Aaron D. Lanterman

The Rician distribution, which arises in radar, communications, and magnetic resonance imaging, is characterized by a noncentrality parameter and a scale parameter. The Rayleigh distribution is a special case of the Rician distribution with a noncentrality parameter of zero. This paper considers generalized hypothesis testing for Rayleigh and Rician distributions using Rissanen’s stochastic complexity, particularly his approximation employing Fisher information matrices. The Rayleigh distribution is a member of the exponential family, so its normalized maximum likelihood density is readily computed, and shown to asymptotically match the Fisher information approximation. Since the Rician distribution is not a member of the exponential family, its normalizing term is difficult to compute directly, so the Fisher information approximation is employed. Because the square root of the determinant of the Fisher information matrix is not integrable, we restrict the integral to a subset of its range, and separately encode the choice of subset.

Jump-diffusion algorithms are applied to sampling from Bayesian posterior distributions. We consider a class of random sampling algorithms based on continuous-time jump processes. The semigroup theory of random processes lets us show that limiting cases of certain jump processes acting on discretized spaces converge to diffusion processes as the discretization is refined. One of these processes leads to the familiar Langevin diffusion equation; another leads to an entirely new diffusion equation.

Image formation in radio astronomy is often posed as a problem of constructing a nonnegative function from sparse samples of its Fourier transform. We explore an alternative approach that reformulates the problem in terms of estimating the entries of a diagonal covariance matrix from Gaussian data. Maximum-likelihood estimates of the covariance cannot be readily computed analytically; hence, we investigate an iterative algorithm originally proposed by Snyder, O’Sullivan, and Miller in the context of radar imaging. The resulting maximum-likelihood estimates tend to be unacceptably rough due to the ill-posed nature of the maximum-likelihood estimation of functions from limited data, so some kind of regularization is needed. We explore penalized likelihoods based on entropy functionals, a roughness penalty proposed by Silverman, and an information-theoretic formulation of Good’s roughness penalty crafted by O’Sullivan. We also investigate algorithm variations that perform a generic smoothing step at each iteration. The results illustrate that tuning parameters allow for a tradeoff between the noise and blurriness of the reconstruction.

This paper analyzes an unusual active bandpass filter employed in the Buchla Model 295 10 Channel Comb Filter, a synthesizer module developed as part of the Buchla 200 Electric Music Box by Donald Buchla. The filter consists of a peculiar rearrangement of elements in a classic Twin-T configuration; to our knowledge, it has not been previously addressed in the literature. As an example, we explore its specific application in the Model 295.

In 1973, David Blackmer introduced a voltage-controlled amplifier consisting of a pair of negative-positive-negative transistors performing logging and antilogging functions coupled with a complementary positive-negative-positive pair. This “Blackmer cell” has been widely used in studio equipment such as compressors and mixers. The authors consider replacing the bipolar junction transistors with metal-oxide-semiconductor field-effect transistors in the subthreshold region to exploit the resulting exponential voltage/current relationship, particularly focusing on its implementation on a field-programmable analog array. Resistors used for input voltage-to-current conversion and output current-to-voltage current conversion are replaced with operational transconductance amplifiers. Simulations show that the circuit may be expected to work well as a voltage-controlled attenuator but may react catastrophically when attempting gains greater than unity due to the nonlinearity of the output operational transconductance amplifier. The effect of various mismatches in transistor parameters is studied.

We employ right-censored Poisson point process models to develop maximum-likelihood procedures for estimating the time of arrival of transient optical signals subject to saturation distortion. The Poisson intensity is modeled as a template with an unknown scaling factor with additive background counts. Using Monte Carlo simulations, we explore the performance of different algorithms as a function of signal magnitude and saturation threshold. In particular, we characterize the benefit our procedures have over algorithms that are unaware of the censoring.

In this paper, we express Thévenin equivalent circuits seen looking into the terminals of the small-signal model of the vacuum tube triode in terms of the Thévenin equivalent circuits seen looking out of the other terminals and apply them to the analysis of the common-cathode, common-plate, and common-grid single-tube amplifier configurations, as well as a differential pair amplifier. This is an adaptation of equivalent circuit techniques for transistor circuits pioneered by Marshall Leach. The use of equivalent circuits can yield intuitive solutions that avoid solving sets of equations.

This paper explores voltage-controlled amplifier (VCA) designs based on operational transconductance amplifiers (OTAs) on a floating-gate—based Field-Programmable Analog Array (FPAA). Although preconfigured OTAs are available on the target FPAA, their gain must be fixed during the programming stage. Hence, the OTA that forms the variable-gain element the VCA must be constructed from the individual transistors that are also available on the FPAA. The current output of this more-flexible OTA is...

Most research regarding passive radar exploiting ‘illuminators of opportunity’, such as FM radio, has focused on detecting and tracking targets. This study explores adding automatic target recognition (ATR) capabilities to such systems. The ATR algorithms described here use the radar cross‐section (RCS) of potential targets, collected over a short period of time. The received signal model accounts for aircraft position and orientation, propagation losses, and antenna gain patterns. One proposed algorithm uses a coordinated flight model to estimate aircraft orientations, while a more sophisticated algorithm uses an extended Kalman filter to estimate the target orientations along with measures of uncertainty in those estimates. In both cases, the orientations are estimated using velocity measurements obtained from a tracking algorithm. The radar return of each aircraft in the target library is simulated as though each is executing the same manoeuvre as the target detected by the system. To improve the robustness of the result, the more sophisticated algorithm jointly optimises over feasible orientation profiles and target types via dynamic programming.

This paper addresses parameter estimation for an optical transient signal when the received data has been right- censored. We develop an expectation-maximization (EM) algorithm to estimate the amplitude of a Poisson intensity with a known shape in the presence of additive background counts, where the measurements are subject to saturation effects. We compare the results of our algorithm with those of an EM algorithm that is unaware of the censoring. (C) 2018 Optical Society of America