gi.i en by Langdon in 1968. The energy conversion efficiency for the production of He ( 2 3S) atoms deduced from the foregoing results is between 1 5 and 30q6.f lvow at hlarconi Ltd., Chelmsford, Essex. 61 1
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