Integrated electromagnetic-acoustic sensor and sensing
One illustrative integrated electromagnetic-acoustic sensor includes: a ground plane; a patch antenna above the ground plane to send or receive an electromagnetic (EM) signal having an EM signal frequency; and an array of capacitive micromachined acoustic transducers formed by cavities between the patch antenna and a base electrode to send or receive an acoustic signal having an acoustic signal frequency. One illustrative sensing method includes: driving or sensing a EM signal between a ground plane and a patch antenna; and driving or sensing an acoustic signal between the patch antenna and a base electrode, the base electrode and the patch antenna having an array of capacitive micromachined acoustic transducer cavities therebetween.
1. An integrated electromagnetic-acoustic sensor comprising:
a ground plane;
a patch antenna above the ground plane configured to send or receive an electromagnetic (EM) signal having an EM signal frequency; and
an array of capacitive micromachined acoustic transducers formed by cavities between the patch antenna and a base electrode configured to send or receive an acoustic signal having an acoustic signal frequency, wherein the base electrode lies between the ground plane and the patch antenna.
2. The integrated electromagnetic-acoustic sensor of claim 1 , further comprising:
first and second differential signal nodes configured to convey the acoustic signal to or from the sensor;
a first filter that couples the first differential signal node to the patch antenna; and
a second filter that couples the second differential signal node to the base electrode, the first and second filters configured to pass the acoustic signal frequency while blocking the EM signal frequency.
3. The integrated electromagnetic-acoustic sensor of claim 2 , wherein the first filter couples the first differential signal node to the patch antenna with a first EM frequency choke and couples the first differential signal node to the ground plane with a first capacitor, and
wherein the second filter couples the second differential signal node to the base electrode with a second EM frequency choke and couples the second differential signal node to the ground plane with a second capacitor.
4. The integrated electromagnetic-acoustic sensor of claim 3 , wherein the first and second EM frequency chokes each comprise a quarter-wave microstrip transmission line.
5. The integrated electromagnetic-acoustic sensor of claim 3 , wherein the first and second EM frequency chokes each comprise an inductor.
6. The integrated electromagnetic-acoustic sensor of claim 3 , wherein the EM signal frequency is 10 GHz or more, and wherein the acoustic signal frequency is 1 GHz or less.
7. The integrated electromagnetic-acoustic sensor of claim 2 , further comprising:
an EM signal node configured to convey a radio frequency signal to or from the sensor; and
a capacitor that couples the patch antenna to the EM signal node.
8. The integrated electromagnetic-acoustic sensor of claim 1 , wherein the patch antenna is separated from the base electrode by no more than 2 microns, and is separated from the ground plane by at least 200 microns.
9. The integrated electromagnetic-acoustic sensor of claim 1 , wherein the base electrode is patterned to provide a high impedance surface at the EM signal frequency.
10. A method of using an integrated electromagnetic-acoustic sensor, the method comprising:
driving or sensing an EM signal between a ground plane and a patch antenna; and
driving or sensing an acoustic signal between the patch antenna and a base electrode, the base electrode and the patch antenna having an array of capacitive micromachined acoustic transducer cavities therebetween.
11. The method of claim 10 , wherein driving or sensing the acoustic signal comprises:
supplying or receiving the acoustic signal to or from the sensor via first and second differential signal nodes, the first differential signal node coupled to the patch antenna by a first filter configured to pass the acoustic signal while blocking the EM signal and the second differential signal node coupled to the base electrode by a second filter configured to pass the acoustic signal while blocking the EM signal.
12. The method of claim 11 , wherein the EM signal frequency is 10 GHz or more, and wherein the acoustic signal frequency is 1 GHz or less.
13. The method of claim 11 , wherein driving or sensing the EM signal comprises:
supplying or receiving the EM signal to or from the sensor via an EM node that is capacitor-coupled to the patch antenna.
14. The method of claim 10 , wherein the patch antenna is separated from the base electrode by no more than 2 microns, and is separated from the ground plane by at least 200 microns.
15. The method of claim 10 , wherein the base electrode lies between the ground plane and the patch antenna.
16. The method of claim 15 , wherein the base electrode is patterned to provide a high impedance surface at the EM signal frequency.