METHOD FOR LOCATING ITEMS

• US 20110279238A1
• Filed: 07/21/2011
• Published: 11/17/2011
• Est. Priority Date: 01/27/2009
• Status: Active Grant

• Current Assignee: RadioFIDO LLC
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: BROMMER, Karl D., GILI, Paul E., LOGAN, Cedric L., ROSSMAN, Court E.
• Granted Patent: US 8,319,636 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: G06K 17/00 Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations
• CPC Class Codes: G06K 19/0675 the resonating marks being of the surface acoustic wave [SAW] kind SAW devices per se H03H9/64

Abstract

A convenient handheld locator is provided for locating an item in an urban environment in which the locator is programmed to search for and locate specific items, with the detected item being displayed on the locator as to its identity or name, also displaying where the item is relative to the locator, as to position and range.

Claims

1-26. -26. (canceled)

27. A method for extending the range of an RFID system which employs a transmitter for transmitting an interrogation beam towards an RFID tag and an RFID tag that uses a non-linear element including a diode for extracting the energy from the interrogation beam and backscatters a coded signal, comprising the step of biasing the diode with a battery, whereby the range of the RFID system is improved over an unbiased diode.

29. The method of claim 27, wherein the RFID system includes a transmit antenna and a tag having a SAW device that has an impulse characteristic which codes the output of the tag, and wherein the SAW device is coupled between the diode and the transmit antenna for the tag.

30. The method of claim 27, wherein the diode biasing improves the harmonic response of the diode.

31. The method of claim 27, wherein the step of battery biasing the diode includes utilizing a lithium ion battery.

32. The method of claim 31, wherein the battery is a thin film battery.

33. The method of claim 27, wherein the battery includes a lithium battery having silicon nano wire anodes.

40. The method of claim 27, further comprising increasing the signal-to-noise ratio by frequency sweeping in conjunction with pseudo noise code.

41. The method of claim 27, further comprising correcting for frequency and range with a cross ambiguity function.

42. The method of claim 41, wherein the cross ambiguity function is given by:

Φ

(τ

, f)=|∫

_∞

^∞

s_R(t−

τ

/2)s_T*(t+τ

/2)e<sup>j2π

ft</sup>dt|², wherein s_T(t) is the envelope of the transmitted signal, and s_R(t) is a received signal after frequency-down conversion.

43. The method of claim 27, further comprising correcting for oscillator shift using a frequency estimation system.

44. The method of claim 41, further comprising estimating the proximity of an article using a ranging algorithm.

45. The method of claim 27, wherein the transmitter employs a highly directional antenna.

46. The method of claim 27, further comprising correlating a received signal with an anticipated signal in order to estimate signal amplitude.

34. A method for extending the range of a parasitically-powered regenerative tag that includes a number of diodes in a diode rectifier circuit used to rectify incoming RF energy from an interrogation beam, comprising the step of:

biasing one or more of the diodes in the rectifier circuit with a battery to improve the efficiency of the diode circuit and to extend the range of the tag over that of a tag having unbiased diodes.

35. The method of claim 34, wherein the range extension is 10×

over that of a tag having unbiased diodes.

36. The method of claim 34, wherein said diodes are in a rectenna circuit.

37. The method of claim 36, wherein the rectenna circuit is coupled to an energy storage element and wherein the energy storage element is coupled to a transmitter.

38. The method of claim 37, and further including the step of:

providing a hysteretic switch between the energy storage element and the transmitter, and wherein the hysteretic switch couples the output of the energy storage element to the transmitter upon an output from a nanowatt comparator.

39. The method of claim 34, wherein the transmitter includes a diode oscillator circuit and wherein the frequency to which the output of the transmitter is tuned is determined by an LC circuit coupled to the diode.