This thesis compares the Peak Sidelobe Levels (PSLs) of the beam patterns of filled and sparse arrays as a function of aperture both with numerical simulations and experimental data. Four array geometries are compared. A Uniform Linear Array (ULA) evenly spaces sensor elements to achieve low PSLs. Minimum Redundancy Arrays (MRAs) and Minimum Hole Arrays (MHAs) span the equivalent aperture of a ULA with fewer sensors. Another category of sparse arrays, Co-prime Sensor Arrays (CSAs) interleave a pair of ULAs undersampled by co-prime factors. CSA measurements can be processed by either conventional delay-and-sum processing or product processing of the subarrays. This work finds that the PSLs of MRAs, MHAs and the conventionally processed CSAs are much higher than the ULA PSL and nearly insensitive to aperture extension. In contrast, CSA product processing decreases the PSL with increasing aperture, eventually matching the PSL of a ULA. The PSLs measured from experimental data support the theoretical findings..