Methods and Apparatus for Analog Relay

• US 20180234161A1
• Filed: 02/12/2018
• Published: 08/16/2018
• Est. Priority Date: 02/11/2017
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Ma, Yunfei, Selby, Nicholas, Adib, Fadel
• Granted Patent: US 10,389,429 B2
• Time in Patent Office: Days
• CPC Class Codes: G06K 19/067 Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
• CPC Class Codes: H04B 7/145 Passive relay systems
• CPC Class Codes: H04B 7/15564 Relay station antennae loop interference reduction

Abstract

A full-duplex analog relay may comprise an analog uplink relay and an analog downlink relay, and may relay signals between a transmitter and a backscatter node. The spectrum of the downlink signal transmitted by the downlink relay may be different than the spectrum of the uplink signal received by the uplink relay. Filtering may attenuate leakage from the downlink relay to the uplink relay, and vice versa. The uplink relay may create a phase offset that is opposite in sign and substantially equal in magnitude to the phase offset created by the downlink relay. The downlink and uplink relays, taken together, may created a substantially constant net phase offset. The full-duplex relay may be housed in a vehicle that moves, and may be used to determine spatial coordinates of backscatter sources that are located in the relay'"'"'s environment.

Claims

1. A full-duplex analog relay comprising:

(a) an analog uplink relay; and

(b) an analog downlink relay,

wherein

(i) the downlink relay is configured to receive wireless downlink signals from a transmitter and to transmit the downlink signals to a backscatter node, the downlink signals having a first spectrum when transmitted by the downlink relay,

(ii) the uplink relay is configured to receive wireless uplink signals from the backscatter node and to transmit the uplink signals to the transmitter, the uplink signals having a second spectrum when received by the uplink relay from the backscatter node, the second spectrum being different than the first spectrum,

(iii) the downlink relay includes an analog downlink filter,

(iv) the uplink relay includes an analog uplink filter, and

(v) the uplink and downlink filters are configured to filter the uplink and downlink signals, respectively, in such a way as to attenuate a first leakage and a second leakage, the first leakage being leakage, to the uplink relay, of downlink signals transmitted by the downlink relay, and the second leakage being leakage, to the downlink relay, of uplink signals transmitted by the uplink relay.

2. The full-duplex analog relay of claim 1, wherein:

(a) the downlink relay is configured

(i) to downconvert the downlink signals, to lowpass filter the downlink signals in baseband, and to upconvert the downlink signals, or

(ii) to shift center frequency of the downlink signals and to bandpass filter the downlink signals; and

(b) the uplink relay is configured

(i) to downconvert the uplink signals, to bandpass filter the uplink signals in baseband, and to upconvert the uplink signals, or

(ii) to shift center frequency of the uplink signals and to bandpass filter the uplink signals.

3. The full-duplex analog relay of claim 1, wherein:

(a) the downlink relay is configured to receive the downlink signal at a first center frequency and to transmit the downlink signal at a second center frequency; and

(b) the uplink relay is configured to receive the uplink signal at the second center frequency and to transmit the uplink signal at the first center frequency.

4. The full-duplex analog relay of claim 1, wherein:

(a) the downlink relay is configured to create a first phase offset in the downlink signals;

(b) the uplink relay is configured to create a second phase offset in the uplink signals; and

(c) the second phase offset is opposite in sign and substantially equal in magnitude to the first phase offset.

5. The full-duplex analog relay of claim 1, wherein the full-duplex analog relay is configured to relay the downlink and uplink signals in such a way that, for a specific phase and a specific frequency of downlink signal received by the downlink relay, the downlink and uplink relays together create a net phase offset that is substantially constant, the net phase offset being equal to the absolute value of the difference between the first and second phase offsets.

