Ultrahigh Frequency Ultrasonic Transducers Design with Low Noise Amplifier Integrated Circuit.

Di Li,Chunlong Fei,Qidong Zhang,Yani Li,Qifa Zhou,Yintang Yang

doi:10.3390/mi9100515

Di Li, Chunlong Fei + Show 4 more

Open Access

https://doi.org/10.3390/mi9100515

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Abstract

This paper describes the design of an ultrahigh frequency ultrasound system combined with tightly focused 500 MHz ultrasonic transducers and high frequency wideband low noise amplifier (LNA) integrated circuit (IC) model design. The ultrasonic transducers are designed using Aluminum nitride (AlN) piezoelectric thin film as the piezoelectric element and using silicon lens for focusing. The fabrication and characterization of silicon lens was presented in detail. Finite element simulation was used for transducer design and evaluation. A custom designed LNA circuit is presented for amplifying the ultrasound echo signal with low noise. A Common-source and Common-gate (CS-CG) combination structure with active feedback is adopted for the LNA design so that high gain and wideband performances can be achieved simultaneously. Noise and distortion cancelation mechanisms are also employed in this work to improve the noise figure (NF) and linearity. Designed by using a 0.35 μm complementary metal oxide semiconductor (CMOS) technology, the simulated power gain of the echo signal wideband amplifier is 22.5 dB at 500 MHz with a capacitance load of 1.0 pF. The simulated NF at 500 MHz is 3.62 dB.

Highlights

Ultrahigh frequency ultrasound has recently been investigated as a tool in the field of microbiology
Applications include acoustic microscopy for the non-invasive investigation of biological tissue and living cells [1–4] and non-contact manipulation of microparticles or cells that are based on radiation force principle [5–7]
When comparing with a sapphire lens for ultrahigh frequency ultrasonic transducer design, a silicon lens might be more appropriate for the following reasons: (1) the silicon wafer is cheaper than the sapphire crystal; (2) good uniformity can be utilized using microelectromechanical systems (MEMS) lithography and etching techniques for the silicon lens rather than the grinding method for the sapphire lens; Micromachines 2018, 9, 515; doi:10.3390/mi9100515

Summary

Introduction

Ultrahigh frequency ultrasound has recently been investigated as a tool in the field of microbiology. State of the art in acoustic microscopy is to work with single element focusing transducers. The transducers in the ultrahigh frequency range are based on ZnO thin films on sapphire with a grind spherical cavity as a focusing element on the opposite side of the ZnO layer. With the increasing operation frequency, the focus distance of the transducer should decrease, demand smaller radius and higher sphericity of the lens. When comparing with a sapphire lens for ultrahigh frequency ultrasonic transducer design, a silicon lens might be more appropriate for the following reasons: (1) the silicon wafer is cheaper than the sapphire crystal; (2) good uniformity can be utilized using microelectromechanical systems (MEMS) lithography and etching techniques for the silicon lens rather than the grinding method for the sapphire lens; Micromachines 2018, 9, 515; doi:10.3390/mi9100515 www.mdpi.com/journal/micromachines. The gap between the brass tube and the device was filled by insulating epoxy

Echo signal processing system

Front load

LNA core

Increasing of