Systems and techniques for communication using multiple-input-multiple-output processing of orbital angular momentum modes

Patent metadata

Field	Value
Publication number	US-2017163451-A1
Application number	US-201615372255-A
Country	US
Kind code	A1
Filing date	Dec 7, 2016
Priority date	Dec 7, 2015
Publication date	Jun 8, 2017
Grant date	—

Abstract

A system includes a transmitter having a first transmit device having a first transmit antenna and a first OAM multiplexer designed to receive two input signals and to convert the input signals to orthogonal OAM beams. The first transmit antenna is designed to transmit a first output signal that includes the OAM beams. The transmitter also includes a second transmit device that functions in a similar manner as the first transmit device. A receiver includes a first receive device having a first receive antenna designed to receive the first output signal and a first OAM demultiplexer designed to convert the first output signal to received signals corresponding to the input signals. The receiver also includes a second receive device having similar features as the first receive device. The receiver also includes a MIMO processor designed to reduce interference between the received signals.

First claim

What is claimed is:

1 . A system for radio frequency communication comprising:
a transmitter having:
a first transmit device having a first transmit antenna and a first orbital-angular-momentum (OAM) multiplexer coupled to the first transmit antenna and configured to receive a first input signal and a second input signal, to convert the first input signal to a first OAM beam, and to convert the second input signal to a second OAM beam that is orthogonal to the first OAM beam, the first transmit antenna being configured to transmit a first output signal that includes the first OAM beam and the second OAM beam, and
a second transmit device having a second transmit antenna and a second OAM multiplexer coupled to the second transmit antenna and configured to receive a third input signal and a fourth input signal, to convert the third input signal to a third OAM beam, and to convert the fourth input signal to a fourth OAM beam that is orthogonal to the third OAM beam, the second transmit antenna being configured to transmit a second output signal that includes the third OAM beam and the fourth OAM beam; and
a receiver having:
a first receive device having a first receive antenna configured to receive the first output signal and a first OAM demultiplexer coupled to the first receive antenna and configured to convert the first output signal to a first received signal corresponding to the first input signal and a second received signal corresponding to the second input signal,
a second receive device having a second receive antenna configured to receive the second output signal and a second OAM demultiplexer coupled to the second receive antenna and configured to convert the second output signal to a third received signal corresponding to the third input signal and a fourth received signal corresponding to the fourth input signal, and
a multiple-input-multiple-output (MIMO) processor coupled to the first receive device and the second receive device and configured to reduce interference between the first received signal, the second received signal, the third received signal, and the fourth received signal.

2 . The system of claim 1 , wherein:
the first OAM multiplexer includes:
a first transmit spiral phase plate (SPP) having a thickness that increases about a circumference of the first SPP and a first thickness delta that corresponds to a difference between a minimum thickness of the first SPP and a maximum thickness of the first SPP and configured to convert the first input signal that corresponds to a Gaussian beam to the first OAM beam, and
a second transmit SPP having a thickness that increases about a circumference of the second transmit SPP and a second thickness delta that corresponds to a difference between a minimum thickness of the second transmit SPP and a maximum thickness of the second transmit SPP, and configured to convert the second input signal that corresponds to a Gaussian beam to the second OAM beam;
the second thickness delta is different than the first thickness delta; and the first thickness delta and the second thickness delta are selected such that the first OAM beam is orthogonal to the second OAM beam.

3 . The system of claim 2 wherein the first OAM demultiplexer includes a first receive SPP corresponding to the first transmit SPP and configured to convert the first OAM beam to the first received signal that corresponds to a Gaussian beam, and a second receive SPP corresponding to the second transmit SPP and configured to convert the second OAM beam to the second received signal that corresponds to a Gaussian beam.

4 . The system of claim 1 wherein the first input signal, the second input signal, the third input signal, and the fourth input signal are each modulated to a first modulation frequency that is within a radio frequency band, and the receiver further includes a demodulator positioned between the MIMO processor and a combination of the first receive device and the second receive device and configured to demodulate the first received signal, the second received signal, the third received signal, and the fourth received signal.

5 . The system of claim 4 , wherein:
the demodulator is configured to demodulate the first received signal, the second received signal, the third received signal, and the fourth received signal by a second modulation frequency that is different than the first modulation frequency; and the MIMO processor is further configured to:
receive the first received signal, the second received signal, the third received signal, and the fourth received signal from the demodulator,
further demodulate the first received signal, the second received signal, the third received signal, and the fourth received signal by a third modulation frequency that corresponds to a difference between the first modulation frequency and the second modulation frequency,
determine a frequency delta corresponding to a difference between the first modulation frequency and a sum of the second modulation frequency and the third modulation frequency, and
further adjust the first received signal, the second received signal, the third received signal, and the fourth received signal based on the frequency delta such that the first received signal, the second received signal, the third received signal, and the fourth received signal have frequencies that correspond to baseband frequencies of the first input signal, the second input signal, the third input signal, and the fourth input signal after adjustment.

6 . The system of claim 5 wherein the MIMO processor is configured to further demodulate the first received signal, the second received signal, the third received signal, and the fourth received signal by:
converting each of the first received signal, the second received signal, the third received signal, and the fourth received signal to frequency domain signals;
bandpass filtering the frequency domain signals about the third modulation frequency;
shifting the frequency domain signals by the third modulation frequency;
converting each of the frequency domain signals to time domain signals; and
resampling each of the first received signal, the second received signal, the third received signal, and the fourth received signal.

7 . The system of claim 1 wherein the first transmit antenna and the second transmit antenna are spaced apart by a distance that is sufficiently small that the first OAM beam and the second OAM beam overlap with the third OAM beam and the fourth OAM beam at the first receive antenna and the second receive antenna.

8 . The system of claim 1 wherein the first transmit device includes a first transmit beam splitter positioned between the first OAM multiplexer and the first transmit antenna and configured to combine the first OAM beam and the second OAM beam into the first output signal.

9 . The system of claim 1 wherein the MIMO processor is further configured to reduce interference between the first received signal, the second received signal, the third received signal, and the fourth received signal using an equalizer such that an output of the equalizer for each of the first received signal, the second received signal, the third received signal, and the fourth received signal is represented by an equation y j =Σ i=1 4 {right arrow over (w)} ij *{right arrow over (x)} i where y j represents an output of the equalizer, {right arrow over (w)} ij represents a coefficient vector of the equalizer and corresponds to the interference, {right arrow over (x)} i represents a signal vector of a corresponding received signal, and * represents a convolution operation.

10 . A method for radio frequency communication comprising:
receiving, by a first

Assignees

• Univ Southern California

Inventors

• Willner Alan E
• Ren Yongxiong
• Li Long

Classifications

• H04B7/0413 Primary

  MIMO systems · CPC title

• H04L25/03891

  Spatial equalizers (MIMO diversity systems H04B7/0413) · CPC title

• H04L25/03006 Primary

  Arrangements for removing intersymbol interference · CPC title

• H04B7/08

  at the receiving station · CPC title