Microsystems-based method and apparatus for passive detection and processing of radio-frequency signals
A radio frequency (RF) receiver comprises a passive impedance transforming voltage amplifier and a resonant, latching micromechanical switch having a deflectable bridge, an RF actuation electrode receivingly connected to the amplifier, and a DC bias electrode positioned to latch the switch in a closed position by electrostatic attraction when energized by a suitable voltage. The bridge is configured with a mechanical mode of vibration that periodically urges the switch toward the closed position.
1. A radiofrequency device, comprising:
a passive impedance transforming voltage amplifier receivingly connected to an antenna for receiving radiofrequency (RF) signals, the impedance transforming voltage amplifier adapted to produce an RF actuation signal; and
a MEMS switch having a radiofrequency (RF) actuation electrode receivingly connected to the impedance transforming voltage amplifier;
wherein:
the MEMS switch further comprises a DC bias electrode positioned to latch the MEMS switch in a closed position by electrostatic attraction when energized by a suitable voltage;
the MEMS switch further comprises a bridge that physically and electrically contacts at least the DC bias electrode when the MEMS switch is in the closed position; and
the bridge is configured with a mechanical mode of vibration that, when subjected to the RF actuation signal having a fundamental frequency that matches at least one frequency of the said mechanical mode of vibration, allows the MEMS switch to be periodically urged toward the closed position.
2. The radiofrequency device of claim 1 , wherein the bridge physically and electrically contacts both the RF actuation electrode and the DC bias electrode when the switch is in the closed position.
3. The radiofrequency device of claim 1 , wherein the impedance-transforming voltage amplifier is configured to amplify modulations of RF carrier energy in a modulated signal, the modulated signal having a fundamental frequency that is lower than a carrier wave frequency and that matches at least one frequency of the said mechanical mode of vibration.
4. The radiofrequency device of claim 3 , wherein the impedance transforming voltage amplifier is in a dispersive circuit that compresses the modulated RF carrier energy in the received radiofrequency (RF) signals.
5. The radiofrequency device of claim 4 , wherein the dispersive circuit comprises a network of acoustic delay elements that compresses the modulations of RF carrier energy in the acoustic domain.
6. The radiofrequency device of claim 3 , wherein the fundamental frequency is variable.
7. The radiofrequency device of claim 3 , wherein the radiofrequency (RF) signal comprises a carrier wave, the carrier wave having a variable carrier frequency within each modulation.
8. The radiofrequency device of claim 1 , wherein the impedance transforming voltage amplifier comprises a resonant voltage transformer.
9. The radiofrequency device of claim 8 , wherein the resonant voltage transformer is a piezoelectric focusing transformer.
10. The radiofrequency device of claim 8 , wherein the resonant voltage transformer is a piezoelectric voltage transformer, and wherein the piezoelectric voltage transformer is included in a circuit that further comprises a frequency-selective network of acoustic time-delay elements.
11. The radiofrequency device of claim 1 in a system that further comprises a transmitter, wherein:
the transmitter is configured to transmit the radiofrequency (RF) signal, the radiofrequency (RF) signal comprising a carrier wave modulated by an envelope; and
the transmitter comprises a configurable modulator circuit that can modulate the carrier wave with the envelope having a fundamental frequency that is lower than a carrier wave frequency and that matches at least one frequency of the said mechanical mode of vibration.
12. The radiofrequency device of claim 11 , wherein:
the transmitter further comprises
a carrier-wave generator for generating the carrier wave, the carrier wave having a variable frequency,
a frequency controller, and
a storage device;
the carrier-wave generator is configured to vary the carrier wave frequency in response to control signals from the frequency controller; and
the frequency controller is configured to retrieve at least one stored pattern of frequency variation from the storage device.
13. The radiofrequency device of claim 11 , wherein the fundamental frequency is variable.
14. A method for operating a radiofrequency device, comprising:
in a passive impedance transforming voltage amplifier, amplifying modulations of a radiofrequency (RF) carrier, the modulations having a fundamental frequency, thereby to produce an RF actuation signal;
applying a DC bias to a DC bias electrode positioned to latch a MEMS switch in a closed position by electrostatic attraction when the DC bias electrode is energized by a suitable voltage; and
while applying the DC bias, applying the RF actuation signal to an RF actuation electrode of the MEMS switch;
wherein:
the RF actuation electrode is distinct from the DC bias electrode;
the MEMS switch comprises a bridge that physically and electrically contacts the DC bias electrode when the MEMS switch is in the closed position;
the bridge is configured with a mechanical mode of vibration that, when subjected to the RF actuation signal having the fundamental frequency that matches at least one frequency of the said mechanical mode of vibration, allows the MEMS switch to be periodically urged toward the closed position; and
the RF actuation signal is applied such that when the RF actuation signal includes the fundamental frequency that matches at least one frequency of the said mechanical mode of vibration, the RF actuation signal increasingly excites the said mechanical mode of vibration until the MEMS switch reaches the closed position.
15. The method of claim 14 , wherein the modulations are amplified in the acoustic domain.
16. The method of claim 15 , wherein the modulations are time-compressed in the acoustic domain.
17. The method of claim 16 , wherein:
the carrier wave has a frequency that is varied within each of said modulations; and
the time-compression of the modulations comprises dividing each pulse modulation into segments in a frequency-selective manner, subjecting each segment to a respective time delay, and recombining the time-delayed segments.
18. The method of claim 14 , further comprising transmitting the modulations of radiofrequency (RF) carrier from a transmitting device to an antenna coupled to the passive impedance transforming voltage amplifier.
19. The method of claim 16 , wherein the transmitting device generates the modulations by modulating an RF carrier wave.
20. The method of claim 17 , wherein:
the RF carrier wave has a carrier frequency; and
the method further comprises, in the transmitting device, varying the carrier frequency within each modulation.
21. The method of claim 18 , wherein the carrier frequency is varied such that each modulation comprises a plurality of modulation segments, and at least two of the modulation segments within each modulation contain different carrier frequencies.
22. The method of claim 19 , wherein the fundamental frequency is variable.
23. The method of claim 14 , wherein the fundamental frequency is variable.