Due to the strict size and power constraints of wireless sensor nodes, the design of a compact and energy efficient antenna module with adaptive directive gains is an extremely crucial problem. Conventional solutions are often prohibitive for such applications, as they require multiple radiofrequency (RF) chains that increase dramatically the hardware complexity and the power consumption. Motivated however by the benefits of adaptive antennas, which reflect to significant performance gains in a sensor network, this paper proposes an alternative design with pattern-switching ability, built on parasitic antenna elements that overcomes the aforementioned drawbacks. Indeed, it will be shown that the proposed compact antenna design might be a strong candidate for small-sized sensor nodes with low power constraints, since it requires a single RF chain and provides high directive gain. This implies remarkable hardware and energy savings, but without compromising the performance gains of the sensor network.