In recent decades, frequency selective surfaces (FSS) have attracted a great deal of interest due to their widespread application. The FSS is a periodic structure generally composed of single-layer or multi-layer elements arranged in a periodic manner in two dimensions. The FSS has frequency selection characteristics for the propagation of electromagnetic waves in space, meaning that it can flexibly manipulate the electromagnetic response characteristics at different frequencies, which is equivalent to a spatial electromagnetic wave filter. Meanwhile, the FSS can be applied to reduce the radar cross section of communication systems and antennas and protect these systems from external interference. It has been widely used in radomes [1], [2], [3], spatial filters [4], [5], [6], and other fields [7], [8], [9].

In communication applications, polarization is among the most fundamental properties of electromagnetic waves. Polarization converter (PC) is an efficient option for achieving transmission and reception polarization matching or avoiding interference in the electromagnetic wave propagation process. Traditional PCs are composed of three-dimensional (3D) structures, which may be limited by bulky volume and complexity. In recent years, the artificial structure metamaterials [10], [11], [12] and its two-dimensional form named metasurface [13], [14], [15], [16] have attracted increasing attention from researchers due to the powerful manipulation capabilities of electromagnetic waves. Especially the metasurface, due to its thin thickness and light weight, has significant advantages in many applications [17], [18], [19]. The metasurface has been widely used in the applications of absorber [20], metalens [21], [22], [23], PCs [24], [25], [26], and so on [27], [28], [29].

According to the propagation direction of the transmitting wave, the PCs based on metasurface can be classified into two types: reflection-type [30], [31], [32], [33] and transmission-type [34], [35], [36], [37], [38] . With the transmission-type PCs placed in front of an antenna’s radiating aperture, the polarization conversion of the radiated electromagnetic wave can be achieved by simply inserting a PC without moving or modifying the rest of the system. Therefore, it is important to investigate on the transmission-type PCs. Therefore, the transmission-type PCs have important applications in many conditions, and they have also attracted a great deal of interest from researchers.

In this paper, we propose a transmission-type polarization-insensitive FSS structure to realize cross-polarization conversion (90-degree polarization rotating) for incident linearly polarized (LP) waves at the operating frequency. The proposed FSS-based cross-polarization converter (CPC) structure adopts a substrate integrated waveguide (SIW) structure, which consists of a dielectric substrate in the middle with top and bottom metal layers perforated with metallized holes. The strip slots and L-shaped groove on the top and the bottom metal layers of each element are orthogonal arranged to each other. By combining the FSS-based CPC with SIW structure, it can realize high-efficient cross-polarization conversion by a single-layered-substrate structure. With the LP incident waves at any azimuth, the CPC converts it to their cross-polarization state.