National Instruments Corporation

Ramesh Krishnan

Vijaya Yajnanarayana

I Zakir Ahmed

Krishna Bharadwaj

Nikhil A Deshmukh

Prakash Sethia

A low complexity system and method for operating a receiver in order to estimate an offset between the actual sample clock rate 1/T' of a receiver and an intended sample clock rate 1/T. The receiver captures samples of a received baseband signal at the rate 1/T&#x2032;, operates on the captured samples to generate an estimate for the clock rate offset, and fractionally resamples the captured samples using the clock rate offset. The resampled data represents an estimate of baseband symbols transmitted by the transmitter. The action of operating on the captured samples involves computing an error vector signal and then estimating the clock rate offset using the error vector signal. The error vector signal may be computed in different ways depending on whether or not carrier frequency offset and carrier phase offset are assumed to be present in the received baseband signal.

Estimation of sample clock frequency offset based on error vector magnitude

Using error vector magnitude to estimate sample clock frequency offset

Estimation of sample clock frequency offset using error vector magnitude

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.

IQ impairment estimation in an OFDM signal

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Bengaluru, India

Ramesh Krishnan