# US 10,121,030 B1 · Frequency multiplexed radio frequency identification

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- Number: US 10,121,030 B1
- Document ID: US10121030B1
- Status: Granted
- Kind: B1
- Application number: 15/635,704
- Filed: 2017-06-28
- Granted: 2018-11-06
- Earliest claimed: 2016-06-29
- Assignees: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
- Applicants: The United States of America, as represented by the Administrator of the National Aeronautics and Space Administration
- Inventors: Patrick W. Fink; Gregory Y. Lin; Timothy F. Kennedy; Phong H. Ngo; Lucas S. Kinion
- Web page: https://patentgrep.com/patent/US10121030B1

## CPC

- G06K 7/10356: {using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas}
- G06K 7/10069: {the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other (frequency hopping or spread spectrum techniques H04B7/00)}
- G06K 19/0724: {the arrangement being a circuit for communicating at a plurality of frequencies, e.g. for managing time multiplexed communication over at least two antennas of different types}
- H01Q 1/2216: {used in interrogator/reader equipment}
- H01Q 3/40: with phasing matrix
- H01Q 9/0428: {radiating a circular polarised wave}
- H01Q 9/045: {with particular feeding means (for circular polarisation H01Q9/0428)}
- H01Q 21/0075: {Stripline fed arrays (H01Q21/065 takes precedence)}
- H01Q 21/08: the units being spaced along or adjacent to a rectilinear path {(waveguide fed H01Q21/0037)}
- H01Q 21/205: {providing an omnidirectional coverage (turnstile aerials H01Q21/26)}
- H04L 5/08: each combination of signals in different channels being represented by a fixed frequency
- H04L 5/14: Two-way operation using the same type of signal, i.e. duplex
- G06K 19/0726: {the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier}
- G06K 19/07767: {the first and second communication means being two different antennas types, e.g. dipole and coil type, or two antennas of the same kind but operating at different frequencies}
- H01Q 1/2208: {associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems (methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00)}
- H01Q 3/22: varying the orientation in accordance with variation of frequency of radiated wave
- H01Q 15/0013: {said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective}
- H01Q 15/242: {Polarisation converters}
- H04B 1/713: using frequency hopping
- G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04B: TRANSMISSION

## Abstract

A radio frequency identification (RFID) system for frequency multiplexing includes, in one exemplary embodiment, and RFID interrogator configured for generating an RFID signal, wherein a channel frequency of the RFID signal changes over time; a first narrow band antenna, characterized by a first passband, the first passband corresponding to a first range of frequencies; a second narrow band antenna, characterized by a second passband, the second passband corresponding to a second range of frequencies, wherein the second range of frequencies differs from the first range of frequencies, whereby the second passband differs from the first passband; and first and second feed lines configured for feeding the RFID signal to each of the first and second narrow band antennas, respectively. Other embodiments include systems and methods including similar and different RFID components and aspects for frequency multiplexing.

## Claims

### Claim 1

A system comprising:
an RFID interrogator configured for generating an RFID signal, wherein a channel frequency of the RFID signal changes over time;
a first narrow band antenna, characterized by a first passband, the first passband corresponding to a first range of frequencies;
a second narrow band antenna, characterized by a second passband, the second passband corresponding to a second range of frequencies, wherein the second range of frequencies differs from the first range of frequencies, whereby the second passband differs from the first passband; and
first and second feed lines configured for feeding the RFID signal to each of the first and second narrow band antennas, respectively,
wherein the first narrow band antenna is configured to transmit a first electromagnetic wave in response to and at the channel frequency of the RFID signal fed thereto, if the channel frequency of the RFID signal falls within the first passband, and
wherein the second narrow band antenna is configured to transmit a second electromagnetic wave in response to and at the channel frequency of the RFID signal fed thereto, if the channel frequency of the RFID signal falls within the second passband.

### Claim 2 (depends on 1)

The system according to claim 1, wherein each of the first and second narrow band antennas is a respective microstrip antenna.

### Claim 3 (depends on 1)

The system according to claim 1, wherein the first and second narrow band antennas and the first and second feed lines are configured such that the further the channel frequency of the RFID signal falls outside of the first passband, the more closely the first narrow band antenna appears as an open circuit to the RFID signal and the more closely an apparent impedance presented by the first feed line to the RFID signal approaches an infinite impedance, and the further the channel frequency of the RFID signal falls outside of the second passband, the more closely the second narrow band antenna appears as an open circuit to the RFID signal and the more closely an apparent impedance presented by the second feed line to the RFID signal approaches an infinite impedance.

