Wireless Communication System Using Surface Acoustic Wave (SAW) Second Harmonic Techniques

• US 20100220772A1
• Filed: 05/12/2010
• Published: 09/02/2010
• Est. Priority Date: 06/02/2000
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Campbell, Colin K., Edmonson, Peter J.
• Granted Patent: US 8,099,048 B2
• Time in Patent Office: Days
• US Class Current: 375/219
• CPC Class Codes: G01S 13/755 using delay lines, e.g. acoustic delay lines
• CPC Class Codes: H03H 9/0028 using surface acoustic wave devices
• CPC Class Codes: H03H 9/0042 the balanced terminals being on opposite sides of the track
• CPC Class Codes: H03H 9/6406 Filters characterised by a particular frequency characteristic

Abstract

A system is for encoding information on a passive surface acoustic wave (SAW) device. The system includes a requesting unit configured to wirelessly transmit an impulse signal. The impulse signal is a signal that includes only a single pulse. A SAW device has an interdigital transducer (IDT) configured to physically store coded data. The SAW device is configured to receive the impulse signal. In response to receiving the impulse signal, the SAW device excites the IDT to generate a coded signal that includes the stored coded data and frequency components at a fundamental frequency.

Claims

1. A system for encoding information on a passive surface acoustic wave (SAW) device, comprising:

a requesting unit configured to wirelessly transmit an impulse signal, wherein the impulse signal is a signal that includes only a single pulse; and

a SAW device having an interdigital transducer (IDT) that is configured to physically store coded data, the SAW device being configured to receive the impulse signal and in response to receiving the impulse signal, to excite the IDT to generate a coded signal that includes both the stored coded data and frequency components at a fundamental frequency.

2. The system of claim 1, further comprising an antenna for receiving the impulse signal.

3. The system of claim 1, wherein a second IDT is configured to receive the impulse signal and in response to receiving the impulse signal, to produce a first SAW output that includes frequency components at the fundamental frequency.

4. The system of claim 3, wherein the second IDT is a differential design.

5. A method of wireless communication, comprising:

receiving an impulse signal, wherein the impulse signal is a signal that includes only a single pulse; and

the received impulse signal exciting an interdigital transducer (IDT) to generate a coded signal that is defined by the relative positions of fingers of the IDT.

6. The method of claim 5, wherein a second IDT is configured to receive the impulse signal and in response to receiving the impulse signal, to produce a first SAW output that includes frequency components at the fundamental frequency.

7. The method of claim 6, wherein the second IDT is a differential design.

8. A wireless communication system comprising:

an antenna;

a receive interdigital transducer (IDT) configured to produce a surface acoustic wave (SAW) output when excited by an electrical signal received from the antenna;

an expander/compressor IDT configured to produce an electrical signal when excited by the SAW output from the receive IDT, and further configured to output a SAW output when excited by an electrical signal received from a control device; and

a transmit IDT configured to output, to the antenna, an electrical signal when excited by the SAW output from the expander/compressor IDT.

9. The system of claim 8 wherein the receive and transmit IDTs are each switchably connected to the antenna.

10. The system of claim 8 wherein the receive and transmit IDTs are each configured to operate at a harmonic of the expander/compressor IDT'"'"'s fundamental frequency.

11. The system of claim 8 wherein the expander/compressor IDT'"'"'s SAW output is coded with a code that is based on the relative positions of fingers of the IDT, and the expander/compressor IDT'"'"'s electrical output is based on passively autocorrelating the code with the SAW wave received from the receive IDT.

12. A wireless communication system comprising:

an antenna;

a receive/transmit interdigital transducer (IDT) configured to produce a surface acoustic wave (SAW) output when excited by an electrical signal received from the antenna, and further configured to output, to the antenna, an electrical signal when excited by a SAW output; and

first and second reflecting IDTs, each configured to passively reflect the SAW output from the receive/transmit IDT back to the receive/transmit IDT, which excites the receive/transmit IDT to output, to the antenna, first and second electrical signals from which the antenna respectively outputs first and second RF return signals;

the terminals of the first reflecting IDT being exclusively open circuit or closed circuit for the first RF return signal to be a reference return signal; and

the reflecting IDTs being different distances from the receive/transmit IDT so that the SAW outputs reflected by the first and second reflecting IDTs reach the receive/transmit IDT at different times.

13. The system of claim 12 further comprising a control device configured to apply a variable impedance across the terminals of the second reflecting IDT, for the magnitude and/or phase of the second RF return signal to be a function of the variable impedance.

14. The system of claim 13 wherein the control device is a sensor.

15. The system of claim 13 wherein the terminals of the first reflecting IDT are exclusively open circuit.

16. The system of claim 13 wherein the reflecting IDTs are fabricated for operation in a fundamental frequency, and the receive/transmit IDT is configured for operation at a harmonic of the fundamental frequency.

17. The system of claim 13 wherein at least one of the return signals is coded with a code defined by relative positions of fingers of the respective reflecting IDT.

18. The system of claim 13 further comprising a requesting unit configured to receive both RF return signals, and to compare the magnitude and/or phase of the variable return signal to the magnitude and/or phase of the reference return signal to obtain an indication of the variable impedance.

19. A mobile communication device that includes the system of claim 13.