A high Q piezoelectric resonator as a portable VLF transmitter

Abstract

Very low frequency communication systems (3 kHz–30 kHz) enable applications not feasible at higher frequencies. However, the highest radiation efficiency antennas require size at the scale of the wavelength (here, >1 km), making portable transmitters extremely challenging. Facilitating transmitters at the 10 cm scale, we demonstrate an ultra-low loss lithium niobate piezoelectric electric dipole driven at acoustic resonance that radiates with greater than 300x higher efficiency compared to the previous state of the art at a comparable electrical size. A piezoelectric radiating element eliminates the need for large impedance matching networks as it self-resonates at the acoustic wavelength. Temporal modulation of this resonance demonstrates a device bandwidth greater than 83x beyond the conventional Bode-Fano limit, thus increasing the transmitter bitrate while still minimizing losses. These results will open new applications for portable, electrically small antennas.

A Review of Thin-Film Magnetoelastic Materials for Magnetoelectric Applications

“…[26][27][28][29][30][31][32][33][34][35][36]. Besides, another promising topic that has received the significant research interests during recent years is mechanically actuated ME antennas, which exploit both direct and converse ME couplings [37][38][39][40][41][42][43][44][45][46]. The combined high permeability µ and permittivity ε offer great beneficial in compact RF/microwave devices, for example, miniaturized antennas, etc.…”

The 3D Smith Chart: From Theory to Experimental Reality

“…The power level in 3D is normalized with respect to the square root of the maximum gain (for display reasons). Negative capacitance [26][27][28][29][30] is of interest in many RF applications; however, the negative capacitance and positive inductance S11 parameters of 1-port and 2-port lossless networks share the same paths on the Smith chart. By means of differential geometry, however, we can see that their orientation (oriented curvature [20] of their frequency S11) in either 1-or 2-port configurations is opposed.…”

“…By means of differential geometry, however, we can see that their orientation (oriented curvature [20] of their frequency S11) in either 1-or 2-port configurations is opposed. Their Foster/non-Foster character [27][28][29][30] changes the orientation of their S11 motions as frequency increases on the Smith chart. Fig.13 (a) represents the S11 of a negative capacitor and positive inductor in a 1-port configuration with a 50 Ω load at both ports analyzed between 1-7 GHz.…”

Research on mechanism and key technology of mechanical antenna for a low-frequency transmission

“…grants.gov/grantsws/rest/opportunity/att/download/259390/HR001117S0007_Final for Posting_15 Dec 2016.pdf 倍以上. 加州大学的Selvin等人 [14] 研究了永磁体旋转 的电磁辐射机理, 初步分析了其机械能与磁能之间的 约束关系, 针对ULF/VLF应用, 提出了基于旋转永磁 体阵列并可突破Chu-Harrington极限的MA技术方 案 [11] , 初步给出了对应的Q值极限公式 [15] . 犹他大学的…”

“…如图1所示, 所谓MA, 即通过特殊材料, 如驻极体 对 各类MA的辐射特性进行了对比分析, 并对驻极体旋 转产生的近区磁场进行了实验验证 [13] . 在VLF频段, 美国SLAC国家加速器实验室的Kemp等人 [11] 利用杆 状铌酸锂晶体(长度9.4 cm/直径1.6 cm)及其逆压电效…”