The coding periodic element is able to achieve coded reconfigurable electromagnetic (EM) responses by loading controllable electronic devices. In this work, an electronically controllable ultrathin planar periodic element structure in Ku band is implemented with one PIN diode. When the PIN diode turns ON or OFF by applying a proper biasing voltage, the resonant property of the element changes correspondingly, and hence a 180° phase difference between the two states is obtained. By optimizing the geometrical parameters, the reflection loss less than 0.5 dB is achieved by the proposed element. Therefore, using a proper biasing voltage control network, the PIN diodes of the proposed elements in a periodic arrangement are set at different states, which may be denoted by a binary string with "1"s or "0"s, and the whole array of elements operates as a binary coding periodic structure and exhibits controllable EM functionalities. In order to verify the coding property of the proposed element, the general principle for the biasing circuit design is given. An optimized biasing circuit is thoroughly studied using both field distribution analysis and equivalent circuit theory. Simulated results show that the specially designed biasing hardly affects the element reflection performance. Finally, a group of element prototypes are fabricated with welded PIN diodes and measured using the standard waveguide test method. The difference in mirror image between the waveguide test and the desired periodic arrangement is also discussed. The experimental results validate that the proposed element successfully achieves good coding EM performance by controlling its biasing voltage. The reflection loss of the element is very low, and well distributed phase difference between the two element states is observed. The simulation and experiment results agree well, and the deviation between them is analyzed in detail. The proposed element possesses distinctive favorable features such as coded controllable EM functionalities, simple structure and ultrathin profile, thus exhibiting the promising prospects in tunable stealth surface, agile antennas, and many other applications.