METHODS AND APPARATUS FOR RFID TAG COMMUNICATIONS
The present invention provides backscatter interrogators, communication systems and backscatter communication methods. According to one aspect of the present invention, a backscatter interrogator includes a data path configured to communicate a data signal; a signal generator configured to generate a carrier signal; and a modulator coupled with the data path and the signal generator, the modulator being configured to spread the data signal to define a spread data signal and amplitude modulate the carrier signal using the spread data signal, the modulator being further configured to phase modulate the carrier signal.
1 - 47 . (canceled)
48 . A method of monitoring inventory, comprising:
transmitting a command signal, the command signal generated by:
spreading a data signal to define a spread data signal; and
amplitude and phase modulating the spread data signal;
transmitting an un-modulated signal;
receiving a return signal that identifies a tagged object, the return signal being responsive to the command signal; and
discriminating the tagged object from a potentially large lot of tagged objects using at least the received return signal, thereby allowing for the monitoring of inventory.
49 . The method according to claim 48 , further comprising selectively inverting the spread data signal.
50 . The method according to claim 49 , wherein the phase modulating of the carrier signal is responsive to the inverting.
51 . The method according to claim 49 , further comprising synchronizing the inverting with the spread data signal.
52 . The method according to claim 48 , further comprising randomly inverting the spread data signal using a pseudo-noise sequence.
53 . The method according to claim 48 , further comprising band limiting the spread data signal.
54 . The method according to claim 48 , wherein the spreading comprises encoding a pseudo-noise sequence with the data signal.
55 . The method according to claim 48 , further comprising mounting a tag to the tagged object.
56 . The method according to claim 48 , further comprising mounting a tag to each of a large lot of tagged objects.
57 . A method of monitoring inventory, comprising:
transmitting an interrogation signal, the interrogation signal intended to elicit a response that identifies an object, the interrogation signal generated by:
spreading a data signal to generate a spread data signal; and
modulating a carrier signal using the spread data signal to suppress the carrier signal during communication of the carrier signal;
transmitting a continuous radio frequency signal;
receiving a response to the interrogation signal, the response identifying an object; and
discriminating the object from a potentially large lot of tagged objects using at least the received response thereby allowing for the monitoring of inventory.
58 . The method according to claim 57 , further comprising band limiting the spread data signal.
59 . The method according to claim 57 , wherein the modulating comprises amplitude modulating and phase modulating using the spread data signal.
60 . The method according to claim 57 , where the response is generated by:
spreading a response data signal to define a response spread data signal;
amplitude modulating a response carrier signal using the response spread data signal; and
phase modulating the response carrier signal.
61 . The method according to claim 60 , further comprising selectively inverting the response spread data signal.
62 . The method according to claim 61 , wherein the phase modulating is responsive to the inverting.
63 . The method according to claim 61 , further comprising synchronizing the inverting with the response spread data signal.
64 . The method according to claim 60 , further comprising randomly inverting the response spread data signal using a pseudo-noise sequence.
65 . The method according to claim 60 , further comprising band limiting the response spread data signal.
66 . The method according to claim 60 , wherein the spreading comprises encoding a pseudo-noise sequence with the response data signal.
67 . The method according to claim 57 , further comprising mounting a tag to the object, the tag being configured to generate the response.
68 . The method according to claim 57 , further comprising mounting a tag to each of the potentially large lot of tagged objects.
69 . A method of monitoring inventory, comprising:
spreading a data signal to define a spread data signal;
selectively inverting the spread data signal;
amplitude modulating a carrier signal using the spread data signal;
communicating the modulated carrier signal; and
transmitting a continuous un-modulated radio frequency signal;
wherein the acts of spreading, selectively inverting, amplitude modulating and communicating allow for the discriminating of an object from a potentially large lot of tagged objects, the ability to discriminate among objects allowing for the monitoring of inventory.
70 . The method according to claim 69 , further comprising phase modulating the carrier signal responsive to the inverting.
71 . The method according to claim 69 , further comprising phase modulating the carrier signal using a tri-level signal corresponding to the inverted data signal.
72 . The method according to claim 69 , wherein the inverting comprises random inverting using a pseudo-noise sequence.
73 . The method according to claim 69 , further comprising band limiting the spread data signal.
74 . A method of tracking inventory, comprising:
affixing a radio frequency device to an object of inventory;
disposing said object with said affixed device in a warehouse;
transmitting a command signal, the command signal generated by:
spreading a data signal to define a spread data signal; and
amplitude and phase modulating the spread data signal;
entering into a continuous wave mode;
receiving a return signal that identifies the object, the return signal being responsive to the command signal; and
discriminating the object from a plurality of other objects using at least the received return signal.
75 . The method of claim 74 , further comprising transmitting an un-modulated carrier after said command signal is transmitted.
76 . The method of claim 75 , wherein said return signal is phase shift keyed.
77 . The method of claim 74 , wherein said return signal is phase modulated.
78 . The method of claim 77 , wherein said phase modulation of said return signal comprises phase shift keying.
79 . A method of tracking inventory, comprising:
affixing a radio frequency device to an object of inventory;
disposing said object with said affixed device in a warehouse;
transmitting a command signal, the command signal generated by amplitude modulating, phase modulating, and frequency-hopping a data signal;
entering into a continuous wave mode;
receiving a return signal that identifies the object, the return signal being responsive to the command signal; and
discriminating the object from a plurality of other objects using at least the received return signal.
80 . The method of claim 79 , further comprising transmitting an un-modulated carrier after said command signal is transmitted.
81 . The method of claim 80 , wherein said return signal is phase shift keyed.
82 . The method of claim 79 , wherein said return signal is phase modulated.
83 . The method of claim 82 , wherein said phase modulation of said return signal comprises phase shift keying.