Peter J. Kajenski

Comparison of two theories of angle glint: polarization considerations

Angle glint can be explained as distortions in the radar echo signal phase front, or alternatively, deviations of the direction of power flow from the radial direction. Here we show that these two theories yield identical results when the polarization of the scattered waves and the receiving antenna are considered.

Phase Only Antenna Pattern Notching Via a Semidefinite Programming Relaxation

A phase-only method of generating notches in the beam pattern of a phased array antenna is described. It is shown how the problem can be formulated as a semidefinite programming problem, and solved with readily available solvers. Numerical results simulating the performance of a 32 element uniform linear array are presented.

Phase-only monopulse pattern notching via Semidefinite Programming

A phase-only method of generating notches in the difference beam pattern of a phased array antenna is described. Numerical results are presented for a 32 element uniform linear array utilizing a Bayliss weighting.

Mismatch filter design via convex optimization

Mismatch filters are generally used to reduce the range sidelobes when phase-coded waveforms are used. It is shown that such mismatch filters can be designed with convex optimization techniques by formulating the problem as a second-order cone programming problem. It is also shown that it is possible to make trade-offs between peak sidelobe levels and losses in the main peak gain.

Particle Swarm Optimization of Reduced-size HF Dipoles

Particle swarm optimization is a stochastic evolutionary computation technique that emulates the behavior of swarms. The algorithm was used to optimize the design of reduced-size meandered line and end-loaded dipoles. The performance characteristics of both styles of antenna, optimized to the same criteria, are compared

A circularly polarized mixed loop-dipole yagi antenna

A circularly polarized antenna was designed using dipoles for the driven elements, and loops for the reflector and director elements. The optimization of the antenna was performed using the Particle Swarm Optimization (PSO) and Bounded Optimization By Quadratic Approximation algorithms (BOBYQA). Both algorithms yielded identical results, though the execution times for the BOBYQA routine proved to significantly shorter.

Chirp sine and cosine transforms for a split-step propagation algorithm

Split-step propagation algorithms are widely used to model the propagation of fields in complex environments. Typically one of the slowest steps in such an algorithm is the computation of the forward and inverse transforms. Chirp versions of the sine and cosine transforms were derived, to allow modification of the number of points used in the transforms according to the detail needed in a particular region.

Using 2D Chirp z-Transforms for Near-field to Far-field Calculations

Phased arrays for radar applications are typically characterized in an instrumented near field range (NFR), and the far-field parameters are computed from these measurements. The advantages of using a 2D chirp z-transform for the far-field computations are considered

HF meandered line dipoles optimized with simulated annealing

Electrically small meandered line dipoles for HF (28 MHz) are proposed. The antennas are less than 40% of the length of a conventional half wave dipole, and are self-resonant. The spacing and size of the meandered loops are optimized using simulated annealing; a prototype was constructed to verify the design. Experimental results are consistent with numerical predictions.

An HF batwing antenna

The batwing antenna is widely used at UHF frequencies, and typically has a 1.1:1 VSWR bandwidth of 30% or more. Particle Swarm Optimization was used to design HF versions of the antennas, which demonstrate a similarly wide VSWR bandwidth.