G-band frequency-scanned antenna arrays

Beam steering antenna arrays have many applications, from object tracking and localization to landing systems [1]. The main requirements for such a system are usually a wide scanning angle, low beamwidth and constant gain. Beam steering can be obtained electronically, by controlling the relative phase shift between the array elements. This can be achieved by delay elements, as in phased arrays, or by sweeping the carrier frequency [1–4]. The latter are usually easier to implement, but require a wider operating bandwidth for the same scanning angle. In this work, frequency scanned arrays for wide-angle scanning are described. By operating at G-band, the overall size and weight of the antenna can be reduced, thus making it suitable for space applications. Two architectures, based on slotted waveguides and microcoaxial line fed slots, are introduced to provide a wider scanning angle than conventional structures. The devices are fabricated using the PolyStrata process, which enable low-loss feeds at millimeter-wave frequencies. The PolyStrata process involves sequential deposition of copper layers and photoresist on a silicon wafer [5]. Copper layer thicknesses range from 10µm to 100 µm, with gap-to-height and width-to-height aspect ratios of 1:1.2 and 1:1.5, respectively. After the desired layers are deposited, the photoresist filling is rinsed away (“released”) through 200 µm long holes. This process can be used to fabricate air-supported coaxial lines and waveguides at G-band, with slot antennas acting as release holes.