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Acoustically Actuated Magnetoelectri...

Dong, Cunzheng,

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Acoustically Actuated Magnetoelectric Antennas for VLF Communication and Magnetic Sensing /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Acoustically Actuated Magnetoelectric Antennas for VLF Communication and Magnetic Sensing // Cunzheng Dong.
作者:	Dong, Cunzheng,
面頁冊數:	1 electronic resource (148 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-02, Section: B.
Contained By:	Dissertations Abstracts International86-02B.
標題:	Electrical engineering. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30817231
ISBN:	9798384019220

Acoustically Actuated Magnetoelectric Antennas for VLF Communication and Magnetic Sensing /
Dong, Cunzheng,

Acoustically Actuated Magnetoelectric Antennas for VLF Communication and Magnetic Sensing /Cunzheng Dong. - 1 electronic resource (148 pages)

Source: Dissertations Abstracts International, Volume: 86-02, Section: B.

Antenna miniaturization has been the subject of research efforts for decades. Among different antenna profiles and operating frequencies, very low frequency (VLF) antennas are a very special type, for their unique capability to communicate in underwater and subterranean environment. However, the miniaturization of conventional VLF antennas becomes particularly challenging as the wavelength of electromagnetic waves goes beyond kilometers long. Early studies proved the reduction of antenna size results in a direct limitation on its performance, which translates into an upper boundary on the maximum achievable bandwidth-efficiency product. Recently, mechanical antennas have been intensively investigated as a new approach to reduce the form factor of VLF antennas while maintaining an acceptable radiation efficiency and operating bandwidth. The magnetoelectric (ME) effect refers to the coupling between magnetism and electricity, which can be realized in single-phase materials or composite structures. Based on the coupling direction, ME effect can be classified as the direct ME coupling using magnetic field control of electric polarization; or the converse ME coupling using electric field control of magnetization. At present, two phase ME heterostructures have found more practical applications than single-phase materials due to their giant coupling coefficient. With strong coupling effect and room temperature operation, RF devices based on ME coupling become promising for future wireless communications and internet of things. Meaningrst part of this dissertation, an ultra-compact and sensitive system for measuring thin film magnetomechanical properties is introduced. Magnetomechanical properties are crucial for the performance of ME heterostructures. However, characterization for magnetostrictive thin films is challenging. Using optical detection technique, a 0.015 ppm detection limit of the magnetostriction tester and a frequency resolution of 0.01 Hz of the delta-E effect tester were achieved. After magnetic annealing, a record high piezomagnetic coefficient of 12 ppm/Oe, a giant magnetic field induced Young's modulus changes of 153 GPa, and an effective magnetomechanical coupling factor of 0.84 is reported for FeGaB thin films. The second part is the acoustically actuated VLF mechanical antennas based on converse ME coupling, including the design, fabrication, characterization, and testing of the devices. The ME antenna operates at its acoustic resonance frequency, which is decided by the length of the resonator. Since the speed of acoustic waves are much slower than electromagnetic waves, the ME antennas have three orders form factor reduction than the conventional VLF antennas. The radiation pattern, field strength, power consumption, communication distance, and modulation bandwidth are discussed. Moreover, the field strength and radiation efficiency are linearly enhanced with array structure. Finally, a non-linear antenna modulation (NAM) scheme is proposed for bandwidth extension.The third part is the magnetic sensors based on ME coupling for sensing magnetic fields. Since the ME coupling is a reciprocal process, ME antennas can also be used as receivers and magnetic sensors based on the direct ME coupling. Three different operation mechanism for ME sensors are discussed for receiving VLF magnetic signals at acoustic resonance; sensing DC magnetic fields based on the delta-E effect; and detecting AC magnetic fields at quasi-static frequencies based on non-linear magnetic modulation. 

English

ISBN: 9798384019220Subjects--Topical Terms:

649834
Electrical engineering.
Subjects--Index Terms:

Magnetomechanical properties

Acoustically Actuated Magnetoelectric Antennas for VLF Communication and Magnetic Sensing /
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520 $a Antenna miniaturization has been the subject of research efforts for decades. Among different antenna profiles and operating frequencies, very low frequency (VLF) antennas are a very special type, for their unique capability to communicate in underwater and subterranean environment. However, the miniaturization of conventional VLF antennas becomes particularly challenging as the wavelength of electromagnetic waves goes beyond kilometers long. Early studies proved the reduction of antenna size results in a direct limitation on its performance, which translates into an upper boundary on the maximum achievable bandwidth-efficiency product. Recently, mechanical antennas have been intensively investigated as a new approach to reduce the form factor of VLF antennas while maintaining an acceptable radiation efficiency and operating bandwidth. The magnetoelectric (ME) effect refers to the coupling between magnetism and electricity, which can be realized in single-phase materials or composite structures. Based on the coupling direction, ME effect can be classified as the direct ME coupling using magnetic field control of electric polarization; or the converse ME coupling using electric field control of magnetization. At present, two phase ME heterostructures have found more practical applications than single-phase materials due to their giant coupling coefficient. With strong coupling effect and room temperature operation, RF devices based on ME coupling become promising for future wireless communications and internet of things. Meaningrst part of this dissertation, an ultra-compact and sensitive system for measuring thin film magnetomechanical properties is introduced. Magnetomechanical properties are crucial for the performance of ME heterostructures. However, characterization for magnetostrictive thin films is challenging. Using optical detection technique, a 0.015 ppm detection limit of the magnetostriction tester and a frequency resolution of 0.01 Hz of the delta-E effect tester were achieved. After magnetic annealing, a record high piezomagnetic coefficient of 12 ppm/Oe, a giant magnetic field induced Young's modulus changes of 153 GPa, and an effective magnetomechanical coupling factor of 0.84 is reported for FeGaB thin films. The second part is the acoustically actuated VLF mechanical antennas based on converse ME coupling, including the design, fabrication, characterization, and testing of the devices. The ME antenna operates at its acoustic resonance frequency, which is decided by the length of the resonator. Since the speed of acoustic waves are much slower than electromagnetic waves, the ME antennas have three orders form factor reduction than the conventional VLF antennas. The radiation pattern, field strength, power consumption, communication distance, and modulation bandwidth are discussed. Moreover, the field strength and radiation efficiency are linearly enhanced with array structure. Finally, a non-linear antenna modulation (NAM) scheme is proposed for bandwidth extension.The third part is the magnetic sensors based on ME coupling for sensing magnetic fields. Since the ME coupling is a reciprocal process, ME antennas can also be used as receivers and magnetic sensors based on the direct ME coupling. Three different operation mechanism for ME sensors are discussed for receiving VLF magnetic signals at acoustic resonance; sensing DC magnetic fields based on the delta-E effect; and detecting AC magnetic fields at quasi-static frequencies based on non-linear magnetic modulation. 
546 $a English
590 $a School code: 0160
650 4 $a Electrical engineering. $3 649834
650 4 $a Electromagnetics. $3 3173223
650 4 $a Acoustics. $3 879105
650 4 $a Applied physics. $3 3343996
650 4 $a Engineering. $3 586835
653 $a Magnetomechanical properties
653 $a Antenna miniaturization
653 $a Very low frequency
653 $a Magnetoelectric
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690 $a 0607
690 $a 0986
690 $a 0537
690 $a 0215
710 2 $a Northeastern University. $b Electrical and Computer Engineering. $e degree granting institution. $3 3770414
720 1 $a Sun, Nian $e degree supervisor.
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791 $a Ph.D.
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