Statistical method of modeling and optimization for wireless sensor nodes with different interconnect technologies and substrates

Abstract

Original citationZheng AbstractA comparison study was carried out between a wireless sensor node with a bare die flip-chip mounted and its reference board with a BGA packaged transceiver chip. The main focus is the return loss (S parameter S11) at the antenna connector, which was highly depended on the impedance mismatch. Modeling including the different interconnect technologies, substrate properties and passive components, was performed to simulate the system in Ansoft Designer software. Statistical methods, such as the use of standard derivation and regression, were applied to the RF performance analysis, to see the impacts of the different parameters on the return loss. Extreme value search, following on the previous analysis, can provide the parameters' values for the minimum return loss. Measurements fit the analysis and simulation well and showed a great improvement of the return loss from -5dB to -25dB for the target wireless sensor node. IntroductionAs wireless sensor node being used widely in environment monitoring and medical applications, reducing the weight and size and increasing the mobility are becoming essential. To achieve these goals, lots of technologies are applied to the nodes, such as flip chip, and flexible substrate. There are lots of researches and publications focus on the characterization [1-4] of the above technologies.However, from RF system point of view, very little effort was done in considering these technologies as components which could change the final RF performance of the system. The aim of this paper is to develop a methodology to model the advanced packaging technologies for RF circuit simulation and obtain an optimized solution of the whole system. Statistical methods, like standard deviation, coefficient of variation, regression, curve fitting, are utilized during the parameter sweep procedure to get the optimization results.In this paper, the impacts of a wide range of parameters on RF performance were studied and a statistical based method is proposed to improve the return loss. The paper is organized as the following:  Main focus description: poor return loss caused by improper impedance matching.  Modelling of the RF circuit, including the packaging and substrate.  Description of the statistical methods used during analysis.  Optimization performed to improve the return loss.Measurements were carried out to match the optimized solution.

A Passive Circuit Based RF Optimization Methodology for Wireless Sensor Network Nodes

“…Packaging Interconnect: The packaging technologies of the RF chip were also considered. Two typical packaging technologies, wire-bonding and flip-chip, were modeled, with the interconnect parasitic extracted by Ansoft Q3D Extractor simulation [8].…”

“…By sweeping the parameter with the largest coefficient of variation on return loss, the most significant parameter was targeted. Repeat this sweep procedure for all the relevant parameters, until a desired return loss was finally obtained [8].…”