6. A system comprising two or more full-duplex analog relays, wherein:

(a) each full-duplex analog relay, respectively, in the system comprises

(i) an analog downlink relay that is configured to receive and retransmit wireless downlink signals, and

(ii) an analog uplink relay that is configured to receive and retransmit wireless uplink signals; and

(b) the system is configured to relay the downlink signals and the uplink signals in such a way that

(i) a first full-duplex analog relay in the system receives the downlink signals from a first transmitter,

(ii) a second full-duplex analog relay in the system transmits the downlink signals to a backscatter node,

(iii) the second full-duplex analog relay receives the uplink signals from the backscatter node,

(iv) the first full-duplex analog relay transmits the uplink signals to the first transmitter, and

(v) for each respective full-duplex analog relay in the system

(A) the downlink relay of the respective full-duplex relay transmits at a center frequency that is different than at which all other downlink relays in the system transmit,

(B) the uplink relay of the respective full-duplex relay transmits at a center frequency that is different than at which all other uplink relays in the system transmit,

(C) the downlink signals transmitted by the downlink relay of the respective full-duplex relay have a first spectrum,

(D) the uplink signals received by the uplink relay of the respective full-duplex relay have a second spectrum that is different than the first spectrum,

(E) the downlink relay of the respective full-duplex relay includes an analog downlink filter,

(F) the uplink relay of the respective full-duplex relay includes an analog uplink filter, and

(G) the uplink and downlink filters are configured to filter the uplink and downlink signals, respectively, in such a way as to attenuate a first leakage and a second leakage, the first leakage being leakage, to the uplink relay of the respective full-duplex relay, of downlink signals transmitted by the downlink relay of the respective full-duplex relay, and the second leakage being leakage, to the downlink relay of the respective full-duplex relay, of uplink signals transmitted by the uplink relay of the respective full-duplex relay.

7. A system comprising:

(a) a vehicle; and

(b) a full-duplex analog relay;

wherein

(i) the full-duplex relay is housed in the vehicle,

(ii) the vehicle is configured to move in a trajectory, and

(iii) the full-duplex relay is configured to, at different times while the vehicle moves in the trajectory, relay signals from a first wireless transmitter, in such a way that spatial coordinates of the first wireless transmitter are inferable from the signals relayed by the full-duplex relay and from information about the trajectory.

8. The system of claim 7, wherein:

(a) the system further comprises an optical tracking system, which optical tracking system includes one or more cameras and one or more computers; and

(b) the optical tracking system is configured to track spatial position of the vehicle while the vehicle moves in the trajectory.

9. The system of claim 7, wherein:

(a) the system includes a wireless tracking system that comprises

(i) one or more other wireless transmitters, which one or more other transmitters do not include the first wireless transmitter,

(ii) one or more wireless receivers, and

(iii) one or more computers;

(b) the full-duplex analog relay is configured to receive a set of signals from the one or other transmitters and to retransmit the set of signals to the one or more wireless receivers while the vehicle moves in the trajectory;

(c) the one or more wireless receivers are configured to take measurements of the set of signals; and

(d) the wireless tracking system is configured to track spatial position of the vehicle, based on the measurements taken by the one or more wireless receivers and based on information about spatial coordinates of the one or more other transmitters.

10. The system of claim 7, wherein:

(a) the system includes a wireless tracking system that comprises

(i) wireless receivers, and

(ii) one or more computers;

(b) the wireless receivers are configured to take measurements of the signals at the different times; and

(c) the wireless tracking system is configured to track spatial position of the vehicle, based on the measurements taken by the wireless receivers and based on information about spatial coordinates of the wireless receivers.

11. The system of claim 7, wherein:

(a) the system includes

(i) a wireless receiver, and

(ii) one or more computers;

(b) the wireless receiver is configured to take measurements of the signals at the different times while the vehicle moves through a set of different positions in the trajectory; and

(c) the one or more computers are programmed

(i) to calculate a set of distances, by computing, for each of the different positions, respectively, a distance between the relay and the first wireless transmitter, and

(ii) to calculate, based on the set of distances, spatial coordinates of the first wireless transmitter.

12. The system of claim 11, wherein the one or more computers are programmed to estimate that a distance between the relay and the first wireless transmitter is equal to the shortest distance in a set of calculated distances, each calculated distance, respectively, corresponding to a different direct or indirect path taken by the signals.

13. The system of claim 7, wherein:

(a) the system includes

(i) a wireless receiver, and

(ii) one or more computers;

(b) the wireless receiver is configured to take measurements while the vehicle moves in the trajectory; and

(c) the one or more computers are programmed to determine spatial coordinates of the first wireless transmitter, based on time, as measured in the measurements, at which the wireless receiver detects the signals from the first wireless transmitter.

