This Letter presents the design of a low-profile and low-cost transmitarray antenna operating at 122 GHz. The transmitarray design is based on unit-cells with 1-bit phase resolution. A single RO4350B substrate layer is used to form the unit-cells resulting in a total thickness of 0.326 mm. A wideband shift in the transmission phase of 180° is generated by rotating one metal layer of the unit-cell by 180°. The simulation of the transmitarray with 30 × 30 elements and a feed distance of 35 mm shows a maximum directivity of 28 dBi at 122 GHz. Steering angles of 0° and 15° are investigated. Measurements of the fabricated transmitarrays are performed with an open waveguide and a package antenna as feed showing similar results but slightly different maximum relative gain values of 11.8 and 9.5 dB for the 0° version. The measured main beam directions are in good agreement with the simulations and the design values.
