# A 3-D Metal-Printed Dual-Polarized Ridged Waveguide Slot Array Antenna for X-Band Applications
###### Abstract
The inclined slot suggested in [18] takes the place of the transverse slot to ease fabrication challenges with a simple easy-to-design structure that achieves less than \(-25\) dB cross-polarization in the Ka-band. This result shows that the dual-polarized array has low polarization purity due to the characteristic influence of the inclined slot for the HP. In [19; 20], the authors presented a V-shaped slot structure for an HP array with a good low level of cross-polarization achieved by the combination of the electromagnetic (EM) field perpendicular to both sides of the V-shape. The EM field complements the in-phase horizontal polarized components and eliminates the out-of-phase vertical polarized components. The excitation of the V-shaped slot is through the depth and inclination of the slot, without the need for additional resonant components. The combination of a V-shaped slot array for HP and a longitudinal slot array for VP achieves high polarization purity ideal for dual-polarized arrays. However, the operating bandwidth is still limited, and this is also an inherent disadvantage for resonant waveguide slot arrays. One technique to increase the operating bandwidth is to separate an array into two consecutive subarrays on each side of the feed using a center feed. This also eliminates the beam squinting versus frequency due to the long line effects that occur with the end feed [21]. To facilitate and ease the fabrication of waveguide slot array antennas, three-dimensional (3-D) metal-printing technology has been provided in [22; 23; 24]. It unmistakably demonstrates great benefits, such as accurate machining, high manufacturing efficiency, low cost, and flexibility in structural design. More importantly, opting for monolithic 3-D metal printing helps avoid performance degradation and assembly errors. In this paper, a compact 3-D metal-printed dual-polarized RWSAA is proposed with enhanced performance of wide operating bandwidth, low cross-polarization, high efficiency, and high isolation for X-band applications. In addition to the performance of the array, the configuration factor is also considered in order to provide strong stability with a simple structure, easy manufacturing, and low cost. The dimensions of the waveguides are miniaturized using ridged waveguides and are homogeneity aligned for both VP and HP. At the same time, the distance between the slot elements in the resonant array is also ensured for the horizontal plane. For VP arrays, standard longitudinal slots are employed, whereas V-shaped slots are utilized for HP arrays to create low cross-polarization. The operating bandwidth is improved step by step in the design process by different methods implemented for both the radiated slots and the feed network. Utilizing the structure of periodic unit cells was studied for each pair of slots in VP and HP, separately, and combined with [PERSON]'s design equation to find the optimal resonance values for a 1 \(\times\) 8-element linear array. The central feeding networks are designed for each VP and HP linear slot array, separating an array into two subarrays to expand the operating bandwidth. A two-way power divider providing equal amplitude and a 180\({}^{\circ}\) phase difference is used for the two subarrays of VP. With a T-junction between the radiated waveguide and the coaxial-to-RWG transition in the lower layer, this is excited by a probe attached to the ceiling of the RWG. The HP array uses a direct feed from a coaxial-to-RWG transition that offers equal amplitude and phase to the two subarrays on either side and is excited with a probe attached to the ridge of RWG. The final optimized design of the 2 \(\times\) 8-element dual-polarized array was fabricated by 3-D metal printing. Experimental measurement results are presented to confirm the validity of the design.