National Instruments Corporation

Nikhil A Deshmukh

Baijayanta Ray

Ramesh Krishnan

Michael Loehning

Prakash Sethia

Dynamic range of radio frequency transmitters and receivers may be improved via a multiple-channel phasor configuration in which channels are phased in a manner that distributes the local oscillator phases over π/2 radians. A multiple-channel phasing receiver may include a power splitter to split an input signal into multiple signals, and may further include multiple single-channel receivers providing intermediate signals. Each single-channel receiver may have an input that receives a respective signal of the multiple signals, and may further have an output to provide a respective intermediate signal as a function of the respective input signal, a total gain applied to the respective input signal, a signal frequency of the local oscillator signal, and a respective phase of the local oscillator signal. The multiple-channel receiver may include a digital signal processor that combines the plurality of intermediate signals into a single output signal. A multiple-channel transmitter/transceiver may be similarly implemented.

Dynamic range extension of radio frequency signals using phasing of two or more IQ channels

A system and method for performing frame and symbol timing synchronization on samples of a received signal that includes a series of frames. Each frame includes a known preamble and payload data. A start-of-frame time is estimated by scanning the received signal samples for the self similarity of two successive preambles. A carrier frequency offset (CFO) is estimated by maximizing a correlation between a magnitude spectrum of the received signal and a magnitude spectrum of a known preamble model. A fine estimate for the CFO is determined by computing a phase difference between samples separated by p repetitions of the base pattern for various values of index p, and computing a slope of a least squares affine fit to the phase differences. Additional operations are performed to find an optimal symbol starting point, to perform carrier phase synchronization and to detect the start of payload data.

Frame and symbol timing recovery for unbursted packetized transmissions using constant-amplitude continuous-phase frequency-modulation

Frame and carrier synchronization for unbursted packetized transmissions using constant-amplitude continuous-phase frequency-modulation

System and method for evaluating a transmitter by estimating IQ impairments in an orthogonal frequency division multiplexed (OFDM) signal generated by the transmitter. The OFDM signal may be received. The OFDM signal may represent a stream of symbols, each comprising a plurality of subcarriers. At least a subset of the subcarriers may be pilot subcarriers. The pilot subcarriers may be grouped into one or more groups of pilot subcarriers based on one or more conditions: a pilot subcarrier which satisfies a condition in its relation to a mirror subcarrier may be grouped with other pilot subcarriers which also satisfy the condition in relation to mirror subcarriers. An estimate of one or more of gain imbalance or quadrature skew of the OFDM signal may be calculated based on the one or more groups of pilot subcarriers and the one or more conditions. The estimate may be used to evaluate the transmitter.

Growing community of inventors

Bengaluru, India

Nikhil A Deshmukh