The present invention relates to an ambient backscattering communication system (14), the communication system (14) comprising: an ambient backscattering transmitter (16) suitable for generating an ambient backscattering signal according to a first polarization from an ambient signal incident on the transmitter (16), an ambient backscattering receiver (18) suitable for detecting the ambient backscattering signal transmitted by the ambient backscattering transmitter according to a second polarization, and a reduction device (22) for reducing the interference between the ambient backscattering signal and an ambient signal incident on the receiver, the reduction device (22) controlling the first polarization and the second polarization and wherein at least one of said first and second polarizations is adjustable.

A carrier-phase recovery method includes: (i) applying a first carrier-phase recovery algorithm to complex-valued symbols of a signal received by a product detector, yielding coarse phase-estimates, the signal being modulated per an M-QAM scheme; (ii) modelling the coarse phase-estimates as a weighted sum of M probability-density functions of an M-component mixture model; (iii) optimizing the M probability-density functions with an expectation-maximization algorithm to yield M optimized probability-density functions; (iv) mapping, based on the M optimized probability-density functions, the coarse phase-estimates to one of M symbols corresponding to the QAM scheme, each coarse phase-estimate mapped to a same symbol belonging to a same one of M clusters; (v) applying a second carrier-phase recovery algorithm to each of the M clusters to generate refined phase-estimates each corresponding to a respective coarse phase-estimate; and (vi) mapping, based on the M optimized probability-density functions, each refined phase-estimate to one of the M symbols.

An apparatus for interpolation of polar signals in RF transmitters is disclosed. The apparatus comprises an estimation circuit configured to receive an input in-phase (I) quadrature (Q) signal comprising a plurality of input IQ samples having a first sampling rate associated therewith, and determine a selection metric value indicative of a position of an IQ trajectory associated with one or more input IQ samples of the input IQ signal. The apparatus further comprises a selection circuit configured to receive the input IQ signal and the selection metric value; and adaptively provide the input IQ signal to a first interpolation circuit that implements a first interpolation method or to a second interpolation circuit that implements a second, different interpolation method, for generating interpolated polar samples at a second, different sampling rate, from the input IQ signal, based on the selection metric value.

The present invention is a transmission/reception method in which a reception device measures propagation path characteristics of a communication propagation path, a transmission device generates, based on a measurement result of the propagation path characteristics, a plurality of pseudo propagation path characteristics having propagation path characteristics similar to the propagation path characteristics so as to have low mutual correlation, the transmission device generates a data group including a plurality of parallel and independent data in the same number as the plurality of pseudo propagation path characteristics in a baseband on a transmitting side, obtains a transmission signal by synthesizing a plurality of superimposed data generated by superimposing the pseudo propagation path characteristics on the data one by one, and transmits a plurality of pseudo propagation path characteristic information relating to the plurality of pseudo propagation path characteristics and the transmission signal, and the reception device receives the plurality of pseudo propagation path characteristic information transmitted antecedently from the transmission device and a communication signal transmitted subsequently, and individually extracts the plurality of data from the communication signal based on the plurality of pseudo propagation path characteristic information.

The present invention is a transmission/reception method in which a reception device measures propagation path characteristics of a communication propagation path, a transmission device generates, based on a measurement result of the propagation path characteristics, a plurality of pseudo propagation path characteristics having propagation path characteristics similar to the propagation path characteristics so as to have low mutual correlation, the transmission device generates a data group including a plurality of parallel and independent data in the same number as the plurality of pseudo propagation path characteristics in a baseband on a transmitting side, obtains a transmission signal by synthesizing a plurality of superimposed data generated by superimposing the pseudo propagation path characteristics on the data one by one, and transmits a plurality of pseudo propagation path characteristic information relating to the plurality of pseudo propagation path characteristics and the transmission signal, and the reception device receives the plurality of pseudo propagation path characteristic information transmitted antecedently from the transmission device and a communication signal transmitted subsequently, and individually extracts the plurality of data from the communication signal based on the plurality of pseudo propagation path characteristic information.

An orientation tracking system for a moving platform includes a transmitter which generates an beam having a known polarization with respect to a predefined coordinate system. The moving platform includes an ellipsometric detector capable of detecting the polarized beam when within the line-of-sight of the transmitter, and measuring its polarization state. The polarization state indicates the rotational orientation of the moving platform with respect to the predefined coordinate system. The beam could also be used to convey guidance commands to the platform.

A carrier-phase recovery method includes: (i) applying a first carrier-phase recovery algorithm to complex-valued symbols of a signal received by a product detector, yielding coarse phase-estimates, the signal being modulated per an M-QAM scheme; (ii) modelling the coarse phase-estimates as a weighted sum of M probability-density functions of an M-component mixture model; (iii) optimizing the M probability-density functions with an expectation-maximization algorithm to yield M optimized probability-density functions; (iv) mapping, based on the M optimized probability-density functions, the coarse phase-estimates to one of M symbols corresponding to the QAM scheme, each coarse phase-estimate mapped to a same symbol belonging to a same one of M clusters; (v) applying a second carrier-phase recovery algorithm to each of the M clusters to generate refined phase-estimates each corresponding to a respective coarse phase-estimate; and (vi) mapping, based on the M optimized probability-density functions, each refined phase-estimate to one of the M symbols.

An apparatus for interpolation of polar signals in RF transmitters is disclosed. The apparatus comprises an estimation circuit configured to receive an input in-phase (I) quadrature (Q) signal comprising a plurality of input IQ samples having a first sampling rate associated therewith, and determine a selection metric value indicative of a position of an IQ trajectory associated with one or more input IQ samples of the input IQ signal. The apparatus further comprises a selection circuit configured to receive the input IQ signal and the selection metric value; and adaptively provide the input IQ signal to a first interpolation circuit that implements a first interpolation method or to a second interpolation circuit that implements a second, different interpolation method, for generating interpolated polar samples at a second, different sampling rate, from the input IQ signal, based on the selection metric value.

A carrier-phase recovery method includes: (i) applying a first carrier-phase recovery algorithm to complex-valued symbols of a signal received by a product detector, yielding coarse phase-estimates, the signal being modulated per an M-QAM scheme; (ii) modelling the coarse phase-estimates as a weighted sum of M probability-density functions of an M-component mixture model; (iii) optimizing the M probability-density functions with an expectation-maximization algorithm to yield M optimized probability-density functions; (iv) mapping, based on the M optimized probability-density functions, the coarse phase-estimates to one of M symbols corresponding to the QAM scheme, each coarse phase-estimate mapped to a same symbol belonging to a same one of M clusters; (v) applying a second carrier-phase recovery algorithm to each of the M clusters to generate refined phase-estimates each corresponding to a respective coarse phase-estimate; and (vi) mapping, based on the M optimized probability-density functions, each refined phase-estimate to one of the M symbols.

Circuitry and methods are described for digital signal demodulation. In a configurable receiver, a method includes receiving a radio frequency signal at the configurable receiver, operating the configurable receiver in a first mode, the first mode including providing the radio frequency signal to an amplitude detection circuit to determine an amplitude, providing the radio frequency signal to a phase detection circuit to determine a phase, and providing the amplitude and phase to a coordinate rotation digital computer (CORDIC) logic circuit, and operating the configurable receiver in a low power mode upon receiving an indication to selectively disable the amplitude detection circuit, the low power mode including providing the radio frequency signal to the phase detection circuit to determine the phase, and providing the phase and a predetermined constant value in lieu of the amplitude to the CORDIC logic circuit.