# Feasibility Investigation of SIW Cavity-Backed Patch Antenna Array for Ku Band Applications  
[PERSON]  
1 Dipartimento di Ingegneria Elettrica e dell'Informazione, Politecnico di Bari Via Orabona 4, 70125 Bari, Italy; [EMAIL_ADDRESS] (O.L. ); [EMAIL_ADDRESS] (V.P.) 2 Dipartimento di Ingegneria, Universita di Perugia, Via [PERSON] 93, 06123 Perugia, Italy; [EMAIL_ADDRESS]
3R&D Department, Somacis Spa, Via Jesina 17, 60022 Castelfidardo, Italy; [EMAIL_ADDRESS] (F.B. ); [EMAIL_ADDRESS] (PS. ); [EMAIL_ADDRESS] (C.R. ); [EMAIL_ADDRESS] (P.C.) 4 Dipartimento di Ingegneria dell'Informazione, Universita Politecnica delle Marche Via Brecce Bianche, 60131 Ancona, Italy; [EMAIL_ADDRESS]  
4 Correspondence: [EMAIL_ADDRESS]; Tel. : +39-080-59637814  
at a single frequency, they typically exhibit a narrow relative bandwidth of about 2%; this is a strong drawback that prevents their usage in wide-band applications. There are various approaches to enhance the bandwidth including the employment of suspended substrates, multi-stack [1; 2; 3], and metalized baking cavities [4; 5; 6; 7]. Substrate integrated waveguide (SIW) technology has been largely employed for the construction of couplers, filters, oscillators, amplifiers, mixers, in addition to antennas since it allows for low-cost implementation, fast prototyping, and precise manufacturing [8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. It can be used to improve the antenna radiation characteristics, thus obtaining better performances than those of the conventional microstrip/printed board circuits (PCB) while maintaining the typical advantages of planar technologies. In fact, SIW technology allows for low cost, lightness, easy integration with both passive and active devices, high power levels, feasible mass production, and manufacturing repeatability. Several SIW cavity-backed antennas and feeding geometries have been reported in the literature [16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. For example, a reconfigurable SIW Cavity-Backed Slot (SIW-CBS) antenna with a one octave tuning range and six different tuning states was presented in [16]. A new tuning method based on loading the SIW cavity with shortening posts and manipulating the field distribution within the cavity was proposed. In [17], a SIW-slot feeding structure was introduced in a fully substrate-integrated thin Fabry-Perot cavity (FPC) antenna in order to achieve boresight radiation free of beam squint and low backward radiation levels. Moreover, a single patch with truncated corners has been developed to provide a linear polarized antenna in SIW technology for the Ku-band range of frequency [18]. This technology has been recently proposed as an example in the 57-71 GHz band for 5G [23], X-band [24], and dual-band in K-band [25] applications. In this paper, a broadband SIW cavity-backed microstrip patch antenna was designed and optimized for radiation in the Ku band. Starting from the antennas reported in [18; 26; 27], the patch geometry has been enhanced by introducing lateral cuts and asymmetric feeding of each single radiating element to obtain a wider operation band and frequency downshift. This means that the radiating elements are smaller, allowing more space for the feeding network and improving the isolation among transmission lines. In addition, the particular shape of the radiating element allows for the use of a simpler matching network to the feeding line. A 16 \(\times\) 16 element array was designed and fabricated to obtain a pre-prototype antenna. In particular, the radiating element spacing was optimized to minimize the secondary grating lobes while using the maximum allowable space in the substrate backplane. The single element antenna as well as the antenna arrays were fabricated by using two substrates (top and bottom ones) of the same material and different thicknesses. The top substrate contained the feeding network and patches. Each patch element of the array was coupled with an optimized SIW cavity (backed) lying in the bottom substrate.