Pattern reconfigurable antennas represent an antenna design class that differs from classical fixed-form, fixed-function antennas in that they can reconfigure and adapt their radiation pattern to fit the requirements of a time varying system. The explosion of the variety of satellite applications in the last two decades demands novel, compact antenna designs that allow the capture of ultra-week signals in the presence of RF interference and multipath. Advances in electromagnetic simulation tools and RF/microwave processing technologies have enabled the design of new compact antennas that can be integrated with high quality RF and microwave active and passive components. This dissertation introduces the concept of pattern reconfigurable antenna in a small form factor using novel reactively loaded spiral antennas. The proposed design allows mitigation of reception of intentional or unintentional RF interference sources in the receivers designed for weak (i.e. satellite signal) reception. Two new antennas capable of reconfigurable pattern control are introduced: a dual polarized spiral antenna and x-spiral (cross-spiral) antenna. The novel approach to the creation of sharp nulls in the antenna radiation pattern is presented. The new antenna designs solved various problems associated with classical approach to spiral antenna design and lead to improvements such as lower overall Axial Ratio and higher efficiency/gain at lower end of operating frequency bandwidth. The relevant background work is described and then the design details, computer simulations and measured experimental results are given.