14. The system of claim 7, wherein:

(a) the system includes

(i) a wireless receiver, and

(ii) one or more computers;

(b) the wireless receiver is configured to take measurements of the signals at the different times while the vehicle moves in the trajectory; and

(c) the one or more computers are programmed to determine spatial coordinates of the first wireless transmitter, based on received signal strength of the signals, as measured in the measurements.

15. A system comprising:

(a) a vehicle;

(b) a full-duplex analog relay;

(c) a first transceiver; and

(d) one or more computers;

wherein

(i) the full-duplex analog relay comprises

(A) an analog uplink relay; and

(B) an analog downlink relay,

(ii) the downlink relay is configured to receive wireless downlink signals from the first transceiver and to transmit the downlink signals to a second transceiver,

(iii) the uplink relay is configured to receive wireless uplink signals from the second transceiver and to transmit the uplink signals to the first transceiver,

(iv) the downlink relay is configured to create a first phase offset in the downlink signals,

(v) the uplink relay is configured to create a second phase offset in the uplink signals, the second phase offset being opposite in sign and substantially equal in magnitude to the first phase offset,

(vi) the full-duplex analog relay is housed in the vehicle,

(vii) the vehicle is configured to move in a trajectory, and

(viii) the full-duplex analog relay is configured to, at different times while the vehicle moves in the trajectory, relay the uplink signals in such a way that spatial coordinates of the second transceiver are inferable from information about the trajectory and from phase of the uplink signals as received by the relay.

16. The system of claim 15, wherein the full-duplex analog relay is configured to relay the downlink and uplink signals in such a way that, for a specific phase and a specific frequency of downlink signal received by the downlink relay, the downlink and uplink relay together create a net phase offset that is substantially constant, the net phase offset being equal to the absolute value of the difference between the first and second phase offsets.

17. The system of claim 15, wherein:

(a) the first transceiver is configured to take measurements of the uplink signals at the different times while the vehicle moves through a set of different positions in the trajectory; and

(b) the system includes one or more computers that are programmed

(i) to calculate a set of distance measurements, by computing, for each of the different positions, respectively, phase of the uplink signals as received by the relay, and

(ii) to calculate, based on the set of distance measurements, spatial coordinates of the second transceiver.

18. The system of claim 15, wherein:

(a) the system further comprises an RFID reader, a first RFID tag and a second RFID tag;

(b) the first transceiver is a component of the reader;

(c) the second transceiver is a component of the first tag;

(d) the first tag is configured to be wirelessly powered; and

(e) the second tag and the relay are housed in the vehicle.

19. The system of claim 18, wherein the system further comprises one or more computers that are programmed to perform a division in such a way that:

(a) the division comprises dividing a numerator by a denominator to calculate a quotient;

(b) the numerator is a signal from the first tag, as measured by the reader after being relayed by the relay;

(c) the denominator is a signal that is measured by the reader and that is from the second tag which is housed with the relay in the vehicle;

(d) the quotient is a signal that has a phase; and

(e) the phase of the quotient depends on a first distance and does not depend on a second distance, the first distance being distance between the first tag and the full-duplex analog relay, and the second distance being distance between the full-duplex analog relay and the reader.

20. The system of claim 15, wherein:

(a) the second transceiver comprises a backscatter node;

(b) the system is configured in such a way that

(i) the downlink signals have a first spectrum when transmitted by the downlink relay, and

(ii) the uplink signals have a second spectrum when received by the uplink relay from the second transceiver, the second spectrum being different than the first spectrum;

(c) the downlink relay includes an analog downlink filter;

(d) the uplink relay includes an analog uplink filter; and

(e) the uplink and downlink filters are configured to filter the uplink and downlink signals, respectively, in such a way as to attenuate a first leakage and a second leakage, the first leakage being leakage, to the uplink relay, of downlink signals transmitted by the downlink relay, and the second leakage being leakage, to the downlink relay, of uplink signals transmitted by the uplink relay.