Research On Microstrip Patch Antenna Implanted In Human Body

In this thesis,the calculation of the human tissue's impaction on the microstrip patch antennas'?MPAs?radiatitive performances has been firstly quantized.Moreover,the theory of the inherent radiative modes of MPAs in free-space has been introduced to the MPAs embedded in the human body.Finally,three implantable lineaerly polarized?LP?MPAs with wide impedance bandwidth and three implantable circularly polarized?CP?MPAs with wide axis radio?AR?bandwidth have been designed.This thesis has been divided into five chapters as follows:In the charter 1,the development about the implantable antennas has been reviewed.Then,the current research status of MPAs embedded in human tissue havs been introduced in detail.At present,the research on MPA implanted in human tissue mainly focuses on how to design the characteristics of wide impedance bandwidth and wide AR bandwidth,and the method are all based on the mechanical structures.In the chapter 2,the approach about how to quantify the human tissue's impaction on the MPA's raditive performances has been firstly offered.Firstly,unique electrical parameters of human tissue have been introduced.Specifically,human tissue can be regarded as electromagnetic materials with high relative dielectric constant and high loss tangent.Moreover,the relative dielectric constant and loss tangent vary with frequency,which is quite different from free-space.Secondly,two kinds of human tissue models were also introduced in this chapter.Then,a brief introduction about MPA were made.The calculation processions of the total quality factor?Q_T?of MPA in free-space and in human tissue were given in detail.The results show that the Q_T values of MPA implanted in human tissue are very small,which is totally different from the high Q_T value of MPA working in free-space.Moreover,when the MPA is implanted into the human environment,the Q_T decreases with the increasement of the embeded depth d.This difference brings a new idea to the design of implantable MPAs.In the chapter 3,three LP MPAs with wide impedance bandwidth has been disgned by the high loss of tissue and the radiative modes.In section 3.1,a square metal ring was added around the center patch to generate an additional mode near the basic mode of MPA,and the impedance bandwidth has been widen.In section 3.2,the theory of MPA's inherent multi-radiative modes is introduced.The method of how to restrain and adjust those unwanted modes has been discussed in detail.In section 3.3,the theory in section 3.2 was used to design a differential-fed LP MPA implanted in human tissue.In Section 3.4,the same theory has been used to design an imlantable LP PIFA.The simulations,SAR values,sensitivities,biological compatibilities of the MPA in section3.3 and PIFA in section 3.4 were studied as well.What's more,both of the MPA and PIFA have been used to design wireless pacemakers.In chapter 4,three CP MPAs embedded in human tissue has been designed by the high loss of tissue and the radiative modes.All the 3dB AR bandwidths were impressive.In section 4.1,a CP MPA based on fundamental modes,i.e.,TM₁₀ mode and TM₀₁mode,has been designed.The wide AR bandwidth is based on the structure of MPA itself,i.e.,short pins.In section 4.2,a single-fed CP MPA implanted in human tissue has been designed.The results show that the relative 3dB AR bandwidth is 5.3%,and it has been obtained by using the high loss of human tissue.In section 4.3,the multi-radiative mode theory was used again,and combined the high loss tangent of human tissue,for designing an implantable CP MPA with wide 3dB AR bandwidth.Those inherent radiative modes,i.e.,TM₁₀ mode,TM₀₁ mode,TM₃₀ mode,TM₀₃ mode,have been used.What's more,both the last two CP MPAs have been used to design wireless pacemakers.In chapter 5,all the research work in this thesis has been summarized.The future research work of MPA implanted in human tissue has been prospected.