This paper reports the design and experimental validation of electronically-steerable transmitarrays at Ka-band. Two transmitarrays with 20×20 and 14×14 elements have been prototyped and full characterized, for an operation in switchable circular or linear polarization. They are based on 1-bit and 2-bit phase quantization tunable unit-cells, respectively. To control locally the transmission phase on the transmitarray aperture, two or four p-i-n diodes have been integrated on each unit-cell for the 1- or 2-bit designs, respectively. The measured broadside gain at 29 GHz of the 1-bit prototype is equal to 20.8 dBic with a 3-dB relative bandwidth of 14.6%. For the 2-bit architecture, the measured broadside gain at 29 GHz is equal to 19.8 dBi with a 3-dB bandwidth of 16.2%.