### Claim 4 (depends on 1)

The system according to claim 1, wherein the first electromagnetic wave has a first polarization, and the second electromagnetic wave has a second polarization, the first polarization and the second polarization being characterized by different orientations.

### Claim 5 (depends on 1)

The system according to claim 1, wherein the first feed line feeds the RFID signal to the first narrow band antenna at a first edge of the first narrow band antenna, the second feed line feeds the RFID signal to the second narrow band antenna at a second edge of the second narrow band antenna, the first edge of the first narrow band antenna orthogonal to the second edge of the second narrow band antenna.

### Claim 6 (depends on 1)

The system according to claim 1, wherein the first narrow band antenna is rotated by 90 degrees relative to the second narrow band antenna, whereby the first electromagnetic wave has a first polarization, and the second electromagnetic wave has a second polarization, the first polarization and the second polarization being orthogonal to one another.

### Claim 7 (depends on 1)

The system according to claim 1, further comprising a printed filter, a lumped element filter, or a surface acoustic wave filter configured for filtering the RFID signal based on frequency.

### Claim 8 (depends on 1)

The system according to claim 1, wherein the RFID interrogator is further configured to receive an electromagnetic signal transmitted by an RFID tag in response to the first or second electromagnetic wave transmitted by the first or second narrow band antenna, respectively.

### Claim 9

A system comprising:
an enclosure;
an RFID interrogator configured for generating an RFID signal, wherein a channel frequency of the RFID signal changes over time;
a first narrow band antenna, coupled to the enclosure, characterized by a first passband, the first passband corresponding to a first range of frequencies;
a second narrow band antenna, coupled to the enclosure, characterized by a second passband, the second passband corresponding to a second range of frequencies, wherein the second range of frequencies differs from the first range of frequencies, whereby the second passband differs from the first passband; and
first and second feed lines, configured for feeding the RFID signal to each of the first and second narrow band antennas, respectively,
wherein the first narrow band antenna is configured to transmit a first electromagnetic wave in response to and at the channel frequency of the RFID signal fed thereto, if the channel frequency of the RFID signal falls within the first passband, and
wherein the second narrow band antenna is configured to transmit a second electromagnetic wave in response to and at the channel frequency of the RFID signal fed thereto, if the channel frequency of the RFID signal falls within the second passband.

### Claim 10 (depends on 9)

The system according to claim 9, wherein each of the first and second narrow band antennas is a respective microstrip antenna.

### Claim 11 (depends on 9)

The system according to claim 9, wherein the first and second narrow band antennas and the first and second feed lines are configured such that the further the channel frequency of the RFID signal falls outside of the first passband, the more closely the first narrow band antenna appears as an open circuit to the RFID signal and the more closely an apparent impedance presented by the first feed line to the RFID signal approaches an infinite impedance, and the further the channel frequency of the RFID signal falls outside of the second passband, the more closely the second narrow band antenna appears as an open circuit to the RFID signal and the more closely an apparent impedance presented by the second feed line to the RFID signal approaches an infinite impedance.

### Claim 12 (depends on 9)

The system according to claim 9, wherein the first electromagnetic wave has a first polarization, and the second electromagnetic wave has a second polarization, the first polarization and the second polarization being characterized by different orientations.

### Claim 13 (depends on 9)

The system according to claim 9, wherein the first feed line feeds the RFID signal to the first narrow band antenna at a first edge of the first narrow band antenna, the second feed line feeds the RFID signal to the second narrow band antenna at a second edge of the second narrow band antenna, the first edge of the first narrow band antenna orthogonal to the second edge of the second narrow band antenna.

### Claim 14 (depends on 9)

The system according to claim 9, wherein the first narrow band antenna is rotated by 90 degrees relative to the second narrow band antenna, whereby the first electromagnetic wave has a first polarization, and the second electromagnetic wave has a second polarization, the first polarization and the second polarization being orthogonal to one another.

### Claim 15 (depends on 9)

The system according to claim 9, further comprising a printed filter, a lumped element filter, or a surface acoustic wave filter configured for filtering the RFID signal based on frequency.

### Claim 16 (depends on 9)

The system according to claim 9, wherein the RFID interrogator is further configured to receive an electromagnetic signal transmitted by an RFID tag in response to the first or second electromagnetic wave transmitted by the first or second narrow band antenna, respectively.