Direct conversion (from RF to complex I and Q baseband in one mixing step) architectures are increasingly popular as they enable lower implementation costs. The resulting frequency dependent amplitude and phase imbalance between the I and Q conversion rails can cause significant performance degradations to complex modulation techniques such as 64-QAM and above typically used for high data rate transmission. Conventionally, this IQ imbalance is only corrected at the receiver at power up while the imbalance at the remote transmitter is assumed to be pre-corrected. However, aging, manufacturability, and temperature variations can be difficult to calibrate and can result in performance degradation (e.g., range reduction, etc.). Future ad hoc networks will also require imbalance correction per packet as they might come from many different transmitters. in this paper, we propose an adaptive scheme in the receiver to correct the IQ imbalances at the remote transmitter as well as the receiver. The proposed scheme, as it jointly corrects remote transmitter and local receiver I imbalances in the presence of frequency and timing rate offsets, is therefore more robust than the earlier results.

Direct conversion architectures are increasingly popular as they enable lower implementation costs. However, the receiver is very sensitive to IQ imbalances in particular for complex modulation techniques such as 64-QAM and above typically used for high data rate transmission. Conventionally, this IQ imbalance is only corrected at the receiver while the imbalance at the remote transmitter is assumed to be pre-corrected. However, aging, manufacturability, and temperature variations can be difficult to calibrate and can result in performance degradation (e.g., range reduction, etc.). We propose an adaptive scheme in the receiver to correct the IQ imbalances at the remote transmitter as well as the receiver. The proposed scheme, as it jointly corrects the IQ imbalances, is therefore more robust than the earlier results.

This paper presents a solution for the output signal-to-noise ratio of a bandpass nonlinearity which is attractive for numerical evaluations of certain nonlinearities of interest. The solution is obtained by solving a differential equation which results in an expression for thenth order Chebyshev transform of an odd-order nonlinearity in terms of the(n - 1)st-order Chebyshev transform of the derivative of the nonlinearity. The particular cases treated included a linear-logarithmic amplifier, an arctangent limiter, and a piecewise-linear limiter. The approach and results are related to previous efforts.

The one-sided (or line-by-line) recursive filtering problem for a two-parameter Gaussian random signal in additive white Gaussian noise is considered. For a reasonably large class of models for the signal dynamics, both the filtering equation and the generalized Riccati equation explicitly obtained. As an example, the Riccati equation is solved to give the filter gain in a time-in-variant case and is compared with the infinite-time limiting solution to the Wiener filter solution obtained by spectral factorization techniques.

Application of sequential testing to a Markovian model of cardiac rhythm intervals is investigated. An approximate expression for the expected number of observations is obtained for Wald's sequential test under dependent sampling. The interclass separability of three selected cardiac rhythms is then determined, and the results are used to evaluate the feasibility of an on-line implementation of a sequential classification procedure in a coronary care ward.