Interleaved Array Antennas Design --- (Almost) Deterministic Strategies

Abstract

The synthesis strategies to be used for designing array antennas implementing the shared-aperture concept are described and discussed. The presented techniques range from fully deterministic approaches to semi-deterministic ones up to purely statistical design strategies. The pros and cons of each technique are ascertained. 1. INTRODUCTION The quest for increasingly performing antenna front-ends has been stimulated in the last years by the necessity of implementing complex functions in radars and communication systems. In particular, modern sensing systems require the (array) antennas to be able to perform a number of concurrent tasks, such as, for instance, operating at difierent frequency bands, difierent polar- izations, difierent scanning directions, etc. The coexistence of several array antennas performing concomitantly the difierent tasks often results in bulky antenna systems that are di-cult to deploy on moving platforms such as ships, airplanes or satellites. A convenient way to address this problem is to co-locate the array antennas responsible for the difierent services (functionalities) to be concurrently provided. The so-called shared-aperture concept (1,2) can then be adopted to realize multi-functional array antennas. The difierent func- tionalities are ascribed to sub-arrays of elementary radiators, the sub-arrays sharing a common physical area that constitute the complete antenna aperture. An early implementation of this concept is reported in (3) where the elementary antennas com- posing the sub-arrays are deployed on interleaved, uniform grids. A later contribution (4) proposed a complementary partition of a linear array in two sub-arrays exhibiting narrow radiation beams and grating lobes free operation. The shared-aperture concept was successively exploited to achieve multi-frequency operation (2) and polarization-agility capability (5). Moreover the possibility to integrate the transmitter and the receiver antennas of a frequency modulated, continuous wave (FMCW) radar by making use of the shared-aperture concept was demonstrated in (6). In this paper, some techniques that can be used to design interleaved array antennas imple- menting the shared-aperture concept are described. The reader is conducted through a path that, starts from strictly deterministic methods, passes through an intermediate step, and leads to fully stochastic approaches. The advantages and drawbacks introduced by the difierent techniques are analyzed in detail. It is worth noting that none of the techniques described in this work invokes any kind of iterative optimization procedure, this enabling a time efiective design strategy for any of the presented methods.