Standard Modeling And Design Of Tiny Capacitors Based On Conformal Transformation

With the rapid development of nanotechnology and microelectronics industries,the miniaturization of components has become an important development trend.As one of the three basic impedance components,capacitance is an important parameter for electrical signal transmission.The realization of accurate and convenient sub-pF and micro capacitor standards below the order of magnitude not only contributes to the miniaturization and high integration of the hardware system,but also meets the needs for the traceability and measurement of micro capacitors in the field of AC impedance measurement.This article briefly describes the research background and significance of the establishment of micro-capacitor standards.With the help of the linear relationship between the capacitance units in programmable capacitors,a method for implementing micro-capacity standards using micro-capacitor units in programmable capacitors is proposed.Based on this,an algorithm that uses Schwartz-Christopher transform to calculate the actual capacitance value considering the effects of capacitor edge effects is given.With the help of the finite element analysis software Ansoft Maxwell,the design of the micro-capacitor unit is assisted,and the micro-capacitor standard is finally realized.This paper proposes the design of a standard detection system for micro-capacitors,and gives a hardware design principle of a micro-capacitor detection system based on a single-chip microcomputer STM32F429.With the help of Multisim and Tina,the hardware circuit is guided.The specific research work of this topic is as follows:(1)First introduce the research background and research significance of micro-capacitor standards,and explain its physical meaning and industrial value.Secondly,it analyzes the current international development situation,puts forward the difficulties in achieving the micro-capacitor standard so far,and gives the idea of achieving the micro-capacitor standard.For the standard detection scheme of micro-capacitors,combined with an AC-excited capacitor-voltage conversion circuit,the sources of errors in the circuit system are analyzed to provide guidance for later design.(2)Give the physical background and theoretical analysis of the establishment of micro-capacitor standards,introduce the working principle of programmable fused silica capacitors,and give a method of using micro-capacitor units in programmable capacitors to achieve micro-capacity standards.An analytical model is established for the capacitor unit in a programmable capacitor,a capacitor value calculation algorithm that takes into account the capacitor edge effect is given,and its mathematical background is introduced.Based on the theoretical derivation and research of the small capacitor unit,the finite element analysis software Ansoft is used Maxwell simulation verifies its correctness.Finally,according to the actual production needs,the mechanical model is optimized and improved.(3)An overall design scheme of a standard detection system for micro-capacitors is proposed,and its overall framework and theoretical basis are given.The core circuit is composed of STM32F407 + AD630 + AD9833,which is divided into signal generation unit,signal acquisition unit,signal processing unit,and power supply.In the fourth part of the unit,the circuit simulation is performed in Multisim and Tina to reduce the influence of parasitic capacitance in the AC-excited capacitor-voltage conversion circuit.According to the principle of phase-sensitive detection,the AD630 is used to implement analog signals and references by means of analog multipliers and low-pass filters The signals are mutually calculated to obtain the DC voltage.According to the principle of digital signal direct synthesis,the DDS special chip AD9833 is used to directly synthesize the reference signal,and the signal amplitude adjustable function is implemented to meet the detection of micro-capacitor standards of different magnitudes.(4)Summarizing the research work and further prospects,for the small capacitor unit,the calculated value obtained by the conformal transformation is completed and verified with the aid of Ansoft Maxwell simulation,which guarantees the output of any capacitor value from pF to fF,but Capacitors at fF level and below still do not have accurate capacitance values,and further research is needed.For the micro-capacitor standard detection system solution circuit,the design of the relevant hardware circuit is completed,and the designed micro-capacitor detection circuit is simulated and experimented.The shortcomings in the hardware circuit are analyzed,that is,the overall power consumption of the circuit is relatively large.As a result,circuit components are extremely prone to heat and affect measurement accuracy.