Piezoelectric transmitter
A piezoelectric dipole transmitter is provided that includes a piezoelectric element, an insulating support disposed at a midpoint of said piezoelectric element, or along the piezoelectric element, an external capacitance driver, and an external modulation capacitance disposed proximal to a first end of the piezoelectric element, where the driver capacitance is driven by a signal appropriate to excite a length-extensional acoustic mode of the piezoelectric element, where the piezoelectric element resonates at a piezoelectric element resonance frequency to radiate energy as an electric dipole.
1. A piezoelectric dipole transmitter, comprising:
a) a piezoelectric element;
b) an insulating support disposed at a midpoint of said piezoelectric element, or along said piezoelectric element;
c) an external capacitance driver; and
d) an external capacitor disposed proximal to said piezoelectric element, wherein said external capacitor is capacitively coupled to said piezoelectric element, wherein said external capacitor is driven by said external capacitance driver, wherein said external capacitance driver comprises a signal appropriate to excite a length-extensional acoustic mode of said piezoelectric element, wherein said piezoelectric element resonates at a piezoelectric element resonance frequency to radiate energy as an electric dipole.
2. The piezoelectric dipole transmitter of claim 1 , wherein said piezoelectric element comprises a cylindrical piezoelectric rod, a cuboid rod, or a shape that resonates in said length-extension acoustic mode.
3. The piezoelectric dipole transmitter of claim 1 , wherein said external capacitor comprises a plurality of concentric capacitor rings, or an external conductor having a controllable capacitance-to-ground.
4. The piezoelectric dipole transmitter of claim 1 , wherein said piezoelectric element comprises at least an n=2 vibration mode, wherein a displacement of said midpoint of said piezoelectric element comprises essentially a near zero-displacement.
5. The piezoelectric dipole transmitter of claim 1 , wherein said piezoelectric element has an output signal voltage of at least 100V.
6. The piezoelectric dipole transmitter of claim 1 , wherein said piezoelectric element comprises a material selected from the group consisting of lithium niobate, quartz, PZT, and lithium tantalate.
7. The piezoelectric dipole transmitter of claim 1 , wherein a modulation capacitance charges and discharges at a frequency of at least 1 Hz.
8. The piezoelectric dipole transmitter of claim 1 , wherein an external modulation capacitance and said external capacitance driver are configured for direct antenna modulation (DAM) to dynamically shift said piezoelectric element resonant frequency, wherein a Bode-Fano limit for high-bandwidth communications is bypassed.
9. The piezoelectric dipole transmitter of claim 1 , wherein said external capacitor and said external capacitance driver are configured for modulation of said piezoelectric element by magnetic field biasing, modulating said piezoelectric element by an external stress, or modulating an effective length of said piezoelectric element.
10. The piezoelectric dipole transmitter of claim 1 , wherein said resonating piezoelectric element has a Q-factor as low as 1,000 or a Q-factor greater than 600,000 with no external impedance matching network.
11. The piezoelectric dipole transmitter of claim 1 , wherein said external capacitor comprises metalized electrodes disposed about a perimeter of said piezoelectric element, wherein a voltage applied across said metalized electrodes is said drive signal.
12. The piezoelectric dipole transmitter of claim 1 further comprising a mechanically-free mass load on one end of said piezoelectric element.