Design of Monopulse Antenna Difference Patterns with Low Sidelobes*

Abstract

The flexibility of modern monopulse radar antenna systems makes possible the independent optimization of sum and difference patterns. The two parameter difference pattern, developed here for the circular aperature antenna, is designed to have nearly equal sidelobes similar to those of the Taylor sum pattern. The difference pattern is asymptotic to a model difference pattern which has the greatest slope (angle sensitivity) for a given sidelobe level. The model function is unrealizable because it has uniform sidelobes which are infinite in extent. The two parameter difference pattern is realizable and is expressed in a Fourier—Bessel series of N terms in a manner similar to Taylor's treatment of the sum pattern. The other parameter, A, controls sidelobe level. Comprehensive tables of the Fourier—Bessel coefficients are given for both the circular aperture series and the difference pattern series. Directivity and angle sensitivity are investigated and found to have maximum values that decrease as sidelobe level decreases. The monopulse system performance using the asymptotic difference pattern and the Taylor sum pattern compares favorably with a maximum likelihood angle estimation system. Development of a line source difference pattern is presented in the appendix.

Hybrid approach for sub-arrayed monopulse antenna synthesis

“…It takes advantage from both the convex programming (CP) algorithm described in [6] and the CPM [12]. Starting from the knowledge of the optimal difference excitations [8][9] as well as from their relationships with the optimized sum coefficients [10][11], the sub-array configurations are determined as in [12]. Successively, for a given element clustering, the CP procedure is used to compute the sub-array weights.…”

“…In [6], it has been shown that the functional Ψ is convex with respect to G for a given clustering C , while it is not convex (i.e., local minima exist) with respect to C . On the other hand, by exploiting the knowledge of the optimal excitations of the difference beam [8][9], the method proposed in [7] has strongly reduced the solution space to a limited number of sub-array configurations. As a consequence, the occurrence of sub-optimal solutions has been reduced and the convergence of the sub-arraying process improved.…”

Three-Parameter Elliptical Aperture Distributions for Sum and Difference Antenna Patterns Using Particle Swarm Optimization

“…Normalizing with respect to the square root of the areanormalized aperture power would effectively reduce the slope by the taper efficiency; whereas, the normalization of (27) by the peak of the matching sum pattern sets the (dual) peaks of all difference patterns at the same level of about −2 dB and so provides normalization independent of the taper efficiency. Bayliss [18] suggests comparing distributions by relative angle sensitivity, defined as normalizing by the maximum possible slope. The relative angle sensitivity, based on normalization by the matching sum pattern, is defined in (28), where S normT max is the maximum matching-sum-pattern-normalized angle sensitivity for the class of aperture distributions in consideration.…”

“…The most commonly referenced distribution for a difference pattern appears to be that of Bayliss [18], which presents a two-parameter circular aperture distribution as an analog to the Taylorn sum distribution [17]. Section IV in [3] references the discussion in [4] of a circular Bayliss distribution based on multiplying by cos ψ.…”

“…Figure 15 typically found on the edge of a Pareto front. Bayliss [18] reveals that for a difference pattern to realistically achieve maximum relative angle sensitivity with a given maximum PSLL requires that its first sidelobes be of uniform level, and Figures 16(a)-(c) show that the 3PD distributions determined by PSO with those constraints have that very characteristic. …”