Massachusetts Institute of Technology

James Edwin Vian

Benjamin A Miller

Joel Irwin Goodman

Matthew A Herman

Helen Haeran Kim

Jonathan David Chisum

Andrew K Bolstad

An array-based Compressed sensing Receiver Architecture (ACRA) includes an antenna array with two or more antennas connected to two or more ADCs that are clocked at two or more different sampling rates below the Nyquist rate of the incident signals. Comparison of the individual aliased outputs of the ADCs allows for estimation of signal component characteristics, including signal bandwidth, center frequency, and direction-of-arrival (DoA). Multiple digital signal processing (DSP) techniques, such as sparse fast Fourier transform (sFFT), can be employed depending on the type of detection or estimation.

Methods and apparatus for array-based compressed sensing

Complex polyphase nonlinear equalizer (cpNLEQs) mitigate nonlinear distortions generated by complex in-phase/quadrature (I/Q) time-interleaved analog-to-digital converters (TIADCs). Example cpNLEQs upsample the digital waveform emitted by the TIADC, e.g., by a factor of two, then separate the upsampled digital waveform into upsampled in-phase and quadrature components. Processors in the cpNLEQs create real and imaginary nonlinear compensation terms from the upsampled in-phase and quadrature components. The nonlinear compensation terms are downsampled, and the downsampled imaginary nonlinear compensation term is phase-shifted, then combined with the downsampled real component to produce an estimated residual distortion. Subtracting the estimated residual distortion from the digital waveform emitted by the TIADC yields an equalized digital waveform suitable for further processing.

Method and apparatus for complex in-phase/quadrature polyphase nonlinear equalization

Polyphase nonlinear digital predistorters (pNDPs) mitigate nonlinear distortions generated by time-interleaved digital-to-analog converters (TIDACs). Processors in an example pNDP compute nonlinear and linear compensation terms representative of channel mismatches and other imperfections in the TIDAC based on the digital input to the TIDAC. The pNDP subtracts these compensation terms from a delayed copy of the digital input to yield a predistorted digital input. The TIDAC converts on the predistorted digital input into a fullband analog output that is substantially free of nonlinear distortion.

Polyphase nonlinear digital predistortion

Described is a space-time digital power amplifier that can be used to generate an arbitrary waveform for a carrier signal. The space-time digital power amplifier employs temporal modulation of transmit signals generated by an array of transmitter modules. The RF signals transmitted from the array are spatially combined through free space propagation to generate the desired waveform. Advantageously, no digital-to-analog conversion is required and upconversion is unnecessary. The digital power amplifiers for the transmitter modules can be combined in a single chip package. The space-time digital power amplifier enables high power efficiency to be realized using pulse-shaped waveforms thus eliminating any need for the power amplifiers to operate over a wider bandwidth with a spectrally unconfined waveform.

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Westford, MA, United States of America

James Edwin Vian